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1

The Global Multi-Resolution Topography (GMRT) Synthesis  

NASA Astrophysics Data System (ADS)

Topographic maps provide a backdrop for research in nearly every earth science discipline. There is particular demand for bathymetry data in the ocean basins, where existing coverage is sparse. Ships and submersibles worldwide are rapidly acquiring large volumes of new data with modern swath mapping systems. The science community is best served by a global topography compilation that is easily accessible, up-to-date, and delivers data in the highest possible (i.e. native) resolution. To meet this need, the NSF-supported Marine Geoscience Data System (MGDS; www.marine-geo.org) has partnered with the National Geophysical Data Center (NGDC; www.ngdc.noaa.gov) to produce the Global Multi-Resolution Topography (GMRT) synthesis - a continuously updated digital elevation model that is accessible through Open Geospatial Consortium (OGC; www.opengeospatial.org) Web services. GMRT had its genesis in 1992 with the NSF RIDGE Multibeam Synthesis (RMBS); later grew to include the Antarctic Multibeam Synthesis (AMBS); expanded again to include the NSF Ridge 2000 and MARGINS programs; and finally emerged as a global compilation in 2005 with the NSF Legacy of Ocean Exploration (LOE) project. The LOE project forged a permanent partnership between MGDS and NGDC, in which swath bathymetry data sets are routinely published and exchanged via the Open Archives Initiative Protocol for Metadata Harvesting (OAI-PMH; www.openarchives.org). GMRT includes both color-shaded relief images and underlying elevation values at ten different resolutions as high as 100m. New data are edited, gridded, and tiled using tools originally developed by William Haxby at Lamont-Doherty Earth Observatory. Global and regional data sources include the NASA Shuttle Radar Topography Mission (SRTM; http://www.jpl.nasa.gov/srtm/); Smith & Sandwell Satellite Predicted Bathymetry (http://topex.ucsd.edu/marine_topo/); SCAR Subglacial Topographic Model of the Antarctic (BEDMAP; http://www.antarctica.ac.uk/bedmap/); and International Bathymetric Chart of the Arctic Ocean (IBCAO; http://www.ngdc.noaa.gov/mgg/bathymetry/arctic/). Local data sources include high-resolution bathymetry swaths and grids from over 210 research cruises, submersible dives, and related compilations to date. GMRT is accessible via a OGC Web Map Service (WMS) which offers dynamic resolution and on-the-fly map re- projection. A growing number of commercial and open-source clients support OGC protocols, including recent versions of Google Earth and Google Maps which now support WMS natively. GMRT is incorporated as a primary basemap in science Web portals and geobrowsers including EarthChem (www.earthchem.org) and GeoMapApp (www.geomapapp.org), which also serves the underlying elevation values. Future development work will include extension of GMRT to higher resolutions; addition of the International Bathymetric Chart of the Southern Ocean (IBCSO; www.ibcso.org) and the improved SRTM V2; and deployment of new OGC services including a Web Coverage Service (WCS) and Web Terrain Service (WTS).

Arko, R.; Ryan, W.; Carbotte, S.; Melkonian, A.; Coplan, J.; O'Hara, S.; Chayes, D.; Weissel, R.; Goodwillie, A.; Ferrini, V.; Stroker, K.; Virden, W.

2007-12-01

2

The Global Multi-Resolution Topography (GMRT) Synthesis  

Microsoft Academic Search

Topographic maps provide a backdrop for research in nearly every earth science discipline. There is particular demand for bathymetry data in the ocean basins, where existing coverage is sparse. Ships and submersibles worldwide are rapidly acquiring large volumes of new data with modern swath mapping systems. The science community is best served by a global topography compilation that is easily

R. Arko; W. Ryan; S. Carbotte; A. Melkonian; J. Coplan; S. O'Hara; D. Chayes; R. Weissel; A. Goodwillie; V. Ferrini; K. Stroker; W. Virden

2007-01-01

3

The GMRT: Background, Status, and Upgrades  

NASA Astrophysics Data System (ADS)

This article is based on two presentations made to the LFRU --- a short one in the GTAC session and a longer one in the technical session held at the GMRT. The purpose of the first was to convey to the audience --- largely radio astronomers using the GMRT --- some background relevant to the discussion of what users would like to see at the observatory. The second talk attempted to bring out some of the ground realities governing the current operation and the ongoing upgrade of the GMRT, concentrating on aspects not covered in later talks, and in particular on the `outdoor' aspects involving field work --- the SMEC (for servo, mechanical, electrical, civil) aspects where some features are unique to our location and interaction with the local population. Finally, a brief summary of upgrades to feeds and receivers is given.

Nityananda, R.

2009-09-01

4

Studies of novae at GMRT frequencies  

NASA Astrophysics Data System (ADS)

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.

Kantharia, N. G.

2012-09-01

5

GMRT HI imaging survey of ERIDANUS group of galaxies  

E-print Network

This project aims to image a subset of galaxies in the nearby group Eridanus in HI emission and in radio continuum using the GMRT. The typical resolution of HI images will be $\\sim$1 kpc with a 3$\\sigma$ sensitivity to HI mass of a few times 10$^{7}$ M$_\\odot$. The rotation curves obtained using the HI velocity field together with the 2MASS magnitudes in the near infrared will be used to construct the Tully-Fisher relation for this group. High resolution (sub-kpc) multi-frequency radio continuum images will be used to study star-formation rates, radio morphologies and spectral indices of Eridanus galaxies. About half of the galaxies have already been observed and further observations on some late type galaxies are proposed with the GMRT. We present here the HI image and the rotation curve for a member of this group viz. NGC 1385.

Amitesh Omar; K. S. Dwarakanath; K. R. Anantharamaiah

2002-05-04

6

GMRT Observations of Jupiter's Synchrotron Radio Emission at 610 MHz  

Microsoft Academic Search

The non-thermal decimeteric radio emission from Jupiter is dominated by synchrotron emission originating from high-energy electrons trapped in Jupiter's inner radiation belt (<5 Jovian radii). We observed Jupiter during February 24 -- March 3, 2003 with the GMRT to study its day-to-day variability. Each day's observations lasted for ˜10 hours (the rotation period of Jupiter). These observations suggest a correlation

A. Bhardwaj; C. H. Ishwara-Chandra; N. Udaya Shankar; H. Misawa; K. Imai; Y. Miyoshi; F. Tsuchiya; T. Kondo; A. Morioka

2009-01-01

7

A real-time software backend for the GMRT  

NASA Astrophysics Data System (ADS)

The new era of software signal processing has a large impact on radio astronomy instrumentation. Our design and implementation of a 32 antennae, 33 MHz, dual polarization, fully real-time software backend for the GMRT, using only off-the-shelf components, is an example of this. We have built a correlator and a beamformer, using PCI-based ADC cards and a Linux cluster of 48 nodes with dual gigabit inter-node connectivity for real-time data transfer requirements. The highly optimized compute pipeline uses cache efficient, multi-threaded parallel code, with the aid of vectorized processing. This backend allows flexibility in final time and frequency resolutions, and the ability to implement algorithms for radio frequency interference rejection. Our approach has allowed relatively rapid development of a fairly sophisticated and flexible backend receiver system for the GMRT, which will greatly enhance the productivity of the telescope. In this paper we describe some of the first lights using this software processing pipeline. We believe this is the first instance of such a real-time observatory backend for an intermediate sized array like the GMRT.

Roy, Jayanta; Gupta, Yashwant; Pen, Ue-Li; Peterson, Jeffrey B.; Kudale, Sanjay; Kodilkar, Jitendra

2010-08-01

8

Synthesis of Acoustic Signals from Buried Seismic Sources in the Presence of Surface Topography  

NASA Astrophysics Data System (ADS)

Buried seismic sources (such as explosions and earthquakes) can generate acoustic motions in the atmosphere by mechanical coupling of ground motion to atmospheric overpressure along the solid-fluid boundary. The Rayleigh Integral has been used to synthesize acoustic overpressure signals from seismic sources where acceleration time-histories along the boundary are inversely weighted by distance, delayed by travel time and summed at an observation point in the far-field. Typically Rayleigh Integral calculations assume a flat surface between Earth's solid and fluid regions, however topography can result in variations of the overpressure signals due to ground motion amplitude differences at the surface and phase differences along the direction of propagation. This study considers the Rayleigh Integral to compute far-field overpressure using seismic ground motion simulations that include an accurate representation of surface topography. Through a series of numerical experiments we will investigate the partitioning of seismoacoustic energy for near-surface seismic events and attempt to quantify the effect of surface topography on overpressure signals.

Rodgers, A. J.

2013-12-01

9

A software baseband receiver for pulsar astronomy at GMRT  

E-print Network

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.

Bhal Chandra Joshi; Sunil Ramakrishna

2006-11-10

10

Rate and topography of peptidoglycan synthesis during cell division in Escherichia coli: concept of a leading edge.  

PubMed Central

The rate at which the peptidoglycan of Escherichia coli is synthesized during the division cycle was studied with two methods. One method involved synchronization of E. coli MC4100 lysA cultures by centrifugal elutriation and subsequent pulse-labeling of the synchronously growing cultures with [meso-3H]diaminopimelic acid ([3H]Dap). The second method was autoradiography of cells pulse-labeled with [3H]Dap. It was found that the peptidoglycan is synthesized at a more or less exponentially increasing rate during the division cycle with a slight acceleration in this rate as the cells start to constrict. Apparently, polar cap formation requires synthesis of extra surface components, presumably to accommodate for a change in the surface-to-volume ratio. Furthermore, it was found that the pool size of Dap was constant during the division cycle. Close analysis of the topography of [3H]Dap incorporation at the constriction site revealed that constriction proceeded by synthesis of peptidoglycan at the leading edge of the invaginating cell envelope. During constriction, no reallocation of incorporation occurred, i.e., the incorporation at the leading edge remained high throughout the process of constriction. Impairment of penicillin-binding protein 3 by mutation or by the specific beta-lactam antibiotic furazlocillin did not affect [3H]Dap incorporation during initiation of constriction. However, the incorporation at the constriction site was inhibited in later stages of the constriction process. It is concluded that during division at least two peptidoglycan-synthesizing systems are operating sequentially. Images PMID:2656655

Wientjes, F B; Nanninga, N

1989-01-01

11

GMRT HI observations of the Eridanus group of galaxies  

E-print Network

The GMRT HI 21cm-line observations of galaxies in the Eridanus group are presented. The Eridanus group, at a distance of ~23 Mpc, is a loose group of \\~200 galaxies. The group extends more than 10 Mpc in projection. The velocity dispersion of the galaxies in the group is ~240 km/s. The galaxies are clustered into different sub-groups. The overall population mix of the group is 30% (E+S0) and 70% (Sp+Irr). The observations of 57 Eridanus galaxies were carried out with the GMRT for ~200 hour. HI emission was detected from 31 galaxies. The channel rms of ~1.0 mJy beam^{-1} was achieved for most of the image-cubes made with 4 hour of data. The corresponding HI column density sensitivity (3-sigma) is ~1x10^{20} cm^{-2} for a velocity-width of ~13.4 km/s. The 3-sigma detection limit of HI mass is ~1.2x10^{7} M_sun for a line-width of 50 km/s. Total HI images, HI velocity fields, global HI line profiles, HI mass surface densities, HI disk parameters and HI rotation curves are presented. The velocity fields are analysed separately for the approaching and the receding sides of the galaxies. This data will be used to study the HI and the radio continuum properties, the Tully-Fisher relations, the dark matter halos, and the kinematical and HI lopsidedness in galaxies.

A. Omar; K. S. Dwarakanath

2005-03-24

12

A Deep 150 MHz GMRT Survey in Eridanus  

E-print Network

We present results of a 150 MHz survey of a field centered on Epsilon Eridani, undertaken with the Giant Metrewave Radio Telescope (GMRT). The survey covers an area with a diameter of 2 deg, has a spatial resolution of 30" and a noise level of 3.1 mJy at the pointing centre. These observations provide a deeper and higher resolution view of the 150 MHz radio sky than the 7C survey (although the 7C survey covers a much larger area). A total of 113 sources were detected, most are point-like, but 20 are extended. We present an analysis of these sources, in conjunction with the NVSS (at 1.4 GHz) and VLSS (at 74 MHz). This process allowed us to identify 5 Ultra Steep Spectrum (USS) radio sources that are candidate high redshift radio galaxies (HzRGs). In addition, we have derived the dN/dS distribution for these observations and compare our results with other low frequency radio surveys.

Samuel J. George; Ian R. Stevens

2008-09-24

13

GMRT Low Frequency Observations of Extrasolar Planetary Systems  

E-print Network

Extrasolar planets are expected to emit detectable low frequency radio emission. In this paper we present results from new low frequency observations of two extrasolar planetary systems (Epsilon Eridani and HD 128311) taken at 150 MHz with the Giant Metrewave Radio Telescope (GMRT). These two systems have been chosen because the stars are young (with ages < 1 Gyr) and are likely to have strong stellar winds, which will increase the expected radio flux. The planets are massive (presumably) gas giant planets in longer period orbits, and hence will not be tidally locked to their host star (as is likely to be the case for short period planets) and we would expect them to have a strong planetary dynamo and magnetic field. We do not detect either system, but are able to place tight upper limits on their low frequency radio emission, at levels comparable to the theoretical predictions for these systems. From these observations we have a 2.5sigma limit of 7.8 mJy for Epsilon Eri and 15.5 mJy for HD 128311. In addition, these upper limits also provide limits on the low frequency radio emission from the stars themselves. These results are discussed and also the prospects for the future detection of radio emission from extrasolar planets.

Samuel George; Ian Stevens

2007-08-30

14

Corneal topography  

Microsoft Academic Search

This paper explores the many aspects of the nature and measurement of the corneal surface. Its structure and the factors that influence it are described. The traditional techniques of keratometry are summarized and there is an emphasis on new experimental methods of determining corneal topography including moiré, holographic interferometric and profile techniques. The advantages and disadvantages of these procedures are

Thomas W. Smith

1977-01-01

15

HI Fluctuations at Large Redshifts: III - Simulating the Signal Expected at GMRT  

E-print Network

We simulate the distribution of neutral hydrogen (HI) at the redshifts z=1.3 and 3.4 using a cosmological N-body simulation along with a prescription for assigning HI masses to the particles. The HI is distributed in clouds whose properties are consistent with those of the damped Lyman-\\alpha absorption systems (DLAs) seen in quasar spectra. The clustering properties of these clouds are identical to those of the dark matter. We use this to simulate the redshifted HI emission expected at 610 MHz and 325 MHz, two of the observing bands a the GMRT. These are used to predict the correlations expected between the complex visibilities measured at different baselines and frequencies in radio-interferometric observations with the GMRT. The visibility correlations directly probe the power spectrum of HI fluctuations at the epoch when the HI emission originated, and this holds the possibility of using HI observations to study large-scale structures at high z.

Somnath Bharadwaj; Pennathur Sridharan Srikant

2004-02-11

16

Search for Radio Emission from Extrasolar Planets: Preliminary Analysis of GMRT Data  

NASA Astrophysics Data System (ADS)

In 2004 we carried out a series of short calibration runs using the central square array of the GMRT. At the operating RF of 150 MHz, we have determined that the GMRT has a fantastic sensitivity of 2 mJy over a bandwidth of 5 MHz and a timescale of one hour and is relatively free of RFI between midnight and early morning hours local time. As part of the calibration runs, we have carried out brief observation of UpsAnd with various observing strategies. In early 2005, we were granted observing time on the GMRT during its Cycle 7 observation period. Our focus to date has been in characterizing the large scale structure of the dynamic spectra, identifying RFI and developing filters to remove them. We will present our results from both the short calibrations runs of 2004 as well as those obtained from the 2005 observations. We will also describe techniques for detection of chirps as present in Jupiter observations, including match filter strategies. In addition we will describe some preliminary results for detecting bursts via statistical techniques. We plan to use Jupiter and Saturn data to calibrate our detection efficiency for various strategies. We will also discuss our software package for data analysis and computing strategies that we have adopted on our Beowulf Linux cluster at JPL.

Majid, W. A.; Chandra, I.; Kuiper, T.; Lazio, J.; Winterhalter, D.; Naudet, C.; Treumann, R.; Zarka, P.

2005-05-01

17

Low Frequency Radio Observations of GRS1915+105 with GMRT  

E-print Network

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.

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

2005-12-02

18

Low-frequency GMRT observations of the magnetic Bp star HR Lup (HD 133880)  

NASA Astrophysics Data System (ADS)

We present radio observations of the magnetic chemically peculiar Bp star HR Lup (HD 133880) at 647 and 277 MHz with the GMRT. At both frequencies the source is not detected but we are able to determine upper limits to the emission. The 647 MHz limits are particularly useful, with a 5? value of 0.45 mJy. Also, no large enhancements of the emission were seen. The non-detections, along with previously published higher frequency detections, provide evidence that an optically thick gyrosynchrotron model is the correct mechanism for the radio emission of HR Lup.

George, Samuel J.; Stevens, Ian R.

2012-06-01

19

High dynamic solar radio images by combining visibilities from the Giant Meterwave Radio Telescope (GMRT) and the Nancay Radioheliograph (NRH)  

NASA Astrophysics Data System (ADS)

We present first results from an ongoing program of combining data from NRH and GMRT to produce snapshot images of the sun at meter ?. The data processing includes a superposition of complex visibilities from NRH and GMRT, a Fourier Transform and a cleaning multi-scale algorithm. We present results of a) a simulation and b) an observation of a complex noise storm at 327 MHz on August 27, 2002. This illustrates the capacity of the method to produce high dynamic range snapshot images of a complex sun, and shows that composite images are by far better than images from either instrument alone.

Mercier, C.

2006-06-01

20

Density Isostasy and Topography  

NSDL National Science Digital Library

Density, Isostasy, and Topography Anne Egger, Stanford University The original activity Density, Isostasy, and Topography already exists within the SERC website. This page describes how this activity can be used ...

21

Moiré topography in odontology  

Microsoft Academic Search

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

A. Moreno Yeras

2003-01-01

22

Prospects for GMRT to Observe Radio Waves from UHE Particles Interacting with the Moon  

E-print Network

Ultra high energy (UHE) particles of cosmic origin impact the lunar regolith and produce radio signals through Askaryan effect, signals that can be detected by Earth based radio telescopes. We calculate the expected sensitivity for observation of such events at the Giant Metrewave Radio Telescope (GMRT), both for UHE cosmic rays (CR) and UHE neutrino interactions. We find that for 30 days of observation time a significant number of detectable events is expected above $10^{20}$ eV for UHECR or neutrino fluxes close to the current limits. Null detection over a period of 30 days will lower the experimental bounds on UHE particle fluxes by magnitudes competitive to both present and future experiments at the very highest energies.

Sukanta Panda; Subhendra Mohanty; Padmanabhan Janardhan; Oscar Stål

2007-08-13

23

Prospects for GMRT to Observe Radio Waves from UHE Particles Interacting with the Moon  

E-print Network

Ultra high energy (UHE) particles of cosmic origin impact the lunar regolith and produce radio signals through Askaryan effect, signals that can be detected by Earth based radio telescopes. We calculate the expected sensitivity for observation of such events at the Giant Metrewave Radio Telescope (GMRT), both for UHE cosmic rays (CR) and UHE neutrino interactions. We find that for 30 days of observation time a significant number of detectable events is expected above $10^{20}$ eV for UHECR or neutrino fluxes close to the current limits. Null detection over a period of 30 days will lower the experimental bounds on UHE particle fluxes by magnitudes competitive to both present and future experiments at the very highest energies.

Panda, Sukanta; Janardhan, Padmanabhan; Stål, Oscar

2007-01-01

24

Characterizing the diffuse foreground for redshifted 21-cm HI signal: GMRT 153 MHz observation  

NASA Astrophysics Data System (ADS)

Detailed knowledge of the foreground structure on the angular scales of ~ 1° to sub-arcminute will be essential for extracting the redshifted 21-cm HI signal from the observed data. We have presented results from the GMRT observations at 153 MHz, which was used to characterize the statistical properties of the diffuse radiation, using the multi-frequency angular power spectrum, across sub-degree angular scales. We have detected fluctuations in the diffuse emission on angular scales greater than 10' in a low galactic latitude area. The total intensity angular spectrum shows a power-law behaviour, while the detection of diffuse emission at smaller angular scales is limited by residual point sources. Also, we have estimated the level of foreground contamination.

Ghosh, A.; Prasad, J.; Bharadwaj, S.; Ali, S. S.; Chengalur, J. N.

2014-03-01

25

Multi-frequency GMRT Observations of the HII regions S 201, S 206, and S 209 : Galactic Temperature Gradient  

E-print Network

We present radio continuum images of three Galactic HII regions, S 201, S 206, and S 209 near 232, 327, and 610 MHz using the Giant Meterwave Radio Telescope (GMRT). The GMRT has a mix of short and long baselines, therefore, even though the data have high spatial resolution, the maps are still sensitive to diffuse extended emission. We find that all three HII regions have bright cores surrounded by diffuse envelopes. We use the high resolution afforded by the data to estimate the electron temperatures and emission measures of the compact cores of these HII regions. Our estimates of electron temperatures are consistent with a linear increase of electron temperature with Galacto-centric distance for distances up to 18 kpc (the distance to the most distant HII region in our sample).

A. Omar; J. N. Chengalur; D. Anish Roshi

2002-09-08

26

OpenTopography  

NASA Astrophysics Data System (ADS)

OpenTopography is a cyberinfrastructure-based facility for online access to high-resolution topography and tools. The project is an outcome of the Geosciences Network (GEON) project, which was a research project funded several years ago in the US to investigate the use of cyberinfrastructure to support research and education in the geosciences. OpenTopography provides online access to large LiDAR point cloud datasets along with services for processing these data. Users are able to generate custom DEMs by invoking DEM services provided by OpenTopography with custom parameter values. Users can track the progress of their jobs, and a private myOpenTopo area retains job information and job outputs. Data available at OpenTopography are provided by a variety of data acquisition groups under joint agreements and memoranda of understanding (MoU). These include national facilities such as the National Center for Airborne Lidar Mapping, as well as local, state, and federal agencies. OpenTopography is also being designed as a hub for high-resolution topography resources. Datasets and services available at other locations can also be registered here, providing a "one-stop shop" for such information. We will describe the OpenTopography system architecture and its current set of features, including the service-oriented architecture, a job-tracking database, and social networking features. We will also describe several design and development activities underway to archive and publish datasets using digital object identifiers (DOIs); create a more flexible and scalable high-performance environment for processing of large datasets; extend support for satellite-based and terrestrial lidar as well as synthetic aperture radar (SAR) data; and create a "pluggable" infrastructure for third-party services. OpenTopography has successfully created a facility for sharing lidar data. In the next phase, we are developing a facility that will also enable equally easy and successful sharing of services related to these data.

Baru, C.; Arrowsmith, R.; Crosby, C.; Nandigam, V.; Phan, M.; Cowart, C.

2012-04-01

27

Search for 150 MHz radio emission from extrasolar planets in the TIFR GMRT Sky Survey  

NASA Astrophysics Data System (ADS)

The ongoing radio continuum TIFR GMRT Sky Survey (TGSS) using the Giant Metrewave Radio Telescope (GMRT) at 150 MHz offers an unprecedented opportunity to undertake a fairly deep search for low-frequency radio emission from nearby extrasolar planets. Currently TGSS images are available for a little over a steradian, encompassing 175 confirmed exoplanetary systems. We have searched for their radio counterparts in the TGSS (150 MHz), supplemented with a search in the NRAO VLA Sky Survey (NVSS) and the VLA FIRST survey at 1.4 GHz. For 171 planetary systems, we find no evidence of radio emission in the TGSS maps, placing a 3? upper limit between 8.7 mJy and 136 mJy (median ~24.8 mJy) at 150 MHz. These non-detections include the 55 Cnc system for which we place a 3? upper limit of 28 mJy at 150 MHz. Nonetheless, for four of the extrasolar planetary systems, we find TGSS radio sources coinciding with or located very close to their coordinates. One of these is 61 Vir: for this system a large radio flux density was predicted in the scenario involving magnetosphere-ionosphere coupling and rotation-induced radio emission. We also found 150 MHz emissions toward HD 86226 and HD 164509, where strong radio emission can be produced by the presence of a massive satellite orbiting a rapidly rotating planet. We also detected 150 MHz emission within a synthesized beam from 1RXS1609 b, a pre-main-sequence star harboring a ~14 Jupiter mass planet (or a brown dwarf). With a bright X-ray-UV star and a high mass, the planet 1RXS1609 b presents the best characteristics for rotation-induced emissions with high radio power. Deeper high-resolution observations toward these planetary systems are needed to discriminate between the possibilities of background radio-source and radio-loud planets. At 1.4 GHz, radio emission toward the planet-harboring pulsar PSR B1620-26 is detected in the NVSS. Emissions at 1.4 GHz are also detected toward the very-hot-Jupiter WASP-77A b (in the FIRST survey) and the giant planet HD 43197 b in a highly eccentric orbit (in NVSS). We briefly discuss these detections, as well as the non-detection of the vast majority of exoplanets. Full Table 1 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/562/A108

Sirothia, S. K.; Lecavelier des Etangs, A.; Gopal-Krishna; Kantharia, N. G.; Ishwar-Chandra, C. H.

2014-02-01

28

Moire topography in odontology  

NASA Astrophysics Data System (ADS)

For several decades measurement optical techniques have been used in different branches of Science and Technology and in medicine. One of these techniques is the so-called Moire topography that allows the accurate measurement of different parts of the human body topography. This investigation presents the measurement of topographies of teeth and gums using an automated system of shadow moire, with which precision can be reached up to the order of the microns by the phase shift instrumentation in an original way. Advantages and disadvantages of using the Moire topography and its comparison with other techniques used in the optical metrology are presented. Also, some positive and negative aspects of the implementation of this technique are shown in dentistry.

Moreno Yeras, A.

2001-08-01

29

Foregrounds for redshifted 21 cm studies of reionization: GMRT 153 MHz observations  

E-print Network

Foreground subtraction is the biggest challenge for future redshifted 21 cm observations to probe reionization. We use a short GMRT observation at 153 MHz to characterize the statistical properties of the background radiation across ~ one degree to sub-arcminutes angular scales, and across a frequency band of 5 MHz with 62.5 kHz resolution. The statistic we use is the visibility correlation function, or equivalently the angular power spectrum C_l. We present the results obtained from using relatively unsophisticated, conventional data calibration procedures. We find that even fairly simple minded calibration allows one to estimate the visibility correlation function at a given frequency V_2(U,0). From our observations we find that V_2(U,0) is consistent with foreground model predictions at all angular scales except the largest ones probed by our observations where the the model predictions are somewhat in excess. On the other hand the visibility correlation between different frequencies kappa(U, Delta nu), seems to be much more sensitive to calibration errors. We find a rapid decline in kappa(U, Delta nu), in contrast with the prediction of less than 1 % variation across 2.5 MHz. In this case however, it seems likely that a substantial part of the discrepancy may be due to limitations of data reduction procedures.

SK. Saiyad Ali; Somnath Bharadwaj; Jayaram N. Chengalur

2008-01-16

30

Moiré topography in odontology  

NASA Astrophysics Data System (ADS)

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

Moreno Yeras, A.

2003-07-01

31

Consequences of membrane topography.  

PubMed

The surface of mammalian cells is neither smooth nor flat and cells have several times more plasma membrane than the minimum area required to accommodate their shape. We discuss the biological function of this apparent excess membrane that allows the cells to migrate and undergo shape changes and probably plays a role in signal transduction. Methods for studying membrane folding and topography--atomic force microscopy, scanning ion conductance microscopy, fluorescence polarization microscopy and linear dichroism--are described and evaluated. Membrane folding and topography is frequently ignored when interpreting microscopy data. This has resulted in several misconceptions regarding for instance colocalization, membrane organization and molecular clustering. We suggest simple ways to avoid these pitfalls and invoke Occam's razor--that simple explanations are preferable to complex ones. Topography, i.e. deviations from a smooth surface, should always be ruled out as the cause of anomalous data before other explanations are presented. PMID:23438106

Parmryd, Ingela; Onfelt, Björn

2013-06-01

32

Topography-assisted photoablation  

NASA Astrophysics Data System (ADS)

Topography assisted photoablation (TAP) is an important and logic step for future customized therapeutic photokeratectomy. Its goal is to reshape any irregular corneal surface in order to achieve an ideal sphere. Accuracy and reproducibility of the 2D and 3D topography data, strategies of data acquisition, data modification and transfer are essential elements. Accurate and appropriate subtraction methods for difference mapping are discussed. Furthermore, the properties and algorithms of the lasers' delivery systems, have to be taken into account. The overview paper describes and discusses some of the central elements of TAP.

Jean, Benedikt J.; Bende, Thomas

1999-06-01

33

GMRT and VLA observations of HI and OH from the Seyfert galaxy Mrk 1  

E-print Network

We present Giant Meterwave Radio Telescope (GMRT) observations of the HI 21 cm line and Very Large Array (VLA) observations of the OH 18 cm line from the Seyfert 2 galaxy Mrk 1. HI emission is detected from both Mrk 1 and its companion NGC 451. The HI emission morphology and the velocity field of Mrk 1 are disturbed. We speculate that the nuclear activities of Mrk 1 are triggered by tidal interactions. We have also detected two-component HI 21 cm line and the OH 18 cm line in absorption toward the nucleus of Mrk 1 at blueshifted velocities with respect to its systemic velocity indicating an outflow of atomic and molecular gas. The profile of the OH absorption is qualitatively similar to that of the HI absorption. The higher velocity components of the HI and OH (1667 MHz) absorption lines are blueshifted from the O[III]5007, O[I]6300, and the systemic velocity by ~ 100 km s^{-1}, but are consistent with the O[II]3727 velocity. We explain these velocity discrepancies as due to shock ionization of a region which is pushed forward due to shocks in front of the radio nucleus thereby giving apparent blueshift to HI, OH, and O[II] velocities. The optical depth ratios tau{HI}/tau{OH1667} of both the components of the HI and OH absorption are ~3, indicating their origin in dense molecular clouds. Using OH/A_{v} values for the Galactic molecular clouds, we obtain 9 < A_{v} < 90 toward the line of sight of Mrk 1.

A. Omar; K. S. Dwarakanath; M. Rupen; K. R. Anantharamaiah

2002-08-09

34

Flow Interaction with Topography  

NSDL National Science Digital Library

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

Comet

2001-01-01

35

Flow Interaction with Topography  

NSDL National Science Digital Library

This module explores the fundamental concepts used to determine how air flow interacts with topography. Using the simple analogy of a marble rolling over a hill, this module examines the relationship between wind speed and static stability of the atmosphere. These results are further extended to include three-dimensional terrain barriers as well as the evolution through time of the interaction.

Spangler, Tim

1999-05-01

36

Gallery of Virtual Topography  

NSDL National Science Digital Library

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

Reynolds, Stephen

37

Toward optical coherence topography  

NASA Astrophysics Data System (ADS)

Commercial OCT systems provide pachymetry measurements. Full corneal topographic information of anterior and posterior corneal surfaces for use in cataract surgery and refractive procedures is a desirable goal and would add to the usefulness of anterior and posterior segment evaluation. While substantial progress has been made towards obtaining "average" central corneal power (D Huang), power in different meridians and topography are still missing. This is usually reported to be due to eye movement. We analyze the role of centration, eye movements and develop a model that allows for the formulation of criteria for obtaining reliable topographic data within ¼ diopter.

Sayegh, Samir; Jiang, Yanshui

2012-03-01

38

Corneal topography system  

NASA Astrophysics Data System (ADS)

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

Cambier, James L.; Gao, Yan

1998-03-01

39

Investigation of the solar UV/EUV heating effect on the Jovian radiation belt by GMRT-IRTF observation  

NASA Astrophysics Data System (ADS)

Jupiter's synchrotron radiation (JSR) is the emission from relativistic electrons, and it is the most effective probe for remote sensing of Jupiter's radiation belt from the Earth. Recent intensive observations of JSR revealed short term variations of JSR with the time scale of days to weeks. Brice and McDonough (1973) proposed a scenario for the short term variations; i.e, the solar UV/EUV heating for Jupiter's upper atmosphere causes enhancement of total flux density. The purpose of this study is to investigate whether sufficient solar UV/EUV heating in Jupiter's upper atmosphere can actually causes variation in the JSR total flux and brightness distribution. Previous JSR observations using the Giant Metrewave Radio Telescope (GMRT) suggested important characteristics of short term variations; relatively low energy particles are accelerated by some acceleration processes which might be driven by solar UV/EUV heating and/or Jupiter's own magnetic activities. In order to evaluate the effect of solar UV/EUV heating on JSR variations, we made coordinated observations using the GMRT and NASA Infra-Red Telescope Facility (IRTF). By using IRTF, we can estimate the temperature of Jupiter's upper atmosphere from spectroscopic observation of H_3^+ infrared emission. Hence, we can evaluate the relationship between variations in Jupiter's upper atmosphere initiated by the solar UV/EUV heating and its linkage with the JSR. The GMRT observations were made during Nov. 6-17, 2011 at the frequency of 235/610MHz. The H_3^+ 3.953 micron line was observed using the IRTF during Nov. 7-12, 2011. During the observation period, the solar UV/EUV flux variations expected on Jupiter showed monotonic increase. A preliminary analysis of GMRT 610MHz band showed a radio flux variation similar to that in the solar UV/EUV. Radio images showed that the emission intensity increased at the outer region and the position of equatorial peak emission moved in the outward direction. If radial diffusion increases globally by the solar UV/EUV heating, it is expected that the peak intensity would increase and the peak position move inwards. However, our results are not consistent with the global enhancement of radial diffusion. In addition to that, the equatorial H_3^+ emission indicated that emission intensity decreased from the first day of observation to the last day. It is expected that equatorial temperature of Jupiter's atmosphere decreases during this observation period. Therefore, we propose that radial diffusion increased not globally but only at the outer region around L=2-3 during this period. From this hypothesis, it is expected that enhancement of radial diffusion at the outer region is caused by high latitude temperature enhancement. We discuss possible causes of the short term variations of JSR from the IRTF observation results at high latitude.

Kita, H.; Misawa, H.; Bhardwaj, A.; Tsuchiya, F.; Tao, C.; Uno, T.; Kondo, T.; Morioka, A.

2012-12-01

40

The electron temperatures of HII regions S 201, S 206, and S 209 : Multi-frequency GMRT observations  

E-print Network

Three Galactic HII regions, viz., S 201, S 206, and S 209 have been imaged at three frequencies, viz., 232, 327, and 610 MHz using the GMRT. The resolutions of these images are typically 15" at 232, 10" at 327, and 6" at 610 MHz. These are the highest resolution low frequency images of these HII regions. We found that all three HII regions have core--envelope morphologies. We use the high resolution afforded by the data to estimate the electron temperatures of the compact cores of these HII regions. These estimates of the electron temperatures are consistent with an increase in the temperature with Galacto-centric distance; an effect attributed to a decrease in the heavy elements abundances at large Galacto-centric distances.

Amitesh Omar; J. N. Chengalur; D. A. Roshi

2002-05-04

41

Deep 610-MHz GMRT observations of the Spitzer extragalactic First Look Survey field - I. Observations, data analysis and source catalogue  

E-print Network

Observations of the Spitzer extragalactic First Look Survey field taken at 610 MHz with the Giant Metrewave Radio Telescope are presented. Seven individual pointings were observed, covering an area of 4 square degrees with a resolution of 5.8'' x 4.7'', PA 60 deg. The r.m.s. noise at the centre of the pointings is between 27 and 30 microJy before correction for the GMRT primary beam. The techniques used for data reduction and production of a mosaicked image of the region are described, and the final mosaic, along with a catalogue of 3944 sources detected above 5 sigma, are presented. The survey complements existing radio and infrared data available for this region.

Timothy Garn; David A. Green; Sally E. G. Hales; Julia M. Riley; Paul Alexander

2007-01-18

42

RADAR Reveals Titan Topography  

NASA Technical Reports Server (NTRS)

The Cassini Titan RADAR Mapper is a K(sub u)-band (13.78 GHz, lambda = 2.17 cm) linear polarized RADAR instrument capable of operating in synthetic aperture (SAR), scatterometer, altimeter and radiometer modes. During the first targeted flyby of Titan on 26 October, 2004 (referred to as Ta) observations were made in all modes. Evidence for topographic relief based on the Ta altimetry and SAR data are presented here. Additional SAR and altimetry observations are planned for the T3 encounter on 15 February, 2005, but have not been carried out at this writing. Results from the T3 encounter relevant to topography will be included in our presentation. Data obtained in the Ta encounter include a SAR image swath

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

2005-01-01

43

Topography of Io (color)  

NASA Technical Reports Server (NTRS)

The images used to create this color composite of Io were acquired by Galileo during its ninth orbit (C9) of Jupiter and are part of a sequence of images designed to map the topography or relief on Io and to monitor changes in the surface color due to volcanic activity. Obtaining images at low illumination angles is like taking a picture from a high altitude around sunrise or sunset. Such lighting conditions emphasize the topography of the volcanic satellite. Several mountains up to a few miles high can be seen in this view, especially near the upper right. Some of these mountains appear to be tilted crustal blocks. Most of the dark spots correspond to active volcanic centers.

