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1

76 FR 60475 - Issuance of a Loan Guarantee to Tonopah Solar Energy, LLC, for the Crescent Dunes Solar Energy...  

Federal Register 2010, 2011, 2012, 2013

...ENERGY Issuance of a Loan Guarantee to Tonopah Solar Energy, LLC, for the Crescent Dunes Solar Energy Project AGENCY: U.S. Department of Energy...Act of 2009 (Recovery Act), to Tonopah Solar Energy, LLC (TSE), for construction and...

2011-09-29

2

75 FR 81307 - Notice of Availability of Record of Decision for the Tonopah Solar Energy, LLC, Crescent Dunes...  

Federal Register 2010, 2011, 2012, 2013

...acres of public lands with a nominal capacity of 110 megawatts. The Crescent Dunes Solar Energy Project is a solar facility using concentrated solar thermal power technology. The project facility footprint will disturb approximately 1,620...

2010-12-27

3

75 FR 72836 - Notice of Availability of Final Environmental Impact Statement for the Tonopah Solar Energy...  

Federal Register 2010, 2011, 2012, 2013

...Environmental Impact Statement for the Tonopah Solar Energy Crescent Dunes Solar Energy Project, Nye County, NV AGENCY: Bureau of...Impact Statement (EIS) for the Crescent Dunes Solar Energy Project, Nye County, Nevada, and by this...

2010-11-26

4

75 FR 54177 - Notice of Availability of Draft Environmental Impact Statement for the Tonopah Solar Energy...  

Federal Register 2010, 2011, 2012, 2013

...Environmental Impact Statement for the Tonopah Solar Energy Crescent Dunes Solar Energy Project, Nye County, NV AGENCY: Bureau of...Impact Statement (EIS) for the Crescent Dunes Solar Energy Project, Nye County, Nevada, and by this...

2010-09-03

5

Barchan Dunes  

NASA Technical Reports Server (NTRS)

28 April 2004 One of the simplest forms a sand dune can take is the barchan. The term, apparently, comes from the Arabic word for crescent-shaped dunes. They form in areas with a single dominant wind direction that are also not overly-abundant in sand. The barchan dunes shown here were imaged in March 2004 by the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) as it passed over a crater in western Arabia Terra near 21.1oN, 17.6oW. The horns and steep slope on each dune, known as the slip face, point toward the south, indicating prevailing winds from the north (top). The picture covers an area about 3 km (1.9 mi) across and is illuminated by sunlight from the lower left.

2004-01-01

6

Global Sea Level Stabilization-Sand Dune Fixation: A Solar-powered Sahara Seawater Textile Pipeline  

E-print Network

Could anthropogenic saturation with pumped seawater of the porous ground of active sand dune fields in major deserts (e.g., the westernmost Sahara) cause a beneficial reduction of global sea level? Seawater extraction from the ocean, and its deposition on deserted sand dune fields in Mauritania and elsewhere via a Solar-powered Seawater Textile Pipeline (SSTP) can thwart the postulated future global sea level. Thus, Macro-engineering offers an additional cure for anticipated coastal change, driven by global sea level rise, that could supplement, or substitute for (1) stabilizing the shoreline with costly defensive public works (armoring macroprojects) and (2) permanent retreat from the existing shoreline (real and capital property abandonment). We propose Macro-engineering use tactical technologies that sculpt and vegetate barren near-coast sand dune fields with seawater, seawater that would otherwise, as commonly postulated, enlarge Earth seascape area! Our Macro-engineering speculation blends eremology with...

Badescu, Viorel; Bolonkin, Alexander A

2007-01-01

7

Global Sea Level Stabilization-Sand Dune Fixation: A Solar-powered Sahara Seawater Textile Pipeline  

E-print Network

Could anthropogenic saturation with pumped seawater of the porous ground of active sand dune fields in major deserts (e.g., the westernmost Sahara) cause a beneficial reduction of global sea level? Seawater extraction from the ocean, and its deposition on deserted sand dune fields in Mauritania and elsewhere via a Solar-powered Seawater Textile Pipeline (SSTP) can thwart the postulated future global sea level. Thus, Macro-engineering offers an additional cure for anticipated coastal change, driven by global sea level rise, that could supplement, or substitute for (1) stabilizing the shoreline with costly defensive public works (armoring macroprojects) and (2) permanent retreat from the existing shoreline (real and capital property abandonment). We propose Macro-engineering use tactical technologies that sculpt and vegetate barren near-coast sand dune fields with seawater, seawater that would otherwise, as commonly postulated, enlarge Earth seascape area! Our Macro-engineering speculation blends eremology with hydrogeology and some hydromancy. We estimate its cost at 1 billion dollars - about 0.01 per sent of the USA 2007 Gross Domestic Product.

Viorel Badescu; Richard B. Cathcart; Alexander A. Bolonkin

2007-07-21

8

An agent-based model of dune interactions produces the emergence of patterns in deserts  

NASA Astrophysics Data System (ADS)

Crescent-shaped barchan dunes are highly mobile dunes which are ubiquitous on Earth and other solar system bodies. Although they are unstable when considered separately, they form large assemblies in deserts and spatially organize in narrow corridors that extend in the wind direction. Collision of barchans has been proposed as a mechanism to redistribute sand between dunes and prevent the formation of very large dunes. Here we use an agent-based model with elementary rules of sand redistribution during collisions to access the full dynamics of very large barchan fields. We tune the dune field density by changing the sand load/lost ratio and follow the transition between dilute fields, where barchans barely interact, and dense fields, where dune collisions control and stabilize the dune field. In this dense regime, barchans have a small, well-selected size and form flocks: the dune field self-organizes in narrow corridors of dunes, as it is observed in real dense barchan deserts.

GéNois, Mathieu; Pont, Sylvain Courrech; Hersen, Pascal; GréGoire, Guillaume

2013-08-01

9

An agent-based model of dune interactions produces the emergence of patterns in deserts  

NASA Astrophysics Data System (ADS)

Crescent-shaped barchan dunes are highly mobile dunes which are ubiquitous on Earth and other solar system bodies. Although they are unstable when considered separately, they form large assemblies in deserts and spatially organize in narrow corridors that extend in the wind direction. Collision of barchans has been proposed as a mechanism to redistribute sand between dunes and prevent the formation of very large dunes. Here, we use an agent-based model with elementary rules of sand redistribution during collisions to access the full dynamics of very large barchan fields. We tune the dune field density by changing the sand load/lost ratio and follow the transition between dilute fields, where barchans barely interact, and dense fields, where dune collisions control and stabilize the dune field. In this dense regime, barchans have a small, well selected size and form flocks: the dune field self-organizes in narrow corridors of dunes, as it is observed in real dense barchan deserts. Simulated dense barchan field, with spatial structuring along the wind direction.

Génois, M.; Courrech Du Pont, S.

2013-12-01

10

Crescentic ramp turbine stage  

NASA Technical Reports Server (NTRS)

A turbine stage includes a row of airfoils joined to corresponding platforms to define flow passages therebetween. Each airfoil includes opposite pressure and suction sides and extends in chord between opposite leading and trailing edges. Each platform includes a crescentic ramp increasing in height from the leading and trailing edges toward the midchord of the airfoil along the pressure side thereof.

Lee, Ching-Pang (Inventor); Tam, Anna (Inventor); Kirtley, Kevin Richard (Inventor); Lamson, Scott Henry (Inventor)

2007-01-01

11

Frosty Dunes  

NASA Technical Reports Server (NTRS)

12 April 2006 Today, the MOC Team celebrates the 45th anniversary of the first human flight into space, that of Yuri Gagarin on 12 April 1961, and the 25th anniversary of the first NASA Space Shuttle flight on 12 April 1981, by briefly pondering the wonders of our Solar System and the opportunities of the age in which we live. Although humans have not ventured to the Moon in more than 30 years, and have not yet gone to Mars, we can all go there through the eyes of our robotic explorers.

Mars, perhaps the most Earth-like (yet so very different!) planet in our star's system, is tilted on its axis by about 25o-not all that different than Earth's 23.5o. Thus, Mars, like Earth, experiences a changing of seasons as the planet revolves around the Sun. At high latitudes in each hemisphere during autumn and winter, carbon dioxide frost accumulates on the surface.

This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dunes covered and delineated by seasonal frost in the north polar region of Mars. The winds responsible for the formation of these dunes blew primarily from the northwest (upper left), with additional influences from the north and northeast. During the late spring and summer seasons, these dunes would look much darker than their surroundings, but in this late winter image, the dunes and the plains on which they occur are all covered with carbon dioxide frost.

Location near: 78.4oN, 76.7oW Image width: 3 km (1.9 mi) Illumination from: lower left Season: Northern Winter

2006-01-01

12

The sedimentary structure of linear sand dunes  

PubMed

Linear sand dunes--dunes that extend parallel to each other rather than in star-like or crescentic forms--are the most abundant type of desert sand dune. But because their development and their internal structure are poorly understood, they are rarely recognized in the rock record. Models of linear dune development have not been able to take into account the sub-surface structure of existing dunes, but have relied instead either on the extrapolation of short-term measurements of winds and sediment transport or on observations of near-surface internal sedimentary structures. From such studies, it has not been clear if linear dunes can migrate laterally. Here we present images produced by ground penetrating radar showing the three-dimensional sedimentary structure of a linear dune in the Namib sand sea, where some of the world's largest linear dunes are situated. These profiles show clear evidence for lateral migration in a linear dune. Moreover, the migration of a sinuous crest-line along the dune produces divergent sets of cross-stratification, which can become stacked as the dune height increases, and large linear dunes can support superimposed dunes that produce stacked sets of trough cross-stratification. These clear structural signatures of linear dunes should facilitate their recognition in geological records. PMID:10894538

Bristow; Bailey; Lancaster

2000-07-01

13

Point Pattern Analysis of Star-Dune Fields  

NASA Astrophysics Data System (ADS)

Star dunes are among the largest and most complex aeolian dunes in nature. Varying morphologies of star dunes are well documented; however, the dune-field scale properties of the pattern have received relatively little attention. This study addresses the spatial organization of star dune field patterns in the Erg Oriental, Edeyen Murzuq, Rub-al-Khali and the Gran Desierto. Areas targeted in each dune field display a transition from a simple dune pattern, in which only star forms occur, to a complex dune pattern where star dunes occur superimposed on relict linear and crescentic dune topography. Star-dune peaks determined from SRTM 90 digital elevation data are treated as points for point pattern analysis. Nearest-neighbor statistics are calculated across each dune field over 2500 sqkm intervals to characterize changes in the pattern. Dune peak spacing in simple star-dune patterns is highly disperse (R = 1.8), indicating a significant departure from a random point pattern. Simple star patterns also show a strong correlation between nearest neighbor spacing and height. Complex star dune patterns show a lower degree of dispersion and a weaker correlation between nearest neighbor spacing and height. Ultimately, these differences reflect both the control of the relict-dune pattern on the organization of the superimposed star-dune pattern and the overall maturity of the star-dune pattern.

Ewing, R. C.; McElroy, B. J.; Andrews, B. J.

2007-12-01

14

78 FR 23866 - Safety Zone; Crescent City 4th of July Fireworks; Crescent City Harbor, Crescent City, CA  

Federal Register 2010, 2011, 2012, 2013

...33 CFR Part 165 [Docket No. USCG-2013-0076] RIN 1625-AA00 Safety Zone; Crescent City 4th of July Fireworks; Crescent City Harbor, Crescent City, CA AGENCY: Coast Guard, DHS. ACTION: Notice of proposed...

2013-04-23

15

MAIN STREET WEST COLLEGE CRESCENT  

E-print Network

.................................... 43 David Braley Athletic Centre.... 54 Divinity College............................ 17 Dramatic Arts 11 MAIN STREET WEST COLLEGE CRESCENT COOTESDRIVE WESTAWAY ROAD SCHOLAR'S ROAD STEARN DRIVE EntranceCampus LEGEND McMaster University Entrance Security and Parking Services Parking Lot Location Pay Stations Short

Thompson, Michael

16

Sand Dunes  

NSDL National Science Digital Library

Most will agree that nothing is more relaxing that lying or walking on a beach. While unwinding, have you ever wondered what caused those big mounds of sand that you crossed to get there? This topic in depth addresses this issue, featuring Web sites that discuss sand dune processes and formations. Some of the Web sites also discuss research, mining, and protection activities taking place in areas with sand dune.The Environment Bay of Plenty in New Zealand has an online brochure (1) dealing with the coastal processes that form sand dunes and beaches. From this site, users can obtain a general understanding of how dunes change with time. Ted Brambleby developed the second site (2) for the Marine Education Society of Australasia, Inc. This site gives a great overview of the functions and formations of dunes as well as describing their unique beauty and strategies on how to care for the dunes. Produced by Nova Scotia Museum of Natural History, the third site (3) is an online pamphlet discussing the physical features and locations of sand dunes in Nova Scotia. Visitors can also read about the ecosystem supported by these dynamic features. The forth site (4), created by John Mangimeli for the National Park Service, is a review of the scientific research completed throughout the years dealing with the geology of sand dunes. Visitors will find a more in-depth discussion about sand movement, sand accumulation, and sand dune features. The fifth site is a scientific paper (5 ) written by R.L. Van Dam, et al. Studying the long term evolution of the Parengarenga Sandspit, these researchers used ground penetrating radar (GPR) "to (1) explore the possibilities for mapping lateral continuity of the coffee rock, (2) study the sedimentary architecture and stratigraphy of the solitary dunes, and (3) reconstruct the wind regime on the sandspit." The next two sites discuss the threats to sand dunes and activities taking place to protect them. The Lake Michigan Federation addresses the issues of mining (6). Visitors can learn about alternatives to mining dune sand and the ecological values of dunes. The Department of Environmental Quality in Michigan created a site (7) that provides users with statistical information dealing with the amount of sand harvested, the regulations of mining, and maps of critical dune areas. After learning about the formation, processes, threats, and protections efforts; the last site (8), created by Eva Hornecker with the University of Bremen, will allow users to get a real sense of the beauty of the sand dunes. The site features a collage of spectacular images of the Great Sand Dunes in the San Luis Valley.

Enright, Rachel

17

Dune Geomorphology  

NSDL National Science Digital Library

This activity was developed during the workshop, Teaching Climate Change: Insight from Large Lakes, held in June 2012. Dune Geomorphology by Anthony (Tony) Layzell, University of Kansas Main Campus J. Elmo ...

18

Russell Dunes  

NASA Technical Reports Server (NTRS)

26 March 2004 Dark streaks made by dozens of spring and summer dust devils created a form of martian graffiti on the sand dunes of Russell Crater near 54.5oS, 347.4oW. Gullies have developed on some of the dune slopes, as well. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image covers an area about 3 km (1.9 mi) across. Sunlight illuminates the scene from the upper left.

2004-01-01

19

Dune Variety  

NASA Technical Reports Server (NTRS)

[figure removed for brevity, see original site]

Our topic for the weeks of April 4 and April 11 is dunes on Mars. We will look at the north polar sand sea and at isolated dune fields at lower latitudes. Sand seas on Earth are often called 'ergs,' an Arabic name for dune field. A sand sea differs from a dune field in two ways: 1) a sand sea has a large regional extent, and 2) the individual dunes are large in size and complex in form.

Our final look at the north polar erg was taken at 80 degrees North latitude during Northern summer. This image is of lower resolution than the previous images, but covers a much larger area. The dunes have very little remaining frost cover. Note the large extent of coverage, and the different dune forms.

Image information: VIS instrument. Latitude 80.8, Longitude 184.6 East (175.4 West). 19 meter/pixel resolution.

Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

2005-01-01

20

Dune Exploration: Mars Allegories  

NASA Astrophysics Data System (ADS)

We know of one factual habitable planet, although other factual planets can be imagined as habitable. Sometimes the allegory is obvious. E.g., H. G. Wells imagined Martians exterminating humans as an allegory to Englishmen exterminating the Tasmanian aborigines, whilst Percival Lowell saw the global network of Martian canals as a world civilization that had progressed beyond war. But most habitable planets are overtly fictional. The planet properly known as Arrakis and colloquially known as Dune (Herbert 1965) provides an exceptionally well-developed example of a fictional habitable planet. In its particulars Dune resembles a warmer Mars with a breathable oxygen atmosphere. Like Mars, Dune is now a parched desert planet but there are signs that water flowed in the prehistoric past. Dune has small water ice caps at the poles and more extensive deep polar aquifers. The tropics are exceedingly dry but the polar regions are cool and moist enough to have morning dew. Dune is sparsely inhabited by a mix of indigenous and terran flora and fauna. The fictional Dune asks us to consider how much water is enough, why does oxygen accumulate in an atmosphere, and what actually sets the inner edge to the habitable zone. The inner edge of the habitable zone is conventionally set by the onset of the runaway greenhouse effect. The runaway greenhouse occurs when there is enough water vapor in the atmosphere to lift the planet's thermal photosphere off the ground. For a wet planet the mapping between saturation, temperature and optical depth is unique; together these set an upper limit on the rate the amount of thermal radiation that the planet can emit and still maintain a humid atmosphere. A dry atmosphere has a lower opacity for a given temperature, other things equal. With its vast dry equatorial deserts, a habitable Dune can radiate at a significantly higher effective temperature than a wet planet, and so it can provide an abode for life significantly closer to its sun. We use GCM modeling to show that liquid water can exist at places on the surface of a Dune-like planet at insolation levels as much as 170% of the present solar flux of the Earth.

Zahnle, K.; Sleep, N. H.; Abe, Y.; Abe-Ouchi, A.

2005-12-01

21

Spotty Dunes  

NASA Technical Reports Server (NTRS)

27 July 2004 Frost-covered dunes develop spots and streaks as they begin to defrost in springtime. This April 2004 Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a suite of north polar dunes in the early stages of the defrosting process. At the time the image was acquired, Mars was only 1 month into the northern spring season. The picture is located near 75.9oN, 266.0oW, and is illuminated by sunlight from the lower left. The image covers an area about 3 km (1.9 mi) wide.

2004-01-01

22

Copernicus Dunes  

NASA Technical Reports Server (NTRS)

22 December 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dark teardrop-shaped sand dunes in eastern Copernicus Crater. The winds responsible for these dunes generally blow from the south-southwest (lower left).

Location near: 48.7oS, 167.4oW Image width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Summer

2005-01-01

23

Minimal size of a barchan dune  

NASA Astrophysics Data System (ADS)

Barchans are dunes of high mobility which have a crescent shape and propagate under conditions of unidirectional wind. However, sand dunes only appear above a critical size, which scales with the saturation distance of the sand flux [P. Hersen, S. Douady, and B. Andreotti, Phys. Rev. Lett. 89, 264301 (2002); B. Andreotti, P. Claudin, and S. Douady, Eur. Phys. J. B 28, 321 (2002); G. Sauermann, K. Kroy, and H. J. Herrmann, Phys. Rev. E 64, 31305 (2001)]. It has been suggested by P. Hersen, S. Douady, and B. Andreotti, Phys. Rev. Lett. 89, 264301 (2002)] that this flux fetch distance is itself constant. Indeed, this could not explain the protosize of barchan dunes, which often occur in coastal areas of high litoral drift, and the scale of dunes on Mars. In the present work, we show from three-dimensional calculations of sand transport that the size and the shape of the minimal barchan dune depend on the wind friction speed and the sand flux on the area between dunes in a field. Our results explain the common appearance of barchans a few tens of centimeter high which are observed along coasts. Furthermore, we find that the rate at which grains enter saltation on Mars is one order of magnitude higher than on Earth, and is relevant to correctly obtain the minimal dune size on Mars.

Parteli, E. J. R.; Durán, O.; Herrmann, H. J.

2007-01-01

24

Minimal size of a barchan dune.  

PubMed

Barchans are dunes of high mobility which have a crescent shape and propagate under conditions of unidirectional wind. However, sand dunes only appear above a critical size, which scales with the saturation distance of the sand flux [P. Hersen, S. Douady, and B. Andreotti, Phys. Rev. Lett. 89, 264301 (2002); B. Andreotti, P. Claudin, and S. Douady, Eur. Phys. J. B 28, 321 (2002); G. Sauermann, K. Kroy, and H. J. Herrmann, Phys. Rev. E 64, 31305 (2001)]. It has been suggested by P. Hersen, S. Douady, and B. Andreotti, Phys. Rev. Lett. 89, 264301 (2002)] that this flux fetch distance is itself constant. Indeed, this could not explain the protosize of barchan dunes, which often occur in coastal areas of high litoral drift, and the scale of dunes on Mars. In the present work, we show from three-dimensional calculations of sand transport that the size and the shape of the minimal barchan dune depend on the wind friction speed and the sand flux on the area between dunes in a field. Our results explain the common appearance of barchans a few tens of centimeter high which are observed along coasts. Furthermore, we find that the rate at which grains enter saltation on Mars is one order of magnitude higher than on Earth, and is relevant to correctly obtain the minimal dune size on Mars. PMID:17358139

Parteli, E J R; Durán, O; Herrmann, H J

2007-01-01

25

Origins of barchan dune asymmetry: Insights from numerical simulations  

NASA Astrophysics Data System (ADS)

Barchan dunes — crescent-shaped dunes that form in areas of unidirectional winds and low sand availability — commonly display an asymmetric shape, with one limb extended downwind. Several factors have been identified as potential causes for barchan dune asymmetry on Earth and Mars: asymmetric bimodal wind regime, topography, influx asymmetry and dune collision. However, the dynamics and potential range of barchan morphologies emerging under each specific scenario that leads to dune asymmetry are far from being understood. In the present work, we use dune modeling in order to investigate the formation and evolution of asymmetric barchans. We find that a bimodal wind regime causes limb extension when the divergence angle between primary and secondary winds is larger than 90°, whereas the extended limb evolves into a seif dune if the ratio between secondary and primary transport rates is larger than 25%. Calculations of dune formation on an inclined surface under constant wind direction also lead to barchan asymmetry, however no seif dune is obtained from surface tilting alone. Asymmetric barchans migrating along a tilted surface move laterally, with transverse migration velocity proportional to the slope of the terrain. Limb elongation induced by topography can occur when a barchan crosses a topographic rise. Furthermore, transient asymmetric barchan shapes with extended limb also emerge during collisions between dunes or due to an asymmetric influx. Our findings can be useful for making quantitative inference on local wind regimes or spatial heterogeneities in transport conditions of planetary dune fields hosting asymmetric barchans.

Parteli, Eric J. R.; Durán, Orencio; Bourke, Mary C.; Tsoar, Haim; Pöschel, Thorsten; Herrmann, Hans

2014-03-01

26

Dune Field in Nili Pateria  

NASA Technical Reports Server (NTRS)

The Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) took this image of the southeastern edge of a large dune field within Nili Patera, an irregularly shaped volcanic caldera that is about 65 kilometers (40 miles) in diameter. The image was acquired at 1333 UTC (8:33 a.m. EST) on Feb. 1, 2007, near 8.8 degrees north latitude, 67.3 degrees east longitude. CRISM's image was taken in 544 colors covering 0.36-3.92 micrometers, and shows features as small as 20 meters (66 feet) across. The region covered by the image is just over 10 kilometers (6 miles) wide at its narrowest point.

The top image was constructed from three visible wavelengths that correspond to what our eyes would see; the colors are stretched to bring out subtle color contrast. The bottom image is a spectral map constructed using three infrared wavelengths that usually highlight compositional variations. Areas with high concentrations of iron- and magnesium-rich igneous minerals appear red.

The entire dune field, covering about 500 square kilometers, resides mainly in the southwest quadrant of the caldera, occupying approximately 15% of its floor. Some of the dune forms seen here are 'barchans' -- individual, crescent shaped dunes that form when winds come primarily from one direction, resulting in one slipface. The orientation of the slipfaces indicates that primary winds were coming from the east-northeast. Using images from Mars Global Surveyor's narrow-angle camera, researchers measured approximately 400 slipfaces throughout the dune field and calculated an average azimuth of 245 degrees. Some of the barchans have elongated horns, suggesting that they experienced a slight secondary wind, or that the primary wind direction varied a little. When sufficient sand is available, barchans will coalesce, losing their individual crescentic shape. The resulting dune form, referred to as barchanoid, describes the vast majority of dunes in this image.

In the lower left portion of the image, where the dune pattern is most regular, the distance from dune crest to dune crest is about 400 meters (437 yards). The relationship shown here, with barchans at the margin of a barchanoid dune field, is common on Mars.

CRISM's mission: Find the spectral fingerprints of aqueous and hydrothermal deposits and map the geology, composition and stratigraphy of surface features. The instrument will also watch the seasonal variations in Martian dust and ice aerosols, and water content in surface materials -- leading to new understanding of the climate.

The Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) is one of six science instruments on NASA's Mars Reconnaissance Orbiter. Led by The Johns Hopkins University Applied Physics Laboratory, the CRISM team includes expertise from universities, government agencies and small businesses in the United States and abroad.

2007-01-01

27

The length of the new crescent Moon  

Microsoft Academic Search

Danjon noticed that the length (cusp to cusp) of the new crescent moon was less than 180 degrees and suggested that the cause of the shortening is the shadows of the lunar mountains. McNally, however, attributed the crescent shortening to atmospheric seeing, while Schaefer suggests that length shortening is due to sharp falling off of the brightness towards the cusps.

A. H. Sultan

2005-01-01

28

77 FR 39413 - Safety Zone: Crescent City Fourth of July Fireworks Event, Crescent City, CA  

Federal Register 2010, 2011, 2012, 2013

...will sponsor the Crescent City Fourth of July Fireworks Event on...83) for the Crescent City Fourth of July Fireworks Event. At...Coast Guard respects the First Amendment rights of protesters. Protesters...Safety zone; Crescent City Fourth of July Fireworks Event,...

2012-07-03

29

VIEW OF HOWLAND HILL ROAD, JEDEDIAH SMITH STATE PARK. CRESCENT ...  

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

VIEW OF HOWLAND HILL ROAD, JEDEDIAH SMITH STATE PARK. CRESCENT CITY, DEL NORTE COUNTY, CALIFORNIA. LOOKING W. - Redwood National & State Parks Roads, California coast from Crescent City to Trinidad, Crescent City, Del Norte County, CA

30

VIEW OF HOWLAND HILL ROAD, JEDEDIAH SMITH STATE PARK. CRESCENT ...  

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

VIEW OF HOWLAND HILL ROAD, JEDEDIAH SMITH STATE PARK. CRESCENT CITY, DEL NORTE COUNTY, CALIFORNIA. LOOKING E. - Redwood National & State Parks Roads, California coast from Crescent City to Trinidad, Crescent City, Del Norte County, CA

31

VIEW OF HOWLAND HILL ROAD, JEDEDIAH SMITH STATE PARK. CRESCENT ...  

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

VIEW OF HOWLAND HILL ROAD, JEDEDIAH SMITH STATE PARK. CRESCENT CITY, DEL NORTH COUNTY, CALIFORNIA. LOOKING ESE. - Redwood National & State Parks Roads, California coast from Crescent City to Trinidad, Crescent City, Del Norte County, CA

32

DUNE FOREST RESTORATION  

E-print Network

concepts can be used to manage the restoration of a coastal dune forest in South Africa. The restoration of these dune forests is an essential part of the activities of Richards Bay Minerals (RBM) that mine coastal's economic well- being, and so are the coastal dunes. The forest on these dunes is part

Pretoria, University of

33

Crescentic glomerulonephritis without immune deposits: clinicopathologic features.  

PubMed

Of 46 patients with acute crescentic glomerulonephritis involving 20 to 90% of glomeruli, 16 had no definable systemic disease and no significant glomerular immune deposits by immunofluorescent or electron microscopy. Anti-GBM antibody and circulating immune complexes were further excluded by radioimmunoassay and Raji cell assay in all patients tested. Clinical features included a 10:6 male:female ratio, mean age of 58 years (range, 13-77), disease duration of less than 3 months, rapidly deteriorating renal function, and frequent pulmonary manifestations. Nine patients had oliguria, serum creatinine concentrations over 6 mg/100 ml, and required dialysis, but three of these patients subsequently recovered renal function. These three patients and seven patients with creatinine concentrations of less than 6 mg/100 ml have not progressed to chronic renal failure. In this series, idiopathic acute crescentic glomerulonephritis without immune deposits was more common than was immune complex or anti-GBM nephritis. The clinical, laboratory, and pathologic characteristics of these patients were similar to those reported in anti-GBM and immune-complex-induced glomerulonephritis. These observations expand the spectrum of rapidly progressive crescentic glomerulonephritis. They suggest that glomerular immune deposits may be less important than other factors in determining the extent of renal injury and subsequent clinical course in crescentic glomerulonephritis. PMID:390211

Stilmant, M M; Bolton, W K; Sturgill, B C; Schmitt, G W; Couser, W G

1979-02-01

34

Morphodynamic implications of flow around interacting barchan dunes  

NASA Astrophysics Data System (ADS)

Barchan dunes are three-dimensional topographic features characterized by a crescentic shape. These bedforms are ubiquitous on Earth's surface and are also observed on Mars. Barchan dunes are predominantly found in regions of sediment starvation and unidirectional flow. The barchans-dune migration rates for a given wind speed are a function of their respective volume. A barchan dune field is composed of a widely distributed dune size, which provides the potential for barchan dunes to approach and amalgamate. The mechanisms governing dune-dune interaction, collision and merging remain poorly understood for such complex three-dimensional bedforms due to the complexity of their shape and the high number of geometrical configurations that can occur. In order to quantify the flow structure produced by interacting barchan dunes, particle-image Velocimetry (PIV) is coupled with a refractive-index-matching (RIM) approach, facilitating full optical access to the obstructed regions of flow and eliminates reflections from the liquid-solid boundaries, allowing near-wall data to be collected. Transparent barchan dune models with different volumes are arranged in tandem, immersed in a turbulent flow and rendered invisible through accurate matching of the index of refraction of the solid and fluid phases. The approach applied herein facilitates flow-field measurements in both streamwise-wall-normal planes at varying spanwise positions and streamwise-spanwise planes at varying elevations. Ensemble-averaged flow fields and Reynolds stresses were obtained for different barchan dune spacings and compared to the reference case of an isolated barchan. Additionally, proper orthogonal decomposition (POD) analysis was employed to shed light as to the energetic attributes of the shear-layer interactions. The morphodynamic implications of these results are discussed. Shear-layer interactions between adjacent bedforms, stoss-side erosion and downstream separation of new bedforms from the upstream horn are found to be key aspects of the interaction process.

Tang, Z.; Blois, G.; Best, J.; Jiang, N.; Christensen, K. T.

2013-12-01

35

Creating Sand Dunes  

NSDL National Science Digital Library

This experiment demonstrates the formation and movement of sand dunes. Students will simulate the effects of wind using a hair dryer on bare sand, then add stones and grass to observe how the effects are changed. They should be able to explain how sand dunes are formed, what circumstances effect the movement or formation of sand dunes, and relate this information to soil conservation.

1998-01-01

36

Dynamics of crescent water wave patterns  

NASA Astrophysics Data System (ADS)

The nonlinear dynamics of three-dimensional instabilities of uniform gravity-wave trains evolving to crescent wave patterns is investigated numerically. A new mechanism of generation of oscillating horseshoe patterns is proposed and a detailed discussion on their occurrence in a water wave tank is given. It is suggested that these patterns are more likely to be observed naturally in water of finite depth. A critical wave steepness for the onset of three-dimensional wave breaking due to the nonlinear evolution of quintet resonant interactions corresponding to the phase-locked crescent-shaped structures (class II instability) is provided when the quartet resonant interaction (class I instability) is absent. The nonlinear coupling between quartet resonant interactions (class I instability) and quintet resonant interactions (class II instability) leading to three-dimensional breaking waves, as shown experimentally by Su & Green (1984, 1985), is numerically investigated.

Fructus, D.; Kharif, C.; Francius, M.; Kristiansen, Ø.; Clamond, D.; Grue, J.

2005-08-01

37

Scleroderma with crescentic glomerulonephritis: a case report  

PubMed Central

Introduction Systemic sclerosis or scleroderma is an autoimmune rheumatic disease characterized by organ-based fibrosis. Renal involvement in scleroderma occurs mainly in the form of scleroderma renal crisis, affecting 5 to 10% of patients. It remains one of the most important and immediately life-threatening complications of scleroderma, but the prognosis improves considerably after treatment with angiotensin-converting enzyme inhibitors. Other renal pathologies can occur in scleroderma. These include scleroderma overlap syndromes with associated features of lupus nephritis, myeloperoxidase anti-neutrophil cytoplasmic antibodies (ANCA) or proteinase 3 ANCA-associated glomerulonephritis, or crescentic glomerulonephritis. These alternative pathologies should be suspected in any individual patient with a differing clinical picture and the patient should be appropriately investigated. Crescentic glomerulonephritis occurs very rarely in scleroderma. This report describes a patient with scleroderma and crescentic glomerulonephritis. Case presentation A 52-year-old woman with a known history of scleroderma and hypertension on angiotensin-converting enzyme inhibitors was referred to the nephrologist because of a rapid decline in renal function. Kidney biopsy was performed which revealed immune complex type crescentic glomrulonephritis. Cytoplasmic-staining ANCA was negative. Despite immunosuppressive treatment the patient rapidly went into end-stage renal failure and is still on hemodialysis. Conclusion Scleroderma is a complex disease, and the best characterized renal involvement in scleroderma is scleroderma renal crisis. However, other renal pathologies can occur in scleroderma. These alternative pathologies should be suspected in any patient with a differing clinical picture and the patient should be appropriately investigated, as the clinical course and treatment are different from the more common scleroderma renal crisis. PMID:18474117

Ramaswami, Arunachalam; Kandaswamy, Thiraviam; Rajendran, Tholappan; Jeyakrishnan, Kizhake Pisharam; Aung, Hla; Iqbal, Mohammaed; Jacob, Chakko K; Zinna, Haji Shaukat; Kafeel, Gazala

2008-01-01

38

Suppression of Experimental Crescentic Glomerulonephritis by Deoxyspergualin  

Microsoft Academic Search

Deoxyspergualin is an immunosuppressive drug which is effective in both preventing allograft rejec- tion and suppressing steroid-resistant acute rejec- tion. This study was designed to determine whether deoxyspergualin could suppress the development of rapidly progressive crescentic glomerulonephritis in antigen-primed animals. Accelerated anti-gb- merular basement membrane (GBM) gbomerulo- nephritis was induced by priming rats with rabbit Immunogbobulin G (bgG), followed 5

Hui V. Lan; Mario Zarama; David J. Nikolic-Paterson; Peter G. Kerr; Robert C. Atkins; H. Y. Lan

39

33 CFR 80.1152 - Crescent City Harbor, CA.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 2013-07-01 false Crescent City Harbor, CA. 80.1152 Section 80.1152...LINES Pacific Coast § 80.1152 Crescent City Harbor, CA. A line drawn from Crescent City Entrance Light to the southeasternmost...

2013-07-01

40

33 CFR 80.1152 - Crescent City Harbor, CA.  

Code of Federal Regulations, 2011 CFR

...2011-07-01 2011-07-01 false Crescent City Harbor, CA. 80.1152 Section 80.1152...LINES Pacific Coast § 80.1152 Crescent City Harbor, CA. A line drawn from Crescent City Entrance Light to the southeasternmost...

2011-07-01

41

33 CFR 80.1152 - Crescent City Harbor, CA.  

Code of Federal Regulations, 2012 CFR

...2012-07-01 2012-07-01 false Crescent City Harbor, CA. 80.1152 Section 80.1152...LINES Pacific Coast § 80.1152 Crescent City Harbor, CA. A line drawn from Crescent City Entrance Light to the southeasternmost...

2012-07-01

42

33 CFR 80.1152 - Crescent City Harbor, CA.  

Code of Federal Regulations, 2010 CFR

...2010-07-01 2010-07-01 false Crescent City Harbor, CA. 80.1152 Section 80.1152...LINES Pacific Coast § 80.1152 Crescent City Harbor, CA. A line drawn from Crescent City Entrance Light to the southeasternmost...

2010-07-01

43

A numerical study of crescent waves  

NASA Astrophysics Data System (ADS)

In this paper, a high-order Boussinesq model is used to conduct a systematic numerical study of crescent (or horseshoe) water wave patterns in a tank, arising from the instability of steep deep-water waves to three-dimensional disturbances. The most unstable phase-locked (L2) crescent patterns are investigated, and comparisons with experimental measurements confirm the quantitative accuracy of the model. The unstable growth rate is also investigated, as are the effects of variable nonlinearity. The dominant physical mechanism is clearly demonstrated (through time and space series analysis) to be the established quintet resonant interaction, involving the primary wave with a pair of symmetric satellites. A numerical investigation into oscillating crescent patterns is also included, and a detailed account of the complicated oscillation cycle is presented. These patterns are shown to arise from quintet resonant interactions involving the primary wave with two unsymmetric satellite pairs. Pre-existing methods for analysing the stability of steep deep-water plane waves subject to three-dimensional perturbations are extended to provide accurate quantitative estimates for the oscillation period. A possible explanation for their selection in experiments is also provided. Finally, we use the model to conduct a series of experiments involving competition between various unstable modes. The results generally show that multiple instabilities can grow simultaneously, provided that they are of roughly equivalent strength. Results using random perturbations also match observations in physical experiments both in the form (i.e. two- or three-dimensional) and the location of the initial instability. The computational results are the first examples of highly nonlinear (to the breaking point) deep-water wave modeling in two horizontal dimensions with a Boussinesq model. The efficiency of the model has allowed for a quantitative study of these phenomena at significantly larger spatial and temporal scales than have been demonstrated previously, providing new insight into the complicated physical processes involved.

Fuhrman, David R.; Madsen, Per A.; Bingham, Harry B.

2004-08-01

44

The role of vegetation in shaping dune morphology  

NASA Astrophysics Data System (ADS)

Aeolian dunes naturally emerge under strong winds and sufficient sand supply. They represent the most dynamical feature of the arid and/or coastal landscape and their evolution has the potential to either increase desertification or reduce coastal vulnerability to storms. Although large-scale dune morphology mainly depends on the wind regime and sand availability, vegetation plays an important role in semiarid and/or coastal areas. It is well known that under certain conditions vegetation is able to stabilize dunes, driving a morphological transformation from un-vegetated mobile crescent dunes to static vegetated "parabolic" dunes, de facto paralyzing desertification and initiating land recovery. Furthermore, vegetation is also the primary ingredient in the formation of coastal foredunes, which determine vulnerability to storms, as low dunes are prone to storm-induced erosion and overwash. In both cases, the coupling of biological and geomorphic (physical) processes, in particular vegetation growth and sand transport, governs the evolution of morphology. These processes were implemented in a computational model as part of a previous effort. It was shown that, for a migrating dune, this coupling leads to a negative feedback for dune motion, where an ever denser vegetation implies ever lesser sand transport. The model also predicted the existence of a "mobility index", defined by the vegetation growth rate to sand erosion rate ratio, that fully characterizes the morphological outcome: for indices above a certain threshold biological processes are dominant and dune motion slows after being covered by plants; for lower indices, the physical processes are the dominant ones and the dune remains mobile while vegetation is buried or rooted out. Here, we extend this model to better understand the formation of coastal dunes. We include new physical elements such as the shoreline and water table, as well as different grass species and potential competition among them. Consistent with field observations, we find that basic dune morphology is primarily determined by grass species, with linear or hummocky dunes being built by some species, while others may prevent dune formation. We also find that the evolution of coastal dune morphology is controlled by at least two bio-geomorphic couplings: (1) between vegetation growth and sand transport, which leads to a positive feedback for dune growth, as certain beach grasses maximize growth under sand accretion, which means that an ever denser vegetation implies an ever higher accretion rate; and (2) between vegetation growth and shoreline position through the sand influx. While the first coupling is responsible for dune formation, the second one determines when dunes stop growing and thus controls final dune size. This is particularly relevant for accreting/eroding coastlines where we find that dune size, and thus coastal protection, is maximized for relatively small accretion rates while larger accretion rates lead to formation of a new, smaller dune ridge at the beach.

Duran Vinent, O.; Moore, L. J.; Young, D.

2012-12-01

45

Dynamic Sand Dunes  

Microsoft Academic Search

When sand falling in the spacing between two plates goes past an obstacle, a dynamic dune with a parabolic shape and an inner triangular region of nonflowing or slowly creeping sand forms. The angle of the triangular zone increases with the height of the dune and saturates at a value determined by the geometry of the cell. The width of

Y. Amarouchene; J. F. Boudet; H. Kellay

2001-01-01

46

Giant aeolian dune size determined by the average depth of the atmospheric boundary layer.  

PubMed

Depending on the wind regime, sand dunes exhibit linear, crescent-shaped or star-like forms resulting from the interaction between dune morphology and sand transport. Small-scale dunes form by destabilization of the sand bed with a wavelength (a few tens of metres) determined by the sand transport saturation length. The mechanisms controlling the formation of giant dunes, and in particular accounting for their typical time and length scales, have remained unknown. Using a combination of field measurements and aerodynamic calculations, we show here that the growth of aeolian giant dunes, ascribed to the nonlinear interaction between small-scale superimposed dunes, is limited by the confinement of the flow within the atmospheric boundary layer. Aeolian giant dunes and river dunes form by similar processes, with the thermal inversion layer that caps the convective boundary layer in the atmosphere acting analogously to the water surface in rivers. In both cases, the bed topography excites surface waves on the interface that in turn modify the near-bed flow velocity. This mechanism is a stabilizing process that prevents the scale of the pattern from coarsening beyond the resonant condition. Our results can explain the mean spacing of aeolian giant dunes ranging from 300 m in coastal terrestrial deserts to 3.5 km. We propose that our findings could serve as a starting point for the modelling of long-term evolution of desert landscapes under specific wind regimes. PMID:19242473

Andreotti, Bruno; Fourrière, Antoine; Ould-Kaddour, Fouzia; Murray, Brad; Claudin, Philippe

2009-02-26

47

Giant aeolian dune size determined by the average depth of the atmospheric boundary layer  

NASA Astrophysics Data System (ADS)

Depending on the wind regime, sand dunes exhibit linear, crescent-shaped or star-like forms resulting from the interaction between dune morphology and sand transport. Small-scale dunes form by destabilization of the sand bed with a wavelength (a few tens of metres) determined by the sand transport saturation length. The mechanisms controlling the formation of giant dunes, and in particular accounting for their typical time and length scales, have remained unknown. Using a combination of field measurements and aerodynamic calculations, we show here that the growth of aeolian giant dunes, ascribed to the nonlinear interaction between small-scale superimposed dunes, is limited by the confinement of the flow within the atmospheric boundary layer. Aeolian giant dunes and river dunes form by similar processes, with the thermal inversion layer that caps the convective boundary layer in the atmosphere acting analogously to the water surface in rivers. In both cases, the bed topography excites surface waves on the interface that in turn modify the near-bed flow velocity. This mechanism is a stabilizing process that prevents the scale of the pattern from coarsening beyond the resonant condition. Our results can explain the mean spacing of aeolian giant dunes ranging from 300 m in coastal terrestrial deserts to 3.5 km. We propose that our findings could serve as a starting point for the modelling of long-term evolution of desert landscapes under specific wind regimes.

Claudin, P.; Fourrière, A.; Andreotti, B.; Murray, A. B.

2009-12-01

48

Management of Mediterranean coastal dunes  

Microsoft Academic Search

This paper gives some theoretical concepts of dune management as well as practical examples of how actual measures should be carried out.Dune management is defined as all measures aimed at the preservation and restoration of the natural values of a coastal sand dune area. It is essential that beach and foreshore are seen as parts of a whole dune system.

F. van der Meulen; A. H. P. M. Salman

1996-01-01

49

Dynamic Sand Dunes  

NASA Astrophysics Data System (ADS)

When sand falling in the spacing between two plates goes past an obstacle, a dynamic dune with a parabolic shape and an inner triangular region of nonflowing or slowly creeping sand forms. The angle of the triangular zone increases with the height of the dune and saturates at a value determined by the geometry of the cell. The width of the dune, related to the radius of curvature at the tip, shows universal features versus its height rescaled by geometrical parameters. The velocity profile in the flowing part is determined and found to be nonlinear. The parabolic shape can be accounted for using a simple driven convection-diffusion equation for the interface.

Amarouchene, Y.; Boudet, J. F.; Kellay, H.

2001-05-01

50

Galactic dust measurements with DuneXpress  

NASA Astrophysics Data System (ADS)

DuneXpress is developed to perform in-situ characterisation of galactic interstellar dust and provides crucial information not achievable with astronomical methods. Galactic dust constitutes the solid phase of interstellar matter, from which stars and planetary systems form. Following the discovery by the Ulysses spacecraft of micronsized interstellar dust (ISD) grains passing trough the solar system, the analysis of Helios, Galileo and Cassini data within and beyond the Earth orbit showed that a significant amount of interstellar partciles. The flux of ISD at Earth distance was determined to 2 · 10-5m-2s-1. DuneXpress is an in-situ mission to investigate the directionality, mass distribution and composition of cosmic dust. A dust telescope measures the grain properties for individual particles entering the aperture. DuneXpress is developed by Dutch Space on the basis of the ConeXpress platform. DuneXpress benefits of launch opportunities as secondary payload on-board an Ariane 5 rocket and is injected into a classical geostationary transfer orbit (GTO). Starting from this parking orbit, electric propulsion raises the apocentre beyond moons distance for an injection into the lagrangian point L2. The DuneXpress mission was proposed in the Cosmic Vision frame of ESA in 2007.

Srama, R.; Altobelli, N.; Henkel, H.; Kempf, S.; Landgraf, M.; Krueger, H.; Sternovsky, Z.; Svedhem, H.; Vo, X.; Gruen, E.

2007-08-01

51

Dunes in Twilight  

NASA Technical Reports Server (NTRS)

17 January 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows frost-covered north polar dunes in early January 2004. When this picture was taken, the dunes were in twilight, just before the late winter dawn that would come a few days later. These dunes spent many of the last several months in complete darkness. In this image, they are illuminated only by sunlight that has been scattered over the horizon by the martian atmosphere. These dunes are located near 77.0oN, 246.2oW. The image covers an area 3 km (1.9 mi) wide and has been expanded by 200% from its original 12 meters (39 ft.) per pixel scale. While the sun had not yet risen when the image was obtained, illumination is mostly from the lower left.

2004-01-01

52

Isolated Northern Dunes  

NASA Technical Reports Server (NTRS)

[figure removed for brevity, see original site]

Our topic for the weeks of April 4 and April 11 is dunes on Mars. We will look at the north polar sand sea and at isolated dune fields at lower latitudes. Sand seas on Earth are often called 'ergs,' an Arabic name for dune field. A sand sea differs from a dune field in two ways: 1) a sand sea has a large regional extent, and 2) the individual dunes are large in size and complex in form.

This VIS image was taken at 81 degrees North latitude during Northern spring. In this region, the dunes are isolated from each other. The dunes are just starting to emerge from the winter frost covering appearing dark with bright crests. These dunes are located on top of ice.

Image information: VIS instrument. Latitude 82.1, Longitude 191.3 East (168.7 West). 19 meter/pixel resolution.

Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

2005-01-01

53

Windblown Dunes on the Floor of Herschel Impact Basin  

NASA Technical Reports Server (NTRS)

Herschel Basin, one of many meteor impact craters on Mars, has some dark material on its floor that appeared from earlier spacecraft missions to have been blown and/or deposited by wind. Herschel Basin was imaged at low resolution by the Mariner 9 and Viking orbiters ((A) above) in the 1970s, and again by the Phobos 2 orbiter in 1989.

On June 14, 1998, Mars Global Surveyor's Mars Orbiter Camera revealed that part of the dark surface on the floor of Herschel Basin consists of a field of sand dunes ((B) above). These dunes have a distinct crescent-like shape characteristic of dunes on Earth called barchan dunes. They result from winds that blow from a single dominant direction.

In the case of Herschel Basin, the dunes indicate that the strongest winds blow approximately north-to-south. The crescent horns on the ends of some of the dunes in this image are elongated. This condition indicates that the dominant winds do not always blow in exactly the same direction-- sometimes the winds blow from the northeast, sometimes from the northwest, and sometimes from the north. The local topography probably influences the wind direction--and hence dune shape--because this dune field is located on a narrow, low plain between a high crater rim to the east, and a narrow mountain range-- the inner ring of the Herschel impact basin--to the west (see image (A)).

MOC image 36507 was obtained on Mars Global Surveyor's 365th orbit around 10:51 a.m. PDT on June 14, 1998. This subframe is centered around 14.27oS, 231.68oW.

Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.

1998-01-01

54

Impacts of Vegetation and Development on the Morphology of Coastal Sand Dunes Using Modern Geospatial Techniques: Jockey's Ridge Case Study  

NASA Astrophysics Data System (ADS)

LiDAR surveys acquired in the years 2007 and 2008, combined with previous LiDAR, topographic mapping and aerial imagery collected along the Outer Banks of North Carolina were used for comprehensive geospatial analysis of the largest sand dune on the eastern coast of the United States, Jockey's Ridge. The objective of the analysis was to evaluate whether the dune's evolution has continued as hypothesized in previous studies and whether an increase of development and vegetation has contributed to the dune's stabilization and overall loss of dune height. Geospatial analysis of the dune system evolution (1974 - 2008) was performed using time series of digital elevation models at one meter resolution. Image processing was conducted in order to analyze land cover change (1932 - 2009) using unsupervised classification to extract vegetation, development and sand in and around Jockey's Ridge State Park. The dune system evolution was then characterized using feature-based and raster-based metrics, including vertical and horizontal change of dune peaks, horizontal migration of dune crests, slip face geometry transformation and volume change analysis using the core and dynamic layer concept. Based on the evolutionary data studied, the volume of sand at Jockey's Ridge is consistent throughout time, composed of a stable core and a dynamically migrating layer that is not gaining or losing sand. Although the peak elevation of the Main Dune has decreased from 43m in 1953 to 22m in 2008, the analysis has shown that the sand is redistributed within the dune field. Today, the dune field peaks are increasing in elevation, and all of the dunes within the system are stabilizing at similar heights of 20-22m along with transformation of the dunes from unvegetated, crescentic to vegetated, parabolic dunes. The overall land cover trend indicates that since the 1930s vegetation and development have gradually increased over time, influencing the morphology of the dune field by stabilizing the area of sand that once fed the dunes, limiting aeolian sand transport and migration of the dune system. Not only are vegetation and development increasing around the Jockey's Ridge State Park, but vegetation is increasing inside the park boundaries with the majority of growth along the windward side of the dune system, blocking sand from feeding the dunes. Vegetation growth is also found to increase in front of the dune field, recently causing the migration of the dune to slow down.

Weaver, K.; Mitasova, H.; Overton, M.

2011-12-01

55

Lunar Crescent Detection Based on Image Processing Algorithms  

NASA Astrophysics Data System (ADS)

For many years lunar crescent visibility has been studied by many astronomers. Different criteria have been used to predict and evaluate the visibility status of new Moon crescents. Powerful equipment such as telescopes and binoculars have changed capability of observations. Most of conventional statistical criteria made wrong predictions when new observations (based on modern equipment) were reported. In order to verify such reports and modify criteria, not only previous statistical parameters should be considered but also some new and effective parameters like high magnification, contour effect, low signal to noise, eyestrain and weather conditions should be viewed. In this paper a new method is presented for lunar crescent detection based on processing of lunar crescent images. The method includes two main steps, first, an image processing algorithm that improves signal to noise ratio and detects lunar crescents based on circular Hough transform (CHT). Second using an algorithm based on image histogram processing to detect the crescent visually. Final decision is made by comparing the results of visual and CHT algorithms. In order to evaluate the proposed method, a database, including 31 images are tested. The illustrated method can distinguish and extract the crescent that even the eye can't recognize. Proposed method significantly reduces artifacts, increases SNR and can be used easily by both groups astronomers and who want to develop a new criterion as a reliable method to verify empirical observation.

Fakhar, Mostafa; Moalem, Peyman; Badri, Mohamad Ali

2014-11-01

56

Lunar Crescent Detection Based on Image Processing Algorithms  

NASA Astrophysics Data System (ADS)

For many years lunar crescent visibility has been studied by many astronomers. Different criteria have been used to predict and evaluate the visibility status of new Moon crescents. Powerful equipment such as telescopes and binoculars have changed capability of observations. Most of conventional statistical criteria made wrong predictions when new observations (based on modern equipment) were reported. In order to verify such reports and modify criteria, not only previous statistical parameters should be considered but also some new and effective parameters like high magnification, contour effect, low signal to noise, eyestrain and weather conditions should be viewed. In this paper a new method is presented for lunar crescent detection based on processing of lunar crescent images. The method includes two main steps, first, an image processing algorithm that improves signal to noise ratio and detects lunar crescents based on circular Hough transform (CHT). Second using an algorithm based on image histogram processing to detect the crescent visually. Final decision is made by comparing the results of visual and CHT algorithms. In order to evaluate the proposed method, a database, including 31 images are tested. The illustrated method can distinguish and extract the crescent that even the eye can't recognize. Proposed method significantly reduces artifacts, increases SNR and can be used easily by both groups astronomers and who want to develop a new criterion as a reliable method to verify empirical observation.

