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1

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

Federal Register 2010, 2011, 2012, 2013

...Dunes Solar Energy Project is a solar facility using concentrated solar thermal power technology. The...project area and will include a solar field (consisting of up to 17...combined to form a hybrid-cooling system), electrical equipment...

2010-12-27

2

On the crescentic shape of barchan dune  

E-print Network

Aeolian sand dunes originate from wind flow and sand bed interactions. According to wind properties and sand availability, they can adopt different shapes, ranging from huge motion-less star dunes to small and mobile barchan dunes. The latter are crescentic and emerge under a unidirectional wind, with a low sand supply. Here, a 3d model for barchan based on existing 2d model is proposed. After describing the intrinsic issues of 3d modeling, we show that the deflection of reptating particules due to the shape of the dune leads to a lateral sand flux deflection, which takes the mathematical form of a non-linear diffusive process. This simple and physically meaningful coupling method is used to understand the shape of barchan dunes.

P. Hersen

2003-08-06

3

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

...Project is a proposed 110- megawatt solar power generating facility based on concentrating solar power technology, using mirrors and...Project is a proposed 110-megawatt solar power generating facility based on...

2011-09-29

4

Crescentic dunes on the inner continental shelf off northern California  

USGS Publications Warehouse

These dunes appear to be migrating obliquely to the regional shelf gradient; a preferred offshore direction of tranpsort is indicated by the extended southern wings of many dunes. Over longer time periods (decades), the seaward transport of fine to medium sand in the crescentic dunes is probably an important way by which sand escapes the shallow part of the continental shelf in this region and mixes with the muddy deposits of the central shelf. -from Authors

Cacchione, D.A.; Field, M.E.; Drake, D.E.; Tate, G.B.

1987-01-01

5

Point pattern analysis of north polar crescentic dunes, Mars: A geography of dune self-organization  

Microsoft Academic Search

The geographic signature of dune distribution and self-organization as measured by the R-statistic offers a viewpoint on the geography of crescentic eolian systems and proposes an index from which to determine the degree of self-organization across a variety of spatial scales. Fields of simple dunes (dome, barchan, barchan-seif) are comparatively less regular in distribution than are those fields, or part

Mark A. Bishop

2007-01-01

6

Point pattern analysis of north polar crescentic dunes, Mars: A geography of dune self-organization  

NASA Astrophysics Data System (ADS)

The geographic signature of dune distribution and self-organization as measured by the R-statistic offers a viewpoint on the geography of crescentic eolian systems and proposes an index from which to determine the degree of self-organization across a variety of spatial scales. Fields of simple dunes (dome, barchan, barchan-seif) are comparatively less regular in distribution than are those fields, or part thereof, that consist of compound (barchanoid) morphologies whose patterns are more highly regular.

Bishop, Mark A.

2007-11-01

7

Pilot Study of Higher Order Neighbor Statistics for Crescentic Dunes of the Martian North Polar Region  

NASA Astrophysics Data System (ADS)

This pilot study reports on the geography of simple crescentic dunes (barchans) for the north polar region of Mars using ordered neighbor point pattern analysis within a geographical information system (GIS).

Wheeler, A. J.; Bishop, M. A.

2007-03-01

8

Pilot Study of Higher Order Neighbor Statistics for Crescentic Dunes of the Martian North Polar Region  

Microsoft Academic Search

This pilot study reports on the geography of simple crescentic dunes (barchans) for the north polar region of Mars using ordered neighbor point pattern analysis within a geographical information system (GIS).

A. J. Wheeler; M. A. Bishop

2007-01-01

9

Dunes  

E-print Network

Dunes MICHELLE REED On October SO, 1993, the Mirage Resorts, Inc., imploded the casino and north tower, which was televised. The Dunes's death signified the birth of another resort. n I ily, we're going to be late," Robert says. He paces... to say about the Dunes." Robert sighs loudly as he moves around the room. He fluffs the pillows beside me on the sofa and straightens the pile of magazines on the floor beside his chair. It's not his fault that he doesn't understand. He doesn't know...

Reed, Michelle

2006-01-01

10

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

11

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

12

Morphology and Distribution of Common ‘Sand’ Dunes on Mars: Comparison With the Earth  

Microsoft Academic Search

Massed crescentic ridges are the most common dunes in the north circumpolar erg and crater floor dune fields on Mars; they are similar in plan to dunes that are typical of many desert basin ergs and dune fields on Earth. This correspondence implies that the dynamics of dune formation are similar on the two planets, despite martian constraints on dune

Carol S. Breed; Maurice J. Grolier; John F. McCauley

1979-01-01

13

The temporal crescent syndrome.  

PubMed

Retro-chiasmal lesions almost always give rise to homonymous field defects with only one exception. The nasal visual field extends to 60% of the horizon, whereas the temporal field extends to a further 30°-40° beyond that; this part of the visual field is represented on the contralateral anterior parieto-occipital sulcus. A lesion in this area will give rise to monocular visual field defect affecting the contralateral eye. This is called the temporal crescent or the half moon syndrome. In this case report, a woman presented with seizures secondary to haemorrhagic infarction of the anterior part of the parieto-occipital sulcus. She later presented with right-sided visual disturbance; her examination confirmed temporal crescent syndrome. I explain the pathophysiology of this rare neurological syndrome in this report. PMID:25416654

Ali, Khalid

2015-02-01

14

Barchan dune asymmetry: Numerical investigation  

E-print Network

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 $90^{\\circ}$, 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...

Parteli, Eric J R; Bourke, Mary C; Tsoar, Haim; Poeschel, Thorsten; Herrmann, Hans J

2013-01-01

15

Morphology and distribution of common 'sand' dunes on Mars - Comparison with the earth  

Microsoft Academic Search

A comparative study of Martian and terrestrial dunes was made based on Viking Orbiter pictures and aerial pictures of terrestrial deserts. The morphological similarity between the Martian dunes and terrestrial crescentic dunes implies that the dynamics of dune formation are similar on the two planets, despite Martian constraints on dune formation that include much higher velocity winds required to move

C. S. Breed; M. J. Grolier; J. F. McCauley

1979-01-01

16

Observations of nearshore crescentic sandbars  

Microsoft Academic Search

The temporal and spatial variability of crescentic sandbars is analyzed with hourly long-term (months) video observations collected at four barred sites and are qualitatively compared to the temporal and spatial variability predicted by hypotheses underpinning existing approaches and models for crescentic bar formation (edge-wave template model, linear stability analysis, and nonlinear models). The observations, coming from the single barred beaches

I. M. J. van Enckevort; B. G. Ruessink; Giovanni Coco; K. Suzuki; I. L. Turner; N. G. Plant; R. A. Holman

2004-01-01

17

Eolian reservoir characteristics predicted from dune type  

SciTech Connect

The nature of eolian-dune reservoirs is strongly influenced by stratification types (in decreasing order of quality: grain-flow, grain-fall, wind-ripple deposits) and their packaging by internal bounding surfaces. These are, in turn, a function of dune surface processes and migration behavior, allowing for predictive models of reservoir behavior. Migrating, simple crescentic dunes produce tabular bodies consisting mainly of grain-flow cross-strata, and form the best, most predictable reservoirs. Reservoir character improves as both original dune height and preserved set thickness increase, because fewer grain-fall deposits and a lower percentage of dune-apron deposits occur in the cross-strata, respectively. It is probable that many linear and star dunes migrate laterally, leaving a blanket of packages of wind ripple laminae reflecting deposition of broad, shifting aprons. This is distinct from models generated by freezing large portions of these dunes in place. Trailing margins of linear and star dunes are prone to reworking by sand-sheet processes that decrease potential reservoir quality. The occurrence of parabolic dunes isolated on vegetated sand sheets results in a core of grain-flow and grain-fall deposits surrounded by less permeable and porous deposits. Compound crescentic dunes, perhaps the most preservable dune type, may yield laterally (1) single sets of cross-strate, (2) compound sets derived from superimposed simple dunes, or (3) a complex of diverse sets derived from superimposed transverse and linear elements.

Kocurek, G.; Nielson, J.

1985-02-01

18

Corridors of barchan dunes: Stability and size selection P. Hersen,1  

E-print Network

Corridors of barchan dunes: Stability and size selection P. Hersen,1 K. H. Andersen,2 H. Elbelrhiti 29 January 2004 Barchans are crescentic dunes propagating on a solid ground. They form dune fields in the shape of elongated corridors in which the size and spacing between dunes are rather well selected. We

19

Linear stability analysis of transverse dunes  

E-print Network

Sand-moving winds blowing from a constant direction in an area of high sand availability form transverse dunes, which have a fixed profile in the direction orthogonal to the wind. Here we show, by means of a linear stability analysis, that transverse dunes are intrinsically unstable. Any along-axis perturbation on a transverse dune amplify in the course of dune migration due to the combined effect of two main factors, namely: the lateral transport through avalanches along the dune's slip-face, and the scaling of dune migration velocity with the inverse of the dune height. Our calculations provide a quantitative explanation for recent observations from experiments and numerical simulations, which showed that transverse dunes moving on the bedrock cannot exist in a stable form and decay into a chain of crescent-shaped barchans.

Melo, Hygor P M; Andrade, José S; Herrmann, Hans J

2012-01-01

20

Linear stability analysis of transverse dunes  

E-print Network

Sand-moving winds blowing from a constant direction in an area of high sand availability form transverse dunes, which have a fixed profile in the direction orthogonal to the wind. Here we show, by means of a linear stability analysis, that transverse dunes are intrinsically unstable. Any along-axis perturbation on a transverse dune amplify in the course of dune migration due to the combined effect of two main factors, namely: the lateral transport through avalanches along the dune's slip-face, and the scaling of dune migration velocity with the inverse of the dune height. Our calculations provide a quantitative explanation for recent observations from experiments and numerical simulations, which showed that transverse dunes moving on the bedrock cannot exist in a stable form and decay into a chain of crescent-shaped barchans.

Hygor P. M. Melo; Eric J. R. Parteli; José S. Andrade Jr; Hans J. Herrmann

2012-02-13

21

Relapsing polychondritis with crescentic glomerulonephritis  

Microsoft Academic Search

Relapsing polychondritis is rare and its cause is unknown. The tissues affected are those with a high glycosaminoglycan content, such as cartilage, the aorta, the sclera and cornea, and parts of the ear. Symptoms can usually be controlled with oral steroids, but when there is coexistent progressive crescentic glomerulonephritis quadruple chemotherapy may be used. Three cases of the clinical syndrome

G H Neild; J S Cameron; M H Lessof; C S Ogg; D R Turner

1978-01-01

22

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

23

Modelling of dune patterns by short range interactions Clement Narteau, Eric Lajeunesse, Francois Metivier & Olivier Rozier  

E-print Network

Modelling of dune patterns by short range interactions Cl´ement Narteau, Eric Lajeunesse, Franc on crescentic barchan dunes that are used as a benchmark for our numerical model of bedforms. Length and time scales of isolated barchan dunes are studied in order to constrain the parameters of the model. Then we

Narteau, Clément

24

Springtime Dunes, 2004  

NASA Technical Reports Server (NTRS)

12 April 2004 Today is April 12, 2004, the 43rd anniversary of the first human flight into space (Yuri Gagarin, 1961) and the 23rd anniversary of the first NASA Space Shuttle flight (Columbia, 1981). Meanwhile, on Mars, spring is in full swing in the martian northern hemisphere. With spring comes the annual defrosting of the north polar dunes. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image, acquired on April 7, 2004, shows a field of small barchan (crescent-shaped) dunes covered with the remains of wintertime frost. The dark spots around the base of each dune mark the first signs of the spring thaw. The sand in these dunes is dark, like the black sand beaches of Hawaii or the dark, sandy soil of the rover, Opportunity, landing site, but in winter and spring their dark tone is obscured by bright carbon dioxide frost. This picture is located near 75.9oN, 45.3oW, and covers an area about 3 km (1.9 mi) across. Sunlight illuminates the scene from the lower left.