North is to the top of the picture which merges images obtained with the clear, red, green, and violet filters of the solid state imaging (CCD) system on NASA's Galileo spacecraft. . The resolution is 8.3 kilometers per picture element. The image was taken on June 27, 1997 at a range of 817,000 kilometers by the solid state imaging (CCD) system on NASA's Galileo spacecraft.

The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC. JPL is an operating division of California Institute of Technology (Caltech).

This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://galileo.jpl.nasa.gov. Background information and educational context for the images can be found at URL http://www.jpl.nasa.gov/galileo/sepo

1997-01-01

44

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

45

Synchrotron X-ray topography  

Microsoft Academic Search

The various techniques of X-ray diffraction topography image imperfections in single-crystals by Bragg reflexion, with a spatial resolution of approximately one micrometre. Defects can be studied in relation to crystal growth and physical properties. X-ray interference effects can also be explored in perfect, and nearly perfect, crystals. Synchrotron radiation has given X-ray topography additional powers, including the rapid non-destructive assessment

Moreton Moore

1995-01-01

46

Prospects for detection of the lunar Cerenkov emission by the UHE Cosmic Rays and Neutrinos using the GMRT and the Ooty Radio Telescope  

E-print Network

Searching for the Ultra high energy Cosmic rays and Neutrinos of $> 10^{20} eV$ is of great cosmological importance. A powerful technique is to search for the \\v{C}erenkov radio emission caused by UHECR or UHE neutrinos impinging on the lunar regolith. We examine in this paper feasibility of detecting these events by observing with the Giant Metrewave Radio Telescope (GMRT) which has a large collecting area and operates over a wide frequency range with an orthogonal polarisation capability. We discuss here prospects of observations of the \\v{C}erenkov radio emission with the GMRT at 140 MHZ with 32 MHz bandwidth using the incoherent array and also forming 25 beams of the Central Array to cover the moon. We also consider using the Ooty Radio Telescope (ORT) which was specially designed in 1970 for tracking the Moon. With the ORT (530m long and 30m wide parabolic cylinder) it becomes possible to track the Moon for 9.5 hours on a given day by a simple rotation along the long axis of the parabolic cylinder. ORT operates at 325 MHz and has an effective collecting area of ~ 8000 $m^2.$ Recently a digital system has been installed by scientists of the Raman Research Institute (RRI), Bangalore and the Radio Astronomy Centre (RAC) of NCRA/TIFR, at Ooty allowing a bandwidth of 10 MHz with ~ 40 ns sampling. It is possible to form 6 beams covering the Moon and 7th beam far away for discrimination of any terrestrial RFI. Increasing the bandwidth of the existing 12 beam analogue system of the ORT from 4 MHz to 15 MHz to be sampled digitally is planned. It is shown that by observing the Moon for $\\ge$ 1000 hrs using the ORT it will provide appreciably higher sensitivity than past searches made elsewhere. Using the GMRT and ORT, it may be possible to reach sensitivity to test the Waxman-Bachall limit on UHE neutrino flux.

Govind Swarup; Sukanta Panda

2008-05-28

47

A High Galactic Latitude HI 21cm-line Absorption Survey using the GMRT: II. Results and Interpretation  

E-print Network

We have carried out a sensitive high-latitude (|b| > 15deg.) HI 21cm-line absorption survey towards 102 sources using the GMRT. With a 3-sigma detection limit in optical depth of ~0.01, this is the most sensitive HI absorption survey. We detected 126 absorption features most of which also have corresponding HI emission features in the Leiden Dwingeloo Survey of Galactic neutral Hydrogen. The histogram of random velocities of the absorption features is well-fit by two Gaussians centered at V(lsr) ~ 0 km/s with velocity dispersions of 7.6 +/- 0.3 km/s and 21 +/- 4 km/s respectively. About 20% of the HI absorption features form the larger velocity dispersion component. The HI absorption features forming the narrow Gaussian have a mean optical depth of 0.20 +/- 0.19, a mean HI column density of (1.46 +/- 1.03) X 10^{20} cm^{-2}, and a mean spin temperature of 121 +/- 69 K. These HI concentrations can be identified with the standard HI clouds in the cold neutral medium of the Galaxy. The HI absorption features forming the wider Gaussian have a mean optical depth of 0.04 +/- 0.02, a mean HI column density of (4.3 +/- 3.4) X 10^{19} cm^{-2}, and a mean spin temperature of 125 +/- 82 K. The HI column densities of these fast clouds decrease with their increasing random velocities. These fast clouds can be identified with a population of clouds detected so far only in optical absorption and in HI emission lines with a similar velocity dispersion. This population of fast clouds is likely to be in the lower Galactic Halo.

Rekhesh Mohan; K. S. Dwarakanath; G. Srinivasan

2004-10-26

48

Noninvasive measurement of corneal topography  

Microsoft Academic Search

The authors present a brief overview of the surface to be measured (the cornea of the eye), review the current state of the technology designed to measure the corneal topography, and define the outstanding issues of current significance. The topics discussed include: eye movements; fundamental operating principles of new systems; videokeratographic systems; fundamental limitations of the operating principles; limitations of

R. A. Applegate; H. C. Howland

1995-01-01

49

Reactions of cells to topography  

Microsoft Academic Search

Though contact guidance has been known since the very early days of cell culture very little quantitative examination of the reaction of cells to topography has been made. Exceptions to this subjective approach are given prominence below. Yet if we are to understand how cells react and if we are to be able to design ideal substrata for particular cells

Adam S. G. Curtis; Chris D. W. Wilkinson

1998-01-01

50

Whitebeam X-ray topography  

Microsoft Academic Search

After radiography, white-beam X-ray topography (XRT) is the simplest X-ray imaging technique for crystals. An X-ray topograph is formed by a Bragg reflexion and is in effect a high-spatial-resolution Laue ‘spot’. Synchrotron radiation has given XRT additional powers, with its broad continuous spectrum, small beam divergence, high intensity, strong polarization and regular pulsed time structure. Each Laue image, however, may

Moreton Moore

2012-01-01

51

Topography, Cell Response, and Nerve Regeneration  

PubMed Central

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

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

2010-01-01

52

Plasma processing for nanostructured topographies  

NASA Astrophysics Data System (ADS)

Plasma and directed ion interactions with materials have been widely observed to create complex surface patterns on a micro- and nano- scale. Generally, these texturizations are byproducts of another intended application (such as a feature formation on a sputtering target) and patterning is considered inconsequential or even detrimental. This work examined the possibility of using these phenomena as primary methods for producing beneficial topographies. Specifically, investigations focused on the use of helium plasma exposure and directed ion etching to create nanostructured surfaces capable of affecting biological interactions with implanted materials. Orthogonal argon ion etching and low energy helium plasma texturization of titanium were considered for use on orthopedic and dental implants as a means of increasing osteoblast activity and bone attachment; and oblique angle etching was evaluated for its use in creating topographies with cell deterrent or anti-thrombogenic properties. In addition, the helium driven evolution of surface features on 6061 aluminum alloy was characterized with respect to ion energy and substrate temperature. These surfaces were then considered for ice phobic applications.

Riedel, Nicholas Alfred

53

Quantifying turbidity current interactions with topography  

E-print Network

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

Straub, Kyle M

2007-01-01

54

Tidal Conversion by Rough Topography  

NASA Astrophysics Data System (ADS)

The barotropic tide generates internal gravity waves due to sea floor topography, which leads to conversion of tidal energy into smaller scale waves and eventually dissipation. New measurements indicate that the tidal dissipation in the open ocean is substantially higher than predicted by theoretical models. Hence, the search is on for an effect that enhances the energy conversion rate. Using functional equations techniques, one can show that the solution for a steep triangular seamount is exactly equivalent to a triangular seamount with a slope at the angle of wave propagation. The stream function develops spatial discontinuities (shocks) as the maximum topographic slope approaches the critical slope from below. Nonlinear effects become important in a vortex forming above the seamount, which may cause significant changes in the conversion rate.

Schorghofer, Norbert; Khatiwala, Samar; Aharonson, Oded

2003-03-01

55

Topography and Landforms of Ecuador  

USGS Publications Warehouse

EXPLANATION The digital elevation model of Ecuador represented in this data set was produced from over 40 individual tiles of elevation data from the Shuttle Radar Topography Mission (SRTM). Each tile was downloaded, converted from its native Height file format (.hgt), and imported into a geographic information system (GIS) for additional processing. Processing of the data included data gap filling, mosaicking, and re-projection of the tiles to form one single seamless digital elevation model. For 11 days in February of 2000, NASA, the National Geospatial-Intelligence Agency (NGA), the German Aerospace Center (DLR), and the Italian Space Agency (ASI) flew X-band and C-band radar interferometry onboard the Space Shuttle Endeavor. The mission covered the Earth between 60?N and 57?S and will provide interferometric digital elevation models (DEMs) of approximately 80% of the Earth's land mass when processing is complete. The radar-pointing angle was approximately 55? at scene center. Ascending and descending orbital passes generated multiple interferometric data scenes for nearly all areas. Up to eight passes of data were merged to form the final processed SRTM DEMs. The effect of merging scenes averages elevation values recorded in coincident scenes and reduces, but does not completely eliminate, the amount of area with layover and terrain shadow effects. The most significant form of data processing for the Ecuador DEM was gap-filling areas where the SRTM data contained a data void. These void areas are a result of radar shadow, layover, standing water, and other effects of terrain, as well as technical radar interferometry phase unwrapping issues. To fill these gaps, topographic contours were digitized from 1:50,000 - scale topographic maps which date from the mid-late 1980's (Souris, 2001). Digital contours were gridded to form elevation models for void areas and subsequently were merged with the SRTM data through GIS and remote sensing image-processing techniques. The data contained in this publication includes a gap filled, countrywide SRTM DEM of Ecuador projected in Universal Transverse Mercator (UTM) Zone 17 North projection, Provisional South American, 1956, Ecuador datum and a non gap filled SRTM DEM of the Galapagos Islands projected in UTM Zone 15 North projection. Both the Ecuador and Galapagos Islands DEMs are available as an ESRI Grid, stored as ArcInfo Export files (.e00), and in Erdas Imagine (IMG) file formats with a 90 meter pixel resolution. Also included in this publication are high and low resolution Adobe Acrobat (PDF) files of topography and landforms maps in Ecuador. The high resolution map should be used for printing and display, while the lower resolution map can be used for quick viewing and reference purposes.

Chirico, Peter G.; Warner, Michael B.

2005-01-01

56

Phobos' shape and topography models  

NASA Astrophysics Data System (ADS)

The global shape and the dynamic environment are fundamental properties of a body. Other properties such as volume, bulk density, and models for the dynamic environment can subsequently be computed based on such models. Stereo-photogrammetric methods were applied to derive a global digital terrain model (DTM) with 100 m/pixel resolution using High Resolution Stereo Camera images of the Mars Express mission and Viking Orbiter images. In a subsequent least-squares fit, coefficients of the spherical harmonic function to degree and order 45 are computed. The dynamic models for Phobos were derived from a polyhedron representation of the DTM. The DTM, spherical harmonic function model, and dynamic models, have been refined and represent Phobos' dynamic and geometric topography with much more detail when compared to Shi et al. (2012) and Willner et al. (2010) models, respectively. The volume of Phobos has been re-determined to be in the order of 5741 km3 with an uncertainty of only 0.6% of the total volume. This reduces the bulk density to 1.86±0.013 g/cm3 in comparison to previous results. Assuming a homogeneous mass distribution a forced libration amplitude for Phobos of 1.14° is computed that is in better agreement with observations by Willner et al. (2010) than previous estimates.

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

2014-11-01

57

Genetic topography of brain morphology  

PubMed Central

Animal data show that cortical development is initially patterned by genetic gradients largely along three orthogonal axes. We previously reported differences in genetic influences on cortical surface area along an anterior-posterior axis using neuroimaging data of adult human twins. Here, we demonstrate differences in genetic influences on cortical thickness along a dorsal-ventral axis in the same cohort. The phenomenon of orthogonal gradations in cortical organization evident in different structural and functional properties may originate from genetic gradients. Another emerging theme of cortical patterning is that patterns of genetic influences recapitulate the spatial topography of the cortex within hemispheres. The genetic patterning of both cortical thickness and surface area corresponds to cortical functional specializations. Intriguingly, in contrast to broad similarities in genetic patterning, two sets of analyses distinguish cortical thickness and surface area genetically. First, genetic contributions to cortical thickness and surface area are largely distinct; there is very little genetic correlation (i.e., shared genetic influences) between them. Second, organizing principles among genetically defined regions differ between thickness and surface area. Examining the structure of the genetic similarity matrix among clusters revealed that, whereas surface area clusters showed great genetic proximity with clusters from the same lobe, thickness clusters appear to have close genetic relatedness with clusters that have similar maturational timing. The discrepancies are in line with evidence that the two traits follow different mechanisms in neurodevelopment. Our findings highlight the complexity of genetic influences on cortical morphology and provide a glimpse into emerging principles of genetic organization of the cortex. PMID:24082094

Chen, Chi-Hua; Fiecas, Mark; Gutierrez, E. D.; Panizzon, Matthew S.; Eyler, Lisa T.; Vuoksimaa, Eero; Thompson, Wesley K.; Fennema-Notestine, Christine; Hagler, Donald J.; Jernigan, Terry L.; Neale, Michael C.; Franz, Carol E.; Lyons, Michael J.; Fischl, Bruce; Tsuang, Ming T.; Dale, Anders M.; Kremen, William S.

2013-01-01

58

Sensory properties of menthol and smoking topography  

PubMed Central

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

2011-01-01

59

Scholte waves generated by seafloor topography  

E-print Network

Seafloor topography can excite strong interface waves called Scholte waves that are often dispersive and characterized by slow propagation but large amplitude. This type of wave can be used to invert for near seafloor shear ...

Zheng, Yingcai

2012-01-01

60

Enhanced Characterization of Niobium Surface Topography  

SciTech Connect

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.

Chen Xu, Hui Tian, Charles Reece, Michael Kelley

2011-12-01

61

Visualization of pressure distribution by applying moire topography to free-surface water table  

NASA Astrophysics Data System (ADS)

Moire topography is applied to a free-surface water table in order to observe the pressure distribution in a gas flow. Given the water table, the time and size of a gas flow can be extended (Takasaki, 1970), while by using moire topography, the contour line map of water depth, and thus the isobaric line map for a gas flow, can be visualized (Barclay et al., 1963). The inclined grid method was developed to discriminate between the rise and fall of the water surface and to achieve high sensitivity. The switching action of an attachment jet by a control jet is used as an experimental example. Results show that the pressure visualization technique applying moire topography to a free-surface water table is adequate for observing an unsteady flow, and can give effective data for the analysis and synthesis of fluidic elements.

Yamamoto, K.; Nomoto, A.; Yamashita, H.

62

Earth's CMB topography and mantle convection  

NASA Astrophysics Data System (ADS)

Better understanding topography on Earth's core-mantle boundary (CMB) may provide important constraints on mantle dynamics, specifically the style of mantle convection, and on lower mantle heterogeneity. For example, the origin of large, lowermost mantle low shear wave velocity provinces beneath the central Pacific and Africa is not well constrained, but are likely related to both mantle dynamics and CMB topography. Two competing hypotheses for these anomalies are: thermal upwellings (e.g., plume clusters) or large intrinsically dense piles of primitive mantle material (e.g., thermochemical piles). Here we discuss the results from our current 3D investigation of CMB topography in two styles of mantle convection: 1) an isochemical mantle with plume clusters, and 2) a thermochemical mantle with large, intrinsically dense piles. In this study, we numerically investigate 3D spherical models of mantle convection and calculate maps of topography (CMB and surface, with self-gravitation included) and geoid (CMB and surface). Maps of CMB topography and geoid (CMB and surface) are produced, and compared to observed CMB topography (e.g., Morelli and Dziewonski, 1987; Boschi and Dziewonski, 2000; Sze and van der Hilst, 2003) and surface geoid (e.g., Earth Geopotential Model, 1996). Our predicted surface geoid maps provide a key image of how CMB topography, for any given model, will affect the geoid. The results of this work emphasize the importance in using a suite of observables (in this case, topography and geoid maps for CMB and surface) to constrain whole mantle dynamics and lower mantle structure.

Lassak, T. M.; McNamara, A. K.; Zhong, S.; Garnero, E.

2008-12-01

63

Corneal topography measurements for biometric applications  

NASA Astrophysics Data System (ADS)

The term biometrics is used to describe the process of analyzing biological and behavioral traits that are unique to an individual in order to confirm or determine his or her identity. Many biometric modalities are currently being researched and implemented including, fingerprints, hand and facial geometry, iris recognition, vein structure recognition, gait, voice recognition, etc... This project explores the possibility of using corneal topography measurements as a trait for biometric identification. Two new corneal topographers were developed for this study. The first was designed to function as an operator-free device that will allow a user to approach the device and have his or her corneal topography measured. Human subject topography data were collected with this device and compared to measurements made with the commercially available Keratron Piccolo topographer (Optikon, Rome, Italy). A third topographer that departs from the standard Placido disk technology allows for arbitrary pattern illumination through the use of LCD monitors. This topographer was built and tested to be used in future research studies. Topography data was collected from 59 subjects and modeled using Zernike polynomials, which provide for a simple method of compressing topography data and comparing one topographical measurement with a database for biometric identification. The data were analyzed to determine the biometric error rates associated with corneal topography measurements. Reasonably accurate results, between three to eight percent simultaneous false match and false non-match rates, were achieved.

Lewis, Nathan D.

64

GMRT Radio Halo Survey in galaxy clusters at z = 0.2 -- 0.4 I.The REFLEX sub--sample  

E-print Network

Aims. We present the first results of an ongoing project devoted to the search of giant radio halos in galaxy clusters located in the redshift range z=0.2--0.4. One of the main goals of our study is to measure the fraction of massive galaxy clusters in this redshift interval hosting a radio halo, and to constrain the expectations of the particle re--acceleration model for the origin of non--thermal radio emission in galaxy clusters. Methods. We selected 27 REFLEX clusters and here we present Giant Metrewave Radio Telescope (GMRT) observations at 610 MHz for 11 of them. The sensitivity (1$\\sigma$) in our images is in the range 35--100~$\\mu$Jy beam$^{-1}$ for all clusters. Results. We found three new radio halos, doubling the number of halos known in the selected sample. In particular, giant radio halos were found in A 209 and RXCJ 2003.5--2323, and one halo (of smaller size) was found in RXCJ 1314.4--2515. Candidate extended emission on smaller scale was found around the central galaxy in A 3444 which deserves further investigation. Furthermore, a radio relic was found in A 521, and two relics were found in RXCJ 1314.5--2515. The remaining six clusters observed do not host extended emission of any kind.

T. Venturi; S. Giacintucci; G. Brunetti; R. Cassano; S. Bardelli; D. Dallacasa; G. Setti

2006-10-10

65

Shuttle radar topography mapper (SRTM)  

NASA Astrophysics Data System (ADS)

The use of interferometric SAR (IFSAR) to measure elevation is one of the most powerful and promising capabilities of radar. A properly equipped spaceborne IFSAR system can produce a highly accurate global digital elevation map, including cloud-covered areas, in significantly less time and at significantly lower cost than with other systems. For accurate topography, the interferometric measurements must be performed simultaneously in physically sperate receive system, since measurements made at different times with the same system suffer significant decorrelation. The US/German/Italian spaceborne imaging radar C/X-band SAR (SIR-C/X-SAR), successfully flown twice in 1994 aboard the Space Shuttle Endeavor, offers a unique opportunity for global multifrequency elevation mapping by the year 2000. With appropriate augmentation, SIR-C/X-SAR is capable of producing an accurate elevation map covering 80 percent of the Earth's land surface in a single 10-day Shuttle flight. The existing US SIR-C SCANSAR mode provides a 225-km swath at C-band, which makes this coverage possible. Addition of a C-band receive antenna, extended from the Shuttle bay on a mast and operating in concert with the existing SIR-C antenna, produces an interferometric pair. Accuracy is enhanced by utilizing the SIR-C dual polarizations simultaneously to form separate SCANSAR beams. Due to the practical limitation of approximately 60 meters for the mast length, the longer SIR-C L-band wavelength does not produce useful elevation measurement accuracy. IFSAR measurements can also be obtained by the German/Italian X-SAR, simultaneously with SIR-C, by utilizing an added outboard antenna at X-band to produce a swath coverage of about 50 km. Accuracy can be enhanced at both frequencies by processing both ascending and descending data takes. It is estimated that the 90 percent linear absolute elevation error achievable is less that 16 meters for elevation postings of 30 meters. This will be the first use of spaceborne IFSAR to acquire accurate topographic data on a global scale.

Jordan, Rolando L.; Caro, Edward R.; Kim, Yunjin; Kobrick, Michael; Shen, Yuhsyen; Stuhr, Frederick V.; Werner, Marian U.

1996-12-01

66

Transient thermal effects below complex topographies  

NASA Astrophysics Data System (ADS)

The topographical perturbation of steady-state subsurface temperature fields has been an important issue in geothermal interpretations throughout the past century. This paper reports a numerical study, which considers the possible influence of terrain topography on transient temperature signals. Typical morphological situations over wide areas in central Europe affect most likely that same depth range which also contains the temperature signals resulting from the most interesting ground surface temperature changes (i.e. during the last 200 years). The evaluation of the interaction is performed on a synthetic sinusoidal topography with varying wavelength and amplitude. Vertical profiles (i.e. temperature logs) were extracted from these numerical forward 2-D calculations. Thereby, the error could be estimated by comparing ground surface temperature time-histories inverted from temperature logs both with and without topographic correction. The results show that a topographic correction of temperature data is absolutely necessary to achieve a consistent inversion result. Even rather flat topographies with 20-km wavelengths and 100-m amplitudes may introduce topographical effects which confuse the inversion process. On the other hand, the palaeoclimatically induced temperature signal persists even in rough topographies and will show correct inversion results when data are adequately treated. Only extreme situations cause a lateral interference of these transient signals with depth. The results from such 2-D synthetic models have been confirmed by an analysis of a real situation. The example chosen is the area surrounding the German Continental Deep Drilling (KTB) project. The area is situated in a moderately undulating surface topography with maximum altitude variations of the order of 250 m. The additional 3-D simulation demonstrates that a strong topography-dependent variation of the transient temperature signal can occur even at greater depths. The introduction of corrections for topography influence, reduces apparent differences in profiles from different locations in the surroundings of the KTB site to a maximum of 0.2 K.

Kohl, Thomas

1999-06-01

67

Evaluation of corneal thickness and topography in normal eyes using the Orbscan corneal topography system  

Microsoft Academic Search

AIMSTo map the thickness, elevation (anterior and posterior corneal surface), and axial curvature of the cornea in normal eyes with the Orbscan corneal topography system.METHODS94 eyes of 51 normal subjects were investigated using the Orbscan corneal topography system. The anterior and posterior corneal elevation maps were classified into regular ridge, irregular ridge, incomplete ridge, island, and unclassified patterns, and the

Zuguo Liu; Andrew J Huang; Stephen C Pflugfelder

1999-01-01

68

Effects of patterned topography on biofilm formation  

NASA Astrophysics Data System (ADS)

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

Vasudevan, Ravikumar

69

Detecting and Quantifying Topography in Neural Maps  

PubMed Central

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

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

2014-01-01

70

Transient thermal effects below complex topographies  

Microsoft Academic Search

The topographical perturbation of steady-state subsurface temperature fields has been an important issue in geothermal interpretations throughout the past century. This paper reports a numerical study, which considers the possible influence of terrain topography on transient temperature signals. Typical morphological situations over wide areas in central Europe affect most likely that same depth range which also contains the temperature signals

Thomas Kohl

1999-01-01

71

Interpretation of X-Ray topography  

Microsoft Academic Search

X-Ray topography is a powerfull method to study isolated defects in macroscopic crystals. The contrast of the most common defects is rather well-known and their study may be done without a good knowledge of the dynamical theory. Very simples rules permit to everybody the use of this method. An accurate model for the deformation due to a defect may be

Y. Epelboin; M. Curie

1980-01-01

72

Ice sheet motion and topography from radar interferometry  

Microsoft Academic Search

Both topography and motion information are present in repeat pass ERS-1 interferograms over ice sheets. The authors demonstrate that the topography is separable from the surface displacement field when a sequence of radar images are available. If the velocity field is constant over the time span of observation, the topography can be derived from differential interferograms formed from sequential observations.

Ronald Kwok; Mark A. Fahnestock

1996-01-01

73

New null screen design for corneal topography  

NASA Astrophysics Data System (ADS)

In this work we report the design of a null screen for corneal topography. Here we assume that the corneal surface is an ellipsoid with a diameter of 12 mm and a curvature radius of 7.8 mm. To avoid the difficulties in the alignment of the test system due to the face contour (eyebrows, nose, or eyelids), we design a conical null-screen with spots (similar to ellipses) drawn on it in such a way that its image, which is formed by reflection on the test surface, becomes an exact radial array of circular spots if the surface is perfect. Additionally, we performed a numerical simulation introducing Gaussian random errors in the coordinates of the centroids of the spots on the image plane, and in the coordinates of the sources (spots on the null-screen) in order to obtain the conical null-screen that reduces the error in the evaluation of the topography.

Campos-García, Manuel; Estrada-Molina, Amilcar; Díaz-Uribe, Rufino

2011-09-01

74

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

NASA Astrophysics Data System (ADS)

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

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

2005-10-01

75

Sensory properties of menthol and smoking topography  

Microsoft Academic Search

Although there is a great deal known about menthol as a flavoring agent in foods and confections, less is known about the\\u000a particular sensory properties of menthol cigarette smoke. Similarly, although smoking topography (the unique way an individual\\u000a smokes a cigarette) has been well studied using non-menthol cigarettes, there is relatively less known about how menthol affects\\u000a smoking behavior. The

Deirdre Lawrence; Brie Cadman; Allison C Hoffman

2011-01-01

76

Global relationship between oceanic geoid and topography  

NASA Technical Reports Server (NTRS)

The transfer function of geoid over topography as a function of wavelength is derived. The relationship between oceanic geoid and seafloor depth is analyzed. The correction of the geoid and topological data for thermal cooling of the oceanic lithosphere, sediment loading, and crustal thickening induced by volcanism under large ocean plateaus is discussed. The global residual depth and geoid anomalies are computed. The admittance and correlation between residual depth and geoid anomalies as a function of wavelength are examined.

Cazenave, A.; Dominh, K.; Allegre, C. J.; Marsh, J. G.

1986-01-01

77

Topography over South America from ERS altimetry  

NASA Technical Reports Server (NTRS)

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.

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

1997-01-01

78

Diffraction imaging (topography) with monochromatic synchrotron radiation  

NASA Technical Reports Server (NTRS)

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

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

1988-01-01

79

Impacts of Topography on Sea Level Change  

NSDL National Science Digital Library

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

Whitfield, Lise; Mcmillon, Bill; Scotchmoor, Judy; Stoffer, Phil; DLESE (Digital Library for Earth System Education)

80

Evolution of Neogene Dynamic Topography in Africa  

NASA Astrophysics Data System (ADS)

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

Paul, Jonathan; Roberts, Gareth; White, Nicky

2013-04-01

81

EAARL topography: Gateway National Recreation Area  

USGS Publications Warehouse

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

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

2007-01-01

82

Macromolecular Topography Leaps into the Digital Age  

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

83

GMRT Recreation Club Annual Report  

E-print Network

's.........................................................................26 14.Inter Departmental cricket matches's.....................................................................................................................38 19.Sports and Recreation Facilities their sports and cultural activities. GRC is also a forum for nurturing creativity and talent. The report

Udgaonkar, Jayant B.

84

EAARL Coastal Topography - Sandy Hook 2007  

USGS Publications Warehouse

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

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

2008-01-01

85

Comparison of parameters describing stratified surface topography  

NASA Astrophysics Data System (ADS)

There are a lot of methods of two-process surface topography description. Some parameters can be computed from material ratio graph. There are included in ISO standards. The methods described in ISO standards 13565-2 (Pk, Ppk, Pvk, Pmr1 and Pmr2) and 13565-3 (Pmq, Pvq and Pmq) are compared in this paper. Profiles with given values of Pmq, Pvq and Pmq parameters and wavelengths were modelled. For these profiles, material ratio curve and Pk, Ppk, Pvk, Pmr1 and Pmr2 parameters were calculated. As a result, dependencies among parameters from ISO 13565-3 and ISO 13565-2 standard were found.

Pawlus, P.; Reizer, R.; Lenart, A.

2014-03-01

86

Evaluation of entire-cornea topography measurement  

NASA Astrophysics Data System (ADS)

We quantitatively evaluated a technique for combining multiple videokeratograph views of different areas of cornea. To achieve this we first simulated target reflection from analytic descriptions of various shapes believed to mimic common corneal topographies. The splicing algorithm used the simulated reflections to achieve a good quality estimation of the shapes. Actual imagery was then acquired of manufactured models of the same shapes and the splicing algorithm was found to achieve a less perfect estimation. The cause was thought mainly to be image blur due to defocus. To investigate this, blur was introduced into the reflection simulation, and the results of the splicing algorithm compared to those found from the actual imagery.

Shevlin, Fergal P.; Klein, Stanley A.; Mandell, Robert B.; Carney, Thom

2000-06-01

87

Bessel Function Model for Corneal Topography  

E-print Network

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%.

Okrasi?ski, Wojciech

2011-01-01

88

Moiré topography by slit beam scanning.  

PubMed

A new method of moiré topography is suggested in which a slit beam is used in a scanning mode to generate moiré fringes. One remarkable feature of this method is that, as opposed to existing shadow and projection types, height differences between two consecutive fringes become constant so that absolute fringe orders need not be identified. This advantage makes it possible to measure three-dimensional surface profiles in an automatic manner simply by using a computer-aided image-processing technique. In addition this method can be easily implemented in a conventional coordinate measuring machine with a minimum addition of optical hardware. PMID:20733823

Kim, S W; Park, H G

1992-10-01

89

Measurement of the topography of human cadaver lenses using the PAR corneal topography system  

NASA Astrophysics Data System (ADS)

To measure the radius of curvature and asphericity of the anterior and posterior surfaces of crystalline lenses of human Eye-Bank eyes using the PAR Corneal Topography System. The measured values will be used in an optical model of the eye for lens refilling procedures.

Fernandez, Viviana; Manns, Fabrice; Zipper, Stanley; Sandadi, Samith; Hamaoui, Marie; Tahi, Hassan; Ho, Arthur; Parel, Jean-Marie A.

2001-06-01

90

A puzzle about the Scandinavian topography  

NASA Astrophysics Data System (ADS)

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

Hergarten, S.; Stüwe, K.

2012-04-01

91

Retrieving lunar topography from multispectral LROC images  

NASA Astrophysics Data System (ADS)

A technique for retrieving information about the lunar topography from any individual multispectral LROC Wide Angle Camera (WAC) image has been developed. This technology is possible, since images acquired at different wavelengths correspond to different viewing angles and the influence of color differences between the images on the parallax assessments is small. This method provides the precision of Digital Elevation Models (DEMs) comparable to the global lunar 100 m raster DTM retrieved from the LROC WAC stereo model (GLD100). It potentially allows one to obtain maps of the elevations with better horizontal resolution than those of the GLD100. An empirical model of the distortion for LROC WAC has been developed and used for correction of the initial WAC images. In contrast to the standard pre-flight model, our model allows for compensation of the radial distortion, decentering the optics, and tilt of the CCD array almost fully. The DEMs obtained using our approach exhibit real morphological details in some cases that are invisible in GLD100 maps. Thus, our method suggests additional independent information about the lunar topography. The fact that our elevation maps have the same projection as the initial images allows valid corrections of these images to account for topographic effects (i. e. orthorectification) in contrast to the use of the GLD100 that may have slightly different coordinates referencing in comparison to individual WAC images.

Korokhin, Viktor V.; Velikodsky, Yuri I.; Shalygin, Eugene V.; Shkuratov, Yuriy G.; Kaydash, Vadym G.; Videen, Gorden

2014-03-01

92

Analysis Of Scoliosis By Back Shape Topography  

NASA Astrophysics Data System (ADS)

The use of surface topography for the assessment of scoliotic deformity in the clinic depends firstly on the quality of measures which reliably characterise deformity of the back, and secondly on the ease and speed with which these measures can be applied. A method of analysis of back shape measurements is presented which can be applied to any topographic measurement system. Measures presented are substantially independent of minor changes in the patient's posture in rotation and flexion from one clinic to the next, and yet sensitive enough to indicate significant improvement or degeneration of the disease. The presentation shows (1) horizontal cross-sections at ten levels up the back from sacrum to vertebra prominens, (2) angles of rotation of the surface over a small region about the spine, (3) three vertical profiles following the line of the spine, and (4) measures of maximum kyphosis and lordosis. Dependence on the operator has been reduced to a minimum. Extreme care in positioning the patient is unnecessary and those spinous processes which are easily palpable, the vertebra prominens and the two dimples over the posterior superior iliac spines are marked. Analysis proceeds entirely automatically once the basic shape data have been supplied. Applications of the technique to indirect moire topography and a television topographic measurement system are described.

Turner-Smith, Alan R.; Harris, John D.

1983-07-01

93

Hydrothermal circulation in fault slots with topography  

NASA Astrophysics Data System (ADS)

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

Titarenko, Sofya; McCaig, Andrew

2014-05-01

94

Imaging defects in macromolecular crystals with x-ray topography  

Microsoft Academic Search

X-ray topography is a well established technique to characterize growth or process induced defects. As a characterization tool for crystal growers X-ray topography is probably the simplest non destructive imaging technique available. However, only recently it has been applied to image growth induced defects in protein crystals.We will discuss the use of white and monochromatic x-ray topography methods in understanding

V. Stojanoff; D. P. Siddons

1996-01-01

95

The Influence of Topography on Volatile Transport  

NASA Astrophysics Data System (ADS)

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.

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

2014-11-01

96

EAARL submarine topography: Biscayne National Park  

USGS Publications Warehouse

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, and 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.

Brock, John C.; Wright, C. Wayne; Patterson, Matt; Nayegandhi, Amar; Patterson, Judd; Harris, Melanie S.; Mosher, Lance

2006-01-01

97

Architecture and development of olivocerebellar circuit topography  

PubMed Central

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

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

2013-01-01

98

Assimilation of altimeter topography into oceanic models  

NASA Technical Reports Server (NTRS)

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.

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

1991-01-01

99

Australian topography from Seasat overland altimetry  

NASA Technical Reports Server (NTRS)

Retracking of overland returns from the Seasat altimeter using algorithms originally developed for recovering elevations over ice has led to the successful recovery of high quality continental topography over Australia and other continents. Cross-over analysis both before and after orbit adjustment shows the altimetric data over land to have a 2-3 m quality. Direct comparison of gridded Seasat data with surface data re-averaged in the same way shows excellent agreement except where Seasat data are sparse, due either to poor track spacing or to dropouts caused by loss of tracker lock over steeply sloping ground. These results suggest that useful topographic data can be derived from Seasat and the more recent Geosat altimeters for parts of the world where surface data are few or of poor quality.

Frey, Herbert; Brenner, Anita C.

1990-01-01

100

Temporal and spatial distribution of exhumed topography  

NASA Technical Reports Server (NTRS)

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

Rhodes, D. D.

1984-01-01

101

Episodic growth of topography in eastern Tibet  

NASA Astrophysics Data System (ADS)

High topography associated with the eastern portions of the Tibetan Plateau is thought to have developed as eastward flow of deep crust from beneath central Tibet drove crustal thickening and attendant surface uplift along the periphery of the plateau. The onset of rapid Late Miocene exhumation (ca. 10-15 Ma) in deep canyons of eastern Tibet is inferred to herald surface uplift which enabled rapid fluvial incision and the development of high topographic relief. Although consistent with geophysical data, this model struggles to explain the timing and amount of Cenozoic shortening adjacent to the Sichuan Basin. Here we report cooling histories of rocks currently exposed along a ~3 km vertical section adjacent to the Sichuan Basin derived from multiple low-temperature thermochronologic systems including apatite and zircon fission-track and (U-Th)/He. Our results reveal that this margin of the plateau was subject to slow, steady exhumation during early Cenozoic time, requiring that limited topographic relief (<1000m) was present prior to initial collision of India and Asia. Moreover, thermal models of exhumation-driven cooling demonstrate that subsequent exhumation of >10 km occurred in two temporally-distinct episodes, during Oligocene (~30-25 Ma) and Late Miocene (~10-15 Ma) time, separated by a hiatus of at least 10 Ma. These results challenge the notion that the plateau in eastern Tibet developed as a singular consequence of lower crustal flow. Rather, our findings require a punctuated history of mountain building that potentially reconciles conflicting models for relative roles of upper crustal shortening and lower crustal flow in the development of topography adjacent to the Sichuan Basin.

Kirby, E.; Furlong, K.; Wang, E.; Shi, X.; van Soest, M.; Xu, G.; Kamp, P.; Hodges, K.