Fakhar, Mostafa; Moalem, Peyman; Badri, Mohamad Ali

2014-09-01

57

Holden Crater Dune Field  

NASA Technical Reports Server (NTRS)

[figure removed for brevity, see original site]

Our topic for the weeks of April 4 and April 11 is dunes on Mars. We will look at the north polar sand sea and at isolated dune fields at lower latitudes. Sand seas on Earth are often called 'ergs,' an Arabic name for dune field. A sand sea differs from a dune field in two ways: 1) a sand sea has a large regional extent, and 2) the individual dunes are large in size and complex in form.

A common location for dune fields on Mars is in the basin of large craters. This dune field is located in Holden Crater at 25 degrees South atitude.

Image information: VIS instrument. Latitude -25.5, Longitude 326.8 East (33.2 West). 19 meter/pixel resolution.

Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

2005-01-01

58

Crater Floor Dune Field  

NASA Technical Reports Server (NTRS)

[figure removed for brevity, see original site]

Our topic for the weeks of April 4 and April 11 is dunes on Mars. We will look at the north polar sand sea and at isolated dune fields at lower latitudes. Sand seas on Earth are often called 'ergs,' an Arabic name for dune field. A sand sea differs from a dune field in two ways: 1) a sand sea has a large regional extent, and 2) the individual dunes are large in size and complex in form.

Our final dune image shows a small dune field inside an unnamed crater south of Nili Fossae.

Image information: VIS instrument. Latitude 20.6, Longitude 79 East (281 West). 19 meter/pixel resolution.

Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

2005-01-01

59

Sand ripples and dunes 1 Sand ripples and dunes  

E-print Network

Sand ripples and dunes 1 Sand ripples and dunes Franc¸ois Charru Institut de M´ecanique des Fluides of environments: in water channels, rivers and coastal ar- eas (Best 2005), in deserts on Earth (Bagnold 1941, Pye

60

Bright dunes on mars  

USGS Publications Warehouse

Seasonal changes observed on the surface of Mars can in part be attributed to the transport of geological materials by wind. Images obtained by orbiting spacecraft in the 1970s showed large wind-formed features such as dunes, and revealed regional time-varying albedos that could be attributed to the effects of dust erosion and deposition. But the resolution of these images was insufficient to identify different types and sources of aeolian materials, nor could they reveal aeolian deposits other than large dunes or extensive surface coverings that were redistributed by dust storms. Here we present images of Mars with up to 50 times better resolution. These images show that martian dunes include at least two distinct components, the brighter of which we interpret to be composed of relatively soft minerals, possibly sulphates. We also find large areas of the martian surface that have several metres or more of aeolian mantle lacking obvious bedforms.

Thomas, P. C.; Malin, M. C.; Carr, M. H.; Danielson, G. E.; Davies, M. E.; Hartmann, W. K.; Ingersoll, A. P.; James, P. B.; McEwen, A. S.; Soderblom, L. A.; Veverka, J.

1999-01-01

61

Can a Crescent Mars Ever Be Seen from Earth?  

ERIC Educational Resources Information Center

Described is an activity that incorporates a computer, geometry, algebra, trigonometry, and calculus to answer questions about the planet Mars. A possible crescent of Mars is compared to those of Venus and Mercury. (KR)

Lamb, John F., Jr.

1990-01-01

62

Nili Patera Dune Field  

NASA Technical Reports Server (NTRS)

[figure removed for brevity, see original site]

Our topic for the weeks of April 4 and April 11 is dunes on Mars. We will look at the north polar sand sea and at isolated dune fields at lower latitudes. Sand seas on Earth are often called 'ergs,' an Arabic name for dune field. A sand sea differs from a dune field in two ways: 1) a sand sea has a large regional extent, and 2) the individual dunes are large in size and complex in form.

This VIS image shows a dune field within Nili Patera, the northern caldera of a large volcanic complex in Syrtis Major.

Image information: VIS instrument. Latitude 9, Longitude 67 East (293 West). 19 meter/pixel resolution.

Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

2005-01-01

63

Frosted Chasma Boreale Dunes  

NASA Technical Reports Server (NTRS)

MGS MOC Release No. MOC2-390, 13 June 2003

This is a Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) view of frost-covered sand dunes in Chasma Boreale in the early northern spring season. Dark spots, some of them with bright halos of re-precipitated frost, have formed as the dunes begin to defrost. Most of the frost is carbon dioxide which freezes out of the atmosphere during the cold martian polar winters. This picture is located near 84.7oN, 358.8oW, and is illuminated from the lower left.

2003-01-01

64

Polar Dunes, Spotted  

NASA Technical Reports Server (NTRS)

23 August 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows sand dunes in the martian north polar region in mid-spring, July 2004. In summer, the dunes will be dark. As they defrost, dark spots form on their surfaces. This image is located near 82.8oN, 219.6oW. The image covers an area about 3 km (1.9 mi) across and sunlight illuminates the scene from the lower left.

2004-01-01

65

Large eddy simulation of interacting barchan dunes in a steady, unidirectional flow  

NASA Astrophysics Data System (ADS)

Barchan dunes are bed forms found in many sedimentary environments with a limited supply of sediment, and may occur in isolation or in more complex dune fields. Barchans have a crescentic planform morphology with horns elongated in the downflow direction. To study flow over barchan dunes, we performed large eddy simulations in a channel with different interdune spacings at a flow Reynolds number, Re??26,000 (based on the free stream velocity and channel height). The largest interdune spacing (2.38?, where ? is the wavelength of the barchan dune) presents similar characteristics to a solitary dune in isolation, indicating that, at this distance, the sheltering effect of the upstream dune is rather weak. Barchan dunes induce two counterrotating streamwise vortices, one along each of the horns, which direct high-momentum fluid toward the symmetry plane and low-momentum fluid near the bed away from the centerline. The flow close to the centerline plane separates at the crest, but away from the centerline plane, and along the horns, flow separation occurs intermittently. The flow in the separation bubble is directed toward the horns and leaves the dune at its tips. The internal boundary layer developing on the bed downstream of the reattachment region develops similarly for various interdune spacings; the development slows down 14.5 dune heights downstream. The turbulent kinetic energy budgets show the importance of pressure transport and mean flow advection in transferring energy from the overlying wake layer to the internal boundary layer over the stoss side. For closely spaced dunes, the bed shear stress is 30% larger than at the largest spacing, and instantaneous coherent high- and low-speed streaks are shorter but stronger. Coherent eddies in the separated shear layer are generated more frequently for smaller interdune spacing, where they move farther away from the bed, toward the free surface, and remain located between the horns.

Omidyeganeh, Mohammad; Piomelli, Ugo; Christensen, Kenneth T.; Best, James L.

2013-12-01

66

Efficiency characteristics of crescent-shaped wings and caudal fins  

NASA Technical Reports Server (NTRS)

Caudal (tail) fins of fish and aquatic mammals that cruise long distances, and wings of certain birds, often have the shape of a crescent moon. This study investigates how the crescent shape contributes to the traveling performance of these animals. A steady-flow theory (Maskew, 1982) that correctly models the trailing wake was used to analyze lifting surface efficiency, which is dependent on the level of induced (or vortex) drag for a given lift and span of the lifting surface. This analysis shows that backward curvature of a wing improves induced efficiency to a value greater than that of the flat untwisted wing of elliptical shape considered optimal in classical wing theory (Prandt, 1921 and Munk, 1921). This increase of induced efficiency results from the nonplanar trailing vortex sheet produced by the crescent-shaped wing at a given angle of attack.

Van Dam, C. P.

1987-01-01

67

City-swallowing Sand Dunes  

NSDL National Science Digital Library

At this Science at NASA site, you'll learn about the physics of sand movement and the research done to understand mechanisms of dune migration. The physics and the landforms are interesting because granular materials like sand show properties of both solids and fluids, including saltation, sheet flow, and avalanches. This site provides a summary of the physics involved along with photographs of sand dunes on Mars, close-ups of sand particles, and a sand dune advancing on a town.

Bell, Trudy E.

2007-06-19

68

The Muslim Brotherhood and the Emerging ‘Shia Crescent’  

Microsoft Academic Search

To form a more prudent foreign policy toward the Muslim Brotherhood, we must understand it not only as a domestic actor, but also as a major regional player. In fact, the Brotherhood has a complex relationship with Iran and the Shias, which blurs the lines of the so-called Shia Crescent. This article addresses the Muslim Brotherhood's foreign\\/regional policy by analyzing

Samuel Helfont

2009-01-01

69

Study of Danjon limit in moon crescent sighting  

NASA Astrophysics Data System (ADS)

About 70 years ago "André Danjon" a French astrophysicist showed that as elongation of the moon decreases the arc length of crescent gets less too. By studying the recent observational data, he concluded that at 7 degree elongation, the length of arc (cusp to cusp) will reach zero degree. Today, this value is named as Danjon limit, which points to the limit at which the moon crescent is formed. Danjon believed that the effective factor for occurring this limit was the shadows of moon's mountains. Later researchers have obtained different values for this limit. In this research based on the new data, the decreasing dependence of length of arc versus elongation was obtained. The results show that the Danjon limit is about 5 degrees. The effective factors to form the Danjon limit are then given and discussed. By considering the effects of astronomical seeing and shadows of lunar features, the values of the arc length were calculated and compared with the observational data curve. The results of this study show good agreement with the observational data. The present research shows that the above-mentioned effects can reduce the length of arc. The effect of libration and roughness of the lunar terrain of the moon in forming the moon crescent were also considered, and the possibility of observing thinner crescents by photometric model and breaking the Danjon limit were given.

Hasanzadeh, Amir

2012-06-01

70

Martian Dunes in Infrared  

NASA Technical Reports Server (NTRS)

This collage of six images taken by the camera system on NASA's Mars Odyssey, shows examples of the daytime temperature patterns of martian dunes seen by the infrared camera. The dunes can be seen in this daytime image because of the temperature differences between the sunlit (warm and bright) and shadowed (cold and dark) slopes of the dunes. The temperatures in each image vary, but typically range from approximately -35 degrees Celsius (-31 degrees Fahrenheit) to -15degrees Celsius (5 degrees Fahrenheit). Each image covers an area approximately 32 by 32 kilometers (20 by 20 miles) and was acquired using the infrared Band 9, centered at 12.6 micrometers. Clockwise from the upper left, these images are: (a) Russel crater, 54 degrees south latitude, 13 degrees east longitude; (b) Kaiser crater. 45degrees south latitude, 19 degrees east longitude; (c) Rabe crater, 43south latitude, 35 east longitude; (d) 22 north latitude, 66 degrees east longitude; (e) Proctor crater. 47 degrees south latitude, 30 degrees east longitude; (f) 61 degrees south latitude, 201 degrees east longitude.

The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the 2001 Mars Odyssey mission for NASA's Office of Space Science in Washington, D.C. Investigators at Arizona State University in Tempe, the University of Arizona in Tucson and NASA's Johnson Space Center, Houston, operate the science instruments. Additional science partners are located at the Russian Aviation and Space Agency and at Los Alamos National Laboratories, New Mexico. Lockheed Martin Astronautics, Denver, is the prime contractor for the project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL.

2002-01-01

71

Biogenic crust dynamics on sand dunes.  

PubMed

Sand dunes are often covered by vegetation and biogenic crusts. Despite their significant role in dune stabilization, biogenic crusts have rarely been considered in model studies of dune dynamics. Using a simple model, we study the existence and stability ranges of different dune-cover states along gradients of rainfall and wind power. Two ranges of alternative stable states are identified: fixed crusted dunes and fixed vegetated dunes at low wind power; and fixed vegetated dunes and active dunes at high wind power. These results suggest a crossover between two different forms of desertification. PMID:23496449

Kinast, Shai; Meron, Ehud; Yizhaq, Hezi; Ashkenazy, Yosef

2013-02-01

72

Sojourner at Mermaid Dune  

NASA Technical Reports Server (NTRS)

This color image of the Sojourner rover was taken at the end of day on Sol 30. The rover is perched atop Mermaid Dune, a dark material distinct from the surrounding bright surface. Dark red rover tracks extend from the foreground to the base of the rover's wheels.

Mars Pathfinder is the second in NASA's Discovery program of low-cost spacecraft with highly focused science goals. The Jet Propulsion Laboratory, Pasadena, CA, developed and managed the Mars Pathfinder mission for NASA's Office of Space Science, Washington, D.C. JPL is a division of the California Institute of Technology (Caltech).

1997-01-01

73

Ripples or Dunes?  

NASA Technical Reports Server (NTRS)

This approximate true-color image taken by the Mars Exploration Rover Spirit's panoramic camera shows the windblown waves of soil that characterize the rocky surface of Gusev Crater, Mars. Scientists were puzzled about whether these geologic features were 'ripples' or 'dunes.' Ripples are shaped by gentle winds that deposit coarse grains on the tops or crests of the waves. Dunes are carved by faster winds and contain a more uniform distribution of material. Images taken of these features by the rover's microscopic imager on the 41st martian sol, or day, of the rover's mission revealed their identity to be ripples. This information helps scientists better understand the winds that shape the landscape of Mars. This image was taken early in Spirit's mission.

[figure removed for brevity, see original site] Click on image for larger view [Image credit: NASA/JPL/ASU]

This diagram illustrates how windblown sediments travel. There are three basic types of particles that undergo different motions depending on their size. These particles are dust, sand and coarse sand, and their sizes approximate flour, sugar, and ball bearings, respectively. Sand particles move along the 'saltation' path, hitting the surface downwind. When the sand hits the surface, it sends dust into the atmosphere and gives coarse sand a little shove. Mars Exploration Rover scientists are studying the distribution of material on the surface of Mars to better understand how winds shaped the landscape.

2004-01-01

74

Closeup of Mermaid Dune  

NASA Technical Reports Server (NTRS)

This pair of images shows a broad view (upper image) and detailed close-up view (lower image) of the disturbed surface near and on Mermaid Dune. Seen slightly right of center in the upper image are two diggings by the rover's wheel. The uppermost rut is in the surface away from Mermaid and is considered to be typical of the surface at the landing site. The closer rut represents the surface at the base of Mermaid on the upwind side. The lower image is an enlargement of the disturbed Mermaid sediments plus those of the underlying substrate; that is, the ground upon which the dune lies. Seen in the close-up are at least two types of sediment, one that seems to be approximately 1.4 cm thick and forms piles with sides sloping at approximately 35 degrees, and another at least 3 cm deep composed of sediment that has a characteristic slope of 41 degrees when piled. It is apparent in the images that there is a size range of sediment present in the rut, sediment that ranges from a few millimeters in size down to below the resolution of the camera.

Mars Pathfinder is the second in NASA's Discovery program of low-cost spacecraft with highly focused science goals. The Jet Propulsion Laboratory, Pasadena, CA, developed and manages the Mars Pathfinder mission for NASA's Office of Space Science, Washington, D.C. JPL is a division of the California Institute of Technology (Caltech).

1997-01-01

75

Crescent Wing Planforms Reduce Lift-Dependent Drag  

NASA Technical Reports Server (NTRS)

New understanding of optimization of design of wing to minimize induced drag developed by use of computational methods that account properly for nonlinear effects of deflected wake, nonplanar shape of wing, and vortex rollup. Crescent planforms are lunate shapes like some found in nature, similar to certain bird wings and fish fins. Theoretical and experimental analyses reveals superior aerodynamic efficiency and improved high-angle-of-attack characteristics.

Holmes, Bruce J.; Vijgen, Paul M. H. W.; Vandam, C. P.

1991-01-01

76

Techniques for GIS modeling of coastal dunes  

Microsoft Academic Search

Coastal dunes present a unique problem to coastal scientists because of the dynamic nature of most coastal dune systems. Coastal dunes can change shape quickly and frequently due to storm-generated winds and waves. Prevailing winds can transport significant amounts of sand throughout the dune system. Topographic and volumetric changes in a 150×40 m site on the Outer Banks of North

Brian D. Andrews; Paul A. Gares; Jeffrey D. Colby

2002-01-01

77

Numerical modeling of the wind flow over a transverse dune  

PubMed Central

Transverse dunes, which form under unidirectional winds and have fixed profile in the direction perpendicular to the wind, occur on all celestial objects of our solar system where dunes have been detected. Here we perform a numerical study of the average turbulent wind flow over a transverse dune by means of computational fluid dynamics simulations. We find that the length of the zone of recirculating flow at the dune lee — the separation bubble — displays a surprisingly strong dependence on the wind shear velocity, u*: it is nearly independent of u* for shear velocities within the range between 0.2?m/s and 0.8?m/s but increases linearly with u* for larger shear velocities. Our calculations show that transport in the direction opposite to dune migration within the separation bubble can be sustained if u* is larger than approximately 0.39?m/s, whereas a larger value of u* (about 0.49?m/s) is required to initiate this reverse transport. PMID:24091456

Araujo, Ascanio D.; Parteli, Eric J. R.; Poschel, Thorsten; Andrade, Jose S.; Herrmann, Hans J.

2013-01-01

78

Three-dimensional modeling of an aeolian dune/interdune system: Applications to hydrocarbon production  

SciTech Connect

The Al Liwa region of the northeast Rub Al Khali, United Arab Emirates, comprises compound crescentic draa and subcircular inland sabkhas that are flanked to their north by a sand sea of smaller dunes extending almost to the coast of the Arabian Gulf. This controlled the supply of sand from the north and influenced water-table positions within interdune areas. The draa, up to 170 m high, comprise both fine and coarse sands with a strong carbonate component, and are migrating very slowly to the south-southeast. The evaporite-encrusted interdune sabkhas often are underlain by foreset dune sands that also indicate transport to the south-southeast. The northern fringe of smaller dunes migrates southward more rapidly than the draa, but their northern supply of sand now has been cut off by flooding of the Gulf, initiating the deflation of coastal areas down to the water table. A deep-penetrating radar survey, coupled with large-scale trenching, provides a three-dimensional model of dune/interdune systems. This fieldwork aids a clearer understanding of dune/interdune heterogeneities and interconnectedness, which in turn is providing more realistic reservoir models for interwell simulation studies within the Permian Rotliegende gas fields of northwest Europe.

Pugh, J.M.; Glennie, K.W.; Williams, B.P.J. (Univ. of Aberdeen, Aberdeen (United Kingdom))

1993-09-01

79

Summary of the Third International Planetary Dunes Workshop: remote sensing and image analysis of planetary dunes  

USGS Publications Warehouse

The Third International Planetary Dunes Workshop took place in Flagstaff, AZ, USA during June 12–15, 2012. This meeting brought together a diverse group of researchers to discuss recent advances in terrestrial and planetary research on aeolian bedforms. The workshop included two and a half days of oral and poster presentations, as well as one formal (and one informal) full-day field trip. Similar to its predecessors, the presented work provided new insight on the morphology, dynamics, composition, and origin of aeolian bedforms on Venus, Earth, Mars, and Titan, with some intriguing speculation about potential aeolian processes on Triton (a satellite of Neptune) and Pluto. Major advancements since the previous International Planetary Dunes Workshop include the introduction of several new data analysis and numerical tools and utilization of low-cost field instruments (most notably the time-lapse camera). Most presentations represented advancement towards research priorities identified in both of the prior two workshops, although some previously recommended research approaches were not discussed. In addition, this workshop provided a forum for participants to discuss the uncertain future of the Planetary Aeolian Laboratory; subsequent actions taken as a result of the decisions made during the workshop may lead to an expansion of funding opportunities to use the facilities, as well as other improvements. The interactions during this workshop contributed to the success of the Third International Planetary Dunes Workshop, further developing our understanding of aeolian processes on the aeolian worlds of the Solar System.

Fenton, Lori K.; Hayward, Rosalyn K.; Horgan, Briony H.N.; Rubin, David M.; Titus, Timothy N.; Bishop, Mark A.; Burr, Devon M.; Chojnacki, Matthew; Dinwiddie, Cynthia L.; Kerber, Laura; Gall, Alice Le; Michaels, Timothy I.; Neakrase, Lynn D.V.; Newman, Claire E.; Tirsch, Daniela; Yizhaq, Hezi; Zimbelman, James R.

2013-01-01

80

Recent Aeolian Dune Change on Mars  

NASA Technical Reports Server (NTRS)

Previous comparisons of Martian aeolian dunes in satellite images have not detected any change in dune form or position. Here, we show dome dunes in the north polar region that shrank and then disappeared over a period of 3.04 Mars years (5.7 Earth years), while larger, neighboring dunes showed no erosion or movement. The removal of sand from these dunes indicates that not only is the threshold wind speed for saltation exceeded under present conditions on Mars, but that any sand that is available for transport is likely to be moved. Dunes that show no evidence of change could be crusted, indurated. or subject to infrequent episodes of movement.

Bourke, M. C.; Edgett, K. S.; Cantor, B. A.

2007-01-01

81

Channels on Dunes in Russell Crater  

NASA Technical Reports Server (NTRS)

Hundreds of enigmatic small channels are seen to carve into the slopes of these dark sand dunes lying within Russell Crater on Mars. These features were previously identified as gullies in images from the Mars Orbiter Camera (MOC) on Mars Global Surveyor, but the higher resolution HiRISE image brings out many new details and mysteries. The channels extend from near the top of the dunes to their bases, indicating that some fluid material carved into the sand. The channels commonly begin as smaller tributaries joined together, suggesting several sources of fluid. Distinct dark spots are located near where the channels seem to originate. Several channels appear to originate at alcoves. Several of these channels have sinuous middle reaches while others are straighter. Further down slope, some channel edges appear elevated above the surrounding terrain, particularly in the lower reaches. The channels seem to terminate abruptly, with no deposition of material, unlike at the bases of some other gullies on Mars that are not on dunes.

One hypothesis for the origin of the channels, which has previously been proposed by the MOC team, is that CO2 (or maybe H2O) frost is deposited on the dunes in shadows or at night. Some frost may also be incorporated into the internal parts of the dunes due to natural avalanching. When the frost is eventually heated by sunlight, rapid sublimation triggers an avalanche of fluidized sand, forming a gully. HiRISE will continue to target small channel features such as these and may return to search for any changes over time.

Image PSP_001440_1255 was taken by the High Resolution Imaging Science Experiment (HiRISE) camera onboard the Mars Reconnaissance Orbiter spacecraft on November 16, 2006. The complete image is centered at -54.2 degrees latitude, 12.9 degrees East longitude. The range to the target site was 251.4 km (157.1 miles). At this distance the image scale is 50.3 cm/pixel (with 2 x 2 binning) so objects 151 cm across are resolved. The image shown here has been map-projected to 50 cm/pixel and north is up. The image was taken at a local Mars time of 3:41 PM and the scene is illuminated from the west with a solar incidence angle of 85 degrees, thus the sun was about 5 degrees above the horizon. At a solar longitude of 136.3 degrees, the season on Mars is Northern Summer.

NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Mars Reconnaissance Orbiter for NASA's Science Mission Directorate, Washington. Lockheed Martin Space Systems, Denver, is the prime contractor for the project and built the spacecraft. The High Resolution Imaging Science Experiment is operated by the University of Arizona, Tucson, and the instrument was built by Ball Aerospace and Technology Corp., Boulder, Colo.

2006-01-01

82

Mesopotamian fertile crescent nearly gone, new study indicates  

NASA Astrophysics Data System (ADS)

Something is terribly amiss in the marshlands of the fertile crescent of Mesopotamia, where the Tigris and Euphrates Rivers flow, and where Gilgamesh, the hero of an epic that dates at least as far back as the third millennium B.C., ruled.The marshlands, which are located primarily in Iraq and once extended between 15,000 and 20,000 square kilometers, now have been reduced to less than 1,500 to 2,000 square kilometers, according to a new study issued May 18 by the United Nations Environment Programme (UNEP). The marshlands could disappear in the near future if no immediate corrective actions are taken, according to Hassan Partow, the principal author of the UNEP study and a scientist within the agency's division of early warning and assessment.

Showstack, Randy

83

Geology Fieldnotes: Indiana Dunes National Lakeshore  

NSDL National Science Digital Library

The Indiana Dunes National Lakeshore site contains park geology information, park maps, related links, and visitor information. The park geology section discusses the park's geologic history, dunes, moraines, and vegetation. The park maps section contains links to a park features map and a map of the Indiana Dunes National Lakeshore.

84

Mean residence time in barchan dunes  

NASA Astrophysics Data System (ADS)

A barchan dune migrates when the sediment trapped on its lee side is remobilized by the flow. Then, sand grains may undergo many dune turnover cycles before their ejection along the horns, but the amount of time a sand grain contributes to the dune morphodynamics remains unknown. To estimate such a residence time, we analyze sediment particle motions in steady-state barchan dunes by tracking individual cells of a 3D cellular automaton dune model. The overall sediment flux may be decomposed into advective and dispersive fluxes to estimate the relative contribution of the underlying physical processes to the barchan dune shape. The net lateral sediment transport from the center to the horns indicates that dispersion on the stoss slope is more efficient than avalanches on the lee slope. The combined effect of these two antagonistic dispersive processes restricts the lateral mixing of sediment particles in the central region of barchan dunes. Then, for different flow strengths and dune sizes, we find that the mean residence time of sediment particles in barchan dunes is equal to the surface of the central longitudinal dune slices divided by the input sand flux. We infer that this central slice contains most of the relevant information about barchan dune morphodynamics. Finally, we initiate a discussion about sediment transport and memory in presence of bed forms using the advantages of the particle tracking technique.

Zhang, D.; Yang, X.; Rozier, O.; Narteau, C.

2013-12-01

85

A high spatio-temporal methodology for monitoring dunes morphology based on precise GPS-NRTK profiles: Test-case of Dune of Mónsul on the south-east Spanish coastline  

NASA Astrophysics Data System (ADS)

The effects of erosion and accretion of sand dune systems are often underestimated due to the coarse spatial and temporal resolution data set. This paper shows a specific methodology to monitor, at local scale and high repeatability, the crescentic dune of Mónsul in Almería (SE Spain). Precise spatial information based on high resolution profiles has been obtained periodically by repeated GPS surveys. The dune morphology and associated changes due to erosion and accretion are investigated using the GPS methodology in RTK (Real Time Kinematic) mode. This technique introduces significant improvements compared to other techniques for monitoring small areas such as better repeatability, accuracy, reliability, etc. The availability of the Andalusian Positioning Network, an active network over the region, allowed us to monitor the dune throughout GPS profiles capturing its evolution for the period of April-September, 2010. Three GPS campaigns spaced over time were performed. The framework is established by the active network, avoiding the placement of a local control network in this protected area. The main objective of this study is to perform a control methodology based on NRTK (network RTK) positioning supported by a regional active network, with special emphasis on checking and filtering the surveyed data. The numerical and graphical results presented show a balance between the values of erosion and accretion of sand on the dune.

Garrido, M. S.; Giménez, E.; Ramos, M. I.; Gil, A. J.

2013-03-01

86

Mars global digital dune database: MC-30  

USGS Publications Warehouse

The Mars Global Digital Dune Database (MGD3) provides data and describes the methodology used in creating the global database of moderate- to large-size dune fields on Mars. The database is being released in a series of U.S. Geological Survey Open-File Reports. The first report (Hayward and others, 2007) included dune fields from lat 65° N. to 65° S. (http://pubs.usgs.gov/of/2007/1158/). The second report (Hayward and others, 2010) included dune fields from lat 60° N. to 90° N. (http://pubs.usgs.gov/of/2010/1170/). This report encompasses ~75,000 km2 of mapped dune fields from lat 60° to 90° S. The dune fields included in this global database were initially located using Mars Odyssey Thermal Emission Imaging System (THEMIS) Infrared (IR) images. In the previous two reports, some dune fields may have been unintentionally excluded for two reasons: (1) incomplete THEMIS IR (daytime) coverage may have caused us to exclude some moderate- to large-size dune fields or (2) resolution of THEMIS IR coverage (100 m/pixel) certainly caused us to exclude smaller dune fields. In this report, mapping is more complete. The Arizona State University THEMIS daytime IR mosaic provided complete IR coverage, and it is unlikely that we missed any large dune fields in the South Pole (SP) region. In addition, the increased availability of higher resolution images resulted in the inclusion of more small (~1 km2) sand dune fields and sand patches. To maintain consistency with the previous releases, we have identified the sand features that would not have been included in earlier releases. While the moderate to large dune fields in MGD3 are likely to constitute the largest compilation of sediment on the planet, we acknowledge that our database excludes numerous small dune fields and some moderate to large dune fields as well. Please note that the absence of mapped dune fields does not mean that dune fields do not exist and is not intended to imply a lack of saltating sand in other areas. Where availability and quality of THEMIS visible (VIS), Mars Orbiter Camera (MOC) narrow angle, Mars Express High Resolution Stereo Camera, or Mars Reconnaissance Orbiter Context Camera and High Resolution Imaging Science Experiment images allowed, we classified dunes and included some dune slipface measurements, which were derived from gross dune morphology and represent the approximate prevailing wind direction at the last time of significant dune modification. It was beyond the scope of this report to look at the detail needed to discern subtle dune modification. It was also beyond the scope of this report to measure all slipfaces. We attempted to include enough slipface measurements to represent the general circulation (as implied by gross dune morphology) and to give a sense of the complex nature of aeolian activity on Mars. The absence of slipface measurements in a given direction should not be taken as evidence that winds in that direction did not occur. When a dune field was located within a crater, the azimuth from crater centroid to dune field centroid was calculated, as another possible indicator of wind direction. Output from a general circulation model is also included. In addition to polygons locating dune fields, the database includes ~700 of the THEMIS VIS and MOC images that were used to build the database.

Hayward, R.K.; Fenton, L.K.; Titus, T.N.; Colaprete, A.; Christensen, P.R.

2012-01-01

87

Mammalian target of rapamycin complex 1 activation in podocytes promotes cellular crescent formation.  

PubMed

Podocytes play a key role in the formation of cellular crescents in experimental and human diseases. However, the underlying mechanisms for podocytes in promoting crescent formation need further investigation. Here, we demonstrated that mammalian target of rapamycin complex 1 (mTORC1) signaling was remarkably activated and hypoxia-inducible factor (HIF) 1? expression was largely induced in cellular crescents from patients with crescentic glomerular diseases. Specific deletion of Tsc1 in podocytes led to mTORC1 activation in podocytes and kidney dysfunction in mice. Interestingly, 33 of 36 knockouts developed cellular or mixed cellular and fibrous crescents at 7 wk of age (14.19 ± 3.86% of total glomeruli in knockouts vs. 0% in control littermates, n = 12-36, P = 0.04). All of the seven knockouts developed crescents at 12 wk of age (30.92 ± 11.961% of total glomeruli in knockouts vs. 0% in control littermates, n = 4-7, P = 0.002). Most notably, bridging cells between the glomerular tuft and the parietal basement membrane as well as the cellular crescents were immunostaining positive for WT1, p-S6, HIF1?, and Cxcr4. Furthermore, continuously administrating rapamycin starting at 7 wk of age for 5 wk abolished crescents as well as the induction of p-S6, HIF1?, and Cxcr4 in the glomeruli from the knockouts. Together, it is concluded that mTORC1 activation in podocytes promotes cellular crescent formation, and targeting this signaling may shed new light on the treatment of patients with crescentic glomerular diseases. PMID:24990893

Mao, Junhua; Zeng, Zhifeng; Xu, Zhuo; Li, Jiangzhong; Jiang, Lei; Fang, Yi; Xu, Xianlin; Hu, Zhangxue; He, Weichun; Yang, Junwei; Dai, Chunsun

2014-11-01

88

Daily cycles in coastal dunes  

USGS Publications Warehouse

Daily cycles of summer sea breezes produce distinctive cyclic foreset deposits in dune sands of the Texas and Oregon coasts. In both areas the winds are strong enough to transport sand only during part of the day, reach a peak during the afternoon, and vary little in direction during the period of sand transport. Cyclicity in the foreset deposits is made evident by variations in the type of sedimentary structure, the texture, and the heavy-mineral content of the sand. Some of the cyclic deposits are made up entirely of one basic type of structure, in which the character of the structure varies cyclically; for example, the angle of climb in a climbing-wind-ripple structure may vary cyclically. Other cyclic deposits are characterized by alternations of two or more structural types. Variations in the concentration of fine-grained heavy minerals, which account for the most striking cyclicity, arise mainly because of segregation on wind-rippled depositional surfaces: where the ripples climb at low angles, the coarsegrained light minerals, which accumulate preferentially on ripple crests, tend to be excluded from the local deposit. Daily cyclic deposits are thickest and best developed on small dunes and are least recognizable near the bases of large dunes. ?? 1988.

Hunter, R.E.; Richmond, B.M.

1988-01-01

89

Growth mechanisms and dune orientation on Titan  

NASA Astrophysics Data System (ADS)

Dune fields on Titan cover more than 17% of the moon's surface, constituting the largest known surface reservoir of organics. Their confinement to the equatorial belt, shape, and eastward direction of propagation offer crucial information regarding both the wind regime and sediment supply. Herein, we present a comprehensive analysis of Titan's dune orientations using automated detection techniques on nonlocal denoised radar images. By coupling a new dune growth mechanism with wind fields generated by climate modeling, we find that Titan's dunes grow by sediment transport on a nonmobile substratum. To be fully consistent with both the local crestline orientations and the eastward propagation of Titan's dunes, the sediment should be predominantly transported by strong eastward winds, most likely generated by equinoctial storms or occasional fast westerly gusts. Additionally, convergence of the meridional transport predicted in models can explain why Titan's dunes are confined within ±30° latitudes, where sediment fluxes converge.

Lucas, Antoine; Rodriguez, Sébastien; Narteau, Clément; Charnay, Benjamin; Pont, Sylvain Courrech; Tokano, Tetsuya; Garcia, Amandine; Thiriet, Mélanie; Hayes, Alexander G.; Lorenz, Ralph D.; Aharonson, Oded

2014-09-01

90

Investigation of Reversing Sand Dunes at the Bruneau Dunes, Idaho, as Analogs for Features on Mars  

NASA Astrophysics Data System (ADS)

The Bruneau Dunes in south-central Idaho include several large reversing sand dunes located within a cut-off meander of the Snake River. These dunes include the largest single-structured sand dune present in North America. Wind records from the Remote Automated Weather Station (RAWS) installation at the Mountain Home Air Force Base, which is ~21 km NW of the Bruneau Dunes, have proved to be very helpful in assessing the regional wind patterns at this section of the western Snake River Plains province; a bimodal wind regime is present, with seasonal changes of strong (sand-moving) winds blowing from either the northwest or the southeast. During April of 2011, we obtained ten precision topographic surveys across the southernmost reversing dune using a Differential Global Positioning System (DGPS). The DGPS data document the shape of the dune going from a low, broad sand ridge at the southern distal end of the dune to the symmetrically shaped 112-m-high central portion of the dune, where both flanks of the dune consist of active slopes near the angle of repose. These data will be useful in evaluating the reversing dune hypothesis proposed for enigmatic features on Mars called Transverse Aeolian Ridges (TARs), which could have formed either as large mega-ripples or small sand dunes. The symmetric profiles across TARs with heights greater than 1 m are more consistent with measured profiles of reversing sand dunes than with measured profiles of mega-ripples (whose surfaces are coated by large particles ranging from coarse sand to gravel, moved by saltation-induced creep). Using DGPS to monitor changes in the three-dimensional location of the crests of the reversing dunes at the Bruneau Dunes should provide a means for estimating the likely timescale for changes of TAR crests if the Martian features are indeed formed in the same manner as reversing sand dunes on Earth.

Zimbelman, J. R.; Scheidt, S. P.

2012-12-01

91

Expression of Tight Junction Protein Claudin-1 in Human Crescentic Glomerulonephritis  

PubMed Central

The origin of crescent forming cells in human glomerulonephritis (GN) remains unknown. Some animal studies demonstrated that parietal epithelial cells of Bowman's capsule (PECs) were the main component of proliferating cells and PEC-specific tight junction protein claudin-1 was expressed in crescentic lesions. We investigated the expression of claudin-1 in human GN. Immunohistochemistry for claudin-1 was performed on 17 kidney biopsy samples with crescent formation. Colocalization of claudin-1 with intracellular tight junction protein ZO-1 was also evaluated by immunofluorescence double staining. Claudin-1 is expressed mainly at the cell to cell contact site of proliferating cells in cellular crescentic lesions in patients with these forms of human GN. Small numbers of crescent forming cells showed extrajunctional localization of claudin-1. Colocalization of claudin-1 with ZO-1 was found at cell to cell contact sites of adjacent proliferating cells. In control samples, staining of claudin-1 was positive in PECs, but not in podocytes. Our findings suggest that claudin-1 contributes to crescent formation as a component of the tight junction protein complex that includes ZO-1. Co-localization of claudin-1 with ZO-1 implies the formation of functional tight junction complexes in crescentic lesions to prevent the interstitial damage caused by penetration of filtered molecules from Bowman's space. PMID:24868462

Koda, Ryo; Yoshino, Atsunori; Imanishi, Yuji; Kawamoto, Shinya; Ueda, Yoshihiko; Yaoita, Eishin; Kazama, Junichiro James; Narita, Ichiei; Takeda, Tetsuro

2014-01-01

92

Interdisciplinary Research Produces Results in the Understanding of Planetary Dunes  

NASA Astrophysics Data System (ADS)

Second International Planetary Dunes Workshop: Planetary Analogs—Integrating Models, Remote Sensing, and Field Data; Alamosa, Colorado, 18-21 May 2010; Dunes and other eolian bed forms are prominent on several planetary bodies in our solar system. Despite 4 decades of study, many questions remain regarding the composition, age, and origins of these features, as well as the climatic conditions under which they formed. Recently acquired data from orbiters and rovers, together with terrestrial analogs and numerical models, are providing new insights into Martian sand dunes, as well as eolian bed forms on other terrestrial planetary bodies (e.g., Titan). As a means of bringing together terrestrial and planetary researchers from diverse backgrounds with the goal of fostering collaborative interdisciplinary research, the U.S. Geological Survey (USGS), the Carl Sagan Center for the Study of Life in the Universe, the Desert Research Institute, and the U.S. National Park Service held a workshop in Colorado. The small group setting facilitated intensive discussion of problems and issues associated with eolian processes on Earth, Mars, and Titan.

Titus, Timothy N.; Hayward, Rosalyn Kay; Bourke, Mary C.

2010-08-01

93

Paleomagnetism and tectonics of the Crescent Formation, northern Olympic Mountains, Washington  

NASA Technical Reports Server (NTRS)

Results are presented of a paleomagnetic analysis of the Crescent Formation basalts of the northern Olympic Mountains, carried out with the purpose of constraining the emplacement and deformation history of the rocks of the northern Coast Range. It was found that (1) the stable remanent magnetization measured within the Crescent Formation appears to be early, predating significant deformation, and probably is primary; (2) a correction for bedding rotations about strike within four different structural domains produces a circular distribution of virtual geomagnetic poles; and (3) the Crescent Formation, where sampled in the north, records no significant net rotation or displacement.

Warnock, Andrew C.; Burmester, Russell F.; Engebretson, David C.

1993-01-01

94

Hematite Outlier and Sand Dunes  

NASA Technical Reports Server (NTRS)

[figure removed for brevity, see original site]

Released 4 December 2003

This image shows a crater just south of the edge of the famous hematite-bearing surface, which is visible in the context image as a smooth area to the north. The crater has two features of immediate note. The first is a layered mound in the north part of the crater floor. This mound contains hematite, and it is an outlying remnant of the greater deposits to the north that have otherwise completely disappeared in this crater. The second feature is a dune field in the center of the crater floor, with dark dunes indicating winds from the northwest. The dunes grade into a dark sand sheet with no coherent structure, indicating that the sand layer thins out to the south and east.

Image information: VIS instrument. Latitude -4.4, Longitude 357.3 East (2.7 West). 19 meter/pixel resolution.

Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

2003-01-01

95

Dunes on Titan: A major landform revealing atmospheric and surface processes  

NASA Astrophysics Data System (ADS)

The surface of Saturn’s moon Titan is covered in features that herald an active atmosphere and perhaps interior, such as dunes, rivers, lakes, mountain chains, and possible cryovolcanoes. Examining the geomorphology of these features helps us approach an understanding of the processes that are occurring or have occurred in the atmosphere and subsurface. A major landform on Titan is dunes, composed of organic sands ultimately derived from upper atmospheric processing of methane, subsequently perhaps eroded from organic sedimentary layers by methane rainfall and fluvial flow. Dunes fill vast fields, termed sand seas, similar to those observed in the Sahara, Namibia, and the Arabian peninsula. The equatorial region of Titan contains five separate sand seas as observed by the Cassini Synthetic Aperture Radar (SAR), Imaging Science Subsystem (ISS) and Visual and Infrared Mapping Spectrometer (VIMS) instruments. Together these sand seas cover 14 percent of the surface, totaling 12 million km2, and each have areas on the scale of the Saharan Great Sand Sea. They adjoin each other through sediment pathways around landmasses, and these large-scale connections as well as individual dune interactions with topography indicate a general transport of sediment from west to east. Measurements of dune height, width and spacing in Cassini SAR images reveal all of Titan’s thousands of linear dunes are of the same population. This indicates there was general uniformity in the wind and sediment supply conditions that led to the current dune forms. Variations in the parametric values result from deviations from these conditions, in some locations where elevated terrains have deflected winds. Dunes and sand seas are among the stratigraphically youngest features on Titan, showing little evidence of being affected by impact cratering or fluvial flow. However, individual dunes may be relatively stable, as the reorganization time scale for these features on Earth can be tens to hundreds of thousands of years. Recent field studies of large, linear dunes in Namibia reveal a complex reworking of the dune interior, overprinted on the main duneform, as a result of changing regional conditions. These field studies, which can be undertaken at a level of detail not yet possible to obtain on Titan, help us better understand the history of similar landforms on a distant solar system body.

Radebaugh, Jani; Lorenz, Ralph; Arnold, Karl; Savage, Christopher; Williams, Brigitte

96

Defrosting North Polar Dune Field  

NASA Technical Reports Server (NTRS)

MGS MOC Release No. MOC2-331, 15 April 2003

This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image captures frost-covered north polar sand dunes in springtime as they are beginning to defrost. Dark spots and streaks indicate areas where frozen carbon dioxide has started to be removed by sublimation and wind. The picture covers an area 3 km (1.9 mi) wide near 76.3oN, 264.9oW. Sunlight illuminates the scene from the lower left.

2003-01-01

97

Pathfinder Rover Atop Mermaid Dune  

NASA Technical Reports Server (NTRS)

Mars Pathfinder Lander camera image of Sojourner Rover atop the Mermaid 'dune' on Sol 30. Note the dark material excavated by the rover wheels. These, and other excavations brought materials to the surface for examination and allowed estimates of mechanical properties of the deposits.

NOTE: original caption as published in Science Magazine

Mars Pathfinder is the second in NASA's Discovery program of low-cost spacecraft with highly focused science goals. The Jet Propulsion Laboratory, Pasadena, CA, developed and manages the Mars Pathfinder mission for NASA's Office of Space Science, Washington, D.C. JPL is a division of the California Institute of Technology (Caltech).

1997-01-01

98

Antibodies to Intercellular Adhesion Molecule 1\\/Lymphocyte Function-associated Antigen 1 Prevent Crescent Formation in Rat Autoimmune Glomerulonephritis  

Microsoft Academic Search

SBmlTlftry In patients with glomerulonephritis widespread crescents are associated with a poor prognosis. Crescent formation appears to depend on the migration of mononuclear cells into Bowman's space, and therefore the interaction between leukocytes and glomerular endothelium may be a critical event in the genesis of crescents. We performed the present study to determine the effects of mouse monoclonal antibodies to

Kazuhiro Nishikawa; Ya-Jun Guo; Masayuki Miyasaka; Takuya Tamatani; A. Bernard Collins; Man-Sun Sy; Robert T. McCluskey; Giuseppe Andres

99

Invasive plants on disturbed Korean sand dunes  

Microsoft Academic Search

The sand dunes in coastal regions of South Korea are important ecosystems because of their small size, the rare species found in this habitat, and the beautiful landscapes they create. This study investigated the current vegetative status of sand dunes on three representative coasts of the Korean peninsula, and on the coasts of Cheju Island, and assessed the conditions caused

Kee Dae Kim

2005-01-01

100

Stability domains in barrier island dune systems  

Microsoft Academic Search

Early ecological descriptions of barrier island dune landscapes recognized the importance of biogeomorphic feedbacks and thresholds. However, these dynamics have not been formally linked to complexity theory. In this article, I develop models of dune landscape phase states, or stability domains, based on a synthesis of these prior studies and statistical analyses. Data for these analyses were obtained from compositional

J. Anthony Stallins

2005-01-01

101

Valles Marineris dune sediment provenance and pathways  

NASA Astrophysics Data System (ADS)

Although low-albedo sand is a prevalent component of the martian surface, sources and pathways of the sands are uncertain. As one of the principal present-day martian sediment sinks, the Valles Marineris (VM) rift system hosts a diversity of dune field populations associated with a variety of landforms that serve as potential sediment sources, including spur-and-gully walls, interior layered deposits (ILDs), and landslides. Here, we test the hypothesis that VM dune fields are largely derived from a variety of local and regional (intra-rift) sediment sources. Results show several dune fields are superposed on ancient wall massifs and ILDs that are topographically isolated from extra-rift sand sources. Spectral analysis of dune sand reveals compositional heterogeneity at the basinal-, dune field-, and dune-scales, arguing for discrete, relatively unmixed sediment sources. In Coprates and Melas chasmata, mapping is consistent with the principle sand source for dunes being Noachian-aged upper and lower wall materials composed of primary (igneous) minerals and glasses, some of which show evidence for alteration. In contrast, dune fields in Capri, Juventae, and Ganges chasmata show evidence for partial sediment derivation from adjacent Early Hesperian-aged hydrated sulfate-bearing ILD units. This finding indicates that these ILDs act as secondary sand sources. Dunes containing “soft” secondary minerals (e.g., monohydrated sulfate) are unlikely to have been derived from distant sources due to the physical weathering of sand grains during transport. Isolated extra-rift dune fields, sand sheets, and sand patches are located on the plateaus surrounding VM and the adjoining areas, but do not form interconnected networks of sand pathways into the rift. If past wind regimes (with respect to directionality and seasonality) were consistent with more recent regimes inferred from morphological analysis (i.e., dune slip faces, wind streaks), and were sufficient in strength and duration, small dune populations within Aurorae Chaos and north of eastern VM might have resulted from extended sand pathways into VM. However, we favor local and regional derivation of dune sand from a variety of intra-rift lithologic sources for most cases. Dune sand sources and the mechanism by which the sand is liberated are discussed in the context of findings described herein, but are broadly applicable to analysis of sediment production elsewhere on Mars.

Chojnacki, Matthew; Burr, Devon M.; Moersch, Jeffrey E.; Wray, James J.

2014-04-01

102

Titan's Longitudinal Dunes in the Lab.  

NASA Astrophysics Data System (ADS)

Cassini Radar observations of Titan's surface have revealed various landscapes. In particular, flybys probing Titan's equator unveiled linear features [1], which are morphologically similar to longitudinal dunes [2,3]. They appear pervasive in the range +-30° in latitude and could cover up to 20% of Titan's surface [4]. Their characteristics in term of width, length and spacing [1,4,5], or height and slope [6] are comparable to dunes of the Namib Desert [2]. On Earth, longitudinal dunes are the most commonly encountered dune and are observed in regions where the wind regime is composed of two main directions, the dunes orientation giving the mean sand transport. While terrestrial dunes are mostly formed by quartz sand grains, Titan's dunes are likely to be composed of hydrocarbon particulates [7]. Despite their different compositions, their morphological resemblances suggest similar processes of formation. Thus studying the formation of such structures could help to constrain models of Titan's winds [8]. However, formation of longitudinal dunes or even more generally longitudinal bedforms [9] have rarely been observed or reproduced in controlled conditions. Underwater experiments, in which sand transport timescale and lengthscale are decreased, have been used to successfully reproduce the dynamics of barchan dunes [10]. We show here how it is possible to explore the morphogenesis of longitudinal dunes using such a method combined with a numerical model. References: [1] Boubin et al. DPS 2005. [2] Lorenz et al. LPSC 2006. [3] Lorenz et al. Science 2006. [4] Radebaugh et al. Icarus (in revision). [5] Radebaugh et al. LPSC 2006. [6] Kirk et al. LPSC 2005. [7] Soderblom et al. P&SS (in press). [8] Tokano et al. Icarus 2002. [9] Rubin et al. Science 1987. [10] Hersen et al. PRL, 2003.

Reffet, Erwan; Courrech du Pont, S.; Hersen, P.; Douady, S.; Radebaugh, J.; Lorenz, R.; Lunine, J.; Boubin, G.; Fulchignoni, M.

2007-10-01

103

Solar  

NSDL National Science Digital Library

What part does solar energy play in satisfying energy demands? This informational piece, part of a series about the future of energy, introduces students to solar energy. Here students read about the uses, benefits, and active and passive methods of solar energy. Information is also presented about limitations, geographical considerations of solar power in the United States, and current uses of solar energy around the world. Thought-provoking questions afford students chances to reflect on what they've read about the uses of solar energy. Articles and information about a solar power plant in the Mohave Desert, the use of solar energy in Iowa, and statistics about solar energy are provided in a sidebar.

Project, Iowa P.

2004-01-01

104

Bedform-field pattern formation through bedform interactions within a set of boundary conditions: Example from White Sands Dune Field, New Mexico  

NASA Astrophysics Data System (ADS)

The emergence of bedform patterns is explored within the context of self-organizing systems and the imposition of boundary conditions that affect the types and frequency of bedform interactions. One explanation for bedform patterns is self-organization in which the pattern emerges because of interactions among the bedforms themselves. Models, remote images, field studies and lab experiments have identified bedform interactions that involve whole bedforms, only bedform defects, or that are remote interactions between bedforms. It is proposed that bedform interactions form a spectrum from constructive to regenerative in pattern development. Constructive interactions, including merging, lateral linking, cannibalization, and remote transfer of sediment, push the system toward fewer, larger, more widely spaced bedforms. Regenerative interactions, including bedform splitting, defect creation and calving, push the system back toward a more initial state. Other interactions, including off-center collision, defect migration, and bedform and defect repulsion, cause pattern change, but may not be strongly constructive or regenerative. We argue that the rich diversity of bedform-field patterns arises because of boundary conditions, which are the unique set of environmental variables within which each field evolves. Boundary conditions are broadly similar within system types, but are unique for each bedform field so that no two are ever exactly alike. Boundary conditions guide the uniqueness of each pattern by altering the type and frequency of interactions. These hypotheses are tested using time-series aerial photographs and airborne LiDAR at White Sands Dune Field, New Mexico. Time-series imagery shows that fully developed, crescentic aeolian dunes, interact and the dune pattern organizes in systematically similar ways as wind ripples and subaqueous dunes and ripples. Documented interactions include: (1) merging, (2) lateral linking, (3) defect repulsion, (4) bedform repulsion, (5) off-center collision, (6) defect creation, and (7) dune splitting. Measurements of pattern parameters (number of dunes, crest length, defect density, crest spacing, dune height), dune migration rates, and the type and frequency of dune interactions within a 3,500 m box transect from the upwind margin to the core of the dune field show that most pattern organization occurs within the upwind field. Upwind dominance by constructive interactions yields to neutral and regenerative interactions in the field center. This spatial change reflects upwind line-source and sediment-availability boundary conditions arising from antecedent paleo-lake topography. Pattern evolution is most strongly coupled to the pattern parameters of dune spacing and defect density, such that spatially or temporally the frequency of bedform interactions decreases as the dunes become farther apart and have fewer defects.

Ewing, R. C.; Kocurek, G.; Mohrig, D.

2009-12-01

105

Mars Global Digital Dune Database; MC-1  

USGS Publications Warehouse

The Mars Global Digital Dune Database presents data and describes the methodology used in creating the global database of moderate- to large-size dune fields on Mars. The database is being released in a series of U.S. Geological Survey (USGS) Open-File Reports. The first release (Hayward and others, 2007) included dune fields from 65 degrees N to 65 degrees S (http://pubs.usgs.gov/of/2007/1158/). The current release encompasses ~ 845,000 km2 of mapped dune fields from 65 degrees N to 90 degrees N latitude. Dune fields between 65 degrees S and 90 degrees S will be released in a future USGS Open-File Report. Although we have attempted to include all dune fields, some have likely been excluded for two reasons: (1) incomplete THEMIS IR (daytime) coverage may have caused us to exclude some moderate- to large-size dune fields or (2) resolution of THEMIS IR coverage (100m/pixel) certainly caused us to exclude smaller dune fields. The smallest dune fields in the database are ~ 1 km2 in area. While the moderate to large dune fields are likely to constitute the largest compilation of sediment on the planet, smaller stores of sediment of dunes are likely to be found elsewhere via higher resolution data. Thus, it should be noted that our database excludes all small dune fields and some moderate to large dune fields as well. Therefore, the absence of mapped dune fields does not mean that such dune fields do not exist and is not intended to imply a lack of saltating sand in other areas. Where availability and quality of THEMIS visible (VIS), Mars Orbiter Camera narrow angle (MOC NA), or Mars Reconnaissance Orbiter (MRO) Context Camera (CTX) images allowed, we classified dunes and included some dune slipface measurements, which were derived from gross dune morphology and represent the prevailing wind direction at the last time of significant dune modification. It was beyond the scope of this report to look at the detail needed to discern subtle dune modification. It was also beyond the scope of this report to measure all slipfaces. We attempted to include enough slipface measurements to represent the general circulation (as implied by gross dune morphology) and to give a sense of the complex nature of aeolian activity on Mars. The absence of slipface measurements in a given direction should not be taken as evidence that winds in that direction did not occur. When a dune field was located within a crater, the azimuth from crater centroid to dune field centroid was calculated, as another possible indicator of wind direction. Output from a general circulation model (GCM) is also included. In addition to polygons locating dune fields, the database includes THEMIS visible (VIS) and Mars Orbiter Camera Narrow Angle (MOC NA) images that were used to build the database. The database is presented in a variety of formats. It is presented as an ArcReader project which can be opened using the free ArcReader software. The latest version of ArcReader can be downloaded at http://www.esri.com/software/arcgis/arcreader/download.html. The database is also presented in an ArcMap project. The ArcMap project allows fuller use of the data, but requires ESRI ArcMap(Registered) software. A fuller description of the projects can be found in the NP_Dunes_ReadMe file (NP_Dunes_ReadMe folder_ and the NP_Dunes_ReadMe_GIS file (NP_Documentation folder). For users who prefer to create their own projects, the data are available in ESRI shapefile and geodatabase formats, as well as the open Geography Markup Language (GML) format. A printable map of the dunes and craters in the database is available as a Portable Document Format (PDF) document. The map is also included as a JPEG file. (NP_Documentation folder) Documentation files are available in PDF and ASCII (.txt) files. Tables are available in both Excel and ASCII (.txt)

Hayward, R.K.; Fenton, L.K.; Tanaka, K.L.; Titus, T.N.; Colaprete, A.; Christensen, P.R.