2004-01-01

25

Dune Variety  

NASA Technical Reports Server (NTRS)

9 November 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a variety of dark sand dune patterns and shapes in the north polar region of Mars. Small, aligned dunes in some cases have merged to form elongated dunes. These features are located near 76.4oN, 272.9oW. The image covers an area approximately 3 km (1.9 mi) across and is illuminated by sunlight from the lower left.

2004-01-01

26

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

27

When dunes move together, structure of deserts emerges  

E-print Network

Crescent shaped barchan dunes are highly mobile dunes that are usually presented as a prototypical model of sand dunes. Although they have been theoretically shown to be unstable when considered separately, it is well known that they form large assemblies in desert. Collisions of dunes have been proposed as a mechanism to redistribute sand between dunes and prevent the formation of heavily large dunes, resulting in a stabilizing effect in the context of a dense barchan field. Yet, no models are able to explain the spatial structures of dunes observed in deserts. Here, we use an agent-based model with elementary rules of sand redistribution during collisions to access the full dynamics of very large barchan dune fields. Consequently, stationnary, out of equilibrium states emerge. Trigging the dune field density by a sand load/lost ratio, we show that large dune fields exhibit two assymtotic regimes: a dilute regime, where sand dune nucleation is needed to maintain a dune field, and a dense regime, where dune c...

Génois, Mathieu; Pont, Sylvain Courrech du; Grégoire, Guillaume

2012-01-01

28

Development of spatially diverse and complex dune-field patterns: Gran Desierto Dune Field, Sonora, Mexico  

USGS Publications Warehouse

The pattern of dunes within the Gran Desierto of Sonora, Mexico, is both spatially diverse and complex. Identification of the pattern components from remote-sensing images, combined with statistical analysis of their measured parameters demonstrate that the composite pattern consists of separate populations of simple dune patterns. Age-bracketing by optically stimulated luminescence (OSL) indicates that the simple patterns represent relatively short-lived aeolian constructional events since ???25 ka. The simple dune patterns consist of: (i) late Pleistocene relict linear dunes; (ii) degraded crescentic dunes formed at ???12 ka; (iii) early Holocene western crescentic dunes; (iv) eastern crescentic dunes emplaced at ???7 ka; and (v) star dunes formed during the last 3 ka. Recognition of the simple patterns and their ages allows for the geomorphic backstripping of the composite pattern. Palaeowind reconstructions, based upon the rule of gross bedform-normal transport, are largely in agreement with regional proxy data. The sediment state over time for the Gran Desierto is one in which the sediment supply for aeolian constructional events is derived from previously stored sediment (Ancestral Colorado River sediment), and contemporaneous influx from the lower Colorado River valley and coastal influx from the Bahia del Adair inlet. Aeolian constructional events are triggered by climatic shifts to greater aridity, changes in the wind regime, and the development of a sediment supply. The rate of geomorphic change within the Gran Desierto is significantly greater than the rate of subsidence and burial of the accumulation surface upon which it rests. ?? 2006 The Authors. Journal compilation 2006 International Association of Sedimentologists.

Beveridge, C.; Kocurek, G.; Ewing, R.C.; Lancaster, N.; Morthekai, P.; Singhvi, A.K.; Mahan, S.A.

2006-01-01

29

Cold dust around nearby stars (DUNES). First results: A resolved exo-Kuiper belt around the solar-like star zeta^2 Ret  

E-print Network

We present the first far-IR observations of the solar-type stars delta Pav, HR 8501, 51 Peg and zeta^2 Ret, taken within the context of the DUNES Herschel Open Time Key Programme (OTKP). This project uses the PACS and SPIRE instruments with the objective of studying infrared excesses due to exo-Kuiper belts around nearby solar-type stars. The observed 100 um fluxes from delta Pav, HR 8501, and 51 Peg agree with the predicted photospheric fluxes, excluding debris disks brighter than Ldust/Lstar ~ 5 x 10^-7 (1 sigma level) around those stars. A flattened, disk-like structure with a semi-major axis of ~ 100 AU in size is detected around zeta^2 Ret. The resolved structure suggests the presence of an eccentric dust ring, which we interpret as an exo-Kuiper belt with Ldust/Lstar ~ 10^-5.

Eiroa, C; Maldonado, J; González-García, B M; Rodmann, J; Heras, A M; Pilbratt, G L; Augereau, J -Ch; Mora, A; Montesinos, B; Ardila, D; Bryden, G; Liseau, R; Stapelfeldt, K; Launhardt, R; Solano, E; Bayo, A; Absil, O; Ar?evalo, M; Barrado, D; Beichmann, C; Danchi, W; del Burgo, C; Ertel, S; Fridlund, M; Fukagawa, M; Gutiérrez, R; Grün, E; Kamp, I; Krivov, A; Lebreton, J; Löhne, T; Lorente, R; Marshall, J; Martínez-Arnáiz, R; Meeus, G; Montes, D; Morbidelli, A; Müller, S; Mutschke, H; Nakagawa, T; Olofsson, G; Ribas, I; Roberge, A; Sanz-Forcada, J; Thébault, P; Walker, H; White, G J; Wolf, S

2010-01-01

30

Spring Dunes  

NASA Technical Reports Server (NTRS)

22 July 2006 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dunes in the north polar region of Mars. In this scene, the dunes, and the plain on which the dunes reside, are at least in part covered by a bright carbon dioxide frost. Dark spots indicate areas where the frost has begun to change, either by subliming away to expose dark sand, changing to a coarser particle size, or both. The winds responsible for the formation of these dunes blew from the lower left (southwest) toward the upper right (northeast).

Location near: 76.3oN, 261.2oW Image width: 3 km (1.9 mi) Illumination from: lower left Season: Northern Spring

2006-01-01

31

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 ...

32

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

Federal Register 2010, 2011, 2012, 2013

...the Docket Management Facility. We recommend that...that they reached the Facility, please enclose a stamped...self-addressed postcard or envelope. We will consider all...the Docket Management Facility in Room W12-140 on...Coast Guard to establish safety zones. Crescent...

2013-04-23

33

Origins of barchan dune asymmetry: insights from numerical simulations  

E-print Network

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 $90^{\\circ}$, 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.

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

2013-04-24

34

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

35

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

36

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

37

Frosty Dunes  

NASA Technical Reports Server (NTRS)

29 August 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows frost-covered sand dunes in the martian north polar region. The winds responsible for these dunes generally blew from the southwest (lower left).

Location near: 80.0oN, 114.6oW Image width: width: 3 km (1.9 mi) Illumination from: lower left Season: Northern Spring

2005-01-01

38

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

39

Corridors of barchan dunes: Stability and size selection.  

PubMed

Barchans are crescentic dunes propagating on a solid ground. They form dune fields in the shape of elongated corridors in which the size and spacing between dunes are rather well selected. We show that even very realistic models for solitary dunes do not reproduce these corridors. Instead, two instabilities take place. First, barchans receive a sand flux at their back proportional to their width while the sand escapes only from their horns. Large dunes proportionally capture more sand than they lose, while the situation is reversed for small ones: therefore, solitary dunes cannot remain in a steady state. Second, the propagation speed of dunes decreases with the size of the dune: this leads, through the collision process, to a coarsening of barchan fields. We show that these phenomena are not specific to the model, but result from general and robust mechanisms. The length scales needed for these instabilities to develop are derived and discussed. They turn out to be much smaller than the dune field length. As a conclusion, there should exist further, yet unknown, mechanisms regulating and selecting the size of dunes. PMID:14995611

Hersen, P; Andersen, K H; Elbelrhiti, H; Andreotti, B; Claudin, P; Douady, S

2004-01-01

40

International Federation of Red Cross and Red Crescent Societies  

MedlinePLUS

... Abdul Rahman Attar, President of the Syrian Arab Red Crescent, welcomed Mr. Elhadj As Sy, ... Featured video ... of fraudulent web sites which are using the Red Cross Red Crescent emblems to request donations for ...

41

COPPICE DUNES Duned (39,880 -22)  

E-print Network

COPPICE DUNES Duned (39,880 - 22) Unduned (144,160 - 78) Numbers in parentheses are acres and percentages respectively Occurrence of coppice dunes is as shown on 1936 aerial photographs; many of these areas are now occupied by buildings and roads. These dunes tend to occur primarily in areas where

42

Frosted Dunes  

NASA Technical Reports Server (NTRS)

17 June 2006 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a group of sand dunes, covered by seasonal carbon dioxide frost, in the martian north polar region. Over the course of northern hemisphere spring, the carbon dioxide frost sublimes away, slowly revealing the dark sand that makes up the dunes. The dark spots in this image may be patches of freshly-exposed sand, or they could be places where the CO2 frost has changed, either becoming rougher, coarser-grained (larger crystals), or both. A rougher or coarser-grained surface will appear darker because of an increase in shadowing of the surface by the small-scale roughness elements.

Location near: 75.2oN, 51.3oW Image width: 3 km (1.9 mi) Illumination from: lower left Season: Northern Spring

2006-01-01

43

December's Dunes  

NASA Technical Reports Server (NTRS)

This Mars Global Surveyor (MGS) Orbiter Camera (MOC) image shows sand dunes in the north polar region of Mars, as they appeared during northern summer in December 2004.

Location near: 78.1oN, 227.2oW Image width: 3.0 km (1.9 mi) Illumination from: lower left Season: Northern Summer

2005-01-01

44

Defrosty Dunes  

NASA Technical Reports Server (NTRS)

19 July 2006 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a portion of a sand dune field in the north polar region of Mars. The dunes are covered with frozen carbon dioxide which accumulated over the autumn and winter months in the northern hemisphere. During the spring, the time at which this image was acquired, the carbon dioxide begins to sublime away, going directly from solid to gas, just as dry ice does here on Earth. The dark spots, streaked by blowing winds, may be places where the frost has been removed (exposing underlying dark sand), places where the grain size or roughness of the frost has increased (increasing shadowing due to the change in texture), or both.

Location near: 79.7oN, 148.3oW Image width: 3 km (1.9 mi) Illumination from: lower left Season: Northern Spring

2006-01-01

45

Color Voyager 2 Image Showing Crescent Uranus  

NASA Technical Reports Server (NTRS)

This image shows a crescent Uranus, a view that Earthlings never witnessed until Voyager 2 flew near and then beyond Uranus on January 24, 1986. This planet's natural blue-green color is due to the absorption of redder wavelengths in the atmosphere by traces of methane gas. Uranus' diameter is 32,500 miles, a little over four times that of Earth. The hazy blue-green atmosphere probably extends to a depth of around 5,400 miles, where it rests above what is believed to be an icy or liquid mixture (an 'ocean') of water, ammonia, methane, and other volatiles, which in turn surrounds a rocky core perhaps a little smaller than Earth.

1990-01-01

46

ASTER Dunes  

NASA Technical Reports Server (NTRS)

This image of Saudi Arabia shows a great sea of linear dunes in part of the Rub' al Khali, or the Empty Quarter. Acquired on June 25, 2000, the image covers an area 37 kilometers (23 miles) wide and 28 kilometers (17 miles) long in three bands of the reflected visible and infrared wavelength region. The dunes are yellow due to the presence of iron oxide minerals. The inter-dune area is made up of clays and silt and appears blue due to its high reflectance in band 1. The Rub' al Khali is the world's largest continuous sand desert. It covers about 650,000 square kilometers (250,966 square miles) and lies mainly in southern Saudi Arabia, though it does extend into the United Arab Emirates, Oman, and Yemen. One of the world's driest areas, it is uninhabited except for the Bedouin nomads who cross it. The first European to travel through the desert was Bertram Thomas in 1930.

Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is one of five Earth-observing instruments launched December 18, 1999, on NASA's Terra satellite. The instrument was built by Japan's Ministry of International Trade and Industry. A joint U.S./Japan science team is responsible for validation and calibration of the instrument and the data products. Dr. Anne Kahle at NASA's Jet Propulsion Laboratory, Pasadena, California, is the U.S. science team leader; Moshe Pniel of JPL is the project manager. ASTER is the only high-resolution imaging sensor on Terra. The primary goal of the ASTER mission is to obtain high-resolution image data in 14 channels over the entire land surface, as well as black and white stereo images. With revisit time of between 4 and 16 days, ASTER will provide the capability for repeat coverage of changing areas on Earth's surface.

The broad spectral coverage and high spectral resolution of ASTER will provide scientists in numerous disciplines with critical information for surface mapping and monitoring dynamic conditions and temporal change. Examples of applications include monitoring glacial advances and retreats, potentially active volcanoes, thermal pollution, and coral reef degradation; identifying crop stress; determining cloud morphology and physical properties; evaluating wetlands; mapping surface temperature of soils and geology; and measuring surface heat balance.

2000-01-01

47

Polar Dunes  

NASA Technical Reports Server (NTRS)

[figure removed for brevity, see original site]

Dunes in the Vastitas Borealis region of Mars. These sand seas migrate around the north polar cap following the strong polar vortex winds.

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.

Image information: VIS instrument. Latitude 77.3, Longitude 87.3 East (272.7 West). 19 meter/pixel resolution.

2003-01-01

48

'Endurance Crater's' Dazzling Dunes  

NASA Technical Reports Server (NTRS)

As NASA's Mars Exploration Rover Opportunity creeps farther into 'Endurance Crater,' the dune field on the crater floor appears even more dramatic. This approximate true-color panoramic camera image highlights the reddish-colored dust present throughout the scene.

Sinuous tendrils of sand less than 1 meter (3.3 feet) high extend from the main dune field toward the rover. Scientists hope to send the rover down to one of these tendrils in an effort to learn more about the characteristics of the dunes. Dunes are a common feature across the surface of Mars, and knowledge gleaned from investigating the Endurance dunes close-up may apply to similar dunes elsewhere.

Before the rover heads down to the dunes, rover drivers must first establish whether the slippery slope that leads to them is firm enough to ensure a successful drive back out of the crater. Otherwise, such hazards might make the dune field a true sand trap.

2004-01-01

49

Fire scars and ancient sand dunes in southern Australia  

NASA Technical Reports Server (NTRS)

The rectangular green areas in this view of southern Australia are protected areas of natural forest (national parks and biospheric reserves), and the lighter surrounding colors (tan-brown) are agricultural croplands occupying land which once must have looked as green as the nature reserves but are now cleared of forest. The major green patch has been recently burned, as shown by the irregular pattern of a large, multiple burn scar. The pattern of the fire scar indicates that the fires were driven by winds blowing from left to right. Close examination of the view shows that the forests are rooted in a soil made up of a widespread sheet of ancient dune sand. The dunes can be seen best within the area of the large fire scar where the characteristic wavy, scalloped pattern of crescent dunes can be detected. The crescents indicate that the sand was heaped up by winds blowing from right to left in this view, in the opposite direction to the winds which fanned the fires. A few straight dunes

1994-01-01

50

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

51

Activated (IL2R+) intraglomerular mononuclear cells in crescentic glomerulonephritis  

Microsoft Academic Search

Activated (IL-2R+) intraglomerular mononuclear cells in crescentic glomerulonephritis. We recently reported evidence for the involvement of local cellular immune activation in the immunopathogenesis of human IgA nephropathy, particularly in cases of IgA disease featuring crescent formation. In the current study, using monoclonal antibodies, we investigated whether mononuclear cells bearing receptors for inter-leukin 2 (IL-2R+ MNC) were present within glomeruli or

Hai-Ling Li; Wayne W Hancock; John P Dowling; Robert C Atkins

1991-01-01

52

Transverse instability of dunes  

E-print Network

The simplest type of dune is the transverse one, which propagates with invariant profile orthogonally to a fixed wind direction. Here we show numerically and with a linear stability analysis that transverse dunes are unstable with respect to along-axis perturbations in their profile and decay on the bedrock into barchan dunes. Any forcing modulation amplifies exponentially with growth rate determined by the dune turnover time. We estimate the distance covered by a transverse dune before fully decaying into barchans and identify the patterns produced by different types of perturbation.

Eric J. R. Parteli; José S. Andrade Jr.; Hans J. Herrmann

2011-09-22

53

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

54

Defrosting of Russell Crater Dunes  

NASA Technical Reports Server (NTRS)

These two images (at right) were acquired by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) 39 days apart at 19:10 UTC (2:10 PM EST) on December 28, 2006 (upper right) and at 20:06 UTC (3:06 PM EST) on February 5, 2007 (lower right). These CRISM data were acquired in 544 colors covering the wavelength range from 0.36-3.92 micrometers, and show features as small as 20 meters (about 65 feet) across. Both images are false color composites of bands at 2.5, 1.5, and 1.25 micrometers, and are nearly centered at the same location, 54.875oS, 12.919oE (upper right) and 54.895oS, 12.943oE (lower right). Each image is approximately 11 kilometers (7 miles) across at its narrowest. These are part of a series of images capturing the evolution of carbon dioxide frost on the surface of the dunes in Russell Crater.

Russell Crater is one of many craters in the southern highland region of Mars that contain large areas of sand dunes. The sand in these dunes has accumulated over a very long time period -- perhaps millions of years -- as wind blows over the highland terrain, picking up sand in some places and depositing in others. The topography of the craters forces the wind to blow up and over the crater rims, and the wind often isn't strong enough to keep the tiny grains suspended. This makes the sand fall to the ground and gradually pile up, and over time the surface breezes shape the sand into ripples and dunes. A similar process is at work at the Great Sand Dunes National Park and Preserve in Colorado, USA.

The above left image shows a THEMIS daytime infrared mosaic of Russell Crater and the location of its (approximately) 30-kilometer wide dune field in the northeastern quadrant of the crater floor. Superposed on this view and shown enlarged at the upper right is CRISM image FRT000039DF. This CRISM image was acquired during the late Martian southern winter (solar longitude = 157.7o), and the bright blue in this false color composite indicates the presence of carbon dioxide frost (dry ice) on the dunes. Sunlight is coming from the northeast, and the sunlit faces of the dunes appear red because they show very little frost compared to the colder, more shadowed areas. Thirty-nine days later at the beginning of southern spring (solar longitude = 178.9o), CRISM image FRT000042AA (lower right) was acquired almost at the same location. Notably, the bright blue frost-rich areas are considerably smaller and subdued, with slim patches only observed on the shadowed sides of the dunes that are most protected from the warmth of the rising sun. As the southern season continues to march toward summer, all of the frost will soon be gone and won't return until the next Martian winter.

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

55

Unchanging Desert Sand Dunes  

NASA Astrophysics Data System (ADS)

Deserts are one of the major landforms on earth. They occupy nearly 20% of the total land area but are relatively less studied. With the rise in human population, desert regions are being gradually occupied for settlement posing a management challenge to the concerned authorities. Unrestrained erosion is generally a feature of bare dunes. Stabilized dunes, on the other hand, do not undergo major changes in textures, and can thus facilitate the growth of vegetation. Keeping in view of the above factors, better mapping and monitoring of deserts and particularly of sand dunes is needed. Mapping dunes using field instruments is very arduous and they generate relatively sparse data. In this communication, we present a method of clustering and monitoring sand dunes through imagery captured by remote sensing sensors. Initially Radon spectrum of an area is obtained by decomposition of the image into various projections sampled at finer angular directions. Statistical features such as mode, entropy and standard deviation of Radon spectrum are used in delineation and clustering of regions with different dune orientations. These clustered boundaries are used to detect if there are any changes occurring in the dune regions. In the experiment's, remote sensing data covering various dune regions of the world are observed for possible changes in dune orientations. In all the cases, it is seen that there are no major changes in desert dune orientations. While these findings have implications for understanding of dune geomorphology and changes occurring in dune directions, they also highlight the importance of a wider study of dunes and their evolution both at regional and global scales. Results for Dataset 1 & Dataset 2 Results for Dataset 3

Gadhiraju, S.; Banerjee, B.; Buddhiraju, K.; Shah, V.

2013-12-01

56

Modelling vegetated dune landscapes  

NASA Astrophysics Data System (ADS)

This letter presents a self-organising cellular automaton model capable of simulating the evolution of vegetated dunes with multiple types of plant response in the environment. It can successfully replicate hairpin, or long-walled, parabolic dunes with trailing ridges as well as nebkha dunes with distinctive deposition tails. Quantification of simulated landscapes with eco-geomorphic state variables and subsequent cluster analysis and PCA yields a phase diagram of different types of coastal dunes developing from blow-outs as a function of vegetation vitality. This diagram indicates the potential sensitivity of dormant dune fields to reactivation under declining vegetation vitality, e.g. due to climatic changes. Nebkha simulations with different grid resolutions demonstrate that the interaction between the (abiotic) geomorphic processes and the biological vegetation component (life) introduces a characteristic length scale on the resultant landforms that breaks the typical self-similar scaling of (un-vegetated) bare-sand dunes.

Baas, A. C. W.; Nield, J. M.

2007-03-01

57

Frosted Sand Dunes  

NASA Technical Reports Server (NTRS)

[figure removed for brevity, see original site] (Released 22 July 2002) This image, located near 79.6 N and 142.7 E, displays sand dunes covered in CO2 frost. This is a region of Mars that contains circumpolar sand seas. The large sand deposits and the high winds that circulate around the pole allow for the formation of a huge dune field that surrounds the north polar cap. As the northern hemisphere progresses towards winter, CO2 frost condenses out of the atmosphere and covers the dunes. During northern spring, the CO2 sublimates and the dunes are once again uncovered and active. This image was taken as northern spring progresses and the crests of the dunes are just starting to be exposed. The dark dune material absorbs sunlight more efficiently than the brighter frost, aiding in the sublimation of the remaining frost.

2002-01-01

58

North Polar Sand Dunes  

NASA Technical Reports Server (NTRS)

MGS MOC Release No. MOC2-417, 10 July 2003

The martian north polar ice cap is surrounded by fields of dark, windblown sand dunes. This March 2003 Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dunes near 76.5oN, 264.7oW. The steep dune slip faces indicate wind transport of sand from the lower left toward the upper right. Sunlight illuminates the scene from the lower left.

2003-01-01

59

Crescentic glomerulonephritis in a polar bear (Ursus maritimus).  

PubMed

Spontaneous crescentic glomerulonephritis (CrGN) in animals has only been reported in dog and sheep. We report the pathological features of CrGN in a 17-year-old male polar bear that died due to renal failure. Histologically, the lesions were characterized by fibrocellular crescents, adhesion between Bowman's capsule and the glomerular capillary tuft and an increase in the mesangial matrix in glomeruli. The proliferating cells in the crescent were partly immunopositive for cytokeratin and intensely positive for vimentin, WT-1 and ?-smooth muscle actin, suggesting they originated from parietal epithelial cells. Ultrastructually, thickening of the glomerular basement membrane and loss of epithelial cell foot processes were observed with electron-dense deposits. PMID:23856758

Baba, Hiroshi; Kudo, Tomoo; Makino, Yoshinori; Mochizuki, Yasumasa; Takagi, Takayo; Une, Yumi

2013-11-01

60

Suppression of experimental crescentic glomerulonephritis by interleukin-10 gene transfer  

Microsoft Academic Search

Suppression of experimental crescentic glomerulonephritis by interleukin-10 gene transfer.BackgroundInvestigated were effects of overexpression of interleukin-10 (IL-10) on the outcome and progression of crescentic glomerulonephritis in Wistar-Kyoto (WKY) rats.MethodsRats were singly or simultaneously injected with antiglomerular basement membrane (a-GBM) antibody and adenoviral vector encoding rat IL-10 (Ad-rIL-10) or LacZ (Ad-LacZ) (3 × 1010 pfu\\/rat) intravenously, and were sacrificed at day 7.