2012-04-01

102

Bedrock topography beneath the Red Lake peatlands  

SciTech Connect

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

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

1992-01-01

103

The Role of Topography in Glacial Inception  

NASA Astrophysics Data System (ADS)

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

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

2009-12-01

104

Surface Water and Ocean Topography (SWOT) mission  

NASA Astrophysics Data System (ADS)

The Surface Water Ocean Topography (SWOT) mission was recommended in 2007 by the National Research Council's Decadal Survey, "Earth Science and Applications from Space: National Imperatives for the Next Decade and Beyond", for implementation by NASA. The SWOT mission is a partnership between two communities, the physical oceanography and the hydrology, to share high vertical accuracy and high spatial resolution topography data produced by the science payload, principally a Ka-band radar Interferometer (KaRIn). The SWOT payload also includes a precision orbit determination system consisting of GPS and DORIS receivers, a Laser Retro-reflector Assembly (LRA), a Jason-class nadir radar altimeter, and a JASON-class radiometer for tropospheric path delay corrections. The SWOT mission will provide large-scale data sets of ocean sea-surface height resolving scales of 15km and larger, allowing the characterization of ocean mesoscale and submesoscale circulation. The SWOT mission will also provide measurements of water storage changes in terrestrial surface water bodies and estimates of discharge in large (wider than 100m) rivers globally. The SWOT measurements will provide a key complement to other NASA spaceborne global measurements of the water cycle measurements by directly measuring the surface water (lakes, reservoirs, rivers, and wetlands) component of the water cycle. The SWOT mission is an international partnership between NASA and the Centre National d'Etudes Spatiales (CNES). The Canadian Space Agency (CSA) is also expected to contribute to the mission. SWOT is currently nearing entry to Formulation (Phase A). Its launch is targeted for October 2020.

Neeck, Steven P.; Lindstrom, Eric J.; Vaze, Parag V.; Fu, Lee-Lueng

2012-09-01

105

Geophysical implications of the longwavelength topography of the Saturnian satellites  

E-print Network

Geophysical implications of the longwavelength topography of the Saturnian satellites F. Nimmo,1 B may also play a role in determining the variance spectra of some bodies. Citation: Nimmo, F., B. G thickness variations likely cause the observed longwavelength topography on Titan [Nimmo and Bills, 2010

Nimmo, Francis

106

Surface mining simulator for application in steep slope topography  

Microsoft Academic Search

A surface mining simulator has been developed for application in steep slope topography. The simulator is designed to model haulback mining, as commonly practiced in Appalachian areas, and is applicable to contour mining and mountain top removal mining. Its primary use will be comparison of alternative overburden handling plans. Major inputs include pre-mining topography as a sequence of mining block

C. E. Zipper; A. Chakraborty; E. Topuz; W. L. Daniels

1985-01-01

107

X-ray topography and precision diffractometry of semiconducting materials  

Microsoft Academic Search

The application of double axis x-ray diffractometry to the nondestructive evaluation of semiconducting materials is reviewed. Particular emphasis is placed on the data which can be obtained in standard geometry from commercially available instruments. Following a brief summary of the state of the art, x-ray topography techniques are discussed in relation to their application for quality control. Section topography is

B. K. Tanner

1989-01-01

108

Rigorous topography simulation of contamination to defect transformation  

Microsoft Academic Search

Particulate contamination deposited on silicon wafers is typically the dominant reason for yield loss in VLSI manufacturing. The transformation of contaminating particles into defects and then electrical faults is a very complex process which depends on the defect location, size, material and the underlying IC topography. Rigorous 2D and 3D topography simulators based on the waveguide method have been developed

Xiaolei Li; Andrzej Strojwas; A. Swecker; L. Milor; Yung-Tao Linb

1997-01-01

109

Cokriging surface elevation and seismic refraction data for bedrock topography  

SciTech Connect

Analysis of seismic refraction data collected at a proposed site of the Advanced Neutron Source (ANS) Facility showed a strong correlation between surface and bedrock topography. By combining seismically determined bedrock elevation data with surface elevation data using cokriging, we were able to significantly improve our map of bedrock topography without collecting additional seismic data.

Nyquist, J.E.; Doll, W.E. [Oak Ridge National Lab., TN (United States); Davis, R.K. [Automated Sciences Group, Inc., Oak Ridge, TN (United States); Hopkins, R.A. [Marrich, Inc., Knoxville, TN (United States)

1992-11-01

110

Cokriging surface elevation and seismic refraction data for bedrock topography  

SciTech Connect

Analysis of seismic refraction data collected at a proposed site of the Advanced Neutron Source (ANS) Facility showed a strong correlation between surface and bedrock topography. By combining seismically determined bedrock elevation data with surface elevation data using cokriging, we were able to significantly improve our map of bedrock topography without collecting additional seismic data.

Nyquist, J.E.; Doll, W.E. (Oak Ridge National Lab., TN (United States)); Davis, R.K. (Automated Sciences Group, Inc., Oak Ridge, TN (United States)); Hopkins, R.A. (Marrich, Inc., Knoxville, TN (United States))

1992-01-01

111

Characterizing topography-induced contrast in photoelectron emission microscopy  

Microsoft Academic Search

As part of an ongoing study to quantify the imaging response of the photoelectron emission microscope (PEEM), we have investigated the effect of sample topography on PEEM contrast. Both numerical simulations and well characterized samples were used to investigate topography-induced contrast. As expected, numerical simulations show that the lateral field strength that is present at a step edge is the

K. Siegrist; E. D. Williams; V. W. Ballarotto

2003-01-01

112

The relationship between topography and gravity on Earth and Venus  

Microsoft Academic Search

The measurement of the admittance between the topography and the gravity of a planet as a function of wavelength provides important constraints on its interior processes. A detailed discussion of the influence of noise on such measurements shows that at long wavelengths the admittance is best determined in the frequency domain, using gravity as input and topography as output. This

Dan McKenzie

1994-01-01

113

Study of the tear topography dynamics using a lateral shearing interferometer  

E-print Network

topography/index.htm Abstract: The dynamics of the pre-corneal tear film topography are studied on 21Study of the tear topography dynamics using a lateral shearing interferometer Alfredo Dubra in quantitative tear topography estimation. Based on the reconstructed tear topography maps, the effects of tear

Dainty, Chris

114

Mask topography effect in chromeless phase lithography  

NASA Astrophysics Data System (ADS)

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

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

2004-12-01

115

Topography and Volcanoes on Io (color)  

NASA Technical Reports Server (NTRS)

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

North is to the top of this picture which merges images obtained with the clear, red, green, and violet filters of the solid state imaging (CCD) system on NASA's Galileo spacecraft. The resolution is 6.1 kilometers per picture element. The images were taken on April 4th, 1997 at a range of 600,000 kilometers.

The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC. JPL is an operating division of California Institute of Technology (Caltech).

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

This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://galileo.jpl.nasa.gov. Background information and educational context for the images can be found at URL http://www.jpl.nasa.gov/galileo/sepo

1997-01-01

116

Topography of lactose permease from Escherichia coli.  

PubMed

The topography of lactose permease, in native membrane vesicles and after reconstitution of the purified protein into proteoliposomes, has been investigated by labeling the membrane-embedded portions of the protein using photoactivatable, hydrophobic reagents and by labeling the exposed portions of the protein with water-soluble, electrophilic reagents. Some sites of modification have been localized in fragments of the protein produced by chemical and enzymatic cleavage. These define a number of hydrophilic loops and membrane-spanning regions and give some substance to topographic models of the permease. The N-terminal third of the molecule was labeled by three photoactivatable reagents (3-(trifluoromethyl)-3-m-iodophenyldiazirine and the phospholipid analogues 2-(aceto-(4-benzoylphenylether]-1-palmitoylphosphatidylcholine) and 2-(4-azido-2-nitrophenylaminoacetyl)-1-palmitoylphosphatidylcholin e) as well as the water soluble, electrophilic reagents. The C-terminal part of the molecule is labeled by the diazirine and, to a lesser extent, by the phospholipid analogues. It apparently has more nucleophilic groups accessible to water-soluble reagents than the N-terminal domain, in which the density of apparently unreactive ionizable residues proved to be unexpectedly high. The apparent lack of reactivity of some of these residues may be explained either by their being buried in the protein moiety within the membrane domain, or by their close association with other ionizable residues on the surface of the protein. PMID:3053685

Page, M G; Rosenbusch, J P

1988-11-01

117

The length-scaling properties of topography  

NASA Technical Reports Server (NTRS)

The scaling properties of synthetic topographic surfaces and digital elevation models (DEMs) of topography are examined by analyzing their 'structure functions,' i.e., the qth order powers of the absolute elevation differences: delta h(sub q) (l) = E((absolute value of h(x + l) - h(x))(exp q)). We find that the relation delta h(sub 1 l) approximately equal cl(exp H) describes well the scaling behavior of natural topographic surfaces, as represented by DEMs gridded at 3 arc sec. Average values of the scaling exponent H between approximately 0.5 and 0.7 characterize DEMs from Ethiopia, Saudi Arabia, and Somalia over 3 orders of magnitude range in length scale l (approximately 0.1-150 km). Differences in appparent topographic roughness among the three areas most likely reflect differences in the amplitude factor c. Separate determination of scaling properties in the x and y coordinate directions allows us to assess whether scaling exponents are azimuthally dependent (anisotropic) or whether they are isotropic while the surface itself is anisotropic over a restricted range of length scale. We explore ways to determine whether topographic surfaces are characterized by simple or multiscaling properties.

Weissel, Jeffrey K.; Pratson, Lincoln F.; Malinverno, Alberto

1994-01-01

118

Dynamic and reversible surface topography influences cell morphology.  

PubMed

Microscale and nanoscale surface topography changes can influence cell functions, including morphology. Although in vitro responses to static topography are novel, cells in vivo constantly remodel topography. To better understand how cells respond to changes in topography over time, we developed a soft polyacrylamide hydrogel with magnetic nickel microwires randomly oriented in the surface of the material. Varying the magnetic field around the microwires reversibly induced their alignment with the direction of the field, causing the smooth hydrogel surface to develop small wrinkles; changes in surface roughness, ?RRMS , ranged from 0.05 to 0.70 ?m and could be oscillated without hydrogel creep. Vascular smooth muscle cell morphology was assessed when exposed to acute and dynamic topography changes. Area and shape changes occurred when an acute topographical change was imposed for substrates exceeding roughness of 0.2 ?m, but longer-term oscillating topography did not produce significant changes in morphology irrespective of wire stiffness. These data imply that cells may be able to use topography changes to transmit signals as they respond immediately to changes in roughness. PMID:23355509

Kiang, Jennifer D; Wen, Jessica H; del Álamo, Juan C; Engler, Adam J

2013-08-01

119

Spreading of droplet with insoluble surfactant on corrugated topography  

NASA Astrophysics Data System (ADS)

The flow of microscale fluid on a topography surface is a key to further development of MEMS, nanoscience and technology. In the present paper, a theoretical model of the droplet spreading with insoluble surfactant over corrugated topography is established with the lubrication theory, and the evolution equations of film thickness and surfactant concentration in base state and disturbance state are formulated. The droplet dynamics, the nonlinear stability based on nonmodal stability theory, and the effects of topography structure and Marangoni stress are numerically simulated with PDECOL scheme. Results show that the impact of topographical surface is strengthened apparently while the Marangoni stress driven by surfactant concentration is weakened in the mid-late stages of the spreading. The droplet radius on the topography advances faster and the lowest height of liquid/gas interface near the droplet edge reduces remarkably in the intermediate stage compared with those on the flat wall. The quantity of the wavelet similar to the topography increases gradually, with the characteristics of wavelet crest height with time exhibiting a single-hump feature. The spreading stability is enhanced under the disturbance wavenumber of 4, however, is to deteriorate and even to transform into instability when wavenumber increases further. In addition, the reductive Marangoni number, enhancive capillary number, modest Peclet number, the low height of the topography as well as small wavenumber of topography can make contributions to the evident stability of droplet spreading.

Li, Chunxi; Pei, Jianjun; Ye, Xuemin

2014-09-01

120

Shape, topography, gravity anomalies and tidal deformation of Titan  

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

121

Science in Motion: Isolated Araneiform Topography  

NASA Technical Reports Server (NTRS)

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

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

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

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

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

2007-01-01

122

X-ray topography of a lysozyme crystal  

SciTech Connect

X-ray topography methods were employed to identify defects in lysozyme crystals. White-beam and monochromatic topographs of lysozyme crystals obtained at the National Synchrotron Light Source are presented.

Stojanoff,V.; Siddons, D.

1996-01-01

123

Superoleophobic Surfaces through Control of Sprayed-on Stochastic Topography  

E-print Network

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

Campos, Raymond

124

Calculation of irrotational wind pattern with application to Cleveland topography  

NASA Technical Reports Server (NTRS)

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

Siegel, R.

1972-01-01

125

Crustal thickness and support of topography on Venus  

E-print Network

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

James, Peter Benjamin

126

Teleseismic traveltimes, topography and the lithospheric structure across central Mongolia  

E-print Network

Teleseismic traveltimes, topography and the lithospheric structure across central Mongolia Carole to constrain the deep lithospheric structure of this region. Time residuals appear positively correlated-fitting Moho and lithosphere-asthenosphere boundary (LAB) geometries which satisfyingly reproduce the observed

Paris-Sud XI, Université de

127

X-Ray Topography of Shock Loaded Copper Crystals.  

National Technical Information Service (NTIS)

Single crystals of high purity copper subjected to shock loading have been examined by X-ray diffraction topography. The topographs reveal a basic substructure consisting of narrow, close packed kinks normal to highly stressed slip directions and extendin...

P. W. Kingman

1973-01-01

128

Infragravity waves over topography: generation, dissipation, and reflection  

E-print Network

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

Thomson, James M. (James McArthur)

2006-01-01

129

Phase contrast in Simultaneous Topography and Recognition imaging.  

PubMed

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

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

2009-08-01

130

Defect analysis in crystals using X-ray topography  

Microsoft Academic Search

A brief review of X-ray topography—a nondestructive method for direct observation and characterization of defects in single crystals—is presented here. The origin and development of this characterization method and the different techniques derived from it are described. Emphasis is placed on synchrotron X-ray topography and its application in studying various crystal imperfec- tions. Mechanisms of contrast formation on X-ray topographs

Balaji Raghothamachar; Govindhan Dhanaraj; Jie Bai; Michael Dudley

2006-01-01

131

X ray topography study of gallium phosphate crystals and resonators  

Microsoft Academic Search

Using the synchrotron radiation delivered by the DCI storage ring at LURE (Orsay, France), the X-ray topography technique was used to study the crystalline perfection of GaPO4 samples grown under different conditions. The growth of gallium phosphate on a berlinite seed is analyzed by X-ray section topography. The results obtained demonstrate the feasibility of gallium phosphate epitaxy on large berlinite

B. Capelle; A. Zarka; J. Schwartzel; J. Detaint; Y. Zheng; A. Ibanez; E. Philippot

1993-01-01

132

X-ray topography study of microsegregation in crystals  

Microsoft Academic Search

Concentration microinhomogeneities in crystals were characterized using x-ray topography, digital image processing, and spectral\\u000a analysis of signals. Based on the features in lattice strains in such layered inhomogeneous crystals, methods for optimizing\\u000a the conditions of x-ray topography detection of growth striations were proposed to obtain quantitative information on the\\u000a composition fluctuation amplitude and spatial characteristics.

I. A. Prokhorov; I. Z. Bezbakh; B. G. Zakharov; I. L. Shul’pina

2007-01-01

133

Feedback Control Scheme for Scanning X-Ray Topography  

Microsoft Academic Search

Feedback control of scanning x-ray topography is described. A control scheme is developed that maintains the x-ray topography system at all times at the peak of the rocking curve I(?). The mathematical control scheme is implemented through an angular derivative generator capable of generating the signal dI?d? on a continuous basis. Circuit requirements to measure dI?d? continuously are established. Actual

L. J. van Mellaert; G. H. Schwuttke

1972-01-01

134

Asymmetric three-dimensional topography over mantle plumes  

NASA Astrophysics Data System (ADS)

The role of mantle-lithosphere interactions in shaping surface topography has long been debated. In general, it is supposed that mantle plumes and vertical mantle flows result in axisymmetric, long-wavelength topography, which strongly differs from the generally asymmetric short-wavelength topography created by intraplate tectonic forces. However, identification of mantle-induced topography is difficult, especially in the continents. It can be argued therefore that complex brittle-ductile rheology and stratification of the continental lithosphere result in short-wavelength modulation and localization of deformation induced by mantle flow. This deformation should also be affected by far-field stresses and, hence, interplay with the `tectonic' topography (for example, in the `active/passive' rifting scenario). Testing these ideas requires fully coupled three-dimensional numerical modelling of mantle-lithosphere interactions, which so far has not been possible owing to the conceptual and technical limitations of earlier approaches. Here we present new, ultra-high-resolution, three-dimensional numerical experiments on topography over mantle plumes, incorporating a weakly pre-stressed (ultra-slow spreading), rheologically realistic lithosphere. The results show complex surface evolution, which is very different from the smooth, radially symmetric patterns usually assumed as the canonical surface signature of mantle upwellings. In particular, the topography exhibits strongly asymmetric, small-scale, three-dimensional features, which include narrow and wide rifts, flexural flank uplifts and fault structures. This suggests a dominant role for continental rheological structure and intra-plate stresses in controlling dynamic topography, mantle-lithosphere interactions, and continental break-up processes above mantle plumes.

Burov, Evgueni; Gerya, Taras

2014-09-01

135

Shuttle Topography Data Inform Solar Power Analysis  

NASA Technical Reports Server (NTRS)

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

2013-01-01

136

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

E-print Network

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 for corneal topography. 3. an examination of problems still facing corneal topography. OCIS codes: (120

Klein, Stanley

137

Smoking topography and abstinence in adult female smokers.  

PubMed

Preliminary evidence, within both adults and adolescents, suggests that the intensity with which cigarettes are smoked (i.e., smoking topography) is predictive of success during a cessation attempt. These reports have also shown topography to be superior compared to other variables, such as cigarettes per day, in the prediction of abstinence. The possibility that gender may influence this predictive relationship has not been evaluated but may be clinically useful in tailoring gender-specific interventions. Within the context of a clinical trial for smoking cessation among women, adult daily smokers completed a laboratory session that included a 1-hour ad libitum smoking period in which measures of topography were collected (N=135). Participants were then randomized to active medication (nicotine patch vs. varenicline) and abstinence was monitored for 4weeks. Among all smoking topography measures and all abstinence outcomes, a moderate association was found between longer puff duration and greater puff volume and continued smoking during the active 4-week treatment phase, but only within the nicotine patch group. Based on the weak topography-abstinence relationship among female smokers found in the current study, future studies should focus on explicit gender comparisons to examine if these associations are specific to or more robust in male smokers. PMID:24018226

McClure, Erin A; Saladin, Michael E; Baker, Nathaniel L; Carpenter, Matthew J; Gray, Kevin M

2013-12-01

138

Effects of latent heat release at phase boundaries on flow in the Earth’s mantle, phase boundary topography and dynamic topography at the Earth’s surface  

Microsoft Academic Search

Mantle flow models that do not consider the effects of latent heat on phase boundaries typically predict dynamic surface topography too large to be compatible with observations. Here these effects were implemented in a mantle flow model and resulting changes in dynamic topography and topography of phase boundaries were computed. Inclusion of these effects was found to reduce the rms

Bernhard Steinberger

2007-01-01

139

Influence of nanophase titania topography on bacterial attachment and metabolism  

PubMed Central

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

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

2008-01-01

140

Ulva linza zoospore sensitivity to systematic variation of surface topography  

NASA Astrophysics Data System (ADS)

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

Sheats, Julian Taylor

141

Static and dynamic support of the Pannonian basin topography  

NASA Astrophysics Data System (ADS)

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).

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

2014-05-01

142

Research of the Method of Local Topography Rapid Reconstructed  

NASA Astrophysics Data System (ADS)

For fast and convenient access to the environment based on the geomorphic characteristics of camouflage regional model for the complexity of topography, this article analyzes a variety of terrain modeling method’s advantages and limitations, discussed a variety of modeling methods in the set up of the study of basic on the hybrid modeling method and the integrated use of research results to generate the details of the existing landform characteristics can be controlled on all-terrain results. Generate local terrain adaptive modeling method, as a regional model disguised form with the local terrain topography of the region to adapt to a good camouflage effect.

Zhao, Minrong; Deng, Shengli; Shi, Ze

143

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

NASA Technical Reports Server (NTRS)

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

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

2010-01-01

144

Adaptation of an Asperity Ploughing Model to Measured Roll Topographies  

NASA Astrophysics Data System (ADS)

A previously published asperity ploughing model has been adapted in order to approximate the measured as-ground roll surface topography. The model is then integrated with classical cold rolling plastic deformation equations including coupling to the lubricant film evolution through the roll bite. The friction distribution through the roll bite is thus a function of the specific details of the roll surface topography as well as the process parameters. predictions of roll force, torque and forward slip as well as sliding distance and volume of metal swept out by the asperities are then made and compared to experimental measurements for an aluminum alloy rolled on a laboratory rolling mill.

Lalli, L. A.; Malkani, H. G.; Sheu, S.

2004-06-01

145

Interaction of dipolar vortices with a step-like topography  

NASA Astrophysics Data System (ADS)

The interaction of a barotropic, dipolar vortex with a step-like topography is studied by means of laboratory experiments in a rotating tank and by numerical simulations based on a quasi-two-dimensional model. Two main configurations are analyzed: when the dipole approaches a "low" or a "high" step with respect to the maximum water depth. For relatively low steps, the vortex crosses the topography with a deflected trajectory, while maintaining its dipolar structure. The sense of this deflection depends on whether the dipole reaches a step-up or a step-down. For high steps, in contrast, the dipole is not able to cross the topography, and the reflection of one of the dipole structures is observed. In both cases, one observes a weak flow along the topography with shallow water on its right. The essential features of the flow evolution for low and high steps can be explained by using arguments of potential vorticity conservation (due to the weakness of viscous effects). In order to determine whether a barotropic dipole is able to cross the step or is reflected, qualitative criteria based on the step height and dipole strength are derived using inviscid arguments.

Tenreiro, M.; Zavala Sansón, L.; van Heijst, G. J. F.

2006-05-01

146

Evidence from gravity and topography data for folding of Tibet  

Microsoft Academic Search

Bouguer gravity and topography data from Tibet suggest that the surface of the plateau and the subsurface density interfaces are warped into two series of ridges and troughs trending parallel to the collision zone with wavelengths of 150 and 500 km. These folds are superimposed on an overall state of isostatic compensation owing to crustal thickening. Such folding is predicted

Yu Jin; Marcia K. McNutt; Yongsheng Zhu

1994-01-01

147

Estimates of Martian crustal thickness from viscous relaxation of topography  

Microsoft Academic Search

Isostatically compensated crustal thickness variations and associated topographic contrasts at the surface of a planet result in lateral pressure gradients, which may cause the lower crust to flow and reduce the relief. Areas of thicker crust are generally associated with more rapid relaxation of topography. On Mars, topographic features such as impact basins and the hemispheric dichotomy have survived for

F. Nimmo; D. J. Stevenson

2001-01-01

148

Geophysical implications of the longwavelength topography of Rhea  

E-print Network

Geophysical implications of the longwavelength topography of Rhea F. Nimmo,1 B. G. Bills,2 P. C. Citation: Nimmo, F., B. G. Bills, P. C. Thomas, and S. W. Asmar (2010), Geophysical implications; Nimmo et al., 2007], impact cratering [e.g., Thomas et al., 2002], flexure [Luttrell and Sandwell, 2006

Nimmo, Francis

149

Topography within the axial channels of Monterey and Soquel Canyons  

Microsoft Academic Search

Ultrahigh resolution surveys have been conducted that outline the topography and near seafloor structure within the axial channels of Monterey and Soquel Canyons. Multibeam bathymetry (vertical precision of 0.15 m and horizontal resolution of 1.0 m at 50 m survey altitude) were collected using an autonomous underwater vehicle (AUV). An inertial navigation system combined with a doppler velocity sonar allows

E. Lundsten; C. K. Paull; D. W. Caress; W. Ussler; H. Thomas

2009-01-01

150

An anatomical and functional topography of human auditory cortical areas  

PubMed Central

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

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

2014-01-01

151

Mars Mantle (MOHO) Topography with Mantle Elevation Texture Map  

NSDL National Science Digital Library

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.

Studio, Nasa/goddard S.; Nasa

152

SWOT: The Surface Water & Ocean Topography Satellite Mission  

E-print Network

SWOT: The Surface Water & Ocean Topography Satellite Mission Doug Alsdorf Byrd Polar Research Arctic Lakes, Science, 2005 Arctic lakes are losing storage, despite a slight increase in precipitation of Oceans ECCO-2 MIT JPL ocean current model Although altimetry data have significantly advanced the study

153

Plasma Molding over Surface Topography: IED and IAD over Steps  

Microsoft Academic Search

Plasma molding over surface topography finds applications in MEMS microfabrication, plasma extraction through grids, and plasma contact with internal reactor parts (e.g., wafer chuck edge). The flux, energy and angular distributions of ions incident on the target are of primary importance in these applications. These quantities depend critically on the shape of the meniscus (plasma-sheath boundary) formed over the surface

Demetre Economou; Doosik Kim

2001-01-01

154

Global Topography of Titan from Cassini RADAR Data (Invited)  

NASA Astrophysics Data System (ADS)

Cassini RADAR data are used to construct a global, albeit sparsely-sampled, topography map, and to generate a hypsometric profile to compare with other planetary bodies. Titan’s hypsogram is unimodal and strikingly narrow compared with the terrestrial planets. To investigate topographic extremes, a novel variant on the classic hypsogram is introduced, with a logarithmic abscissa to highlight mountainous terrain. In such a plot, the top of the terrestrial hypsogram is quite distinct from those of Mars and Venus due to the ‘glacial buzz-saw’ that clips terrestrial topography above the snowline. In contrast to the positive skew seen in other hypsograms, with a long tail of positive relief due to mountains, there is an indication (weak, given the limited data for Titan so far) that the Titan hypsogram appears slightly negatively skewed, suggesting a significant population of unfilled depressions. Limited data permit only a simplistic comparison of Titan topography with other icy satellites but we find that the standard deviation of terrain height (albeit at different scales) is similar to those of Ganymede and Europa. The topography of terrestrial planets is sampled with the same coverage that we have for Titan to gauge what as-yet-undiscovered topographic surprises may yet be hidden by Titan’s haze.

Lorenz, R. D.; Cassini RADAR Team

2010-12-01

155

The Lang method of X-ray diffraction topography  

Microsoft Academic Search

The paper sets forth the basic principles of the Lang method of X-ray diffraction topography for the investigation of imperfections in crystals. Main Techniques for its experimental implementation are described, and relations and procedures used in the interpretation of the topograms are examined. The problem of resolution is analyzed along with the main factors determining contrast at dislocations. Some of

R. Fiedler; M. Polcarova

1975-01-01

156

Some Bristol Prague explorations in x-ray topography  

Microsoft Academic Search

This paper briefly chronicles a long-standing and productive collaboration between the Institute of Physics, Czech Academy of Science and the H H Wills Physics Laboratory. It began in early 1962 with a brief visit to Bristol by Milena Polcarová. The initial aim, successfully achieved, was the mapping by transmission topography of dislocations in melt-grown single crystals of a Fe Si

A. R. Lang

2005-01-01

157

Stroboscopic X-Ray Topography of Surface Acoustic Wave Devices  

Microsoft Academic Search

X-ray topography can be used to obtain images of microscopic strains in single crystals. inely applied to the characterisation of defects such as dislocations and low angle grain boundaries. Pre- vious studies have shown that the average strain fields associated with travelling surface waves can be imaged on an x-ray topograph, together with the defects in the crystal substrate. This

R. W. Whatmore; P. A. Goddard; B. K. Tanner

1982-01-01

158

Extraction of Martian valley networks from digital topography  

E-print Network

are inferred from digital topography by an autonomous computer algorithm as drainage networks, instead of being. Slopes of ``streams'' in Martian valley networks decrease downstream at a slower rate than slopes resemblance gave rise to an early suggestion [Masursky, 1973; Milton, 1973] of a common origin of VNs

Stepinski, Tomasz F.

159

Tidal Conversion by Supercritical Topography NEIL J. BALMFORTH  

E-print Network

of internal waves as the barotropic tide flows over topography on the ocean floor has lately received wide that the breaking of such waves could play an important role in setting up large-scale ocean circula- tion (Munk, Massachusetts (Manuscript received 22 May 2008, in final form 20 January 2009) ABSTRACT Calculations

Balmforth, Neil

160

Very high-resolution mapping of river-immersed topography  

E-print Network

techniques used for river bathymetry are reviewed. Frequently, these techniques have been developedVery high-resolution mapping of river-immersed topography by remote sensing Denis Feurer,1,2 * Jean cases: inaccessible rivers, large-scale depth mapping, very shallow rivers. The remote sensing

Paris-Sud XI, Université de

161

Generation of internal undular bores by transcritical flow over topography  

E-print Network

Generation of internal undular bores by transcritical flow over topography R.H.J. Grimshaw1 , D. H propagating internal solitary waves. Often these waves appear as a wave-train, or undular bore description of undular bores, for flow over isolated obstacles and for flow over a step. 1 Introduction

162

Invariance of operant topography throughout changes in motivational conditions  

Microsoft Academic Search

To determine the extent that distribution of responses established through reinforcement contingencies would be affected by motivational changes, 11 male rats were trained to manipulate a lever that could be displaced in any of 8 directions within a circular aperture. Both frequency (total number of contacts) and response topography (frequency of contact at various positions) were recorded. Groups were tested

Charles D. Corman; Raymond C. Miles

1966-01-01

163

Short wavelength topography on the inner-core boundary  

PubMed Central

Constraining the topography of the inner-core boundary is important for studies of core–mantle coupling and the generation of the geodynamo. We present evidence for significant temporal variability in the amplitude of the inner core reflected phase PKiKP for an exceptionally high-quality earthquake doublet, observed postcritically at the short-period Yellowknife seismic array (YK), which occurred in the South Sandwich Islands within a 10-year interval (1993/2003). This observation, complemented by data from several other doublets, indicates the presence of topography at the inner-core boundary, with a horizontal wavelength on the order of 10 km. Such topography could be sustained by small-scale convection at the top of the inner core and is compatible with a rate of super rotation of the inner core of ?0.1–0.15° per year. In the absence of inner-core rotation, decadal scale temporal changes in the inner-core boundary topography would provide an upper bound on the viscosity at the top of the inner core. PMID:17190798

Cao, Aimin; Masson, Yder; Romanowicz, Barbara

2007-01-01

164

Corneal topography of photorefractive keratectomy versus laser in situ keratomileusis  

Microsoft Academic Search

ObjectiveThis study aimed to compare qualitative patterns of corneal topography early in the postoperative course after excimer laser photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) when used for the treatment of myopia of 6.0 to 15.0 diopters.

Peter S Hersh; Kevin S Scher; Rashna Irani

1998-01-01

165

THE INFLUENCE OF TOPOGRAPHY AND TEMPERATURE ON QUERCUS ILICIFOLIA SUCCESSION  

E-print Network

and tree oak plot. I found that colder microclimates are created by the effects of the low topography as well as by the unique structure of the low scrub oak canopy. Data shows that these microclimates oak thickets can become widespread due to forest fires (Mouw 2000). The landscape of Martha's Vineyard

Vallino, Joseph J.

166

Nanoscale surface topography reshapes neuronal growth in culture  

E-print Network

that contrasts with the complex tri-dimensional topography of the embryonic brain1 . Moreover, cellular adhesion on the micrometric2 and ever sub-micrometric scale3 . Understanding the mechanisms of cell adhesion might therefore spaced adhesive gold nanoparticles to demonstrate that cell spreading is an active process controlled

Boyer, Edmond

167

Rapid topography mapping of scalar fields: large molecular clusters.  

PubMed

An efficient and rapid algorithm for topography mapping of scalar fields, molecular electron density (MED) and molecular electrostatic potential (MESP) is presented. The highlight of the work is the use of fast function evaluation by Deformed-atoms-in-molecules (DAM) method. The DAM method provides very rapid as well as sufficiently accurate function and gradient evaluation. For mapping the topography of large systems, the molecular tailoring approach (MTA) is invoked. This new code is tested out for mapping the MED and MESP critical points (CP's) of small systems. It is further applied to large molecular clusters viz. (H(2)O)(25), (C(6)H(6))(8) and also to a unit cell of valine crystal at MP2/6-31+G(d) level of theory. The completeness of the topography is checked by extensive search as well as applying the Poincaré-Hopf relation. The results obtained show that the DAM method in combination with MTA provides a rapid and efficient route for mapping the topography of large molecular systems. PMID:22920112

Yeole, Sachin D; López, Rafael; Gadre, Shridhar R

2012-08-21

168

Moire Topography For The Detection Of Orthopaedic Defects  

NASA Astrophysics Data System (ADS)

Moire topography is applied for the follow-up of scoliosis patients. The results are then compared with the X-rays. A special lamp and scale arrangement is utilized for patient alignment. It is suggested that this technique will be used for the detection of all orthopaedic defects.

Kamal, Syed A.; Lindseth, Richard E.

1981-02-01

169

Causes and Consequences of Time-Varying Dynamic Topography  

NASA Astrophysics Data System (ADS)

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.

White, Nicky

2013-04-01

170

Impact of lithosphere rheology on the dynamic topography  

NASA Astrophysics Data System (ADS)

Dynamic topography is a key observable signature of the Earth's and planetary (e.g. Venus) mantle dynamics. In general view, it reflects complex mantle flow patterns, and hence is supposed to correlate at different extent with seismic tomography, SKS fast orientations, geodetic velocity fields and geoid anomalies. However, identification of dynamic topography had no systematic success, specifically in the Earth's continents. Here we argue that lithosphere rheology, in particular, rheological stratification of continents, results in modulation of dynamic topography, converting commonly expected long-wavelength/small amplitude undulations into short-wavelength surface undulations with wide amplitude spectrum, superimposed onto "tectonic" topography. These ideas are explored in 3D using unprecedentedly high resolution numerical experiments (grid step size 2-3 km for 1500x1500x600 km computational area) incorporating realistic rheologically stratified lithosphere. Such high resolution is actually needed to resolve small-scale crustal faulting and inter-layer coupling/uncoupling that shape surface topography. The results reveal strikingly discordant, counterintuitive features of 3D dynamic topography, going far beyond the inferences from previous models. In particular, even weak anisotropic tectonic stress field results both in large-scale small-amplitude dynamic topography and in strongly anisotropic short-wavelength (at least in one direction) dynamic topography with wide amplitude range (from 100 to 2000-3000 m), including basins and ranges and large-scale linear normal and strike-slip faults. Even very slightly pre-stressed strong lithosphere yields and localizes deformation much easier , than un-prestressed one, in response to plume impact and mantle flow. The results shed new light on the importance of lithosphere rheology and active role of lithosphere in mantle-lithosphere interactions as well as on the role of mantle flow and far-field stresses in tectonic-scale deformation. We show, for example, that crustal fault patterns initiated by plume impact are rapidly re-organized in sub-linear rifts and spreading centers, which orientation is largely dictated (e.g., perpendicular to) by the direction of the tectonic far-field stress field, as well as the plume-head material soon starts to flow along the sub-linear rifted shear zones in crustal and mantle lithosphere further amplifying their development. The final surface deformation and mantle flow patterns rapidly loose the initial axisymmetric character and take elongated sub-linear shapes whereas brittle deformation at surface is amplified and stabilized by coherent flow of mantle/plume-head material from below. These "tectonically" looking dynamic topography patterns are quite different from those expected from conventional models as well as from those directly observed, for example, on Venus where plume-lithosphere interactions produce only axisymmetric coronae domal-shaped features with radiating extensional rifts, suggesting that the Venusian lithosphere is rheologically too weak , and its crust is too thin, to produce any significant impact on the dynamic topography.

Burov, Evgueni; Gerya, Taras; Koptev, Alexander

2014-05-01

171

Seismic waveform inversion for core-mantle boundary topography  

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

172

Influence of lunar topography on simulated surface temperature  

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

173

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

E-print Network

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

Nikurashin, Maxim (Maxim Anatolevich)

2009-01-01

174

Balance of chemistry, topography, and mechanics at the cellbiomaterial interface: Issues and challenges for  

E-print Network

Balance of chemistry, topography, and mechanics at the cell­biomaterial interface: Issues of physicochemical cues: chemical, topographical, and mechanical. While sur- face chemistry and topography have been of creating surfaces with well-defined chemistry and topography combined with sensitive surface

175

Gaussian Power with Cylinder Vector Field Representation for Corneal Topography Maps Brian A. Barsky  

E-print Network

Gaussian Power with Cylinder Vector Field Representation for Corneal Topography Maps Brian A on commercially available corneal topography instru- ments are really one-dimensional, defining quantities only on the videokeratograph axis or on the location of asymmetries. We propose a new repre- sentation for corneal topography

California at Irvine, University of

176

Ice sheet topography from retracked ERS-1 altimetry  

NASA Technical Reports Server (NTRS)

An objective of the ERS-1 radar altimeter is to measure the surface topography of the polar ice sheets to a precision on the order of a meter. ERS-1 Waveform Altimeter Product (WAP) data was corrected for several processing errors. A range correction from the WAP waveforms, using the multiparameter retracking algorithm to account for range tracking limitations inherent to radar altimetry, was derived. From crossover analysis, the resulting precision is shown to be about 2.1 m in ocean mode and 2.2 m in ice mode. A topography map, produced with 23 days of corrected data, shows details of the western part of west Antarctic ice sheet and part of the Ross ice shelf including ice divides, ice stream boundaries, and ice shelf grounding lines.