2010-01-01

106

Conceptual models of the evolution of transgressive dune field systems  

NASA Astrophysics Data System (ADS)

This paper examines the evolutionary paths of some transgressive dune fields that have formed on different coasts of the world, and presents some initial conceptual models of system dynamics for transgressive dune sheets and dune fields. Various evolutionary pathways are conceptualized based on a visual examination of dune fields from around the world. On coasts with high sediment supply, dune sheets and dune fields tend to accumulate as large scale barrier systems with little colonization of vegetation in arid-hyper to arid climate regimes, and as multiple, active discrete phases of dune field and deflation plain couplets in temperate to tropical environments. Active dune fields tend to be singular entities on coasts with low to moderate sediment supply. Landscape complexity and vegetation richness and diversity increases as dune fields evolve from simple active sheets and dunes to single and multiple deflation plains and basins, precipitation ridges, nebkha fields and a host of other dune types associated with vegetation (e.g. trailing ridges, slacks, remnant knobs, gegenwalle ridges and dune track ridges, 'tree islands' and 'bush pockets'). Three principal scenarios of transgressive dune sheet and dune field development are discussed, including dune sheets or dune fields evolving directly from the backshore, development following foredune and/or dune field erosion, and development from the breakdown or merging of parabolic dunes. Various stages of evolution are outlined for each scenario. Knowledge of evolutionary patterns and stages in coastal dune fields is very limited and caution is urged in attempts to reverse, change and/or modify dune fields to 'restore' some perceived loss of ecosystem or dune functioning.

Hesp, Patrick A.

2013-10-01

107

Conceptual models of the evolution of transgressive dune field systems  

NASA Astrophysics Data System (ADS)

This paper examines the evolutionary paths of some transgressive dune fields that have formed on different coasts of the world, and presents some initial conceptual models of system dynamics for transgressive dune sheets and dune fields. Various evolutionary pathways are conceptualized based on a visual examination of dune fields from around the world. On coasts with high sediment supply, dune sheets and dune fields tend to accumulate as large scale barrier systems with little colonization of vegetation in arid-hyper to arid climate regimes, and as multiple, active discrete phases of dune field and deflation plain couplets in temperate to tropical environments. Active dune fields tend to be singular entities on coasts with low to moderate sediment supply. Landscape complexity and vegetation richness and diversity increases as dune fields evolve from simple active sheets and dunes to single and multiple deflation plains and basins, precipitation ridges, nebkha fields and a host of other dune types associated with vegetation (e.g. trailing ridges, slacks, remnant knobs, gegenwalle ridges and dune track ridges, ‘tree islands' and ‘bush pockets'). Three principal scenarios of transgressive dune sheet and dune field development are discussed, including dune sheets or dune fields evolving directly from the backshore, development following foredune and/or dune field erosion, and development from the breakdown or merging of parabolic dunes. Various stages of evolution are outlined for each scenario. Knowledge of evolutionary patterns and stages in coastal dune fields is very limited and caution is urged in attempts to reverse, change and/or modify dune fields to ‘restore' some perceived loss of ecosystem or dune functioning.

A. Hesp, Patrick

2013-10-01

108

Reproducibility and utility of dune luminescence chronologies  

NASA Astrophysics Data System (ADS)

Optically stimulated luminescence (OSL) dating of dune deposits has increasingly been used as a tool to investigate the response of aeolian systems to environmental change. Amalgamation of individual dune accumulation chronologies has been employed in order to distinguish regional from local geomorphic responses to change. However, advances in dating have produced chronologies of increasing complexity. In particular, questions regarding the interpretation of dune ages have been raised, including over the most appropriate method to evaluate the significance of suites of OSL ages when local 'noisy' and discontinuous records are combined. In this paper, these issues are reviewed and the reproducibility of dune chronologies is assessed. OSL ages from two cores sampled from the same dune in the northeast Rub' al Khali, United Arab Emirates, are presented and compared, alongside an analysis of previously published dune ages dated to within the last 30 ka. Distinct periods of aeolian activity and preservation are identified, which can be tied to regional climatic and environmental changes. This case study is used to address fundamental questions that are persistently asked of dune dating studies, including the appropriate spatial scale over which to infer environmental and climatic change based on dune chronologies, whether chronological hiatuses can be interpreted, how to most appropriately combine and display datasets, and the relationship between geomorphic and palaeoclimatic signals. Chronological profiles reflect localised responses to environmental variability and climatic forcing, and amalgamation of datasets, with consideration of sampling resolution, is required; otherwise local factors are always likely to dominate. Using net accumulation rates to display ages may provide an informative approach of analysing and presenting dune OSL chronologies less susceptible to biases resulting from insufficient sampling resolution.

Leighton, Carly L.; Thomas, David S. G.; Bailey, Richard M.

2014-02-01

109

Scaling coastal dune elevation changes across storm-impact regimes  

USGS Publications Warehouse

Extreme storms drive change in coastal areas, including destruction of dune systems that protect coastal populations. Data from four extreme storms impacting four geomorphically diverse barrier islands are used to quantify dune elevation change. This change is compared to storm characteristics to identify variability in dune response, improve understanding of morphological interactions, and provide estimates of scaling parameters applicable for future prediction. Locations where total water levels did not exceed the dune crest experienced elevation change of less than 10%. Regions where wave-induced water levels exceeded the dune crest exhibited a positive linear relationship between the height of water over the dune and the dune elevation change. In contrast, a negative relationship was observed when surge exceeded the dune crest. Results indicate that maximum dune elevation, and therefore future vulnerability, may be more impacted from lower total water levels where waves drive sediment over the dune rather than surge-dominated flooding events.

Long, Joseph W.; de Bakker, Anouk T. M.; Plant, Nathaniel G.

2014-01-01

110

Scaling coastal dune elevation changes across storm-impact regimes  

NASA Astrophysics Data System (ADS)

Extreme storms drive change in coastal areas, including destruction of dune systems that protect coastal populations. Data from four extreme storms impacting four geomorphically diverse barrier islands are used to quantify dune elevation change. This change is compared to storm characteristics to identify variability in dune response, improve understanding of morphological interactions, and provide estimates of scaling parameters applicable for future prediction. Locations where total water levels did not exceed the dune crest experienced elevation change of less than 10%. Regions where wave-induced water levels exceeded the dune crest exhibited a positive linear relationship between the height of water over the dune and the dune elevation change. In contrast, a negative relationship was observed when surge exceeded the dune crest. Results indicate that maximum dune elevation, and therefore future vulnerability, may be more impacted from lower total water levels where waves drive sediment over the dune rather than surge-dominated flooding events.

Long, Joseph W.; de Bakker, Anouk T. M.; Plant, Nathaniel G.

2014-04-01

111

Longitudinal dunes on Mars: Relation to current wind regimes  

NASA Technical Reports Server (NTRS)

Longitudinal dunes are extremely rare on Mars, but constitute a substantial fraction of terrestrial desert dunes. We report finding isolated examples of longitudinal dunes on Mars and relate their occurrence to expected sand transport regimes. Terrestrial longitudinal dunes form in bimodal and multimodal transport regimes. General circulation models and streak data indicate that bimodal and multimodal transport of sand should be very rare on Mars. Thus the dearth of longitudinal dunes on Mars is consistent with their apparent formation conditions on Earth.

Lee, Pascal; Thomas, Peter C.

1995-01-01

112

Priorities for Future Research on Planetary Dunes  

NASA Astrophysics Data System (ADS)

Planetary Dunes Workshop: A Record of Climate Change; Alamogordo, New Mexico, 28 April to 2 May 2008; Landforms and deposits created by the dynamic interactions between granular material and airflow (eolian processes) occur on several planetary bodies, including Earth, Mars, Titan, and Venus. To address many of the outstanding questions within planetary dune research, a workshop was organized by the U.S. Geological Survey, the Planetary Science Institute, the Desert Research Institute, and the Search for Extraterrestrial Intelligence Institute and was sponsored by the Lunar and Planetary Institute and the Jet Propulsion Laboratory. The workshop brought together researchers from diverse backgrounds, ranging from image analysis and modeling to terrestrial analog studies. The group of approximately 45 international researchers had intense discussions in an attempt to identify the most promising approaches to understanding planetary dune systems. On the basis of these discussions, the group identified the following 10 priorities for future planetary dune research.

Titus, Timothy N.; Lancaster, Nick; Hayward, Rose; Fenton, Lori; Bourke, Mary

2008-11-01

113

Invasive plants on disturbed Korean sand dunes  

NASA Astrophysics Data System (ADS)

The sand dunes in coastal regions of South Korea are important ecosystems because of their small size, the rare species found in this habitat, and the beautiful landscapes they create. This study investigated the current vegetative status of sand dunes on three representative coasts of the Korean peninsula, and on the coasts of Cheju Island, and assessed the conditions caused by invasive plants. The relationships between the degree of invasion and 14 environmental variables were studied. Plots of sand dunes along line transects perpendicular to the coastal lines were established to estimate vegetative species coverage. TWINSPAN (Two-Way Indicator Species Analysis), CCA (Canonical Correspondence Analysis), and DCCA (Detrended Canonical Correspondence Analysis) were performed to classify communities on sand dunes and assess species composition variation. Carex kobomugi, Elymus mollis, and Vitex rotundifolia were found to be the dominant species plotted on the east, the west, and the peripheral coasts of Cheju Island, respectively. Vegetation on the south coast was totally extinct. The 19 communities, including representative C. kobomugi, C. kobomugi- Ixeris repens, C. kobomugi- Oenothera biennis, E. mollis, Lolium multiflorum- Calystegia soldanella, and V. rotundifolia- C. kobomugi, were all classified according to TWINSPAN. Oenothera biennis and L. multiflorum were exotics observed within these native communities. CCA showed that invasive native and exotic species distribution was segregated significantly, according to disturbance level, exotic species number, gravel, sand and silt contents, as well as vegetation size. It further revealed that human disturbance can strongly favor the settlement of invasive and exotic species. Restoration options to reduce exotic plants in the South Korean sand dune areas were found to be the introduction of native plant species from one sand dune into other sand dune areas, prohibition of building and the introduction of exotic soils, and conservation of surrounding sand dune areas.

Kim, Kee Dae

2005-01-01

114

Palaeoclimatic Interpretations From Desert Dunes and Sediments  

Microsoft Academic Search

During the late Quaternary, the world’s major deserts experienced dramatic changes in the nature and frequency of aeolian\\u000a processes (Fig. 26.1). Sand seas (ergs) cover 5% of the global land surface and reveal evidence of repeated phases of dune\\u000a formation (Thomas et al. 2005). This paper presents a review of dune-building episodes during late Quaternary time and their\\u000a palaeoclimatic significance.

Vatche P. Tchakerian

115

Mean sediment residence time in barchan dunes  

NASA Astrophysics Data System (ADS)

When a barchan dune migrates, the sediment trapped on its lee side is later mobilized when exposed on the stoss side. Then sand grains may undergo many dune turnover cycles before their ejection along the horns, but the amount of time a sand grain contributes to the dune morphodynamics remains unknown. To estimate such a residence time, we analyze sediment particle motions in steady state barchans by tracking individual cells of a 3-D cellular automaton dune model. The overall sediment flux may be decomposed into advective and dispersive fluxes to estimate the relative contribution of the underlying physical processes to the barchan shape. The net lateral sediment transport from the center to the horns indicates that dispersion on the stoss slope is more efficient than the convergent sediment fluxes associated with avalanches on the lee slope. The combined effect of these two antagonistic dispersive processes restricts the lateral mixing of sediment particles in the central region of barchans. Then, for different flow strengths and dune sizes, we find that the mean residence time of sediment particles in barchans is equal to the surface of the central longitudinal dune slices divided by the input sand flux. We infer that this central slice contains most of the relevant information about barchan morphodynamics. Finally, we initiate a discussion about sediment transport and memory in the presence of bed forms using the advantages of the particle tracking technique.

Zhang, D.; Yang, X.; Rozier, O.; Narteau, C.

2014-03-01

116

Effect of harbor modifications on the tsunami vulnerability of Crescent City, California  

NASA Astrophysics Data System (ADS)

Crescent City, California has experienced more damaging tsunami events in historic times than any other location on the West Coast of the United States. Thirty-one tsunamis have been observed at Crescent City since a tide gauge was established in 1933, including eleven events with maximum peak to trough wave range exceeding one meter and four that caused damage. The most damaging event occurred in 1964 as a result of the great Alaska earthquake. The ensuing tsunami flooded 29 city blocks and killed 11 in the Crescent City area. As a result of the 1964 tsunami and redevelopment projects, the Crescent City harbor was significantly modified in the early 1970s. A 200 x 300 meter small boat basin was carved into the preexisting shore line, a 123 meter dog leg extension was added to the central breakwater and significant deepening occurred on the eastern side of the harbor. In 2006, a Mw 8.3 earthquake in the Kuril Islands generated a moderate Pacific-wide tsunami. The only location with significant damage was the Crescent City harbor where strong currents damaged docks and boats, causing an estimated 9.2 million (US dollars) in damages. Strong currents estimated by the Harbor Master at 12 knots were observed near the entrance to the small boat basin. Past earthquakes from the northwestern Pacific including the 1933 M 8.3 Sanriku Japan earthquake may have produced similar amplitudes at Crescent City to the 2006 event but caused no damage. We have obtained the pre-modification harbor bathymetry and use the MOST model to compare tsunami water heights and current velocities for the 1933 and 2006 sources using modern and pre- modification bathymetry. We also examine model the 1964 inundation using the actual bathymetry and compare the results to numerical simulations that have only used the modern data.

Dengler, L.; Uslu, B.

2008-12-01

117

Modeling emergent large-scale structures of barchan dune fields  

NASA Astrophysics Data System (ADS)

In nature, barchan dunes typically exist as members of larger fields that display striking, enigmatic structures that cannot be readily explained by examining the dynamics at the scale of single dunes, or by appealing to patterns in external forcing. To explore the possibility that observed structures emerge spontaneously as a collective result of many dunes interacting with each other, we built a numerical model that treats barchans as discrete entities that interact with one another according to simplified rules derived from theoretical and numerical work, and from field observations: Dunes exchange sand through the fluxes that leak from the downwind side of each dune and are captured on their upstream sides; when dunes become sufficiently large, small dunes are born on their downwind sides ('calving'); and when dunes collide directly enough, they merge. Results show that these relatively simple interactions provide potential explanations for a range of field-scale phenomena including isolated patches of dunes and heterogeneous arrangements of similarly sized dunes in denser fields. The results also suggest that (1) dune field characteristics depend on the sand flux fed into the upwind boundary, although (2) moving downwind, the system approaches a common attracting state in which the memory of the upwind conditions vanishes. This work supports the hypothesis that calving exerts a first order control on field-scale phenomena; it prevents individual dunes from growing without bound, as single-dune analyses suggest, and allows the formation of roughly realistic, persistent dune field patterns.

Worman, S. L.; Murray, A.; Littlewood, R. C.; Andreotti, B.; Claudin, P.

2013-12-01

118

76 FR 7844 - Environmental Impacts Statements; Notice of Availability  

Federal Register 2010, 2011, 2012, 2013

...20100444, Final EIS, BLM, NV, Tonopah Solar Energy Crescent Dunes Solar Energy Project, a 7,680-Acre Right-of-Way (ROW) on Public Lands to Construct a Concentrated Solar Thermal Power Plant Facility, Nye County, NV,...

2011-02-11

119

75 FR 70917 - Environmental Impacts Statements; Notice Of Availability  

Federal Register 2010, 2011, 2012, 2013

...20100444, Final EIS, BLM, NV, Tonopah Solar Energy Crescent Dunes Solar Energy Project, a 7,680-Acre Right-of-Way (ROW) on Public Lands to Construct a Concentrated Solar Thermal Power Plant Facility, Nye County, NV, Wait...

2010-11-19

120

75 FR 54145 - Environmental Impacts Statements; Notice of Availability  

Federal Register 2010, 2011, 2012, 2013

...20100343, Draft EIS, BLM, NV, Tonopah Solar Energy Crescent Dunes Solar Energy Project, a 7,680-Acre Right-of-Way (ROW) on Public Lands to Construct a Concentrated Solar Thermal Power Plant Facility, Nye County, NV,...

2010-09-03

121

Northern polar dunes: a spring activity analog to that seen in southern polar terrains  

NASA Astrophysics Data System (ADS)

The High Resolution Imaging Science Experiment (HiRISE) on the Mars Reconnaissance Or-biter (MRO) is presently (February 2010) observing its second northern spring on Mars. Com-plimentary spectral information from CRISM is available to gain insight into the composition and physical state of the surface. In the north polar areas, there are active regions. Here, dark dunes extend almost circumferen-tially around the permanent polar cap. This area exhibits phenomena similar to those observed in south polar areas in southern spring. Among these phenomena are cracks in a translucent ice layer which are considered to be manifestations of ice damage by increasing pressure at the interface between the ice layer and substrate underlying it [1]. Bright and dark fans, attributed to cold jet activity, are also observed on top of dunes [2]. The presence of these features indi-cates that dunes are covered by a conformal ice layer and that this layer is at least partially transparent to solar radiation. CO2 ice sublimation and processes connected to it appear to produce a variety of observable features. Yet another distinctive feature observed in this area (and rarely present in the south) is the presence of dark slope streaks on dunes. They originate from the crests of dunes and run down following the gravitational potential. They lengthen as the season progresses. Their origin has been discussed to be possible liquid brine flows [3, 4]. In the present work we report on indications that these slope streaks are instead dry mass wasting process. Due to geometry of solar illumination at local latitude the energy input on the crest is higher than in the valley between dunes. The ice cover thins most quickly in areas closest to the crest. In addition, applying stress distribution calculations to the conformal ice layer on realistic dune geometry, we show that the crest of the dune is the weakest point for the ice bending stress. The rupture of the ice layer therefore happens close to the dune's crest on the slip face and is followed by the escape of dry dune material from its top layer downslope. Streaks are overlaid on the ice layer and produce the observed contrast changes. Seasonal lengthening of the streaks can be attributed to the repeatability of this process when more and more dune material gets freed from the ice layer. An enhancement of this effect can occur if the rupture of the ice layer gives rise to an escape of gas trapped under it. The gas pressure, in this case, is produced by the same process that is proposed for araneiform formation in south polar areas [5]. Gas movement mobilises fine dune material and transports it towards the slip slope whereupon it runs down the slope. The described model does not involve liquid flows but is nonetheless fully consistent with HiRISE observations of this phenomenon. [1] G. Portyankina et al., 2010, 41st Lunar and Planetary Science Conference, Abstract #2671 [2] C. Hansen et al., 2010, 41st Lunar and Planetary Science Conference, Abstract #2029 [3] D. Moehlmann, 2008, Icarus, 195:131-139. [4] A. Kereszturi et al., 2009, Icarus 201:492-503. [5] H. Kieffer, 2007, JGR, 112.

Portyankina, Ganna; Thomas, Nicolas; Pommerol, Antoine; Aye, Klaus-Michael

122

Major Histocompatibility Complex Class II Expression by Intrinsic Renal Cells Is Required for Crescentic Glomerulonephritis  

PubMed Central

The requirement for major histocompatibility complex class II (MHC II) to initiate immune renal injury was studied in a murine model of CD4+ T cell–dependent crescentic glomerulonephritis (GN). C57BL/6 (MHC II+/+) mice developed crescentic GN with glomerular CD4+ T cell infiltration and renal injury, in response to a nephritogenic antigen (sheep globulin) planted on their glomerular basement membrane. MHC II–deficient C57BL/6 mice (MHC II?/?) did not develop crescentic GN, CD4+ T cell infiltration, or injury, indicating that this form of immune glomerular injury is MHC II dependent. The requirement for MHC II expression by intrinsic renal cells was studied in chimeric mice, which expressed MHC II on bone marrow–derived cells and in the thymus, but not in the kidneys. These chimeric mice had normal T and B cell populations and MHC II expression in their spleens and lymph nodes and developed an immune response to systemically and cutaneously administered sheep globulin. However, they did not develop crescentic GN, CD4+ T cell infiltration, or renal injury in response to the sheep globulin planted in their glomeruli. These studies demonstrate that interaction of CD4+ T cells with intrinsic renal cells expressing MHC II is required for development of cell-mediated immune renal injury. PMID:9687536

Li, Shuo; Kurts, Christian; Kontgen, Frank; Holdsworth, Stephen R.; Tipping, Peter G.

1998-01-01

123

Projection of statocyst sensory neurons associated with crescent hairs in the crayfish Procambarus clarkii Girard  

Microsoft Academic Search

The central projection of statocyst sensory neurons associated with the crescent hairs of the crayfish Procambarus clarkii was investigated. Cobalt fills of statocyst nerves revealed that they entered the brain as the two discrete fiber bundles and terminated in different portions of the brain. One terminates in the ipsilateral half of the brain and the other in the contralateral half.

M. Yoshino; Y. Kondoh; M. Hisada

1983-01-01

124

Tsunami inundation at Crescent City, California generated by earthquakes along the Cascadia Subduction Zone  

Microsoft Academic Search

We model tsunami inundation and runup heights in Crescent City, California triggered by possible earthquakes on the Cascadia Subduction Zone (CSZ). The CSZ is believed capable of producing great earthquakes with magnitudes of M w ~ 9.0 or greater. We simulate plausible CSZ rupture scenarios and calculate inundation using MOST. We benchmark our CSZ inundation projections against mapped flooded areas

Burak Uslu; José C. Borrero; Lori A. Dengler; Costas E. Synolakis

2007-01-01

125

Tsunami inundation at Crescent City, California generated by earthquakes along the Cascadia Subduction Zone  

Microsoft Academic Search

We model tsunami inundation and runup heights in Crescent City, California triggered by possible earthquakes on the Cascadia Subduction Zone (CSZ). The CSZ is believed capable of producing great earthquakes with magnitudes of Mw ? 9.0 or greater. We simulate plausible CSZ rupture scenarios and calculate inundation using MOST. We benchmark our CSZ inundation projections against mapped flooded areas and

Burak Uslu; José C. Borrero; Lori A. Dengler; Costas E. Synolakis

2007-01-01

126

The relationship between peripapillary crescent and axial length: Implications for differential eye growth.  

PubMed

We evaluated the relationship between the size of the peripapillary crescent and the axial length (AL) of the eye as well as the fine structure of the peripapillary crescent in selected eyes. Infrared fundus imaging and spectral domain optical coherence tomography (SDOCT) (Spectralis HRA+OCT, Heidelberg Engineering, Germany) centered at the fovea were performed on 72 healthy adults. On the infrared fundus images, we measured (a) the distance between the foveola and the temporal edge of the optic disc (FOD) and (b) the distance between the foveola and the temporal edge of the peripapillary crescent (FOC) (if present). A peripapillary crescent presented at the nasal margin of the disc in 64% of the subjects. The FOD and FOC were 4.22mm±0.46 and 3.97mm±0.25, respectively. Only the FOD was significantly correlated with axial length. As AL increased by 10%, the FOD increased by 13%, the outer neural retina only expanded by 4% (as indicated by the FOC). This result emphasizes that retinal stretching may not mirror scleral growth, and the existence in some eyes of a difference between the photoreceptor margin and retinal pigment epithelium (RPE) margin suggests that within the retina there could be slippage during eye growth. PMID:21864558

Chui, Toco Y P; Zhong, Zhangyi; Burns, Stephen A

2011-10-01

127

Crescent and star shapes of members of the Chlamydiales order: impact of fixative methods.  

PubMed

Members of the Chlamydiales order all share a biphasic lifecycle alternating between small infectious particles, the elementary bodies (EBs) and larger intracellular forms able to replicate, the reticulate bodies. Whereas the classical Chlamydia usually harbours round-shaped EBs, some members of the Chlamydia-related families display crescent and star-shaped morphologies by electron microscopy. To determine the impact of fixative methods on the shape of the bacterial cells, different buffer and fixative combinations were tested on purified EBs of Criblamydia sequanensis, Estrella lausannensis, Parachlamydia acanthamoebae, and Waddlia chondrophila. A linear discriminant analysis was performed on particle metrics extracted from electron microscopy images to recognize crescent, round, star and intermediary forms. Depending on the buffer and fixatives used, a mixture of alternative shapes were observed in varying proportions with stars and crescents being more frequent in C. sequanensis and P. acanthamoebae, respectively. No tested buffer and chemical fixative preserved ideally the round shape of a majority of bacteria and other methods such as deep-freezing and cryofixation should be applied. Although crescent and star shapes could represent a fixation artifact, they certainly point towards a diverse composition and organization of membrane proteins or intracellular structures rather than being a distinct developmental stage. PMID:23942615

Rusconi, Brigida; Lienard, Julia; Aeby, Sébastien; Croxatto, Antony; Bertelli, Claire; Greub, Gilbert

2013-10-01

128

Expression of Ser729 Phosphorylated PKC Epsilon in Experimental Crescentic Glomerulonephritis: An Immunohistochemical Study  

PubMed Central

PKC?, a DAG-dependent, Ca2+- independent kinase attenuates extent of fibrosis following tissue injury, suppresses apoptosis and promotes cell quiescence. In crescentic glomerulonephritis (CGN), glomerular epithelial cells (GEC) contribute to fibro-cellular crescent formation while they also transdifferentiate to a mesenchymal phenotype. The aim of this study was to assess PKC? expression in CGN. Using an antibody against PKC-? phosphorylated at Ser729, we assessed its localization in rat model of immune-mediated rapidly progressive CGN. In glomeruli of control animals, pPKC? was undetectable. In animals with CGN, pPKC? was expressed exclusively in glomerular epithelial cells (GEC) and in GEC comprising fibrocellular crescents that had acquired a myofibroblasttype phenotype. In non-immune GEC injury induced by puromycin aminonucleoside and resulting in proteinuria of similar magnitude as in CGN, pPKC? expression was absent. There was constitutive pPKC? expression in distal convoluted tubules, collecting ducts and thick segments of Henley’s loops in both control and experimental animals. We propose that pPKC? expression occurring in GEC and in fibrocellular crescentic lesions in CGN may facilitate PKC? dependent pathologic processes. PMID:24998921

Karavana, V.N.; Gakiopoulou, H.; Lianos, E.A.

2014-01-01

129

Ecology of Pacific Northwest coastal sand dunes: a community profile  

SciTech Connect

Sand dunes occur in 33 localities along the 950 km of North American Pacific coast between the Straits of Juan de Fuca (49/sup 0/N) and Cape Mendocino (40/sup 0/). The dune landscape is a mosaic of dune forms: transverse ridge, oblique dune, retention ridge, foredune, parabola dune, sand hummock, blowout, sand plain, deflation plain, dune ridge, swale, remnant forest, and ponds and lakes. These forms are the basic morphological units making up the four dune systems: parallel ridge, parabola dune, transverse ridge, and bay dune. Vegetation is well-developed on stabilized dunes. Of the 21 plant communities identified, nine are herbaceous, five are shrub, and seven are forest. A wide variety of vertebrate animals occur in seven distinct habitats: open dunes, grassland and meadow, shrub thicket, forest, marsh, riparian, and lakes and ponds. Urban development, increased rate of stabilization due to the introduction of European beachgrass (Ammophila arenaria (L.) Link), and massive disturbance resulting from heavy off-road vehicle traffic are the greatest threats to the long-term survival and stability of a number of sand dune habitats. Two animals and three plants dependent on dune habitats are listed as rare, threatened, or endangered. 93 references, 52 figures, 13 tables.

Wiedemann, A.M.

1984-03-01

130

36 CFR 7.80 - Sleeping Bear Dunes National Lakeshore.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 2013-07-01 false Sleeping Bear Dunes National Lakeshore. 7...THE NATIONAL PARK SYSTEM § 7.80 Sleeping Bear Dunes National Lakeshore. (a...allowed. (c) Bicycling. (1) The Sleeping Bear Heritage Trail,...

2013-07-01

131

Dynamics of a cliff top dune  

NASA Astrophysics Data System (ADS)

Morphological changes during more than 100 years have been investigated for a cliff-top dune complex at Rubjerg at the Danish North Sea coast. Here the lower 50 m of the cliff front is composed of Pleistocene steeply inclined floes of silt and clay with coarse sand in between which gives it a saw-tooth appearance. On top of this the dunes are found for several kilometres along the coastline. Due to erosion by the North Sea the cliff has retreated about 120 m between approximately 1880 and 1970 as indicated from two national surveys, and recent GPS-surveys indicate that erosion is continuing at a similar rate. Nevertheless the cliff top dune complex has survived, but its morphology has undergone some changed. The old maps indicate that around 1880 the dune complex was composed of several up to about 20 m high dunes streamlined in the East-West direction which is parallel to the prevailing wind direction. When protective planting started during the first half of the 20th Century the cliff top dunes gradually merged together forming a narrow, tall ridge parallel to the shore line with the highest part reaching about 90 m near 1970. In 1993 the highest points along the ridge was almost 95 m high, but then the protective planting was considerably reduced and recent annual GPS-surveys indicate that the dunes respond quickly to this by changing their morphology towards the original appearance. It is remarkable that despite the mass wasting caused by the constant erosion of the cliff front the dunes have remained more or less intact. Theoretical studies of hill flow indicate given the proper geometry of the cliff then suspension of even coarse grains can be a very effective agent for carrying sand from the exposed parts of the cliff front to and beyond the cliff-top. Mostly the sand grains are deposited within some hundred meters downwind of the cliff dune while silt is often carried more than 10 km inland. Field observations indicate that where the dislodged floes and beds of coarse sand are missing the cliff is steep and dunes are absent at the cliff top. On the other hand when floes are present then some parts of the cliff are less steep and where sand is abundant cliff top dunes seem to be abundant, too. In order to investigate how flow conditions at the cliff front responds to its geometry, scale models of the cliff front approximately 1:10, but with different steepness have been tested in a boundary layer wind tunnel. All runs have been made with proper roughness scaling and besides a variation in their longitudinal profiles some variation in their transverse profiles has also been tested. The surface-near flow has been mapped with high resolution 2-D laser-Doppler profiling, and one of the important aims is to demonstrate the interaction between sediment and geological structure on one side and flow and dune state on the other side. A particular aim is to investigate if and how the separation bubble may have a profound control on mobilization and transport of sediment.

Rasmussen, K. R.

2012-12-01

132

Crescentic glomerulonephritis in CD4- and CD8-deficient mice. Requirement for CD4 but not CD8 cells.  

PubMed Central

The contribution of CD4 and CD8 cells to crescentic glomerulonephritis (GN) was studied in mice genetically deficient in CD4, CD8, and with combined CD4 and CD8 (CD4/CD8) deficiency. Wild-type (C57BL/6) mice developed GN with mild proliferative changes 7 days after an intravenous dose of sheep anti-mouse glomerular basement membrane globulin. Crescents were observed in 12.5 +/- 6.1% of glomeruli on day 14. On day 21, 51.5 +/- 7.3% of glomeruli were affected by crescents, and mice had marked azotemia and proteinuria. CD4 and combined CD4/CD8-deficient mice developed minimal evidence of GN. On day 21, their glomeruli showed only mild proliferative changes and crescents, azotemia, and proteinuria were absent. In contrast, CD8-deficient mice developed severe crescentic GN with three of five mice dying on day 20 with ascites and edema. The two mice surviving to day 21 had severe azotemia. Crescent development was accelerated (day 14, 51.6 +/- 2.4% of glomeruli; day 20 or 21, 62.0 +/- 4.0% of glomeruli). These studies demonstrate that CD4 cells are crucial for the development of crescentic GN in mice and that genetic absence of CD8 cells accelerates disease. They support the hypothesis that crescent formation is a manifestation of CD4-dependent (and CD8-independent) delayed type hypersensitivity in the glomerulus. Images Figure 1 Figure 2 PMID:9626058

Tipping, P. G.; Huang, X. R.; Qi, M.; Van, G. Y.; Tang, W. W.

1998-01-01

133

Linking restoration ecology with coastal dune restoration  

NASA Astrophysics Data System (ADS)

Restoration and preservation of coastal dunes is urgently needed because of the increasingly rapid loss and degradation of these ecosystems because of many human activities. These activities alter natural processes and coastal dynamics, eliminate topographic variability, fragment, degrade or eliminate habitats, reduce diversity and threaten endemic species. The actions of coastal dune restoration that are already taking place span contrasting activities that range from revegetating and stabilizing the mobile substrate, to removing plant cover and increasing substrate mobility. Our goal was to review how the relative progress of the actions of coastal dune restoration has been assessed, according to the ecosystem attributes outlined by the Society of Ecological Restoration: namely, integrity, health and sustainability and that are derived from the ecological theory of succession. We reviewed the peer reviewed literature published since 1988 that is listed in the ISI Web of Science journals as well as additional references, such as key books. We exclusively focused on large coastal dune systems (such as transgressive and parabolic dunefields) located on natural or seminatural coasts. We found 150 articles that included "coastal dune", "restoration" and "revegetation" in areas such as title, keywords and abstract. From these, 67 dealt specifically with coastal dune restoration. Most of the studies were performed in the USA, The Netherlands and South Africa, during the last two decades. Restoration success has been assessed directly and indirectly by measuring one or a few ecosystem variables. Some ecosystem attributes have been monitored more frequently (ecosystem integrity) than others (ecosystem health and sustainability). Finally, it is important to consider that ecological succession is a desirable approach in restoration actions. Natural dynamics and disturbances should be considered as part of the restored system, to improve ecosystem integrity, health and sustainability.

Lithgow, D.; Martínez, M. L.; Gallego-Fernández, J. B.; Hesp, P. A.; Flores, P.; Gachuz, S.; Rodríguez-Revelo, N.; Jiménez-Orocio, O.; Mendoza-González, G.; Álvarez-Molina, L. L.

2013-10-01

134

Mobile dunes and eroding salt marshes  

NASA Astrophysics Data System (ADS)

The paper deals with general outlines of salt marsh and dune vegetation in the Ellenbogen and Listland area on Sylt (Schleswig-Holstein, FRG). The composition of current salt marsh vegetation is considered to be mainly the result of a long-lasting process of tidal inundation, grazing, and a permanent influence of groundwater seepage from the surrounding dunes. The lower salt marsh communities have shown constancy for 67 years, due to the effect of heavy grazing. The mid-upper salt marsh communities demonstrated a succession from a Puccinellia maritima-dominated community of the lower marsh to a Juncus gerardii-dominated community of the mid-upper salt marsh, which may be due to the transport of sand — over a short time — on the surface of the marsh. The area covered by plant communities of annuals below Mean High Water (MHW) seemed to diminish. Salt marsh soils, especially of the mid-upper marsh, indicate sandy layers resulting from sand drift of the dunes. Dry and wet successional series of the dunes in the Listland/Ellenbogen area both show grassy stages shifting to dwarf shrubs as final stages. White primary dunes can only be found on the accreting shoreline of the Ellenbogen, which is also grazed by sheep; vegetation cover therefore remains dominated by grasses, mosses and lichens. Three mobile dunes (as the most prominent features of this landscape) have been left unaffected by seeding and planting by local authorities. Grazing is considered to be an inadequate tool in nature conservation as long as natural processes are to prevail in the landscape as major determinants.

Neuhaus, R.

1994-06-01

135

Lateral migration of linear dunes in the Strzelecki Desert, Australia  

USGS Publications Warehouse

Preferential accumulation of sand on east-facing flanks indicates that the dunes migrated eastward several metres during the Holocene. Moreover, the west-facing flanks of some dunes have experienced a minimum of tens of metres of erosion. This asymmetric erosion and deposition were caused by dune obliquity and lateral migration that may have begun as early as the Pleistocene. Dunes in the Strzelecki Desert and in the adjacent Simpson Desert display a variety of grossly different internal structures. -from Author

Rubin, D.M.

1990-01-01

136

Polar margin dunes and winds on Mars  

NASA Technical Reports Server (NTRS)

The approximately concentric arrangement of layered deposits and dune fields at the two Martian poles may reflect a nearly steady state dispersal of material from the polar deposits. Data on effective surface winds from high resolution Viking Images combined with theory of local winds suggest that the northern dunes are in part confined to a latitude band by winds generated by their own low albedo. Dispersal of the dark sand from the southern polar region is not subject to this kind of feedback because the irregular topography prevents areal accumulations sufficiently extensive to produce winds.

Thomas, Peter C.; Gierasch, Peter

1995-01-01

137

Geology Fieldnotes: Sleeping Bear Dunes National Lakeshore, Michigan  

NSDL National Science Digital Library

The Sleeping Bear Dunes National Lakeshore site contains park geology information, park maps, photographs, related links, and visitor information. The park geology section discusses the geologic history of the region and formation of Sleeping Bear Dunes through westerly winds from Lake Michigan. The park maps section includes a map of the Sleeping Bear Dunes National Lakeshore and the surrounding area.

138

Restoration of coastal dune slacks in the Netherlands  

Microsoft Academic Search

In order to stop the continuous decline of typical dune slack communities along the Dutch coast, restoration projects have been carried out since 1952. Restoration measures consisted of re-introducing traditional management techniques in dune slacks, such as mowing, grazing and sod removal, or constructing artificial dune slacks to compensate for lost biodiversity elsewhere. An analysis of successful and unsuccessful projects

A. P. Grootjans; H. W. T. Geelen; A. J. M. Jansen; E. J. Lammerts

2002-01-01

139

Climate and coastal dune vegetation: disturbance, recovery, and succession  

E-print Network

Climate and coastal dune vegetation: disturbance, recovery, and succession Thomas E. Miller � Elise. Foredune, interdune, and backdune habitats common to most coastal dunes have very different vegetation deterministic trajectories. Keywords Dune habitats Á Succession Á Disturbance Á Coastal vegetation Á Hurricane Á

Miller, Thomas E.

140

Coastal Dune Forest Development and the Regeneration of Millipede Communities  

E-print Network

Coastal Dune Forest Development and the Regeneration of Millipede Communities Bereket H. Redi,1 to a post-mining coastal dune for- est rehabilitation program with those developing spon- taneously farther away. Key words: coastal dune forests, millipedes, regeneration, rehabilitation, succession

Pretoria, University of

141

Dune field pattern formation and recent transporting winds in the Olympia Undae Dune Field, north polar region of Mars  

Microsoft Academic Search

High-Resolution Imaging Science Experiment (HiRISE) imagery of the central Olympia Undae Dune Field in the north polar region of Mars shows a reticulate dune pattern consisting of two sets of nearly orthogonal dune crestlines, with apparent slipfaces on the primary crests, ubiquitous wind ripples, areas of coarse-grained wind ripples, and deflated interdune areas. Geomorphic evidence and dune field pattern analysis

Ryan C. Ewing; Aymeric-Pierre B. Peyret; Gary Kocurek; Mary Bourke

2010-01-01

142

Broadband colored-crescent generation in a single ?-barium-borate crystal by intense femtosecond pulses  

NASA Astrophysics Data System (ADS)

A visible colored crescent with a bandwidth broader than 220 nm is observed experimentally by loosely focused femtosecond pulses in a bulk quadratic nonlinear crystal (?-BBO crystal) at certain incident angles. Through the analysis based on a simple collinear phase-matching model, we suggest that the colored crescent might be the coexistence of spontaneous parametric down-conversions (SPDCs) in the infrared range and the corresponding efficient second-order harmonic generations (SHGs) that occur in a wide spectrum. We further provide a possible mechanism for the SHG process in which the phase-mismatching angles of the frequency doubling of SPDCs in ?-BBO crystal are assumed to be compensated by the strong diffraction effect during the self-focusing process of the generated intense SPDC signals.

Wang, L.; Fan, Y. X.; Zhu, H.; Yan, Z. D.; Zeng, H.; Wang, H.-T.; Zhu, S. N.; Wang, Z. L.

2011-12-01

143

Dfinition d'une stratgie collective de matrise d'une maladie animale  

E-print Network

Définition d'une stratégie collective de maîtrise d'une maladie animale Anne-France Viet1, Coopération En santé animale, une amélioration de la situation sanitaire dans une région pour certains agents animales réglementées, les stratégies de maîtrise sont définies par les pouvoirs publics. Pour les autres

Boyer, Edmond

144

Prevention of crescentic glomerulonephritis by immunoneutralization of the fractalkine receptor CX3CR1  

Microsoft Academic Search

Prevention of crescentic glomerulonephritis by immunoneutralization of the fractalkine receptor CX3CR1.BackgroundFractalkine is a newly identified T-cell and monocyte\\/macrophage (M?) chemokine with a transmembrane domain and is a cell-surface protein on activated endothelium. It can mediate adhesion of cells expressing the fractalkine receptor CX3CR1. These unique features make fractalkine well suited for leukocyte recruitment in tissues with high blood flow as

Lili Feng; Shizhong Chen; Gabriela E. Garcia; Yiyang Xia; Mike A. Siani; Paulo Botti; Curtis B. Wilson; Jeffrey K. Harrison; Kevin B. Bacon

1999-01-01

145

Anti-perforin antibody treatment ameliorates experimental crescentic glomerulonephritis in WKY rats  

Microsoft Academic Search

The depletion of CD8+ cells has been shown to prevent the initiation and progression of antiglomerular basement membrane (GBM) crescentic glomerulonephritis (GN) in Wistar–Kyoto (WKY) rats. In this study, we asked whether CD8+ cells produce their effects by perforin\\/granzyme-mediated or by Fas ligand (FasL)-mediated pathways. The glomerular mRNA expression of perforin and granzyme B corresponded with the number of CD8+

H Fujinaka; T Yamamoto; L Feng; M Nameta; G Garcia; S Chen; Ag A El-shemi; K Ohshiro; K Katsuyama; Y Yoshida; E Yaoita; C B Wilson

2007-01-01

146

Membranous lupus nephritis with antineutrophil cytoplasmic antibody-associated segmental necrotizing and crescentic glomerulonephritis  

Microsoft Academic Search

Focal segmental necrotizing and crescentic lupus nephritis accompanied by perinuclear antineutrophil cytoplasmic antibody (P-ANCA) seropositivity is an unusual occurrence. We report the first biopsy-documented cases of membranous lupus nephritis class V with associated “pauci-immune” segmental necrotizing glomerulonephritis and P-ANCA seropositivity. The absence of subendothelial electron-dense deposits favored a manifestation of superimposed ANCA-associated glomerulonephritis rather than class III lupus nephritis. The

Susan Marshall; Robert Dressler; Vivette D'Agati

1997-01-01

147

Monitoring of crescentic sandbar migration processes associated with seasonal wave climate  

NASA Astrophysics Data System (ADS)

This study conducted eight nearshore bathymetry surveys using a single-beam echosounder, a IMU sensor and a real-time kinematic (RTK) GPS system at the Hujeong Beach, South Korea from June 2011 to May 2012 in order to examine nearshore-sandbar migration processes in a wave-dominant coastal environment. Directional wave data collected from a waverider buoy moored offshore at 30-m water depth were used to examine the relationship between the sandbar migration and seasonal wave-climate pattern. Results of the bathymetric surveys showed that six crescentic sandbars well developed along the shore. The crescentic sandbars appeared to be about 370 m in average length, while maximum distance between the bar crest and shore was about 230 m. The crescentic sandbars of June 2011 were symmetric rhythmic-bar and beach (RBB). The sandbars in September 2011 were changed to northwesterly oblique transverse bar and rip (TBR)/RBB. In March 2012, sandbars became TBR with easterly oblique rip channel. During the winter waves of higher than 3 m in wave height (Hs) occurred more frequently than during the summer. Incidence directions of the winter waves were NE or NNE whereas E or SE during the summer. Based on bathymetric survey results, the sandbars were northwesterly migrated by a maximum of 202 m between June 2011 to September 2011 and were then migrated southeasterly by a maximum of 252 m between September 2011 to March 2012. This result indicates that seasonal pattern of wave climate might influence strongly on the deformation and migration of crescentic sandbars in the study site.

Jeong, E.; Park, J.

2012-12-01

148

Activation and cellular localization of the p38 and JNK MAPK pathways in rat crescentic glomerulonephritis  

Microsoft Academic Search

Activation and cellular localisation of the p38 and JNK MAPK pathways in rat crescentic glomerulonephritis.BackgroundThe p38 and c-Jun N-terminal kinase (JNK) mitogen-activated protein kinase (MAPK) are intracellular signal transduction pathways involved in the production of inflammatory mediators. Little, however, is known about the contribution of these pathways to renal inflammation, nor the cell types in which these pathways are activated

COSIMO STAMBE; Robert C. Atkins; Prudence A. Hill; David J. Nikolic-Paterson

2003-01-01

149

Diffusion au sommet d'une  

E-print Network

Diffusion au sommet d'une barri`ere de potentiel (I) Diffusion clas- sique/quantique Trajectoires classiques L'´equation de Schr¨odinger Op´erateur de diffusion Diffusion quantique en dimension 1 Matrice de diffusion Quelques r´esultats R´esonances Le Th´eor`eme de D. Robert et H. Tamura Trajectoires capt

Ramond, Thierry

150

Barchan and Linear Dunes on Earth and Mars - Comparative Research  

NASA Astrophysics Data System (ADS)

High resolution images from MGS and MRO reveal, in detail, ripples and dunes on Mars that were not discerned in old Viking images. The two basic dune types known on Earth, barchan (and transverse) and seif (linear), are also common on Mars, although seif dunes are quite rare on that planet. Some Martian barchan and seif dunes have a different morphology, particularly as evident in the Martian north polar region. Some of the barchans have an elongated, elliptical shape, while some of the linear dunes lack the sinuosity commonly associated with terrestrial seif dunes. These barchan and linear dunes occur together, side-by-side, and in some cases are merged to create a single bed-form. Induration of the dunes, or crust formation, can explain the occurrence of these dunes of unusual morphology in the Martian north polar region. Crusts may form as water vapor diffuses into and out of the fine-grained materials on the planet's surface. Salts would be deposited as intergranular cement. Because these bedforms occur in the polar region, the cementing agent could be ice instead of salts; indeed, the dunes spend more than half each Martian year beneath a covering of seasonal frost, mostly frozen carbon dioxide. Elliptical shaped barchans were created artificially in Saudi Arabia by spraying advancing barchan dunes with crude oil to stabilize them until the dunes reached a streamlined body shape. Simulation work indicates that the same process can occur on the indurated Martian barchans, but by cementation of grains rather than introduction of oil. Short lee dunes that have a linear shape with a sharp-edged crest are known to form from sand accumulation at the lee side of obstacles. Once a dune is stabilized by induration or crust, it functions as an obstacle to the wind. Linear lee dunes stabilized by ice (water or carbon dioxide) or mineral crust may elongate and form a long linear dune that aligns parallel to the wind. Melting of the ice will set up a straight linear dune, with loose sand, parallel to the dominant wind. Field observations on terrestrial deserts show that such a dune can only be formed when it is covered by vegetation. If vegetation is removed the bare linear dune disintegrates into small barchans. Simulation also shows that linear dune is unstable and deforms until it takes the shape of a string of barchans, which are the stable shape under unidirectional winds.

Tsoar, H.; Edgett, K. S.; Schatz, V.; Parteli, E. J.; Herrmann, H. J.

2007-05-01

151

High angle-of-attack aerodynamic characteristics of crescent and elliptic wings  

NASA Technical Reports Server (NTRS)

Static longitudinal and lateral-directional forces and moments were measured for elliptic- and crescent-wing models at high angles-of-attack in the NASA Langley 14 by 22-Ft Subsonic Tunnel. The forces and moments were obtained for an angle-of-attack range including stall and post-stall conditions at a Reynolds number based on the average wing chord of about 1.8 million. Flow-visualization photographs using a mixture of oil and titanium-dioxide were also taken for several incidence angles. The force and moment data and the flow-visualization results indicated that the crescent wing model with its highly swept tips produced much better high angle-of-attack aerodynamic characteristics than the elliptic model. Leading-edge separation-induced vortex flow over the highly swept tips of the crescent wing is thought to produce this improved behavior at high angles-of-attack. The unique planform design could result in safer and more efficient low-speed airplanes.

Vandam, C. P.

1989-01-01

152

Defrosting Polar Dunes--'The Snow Leopard'  

NASA Technical Reports Server (NTRS)

The patterns created by dark spots on defrosting south polar dunes are often strange and beautiful. This picture, which the Mars Orbiter Camera team has dubbed, 'the snow leopard,' shows a dune field located at 61.5oS, 18.9oW, as it appeared on July 1, 1999. The spots are areas where dark sand has been exposed from beneath bright frost as the south polar winter cap begins to retreat. Many of the spots have a diffuse, bright ring around them this is thought to be fresh frost that was re-precipitated after being removed from the dark spot. The spots seen on defrosting polar dunes are a new phenomenon that was not observed by previous spacecraft missions to Mars. Thus, there is much about these features that remains unknown. For example, no one yet knows why the dunes become defrosted by forming small spots that grow and grow over time. No one knows for sure if the bright rings around the dark spots are actually composed of re-precipitated frost. And no one knows for sure why some dune show spots that appear to be 'lined-up' (as they do in the picture shown here).

This Mars Global Surveyor Mars Orbiter Camera image is illuminated from the upper left. North is toward the upper right. The scale bar indicates a distance of 200 meters (656 feet).

Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.

1999-01-01

153

Geomorphology of coastal sand dunes, Baldwin County, Alabama  

USGS Publications Warehouse

Alabama's coastal eolian deposits are primarily vegetated dunes that are exemplified by sand ridges with flat to undulating upper surfaces and continuous irregular crests. Dune fields occur along Morgan peninsula between the foredune line and Little Lagoon and the Mobile Bay area. These dune fields consist primarily of one or more continuous ridges that parallel the coast and are generally vegetaed to grassy. Washover of the beach and backshore during Hurricane Frederic (1979) and subsequent smaller scale storms resulted in significant erosion of many of Alabama's dune fields. The primary dunes or foredunes are beginning to recover from the effects of these storms; however, numerous breaks in the primary dune line are present. Sand dunes in coastal Alabama provide protection against storm-generated waves and washover. The foredunes are protected by adherence to a Coastal Construction Control Line (CCCL) or construction setback line identified by markers along coastal Baldwin County.

Bearden, Bennett L.; Hummell, Richard L.; Mink, Robert M.

1989-01-01

154

Summary of the Third International Planetary Dunes Workshop: Remote Sensing and Image Analysis of Planetary Dunes, Flagstaff, Arizona, USA, June 12-15, 2012  

NASA Astrophysics Data System (ADS)

The Third International Planetary Dunes Workshop took place in Flagstaff, AZ, USA during June 12-15, 2012. This meeting brought together a diverse group of researchers to discuss recent advances in terrestrial and planetary research on aeolian bedforms. The workshop included two and a half days of oral and poster presentations, as well as one formal (and one informal) full-day field trip. Similar to its predecessors, the presented work provided new insight on the morphology, dynamics, composition, and origin of aeolian bedforms on Venus, Earth, Mars, and Titan, with some intriguing speculation about potential aeolian processes on Triton (a satellite of Neptune) and Pluto. Major advancements since the previous International Planetary Dunes Workshop include the introduction of several new data analysis and numerical tools and utilization of low-cost field instruments (most notably the time-lapse camera). Most presentations represented advancement towards research priorities identified in both of the prior two workshops, although some previously recommended research approaches were not discussed. In addition, this workshop provided a forum for participants to discuss the uncertain future of the Planetary Aeolian Laboratory; subsequent actions taken as a result of the decisions made during the workshop may lead to an expansion of funding opportunities to use the facilities, as well as other improvements. The interactions during this workshop contributed to the success of the Third International Planetary Dunes Workshop, further developing our understanding of aeolian processes on the aeolian worlds of the Solar System.

Fenton, Lori K.; Hayward, Rosalyn K.; Horgan, Briony H. N.; Rubin, David M.; Titus, Timothy N.; Bishop, Mark A.; Burr, Devon M.; Chojnacki, Matthew; Dinwiddie, Cynthia L.; Kerber, Laura; Le Gall, Alice; Michaels, Timothy I.; Neakrase, Lynn D. V.; Newman, Claire E.; Tirsch, Daniela; Yizhaq, Hezi; Zimbelman, James R.