Adel G. A. El-Shemi; HIDEHIKO FUJINAKA; ASAKO MATSUKI; JUNICHI KAMIIE; PAVEL KOVALENKO; ZHENYUN QU; VLADIMIR BILIM; GORO NISHIMOTO; EISHIN YAOITA; YUATKA YOSHIDA; IGNACIO ANEGON; TADASHI YAMAMOTO

2004-01-01

61

Temperature and humidity measurements within desert barchan sand dunes, relation to dune aeolian mobility and microbial growth  

NASA Astrophysics Data System (ADS)

We present diurnal variations of temperature and humidity profiles below the surface of hyper-arid aeolian crescent-shaped "barchan" dunes in Qatar and Mauritania, measured using a thermal probe and a new ultra-sensitive capacitance instrument that we developed for this purpose. We also report long-term measurements from a probe sunk on the downwind avalanche face of a mobile Qatar barchan, recording temperature and humidity until it emerged on the upwind slope 15 months later. We interpret the data by modeling heat and moisture transfer at the surface in terms of measured net surface radiation, wind, and atmospheric conditions. We demonstrate the presence of microbes on sand grains within these mobile dunes using microscopic observations, fluorescence counts, metagenomic sequencing, and C12/C13 isotope analysis of carbon dioxide sampled below the surface. By determining how water activity grows with moisture adsorbed on these sands, we delimit regions within the dune where our instruments recorded humidity conducive to microbial growth. Finally, we compare the mobility of two adjacent Mauritania barchans having distinct surface grain size, shape, and depth humidity profiles. Armored by large grains on its surface, the smaller dune was more oblong. As a result, it lacked flow recirculation in its wake, trapped less aeolian sand downwind, and was much less mobile than its smaller size would suggest. This slower mobility led to greater humidity and cohesion at depth than the larger dune exposed to the same atmospheric and wind conditions.

Louge, Michel; Hay, Anthony; Richer, Renee; Valance, Alexandre; Ould el Moctar, Ahmed; Xu, Jin; Abdul-Majid, Sara

2013-04-01

62

Nearly-defrosted Dunes  

NASA Technical Reports Server (NTRS)

22 December 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a group of north polar dunes in late spring, just before the final patches of wintertime frost sublimed away. The dunes beneath the frost are dark because they contain minerals rich in reduced (unoxidized) iron. The dune slip faces (the steepest slopes on the dunes) point toward the upper right (northeast), indicating that the dominant winds involved in sand transport in this region blow from the lower left (southwest). These dunes are located near 76.3oN, 261.1oW. The image covers an area about 3 km (1.9 mi) wide and sunlight illuminates the scene from the lower left.

2004-01-01

63

Frosty North Polar Dunes  

NASA Technical Reports Server (NTRS)

10 January 2004 While it is summer in Gusev Crater, where the Mars Exploration Rover, Spirit, is operating, it is winter in the martian northern hemisphere. Just this week, the north polar dune fields began to emerge into sunlight after months of frigid darkness. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) view of frost-covered north polar dunes was acquired on 8 January 2004. The steepest slopes on the dunes--their slipfaces--point toward the upper right (northeast), indicating that the dominant winds responsible for their formation came from the opposite direction (lower left, southwest). Sunlight illuminates these dunes from the lower left, which may seem surprising because the brightest slopes on the dunes face the lower right. The brighter slopes are a frost phenomenon; most likely, these are areas with thicker frost deposits. In summer, the dunes would not have frost and would appear much darker than their surroundings. This early view of north polar dunes in winter is located near 75.8oN, 266.3oW. This view covers an area 3 km (1.9 mi) wide.

2004-01-01

64

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

65

North Polar Dunes  

NASA Technical Reports Server (NTRS)

23 January 2006 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dark sand dunes in the north polar region of Mars. Surrounding much of the north polar ice cap are fields of sand dunes. In this case, the strongest winds responsible for the dunes blew off the polar cap (not seen here), from the north-northwest (upper left).

Location near: 76.5oN, 63.7oW Image width: 3 km (1.9 mi) Illumination from: lower left Season: Northern Summer

2006-01-01

66

Frosty Dune Field  

NASA Technical Reports Server (NTRS)

1 May 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows frost-covered sand dunes in the early northern spring of 2004 in the north polar region. Sunlight illuminates the dunes from the bottom/lower left, but frost on slopes facing the lower right create the illusion of sunlight from that direction. This dune field, which would appear quite dark in summertime, is located near 80.3oN, 148.7oW. The picture covers an area about 3 km (1.9 mi) across.

2004-01-01

67

Dark Polar Dunes  

NASA Technical Reports Server (NTRS)

20 January 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image, acquired during northern summer in December 2004, shows dark, windblown sand dunes in the north polar region of Mars. A vast sea of sand dunes nearly surrounds the north polar cap. These landforms are located near 80.3oN, 144.1oW. Light-toned features in the image are exposures of the substrate that underlies the dune field. The image covers an area about 3 km (1.9 mi) wide and is illuminated by sunlight from the lower left.

2005-01-01

68

North Polar Dunes  

NASA Technical Reports Server (NTRS)

14 April 2004 The north polar cap of Mars is nearly surrounded by fields of dark sand dunes. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows some of the north polar dunes as they appeared in late winter in January 2004. At the time, the dunes were covered with frost. The image is located near 77.8oN, 52.8oW. The image covers an area about 3 km (1.9 mi) across. Sunlight illuminates the scene from the lower left.

2004-01-01

69

Fortune Cookie Sand Dunes  

NASA Technical Reports Server (NTRS)

MGS MOC Release No. MOC2-432, 25 July 2003

This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a field of small barchan sand dunes in the north polar region near 71.7oN, 51.3oW. Some of them are shaped like fortune cookies. The message these dunes provide: winds blow through this region from the lower right toward the upper left. The steep slip face slopes of these dunes, which point toward the upper left, indicate the wind direction. The scene is illuminated by sunlight from the upper right. The image is 3 km (1.9 mi) wide.

2003-01-01

70

Chasma Boreale Dunes  

NASA Technical Reports Server (NTRS)

MGS MOC Release No. MOC2-354, 8 May 2003

In this Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image, wind has streaked a field of defrosting sand dunes in Chasma Boreale in the martian north polar region. Dune slip faces--the steep slope formed by avalanching sand on each dune--and the dark streaks indicate that wind transports sediment from the lower left toward the upper right. The picture covers an area about 3 km (1.9 mi) wide near 84.6oN, 358.5oW. Sunlight illuminates the scene from the lower left.

2003-01-01

71

North Polar Dunes  

NASA Technical Reports Server (NTRS)

20 December 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a grouping of elongated, dark (low albedo) sand dunes in the north polar region of Mars. This picture was acquired during early summer in October 2004. The larger dune mass in this image may have accumulated through the coalescence of smaller dunes. These features are located near 85.7oN, 180.4oW. The image covers an area about 3 km (1.9 mi) wide and is illuminated by sunlight from the lower left.

2004-01-01

72

Dune Avalanche Scars  

NASA Technical Reports Server (NTRS)

05 August 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows large, low albedo (dark) sand dunes in Kaiser Crater near 47.2oS, 340.4oW. The dunes are--ever so slowly--moving east to west (right to left) as sand avalanches down the steeper, slip face slopes of each. Avalanching sand in the Kaiser dune field has left deep scars on these slopes, suggesting that the sand is not loose but is instead weakly cemented. The image covers an area approximately 3 km (1.9 mi) wide and is illuminated by sunlight from the upper left.

2004-01-01

73

Polar Sand Dunes  

NASA Technical Reports Server (NTRS)

MGS MOC Release No. MOC2-495, 26 September 2003

This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows windblown sand dunes in Chasma Boreale, a wide trough in the north polar region of Mars. The dunes are shown here in their summertime configuration; that is, they are not covered with seasonal frost. The dunes are dark because the grains that make up these sandy landforms consist of dark minerals and/or fragments of dark-toned rock. The steepest slopes on these dunes, their slipfaces, point toward the top/upper left (northwest), indicating that winds blow the sand from the lower right (southeast). This picture is located near 84.7oN, 359.3oW, and covers an area 3 km (1.9 mi) across. Sunlight illuminates the scene from the lower left.

2003-01-01

74

Springtime for Dunes  

NASA Technical Reports Server (NTRS)

06 August 2004 The springtime retreat of the north polar seasonal frost cap is progressing on schedule. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows the state of defrosting north polar sand dunes just three days ago on 3 August 2004. Dark areas on the dunes are patches of bare sand; bright areas are remnants of frost deposited during the previous winter. Summer will arrive on 20 September 2004. These dunes are located near 76.3oN, 263.5oW. Their steepest slopes, known as the slip face of each dune, point toward the northeast (upper right), indicating wind transport of sand from the southwest (lower left). The image covers an area about 3 km (1.9 mi) across and is illuminated by sunlight from the lower left.

2004-01-01

75

Spring Time View of North Polar Sand Dunes  

NASA Technical Reports Server (NTRS)

Spring has come to the martian northern hemisphere. The northern spring season began in mid-July 1998. With the arrival of spring comes the annual shrinkage of the north polar frost cap. Sunlight is now falling on the north polar cap, and all of the carbon dioxide frost and snow that accumulated during winter has been sublimating--going directly from solid to gas--and the surface beneath the frost is being revealed.

The MOC image shown above, 45205, was obtained during the 452nd orbit of Mars Global Surveyor at 3:10 p.m. PDT on July 26, 1998. The image is located near latitude 76.87oN, longitude 253.81oW, and it shows a close-up view of martian sand dunes. These dunes were not visible to MOC until the last week of July. Just a few months earlier, the dunes were likely covered with frost, obscured by thick clouds, and cloaked by the darkness of the martian polar winter. Indeed, small patches of bright frost were still present when the picture was taken (e.g., the bright patches on the west (left) side of each crescentic dune in (left image).

As the above picture illustrates, the camera on board Mars Global Surveyor (MOC) continued to take exciting new views of the martian surface throughout July 1998. As the month progressed, the ground track-- the area visible to the camera--migrated farther north. Simultaneously, sunlight began falling on the north polar regions, making it possible to take some pictures at far northern latitudes. However, these regions have been tricky to photograph because of thick clouds and hazes. The image shown here, for example, is relatively bland gray (has relatively low contrast) because of clouds.

As first seen by the Viking 2 Orbiter in 1976, a vast 'sea' of sand dunes surrounds the north polar cap. The dunes imaged by MOC (above) are classic forms known as barchan dunes--the small, crescent-shaped hills (see left image above)-- and transverse dunes--ridges that resemble coalesced barchans (shown in right image above). These dunes are similar in size and shape to familiar sand dunes found in desert regions on Earth. These two varieties form from winds that persistently come from a single direction (in this case, from the southwest).

Over the next several months, the sky above these dunes will clear. Northern Summer will arrive near the end of January 1999, and Mars Global Surveyor should have an excellent view of this region when it begins its mapping mission in late March 1999. Because it is in a polar orbit, Mars Global Surveyor will have many opportunities to revisit the north polar dunes in 1999. The images in 1999 will have resolutions around 1.5 meters (5 feet) per pixel--a substantial improvement even over the pictures shown here.