Zwally, H. Jay; Brenner, Anita C.; Dimarzio, John; Seiss, Timothy

1994-01-01

177

The long wavelength topography of Beethoven and Tolstoj basins, Mercury  

NASA Astrophysics Data System (ADS)

Topography derived from Mariner 10 stereo images is used to characterize the interior structure of two mercurian basins, Beethoven and Tolstoj. Beethoven and Tolstoj basins are shallow (~2.5 km and ~2 km deep, respectively) and relatively flat-floored. Beethoven basin has an interior topographic rise near the northwest margin. The topography of Beethoven and Tolstoj basins is similar to that of lunar mare-filled basins. Well-developed basin-concentric wrinkle ridges and arcuate graben associated with lunar mascons are absent in both Beethoven and Tolstoj basins. The lack of mascon tectonic features suggests that either 1) the mercurian basins have a relatively thin veneer of fill material, 2) Mercury's elastic lithosphere was too strong for significant lithospheric flexure and subsidence to occur, or 3) the basin fill material has little or no density contrast with the surrounding crust and thus exerts little net load on the mercurian lithosphere.

André, Sarah L.; Watters, Thomas R.; Robinson, Mark S.

2005-11-01

178

Irregular topography at the Earth's inner core boundary.  

PubMed

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

Dai, Zhiyang; Wang, Wei; Wen, Lianxing

2012-05-15

179

Noise-Sustained currents in quasigeostrophic turbulence over topography  

E-print Network

We study the development of mean structures in a nonlinear model of large scale ocean dynamics with bottom topography and dissipation, and forced with a noise term. We show that the presence of noise in this nonlinear model leads to persistent average currents directed along isobaths. At variance with previous works we use a scale unselective dissipation, so that the phenomenon can not be explained in terms of minimum enstrophy states. The effect requires the presence of both the nonlinear and the random terms, and can be though of as an ordering of the stochastic energy input by the combined effect of nonlinearity and topography. The statistically steady state is well described by a generalized canonical equilibrium with mean energy and enstrophy determined by a balance between random forcing and dissipation. This result allows predicting the strengh of the noise-sustained currents. Finally we discuss the relevance that these noise-induced currents could have on real ocean circulation.

Alberto Alvarez; Emilio Hernandez-Garcia; Joaquin Tintore

1997-01-09

180

Irregular topography at the Earth's inner core boundary  

PubMed Central

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

Dai, Zhiyang; Wang, Wei; Wen, Lianxing

2012-01-01

181

Keratometry and corneal topography using multiple delay element OCT  

NASA Astrophysics Data System (ADS)

We have presented previously a novel method for the evaluation of the surface shape of an object, with immediate application to measurement of cornea shape. This method uses single shot C-scans obtained by using a multiple delay element (MDE) in the reference path of an OCT system. A calibrated MDE-OCT system can be used to measure the elevation of points on the cornea, in contrast to existing methods which are based on measurement of the cornea slope. The associated algorithm for extracting corneal topography data points from the MDE-OCT C-Scan image will be presented, data points which can then be used to calculate the Zernike coefficients for the cornea shape. The differences between the existing systems and the MDE-OCT method for keratometry and corneal topography are discussed.

Plesea, Lucian; Podoleanu, Adrian G.

2008-02-01

182

Synchronous interferometric demodulation of Placido mires applied to corneal topography  

E-print Network

This paper presents a novel digital interferometric method to demodulate Placido fringe patterns. This is a synchronous method which uses a computer-stored conic-wavefront as demodulating reference. Here we focuses on the experimental aspects to phase-demodulate Placido mires applied to corneal topography. This synchronous method is applied to two topographic Placido images and their de-modulated corneal-slope deformation is estimated. This conic-interferometric method is highly robust against typical "noisy" signals in Placido topography such as: reflected eyelashes and iris structures. That is because the eyelashes and the iris structure are high frequency "noisy" signals corrupting the reflected Placido mire, so they are filtered-out by this method. Digital synchronous interferometry is here applied for the first time to demodulate corneal topographic concentric-rings images (Patent pending at the USPTO).

Servin, Manuel

2012-01-01

183

Sound propagation over uneven ground and irregular topography  

NASA Technical Reports Server (NTRS)

The goal of this research is to develop theoretical, computational, and experimental techniques for predicting the effects of irregular topography on long range sound propagation in the atmosphere. Irregular topography here is understood to imply a ground surface that is not idealizable as being perfectly flat or that is not idealizable as having a constant specific acoustic impedance. The interest of this study focuses on circumstances where the propagation is similar to what might be expected for noise from low-attitude air vehicles flying over suburban or rural terrain, such that rays from the source arrive at angles close to grazing incidence. The activities and developments that have resulted during the period, August 1986 through February 1987, are discussed.

Berthelot, Yves H.; Kearns, James A.; Pierce, Allan D.; Main, Geoffrey L.

1987-01-01

184

Topography and refractometry of nanostructures using spatial light interference microscopy.  

PubMed

Spatial light interference microscopy (SLIM) is a novel method developed in our laboratory that provides quantitative phase images of transparent structures with a 0.3 nm spatial and 0.03 nm temporal accuracy owing to the white light illumination and its common path interferometric geometry. We exploit these features and demonstrate SLIM's ability to perform topography at a single atomic layer in graphene. Further, using a decoupling procedure that we developed for cylindrical structures, we extract the axially averaged refractive index of semiconductor nanotubes and a neurite of a live hippocampal neuron in culture. We believe that this study will set the basis for novel high-throughput topography and refractometry of man-made and biological nanostructures. PMID:20081970

Wang, Zhuo; Chun, Ik Su; Li, Xiuling; Ong, Zhun-Yong; Pop, Eric; Millet, Larry; Gillette, Martha; Popescu, Gabriel

2010-01-15

185

Evaluation of Esophageal Contractile Propagation using Esophageal Pressure Topography  

PubMed Central

Background High-resolution manometry and esophageal pressure topography have ienhanced our ability to analyze esophageal motor disturbances by improving the detail and accuracy of measurements of peristaltic activity. This has been extremely helpful in the evaluation of disorders of rapid propagation as the technique is able to define important time points and physiologic landmarks that are crucial in defining peristaltic velocity and latency intervals. Purpose The goal of the current review will be to assess how esophageal pressure topography has impacted our ability to define important phenotypes of rapid propagation. Additionally, this review will also be utilized to complement the description of the Chicago Classification of Esophageal Motor Disorders, which is presented in this supplement issue. PMID:22248104

Pandolfino, J.E.; Sifrim, D.

2013-01-01

186

Printability of topography in alternating aperture phase-shift masks  

Microsoft Academic Search

Alternating aperture phase-shift mask (AAPSM) technology in combination with conventional illumination enables the imaging needed in the 65nm node and beyond, thanks to its high image contrast and small mask error factor (MEF). It is a known point of attention that AAPSM topography induces an image intensity imbalance between the light propagating through the zero and pi-shifted space. There are

Vicky Philipsen; Rik Jonckheere

2004-01-01

187

Correcting for surface topography in X-ray fluorescence imaging.  

PubMed

Samples with non-planar surfaces present challenges for X-ray fluorescence imaging analysis. Here, approximations are derived to describe the modulation of fluorescence signals by surface angles and topography, and suggestions are made for reducing this effect. A correction procedure is developed that is effective for trace element analysis of samples having a uniform matrix, and requires only a fluorescence map from a single detector. This procedure is applied to fluorescence maps from an incised gypsum tablet. PMID:25343805

Geil, E C; Thorne, R E

2014-11-01

188

Stroboscopic X-ray topography of quartz resonators  

Microsoft Academic Search

Stroboscopic X-ray topography of 1-ns time resolution with synchrotron radiation has been used to study the vibrations in quartz resonators. Time-resolved images of the vibration reveal the existence of particular modes which cannot be observed on time-integrated images by conventional methods. A theoretical calculation is carried out to characterize pendellosung fringes on stroboscopic X-ray section topographs in weakly vibrating crystals.

A. Zarka; B. Capelle; Y. Zheng; J. Detaint; J. Schwartzel

1988-01-01

189

Mode shape analysis techniques using synchrotron X-ray topography  

Microsoft Academic Search

X-ray topography using synchrotron radiation is used to investigate vibrational states in quartz resonators. After a brief review of different methods and possibilities obtained with synchrotron radiation, some observations on vibration modes, especially on coupled piezo-electric components in quartz AT and BT resonators, are reported. The results from experiments reveal time-progressive components and several complex coupled components in AT and

B. Capelle; J. Detaint; A. Zarka; Y. Zheng; J. Schwartzel

1990-01-01

190

Some Bristol–Prague explorations in x-ray topography  

Microsoft Academic Search

This paper briefly chronicles a long-standing and productive collaboration between the Institute of Physics, Czech Academy of Science and the H H Wills Physics Laboratory. It began in early 1962 with a brief visit to Bristol by Milena Polcarov. The initial aim, successfully achieved, was the mapping by transmission topography of dislocations in melt-grown single crystals of a Fe–Si alloy.

A R Lang

2005-01-01

191

X-ray topography analysis of bulk acoustic wave resonators  

Microsoft Academic Search

X-ray topography is first used to totally examine the fundamental modes of acoustic oscillations in the bulk-acoustic-wave\\u000a (BAW) resonator on the base of an AT-cut quartz crystal at the first and third harmonics. As is evident from the experiments,\\u000a the anharmonic longitudinal oscillations of the resonator can be visualized, just as the fundamental transverse acoustic oscillations\\u000a can be. The amplitude-frequency

D. V. Irzhak; D. V. Roshchupkin; D. V. Punegov; S. A. Sakharov

2007-01-01

192

X-ray diffraction topography image materials by molecular probe  

Microsoft Academic Search

Crystallinity, composition, homogeneity and anisotropy determine the mechanical properties of materials significantly, but the performance of most non-destructive techniques is too poor for measuring these micro structures as they are optimized for finding individual flaws\\/defects. X-ray (wide angle) Diffraction Topography by single beam scanning images molecular information at a spatial resolution of several ten micrometers even in three dimensions. Especially

Manfred P. Hentschel; Axel Lange; Joerg Schors; Oliver Wald

2005-01-01

193

X-ray topography study of complex silicon microcircuits  

Microsoft Academic Search

The correlation between the yield of silicon microcircuits wafers versus defects observed in X-ray topographs produced by a high speed curved wafer X-ray topographic camera was investigated. Most of the topographs were made after final wafer probe. Results indicated that most high volume silicon wafer processing does not need X-ray topography as a routine process control. It is further indicated

D. L. Parker

1981-01-01

194

Research of the Method of Local Topography Rapid Reconstructed  

Microsoft Academic Search

\\u000a For fast and convenient access to the environment based on the geomorphic characteristics of camouflage regional model for\\u000a the complexity of topography, this article analyzes a variety of terrain modeling method’s advantages and limitations, discussed\\u000a a variety of modeling methods in the set up of the study of basic on the hybrid modeling method and the integrated use of\\u000a research

Minrong Zhao; Shengli Deng; Ze Shi

2009-01-01

195

Intraocular lens power calculations using corneal topography after photorefractive keratectomy  

Microsoft Academic Search

PURPOSE: To report two patients (two eyes) with previous photorefractive keratectomy, who subsequently underwent cataract extraction years later.DESIGN: Case reports.METHODS: Corneal topography was used to determine corneal power used in intraocular lens power calculations.RESULTS: In two eyes of two patients, intraocular lens calculations after photorefractive keratectomy were inadequate, which resulted in a hyperopic postoperative refractive error requiring implantation of a

John G Ladas; Brian S Boxer Wachler; John D Hunkeler; Daniel S Durrie

2001-01-01

196

On fractional Bessel equation and the description of corneal topography  

E-print Network

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.

Okrasi?ski, Wojciech

2012-01-01

197

Electronic cigarettes: abuse liability, topography and subjective effects  

PubMed Central

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

Evans, Sarah E; Hoffman, Allison C

2014-01-01

198

Core-mantle boundary topography and whole-mantle convection  

NASA Astrophysics Data System (ADS)

The seismically observed topography of the core-mantle boundary (CMB) and the velocities of the surface tectonic plates together provide important observational constraints on viscous flow models of the earth's mantle. It is shown here that the CMB deflections inferred by Morelli and Dziewonski (1987) may be explained in terms of a simple model of whole-mantle convection. A new method for inferring the penetration depths of subducted slabs is presented.

Forte, Alessandro; Peltier, W. Richard

1989-07-01

199

Bridges of the sella turcica - anatomy and topography.  

PubMed

This paper presents anatomy and topography of the inconstant osseous bridges that may occur in the sella turcica region. The interclinoid bridge and the caroticoclinoid bridge can be formed in consequence of abnormal ossification of the dural folds or disturbances in development of the sphenoid bone. Their presence may be of clinical importance because of potential influence on the neurovascular structures passing in the vicinity of the clinoid processes of the sphenoid bone. PMID:24852690

Skrzat, Janusz; Mroz, Izabela; Marchewka, Justyna

2012-01-01

200

Evaluating Marie Byrd Land stability using an improved basal topography  

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

201

Moho depth and residual topography of the Antarctic continent  

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

202

Anomalous topography on the continental shelf around Hudson Canyon  

USGS Publications Warehouse

Recent seismic-reflection data show that the topography on the Continental Shelf around Hudson Canyon is composed of a series of depressions having variable spacings (< 100 m to 2 km), depths (1-10 m), outlines, and bottom configurations that give the sea floor an anomalous "jagged" appearance in profile. The acoustic and sedimentary characteristics, the proximity to relict shores, and the areal distribution indicate that this rough topography is an erosional surface formed on Upper Pleistocene silty sands about 13,000 to 15,000 years ago by processes related to Hudson Canyon. The pronounced southward extension of the surface, in particular, may reflect a former increase in the longshore-current erosion capacity caused by the loss of sediments over the canyon. Modern erosion or nondeposition of sediments has prevented the ubiquitous sand sheet on the Middle Atlantic shelf from covering the surface. The "anomalous" topography may, in fact, be characteristic of areas near other submarine canyons that interrupt or have interrupted the longshore drift of sediments. ?? 1979.

Knebel, H. J.

1979-01-01

203

Geophysics of Titan from gravity, topography and spin state  

NASA Astrophysics Data System (ADS)

For the terrestrial planets, combined analyses of gravity and topography have greatly improved our understanding of these bodies' interiors [1]. The spin state and orientation of a planetary body can also be diagnostic of its internal structure [2]. Recently acquired topography [3], gravity [4] and spin pole constraints [5] now permit these kinds of geophysical analyses at Titan. Titan's degree-two gravity coefficients, but not those of its topography, are in the 10/3 ratio expected for a hydrostatic body. One explanation for this discrepancy is the existence of a floating isostatic ice shell whose thickness varies spatially due to tidal dissipation [6]. Shell thickness variations can result in slow non-synchronous rotation [7]. Furthermore, such variations will affect the gravity, an effect that should be taken into account when using gravity to calculate Titan's moment of inertia [4]. The relationship between the degree-three gravity and topography can be used to place constraints on the thickness and rigidity of the ice shell. Based on the inferred heat fluxes of [6], Titan's ice shell is unlikely to be less than 90% compensated at degree three. The measured degree-three gravity [4] and topography [3] coefficients show a strong correlation (r=0.84). For a completely compensated ice shell, the implied shell thickness is about 350 km, while if the shell is 90% compensated the thickness is 250 km. These shell thickness estimates significantly exceed those based on theoretical models [8,9] and surface topography [6]. One possible explanation for this discrepancy is that there are other sources of degree-three gravity (e.g. bumps on the presumed silicate core) that do not contribute significantly to the surface topography. Further gravity observations will help to resolve this issue. If a satellite's spin and orbit poles remain coplanar as the latter precesses around the invariable pole, the satellite is said to occupy a damped Cassini state and the obliquity (angle between spin and orbit pole) is diagnostic of its moment of inertia [10]. Titan's spin pole is very nearly coplanar with the orbit and invariable poles, suggesting occupation of a Cassini state. Its obliquity of 0.32 degrees [5] corresponds to a normalized moment of inertia of 0.45, much larger than the value of 0.34 derived from gravity [4]. This discrepancy is probably due mostly to decoupling of the ice shell from the interior by an ocean, though excitation of the obliquity by the atmosphere [11] or ocean may also play a role. [1] Wieczorek, M.A., Treatise Geophys. 10, 165-206, 2007. [2] Williams, J.G. et al., JGR 106, 27933-27968, 2001. [3] Zebker, H.A. et al., Science 324, 921-923, 2009. [4] Iess, L. et al., Science 327, 1367-1369, 2010. [5] Stiles, B.W. et al., Astron. J. 135, 1669-1680, 2008. [6] Nimmo, F., B.G. Bills, Icarus 208, 896-904, 2010. [7] Ojakangas, G.W., D.J. Stevenson, Icarus 81, 220-41, 1989. [8] Tobie, G. et al., Nature 440, 61-64, 2006. [9] Sohl, F. et al., JGR 108, 5130, 2003. [10] Bills, B.G., F. Nimmo, Icarus 214, 351-355, 2011. [11] Tokano, T. et al., JGR 116, E05002, 2011.

Nimmo, F.; Bills, B. G.

2011-12-01

204

Crater topography on Titan: Implications for landscape evolution  

NASA Astrophysics Data System (ADS)

Unique among the icy satellites, Titan’s surface shows evidence for extensive modification by fluvial and aeolian erosion, which act to change the topography of its surface over time. Quantifying the extent of this landscape evolution is difficult, since the original, ‘non-eroded’ surface topography is generally unknown. However, fresh craters on icy satellites have a well-known shape and morphology, which has been determined from extensive studies on the airless worlds of the outer solar system (Schenk et al., 2004). By comparing the topography of craters on Titan to similarly sized, pristine analogues on airless bodies, we can obtain one of the few direct measures of the amount of erosion that has occurred on Titan. Cassini RADAR has imaged >30% of the surface of Titan, and more than 60 potential craters have been identified in this data set (Wood et al., 2010; Neish and Lorenz, 2012). Topographic information for these craters can be obtained from a technique known as ‘SARTopo’, which estimates surface heights by comparing the calibration of overlapping synthetic aperture radar (SAR) beams (Stiles et al., 2009). We present topography data for several craters on Titan, and compare the data to similarly sized craters on Ganymede, for which topography has been extracted from stereo-derived digital elevation models (Bray et al., 2012). We find that the depths of craters on Titan are generally within the range of depths observed on Ganymede, but several hundreds of meters shallower than the average (Fig. 1). A statistical comparison between the two data sets suggests that it is extremely unlikely that Titan’s craters were selected from the depth distribution of fresh craters on Ganymede, and that is it much more probable that the relative depths of Titan are uniformly distributed between ‘fresh’ and ‘completely infilled’. This is consistent with an infilling process that varies linearly with time, such as aeolian infilling. Figure 1: Depth of craters on Titan (gray diamonds) compared to similarly sized, fresh craters on Ganymede (central peaks, +; central pits, *) and a handful of relaxed craters (black squares) from Bray et al. (2012). References: Bray, V., et al.: "Ganymede crater dimensions - implications for central peak and central pit formation and development". Icarus, Vol. 217, pp. 115-129, 2012. Neish, C.D., Lorenz, R.D.: "Titan’s global crater population: A new assessment". Planetary and Space Science, Vol. 60, pp. 26-33, 2012. Schenk, P.M., et al.: "Ages and interiors: the cratering record of the Galilean satellites". In: Bagenal, F., McKinnon, W.B. (Eds.), Jupiter: The Planet, Satellites, and Magnetosphere, Cambridge University Press, Cambridge, UK, pp. 427-456, 2004. Stiles, B.W., et al.: "Determining Titan surface topography from Cassini SAR data". Icarus, Vol. 202, pp. 584-598, 2009. Wood, C.A., et al.: "Impact craters on Titan". Icarus, Vol. 206, pp. 334-344, 2010.

Neish, C.; Kirk, R.; Lorenz, R.; Bray, V.; Schenk, P.; Stiles, B.; Turtle, E.; Cassini Radar Team

2012-04-01

205

Wide angle cornea-sclera (ocular) topography Stanley A. Klein, John Corzine, School of Optometry, University of California, Berkeley  

E-print Network

OCULAR TOPOGRAPHY During the period from 1992 to 1999 corneal topography became a major focus for cornea topography. There were two principal reasons for the interest in corneal shape: screening candidates for refractive surgery and fitting contact lenses. However, the enthusiasm for corneal topography has subsided

Klein, Stanley

206

TIME SPENT WITH SMOKING PARENTS AND SMOKING TOPOGRAPHY IN ADOLESCENTS  

PubMed Central

Although the relationship between parental and adolescent smoking has been linked to health consequences of smoking, limited study has explored the specific association between exposure to smoking and adolescent smoking topography (the way a cigarette is smoked). As a first step in this line of enquiry, smoking topography measures were collected from 67 adolescent dependent smokers. Participants smoked one cigarette of their own brand while being monitored by a computer-based smoking-topography unit and completed questionnaires about their time spent daily with parents who smoke. Pearson’s correlation analysis revealed that time spent daily with parents who smoke was significantly associated with maximum puff velocity (r = 0.285, p = .019), a parameter predicting later pulmonary morbidity. ANOVAs, after a median split, were consistent with correlation analyses. There was a significant group effect on puff velocity (F(2,66) = 5.197, p = .008); no significant relationship was found with puff volume (F(2,66) = .617) or puff duration (F(2,66) = .776). A post hoc Tukey HSD test indicated puff velocity was higher in the “high time spent” (M = 54.37, SD = 12.03) than in the “low time spent” group (M 0 45.59, SD = 9.91) and in the group with non-smoking parents (M = 44.96, SD = 10.17). Future research with a larger non-treatment seeking sample of adolescents aimed at preventing tobacco smoking related diseases should further examine parental influences on adolescent smoking, including potential modeling effects. PMID:18755550

Collins, Charles C.; Lippmann, Brad M.; Lo, Suzanne J.; Moolchan, Eric T.

2008-01-01

207

Topography and biological noise determine acoustic detectability on coral reefs  

NASA Astrophysics Data System (ADS)

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.

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

2013-12-01

208

Scaling of shortwave radiation fluxes for sub grid topography  

NASA Astrophysics Data System (ADS)

Shortwave radiation plays an important role in the surface energy balance for understanding mass balances, snow cover distribution as well as snow melt. Incident shortwave radiation is greatly altered by mountainous terrain. While distributed radiation balance models can account for all topographic influences at small scales, for larger scale applications, such as climate and hydrological models, physically based sub grid parameterizations are required. We present a complete shortwave radiation parameterization scheme for sub grid topography accounting for shading, limited sky view and terrain reflections. Each radiative flux is parameterized individually. The parameters required are sun elevation angle, domain-averaged surface albedo and terrain parameters such as slope angle, slope distribution and sky view factor. We show that the domain-averaged sky view factor as an important parameter of the scheme can be theoretically related to the slope distribution. This suggests that the parametrization can solely be computed from slope characteristics and the numerically expensive computation of horizons angles can be abandoned. To validate the parameterization scheme we used domain-averaged values from a detailed radiation balance model for the three-dimensional radiative transfer in complex terrain. In order to minimize influences in the modeled distributed radiation arising from specific geomorphology and climate we compiled a large ensemble of several thousand Gaussian topographies with a broad range of characteristic scales and used fixed sun positions. Overall, modeled radiation from the simulated topographies compared well with parameterized values. We found that depending on sun elevation angles, shading and limited sky view alter direct beam and diffuse sky radiation by up to 40% each. We confirmed that when using domain-averaged values, multiple, anisotropic terrain reflections can be approximated with single, isotropic terrain reflections.

Helbig, N.; Loewe, H.; Adams, E. E.

2011-12-01

209

The combined effects of topography and vegetation on catchment connectivity  

NASA Astrophysics Data System (ADS)

The deconvolution of whole catchment runoff response into its temporally dynamic source areas is a grand challenge in hydrology. The extent to which the intersection of static and dynamic catchment characteristics (e.g. topography and vegetation) influences water redistribution within a catchment and the hydrologic connectivity of hillslopes to the riparian and stream system is largely unknown. Over time, patterns of catchment storage shift and, because of threshold connectivity behavior, catchment areas become disconnected from the stream network. We developed a simple but spatially distributed modeling framework that explicitly incorporates static (topography) and dynamic (vegetation) catchment structure to document the evolution of catchment connectivity over the course of a water year. We employed directly measured eddy-covariance evapotranspiration data co-located within a highly instrumented (>150 recording groundwater wells) and gauged catchment to parse the effect of current and zero vegetation scenarios on the temporal evolution of hydrologic connectivity. In the absence of vegetation, and thus in the absence of evapotranspiration, modeled absolute connectivity was 4.5% greater during peak flow and 3.9% greater during late summer baseflow when compared to the actual vegetation scenario. The most significant differences in connected catchment area between current and zero vegetation (14.9%) occurred during the recession period in early July, when water and energy availability were at an optimum. However, the greatest relative difference in connected area occurs during the late summer baseflow period when the absence of evapotranspiration results in a connected area approximately 500% greater than when vegetation is present, while the relative increase during peak flow is just 6%. Changes in connected areas ultimately lead to propose a biologically modified geomorphic width function. This biogeomorphic width function is the result of lateral water redistribution driven by topography and water uptake by vegetation.

Nippgen, F.; McGlynn, B. L.; Emanuel, R. E.

2012-12-01

210

An ice topography observation system (ITOS) on the ODIN platform  

NASA Astrophysics Data System (ADS)

ITOS, for Ice Topography Observation System, is a mission concept which has been studied by a scientific and industrial team led by the Swedish Space Corporation for ESA in the frame of its Earth Observation Preparatory Program. The study has contributed to support the definition of the candidate missions for a potential Earth Explorer program of scientific and research missions. The study shows the utility of an ODIN type of platform, developed by Swedish Space Corporation, for advanced remote sensing missions. The paper gives a brief description of the mission and the defined elements of the mission architecture, i.e. the mission parameters, the payload (laser altimeter) and the spacecraft.

Månsson, Peter

1996-11-01

211

Links Between Lithospheric Structure and Topography SE Tibet  

NASA Astrophysics Data System (ADS)

The Himalaya and high Tibetan Plateau, one of the most remarkable topographic features on Earth, are widely taken to be the classic example of continent-continent collision. Across the northeastern margin of the Indian plate in southeastern Tibet, the Himalayan orogen terminates abruptly. Collisional processes responsible for the elevation of Tibet and the tectonics of the main Himalayan range are replaced by the strike-slip tectonics of the eastern Himalayan syntaxis as lithospheric material, enters the clockwise deformation regime of the eastern syntaxis. As part of a larger multidisciplinary study we deployed a broadband temporary seismic array extending east from Lhasa, through the eastern Himalayan syntaxis, to the eastern margin of the Tibetan plateau to examine how changes in lithospheric structure and rheology are linked to changes in topography and lithospheric mechanics. A denser short period array was deployed in the core of the syntaxis around the Gyala Peri Namche Barwa Massif, the site of high relief, high topography, and rapid exhumation exposing mid to lower crustal rocks of the Indian plate at the surface. In southeastern Tibet, the fast directions of seismic anisotropy in the lithospheric mantle correlate with surficial geology including major sutures and shear zones, and with the surface strain derived from the GPS velocity field. These observations are consistent with a clockwise rotation of material around the eastern Himalayan syntaxis and suggest coherent and distributed lithospheric deformation beneath much of southeastern Tibet. Receiver function analysis reveals considerable topography on the Moho (coincident with the Gyala Peri and Namche Barwa massifs), and lateral changes in Moho and crustal reflectivity and Poisson's ratio. To first order, structure at depth correlates with significant changes in topography and a number of geomorphic metrics associated with the transition from the high elevation low relief plateau in central Tibet to deeply incised linear valleys in southeastern Tibet. Our observations document a fundamental change in the relationship between upper-crustal and mantle deformation between southeastern Tibet and its adjacent eastern plateau margins. The data suggest that lateral heterogeneities play an important role in the geodynamic evolution of the region. Fully 3-D geodynamic models incorporating lateral heterogeneity in boundary conditions and lithospheric properties are required to more accurately describe the development of collisional orogens.

Meltzer, A.; Sol, S.; Zurek, B.; Ault, A.; Zeitler, P.; Liu, Y.; Zhang, J.

2006-12-01

212

X-Ray Topography Techniques for Defect Characterization of Crystals  

Microsoft Academic Search

\\u000a \\u000a X-ray topography is the general term for a family of x-ray diffraction imaging techniques capable of providing information\\u000a on the nature and distribution of structural defects such as dislocations, inclusions\\/precipitates, stacking faults, growth\\u000a sector boundaries, twins, and low-angle grain boundaries in single-crystal materials. From the first x-ray diffraction image,\\u000a recorded by Berg in 1931, to the double-crystal technique developed by Bond

Balaji Raghothamachar; Michael Dudley; Govindhan Dhanaraj

2010-01-01

213

Experimental and numerical modeling of wind flow over complex topography  

NASA Astrophysics Data System (ADS)

Wind mapping is of utmost importance in various wind engineering, wind environment, and wind energy applications. The available wind atlases usually provide wind data with low resolutions relative to the wind turbine height and size and usually neglect the effect of topographic features with relatively large or sudden changes in elevation. Developing a cost effective methodology to predict the wind patterns and to obtain wind maps over any topographic terrain is absolutely needed for wind turbine/farm siting. As the previous analytic and empirical attempts to resolve the flow over topographic features were limited to basic geometries that hardly exist in nature, applying Particle Image Velocimetry (PIV) measurement techniques in wind tunnel and Computational Fluid Dynamics (CFD) techniques in numerical simulation of the flow over topography seems to be the best alternative solution to the problem. PIV measurements and CFD simulations are carried out on a 1:3000 scale model of complex topographic area. Three distinct topographic features are investigated: a valley, a ridge and a hill. The PIV measurements compare well with hot-wire based mean velocity profiles for the three cases. Moreover, the turbulence intensity profiles match well for flow regions without recirculation. The ridge wake region shows discrepancies between the two techniques which are attributed to the complexity of the flow in this region and limitations of both techniques. A procedure incorporating Geographic Information System (GIS) and surface modeling techniques is introduced to build the CFD model of a complex terrain starting from the existing topography maps with desired resolutions. Moreover, a new approach is made to simulate the terrain roughness up to ultimate roughness heights, by implementing arrays of bell-shaped roughness elements in the CFD model. The velocity profiles and velocity vectors were compared with the PIV measurements and were found to be in good agreement near the ground and up to the full scale height of 300m. The study shows that PIV measurements and CFD simulations can be successfully used in qualifying and quantifying the flow over complex topography consisting of a wide range of roughness heights, enabling to map the flow structure with very high spatial resolution. KEYWORDS: Wind mapping, Complex topography, Computational fluid dynamics (CFD), Particle image velocimetry (PIV).

Rasouli, Ashkan

214

Estimating Titan Surface Topography from Cassini Synthetic Aperture RADAR Data  

NASA Astrophysics Data System (ADS)

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.

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

215

X-ray topography study of complex silicon microcircuits  

NASA Technical Reports Server (NTRS)

The correlation between the yield of silicon microcircuits wafers versus defects observed in X-ray topographs produced by a high speed curved wafer X-ray topographic camera was investigated. Most of the topographs were made after final wafer probe. Results indicated that most high volume silicon wafer processing does not need X-ray topography as a routine process control. It is further indicated that in changing any existing process or developing a new process the technique can be of significant benefit.

Parker, D. L.

1981-01-01

216

Dynamic wetting and spreading and the role of topography.  

PubMed

The spreading of a droplet of a liquid on a smooth solid surface is often described by the Hoffman-de Gennes law, which relates the edge speed, v(e), to the dynamic and equilibrium contact angles ? and ?(e) through [Formula: see text]. When the liquid wets the surface completely and the equilibrium contact angle vanishes, the edge speed is proportional to the cube of the dynamic contact angle. When the droplets are non-volatile this law gives rise to simple power laws with time for the contact angle and other parameters in both the capillary and gravity dominated regimes. On a textured surface, the equilibrium state of a droplet is strongly modified due to the amplification of the surface chemistry induced tendencies by the topography. The most common example is the conversion of hydrophobicity into superhydrophobicity. However, when the surface chemistry favors partial wetting, topography can result in a droplet spreading completely. A further, frequently overlooked consequence of topography is that the rate at which an out-of-equilibrium droplet spreads should also be modified. In this report, we review ideas related to the idea of topography induced wetting and consider how this may relate to dynamic wetting and the rate of droplet spreading. We consider the effect of the Wenzel and Cassie-Baxter equations on the driving forces and discuss how these may modify power laws for spreading. We relate the ideas to both the hydrodynamic viscous dissipation model and the molecular-kinetic theory of spreading. This suggests roughness and solid surface fraction modified Hoffman-de Gennes laws relating the edge speed to the dynamic and equilibrium contact angle. We also consider the spreading of small droplets and stripes of non-volatile liquids in the capillary regime and large droplets in the gravity regime. In the case of small non-volatile droplets spreading completely, a roughness modified Tanner's law giving the dependence of dynamic contact angle on time is presented. We review existing data for the spreading of small droplets of polydimethylsiloxane oil on surfaces decorated with micro-posts. On these surfaces, the initial droplet spreads with an approximately constant volume and the edge speed-dynamic contact angle relationship follows a power law [Formula: see text]. As the surface texture becomes stronger the exponent goes from p = 3 towards p = 1 in agreement with a Wenzel roughness driven spreading and a roughness modified Hoffman-de Gennes power law. Finally, we suggest that when a droplet spreads to a final partial wetting state on a rough surface, it approaches its Wenzel equilibrium contact angle in an exponential manner with a time constant dependent on roughness. PMID:21715886

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

2009-11-18

217

Reconstruction of the corneal topography from lateral-shearing interferograms  

NASA Astrophysics Data System (ADS)

The paper presents an approach for measurements of the corneal topography by use of lateral-shearing interferometry. In shearing interferometry the wavefront reflected from the object is split in two wavefronts. The introduction of lateral shift and superposition of the wavefronts produces interference pattern. We used phase shifting algorithm to obtain the phase differences of the wavefront reflected from the cornea. The measurements of the phase differences are carried out in two orthogonal directions. The phase of the wavefront is reconstructed by use of algorithm for the large grid based on the discrete integration. The computer-generated interferograms are used to test the procedure and to estimate its accuracy.

Licznerski, Tomasz J.; Kasprzak, Henryk T.

1999-07-01

218

Barotropic flow over bottom topography— experiments and nonlinear theory  

NASA Astrophysics Data System (ADS)

Barotropic flow over finite amplitude two-wave bottom topography is investigated both experimentally and theoretically over a broad parameter range. In the experiments, the fluid is contained in a vertically oriented, rotating circular cylindrical annulus. It is forced into motion relative to the annulus by a differentially rotating, rigid, radially sloping lid in contact with the top surface of the fluid. The radial depth variation associated with the slope of the lid, and an equal and opposite slope of the bottom boundary, simulates the effect of the variation of the Coriolis parameter with latitude (?) in planetary atmospheres and in the ocean. The dimensionless parameters which control the fluid behavior are the Rossby number (?), the Ekman number (E), the ? parameter, the aspect ratio (?), the ratio of the mean radius to the gap width (?) and the ratio of the topographic height to the mean fluid depth (?). The Rossby and Ekman numbers are varied over an order of magnitude by conducting experiments at different rotation rates of the annulus. Velocity measurements using photographs of tracer particles suspended in the fluid reveal the existence of a stationary, topographically forced wave superimposed on an azimuthal mean current. With successively larger rotation rates (i.e. lower ? and E) the wave amplitude increases and then levels off, the phase displacement of the wave upstream of the topography increases and the azimuthal mean velocity decreases and then levels off. Linear quasigeostophic theory accounts qualitatively, but not quantitatively, for the phase displacement, predicts the wave amplitude poorly and provides no basis for predicting the zonal mean velocity. Accordingly, we have solved the nonlinear, steady-state, quasigeostrophic barotrophic vorticity equation with both Ekman layer and internal dissipation using a spectral colocation method with Fourier representation in the azimuthal direction and Chebyshev polynomial representation in the radial direction. For boundary conditions at the side walls, we specified zero velocity. Side wall boundary layers then appear explicitly in the numerical solution. At the bottom and top of the fluid, we specified that the vertical velocity at the mean height of each boundary is the sum of two components—one forced by Ekman suction in the absence of topography and the other by the condition that there can be no flow normal to the rigid boundary. We justify this choice by the smallness of the Ekman number and of the radial and azimuthal slopes of the topography. We have found that the use of three Fourier components and seven Chebyshev polynomials is sufficient to account qualitatively for the experimental results, although small quantitative discrepancies suggest that further investigation of the neglect of effects originally considered to be small is needed.