2013-03-01

155

Valles Marineris dune fields as compared with other martian populations: Diversity of dune compositions, morphologies, and thermophysical properties  

NASA Astrophysics Data System (ADS)

Planetary dune field properties and their bulk bedform morphologies relate to regional wind patterns, sediment supply, climate, and topography. On Mars, major occurrences of spatially contiguous low-albedo sand dunes are primarily found in three major topographic settings: impact craters, high-latitude basins, and linear troughs or valleys, the largest being the Valles Marineris (VM) rift system. As one of the primary present day martian sediment sinks, VM holds nearly a third of the non-polar dune area on Mars. Moreover, VM differs from other regions due to its unusual geologic, topographic, and atmospheric setting. Herein, we test the overarching hypothesis that VM dune fields are compositionally, morphologically, and thermophysically distinct from other low- and mid-latitude (50°N-50°S latitude) dune fields. Topographic measurements of dune fields and their underlying terrains indicate slopes, roughnesses, and reliefs to be notably greater for those in VM. Variable VM dune morphologies are shown with topographically-related duneforms (climbing, falling, and echo dunes) located among spur-and-gully wall, landslide, and chaotic terrains, contrasting most martian dunes found in more topographically benign locations (e.g., craters, basins). VM dune fields superposed on Late Amazonian landslides are constrained to have formed and/or migrated over >10s of kilometers in the last 50 My to 1 Gy. Diversity of detected dune sand compositions, including unaltered ultramafic minerals and glasses (e.g., high and low-calcium pyroxene, olivine, Fe-bearing glass), and alteration products (hydrated sulfates, weathered Fe-bearing glass), is more pronounced in VM. Observations show heterogeneous sand compositions exist at the regional-, basinal-, dune field-, and dune-scales. Although not substantially greater than elsewhere, unambiguous evidence for recent dune activity in VM is indicated from pairs of high-resolution images that include: dune deflation, dune migration, slip face modification (e.g., alcoves), and ripple modification or migration, at varying scales (10s-100s m2). We conclude that VM dune fields are qualitatively and quantitatively distinct from other low- and mid-latitude dune fields, most readily attributable to the rift's unusual setting. Moreover, results imply dune field properties and aeolian processes on Mars can be largely influenced by regional environment, which may have their own distinctive set of boundary conditions, rather than a globally homogenous collection of aeolian sediment and bedforms.

Chojnacki, Matthew; Burr, Devon M.; Moersch, Jeffrey E.

2014-02-01

156

KoG132009 G. Glaeser, K.H. Schott: Geometric Considerations About Seemingly Wrong Tilt of Crescent Moon Original scientific paper  

E-print Network

of Crescent Moon Original scientific paper Accepted 20. 12. 2009 Georg Glaeser, Karlheinz Schott Geometric Considerations About Seemingly Wrong Tilt of Crescent Moon Geometric Considerations About Seemingly Wrong Tilt of Crescent Moon ABSTRACT The following phenomenon is well-known and again and again appears as an unanswered

Stachel, Hellmuth

157

Multiple origins of linear dunes on Earth and Titan  

USGS Publications Warehouse

Dunes with relatively long and parallel crests are classified as linear dunes. On Earth, they form in at least two environmental settings: where winds of bimodal direction blow across loose sand, and also where single-direction winds blow over sediment that is locally stabilized, be it through vegetation, sediment cohesion or topographic shelter from the winds. Linear dunes have also been identified on Titan, where they are thought to form in loose sand. Here we present evidence that in the Qaidam Basin, China, linear dunes are found downwind of transverse dunes owing to higher cohesiveness in the downwind sediments, which contain larger amounts of salt and mud. We also present a compilation of other settings where sediment stabilization has been reported to produce linear dunes. We suggest that in this dune-forming process, loose sediment accumulates on the dunes and is stabilized; the stable dune then functions as a topographic shelter, which induces the deposition of sediments downwind. We conclude that a model in which Titan's dunes formed similarly in cohesive sediments cannot be ruled out by the existing data.

Rubin, David M.; Hesp, Patrick A.

2009-01-01

158

12 I The Johns Hopkins and the International Federation of Red Cross and Red Crescent Societies Abbreviations Acronyms/Abbreviations  

E-print Network

Airway, Breathing and Circulation AIDS Acquired Immune Deficiency Syndrome ANC Ante Natal Care API Annual/Red Crescent Health Initiative 2010 ARDS Acute Respiratory Distress Syndrome ARI Acute Respiratory Infection

Scharfstein, Daniel

159

Pooh Bear rock and Mermaid Dune  

NASA Technical Reports Server (NTRS)

One of the two forward cameras aboard Sojourner imaged this area of Martian terrain on Sol 26. The large rock dubbed 'Pooh Bear' is at far left, and stands between four and five inches high. Mermaid Dune is the smooth area stretching horizontally across the top quarter of the image. The Alpha Proton X-Ray Spectrometer (APXS) instrument aboard Sojourner will be deployed on Mermaid Dune, and the rover will later use its cleated wheels to dig into it.

Mars Pathfinder is the second in NASA's Discovery program of low-cost spacecraft with highly focused science goals. The Jet Propulsion Laboratory, Pasadena, CA, developed and manages and Mars Pathfinder mission for NASA's Office of Space Science, Washington, D.C. JPL is an operating division of the California Institute of Technology (Caltech). The Imager for Mars Pathfinder (IMP) was developed by the University of Arizona Lunar and Planetary Laboratory under contract to JPL. Peter Smith is the Principal Investigator.

1997-01-01

160

D and D (Dunes and Devils)  

NASA Technical Reports Server (NTRS)

3 February 2006 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows streaks created by late spring and early summer dust devils on a field of dark sand dunes on the floor of Hooke Crater.

Location near: 45.0oS, 44.8oW Image width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Summer

2006-01-01

161

Winter Frosted Dunes in Kaiser Crater  

NASA Technical Reports Server (NTRS)

As the Mars Global Surveyor Primary Mission draws to an end, the southern hemisphere of Mars is in the depths of winter. At high latitudes, it is dark most, if not all, of the day. Even at middle latitudes, the sun shines only thinly through a veil of water and carbon dioxide ice clouds, and the ground is so cold that carbon dioxide frosts have formed. Kaiser Crater (47oS, 340oW) is one such place. At a latitude comparable to Seattle, Washington, Duluth, Minnesota, or Helena, Montana, Kaiser Crater is studied primarily because of the sand dune field found within the confines of its walls (lower center of the Mars Orbiter Camera image, above). The normally dark-gray or blue-black sand can be seen in this image to be shaded with light-toned frost. Other parts of the crater are also frosted. Kaiser Crater and its dunes were the subject of an earlier presentation of results. Close-up pictures of these and other dunes in the region show details of their snow-cover, including small avalanches. The two Mars Global Surveyor Mars Orbiter Camera images that comprise this color view (M23-01751 and M23-01752) were acquired on January 26, 2001.

2001-01-01

162

Ecology, management and monitoring of grey dunes in Flanders  

Microsoft Academic Search

Grey dunes are a priority habitat type of the European Union Habitats Directive and demand special attention for conservation\\u000a and management. Knowledge of the ecology of coastal grey dunes can contribute to this policy. Dune grassland succession is\\u000a initiated by fixation and driven by the complex of soil formation (humus accumulation) and vegetation development. Leaching\\u000a and mobilization of CaCO3. which

Dries Bonte; Eric Cosyns; Maurice Hoffmann

2004-01-01

163

Dune migration in a steep, coarse-bedded stream  

USGS Publications Warehouse

In the North Fork Toutle River at Kid Valley, Washington, weak correlation between flow depth and the standard deviation of bed elevation was noted. Dunes were often superposed on larger bed forms with wave periods between 10 and 30 min. Gradual changes in waveform height and periodicity occurred over several hours during storm runoff. Rates of migration for typical dunes were estimated to be 3 cm s-1, and dune wavelengths were estimated to be 6 to 7 m. -from Author

Dinehart, R.L.

1989-01-01

164

Lutheran/basal cell adhesion molecule accelerates progression of crescentic glomerulonephritis in mice  

PubMed Central

Migration of circulating leukocytes from the vasculature into the surrounding tissue is an important component of the inflammatory response. Among the cell surface molecules identified as contributing to leukocyte extravasation is VCAM-1, expressed on activated vascular endothelium, which participates in all stages of leukocyte–endothelial interaction by binding to leukocyte surface expressed integrin VLA-4. However, not all VLA-4-mediated events can be linked to VCAM-1. A novel interaction between VLA-4 and endothelial Lutheran (Lu) blood group antigens and basal cell adhesion molecule (BCAM) proteins has been recently shown, suggesting that Lu/BCAM may have a role in leukocyte recruitments in inflamed tissues. Here, we assessed the participation of Lu/BCAM in the immunopathogenesis of crescentic glomerulonephritis. High expression of Lu/BCAM in glomeruli of mice with rapidly progressive glomerulonephritis suggests a potential role for the local expression of Lu/BCAM in nephritogenic recruitment of leukocytes. Genetic deficiency of Lu/BCAM attenuated glomerular accumulation of T cells and macrophages, crescent formation, and proteinuria, correlating with reduced fibrin and platelet deposition in glomeruli. Furthermore, we found a pro-adhesive interaction between human monocyte ?4?1 integrin and Lu/BCAM proteins. Thus, Lu/BCAM may have a critical role in facilitating the accumulation of monocytes and macrophages, thereby exacerbating renal injury. PMID:24429403

Huang, Jin; Filipe, Anne; Rahuel, Cecile; Bonnin, Philippe; Mesnard, Laurent; Guerin, Coralie; Wang, Yu; Le Van Kim, Caroline; Colin, Yves; Tharaux, Pierre-Louis

2014-01-01

165

Toll-Like Receptor 9 Enhances Nephritogenic Immunity and Glomerular Leukocyte Recruitment, Exacerbating Experimental Crescentic Glomerulonephritis  

PubMed Central

Glomerular disease can be triggered or exacerbated by microbes that activate the immune system by Toll-like receptor (TLR) ligation. TLR9 activation promotes host defenses through the enhancement of innate and adaptive immune responses that facilitate the recruitment of leukocytes to areas of inflammation. We defined the role of TLR9 in experimental crescentic glomerulonephritis. Wild-type mice administered a TLR9 ligand and sheep anti-mouse glomerular basement membrane antibody developed histological injury with impaired renal function, which was attenuated in TLR9 knockout mice. Consistent with enhanced renal injury, wild-type mice exhibited enhanced T helper 1 and T helper 17 cellular immune responses. Kidney mRNA expression of inflammatory cytokines and chemokines as well as leukocyte recruitment were increased in wild-type mice. The use of bone marrow chimeric mice demonstrated that while both bone marrow and tissue cell TLR9 are required for maximal injury, bone marrow TLR9 is more important. Administration of a TLR9 inhibitor before sheep anti-mouse glomerular basement membrane globulin in wild-type mice attenuated cellular nephritogenic immunity that resulted in decreased renal injury. Administration of the inhibitor 7 days after disease initiation decreased glomerular leukocyte recruitment as well as renal injury. These results define the role of TLR9 in experimental crescentic glomerulonephritis and identify therapeutic potential for TLR9 inhibitors in attenuating renal injury, decreasing cellular nephritogenic immunity early in disease, and decreasing kidney effector responses later. PMID:20847283

Summers, Shaun A.; Steinmetz, Oliver M.; Ooi, Joshua D.; Gan, Poh-yi; O'Sullivan, Kim M.; Visvanathan, Kumar; Akira, Shizuo; Kitching, A. Richard; Holdsworth, Stephen R.

2010-01-01

166

Trophic status and assessment of non-point nutrient enrichment of Lake Crescent Olympic National Park  

USGS Publications Warehouse

A limited effort study was conducted in Lake Crescent, Olympic National Park to determine the trophic status and assess whether non-point nutrients were leaching into the lake and affecting biological resources. The concentration of chlorophyll a, total nitrogen concentration, and Secchi disk transparency used as parameters of the Trophic Status Index revealed that Lake Crescent in Olympic National Park was in the oligotrophic range. Evaluation of the nitrogen to phosphorous ration revealed that nitrogen was the nutrient limiting to overall lake productivity. Single species and community bioassays indicated that other nutrients, possibly iron, had some secondary control over community composition of the algal community. Assessment of six near-shore sites for the presence and effects of non-point nutrients revealed that La Poel Point which formerly was the site of a resort had slightly higher algal bioassay and periphyton response than the other sites. No conditions that would require immediate action by resource management of Olympic National Park were identified. The general recommendations for a long term lake monitoring plan are discussed.

Boyle, Terence P.; Beeson, David R.

1991-01-01

167

Model for a dune field with exposed water table  

E-print Network

Aeolian transport in coastal areas can be significantly affected by the presence of an exposed water table. In some dune fields, such as in Len\\c{c}\\'ois Maranhenses, northeastern Brazil, the water table oscillates in response to seasonal changes of rainfall and rates of evapotranspiration, rising above the ground during the wet season and sinking below in the dry period. A quantitative understanding of dune mobility in an environment with varying groundwater level is essential for coastal management as well as for the study of long-term evolution of many dune fields. Here we apply a model for aeolian dunes to study the genesis of coastal dune fields in presence of an oscillating water table. We find that the morphology of the field depends on the time cycle, $T_{\\mathrm{w}}$, of the water table and the maximum height, $H_{\\mathrm{w}}$, of its oscillation. Our calculations show that long chains of barchanoids alternating with interdune ponds such as found at Len\\c{c}\\'ois Maranhenses arise when $T_{\\mathrm{w}}$ is of the order of the dune turnover time, whereas $H_{\\mathrm{w}}$ dictates the growth rate of dune height with distance downwind. We reproduce quantitatively the morphology and size of dunes at Len\\c{c}\\'ois Maranhenses, as well as the total relative area between dunes.

Marco Cesar M. de M. Luna; Eric J. R. Parteli; Hans J. Herrmann

2011-09-01

168

A Comparative Analysis of Barchan Dunes in the Intra-Crater Dune Fields and the North Polar Sand Sea  

NASA Technical Reports Server (NTRS)

Martian sand dunes have the potential to contribute data on geological history through a study of their form. Recognition of the characteristics of both recent and ancient dunes is the first step towards understanding the present as well as past aeolian systems, and by proxy, climatic conditions on Mars. Dunes studied in detail in Viking 1 and 2 Orbiter images have been classified as barchan, barchanoid, transverse, and complex. Regionally, they are concentrated in four locations: The North and South Polar regions, in intra crater dune fields and in troughs and valleys. Here we present the results of a morphometric analysis of barchan dunes in two of these locations: the North Polar Sand Sea (NPSS) and intra-crater dunes.

Bourke, M. C.; Balme, M.; Zimbelman, J.

2004-01-01

169

Observed and modeled tsunami current velocities in Humboldt Bay and Crescent City Harbor, northern California  

NASA Astrophysics Data System (ADS)

A pilot project was initiated in 2009 in Humboldt Bay, about 370 kilometers (km) north of San Francisco, California, to measure the currents produced by tsunamis. Northern California is susceptible to both near- and far-field tsunamis and has a historic record of damaging events. Crescent City Harbor, located approximately 100 km north of Humboldt Bay, suffered US 20 million in damages from strong currents produced by the 2006 Kuril Islands tsunami and an additional US 20 million from the 2011 Japan tsunami. In order to better evaluate these currents in northern California, we deployed a Nortek Aquadopp 600kHz 2D Acoustic Doppler Current Profiler (ADCP) with a one-minute sampling interval in Humboldt Bay, near the existing National Oceanic and Atmospheric Administration (NOAA) National Ocean Service (NOS) tide gauge station. The instrument recorded the tsunamis produced by the Mw 8.8 Chile earthquake on February 27, 2010 and the Mw 9.0 Japan earthquake on March 11, 2011. Currents from the 2010 tsunami persisted in Humboldt Bay for at least 30 hours with peak amplitudes of about 0.3 meters per second (m/s). The 2011 tsunami signal lasted for over 86 hours with peak amplitude of 0.95 m/s. Strongest currents corresponded to the maximum change in water level as recorded on the NOAA NOS tide gauge, and occurred 90 minutes after the initial wave arrival. No damage was observed in Humboldt Bay for either event. In Crescent City, currents for the first three and a half hours of the 2011 Japan tsunami were estimated using security camera video footage from the Harbor Master building across from the entrance to the small boat basin, approximately 70 meters away from the NOAA NOS tide gauge station. The largest amplitude tide gauge water-level oscillations and most of the damage occurred within this time window. The currents reached a velocity of approximately 4.5 m/s and six cycles exceeded 3 m/s during this period. Measured current velocities both in Humboldt Bay and in Crescent City were compared to calculated velocities from the Method of Splitting Tsunamis (MOST) numerical model. For Humboldt Bay, the 2010 model tsunami frequencies matched the actual values for the first two hours after the initial arrival however the amplitudes were underestimated by approximately 65%. MOST replicated the first four hours of the 2011 tsunami signal in Humboldt Bay quite well although the peak flood currents were underestimated by about 50%. MOST predicted attenuation of the signal after four hours but the actual signal persisted at a nearly constant level for more than 48 hours. In Crescent City, the model prediction of the 2011 frequency agreed quite well with the observed signal for the first two and a half hours after the initial arrival with a 50% underestimation of the peak amplitude. The results from this project demonstrate that ADCPs can effectively record tsunami currents for small to moderate events and can be used to calibrate and validate models (i.e. MOST) in order to better predict hazardous tsunami conditions and improve planned responses to protect lives and property, especially within harbors. An ADCP will be installed in Crescent City Harbor and four additional ADCPs are being deployed in Humboldt Bay during the fall of 2012.

Admire, A. R.; Dengler, L.; Crawford, G. B.; uslu, B. U.; Montoya, J.

2012-12-01

170

44 CFR 65.11 - Evaluation of sand dunes in mapping coastal flood hazard areas.  

Code of Federal Regulations, 2013 CFR

...Evaluation of sand dunes in mapping coastal flood hazard areas. (a...consider storm-induced dune erosion potential in its determination of coastal flood hazards and risk mapping...in the evaluation of dune erosion will apply to primary...

2013-10-01

171

44 CFR 65.11 - Evaluation of sand dunes in mapping coastal flood hazard areas.  

Code of Federal Regulations, 2012 CFR

...Evaluation of sand dunes in mapping coastal flood hazard areas. (a...consider storm-induced dune erosion potential in its determination of coastal flood hazards and risk mapping...in the evaluation of dune erosion will apply to primary...

2012-10-01

172

Modelling Desert Dune Fields Based on Discrete Dynamics STEVEN R. BISHOPa,  

E-print Network

it is a typical landform where aeolian processes dominate. Such aeolian landforms are estimated to cover about one flat desert. These dunes are called free dunes. In such a dune field, any landform is a result

173

76 FR 68503 - Ungulate Management Plan/Environmental Impact Statement, Great Sand Dunes National Park and...  

Federal Register 2010, 2011, 2012, 2013

...Environmental Impact Statement, Great Sand Dunes National Park and Preserve, CO AGENCY...for the Ungulate Management Plan, Great Sand Dunes National Park and Preserve...for the Ungulate Management Plan, Great Sand Dunes National Park and Preserve,...

2011-11-04

174

Xylocopa bees in tropical coastal sand dunes: use of resources and their floral syndromes.  

PubMed

Large bees such as species from Xylocopa Latreille are usually associated with pollination in tropical sand dune areas, which frequently present shrubby herbaceous vegetation adapted to conditions of high salinity, high solar radiation and strong winds. We report on the diversity of Xylocopa and the plants they visited to collect nectar and pollen, focusing on the floral syndromes they present in these plants and on the breadth of the trophic niche in a tropical sand dune fragment over the year. The field work was carried out monthly in Baixio (Bahia, Brazil; Northern Coast Environmental Protection Area) from April 2008 to March 2009, over two consecutive days, from 06:30?AM to 05:00?PM. The medium-large body sized Xylocopa (Neoxylocopa) cearensis Ducke and Xylocopa (Schonnherria) subcyanea Pérez were noticeable for their frequency, constancy on the flowers and sharing of plant species. Xylocopa spp. visited plants with flowers of different shapes, colors, inflorescence arrangement and syndromes. However, their resource collections were mainly concentrated on Cuphea brachiata, Waltheria cinerascens, Croton sellowii and Chamaecrista ramosa, which may be considered key species for Xylocopa spp. maintenance in coastal sand dune and restinga environments in Northeast Brazil. PMID:23949807

Figueiredo, N; Gimenes, M; de Miranda, M D; Oliveira-Rebouças, P

2013-06-01

175

Precision topography of a reversing sand dune at Bruneau Dunes, Idaho, as an analog for Transverse Aeolian Ridges on Mars  

NASA Astrophysics Data System (ADS)

Ten high precision topographic profiles across a reversing dune were created from a differential global position system (DGPS). The shapes of the profiles reveal a progression from immature to transitional to mature characteristics moving up the dune. When scaled by the basal width along each profile, shape characteristics can be compared for profiles whose horizontal scales differ by orders of magnitude. The comparison of width-scaled Bruneau Dunes profiles to similarly scaled profiles of Transverse Aeolian Ridges (TARs) on Mars indicates that many TARs are likely similar to transitional or mature reversing sand dunes.

Zimbelman, James R.; Scheidt, Stephen P.

2014-02-01

176

Relating climate and sand transport to incipient dune development.  

NASA Astrophysics Data System (ADS)

Sea levels are continuously rising, increasing the risk of flooding and coastal erosion in low-elevation countries, such as the Netherlands. Coastal dunes are seen as a flexible and natural type of coastal defence, that is able to keep pace with rising water levels. Until now most research has focussed on dynamics and maintenance of established dunes, largely ignoring two critical transitions in early dune development: the transition from bare beach to vegetated incipient dune and that from incipient dune to established foredune. This knowledge is essential to enable more accurate prediction and even stimulation of new dune formation through sand nourishment. We explored the relative contributions of climate and sand transport to incipient dune development combining a 30 year time-series of aerial photographs (1979 - 2010) of the natural Wadden Island coast with high-resolution monitoring data of sand volume changes and climatic parameters. We selected 20 strips of 2.5 km in length along the coast of the Wadden Islands, with a 2 km buffer between them to avoid autocorrelation. For each of these strips of coast we assessed the changes in presence and area of incipient dunes over periods of 5-6 years. Change in fore dune volume and beach width were derived from high resolution beach elevation data. Seawater level and climate data were derived from a nearby meteorological station Preliminary analysis of the first half of the dataset showed that incipient dune area was positively related to beach width, but negatively to storm intensity. In our poster we will present the whole dataset and discuss the implications of our results for future dune development and anthropogenic sand nourishment schemes.

van Puijenbroek, Marinka; Limpens, Juul; Gleichman, Maurits; Berendse, Frank

2014-05-01

177

Titan dune heights retrieval by using Cassini Radar Altimeter  

NASA Astrophysics Data System (ADS)

The Cassini Radar is a Ku band multimode instrument capable of providing topographic and mapping information. During several of the 93 Titan fly-bys performed by Cassini, the radar collected a large amount of data observing many dune fields in multiple modes such as SAR, Altimeter, Scatterometer and Radiometer. Understanding dune characteristics, such as shape and height, will reveal important clues on Titan's climatic and geological history providing a better understanding of aeolian processes on Earth. Dunes are believed to be sculpted by the action of the wind, weak at the surface but still able to activate the process of sand-sized particle transport. This work aims to estimate dunes height by modeling the shape of the real Cassini Radar Altimeter echoes. Joint processing of SAR/Altimeter data has been adopted to localize the altimeter footprints overlapping dune fields excluding non-dune features. The height of the dunes was estimated by applying Maximum Likelihood Estimation along with a non-coherent electromagnetic (EM) echo model, thus comparing the real averaged waveform with the theoretical curves. Such analysis has been performed over the Fensal dune field observed during the T30 flyby (May 2007). As a result we found that the estimated dunes' peak to trough heights difference was in the order of 60-120 m. Estimation accuracy and robustness of the MLE for different complex scenarios was assessed via radar simulations and Monte-Carlo approach. We simulated dunes-interdunes different composition and roughness for a large set of values verifying that, in the range of possible Titan environment conditions, these two surface parameters have weak effects on our estimates of standard dune heights deviation. Results presented here are the first part of a study that will cover all Titan's sand seas.

Mastrogiuseppe, M.; Poggiali, V.; Seu, R.; Martufi, R.; Notarnicola, C.

2014-02-01

178

Shifting Sands: Quantifying Shoreline and Dune Migration at Indiana Dunes National Lakeshore  

NSDL National Science Digital Library

Spreadsheets Across the Curriculum module/Geology of National Parks course. Students use weighted averages and data from air photos from 1939 to 2005 to calculate the rate of retreat of the shoreline and the advance of the front of dunes along the shoreline.

Module by: Mark Horwitz, University of South Florida Cover Page by: Len Vacher and Denise Davis, University of South Florida

179

Classification of satellite time series-derived land surface phenology focused on the northern Fertile Crescent  

NASA Astrophysics Data System (ADS)

Land surface phenology describes events in a seasonal vegetation cycle and can be used in a variety of applications from predicting onset of future drought conditions, to revealing potential limits of historical dry farming, to guiding more accurate dating of archeological sites. Traditional methods of monitoring vegetation phenology use data collected in situ. However, vegetation health indices derived from satellite remote sensor data, such as the normalized difference vegetation index (NDVI), have been used as proxy for vegetation phenology due to their repeated acquisition and broad area coverage. Land surface phenology is accessible in the NDVI satellite record when images are processed to be intercomparable over time and temporally ordered to create a time series. This study utilized NDVI time series to classify areas of similar vegetation phenology in the northern Fertile Crescent, an area from the middle Mediterranean coast to southern/south-eastern Turkey to western Iran and northern Iraq. Phenological monitoring of the northern Fertile Crescent is critical due to the area's minimal water resources, susceptibility to drought, and understanding ancient historical reliance on precipitation for subsistence dry farming. Delineation of phenological classes provides areal and temporal synopsis of vegetation productivity time series. Phenological classes were developed from NDVI time series calculated from NOAA's Advanced Very High Resolution Radiometer (AVHRR) imagery with 8 × 8 km spatial resolution over twenty-five years, and by NASA's Moderate Resolution Imaging Spectroradiometer (MODIS) with 250 × 250 m spatial resolution over twelve years. Both AVHRR and MODIS time series were subjected to data reduction techniques in spatial and temporal dimensions. Optimized ISODATA clusters were developed for both of these data reduction techniques in order to compare the effects of spatial versus temporal aggregation. Within the northern Fertile Crescent study area, the spatial reduction technique showed increased cluster cohesion over the temporal reduction method. The latter technique showed an increase in temporal smoothing over the spatial reduction technique. Each technique has advantages depending on the desired spatial or temporal granularity. Additional work is required to determine optimal scale size for the spatial data reduction technique.

Bunker, Brian

180

Dune Sand Fixation: Mauritania Seawater Pipeline Macroproject  

Microsoft Academic Search

\\u000a Wide-spreading actively migratory sand dune fields are mainly found in the Earth’s climatically designated desert regions—“hot\\u000a deserts” cover ~14.2% of Earth’s land (Peel et al. 2007; Parsons and Abrahams 2009). Some eremologists suspect that “global desertification”, a persistent decline of ecosystems’ benefits for humans—loss of\\u000a utility or potential utility of land—in already dry regions, is occurring and will increase as

Viorel Badescu; Richard B. Cathcart

181

Evidence for community structure and habitat partitioning in coastal dune stiletto flies at the Guadalupe-Nipomo dunes system, California.  

PubMed

This study provides empirical evidence for habitat selection by North American species of stiletto flies (Diptera: Therevidae), based on local distributions of adults and immatures, and the first hypothesis of community assemblages proposed for a stiletto fly community. Sites at three localities within the Guadalupe-Nipomo dune system were sampled for stiletto flies in 1997 and 2001 by sifting sand, malaise trapping, and hand netting. Nine species were collected from four ecological zones and three intermediate ecological zones: Acrosathe novella (Coquillett), Brachylinga baccata (Loew), Nebritus powelli (Webb and Irwin), Ozodiceromyia sp., Pherocera sp., Tabudamima melanophleba (Loew), Thereva comata Loew, Thereva elizabethae Holston and Irwin, and Thereva fucata Loew. Species associations of adults and larvae with habitats and ecological zones were consistent among sites, suggesting that local distributions of coastal dune stiletto fly species are influenced by differences in habitat selection. In habitats dominated by the arroyo willow,Salix lasiolepsis, stiletto fly larvae of three species were collected in local sympatry, demonstrating that S. lasiolepsis stands along stabilized dune ridges can provide an intermediate ecological zone linking active dune and riparian habitat in the Guadalupe-Nipomo dune system. Sites dominated by European beach grass, Ammophilia arenaria, blue gum, Eucalyptus globulus, and Monterey cypress, Cupressus macrocarpa, are considered unsuitable for stiletto flies, which emphasizes the importance of terrestrial habitats with native vegetation for stiletto fly species. The local distributions of stiletto fly species at the Guadalupe-Nipomo dune system allow the community to be divided into three assemblages; active dune, pioneer scrub, and scrub-riparian. These assemblages may be applicable to other coastal dune stiletto fly communities, and may have particular relevance to stiletto fly species collected in European coastal dunes. The results from this study provide a descriptive framework for studies testing habitat selection in coastal dune stiletto fly species and inform conservation of threatened dune insects. PMID:17119624

Holston, Kevin C

2005-01-01

182

Evidence for community structure and habitat partitioning in coastal dune stiletto flies at the Guadalupe-Nipomo dunes system, California  

PubMed Central

This study provides empirical evidence for habitat selection by North American species of stiletto flies (Diptera: Therevidae), based on local distributions of adults and immatures, and the first hypothesis of community assemblages proposed for a stiletto fly community. Sites at three localities within the Guadalupe-Nipomo dune system were sampled for stiletto flies in 1997 and 2001 by sifting sand, malaise trapping, and hand netting. Nine species were collected from four ecological zones and three intermediate ecological zones: Acrosathe novella (Coquillett), Brachylinga baccata (Loew), Nebritus powelli (Webb and Irwin), Ozodiceromyia sp., Pherocera sp., Tabudamima melanophleba (Loew), Thereva comata Loew, Thereva elizabethae Holston and Irwin, and Thereva fucata Loew. Species associations of adults and larvae with habitats and ecological zones were consistent among sites, suggesting that local distributions of coastal dune stiletto fly species are influenced by differences in habitat selection. In habitats dominated by the arroyo willow,Salix lasiolepsis, stiletto fly larvae of three species were collected in local sympatry, demonstrating that S. lasiolepsis stands along stabilized dune ridges can provide an intermediate ecological zone linking active dune and riparian habitat in the Guadalupe-Nipomo dune system. Sites dominated by European beach grass, Ammophilia arenaria, blue gum, Eucalyptus globulus, and Monterey cypress, Cupressus macrocarpa, are considered unsuitable for stiletto flies, which emphasizes the importance of terrestrial habitats with native vegetation for stiletto fly species. The local distributions of stiletto fly species at the Guadalupe-Nipomo dune system allow the community to be divided into three assemblages; active dune, pioneer scrub, and scrub-riparian. These assemblages may be applicable to other coastal dune stiletto fly communities, and may have particular relevance to stiletto fly species collected in European coastal dunes. The results from this study provide a descriptive framework for studies testing habitat selection in coastal dune stiletto fly species and inform conservation of threatened dune insects. PMID:17119624

Holston, Kevin C.

2005-01-01

183

36 CFR 7.80 - Sleeping Bear Dunes National Lakeshore.  

Code of Federal Regulations, 2012 CFR

...Public Property 1 2012-07-01 2012-07-01 false Sleeping Bear Dunes National Lakeshore. 7.80 Section 7.80...REGULATIONS, AREAS OF THE NATIONAL PARK SYSTEM § 7.80 Sleeping Bear Dunes National Lakeshore. (a) Powerless...

2012-07-01

184

36 CFR 7.80 - Sleeping Bear Dunes National Lakeshore.  

Code of Federal Regulations, 2010 CFR

...Public Property 1 2010-07-01 2010-07-01 false Sleeping Bear Dunes National Lakeshore. 7.80 Section 7.80...REGULATIONS, AREAS OF THE NATIONAL PARK SYSTEM § 7.80 Sleeping Bear Dunes National Lakeshore. (a) Powerless...

2010-07-01

185

36 CFR 7.80 - Sleeping Bear Dunes National Lakeshore.  

Code of Federal Regulations, 2011 CFR

...Public Property 1 2011-07-01 2011-07-01 false Sleeping Bear Dunes National Lakeshore. 7.80 Section 7.80...REGULATIONS, AREAS OF THE NATIONAL PARK SYSTEM § 7.80 Sleeping Bear Dunes National Lakeshore. (a) Powerless...

2011-07-01

186

Coastal Sand Dune Plant Ecology: Field Phenomena and Interpretation  

ERIC Educational Resources Information Center

Discusses the advantages and disadvantages of selecting coastal sand dunes as the location for field ecology studies. Presents a descriptive zonal model for seaboard sand dune plant communities, suggestions concerning possible observations and activities relevant to interpreting phenomena associated with these forms of vegetation, and additional…

McDonald, K.

1973-01-01

187

Luminescence chronology of the inland sand dunes from SE India  

NASA Astrophysics Data System (ADS)

Records of past climate changes have been preserved variously on the earth's surface. Sand dunes are one such prominent imprint, and it is suggested that their presence is an indicator of periods of transition from arid to less arid phases. We report inland sand dunes from Andhra Pradesh (SE India) spread over an area of ~ 500 km2, ~ 75 km inland from the east coast. The dune sands are examined to understand their provenance, transportation, timing of sand aggradation and their relationship to past climates. The dune distribution, grain morphology and the grain-size studies on sands suggest an aeolian origin. Physiography of the study area, heavy mineral assemblage, and abundance of quartz in the parent rocks indicate that the dune sands are largely derived from first-order streams emanating from hills in the region and from weathering of the Nellore schist belt. It appears that the geomorphology and wind direction pattern both facilitated and restricted the dune aggradation and preservation to a limited area. OSL dating of 47 dune samples ranged from the present to ~ 50 ka, thereby suggesting a long duration of sand-dune aggradation and/or reworking history.

Reddy, Dontireddy Venkat; Singaraju, Vuddaraju; Mishra, Rakesh; Kumar, Devender; Thomas, Puthusserry Joseph; Rao, Karra Kameshwa; Singhvi, Ashok Kumar

2013-09-01

188

36 CFR 7.88 - Indiana Dunes National Lakeshore.  

Code of Federal Regulations, 2012 CFR

...Public Property 1 2012-07-01 2012-07-01 false Indiana Dunes National Lakeshore. 7.88 Section 7.88 Parks...REGULATIONS, AREAS OF THE NATIONAL PARK SYSTEM § 7.88 Indiana Dunes National Lakeshore. (a) Fishing. Unless...

2012-07-01

189

36 CFR 7.88 - Indiana Dunes National Lakeshore.  

Code of Federal Regulations, 2010 CFR

...Public Property 1 2010-07-01 2010-07-01 false Indiana Dunes National Lakeshore. 7.88 Section 7.88 Parks...REGULATIONS, AREAS OF THE NATIONAL PARK SYSTEM § 7.88 Indiana Dunes National Lakeshore. (a) Fishing. Unless...

2010-07-01

190

36 CFR 7.88 - Indiana Dunes National Lakeshore.  

Code of Federal Regulations, 2011 CFR

...Public Property 1 2011-07-01 2011-07-01 false Indiana Dunes National Lakeshore. 7.88 Section 7.88 Parks...REGULATIONS, AREAS OF THE NATIONAL PARK SYSTEM § 7.88 Indiana Dunes National Lakeshore. (a) Fishing. Unless...

2011-07-01

191

36 CFR 7.88 - Indiana Dunes National Lakeshore.  

Code of Federal Regulations, 2013 CFR

...Public Property 1 2013-07-01 2013-07-01 false Indiana Dunes National Lakeshore. 7.88 Section 7.88 Parks...REGULATIONS, AREAS OF THE NATIONAL PARK SYSTEM § 7.88 Indiana Dunes National Lakeshore. (a) Fishing. Unless...

2013-07-01

192

Full-disk Color Image of Crescent Saturn with Rings and Ring Shadows  

NASA Technical Reports Server (NTRS)

Voyager 1 image of Saturn and its ring taken Nov. 16, 1980 four days after closest approach to Saturn, from a distance of 5,300, 000 km (3,300,000 miles). This viewing geometry, which shows Saturn as a crescent, is never achieved from Earth. The Saturnian rings, like the cloud tops of Saturn itself, are visible because they reflect sunlight. The translucent nature of the rings is apparent where Saturn can be seen through parts of the rings. Other parts of the rings are so dense with orbiting ice particles that almost no sunlight shines through them and a shadow is cast onto the yellowish cloud tops of Saturn, which in turn, casts a shadow across the rings at right. The black strip within the rings is the Cassini Division, which contains much less orbiting ring material than elsewhere in the rings.

1989-01-01

193

Toward Probabilistic Risk Analyses - Development of a Probabilistic Tsunami Hazard Assessment of Crescent City, CA  

NASA Astrophysics Data System (ADS)

Risk is defined in many ways, but most are consistent with Crichton's [1999] definition based on the ''risk triangle'' concept and the explicit identification of three risk elements: ''Risk is the probability of a loss, and this depends on three elements: hazard, vulnerability, and exposure. If any of these three elements in risk increases or decreases, then the risk increases or decreases respectively." The World Meteorological Organization, for example, cites Crichton [1999] and then defines risk as [WMO, 2008] Risk = function (Hazard x Vulnerability x Exposure) while the Asian Disaster Reduction Center adopts the more general expression [ADRC, 2005] Risk = function (Hazard, Vulnerability, Exposure) In practice, probabilistic concepts are invariably invoked, and at least one of the three factors are specified as probabilistic in nature. The Vulnerability and Exposure factors are defined in multiple ways in the relevant literature; but the Hazard factor, which is the focus of our presentation, is generally understood to deal only with the physical aspects of the phenomena and, in particular, the ability of the phenomena to inflict harm [Thywissen, 2006]. A Hazard factor can be estimated by a methodology known as Probabilistic Tsunami Hazard Assessment (PTHA) [González, et al., 2009]. We will describe the PTHA methodology and provide an example -- the results of a previous application to Seaside, OR. We will also present preliminary results for a PTHA of Crescent City, CA -- a pilot project and coastal modeling/mapping effort funded by the Federal Emergency Management Agency (FEMA) Region IX office as part of the new California Coastal Analysis and Mapping Project (CCAMP). CCAMP and the PTHA in Crescent City are being conducted under the nationwide FEMA Risk Mapping, Assessment, and Planning (Risk MAP) Program which focuses on providing communities with flood information and tools they can use to enhance their mitigation plans and better protect their citizens.

González, F. I.; Leveque, R. J.; Hatheway, D.; Metzger, N.

2011-12-01

194

Spatiotemporal model for the progression of transgressive dunes  

NASA Astrophysics Data System (ADS)

Transgressive dune fields, which are active sand areas surrounded by vegetation, exist on many coasts. In some regions like in Fraser Island in Australia, small dunes shrink while large ones grow, although both experience the same climatic conditions. We propose a general mathematical model for the spatiotemporal dynamics of vegetation cover on sand dunes and focus on the dynamics of transgressive dunes. Among other possibilities, the model predicts growth parallel to the wind with shrinkage perpendicular to the wind, where, depending on geometry and size, a transgressive dune can initially grow although eventually shrink. The larger is the initial area the slower its stabilization process. The model’s predictions are supported by field observations from Fraser Island in Australia.

Yizhaq, Hezi; Ashkenazy, Yosef; Levin, Noam; Tsoar, Haim

2013-10-01

195

Late Pleistocene dune activity in the central Great Plains, USA  

USGS Publications Warehouse

Stabilized dunes of the central Great Plains, especially the megabarchans and large barchanoid ridges of the Nebraska Sand Hills, provide dramatic evidence of late Quaternary environmental change. Episodic Holocene dune activity in this region is now well-documented, but Late Pleistocene dune mobility has remained poorly documented, despite early interpretations of the Sand Hills dunes as Pleistocene relicts. New optically stimulated luminescence (OSL) ages from drill cores and outcrops provide evidence of Late Pleistocene dune activity at sites distributed across the central Great Plains. In addition, Late Pleistocene eolian sands deposited at 20-25 ka are interbedded with loess south of the Sand Hills. Several of the large dunes sampled in the Sand Hills clearly contain a substantial core of Late Pleistocene sand; thus, they had developed by the Late Pleistocene and were fully mobile at that time, although substantial sand deposition and extensive longitudinal dune construction occurred during the Holocene. Many of the Late Pleistocene OSL ages fall between 17 and 14 ka, but it is likely that these ages represent only the later part of a longer period of dune construction and migration. At several sites, significant Late Pleistocene or Holocene large-dune migration also probably occurred after the time represented by the Pleistocene OSL ages. Sedimentary structures in Late Pleistocene eolian sand and the forms of large dunes potentially constructed in the Late Pleistocene both indicate sand transport dominated by northerly to westerly winds, consistent with Late Pleistocene loess transport directions. Numerical modeling of the climate of the Last Glacial Maximum has often yielded mean monthly surface winds southwest of the Laurentide Ice Sheet that are consistent with this geologic evidence, despite strengthened anticyclonic circulation over the ice sheet. Mobility of large dunes during the Late Pleistocene on the central Great Plains may have been the result of cold, short growing seasons with relatively low precipitation and low atmospheric CO2 that increased plant moisture stress, limiting the ability of vegetation to stabilize active dune sand. The apparent coexistence of large mobile dunes with boreal forest taxa suggests a Late Pleistocene environment with few modern analogs. ?? 2011 Elsevier Ltd.

Mason, J.A.; Swinehart, J.B.; Hanson, P.R.; Loope, D.B.; Goble, R.J.; Miao, X.; Schmeisser, R.L.

2011-01-01

196

Flow Fields Over Unsteady Three Dimensional Dunes  

NASA Astrophysics Data System (ADS)

The flow field over dunes has been extensively measured in laboratory conditions and there is general understanding on the nature of the flow over dunes formed under equilibrium flow conditions. However, fluvial systems typically experience unsteady flow and therefore the sediment-water interface is constantly responding and reorganizing to these unsteady flows, over a range of both spatial and temporal scales. This is primarily through adjustment of bed forms (including ripples, dunes and bar forms) which then subsequently alter the flow field. This paper investigates, through the application of a numerical model, the influence of these roughness elements on the overall flow and the increase in flow resistance. A series of experiments were undertaken in a flume, 16m long and 2m wide, where a fine sand (D50 of 239?m) mobile bed was water worked under a range of unsteady hydraulic conditions to generate a series of quasi-equilibrium three dimensional bed forms. During the experiments flow was measured with acoustic Doppler velocimeters, (aDv's). On four occasions the flume was drained and the bed topography measured with terrestrial LiDAR to create digital elevation models. This data provide the necessary boundary conditions and validation data for a Large Eddy Simulation (LES) model, which provided a three dimensional time dependent prediction of flow over the four static beds. The numerical predicted flow is analyzed through a series of approaches, and included: i) standard Reynolds decomposition to the flow fields; ii) Eulerian coherent structure detection methods based on the invariants of the velocity gradient tensor; iii) Lagrangian coherent structure identification methods based upon direct Lyapunov exponents (DLE). The results show that superimposed bed forms can cause changes in the nature of the classical separated flow region in particularly the number of locations where vortices are shed and the point of flow reattachment, which may be important for sediment entrainment and sediment transport dynamics during bed form adjustment. Finally, the flow predictions enable a reassessment of the drag caused by the superimposed bed forms generated by unsteady flow.

Hardy, R. J.; Reesink, A.; Parsons, D. R.; Ashworth, P. J.; Best, J.

2013-12-01

197

Vegetation controls on the maximum size of coastal dunes  

NASA Astrophysics Data System (ADS)

Coastal dunes, in particular foredunes, support a resilient ecosystem and reduce coastal vulnerability to storms. In contrast to dry desert dunes, coastal dunes arise from interactions between biological and physical processes. Ecologists have traditionally addressed coastal ecosystems by assuming that they adapt to preexisting dune topography, whereas geomorphologists have studied the properties of foredunes primarily in connection to physical, not biological, factors. Here, we study foredune development using an ecomorphodynamic model that resolves the co-evolution of topography and vegetation in response to both physical and ecological factors. We find that foredune growth is eventually limited by a negative feedback between wind flow and topography. As a consequence, steady state foredunes are scale invariant, which allows us to derive scaling relations for maximum foredune height and formation time. These relations suggest that plant zonation (in particular for strand `dune-building' species) is the primary factor controlling the maximum size of foredunes and therefore the amount of sand stored in a coastal dune system. We also find that aeolian sand supply to the dunes determines the time scale of foredune formation. These results offer a potential explanation for the empirical relation between beach type and foredune size, in which large (small) foredunes are found on dissipative (reflective) beaches: higher waves associated with dissipative beaches increase the disturbance of strand species which shifts foredune formation landwards and thus leads to larger foredunes.

Duran Vinent, Orencio; Moore, Laura J.

2014-05-01

198

Mapping sand dunes risk related to their terrain characteristics using SRTM data and cartographic modeling  

Microsoft Academic Search

Sand dunes encroachment is a challenge that faces land development in North African countries. Movement of these dunes threatens cultivated lands, roads, and urban settlements. Geographic information system (GIS) provides a tool for cartographic modeling of risk of sand dunes encroachment. This study modeled the potential risk of sand dunes encroachment related to their terrain characteristics in the Western Desert

Hala A. Effat; Mohamed N. Hegazy; Barry Haack

2011-01-01

199

Non-target effects of invasive species management: beachgrass, birds, and bulldozers in coastal dunes  

E-print Network

may have knock-on effects on non-target native species and ecosystems. For example, coastal dunes and dune function. Based on these findings, we suggest that the Pacific Northwest coastal dune ecosystem; Ammophila breviligulata; beachgrass; Charadrius alexandrinus nivosus; coastal dune; ecosystem engineer

200

Using Long-Term Census Data to Inform Restoration Methods for Coastal Dune Vegetation  

E-print Network

Using Long-Term Census Data to Inform Restoration Methods for Coastal Dune Vegetation Elise S Barrier Island . Coastal ecology . Dune zone . Disturbance . Dune vegetation . Storm response Introduction), with varied results. Restoration strategies can be difficult to implement successfully in coastal dune systems

Miller, Thomas E.

201

Techniques for GIS modeling of coastal dunes Brian D. Andrews a,*, Paul A. Gares b  

E-print Network

Techniques for GIS modeling of coastal dunes Brian D. Andrews a,*, Paul A. Gares b , Jeffrey D in revised form 5 September 2001; accepted 24 January 2002 Abstract Coastal dunes present a unique problem to coastal scientists because of the dynamic nature of most coastal dune systems. Coastal dunes can change

Thaxton, Christopher S.

202

Soil chronosequence development in dunes on the southeast African coastal plain, Maputaland, South Africa  

Microsoft Academic Search

Dunes have accreted on the southeast African coastal plain in coast-parallel patterns of degraded whaleback ridges, sand megaridges and extended parabolic dunes since the Pliocene. In the Maputaland dune field, relative dating is complicated by soil degradation, erosion and vegetation cover. This project assessed alternative relative and numeric dating techniques that can be used to differentiate dune systems and eolian

Greg Botha; Naomi Porat

2007-01-01

203

Sand dunes on the central Delmarva Peninsula, Maryland and Delaware  

USGS Publications Warehouse

Inconspicuous ancient sand dunes are present in parts of the central Delmarva Peninsula, Maryland and Delaware. Many dunes are roughly V-shaped, built by northwest winds, especially on the east sides of some of the large rivers. On the uplands, the form and spacing of the dunes are variable. A surficial blanket composed mainly of medium and fine-grained sand-the Parsonsburg Sand-forms both the ancient dunes and the broad plains between the dunes. The sand that forms the dunes is massive and intensely burrowed in the upper part; traces of horizontal or slightly inclined bedding appear near the base. Quartz is the dominant mineral constituent of the sand. Microline is abundant in the very fine to fine sand fraction. The heavy-mineral assemblages (high zircon, tourmaline, rutile) are more mature than in most of the possible source rocks. The most abundant minerals in the clay-sized fraction are dioctahedral vermiculite, kaolinite, illite, montmorillonite, and gibbsite. The first four minerals are common in deposits of late Wisconsin and Holocene age. The gibbsite may be detrital, coming from weathered rocks of Tertiary age. The soil profile in the dune sand is weakly to moderately developed. At or near the base of the Parsonsburg Sand are peaty beds that range in age from about 30,000 to about 13,000 radiocarbon years B.P. Microfloral assemblages in the peaty beds suggest that the dunes on the uplands formed in a spruce parkland during the late Wisconsin glacial maximum. The river dunes may also be of late Wisconsin age, but could be Holocene.

Denny, Charles Storrow; Owens, James Patrick

1979-01-01

204

Is Titan's Dune Orientation Controlled by Tropical Methane Storms?  

NASA Astrophysics Data System (ADS)

Titan’s equatorial regions are covered by eastward oriented linear dunes. This direction is opposite to mean surface winds simulated by Global Climate Models (GCMs) at these latitudes, oriented westward as trade winds on Earth [1, 2].Here, we propose that Titan’s dune orientation is actually determined by equinoctial tropical methane storms producing a coupling with superrotation and dune formation. Using meso-scale simulations of convective methane clouds [3, 4] with a GCM wind profile featuring the superrotation [5, 6], we show that Titan’s storms should produce fast eastward gust fronts above the surface. Such gusts dominate the aeolian transport. Using GCM wind roses and analogies with terrestrial dune fields [7], we show that Titan's dune growth occurs eastward under these conditions. Finally, this scenario combining global circulation winds and methane storms can explain other major features of Titan's dunes (i.e. divergence from the equator, size and spacing).References:[1] Lorenz et al.: The Sand Seas of Titan: Cassini RADAR Observations of Longitudinal Dunes, Science (2006)[2] Lorenz & Radebaugh: Global pattern of Titan’s dunes: Radar survey from the Cassini prime mission, Geophysical Research Letter (2009)[3] Barth & Rafkin.: TRAMS: A new dynamic cloud model for Titan’s methane clouds, Geophysical Research Letter (2007)[4] Barth & Rafkin.: Convective cloud heights as a diagnostic for methane environment on Titan, Icarus (2010)[5] Charnay & Lebonnois: Two boundary layers in Titan's lower troposphere inferred from a climate model, Nature Geoscience (2012)[6] Lebonnois et al.: Titan global climate model: A new 3-dimensional version of the IPSL Titan GCM, Icarus (2012)[7] Courrech du Pont, Narteau & Gao: Two modes for dune orientation, Geology (2014)

Charnay, Benjamin; Barth, Erika; Rafkin, Scot; Narteau, Clément; Lebonnois, Sébastien; Rodriguez, Sébastien; Courrech du Pont, Sylvain; Lucas, Antoine

2014-11-01

205

Titan's dunes and interdunes: new insights from Cassini Radar observations  

NASA Astrophysics Data System (ADS)

Since 2004, the Cassini Titan RADAR Mapper instrument, a multimode microwave multiple-beam sensor has observed the surface of Titan at 13.78 GHz. This instrument can operate as a high-resolution synthetic- aperture radar (SAR) imager, profiling altimeter, scatterometer, and radiometer, the latter able to observe simultaneously with, or separately from, the active measurements. The comparison of the data collected in these different modes of operation addresses a number of compositional and geological questions. In particular, radiometry observations near closest approach provide a powerful complement to SAR reflectivity measurements, despite the difference in the resolution. Among the 23 flybys of the Cassini prime mission for which SAR measurements were performed, 14 provided observations of Titan's linear dunes. They revealed that the fields of dunes cover a large portion of Titan's surface, mainly in low-latitudes, within ± 30°. They are radar-dark and exhibit a very high emissivity (with brightness temperatures from 3 to 5 K above that of their surroundings), consistent with a smooth surface and a low dielectric constant. Yet, many questions remain relative to their composition and geometry. We will present the results of our investigation of the correlation between the radar backscatter and the brightness temperature of the dune fields that suggests that interdunes are flat and with a higher dielectric constant than the dunes. This interpretation is supported by data from scatterometry and altimetry. It also accounts for the fact that the look direction seems to have no significant importance in the identification of the dunes. Also, both the emissivity and the reflectivity of the dune fields depend on the incidence (or emission) angle and the look direction. A few dunes were observed with a variety of geometries, especially the ones at the overlap of several swaths. The backscatter properties of these dunes as a function of the look geometry are examined to provide an estimate of the dunes slopes.

Le Gall, A. A.; Janssen, M. A.; Lorenz, R. D.; Wye, L.; Callahan, P. S.; Hayes, A. G.; Paganelli, F.; Zebker, H. A.

2008-12-01

206

Slow Progress in Dune (Left Rear Wheel)  

NASA Technical Reports Server (NTRS)

The left rear wheel of NASA's Mars Exploration Rover Opportunity makes slow but steady progress through soft dune material in this movie clip of frames taken by the rover's rear hazard identification camera over a period of several days. The sequence starts on Opportunity's 460th martian day, or sol (May 10, 2005) and ends 11 days later. In eight drives during that period, Opportunity advanced a total of 26 centimeters (10 inches) while spinning its wheels enough to have driven 46 meters (151 feet) if there were no slippage. The motion appears to speed up near the end of the clip, but that is an artifact of individual frames being taken less frequently.