1998-01-01

76

Frost on Dunes  

NASA Technical Reports Server (NTRS)

18 March 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dark dunes on a crater floor during the southern spring. Some of the dunes have frost on their south-facing slopes.

Location near: 52.3oS, 326.7oW Image width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Spring

2005-01-01

77

Dark Sand Dunes  

NASA Technical Reports Server (NTRS)

13 January 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dark sand dunes in the north polar region of Mars. The dominant winds responsible for these dunes blew from the lower left (southwest). They are located near 76.6oN, 257.2oW. The picture covers an area 3 km (1.9 mi) across; sunlight illuminates the scene from the upper right.

2005-01-01

78

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

79

Moving sand dunes  

E-print Network

In several desert areas, the slow motion of sand dunes can be a challenge for modern human activities and a threat for the survival of ancient places or archaeological sites. However, several methods exist for surveying the dune fields and estimate their migration rate. Among these methods, the use of satellite images, in particular of those freely available on the World Wide Web, is a convenient resource for the planning of future human settlements and activities.

Sparavigna, Amelia Carolina

2011-01-01

80

International Federation of Red Cross and Red Crescent Societies  

NSDL National Science Digital Library

With a broad mission, the International Federation of Red Cross and Red Crescent Societies are involved in everything from disaster response and management to capacity building all over the globe. As one might expect, visitors to the site can learn about some of their more well-known programs in the "Get Involved" area on the homepage. Their homepage is also an excellent place to learn about some of their research publications, which include their annual "World Disasters Report" and their in-house magazine, "Red Cross, Red Crescent". For more nuts-and-bolts type information on the organization, visitors should browse through the "Who We Are", "What We Do", and "Where We Work" sections. Additionally, visitors can enter the "Our Programmes" section to learn about their various outreach efforts in different regions of the world.

81

Dark Barchan Dunes  

NASA Technical Reports Server (NTRS)

13 May 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows north polar sand dunes in the summertime. During winter and early spring, north polar dunes are covered with bright frost. When the frost sublimes away, the dunes appear darker than their surroundings. To a geologist, sand has a very specific meaning. A sand grain is defined independently of its composition; it is a particle with a size between 62.5 and 2000 microns. Two thousand microns equals 2 millimeters. The dunes are dark because they are composed of sand grains made of dark minerals and/or rock fragments. Usually, dark grains indicate the presence of unoxidized iron, for example, the dark volcanic rocks of Hawaii, Iceland, and elsewhere. This dune field is located near 71.7oN, 51.3oW. Dune slip faces indicate winds that blow from the upper left toward lower right. This picture covers an area approximately 3 km (1.9 mi) across and is illuminated by sunlight from the lower left.

2004-01-01

82

Mesopotamian fertile crescent nearly gone, new study indicates  

Microsoft Academic Search

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

Randy Showstack

2001-01-01

83

Tsunami Hazard Assessment and Inundation Maps for Crescent City  

NASA Astrophysics Data System (ADS)

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 (Titov and Synolakis, 1998). We benchmark our CSZ inundation projections against mapped flooded areas and tide gauge data from the 1964 tsunami, which destroyed 29 city blocks, and also from the damaging 15 November 2006 Kuril Islands tsunami. Results suggest that inundation from CSZ tsunamis could extend over 3 km inland, twice as far as the limits of the 1964 inundation. Crescent City is most vulnerable to slip on the Gorda segment of the CSZ. Rupture of the northern or Juan De Fuca segment produces lower water heights than the 1964 event. At Crescent City, the tsunami surges a leading elevation wave just after the earthquake. Educational and preparedness for self-evacuation are essential to save lives. Titov V.V. and Synolakis, C.E., 1998, Numerical modeling of Tidal Wave Runup, J. Waterway, Port, Coast. Eng., vol 124 (4) 157-171.

Uslu, B.; Borrero, J. C.; Barberopoulou, A. E.; Synolakis, C. E.

2007-12-01

84

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

85

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

86

Ripples and Dunes  

NASA Technical Reports Server (NTRS)

27 May 2006 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dark sand dunes on the floor of an impact crater west of Hellas Planitia. Portions of the crater floor are exposed near the center and lower right corner of the image but, in general, the floor is covered by large, windblown ripples. The dark dune sand typically covers ripples, indicating that the dunes are younger and made of a more mobile material.

Location near: 43.7oS, 320.4oW Image width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Summer

2006-01-01

87

Dunes with Frost  

NASA Technical Reports Server (NTRS)

31 May 2004 Springtime for the martian northern hemisphere brings defrosting spots and patterns to the north polar dune fields. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows an example located near 76.7oN, 250.4oW. In summer, these dunes would be darker than their surroundings. However, while they are still covered by frost, they are not any darker than the substrate across which the sand is slowly traveling. Dune movement in this case is dominated by winds that blow from the southwest (lower left) toward the northeast (upper right). The picure covers an area about 3 km (1.9 mi) across and is illuminated by sunlight from the lower left.

2004-01-01

88

Dunes of the North  

NASA Technical Reports Server (NTRS)

30 March 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows linear and barchan sand dunes in Chasma Boreale, a broad erosional trough in the martian north polar region. Winds responsible for these dunes generally blow from upper right toward the lower left. Martian dunes tend to be darker than their counterparts on Earth because they are composed of darker, iron-bearing minerals and rock fragments.

Location near: 84.2oN, 37.9oW Image width: 3 km (1.9 mi) Illumination from: lower left Season: Northern Summer

2005-01-01

89

Defrosting North Polar Dunes  

NASA Technical Reports Server (NTRS)

MGS MOC Release No. MOC2-323, 12 December 2002

Each spring as the sun comes up over the polar regions, the seasonal frosts that have accumulated there during winter begin to sublime away. Dunes are among the first features to show spots and streaks resulting from the defrosting process. Unknown is whether the dark spots and streaks are sand (from the dune) that has been mobilized by wind, or frost that has become disrupted and coarse-grained (coarse grains of ice can look darker than fine grains). This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows north polar dunes near 76.6oN, 255.9oW in early spring. The image, acquired in June 2002, is 3 km (1.9 mi) across. Sunlight illuminates the scene from the lower left.

2002-01-01

90

Aligned Defrosting Dunes  

NASA Technical Reports Server (NTRS)

17 August 2004 This July 2004 Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a group of aligned barchan sand dunes in the martian north polar region. At the time, the dunes were covered with seasonal frost, but the frost had begun to sublime away, leaving dark spots and dark outlines around the dunes. The surrounding plains exhibit small, diffuse spots that are also the result of subliming seasonal frost. This northern spring image, acquired on a descending ground track (as MGS was moving north to south on the 'night' side of Mars) is located near 78.8oN, 34.8oW. The image covers an area about 3 km (1.9 mi) across and sunlight illuminates the scene from the upper left.

2004-01-01

91

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

92

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

93

Sand Dunes in Hellas  

NASA Technical Reports Server (NTRS)

MGS MOC Release No. MOC2-537, 7 November 2003

The smooth, rounded mounds in this Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) picture are sand dunes. The scene is located in southern Hellas Planitia and was acquired in mid-southern autumn, the ideal time of year for Hellas imaging. Sunlight illuminates the scene from the upper left. These dunes are located near 49.1oS, 292.6oW. The picture covers an area 3 km (1.9 mi) wide.

2003-01-01

94

North Polar Dunes  

NASA Technical Reports Server (NTRS)

10 April 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows low-albedo sand dunes in the north polar region. The slip faces on the dunes face toward the lower left, indicating that the dominant winds in this region blow or blew from the upper right.

Location near: 82.4oN, 46.5oW Image width: 3 km (1.9 mi) Illumination from: lower left Season: Northern Summer

2005-01-01

95

North Polar Dunes  

NASA Technical Reports Server (NTRS)

MGS MOC Release No. MOC2-499b, 30 September 2003

The steepest slope on a sand dune, the slipface, indicates the general direction that wind has been transporting sediment. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows several dark sand dunes in the north polar region. Sand transport in this case is from the lower left (southwest) toward the upper right (northeast). The picture is located near 76.5oN, 257.4oW, and covers an area 3 km (1.9 mi) across. Sunlight illuminates the scene from the lower left.

2003-01-01

96

Dark Polar Dunes  

NASA Technical Reports Server (NTRS)

26 May 2004 The north polar cap of Mars is surrounded by fields of dark sand dunes. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows several dunes in the north polar region. The winds responsible for them blow from the lower left toward the upper right. The picture is located near 78.6oN, 243.9oW. Sunlight illuminates the scene from the lower left, and the picture covers an area about 3 km (1.9 mi) across.

2004-01-01

97

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

98

Sand Dunes with Frost  

NASA Technical Reports Server (NTRS)

9 May 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a suite of frost-covered sand dunes in the north polar region of Mars in early spring, 2004. The dunes indicate wind transport of sand from left to right (west to east). These landforms are located near 78.1oN, 220.8oW. This picture is illuminated by sunlight from the lower left and covers an area about 3 km (1.9 mi) across.

2004-01-01

99

Martian Sand Dunes  

NASA Technical Reports Server (NTRS)

6 January 2004

The north polar cap of Mars is nearly surrounded by fields of dark, windblown sand dunes. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows an example located near 73.5oN, 75.0oW. The orientation of these dunes indicate that the dominant winds--particularly those that occur during storms--come from the upper left (northwest). The picture covers an area about 3 km (1.9 mi) across, and is illuminated by sunlight from the lower left.

2005-01-01

100

The Algodones Dunes, California  

NSDL National Science Digital Library

The Center for Biological Diversity blends "conservation biology with litigation, policy advocacy, and an innovative strategic vision" in efforts to protect endangered species and wild places, focusing on the western US. This Web site contains a slide show of images from the Algodones Dunes, California's largest dune system. The fourteen slides show images of the area's natural history and environmental threats, such as effects from off-road vehicles. Each slide is accompanied by a brief description. While not overly informative, this Web site offers visitors a quick overview look at this unique natural area.

2002-01-01

101

CLASS XI NRLI COASTAL DUNE  

E-print Network

SESSION NOVEMBER 2011 04 REPORT BY CLASS XI NRLI COASTAL DUNE LAKES: MANAGE- MENT OF A UNIQUE NATURAL RESOURCE T he Walton County area in Florida's panhandle is home to 15 named "coastal dune lakes". Dune lakes are rare geological/ecological features that are found in only five loca ons around

Florida, University of

102

[IgA nephropathy with crescentic glomerulonephritis and ANCA positive].  

PubMed

We present a case of IgA nephropathy diagnosed by renal biopsy that presents after 2 years of folow-up an impairment of the renal function associate histoligically to a crescentic glomerulonephritis. The immunologic determinations showed of high titers of antineutrophil cytoplamic antibodies (ANCA) (P-ANCA IgG antiMPO and P-ANCA IgA anti-MPO). The patient began treatment with haemodyalisis and one year later she received a cadaveric kidney transplantation with good result. Two years later she had normal urine sediment, negative proteinuria, normal renal function but high titers of IgG and IgA PANCA anti-MPO. In summary, we believe that the determination ANCA in acute renal failure due to IgA nephropathy can indicate the existence of a IgA crescentic glomerulonephritis superimposed or an associated small vessel vasculitis and it confers a worse prognosis. The positive maintenance of IgG P-ANCA anti-MPO IgG anti-MPO titers during the course suggests that the sequential determination of ANCA in this entity is not useful to the monitoring of the clinical activity. PMID:16514914

Ara, J; Bonet, J; Rodríguez, R; Mirapeix, E; Agraz, I; Romero, R

2005-01-01

103

Frost-covered dunes  

NASA Technical Reports Server (NTRS)

MOC image of dunes in Chasma Boreale, a giant trough in the north polar cap. This September 1998 view shows dark sand emergent from beneath a veneer of bright frost left over from the northern winter that ended in July 1998.