Pfeffer, Richard L.; Kung, Robin; Ding, Wen; Li, Guo-Qing

1993-10-01

219

EAARL Topography - Vicksburg National Military Park 2008: Bare Earth  

USGS Publications Warehouse

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.

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

2008-01-01

220

EAARL Topography-Vicksburg National Military Park 2007: First Surface  

USGS Publications Warehouse

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 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 September 12, 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 first surface topography. Specialized filtering algorithms have been implemented to determine the 'bare earth' under vegetation from a point cloud of last return elevations.

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

2009-01-01

221

EAARL Topography - Natchez Trace Parkway 2007: First Surface  

USGS Publications Warehouse

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 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 a portion of the Natchez Trace Parkway in Mississippi, acquired on September 14, 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 first surface topography. Specialized filtering algorithms have been implemented to determine the 'bare earth' under vegetation from a point cloud of last return elevations.

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

2008-01-01

222

EAARL Coastal Topography - Northeast Barrier Islands 2007: First Surface  

USGS Publications Warehouse

These remotely sensed, geographically referenced elevation measurements of Lidar-derived first surface (FS) topography were produced collaboratively by the U.S. Geological Survey (USGS), Florida Integrated Science Center (FISC), St. Petersburg, FL, and the National Aeronautics and Space Administration (NASA), Wallops Flight Facility, VA. This project provides highly detailed and accurate datasets of the 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.

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

2009-01-01

223

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

USGS Publications Warehouse

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.

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

2011-01-01

224

EAARL Coastal Topography-Pearl River Delta 2008: First Surface  

USGS Publications Warehouse

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.

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

2009-01-01

225

Influence of atmospheric structure and topography on infrasonic wave propagation  

NASA Astrophysics Data System (ADS)

The effects of topography and atmospheric structures on infrasonic wave propagation from a volcanic source were investigated using observations and numerical modeling. This paper presents the first long-term observational data set showing spatiotemporal variations in patterns of infrasound propagation at distances of up to 60 km from a persistently active infrasound source (Sakurajima Volcano, Japan). The data show that the amplitudes of infrasonic waves received at distant stations relative to those received at a reference station close to the source can vary up to an order of magnitude over short time intervals and short distances and that they do not follow the theoretical geometric decay expected for homogeneous media. Moreover, waveforms also change significantly in both time and space. Numerical simulations were performed using a two-dimensional finite difference time domain (2-D FDTD) method. Effects of atmospheric structure and topography are included in a vertical section parallel to the wave propagation direction. The simulation successfully reproduced the variations of amplitudes and waveforms. Results are interpreted in terms of wave refraction due to sound and wind speed gradients and wave diffraction at topographic barriers. Our numerical results indicate that both atmospheric and topographic propagation effects are nonnegligible. To evaluate the propagation effects and determine source processes in spatially and temporally varying infrasound data, atmospheric data with a time resolution higher than is currently available are required. If the data are available, the present results suggest that the propagation effects could be evaluated using 2-D FDTD modeling at realistic calculation times.

Lacanna, G.; Ichihara, M.; Iwakuni, M.; Takeo, M.; Iguchi, M.; Ripepe, M.

2014-04-01

226

Tropical Pacific response to continental ice sheet topography  

NASA Astrophysics Data System (ADS)

The Last Glacial Maximum was marked by maximum land ice extent and lowest greenhouse gases concentration during the last ice age. We explore the impact of glacial continental ice sheet topography (as opposed to albedo) had on the large-scale tropical ocean-atmosphere climate, in particular the tropical Pacific in an intermediate coupled model. Increasing the thickness of continental ice sheets causes a southward displaced Pacific ITCZ and a strengthening (weakening) of northern (southern) hemisphere winter Hadley cell. The equatorial zonal sea surface temperature (SST) gradient weakened with an increased continental ice sheets thickness, the reduction being caused by cooling in the western equatorial Pacific and warming in the eastern equatorial Pacific. The evolution of the tropical climate with changing ice thickness has distinct quasi-linear and nonlinear parts. While the linear part is a direct response to the ice topographic changes, the nonlinear part was a result of the tropical thermocline adjustment. Our analysis of a fully-coupled transient deglacial simulation strongly indicates the dominant role of ice sheet topography in determining the deglacial evolution of the simulated Pacific climate. The thickness of continental ice sheet, separate from ice albedo effect, has significant impact on the tropical ocean-atmosphere climate in particular with shifting the Pacific ITCZ meridionally. Our results may aid in interpreting the relationship between tropical and high-latitude climate records in glacial-interglacial cycles.

Chiang, J. C.; Lee, S.

2013-12-01

227

Photoswitchable hydrogel surface topographies by polymerisation-induced diffusion.  

PubMed

Herein, we describe the preparation of patterned photoresponsive hydrogels by using a facile method. This polymer-network hydrogel coating consists of N-isopropylacrylamide (NIPAAM), cross-linking agent tripropylene glycol diacrylate (TPGDA), and a new photochromic spiropyran monoacrylate. In a pre-study, a linear NIPAAM copolymer (without TPGDA) that contained the spiropyran dye was synthesised, which showed relatively fast photoswitching behaviour. Subsequently, the photopolymerisation of a similar monomer mixture that included TPGDA afforded freestanding hydrogel polymer networks. The light-induced isomerisation of protonated merocyanine into neutral spiropyran under slightly acidic conditions resulted in macroscopic changes in the hydrophilicity of the entire polymer film, that is, shrinkage of the hydrogel. The degree of shrinkage could be controlled by changing the chemical composition of the acrylate mixture. After these pre-studies, a hydrogel film with spatially modulated cross-link density was fabricated through polymerisation-induced diffusion, by using a patterned photomask. The resulting smooth patterned hydrogel coating swelled in slightly acidic media and the swelling was higher in the regions with lower cross-linking densities, thus yielding a corrugated surface. Upon exposure to visible light, the surface topography flattened again, thus showing that a hydrogel coating could be created, the topography of which could be controlled by light irradiation. PMID:23821576

Stumpel, Jelle E; Liu, Danqing; Broer, Dirk J; Schenning, Albertus P H J

2013-08-12

228

Eyelid response topography in differential interstimulus interval conditioning.  

PubMed

The problem of conditioned eyelid discrimination was investigated with a differential interstimulus interval (ISI) conditioning procedure. In two groups, conditioned stimulus (CS) lights presented in the left or right visual fields signaled ISIs of 800 or 1,200 msec before delivery of an airpuff unconditioned stimulus. Two additional groups received one or the other ISI with both CSs. Somewhat unexpectedly, none of the response-frequency or topography measures showed evidence of conditioned discrimination in the differential ISI groups. Instead, the latencies and puff-attenuating topographies of responses were much more appropriate to the ISI given on the preceding trial, n--1, than to the ISI cued on trial n. Neither the absence of conditioned discrimination nor the presence of ISI sequential effects was related to subjects' reported awareness of the CS-ISI contingencies, suggesting that the overriding process was a relatively "automatic" shaping and reshaping of responses in accord with recent ISI experience. These results are discussed in terms of the complex stimulus- and response-processing requirements of the task. Across all four groups there was some evidence of a relative excitatory response bias to CSs presented in the right visual field, and it was found that voluntary-form responders (but not conditioned-form responders) initially gave more alpha responses to the right-field CS than to the left-field CS. These results were examined for possible hemispheric processing implications. PMID:870612

Kadlac, J A; Grant, D A

1977-05-01

229

Smoking topography and outcome expectancies among individuals with schizotypy  

PubMed Central

Compared to smokers in the general population, smokers with schizophrenia smoke more cigarettes per day and have higher nicotine dependence and biochemical indicators of nicotine intake. They also have more intense smoking topography and greater positive smoking expectancies. Little is known about the relationship between smoking and schizotypy, defined as the personality organization reflecting a vulnerability to schizophrenia-spectrum pathology. This study assessed schizotypy symptoms, smoking characteristics and behaviors, and smoking expectancies in young adults with psychometrically defined schizotypy and demographically matched controls without schizotypy. Smokers with schizotypy had higher nicotine dependence and smoked more cigarettes per week compared to control smokers. They were also more likely to endorse greater positive consequences (i.e., improved state enhancement, stimulation, social facilitation, taste/sensorimotor manipulation, reduced negative affect and boredom) and fewer negative consequences of smoking. Smokers with schizotypy and control smokers did not differ on smoking topography or carbon monoxide levels. This is the first known study to investigate relationships between these smoking-related variables in smokers with schizotypy. Individuals with schizotypy possessed certain smoking-related characteristics and smoking expectancies similar to those with schizophrenia. This offers preliminary insight into unique smoking-related factors among individuals with schizotypy and highlights the importance of continued research in this area. PMID:23261186

Stewart, Diana W.; Vinci, Christine; Adams, Claire E.; Cohen, Alex S.; Copeland, Amy L.

2013-01-01

230

Multiview hyperspectral topography of tissue structural and functional characteristics  

NASA Astrophysics Data System (ADS)

Accurate and in vivo characterization of structural, functional, and molecular characteristics of biological tissue will facilitate quantitative diagnosis, therapeutic guidance, and outcome assessment in many clinical applications, such as wound healing, cancer surgery, and organ transplantation. However, many clinical imaging systems have limitations and fail to provide noninvasive, real time, and quantitative assessment of biological tissue in an operation room. To overcome these limitations, we developed and tested a multiview hyperspectral imaging system. The multiview hyperspectral imaging system integrated the multiview and the hyperspectral imaging techniques in a single portable unit. Four plane mirrors are cohered together as a multiview reflective mirror set with a rectangular cross section. The multiview reflective mirror set was placed between a hyperspectral camera and the measured biological tissue. For a single image acquisition task, a hyperspectral data cube with five views was obtained. The five-view hyperspectral image consisted of a main objective image and four reflective images. Three-dimensional topography of the scene was achieved by correlating the matching pixels between the objective image and the reflective images. Three-dimensional mapping of tissue oxygenation was achieved using a hyperspectral oxygenation algorithm. The multiview hyperspectral imaging technique is currently under quantitative validation in a wound model, a tissue-simulating blood phantom, and an in vivo biological tissue model. The preliminary results have demonstrated the technical feasibility of using multiview hyperspectral imaging for three-dimensional topography of tissue functional properties.

Zhang, Shiwu; Liu, Peng; Huang, Jiwei; Xu, Ronald

2012-12-01

231

Three Dimensional Surface Topography Using LCD Pattern Transfer Method  

NASA Astrophysics Data System (ADS)

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).

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

2012-03-01

232

Ground motion in the presence of complex topography  

USGS Publications Warehouse

To study the influence of topography on ground motion, eight seismic recorders were deployed for a period of one year over Poverty Ridge on the east side of the San Francisco Bay Area, California. This location is desirable because of its proximity to local earthquake sources and the significant topographic relief of the array (439 m). Topographic amplification is evaluated as a function of frequency using a variety of methods, including reference?site?based spectral ratios and single?station horizontal?to?vertical spectral ratios using both shear waves from earthquakes and ambient noise. Field observations are compared with the predicted ground motion from an accurate digital model of the topography and a 3D local velocity model. Amplification factors from the theoretical calculations are consistent with observations. The fundamental resonance of the ridge is prominently observed in the spectra of data and synthetics; however, higher?frequency peaks are also seen primarily for sources in line with the major axis of the ridge, perhaps indicating higher resonant modes. Excitations of lateral ribs off of the main ridge are also seen at frequencies consistent with their dimensions. The favored directions of resonance are shown to be transverse to the major axes of the topographic features.

Hartzell, Stephen; Meremonte, Mark; Ramírez-Guzmán, Leonardo; McNamara, Daniel

2014-01-01

233

X-Ray Topography Techniques for Defect Characterization of Crystals  

NASA Astrophysics Data System (ADS)

X-ray topography is the general term for a family of x-ray diffraction imaging techniques capable of providing information on the nature and distribution of structural defects such as dislocations, inclusions/precipitates, stacking faults, growth sector boundaries, twins, and low-angle grain boundaries in single-crystal materials. From the first x-ray diffraction image, recorded by Berg in 1931, to the double-crystal technique developed by Bond and Andrus in 1952 and the transmission technique developed by Lang in 1958 through to present-day synchrotron-radiation-based techniques, x-ray topography has evolved into a powerful, nondestructive method for the rapid characterization of large single crystals of a wide range of chemical compositions and physical properties, such as semiconductors, oxides, metals, and organic materials. Different defects are readily identified through interpretation of contrast using well-established kinematical and dynamical theories of x-ray diffraction. This method is capable of imaging extended defects in the entire volume of the crystal and in some cases in wafers with devices fabricated on them. It is well established as an indispensable tool for the development of growth techniques for highly perfect crystals (for, e.g., Czochralski growth of silicon) for semiconductor and electronic applications. The capability of in situ characterization during crystal growth, heat treatment, stress application, device operation, etc. to study the generation, interaction, and propagation of defects makes it a versatile technique to study many materials processes.

Raghothamachar, Balaji; Dudley, Michael; Dhanaraj, Govindhan

234

Topography of Striate-Extrastriate Connections in Neonatally Enucleated Rats  

PubMed Central

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

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

2013-01-01

235

A Martian general circulation experiment with large topography  

NASA Astrophysics Data System (ADS)

A three-layer general circulation model of the Martian atmosphere is described, and the assumptions governing the model are discussed. The simulated, zonally averaged circulation is found to have only limited sensitivity to differences between this model and an earlier general circulation model; this circulation compares reasonably well with observations. It is also found that the meridional mass flow produced by the seasonal condensation of CO2 in the winter polar region has a major influence on the circulation; owing to the weak influence of atmospheric heat transport, however, the mass flow is governed almost entirely by radiation. Quasi-barotropic stationary waves, which are forced kinematically by the topography and which resemble topographically forced terrestrial planetary waves, are generated by the model in the winter hemisphere region of strong eastward flow, while baroclinic stationary waves are thermally forced by topography in the tropics and summer subtropics. It is also concluded that transient baroclinically unstable waves, of somewhat lower dominant wavenumber than those found on the earth, are generated in winter midlatitudes; their amplitudes, wavenumbers, and phase speeds closely agree with what has been deduced from the Viking lander observations.

Pollack, J. B.; Leovy, C. B.; Greiman, P. W.; Mintz, Y.

1981-01-01

236

Topography and areal organization of mouse visual cortex.  

PubMed

To guide future experiments aimed at understanding the mouse visual system, it is essential that we have a solid handle on the global topography of visual cortical areas. Ideally, the method used to measure cortical topography is objective, robust, and simple enough to guide subsequent targeting of visual areas in each subject. We developed an automated method that uses retinotopic maps of mouse visual cortex obtained with intrinsic signal imaging (Schuett et al., 2002; Kalatsky and Stryker, 2003; Marshel et al., 2011) and applies an algorithm to automatically identify cortical regions that satisfy a set of quantifiable criteria for what constitutes a visual area. This approach facilitated detailed parcellation of mouse visual cortex, delineating nine known areas (primary visual cortex, lateromedial area, anterolateral area, rostrolateral area, anteromedial area, posteromedial area, laterointermediate area, posterior area, and postrhinal area), and revealing two additional areas that have not been previously described as visuotopically mapped in mice (laterolateral anterior area and medial area). Using the topographic maps and defined area boundaries from each animal, we characterized several features of map organization, including variability in area position, area size, visual field coverage, and cortical magnification. We demonstrate that higher areas in mice often have representations that are incomplete or biased toward particular regions of visual space, suggestive of specializations for processing specific types of information about the environment. This work provides a comprehensive description of mouse visuotopic organization and describes essential tools for accurate functional localization of visual areas. PMID:25209296

Garrett, Marina E; Nauhaus, Ian; Marshel, James H; Callaway, Edward M

2014-09-10

237

Feasibility of skin surface elastography by tracking skin surface topography.  

PubMed

Recent advances have led to a multitude of image modalities being used for visualization of tissue stiffness. High-resolution images of tissue stiffness are desirable, as they have the potential to provide useful diagnostic information. A noncontact optical imaging method has the attractions of low cost, simplicity, and utility when skin contact is undesirable. However, previous optical techniques have required the application of paint or ink to the surface of the skin and so have required contact. Therefore, the present study assessed the feasibility of tracking skin surface topography to produce elastograms. The study showed, by analyzing a variety of silicone skin surface replicas from various body sites of subjects of different ages, that skin surface elastography by tracking surface topography would be feasible. The study further showed that the quality of the strain images can be optimized by measuring skin line pattern frequency. Skin samples with high skin line frequency will achieve best spatial resolution, in the order of 1 mm, comparable to contact techniques reported previously. A mechanically inhomogeneous silicone replica was then imaged, illustrating the technique's ability to detect strain contrast. Finally, the feasibility of implementing the technique in vivo was illustrated using a single pigmented skin lesion. PMID:24343434

Coutts, Louise V; Miller, Naomi R; Harland, Christopher C; Bamber, Jeffrey C

2013-12-01

238

Near-Field Scattering due to Topography and Lateral Velocity Heterogeneity  

NASA Astrophysics Data System (ADS)

The scattering of seismic waves traveling in the Earth is not only caused by velocity heterogeneity, but also by rough surface topography. Both factors are known to play an important role on ground motion complexity even at short distances from the source. In this study, we simulate ground motion with a 3D finite-difference wave propagation solver in the frequency band 0-5 Hz using different rough topography models and realistic heterogeneous media characterized by Von Karman correlation functions. We analyze the characteristics of the scattered wave-field, focusing in particular on coda waves. Our study shows that topography and velocity heterogeneity scattering generate coda waves with different characteristics. We notice that, while coda waves originated by velocity heterogeneity have a more diffusive nature presenting envelope broadening as a result of forward scattering, coda waves caused by topography scattering are composed of more coherent body and surface waves reflected and diffracted by irregular topography surface. Results indicate that, for shallow sources, topography scattering can generate more intense early-coda waves at short and intermediate distances from the source. As distance increases, velocity heterogeneity scattering starts to dominate. However results show a rather high degree of variability as topography scattering is very sensitive to source position and features of the topography model. On the other hand, velocity perturbations generate more intense late-coda waves We conclude that topography scattering cannot be used as a proxy for velocity heterogeneity scattering.

Imperatori, Walter; Mai, Martin

2014-05-01

239

Mapping the Topography of Europa: The Galileo-Clipper Story  

NASA Astrophysics Data System (ADS)

The renewed effort to return to Europa for global mapping and landing site selection raises the question: What do we know about Europa topography and how do we know it? The question relates to geologic questions of feature formation, to the issue of ice shell thickness, mechanical strength, and internal activity, and to landing hazards. Our topographic data base for Europa is sparse indeed (no global map is possible), but we are not without hope. Two prime methods have been employed in our mapping program are stereo image and shape-from-shading (PC) slope analyses. On Europa, we are fortunate that many PC-DEM areas are also controlled by stereo-DEMs, mitigating the long-wavelength uncertainties in the PC data. Due to the Galileo antenna malfunction, mapping is limited to no more than 20% of the surface, far less than for any of the inner planets. Thirty-seven individual mapping sites have been identified, scattered across the globe, and all have now been mapped. Excellent stereo mapping is possible at all Sun angles, if resolution is below ~350 m. PC mapping is possible at Sun angles greater than ~60 degrees, if emission angles are less than ~40 degrees. The only extended contiguous areas of topographic mapping larger than 150 km across are the two narrow REGMAP mapping mosaics extending pole-to-pole along longitudes 85 and 240 W. These are PC-only and subject to long-wavelength uncertainties and errors, especially in the north/south where oblique imaging produces layover. Key findings include the mean slopes of individual terrain types (Schenk, 2009), topography across chaos (Schenk and Pappalardo, 2004), topography of craters and inferences for ice shell thickness (Schenk, 2002; Schenk and Turtle, 2009), among others. A key discovery, despite the limited data, is that Europan terrains rarely have topographic amplitude greater than 250 meters, but that regionally Europa has imprinted on it topographic amplitudes of +/- 1 km, in the form of raised plateaus and bowed-down arcuate troughs. Such amplitudes imply that the ice shell is capable of supporting relief and is not extremely thin.

Schenk, Paul M.

2014-11-01

240

Antarctic hypsometry and the source of East Antarctica's anomalous topography  

NASA Astrophysics Data System (ADS)

The re-examined hypsometry of Antarctica based on BEDMAP2 data reveals deglaciated modal elevations of ~-450 m and ~650 m for West and East Antarctica, respectively. Although the East Antarctic modal elevation is 300 m lower than the original measurement, it still renders the plateau topographically anomalous by ~400-600 m with respect to the existing global continental modal elevation estimates of 87 m and 250 m. Superimposed on the plateau are the Gamburtsev Subglacial Mountains, the Dronning Maud Land Mountains and the Vostok Highlands with modal elevations ~400 m in excess of the East Antarctic mode. To ascertain whether East Antarctica's anomalous topography can be attributed to Airy-type crustal compensation, a continental-scale crustal thickness model is derived from the inversion of GOCO03S satellite gravity data constrained by seismic crustal thickness measurements. The average crustal thickness of East Antarctica is ~40 km (for West Antarctica ~24 km), a value typical of Archean shields. While crustal thickening to >50 km locally beneath the Gamburtsev Subglacial Mountains and Dronning Maud Land can account for their differential modal elevation above the plateau, the evidently typical Archean crust elsewhere across East Antarctica offers no suggestion of crustal-level continental-scale support for the broader plateau. The plateau of southern Africa offers a tectonic analogue: Like East Antarctica, the lithosphere is largely Archean and cratonic, the crust is of typical shield thickness, there is no obvious Cenozoic tectonism and the upper mantle does not appear to be unduly perturbed. The relative accessibility of the African continent, meanwhile, has led to conclusive imaging of large-scale perturbations in the lower mantle beneath the southern African plateau pointing to dynamic, rather that isostatic, support of the associated long wavelength topography. While several global seismic tomography models infer somewhat anomalously slow lower mantle structure beneath Antarctica, the resolution presently offered by such models in this region is poor. That said, the apparent absence of crustal-level continental-scale support for the East Antarctic plateau coupled with the fact that the underlying upper mantle does not appear unduly anomalous suggest, by analogy with southern Africa, lower mantle generated epeirogeny as a likely explanation for the anomalous topography. The incorporation of data from the Antarctic seismic deployments of recent years in the next generation of global tomography models should resolve the issue.

O'Donnell, J.; Nyblade, A.

2013-12-01

241

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

PubMed

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

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

2012-01-01

242

EAARL Coastal Topography - Northern Gulf of Mexico, 2007: First Surface  

USGS Publications Warehouse

These remotely sensed, geographically referenced elevation measurements of Lidar-derived first surface (FS) elevation data 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 project provides highly detailed and accurate datasets of select barrier islands and peninsular regions of Louisiana, Mississippi, Alabama, and Florida, acquired 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.

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

2009-01-01

243

Aperture synthesis  

Microsoft Academic Search

The article reviews the principles of aperture synthesis theory, with emphasis on earth rotation aperture synthesis, and the main data processing techniques for aperture synthesis telescope systems. A derivation is given for the formula giving the brightness distribution recorded by a continuum aperture synthesis system which samples the complex autocorrelation function of the electric field. The basic formulas are presented

W. N. Brouw

1975-01-01

244

Topography measurements for correlations of standard cartridge cases  

NASA Astrophysics Data System (ADS)

The National Institute of Standards and Technology Standard Reference Materials (SRM) 2460 Standard Bullets and 2461 Standard Cartridge Cases are intended for use as check standards for crime laboratories to help verify that their computerized optical imaging equipment for ballistics image acquisitions and correlations is operating properly. Using topography measurements and cross-correlation methods, our earlier results for the SRM bullets and recent results for the SRM cartridge cases both demonstrate that the individual units of the SRMs are highly reproducible. Currently, we are developing procedures for topographic imaging of the firing pin impressions, breech face impressions, and ejector marks of the standard cartridge cases. The initial results lead us to conclude that all three areas can be measured accurately and routinely using confocal techniques. We are also nearing conclusion of a project with crime lab experts to test sets of both SRM cartridge cases and SRM bullets using the automated commercial systems of the National Integrated Ballistics Information Network.

Vorburger, T. V.; Song, J.; Chu, W.; Renegar, T. B.; Zheng, A.; Yen, J.; Thompson, R. M.; Silver, R.; Bachrach, B.; Ols, M.

2010-06-01

245

Different Approach to the Aluminium Oxide Topography Characterisation  

SciTech Connect

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.

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

246

Ion-beam-induced topography and surface diffusion  

NASA Technical Reports Server (NTRS)

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.

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

1982-01-01

247

Kapalabhati--yogic cleansing exercise. II. EEG topography analysis.  

PubMed

Topography of brain electrical activity was studied in 11 advanced yoga practitioners during yogic high-frequency breathing kapalabhati (KB). Alpha activity was increased during the initial five min of KB. Theta activity mostly in the occipital region was increased during later stages of 15 min KB compared to the pre-exercise period. Beta 1 activity increased during the first 10 min of KB in occipital and to a lesser degree in parietal regions. Alpha and beta 1 activity decreased and theta activity was maintained on the level of the initial resting period after KB. The score of General Deactivation factor from Activation Deactivation Adjective Checklist was higher after KB exercise than before the exercise. The results suggest a relative increase of slower EEG frequencies and relaxation on a subjective level as the after effect of KB exercise. PMID:1818698

Stancák, A; Kuna, M; Srinivasan; Dostálek, C; Vishnudevananda, S

1991-01-01

248

Mercury's global shape and topography from MESSENGER limb images  

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

249

Leaf cuticle topography retrieved by using fringe projection  

NASA Astrophysics Data System (ADS)

The combination (often referred to as phase-stepping profilometry, PSP) of the fringe projection technique and the phase-stepping method allowed us to retrieve topographic maps of cuticles isolated from the abaxial surface of leaves; these were in turn sampled from an apple tree ( Malus domestica) of the variety Golden Delicious. The topographic maps enabled us to assess the natural features on the illuminated surface and also to detect the whole-field spatial variations in the thickness of the cuticle. Most of our attention was paid to retrieve the highly-resolved elevation information from the cuticle surface, which included the trace (in the order of tens of micrometers) left by ribs and veins. We expect that the PSP application for retrieving the cuticle topography will facilitate further studies on the dispersion and coverage of state-of-the-art agrochemical compounds meant to improve the defending properties of the cuticle. Methodological details are provided below.

Martínez, Amalia; Rayas, J. A.; Cordero, Raúl R.; Balieiro, Daniela; Labbe, Fernando

2012-02-01

250

Geologic structure of shallow maria. [topography of lunar maria  

NASA Technical Reports Server (NTRS)

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.

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

1975-01-01

251

Surface topography of the optic nerve head from digital images  

NASA Astrophysics Data System (ADS)

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.

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

1992-06-01

252

Forecasting hurricane impact on coastal topography: Hurricane Ike  

USGS Publications Warehouse

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

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

2010-01-01

253

Different Approach to the Aluminium Oxide Topography Characterisation  

NASA Astrophysics Data System (ADS)

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.

Poljacek, Sanja Mahovic; Gojo, Miroslav; Raos, Pero; Stoic, Antun

2007-04-01

254

Novel double path shearing interferometer in corneal topography measurements  

NASA Astrophysics Data System (ADS)

The paper presents an approach for measurements of corneal topography by use of a patent pending double path shearing interferometer (DPSI). Laser light reflected from the surface of the cornea is divided and directed to the inputs of two interferometers. The interferometers use lateral shearing of wavefronts in two orthogonal directions. A tilt of one of the mirrors in each interferometric setup perpendicularly to the lateral shear introduces parallel carrier frequency fringes at the output of each interferometer. There is orthogonal linear polarization of the laser light used in two DPSI. Two images of fringe patters are recorded by a high resolution digital camera. The obtained fringe patterns are used for phase difference reconstruction. The phase of the wavefront was reconstructed by use of algorithms for a large grid based on discrete integration. The in vivo method can also be used for tear film stability measurement, artificial tears and contact lens tests.

Licznerski, Tomasz J.; Jaronski, Jaroslaw; Kosz, Dariusz

2005-09-01

255

The evolution of polymer surface topography in annealing  

NASA Astrophysics Data System (ADS)

Ultrasmooth polymer films are of great importance in a large body of technical application. Photoresist technology plays a very important role in MEMS, and usually is to use optical coatings to transfer the smooth surface. In order to form different value of roughness is bright and clean surface or sacrifice layer microstructure, surface topography and its effect on the microstructure is crucial. Photoresist thin film EPG533 having different thicknesses of 270nm, 500nm, and 1 ?m were deposited onto well-cleaned n-type silicon substrates by spin coating and annealed in the range from 100°C to 200°C.The effects of thermal annealing and thickness variation on the crystalline quality and surface morphology of the films were investigated by white light interferometry measurements. It was found that the film quality and morphology depend on the annealing temperature. The root-mean-square roughness and waviness on the surface change, as a result of increasing film thickness.

Ma, Pengfei; Liu, Weiguo; Liu, Huan

2013-12-01

256

New Orleans Topography, Radar Image with Colored Height  

NASA Technical Reports Server (NTRS)

[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

2005-01-01

257

Recent and relict topography of Boo Bee patch reef, Belize  

USGS Publications Warehouse

Five core borings were taken on and around Boo Bee Patch Reef to better understand the origin of such shelf lagoon reefs. The cores reveal 4 stages of development: (1) subaerial exposure of a Pleistocene "high" having about 8 meters of relief, possibly a Pleistocene patch reef; (2) deposition of peat and impermeable terrigenous clay 3 meters thick around the high; (3) initiation of carbonate sediment production by corals and algae on the remaining 5 meters of hard Pleistocene topography and carbonate mud on the surrounding terrigenous clay; and (4) accelerated organic accumulation on the patch reef. Estimates of patch reef sedimentation rates (1.6 m/1000 years) are 3 to 4 times greater than off-reef sedimentation rates (0.4-0.5 m/1000 years). During periods of Pleistocene sedimentation on the Belize shelf, lagoon patch reefs may have grown above one another, stacking up to form reef accumulation of considerable thickness.

Halley, R.B.; Shinn, E.A.; Hudson, J.H.; Lidz, B.

1977-01-01

258

Dynamic wetting and spreading and the role of topography  

NASA Astrophysics Data System (ADS)

The spreading of a droplet of a liquid on a smooth solid surface is often described by the Hoffman-de Gennes law, which relates the edge speed, ve, to the dynamic and equilibrium contact angles ? and ?e through v_{\\mathrm {e}} \\propto \\theta (\\theta^{2}-\\theta_{\\mathrm {e}}^{2}) . When the liquid wets the surface completely and the equilibrium contact angle vanishes, the edge speed is proportional to the cube of the dynamic contact angle. When the droplets are non-volatile this law gives rise to simple power laws with time for the contact angle and other parameters in both the capillary and gravity dominated regimes. On a textured surface, the equilibrium state of a droplet is strongly modified due to the amplification of the surface chemistry induced tendencies by the topography. The most common example is the conversion of hydrophobicity into superhydrophobicity. However, when the surface chemistry favors partial wetting, topography can result in a droplet spreading completely. A further, frequently overlooked consequence of topography is that the rate at which an out-of-equilibrium droplet spreads should also be modified. In this report, we review ideas related to the idea of topography induced wetting and consider how this may relate to dynamic wetting and the rate of droplet spreading. We consider the effect of the Wenzel and Cassie-Baxter equations on the driving forces and discuss how these may modify power laws for spreading. We relate the ideas to both the hydrodynamic viscous dissipation model and the molecular-kinetic theory of spreading. This suggests roughness and solid surface fraction modified Hoffman-de Gennes laws relating the edge speed to the dynamic and equilibrium contact angle. We also consider the spreading of small droplets and stripes of non-volatile liquids in the capillary regime and large droplets in the gravity regime. In the case of small non-volatile droplets spreading completely, a roughness modified Tanner's law giving the dependence of dynamic contact angle on time is presented. We review existing data for the spreading of small droplets of polydimethylsiloxane oil on surfaces decorated with micro-posts. On these surfaces, the initial droplet spreads with an approximately constant volume and the edge speed-dynamic contact angle relationship follows a power law v_{\\mathrm {e}} \\propto \\theta ^p . As the surface texture becomes stronger the exponent goes from p = 3 towards p = 1 in agreement with a Wenzel roughness driven spreading and a roughness modified Hoffman-de Gennes power law. Finally, we suggest that when a droplet spreads to a final partial wetting state on a rough surface, it approaches its Wenzel equilibrium contact angle in an exponential manner with a time constant dependent on roughness.

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

2009-11-01

259

Topography-guided custom ablation treatment for treatment of keratoconus.  

PubMed

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

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

2013-08-01

260

Topography and geomorphology of the Huygens landing site on Titan  

USGS Publications Warehouse

The Descent Imager/Spectral Radiometer (DISR) aboard the Huygens Probe took several hundred visible-light images with its three cameras on approach to the surface of Titan. Several sets of stereo image pairs were collected during the descent. The digital terrain models constructed from those images show rugged topography, in places approaching the angle of repose, adjacent to flatter darker plains. Brighter regions north of the landing site display two styles of drainage patterns: (1) bright highlands with rough topography and deeply incised branching dendritic drainage networks (up to fourth order) with dark-floored valleys that are suggestive of erosion by methane rainfall and (2) short, stubby low-order drainages that follow linear fault patterns forming canyon-like features suggestive of methane spring-sapping. The topographic data show that the bright highland terrains are extremely rugged; slopes of order of 30?? appear common. These systems drain into adjacent relatively flat, dark lowland terrains. A stereo model for part of the dark plains region to the east of the landing site suggests surface scour across this plain flowing from west to east leaving ???100-m-high bright ridges. Tectonic patterns are evident in (1) controlling the rectilinear, low-order, stubby drainages and (2) the "coastline" at the highland-lowland boundary with numerous straight and angular margins. In addition to flow from the highlands drainages, the lowland area shows evidence for more prolific flow parallel to the highland-lowland boundary leaving bright outliers resembling terrestrial sandbars. This implies major west to east floods across the plains where the probe landed with flow parallel to the highland-lowland boundary; the primary source of these flows is evidently not the dendritic channels in the bright highlands to the north. ?? 2007 Elsevier Ltd. All rights reserved.

Soderblom, L. A.; Tomasko, M. G.; Archinal, B. A.; Becker, T. L.; Bushroe, M. W.; Cook, D. A.; Doose, L. R.; Galuszka, D. M.; Hare, T. M.; Howington-Kraus, E.; Karkoschka, E.; Kirk, R. L.; Lunine, J. I.; McFarlane, E. A.; Redding, B. L.; Rizk, B.; Rosiek, M. R.; See, C.; Smith, P. H.

2007-01-01

261

A Link between Adolescent Nicotine Metabolism and Smoking Topography  

PubMed Central

Adult slow nicotine metabolizers have lower smoke exposure, carbon monoxide levels, and plasma nicotine levels than normal and fast metabolizers. Emerging evidence suggests nicotine metabolism influences smoking topography. This study investigated the association of nicotine metabolism (the ratio of plasma 3-hydroxycotinine to cotinine; 3OHCOT/COT) with smoking topography in adolescent smokers (N=85, 65% female, 68% European American, mean age 15.3 ± 1.2, mean cigarettes per day (CPD) 18.5 ± 8.5, mean Fagerström Test for Nicotine Dependence (FTND) 7.0 ± 1.2) presenting for a nicotine replacement therapy trial. Measures obtained included puff volume, inter-puff interval, number of puffs, puff duration, and puff velocity. Linear regression analysis controlling for hormonal contraception use showed that 3OHCOT/COT ratios predicted mean puff volume in the overall sample (t = 2.126, p = .037, adjusted R2 = .067). After gender stratification, faster metabolism predicted higher mean puff volume (t = 2.81, p = .009, adjusted R2 = .192) but fewer puffs (t = ?3.160, p=0.004, adjusted R2 = .237) and lower mean puff duration (t = ?2.06, p = .048, adjusted R2 = .101) among boys only, suggesting that as nicotine metabolism increases, puff volume increases but puffing frequency decreases. No significant relationships were found between nicotine metabolism and total puff volume, mean puff duration, inter-puff interval, or puff velocity. If confirmed in a broader sample of adolescent smokers, these findings suggest that, as among dependent adult smokers, rate of metabolism among adolescent boys is linked to select parameters of puffing behavior that may impact cessation ability. PMID:19423535

Moolchan, Eric T.; Parzynski, Craig S.; Jaszyna-Gasior, Maria; Collins, Charles C.; Leff, Michelle K.; Zimmerman, Debra L.

2009-01-01

262

Density constraints of lunar upper crust from gravity and topography  

NASA Astrophysics Data System (ADS)

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.