2005-01-01

207

Slow Progress in Dune (Left Front Wheel)  

NASA Technical Reports Server (NTRS)

The left front wheel of NASA's Mars Exploration Rover Opportunity makes slow but steady progress through soft dune material in this movie clip of frames taken by the rover's front hazard identification camera over a period of several days. The sequence starts on Opportunity's 460th martian day, or sol (May 10, 2005) and ends 11 days later. In eight drives during that period, Opportunity advanced a total of 26 centimeters (10 inches) while spinning its wheels enough to have driven 46 meters (151 feet) if there were no slippage. The motion appears to speed up near the end of the clip, but that is an artifact of individual frames being taken less frequently.

2005-01-01

208

Great Sand Dunes National Monument and Preserve  

NSDL National Science Digital Library

This National Park Service website describes the natural resources of this park such as plants, mammals and birds (with species lists); endemic or rare species; geology; hydrology; and wind (eolian) systems. These natural resources include a high mountain valley holding the tallest dunes in North America and flanked by some of the highest peaks in the Rocky Mountains; unique wind-powered geologic systems; insects physically adapted to life in the sand and found nowhere else; alpine lakes and tundra; disappearing ponds; and interdunal wetlands. There is information on hiking and camping in the park and planning a visit; cultural history of the park area including that of ancient Americans; and a photo gallery.

209

136 I The Johns Hopkins and the International Federation of Red Cross and Red Crescent Societies Reproductive  

E-print Network

Reproductive healthcare 4 Health Centre - Treguine refugee camp, Chad Daniel Cima/International Federation of Red Cross and Red Crescent Societies #12;Public health guide for emergencies I 137 Reproductive healthcare 4 Reproductive health care Description This chapter provides guidance on key topics

Scharfstein, Daniel

210

Interdisciplinary research produces results in understanding planetary dunes  

NASA Astrophysics Data System (ADS)

Third International Planetary Dunes Workshop: Remote Sensing and Image Analysis of Planetary Dunes; Flagstaff, Arizona, 12-16 June 2012 This workshop, the third in a biennial series, was convened as a means of bringing together terrestrial and planetary researchers from diverse backgrounds with the goal of fostering collaborative interdisciplinary research. The small-group setting facilitated intensive discussions of many problems associated with aeolian processes on Earth, Mars, Venus, Titan, Triton, and Pluto. The workshop produced a list of key scientifc questions about planetary dune felds.

Titus, Timothy N.; Hayward, Rosalyn K.; Dinwiddie, Cynthia L.

2012-09-01

211

Coherent structures in flow over two-dimensional dunes  

NASA Astrophysics Data System (ADS)

The instantaneous turbulent flow fields over a smooth bed and a bed containing large-scale roughness elements are characterized by the presence of elongated low and high streamwise momentum regions or streaks. If the bed contains large-scale roughness elements (e.g., dunes), the size of the streaks increases and is of the order of the size of these elements and the flow depth. The present large eddy simulation (LES) study focuses on the case of developing flow within wide channels containing at the bottom a long array of spanwise-oriented sinusoidal 2-D dunes (2a/h = 0.1, ?/h = 1, ? is the wavelength, 2a is the dune height, and h is the mean flow depth) and an array of 2-D asymmetric dunes (2a/h = 0.25, ?/h = 3.75) of closer shape to the ones observed in natural streams. For the case of an incoming steady flow, the instantaneous flow fields, in the region where the flow transitions toward a fully developed turbulent flow regime, contain arrays of highly organized hairpin vortices, whose dimensions are larger than the dune height. The LES shows that for relatively shallow channels (e.g., channels with 2a/h = 0.25), the large-scale hairpins and the streaks penetrate regularly up to the free surface, thus affecting mass transport and mixing over the whole water column. This paper explained the mechanism for the formation of these arrays of hairpin vortices and discussed the changes between a case with asymmetric dunes that are characterized by a large value of ?/2a (= 15) and a long upslope face and a case with symmetric dunes for which ?/2a = 10, the upslope face is relatively short, and the rate of change of the bed curvature around the dune's crest is relatively small. The study discusses the main mechanisms through which large-scale hairpin form and how these mechanisms change between two dune geometries (sinusoidal versus asymmetric dunes). This study also shows that hairpin eddies play the primary role in the formation of the streaks over the region containing dunes and provides an estimation of the average dimensions of these streaks. The presence of resolved turbulence in the incoming flow reduces the streamwise distance needed for the streaks to develop over the region containing dunes, but does not qualitatively affect the transition process toward the fully developed flow regime nor the spacing of the streaks in the fully developed flow region.

Chang, Kyungsik; Constantinescu, George

2013-05-01

212

Tissue factor initiates glomerular fibrin deposition and promotes major histocompatibility complex class II expression in crescentic glomerulonephritis.  

PubMed Central

Increased glomerular tissue factor (TF) expression is associated with glomerular fibrin deposition and renal failure in human and experimental crescentic glomerulonephritis (GN). However, the in vivo functional contribution of TF to the development of glomerular fibrin deposition, crescent formation, and renal failure in GN has not been established. The contribution of TF to fibrin deposition and renal injury was studied in a rabbit model of crescentic GN in which glomerular macrophage infiltration, augmented TF expression, and fibrin deposition are prominent. Administration of anti-TF antibody inhibited glomerular TF activity in nephritic glomeruli by 96%, without affecting macrophage accumulation or systemic indices of coagulation. Anti-TF antibody significantly reduced glomerular fibrin deposition (fibrin scores, 0.43 +/- 0.10 (treated) and 1.40 +/- 0.19 (control); P < 0.0005), crescent formation (0.33 +/- 0.05 (treated) and 1.0 +/- 0.06 (control); P < 0.0005), and development of renal failure (serum creatinine, 168 +/- 22 mumol/l (treated) and 267 +/- 35 mumol/l (control); P < 0.04). This was associated with significant reduction in proteinuria (1189 +/- 277 mg/24 hours (treated) and 2060 +/- 336 mg/24 hours (control); P < 0.03) and expression of MHC class II antigen in glomeruli (1.25 +/- 0.41 (treated) and 2.83 +/- 0.53 (control); P < 0.03) and in tubules and interstitial areas. These data demonstrate that TF is the major in vivo initiator of fibrin deposition in crescentic GN. The reduction in proteinuria and glomerular major histocompatibility class II antigen expression by TF inhibition suggests that TF may also activate other mediators that contribute to glomerular injury. Images Figure 1 PMID:9060825

Erlich, J. H.; Holdsworth, S. R.; Tipping, P. G.

1997-01-01

213

Geomorphic history of low-perched, transgressive dune complexes along the southeastern shore of Lake Michigan  

Microsoft Academic Search

A general geomorphic history of low-perched coastal dunes along southeastern Lake Michigan is developed by combining new chronological data from P.J. Hoffmaster and Warren Dunes State Parks (SP) with published data from Van Buren SP, Silver Lake SP and dunes near Holland, Michigan. Fragmentary evidence of dunes older than 6ka has been almost obliterated by active dune growth since the

Edward C. Hansen; Timothy G. Fisher; Alan F. Arbogast; Mark D. Bateman

2010-01-01

214

Spatiotemporal model for the progression of transgressive dunes  

E-print Network

from the blowout walls is being deposited). The dunefield margins are often formed by ridges of sand;Transgressive dunes can be formed after plant destruction by for example fire [11], tsunami, intense tropical

Ashkenazy, Yossi "Yosef"

215

Ideal Microhabitats on Mars: The Astrobiological Potential of Polar Dunes  

NASA Astrophysics Data System (ADS)

Astrobiological potential of polar Dark Dunes: they may hold less oxidants, trap water-ice, mm layer of them shields UV radiation, allows light income for photosynthesis. Water uptake in nighttime, temperature in daytime is favorable for metabolism.

Gánti, T.; Pócs, T.; Bérczi, Sz.; Horváth, A.; Kereszturi, A.; Sik, A.; Szathmáry, E.

2009-03-01

216

Song of the Dunes as a Self-Synchronized Instrument  

NASA Astrophysics Data System (ADS)

Since Marco Polo it has been known that some sand dunes have the peculiar ability to emit a loud sound with a well-defined frequency, sometimes for several minutes. The origin of this sustained sound has remained mysterious, partly because of its rarity in nature. It has been recognized that the sound is not due to the air flow around the dunes but to the motion of an avalanche, and not to an acoustic excitation of the grains but to their relative motion. By comparing singing dunes around the world and two controlled experiments, in the laboratory and the field, we prove that the frequency of the sound is the frequency of the relative motion of the sand grains. Sound is produced because moving grains synchronize their motions. The laboratory experiment shows that the dune is not needed for sound emission. A velocity threshold for sound emission is found in both experiments, and an interpretation is proposed.

Douady, S.; Manning, A.; Hersen, P.; Elbelrhiti, H.; Protière, S.; Daerr, A.; Kabbachi, B.

2006-07-01

217

Song of the dunes as a self-synchronized instrument.  

PubMed

Since Marco Polo it has been known that some sand dunes have the peculiar ability to emit a loud sound with a well-defined frequency, sometimes for several minutes. The origin of this sustained sound has remained mysterious, partly because of its rarity in nature. It has been recognized that the sound is not due to the air flow around the dunes but to the motion of an avalanche, and not to an acoustic excitation of the grains but to their relative motion. By comparing singing dunes around the world and two controlled experiments, in the laboratory and the field, we prove that the frequency of the sound is the frequency of the relative motion of the sand grains. Sound is produced because moving grains synchronize their motions. The laboratory experiment shows that the dune is not needed for sound emission. A velocity threshold for sound emission is found in both experiments, and an interpretation is proposed. PMID:16907409

Douady, S; Manning, A; Hersen, P; Elbelrhiti, H; Protière, S; Daerr, A; Kabbachi, B

2006-07-01

218

Nematode community and trophic structure along a sand dune succession  

Microsoft Academic Search

Changes in below-ground nematode communities, in terms of abundance, diversity and trophic structure and the composition of the community in terms of sex bias and adult:juvenile ratio were related to edaphic factors from sites that represented a known sand dune succession. Nematode abundance increased along a 1-km transect from sandy beach (no vegetation cover, early successional stage) through active dune

John W. Wall; Keith R. Skene; Roy Neilson

2002-01-01

219

Soil pH and species diversity in coastal dunes  

Microsoft Academic Search

Soil pH was measured at two different spatial scales in coastal dunes on Norderney, North Sea, and in Mecklenburg-Vorpommern, Baltic Sea, Germany. Relationships between the variability in soil pH, species richness and species diversity are presented. Species richness and diversity were highest in grey dunes, where soil pH was at intermediate levels; both variables were lower in yellow and brown

M. Isermann

2005-01-01

220

Rip currents, mega-cusps, and eroding dunes  

USGS Publications Warehouse

Dune erosion is shown to occur at the embayment of beach mega-cusps O(200 m alongshore) that are associated with rip currents. The beach is the narrowest at the embayment of the mega-cusps allowing the swash of large storm waves coincident with high tides to reach the toe of the dune, to undercut the dune and to cause dune erosion. Field measurements of dune, beach, and rip current morphology are acquired along an 18 km shoreline in southern Monterey Bay, California. This section of the bay consists of a sandy shoreline backed by extensive dunes, rising to heights exceeding 40 m. There is a large increase in wave height going from small wave heights in the shadow of a headland, to the center of the bay where convergence of waves owing to refraction over the Monterey Bay submarine canyon results in larger wave heights. The large alongshore gradient in wave height results in a concomitant alongshore gradient in morphodynamic scale. The strongly refracted waves and narrow bay aperture result in near normal wave incidence, resulting in well-developed, persistent rip currents along the entire shoreline. The alongshore variations of the cuspate shoreline are found significantly correlated with the alongshore variations in rip spacing at 95% confidence. The alongshore variations of the volume of dune erosion are found significantly correlated with alongshore variations of the cuspate shoreline at 95% confidence. Therefore, it is concluded the mega-cusps are associated with rip currents and that the location of dune erosion is associated with the embayment of the mega-cusp.

Thornton, E.B.; MacMahan, J.; Sallenger, A.H., Jr.

2007-01-01

221

Habitat change in a perched dune system along Lake Superior  

USGS Publications Warehouse

Episodes of habitat change, driven by changes in levels of the Great Lakes, must be considered when assessing human effects upon coastal vegetation and rare species. Paleoecological studies, baseline inventories, and long-term monitoring programs within the Grand Sable Dunes, a perched-dune system along Lake Superior, provide a window on vegetation change at different spatial and temporal scales and also provide an illustrative case study.

Loope, Walter L.; McEachern, A. Kathryn

1998-01-01

222

The Dark UNiverse Explorer (DUNE): Proposal to ESA's Cosmic Vision  

E-print Network

The Dark UNiverse Explorer (DUNE) is a wide-field space imager whose primary goal is the study of dark energy and dark matter with unprecedented precision. For this purpose, DUNE is optimised for the measurement of weak gravitational lensing but will also provide complementary measurements of baryonic accoustic oscillations, cluster counts and the Integrated Sachs Wolfe effect. Immediate auxiliary goals concern the evolution of galaxies, to be studied with unequalled statistical power, the detailed structure of the Milky Way and nearby galaxies, and the demographics of Earth-mass planets. DUNE is an Medium-class mission which makes use of readily available components, heritage from other missions, and synergy with ground based facilities to minimise cost and risks. The payload consists of a 1.2m telescope with a combined visible/NIR field-of-view of 1 deg^2. DUNE will carry out an all-sky survey, ranging from 550 to 1600nm, in one visible and three NIR bands which will form a unique legacy for astronomy. DUNE will yield major advances in a broad range of fields in astrophysics including fundamental cosmology, galaxy evolution, and extrasolar planet search. DUNE was recently selected by ESA as one of the mission concepts to be studied in its Cosmic Vision programme.

Alexandre Refregier; the DUNE collaboration

2008-02-18

223

POSSIBLE ORIGIN OF UNEXPECTEDLY HIGH ALKALINITIES IN QUARTZ SANDS OF HIGH DUNES AT WARREN DUNES STATE PARK, MICHIGAN1  

Microsoft Academic Search

Unexpectedly high pH values (generally 7.9), encountered on loose dune sand and sandy soils on the Warren Dunes of southwest Michigan, were identified initially by the presence of certain lime-loving tree species (hackberry, hoptree, red cedar). Earlier workers (Kurz, 1923; Olson, 1958) had recognized this condition, though their published values do not exceed pH 7.G5, and had explained it as

JANE L. PORSYTH; ERNEST S. HAMILTON

224

Dark Dune Spots: possible biomarkers on Mars?  

PubMed

Dark Dune Spots (DDSs) are transitional geomorphologic formations in the frost-covered polar regions of Mars. Our analysis of the transformations and arrangements of subsequent stages of DDSs into time sequence revealed their: (i) hole-like characteristics, (ii) development and formation from the bottom of the frosted layer till the disapperance of the latter, (iii) repeated (seasonal and annual) appearance in a pattern of multiple DDSs on the surface, and (iv) probable origin. We focused our studies on a model in which DDSs were interpreted as objects triggered by biological activity involved in the frosting and melting processes. We discuss two competing interpretations of DDSs: development by defrosting alone, and by defrosting and melting enhanced by the activity of Martian Surface Organisms (MSOs). MSOs are hypothetical Martian photosynthetic surface organisms thought to absorb sunlight. As a result they warm up by late winter and melt the ice around them, whereby their growth and reproduction become possible. The ice cover above the liquid water lens harbouring the MSOs provides excellent heat and UV insulation, prevents fast evaporation, and sustains basic living conditions until the ice cover exists. When the frost cover disappears MSOs go to a dormant, desiccated state. We propose further studies to be carried out by orbiters and landers travelling to Mars and by analysis of partial analogues on earth. PMID:14604189

Gánti, Tibor; Horváth, András; Bérczi, Szaniszló; Gesztesi, Albert; Szathmáry, Eörs

2003-10-01

225

Broadband colored-crescent generation in a single {beta}-barium-borate crystal by intense femtosecond pulses  

SciTech Connect

A visible colored crescent with a bandwidth broader than 220 nm is observed experimentally by loosely focused femtosecond pulses in a bulk quadratic nonlinear crystal ({beta}-BBO crystal) at certain incident angles. Through the analysis based on a simple collinear phase-matching model, we suggest that the colored crescent might be the coexistence of spontaneous parametric down-conversions (SPDCs) in the infrared range and the corresponding efficient second-order harmonic generations (SHGs) that occur in a wide spectrum. We further provide a possible mechanism for the SHG process in which the phase-mismatching angles of the frequency doubling of SPDCs in {beta}-BBO crystal are assumed to be compensated by the strong diffraction effect during the self-focusing process of the generated intense SPDC signals.

Wang, L.; Fan, Y. X.; Zhu, H.; Yan, Z. D.; Zhu, S. N.; Wang, Z. L. [Department of Physics and National Laboratory of Solid State Microstructures, Nanjing University, 210093 Nanjing (China); Zeng, H. [State Key Laboratory of Precision Spectroscopy, East China Normal University, 200062 Shanghai (China); Wang, H.-T. [Department of Physics and National Laboratory of Solid State Microstructures, Nanjing University, 210093 Nanjing (China); School of Physics, Nankai University, 300071 Tianjin (China)

2011-12-15

226

Glomerular tissue factor expression in crescentic glomerulonephritis. Correlations between antigen, activity, and mRNA.  

PubMed Central

Correlations between glomerular expression of tissue factor (TF) activity and antigen and cellular localization of TF mRNA was studied in crescentic glomerulonephritis (GN) in rabbits. Glomerular TF activity increased 8.7-fold 24 hours after initiation of GN (234 +/- 49 mU/10(3) glomeruli; normal, 27 +/- 10 mU/10(3) glomeruli; P = 0.003) in association with a 2.1-fold increase in TF antigen (154 +/- 34 ng/10(3) glomeruli; normal, 72 +/- 10 ng/10(3) glomeruli; P = 0.055), early macrophage infiltration, and no significant increase in TF mRNA. At the peak glomerular macrophage infiltration (day 4), TF activity remained augmented (230 +/- 63 mU/10(3) glomeruli) and TF mRNA, colocalized within macrophages, was significantly increased compared with normal (267 +/- 42%; P = 0.001). TF antigen was not increased in glomeruli (114 +/- 17 ng/10(3) glomeruli), although significant urinary excretion of TF antigen was detectable (478 +/- 121 ng/24 hours; normal, < 1 ng/24 hours; P = 0.032). At this time, the M(r) of glomerular TF (49 to 61 kd) was increased compared with TF in normal glomeruli (49 to 58 kd) as a result of increased glycosylation. At day 7, TF activity and antigen within glomeruli had decreased, although urinary excretion of TF antigen and glomerular TF mRNA remained elevated. These studies suggest that early up-regulation of TF activity is largely a result of functional up-regulation of constitutive TF in intrinsic glomerular cells. In more advanced disease, infiltrating macrophages are the major site of TF synthesis. The increased M(r) of glomerular TF, as a result of synthesis of more highly glycosylated protein by macrophages and the shedding of TF into the urine, suggests that substantial turnover of glomerular TF occurs at this stage. Images Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 PMID:7495298

Tipping, P. G.; Erlich, J. H.; Apostolopoulos, J.; Mackman, N.; Loskutoff, D.; Holdsworth, S. R.

1995-01-01

227

Hydrologic Modeling of the White Sands Dune Field, New Mexico  

NASA Astrophysics Data System (ADS)

The shallow groundwater flow system of White Sands dune field, located within the Tularosa Basin of Southern New Mexico, likely stabilizes the base of the largest gypsum dunefield in the world. Water table geometry and elevation play a critical role in controlling dune thickness, spatial extent, and migration rates. The White Sands National Monument (WHSA) is concerned that lowering the water table may lead to increased scour and migration of the dune field, which could be unfavorable to the preservation of the flora and fauna that have adapted to survive there. In response to projected increases in groundwater pumping in the regional Tularosa Basin groundwater system, changes in surface water use, and the threat of climate change, the WHSA is interested in understanding how these changes on a regional scale may impact the shallow dune aquifer. We have collected hydrological, geochemical, and geophysical data in order to identify the sources of recharge that contribute to the shallow dune aquifer and to assess interactions between this water table aquifer and the basin-scale, regional system. Vertical head gradients, temperature, and water quality data strongly suggest that local precipitation is the primary source of recharge to the dune aquifer today. This suggests that the modern dune system is relatively isolated from the deeper regional system. However, geochemical and electrical resistivity data indicates that the deeper basin groundwater system does contribute to the shallow system and suggests that hydrologic conditions have changed on geologic time scales. We have constructed a preliminary cross-sectional hydrologic model to attempt to characterize the interaction of the shallow dune aquifer with the deeper basin groundwater. The model cross-section extends about 80 km across the Tularosa Basin in a NW-SE direction parallel to the primary flow path. We represented 6 km of Precambrian crystalline basement, Paleozoic sedimentary rocks as well as Pleistocene and Quaternary units. Preliminary results indicate a component of deep groundwater flows to a depth of 5 km and is discharged near Lake Lucero located west of the WHSA. Computed and observed salinity and groundwater residence times are the primary means of model calibration. The results will allow for an improved understanding of the interaction between the basin- and dune-scale groundwater flow systems.

Bourret, S. M.; Newton, B. T.; Person, M. A.

2013-12-01

228

Interplay between seasonal frost and aeolian processes on Matara crater dunes (Mars)  

NASA Astrophysics Data System (ADS)

Matara crater dune field exhibits a complex and fascinating geologic history. It first gained scientific attention when dune gullies (of alcove-channel-apron morphology, a few hundred meters to 3 km in length) were observed in MOC and HiRISE images to be actively evolving during the last Mars decade. These gullies are located on the slopes of both types of dunes found here: the field is predominantly composed of long-wavelength transverse dunes with slipfaces to the east, and small barchans dunes originating along the eastern boundary of the field clamber over these dunes, towards the north-west. Although these dunes have not been observed to migrate (yet), aeolian processes are clearly active as the dune brinks are quite crisp in appearance, ripples on the surfaces of these dunes have been observed to migrate, and ripples have formed within sediment recently remobilized by dune-gully activity. This study seeks to understand how sediment has been redistributed/mobilized through both aeolian processes and seasonal processes leading to gully formation/evolution, and possible influences these processes have on each other. The aim is to connect the field's present-day morphology with the field's formation history and thus identify and quantify relevant processes (and process-interactions) and environmental/atmospheric conditions. Beatiful large (3km long) dune gully on eastern margin of Matara crater dune field. It originates along the crest of a large transverse dune; also visible are the smaller barchans that march up and over the field.

Diniega, S.

2012-12-01

229

Sand transport on an estuarine submarine dune field  

NASA Astrophysics Data System (ADS)

By means of surveys carried out with a Phase Measuring Bathymetric System and current profiles obtained through an ADCP of the internal area of the Bahía Blanca estuary, a field of large dunes was analysed. There are two different and well-defined zones characterized by particular dune morphology and differing hydrodynamics. The reduction in the channel cross-section by a geological control leads to the increase in tidal current velocity, which together with the available sediment leads to the formation of Very Large Dunes ( H > 4 m and L > 100 m) with the typical morphology of a limited amount of sediment overlying a rigid substrate. The migration rate of these dunes, between 65 and 130 m year - 1 , decreases as the bedform height increases. Differing sediment transport rates across the channel result in a non-uniform migration rate, which is responsible for the formation of dunes with linear crests oblique to the tidal current direction. This fact indicates that determination of the sediment transport direction by using only large bedform orientation may be subject to a significant error.

Gómez, Eduardo A.; Cuadrado, Diana G.; Pierini, Jorge O.

2010-09-01

230

Near surface airflow modelling over dunes in Proctor Crater, Mars  

NASA Astrophysics Data System (ADS)

Multiple dune forms inside Martian craters is evident on much of the recent Hi-Rise imagery available. Typically, multiple length scales are present with progressively smaller bedform features superimposed on larger dunes. This has produced complex but regular topographical aeolian-driven patterns. Understanding the airflow conditions over and around these features will help in our understanding of the formational patterns and orientation of the aeolian bedforms relative to localised wind flow forcing. Here we use computational fluid dynamics modelling and present preliminary findings within Mars' Proctor Crater over a dune area measuring 4.5km x 5.0km running with a computational cell resolution of 5m x 5m. A range of wind speed and directions are investigated and results are compared to bedform orientation, length scale and migration of ripples evident from recent HiRise imagery. Results reveal a distinctive relationship between steered airflow and localised bedform orientation, mapping orthogonally onto the crestal ridges present. This work has important implications for evolutionary reconstruction of aeolian dunes within craters on Mars and helps lend further support to studies examining recent activity of Martian dune migration.

Jackson, Derek; Bourke, Mary; Smyth, Thomas

2014-05-01

231

Morphological characteristics and sand volumes of different coastal dune types in Essaouira Province, Atlantic Morocco  

NASA Astrophysics Data System (ADS)

Altogether three coastal dune fields, one located north and two south of the city of Essaouira, Atlantic Morocco, have been investigated to establish the distribution and overall sand volumes of various dune types. The purpose of the study was to characterize and classify the aeolian landforms of the coastal dune belt, to estimate their sand volumes and to assess the effectiveness of coastal dune stabilization measures. The northern dune field is 9 km long and lined by a wide artificial foredune complex fixed by vegetation, fences and branches forming a rectangular grid. Active and ephemeral aklé dunes border the inner backshore, while some intrusive dunes have crossed the foredune belt and are migrating farther inland. The total sand volume of the northern dune belt amounts 13,910,255 m3. The central coastal sector comprises a much smaller dune field located just south of the city. It is only 1.2 km long and, with the exception of intrusive dunes, shows all other dune types. The overall sand volume of the central dune field amounts to about 172,463 m3. The southern dune field is characterized by a narrower foredune belt and overall lower dunes that, in addition, become progressively smaller towards the south. In this sector, embryonic dunes (coppice, shadow dunes), tongue-like and tabular dunes, and sand sheets intrude from the beach, the profile of which has a stepped appearance controlled by irregular outcrops of old aeolianite and beach rock. The total volume of the southern dune field amounts 1,446,389 m3. For the whole study area, i.e. for all three dune fields combined, a sand volume of about 15,529,389 m3 has been estimated. The sand of the dune fields is derived from coastal erosion and especially the Tensift River, which enters the sea at Souira Qedima some 70 km north of Essaouira. After entering the sea, the sand is transported southwards by littoral drift driven by the mainly north-westerly swell climate and the Trade Winds blowing from the NNE. This sand feeds the beaches along the coast, from where it is blown obliquely onshore to generate the dune fields. The maximum sand input occurs in the north, from where it gradually decreases southwards, this being also reflected in the grain size and dune typologies. The study shows that dune stabilization measures have been reasonably effective along most of the coast, with the exception of a large area immediately north of Essaouira where the almost complete destruction of the plant cover has reactivated sand mobility—this may in the future threaten the city.

Flor-Blanco, Germán; Flor, Germán; Lharti, Saadia; Pando, Luis

2013-04-01

232

Equatorial Cross-Cutting Ripples on Titan - Regularly Warped Subsiding Methane Plains, not Eolian Dunes.  

NASA Astrophysics Data System (ADS)

Widely circulating opinion that titanian methane lowlands in a broad equatorial region are covered with eolian formations needs to be carefully checked. Of coarse, all three solid bodies with atmospheres in the inner solar system have dunes. Why do not have them on Titan? Most probably they do exist but discovered by radar up to now cross-cutting rippling features cannot be taken for them. For this there are several reasons. How it can be that prevailing "dune" strike coincides with prevailing wind direction? Normally (with some African exceptions) one sees real terrestrial dunes stretching across winds. And this is understandable from a point of view eolian dunes formation. This formation gives particular cross profile to dunes. Asymmetric profile - one slope is long and gentle and another one short and abrupt. But titanian "dunes" are mostly uniform and symmetric. And this characteristic is preserved for many hundreds of kilometers of very straight features. Then, the finest solid particles precipitation from the thick atmosphere of Titan should be distributed on the satellite surface more uniformly and cover dark lowlands and light icy highlands of the wide equatorial belt more or less evenly. But "dunes" are strictly associated with dark lowlands and tend to turn round light icy obstacles. Cindering smoggy particles to produce sands for making dunes is a pure imagination. Then, radar preferably sees one direction but nevertheless one or more crossing directions of rippling are distinguished (Fig.3, 4) They mean two wind directions at the same time or another wind direction at another time? If so, the earlier "dunes" should be more or less obliterated by the later ones. Nothing of the kind! Both crossing ripples directions are fresh. Then, eolian action is not seen at the higher latitudes (Fig. 5). There are no winds there? Probably it is not so. Only a liquid state of methane can help (but liquid should be disturbed by winds). Solid methane there is also probable. Very regular cross-cutting wavy forms hundred and thousand kilometers long have a spacing between ridges or grooves about 1-2 km (?) (PIA03555, PIA03566, PIA03567, PIA03568 ) or 10-20 km (PIA08454) -so called "cat scratches". The most long and wide ridge-groove system observed up to now (PIA08454 - a swath 6150 km long, 1120 km wide, almost a half length of the great planetary circle!) has the ridge-to-ridge spacing about 10-20 km; a width of ridges and grooves is nearly equal with variations to both sides; ridges are more bright, grooves are more dark; intersections of the ridge-groove systems creates chains of roundish features ("craters") of characteristic size (Fig. 3, 4). Observed wavy systems resemble dunes only at the first glance but actually are deformations of the ice-methane crust by very fine inertia-gravity waves aroused by the satellite movement in non-round elliptical keplerian orbit [3]. This movement with periodically changing accelerations arouse inertia-gravity forces and waves warping any celestial body notwithstanding its size, mass, density, chemical composition or physical state. In rotating bodies (but all bodies rotate!) these warping waves have a stationary character and 4 cross-cutting directions- ortho- and diagonal - producing uplifted (+), subsided (-) and neutral (0) tectonic blocks. Wavelengths are different but tied as harmonics. The fundamental wave1 produces ubiquitous tectonic dichotomy -two segments (2?R-structure), the first harmonics wave2 produces tectonic sectors (?R-structures) [1]. This structurization is adorned by individual for any body waves whose lengths are inversely proportional to their orbital frequencies: higher frequency - smaller waves and, vice versa, lower frequency - larger waves. These waves produce tectonic granules. There is a row of increasing granule sizes strictly tied to orbital frequencies: Mercury ?R/16, Venus ?R/6, Earth ?R/4, Mars ?R/2, asteroids ?R/1. In this row Titan with its orbital frequency around its central body Sat

Kochemasov, G. G.

2008-09-01

233

78 FR 11981 - Special Regulations; Areas of the National Park System, Sleeping Bear Dunes National Lakeshore...  

Federal Register 2010, 2011, 2012, 2013

...Areas of the National Park System, Sleeping Bear Dunes National Lakeshore, Bicycling...SUMMARY: This rule designates the Sleeping Bear Heritage Trail currently under construction within Sleeping Bear Dunes National Lakeshore as a...

2013-02-21

234

77 FR 62476 - Special Regulations; Areas of the National Park System, Sleeping Bear Dunes National Lakeshore...  

Federal Register 2010, 2011, 2012, 2013

...Areas of the National Park System, Sleeping Bear Dunes National Lakeshore, Bicycling...Park Service proposes to designate the Sleeping Bear Heritage Trail currently under construction within Sleeping Bear Dunes National Lakeshore as a...

2012-10-15

235

Defrosting Polar Dunes--'They Look Like Bushes!'  

NASA Technical Reports Server (NTRS)

'They look like bushes!' That's what almost everyone says when they see the dark features found in pictures taken of sand dunes in the polar regions as they are beginning to defrost after a long, cold winter. It is hard to escape the fact that, at first glance, these images acquired by the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) over both polar regions during the spring and summer seasons, do indeed resemble aerial photographs of sand dune fields on Earth--complete with vegetation growing on and around them! Of course, this is not what the features are, as we describe below and in related picture captions. Still, don't they look like vegetation to you? Shown here are two views of the same MGS MOC image. On the left is the full scene, on the right is an expanded view of a portion of the scene on the left. The bright, smooth surfaces that are dotted with occasional, nearly triangular dark spots are sand dunes covered by winter frost.

The MGS MOC has been used over the past several months (April-August 1999) to monitor dark spots as they form and evolve on polar dune surfaces. The dark spots typically appear first along the lower margins of a dune--similar to the position of bushes and tufts of grass that occur in and among some sand dunes on Earth.

Because the martian air pressure is very low--100 times lower than at Sea Level on Earth--ice on Mars does not melt and become liquid when it warms up. Instead, ice sublimes--that is, it changes directly from solid to gas, just as 'dry ice' does on Earth. As polar dunes emerge from the months-long winter night, and first become exposed to sunlight, the bright winter frost and snow begins to sublime. This process is not uniform everywhere on a dune, but begins in small spots and then over several months it spreads until the entire dune is spotted like a leopard.

The early stages of the defrosting process--as in the picture shown here--give the impression that something is 'growing' on the dunes. The sand underneath the frost is dark, just like basalt beach sand in Hawaii. Once it is exposed to sunlight, the dark sand probably absorbs sunlight and helps speed the defrosting of each sand dune.

This picture was taken by MGS MOC on July 21, 1999. The dunes are located in the south polar region and are expected to be completely defrosted by November or December 1999. North is approximately up, and sunlight illuminates the scene from the upper left. The 500 meter scale bar equals 547 yards; the 300 meter scale is also 328 yards.

Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.

1999-01-01

236

Orographic forcing of dune forming winds on Titan  

NASA Astrophysics Data System (ADS)

Cassini has observed hundreds of dune fields on Titan, nearly all of which lie in the tropics and suggest westerly (from west to east) winds dominate at the surface [1,2]. Most GCMs however have obtained easterly surface winds in the tropics, seemingly contradicting the wind direction suggested by the dunes. This has led to an active debate in the community about the origin of the dune forming winds on Titan and their direction and modality. This discussion is mostly driven by a study of Earth dunes seen as analogous to Titan [1,2,3]. One can find examples of dunes on Earth that fit several wind regimes. To date only one GCM, that of Tokano [4,5], has presented detailed analysis of its near surface winds and their dune forming capabilities. Despite the bulk of the wind being easterly, this GCM produces faster westerlies at equinox, thus transporting sand to the east. Our model, the Titan CAM [6], is unable to reproduce the fast westerlies, although it is possible we are not outputting frequently enough to catch them. Our GCM has been updated to include realistic topography released by the Cassini radar team. Preliminary results suggest our tropical wind regime now has net westerly winds in the tropics, albeit weak. References: [1], Lorenz, R. et al. 2006. Science, 312, 724-727. [2], Radebaugh, J. et al. 2008. Icarus, 194, 690-703. [3] Rubin, D. and Hesp, P. 2009. Nature Geoscience 2, 653-658. [4] Tokano, T. 2008. Icarus 194, 243-262. [5] Tokano, T. 2010. Aeolian Research 2, 113-127. [6] Friedson, J. et al. 2009. Planetary Space Science, 57, 1931-1949.

Larson, E. J.; Toon, O. B.; Friedson, A. J.

2013-12-01

237

A Probabilistic Tsunami Hazard Assessment Methodology and Its Application to Crescent City, CA  

NASA Astrophysics Data System (ADS)

A PTHA methodology, based in large part on Probabilistic Seismic Hazard Assessment methods (e.g., Cornell, 1968; SSHAC, 1997; Geist and Parsons, 2005), was previously applied to Seaside, OR (Gonzalez, et al., 2009). This initial version of the method has been updated to include: a revised method to estimate tidal uncertainty; an improved method for generating stochastic realizations to estimate slip distribution uncertainty (Mai and Beroza, 2002; Blair, et al., 2011); additional near-field sources in the Cascadia Subduction Zone, based on the work of Goldfinger, et al. (2012); far-field sources in Japan, based on information updated since the 3 March 2011 Tohoku tsunami (Japan Earthquake Research Committee, 2011). The GeoClaw tsunami model (Berger, et. al, 2011) is used to simulate generation, propagation and inundation. We will discuss this revised PTHA methodology and the results of its application to Crescent City, CA. Berger, M.J., D. L. George, R. J. LeVeque, and K. T. Mandli, The GeoClaw software for depth-averaged flows with adaptive refinement, Adv. Water Res. 34 (2011), pp. 1195-1206. Blair, J.L., McCrory, P.A., Oppenheimer, D.H., and Waldhauser, F. (2011): A Geo-referenced 3D model of the Juan de Fuca Slab and associated seismicity: U.S. Geological Survey Data Series 633, v.1.0, available at http://pubs.usgs.gov/ds/633/. Cornell, C. A. (1968): Engineering seismic risk analysis, Bull. Seismol. Soc. Am., 58, 1583-1606. Geist, E. L., and T. Parsons (2005): Probabilistic Analysis of Tsunami Hazards, Nat. Hazards, 37 (3), 277-314. Goldfinger, C., Nelson, C.H., Morey, A.E., Johnson, J.E., Patton, J.R., Karabanov, E., Gutiérrez-Pastor, J., Eriksson, A.T., Gràcia, E., Dunhill, G., Enkin, R.J., Dallimore, A., and Vallier, T. (2012): Turbidite event history—Methods and implications for Holocene paleoseismicity of the Cascadia subduction zone: U.S. Geological Survey Professional Paper 1661-F, 170 p. (Available at http://pubs.usgs.gov/pp/pp1661f/). González, F.I., E.L. Geist, B. Jaffe, U. Kânoglu, H. Mofjeld, C.E. Synolakis, V.V Titov, D. Arcas, D. Bellomo, D. Carlton, T. Horning, J. Johnson, J. Newman, T. Parsons, R. Peters, C. Peterson, G .Priest, A. Venturato, J. Weber, F. Wong, and A. Yalciner (2009): Probabilistic Tsunami Hazard Assessment at Seaside, Oregon, for Near- and Far-Field Seismic Sources, J. Geophys. Res., 114, C11023, doi:10.1029/2008JC005132. Japan Earthquake Research Committee, (2011): http://www.jishin.go.jp/main/p_hyoka02.htm Mai, P. M., and G. C. Beroza (2002): A spatial random field model to characterize complexity in earthquake slip, J. Geophys. Res., 107(B11), 2308, doi:10.1029/2001JB000588. SSHAC (Senior Seismic Hazard Analysis Committee) (1997): Recommendations for Probabilistic Seismic Hazard Analysis: Guidance on Uncertainty and Use of Experts, Main Report Rep. NUREG/CR-6372 UCRL-ID-122160 Vol. 1, 256 pp, U.S. Nuclear Regulatory Commission.

Gonzalez, F. I.; Leveque, R. J.; Waagan, K.; Adams, L.; Lin, G.

2012-12-01

238

Martian linear dunes : observation and modelling from the LMD GCM data base  

NASA Astrophysics Data System (ADS)

Dunes are common on Earth and Mars and have similar geometries on both planets. Martian dunes are larger than terrestrial one and are shaped by winds less efficient than terrestrial winds. Martian dunes move thus much more slowly than terrestrial dunes. Their characteristic time could be similar to the characteristic time of climate change on Mars. Their geometry could thus reflect past climate conditions. Linear dunes are a family of elongated dunes shaped by at least 2 winds that blow at an obtuse angle alternatively along the year. Contrary to simple dunes as barkhanes, it is therefore difficult to invert the shape of these dunes in term of wind direction and intensity. It is thus difficult to demonstrate if their geometry is coherent or not with the current wind regimes. We mapped 10 dune fields located inside impact craters of the southern hemisphere of Mars. Five fields are composed of barkhanes and 5 by linear dunes. For each dune field location, we extracted the annual wind velocity at 20m above the surface at a temporal resolution of 1 hour every 30 martian days from the Mars Climate Database of the LMD (www-mars.lmd.jussieu.fr/). The annual wind rose was calculated for each dune field. The sand flux along the year was also computed assuming a classical law of transport with threshold. Assuming that the avalanche face of barkhanes is perpendicular to the sand flux direction, we predicted the orientation of the avalanche face for each barkhane fields. These results are coherent with the observations. Assuming that linear dunes are aligned along the average sand flux direction, we predicted the orientation of the linear dunes and compared them to the observations. In 4 cases, the predicted dune orientation is consistent with observations. In one case, there is a strong discrepancy between the predicted and observed orientation that could indicate that this linear dune field is fossil.

allemand, pascal; Quiquerez, Amélie; Quantin, Cathy

2014-05-01

239

Observations Regarding Small Eolian Dunes and Large Ripples on Mars  

NASA Technical Reports Server (NTRS)

Eolian bedforms occur at the interface between a planetary surface and its atmosphere; they present a proxy record of the influence of climate, expressed in sediment transport, over that surface. High resolution images (1.5 - 12 m/pixel) from the Mars Global Surveyor (MGS) Mars Orbiter Camera provide glimpses of the most recent events shaping the martian landscape. Thousands of images exhibit small transverse dunes or large eolian ripples that have crest-to-crest spacings of 10 to 60 m, heights of a few to 10 m. Bedforms of the size and patterns seen in the Mars photographs are rarely described among Earth's eolian landforms; in terms of size and morphology, most of these fall between traditional definitions of "ripples" and "dunes". Dunes are composed chiefly of materials transported by saltation, ripples are smaller forms moved along by the impact of saltating grains (traction). The largest reported eolian ripples on Earth (granule ripples, megaripples) are typically smaller than the bedforms observed on Mars; likewise, most dunes are typically larger. The small dunes and large ripples on Mars come in a variety of relative albedos, despite an early MGS impression that they are all of high albedo. Some ripples occur on the surfaces of sand dunes; these are most likely true granule ripples. However, most of these bedforms occur in troughs, pits, craters, and on deflated plains. Despite impressions early in the MGS mission, they do not occur everywhere (e.g., they are rare on the northern plains) but they do occur at a range of elevations from the highest volcanoes to the deepest basins. Where they occur on a hard substrate among larger sand dunes, the big dunes have over-ridden the smaller bedforms, indicating that the smaller features are older and perhaps indurated or very coarse-grained. At other locales, the small bedforms have been mantled by material settled from suspension, in other cases they are being exhumed and may be lithified. Still other examples are peppered with small impact craters, implying considerable age. These bedforms present a complicated record of the geologically-recent past, one that has involved changes in climate, sediment transport capabilities, and sediment sources and sinks over time.

Edgett, Kenneth S.

2001-01-01

240

Winter variability of aeolian sediment transport threshold on a cold-climate dune  

NASA Astrophysics Data System (ADS)

Changes in surface conditions on cold-climate aeolian dunes are pronounced; during winter dunes are wet, snow covered, and/or frozen for extended periods of time. It is unknown how the critical wind speed for sediment transport (“threshold”) varies and how threshold may influence sediment transport predictions. Although the impact of surface conditions on threshold has been examined in synthetic experiments (wind tunnels), complicated feedbacks between threshold, sand transport, and surface conditions that occur in natural environments suggest that a ground-based empirical approach may provide enhanced insight. In this study we investigate threshold variability for 73 days during fall-winter-spring surface conditions from 18 November 2008 to 30 May 2009 in the Bigstick Sand Hills of Saskatchewan, Canada. Simultaneous measurements of threshold and atmospheric variables (air temperature, relative humidity, solar radiation, wind speed and direction) were used to examine the extent to which surface erodibility was regulated by meteorology. Time-lapse images of the surface from a co-located camera were used for quality control and interpreting changes in the surface affecting threshold. Results reveal that threshold varied throughout the deployment (25-75% quartiles: 6.92-8.28 m s- 1; mean: 7.79 m s- 1). Threshold variability was especially evident at two scales: (i) event timescale and (ii) seasonal timescale. Event-scale variability peaked during mid-winter; in one event the threshold varied by 6 m s- 1 in 2 h with freezing and re-freezing of the surface and relatively constant atmospheric conditions. The causes of event-scale variability are complex though qualitatively related to changes of wind direction, antecedent meteorological conditions, and vertical variations of grain-scale bonding agents such as pore ice and moisture. Seasonal-scale changes manifested as an increase in threshold during fall, peaking in mid-winter, and decreasing in spring. Increased threshold in mid-winter was linked to lower insolation and air temperature, suggesting low erodibility due to the presence of pore ice. Correlation coefficients of threshold versus atmospheric variables yielded relatively weak correlations (air temperature: r = - 0.322; relative humidity: r = 0.388; solar radiation: r = - 0.309) that also varied according to wind direction, suggesting that the link between atmospheric conditions and surface erodibility on cold-climate dunes is complex. This contrasts with results from field-based studies in warmer climates and controlled wind tunnel experiments, which show a more direct link between atmospheric variables (temperature and humidity) and surface erodibility. Nevertheless, our results do show a seasonal pattern of threshold that could be important for modeling cold-climate aeolian sediment transport.

Barchyn, Thomas E.; Hugenholtz, Chris H.

2012-12-01

241

An experimental study of turbulent flow over a low-angle dune  

Microsoft Academic Search

Many large, sand bed alluvial channels are dominated by dunes that possess low-angle lee sides, often <10°, which play a critical role in the transportation of sediment and generation of significant bed form roughness. Despite the fact that these low-angle dunes are very common in such channels many current models of dune flow dynamics are based on bed forms with

Jim Best; Ray Kostaschuk

2002-01-01

242

Elucidating aeolian dune history from lacustrine sand records in the Lake Michigan Coastal Zone, USA  

Microsoft Academic Search

Aeolian sand in two small lakes within a Lake Michigan coastal-dune complex southwest of Holland, Michigan, provides a more detailed higher-resolution history of dune activity, during the later half of the Holocene, than do combined palaeosol and OSL ages from the dunes themselves. The sand signal from four cores within these lakes consists of visible sand laminae and invisible sand

Emily A. Timmons; Timothy G. Fisher; Edward C. Hansen; Elliott Eisaman; Trevor Daly; Michaele Kashgarian

2007-01-01

243

Reconstructing the geomorphic evolution of large coastal dunes along the southeastern shore of Lake Michigan  

Microsoft Academic Search

Coastal dunes are common along the eastern shore of Lake Michigan, with the most common being large (>30 m high), parabolic dunes that mantle lake terraces south of Manistee, MI. Although these dunes are an important resource in Michigan, and thus intensely managed by various state agencies, their geomorphic history is poorly understood. This study examines four sites near Holland,

Alan F Arbogast; Edward C Hansen; Martin D Van Oort

2002-01-01

244

DIGITAL PHOTOGRAMMETRIC CHANGE ANALYSIS AS APPLIED TO ACTIVE COASTAL DUNES IN MICHIGAN  

E-print Network

DIGITAL PHOTOGRAMMETRIC CHANGE ANALYSIS AS APPLIED TO ACTIVE COASTAL DUNES IN MICHIGAN Daniel G COASTAL DUNES IN MICHIGAN Abstract A pilot study was conducted to investigate the applicability of digital; Arbogast, 1996), and coastal dunes being a basis for development and recreation (Santer, 1993). In general

Brown, Daniel G.

245

The Song of Dunes as a Wave-Particle Mode Locking B. Andreotti*  

E-print Network

measurements in the Atlantic Sahara (Morocco), a coastal desert where all the dunes--more than 10 000 barchansThe Song of Dunes as a Wave-Particle Mode Locking B. Andreotti* Matie`re et Syste`mes Complexes, University Paris 7, FR CNRS 2438, (Received 27 April 2004; published 1 December 2004) Singing dunes, which

246

Seed dispersal by vervet monkeys in rehabilitating coastal dune forests at Richards Bay  

E-print Network

Seed dispersal by vervet monkeys in rehabilitating coastal dune forests at Richards Bay S.H. Foard and function of rehabilitating coastal dune forest communities. Vervet monkeys feed on a great variety of coastal sand dunes north of Richards Bay, KwaZululNatal is initiated through spreading topsoil, collected

Pretoria, University of

247

CHENOPODIUM LITTOREUM (CHENOPODIACEAE), A NEW GOOSEFOOT FROM DUNES OF SOUTH-CENTRAL COASTAL CALIFORNIA  

E-print Network

CHENOPODIUM LITTOREUM (CHENOPODIACEAE), A NEW GOOSEFOOT FROM DUNES OF SOUTH-CENTRAL COASTAL only from coastal dunes of San Luis Obispo Co. and Santa Barbara Co. of the Central Coast of California: Chenopodium, C. carnosulum var. patagonicum, C. patagonicum, C. philippianum, Chenopodiaceae, dune flora

Simpson, Michael G.

248

J. Zool., Lond. (1996) 238, 703 712 Millipede communities in rehabilitating coastal dune forests  

E-print Network

J. Zool., Lond. (1996) 238, 703 712 Millipede communities in rehabilitating coastal dune forests figure in the text) The rehabilitation. aftcr mining. or coastal sand dunes north or Richards Bay hyI' a known-aged series of stands representative or coastal dune ["orest suceesslun. A survey of the millipede

Pretoria, University of

249

Problems of scale in the modeling and interpretation of coastal dunes  

Microsoft Academic Search

Coastal dune systems are studied at time scales from seconds to millennia, and space scales from millimeters to kilometers. Present approaches to the study of coastal dunes make it difficult to integrate models and interpretations of these systems over these scale ranges and arrive at reasonable conclusions. It is argued that identification of key controls on dune development, measurement of

Douglas J. Sherman

1995-01-01

250

Decline of Birds in a Human Modified Coastal Dune Forest Landscape in South Africa  

E-print Network

Decline of Birds in a Human Modified Coastal Dune Forest Landscape in South Africa Morgan J modified coastal dune forest landscape in northern KwaZulu-Natal, South Africa. However, occurrence does) Decline of Birds in a Human Modified Coastal Dune Forest Landscape in South Africa. PLoS ONE 6(1): e16176

Pretoria, University of

251

Coherent Flow Structures and Suspension Events over Low-angle Dunes: Fraser River,  

E-print Network

Coherent Flow Structures and Suspension Events over Low-angle Dunes: Fraser River, Canada by Ryan) Title of Thesis: Coherent Flow Structures and Suspension Events over Low-angle Dunes: Fraser River of the Fraser Estuary, Canada. Dune field bathymetry was mapped using a multibeam echo sounder while an acoustic

Venditti, Jeremy G.

252

Geohazard assessment of sand dunes between Jeddah and Al-Lith, western Saudi Arabia  

Microsoft Academic Search

Serious hazards have taken place in urban areas and road construction in Saudi Arabia because of the presence of accumulations of drifting sand dunes. Several researches, which carried out investigative work to solve this problem, were reviewed. Three locations of dune fields along the area between Jeddah and Al-Lith were investigated. The dune forms was identified. Detailed field investigations showed

Abbas Aifan Al-Harthi

2002-01-01

253

Orbital observations of contemporary dune activity in Endeavor crater, Meridiani Planum, Mars  

E-print Network

Orbital observations of contemporary dune activity in Endeavor crater, Meridiani Planum, Mars] Despite a dynamic atmosphere and plentiful sediment supply, orbital detection of dune movement on Mars has., 2007]. The Mars Global Surveyor's (MGS) Mars Orbiter Camera (MOC) experiment was used to look for dune

Tennessee, University of

254

Influence des tempetes sur la mobilitedes dunes tidales dans le detroit du Pas-de-Calais  

Microsoft Academic Search

Influence of storms on tidal dune mobility in the Strait of Dover. The present paper deals with dune dynamics in a zone of the Strait of Dover located in the sea lane running into the North Sea. The dunes, widespread in this 35-m depth area, are mobile sedimentary structures (up to 40 m·yr 1) that culminate at a maximum of

Sophie LE BOT; Alain TRENTESAUX; Thierry GARLAN; Serge BERNE

255

The fluid dynamics of river dunes: A review and some future research directions  

E-print Network

The fluid dynamics of river dunes: A review and some future research directions Jim Best Earth, and deposition within many rivers. Progress in understanding the fluid dynamics associated with alluvial dunes morphology. Citation: Best, J. (2005), The fluid dynamics of river dunes: A review and some future research

Venditti, Jeremy G.

256

76 FR 57074 - Transfer of Administrative Jurisdiction at or Near Great Sand Dunes National Park  

Federal Register 2010, 2011, 2012, 2013

...Administrative Jurisdiction at or Near Great Sand Dunes National Park AGENCY: National Park...lands acquired for the benefit of Great Sand Dunes National Park, Baca National Wildlife...interests in land for the benefit of Great Sand Dunes National Park, Baca National...

2011-09-15

257

44 CFR 65.11 - Evaluation of sand dunes in mapping coastal flood hazard areas.  

Code of Federal Regulations, 2011 CFR

... 2011-10-01 false Evaluation of sand dunes in mapping coastal flood hazard areas...HAZARD AREAS § 65.11 Evaluation of sand dunes in mapping coastal flood hazard areas...vegetative cover, such as the placement of sand materials in a dune-like...

2011-10-01

258

44 CFR 65.11 - Evaluation of sand dunes in mapping coastal flood hazard areas.  

Code of Federal Regulations, 2010 CFR

... 2010-10-01 false Evaluation of sand dunes in mapping coastal flood hazard areas...HAZARD AREAS § 65.11 Evaluation of sand dunes in mapping coastal flood hazard areas...vegetative cover, such as the placement of sand materials in a dune-like...