1999-01-01

104

Small Dunes in Hellas  

NASA Technical Reports Server (NTRS)

4 July 2004 This April 2004 Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a small dune field in southeastern Hellas Planitia near 41.4oS, 275.6oW. The image covers an area about 3 km (1.9 mi) wide; sunlight illuminates the scene from the upper left.

2004-01-01

105

North Polar Dunes  

NASA Technical Reports Server (NTRS)

14 March 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows north polar dune morphologies.

Location near: 78.0oN, 256.1oW Image width: 3 km (1.9 mi) Illumination from: lower left Season: Northern Summer

2005-01-01

106

Proctor Crater Dunes  

NASA Technical Reports Server (NTRS)

[figure removed for brevity, see original site]

This image, located near 30E and 47.5S, displays sand dunes within Proctor Crater. These dunes are composed of basaltic sand that has collected in the bottom of the crater. The topographic depression of the crater forms a sand trap that prevents the sand from escaping. Dune fields are common in the bottoms of craters on Mars and appear as dark splotches that lean up against the downwind walls of the craters. Dunes are useful for studying both the geology and meteorology of Mars. The sand forms by erosion of larger rocks, but it is unclear when and where this erosion took place on Mars or how such large volumes of sand could be formed. The dunes also indicate the local wind directions by their morphology. In this case, there are few clear slipfaces that would indicate the downwind direction. The crests of the dunes also typically run north-south in the image. This dune form indicates that there are probably two prevailing wind directions that run east and west (left to right and right to left).

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.

2002-01-01

107

Dunes reveal Titan's recent history  

NASA Astrophysics Data System (ADS)

Large fields of linear dunes are abundant on Titan, covering nearly 20% of the surface. They are among the youngest features and represent interactions between near-surface winds and sediment. This interaction may vary from area to area creating unique populations of eolian features identified by dune field parameters such as crest-to-crest spacing, dune width and orientation. These parameters respond to changes in near-surface conditions over periods of time ranging from minutes to many thousands of years depending on dune size and the duration of the changes. While pattern analysis of dune field parameters on Earth and, in this study, Titan reveals much about current climatic conditions, such as wind regimes and wetter vs. drier areas, many inferences about past conditions can also be made. Initial pattern analysis of linear dunes on Titan reveals a single population of linear dunes representing a large percentage of all observed dunes. This single population is the result of two leading possibilities: Either there has been only one long period of dune building, leading to very old cores that have been built upon over long periods of time, perhaps punctuated with few or many intervals of non-deposition; or the current conditions of dune building have persisted long enough to completely erase any evidence of previous conditions. We have not yet worked through all the input parameters to adjust Earth's time scales to Titan's, and thus it is not yet possible to give a precise age for Titan's dunes. However, if these large linear dunes are similar to Earth's large linear dunes, they may represent at least several thousand years of dune building.

Savage, Christopher J.; Radebaugh, Jani

2010-04-01

108

Great Kobuk Sand Dunes, Alaska: A Terrestrial Analog Site for Polar, Topographically Confined Martian Dune Fields  

NASA Astrophysics Data System (ADS)

Martian dune systems belong to two broad categories: (i) the sprawling north polar erg, rich in and immobilized by seasonal and perennial volatiles; and (ii) isolated low- to high-latitude dune fields confined by topography. While modern dune migration on Mars is nearly imperceptibly slow, recent studies are producing robust evidence for aeolian activity, including bedform modification. Cold-climate terrestrial dunes containing volatile reservoirs provide an important analog to Martian polar dunes because permafrost and seasonal cycles of CO2 and H2O frost mantling are thought to partially decouple Martian polar dunes from atmospheric forcing. The 67°N latitude, 62 km2 Great Kobuk Sand Dunes (GKSD) are a terrestrial analog for polar, intercrater dune fields on Mars. Formative winds affected by complex topography and the presence of volatiles and intercalated snow within the GKSD have direct analogy to factors that impede migration of Martian polar dunes. This system offers the opportunity to study cold-climate, noncoastal, topographically constrained, climbing and reversing barchanoid, transverse, longitudinal, and star dunes. The Kobuk Valley climate is subarctic and semiarid with long, cold winters and brief, warm summers. Niveoaeolian sedimentation occurs within west-facing lee slope catchments. In March 2010, we found the seasonally frozen layer to range in thickness from 1.5 to 4.0 m, and no evidence for shallow permafrost. Instead, using GPR and boreholes, we found a system-wide groundwater aquifer that nearly parallels topography and cuts across steeply dipping bedforms. GPR cannot uniquely detect ice and water; however, a similar analysis of rover-based GPR might be used to detect volatiles in Martian dunes. The perennial volatile reservoir is liquid because of mean annual air temperature, intense solar heating before, during, and after 38 days of continuous summer daylight, high dry sand thermal conductivity, higher wet sand thermal conductivity, infiltration of relatively warm summer precipitation, and the insulative properties of longlived snowcover. We hypothesize that the seasonally frozen layer and niveoaeolian deposits combined with a shallow aqueous reservoir are responsible for the low migration rate of the GKSD (i.e., ~1.3 m/yr over a recent 5-year period). Just as migration of the GKSD is affected by partial to full snowcover for 70% of the year, Martian polar dunes are affected by partial to full frost mantling for 70% of the year, significantly limiting the duration of aeolian transport. Thin water films surrounding sand grains at the GKSD make moist sand cohesive and structurally stable, like a solid. The partially saturated sand above the capillary fringe of an unconfined aquifer in the GKSD will limit sand available for aeolian transport, potentially similar to effects of permafrost within a Martian dune. We will present our geophysical, geomorphologic, and meteorologic field data and modeling analyses.

Dinwiddie, C. L.; Hooper, D. M.; Michaels, T. I.; McGinnis, R. N.; Stillman, D.; Bjella, K.; Stothoff, S.; Walter, G. R.; Necsoiu, M.; Grimm, R. E.

2010-12-01

109

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

110

Dune formation under bimodal winds  

PubMed Central

The study of dune morphology represents a valuable tool in the investigation of planetary wind systems—the primary factor controlling the dune shape is the wind directionality. However, our understanding of dune formation is still limited to the simplest situation of unidirectional winds: There is no model that solves the equations of sand transport under the most common situation of seasonally varying wind directions. Here we present the calculation of sand transport under bimodal winds using a dune model that is extended to account for more than one wind direction. Our calculations show that dunes align longitudinally to the resultant wind trend if the angle ?w between the wind directions is larger than 90°. Under high sand availability, linear seif dunes are obtained, the intriguing meandering shape of which is found to be controlled by the dune height and by the time the wind lasts at each one of the two wind directions. Unusual dune shapes including the “wedge dunes” observed on Mars appear within a wide spectrum of bimodal dune morphologies under low sand availability. PMID:20018703

Parteli, Eric J. R.; Durán, Orencio; Tsoar, Haim; Schwämmle, Veit; Herrmann, Hans J.

2009-01-01

111

Polar Layers and Dunes  

NASA Technical Reports Server (NTRS)

23 July 2004 Acquired just a few days ago on 21 July 2004, this 1.7 m/pixel (5.6 ft/pixel) Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows layer outcrops and sand dunes in the Chasma Boreale portion of the martian north polar cap. At this time, it is spring and these polar landforms are still covered by frost left over from the winter that ended back in March 2004. In summer, the dunes in this image will be darker than anything else in the scene. The picture is located near 85.1oN, 3.7oW, and covers an area about 1.5 km (0.9 mi) wide. This view is illuminated by sunlight from the upper right.

2004-01-01

112

Dunes and Wind Streaks  

NASA Technical Reports Server (NTRS)

12 June 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows small, dark, north polar sand dunes and attendant wind streaks located near 76.7oN, 317.6oW. The dominant winds responsible for these features blow from the southwest (lower left). The image covers an area about 3 km (1.9 mi) across. The scene is illuminated by sunlight from the lower left.

2004-01-01

113

Chasma Boreale Dunes  

NASA Technical Reports Server (NTRS)

9 February 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dark sand dunes overlying an eroded, layered substrate in Chasma Boreale, amid the materials of the martian north polar cap.

Location near: 84.5oN, 358.3oW Image width: 3.0 km (1.9 mi) Illumination from: lower left Season: Northern Summer

2005-01-01

114

North Polar Dunes  

NASA Technical Reports Server (NTRS)

This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dark, windblown sand dunes in the north polar region of Mars. The scene, obtained in December 2004, is located near 85.2oN, 169.1oW. The image covers an area about 3 km (1.9 mi) wide and is illuminated by sunlight from the upper right.

2005-01-01

115

Spectroscopic Studies of Nearby Cool Stars: The DUNES Sample  

E-print Network

dust disks around nearby stars. In this contribution we present some preliminary results.I: C. Eiroa). DUNES aims at detecting cold dusty disks, at flux levels as low as the Solar Edgeworth by using the routine apall and Thorium-Argon spectra have been used for wavelength calibration. Additional

Complutense de Madrid, Universidad

116

Dunes et plages Derrire les plages se trouvent les dunes,  

E-print Network

Dunes et plages Derrière les plages se trouvent les dunes, constituées par le sable déplacé par le développe ensuite. Si cette végétation est détruite, les dunes disparaissent et ne protégent plus les côtes et d'autres se déplaçant sur le fond. Dunes occupées par la végétation pionnière Végétation maritime

117

Frost-free Dunes  

NASA Technical Reports Server (NTRS)

[figure removed for brevity, see original site] Context image for PIA03291 Frost-free Dunes

These dark dunes are frost covered for most of the year. As southern summer draws to a close, the dunes have been completely defrosted.

Image information: VIS instrument. Latitude -66.6N, Longitude 37.0E. 34 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.

2006-01-01

118

Low-Dose Local Kidney Irradiation Inhibits Progression of Experimental Crescentic Nephritis by Promoting Apoptosis  

Microsoft Academic Search

Background: Crescentic glomerulonephritis is a rapidly progressive form of nephritis and is usually resistant to therapeutic intervention. Apoptosis plays a role in the resolution of glomerulonephritis. We investigated the effects of local kidney irradiation on the progression of experimental crescentic glomerulonephritis. Methods: The following three experimental rat groups were generated: (1) Group I, sham-operated control (n = 12); (2) Group

Diange Liu; Arifa Nazneen; Takashi Taguchi; M. Shawkat Razzaque

2008-01-01

119

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

120

Biogenic crust dynamics on sand dunes  

E-print Network

Sand dunes are often covered by vegetation and biogenic crusts. Despite their significant role in dune stabilization, biogenic crusts have rarely been considered in 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 cross-over between two different forms of desertification.

Kinast, Shai; Yizhaq, Hezi; Ashkenazy, Yosef

2012-01-01

121

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

122

Sedimentary Rocks and Dunes  

NASA Technical Reports Server (NTRS)

25 November 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows buttes composed of light-toned, sedimentary rock exposed by erosion within a crater occurring immediately west of Schiaparelli Basin near 4.0oS, 347.9oW. Surrounding these buttes is a field of dark sand dunes and lighter-toned, very large windblown ripples. The sedimentary rocks might indicate that the crater interior was once the site of a lake. The image covers an area about 3 km (1.9 mi) wide. Sunlight illuminates the scene from the lower left.

2004-01-01

123

North Polar Dunes  

NASA Technical Reports Server (NTRS)

31 December 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dark sand dunes in the north polar region of Mars. They are streaming away (toward the left) from a low escarpment at the edge of an outlier of polar water ice (the bright area on the right). The picture covers an area about 3 km (1.9 mi) wide and is located near 80.7oN, 80.2oW. Sunlight illuminates the scene from the lower left.