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

2011-12-01

263

Pre-LGM Northern Hemisphere paleo-ice sheet topography  

NASA Astrophysics Data System (ADS)

We here reconstruct the paleotopgraphy of Northern Hemisphere ice sheets during the glacial maxima of marine isotope stages (MIS) 5b and 4. We employ two approaches, geologically based reconstruction and numerical modeling, in mutually supportive roles to arrive at probable ice sheet extents and topographies for each of these two time slices. For a physically based 3-D calculation based on geologically derived 2-D constraints, we use the University of Maine Ice Sheet Model (UMISM) to calculate ice-sheet thickness and topography. The approach and ice-sheet modeling strategy is designed to provide robust data sets of sufficient resolution for atmospheric circulation experiments for these previously elusive time periods. Two tunable parameters, a temperature scaling function applied to a spliced Vostok-GRIP record, and spatial adjustment of climatic pole position, were employed iteratively to achieve a good fit to geological constraints where such were available. The model credibly reproduces the first-order pattern of size and location of geologically indicated ice sheets during marine isotope stages (MIS) 5b (86.2 kyr model age) and 4 (64 kyr model age). From the interglacial state of two north-south obstacles to atmospheric circulation (Rocky Mountains and Greenland), by MIS 5b combined Quebec-Central Arctic and Scandinavian-Barents/Kara ice sheets had effectively increased the number of such highland obstacles to four. This number remained constant through MIS 4, but at the last glacial maximum (LGM) dropped to three, through the merging of the Cordilleran and the proto-Laurentide Ice Sheet to a single continent-wide North American ice sheet.

Kleman, J.; Fastook, J.; Ebert, K.; Nilsson, J.; Caballero, R.

2013-05-01

264

Pre-LGM Northern Hemisphere ice sheet topography  

NASA Astrophysics Data System (ADS)

We here reconstruct the paleotopography of Northern Hemisphere ice sheets during the glacial maxima of marine isotope stages (MIS) 5b and 4.We employ a combined approach, blending geologically based reconstruction and numerical modeling, to arrive at probable ice sheet extents and topographies for each of these two time slices. For a physically based 3-D calculation based on geologically derived 2-D constraints, we use the University of Maine Ice Sheet Model (UMISM) to calculate ice sheet thickness and topography. The approach and ice sheet modeling strategy is designed to provide robust data sets of sufficient resolution for atmospheric circulation experiments for these previously elusive time periods. Two tunable parameters, a temperature scaling function applied to a spliced Vostok-GRIP record, and spatial adjustment of the climatic pole position, were employed iteratively to achieve a good fit to geological constraints where such were available. The model credibly reproduces the first-order pattern of size and location of geologically indicated ice sheets during marine isotope stages (MIS) 5b (86.2 kyr model age) and 4 (64 kyr model age). From the interglacial state of two north-south obstacles to atmospheric circulation (Rocky Mountains and Greenland), by MIS 5b the emergence of combined Quebec-central Arctic and Scandinavian-Barents-Kara ice sheets had increased the number of such highland obstacles to four. The number of major ice sheets remained constant through MIS 4, but the merging of the Cordilleran and the proto-Laurentide Ice Sheet produced a single continent-wide North American ice sheet at the LGM.

Kleman, J.; Fastook, J.; Ebert, K.; Nilsson, J.; Caballero, R.

2013-10-01

265

Swath Measurements of Ice Sheet Bottom Topography and Radar Reflectivity  

NASA Astrophysics Data System (ADS)

Ice sheet thickness is a fundamental measurement for understanding the dynamics of large ice sheets (terrestrial or extraterrestrial). Radar is the primary tool used to measure ice thickness but a major challenge is accurately measuring the arrival time of the basal echo in the presence of surface clutter, which may arise from processes such as wind driven deposition and erosion or crevassing. Essentially, the basal echo strength, which is weak because of attenuation through the ice, becomes comparable to the surface scattering signal even though the coincident surface return comes from a large, off-nadir angle. During the past 4 years, we explored three surface clutter rejection techniques and applied them to data collected with 150/450 MHz radars operated from aircraft over the Greenland Ice Sheet. We also investigated how the techniques could be used to go beyond nadir sounding of ice sheets and, when operated used with broad-beam antennas, could successfully acquire 3-dimensional intensity images of the ice sheet base. In this paper, we describe experiments to image the ice sheet base using: synthetic aperture radar (SAR) interferogram filtering; SAR tomography; and beam steering. For the case of a broad beam antenna array, we show that interferograms filtering provides the highest quality topographic data from both the left and right sides of the aircraft but only under optimal conditions. We show that a beam-steering/radar tomography hybrid algorithm provides the most robust topography and also yields an intensity map. We provide example topographies for the base of the Greenland Ice Sheet and suggest how the approach could be used for future sounding of extraterrestrial ice. The research described in this paper was carried out by the Jet Propulsion Laboratory, California Institute of Technology, under a grant from the National Aeronautics and Space Administration. 3-d radar image of the base of the ice sheet. Scene is an orthorectified mosaic located just south of the main Jacobshavn Drainage Channel

Freeman, A.; Gogineni, P. S.; Jezek, K. C.; Rodriguez, E.; Wu, X.

2009-12-01

266

Thermally tailored gradient topography surface on elastomeric thin films.  

PubMed

We report a simple method for creating a nanopatterned surface with continuous variation in feature height on an elastomeric thin film. The technique is based on imprinting the surface of a film of thermo-curable elastomer (Sylgard 184), which has continuous variation in cross-linking density introduced by means of differential heating. This results in variation of viscoelasticity across the length of the surface and the film exhibits differential partial relaxation after imprinting with a flexible stamp and subjecting it to an externally applied stress for a transient duration. An intrinsic perfect negative replica of the stamp pattern is initially created over the entire film surface as long as the external force remains active. After the external force is withdrawn, there is partial relaxation of the applied stresses, which is manifested as reduction in amplitude of the imprinted features. Due to the spatial viscoelasticity gradient, the extent of stress relaxation induced feature height reduction varies across the length of the film (L), resulting in a surface with a gradient topography with progressively varying feature heights (hF). The steepness of the gradient can be controlled by varying the temperature gradient as well as the duration of precuring of the film prior to imprinting. The method has also been utilized for fabricating wettability gradient surfaces using a high aspect ratio biomimetic stamp. The use of a flexible stamp allows the technique to be extended for creating a gradient topography on nonplanar surfaces as well. We also show that the gradient surfaces with regular structures can be used in combinatorial studies related to pattern directed dewetting. PMID:24697617

Roy, Sudeshna; Bhandaru, Nandini; Das, Ritopa; Harikrishnan, G; Mukherjee, Rabibrata

2014-05-14

267

Interpretation of Lunar Topography: Impact Cratering and Surface Roughness  

NASA Astrophysics Data System (ADS)

This work seeks to understand past and present surface conditions on the Moon using two different but complementary approaches: topographic analysis using high-resolution elevation data from recent spacecraft missions and forward modeling of the dominant agent of lunar surface modification, impact cratering. The first investigation focuses on global surface roughness of the Moon, using a variety of statistical parameters to explore slopes at different scales and their relation to competing geological processes. We find that highlands topography behaves as a nearly self-similar fractal system on scales of order 100 meters, and there is a distinct change in this behavior above and below approximately 1 km. Chapter 2 focuses this analysis on two localized regions: the lunar south pole, including Shackleton crater, and the large mare-filled basins on the nearside of the Moon. In particular, we find that differential slope, a statistical measure of roughness related to the curvature of a topographic profile, is extremely useful in distinguishing between geologic units. Chapter 3 introduces a numerical model that simulates a cratered terrain by emplacing features of characteristic shape geometrically, allowing for tracking of both the topography and surviving rim fragments over time. The power spectral density of cratered terrains is estimated numerically from model results and benchmarked against a 1-dimensional analytic model. The power spectral slope is observed to vary predictably with the size-frequency distribution of craters, as well as the crater shape. The final chapter employs the rim-tracking feature of the cratered terrain model to analyze the evolving size-frequency distribution of craters under different criteria for identifying "visible" craters from surviving rim fragments. A geometric bias exists that systematically over counts large or small craters, depending on the rim fraction required to count a given feature as either visible or erased.

Rosenburg, Margaret A.

268

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

Microsoft Academic Search

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

Charles A. Williams; Geoff Wadge

1998-01-01

269

Probing tectonic topography in the aftermath of continental convergence in central Europe  

Microsoft Academic Search

Continental topography is at the interface of processes taking place at depth in the Earth, at its surface, and above it. Topography influences society, not only in terms of slow processes of landscape change and earthquakes, but also in terms of how it affects climate. The Pannonian Basin-Carpathian Orogen System in Central and Eastern Europe represents a key natural laboratory

S. Cloetingh; F. Horváth; C. Dinu; R. A. Stephenson; G. Bertotti; G. Bada; L. Matenco; D. Garcia-Castellanos

2003-01-01

270

TECTOP - Probing tectonic topography at the aftermath of continental convergence in the Pannonian-Carpathian system  

Microsoft Academic Search

Continental topography is at the interface of processes taking place at depth in the Earth at its surface, and above it. Topography influences society, not only in terms of slow processes of change and earthquakes but also in terms of how it affects climate. The Pannonian Basin Carpathian Orogen System in Central and Eastern Europe offers a key natural laboratory

S. Cloetingh; F. Horváth; R. A. Stephenson; G. Bertotti; G. Bada; L. Matenco

2003-01-01

271

Behavioral/Systems/Cognitive Optical Imaging of SI Topography in Anesthetized and  

E-print Network

Behavioral/Systems/Cognitive Optical Imaging of SI Topography in Anesthetized and Awake Squirrel of areas 3b and 1 in awake squirrel monkeys. Monkeys were imaged repeatedly for a period of 2 years in the awake animal or is dependent on behavioral context. The long-standing view that sensory topography

Roe, Anna Wang

272

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

E-print Network

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

Steinberger, Bernhard

273

Modeling the dynamic component of the geoid and topography of Venus  

E-print Network

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

Cerveny, Vlastislav

274

A Topographic Analysis of the Colorado River Drainage: Insights into Interaction Between Topography and Incision History  

Microsoft Academic Search

Topography is a fundamental geophysical observable that reflects the geodynamic, geologic, and climatic history of a region. A number of recent studies have explored ways to extract tectonic information from topography and several provocative interpretations have been made about the topographic fabric in the Western U.S., including: 1) The topographic spectral power decreases systematically as the tectonic age of the

D. D. Coblentz; K. Karlstrom

2003-01-01

275

Application of rigorous topography simulation for modeling of defect propagation\\/growth in VLSI fabrication  

Microsoft Academic Search

Particulate contamination deposited on silicon wafers is typically the dominant reason for yield loss in VLSI manufacturing. The transformation of contaminating particles into defects and then electrical faults is a very complex process which depends on the effect location, size, material and the underlying IC topography. A rigorous 2D topography simulator based on the photolithography simulator METROPOLE, has been developed

Xiaolei Li; Mahesh Reddy; Andrzej J. Strojwas; Linda Milor; Yung-Tao Lin

1997-01-01

276

Spatial Statistics Of Windflow And Blowing-Snow Fluxes Over Complex Topography  

Microsoft Academic Search

A linear theory is used to model windflow over a tundra landscape, taken as an example of complex topography. The autocorrelation between gradients at different points in this landscape has an exponential dependence on separation, characterized by a correlation length. Areal variances of simulated windspeeds are proportional to the variance of the topographic gradient. Simulations with synthetic topographies having the

Richard Essery

2001-01-01

277

THE FORCED KORTEWEGDE VRIES EQUATION AS A MODEL FOR WAVES GENERATED BY TOPOGRAPHY  

E-print Network

THE FORCED KORTEWEG­DE VRIES EQUATION AS A MODEL FOR WAVES GENERATED BY TOPOGRAPHY PAUL A. MILEWSKI is near 1). We derive Korteweg-de Vries and Burgers' equations, and consider both steady configurations a topography h: + f - 1 6 - 3 2 = 1 2 h.(1.1) This equation is known as the forced Korteweg-de Vries (Kd

Milewski, Paul

278

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

Microsoft Academic Search

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

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

1996-01-01

279

Multiscale Biomimetic Topography for the Alignment of Neonatal and Embryonic Stem Cell-Derived Heart Cells  

E-print Network

Multiscale Biomimetic Topography for the Alignment of Neonatal and Embryonic Stem Cell for maintaining proper physiological function.1,2 The role of substrate topography in controlling cell behavior corneal and lens epi- thelial cells.3­13 The addition of a robust, scalable, and tunable biomimetic

Fowlkes, Charless

280

Shape andRefractive Powers in Corneal Topography Stanley A. Klein and Robert B. Mandell  

E-print Network

Shape andRefractive Powers in Corneal Topography Stanley A. Klein and Robert B. Mandell Purpose;36:2096-2109. An the field of cortical topography there is ambiguity for the term corneal power, which implies refractive. To compare the relative advantages and disadvantages of four different representa- tions of corneal power

Klein, Stanley

281

Estimating Corneal Surface Topography in Videokeratoscopy in the Presence of Strong Signal Interference  

Microsoft Academic Search

Videokeratoscopy techniques rely on a number of factors in order to achieve accurate estimates of corneal surface topography. Good tear film quality, minimal reflections from eyelashes, and minimal eye movements are essential for corneal topography estimates to be reliable. However, in practice, these ideal conditions may not always be fulfilled, especially in cases of subjects diagnosed with dry eye syndrome,

David Alonso-Caneiro; D. Robert Iskander; Michael J. Collins

2008-01-01

282

Localized gravity/topography admittance and correlation spectra on Mars: Implications for  

E-print Network

of an elastic/plastic shell. In regions of high topography on Mars (e.g., the Tharsis rise and associated shield volcanoes), the mass-sheet (small-amplitude) approximation for the calculation of gravity from topography are not required to explain the observed admittances for the Tharsis Montes or Olympus Mons volcanoes when

Zuber, Maria

283

Seafloor topography, ocean infragravity waves and background Love and Rayleigh waves  

Microsoft Academic Search

We propose that background Love and Rayleigh waves in a frequency range 5-20 mHz are generated primarily by ocean infragravity waves in the same frequency range by a linear coupling process with seafloor topography. Wavelengths of infragravity waves in this frequency range are on the order of 10 to 40 km in the deep ocean. The seafloor topography with the

Y. Fukao; K. Nishida; N. Kobayashi

2009-01-01

284

Seafloor topography, ocean infragravity waves, and background Love and Rayleigh waves  

Microsoft Academic Search

We propose that background Love and Rayleigh waves in a frequency range 5-20 mHz are generated primarily by ocean infragravity waves in the same frequency range by a linear coupling process with seafloor topography. Wavelengths of infragravity waves in this frequency range are on the order of 10 to 40 km in the deep ocean. The seafloor topography with wavelengths

Yoshio Fukao; Kiwamu Nishida; Naoki Kobayashi

2010-01-01

285

Seafloor topography, ocean infragravity waves, and background Love and Rayleigh waves  

Microsoft Academic Search

We propose that background Love and Rayleigh waves in a frequency range 5–20 mHz are generated primarily by ocean infragravity waves in the same frequency range by a linear coupling process with seafloor topography. Wavelengths of infragravity waves in this frequency range are on the order of 10 to 40 km in the deep ocean. The seafloor topography with wavelengths

Yoshio Fukao; Kiwamu Nishida; Naoki Kobayashi

2010-01-01

286

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

E-print Network

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

Economou, Demetre J.

287

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

Microsoft Academic Search

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

Alistair Adcroft; Chris Hill; John Marshall

1997-01-01

288

Amplitude of the core–mantle boundary topography estimated by stochastic analysis of core phases  

Microsoft Academic Search

The core–mantle boundary (CMB) topography is an important parameter for constraining the models of mantle dynamics and core–mantle coupling. However, the various large wavelength seismological models of the CMB topography, which have been obtained up to now, are poorly correlated. Moreover, their maximum amplitudes vary considerably from one model to another, with values ranging from ±4 to ±12 km. These

R. Garcia; A. Souriau

2000-01-01

289

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

E-print Network

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

Miami, University of

290

Some Bristol Prague explorations in x-ray topography  

NASA Astrophysics Data System (ADS)

This paper briefly chronicles a long-standing and productive collaboration between the Institute of Physics, Czech Academy of Science and the H H Wills Physics Laboratory. It began in early 1962 with a brief visit to Bristol by Milena Polcarová. The initial aim, successfully achieved, was the mapping by transmission topography of dislocations in melt-grown single crystals of a Fe Si alloy. A novel by-product was the x-ray topographic observation of internal magnetic domain structures in specimen plates prepared in both (110) and (112) orientations. In the alloy studied, which contained about 3 wt% Si, the directions of easy magnetization are lang 100 rang, and domain boundaries are either 180° or 90° Bloch walls. The latter walls can generate strong x-ray diffraction contrast, but no contrast from 180° walls is expected. In the (110) plates x-ray topography revealed complex internal domain structures containing 90° walls, some previously unsuspected on evidence of optical micrography of colloid patterns (Bitter patterns). Certain details of these structures remain a puzzle to this day! In (112) specimens, in which no direction of easy magnetization lies in the plate surface, the specimen is filled with a hierarchy of domains, diminishing in scale towards the surfaces in order to minimize magnetostatic energy due to free poles. However, in (112) plate thicknesses less than ~20 µm, x-ray topographs recorded internal domain structures sufficiently uncomplicated for their main features to be interpreted. This was achieved by F C Frank in the early 1960s, but not published till 1993! During a 1968 visit to Bristol by Polcarová it was discovered that under appropriate diffraction conditions x-ray topographic contrast from 180° Bloch walls was just detectable. This finding was not published till 1991. More recent work with Prague specimens has applied synchrotron x-ray reticulography at Daresbury, showing that this technique can be informatively used with lightly-deformed Fe Si bicrystals. A very different enterprise was the Bristol method of producing x-ray moiré patterns by superposing one crystal plate upon another, achieved in 1967. This project gained from Czech collaboration through the skilful participation of J Brádler, on leave from Prague.

Lang, A. R.

2005-05-01

291

Printability of topography in alternating aperture phase-shift masks  

NASA Astrophysics Data System (ADS)

Alternating aperture phase-shift mask (AAPSM) technology in combination with conventional illumination enables the imaging needed in the 65nm node and beyond, thanks to its high image contrast and small mask error factor (MEF). It is a known point of attention that AAPSM topography induces an image intensity imbalance between the light propagating through the zero and pi-shifted space. There are several ways to compensate for such imbalance in the mask making process. The most common approaches are applying an undercut or a bias of the pi-shifted space. The guaranteed quartz etch depth of the pi-shifted space through pitch is another challenge in the mask making process of an AAPSM. This paper reports on the methodology to evaluate the mask making quality of AAPSM for both 193nm and 157nm lithography through printability. For this purpose rigorous electro-magnetic field simulations through the 3D mask topography using Solid-CM (software from Sigma-C) are performed. The parameter for the quantification of the image imbalance is the difference between the measured width of neighbouring zero and pi-shifted spaces on the wafer print. As a first step in the methodology the amount of undercut or bias applied on the mask is deduced from the correlation between the experimentally measured and simulated space difference. Once the amount of undercut or bias is known, the phase error for the evaluated structure is estimated by evaluating the through focus behaviour of the space difference. This gives an indication of the quality of the etch process through pitch during mask making. For the 193nm lithography the wafers are exposed on an ASML PAS5500/1100 ArF scanner working with a 0.75NA projection lens. The 157nm AAPSM masks are printed with an ASML Micrascan VII equipped with a 0.75NA projection lens. The wafers and masks are evaluated on a top-down mask-compatible CD-SEM (KLA-Tencor 8250XR).

Philipsen, Vicky; Jonckheere, Rik

2004-12-01

292

Topography on Titan : New Results on Large and Small Scales  

NASA Astrophysics Data System (ADS)

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).

Lorenz, R. D.; Cassini Radar Team

2011-12-01

293

Observations and HighObservations and High--Resolution Modeling of SmallResolution Modeling of Small--Scale FlowScale Flow--TopographyTopography Interactions Near Caribbean Coral ReefsInteractions Near Caribbean Coral Reefs  

E-print Network

of Small--Scale FlowScale Flow--TopographyTopography Interactions Near Caribbean Coral ReefsInteractions Near Caribbean Coral Reefs Tal Ezer Center for Coastal Physical Oceanography, Old Dominion University-topography interactions near coral reefs off the coast of Belize. Model results show that reefs with a unique shape

Ezer,Tal

294

Contribution of x-ray topography and high-resolution diffraction to the study of defects in SiC  

Microsoft Academic Search

A short review is presented of the various synchrotron white beam x-ray topography (SWBXT) imaging techniques developed for characterization of silicon carbide (SiC) crystals and thin films. These techniques, including back-reflection topography, reticulography, transmission topography, and a set of section topography techniques, are demonstrated to be particularly powerful for imaging hollow-core screw dislocations (micropipes) and closed-core threading screw dislocations, as

Michael Dudley; Xian Rong Huang; William M. Vetter

2003-01-01

295

OCT 3-D surface topography of isolated human crystalline lenses  

PubMed Central

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

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

2014-01-01

296

Interferometric estimation of ice sheet motion and topography  

NASA Technical Reports Server (NTRS)

With ERS-1/2 satellite radar interferometry, it is possible to make measurements of glacier motion with high accuracy and fine spatial resolution. Interferometric techniques were applied to map velocity and topography for several outlet glaciers in Greenland. For the Humboldt and Petermann glaciers, data from several adjacent tracks were combined to make a wide-area map that includes the enhanced flow regions of both glaciers. The discharge flux of the Petermann glacier upstream of the grounding line was estimated, thereby establishing the potential use of ERS-1/2 interferometric data for monitoring ice-sheet discharge. Interferograms collected along a single track are sensitive to only one component of motion. By utilizing data from ascending and descending passes and by making a surface-parallel flow assumption, it is possible to measure the full three-dimensional vector flow field. The application of this technique for an area on the Ryder glacier is demonstrated. Finally, ERS-1/2 interferograms were used to observe a mini-surge on the Ryder glacier that occurred in autumn of 1995.

Joughlin, Ian; Kwok, Ron; Fahnestock, Mark; Winebrenner, Dale; Tulaczyk, Slawek; Gogenini, Prasad

1997-01-01

297

Substrate Topography Determines Neuronal Polarization and Growth In Vitro  

PubMed Central

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

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

2013-01-01

298

Accurate measurements of residual topography from the oceanic realm  

NASA Astrophysics Data System (ADS)

In the oceans, our understanding of plate subsidence as a function of age permits residual depth anomalies to be identified and mapped. These anomalies may reflect dynamic topography and could be an important means for constraining convective circulation of the sublithospheric mantle. Here we analyze a global database of seismic reflection and wide-angle profiles from heavily sedimented oceanic crust, which abuts continental lithosphere. At 449 locations, we calculated water-loaded subsidence, compared it with a reference age-depth relationship, and determined residual depth. We then combined these spot measurements of residual depth with observations from mid-oceanic ridges and from selected ship track bathymetry to construct a global map of residual depth. Our results suggest that the amplitude of residual depth varies by up to ±1 km with wavelengths of order 103 km. We compare our residual depths with free-air gravity and seismic tomographic anomalies. Our results show that residual depths correlate with long-wavelength gravity anomalies. In contrast, correlations between residual depths and vertically averaged shear velocity anomalies within the upper and/or the lower mantle are weaker. The largest discrepancies occur at short (˜1000 km) wavelengths. These combined observations suggest that residual depth anomalies could be generate by density variations within a thin (˜102 km) low-viscosity layer beneath the lithosphere. Our global compilation should play a significant role in helping to refine predictive geodynamical models.

Winterbourne, Jeffrey; White, Nicky; Crosby, Alistair

2014-06-01

299

STS-99 Shuttle Radar Topography Mission Stability and Control  

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

300

Shielded piezoresistive cantilever probes for nanoscale topography and electrical imaging  

NASA Astrophysics Data System (ADS)

This paper presents the design and fabrication of piezoresistive cantilever probes for microwave impedance microscopy (MIM) to enable simultaneous topographic and electrical imaging. Plasma enhanced chemical vapor deposited Si3N4 cantilevers with a shielded center conductor line and nanoscale conductive tip apex are batch fabricated on silicon-on-insulator wafers. Doped silicon piezoresistors are integrated at the root of the cantilevers to sense their deformation. The piezoresistive sensitivity is 2 nm for a bandwidth of 10 kHz, enabling topographical imaging with reasonable speed. The aluminum center conductor has a low resistance (less than 5 ?) and small capacitance (?1.7 pF) to ground; these parameters are critical for high sensitivity MIM imaging. High quality piezoresistive topography and MIM images are simultaneously obtained with the fabricated probes at ambient and cryogenic temperatures. These new piezoresistive probes remarkably broaden the horizon of MIM for scientific applications by operating with an integrated feedback mechanism at low temperature and for photosensitive samples.

Yang, Yongliang; Ma, Eric Yue; Cui, Yong-Tao; Haemmerli, Alexandre; Lai, Keji; Kundhikanjana, Worasom; Harjee, Nahid; Pruitt, Beth L.; Kelly, Michael; Shen, Zhi-Xun

2014-04-01

301

Hydrodynamic modeling for river delta salt marshes using lidar topography  

NASA Astrophysics Data System (ADS)

Topographic data from lidar and multi-beam sonar create new challenges for hydrodynamic models of estuaries, tidelands, and river deltas. We now can readily obtain detailed elevation data on 1 m scales and finer, but solving hydrodynamics with model grid cells at these small scales remains computationally prohibitive (primarily because of the small time step required for small grid cells). Practical estuarine models for the next decade or so will likely have grid scales in the range of 5 to 15 m. So how should we handle known subgrid-scale features? Simply throwing out known data does not seem like a good idea, but there is no consensus on how best to incorporate knowledge of subgrid topography into either hydrodynamic or turbulence models. This presentation discusses both the theoretical foundations for modeling subgrid-scale features and the challenges in applying these ideas in the salt marshes of a river delta. The subgrid problem highlights some important areas for field and laboratory research to provide calibration parameters for new models that upscale the effects of known subgrid features.

Hodges, Ben R.

2014-05-01

302

Surface topography effects in protein adsorption on nanostructured carbon allotropes.  

PubMed

We report a molecular dynamics (MD) simulation study of protein adsorption on the surface of nanosized carbon allotropes, namely single-walled carbon nanotubes (SWNT) considering both the convex outer surface and the concave inner surface, together with a graphene sheet for comparison. These systems are chosen to investigate the effect of the surface curvature on protein adsorption at the same surface chemistry, given by sp(2) carbon atoms in all cases. The simulations show that proteins do favorably interact with these hydrophobic surfaces, as previously found on graphite which has the same chemical nature. However, the main finding of the present study is that the adsorption strength does depend on the surface topography: in particular, it is slightly weaker on the outer convex surfaces of SWNT and is conversely enhanced on the inner concave SWNT surface, being therefore intermediate for flat graphene. We additionally find that oligopeptides may enter the cavity of common SWNT, provided their size is small enough and the tube diameter is large enough for both entropic and energetic reasons. Therefore, we suggest that proteins can effectively be used to solubilize in water single-walled (and by analogy also multiwalled) carbon nanotubes through adsorption on the outer surface, as indeed experimentally found, and to functionalize them after insertion of oligopeptides within the cavity of nanotubes of appropriate size. PMID:23517008

Raffaini, Giuseppina; Ganazzoli, Fabio

2013-04-16

303

Crater topography on Titan: Implications for landscape evolution  

NASA Astrophysics Data System (ADS)

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.

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

304

Display of Magellan SAR and Topography Data in Google Earth  

NASA Astrophysics Data System (ADS)

Much of our understanding of the geodynamics and geology of Venus has been derived from radar imagery and topography from the Magellan mission (NASA 1989-1994). These data were archived at the Planetary Data System (PDS) and are easily and freely available. Unfortunately, the Magellan Venus data are far less accessible than those of the Earth, Mars, and the Moon. Data for these bodies are available via the Google Earth geobrowser, allowing anyone to easily explore the latest imagery and surface information. In an effort to promote public interest in Venus, we have created content for Google Earth that displays three types of information from the Magellan-era. First the FMAP compilation of the Magellan SAR imagery has been assembled into a global overlay image for rapid panning and zooming. Second, the reprocessed altimetry data [Ford and Pettingell, 1992; Rappaport et al. 1999] have been carefully edited and merged with a global spherical harmonic analysis [Wieczorek, 2007] to form a 10-km resolution global DEM of the planet. Finally the IAU feature names along with the content from ``The Face of Venus'' [Roth and Wall, 1995] have been assembled as an overlay to provide basic naming and geology information. A draft version of this material is available by adding this Network Link in Google Earth: http://byss.arc.nasa.gov/ge-venus/venus.kml. We welcome comments and suggestions on how to best represent Venus data for the public

Beyer, R. A.; Mehnert, E.; Sandwell, D. T.; Kolb, E.; Austin Foulkes, J.; Schwehr, K.; Johnson, C. L.

2012-12-01

305

Corneal topography reinterpretation through separate analysis of the projected rings  

NASA Astrophysics Data System (ADS)

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.

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

2012-06-01

306

Wide-angle cornea-sclera (OCULAR) topography  

NASA Astrophysics Data System (ADS)

Most corneal topographers are slope-based instruments, measuring corneal slope based on light reflected by the cornea acting as a mirror. This mirror method limits corneal coverage to about 9 mm diameter. Both refractive surgery and contact lens fitting actually require a larger coverage than is obtainable using slope-based instruments. Height-based instruments should be able to measure a cornea/sclera area that is twice the size (four times the area) of slope-based topographers with an accuracy of a few microns. We have been testing a prototype of a new model height-based topographer manufactured by Euclid Systems. We find that single shots can produce a corneal coverage of up to 16 mm vertical and 20 mm horizontal. The heights and slopes in the corneal region have good replicability. Although the scleral region is noisier, it is the only topographer available able to measure scleral topography that is critically important to contact lens fitting. There are a number of improvements to the Euclid software and hardware that would enable it to fill an important niche in eye care and eye research.

Klein, Stanley A.; Corzine, John; Corbin, Jacob A.; Wechsler, Sheldon; Carney, Thom

2002-06-01

307

Paleoyardangs: wind-scoured topography at Permian unconformity  

SciTech Connect

At least 28 elongate, parallel ridges exhibiting 5-14 m of positive relief are preserved on the upper surface of the White Rim Sandstone (Permian) near its eastern stratigraphic pinch-out in Canyonlands National Park, southeastern Utah. The ridges show extreme consistency in size, shape, and directional trend. Ridges average 250 m in width, are less than one to possibly several kilometers in length, and trend N20/degree/W /plus minus/ 5/degree/. Ridge flanks dip as steeply as 30/degree/ and are commonly covered with a thin lag of coarse sand. Sand-filled polygonal fissures are abundant on ridges and intervening flats. The unimodal southeastward dip of the cross-strata within the White Rim and the relationship between eolian bounding surfaces and ridge morphology negate a depositional origin for the ridges. The presence of lag grains within polygonal fissures indicates that the lithification required for fissuring took place prior to deposition of the lag. The authors interpret the ridges as paleoyardangs that were shaped from partially lithified eolian sand by the same unidirectional winds that prevailed during deposition. Similar wind-eroded topography has been repeatedly documented from modern hyperarid regions with unimodal winds but has not been previously described from the stratigraphic record. Wind erosion as well as deposition must be considered when investigating ancient eolian sequences.

Tewes, D.W.; Loope, D.B.

1989-03-01

308

Automated object-based classification of topography from SRTM data  

PubMed Central

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. PMID:22485060

Dragut, Lucian; Eisank, Clemens

2012-01-01

309

Contact Line Pinning by Microfabricated Patterns: Effects of Microscale Topography  

PubMed Central

We study how the microscale topography of a solid surface affects the apparent advancing and receding angles at the contact line of a liquid drop pinned to this surface. Photolithographic methods are used to produce continuous circular polymer rings of varying cross-sectional size and shape on hydrophilic silicon wafer surfaces. Drops of water and glycerol are dispensed into the areas bounded by these rings, and critical apparent advancing and receding angles are measured and correlated with the parameters that characterize the ring cross-section. For much of the examined parameter space, the apparent critical angles are independent of ring height and width and are determined primarily by the slope of the ring's sidewalls, consistent with a model due to Gibbs. For ring heights below a few micrometers, the critical angles decrease below the values predicted by the sidewall slopes alone. These results provide data for calculation of hysteresis on naturally rough surfaces, and demonstrate a simple method for controlling and enhancing contact line pinning on solid surfaces. PMID:19317420

Kalinin, Yevgeniy V.; Berejnov, Viatcheslav; Thorne, Robert E.

2010-01-01

310

Relative effects of wind stress curl, topography, and stratification on large-scale circulation in Lake Michigan  

E-print Network

, topography, and stratification on large-scale circulation in Lake Michigan, J. Geophys. Res., 108(C2), 3044, topography, and stratification on large- scale circulation in the Great Lakes and other water bodies. The RaoRelative effects of wind stress curl, topography, and stratification on large-scale circulation

311

Lexicometrica : Topographie et topologie textuelles, 2007 L'analyse de donnes textuelles aujourd'hui : du corpus comme  

E-print Network

Lexicometrica : Topographie et topologie textuelles, 2007 L'analyse de données textuelles aujourd'hui : du corpus comme une urne au corpus comme un plan. Retour sur les travaux actuels de topographie/topologie préoccupations fondamentales. MOTS-CLES : topologie textuelle, topographie textuelle, statistique textuelle, ADT

Paris-Sud XI, Université de

312

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

NASA Technical Reports Server (NTRS)

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.

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

1997-01-01

313

Measurement of fine dynamic changes of corneal topography by use of interferometry  

NASA Astrophysics Data System (ADS)

Paper presents results of in vivo measurements of dynamic variations of the corneal topography by use of the Twyman Green interferometer. Sequence of interferograms were recorded by the CCD camera and stored in the computer memory. Then the fringe tracking method was used separately to each interferogram giving the phase surface of the wave reflected from the cornea in the numerical form. Results from neighboring interferograms were subtracted giving new sequence of changes of the corneal topography within 40 ms. Obtained results show the complex space distribution of the corneal topography variations.

Kasprzak, Henryk T.; Jaronski, Jaroslaw W.

2002-06-01

314

Vegetation-precipitation controls on Central Andean topography  

NASA Astrophysics Data System (ADS)

controls on fluvial landscapes are commonly characterized in terms of mean annual precipitation. However, physical erosion processes are driven by extreme events and are therefore more directly related to the intensity, duration, and frequency of individual rainfall events. Climate also influences erosional processes indirectly by controlling vegetation. In this study, we explore how interdependent climate and vegetation properties affect landscape morphology at the scale of the Andean orogen. The mean intensity, duration, and frequency of precipitation events are derived from the TRMM 3B42v7 product. Relationships between mean hillslope gradients and precipitation event metrics, mean annual precipitation, vegetation, and bedrock lithology in the central Andes are examined by correlation analyses and multiple linear regression. Our results indicate that mean hillslope gradient correlates most strongly with percent vegetation cover (r = 0.56). Where vegetation cover is less than 95%, mean hillslope gradients increase with mean annual precipitation (r = 0.60) and vegetation cover (r = 0.69). Where vegetation cover is dense (>95%), mean hillslope gradients increase with increasing elevation (r = 0.74), decreasing inter-storm duration (r = -0.69), and decreasing precipitation intensity by ~0.5°/(mm d-1) (r = -0.56). Thus, we conclude that at the orogen scale, climate influences on topography are mediated by vegetation, which itself is dependent on mean annual precipitation (r = 0.77). Observations from the central Andes are consistent with landscape evolution models in which hillslope gradients are a balance between rock uplift, climatic erosional efficiency and erosional resistance of the landscape determined by bedrock lithology and vegetation.

Jeffery, M. Louise; Yanites, Brian J.; Poulsen, Christopher J.; Ehlers, Todd A.

2014-06-01

315

Erosion of Terrestrial Rift Flank Topography: A Quantitative Study  

NASA Technical Reports Server (NTRS)

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.

Weissel, Jeffrey K.

1999-01-01

316

Optical fiber arrangement of optical topography for spatial resolution improvement  

NASA Astrophysics Data System (ADS)

In medical instrumentation, optical topography (OT) refers to the use of near-infrared spectroscopy for measuring brain function in systems. Arrays of optical fibers are attached to the scalps of subjects; infrared light is passed through the fibers, and changes in the reflections depict blood-volume changes in the cortex. In this study, the spatial resolution and locational accuracy of topographical images obtained by three arrangements of optical fibers was analyzed through simulation. Three arrangements, a "lattice arrangement" (LA), "double-density arrangement" (DA), and "quadruple density arrangement" (QA) were investigated. The density of spatial-sapling points is higher in the DA and QA than in the LA, i.e. the distance between sampling points for these arrangements were 21, 15 and 11 mm, respectively. The efficacy of these arrangements was evaluated. An adult head-structure phantom was prepared. The absorption coefficient in the phantom was varied to simulate brain activation in the cortex, and the resulting absorbance change (?OD) was thus obtained. The 'activated' area in the overall measurement area was fixed and the ?OD at each of the sampling point in each arrangement was obtained. The resulting distributions of ?OD were spatially interpolated to obtain topographical images. The spatial resolution and locational accuracy was obtained for each of the images; the results indicated that the DA is the most efficacious of the three arrangements. An experimental DA-OT system was then built. Topographical images of motor-function activation obtained by this system and a commercial LA-based system were compared; the DA-OT system provided the higher spatial resolution.