2010-10-01

259

Uncertainty Assessment for Numerical Modeling of Dune and Backshore Evolution Under Sea-Level Rise Scenarios  

Microsoft Academic Search

The beach dunes play an essential role in the evolution of barrier island shapes and coastlines. The dunes protect the beaches and beach ecology by absorbing energy from the storms and provide sediment to the beaches or backshores when erosion occurs. While a number of models have been developed to simulate the evolution of dunes and backshores, few of the

H. Dai; M. Ye; A. W. Niedoroda; S. Kish; J. F. Donoghue; B. Saha

2010-01-01

260

Responses of dune mosses to experimental burial by sand under natural and greenhouse conditions  

Microsoft Academic Search

Sand movement is a predominant feature of mobile coastal and lake-shoreline sand dunes. Plants growing in these environments are able to withstand and survive periods of burial by sand. Although mosses are important dune stabilizers in temperate dunes, there are few studies focused on their response to burial by sand. In this study we examined the effects of burial by

M. Luisa Martínez; M. A. Maun

1999-01-01

261

Sources and sinks of nitrogen and phosphorus to a deep, oligotrophic lake, Lake Crescent, Olympic National Park, Washington  

USGS Publications Warehouse

Lake Crescent, in Olympic National Park in the northwest corner of Washington State is a deep-water lake renowned for its pristine water quality and oligotrophic nature. To examine the major sources and sinks of nutrients (as total nitrogen, total phosphorus, and dissolved nitrate), a study was conducted in the Lake Crescent watershed. The study involved measuring five major inflow streams, the Lyre River as the major outflow, recording weather and climatic data, coring lake bed sediment, and analyzing nutrient chemistry in several relevant media over 14 months. Water samples for total nitrogen, total phosphorous, and dissolved nitrate from the five inflow streams, the outlet Lyre River, and two stations in the lake were collected monthly from May 2006 through May 2007. Periodic samples of shallow water from temporary sampling wells were collected at numerous locations around the lake. Concentrations of nutrients detected in Lake Crescent and tributaries were then applied to the water budget estimates to arrive at monthly and annual loads from various environmental components within the watershed. Other sources, such as leaf litter, pollen, or automobile exhaust were estimated from annual values obtained from various literature sources. This information then was used to construct a nutrient budget for total nitrogen and total phosphorus. The nitrogen budget generally highlights vehicle traffic-diesel trucks in particular-along U.S. Highway 101 as a potential major anthropogenic source of nitrogen compounds in the lake. In contrast, contribution of nitrogen compounds from onsite septic systems appears to be relatively minor related to the other sources identified.

Moran, P.W.; Cox, S.E.; Embrey, S.S.; Huffman, R.L.; Olsen, T.D.; Fradkin, S.C.

2012-01-01

262

Fly over of Mars Mesa, Tounge, Dunes, Sasquatch Crater  

NSDL National Science Digital Library

This site from NASA's Scientific Visualization Studio features fly overs of Mesa, Tounge, Dunes, and Sasquatch Crater. Data for topography is based on the Mars Orbiting Laser Altimeter (MOLA) with Viking data used for color. Vertical exaggeration is about 300 times.

Studio, Nasa/goddard S.; Nasa

263

Luminescence studies of dunes from North-Eastern Tasmania  

Microsoft Academic Search

Northern Tasmania has a geographically extensive cover of Quaternary aeolian features and although the morphology and stratigraphy of many of these have been studied it is difficult to assign a reliable chronology because of the lack of material suitable for radiocarbon dating. The dunes are primarily composed of quartz and hence are ideally suited for the application of luminescence dating.

G. A. T. Duller; P. Augustinus

1997-01-01

264

Parabolic halite dunes on the Salar de Uyuni, Bolivia  

Microsoft Academic Search

Palaeoenvironmental interpretation in desert and evaporitic sediments is often ambiguous. Consequently, the recognition of primary sedimentary structures that indicate subaerial exposure or shallow marine conditions are therefore of crucial importance when interpreting marginal sedimentary evaporite facies. Parabolic halite dunes, described here for the first time, are observed on the salt crust of the largest salt flat in the world, the

Johan B Svendsen

2003-01-01

265

Rivers, Lakes, Dunes, and Rain: Crustal Processes in Titan's  

E-print Network

Rivers, Lakes, Dunes, and Rain: Crustal Processes in Titan's Methane Cycle Jonathan I. Lunine1-6597/09/0530-0299$20.00 Key Words hydrology, climate, hydrocarbons, atmospheres, planets, clouds Abstract Titan exhibits ample SETTING FOR A METHANE CYCLE ON TITAN Titan is Saturn's largest natural satellite and the second

Reiners, Peter W.

266

Nitrogen translocation in a clonal dune perennial, Hydrocotyle bonariensis  

Microsoft Academic Search

Hydrocotyle bonariensis, a common rhizomatous perennial of coastal North Carolina, forms extensive clones in dune systems characterized by a patchy nitrogen distribution. An experiment was conducted in which Hydrocotyle clones were grown across artificially created soil nitrogen gradients to determine: (1) the effect of soil nitrogen availability and nitrogen translocation on clonal structure and (2) the costs versus benefits of

Jonathan P. Evans

1988-01-01

267

Disturbance drives phylogenetic community structure in coastal dune vegetation  

E-print Network

values. We calculated phylogenetic signal for Grime's C, S and R values using Blomberg's K3 and Abouheif and evolutionary time- scales. The study region was the coastal dune area along the west coast of Jutland, Denmark the relationship between Grime's CSR values and phylogenetic community structure we correlated NRI with C, S and R

Schierup, Mikkel Heide

268

Monitoring Coastal Erosion Natural Resilience by Indexing Coastal Dunes State  

Microsoft Academic Search

SUMMARY The paper describes the results outcoming from a study done inside a Life Environment SELSY Project. Along Puglia littoral (southern Italy) the coastal susceptibility to erosion and dune state have been quantitatively evaluated, A complex complex database has been built and this will be available to local Public Administrations. The database contains, and relates, information that make possible, through

Valpreda Edi; Gragnaniello Simona; Rotunno Michele

269

The Influence of Physical & Biological Cohesion on Dune Development  

NASA Astrophysics Data System (ADS)

Existing predictions for dune bedforms are based on simplified physical parameters, with assumptions that sediment consists only of cohesionless sand. They do not include the complexities of mud: physical cohesion is imparted by cohesive clays and biological cohesion is created by the presence of organisms which, among other things, generate extra-cellular polymers (EPS). Using controlled experiments we show the profound influence on the size, development and equilibrium morphology of dune bedforms of both physical and biological cohesion. Experiments were completed at the Total Environment Simulator facility at Hull University, UK in a 10 x 2 m channel. A flat sediment bed was laid to 0.15 m depth. A unidirectional flow of 0.25 m depth was passed over the sediment for 10 h. In Phase 1 eight different sand:clay mixes were examined, where clay content was 18.0 - 2.1%. In Phase 2, the same mixtures were used with additions of EPS. A velocity of 0.8 m s-1 was used throughout, corresponding to the dune regime for the selected sand. Bedform development was monitored via ultrasonic ranging transducers, sediment cores and water samples. Phase 1 showed substantial differences in bedform type with clay content, with size inversely related to clay content, e.g. Run 1 (18.0% clay) generated 2D ripples; Run 7 (2.1% clay) generated 3D dunes. Transitional forms, included dunes with superimposed ripples, were present between these extremes. In Phase 2, EPS contents equivalent to only 1/30th of 1% by mass prevented the development of bedforms. Bedforms were generated in sediments with 1/20th and 1/10th of 1%, with an inverse relationship between bedform size and EPS content. Comparison of Phase 1 and Phase 2 runs with equal sand:mud ratios reveals that EPS acts to severely inhibit bedform development compared with the mud-only case. We can conclude that (1) the ripple-dune transition can occur under constant flow conditions, i.e. clay content may dictate bedform type, that (2) EPS can severely constrain the development of bedforms, at masses two orders of magnitude smaller than mud, ultimately preventing their development in conditions that would yield dunes in non-cohesive sands and that (3) biological cohesion appears to be greater than physical cohesion at ratios found in natural estuaries. We can conclude that, if the effects of physical and biological cohesion are not included when they are present, predictive models describing bedform growth, morphological equilibrium and migration will be inaccurate and in many cases misleading.

Schindler, Robert; Parsons, Daniel; Ye, Leiping; Baas, Jaco; Hope, Julie; Manning, Andy; Malarkey, Jonathan; Aspden, Rebecca; Lichtman, Dougal; Thorne, Peter; Peakall, Jeff; Patterson, David; Davies, Alan; Bass, Sarah; O'Boyle, Louise

2014-05-01

270

Volcaniclastic dunes from the 2006 deposits of Tungurahua volcano, Ecuador  

NASA Astrophysics Data System (ADS)

Tungurahua volcano has been in eruption intermittently since 1999 and showed peaks in activity in 2006, 2008, and 2010. This study focuses on the deposits from August 2006 small volume pyroclastic density currents (PDC). These deposits show two different facies types, due to interaction with topography. A poorly sorted coarse unit of blocks and ash is mainly found within valleys that had confined the PDCs and was driven by gravity, probably traveling partially fluidized. A stratified, coarse depleted, ash unit, up to 5 meters in thickness, is usually found outside the valleys on outer sides of curves, or at changes of topography. The difference in emplacement position shows that inertial forces were more important than gravity forces for the ash unit. Deposition of the coarse depleted unit is caused by a hydraulic jump. The main characteristic feature of the ash unit is the presence of fields of dunes on its surface. Dunes (also referred as sand waves) produced in PDCs have been reported in various places and several types can be characterized. Their length ranges from 1 to several tens of meters for a length/ height ratio (L/H) that is usually in the range of 10 to 20. Grain size varies from fine ash to lapilli sizes. Most volcanic dunes are interpreted as deposited by supercritical flow (antidunes) because of the occurrence of upstream side aggradation and the low angle slopes. However, dunes were sometimes related with high depositional rates because of the occurrence of a climbing structure (Taal volcano). Tungurahua type dunes are atypical. They are much steeper with L/H=5, for length ranging from 1 to 8 meters. Interestingly, the steepest slope is usually the one facing to the vent. The largest dunes have linear transverse shapes, smaller ones also show lunate shapes. Internally, cross stratification is well defined by layers of fine ash alternating with layers of coarse ash. The structure exhibits different patterns, showing aggradation on the downslope, on the upslope, or both sides (climbing dunes). Usually, Tungurahua dunes don't show migration of the entire structure as commonly observed in fluvial or aeolian conditions. Here, stoss side reworking of deposited material by the flow is minor, only the position of the crest is migrating. Two scenarios are possible for the observed features: 1) A very high deposition rate in low wind conditions, leading to climbing structures (high deposition) and steep slopes (low wind). These conditions are in agreement with the presence of a hydraulic jump. 2) The occurrence of a large scale backflow (flowing upslope) due to the detachment of the entire flow from the ground in some places. This latter interpretation explains why the upslope side (thus lee side!) is steeper, the upward crest migration of climbing dunes, and the low L/H ratio, but is more difficult to imagine. From our data set we infer that in both cases the dunes at Tungurahua volcano result from highly depositional conditions but are not antidunes. Experimental and simulational approaches to understanding the deposition of these structures are being developed.

Douillet, G.; Hanson, J. B.; Goldstein, F.; Kueppers, U.; Tsang-Hin-Sun; Bustillos, J.; Robin, C.; Dingwell, D. B.

2010-12-01

271

Three-component entanglements consisting of three crescent-shaped bidentate ligands coordinated to an octahedral metal centre.  

PubMed

3,3'-biisoquinoline ligands (biiq) L, bearing aromatic substituents on their 8 and 8' positions, have been used to generate interwoven systems consisting of three crescent-shaped ligands disposed around an octahedral metal centre. Mono-ligand complexes of the type [ReL(CO)3py]+ (py: pyridine) have also been prepared, leading to sterically non-hindering complexes in spite of the endotopic nature of the chelate used. The three-component entanglements have been prepared by using either FeII or RuII as gathering metal centre. The synthetic procedure is simple and efficient, affording fully characterised complexes as their PF6 or SbCl6 salts. X-ray crystallography clearly shows that the crescent-shaped ligands do not repel each other in the tris-chelate complexes. In an analogous way, the ReI complexes show open structures with no steric repulsion between the L ligand and the ancillary CO or py groups. The FeL3 or RuL3 compounds are very unusual in the sense that, contrary to all the other tris-bidentate chelate complexes made till now, the three organic components are tangled up, in a situation which will be very favourable to the formation of new non trivial topologies of the catenane type. PMID:17639547

Durola, Fabien; Russo, Luca; Sauvage, Jean-Pierre; Rissanen, Kari; Wenger, Oliver S

2007-01-01

272

Patterns of wind flow and aeolian deposition on a parabolic dune on the southeastern shore of Lake Michigan  

Microsoft Academic Search

Sand deposition and patterns of wind flow were studied on Green Mountain Beach (GMB) dune, a large Lake Michigan coastal dune that is transitional between a trough blowout and a fully-developed parabolic dune. Deposition pins were used to study the amount and pattern of aeolian sand deposition on the lee slopes of GMB dune over 20 months. In the late fall

Edward Hansen; Suzanne DeVries-Zimmerman; Deanna van Dijk; Brian Yurk

2009-01-01

273

The origin and fate of the sediments composing a migrating dune field, Amagansett, NY  

SciTech Connect

The migrating dune system, located in Amagansett, NY, consists of a series of three parabolic dunes ranging in heights from 10 to 30 meters. The dunes are migrating under the influence of the prevailing winds, in a southeasterly direction. The migration continues until the dunes encounter the countervailing prevailing winds, off the Atlantic Ocean. A series of flow charts have been prepared to indicate the possible sources of sediment for this system. These charts, in conjunction with geomorphic analysis, stratigraphic data and various sediment characteristics indicate that the sediments are transported by coastal currents. Once deposited they form a linear dune system. Eolian transport from this dune then supplies the sediment to the migrating dune system.

Maher, T. (Suffolk Community Coll., Selden, NY (United States). Environmental Science Dept.); Kandelin, J. (Suffolk Community Coll., Selden, NY (United States). Dept. of Earth and Space Science); Black, J.A. (Geosciences Inc., Patchogue, NY (United States))

1993-03-01

274

A comparison of seed banks across a sand dune successional gradient at Lake Michigan dunes (Indiana, USA)  

USGS Publications Warehouse

In habitats where disturbance is frequent, seed banks are important for the regeneration of vegetation. Sand dune systems are dynamic habitats in which sand movement provides intermittent disturbance. As succession proceeds from bare sand to forest, the disturbance decreases. At Indiana Dunes National Lakeshore, we examined the seed banks of three habitat types across a successional gradient: foredunes, secondary dunes, and oak savanna. There were differences among the types of species that germinated from each of the habitats. The mean seed bank density increased across the successional gradient by habitat, from 376 to 433 to 968 seeds m-2, but with foredune and secondary dune seed bank densities being significantly lower than the savanna seed bank density. The number of seeds germinated was significantly correlated with soil organic carbon, demonstrating for this primary successional sequence that seed density increases with stage and age. The seed bank had much lower species richness than that of the aboveground vegetation across all habitats. Among sites within a habitat type, the similarity of species germinated from the seed banks was very low, illustrating the variability of the seed bank even in similar habitat types. These results suggest that restoration of these habitats cannot rely on seed banks alone. ?? 2008 Springer Science+Business Media B.V.

Leicht-Young, S. A.; Pavlovic, N.B.; Grundel, R.; Frohnapple, K.J.

2009-01-01

275

Morphology and origin of the Fair Oaks Dunes in NW Indiana, USA  

NASA Astrophysics Data System (ADS)

The Fair Oaks Dunes (FOD) of NW Indiana, USA is a large (~ 4500 km 2) inland dune field associated with the late Wisconsin deglaciation of the Laurentide Ice Sheet. Meltwaters released by the Michigan, Saginaw, and Huron-Erie lobes transported fluvioglacial sediment through the Kankakee and Tippecanoe Valleys and their tributaries. The texture and composition of the sand in the FOD suggest a Saginaw Lobe origin of sediment with some Huron-Erie Lobe sediment. Sub-mature sand with sub-angular grains and a large feldspar content suggests relatively short distance of transport during two or possibly three dune-building and dune reworking events. We propose a model which explains the development of the dunes in three stages. Dune development began during the Bølling-Allerød (stage 1, ~ 15-13 ka) interval. During this stage anticyclonic easterly and north-easterly winds deflated the sand from outwash deposits and built transverse and barchanoid dunes on the western sides of the Tippecanoe Valley and paleo-channels. Further downwind, on the western and southwestern windward margins of the FOD, loess was deposited. During the early Younger Dryas (stage 2, ~ 12.5 ka) atmospheric circulation changed, and westerly winds reworked the original dunes to create a great variety of parabolic dunes. Simple, hemicyclic and lobate parabolic dunes developed in the western FOD, while further downwind, in the eastern and the southern FOD, more elongated hairpin and windrift dunes developed. On the upwind side of the dune field, loess deposits remained stable and were not remobilized during the second stage dune development. By the early Holocene the FOD dunes were stabilized until their minor remobilization during the Middle Holocene (stage 3). Minor disturbances caused by anthropogenic activities have occurred in last two centuries.

Kilibarda, Z.; Blockland, J.

2011-01-01

276

Airglow from Jupiter's nightside and crescent - Ultraviolet spectrometer observations from Voyager 2  

SciTech Connect

The Voyager Ultraviolet Spectrometer has made extensive observations of airglow from Jupiter's dark-side equatorial latitudes. The brightness of H Lyman alpha, the only emission detected, varies between 700 and 1000 rayleighs (R) as a function of longitude. The dark side of Jupiter is illuminated by sky background Lyman alpha arising from resonance scattering of the solar Lyman alpha line by the neutral hydrogen of the interstellar medium. Calculations show that resonance scattering of this sky background by hydrogen in Jupiter's thermosphere will produce about 300 R of Lyman alpha emission. The additional Lyman alpha observed is probably excited by electrons and protons precipitating at equatorial latitudes. Based on the 500-R upper limit set here on the dark-side H2 Lyman and Werner bands, and the Lyman alpha measurements, the exciting particles are thought to have a soft energy spectrum and deposit about 0.04 erg/sq cm per sec in the atmosphere. There is evidence for an asymmetrical precipitation pattern associated with the longitudinal variation in Lyman alpha emission, and a suggestion of a strong day-night difference in precipitation as well.

Mcconnell, J.C.; Sandel, B.R.; Broadfoot, A.L.

1980-01-01

277

Spectral analysis of dark dunes sands of Ka'u Desert (Hawaii) with regard to their applicability as terrestrial analogs to Martian dunes  

NASA Astrophysics Data System (ADS)

Dark basaltic dunes represent the majority of Martian eolian bedforms. However, on Earth there are only few places where basaltic dunes can be found. Is has been suggested that the Marian dunes sands are volcanic in origin because their mineralogical composition consists of pyroxene and olivine. The dark dunes in Ka'u Desert on the Big Island of Hawaii are located on the western flank of Kilauea volcano. The dark sands are derived from volcanic ash and reworked pyroclastic material. Thus, the Hawaiian dark sand dunes could be an adequate analog to Martian dunes, particularly for testing the hypothesis of volcanic origin and to determine basic spectral characteristics that may be associated with differences in grain size and chemistry indicative of maturity and transport distances. Samples of different dark dunes in Ka'u Desert were collected during a field trip in summer 2009. We measured the samples with an ASD field spectrometer in a laboratory. We compared the terrestrial spectra with typical OMEGA and CRISM near-infrared spectra of different Martian dark dune fields. The overall spectral shape of the terrestrial spectra reflects a basaltic composition of the sands fairly similar to that of Martian dunes, dominated by olivine. These rock-forming minerals form as the lava cools, and are commonly found in basaltic volcanic ash. The correlation in mineralogical composition of terrestrial and Martian dunes hints to a similar origin of the dark sands on Mars and Earth. Since some terrestrial spectra show a beginning aqueous alteration of the dark sands these samples could be used to analyse alteration features of Martian dark dunes.

Tirsch, Daniela; Jaumann, Ralf; Craddock, Robert A.

278

Sedimentological, Mineralogical and Geochemical Characterization of Sand Dunes in Saudi Arabia  

NASA Astrophysics Data System (ADS)

Sedimentological, mineralogical, morphological and geochemical studies of sand dunes from ten locations in Saudi Arabia were conducted in order to determine the differences between them and to find out the provenance and tectonic setting of these sand dunes. Sixty seven samples were collected from different sand dunes types ranging in morphology from linear, barchans, parabolic to stars dunes. In overall, the sand dunes are fine to coarse grained mean grain size, moderately sorted, near symmetrical skewness with mesokurtic distribution characterized sand dunes in most locations. The sand dunes grains are subrounded in all locations except in the Red sea, Qassim, central Arabia and the eastern province which showed sub-angular grains. The main mineral compositions of studied aeolian sand dunes are quartz, feldspar, calcite, and mica. Quartz is the dominant mineral in locations with significant amount of feldspars and mica in Najran, Red sea and Central Arabia locations. Moreover, calcite is present in Sakaka and NW Empty Quarter (Jafurah). Basement related sand dunes in Najran, Central Arabia and Red sea locations are sub-mature in terms of their mineralogical maturity. Whereas, sand dunes in other locations are texturally mature except those from the Red sea which showed sub-mature sand. The sands are classified as quartz arenite, except in the basement related sand dunes in Najran, central Arabia and the Red sea are ranging from sub-arkose, sub-litharenite and lithraenite. Morphologically, parallel to sub-parallel sand ridges with NE-SW orientation occurred in east and north parts of Empty Quarter (Najran and Jafurah) and NW-SE orientation in Dahna and Nafud deserts in central and north regions of Saudi Arabia. Parabolic sand dunes characterized the Nafud desert (Hail, Sakaka, Tayma locations). Barchans and star sand dunes characterize the Empty Quarter (Jafurah). Major, trace, and rare earth elements studies were carried out to determine the composition, provenance and tectonic history of the sand dunes. Geochemical analysis indicated that most of sand dunes are quartz arenite type, except in the Red sea, basement related central Saudi Arabia and Najran areas, the sand dunes are sub-arkoses, sub-litharenite and litharenite. The concentration of major,trace and rare elements showed active continental margins as a tectonic setting of Red sea, basement related Najran and central Arabia sand dune. In contrast, passive continental margins for the other locations. The distribution of major, trace and rare earth elements showed similarity in chemical composition between basement related sand dunes in Red sea, Najran and central Arabia.

Benaafi, Mohammed; Abdullatif, Osman

2014-05-01

279

Dates in the desert: Interpreting over 600 luminescence ages from southern African desert dune systems  

NASA Astrophysics Data System (ADS)

Over 600 published luminescence ages from southern Africa's extensive continental dunefields and isolated dunes provide a rich record of aeolian system dynamics during the late Quaternary. Included in the Chronologic Database of INQUA's Dunes Atlas project, the majority of records come from sites within linear dune-dominated Kalahari dunefields, with lesser representation of both other dunefields (Namib, West Coast) and dune types ( lunette, transverse, sand ramp). Records are analysed not only for the evidence they provide of Late Quaternary environmental changes over the last 190ka, but in terms of the analytical techniques used, data quality and data presentation, as these all impact on how dune luminescence ages have been, or should be, interpreted as a tool for palaeoenvironmental and dune development studies. Although the sub-continent has yielded a substantial body of dune ages, the spatial unevenness of sampling for dating inhibits our ability to fully interrogate southern Africa's aeolian history. However, we argue that this is not a situation that can simply be improved by adding more and more ages to the full set of records. It is essential to 1) appreciate the spatial differences in dune sensitivities to activation; 2) the relationships of dune activity to potential changes in hydrological and other activity controls, and 3) establish better tools and approaches for analysing a rich but presently environmentally ambiguous record of dune accumulation.

Thomas, David; Burrough, Sallie

2014-05-01

280

Hybrid Repair of Large Crescent Rotator Cuff Tears Using a Modified SpeedBridge and Double-Pulley Technique.  

PubMed

An ideal rotator cuff repair maximizes the tendon-bone interface and has adequate biomechanical strength that can withstand a high level of demand. Arthroscopic transosseous-equivalent rotator cuff repairs have become popular and have been shown to be superior to many other methods of fixation. We present an alternative method of repair for large crescent rotator cuff tears that combines 2 well-known methods of fixation: modified SpeedBridge (Arthrex, Naples, FL) and double-pulley techniques. These 2 repair constructs were combined to provide the greatest amount of compression across the footprint while also providing rigid fixation. Ultimately, this can provide an optimal environment for healing in otherwise significant injuries. PMID:25126513

Chauhan, Aakash; Regal, Steven; Frank, Darren A

2014-06-01

281

Soins primaires des personnes victimes d’une lésion médullaire  

PubMed Central

Résumé Objectif Effectuer une étude de la portée des données empiriques, entre 1980 et 2009, concernant les soins primaires aux adultes victimes d’une lésion médullaire (LME). Sources des données Une recension dans des revues révisées par des pairs de1980 à 2009 à l’aide de CINAHL, PubMed-MEDLINE, EMBASE, PsycINFO, Social Sciences Abstracts et Social Work Abstracts. Sélection des études La recherche électronique au moyen de mots-clés a permis de cerner 42 articles sur les soins primaires et les LME. Des critères d’inclusion ont servi à réduire la liste à un ensemble de 21 articles publiés en anglais qui portaient sur un échantillon de plus de 3 et présentaient une analyse empirique. Synthèse Environ 90 % des personnes atteintes d’une LME ont identifié leur médecin de famille comme étant leur docteur habituel; 63 % avaient un spécialiste des LME. Les personnes vivant à long terme avec une LME développent des rubriques complexes pour naviguer dans leurs systèmes de soins de santé personnels. Les données scientifiques ne sont pas unanimes quant à l’efficacité des programmes d’intervention directe pour le maintien de la santé et la prévention des complications à la suite d’une LME. Les données appuient cependant le suivi périodique par une équipe spécialisée et un bilan de santé annuel complet. La recherche fait valoir un fort degré d’uniformité dans l’identification des problèmes les plus courants soulevés par les personnes atteintes d’une LME en soins primaires, dont la plupart concernent l’incapacité, plus précisément les complications secondaires, comme la dysfonction intestinale ou vésicale et la douleur. Il existe aussi de bonnes données probantes à l’effet que de nombreux problèmes de santé généraux exigent de l’attention dans une telle population, comme les problèmes de la densité osseuse, la dépression et les questions entourant la santé sexuelle et la reproduction. Il y a des données de niveaux 4 et 5 concernant des besoins en matière de santé non satisfaits qu’ont des personnes victimes d’une LME vivant dans la communauté. En dépit du fait que les patients atteints d’une LME utilisent beaucoup les soins primaires et les services de santé en général, les données scientifiques font valoir que les besoins de renseignements de ces patients en particulier ne sont pas adéquatement satisfaits. Conclusion Un solide système de soins primaires représente la meilleure assurance de bons résultats sur le plan de la santé et d’une utilisation raisonnable des services de santé chez les personnes victimes d’une LME, notamment un bilan de santé annuel complet, un recours approprié aux autres spécialistes et une attention accordée à l’accessibilité et aux besoins insatisfaits.

McColl, Mary Ann; Aiken, Alice; McColl, Alexander; Sakakibara, Brodie; Smith, Karen

2012-01-01

282

Article original Utilisation d'une chambre de transpiration portable  

E-print Network

Article original Utilisation d'une chambre de transpiration portable pour l'estimation de l chambre de transpiration légère, close, couvrant une surface au sol de 0,5 m2 a été utilisée pour mesurer comparées avec la transpiration des arbres estimée à partir de mesures de flux de sève. Quand le stock

Paris-Sud XI, Université de

283

Seasonality of mycorrhizae in coastal sand dunes of Baja California  

Microsoft Academic Search

Populations of arbuscular mycorrhizal fungi were estimated from spores associated with seven plant species in coastal dunes\\u000a at El Socorro, near Ensenada, Baja California, during six months in 1992. The seasonal patterns of percent root colonization\\u000a were also described in the same species during the wet season (January–March) and the dry season (April–July). Comparisons\\u000a were made between the pioneer species

Concepción Sigüenza; Ileana Espejel; Edith B. Allen

1996-01-01

284

Understorey gaps influence regeneration dynamics in subtropical coastal dune forest  

Microsoft Academic Search

Dominant understorey species influence forest dynamics by preventing tree regeneration at the seedling stage. We examined\\u000a factors driving the spatial distribution of the monocarpic species Isoglossa woodii, a dominant understorey herb in coastal dune forests, and the effect that its cover has on forest regeneration. We used line\\u000a transects to quantify the area of the forest understorey with I. woodii

Megan E. Griffiths; Michael J. Lawes; Zivanai Tsvuura

2007-01-01

285

COMPORTEMENT D'UNE SOUCHE ATTNUE DU PIGEON HERPESVIRUS 1  

E-print Network

COMPORTEMENT D'UNE SOUCHE ATT�NU�E DU PIGEON HERPESVIRUS 1 ET DE SOUCHES PATHOG�NES LORS D'INFECTIONS SUCCESSIVES CHEZ LE PIGEON H. VINDEVOGEL P.P. PASTORET P. LEROY Faculté de Médecine Vétérinaire de l IN SUCCESSIVE INFECTIONS OF PIGEONS. - Behaviour in pigeons of an attenuated strain of Pigeon herpesvirus 1

Boyer, Edmond

286

Hippophae rhamnoides on a coastal dune system: a thorny issue?  

Microsoft Academic Search

The study mapped the spread of the invasive non-native shrub, Hippophae rhamnoides, on a coastal dune system in South Wales. H. rhamnoides colonies spread across the system, covering around 60.9 ha in 1996 compared to 2.4 ha in 1957. Clearance activities have\\u000a since decreased the total to around 23 ha. The effects of this expansion on ground flora were assessed through comparison\\u000a of

Elen Gwenllian Richards; Helene Burningham

2011-01-01

287

Evidence for sensitivity of dune wetlands to groundwater nutrients.  

PubMed

Dune slacks are seasonal wetlands, high in biodiversity, which experience considerable within-year and between-year variations in water-table. They are subject to many pressures including climate change, land use change and eutrophication. Despite their biological importance and the threats facing them, the hydrological and nutrient parameters that influence their soil properties and biodiversity are poorly understood and there have been no empirical studies to date testing for biological effects in dune systems resulting from groundwater nutrients at low concentrations. In this study we examined the impact of groundwater nutrients on water chemistry, soil chemistry and vegetation composition of dune slacks at three distance classes (0-150 m, 150-300 m, 300-450 m) away from known (off-site) nutrient sources at Aberffraw dunes in North Wales, whilst accounting for differences in water-table regime. Groundwater nitrate and dissolved inorganic nitrogen (DIN) and soil nitrate and nitrite all had significantly higher concentrations closest to the nutrient source. Multivariate analysis showed that although plant species composition within this site was primarily controlled by water table depth and water table fluctuation, nitrogen from groundwater also influenced species composition, independently of water table and soil development. A model containing all hydrological parameters explained 17% of the total species variance; an additional 7% was explained following the addition of NO3 to this model. Areas exposed to elevated, but still relatively low, groundwater nutrient concentrations (mean 0.204 mg/L+/-0.091 of DIN) had greater abundance of nitrophilous species and fewer basipholous species than in areas with lower concentrations. This shows that clear biological impact occurs below previously suggested DIN thresholds of 0.20-0.40 (mg/L). PMID:24846404

Rhymes, Jennifer; Wallace, Hilary; Fenner, Nathalie; Jones, Laurence

2014-08-15

288

Turbulence and sediment transport over sand dunes and ripples  

NASA Astrophysics Data System (ADS)

Several bedforms are present near to the surfzone of natural beaches. Dunes and ripples are frequently observed. Understanding the turbulence over these forms is essential for the sediment transport. The turbulent flow and the suspended sand particles interact with each other. At the moment, the modelling strategy for turbulence is still a challenge. According to the spatial scales, some different methods to model the turbulence are employed, in particular the RANS (Reynolds Averaged Navier-Stokes) and the LES (Large Eddy Simulation). A hybrid method combining both RANS and LES is set up here. We have adapted this method, initially developed for atmospheric flow, to the oceanic flow. This new method is implemented inside the 3D hydrodynamic model, MARS 3D, which is forced by waves. LES is currently the best way to simulate turbulent flow but its higher cost prevents it from being used for large scale applications. So, here we use RANS near the bottom while LES is set elsewhere. It allows us minimize the computational cost and ensure a better accuracy of the results than with a fully RANS model. In the case of megaripples, the validation step was performed with two sets of field data (Sandy Duck'97 and Forsoms'13) but also with the data from Dune2D model which uses only RANS for turbulence. The main findings are: a) the vertical profiles of the velocity are similar throughout the data b) the turbulent kinetic energy, which was underestimated by Dune2D, is in line with the observations c) the concentration of the suspended sediment is simulated with a better accuracy than with Dune2D but this remains lower than the observations.

Bennis, A.; Le Bot, S.; lafite, R.; Bonneton, P.; Ardhuin, F.

2013-12-01

289

Archaeology and holocene sand dune stratigraphy on Chatham Island  

Microsoft Academic Search

Four depositional episodes based on sand deposits and the soils on them are proposed for Holocene coastal sand dunes on Chatham Island: Te Onean Depositional Episode (c. 5,000 to 2,200 years BP), Okawan Depositional Episode (c. 2,200 to 450 years BP), Kekerionean Depositional Episode (c. 450 to 150 years BP) and Waitangian Depositional Episode (c. 150 years BP to present

B. G. McFadgen

1994-01-01

290

Reflectance characteristics and surface processes in stabilized dune environments  

NASA Technical Reports Server (NTRS)

Analysis of multitemporal TM data for three environmentally related field areas yields information on the response characteristics of stabilized dunes and desert-fringe environments. The three field sites studied include dune fields in Egypt, Mali, and Botswana, ranging in climate from hyperarid to semiarid, and may be classed as an environmental series relating surface processes under Saharan, Sahelian, and Savanna conditions. Sites were field mapped and monitored with TM data for lengths of time up to a year. The complexity of spectral response characteristics is greatest where vegetation is dense and diverse, but study of the three environments together places constraints on the importance of vegetation to spectral response as well as to mechanisms of sand transport. In both Mali and Botswana, the Sahelian and Savanna environments, contrast reversals occur on dune crests and reflectance patterns change through the dry season to resemble the response curves of the hyperarid study site in Egypt. In these analyses, overall surface brightness is controlled by sand composition, while spectral features are controlled by vegetation dynamics.

Jacobberger, P. A.

1989-01-01

291

Aeolian processes and dune morphology in Gale Crater  

NASA Astrophysics Data System (ADS)

Datasets at resolutions many times greater than previously available were used to study aeolian features within Gale Crater. High resolution thermal inertia data allowed for detailed particle size estimation, with the data sufficient to resolve dunefields. A wide range of grain sizes have now been identified in the Gale Crater dunefields, ranging from medium to very coarse sand. High Resolution Imaging Science Experiment (HiRISE) and THEMIS VIS data allowed for detailed analysis of the dune morphology and slip-faces, which shows that the dunes have responded to topographic influences on prevailing wind directions under a present day wind regime. This result was corroborated by a regional mesoscale model for the crater under dust storm conditions. The central mound and smaller scale crater floor topography has altered the prevailing wind regime and dune patterns. Aeolian activity has thus played, and continues to play, an important role in shaping many of the present surface features of Gale Crater. The arrival of a future lander mission such as the Mars Science Laboratory would be able to sample these surface features directly and add a wealth of data to the understanding of Gale Crater.

Hobbs, Steven W.; Paull, David J.; Bourke, Mary C.

2010-11-01

292

Morpho-chronology of coastal dunes in Médoc. A new interpretation of Holocene dunes in Southwestern France  

Microsoft Academic Search

Previous work on the coastal dunes in the Médoc region was carried out by the BRGM [Marionnaud, J.M., 1972. Carte géologique de la France (1\\/50000), Feuille St-Vivien-de-Médoc-Soulac-sur-Mer (729–730), Orléans: BRGM Notice explicative par J. Dubreuilh, J.M. Marionnaud (1973), 45 pp.; Dubreuilh, J., Marionnaud, J.M., 1973. Carte géologique de la France (1\\/50000), Feuille Lesparre-Médoc - Le Junca (753–754), Orléans: BRGM Notice

Jean-Pierre Tastet; Nigel I. Pontee

1998-01-01

293

Measurements of Dune Parameters on Titan Suggest Differences in Sand Availability  

NASA Astrophysics Data System (ADS)

The equatorial region of Saturn’s moon Titan has five large sand seas with dunes similar to large linear dunes on Earth. Cassini Radar SAR swaths have high enough resolution (300 m) to measure dune parameters such as width and spacing, which helps inform us about formation conditions and long-term evolution of the sand dunes. Previous measurements in locations scattered across Titan have revealed an average width of 1.3 km and spacing of 2.7 km, with variations by location. We have taken over 1200 new measurements of dune width and spacing in the T8 swath, a region on the leading hemisphere of Titan in the Belet Sand Sea, between -5 and -9 degrees latitude. We have also taken over 500 measurements in the T44 swath, located on the anti-Saturn hemisphere in the Shangri-La Sand Sea, between 0 and 20 degrees latitude. We correlated each group of 50 measurements with the average distance from the edge of the dune field to obtain an estimate of how position within a dune field affects dune parameters. We found that in general, the width and spacing of dunes decreases with distance from the edge of the dune field, consistent with similar measurements in sand seas on Earth. We suggest that this correlation is due to the lesser availability of sand at the edges of dune fields. These measurements and correlations could be helpful in determining differences in sand availability across different dune fields, and along the entire equatorial region of Titan.

Stewart, Brigitte W.; Radebaugh, Jani

2014-11-01

294

An eco-spatial index for evaluating stabilization state of sand dunes  

NASA Astrophysics Data System (ADS)

Geomorphologies tend to categorize dunes into three major states (mobile, semi-stabilized and stabilized) based on their shape and mobility rate. However, the ecologists try to find bio-indicators that can characterize the mobility rate and the ecological features of the various dune states. Unfortunately, there are limited numbers of significant bio-indicators, if any. The aim of our study was to develop a Dune Assemblage Index (DAI) in order to indicate the affinity of annual plants and arthropods assemblages to dune mobility. The DAI values range between 0 for stabilized dunes and 1 for bare and active dunes. The index was calculated for 10 coastal dunes in Nizzanim nature reserve, located at the southern part of the Israeli Mediterranean coast, from data that were collected in the years 2006 and 2007. Generally, the lower the vegetation cover is, the higher are DAI values for both taxon groups. Generalist species tend to mask the differences between active and stabilized dunes whereas psammophiles (sand-dwelling species) tend to increase the DAI values. Additionally, the DAI may differ among dunes with the same perennial coverage due to differences in the spatial plant distribution patterns. Likewise, the DAI depends also on the distance of the dunes from rural areas, which encourage invasion of generalist species, thus decreases the DAI value. This new defined spatial index that relies on plant and animal assemblages, rather than on individual bio-indicators, can be adapted to any taxon and dune ecosystems. The use of several taxons may support better understanding of the ecosystem state of the dune.

Rubinstein, Yehonathan; Groner, Elli; Yizhaq, Hezi; Svoray, Tal; Bar (Kutiel), Pua

2013-06-01

295

Mapping and Analysis of 'Dunes' in the Ejecta Blankets of Fresh Lunar Craters  

NASA Astrophysics Data System (ADS)

Lunar concentric ‘dunes’ are ridge-like features that appear in the ejecta blankets of fresh craters on the Moon. These ‘dunes’ are oriented roughly perpendicular to ejecta flow, and are found between ~1.2 to several crater radii. We have been mapping and measuring these features using the high-resolution images from the Lunar Reconnaissance Orbiter Camera (LROC). In our survey of the Moon we have so far found fifty-seven craters where the facies of the Lunar concentric ‘dunes’ can be seen, ranging in diameter from one to eleven kilometers, in both the mare and the highlands. We have created mosaics from high-resolution LROC Narrow Angle Camera (NAC) images for fourteen of these craters which allow us to examine the morphology of these dunes in detail. We note a general progression in dune morphology as distance from the crater increases (the following measurements are not standard from crater to crater and reflect the mapping results for crater Piton B): ‘dunes’ are most distinct between 1.5 to 3 crater radii from the crater center. Between 3 and 6 crater radii, dunes are commonly accompanied by a trough on the crater-facing side of the dune. As distance from the crater increases, dune morphology subsides and troughs become the most notable feature within the ejecta blanket. Using Lunar Orbiter Laser Altimeter (LOLA) data we are able to examine how the ‘dunes’ form in the context of local pre-existing slopes. These ‘dunes’ are known to form predominantly on level and crater facing slopes, however we have found at some highlands craters, like Stevinus A, that they can form on slopes facing away from the crater. We have observed a number of morphological features of the ‘dunes’ that do not seem to support the previously proposed ballistic impact sedimentation and erosion hypothesis for the formation of this facies. Thus we will need to formulate and test new hypotheses for how this interesting lunar facies forms.

Atwood-Stone, Corwin; Bray, Veronica; McEwen, Alfred

2014-11-01

296

Defrosting Polar Dunes--Dark Spots and Wind Streaks  

NASA Technical Reports Server (NTRS)

The first time that the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC)team saw dark spots on defrosting dune surfaces was in August and September of 1998. At that time, it was the north polar seasonal frost cap that was subliming away (more recent images from 1999 have shown the south polar frosts). This picture (above) shows a small portion of the giant dune field that surrounds the north polar region, as it appeared on August 23, 1998. At the time, it was early northern spring and the dunes were still covered with winter frost.

Dark spots had appeared on the north polar dunes, and many of them exhibited a radial or semi-radial pattern of dark streaks and streamers. At first, there was speculation that the streaks indicated that the defrosting process might somehow involve explosions! The dark spots seemed to resemble small craters with dark, radial ejecta. It seemed possible that frozen carbon dioxide trapped beneath water ice might somehow heat up, turn to gas, expand, and then 'explode' in either a small blast or at least a 'puff' of air similar to that which comes from the blowhole of a surfacing whale or seal.

The image shown here changed the earlier impression. The dark spots and streaks do not result from explosions. The spots--though not well understood--represent the earliest stages of defrosting on the sand dunes. The streaks, instead of being caused by small explosions, are instead the result of wind. In this picture, the fine, dark streaks show essentially identical orientations from spot to spot (e.g., compare the spots seen in boxes (a) and (b)). Each ray of dark material must result from wind blowing from a particular direction--for example, all of the spots in this picture exhibit a ray that points toward the upper left corner of the image, and each of these rays indicates the same wind regime. Each spot also has a ray pointing toward the lower right and top/upper-right. These, too, must indicate periods when the wind was strong enough to move materials, consistently, in only one direction.

The sand that makes up the north polar dunes is dark. Each spot and streak is composed of the dune sand. The bright surfaces are all covered with frost. This picture is located near 76.9oN, 271.2oW, in the north polar sand sea. Illumination is from the lower left. The 200 meter scale also indicates a distance of 656 feet.

Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.

1999-01-01

297

Cassini SAR, radiometry, scatterometry and altimetry observations of Titan's dune fields  

USGS Publications Warehouse

Large expanses of linear dunes cover Titan's equatorial regions. As the Cassini mission continues, more dune fields are becoming unveiled and examined by the microwave radar in all its modes of operation (SAR, radiometry, scatterometry, altimetry) and with an increasing variety of observational geometries. In this paper, we report on Cassini's radar instrument observations of the dune fields mapped through May 2009 and present our key findings in terms of Titan's geology and climate. We estimate that dune fields cover ???12.5% of Titan's surface, which corresponds to an area of ???10millionkm2, roughly the area of the United States. If dune sand-sized particles are mainly composed of solid organics as suggested by VIMS observations (Cassini Visual and Infrared Mapping Spectrometer) and atmospheric modeling and supported by radiometry data, dune fields are the largest known organic reservoir on Titan. Dune regions are, with the exception of the polar lakes and seas, the least reflective and most emissive features on this moon. Interestingly, we also find a latitudinal dependence in the dune field microwave properties: up to a latitude of ???11??, dune fields tend to become less emissive and brighter as one moves northward. Above ???11?? this trend is reversed. The microwave signatures of the dune regions are thought to be primarily controlled by the interdune proportion (relative to that of the dune), roughness and degree of sand cover. In agreement with radiometry and scatterometry observations, SAR images suggest that the fraction of interdunes increases northward up to a latitude of ???14??. In general, scattering from the subsurface (volume scattering and surface scattering from buried interfaces) makes interdunal regions brighter than the dunes. The observed latitudinal trend may therefore also be partially caused by a gradual thinning of the interdunal sand cover or surrounding sand sheets to the north, thus allowing wave penetration in the underlying substrate. Altimetry measurements over dunes have highlighted a region located in the Fensal dune field (???5?? latitude) where the icy bedrock of Titan is likely exposed within smooth interdune areas. The hemispherical assymetry of dune field properties may point to a general reduction in the availability of sediments and/or an increase in the ground humidity toward the north, which could be related to Titan's asymmetric seasonal polar insolation. Alternatively, it may indicate that either the wind pattern or the topography is less favorable for dune formation in Titan's northern tropics. ?? 2011 Elsevier Inc.

Le, Gall, A.; Janssen, M. A.; Wye, L. C.; Hayes, A. G.; Radebaugh, J.; Savage, C.; Zebker, H.; Lorenz, R. D.; Lunine, J. I.; Kirk, R. L.; Lopes, R. M. C.; Wall, S.; Callahan, P.; Stofan, E. R.; Farr, T.

2011-01-01

298

Declining sand dune activity in the southern Canadian prairies: Historical context, controls and ecosystem implications  

NASA Astrophysics Data System (ADS)

Sandhills are islands of biodiversity in the southern Canadian prairies that sustain habitat for many rare and endangered species. These unique areas consist of large expanses of dune fields now mostly stabilized by grassland vegetation. Historically, the number of active dunes has decreased significantly due to vegetation stabilization, resulting in a dramatic decline of open-sand habitat for a variety of dune-dependent species. Without a certain level of wind erosion, opportunities for establishment of early-stage, species-rich vegetation types are diminished and open-sand habitat decreases by encroachment of the surrounding grassland vegetation. The current trend of dune stabilization, however, implies that wind erosion is decreasing, thereby threatening the continued existence of a variety of dune-dependent plants, arthropods and vertebrates, as well as other less-specialized species that benefit indirectly from these habitats. By reviewing factors contributing to the historical decline of active dunes, as well as the ecological implications of dune stabilization, the aim of this paper is to establish the biophysical context for new land management strategies that conserve valued landscape components, such as active dunes, and the processes therein. As dune stabilization continues management interventions will be required to sustain or re-establish open sand and the species that rely on these habitats.

Hugenholtz, Chris H.; Bender, Darren; Wolfe, Stephen A.

2010-11-01

299

Landslide Deposits, Cookie Bites, and Crescentic Fracturing Along the Northern Puerto Rico-Virgin Islands Margin: Implications for Potential Tsunamigenesis  

NASA Astrophysics Data System (ADS)

The seismogenic North America-Caribbean oblique-slip plate boundary forms the 8-km-deep Puerto Rico trench north of the densely populated islands of Puerto Rico and Virgin Islands (combined population of just over 4 million people). The southern slope of the Puerto Rico trench adjacent to the Puerto Rico-Virgin Islands (PRVI) carbonate platform is characterized by frequent seismicity, rapid trenchward tilting, oversteepened slopes, and mass wasting. We present high-resolution bathymetry, HMR1 sidescan imagery, and single-channel seismic data to document extensive landslide deposits that we infer to have been the result of multiple slide events capable of producing prehistoric tsunamis along the coasts of Puerto Rico and the Virgin Islands. Landslide deposits can be traced upslope to two, 45-55 km-wide arcuate-shaped embayments or "cookie bites" carved out of the PRVI platform. Three-dimensional visualization of the debris field and the slope of the largest of the arcuate-shaped embayments centered at 66° 40' constrain volume removal to 1.1 km3 of the PRVI carbonate platform and underlying volcanic and volcaniclastic basement. Sidescan sonar and single-channel seismic data reveal crescentic cracks in the seafloor of the PRVI platform 35-45 km in length located 35 km offshore the northwestern tip of Puerto Rico. These cracks, interpreted to represent the sites of future breakaway scarps and landslides, are similar in shape and length to the head wall scarps of the amphitheaters to the east. An ˜500 km2 section of the PRVI platform (750 m thick) has begun to detach and slump trenchward along the larger of these cracks. Investigation of the existing arcuate-shaped embayments is essential because massive (tens to hundreds of km3) and instantaneous slope failure has the potential to be tsunamigenic. Puerto Rico and the Virgin Islands were inundated by tsunamis in 1867 (mainly affecting St. Thomas and St. Croix, 7 m of runup, casualties in the hundreds) and 1918 (mainly affecting western and northwestern Puerto Rico; 6 m of runup, 120 casualties). Calculation of the potential volume, runout extent, and triggering mechanisms of past submarine landslides will better constrain the tsunamigenic potential of the newly discovered crescentic faults.

Hearne, M. E.; Grindlay, N. R.; Mann, P.

2003-12-01

300

Iron mineralogy and bioaccessibility of dust generated from soils as determined by reflectance spectroscopy and magnetic and chemical properties--Nellis Dunes recreational area, Nevada  

USGS Publications Warehouse

Atmospheric mineral dust exerts many important effects on the Earth system, such as atmospheric temperatures, marine productivity, and melting of snow and ice. Mineral dust also can have detrimental effects on human health through respiration of very small particles and the leaching of metals in various organs. These effects can be better understood through characterization of the physical and chemical properties of dust, including certain iron oxide minerals, for their extraordinary radiative properties and possible effects on lung inflammation. Studies of dust from the Nellis Dunes recreation area near Las Vegas, Nevada, focus on characteristics of radiative properties (capacity of dust to absorb solar radiation), iron oxide mineral type and size, chemistry, and bioaccessibility of metals in fluids that simulate human gastric, lung, and phagolysosomal fluids. In samples of dust from the Nellis Dunes recreation area with median grain sizes of 2.4, 3.1, and 4.3 micrometers, the ferric oxide minerals goethite and hematite, at least some of it nanosized, were identified. In one sample, in vitro bioaccessibility experiments revealed high bioaccessibility of arsenic in all three biofluids and higher leachate concentration and bioaccessibility for copper, uranium, and vanadium in the simulated lung fluid than in the phagolysosomal fluid. The combination of methods used here to characterize mineral dust at the Nellis Dunes recreation area can be applied to global dust and broad issues of public health.

Goldstein, Harland L.; Reynolds, Richard L.; Morman, Suzette A.; Moskowitz, Bruce; Kokaly, Raymond F.; Goossens, Dirk; Buck, Brenda J.; Flagg, Cody; Till, Jessica; Yauk, Kimberly; Berquó, Thelma S.

2013-01-01

301

Changes in Water Vapor Transport and the Production of Precipitation in the Eastern Fertile Crescent as a Result of Global Warming  

E-print Network

in an area stretching from Turkey and the eastern Mediterranean across to northeastern Iran and an increase The Fertile Crescent is defined here as an area en- compassing southeast Turkey, northeastern Syria, northern bodies: the Black Sea to the northwest, the Caspian Sea to the northeast, the Mediterranean Sea

Evans, Jason

302

Natural versus Urban dunes along the Emilia-Romagna coast, Northern Adriatic (Italy)  

NASA Astrophysics Data System (ADS)

Beach-dune interaction models can be precious tools for land managers and policymakers. However, if the models are inaccurate, land use policies may be designed based on false pretences or assumptions leading to poor land management, long-term erosion and sustainability issues, and increased difficulties in maintaining the dynamic coastal systems. From the literature, it appears that even the most reliable beach-dunes interactions models are not applicable to all coastal systems (Short and Hesp, 1982; Psuty, 1988; Sherman and Bauer, 1993). The study aims to identify the morphological evolution of the Emilia-Romagna coastal dunes according to its natural and "human" characteristics and to classify groups of dunes with similar evolutionary patterns. The coastal area consists essentially of 130 km of low sandy coast, interrupted by vast lagoon areas, harbor jetties and numerous hard coastal defense structures that were built during the first half of the 20th century to protect the Emilia-Romagna coast against erosion. Today about 57% of the littoral is protected by hard defenses, which have modified the morphodynamic characteristics of the beach without inverting the negative coastal evolution's trend. From recent aerial photographs (2011), 62 coastal dunes have been identified and mapped. Furthermore, the dune analysis shows a variability of the "physical characteristics" of coastal-dune systems along the Emilia-Romagna coast. The dune height varies from 1 to 7 meters, the width of the beach and of the active dunes range respectively from 10 to 150 m and from 10 to 65 m. Three main factors may explain the variability of the "physical characteristics": 1- Firstly the frontal dunes may be of different states according to the classification of Hesp (2002) since they correspond to incipient foredunes, well-developed foredunes, blowouts, residual foredunes as well as reactivated relict foredunes, 2- This could also be related to a different orientation of the coastline and foredune's line to the dominant onshore winds and, 3- Human impacts may also explain this variability since most of the dune-beach systems of Emilia-Romagna are characterized by important anthropogenic features that do not adequately describe beach-foredune interactions. A factor analysis of the coastal dunes has allowed formulating hypotheses about their evolutionary trends according to the importance and interference of factors, both natural and anthropic, acting on the beach-dune system. Four groups of dunes have been identified corresponding to natural dunes, semi-anthropic dunes with major natural features, semi-anthropic dunes with major anthropic feature and "urban" dunes. Furthermore, while human activities impede the formation and development of new incipient dunes, other human activities favor the conservation and development of the human-altered foredunes. Hesp, P., 2002: Foredunes and blowouts: initiation, geomorphology and dynamics, Geomorphology, 245-268. Psuty, N. P. 1988. Sediment budget and dune/beach interaction. Journal of Coastal Research Special Issue 3: 1-4. Sherman, D. J., and B. O. Bauer. 1993. Dynamics of beach-dune systems. Progress in Physical Geography 17 (4): 413-447 Short, A. D., and P. A. Hesp. 1982. Wave, beach and dune interactions in South Eastern Australia. Marine Geology 48: 259-284.