2004-01-01

124

North Polar Dune Patterns  

NASA Technical Reports Server (NTRS)

MGS MOC Release No. MOC2-478, 9 September 2003

Dark, windblown sand forms spectacular geometric patterns in the north polar sand seas, particularly in regions where strong winds converge from different directions over the course of a year. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) picture shows some of these dark dune patterns near 77.8oN, 284.4oW. The picture covers an area 3 km (1.9 mi) across and is illuminated by sunlight from the lower left.

2003-01-01

125

Dune-tastic  

NASA Technical Reports Server (NTRS)

6 March 2006 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a frosty, springtime scene in the north polar region of Mars. The area is blanketed by a maze of sand dunes; their appearance is enhanced by subliming, seasonal carbon dioxide frost.

Location near: 80.2oN, 168.8oW Image width: 3 km (1.9 mi) Illumination from: lower left Season: Northern Winter

2006-01-01

126

Chasma Boreale Dunes  

NASA Technical Reports Server (NTRS)

MGS MOC Release No. MOC2-517, 18 October 2003

Frost covers dark sand dunes in this springtime view from Chasma Boreale in the martian north polar region. Dark spots indicate areas where the cold, carbon dioxide frost has begun to sublime away. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image is located near 84.7oN, 359.3oW and covers an area 3 km (1.9 mi) wide. The scene is illuminated by sunlight from the lower left.

2003-01-01

127

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

128

A geometric crescent model for black hole images  

NASA Astrophysics Data System (ADS)

The Event Horizon Telescope (EHT), a global very long baseline interferometry array operating at millimetre wavelengths, is spatially resolving the immediate environments of black holes for the first time. The current observations of the Galactic centre black hole, Sagittarius A* (Sgr A*), and M87 have been interpreted in terms of either geometric models (e.g. a symmetric Gaussian) or detailed calculations of the appearance of black hole accretion flows. The former are not physically motivated, while the latter are subject to large systematic uncertainties. Motivated by the dominant relativistic effects of Doppler beaming and gravitational lensing in many calculations, we propose a geometric crescent model for black hole images. We show that this simple model provides an excellent statistical description of the existing EHT data of Sgr A* and M87, superior to other geometric models for Sgr A*. It also qualitatively matches physically predicted models, bridging accretion theory and observation. Based on our results, we make predictions for the detectability of the black hole shadow, a signature of strong gravity, in future observations.

Kamruddin, Ayman Bin; Dexter, Jason

2013-09-01

129

Tocilizumab improves systemic rheumatoid vasculitis with necrotizing crescentic glomerulonephritis.  

PubMed

Abstract We report a Japanese woman with systemic rheumatoid vasculitis (SRV) complicated by necrotizing crescentic glomerulonephritis (NCGN). Rheumatoid arthritis first occurred at the age of 19 years, followed by interstitial pneumonia, hepatitis, rheumatoid nodules, mononeuritis multiplex, and hypocomplementemia in chronological order. At the age of 51 years, rapidly progressive renal failure occurred with nephrotic proteinuria, and NCGN with subepithelial deposits was revealed by renal biopsy. Severe destructive changes of multiple joints and scleritis were detected, but anti-neutrophil cytoplasmic antibody was negative on enzyme-linked immunosorbent assays and indirect immunofluorescence. SRV was diagnosed due to involvement of multiple extra-articular organs. An anti-interleukin (IL)-6 receptor antibody (tocilizumab) was started at dosage of 280 mg (8 mg/kg) monthly. After 18 months, her serum creatinine decreased from 1.7 to 1.3 mg/dL, and urinary protein excretion declined from 5.2 to 1.2 g daily. Tocilizumab may be a therapeutic option for SRV associated with NCGN. PMID:24533557

Iijima, Takashi; Suwabe, Tatsuya; Sumida, Keiichi; Hayami, Noriko; Hiramatsu, Rikako; Hasegawa, Eiko; Yamanouchi, Masayuki; Hoshino, Junichi; Sawa, Naoki; Takaichi, Kenmei; Oohashi, Kenichi; Fujii, Takeshi; Ubara, Yoshifumi

2015-01-01

130

Lethal Sandslides from Eolian Dunes  

Microsoft Academic Search

Fossil vertebrates entombed within the Upper Cretaceous Djadokhta Formation of southern Mongolia bear testimony to a heretofore unknown geologic phenomenon: mass wasting of eolian dunes during heavy rainstorms. Evaporation of shallow-penetrating rainwater led to progressive calcite accumulation in a thin layer of sand about 0.5 m below the surface of dune lee slopes. During rare heavy rainstorms, a perched water

David B. Loope; Joseph A. Mason; Lowell Dingus

1999-01-01

131

Predicting vegetation-stabilized dune field morphology  

NASA Astrophysics Data System (ADS)

The morphology of vegetation-stabilized dune fields on the North American Great Plains (NAGP) mostly comprises parabolic dunes; stabilized barchan and transverse dunes are rare, with the exception of transverse and barchan mega-dunes in the Nebraska Sand Hills. We present a hypothesis from a numerical dune field model explaining the vegetation-stabilized morphology of dunes under unidirectional wind. Simulations with a range of initial dune morphologies (closely-spaced transverse to disperse barchans) indicate that stabilized morphology is determined by the ratio of slipface deposition rate to deposition tolerance of vegetation. Slipface deposition rate is related to dune height, flux, and celerity. With a fixed depositional tolerance, large, slow-moving dunes have low slipface deposition rates and ‘freeze’ in place once vegetation is introduced. Relatively small, fast dunes have high slipface deposition rates and evolve into parabolic dunes, often colliding during stabilization. Our hypothesis could explain differences in stabilized morphology across the NAGP and elsewhere.

Barchyn, Thomas E.; Hugenholtz, Chris H.

2012-09-01

132

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

133

Storm over Dunes  

NASA Technical Reports Server (NTRS)

[figure removed for brevity, see original site]

Today's image shows a storm front moving across an area of the north pole populated with hundreds of small dark sand dunes. The north polar region contains large regions of sand dunes, perhaps providing the some of the material raised into these clouds.

Image information: VIS instrument. Latitude 75.7, Longitude 323.7 East (36.3 West). 40 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.

2004-01-01

134

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

135

Recent drying of the Fertile Crescent: natural or externally forced?  

NASA Astrophysics Data System (ADS)

There has been a reduction in observed precipitation over the greater Mediterranean region since the middle of the 20th Century. Recent studies suggest that while anthropogenic forcing has already begun to assert itself in recent decades, the preponderance of the winter drying trend is attributable to the large natural multidecadal variability of the North Atlantic Oscillation (NAO), while over the eastern Mediterranean, the anthropogenic, or forced drying signal is more clearly evident. This forced drying is projected to increase during the 21st Century according to the newest global climate models and this aridification would present significant challenges for a region that is already water-stressed. Although the Fertile Crescent is historically known for its agricultural prosperity, the severity and persistence of the recent multiyear drought in Syria, directly prior to the 2011 uprising there, leads us to ask whether this is evidence of emerging global warming influence. This drought exacerbated existing water insecurity, resulting in an agricultural collapse and a mass migration of rural drought refugees to the urban areas in Syria's west. This migration followed the previous influx of Iragi refugees and combined with strong natural population growth to place a severe strain on resources. Here we examine observations of precipitation and temperature, both gridded and stations, along with simulations and projections from the newest global climate models, to estimate the forced contribution to the recent Syrian drought, and assess the uncertainty in future drying according to the models. We find that this region has experienced a long-term downward trend in precipitation, and a concomitant increase in temperature, serving to further dry the soil, and in surface pressure. We find that the shift in the distributions of three-year running means of surface pressure and precipitation due to the forcing make severe events such as the recent Syrian drought several times more likely. Next we examine the moisture budget in the models and compare with the ground truth of atmospheric reanalyses to determine the relative contributions from the mean flow and the transient eddies. We find that the mean and transient patterns of moisture budget change over the eastern Mediterranean under forcing resemble the patterns of the NAO-induced moisture budget anomaly, but that over the greater Mediterranean there are distinct differences. Under forced moisture budget change, as noted in a recent study, the mean flow serves to strongly dry the greater Mediterranean, with a smaller contribution from the transients. For the eastern Mediterranean however, the transients oppose the drying by the mean flow, under climate change and under a positive phase of the NAO. These results suggest that anthropogenically forced drying of the Fertile Crescent may already be underway, primarily through a poleward shift in the mean flow, and represent a step forward toward a better understanding of the mechanisms associated with eastern Mediterranean hydroclimate change and variability and how they compare.

Kelley, Colin

2014-05-01

136

Numerical modeling of the wind flow over a transverse dune  

E-print Network

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 {\\em{separation bubble}} --- displays a surprisingly strong dependence on the wind shear velocity, $u_{\\ast}$: it is nearly independent of $u_{\\ast}$ for shear velocities within the range between $0.2\\,$m$$s and $0.8\\,$m$$s but increases linearly with $u_{\\ast}$ for larger shear velocities. Our calculations show that transport in the direction opposite to dune migration within the separation bubble can be sustained if $u_{\\ast}$ is larger than approximately $0.39\\,$m$$s, whereas a larger value of $u_{\\ast}$ (about $0.49\\,$m$$s) is required to initiate this reverse transport.

Araújo, Ascânio D; Poeschel, Thorsten; Andrade, José S; Herrmann, Hans J

2013-01-01

137

Numerical modeling of the wind flow over a transverse dune  

E-print Network

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 {\\em{separation bubble}} --- displays a surprisingly strong dependence on the wind shear velocity, $u_{\\ast}$: it is nearly independent of $u_{\\ast}$ for shear velocities within the range between $0.2\\,$m$$s and $0.8\\,$m$$s but increases linearly with $u_{\\ast}$ for larger shear velocities. Our calculations show that transport in the direction opposite to dune migration within the separation bubble can be sustained if $u_{\\ast}$ is larger than approximately $0.39\\,$m$$s, whereas a larger value of $u_{\\ast}$ (about $0.49\\,$m$$s) is required to initiate this reverse transport.

Ascânio D. Araújo; Eric J. R. Parteli; Thorsten Poeschel; José S. Andrade Jr.; Hans J. Herrmann

2013-07-26

138

Numerical modeling of the wind flow over a transverse dune.  

PubMed

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

Araújo, Ascânio D; Parteli, Eric J R; Pöschel, Thorsten; Andrade, José S; Herrmann, Hans J

2013-01-01

139

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

Araújo, Ascânio D.; Parteli, Eric J. R.; Pöschel, Thorsten; Andrade, José S.; Herrmann, Hans J.

2013-01-01

140

Numerical modeling of the wind flow over a transverse dune  

NASA Astrophysics Data System (ADS)

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.

Araújo, Ascânio D.; Parteli, Eric J. R.; Pöschel, Thorsten; Andrade, José S.; Herrmann, Hans J.

2013-10-01

141

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

142

First Evidence of Dune Movement on Mars  

Microsoft Academic Search

Many sand dunes on Mars have pristine morphology, fresh grain flows on avalanche faces and sand streamers extending from barchan horns. This suggests that the saltation threshold for sand is exceeded and dune migration is possible under the current Martian climate. However, sand dune movement has not been observed and there is evidence that many of the dunes may be

M. C. Bourke; K. S. Edgett

2006-01-01

143

Laboratory Observations of Dune Erosion  

NASA Astrophysics Data System (ADS)

Coastal dunes are an important feature along many coastlines, owing to their input to the sediment supply, use as habitat, and ability to protect onshore resources from wave attack. Correct predictions of the erosion and overtopping rates of these features are needed to develop improved responses to coastal dune damage events, and to determining the likelihood and magnitude of future erosion and overtopping on different beaches. We have conducted a large-scale laboratory study at Oregon State University's O.H. Hinsdale Wave Research Laboratory (HWRL) with the goal of producing a comprehensive, near prototype-scale, physical model data set of hydrodynamics, sediment transport, and morphological evolution during extreme dune erosion events. The two goals of this work are (1) to develop a better understanding of swash/dune dynamics and (2) to evaluate and guide further development of dune erosion models. We present initial results from the first phase of the experimental program. An initial beach and dune profile was selected based on field LIDAR-based observations of various U.S. east coast and Gulf coast dune systems. The laboratory beach was brought to equilibrium with pre-storm random wave conditions. It was subsequently subjected to attack from steadily increasing water level and offshore wave heights. Observations made include inner surf zone and swash free surface and velocities as well as wave-by-wave estimates of topographical change at high spatial resolution through the use of stereo video imagery. Future work will include studies of fluid overtopping of the dune and sediment overwash and assessment of the resilience of man-made "push-up" dunes to wave attack in comparison with their more-compacted "natural" cousins.