Yamamoto, Tsuyoshi; Okada, Eiji; Kawaguchi, Fumio; Maki, Atsushi; Yamada, Yukio; Koizumi, Hideaki

2003-07-01

317

Mapping the Topography of Mercury with MESSENGER Laser Altimetry  

NASA Technical Reports Server (NTRS)

The Mercury Laser Altimeter onboard MESSENGER involves unique design elements that deal with the challenges of being in orbit around Mercury. The Mercury Laser Altimeter (MLA) is one of seven instruments on NASA's MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft. MESSENGER was launched on 3 August 2004, and entered into orbit about Mercury on 18 March 2011 after a journey through the inner solar system. This involved six planetary flybys, including three of Mercury. MLA is designed to map the topography and landforms of Mercury's surface. It also measures the planet's forced libration (motion about the spin axis), which helps constrain the state of the core. The first science measurements from orbit taken with MLA were made on 29 March 2011 and continue to date. MLA had accumulated about 8.3 million laser ranging measurements to Mercury's surface, as of 31 July 2012, i.e., over six Mercury years (528 Earth days). Although MLA is the third planetary lidar built at the NASA Goddard Space Flight Center (GSFC), MLA must endure a much harsher thermal environment near Mercury than the previous instruments on Mars and Earth satellites. The design of MLA was derived in part from that of the Mars Orbiter Laser Altimeter on Mars Global Surveyor. However, MLA must range over greater distances and often in off-nadir directions from a highly eccentric orbit. In MLA we use a single-mode diode-pumped Nd:YAG (neodymium-doped yttrium aluminum garnet) laser that is highly collimated to maintain a small footprint on the planet. The receiver has both a narrow field of view and a narrow spectral bandwidth to minimize the amount of background light detected from the sunlit hemisphere of Mercury. We achieve the highest possible receiver sensitivity by employing the minimum receiver detection threshold.

Sun, Xiaoli; Cavanaugh, John F.; Neumann, Gregory A.; Smith, David E..; Zubor, Maria T.

2012-01-01

318

High Resolution Global Topography of Itokawa from Hayabusa Imaging and LIDAR Data  

NASA Technical Reports Server (NTRS)

This viewgraph document reviews the topography of the Itokawa asteroid. It summarizes some of the relevant information about the asteroid, and how using the imaging from Hayabusa and LIDAR data, a topographic image of Itokawa was derived.

Gaskell, Robert W.; Barnouin-Jha, O. S.; Scheeres, D. J.; Mukai, T.; Hirata, N.; Abe, S.; Saito, J.; Hashimoto, T.; Ishiguro, M.; Kubota, T.

2006-01-01

319

OROGRAPHIC PRECIPITATION Precipitation that has been generated or modified by topography, typically through the forcing of  

E-print Network

physical processes controlling orographic precipitation, and the observational and modeling techniquesOROGRAPHIC PRECIPITATION Precipitation that has been generated or modified by topography, typically rainfall). Orographic effects on precipitation are also responsible for some of the planet's sharpest

Roe, Gerard

320

Tectonics of the Tharsis Region of Mars: Insights from MGS Topography and Gravity  

NASA Technical Reports Server (NTRS)

We have investigated the Tharsis region using gravity, topography, and geology to constrain a spherical thin shell model. We find that Tharsis likely formed primarily by volcanic construction, and has been largely unchanged since the Noachian.

Banerdt, W. Bruce; Golombek, Matthew P.

2000-01-01

321

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

E-print Network

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 ...

Assimaki, Dominic, 1975-

2004-01-01

322

Relationships Between Pahoehoe Surface Texture, Topography, and Lava Tubes at Mauna Ulu, Kilauea Volcano, Hawaii  

Microsoft Academic Search

GIS analysis of the Mauna Ulu compound flow field demonstrates that the distribution of pahoehoe surface textures is related to pre-flow topography and not directly dependent on the major lava tube network.

J. M. Byrnes; D. A. Crown

1999-01-01

323

Not All Ponds are Flat: A Stereophotoclinometric Analysis of Eros Topography  

NASA Astrophysics Data System (ADS)

We investigate the topography of ponds on Eros, using a new shape model derived from sterophotoclinometric analysis. We find that a significant fraction (~75%) of ponds do not have flat floors, and evaluate hypotheses for pond formation.

Roberts, J. H.; Barnouin, O. S.; Prockter, L. M.; Kahn, E. G.; Gaskell, R. W.

2012-03-01

324

Puffing Topography and Interpersonal Bonding Behavior Observed Among Recovering Drug Addicts Versus General Smokers  

E-print Network

) and Intensive Outpatients (IOP). PHP and IOP form tight interpersonal bonds and friendships with each other of smoking behavior may be determined by using complex forms of smoking topography in laboratory settings

Zhou, Yaoqi

325

INFLUENCE OF VEGETATION, TOPOGRAPHY, AND ROADS ON COUGAR MOVEMENT IN SOUTHERN CALIFORNIA  

E-print Network

- nivore studies. We examined the movements of 10 female and 7 male cougars (Puma concolor) at 15-min, cougar, habitat selection, movement, prey trap, Puma concolor, ripar- ian, roads, scale, topography

Beier, Paul

326

Global dynamic topography at very-high resolution for Geohazards, Climate Change and Vulnerability mapping  

E-print Network

the mission life-time > Monitor seasonnal 3D topography dynamics > Instrument · Combination of active the time, nor everywhere · Optical system impeded by clouds ­ Orbits minimize cloud potential (local time

Berthier, Etienne

327

Study of the tear topography dynamics using a lateral shearing interferometer  

NASA Astrophysics Data System (ADS)

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.

Dubra, Alfredo; Paterson, Carl; Dainty, Christopher

2004-12-01

328

Corneal topography measurement by means of radial shearing interference: Part II - experiment results  

NASA Astrophysics Data System (ADS)

The method of the measurement of the corneal topography was worked out. This measurement system uses an interferometer based on radial shearing. This paper presents the preliminary results of the experiments. The results are compared with other methods.

Garncarz, Beata E.; Kowalik, Waldemar W.; Kasprzak, Henryk T.

329

Corneal topography measurement of the eye by means of radial shearing interferometer  

NASA Astrophysics Data System (ADS)

The method of the measurement of the corneal topography was worked out. This measurement system uses an interferometer based on radial shearing. This paper presents the preliminary results of the experiments. The results are compared with other methods.

Kowalik, Waldemar; Garncarz, Beata E.; Kasprzak, Henryk T.

2001-03-01

330

Ultrastructure of Epicorneal Topography and Morphogenesis in Insects with Aspects on Phylogenesis and Function.  

National Technical Information Service (NTIS)

The review is based upon the studies described in the following articles: Ontogenesis of corneal surface ultrastructure in nocturnal Lepidoptera; Comparative ultrastructure of corneal surface topography in insects with aspects on phylogenesis and function...

G. Gemne

1970-01-01

331

Corneal thickness measurements: scanning-slit corneal topography and noncontact specular microscopy versus ultrasonic pachymetry  

Microsoft Academic Search

PurposeTo compare central corneal thickness measurements taken with 3 pachymetry systems: Orbscan scanning-slit corneal topography\\/pachymetry, Topcon SP2000P noncontact specular microscopy, and Tomey ultrasonic pachymetry.

Shigenobu Suzuki; Tetsuro Oshika; Kotaro Oki; Isao Sakabe; Aiko Iwase; Shiro Amano; Makoto Araie

2003-01-01

332

Large Volcanic Edifices and Rises on Venus: The Benefits of Improved Topography and Gravity Data  

NASA Astrophysics Data System (ADS)

Venus is a volcanological laboratory, replete with edifices and rises that offer potentially deep insights into its evolution. However, this potential can only be realized with improved topography and gravity data, requiring a new orbital mission.

McGovern, P. J.

2014-05-01

333

The role of background flow variations in stratified flows over topography  

E-print Network

As the atmosphere and oceans feature density variations with depth, the flow of a density-stratified fluid over topography is central to various geophysical and meteorological applications and has been studied extensively. ...

Skopovi, Ivan, 1976-

2006-01-01

334

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

NASA Astrophysics Data System (ADS)

Geostrophic surface velocities can be derived from the gradients of the mean dynamic topography—the difference between the mean sea surface and the geoid. Therefore, independently observed mean dynamic topography data are valuable input parameters and constraints for ocean circulation models. For a successful fit to observational dynamic topography data, not only the mean dynamic topography on the particular ocean model grid is required, but also information about its inverse covariance matrix. The calculation of the mean dynamic topography from satellite-based gravity field models and altimetric sea surface height measurements, however, is not straightforward. For this purpose, we previously developed an integrated approach to combining these two different observation groups in a consistent way without using the common filter approaches (Becker et al. in J Geodyn 59(60):99-110, 2012; Becker in Konsistente Kombination von Schwerefeld, Altimetrie und hydrographischen Daten zur Modellierung der dynamischen Ozeantopographie 2012). Within this combination method, the full spectral range of the observations is considered. Further, it allows the direct determination of the normal equations (i.e., the inverse of the error covariance matrix) of the mean dynamic topography on arbitrary grids, which is one of the requirements for ocean data assimilation. In this paper, we report progress through selection and improved processing of altimetric data sets. We focus on the preprocessing steps of along-track altimetry data from Jason-1 and Envisat to obtain a mean sea surface profile. During this procedure, a rigorous variance propagation is accomplished, so that, for the first time, the full covariance matrix of the mean sea surface is available. The combination of the mean profile and a combined GRACE/GOCE gravity field model yields a mean dynamic topography model for the North Atlantic Ocean that is characterized by a defined set of assumptions. We show that including the geodetically derived mean dynamic topography with the full error structure in a 3D stationary inverse ocean model improves modeled oceanographic features over previous estimates.

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

2014-11-01

335

Push in South of the Hellas Basin Showing Topography from MOLA: New Color Map  

NSDL National Science Digital Library

Zoom into the region of Mars just south of the Hellas Basin showing topography data from MOLA. This animation uses a color table designed to highlight the topography at the south pole. White colors indicate elevations in excess of 3012 meters, red shows elevations between 2500 and 3012 meters, yellow shows elevations from 2450 to 2500 meters, dark cyan shows elevations from 2150 to 2450 meters, dark violet shows elevations from 320 to 2150 meters.

Biddlecome, Tom; Smith, David

1999-11-22

336

Plane-wave x-ray topography and its application to semiconductor problems  

Microsoft Academic Search

The applications of x-ray topography as compared to other imaging techniques are briefly discussed and the general advantages of plane-wave topography in comparison with other x-ray topographic techniques are outlined. These advantages are then illustrated by a number of examples including selected area epitaxy, device structures, processing and mismatch dislocations. The latter is demonstrated for the case of an in

1999-01-01

337

Single crystal diamond study with rotating anode x-ray topography  

Microsoft Academic Search

Synthetic high-temperature-high-pressure diamond crystals of type Ib having (100) and (111) surface orientations were studied using x-ray topography method. An asymmetrically cut monochromator was applied to expand the x-ray beam from a rotating anode source up to 70mm. Double crystal rocking curve measurements were performed on each crystal and the topography images were taken at each position on rocking curve.

Yuncheng Zhong

2005-01-01

338

Analysis of the SAW propagation in langasite crystal by X-ray topography  

Microsoft Academic Search

X-ray Bragg diffraction on the X, Y, and (011) cuts of a langasite crystal (La3Ga5SiO14, LGS) modulated by a Rayleigh surface acoustic wave (SAW) has been studied using a high-resolution X-ray topography method. This X-ray topography technique was used for direct imaging of the standing SAW in LGS, to measure the SAW amplitudes and power flow angles, to visualize the

D. V. Roshchupkin; H. D. Roshchupkina; D. V. Irzhak; O. A. Buzanov

2004-01-01

339

Forced solitary Rossby waves under the influence of slowly varying topography with time  

NASA Astrophysics Data System (ADS)

By using a weakly nonlinear and perturbation method, the generalized inhomogeneous Korteweg—de Vries (KdV)—Burgers equation is derived, which governs the evolution of the amplitude of Rossby waves under the influence of dissipation and slowly varying topography with time. The analysis indicates that dissipation and slowly varying topography with time are important factors in causing variation in the mass and energy of solitary waves.

Yang, Hong-Wei; Yin, Bao-Shu; Yang, De-Zhou; Xu, Zhen-Hua

2011-12-01

340

Corneal topography in asymptomatic family members of a patient with pellucid marginal degeneration  

Microsoft Academic Search

PURPOSE: To report corneal topographic patterns in asymptomatic family members of a patient with pellucid marginal degeneration.METHODS: Computer-assisted corneal topography was used to study the corneas of five family members of a patient with pellucid marginal degeneration.RESULTS: In all five asymptomatic family members, corneal biomicroscopy was normal. Corneal topography, however, showed various abnormalities in different members of this family, particularly

Ruth M Santo; Samir J Bechara; Newton Kara-José

1999-01-01

341

Emmetropisation, axial length, and corneal topography in teenagers with Down’s syndrome  

Microsoft Academic Search

AIMTo study the refractive status and corneal topography in Down’s syndrome.METHODA matched cohort subgroup of 50 individuals with Down’s syndrome in the Manchester area aged 15–22 years was studied by refraction, corneal topography, A-scan biometry, slit lamp examination, and orthoptic examination.RESULTS(1) A linear relation was found between axial length and spherical equivalent refraction. There was no statistical relation between keratometry

Stephen J Doyle; John Bullock; Cath Gray; Alison Spencer; Cliff Cunningham

1998-01-01

342

High Resolution Topography Analysis on Threading Edge Dislocations in 4H-SiC Epilayers  

SciTech Connect

Threading edge dislocations (TEDs) in a 4H-SiC epitaxial layer are investigated using high-resolution synchrotron topography. Six types of TED image are confirmed to correspond to the Burgers vector directions by a comparison of computer simulated images and observed topography images in crystal boundaries. Using a mapping method, a wide spatial distribution of the six types of TED is examined in a quarter section of a 2-inch wafer.

Kamata, I.; Nagano, M; Tsuchida, H; Chen, Y; Dudley, M

2009-01-01

343

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

NSDL National Science Digital Library

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.

Alpha, Tau; Galloway, John; Tinsley, John

344

Insect Wing Membrane Topography Is Determined by the Dorsal Wing Epithelium  

PubMed Central

The Drosophila wing consists of a transparent wing membrane supported by a network of wing veins. Previously, we have shown that the wing membrane cuticle is not flat but is organized into ridges that are the equivalent of one wing epithelial cell in width and multiple cells in length. These cuticle ridges have an anteroposterior orientation in the anterior wing and a proximodistal orientation in the posterior wing. The precise topography of the wing membrane is remarkable because it is a fusion of two independent cuticle contributions from the dorsal and ventral wing epithelia. Here, through morphological and genetic studies, we show that it is the dorsal wing epithelium that determines wing membrane topography. Specifically, we find that wing hair location and membrane topography are coordinated on the dorsal, but not ventral, surface of the wing. In addition, we find that altering Frizzled Planar Cell Polarity (i.e., Fz PCP) signaling in the dorsal wing epithelium alone changes the membrane topography of both dorsal and ventral wing surfaces. We also examined the wing morphology of two model Hymenopterans, the honeybee Apis mellifera and the parasitic wasp Nasonia vitripennis. In both cases, wing hair location and wing membrane topography are coordinated on the dorsal, but not ventral, wing surface, suggesting that the dorsal wing epithelium also controls wing topography in these species. Because phylogenomic studies have identified the Hymenotera as basal within the Endopterygota family tree, these findings suggest that this is a primitive insect character. PMID:23316434

Belalcazar, Andrea D.; Doyle, Kristy; Hogan, Justin; Neff, David; Collier, Simon

2013-01-01

345

Topography within the axial channels of Monterey and Soquel Canyons  

NASA Astrophysics Data System (ADS)

Ultrahigh resolution surveys have been conducted that outline the topography and near seafloor structure within the axial channels of Monterey and Soquel Canyons. Multibeam bathymetry (vertical precision of 0.15 m and horizontal resolution of 1.0 m at 50 m survey altitude) were collected using an autonomous underwater vehicle (AUV). An inertial navigation system combined with a doppler velocity sonar allows the AUV to fly through the sinuous canyons at 3 knots on a pre-programmed route while maintaining an altitude of 50 m above the bottom. The AUV has flown down through the sinuous canyons, passed where they join, to 1,900 m water depths, and obtained three or more overlapping swaths covering the axial channel floor and some of its adjacent flanks. One feature revealed in the multibeam bathymetry data are wave-like bedforms with wavelengths of 20 to 100 m and amplitudes up to 2.5 m oriented roughly perpendicular to the channel axis. These bedforms occur throughout the channel of Monterey Canyon. They are asymmetric with a steep face on the down-canyon side while the other face is nearly horizontal or dips up-canyon, and form crescent-shaped ridges oriented down-canyon. Combined with previous mapping of the upper end of Monterey Canyon by CSUMB, we now know that these features extend between 11 m and >1900 m water depths in Monterey Canyon. Repeat mapping shows that these bedforms change position between surveys. Sediment coring and experiments to track seafloor motion show that these changes occur during discrete mass transport events. In contrast the seafloor within the axis of Soquel Canyon is smooth. Chirp profiler data collected simultaneously with the multibeam data failed to resolve sub-bottom structures within the floor of Monterey Canyon, but show that the floor of Soquel Canyon contains up to15 m of horizontally layered fill. These differences are attributed to the processes within an active (e.g., Monterey) versus inactive (e.g., Soquel) submarine canyon and are hypothesized to be associated with the nature of the fill (cohesion-less sand and gravel versus cohesive fine sediments) within these canyons.

Lundsten, E.; Paull, C. K.; Caress, D. W.; Ussler, W.; Thomas, H.

2009-12-01

346

Jet Formation Mechanisms in the presence of Topography  

NASA Astrophysics Data System (ADS)

Despite over 35 years of discussion, there still remain a range of theories describing the formation of jets on a beta plane. One such theory, first proposed by Rhines (1975), is that jets form as a result of an inverse cascade of energy that is halted by the excitation of Rossby waves. We present the results of an investigation in which we attempt to apply this theory to the case of tilted jets forming over a uniform slope in bottom topography in a quasi-geostrophic, two-layer, doubly periodic model. The forms of the Rossby wave frequencies of this system depend on the Rossby deformation radius, and have two limits: a shortwave limit in which the two frequencies are the equivalent layer-wise frequencies, and orientated with the layer-wise PV gradients; and a longwave limit in which the two frequencies are barotropic- and baroclinic-like, and orientated with the barotropic PV gradient. Freely decaying simulations of the system show that the anisotropy of the frequencies successfully predicts the orientation of the jets that form, which are found to be decoupled and follow layer-wise PV gradients in the shortwave limit, and to be coupled and follow the barotropic PV gradient in the longwave limit. Introducing shear and bottom friction does not change the qualitative form of the Rossby wave frequencies, but due to the forcing by baroclinic instability occurring close to the deformation radius, all such quasi-equilibrated simulations are in the longwave limit and jets follow the barotropic PV gradient. However, only some simulations demonstrate the predicted inverse cascade and associated cascade barrier. Other simulations do not have a well developed inverse cascade, and yet still show jet formation. Previous studies have also shown that significant non-local transfers of energy occur in quasi-geostrophic systems with jets, which suggests a richer picture of jet formation. We thus propose that Rossby waves provide a barrier to further energy transfer, and their anisotropy predicts the jet orientation, but that the energy transfer does not necessarily take the form of an inverse cascade. This work is a significant step towards understanding the formation of jets in quasi-geostrophic turbulence, and is also of relevance to the regions of the ocean where strong non-zonal jets are present.

Boland, Emma; Haynes, Peter; Shuckburgh, Emily

2013-04-01

347

Gravity, Topography, and Magnetic Field of Mercury from Messenger  

NASA Technical Reports Server (NTRS)

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

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

2012-01-01

348

Intraplate Seismicity, Oceanic Basement Topography and Marine Gravity  

NASA Astrophysics Data System (ADS)

The in traplate seismicity that affects the ocean seaf loor is poorly known, while it is of critical importance to understand th e thermal structur e of the oceanic lithospher e and assess th e pecularities - if any - of the earthquake g eneration processes in submarin e env ironmen ts. T-waves generated by submarine earthquak es can propagate almost w ithout attenuation in the SOFA R (Sound Fixing And Rang ing) channel, as f ar as a few thousands kilometers aw ay from th e epicenter. Hydrophones arrays have thus been recently used to detect small- magnitude earthquakes (Ms<3) that are undetectable or impr ecisely located by land-based seismolog ical n etworks, providing unpreceden ted data and new insights on the low-level seismicity of the oceanic lithosphere, over areas extend ing over a few millions squar e kilometers. However, to fu lly intr epret hydrophone arrays, it is necessary to recogn ize the tectonic environmen t near the ep icenter, using structural maps of the seafloor. Marine gr avity and bathymetry der ived from satellite altimetry ar e, to date, the only means to improve th is knowledg e at a global scale, esp ecially in th e r emotest areas of the world's ocean s,for at least two reasons : 1) deep seaf loor areas w ill not be exhaustively surveyed with shipboard mu ltibeam systems in a foreseeab le future ; 2) some ar eas, such as for instan ce,th e Centr al Indian O cean Basin, where a very active intrap late seismicity occurs, are thick ly cover ed with sediments. Marine gravity thus remains the only w ay to map the structure of the rough igneous at a b asin scale. Here, we pr esen t some examp les showing the benefit that would be gained by improving the resolution of satellite der ived models of mar ine gravity and bathymetry in deriv ing a detailed basement topography grid. Such a gr id would in turn represen t a most v alu able framework to study intrap late seismicity from the interpretation of hydrophone acoustic data. Th ese ex amples concern the study of : intrap late seismicity within the Indian Ocean through th e ION ETH Project intrap late seismicity within the North Atlantic Ocean seismic precursors prior to large earthquak es at ocean ic fr acture zones the rheology of the o ceanic lithosphere

Géli, L.; Royer, J.-Y.; Goslin, J.; Dziak, R. D.

2006-07-01

349

Modeling the effects of bed topography on fluvial bedrock erosion by saltating bed load  

NASA Astrophysics Data System (ADS)

Abrasion by saltation is an important mechanism of fluvial incision into bedrock. Sklar and Dietrich (2004) introduced an abrasion model in which the erosion rate of an "approximately planar" bed is linearly dependent on the kinetic energy transferred by the vertical velocity of saltating grains. However, most bedrock-floored channels exhibit topographic variations that yield deviations from a planar surface, referred to as "bed topography." Observations show that bed topography affects erosion. Here the saltation-abrasion model is extended for a nonplanar bed. A several-centimeter high bump, transverse to the flow, is repeated every 50 cm. The kinetic energy of grain impacts is calculated in two ways: (1) impact velocity normal to bed topography and (2) vertical impact velocity. By comparing the latter case with the planar model, it is possible to isolate the effects of topography on the interception of saltation trajectories. Incorporating bed topography changes erosion in three ways. First, erosion is 10 to 1000 times faster, depending upon transport stage and grain size. Enhanced erosion results from both the interception of grains by topography and the increased kinetic energy transfer associated with high-angle impacts on the stoss side of bumps. Second, erosion increases monotonically with transport stage, whereas maximum erosion occurs at low to intermediate transport stage with a planar bed. Third, erosion decreases monotonically with grain size, whereas maximum erosion occurs with intermediate-sized grains with a planar bed. Although the model is highly simplified, results show that bed topography should be considered when simulating erosion of bedrock.

Huda, Shahen A.; Small, Eric E.

2014-06-01

350

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

NASA Technical Reports Server (NTRS)

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.

Bryan, J.; Rabine, David L.

1998-01-01

351

Estimating Vegetation Height and Bare-Earth Topography from SRTM Data using Fourier Spectral Decomposition  

NASA Astrophysics Data System (ADS)

In this study, LiDAR vegetation topography (bare-earth + vegetation height), LiDAR bare-earth topography, the National Elevation Data (NED) set, and Shuttle Radar Terrain Mission (SRTM) measurements are used to develop a statistical model to explore the possibility of extracting vegetation height measurements and accurate high resolution bare-earth topography from SRTM data. The key innovation is to obtain the statistical signature of the vegetation height measurements in the Fourier domain by taking advantage of the well-known linearity in additive properties of the Fourier transform. We demonstrate that the power-law relationship, P(k) ? k^(-?), as shown by the bare-earth topography, breaks down approximately at a cross-over wavenumber, k=k_c, due to the vegetation height effect using four different topographic and vegetation study locations in the United States. We document that the vegetation effect mainly dominates the high-frequency contents of the vegetation topography from 2-180 m, 1-60 m, and 1-70 m for the South Fork Eel River, California; Flathead Lake, Montana; and Tenderfoot Creek, Montana, LiDAR data, respectively, and from 1-240 m for 30 m SRTM data for the Jesup, Georgia site. Finally, we demonstrate our ability to obtain a high resolution bare-earth topography with RMSE of 9.6 m, 2.2 m, and 2.9 m and vegetation height with RMSE of 11.0 m (11% error), 4.5 m (12% error), and 1.6 m (8% error) for LiDAR data study sites, whereas for the SRTM data, bare-earth topography and vegetation height are obtained with RMSE values of 5.4 m and 3.1 m, respectively, for the Jesup site. Model Vegetation height

Gangodagamage, C.; Liu, D.; Alsdorf, D.

2010-12-01

352

SWOT, The Surface Water and Ocean Topography Satellite Mission (Invited)  

NASA Astrophysics Data System (ADS)

Surface fresh water is essential for life, yet we have surprisingly poor knowledge of its variability in space and time. Similarly, ocean circulation fundamentally drives global climate variability, yet the ocean current and eddy field that affects ocean circulation and heat transport at the sub-mesoscale resolution and particularly near coastal and estuary regions, is poorly known. About 50% of the vertical exchange of water properties (nutrients, dissovled CO2, heat, etc) in the upper ocean is taking place at the sub-mesoscale. Measurements from the Surface Water and Ocean Topography satellite mission (SWOT) will make strides in understanding these processes and improving global ocean models for studying climate change. SWOT is a swath-based interferometric-altimeter designed to acquire elevations of ocean and terrestrial water surfaces at unprecedented spatial and temporal resolutions. The mission will provide measurements of storage changes in lakes, reservoirs, and wetlands as well as estimates of discharge in rivers. These measurements are important for global water and energy budgets, constraining hydrodynamic models of floods, carbon evasion through wetlands, and water management, especially in developing nations. Perhaps most importantly, SWOT measurements will provide a fundamental understanding of the spatial and temporal variations in global surface waters, which for many countries are the primary source of water. An on-going effort, the “virtual mission” (VM) is designed to help constrain the required height and slope accuracies, the spatial sampling (both pixels and orbital coverage), and the trade-offs in various temporal revisits. Example results include the following: (1) Ensemble Kalman filtering of VM simulations recover water depth and discharge, reducing the discharge RMSE from 23.2% to 10.0% over an 84-day simulation period, relative to a simulation without assimilation. (2) Ensemble-based data assimilation of SWOT like measurements yields bathymetric slope and depth to within 3.0 microradians and 50 cm, respectively. (3) SWOT measurements of storage changes in lakes larger than 1 km2 will have relative errors generally less than 5% whereas errors for one-hectare size lakes will be about 20%. (4) SWOT estimates of discharge compared to a one-year model-based “truth” data set suggest that instantaneous discharge estimates will have a median relative RMSE of 10.9% and that 86% of all instantaneous errors will be less than 25%. (5) Based on a global distribution of gauge-based discharge and candidate SWOT orbits with varying spatial and temporal sampling, SWOT errors in instantaneous discharge will be less than 25% for rivers wider than 50 m, whereas errors in monthly discharge will be less than 20% for rivers with drainage areas larger than 7000 km2. (6) We estimate that currently available satellite nadir altimetry data cannot monitor more than 15% of the global lake volume variation, whereas from 50% to more than 65% of the global lake volume variation will be observed by SWOT.

Alsdorf, D.; Andreadis, K.; Bates, P. D.; Biancamaria, S.; Clark, E.; Durand, M. T.; Fu, L.; Lee, H.; Lettenmaier, D. P.; Mognard, N. M.; Moller, D.; Morrow, R. A.; Rodriguez, E.; Shum, C.

2009-12-01

353

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

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

354

Nanoscale topography and chemistry affect embryonic stem cell self-renewal and early differentiation.  

PubMed

Adherent cells respond to a wide range of substrate cues, including chemistry, topography, hydrophobicity, and surface energy. The cell-substrate interface is therefore an important design parameter in regenerative medicine and tissue engineering applications, where substrate cues are used to influence cell behavior. Thin films comprising 4.5 nm (average diameter) gold nanoparticles coated with a mixture of two alkanethiols can confer hemispherical topography and specific chemistry to bulk substrates. The behavior of murine embryonic stem cells (ESCs) on the thin films can then be compared with their behavior on self-assembled monolayers of the same alkanethiols on vapor-deposited gold, which lack the topographical features. Cells cultured both with and without differentiation inhibitors are characterized by immunofluorescence for Oct4 and qPCR for Fgf5, Foxa2, Nanog, Pou5f1, and Sox2. Nanoscale chemistry and topography are found to influence stem cell differentiation, particularly the early differentiation markers, Fgf5 and Foxa2. Nanoscale topography also affects Oct4 localization, whereas the chemical composition of the substrate does not have an effect. It is demonstrated for the first time that ESCs can sense topographical features established by 4.5 nm particles, and these findings suggest that nanoscale chemistry and topography can act synergistically to influence stem cell differentiation. This study furthers the understanding of the effects of these substrate properties, improving our ability to design materials to control stem cell fate. PMID:23852884

Lapointe, Vanessa L S; Fernandes, Ana Tiago; Bell, Nia C; Stellacci, Francesco; Stevens, Molly M

2013-12-01

355

Mesozoic ocean basins and the link to modeled dynamic topography of the circum-Arctic  

NASA Astrophysics Data System (ADS)

The tectonic evolution of the circum-Arctic is complex, punctuated by the opening and closing of several ocean basins, and the accretion and deformation of numerous autochthonous and allochthonous terranes. Here, we present a new plate tectonic reconstruction for the circum-Arctic and adjacent regions since the start of the Jurassic, incorporating the opening of the Amerasia Basin and associated closure of the South Anuyi Ocean. The location of palaeo-subduction zones can be used to infer mantle heterogeneity structure beneath north-eastern North America, the Canadian Arctic Islands, Northern Atlantic and Russia. We use this kinematic plate reconstruction to drive forward geodynamic models of mantle flow from which we compute the spatio-temporal evolution of dynamic topography. The passage of the evolving circum-Arctic over subducting slabs is expected to impart long-wavelength subsidence followed by uplift. Separating the isostatic and dynamic contributions to circum-Arctic topography is challenging because of the paucity of offshore and onshore regional datasets, and is complicated by multiple processes, including rifting, long-wavelength mantle flow, magmatic underplating, sediment loading, and volcanism. Therefore, we focus on the possible correlation between the evolution of long-wavelength topography and post-Jurassic subduction zones. We compare the dynamic topography predicted by our geodynamic models to residual topography, published palaeo-geographic maps and anomalous tectonic subsidence.

Shephard, Grace; Flament, Nicolas; Heine, Christian; Dietmar Müller, R.

2013-04-01

356

Ion sputtering, surface topography, SPM and surface analysis of electronic materials  

NASA Astrophysics Data System (ADS)

Two side effects introduced on surfaces of electronic materials by ion bombardment, namely compositional changes (for compound semiconductors) and topography changes are discussed. Based on the relative elemental sensitivity factor method with matrix corrections for quantitative AES or XPS analysis, a sputter correction factor is defined to compensate for bombardment induced surface compositional changes. Using several popular preferential sputter models and comparing their predictions to a synopsis of published experimental AES and XPS measurements on argon bombarded binary compound semiconductors, a sputter correction factor for these materials are proposed. The extent of bombardment-induced topography depends primarily on the substrate material while the ion beam characteristics play only a secondary role. Due to the complexity of and the many processes involved in ion/solid interactions, bombardment-induced topography is not well understood. Several quantitative and qualitative theories have been proposed to explain the experimental data. Most of these theories are based on SEM or TEM data. The major disadvantage of these data is the lack of quantitative information. The advent of SPM (scanning probe microscopy) and the subsequent development of software have reversed this. A brief summary of SPM (AFM and STM) investigations of bombardment induced topography on semiconductor surfaces is given. Most studies have concentrated on the topography on Si, Ge, GaAs and InP surfaces with special emphasis on ripple development.

Malherbe, J. B.; Odendaal, R. Q.

1999-04-01

357

Mantle convection and core-mantle boundary topography: explanations and implications  

NASA Astrophysics Data System (ADS)

Recent seismic inferences of the topography on the core-mantle boundary (CMB) constitute a new and potentially important constraint on the dynamics of the thermal convective circulation in the Earth's mantle. We employ viscous flow models for the mantle to predict the flow-induced deflections of the CMB that are expected on the basis of seismic tomographic inferences of internal mantle density heterogeneity. The good agreement between our theoretical predictions and the seismically inferred CMB deflections of Morelli and Dziewonski (1987) suggests that the latter may indeed be good approximations to the dynamically induced CMB topography. The amplitude of the seismically inferred CMB topography may be construed to provide a direct constraint on the temperature derivative of seismic P-wave velocity in the lower mantle and we determine a value for this parameter, in the course of fitting the data, that differs significantly from the value determined by laboratory measurements as appropriate for upper-mantle phases. The seismically observed topography on the CMB is also shown to provide evidence favouring the whole-mantle convection hypothesis and in this connection we argue that deep penetration of subducted lithospheric slabs into the lower mantle is likely to be responsible for controlling many of the features of this topography.

Forte, Alessandro M.; Peltier, W. Richard

1991-02-01

358

Hybrid dimension based modeling of part surface topography and identification of its characteristic parameters  

NASA Astrophysics Data System (ADS)

Since the complete description of complex part surface is difficult to achieve using the existing integral dimensional or fractal dimensional approaches, the novel concept of hybrid dimension and its modeling method of part surface topography are proposed in this paper. The hybrid dimensional model of part surface topography is established based on the deflection method of surface correlation coefficient, which associates the integral dimensional and fractal dimensional surface topographies. Superimposing the normalized fractal dimensional surface altitude field on the B-spline surface, the hybrid dimensional model can express the integral dimensional information of part surface in macro level, and the fractal dimensional detail in micro level. And the correlation of part surface topographies among different scales and different dimensions is established by the Hybrid Dimensional Surface Correlation Coefficient. Moreover, the characteristic parameter identification method for the hybrid dimensional model of part surface topography is proposed. The component information of integral dimension and fractal dimension is separated and extracted by wavelet analysis, and hybrid dimensional characteristic parameters are identified by the generalized surface structure function method and the roughness mapping method. Finally, the proposed method is applied to design and manufacture of turbo expander.

Qiu, Chan; Liu, Zhenyu; Bu, Wanghui; Tan, Jianrong

2012-07-01

359

Molecular response of Escherichia coli adhering onto nanoscale topography  

PubMed Central

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. PMID:23078758

2012-01-01

360

Molecular response of Escherichia coli adhering onto nanoscale topography.  

PubMed

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. PMID:23078758

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

2012-01-01

361

Representation of topography by porous barriers and objective interpolation of topographic data  

NASA Astrophysics Data System (ADS)

We present a porous medium approach to representing topography, and a new algorithm for the objective interpolation of topography, for use in ocean circulation models of fixed resolution. The representation and algorithm makes use of two concepts; impermeable thin walls and porous barriers. Impermeable thin walls allow the representation of knife-edge sub-grid-scale barriers that block lateral flow between model grid cells. Porous barriers permit the sub-grid scale geometry to modulate lateral transport as a function of elevation. We find that the porous representation and the resulting interpolated topography retains key features, such as overflow sill depths, without compromising other dynamically relevant aspects, such as mean ocean depth for a cell. The accurate representation of the ocean depth is illustrated in a simple model of a tsunami that has a cross-basin travel time very much less dependent on horizontal resolution than when using conventional topographic interpolation and representation.

Adcroft, Alistair

2013-07-01

362

Wind Energy Forecasting Utilizing High Resolution Topography in the WRF Model  

NASA Astrophysics Data System (ADS)

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.

Beechler, B. E.; Zupanski, D.

2012-12-01

363

Dependence of image grey values on topography in SIR-B images  

NASA Technical Reports Server (NTRS)

This paper focuses on the use of a high resolution digital elevation model (DEM) to aid in rectifying and enhancing synthetic aperture radar images. Using a synthetic backscatter image, the SIR-B images are manually rectified and resampled to remove geometric distortions caused by topography. In a second step, an improved reflectance function of incidence angle is derived from the DEM and the rectified image and this function is used to reduce radiometric effects of topography yielding an albedo image which clearly shows the thematic, as opposed to topographic content of the image. The procedure is tested on four SIR-B images of a scene in Argentina (crossover point) that is imaged under different azimuth and incidence angles. The similarity of the resulting images indicates that the procedure effectively reduces artefacts from the images that are dependent on topography.

Domik, G.; Leberl, F.; Cimino, J.

1988-01-01

364

An analytic solution for barotropic flow along a variable slope topography  

NASA Astrophysics Data System (ADS)

An analytic solution is derived for the generic oceanographic situation of a barotropic current flowing along sloping topography. It is shown that the shallow water equations can be reduced to a heat-like equation in which ?effect is balanced by Ekman dissipation. For constant topography, the system is found to admit a well-known similarity solution and this solution is generalized to the case of variable topography. Several properties of the solution are explored, and an example is given for flow along the northern Gulf of Mexico slope, between the De Soto Canyon and the Mississippi Canyon. This "Topographic ?-plume" solution may serve as a model for further research concerning the influence exerted by geophysical boundary layers on the interior flow via their structure and stability.