Corbau, Corinne; Simeoni, Umberto

2014-05-01

303

Solar collection  

NASA Astrophysics Data System (ADS)

Solar dishes, photovoltaics, passive solar building and solar hot water systems, Trombe walls, hot air panels, hybrid solar heating systems, solar grain dryers, solar greenhouses, solar hot water worhshops, and solar workshops are discussed. These solar technologies are applied to residential situations.

Cole, S. I.

1984-08-01

304

Tidal dunes versus tidal bars: The sedimentological and architectural characteristics of compound dunes in a tidal seaway, the lower Baronia Sandstone (Lower Eocene), Ager Basin, Spain  

NASA Astrophysics Data System (ADS)

The Lower Eocene Baronia Formation in the Ager Basin is interpreted as a series of stacked compound dunes confined within a tectonically generated embayment or tidal seaway. This differs from the previous interpretation of lower Baronia sand bodies as tidal bars in the front of a delta. The key architectural building block of the succession, the deposit of a single compound dune, forms a 1-3 m-thick, upward coarsening succession that begins with highly bioturbated, muddy, very fine to fine grained sandstone that contains an open-marine Cruziana ichnofacies. This is overlain gradationally by ripple-laminated sandstone that is commonly bioturbated and contains mud drapes. The succession is capped by fine- to coarse-grained sandstones that contain both planar and trough cross-strata with unidirectional or bi-directional paleocurrent directions and occasional thin mud drapes on the foresets. The base of a compound dune is gradational where it migrated over muddy sandstone deposited between adjacent dunes, but is sharp and erosional where it migrated over the stoss side of a previous compound dune. The cross strata that formed by simple superimposed dunes dip in the same direction as the inclined master bedding planes within the compound dune, forming a forward-accretion architecture. This configuration is the fundamental reason why these sandbodies are interpreted as compound tidal dunes rather than as tidal bars, which, in contrast, generate lateral-accretion architecture. In the Baronia, fields of compound dunes generated tabular sandbodies 100s to 1000s of meters in extent parallel to the paleocurrent direction and up to 6 m thick that alternate vertically with highly bioturbated muddy sandstones (up to 10 m thick) that represent the low-energy fringes of the dune fields or periods of high sea level when current speeds decreased. Each cross-stratified sandstone sheet (compound-dune complexes) contains overlapping lenticular "shingles" formed by individual compound dunes, separated by 10-30 cm of bioturbated muddy sandstone, which migrated over each other in an offlapping, progradational fashion. Each compound-dune complex (the best reservoir rock) thins as it downlaps, at average rates of 3-4 m/km in a dip direction. These reservoir units can be comprised of discrete compartments, each formed by a single compound dune, that extend for 500-1000 m in the direction of the current, and are at least 350-600 m wide in a flow-transverse direction. Distinguishing between tidal bars and tidal dunes in an ancient tidal succession can be difficult because both can contain similar cross-bedded facies and have overlapping thicknesses; however, the internal architecture and sandbody orientations are different. Tidal bars have their long axis almost parallel both to the tidal current direction and to the strike of the lateral-accretion master surfaces. In inshore areas, they are bounded by channels and fine upward. Large compound tidal dunes, in contrast, have their crest oriented approximately normal to the tidal currents and contain a forward-accretion architecture. Coeval channels are uncommon within large, sub-tidal dune fields. The above distinctions are very important to reservoir description and modeling, because the long axis of the intra-reservoir compartments in the two cases will be 90° apart.

Olariu, Cornel; Steel, Ronald J.; Dalrymple, Robert W.; Gingras, Murray K.

2012-11-01

305

Dune recovery after storm erosion on a high-energy beach: Vougot Beach, Brittany (France)  

NASA Astrophysics Data System (ADS)

On 10th March 2008, the high energy storm Johanna hit the French Atlantic coast, generating severe dune erosion on Vougot Beach (Brittany, France). In this paper, the recovery of the dune of Vougot Beach is analysed through a survey of morphological changes and hydrodynamic conditions. Data collection focused on the period immediately following storm Johanna until July 2010, i.e. over two and a half years. Results showed that the dune retreated by a maximum of almost 6 m where storm surge and wave attack were the most energetic. Dune retreat led to the creation of accommodation space for the storage of sediment by widening and elevating space between the pre- and post-storm dune toe, and reducing impacts of the storm surge. Dune recovery started in the month following the storm event and is still ongoing. It is characterised by the construction of "secondary" embryo dunes, which recovered at an average rate of 4-4.5 cm per month, although average monthly volume changes varied from - 1 to 2 m 3.m - 1 . These embryo dunes accreted due to a large aeolian sand supply from the upper tidal beach to the existing foredune. These dune-construction processes were facilitated by growth of vegetation on low-profile embryo dunes promoting backshore accretion. After more than two years of survey, the sediment budget of the beach/dune system showed that more than 10,000 m 3 has been lost by the upper tidal beach. We suggest that seaward return currents generated during the storm of 10th March 2008 are responsible for offshore sediment transport. Reconstitution of the equilibrium beach profile following the storm event may therefore have generated cross-shore sediment redistribution inducing net erosion in the tidal zone.

Suanez, Serge; Cariolet, Jean-Marie; Cancouët, Romain; Ardhuin, Fabrice; Delacourt, Christophe

2012-02-01

306

Hazard Impact And Genetic Development Of SandDunes West Of Nile Valley Egypt Egypt  

NASA Astrophysics Data System (ADS)

A SE. dune field extends west of Nile Vally (west Samalut). The dune movement and sand encroachment on the cultivated fields along the margins of the Nile flood plain represents a permanent threat to soil productivity and agricultural production in this region. In this study, the dunes has been investigated by producing geological and geomorphological maps by using Landsa ETM images for the area surrounding the dune field. Fifty sand samples had been collected from sand dunes and 5 samples were collected from substratum. Each field observation locality could be considered as a profile across the sand dune direction of movements. The sand samples are sieved and the separate samples weighed. Carrying out the collective diagrams using the computer program SITA. The granulometric indices were calculated, that is the mean grain diameter, standard deviation (measure of sorting) and skeweens Besides the sand grain features were analyzed, that is grain rounding with the use of a graniformameter, and by undertaking laboratory investigations on samples collected from various dunes. The laboratory investigations involve different granulometric parameters such as the grain rounding and frosting in the binocular microscope and morphoscopic studies. Morphoscopic studies using scanning electronic microscope (SEM) elucidate the surface process affected on sand grains. These dunes seem to have their source from a location found to the north, east and from the substratum of the dunes probably from the extensive sand and gravel deposits of Oligocene and Miocene and Quaternary age. While the sand are shiny and more rounded mat grains in the northern part of these dunes to fluvial processes. However it is not excluded that part of the sediments of the dunes are old intensively reworked aeolian sediments moving in the Western Desert during various arid phases of the Quaternary. SE movement of sands due to wind and become more markedly "aeolinized" in this direction by including less rounded and striated sand grains. They also include less clay material toward the south.

Asayed El Gammal, El; El Din El Sayed, Alaa

2010-05-01

307

Bed load and suspended load contributions to migrating sand dunes in equilibrium  

NASA Astrophysics Data System (ADS)

dominate the bed of sand rivers and are of central importance in predicting flow roughness and water levels. The present study has focused on the details of flow and sediment dynamics along migrating sand dunes in equilibrium. Using a recently developed acoustic system (Acoustic Concentration and Velocity Profiler), new insights are obtained in the behavior of the bed and the suspended load transport along mobile dunes. Our data have illustrated that, due to the presence of a dense sediment layer close to the bed and migrating secondary bedforms over the stoss side of the dune toward the dune crest, the near-bed flow and sediment processes are significantly different from the near-bed flow and sediment dynamics measured over fixed dunes. It was observed that the shape of the total sediment transport distribution along dunes is mainly dominated by the bed load transport, although the bed load and the suspended load transport are of the same order of magnitude. This means that it was especially the bed load transport that is responsible for the continuous erosion and deposition of sediment along the migrating dunes. Whereas the bed load is entirely captured in the dune with zero transport at the flow reattachment point, a significant part of the suspended load is advected to the downstream dune depending on the flow conditions. For the two flow conditions measured, the bypass fraction was about 10% for flow with a Froude number (Fr) of 0.41 and 27% for flow with Froude number of 0.51. This means that respectively 90% (for the Fr = 0.41 flow) and 73% (for the Fr = 0.51 flow) of the total sediment load that arrived at the dune crests contributed to the migration of the dunes.

Naqshband, S.; Ribberink, J. S.; Hurther, D.; Hulscher, S. J. M. H.

2014-05-01

308

Functional Traits Differ between Cereal Crop Progenitors and Other Wild Grasses Gathered in the Neolithic Fertile Crescent  

PubMed Central

The reasons why some plant species were selected as crops and others were abandoned during the Neolithic emergence of agriculture are poorly understood. We tested the hypothesis that the traits of Fertile Crescent crop progenitors were advantageous in the fertile, disturbed habitats surrounding early settlements and in cultivated fields. We screened functional traits related to competition and disturbance in a group of grass species that were increasingly exploited by early plant gatherers, and that were later domesticated (crop progenitors); and in a set of grass species for which there is archaeological evidence of gathering, but which were never domesticated (wild species). We hypothesised that crop progenitors would have greater seed mass, growth rate, height and yield than wild species, as these traits are indicative of greater competitive ability, and that crop progenitors would be more resilient to defoliation. Our results show that crop progenitors have larger seed mass than wild species, germinate faster and have greater seedling size. Increased seed size is weakly but positively correlated with a higher growth rate, which is primarily driven by greater biomass assimilation per unit leaf area. Crop progenitors also tend to have a taller stature, greater grain yield and higher resilience to defoliation. Collectively, the data are consistent with the hypothesis that adaptations to competition and disturbance gave crop progenitors a selective advantage in the areas surrounding early human settlements and in cultivated environments, leading to their adoption as crops through processes of unconscious selection. PMID:24489941

Cunniff, Jennifer; Wilkinson, Sarah; Charles, Michael; Jones, Glynis; Rees, Mark; Osborne, Colin P.

2014-01-01

309

Sedimentological and Mineralogical Evaluation of Sand Deposits in Crescent City, California, to Estimate their Mode of Deposition: Paleotsunami or Storm  

NASA Astrophysics Data System (ADS)

Differentiating storm from tsunami deposits in the geologic record is often difficult to do based on the visible characteristics exposed in outcrops or cores. Such is the case for sandy deposits identified in the subsurface of a marsh north of Crescent City in coastal northwest California. Of five sand units recorded, the lowest deposit was previously determined to be the tsunami deposit associated with the AD 1700 earthquake in the Cascadia Subduction Zone, but the depositional history of the four overlying sand units was unknown. In order to determine the mode of deposition for the four unidentified sand units, 35 sand samples from the five units in the core and as well as eight samples from the modern beach adjacent to the marsh, were processed and tested for variations in particle size and sorting, as well as grain shape, dominate mineralogy, and microscopic textures on individual sand grains. The four unidentified sand units from the core shared more similarities with the modern beach samples than did the samples of the tsunami deposit. The tsunami deposit differs from the modern beach and unidentified core samples based on mean particle size, particle shape, and microtextures as revealed with a scanning electron microscope. Therefore, the upper four sand units were likely emplaced by different hydrodynamic processes than the tsunami deposit, and not deposited by a tsunami, but rather washover from storm generated waves.

Robinson, M.; Hemphill-Haley, E.

2013-12-01

310

How much liquid water was there on Martian dunes?  

NASA Astrophysics Data System (ADS)

Presently, liquid water unlikely to be found on the surface of Mars because of atmospheric pressure/temperature conditions below water's triple-point. However, gullies discovered by Malin and Edgett (2000) suggest that significant amounts of liquid water has flowed on Mars in the recent past. These gullies are among the youngest features on Mars based on the scarcity of cratered gullies (Heldmann et al., 2007) and their superposition on relatively young formations such as dunes. Several hypotheses have been suggested for the formation of gullies: (i) runoff and debris flows with liquid water from groundwater aquifers (Heldmann and Mellon, 2004; Malin et al., 2000), (ii) snow-melt (Christensen, 2003; Dickson et al, 2007), (iii) liquid CO2 breakout (Musselwhite et al., 2001), (iv) melting of near-surface ground ice (< 1 m meter) at high obliquity (Costard et al., 2002), (v) geothermal-heated aquifers (Gaidos, 2001; Hartmann, 2001), (vi) the presence of brines (Knauth et al., 2000; Knauth and Burt, 2003). This study focuses on gully morphologies on the Russell megadune (54.5°S; 12.7°E) and in Kaiser crater (46.2°S; 19.1°E) using High Resolution Imaging Science Experiment (HiRISE) images and Digital Terrain Models (DTM). Gullies on terrestrial sand dunes are rare, and their presence on Mars, as well as their mechanical properties, and the quantity of fluid required for their formation currently remain misunderstood. Based on the scenario of ground ice melting in a periglacial environment, we propose to test the hypothesis that Martian gullies on dunes were triggered by the presence of liquid water. The calculated results for Martian gullies are consistent with terrestrial studies on debris flows. Based on a morphological description and on the estimated physical parameters, we propose a model for gully formation on Martian dunes. The melt water from near-surface ground ice is incorporated in the debris flow and water concentration increases during its propagation. The increase of water concentration in the debris flow can be explained by a progressive increase of water/ice content in the permafrost downslope. Consequently, the lack of a final deposit at the front of some gullies tends to demonstrate that the flow became relatively highly concentrated in liquid downstream and all the water could have been lost in the final stage of the flow. Here we quantify the quantity of liquid necessary to form such a morphology.

Gargani, J.; Jouannic, G.; Costard, F.; Ori, G. G.; Marmo, C.; Schmidt, F.; Lucas, A.; Busson, J.

2012-04-01

311

Association d'une cytost?aton?crose n?onatale, d'une hypertriglyc?ridemie et d'une hypercalc?mie: ? propos d'une observation  

PubMed Central

La cytostéatonécrose du nouveau-né est une hypodermite aigue qui apparaît dans les premières semaines de vie. Nous rapportons les caractéristiques cliniques et histologiques d’une cytostéatonécrose chez un nourrisson âgé de trois semaines, admis pour des lésions cutanées à type de placards sous-cutanées dures, localisées sur le dos. Le nouveau-né a développé une hypercalcémie et une hypertriglycéridemie d’évolution favorable sous traitement symptomatique de même que les lésions cutanées qui ont disparu en quelques semaines. PMID:22514760

Abilkassem, Rachid; Dini, Nezha; Oukabli, Mohamed; Kmari, Mohamed; Agadr, Aomar

2012-01-01

312

Water Use for Cultivation Management of Watermelon in Upland Field on Sand Dune  

NASA Astrophysics Data System (ADS)

Early-maturing cultivation of watermelon in a plastic tunnel was invetigated in upland field on sand dune on the coast of the Japan Sea to find water use to control blowing sand and to transplant seedlings. This region has low precipitation, low humidity, and strong wind in March and April, when sand is readily blown in the field. Water is used to control blowing sand on days with precipitation below 5 mm, minimum humidity below the meteorological average in April, and maximum wind velocity above the meteorological average in April. For the rooting and growth of watermelon seedlings, soil temperature needs to be raised because it is low in April. Ridges are mulched with transparent, porous polyethylene films 10 or more days before transplanting the seedlings and irrigated with sprinklers on fine days for the thermal storage of solar energy. The stored heat steams the mulched ridges to raise soil temperature to 15°C or higher on the day of transplanting the seedlings. The total amount of irrigation water used for watermelon cultivation was 432.7 mm, of which 23.6 mm was for blowing sand control and 26.6 mm was for transplanting the seedlings. The combined amount, 50.2 mm, is 11.6% of the total amount of water used for cultivation management.

Hashimoto, Iwao; Senge, Masateru; Itou, Kengo; Maruyama, Toshisuke

313

Interpreting and modelling late Quaternary dune accumulation in the southern Arabian Peninsula  

NASA Astrophysics Data System (ADS)

One of the fundamental questions in the reconstruction of Quaternary dryland environmental conditions is: what do dune OSL ages mean in terms of palaeoenvironmental change? This paper investigates the relationship between dune chronological records and external environmental forcing in the southern Arabian Peninsula during the last 30 ka. Aeolian records from the region are reviewed with reference to other regional palaeoenvironmental proxies, and these findings are related to a modelled assessment of dune response to the aeolian system state of the northeastern Rub' al Khali. The model replicates a range of features of the regional dune chronology when forced by three external parameters (sediment supply, sediment availability, and transport capacity), including extensive regional dune accumulation during the late Pleistocene-Holocene transition and reduced activity during the early Holocene humid period. Dune chronologies incorporate the influence of both external forcing parameters and localised short-term factors included as stochastic processes. Thick sedimentary units most likely represent external forcing conditions conducive to aeolian sediment transport and deposition, but at the same time these factors may be represented by periods of erosion of sediment at different sites. Confident interpretation of past environmental conditions is therefore not possible based on results from individual stratigraphic records. Sampling at multiple locations is needed in order to distinguish dune accumulation and preservation due to external forcing from stochastic processes of dune development.

Leighton, Carly L.; Bailey, Richard M.; Thomas, David S. G.

2014-10-01

314

The Role of Storm Winds in Shaping Dunes Along Southern and Southeastern Lake Michigan  

Microsoft Academic Search

It has been hypothesized that rates of coastal dune growth and migration depend largely on the frequency and intensity of storms. We are pooling observations from three separate research sites to study effects of storms along Lake Michigan. At our southern site, Indiana Dunes National Lakeshore, we use marked trees and erosion pins to monitor sand movement on two large

Brian P Yurk; Brian E Bodenbender; Z Kilibarda; D van Dijk; Edward C Hansen

2011-01-01

315

PROVOST ET AL. : LAMBDA-CYHALOTHRINE ET PRDATEURS INTRAGUILDES Impact d'une dose subltale de  

E-print Network

1 PROVOST ET AL. : LAMBDA-CYHALOTHRINE ET PR�DATEURS INTRAGUILDES Impact d'une dose sublétale de lambda-cyhalothrine sur les prédateurs intraguildes d'acariens phytophages en vergers de pommiers internationale francophone d'entomologie - Montréal 2002 Les impacts d'une dose sublétale de lambda-cyhalothrine

Lucas, Ã?ric

316

Quantifying Landscape \\/ Ecological Succession in a Coastal Dune System Using Sequential Aerial Photography and GIS  

Microsoft Academic Search

This chapter presents an attempt to measure the path of habitat and vegetation succession in a coastal dune system (Kenfig NNR, south Wales) using remote sensing and GIS. The loss of slack habitats associated with the continuing stabilization of this dune system is a major cause for concern. These habitats support a range of plant species, including the rare fen

S. Shanmugam; M. Barnsley

317

Classification and ordination of coastal sand dune vegetation along the Gulf and Caribbean Sea of Mexico  

Microsoft Academic Search

A classification is presented of community types found in the coastal sand dune systems along the Gulf coast and the Caribbean Sea of Mexico. Twenty-eight dune systems were sampled along transects using the Braun-Blanquet approach. A total of 4444 relevés were subjected to agglomerative classification and table arrangement (program TABORD). Synoptic species values were calculated for the 396 clusters obtained.

Patricia Moreno-Casasola I; Ileana Espejel

1986-01-01

318

Holocene coastal dune development and environmental changes in Apulia (southern Italy)  

Microsoft Academic Search

The coastal area of southern Apulia is characterised by marine deposits of Pleistocene and Holocene ages. It shows the effects of different phases of coastal morphology evolution. During the Middle and Upper Pleistocene, a number of marine terraces were shaped. In some places, they are characterised by thin beach deposits along with a dune belt and relative back dune deposits.Two

Giuseppe Mastronuzzi; Paolo Sansò

2002-01-01

319

Sand movement as a factor in the distribution of plant communities in a coastal dune system  

Microsoft Academic Search

The semi-mobile coastal sand dune system El Morro de La Mancha at the Gulf of Mexico was studied phytosociologically and ecologically. The floristic gradient resulting from a relevé ordination was correlated with the amount of sand movement occurring on the site of each relevé, and the topography of the dune.

Patricia Moreno-Casasola

1986-01-01

320

Geospatial analysis of a coastal sand dune field evolution: Jockey's Ridge, North Carolina  

E-print Network

Geospatial analysis of a coastal sand dune field evolution: Jockey's Ridge, North Carolina Helena Carolina 1. Introduction Highly dynamic coastal topography, characterized by rapidly moving sand dunes and effective management of highly dynamic coastal features located in areas under development pressures

Mitasova, Helena

321

Adaptations enhancing survival and establishment of seedlings on coastal dune systems  

Microsoft Academic Search

Studies on the survival and establishment of seedlings in coastal and lacustrine sand dune systems suggest that nutrient deficiency, lack of moisture, sand accretion, salt spray and predation are probably the most important limiting factors. Seedlings employ both avoidance and tolerance strategies to with-stand the different stresses. For example, seedling recruitment of dune species coincided with periods of high moisture

M. A. Maun

1994-01-01

322

Late-Holocene (post-4000 years BP) coastal dune development in Northumberland, northeast England  

Microsoft Academic Search

The recent environmental history of coastal dune systems in Northumberland, northeast England, has been examined using geomorphological, stratigraphical and sedimentological techniques linked to radiocarbon and infrared-stimulated luminescence (IRSL) dating. Stratigraphies were determined from 22 vibracores and three sections, and dune chronology was based on 28 14 C dates, from peat and soil organic horizons, and 26 IRSL dates on K-feldspar

Peter Wilson; Julian D. Orford; Jasper Knight; Sharon M. Braley; Ann G. Wintle

2001-01-01

323

Middle Holocene aridity, eolian-dune accretion, and the formation of Lake Mattamuskeet, eastern North Carolina  

NASA Astrophysics Data System (ADS)

The stratigraphic record of Lake Mattamuskeet, eastern North Carolina, shows an interval of eolian activity in the middle Holocene. There are about 500,000 elliptical lakes, wetlands, and depressions with elevated rims located on the Atlantic Coastal Plain named Carolina Bays. Lake Mattamuskeet is the largest (162 km2; mean depth 1.0 m), and formed when a blowout depression of a parabolic dune flooded 1540-1635 cal yr. BP. The parabolic dune is up to 2.0-m thick, contains sedimentary structures that indicate rapid deposition, and is composed of a coarsening-upward sequence of silt at the base to sandy silt at the top. Below the dune is an 8420-8605 cal yr. BP paleosol, which corresponds to a wet period in the area. The bottom half of the dune deposit contains abundant charcoal beds and laminae dated at ~6600 cal yr. BP, indicating fire was associated with initial formation of the parabolic dune. Middle Holocene climate of the southeast Atlantic coastal plain is not well constrained. Deposition of the eolian dune could be a local response to fire; or indicate a time of reduced effective moisture in the area. Given that pedogenesis on the dune did not initiate until ~2780-2965 cal yr. BP and flooding of the Lake basin did not occur for ~1000 years after that, effective moisture may have been low for approximately 3600 years after initial dune accretion.

Rodriguez, A. B.; Waters, M. N.; Piehler, M. F.

2009-12-01

324

In rivers, ripples and dunes are patterns at two well-separated wavelengths , that are respectively  

E-print Network

In rivers, ripples and dunes are patterns at two well-separated wavelengths , that are respectively are much shorter than those of the bedform growth, the under- standing of pattern formation in rivers can role of the free surface, we evidence that river dunes can not form from a linear instability. Finally

Claudin, Philippe

325

AlAbAmA Dune RestoRAtion PRoject General Project DescriPtion  

E-print Network

by the Deepwater Horizon oil spill response efforts. Dune habitat in Alabama has been affected by the Deepwater Horizon oil spill, including response efforts. The Trustees plan to restore 55 acres of primary dune of the Deepwater Horizon oil spill, including response efforts. The project will help restore an area of the beach

326

Climbing and falling dunes in Valles Marineris, Mars Matthew Chojnacki,1  

E-print Network

Click Here for Full Article Climbing and falling dunes in Valles Marineris, Mars Matthew Chojnacki. Newly acquired Mars Reconnaissance Orbiter (MRO) images and topography of the walls of Valles Marineris, and D. M. Burr (2010), Climbing and falling dunes in Valles Marineris, Mars, Geophys. Res. Lett., 37, L

Perfect, Ed

327

Large-eddy Simulation of Boundary Layer Flow over Desert Sand Dune Structures  

NASA Astrophysics Data System (ADS)

Complex spatiotemporal coupling exists between desert sand dune topography and surface layer physics of the atmospheric boundary layer (ABL). Although the interactions of individual desert sand dunes have been extensively studied, with categorical interaction mechanisms identified, the aero-mechanical coupling associated with these dune interactions remains an open problem. Large-eddy simulation (LES) is used to simulate turbulent boundary layer flow over dune structures from White Sands, NM. The dunes are resolved with an immersed boundary method (IBM). The flow-forcing (imposed pressure gradient) is varied to simulate the three common prevailing wind conditions at White Sands (southwest, southeast, and northwest, with southwest being the most common). In the present research, comparison between flow statistics (dune wall pressure distribution retrieved from the IBM) and time-difference dune elevation data are used to characterize the mechanisms responsible for erosion (stoss side) and deposition (lee side) of sand. Additionally, statistical details of time series of aerodynamic forcing at different locations on the dune face are evaluated, which may be used to deepen understanding of erosion and deposition events observed in the time-difference lidar data.

Uhlrich, S.; Anderson, W.; Passalacqua, P.; Mohrig, D. C.; Kocurek, G.

2012-12-01

328

Quantifying vegetation and geomorphic patterns within nebkha dune fields using terrestrial laser scanning  

NASA Astrophysics Data System (ADS)

Vegetation and sand in semi-arid and coastal sediment starved environments typically interact and form nebkha dunes. We examine the typical dune and vegetation patterns that form with varying amounts of sediment availability and nebkha maturity at Jornada in the Chihuahuan Desert, New Mexico, USA using terrestrial laser scanning (TLS) to separate the plant and sand elements. Manual and automated TLS shrub height extractions compare well at all sites (p=0.48-0.94) enabling the quantification of both solid and plant roughness element components. We find that there is a switch in orientation of the dune elements with respect to dominant wind direction from perpendicular to parallel as the landscape develops from an incipient to mature configuration and mesquite-nebkha streets are enhanced. As the nebkha dunes develop the surface coverage of bare sand increases and dune surfaces exceed the size of their companion shrubs. Roughness density also increases at the mature dune site. Over a three year period up to 20cm of erosion was measured on the upwind faces of the mature nebkha dunes, in agreement with the dominant annual wind direction. However, deposition patterns were more diffuse and influenced by the vegetation patterns. TLS is a useful tool for examining complex sand-vegetation interactions and dune field development.

Nield, Joanna; Gillies, John; Nickling, William

2014-05-01

329

Sand dune mobility under climate change in the Kalahari and Australian deserts  

E-print Network

maps of DP are introduced, based on real and reanalysis data. Analyses of two global circulation models global warming scenario. According to the GFDL model, both the Australian and Kalahari basin dunes of stabilized dunes in the world, and changes in their mobility have significant economic implications. Global

Ashkenazy, Yossi "Yosef"

330

The Influence of Complex Systems Interactions on Barrier Island Dune Vegetation Pattern and Process  

Microsoft Academic Search

Studies of dune vegetation patterns have emphasized two structuring agents: local environmental gradients that shape the prominent zonation of coastal plant species, and disturbance patches initiated by overwash during coastal storms. For dune systems of two barrier islands in the Georgia Bight, we investigate how the interplay of these two conceptual frames generate patterns in (1) longitudinal (along-shore) and transverse

J. Anthony Stallins; Albert J. Parker

2003-01-01

331

Multifrequency and multipolarization radar scatterometry of sand dunes and comparison with spaceborne and airborne radar images  

NASA Technical Reports Server (NTRS)

Airborne radar scatterometer data on sand dunes, acquired at multiple frequencies and polarizations, are reported. Radar backscatter from sand dunes is very sensitive to the imaging geometry. At small incidence angles the radar return is mainly due to quasi-specular reflection from dune slopes favorably oriented toward the radar. A peak return usually occurs at the incidence angle equal to the angle of repose for the dunes. The peak angle is the same at all frequencies as computed from specular reflection theory. At larger angles the return is significantly weaker. The scatterometer measurements verified observations made with airborne and spaceborne radar images acquired over a number of dune fields in the U.S., central Africa, and the Arabian peninsula. The imaging geometry constraints indicate that possible dunes on other planets, such as Venus, will probably not be detected in radar images unless the incidence angle is less than the angles of repose of such dunes and the radar look direction is approximately orthogonal to the dune trends.

Blom, Ronald; Elachi, Charles

1987-01-01

332

Analysis of coastal dune dynamics, shoreline position, and large woody debris at Wickaninnish  

E-print Network

Analysis of coastal dune dynamics, shoreline position, and large woody debris at Wickaninnish Bay, Pacific Rim National Park, British Columbia Derek K. Heathfield and Ian J. Walker Abstract: Large woody debris (LWD) and colonizing vegetation alter the sediment budgets and stability of coastal dune systems

333

Individual versus community level processes and pattern formation in a model of sand dune plant succession  

Microsoft Academic Search

A cellular automata model of a sand dune plant community on Galveston Island, Texas, USA was utilized to test hypotheses regarding individual plant interactions and their impact upon community organization. Simulations demonstrated that both an environmental gradient and facilitative succession resulted in the formation of characteristic sand dune patterns. The results showed that the plant patterns were due to individual

R. A. Feagin; X. B. Wu; F. E. Smeins; S. G. Whisenant; W. E. Grant

2005-01-01

334

Microbial Nitrogen and Sulfur Cycles at the Gypsum Dunes of White Sands National Monument, New Mexico  

Microsoft Academic Search

The White Sands National Monument from New Mexico (U.S.A) contains one of the largest known gypsum dune fields with unique, rapidly migrating, arid, evaporitic habitats. Deposits from dune sides and interdune areas were collected in order to determine the characteristics of microbial habitat and communities through mineral assemblages, microbial pigments along with investigations of nitrogen and sulfur cycles. The most

Mihaela Glamoclija; Marilyn L. Fogel; Andrew Steele; Adrienne Kish

2012-01-01

335

Florida (Pensacola Beach) dune restoration Project General Project DescriPtion  

E-print Network

of wildlife habitat and private property due to hurricanes, sea level rise, oil spills and other threatsFlorida (Pensacola Beach) dune restoration Project General Project DescriPtion The project 2010. The primary dunes are the first natural line of defense for coastal Florida to prevent the loss

336

The growth responses of coastal dune species are determined by nutrient limitation and sand burial  

Microsoft Academic Search

Past work suggests that burial and low nutrient availability limit the growth and zonal distribution of coastal dune plants. Given the importance of these two factors, there is a surprising lack of field investigations of the interactions between burial and nutrient availability. This study aims to address this issue by measuring the growth responses of four coastal dune plant species

Matthew Gilbert; Norman Pammenter; Brad Ripley

2008-01-01

337

Invasive grasses, climate change, and exposure to storm-wave overtopping in coastal dune ecosystems  

E-print Network

result in increased risk of flooding in coastal areas. In the Pacific Northwest (USA), coastal dunesInvasive grasses, climate change, and exposure to storm-wave overtopping in coastal dune ecosystems, OR 97331-2914, USA, §AECOM, Long Beach, CA 90810, USA Abstract The world's coastal habitats are critical

338

Modeling the SAR backscatter of linear dunes on Earth and Titan  

NASA Astrophysics Data System (ADS)

We modeled the Synthetic Aperture Radar (SAR) response of linear dunes of the Great Sand Sea in Egypt using a single surface scattering term, based on Integral Equation and Physical Optics Models. Using multi-frequency SIR-C/X-SAR radar scenes and topography obtained from the Shuttle Radar Topography Mission (SRTM), we were able to estimate reasonable values for the parameters describing the surface roughness of the dunes. As the linear dunes of the Great Sand Sea are relevant analogs for the linear dunes observed on Titan by the Cassini Radar instrument, these results were thus used as a starting point to simulate the radar response of Titan's dunes, as imaged by the Radar instrument onboard the Cassini spacecraft during the T8 flyby in October 2005. We show that a single surface scattering term is not sufficient to simulate the radar signal backscattered by the dunes on Titan: one has to add a diffuse scattering term, indicating that Titan's dunes are likely to have somewhat inhomogeneous internal structures related to porosity and/or internal layering. Our results also indicate that the dunes on Titan should be close to perfectly smooth, possibly because of the formation of smaller ripples than on Earth, plus smoothing resulting from precipitation events.

Paillou, Ph.; Bernard, D.; Radebaugh, J.; Lorenz, R.; Le Gall, A.; Farr, T.

2014-02-01

339

Preliminary investigations into recent changes of the Goukamma Nature Reserve frontal dune system, South Africa — With management implications  

Microsoft Academic Search

The Goukamma ‘delta’ dune field, pre-1930s, functioned more or less ‘naturally’ since the post-glacial nested-parabolic dune pulses. This dune field, approximately 204 ha in extent, acted as a sediment sink for wind-blown marine derived sands and a surface over which the Goukamma River meandered.Stabilisation of this dune system with Acacia cyclops and Ammophila arenaria in the early 1930s resulted, through

G. B. Hellström

1996-01-01

340

Mapping a local Dune Field, and estimating paleowind speed and direction  

NSDL National Science Digital Library

Students map one large hairpin parabolic dune in the Pinebush Preserve. They also profile the slopes on both proximal and distal sides of the dune. As a group, we take an ~ 2m long core of the dune sand to sample the sand beneath the soil profile. In the lab, students measure the particle size distribution of their sand samples, map the whole dune field from aerial photographs and a DEM, and estimate paleo-wind speed and direction. They then compare these data with modern wind data (available from the web) to answer the question of .just how different conditions were when the dune field was deposited Uses online and/or real-time data Addresses student fear of quantitative aspect and/or inadequate quantitative skills Uses geomorphology to solve problems in other fields

Rodbell, Donald

341

Vegetation and substrate properties of aeolian dune fields in the Colorado River corridor, Grand Canyon, Arizona  

USGS Publications Warehouse

This report summarizes vegetation and substrate properties of aeolian landscapes in the Colorado River corridor through Grand Canyon, Arizona, in Grand Canyon National Park. Characterizing these parameters provides a basis from which to assess future changes in this ecosystem, including the spread of nonnative plant species. Differences are apparent between aeolian dune fields that are downwind of where modern controlled flooding deposits new sandbars (modern-fluvial-sourced dune fields) and those that have received little or no new windblown sand since river regulation began in the 1960s (relict-fluvial-sourced dune fields). The most substantial difference between modern- and relict-fluvial-sourced aeolian dune fields is the greater abundance of biologic soil crust in relict dune fields. These findings can be used with similar investigations in other geomorphic settings in Grand Canyon and elsewhere in the Colorado River corridor to evaluate the health of the Colorado River ecosystem over time.

Draut, Amy E.

2011-01-01

342

Stratification and sedimentation in complex vegetated coastal dunes, Sable Island, Nova Scotia  

NASA Astrophysics Data System (ADS)

A descriptive code for analysing the internal structure of vegetated coastal dunes is presented. The code is based upon three elements—grain size, stratification, and the nature of plant remains. It is used in an analysis of the dunes on Sable Island, Nova Scotia. A description of the stratification within the older dunes of the island provides the basis for a genetic interpretation of the processes operating throughout their history. Particular importance is attached to the role of vegetation in deposition. Four phases of dune development, each with distinct styles of stratification, are recognized in the Sable Island dunes. The first consists of tractional and grainfall deposition within very sparse vegetation. The second phase is dominated by grainfall deposition through increasingly dense vegetation. The third phase is represented by a paleosol. Finally, the fourth phase consists of horizontal, parallel and wavy laminated beds of loosely compacted, finer sand which result from grainfall deposition through dense vegetation.

Byrne, M.-L.; McCann, S. B.

1990-03-01

343

A Comparison of Methods Used to Estimate the Height of Sand Dunes on Mars  

NASA Technical Reports Server (NTRS)

The collection of morphometric data on small-scale landforms from other planetary bodies is difficult. We assess four methods that can be used to estimate the height of aeolian dunes on Mars. These are (1) stereography, (2) slip face length, (3) profiling photoclinometry, and (4) Mars Orbiter Laser Altimeter (MOLA). Results show that there is good agreement among the methods when conditions are ideal. However, limitations inherent to each method inhibited their accurate application to all sites. Collectively, these techniques provide data on a range of morphometric parameters, some of which were not previously available for dunes on Mars. They include dune height, width, length, surface area, volume, and longitudinal and transverse profiles. Thc utilization of these methods will facilitate a more accurate analysis of aeolian dunes on Mars and enable comparison with dunes on other planetary surfaces.

Bourke, M. C.; Balme, M.; Beyer, R. A.; Williams, K. K.; Zimbelman, J.

2006-01-01

344

Holocene dune formation at Ash Meadows National Wildlife Area, Nevada, USA  

NASA Astrophysics Data System (ADS)

Small isolated dune fields in the northern Mojave Desert are important centers of biodiversity and archaeological occupation sites. Currently dunes at Ash Meadows, Nevada, are stabilized by vegetation and are experiencing erosion of their upwind margins, indicating a negative sediment budget. New OSL ages from dunes at Ash Meadows indicate continuous eolian accumulation from 1.5 to 0.8 ka, with further accumulation around 0.2 ka. Prior studies (e.g., Mehringer and Warren, 1976) indicate periods of dune accumulation prior to 3.3 ka; 1.9-1 ka; and after 0.9 ka. These periods of eolian accumulation are largely synchronous with those identified elsewhere in the Mojave Desert. The composition of the Ash Meadows dunes indicates their derivation from regional fluvial sources, most likely during periods when axial washes were active as a result of enhanced winter precipitation.

Lancaster, Nicholas; Mahan, Shannon A.

2012-09-01

345

The regeneration of soil micro-arthropod assemblages in a rehabilitating coastal dune forest at Richards Bay,  

E-print Network

The regeneration of soil micro-arthropod assemblages in a rehabilitating coastal dune forest related to soil properties. Our results suggest that coastal dune forest rehabilitation could give rise, 1998; Frouz et al., 2001). This is also true for a cordon of coastal dune forests in *Correspondence

Pretoria, University of

346

Aust. J. Mar. Freshwater Res., 1993, 44, 437-58 Limnological Characteristics of Two Coastal Dune Lakes,  

E-print Network

Aust. J. Mar. Freshwater Res., 1993, 44, 437-58 Limnological Characteristics of Two Coastal Dune Limnological features of two permanent, closed, coastal dune lakes that are separated by only about 400 m shown the common properties of coastal dune lakes to be low salinity dominated by Na+ and C1-, acidity

Canberra, University of

347

Influence des tempêtes sur la mobilité des dunes tidales dans le détroit du Pas-de-Calais  

Microsoft Academic Search

Influence of storms on tidal dune mobility in the Strait of Dover. The present paper deals with dune dynamics in a zone of the Strait of Dover located in the sea lane running into the North Sea. The dunes, widespread in this 35-m depth area, are mobile sedimentary structures (up to 40 m·yr?1) that culminate at a maximum of 22

Sophie LE BOT; Alain TRENTESAUX; Thierry GARLAN; Serge BERNE; Hervé CHAMLEY

2000-01-01

348

75 FR 45653 - Notice of Re-Opening of Comment Period for the Draft Imperial Sand Dunes Recreation Area...  

Federal Register 2010, 2011, 2012, 2013

...of Comment Period for the Draft Imperial Sand Dunes Recreation Area Management Plan and...the comment period on the Draft Imperial Sand Dunes Recreation Area Management Plan...California 92243. Copies of the Draft Imperial Sand Dunes RAMP/EIS are available in the...

2010-08-03

349

Cause rare d'une perforation de la cloison nasale  

PubMed Central

Les perforations de la cloison nasale constituent une pathologie fréquente en ORL. Leurs causes sont multiples et restent dominées par les traumatismes chirurgicaux. Les étiologies infectieuses et notamment la tuberculose sont rares. Nous présentons le cas d'une patiente ayant bénéficié d'une méatotomie bilatérale et chez laquelle une perforation de la cloison nasale a été découverte lors d'un examen systématique à un an de son intervention. D'abord considérée comme une complication de la chirurgie, la biopsie des berges de la perforation a permis de déterminer son origine tuberculeuse. La présentation clinique des perforations de la cloison nasale n'est pas spécifique. Elles sont souvent asymptomatiques et de découverte fortuite. Les traumatismes notamment chirurgicaux sont le plus siuvent en cause. L?orogine tuberculeuse resta très rare. Le diagnostic de certitude de tuberculose repose sur la biopsie des berges de cette perforation. Le but de ce travail est de mettre en avant l'intérêt de la biopsie dans le diagnostic de la tuberculose de la cloison nasale. Cette biopsie doit être systématique même en cas d'antécédents de chirurgie endonasale qui est le plus souvent en cause dans les perforations de la cloison nasale. PMID:24932334

Jahidi, Ali; Hemmaoui, Bouchaib; Itoua, Wulfran Rosaire; Errami, Noureddine; Benariba, Fouad

2014-01-01

350

Coupling the dynamics of boundary layers and evolutionary dunes.  

PubMed

A theoretical formulation and corresponding numerical solutions are presented for fluid flow and sediment transport past evolutionary sand dunes. Time-dependent curvilinear coordinates are employed to fully couple flow aloft with the developing landform. The differential conservation law that defines shape of the lower boundary depends on details of local surface stress, thereby favoring the large eddy simulation of the boundary layer. To shrink the gap between the time scales characteristic of planetary boundary layer flows O(10(3)) s and sand dune evolution O(10(6)) s, a hypothetical "severe-wind scenario" is adopted with the saltation flux amplified up to 3 orders of magnitude. While the results are largely insensitive to the rescaling, the efficacy of computations is greatly improved. The flux-form partial differential equation for the interface profile--via saltation and sand avalanches--is formulated as an advection-diffusion equation, to facilitate discrete integrations. Numerical experiments verify the adopted theoretical framework by reproducing scaling results reported in the literature. The versatility of the approach is illustrated with evolution of a sandhole--an example of application likely never addressed in the literature, yet realizable in nature. PMID:19518224

Ortiz, Pablo; Smolarkiewicz, Piotr K

2009-04-01

351

Sargassum as a natural solution to enhance dune plant growth.  

PubMed

Many beach management practices focus on creating an attractive environment for tourists, but can detrimentally affect long-term dune integrity. One such practice is mechanical beach raking in which the wrack line is removed from the beach front. In Texas, Sargassum fluitans and natans, types of brown alga, are the main components of wrack and may provide a subsidy to the ecosystem. In this study, we used greenhouse studies to test the hypothesis that the addition of sargassum can increase soil nutrients and produce increased growth in dune plants. We also conducted an analysis of the nutrients in the sargassum to determine the mechanisms responsible for any growth enhancement. Panicum amarum showed significant enhancement of growth with the addition of sargassum, and while Helianthus debilis, Ipomoea stolonifera, Sporobolus virginicus, and Uniola paniculata responded slightly differently to the specific treatments, none were impaired by the addition of sargassum. In general, plants seemed to respond well to unwashed sargassum and multiple additions of sargassum, indicating that plants may have adapted to capitalize on the subsidy in its natural state directly from the ocean. For coastal managers, the use of sargassum as a fertilizer could be a positive, natural, and efficient method of dealing with the accumulation of wrack on the beach. PMID:20859628

Williams, Amy; Feagin, Rusty

2010-11-01

352

Reactivation of supply-limited dune fields from blowouts: A conceptual framework for state characterization  

NASA Astrophysics Data System (ADS)

Aeolian dune fields mantle the Earth in both vegetated (stable) and unvegetated (active) states. Changes in state are poorly understood; in particular, little is known about reactivation (devegetation) from a vegetated state. Available evidence indicates that dune reactivation can be driven by changes in aridity, increased wind speed, fire, biogenic disturbance, human disturbance, or a combination of the previous. How these controls fit together and define the reactivation potential of dune fields is presently unknown. Here we develop a framework to describe reactivation potential for a specific case: presently vegetated, supply-limited dune fields that develop blowouts under a unidirectional wind. We first define a conceptual model of blowout expansion, and then split the functions of vegetation in a stable dune field into: (i) maintenance of a protective skin, and (ii) blowout suppression. We model reactivation as disturbance breaking through the protective skin, which forms a blowout that is either (i) suppressed by colonizer species, or (ii) capable of advancing downwind and reactivating part of the dune field. The capacity for disturbance to break through the protective skin is a function of disturbance magnitude, area, and resistance of the skin. The blowout suppression capacity of a dune field is a function of sediment flux, blowout depth (related to geomorphology), and colonizer species vitality. By plotting a given dune field with two variables (protective skin breach rate and blowout suppression capacity) we define four states: (i) stable, (ii) blowout dominated, (iii) reactivating, or (iv) stable but disturbance susceptible. We reinforce the conceptual model with qualitative examples and discussion of experiments on grassland-stabilized dunes in Canada. Overall, our framework provides a starting point for quantifying the reactivation potential of vegetated dune fields.

Barchyn, Thomas E.; Hugenholtz, Chris H.

2013-11-01

353

Uncertainty Assessment for Numerical Modeling of Dune and Backshore Evolution Under Sea-Level Rise Scenarios  

NASA Astrophysics Data System (ADS)

The beach dunes play an essential role in the evolution of barrier island shapes and coastlines. The dunes protect the beaches and beach ecology by absorbing energy from the storms and provide sediment to the beaches or backshores when erosion occurs. While a number of models have been developed to simulate the evolution of dunes and backshores, few of the models have comprehensively addressed dune growth, dune erosion, and backshore changes. Based on the assumption that dune shapes are stationary, we develop a new model that can estimate the dune and backshore evolution (including both growth and erosion) under the influence of storms with different sea-level rise scenarios. The modeling results are inherently uncertain due to unknown storm variability and sea-level rise scenarios. The storm uncertainty, characterized as parametric uncertainty, and its propagation to the modeling results are assessed using the Monte Carlo (MC) method. A total of 1500 realizations of storm magnitude, frequency, and track through a barrier island are generated and used for the MC simulation. The numerical modeling and uncertainty analysis is conducted for a synthetic barrier island with physical features and hurrucane exposure similar to Santa Rosa Island, in northwest Florida. Uncertainty in the simulated beach dune heights, dune width, and the backshore positions is assessed for five sea-level rise scenarios. The parametric uncertainty is different for different sea-level rise scenarios. For a given scenario, uncertainty of dune height is the largest and it is mainly caused by uncertainty in storm magnitude. This uncertainty analysis provides guidelines for coastal management and protection of coastal ecology.

Dai, H.; Ye, M.; Niedoroda, A. W.; Kish, S.; Donoghue, J. F.; Saha, B.

2010-12-01

354

Reticulated Origin of Domesticated Emmer Wheat Supports a Dynamic Model for the Emergence of Agriculture in the Fertile Crescent  

PubMed Central

We used supernetworks with datasets of nuclear gene sequences and novel markers detecting retrotransposon insertions in ribosomal DNA loci to reassess the evolutionary relationships among tetraploid wheats. We show that domesticated emmer has a reticulated genetic ancestry, sharing phylogenetic signals with wild populations from all parts of the wild range. The extent of the genetic reticulation cannot be explained by post-domestication gene flow between cultivated emmer and wild plants, and the phylogenetic relationships among tetraploid wheats are incompatible with simple linear descent of the domesticates from a single wild population. A more parsimonious explanation of the data is that domesticated emmer originates from a hybridized population of different wild lineages. The observed diversity and reticulation patterns indicate that wild emmer evolved in the southern Levant, and that the wild emmer populations in south-eastern Turkey and the Zagros Mountains are relatively recent reticulate descendants of a subset of the Levantine wild populations. Based on our results we propose a new model for the emergence of domesticated emmer. During a pre-domestication period, diverse wild populations were collected from a large area west of the Euphrates and cultivated in mixed stands. Within these cultivated stands, hybridization gave rise to lineages displaying reticulated genealogical relationships with their ancestral populations. Gradual movement of early farmers out of the Levant introduced the pre-domesticated reticulated lineages to the northern and eastern parts of the Fertile Crescent, giving rise to the local wild populations but also facilitating fixation of domestication traits. Our model is consistent with the protracted and dispersed transition to agriculture indicated by the archaeobotanical evidence, and also with previous genetic data affiliating domesticated emmer with the wild populations in southeast Turkey. Unlike other protracted models, we assume that humans played an intuitive role throughout the process. PMID:24312385

Civá?, Peter; Ivani?ová, Zuzana; Brown, Terence A.

2013-01-01

355

Plasma exchange or immunoadsorption in patients with rapidly progressive crescentic glomerulonephritis. A Swedish multi-center study.  

PubMed

A therapeutic removal of antibodies may be achieved by immunoadsorption (IA) or by plasma exchange (PE). The aim of this prospective randomised study was to compare the efficacy of these different techniques with regard to treatment of patients with rapidly progressive glomerulonephritis (RPG) having at least 50% crescents. Forty-four patients with a RPG were included for treatment either by IA or PE (with albumin as substitution for removed plasma). All patients were additionally treated with immunosuppression. A median of 6 sessions of PEs were performed in 23 patients compared with 6 IAs in 21 patients. Goodpasture's syndrome (GP) was present in 6 patients (PE 3, IA 3). All of them started and ended in dialysis, two died. Among the remaining 38 patients (26 men, 12 women) 87% had antibodies to ANCA. Creatinine clearance for PE versus IA were at a median at start 17.1 and 19.8 ml/min, and at 6 months 49 and 49 ml/min, respectively. At 6 months 7 of 10 patients did not need dialysis (remaining: IA 0/5 and PE 2/5, n.s.). The extent of improvement did not differ between the groups. Three patients died during the observation period of 6 months (IA 2; PE 1, on HD). Although no difference was found between the IA or the PE group this study shows that the protocol used was associated with an improved renal function in most patients (except for Goodpasture's syndrome) whereas 70% of them could leave the dialysis program. PMID:10212042

Stegmayr, B G; Almroth, G; Berlin, G; Fehrman, I; Kurkus, J; Norda, R; Olander, R; Sterner, G; Thysell, H; Wikström, B; Wirén, J E

1999-02-01

356

Association of the Vaccinia Virus A11 Protein with the Endoplasmic Reticulum and Crescent Precursors of Immature Virions  

PubMed Central

The apparent de novo formation of viral membranes within cytoplasmic factories is a mysterious, poorly understood first step in poxvirus morphogenesis. Genetic studies identified several viral proteins essential for membrane formation and the assembly of immature virus particles. Their repression results in abortive replication with the accumulation of dense masses of viroplasm. In the present study, we further characterized one of these proteins, A11, and investigated its association with cellular and viral membranes under normal and abortive replication conditions. We discovered that A11 colocalized in cytoplasmic factories with the endoplasmic reticulum (ER) and L2, another viral protein required for morphogenesis. Confocal microscopy and subcellular fractionation indicated that A11 was not membrane associated in uninfected cells, whereas L2 still colocalized with the ER. Cell-free transcription and translation experiments indicated that both A11 and L2 are tail-anchored proteins that associate posttranslationally with membranes and likely require specific cytoplasmic targeting chaperones. Transmission electron microscopy indicated that A11, like L2, associated with crescent membranes and immature virions during normal infection and with vesicles and tubules near masses of dense viroplasm during abortive infection in the absence of the A17 or A14 protein component of viral membranes. When the synthesis of A11 was repressed, “empty” immature-virion-like structures formed in addition to masses of viroplasm. The immature-virion-like structures were labeled with antibodies to A17 and to the D13 scaffold protein and were closely associated with calnexin-labeled ER. These studies revealed similarities and differences between A11 and L2, both of which may be involved in the recruitment of the ER for virus assembly. PMID:23864611

Maruri-Avidal, Liliana; Weisberg, Andrea S.

2013-01-01

357

Reticulated origin of domesticated emmer wheat supports a dynamic model for the emergence of agriculture in the fertile crescent.  