Kuehl, Joseph J.

2014-11-01

365

A framework for integration of scientific applications into the OpenTopography workflow  

NASA Astrophysics Data System (ADS)

The NSF-funded OpenTopography facility provides online access to Earth science-oriented high-resolution LIDAR topography data, online processing tools, and derivative products. The underlying cyberinfrastructure employs a multi-tier service oriented architecture that is comprised of an infrastructure tier, a processing services tier, and an application tier. The infrastructure tier consists of storage, compute resources as well as supporting databases. The services tier consists of the set of processing routines each deployed as a Web service. The applications tier provides client interfaces to the system. (e.g. Portal). We propose a "pluggable" infrastructure design that will allow new scientific algorithms and processing routines developed and maintained by the community to be integrated into the OpenTopography system so that the wider earth science community can benefit from its availability. All core components in OpenTopography are available as Web services using a customized open-source Opal toolkit. The Opal toolkit provides mechanisms to manage and track job submissions, with the help of a back-end database. It allows monitoring of job and system status by providing charting tools. All core components in OpenTopography have been developed, maintained and wrapped as Web services using Opal by OpenTopography developers. However, as the scientific community develops new processing and analysis approaches this integration approach is not scalable efficiently. Most of the new scientific applications will have their own active development teams performing regular updates, maintenance and other improvements. It would be optimal to have the application co-located where its developers can continue to actively work on it while still making it accessible within the OpenTopography workflow for processing capabilities. We will utilize a software framework for remote integration of these scientific applications into the OpenTopography system. This will be accomplished by virtually extending the OpenTopography service over the various infrastructures running these scientific applications and processing routines. This involves packaging and distributing a customized instance of the Opal toolkit that will wrap the software application as an OPAL-based web service and integrate it into the OpenTopography framework. We plan to make this as automated as possible. A structured specification of service inputs and outputs along with metadata annotations encoded in XML can be utilized to automate the generation of user interfaces, with appropriate tools tips and user help features, and generation of other internal software. The OpenTopography Opal toolkit will also include the customizations that will enable security authentication, authorization and the ability to write application usage and job statistics back to the OpenTopography databases. This usage information could then be reported to the original service providers and used for auditing and performance improvements. This pluggable framework will enable the application developers to continue to work on enhancing their application while making the latest iteration available in a timely manner to the earth sciences community. This will also help us establish an overall framework that other scientific application providers will also be able to use going forward.

Nandigam, V.; Crosby, C.; Baru, C.

2012-12-01

366

Development of ballistics identification—from image comparison to topography measurement in surface metrology  

NASA Astrophysics Data System (ADS)

Fired bullets and ejected cartridge cases have unique ballistics signatures left by the firearm. By analyzing the ballistics signatures, forensic examiners can trace these bullets and cartridge cases to the firearm used in a crime scene. Current automated ballistics identification systems are primarily based on image comparisons using optical microscopy. The correlation accuracy depends on image quality which is largely affected by lighting conditions. Because ballistics signatures are geometrical micro-topographies by nature, direct measurement and correlation of the surface topography is being investigated for ballistics identification. A Two-dimensional and Three-dimensional Topography Measurement and Correlation System was developed at the National Institute of Standards and Technology for certification of Standard Reference Material 2460/2461 bullets and cartridge cases. Based on this system, a prototype system for bullet signature measurement and correlation has been developed for bullet signature identifications, and has demonstrated superior correlation results.

Song, J.; Chu, W.; Vorburger, T. V.; Thompson, R.; Renegar, T. B.; Zheng, A.; Yen, J.; Silver, R.; Ols, M.

2012-05-01

367

A mass conservative scheme for simulating shallow flows over variable topographies using unstructured grid  

NASA Astrophysics Data System (ADS)

Most available numerical methods face problems, in the presence of variable topographies, due to the imbalance between the source and flux terms. Treatments for this problem generally work well for structured grids, but most of them are not directly applicable for unstructured grids. On the other hand, despite of their good performance for discontinuous flows, most available numerical schemes (such as HLL flux and ENO schemes) induce a high level of numerical diffusion in simulating recirculating flows. A numerical method for simulating shallow recirculating flows over a variable topography on unstructured grids is presented. This mass conservative approach can simulate different flow conditions including recirculating, transcritical and discontinuous flows over variable topographies without upwinding of source terms and with a low level of numerical diffusion. Different numerical tests cases are presented to show the performance of the scheme for some challenging problems.

Mohamadian, A.; Le Roux, D. Y.; Tajrishi, M.; Mazaheri, K.

2005-05-01

368

Dependence of Eemian Greenland temperature reconstructions on the ice sheet topography  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

369

Dependence of Eemian Greenland temperature reconstructions on the ice sheet topography  

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

370

Time-domain schemes of optical topography: methodology, simulative and experimental validation  

NASA Astrophysics Data System (ADS)

To cope with the low quantification in the established optical topography that originates from the excessively simplified computation model based on the modified Lambert-Beer's Law (MLBL), we propose a least-squares fitting scheme for time-domain optical topography that seeks for data matching between the time-resolved measurement and the model prediction calculated by analytically solving the time-domain diffusion equation in semi-infinite geometry. Our simulative and phantom experiments demonstrate that the proposed curve-fitting method is overall superior to the conventional MLBL-based one in quantitative performance.

Duan, Linjing; Wang, Xin; Li, Jiao; Yi, Xi; Wu, Linhui; Zhang, Limin; Gao, Feng

2013-03-01

371

Modelled sensitivity of the snow regime to topography, shrub fraction and shrub height  

NASA Astrophysics Data System (ADS)

Recent studies show that shrubs are colonizing higher latitudes and altitudes in the Arctic. Shrubs affect the wind transport, accumulation and melt of snow, but there have been few sensitivity studies of how shrub expansion might affect snowmelt rates and timing. Here, a blowing snow transport and sublimation model is used to simulate premelt snow distributions and a 3-source energy balance model, which calculates vertical and horizontal energy fluxes between the atmosphere, snow, snow-free ground and vegetation, is used to simulate melt. Vegetation is parametrized as shrub cover and the parametrization includes shrub bending and burial in winter and emergence in spring. The models are used to investigate the sensitivity of the snow regime in an upland tundra valley to varying shrub cover and topography. Results show that topography dominates the spatial variability of snow accumulation, which in turn dominates the pre and early melt energy budget. With topography removed from the simulations, modelled snow cover is uniform when there is no vegetation but increasing vegetation introduces spatial variability in snow accumulation which is then decreased as further increases in shrub cover suppress wind-induced redistribution of snow. The domain-averaged simulations of premelt snow accumulation also increases with increasing shrub cover because suppression of blowing snow by shrubs decreases sublimation. In simulations with topography, the increase in snow accumulation and its spatial variability with increasing vegetation is less marked because snow is also held in topography-driven drifts. With topography, the existence of wind-scoured snow-free patches at the onset of snowmelt causes exposed ground to contribute to the energy balance such that sensible, advective and radiative heat fluxes are higher than in the flat domain during this period. However, as snowmelt evolves, differences in the energy budget between runs with and without topography dramatically diminish. These results suggest that, to avoid overestimating the effect of shrub expansion on the energy budget of the Arctic, future large scale investigations should consider wind redistribution of snow, shrub bending and emergence, and sub-grid topography as they affect the variability of snowcover.

Ménard, C. B.; Essery, R.; Pomeroy, J.

2014-01-01

372

Topography and transport properties of oligo(phenylene ethynylene) molecular wires studied by scanning tunneling microscopy  

NASA Technical Reports Server (NTRS)

Conjugated phenylene(ethynylene) molecular wires are of interest as potential candidates for molecular electronic devices. Scanning tunneling microscopic study of the topography and current-voltage (I-V) characteristics of self-assembled monolayers of two types of molecular wires are presented here. The study shows that the topography and I-Vs, for small scan voltages, of the two wires are quite similar and that the electronic and structural changes introduced by the substitution of an electronegative N atom in the central phenyl ring of these wires does not significantly alter the self-assembly or the transport properties.

Dholakia, Geetha R.; Fan, Wendy; Koehne, Jessica; Han, Jie; Meyyappan, M.

2003-01-01

373

OCT corneal topography within ¼ diopter in the presence of saccadic eye movements  

NASA Astrophysics Data System (ADS)

Refractive surgeons and cataract surgeons need accurate measurements of corneal curvature/power. Increased expectations of patients, the increasing number of patients having undergone prior surgeries and patients with corneal pathologies dictate the need for reliable curvature measurements to enhance the predictability and the quality of surgical outcomes. Eye movements can negatively influence these measurements. We present a model of eye movements based on peak saccade velocities and formulate criteria for obtaining OCT topography within ¼ of a diopter. Using these criteria we illustrate how next generation MHz systems will allow full corneal OCT topography in both healthy and pathological corneas

Sayegh, Samir I.

374

Topography of Mercury from Stereophotoclinometric Analysis of MESSENGER Flyby 2 and Mariner 10 Images  

NASA Astrophysics Data System (ADS)

Imaging data acquired during the MESSENGER flybys of Mercury are being used to construct preliminary models of the surface topography of the planet. These models will be improved when additional data become available from the orbital phase of the mission. For all three flybys the inbound and outbound views present a crescent and gibbous Mercury, respectively, each bounded by the terminator on one side and the limb on the other. Longitudes in the lit hemisphere between the two limbs will not be visible, and even less will be useful for topographic analysis due to the obliquity of the view. The first MESSENGER flyby on 14 January 2008 provided useful data for about 25 degrees in longitude from inbound imaging and about 80 degrees outbound; the latter became increasingly degraded as the sub-solar longitude was approached. Ideally, high-resolution topography is determined from stereophotoclinometry (SPC), by which images at different illuminations are used to solve for topography and albedo in small "maplets," the centers of which are control points for stereographic analysis and low-resolution topography. During a single flyby, the illumination does not change, and close to the sub-solar point it is difficult to distinguish brightness variations due to topography from those due to albedo variations. The second MESSENGER flyby of Mercury on 6 October 2008 will image longitudes from about 90 degrees W to 90 degrees E. From our experience with data from the first flyby, we will be able to solve for topography from the images in a latitude range from 90 to 10 degrees W (outbound images) and, at lower resolution, from 75 to 90 degrees E (inbound images). Overlap between the MESSENGER and Mariner 10 data sets will allow for a true SPC analysis in much of the former region. Of particular interest will be the topography of the many craters and scarps in this region as well as the hummocky region antipodal to the Caloris basin. During the first MESSENGER flyby, Mercury Laser Altimeter (MLA) observations were made along a path near the equator from 10 to 90 degrees E. Topography from the inbound images will be compared with the MLA data where the two overlap.

Gaskell, R. W.; Gillis-Davis, J. J.; Sprague, A. L.

2008-12-01

375

Sentinel-3 Surface Topography Mission: Payload, Data Products and Cal/Val Preparation  

NASA Astrophysics Data System (ADS)

Sentinel-3 is an Earth observation satellite mission designed for GMES to ensure the long-term collection of high-quality measurements delivered in an operational manner to GMES ocean, land, atmospheric, emergency and security services. Primary sentinel-3 topography mission measurement requirements have been derived from GMES user needs as follows: • Sea surface topography (SSH), significant wave height (Hs) and surface wind speed derived over the global ocean to an equivalent accuracy and precision as that presently achieved by ENVISAT Radar Altimeter-2 (RA-2). • Enhanced surface topography measurements in the coastal zone, sea ice regions and over inland rivers, their tributaries and lakes. To address the above requirements, the Sentinel-3 Topography payload will carry a Synthetic Aperture Radar Altimeter (SRAL) instrument, a passive microwave radiometer (MWR) a GPS receiver and laser retro-reflector for precise orbit determination providing continuing the legacy of ENVISAT RA-2 and Cryosat. Three level of timeliness are defined within GMES for the S-3 Topography mission: • NRT products, delivered to the users in less than 3 hours after acquisition of data by the sensor, • Short time critical (STC) products, delivered to the users in less than 48 hours after the acquisition and, • Non-time critical (NTC) products delivered not later than 1 month after acquisition or from long-term archives. The Sentinel-3 topography data products will provide continuity of ENVISAT type measurement capability in Europe to determine sea, ice and land surface topography measurements with high accuracy, timely delivery and in a sustained operational manner for GMES users. The Sentinel-3 data will also provide fundamental inputs to a variety of value-adding downstream services for industry, government agencies, commercial users, service providers and appropriate regulatory authorities. The Calibration and Validation of the Sentinel-3 topography products will nominally rely on the cross-comparison with the ESA Envisat Altimetry mission and will be a significant challenge due to the stringent S-3 mission measurement requirements and their safeguarding all over the mission lifetime.

Féménias, P.; Rebhan, H.; Donlon, C.; Buongiorno, A.; Mavrocordatos, C.

2012-04-01

376

The influence of altitude and topography on genetic structure in the long-toed salamander (Ambystoma macrodactulym)  

Microsoft Academic Search

A primary goal of molecular ecology is to understand the influence of abiotic factors on the spatial distribution of genetic variation. Features including altitudinal clines, topography and landscape characteristics affect the proportion of suitable habitat, influence dispersal patterns, and ultimately structure genetic differentiation among populations. We studied the effects of altitude and topography on genetic variation of long-toed salamanders (

ANDREW R. GIORDANO; BENJAMIN J. RIDENHOUR; ANDREW STORFER

2007-01-01

377

Variability in soil chemistry and arbuscular mycorrhizal fungi in harvester ant nests: the influence of topography, grazing and region  

Microsoft Academic Search

Harvester ants are important disturbance agents across western North America, but the effects of ant disturbances on soils may vary considerably with topography and land use. We examined how soil properties and arbuscular mycorrhizal (AM) fungi in harvester ant nests varied across spatial scales according to topography, grazing regime and region. Soils from undisturbed areas were compared with nest disturbances

Season R. Snyder; Thomas O. Crist; Carl F. Friese

2002-01-01

378

The Role of Preflow Topography on the Surface Morphology and Thermal Evolution of Actively Inflating Basaltic Lava Flows  

Microsoft Academic Search

In an attempt to test hypotheses regarding the role of underlying topography on lava flow surface morphology, we acquired pre-, syn- and post-flow topographic data from active pahoehoe flows advancing over hummocky topography at Kilauea volcano, Hawaii. Kilauea volcano (HI) is in a state of eruption that has persisted almost without interruption for over 20 years, and is in a

S. W. Anderson; M. S. Ramsey; D. A. Crown; J. M. Byrnes; E. R. Stofan

2005-01-01

379

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

E-print Network

to characterize the conversion of tidal energy to radiated internal wave power. Whether the hydrostatic ( , shape)/SIW, where Ptide is the effective tidal power that interacts with the topography, and /8 Internal wave and boundary current generation by tidal flow over topography Amadeus Dettner, Harry

Texas at Austin. University of

380

Does tectonics drive topography ? Insights from low - temperature thermochronology and numerical modeling along the Himalayan range  

Microsoft Academic Search

Although the Himalayan range is commonly presented as cylindrical along-strike, geological structures, topography, precipitation rate, convergence rates and low - temperature thermochronological ages all vary significantly from west to east. Here, we focus on the interpretation of thermochronological datasets in term of cylindricity in geometry and kinematics of the MHT along the Himalayan range. We propose a structural and kinematic

X. Robert; P. van der Beek; J. Braun; C. Perry; J. L. Mugnier

2009-01-01

381

Gap Flows through Idealized Topography. Part II: Effects of Rotation and Surface Friction  

E-print Network

Gap Flows through Idealized Topography. Part II: Effects of Rotation and Surface Friction SASA simulations are conducted of geostrophically balanced flow over an isolated mountain cut by a horizontal gap. The relative importance of the along-gap synoptic-scale pressure gradient and terrain- induced mesoscale

382

Characterization of the creep exposed CMSX2 single crystal by neutron diffraction topography and neutron diffractometry  

NASA Astrophysics Data System (ADS)

The single crystal superalloy CMSX2 was studied after a creep exposition at high temperature by neutron diffraction topography and neutron diffractometry. Topographs clearly displayed the dendritic structure of the sample. The topographs and the rocking curves indicate an influence of the creep both on the dendritic structure of the sample and on the individual dendrites.

Strunz, P.; Lukáš, P.; Mikula, P.; Šaroun, J.; Albertini, G.; Rustichelli, F.; Cicognani, G.; di Gianfrancesco, A.

1994-07-01

383

Topography and refractometry of nanostructures using spatial light interference microscopy (SLIM)  

E-print Network

structures with 0.3 nm spatial and 0.03 nm temporal accuracy owing to the white light illumination and itsTopography and refractometry of nanostructures using spatial light interference microscopy (SLIM of Illinois at Urbana-Champaign, Urbana, Illinois 61801 Abstract Spatial Light Interference Microscopy (SLIM

Gillette, Martha U.

384

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

Microsoft Academic Search

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

Masaaki Takyu; Shin-Ichiro Aiba; Kanehiro Kitayama

2002-01-01

385

The History and Social Topography of an Ethnic Island in Alabama  

ERIC Educational Resources Information Center

Along the west bank of the Tombigbee River, about 35 miles north of Mobile, is situated one of the largest and most populous groups of American Isolates: this paper briefly tells the history and describes the situation of this recently formed people, covering such issues as the information and early development, their social topography, and social…

Griessman, B. Eugene; Henson, Curtis T., Jr.

1975-01-01

386

Modeling of glacier bed topography from glacier outlines, central branch lines, and a DEM  

Microsoft Academic Search

Due to the expected future climate change, glacier ice as a resource will be further diminished and its sea-level rise contribution further increased. A key for a more accurate determination of future glacier evolution is to improve our currently sparse knowledge on glacier bedrock topography. Here, we present a simplified method implemented in a geographic information system to approximate subglacial

Frank Paul; Andreas Linsbauer

2012-01-01

387

Visualization of lumbar muscle contraction synergy using surface electromyography (sEMG) streaming topography  

Microsoft Academic Search

Because of the difficulty in analysis and interpretation of surface electromyography (sEMG), the specific muscle contraction synergy associated with low back pain continues to be debated. Streaming topography is a novel method of continuously visualizing the distribution of sEMG signals during dynamic motion to provide a more comprehensive examination and subsequent insight into the synergy of muscle recruitment pattern. The

Yong Hu; J. N. F. Mak; W. W. Lu; K. M. C. Cheung; K. D. K. Luk

2004-01-01

388

Links between topography, wind, deflation, lakes and dust: The case of the Bodele Depression, Chad  

E-print Network

Links between topography, wind, deflation, lakes and dust: The case of the Bode´le´ Depression´le´ Depression, Chad is the planet's largest single source of dust. Deflation from the Bode´le´ could be seen wetter phases, such as the Holocene pluvial. Winds may therefore have helped to create the depression

Washington, Richard

389

Comparison of Greenland Ice Sheet topography measured by TOPSAR and airborne laser altimetry  

Microsoft Academic Search

A digital elevation model (DEM) produced from airborne interferometric synthetic aperture radar (TOPSAR) data of a 5 km×65 km region of the Greenland Ice Sheet is compared with multiple airborne laser altimeter profiles of the same surface. TOPSAR-derived elevation values were calculated on a 10 m×10 m grid. Surface topography at wavelengths greater than one kilometer is accurately reproduced. A

Robert Bindschadler; Mark Fahnestock; Angela Sigmund

1999-01-01

390

Improving Rainfall and Temperature Estimations in Complex Topography: an Application in the Swiss Alps  

Microsoft Academic Search

Within complex topography, the characteristic spatial scales of hydrological forcings are poorly captured by sparse measurements. The aim of this study is to improve temperature and precipitation interpolations during extreme precipitation events by integrating digital terrain information (DTM) and a weather forecast model (LAM) with sparse gauge data. Three previous events were analyzed to determine the factors which have the

Cara Tobin; Ludovico Nicotina; Alexis Berne; Marc Parlange; Andrea Rinaldo

2010-01-01

391

Going Underground: A Field Investigation and Lab Activity on Karst Topography and Water Systems  

ERIC Educational Resources Information Center

Students learn science best with activities that mirror the way scientists work. This article describes how geologists investigate groundwater flow systems in areas of karst topography--geologic formations shaped by dissolving bedrock--and provides a way for students to replicate this research. Students also use electric current to model water…

O'Dell, Gary; Gonzalez-Espada, Wilson

2011-01-01

392

The effect of colony topography on climate signals in coral skeleton  

Microsoft Academic Search

The stable oxygen isotope composition of the aragonitic skeleton of hermatypic corals is a potential archive of paleotemperature and rainfall data. Biological processes also influence coral ?18O although it has been difficult to determine which processes are involved and whether or not they dominate the stable isotope signal. We show here that colony topography, or surface bumpiness, is associated with

Anne L. Cohen; Stanley R. Hart

1997-01-01

393

Investigating the effect of different asphaltene structures on surface topography and wettability alteration  

NASA Astrophysics Data System (ADS)

This paper aims at investigation of the effect of asphaltene structure on wettability and topography alteration of a glass surface as a result of asphaltene precipitation. In order to provide a better insight into the topography alteration, a bi-fractal approach was employed. Such an approach is capable of discriminating topography alteration in two different surface types, namely, macro-asperities and micro-asperities. The observed variation of the fractal dimension in the two surface types could be considered as the consequence of different asphaltene sources. Therefore, the structure of different asphaltene sources was carefully examined. The effect of asphaltene structure is more pronounced for asphaltene precipitation at higher pressure. It was revealed that asphaltene particles of high complexity and with larger poly-aromatic rings tend to be detached easier at higher pressure than those with smaller poly-aromatic rings. Another evidence to emphasize the significance of asphaltene structure was given through wettability alteration. It was found that asphaltene particles with larger poly-aromatic rings turn the surface less oil wet at higher pressure. It seems that the difference in wetting condition and surface topography alteration of different asphaltene sources roots in their different structures.

Amin, J. Sayyad; E. Nikooee; Ghatee, M. H.; Ayatollahi, Sh.; Alamdari, A.; Sedghamiz, T.

394

Bed topography of Store Glacier, Greenland from high-resolution airborne gravity data  

NASA Astrophysics Data System (ADS)

Store Glacier is a major west Greenland outlet tidewater glacier draining an area of 30,000 square km into Uummannaq Fjord, flowing at a speed of 4.8 km per year at the terminus. The bed topography of the glacier is poorly known and the fjord bathymetry has only been partially surveyed for the first time in 2012. In this study, we present a new approach on the modeling of glacier thickness and sea floor bathymetry based on high resolution gravity constrained with other observations. In August 2012, we acquired a 250m spacing grid of free-air gravity data at a speed of 50 knots with accuracy at sub-milligal level. We constrain the 3D inversion of these gravity data with ship-borne bathymetry near the glacier front and radar-derived ice thickness on grounded ice to derive a seamless map of bed topography of grounded ice and sea floor. Comparison of the new topography with prior maps reveals vast differences. Prior bathymetry (IBCAO3) has an ice front grounded at sea level whereas observations show a depth of 550m. On grounded ice, the data reveal the subglacial topography at an unprecedented level of spatial details. We discuss the impact of the results on the modeling of the glacier flow and the understanding of its interaction with ocean thermal forcing and surface mass balance.

An, L.; Rignot, E. J.

2013-12-01

395

Full chip implant correction with wafer topography OPC modeling in 2x nm bulk technologies  

NASA Astrophysics Data System (ADS)

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.

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

396

The Topography of Mars by the Mars Orbiter Laser Altimeter (MOLA)  

NSDL National Science Digital Library

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.

Nasa

397

Satellites images, digitized topography, and the recognition of the Xela Caldera, Quezaltenango Valley, Guatemala  

Microsoft Academic Search

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

D. Foley; A. McEwen; W. Duffield; G. Heiken

1992-01-01

398

Constraints on 3-D stress in the crust from support of mid-ocean ridge topography  

E-print Network

-wavelength topographic stress generally predicts the wrong style of earthquake focal mechanisms at ridges and transform crustal stress with both the ridge and transform focal mechanisms. By adjusting the magnitudeConstraints on 3-D stress in the crust from support of mid-ocean ridge topography Karen Luttrell1

Sandwell, David T.

399

Plasma molding over surface topography and resulting ion\\/fast-neutral distribution functions  

Microsoft Academic Search

Plasma molding over surface topography finds applications in MEMS microfabrication, neutral beam sources, plasma extraction through grids, and plasma contact with internal reactor parts (e.g., wafer chuck edge). The flux, energy and angular distributions of ions incident on the substrate are of primary importance in these applications. These quantities depend critically on the shape of the meniscus (plasma-sheath boundary) formed

Demetre Economou; Doosik Kim

2002-01-01

400

Quantifying rapid changes in coastal topography using modern mapping techniques and GIS  

E-print Network

for representation of many coastal low-relief landscapes with features (e.g., beach dunes, berms, scarpsQuantifying rapid changes in coastal topography using modern mapping techniques and GIS HELENA BERNSTEIN Center For Marine and Wetland Studies, Coastal Carolina University 1270 Atlantic Avenue, Conway

Mitasova, Helena

401

Forward modeling of ice topography on Mars to infer basal shear stress conditions  

Microsoft Academic Search

Understanding the history of ice caps on Mars could reveal important information about Martian geologic and climatic history. To do this, an ice reconstruction model is needed that operates over complex topography and can be constrained with a limited number of free parameters. In this study we developed a threshold-sliding model for ice cap morphology based on the classic model

M. E. Banks; J. D. Pelletier

2008-01-01

402

Polymers with hydro-responsive topography identified using high throughput AFM of an acrylate microarray†  

PubMed Central

Atomic force microscopy has been applied to an acrylate polymer microarray to achieve a full topographic characterisation. This process discovered a small number of hydro-responsive materials created from monomers with disparate hydrophilicities that show reversibility between pitted and protruding nanoscale topographies. PMID:23259005

Hook, Andrew L.; Yang, Jing; Chen, Xinyong; Roberts, Clive J.; Mei, Ying; Anderson, Daniel G.; Langer, Robert; Alexander, Morgan R.; Davies, Martyn C.

2012-01-01

403

Push in South of the Hellas Basin Showing Topography from MOLA  

NSDL National Science Digital Library

Zoom into the region of Mars just south of the Hellas Basin showing topography data from MOLA. Blue tones represent elevations of less than 2 kilometers, while reddish tones are greater than about 2.8 kilometers, relative to the mean equatorial height of Mars.

Biddlecome, Tom; Smith, David

1999-11-22

404

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

NASA Astrophysics Data System (ADS)

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

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

2014-02-01

405

EAARL topography-Three Mile Creek and Mobile-Tensaw Delta, Alabama, 2010  

USGS Publications Warehouse

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.

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

406

Retinal Ganglion Cell Topography of Five Species of Ground-Foraging Birds  

Microsoft Academic Search

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

Tracy Dolan; Esteban Fernández-Juricic

2010-01-01

407

Relationships between pahoehoe surface units, topography, and lava tubes at Mauna Ulu, Kilauea Volcano, Hawaii  

Microsoft Academic Search

Lava flow field development at Mauna Ulu was analyzed by characterizing pahoehoe surface units and their distribution relative to pre-Mauna Ulu topography and the main lava tube system. Four pahoehoe surface units were identified in the field and described on the basis of color, surface texture, and morphology: broad, flat sheets (unit I), networks of interconnected glassy-surfaced toes (unit II),

Jeffrey M. Byrnes; David A. Crown

2001-01-01

408

Soil resources and topography shape local tree community structure in tropical forests.  

PubMed

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

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

409

SAR interferometry at Venus for topography and change detection Franz J. Meyer a,b,n  

E-print Network

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

Sandwell, David T.

410

Steady-state visually evoked potential topography during the Wisconsin card sorting test  

Microsoft Academic Search

This paper describes, for the first time, changes in steady-state visually evoked potential (SSVEP) topography associated with the performance of a computerised version of the Wisconsin card sort test (WCS). The SSVEP was recorded from 64 scalp sites and was elicited by a 13 Hz spatially uniform visual flicker presented continuously while 16 subjects performed the WCS. In the WCS,

R. B. Silberstein; j. Ciorciari; A. Pipingas

1995-01-01

411

X-ray topography studies of the defect depth profile in processed silicon wafers  

Microsoft Academic Search

Intrinsic gettering and other defect control techniques now form an integral part of most silicon device processes. For these methods to be effective in enhancing device performance, the nature and extent of defect introduction must be carefully monitored. X-ray topography provides the only nondestructive means of achieving this. Oxygen precipitation during intrinsic gettering treatment of silicon has been examined by

P. J. Halfpenny; G. S. Green; B. K. Tanner

1993-01-01

412

Mapping of domain structure in Barium Titanate single crystals by synchrotron x-ray topography  

Microsoft Academic Search

Imaging of domains is a key step in understanding the microstructure and hence the properties of ferroelectric single crystals. This understanding is essential for exploiting engineered domain configurations to achieve enhanced performance. In this paper, single crystals of Barium Titanate are observed by reflection topography using unfocussed monochromatic synchrotron X-ray light. A 10 x 10 mm polished surface of an

Prashant R. Potnis; John E. Huber; John P. Sutter; Felix Hofmann; Brian Abbey; Alexander M. Korsunsky

2010-01-01

413

Grown-in defects in natural beryls by x-ray topography and birefringence  

Microsoft Academic Search

The growth sectors and their boundaries, impurity zonings and dislocations in natural beryls have been observed by means of x-ray diffraction topography and birefringence. The displacements of fault surfaces of the sector boundaries are perpendicular to the fault surfaces. The Burgers vectors of some typical dislocations in (0001) sector are , and . It is found that the techniques of

Shu-sheng Jiang; Qi Li

1985-01-01

414

Quantitative strain analysis of single crystals using x-ray topography  

Microsoft Academic Search

The x-ray topography technique images diffraction intensity variations of a crystal. The use of a CCD camera enables the measurement of different spatial resolutions. Currently an x-ray topograph with spatial resolution of 1 micron has been achieved, but the quantitative data analysis has not been explored widely. Quantitative strain analysis on these images extends new capabilities in crystal study. We

Y. Zhong; Y. S. Chu; A. T. Macrander; S. F. Krasnicki

2007-01-01

415

X-Ray Refraction Topography and Computed Tomography for NDE of Lightweight Materials  

Microsoft Academic Search

X-Ray Refraction Topography techniques are based on Ultra Small Angle Scattering by micro structural elements causing phase related effects like refraction and total reflection at a few minutes of arc as the refractive index of X-rays is nearly unity (1 - 10 -5 ). The extraordinary contrast of inner surfaces is far beyond absorption effects. Scanning of specimens results in

Bernd R. MÜLLER; Axel LANGE; Michael HARWARDT; Manfred P. HENTSCHEL

2006-01-01

416

The application of X-ray topography to the study of fatigued aluminium  

Microsoft Academic Search

The Berg-Barrett technique of x-ray topography has been applied to fatigued aluminium single crystals. It has been demonstrated that the technique is successful in revealing persistent slip bands. The mechanism of contrast within the bands is discussed.

D G Teer; G D Brown

1970-01-01

417

Thyroid Cryotherapy in an Experimental Rat Model—Topography of Temperature during Therapy and Functional Results  

Microsoft Academic Search

The aim of this study was to investigate post cryotherapy thyroid function status of normal rat thyroid tissue and to determine the topography of temperature of cryotreated tissues and of tissues adjacent to them. Nitrous oxide cryotherapy was performed in 40 male Wistar rats. They were divided into four groups of 10. In group I, the right thyroid lobe was

Lech Pomorski; Magdalena Bartos; Maciej Amsolik; Jan Ciep?ucha; Krzysztof Jó?wik; Jerzy Nar?bski; Hanna Pisarek; Marek Ko?odziejczyk; Krzysztof Kuzdak

2000-01-01

418

ctoh.legos.obs-mip.fr The Centre for the Topography of Oceans and the  

E-print Network

ctoh.legos.obs-mip.fr ABSTRACT : The Centre for the Topography of Oceans and the Hydrosphere (CTOH), the Altimeter Data Service of the LEGOS laboratory validates ENVISAT RA2 altimetry, in particular over Antarctic-CNES Symposium, 20 Years of Progress in Radar Altimetry, 24-29 September 2012, Venice, Italy LEGOS/CTOH, 14

419

Temperature Dependence of the Surface Topography in Dimyristoylphosphatidylcholine\\/Distearoylphosphatidylcholine Multibilayers  

Microsoft Academic Search

Simple lipid binary systems are intensively used to understand the formation of domains in biological membranes. The size of individual domains present in the gel\\/fluid coexistence region of single supported bilayers, determined by atomic force microscopy (AFM), generally exceeds by two to three orders of magnitude that estimated from multibilayers membranes by indirect spectroscopic methods. In this article, the topography

Marie-Cécile Giocondi; Christian Le Grimellec

2004-01-01

420

An assessment of shuttle radar topography mission digital elevation data for studies of volcano morphology  

E-print Network

An assessment of shuttle radar topography mission digital elevation data for studies of volcano's volcanoes. Although these data were acquired with a nominal spatial resolution of 30 m, such data are only available for volcanoes located within the U.S.A. and its Territories. For the overwhelming majority

Wright, Robert

421

A genetic approach to estimating river bed topography from SWOT observations  

Microsoft Academic Search

River bathymetry plays a key role in estimating river discharge as well as improving our modeling capabilities of fluvial geomorphology. Genetic algorithm techniques can be used to derive river bed topography using only water surface elevations and the corresponding temporal and spatial rates of change. Each river bathymetric estimate, also referred to as a solution, is modeled as a successive

R. Matthew McCann; Konstantinos Andreadis; Douglas Alsdorf; Ernesto Rodriquez; Delwyn Moller

2011-01-01

422

Interplay between river discharge and topography of the basin floor in a hyperpycnal lacustrine delta  

E-print Network

influences the flow path of hyperpycnal plumes and delta morphology during progradation of the Red River total dissolved solids. Because the river plume is a bottom-hugging hyperpycnal flow, lake bathymetry. Keywords Discharge, hyperpycnal, lacustrine delta, Lake Texoma, morphology, Red River, topography

Stern, Robert J.

423

Thermal Model of Europa: Calculating the Effects of Surface Topography and Radiation from Jupiter  

Microsoft Academic Search

Europa's surface temperature distribution results from global effects such as insolation and heat flow, as well as local topography and possibly active tectonic processes. Accurate surface temperature models will greatly benefit future orbital investigations searching for global-scale variations in heat flow and local thermal anomalies resulting from frictional heating on faults or diapirs (Paige et al, this meeting). At the

Kristen Bennett; D. Paige; P. Hayne; B. Greenhagen; P. Schenk

2010-01-01

424

Basement Surface Faulting and Topography for Savannah River Site and Vicinity  

SciTech Connect

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.

Cumbest, R.J.

1998-12-17

425

Elastoviscoplastic relaxation of impact crater topography with application to Ganymede and Callisto  

Microsoft Academic Search

We use an elastoviscoplastic rheological model to study the long-term relaxation of impact crater topography on Ganymede and Callisto. We employ a complete set of rheological parameters for ductile creep in ice Ih and implement a new, shallower initial shape model. Under high heat flow conditions, stresses are relieved in deeper, less viscous material, and the remainder concentrates as flexural

Andrew J. Dombard; William B. McKinnon

2006-01-01

426

Subcellular Topography of Visually Driven Dendritic Activity in the Vertebrate Visual System  

E-print Network

with their anatomical position within the dendritic tree of individual neurons. This topographic distribution+ signals are heterogeneously distributed and topographi- cally biased across a developing dendritic tree distribution of Ca2+ signals in a dendritic tree during sensory stimulation. Optical recordings in higher brain

Engert, Florian

427

Cell Adhesion on Polyelectrolyte Multilayer Coated Polydimethylsiloxane Surfaces with Varying Topographies  

E-print Network

Cell Adhesion on Polyelectrolyte Multilayer Coated Polydimethylsiloxane Surfaces with Varying to the pattern size and pitch influences cell adhesion and proliferation. Extensive research has shown the dependence of cell pro- liferation on substrate chemistry, but the influence of substrate topography on cell

Lee, Ilsoon

428

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

429

Corneal topography measurement by means of radial shearing interference: Part I - theoretical consideration  

NASA Astrophysics Data System (ADS)

The paper presents the principle of radial shearing interference; the build of a simple and stable device for interference measurement; the comparison of this structure with other types of interferometers; presents the results of the examination of corneal topography and discusses the prospects for its future uses.

Kowalik, Waldemar W.; Garncarz, Beata E.; Kasprzak, Henryk T.

430

Comparative ultrastructure of corneal surface topography in insects with aspects on phylogenesis and function  

Microsoft Academic Search

The corneas of some nocturnal Lepidoptera carry an array of surface protuberances (nipples), about 200 mµ high, that acts as an impedance transformer equalizing by gradual transition the refractive index of air to that of the cornea. A screening of the insect class has been carried out in the present study with respect to the variation in corneal topography seen

C. G. Bernhard; G. Gemne; J. Sällström