PubMed

We used supernetworks with datasets of nuclear gene sequences and novel markers detecting retrotransposon insertions in ribosomal DNA loci to reassess the evolutionary relationships among tetraploid wheats. We show that domesticated emmer has a reticulated genetic ancestry, sharing phylogenetic signals with wild populations from all parts of the wild range. The extent of the genetic reticulation cannot be explained by post-domestication gene flow between cultivated emmer and wild plants, and the phylogenetic relationships among tetraploid wheats are incompatible with simple linear descent of the domesticates from a single wild population. A more parsimonious explanation of the data is that domesticated emmer originates from a hybridized population of different wild lineages. The observed diversity and reticulation patterns indicate that wild emmer evolved in the southern Levant, and that the wild emmer populations in south-eastern Turkey and the Zagros Mountains are relatively recent reticulate descendants of a subset of the Levantine wild populations. Based on our results we propose a new model for the emergence of domesticated emmer. During a pre-domestication period, diverse wild populations were collected from a large area west of the Euphrates and cultivated in mixed stands. Within these cultivated stands, hybridization gave rise to lineages displaying reticulated genealogical relationships with their ancestral populations. Gradual movement of early farmers out of the Levant introduced the pre-domesticated reticulated lineages to the northern and eastern parts of the Fertile Crescent, giving rise to the local wild populations but also facilitating fixation of domestication traits. Our model is consistent with the protracted and dispersed transition to agriculture indicated by the archaeobotanical evidence, and also with previous genetic data affiliating domesticated emmer with the wild populations in southeast Turkey. Unlike other protracted models, we assume that humans played an intuitive role throughout the process. PMID:24312385

Civá?, Peter; Ivani?ová, Zuzana; Brown, Terence A

2013-01-01

358

Solar astronomy  

NASA Technical Reports Server (NTRS)

An overview is given of modern solar physics. Topics covered include the solar interior, the solar surface, the solar atmosphere, the Large Earth-based Solar Telescope (LEST), the Orbiting Solar Laboratory, the High Energy Solar Physics mission, the Space Exploration Initiative, solar-terrestrial physics, and adaptive optics. Policy and related programmatic recommendations are given for university research and education, facilitating solar research, and integrated support for solar research.

Rosner, Robert; Noyes, Robert; Antiochos, Spiro K.; Canfield, Richard C.; Chupp, Edward L.; Deming, Drake; Doschek, George A.; Dulk, George A.; Foukal, Peter V.; Gilliland, Ronald L.

1991-01-01

359

Stratigraphic evidence for late Quaternary dune activity near Hudson on the Piedmont of northern Colorado  

SciTech Connect

Stabilized dune fields are common features near Hudson, on the Piedmont of northern Colorado. Exposures in dune and interdune sites expose a sequence of eolian sediments and paleosols that record a complex history of eolian activity during the late Quaternary. Radiocarbon and thermoluminescence age estimates on A horizons buried by eolian sand indicate that dunes were reactivated sometime between 7 and 9 ka. On the basis of morphology of surface soils, the dunes were most recently stabilized <3 ka. At present that are no data to indicate if there were multiple periods of dune movement and stabilization during the Holocene. The penultimate pre-Holocene dune-forming episode probably terminated ca. 13 ka and may be coincident with the Pinedale glaciation. The stratigraphy at interdune sites shows at least two eolian depositional events prior to the penultimate event; they were separated by periods of pedogenesis, one of which may have exceeded 40 ka. This analysis indicates that dunes in northern Colorado were active during both cold-arid and warn-arid periods in the late Quaternary.

Forman, S.L.; Maat, P. (Univ. of Colorado, Boulder (USA))

1990-08-01

360

Evolution of late Holocene coastal dunes in the Cauvery delta region of Tamil Nadu, India  

NASA Astrophysics Data System (ADS)

Widespread occurrences of coastal dunes are observed in the Cauvery delta region of Tamil Nadu in Vedaranniyam in the south east coast of India. These dunes were studied to establish the chronology of their formation and to understand their evolution using optically stimulated luminescence (OSL) dating in combination with sedimentological studies (quartz grain surface morphology using scanning electron microscope, grain size and heavy mineral analysis). The study shows that on the south-east coast of India widespread periodic dune formation/reactivation has taken place during the late Holocene to very recent times due to a variety of reasons such as climatic variation and land use changes. The sand mobility index shows that the dunes in the area have been largely active during the past century in the southern part in Nagapattinam region and many of the crests were active in the northern Cauvery delta in Cuddalore region. The angularity and fresh appearance of sand in the inland dunes suggest a short distance of sand transport and a source proximal sand deposition was proposed for the dune formation. The study demonstrates the sensitivity of sand dunes on the south east coast of India to varying climatic conditions and changes in regional land use.

Alappat, L.; Frechen, M.; Ramesh, R.; Tsukamoto, S.; Srinivasalu, S.

2011-08-01

361

Shaping a dune with wind and frost in Matara crater, Mars  

NASA Astrophysics Data System (ADS)

Matara crater dune field exhibits a complex and fascinating geologic history. It first gained scientific attention when dune gullies (of alcove-channel-apron morphology, a few hundred meters to 3 km in length) were observed in MOC and HiRISE images to be actively evolving during the last Mars decade. Additionally, aeolian processes are clearly active within this field as the dune brinks are quite crisp in appearance, ripples on the surfaces of these dunes have been observed to migrate, and ripples have formed within sediment recently remobilized by dune-gully activity. This study seeks to understand how sediment has been redistributed/mobilized through both aeolian processes and seasonal processes leading to gully and ripple evolution. In particular, we focus on how ripples form and grow due to the wind, and are sometimes erased due to new deposition within the gully apron. We primarily focus on one very large dune-gully apron in Matara crater, where we have observed both dune-gully activity and new ripple formation over the last few Mars years. By mapping out regions with different ripple wavelengths - indicative of different ripple ages, we will examine how seasonal frost and aeolian processes have interacted over the last few decades to centuries.

Diniega, S.

2013-12-01

362

Imaging Sedimentary Structures of Monterey Bay Dune Complex in California Using Ground Penetrating Radar  

NASA Astrophysics Data System (ADS)

Numerous coastal dune studies have successfully used ground penetrating radar (GPR) to image sedimentary structures and correlate them with climatic variations and depositional history during the late Holocene. The Monterey Bay dune complex spans approximately 18 km of the Central California coastline and is the largest coastal dune complex in Central and Northern California. A 100 m2 survey grid consisting of 14 GPR profile lines was recorded at Ford Ord Dunes State Park in Monterey Bay, California, using 50 MHz antennas. Topography along the profiles was surveyed using differential GPS and used to apply elevation corrections to the GPR profiles. GPR data were bandpass filtered, spatially filtered, and migrated. Vertical resolution of the data is approximately 0.5 m. All profiles show four distinct units separated by erosional or depositional surfaces. The uppermost 5 - 6 m of dune sediments primarily exhibit horizontal layering, with some layers gently dipping in the windward direction. A deeper zone of dune sediments shows reflections dipping in both the leeward and windward directions. Some profiles exhibit foreset laminations that appear to correspond to relict slipfaces. Based on the orientation of both relict and active dunes, the dominant wind direction during the Holocene has consistently been from the northwest. The variations in sedimentary structures suggest alternating wind velocity. Parallel beds that are gently dipping in the windward direction are interpreted as accretionary strata that formed during periods of relatively low wind velocity, while a transverse ridge and foreset laminations indicate periods of higher wind velocity.

Chan, J.; Rhett, G.; Swiatlowski, J.; Craig, M. S.

2012-12-01

363

Spectroscopic study of the Moses Lake dune field, Washington: Determination of compositional distributions and source lithologies  

NASA Astrophysics Data System (ADS)

Source lithologies and transport histories of materials within the Ephrata Fan are investigated. Data were collected using a variety of remote-sensing, laboratory spectroscopic, and field observations and techniques. Laboratory thermal emission spectra were collected of bedrock within the Grand Coulee, dune samples, and clast deposits. Factor analysis, target transformation, and end-member recovery techniques were applied to the set of dune samples as well as a set of grain size fractions. The dune sample spectra are composed of three components that represent basalt, granodiorite, and clay compositions. The basalt and granodiorite components are similar to spectra of clast and bedrock samples from the Grand Coulee and the Ephrata Fan. The clay component is similar to weathering surfaces located within the dune field. The same components were recovered from the set of grain size fractions from a single dune sample demonstrating a relatively higher basalt concentration with grain sizes greater than ~250 ?m. Thermal Infrared Multispectral Scanner (TIMS) data display significant intradune compositional variation and no discernable interdune compositional variation, indicating that the basalt and granodiorite components were likely deposited simultaneously and subsequently separated by wind based on grain size. Basalt and granodiorite bedrock units within the Channeled Scablands are source materials for the deposits within the Ephrata Fan and Moses Lake dune field. The Columbia River, located 20 km west of the dune field, is not a likely source of material.

Bandfield, Joshua L.; Edgett, Kenneth S.; Christensen, Philip R.

2002-11-01

364

DIVERSITY OF ARBUSCULAR MYCORRHIZAL FUNGI ALONG A SAND DUNE STABILIZATION GRADIENT: A CASE STUDY AT PRAIA DE JOAQUINA, ILHA DE SANTA CATARINA, SOUTH BRAZIL  

EPA Science Inventory

Species diversity of abuscular mycorrhizal fungi (AMF) was assessed along a dunes stabilization gradient (embyonic dune, foredune and fixed dune) at Praia da Joaquina (Joaquina Beach), Ilha de Santa Catarina. These dunes served as a case study to assess whether diversity and myc...

365

The Holocene 15,8 (2005) pp. 1227-1235 A geoarchaeological chronology of Holocene dune building on San Miguel Island, California  

Microsoft Academic Search

A data base of 114 14C dates from 40 archaeological sites in San Miguel Island sand dunes provides a general chronology for Holocene dune building. Although rising seas have probably submerged earlier evidence, postglacial dune building on San Miguel began as early as 10000 years ago. More intensive dune building dates to the middle and late Holocene, including large parabolic

Jon M. Erlandson; Torben C. Rick; Curt Peterson

2005-01-01

366

Maximum-limiting ages of Lake Michigan coastal dunes: Their correlation with Holocene lake level history  

USGS Publications Warehouse

Coastal geomorphology along the Great Lakes has long been linked with lake-level history. Some of the most spectacular landforms along the eastern shore of Lake Michigan are high-relief dunes that mantle lake terraces. It has been assumed that these dunes developed during the Nipissing high stand of ancestral Lake Michigan. This hypothesis was tested through stratigraphic analyses and radiocarbon dating of buried soils at four sites between Manistee and Grand Haven, Michigan. At each site, thick deposits of eolian sand overlie late-Pleistocene lacustrine sands. Moderately developed Spodosols (Entic Haplorthods) formed in the uppermost part of the lake sediments are buried by thick dune sand at three sites. At the fourth locality, a similar soil occurs in a very thin (1.3 m) unit of eolian sand buried deep within a dune. These soils indicate long-term (~ 4,000 years) stability of the lake deposits following subaerial exposure. Radiocarbon dating of charcoal in the buried sola indicates massive dune construction began between 4,900 and 4,500 cal. yr B.P. at the Nordhouse Dunes site, between 4,300 and 3,900 cal. yr B.P. at the Jackson and Nugent Quarries, and between 3,300 to 2,900 cal. yr B.P. at Rosy Mound. Given these ages, it can be concluded that dune building at one site occurred during the Nipissing high stand but that the other dunes developed later. Although lake levels generally fell after the Nipissing, it appears that dune construction may have resulted from small increases in lake level and destabilization of lake-terrace bluffs.

Arbogast, Alan F.; Loope, Walter L.

1999-01-01

367

Backshore sill beach and dune erosion control system  

SciTech Connect

A backshore sill beach and dune erosion control system is described comprising: a supporting protective apron formed of weather and water resistant cloth. The apron includes a flat base portion and an angularly sloped portion extending seaward of the base portion, a toe scour anchor tube connected to the seaward end of the apron sloped portion, and longitudinal sand-filled geotextile containers placed upon the apron base portion each extending longitudinally shore parallel to the incoming surf. The sand-filled geotextile containers are specifically placed upon the beach in a pyramidal longitudinally extending shore parallel relation to an area being protected whereby wave action impacts upon relatively soft surfaces of the containers and is dissipated before normally impacting surfaces that would otherwise be eroded.

Sample, J.W.

1988-03-08

368

Etude numerique du sillage tourbillonnaire d'une eolienne  

NASA Astrophysics Data System (ADS)

Cette these formalise le concept de la surface actuatrice (SA) et en presente l'implantation dans deux methodes de mecanique des fluides assistee par ordinateur (CFD) bidimensionnelle (2D) et tridimensionnelle (3D), la validation et l'application au probleme de modelisation du sillage tourbillonnaire d'une eolienne. En termes cinetiques, une SA est une nappe tourbillonnaire qui resulte en une discontinuite de vitesse tandis qu'en termes dynamiques, elle est associee a un systeme de forces dont la composante dans la direction normale a la SA resulte en une discontinuite de pression. Les methodes CFD utilisees sont des methodes aux volumes finis, adaptees pour prendre en compte l'action de la SA sur l'ecoulement. L'approche de la SA est validee pour des problemes 2D: aile infinie et disque actuateur, ainsi que pour le probleme 3D de l'aile en translation (aile effilee), avant d'etre appliquee a plusieurs eoliennes.

Sibuet Watters, Christophe

369

Debris disks as seen by Herschel/DUNES  

NASA Astrophysics Data System (ADS)

The far-infrared excesses produced by debris disks are common features of stellar systems. These disks are thought to contain solids ranging from micron-sized dust to planetesimals. Naturally, their formation and evolution are linked to those of potential planets. With this motivation, the Herschel open time key programme DUNES (DUst around NEarby Stars) aims at further characterising known debris disks and discovering new ones in the regime explored by the Herschel space observatory. On the one hand, in their survey of 133 nearby FGK stars, DUNES discovered a class of extremely cold and faint debris disks, different from well-known disks such as the one around Vega in that their inferred typical grain sizes are rather large, indicating low dynamical excitation and low collision rates. On the other hand, for the more massive disk around the sun-like star HD 207129, well-resolved PACS images confirmed the ring-liked structure seen in HST images and provided valuable information for an in-depth study and benchmark for models. Employing both models for power-law fitting and collisional evolution we found the disk around HD 207129 to feature low collision rates and large grains, as well. Transport by means of Poynting-Robertson drag likely plays a role in replenishing the dust seen closer to the star, inside of the ring. The inner edge is therefore rather smooth and the contribution from the extended halo of barely bound grains is small. Both slowly self-stirring and planetary perturbations could potentially have formed and shaped this disk. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

Löhne, T.; Eiroa, C.; Augereau, J.-C.; Ertel, S.; Marshall, J. P.; Mora, A.; Absil, O.; Stapelfeldt, K.; Thébault, P.; Bayo, A.; del Burgo, C.; Danchi, W.; Krivov, A. V.; Lebreton, J.; Letawe, G.; Magain, P.; Maldonado, J.; Montesinos, B.; Pilbratt, G. L.; White, G. J.; Wolf, S.

2012-06-01

370

The interaction of unidirectional winds with an isolated barchan sand dune  

NASA Technical Reports Server (NTRS)

Velocity profile measurements are determined on and around a barchan dune model inserted in the roughness layer on the tunnel floor. A theoretical investigation is made into the factors influencing the rate of sand flow around the dune. Flow visualization techniques are employed in the mapping of streamlines of flow on the dune's surface. Maps of erosion and deposition of sand are constructed for the barchan model, utilizing both flow visualization techniques and friction velocities calculated from the measured velocity profiles. The sediment budget found experimentally for the model is compared to predicted and observed results reported. The comparison shows fairly good agreement between the experimentally determined and predicted sediment budgets.

Gad-El-hak, M.; Pierce, D.; Howard, A.; Morton, J. B.

1976-01-01

371

Nucléation, ascension et éclatement d'une bulle de champagne  

NASA Astrophysics Data System (ADS)

People have long been fascinated by bubbles and foams dynamics, and since the pioneering work of Leonardo da Vinci in the early 16th century, this subject has generated a huge bibliography. However, only quite recently, much interest was devoted to bubbles in Champagne wines and carbonated beverages. Since the time of the benedictine monk dom Pierre Perignon (1638-1715), champagne is the wine of celebration. This fame is largely linked to the elegance of its effervescence and foaming properties. In this book, the latest results about the chemical physics behind the bubbling properties of Champagne and sparkling wines are collected and fully illustrated. The first chapter is devoted to the history of champagne and to a presentation of the tools of the physical chemistry of interfaces needed for a whole comprehension of the book. Then, the three main steps of a fleeting champagne bubble's life are presented in chronological order, that is, the bubble nucleation on the glass wall (Chap.2), the bubble ascent and growth through the liquid matrix (Chap.3), and the bursting of bubbles at the liquid surface (Chap.4), which constitutes the most intriguing, functional, and visually appealing step. L'objectif général de ce travail consacré à l'étude des processus physicochimiques liés à l'effervescence des vins de Champagne était de décortiquer les différentes étapes de la vie d'une bulle de champagne en conditions réelles de consommation, dans une flûte. Nous résumons ci-après les principaux résultats obtenus pour chacune des étapes de la vie de la bulle, depuis sa naissance sur les parois d'une flûte, jusqu'à son éclatement en surface. Nucléation À l'aide d'une caméra rapide munie d'un objectif de microscope, nous avons pu mettre à mal une idée largement répandue. Ce ne sont pas les anfractuosités de la surface du verre ou de la flûte qui sont responsable de la nucléation hétérogène des bulles, mais des particules adsorbées sur les parois du verre ou de la flûte. Dans la majorité des cas, il s'agit de fibres de cellulose creuses dont les propriétés géométriques permettent le piégeage d'une poche d'air en leur sein au moment du versement. Un modèle de piégeage a été construit et met en avant le rôle fondamental joué par la vitesse du versement. Plus cette vitesse augmente, plus on augmente la probabilité de piéger des poches d'air au sein de ces fibres, provoquant ainsi une effervescence plus importante. La dynamique de production des bulles a également été filmée in situ à l'aide de la caméra, puis modélisée en utilisant les équations de la diffusion adaptées à la géométrie de notre fibre supposée approximativement cylindrique. Nous avons montré que le temps caractéristique de production d'une bulle par la fibre est largement gouverné par la croissance de cette petite poche de gaz par diffusion du CO{2} dissous vers la poche. Nous avons démontré que la convection du liquide joue un rôle essentiel lors du transfert de masse du CO{2} dissous vers la poche. En effet, un modèle purement diffusif ne permet pas du tout de reproduire la dynamique de croissance expérimentale de ces poches de gaz piégées au cœur des fibres. Nous avons également pu mettre en évidence des changements spectaculaires dans la dynamique de bullage de certains sites de nucléation suivis au cours du temps pendant le processus de dégazage. Ces observations font de la fibre de cellulose immergée dans le champagne le plus petit système de bullage non-linéaire observé à ce jour. Dynamique ascensionnelle Pour mesurer la vitesse d'une bulle tout au long de son trajet vers la surface libre du champagne, nous avons tiré profit de la production répétitive de bulles au niveau des sites de nucléation. Par la mise en place d'un dispositif expérimental simple qui associe une lumière stroboscopique et un appareil photographique muni de bagues macros, nous avons pu accéder à l'observation fine des trains de bulles ainsi qu'à la détermination de la vitesse ascensionnelle des bulles. Les m

Liger-Belair, G.

2006-03-01

372

Quantification of Barchan Dune Evolution over Monthly to Interannual Time Scales Using Airborne LIDAR and Terrestrial Laser Scanning  

NASA Astrophysics Data System (ADS)

Barchan dunes are among the most rapidly evolving landforms on Earth, with migration rates of up to 100 m/yr. Despite the central importance of barchan dunes in aeolian geomorphology and the relative ease of quantifying changes in their shape and position, basic questions remain about barchan dune evolution. For example, how does the position of a dune relative to its neighbors affect the evolution of a dune? The presence of a dune influences the air flow around the dune, potentially modifying the evolution of neighboring dunes. Also, a dune may grow in size more rapidly if neighboring dunes are located immediately upwind of the dune, thus providing additional sources of sand for the dune relative to the case of an isolated dune. To address these questions, we quantified the change in the position of 14 dunes, and the sand flux among them, in the Salton Sea dune field over two time scales: 1 month and 3 years. The 1-month change map was created using two TLS surveys completed in the summer of 2013, and the 3-year change map was created using the results of a TLS survey in 2013 and an airborne LIDAR survey from 2010. The PHOENICS Computational Fluid Dynamics solver was used to predict the change in the positions of the dunes and the flux of sand among them. PHOENICS was used to model the shear stress over the dune field using DEM data from the beginning of each interval of study, together with data on the wind profile collected at the study site using a wind tower. The output of PHOENICS was used as input to a shear-stress-dependent aeolian transport formula with the effect of slope on the threshold of entrainment included. Preliminary analyses of the ALSM- and TLS-derived change maps indicate that clustered dunes interact via boundary layer effects to alter the migration and growth rates of their downwind neighbors. Additionally, the effects of subdominant, southeasterly winds were observed in the 1-month change map in the form of sand wedges deposited along the southeast-facing portions of all studied slip faces. These wedges are likely the result of a stagnation zone created by the interaction between the subdominant wind direction and the slip face. Further PHOENICS modeling will be performed using the subdominant wind data to determine the amount and source of the sand flux required to create these wedges. The results of this study will provide important constraints on numerical models of barchan dune field evolution.

Hoose, M.; Pelletier, J. D.

2013-12-01

373

Morphology and formation of the upwind margin at White Sands Dune Field  

NASA Astrophysics Data System (ADS)

A remarkable transitional landscape occurs at the upwind margin of White Sands Dune Field. Over the course a few hundred meters the landscape changes from an flat, sand availability-limited playa, to a sand sheet with strong spatial grain-size sorting, to meter high slipfaceless proto-dunes and finally to several meter high dunes with angle-of-repose slip faces. Within one wavelength of the first dune, dunes rise to nearly 10 meters in height above Alkali Flat, the upwind playa that extends for 13 km westward from the dune field. This abrupt rise in topography may perturb the dominant southwesterly wind flow and trigger an internal boundary layer, which causes a spatial decrease in surface wind stress and decline sediment flux, thereby altering the dune dynamics and dune field morphology downwind. Though the emergence of this upwind transition may play a key role in the morphodynamics of the dune field, what are the morphodynamics of the transition? What are the feedbacks between the emerging topography and the wind within the transition? This presentation uses high-resolution aerial photos, time-series airborne LiDAR and terrestrial laser scanning to characterize the transitional morphology the upwind margin of White Sands and discusses these morphologies in the context of the interplay between wind flow and dune field topography. Alkali Flat playa is sparsely sand covered, the amount of which varies temporally. The sparse sand cover occurs as sand patches that form in the lee of bushes or within topographic lows generated by deflated gypsum crust. Adjacent and downwind of the playa is a sand sheet composed of variable wavelength, coarse grained ripples. Ten to thirty meter wide ripple patches organized into a repeating sequence of coarse-grained, > 15 cm wavelength ripples to fine-grained, < 15 cm wavelength ripples occur across the sand sheet. Downwind the ripple patches organize into low-relief protodune hummocks. The protodunes are covered by a range of ripple sizes that are spatially organized similar to the ripple patches within the sand sheet. The coarsest-grained, largest wavelength ripples occur at the protodune crest and fine downwind. The inter-protodune areas are typically free of sand, exposing indurated dune stratigraphy. The protodunes grow in height, but the wavelength remains ~ 70 m downwind until a slipface develops. Rapid growth into 5-10 meter high dunes occurs within one wavelength after slipface development and generates an abrupt topographic increase in topography. Dune migration rates are approximately 6 m/year at the upwind margin and decline to around 3 m/year within a few kilometers of the upwind margin. A generalized model of dune emergence at the upwind margin of dune fields is proposed using examples from other dune fields.

Ewing, R. C.; Jerolmack, D. J.; Martin, R. L.; Reitz, M. D.; Phillips, C. B.; Falcini, F.; Masteller, C.

2012-12-01

374

77 FR 56671 - Draft Shoreline Restoration Management Plan and Environmental Impact Statement for Indiana Dunes...  

Federal Register 2010, 2011, 2012, 2013

...Porter, Indiana 46304; telephone (219) 926-7561, extension 225. FOR FURTHER INFORMATION CONTACT: Superintendent Constantine Dillon, Indiana Dunes National Lakeshore, at the address above, or by telephone at (219) 926-7561, extension...

2012-09-13

375

Snow Dunes: A Controlling Factor of Melt Pond Distribution on Arctic Sea Ice  

NASA Technical Reports Server (NTRS)

The location of snow dunes over the course of the ice-growth season 2007/08 was mapped on level landfast first-year sea ice near Barrow, Alaska. Landfast ice formed in mid-December and exhibited essentially homogeneous snow depths of 4-6 cm in mid-January; by early February distinct snow dunes were observed. Despite additional snowfall and wind redistribution throughout the season, the location of the dunes was fixed by March, and these locations were highly correlated with the distribution of meltwater ponds at the beginning of June. Our observations, including ground-based light detection and ranging system (lidar) measurements, show that melt ponds initially form in the interstices between snow dunes, and that the outline of the melt ponds is controlled by snow depth contours. The resulting preferential surface ablation of ponded ice creates the surface topography that later determines the melt pond evolution.

Petrich, Chris; Eicken, Hajo; Polashenski, Christopher M.; Sturm, Matthew; Harbeck, Jeremy P.; Perovich, Donald K.; Finnegan, David C.

2012-01-01

376

A scaling law for aeolian dunes on Mars, Venus, Earth, and for subaqueous ripples  

E-print Network

A scaling law for aeolian dunes on Mars, Venus, Earth, and for subaqueous ripples Philippe Claudin tunnel reproducing conditions close to Venus' atmosphere and in the low pressure CO2 Martian atmosphere

Claudin, Philippe

377

Deer Management Plan, Final Internal Scoping Report: Indiana Dunes National Lakeshore, February 5, 2003.  

National Technical Information Service (NTIS)

An internal scoping meeting was held to discuss management of white-tailed deer (Odocoileus virginianus) as part of a healthy and functioning ecosystem at Indiana Dunes National Lakeshore (national lakeshore). The goal of this meeting was to determine the...

2003-01-01

378

76 FR 62087 - Draft Conservation Plan and Draft Environmental Assessment; Dunes Sagebrush Lizard, Texas  

Federal Register 2010, 2011, 2012, 2013

...Texas Conservation Plan for the Dunes Sagebrush Lizard (TCP). The draft TCP will function as a Candidate Conservation Agreement with...sagebrush lizard becomes listed in the future, the draft TCP will also serve as a Habitat Conservation Plan...

2011-10-06

379

Generating Explanations for an Emergent Process: The Movement of Sand Dunes  

NSDL National Science Digital Library

The movement of sand dunes in the desert is an emergent process; the overall movement of a dune is influenced both by the random interactions among individual sand particles and by the process of wind adding and subtracting sand. People often misconstrued emergent processes as deterministic processes containing central causality. I present a case study of how one person, an adult, who was not an expert in physics, articulated and refined her explanation of the movement of sand dunes. She began with centralized causality but ended with an explanation containing the cogent emergent ideas. This case study is noteworthy in exemplifying the dynamic process of generating an explanation. The interviewee went through four different explanations at three different levels (macro, micro and mid-level) and concluded with an explanation that simultaneously addressed the movement of sand dunes at all three levels.

Barth-Cohen, Lauren

2011-01-01

380

The impact of devegetated dune fields on North American climate during the late Medieval Climate Anomaly  

NASA Astrophysics Data System (ADS)

During the Medieval Climate Anomaly, North America experienced severe droughts and widespread mobilization of dune fields that persisted for decades. We use an atmosphere general circulation model, forced by a tropical Pacific sea surface temperature reconstruction and changes in the land surface consistent with estimates of dune mobilization (conceptualized as partial devegetation), to investigate whether the devegetation could have exacerbated the medieval droughts. Presence of devegetated dunes in the model significantly increases surface temperatures, but has little impact on precipitation or drought severity, as defined by either the Palmer Drought Severity Index or the ratio of precipitation to potential evapotranspiration. Results are similar to recent studies of the 1930s Dust Bowl drought, suggesting bare soil associated with the dunes, in and of itself, is not sufficient to amplify droughts over North America.

Cook, B. I.; Seager, R.; Miller, R. L.

2011-07-01

381

AEOLIAN DUNE FIELDS OF KANSAS AND THEIR RESPONSE TO LATE-QUATERNARY DROUGHT  

E-print Network

Aeolian dune fields are ubiquitous features of the North American Great Plains, and contained within their stratigraphy are important records of changes in prehistoric climate. Using absolute dating techniques, researchers ...

Halfen, Alan Frederick

2012-12-31

382

Solar Lentigo  

MedlinePLUS

newsletter | contact Share | Solar Lentigo Information for adults A A A This image displays many solar lentigos due to the patient having many sunburns as a child and teenager. Overview A solar lentigo (plural, solar lentigines), also known as a ...

383

Solar Power  

NSDL National Science Digital Library

Students learn about solar energy and how to calculate the amount of solar energy available at a given location and time of day on Earth. The importance of determining incoming solar energy for solar devices is discussed.

Integrated Teaching And Learning Program

384

Last Glacial Maximum Development of Parna Dunes in Panhandle Oklahoma, USA  

NASA Astrophysics Data System (ADS)

Though dunefields are a ubiquitous feature of the North American Great Plains, those studied to date have consisted primarily of sand grains. In Beaver County of the Oklahoma panhandle, however, upland dune forms consist of sand-sized aggregates of silt and clay. These aptly named parna dunes occur in two swarms, range in height from 10-15 m, and have asymmetrical dome morphologies with approximate north-south dune orientations. Despite their morphological similarities to sand dunes of the region, their origin and evolution is unknown. Documenting parna dune formation in the Oklahoma panhandle will help improve our understanding of prehistoric landscape instability and climate change, particularly in the central Great Plains where such records are limited. Panhandle parna dunes are typified by Blue Mound, our best documented parna dune thus far. Coring has documented a basal paleosol buried at a depth equivalent to the surrounding landscape—14C ages from this soil indicate its formation about 25-21 ka. The paleosol is a hydric Mollisol with a pronounced C3 isotopic signature reflecting hydric plant communities, rather than the regionally dominated C4 prairie vegetation. Hydric soils are associated with many of the playas on the surrounding landscape today, which suggests that they may have been more prevalent during the LGM. The overlying 8-10 m of parna is low in organic C and high in calcite, with indications of up to ten major episodes of sediment flux, which are documented with magnetic, isotope, soil-stratigraphic, particle-size, and color data. Near-surface luminescence (OSL) ages from Blue Mound are similar to the 14C ages from the basal paleosol, indicating rapid dune construction, with little or no Holocene accumulation of sediment. Marine isotope stage (MIS) 3 loess records indicate that upland areas of the region were relatively stable with attendant widespread pedogenesis prior to development of the parna dunes. At the onset of the LGM, however, the landscape destabilized, and aeolian processes dominated. Peoria Loess began accumulating throughout parts of Oklahoma and much of Kansas, Nebraska, and beyond, until landscape stabilization was re-attained about 14-13 ka. Our chronological and geomorphic data suggest that parna dune construction in the Oklahoma panhandle was the result of strong, northerly winds, which precipitated aeolian activity at the beginning of MIS 2. Furthermore, these features appear to be more analogous to the regional loess record than the sand dune activation record, and, with more research, may prove to be a reliable record of late-Quaternary landscape change in the central Great Plains.

Johnson, W. C.; Halfen, A. F.; McGowen, S.; Carter, B.; Fine, S.; Bement, L. C.; Simms, A. R.

2012-12-01

385

Large-scale dune erosion tests to study the influence of wave periods  

Microsoft Academic Search

Large-scale physical model tests were performed to quantify the effects of the wave period on dune erosion. Attention was focussed on 2D cross-shore effects in a situation with sandy dunes and extreme water levels and wave conditions. Besides profile measurements, detailed measurements in time and space of water pressure, flow velocities and sediment concentrations were performed in the near near-shore

M. R. A. van Gent; J. S. M. van Thiel de Vries; E. M. Coeveld; J. H. de Vroeg; J. van de Graaff

2008-01-01

386

Quantifying landscape-ecological succession in a coastal dune system using sequential aerial photography and GIS  

Microsoft Academic Search

Summary  This contribution presents an attempt to measure the path of habitat and vegetation succession in a coastal dune system (Kenfig\\u000a Burrows, South Wales) using remote sensing and GIS. The loss of slack habitats associated with the continuing stabilization\\u000a of this dune system is a major cause for concern. These habitats support a range of plant species, including the rare fen

2002-01-01

387

Pedogenesis in coastal wet dune slacks after sod-cutting in relation to revegetation  

Microsoft Academic Search

The development of vegetation and soil was investigated in wet coastal dune slacks in North Holland, The Netherlands (52°36'N, 4°37'E). Sod cutting in the past has created a time series from 1 to 30 years, with an even older undisturbed site as reference. After sod-cutting Schoenus nigricans, a typical pioneer species of wet dune slacks, established and contributed together with

W. H. O. Ernst; Q. L. Slings; H. J. M. Nelissen

1996-01-01

388

Resource heterogeneity generated by shrubs and topography on coastal sand dunes  

Microsoft Academic Search

In early stages of primary succession, colonizing plants can create resource patches that influence the abundance and distribution of other species. To test whether different colonizing shrubs generate contrasting patches on coastal sand dunes, we compared soil characteristics and light availability under the nitrogen-fixing shrub Lupinus arboreus, under the non-nitrogen-fixing shrub Artemisia pycnocephala, and between shrubs on dunes at a

Peter Alpert; Harold A. Mooney

1996-01-01

389

Ecological effects of reactivation of artificially stabilized blowouts in coastal dunes  

Microsoft Academic Search

In an inner dune area in the Dutch coastal dunes several artificially stabilized blowouts were reactivated. The purpose was\\u000a to investigate whether these reactivated blowouts could remain active despite the increased atmospheric deposition of nutrients,\\u000a how much area would be affected by sand from the blowouts, whether the vegetation would respond to the deposition of sand,\\u000a and whether the reactivation

J. H. van Boxel; P. D. Jungerius; N. Kieffer; N. Hampele

1997-01-01

390

Spatial indicators of plant community assembly from a 453-year sand-dune chronosequence  

Microsoft Academic Search

Background: We explored evidence for spatial patterning in vegetation across a sand-dune chronosequence spanning 453 years of primary succession to test for indications of a temporal signature of niche versus neutral processes during community assembly.Methods: The study was conducted on a series of dune-capped beach ridges located in Wilderness State Park in Emmet County of northern Lower Michigan, United States

Jennifer M. Waugh; Lonnie W. Aarssen

2011-01-01

391

Dynastages Page 1 1. Qui peut bnficier d'une bourse Dynastage tudiants / dans  

E-print Network

Dynastages Page 1 1. Qui peut bénéficier d'une bourse Dynastage étudiants / dans quelles conditions bourse Dynastage étudiants durant son cursus. S'il a déjà bénéficié d'une bourse Dynastage étudiants, il non français ne peuvent obtenir de bourse Dynastage pour un stage effectué dans leur pays de résidence

Jeanjean, Louis

392

Plant geography of coastal sand dune vegetation of the Tamaulipan Biotic Province  

E-print Network

range (2 spp. ). Among the most frequent species with wide range were Croton puncfafus, Disffchlis spicafa, Ipomoea imperafa, Paspalum setaceum, and Uniola paniculata. Among the most frequent tropical and subtropical species were Ipomoea pes... of Uniola paniculata on the sand dune vegetation system of the Tamaulipan Biotic Province. . . . . . . . . . . . . . . . . . 53 17 Mean percent coverage of ipomoea pes-caprae on the sand dune vegetation system of the Tamaulipan Biotic Province...

Baro de Jones, Deborah Maria

2012-06-07

393

Sand dunes monitoring using remote sensing and GIS techniques for some sites in Iraq  

NASA Astrophysics Data System (ADS)

This study is aimed at monitoring, mapping and assessing the sand dune encroachment in the northern central part of Iraq. The study area includes six districts suffering from the increasing prevalence of sand dunes, particularly in the recent years, which are characterized by dry weather and a reduction in rainfall averages. Remote sensing "RS" and in particular, Earth observation satellites besides Geographical Information Systems "GIS" provide significant contributions to monitoring sand dunes encroachment. Two Landsat TM images acquired on July of 1988, and July of 2009 were assembled and used to extract the research indices. Satellite image based indices; the Normalized Difference Vegetation Index "NDVI", the Tasseled Cap Wetness Indicator "TCW", the Land Surface Temperature "LST", and the Normalized Difference Sand Index "NDSI" (a new index which has been proposed in this study) with RS and GIS techniques were used for monitoring the sand dune encroachment at two sites in the northern central part of Iraq. The results showed an increase in the sand dunes accumulations by 2,020.6 km2 and 291.1 km2 throughout the 21 years from 1988 to 2009 in Baiji and Al-Aith sites in the region, respectively. Sand dunes movement rates for the same period were 1,155.9 m year-1 and 494.2 m year-1 in the two mentioned sites, respectively. The results showed that the study area in general is exposed to a high risk of sand dune encroachment. The means of soil conditioners and windbreaks has been proposed to mitigate the impacts of sand dune encroachment.

Fadhil, Ayad Mohammed

394

Nicolas Daget Interpolation d'une grille ORCA2 vers une  

E-print Network

Nicolas Daget Interpolation d'une grille ORCA2 vers une grille régulière 29 mars 2006 Technical; Chapitre 1 Introduction Certains outils existaient déjà pour interpoler des champs d'une grille ORCA 1 vers ENACT 3 . Il permet d'interpoler les sorties du modèle sur la grille ORCA 2 degrés vers une grille

395

Optically stimulated luminescence dating of aeolian sand in the otindag dune field and holocene climate change  

USGS Publications Warehouse

The dune system in Otindag sand field of northern China is sensitive to climate change, where effective moisture and related vegetation cover play a controlling role for dune activity and stability. Therefore, aeolian deposits may be an archive of past environmental changes, possibly at the millennial scale, but previous studies on this topic have rarely been reported. In this study, thirty-five optically stimulated luminescence (OSL) ages of ten representative sand-paleosol profiles in Otindag sand field are obtained, and these ages provide a relatively complete and well-dated chronology for wet and dry variations in Holocene. The results indicate that widespread dune mobilization occurred from 9.9 to 8.2 ka, suggesting a dry early Holocene climate. The dunes were mainly stabilized between 8.0 and 2.7 ka, implying a relatively wet climate, although there were short-term penetrations of dune activity during this wet period. After ???2.3 ka, the region became dry again, as inferred from widespread dune activity. The "8.2 ka" cold event and the Little Ice Age climatic deterioration are detected on the basis of the dune records and OSL ages. During the Medieval Warm Period and the Sui-Tang Warm Period (570-770 AD), climate in Otindag sand field was relatively humid and the vegetation was denser, and the sand dunes were stabilized again. These aeolian records may indicate climate changes at millennial time scale during Holocene, and these climatic changes may be the teleconnection to the climate changes elsewhere in the world. ?? Science in China Press and Springer-Verlag GmbH 2008.

Zhou, Y. L.; Lu, H. Y.; Mason, J.; Miao, X. D.; Swinehart, J.; Goble, R.

2008-01-01

396

Strandline and sand dune vegetation of coasts of Greece and some other Aegean countries  

Microsoft Academic Search

The coastal strandline and sand-dune vegetation of Greece has been reviewed. All published relevés available were collected and classified using numerical methods (TWINSPAN). The communities studied belong to three classes, one for strandline vegetation (Cakiletea maritimae), and two for sand-dune vegetation (Ammophiletea and Cisto-Micromerietea). A hierarchical syntaxonomic overview is given. The following communities and associations were distinguished: Salsolo-Matthioletum tricuspidatae, Cakilo-Xanthietum

K. V. Sykora; D. Babalonas; E. S. Papastergiadou

2003-01-01

397

Morphologic and Dynamic Similarities Between Polygonal Dunes on Mars and Interference Ripples on Earth  

NASA Astrophysics Data System (ADS)

Some dunes in craters on Mars are similar in morphology to ripples formed in complicated multidirectional flows on Earth. Similarities in morphology of these ripples on Earth and dunes on Mars include (1) relatively symmetrical cross-sections, and (2) crests with planform polygonal patterns, "tile" patterns, or "ladderback" structure. On Earth, bedforms with these morphologies are produced by complicated directionally-varying flows such as those generated by interfering waves (Figure 1), recirculating flows in the lee of large dunes, and recirculating flows in lateral separation eddies in rivers. Here we hypothesize that dunes with these morphologies on Mars (Figure 2) are also formed by multidirectional flows. Processes that might produce multidirectional winds on Mars include: heating and cooling that cause daily changes in wind direction; winds that vary in direction seasonally or with the passage of storms; and recirculating flows within steep-walled craters or within the troughs of larger dunes. This work was funded by NASA Mars Data Analysis Program.igure 1. Polygonal ripples formed by waves in shallow water; boot print is 30 cm long. igure 2. Polygonal dunes in Victoria Crater, Mars; crater is approximately 700 m in diameter and 70 m deep; image from NASA/JPL-Caltech/University of Arizona.

Rubin, D. M.; Newman, C. E.

2012-12-01

398

Mediterranean coastal dune systems: Which abiotic factors have the most influence on plant communities?  

NASA Astrophysics Data System (ADS)

Mediterranean coastal dunes are dynamic and heterogeneous ecosystems characterised by a strong interaction between abiotic and biotic factors. The present study aimed to adopt a multidisciplinary approach - integrating data on dune morphology, sediment texture and soil parameters as well as shoreline trend - in order to define which are the abiotic factors that most affect the distribution and composition of Mediterranean plant dune communities. The study was carried out in two protected areas, located in central Italy, subjected to different shoreline trends in recent years. 75 plots were identified along eleven randomly positioned cross-shore transects, starting from the beach continuing up to the plant communities of the backdunes. In each plot floristic and environmental data - such as distance to the coastline, plot altitude, inclination, shoreline trend, mean grain-size, sorting, pH, conductivity and organic matter concentration - were collected. The analyses revealed significant changes of vegetational cover, dune morphology and geopedological features along the coast-to-inland gradient. Relationships between vegetation composition and environmental factors were investigated through Canonical Correspondence Analysis (CCA). Four factors - distance to the coastline, mean grain-size, shoreline trend and organic matter - were found to be closely correlated with the floristic composition of plant communities. Finally, soil properties were highlighted as the most determinant factors of community zonation in these Mediterranean coastal dune ecosystems. These results could be taken into account by local managers in conservation actions such as protecting the eroding foredunes as well as in artificial dune reconstructions.

Ruocco, Matteo; Bertoni, Duccio; Sarti, Giovanni; Ciccarelli, Daniela

2014-08-01

399

The growth responses of coastal dune species are determined by nutrient limitation and sand burial.  

PubMed

Past work suggests that burial and low nutrient availability limit the growth and zonal distribution of coastal dune plants. Given the importance of these two factors, there is a surprising lack of field investigations of the interactions between burial and nutrient availability. This study aims to address this issue by measuring the growth responses of four coastal dune plant species to these two factors and their interaction. Species that naturally experience either high or low rates of burial were selected and a factorial burial by nutrient addition experiment was conducted. Growth characteristics were measured in order to determine which characteristics allow a species to respond to burial. Species that naturally experience high rates of burial (Arctotheca populifolia and Scaevola plumieri) displayed increased growth when buried, and this response was nutrient-limited. Stable-dune species had either small (Myrica cordifolia, N-fixer) or negligible responses to burial (Metalasia muricata), and were not nutrient-limited. This interspecific difference in response to burial and/or fertiliser is consistent with the idea that burial maintains the observed zonation of species on coastal dunes. Species that are unable to respond to burial are prevented from occupying the mobile dunes. Species able to cope with high rates of burial had high nitrogen-use efficiencies and low dry mass costs of production, explaining their ability to respond to burial under nutrient limitation. The interaction between burial and nutrient limitation is understudied but vital to understanding the zonation of coastal dune plant species. PMID:18246372

Gilbert, Matthew; Pammenter, Norman; Ripley, Brad

2008-05-01

400

Mesophilic Actinomycetes in the natural and reconstructed sand dune vegetation zones of Fraser Island, Australia.  

PubMed

The natural coastal habitat of Fraser Island located in the State of Queensland, Australia, has been disturbed in the past for mining of the mineral sand ilmenite. Currently, there is no information available on whether these past mining disturbances have affected the distribution, diversity, and survival of beneficial soil microorganisms in the sand dunes of the island. This in turn could deleteriously affect the success of the natural regeneration, plant growth, and establishment on the sand dunes. To support ongoing restoration efforts at sites like these mesophilic actinomycetes were isolated using conventional techniques, with particular emphasis on the taxa previously reported to produce plant-growth-promoting substances and providing support to mycorrhizal fungi, were studied at disturbed sites and compared with natural sites. In the natural sites, foredunes contained higher densities of micromonosporae replaced by increasing numbers of streptomycete species in the successional dune and finally leading to complex actinomycete communities in the mature hind dunes. Whereas in the disturbed zones affected by previous mining activities, which are currently being rehabilitated, no culturable actinomycete communities were detected. These findings suggest that the paucity of beneficial microflora in the rehabilitated sand dunes may be limiting the successful colonization by pioneer plant species. Failure to establish a cover of plant species would result in the mature hind dune plants being exposed to harsh salt and climatic conditions. This could exacerbate the incidence of wind erosion, resulting in the destabilization of well-defined and vegetated successional dunal zones. PMID:17578635

Kurtböke, D I; Neller, R J; Bellgard, S E

2007-08-01

401

Holocene geoarchaeology of the Sixteen Mile Beach barrier dunes in the Western Cape, South Africa  

NASA Astrophysics Data System (ADS)

Holocene evolution and human occupation of the Sixteen Mile Beach barrier dunes on the southwest coast of South Africa between Yzerfontein and Saldanha Bay are inferred from the radiocarbon ages of calcareous dune sand, limpet shell ( Patella spp.) manuports and gull-dropped white mussel shells ( Donax serra). A series of coast-parallel dunes have prograded seaward in response to an overall marine regression since the mid-Holocene with dated shell from relict foredunes indicating periods of shoreline progradation that correspond to drops in sea level at around 5900, 4500 and 2400 calibrated years before the present (cal yr B.P.). However, the active foredune, extensively covered by a layer of gull-dropped shell, has migrated 500 m inland by the recycling of eroded dune sand in response to an approximate 1 m sea level rise over the last 700 yr. Manuported limpet shells from relict blowouts on landward vegetated dunes indicate human occupation of coastal dune sites at 6200 and 6000 cal yr B.P. and help to fill the mid-Holocene gap in the regional archaeological record. Coastal midden shells associated with small hearth sites exposed in blowouts on the active foredune are contemporaneous (1600-500 cal yr B.P.) with large midden sites on the western margin of Langebaan Lagoon and suggest an increase in marine resource utilisation associated with the arrival of pastoralism in the Western Cape.

Compton, John S.; Franceschini, Giuliana

2005-01-01

402

Overland flow in sand dunes: feedbacks between aeolian and hydrological processes  

NASA Astrophysics Data System (ADS)

During the summer of 2005, Hurricane Dennis overwashed the eastern portion of St. George Island, part of the northwest barrier island chain located along the Florida Panhandle. In this paper, LiDAR-based morphological changes of the barrier island are analyzed, along with the short-term post-storm recovery of secondary dunes. Vegetation deterred dune migration, thus favoring dune growth and reducing erosion due to wind. In contrast, the absence of vegetation inhibited dune growth. Low-elevation areas within the dunes were subject to flooding via saturation overland flow following moderate storm surges and rainfall events. Using a high resolution topographic survey and simple hydrology models, we estimate the discharge and velocities from storm surge return flow and saturation overland flow. Results show that return flow velocities are of the same magnitude as the critical velocity necessary to mobilize sand when a hydraulic connection between the watershed and back-barrier bay is present. Storms of moderate strength and rainfall intensity may be sufficient to keep the return channels open within the back-barrier, thus providing natural conduits for water exchange from overwash events during extreme storm surges triggered by hurricanes. We conclude that hydrological and aeolian processes are strictly coupled in dune fields characteristic of many barrier islands along the US coast.

Fagherazzi, S.; Priestas, A. M.

2012-12-01

403

Efficient fog harvesting by Stipagrostis sabulicola (Namib dune bushman grass)  

NASA Astrophysics Data System (ADS)

Stipagrostis sabulicola is an endemic species of the central Namib Desert which settles on extremely arid dune fields. Due to its ability to persistence even during exceptionally dry years it is generally assumed that water supply of this species is substantially based on fog water. In this contribution, the results of a study investigating the capability of S. sabulicola for fog harvesting are presented. For this purpose, stem flow rates of S. sabulicola during fog events, spatial gradient of soil water content (SWC) close to mounds of S. sabulicola and its leaf water potential (LWP) before and after fog events were monitored together with climate parameters. According to the data obtained during this study, S. sabulicola is able to harvest substantial amounts of water by fog catchment from nocturnal fog events. Since culms of S. sabulicola are often stiff with an upright habitus, fog harvesting occurs via stemflow that conducts water directly towards the root zone of a plant. According to this mechanism, the stem runoff is concentrated within the area of the mound. A medium-sized mound of S. sabulicola is able to collect an amount of about 4 l per fog night. This fog harvesting leads to a considerable spatial gradient of soil water content with values decreasing with increasing distance from the mound. As a result of the water input by fog drip, SWC within the mound increases significantly, particularly close to the culm bases where SWC values increased to 2.2 % after a fog event. Due to the uneven distribution of water by stemflow, SWC within a mound shows high spatial heterogeneity which is also illustrated by the numerous outliers and extreme values of SWC within the mound region. This heterogeneity is also due to the fact that several sagging leaves are always present causing fog drip which more or less irregularly scatters moisture. For bare soil outside of a mound, the water content is not substantially increased, amounting to 0.78 % on average during dry days and 0.89 % after fog events. Fog harvesting affects also leaf water potential: whereas leaf water potential declines during dry days, it remains more or less constant on days following fog events. Since mounds of S. sabulicola provide shelter and food for various other organisms such as ants and lizards, their ability for nocturnal fog catchment is of high significance for the ecosystem of the Namib dunes.

Roth-Nebelsick, A.; Ebner, M.; Miranda, T.

2010-07-01

404

Sheet Flows, Avalanches, and Dune Migration on Earth and Mars  

NASA Astrophysics Data System (ADS)

We provide an overview of our research on sheet flows and avalanches of granular materials, primarily in terrestrial conditions. Sheet flows are relatively thin, highly concentrated regions of grains that flow near the ground under the influence of a strong turbulent wind. In them grains are suspended by interparticle collisions and the velocity fluctuations of the turbulent gas. Avalanches are flows of dry, cohesionless granular materials that are driven by gravity down inclines against the frictional and collisional resistance of the grains of the bed. In our study of sheet flows, we have extended existing theories that involve particle-particle and gas-particle interactions to apply to the conditions of a typical terrestrial sand dune during a sandstorm. This has involved the incorporation of both the viscous dissipation of the particle fluctuation energy due to the gas and the turbulent suspension of the grains due to velocity fluctuations of the gas. It has also involved an examination of several different boundary conditions at the bed and a more precise characterization of the conditions that apply at the top of a sheet flow, where the mean-free-path between collisions becomes comparable to the length of a ballistic trajectory. Solutions to the resulting differential equations have been obtained for both steady and unsteady fully-developed flow. The latter solutions provide information on the characteristic time to achieve a steady flow that plays a key role in dune formation. In support of this modeling effort, experiments have been undertaken to provide a better understanding of the interaction of particles colliding with the bed, and the energy of the rebounding particle and additional ejected particles has been measured in two-dimensional situations. The research on avalanches has focused on dense, frictional flows. Experiment and numerical simulations indicate that relatively thin dense flows, on the order of ten particle diameters, occur in layers. In these, momentum transfer occurs by rubbing between contacting particles and bumping between particles falling under gravity, rather than in collisions between freely flying particles. Thicker dense flows, on the other hand, do seem to involve collisional transfer of momentum. Theories based on the appropriated mechanisms of momentum transfer predict velocity profiles that are in agreement with those measured in experiment and numerical simulations, some of which have been carried out in the course of the research.

Jenkins, James; Hanes, D.; Bideau, D.; Berton, G.; Rioual, F.; Valance, A.

2002-11-01

405

A Kinematic Model for Formation of the Yakutat, Siletz, and Crescent Forearc Terranes: Implications for Seismogenic Behavior of the Cascadia Subduction System  

NASA Astrophysics Data System (ADS)

Our kinematic model depicting motion of the Kula, Farallon, and Juan de Fuca plates as well as the Yellowstone hotspot relative to the Pacific plate reconciles previously conflicting interpretations regarding the origin of Paleogene oceanic terranes currently stranded against the western North America continental margin. By explicitly including a defunct Resurrection plate in our reconstruction of the western North America plate boundary, we are able to account for the Yakutat and Resurrection Peninsula oceanic terranes in Alaska as well as the Siletz and Crescent terranes in Oregon, Washington, and British Columbia as remnants of a Farallon-Resurrection ridge segment that transferred to the North America subduction margin from about 53 to 42 Ma. Moreover, the similarity in age, thickness, and geochemistry between Yakutat basalts and Crescent basalts [Davis and Plafker, 1986, Geology] can be explained by their having previously been adjacent parts of the Resurrection plate. Under a simple model that the Resurrection plate was captured by the Pacific plate at the same time as the Kula plate at ~40 Ma [Lonsdale, 1988, GSAB], the distance between Yakutat and Crescent may have been only a few hundred kilometers at 50 Ma, with both formed near the Yellowstone hotspot. Currently separated by more than 1500 km, this distance is large enough that if previously adjacent, they must have been moving apart for most of the time since their formation. The partially subducted Yakutat terrane is associated with the asperity that broke during the M9.2