Maddux, T. B.; Ruggiero, P.; Palmsten, M.; Holman, R.; Cox, D. T.

2006-12-01

144

Lethal Sandslides from Eolian Dunes.  

PubMed

Fossil vertebrates entombed within the Upper Cretaceous Djadokhta Formation of southern Mongolia bear testimony to a heretofore unknown geologic phenomenon: mass wasting of eolian dunes during heavy rainstorms. Evaporation of shallow-penetrating rainwater led to progressive calcite accumulation in a thin layer of sand about 0.5 m below the surface of dune lee slopes. During rare heavy rainstorms, a perched water table developed at the top of calcitic zones. Positive pore water pressure led to translational slides and fast-moving sediment gravity flows that overwhelmed animals on the lee slopes of large dunes and in interdune areas. PMID:10517885

Loope; Mason; Dingus

1999-11-01

145

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

146

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

147

Recent aeolian dune change on Mars  

Microsoft Academic Search

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

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

2008-01-01

148

Grain size dependence of barchan dune dynamics  

E-print Network

The dependence of the barchan dune dynamics on the size of the grains involved is investigated experimentally. Downsized barchan dune slices are observed in a narrow water flow tube. The relaxation time from an initial symmetric triangular heap towards an asymmetric shape attractor increases with dune mass and decreases with grain size. The dune velocity increases with grain size. In contrast, the velocity scaling and the shape of the barchan dune is independent of the size of the grains.

C. Groh; N. Aksel; I. Rehberg; C. Kruelle

2008-11-28

149

Up-regulation of extracellular matrix proteoglycans and collagen type I in human crescentic glomerulonephritis  

Microsoft Academic Search

Up-regulation of extracellular matrix proteoglycans and collagen type I in human crescentic glomerulonephritis.BackgroundThe pathogenesis of crescentic glomerulonephritis (CGN) involves cellular migration and proliferation in the urinary space, frequently followed by fibrous organization. Extracellular matrix proteoglycans (PGs) may regulate these events via effects on cellular migration, interactions with growth factors, including transforming growth factor-? (TGF-?), and control of collagen fibrillogenesis. The

Michael B. Stokes; Kelly L. Hudkins; Valentin Zaharia; Sekiko Taneda; Charles E. Alpers

2001-01-01

150

Gypsum Dunes from White Sands National Monument - Potential Analog to North Polar Dunes on Mars  

Microsoft Academic Search

Three aspects of White Sands gypsum dunes evolution relating to climate variation are discussed in comparison to Olimpia Undae gypsum-rich dunes on Mars: gypsum source, groundwater discharge into interdunes areas, and desiccation of dunes.

A. Szynkiewicz; L. M. Pratt; M. Glamoclija; D. Bustos

2008-01-01

151

Gypsum Dunes from White Sands National Monument - Potential Analog to North Polar Dunes on Mars  

NASA Astrophysics Data System (ADS)

Three aspects of White Sands gypsum dunes evolution relating to climate variation are discussed in comparison to Olimpia Undae gypsum-rich dunes on Mars: gypsum source, groundwater discharge into interdunes areas, and desiccation of dunes.

Szynkiewicz, A.; Pratt, L. M.; Glamoclija, M.; Bustos, D.

2008-03-01

152

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

153

Contrast Threshold of Lunar Crescents Visibility for Ramadan and Syawal 1431 H at Bosscha Observatory  

NASA Astrophysics Data System (ADS)

In this paper we present the prediction of the first lunar crescent visibility using contrast based on Schaefer's model and best time proposed by [12] for the beginning of Ramadhan and Syawal 1431 H at observing place in Bosscha Observatory, [E 107° 36.96', S 6° 49.55', with elevation of 1310 meters above sea level]. The geocentric altitude of the Moon at the sunset time on August 10 is 1° 58.98' and illuminated fraction of crescent (FI) = 0.20%. On August 11, 2010 the altitude of the Moon at the sunset time is 15° 42.71' and FI = 2.57%. The calculated contrast on August 10, 2010 is less than zero. It means that the brightness of the moon is smaller than brightness of the sky. Based on the contrast value, it is impossible to observe the lunar crescent by the naked eye at that time, even equipped by special design telescope for the crescent observation at Bosscha Observatory. Sultan [11] proposed a predicted model it is still possible to observe the very young lunar crescent even under circumstance before the time of sunset, if the contrast of sky is perfect. On August 11, 2010 contrast has its maximum at 50 minutes after sunset. The result of observation of the lunar crescent at Bosscha Observatory, the crescent could be seen before sunset at 17.15 local time (UT+7 hours) using special design telescope with additional nose of 1 meter length [6]. The model used here is tend to predict the brightness for naked eye observation, which less contrast compare to observation with the well design telescope.

Arumaningtyas, E. P.; Raharto, M.

2010-12-01

154

Dorsal–Ventral patterning: Crescent is a dorsally secreted Frizzled-related protein that competitively inhibits Tolloid proteases  

PubMed Central

In Xenopus, dorsal–ventral (D–V) patterning can self-regulate after embryo bisection. This is mediated by an extracellular network of proteins secreted by the dorsal and ventral centers of the gastrula. Different proteins of similar activity can be secreted at these two poles, but under opposite transcriptional control. Here we show that Crescent, a dorsal protein, can compensate for the loss of Sizzled, a ventral protein. Crescent is a secreted Frizzled-Related Protein (sFRP) known to regulate Wnt8 and Wnt11 activity. We now find that Crescent also regulates the BMP pathway. Crescent expression was increased by the BMP antagonist Chordin and repressed by BMP4, while the opposite was true for Sizzled. Crescent knock-down increased the expression of BMP target genes, and synergized with Sizzled morpholinos. Thus, Crescent loss-of-function is compensated by increased expression of its ventral counterpart Sizzled. Crescent overexpression dorsalized whole embryos but not ventral half-embryos, indicating that Crescent requires a dorsal component to exert its anti-BMP activity. Crescent protein lost its dorsalizing activity in Chordin-depleted embryos. When co-injected, Crescent and Chordin proteins greatly synergized in the dorsalization of Xenopus embryos. The molecular mechanism of these phenotypes is explained by the ability of Crescent to inhibit Tolloid metalloproteinases, which normally degrade Chordin. Enzyme kinetic studies showed that Crescent was a competitive inhibitor of Tolloid activity, which bound to Tolloid/BMP1 with a KD of 11 nM. In sum, Crescent is a new component of the D–V pathway, which functions as the dorsal counterpart of Sizzled, through the regulation of chordinases of the Tolloid family. PMID:21295563

Ploper, Diego; Lee, Hojoon X.; De Robertis, Edward M.

2011-01-01

155

Predicting vegetation-stabilized dune morphology  

NASA Astrophysics Data System (ADS)

The morphology of vegetation-stabilized dune fields on the North American Great Plains mostly comprises parabolic dunes; stabilized barchan and transverse dunes are rare. One notable exception is the Nebraska Sand Hills (NSH), where massive grass-covered barchan and transverse dunes bear proof of former desert-like conditions. We present a hypothesis from a numerical dune field model to explain the vegetation-stabilized morphology of dunes. The model incorporates a growth curve that preferentially grows vegetation in regions of sediment deposition with a sharp drop in growth at the peak depositional tolerance of vegetation, qualitatively matching biological response to erosion and deposition. Simulations on a range of pre-stabilization dune morphologies, from large closely-spaced transverse dunes to small dispersed barchans, indicate that the stabilized morphology is largely determined by the ratio of slipface deposition rate to peak depositional tolerance of vegetation. Conceptually, slipface deposition rate is related to dune height and celerity. By keeping depositional tolerance constant (representing a constant vegetation type and climate) the model shows that large slow-moving dunes have low slipface deposition rates and essentially 'freeze' in place once vegetation is introduced, retaining their pre-vegetation morphology. Small fast-moving dunes have higher slipface deposition rates and evolve into parabolic dunes. We hypothesize that, when barchan and transverse dunes are subjected to a stabilizing climate shift that increases vegetation growth rate, they retain their pre-stabilization morphology if deposition rates are below the depositional tolerance of stabilizing vegetation, otherwise they become parabolic dunes. This could explain why NSH dunes are stabilized in barchan and transverse morphologies while elsewhere on the Great Plains dune fields are dominated by smaller parabolic dunes.

Barchyn, T.; Hugenholtz, C.

2012-04-01

156

Breeding and solitary wave behavior of dunes.  

PubMed

Beautiful dune patterns can be found in deserts and along coasts due to the instability of a plain sheet of sand under the action of the wind. Barchan dunes are highly mobile aeolian dunes found in areas of low sand availability and unidirectional wind fields. Up to now modelization mainly focused on single dunes or dune patterns without regarding the mechanisms of dune interactions. We study the case when a small dune bumps into a bigger one. Recently Schwämmle and Herrmann [Nature (London) 426, 610 (2003)] and Katsuki [(e-print cond-mat 0403312)] have shown that under certain circumstances dunes can behave like solitary waves. This means that they can "cross" each other which has been questioned by many researchers before. In other cases we observe coalescence--i.e., both dunes merge into one--breeding--i.e., the creation of three baby dunes at the center and horns of a Barchan dune--or budding--i.e., the small dune, after "crossing" the big one, is unstable and splits into two new dunes. PMID:16196557

Durán, O; Schwämmle, V; Herrmann, H

2005-08-01

157

Backwash-and-swash-oriented current crescents: indicators of beach slope, current direction and environment  

NASA Astrophysics Data System (ADS)

Backwash-and-swash-oriented current crescents, which are confined to the swash zone of beach environments, are reported, with their detailed morphology and formation mechanism, from the siliciclastic fine sandy beaches of Sagar Island and Lower Long Sand, two tidal islands of the Ganga estuary, northeast India. Morphologically, the swash-oriented arms of these current crescents are shorter and less prominent than the backwash-oriented arms. The shorter arms open landward whereas the longer arms open seaward. They generally form around obstacles like armoured mud balls, polychaete tubes, tussocks etc. which are partially set in a scour implying greater anchoring or a semipermanent nature. These current crescents occur on fine to very find sandy beaches ( Mz = 2.9 to 3.1 ?) with a beach slopes of 1:50 to 1:90 (1.4-0.7°). They are very commonly associated with current lineations. The arms of crescents parallel current lineations and are at right angles to the shoreline. In contrast, ordinary backwash-oriented current crescents form on steeper beach slopes, 1:9 to 1:25 (6-3°), in fine to medium sand( Mz = 1.8 to 2 ?). They occur around tiny obstacles which are easily swept away by wave swash and backwash.

Bhattacharya, Asokkumar

1993-04-01

158

Linear Dunes on Earth and Mars — Comparative Research  

NASA Astrophysics Data System (ADS)

Simple linear dunes, rare on Mars, are the most widespread dune type on Earth. Two types of linear dunes are known on Earth: seif dunes and vegetated linear dunes (VLDs). We will discuss the formation of linear dunes on Earth and on Mars.

Tsoar, H.

2014-07-01

159

Mars’ Northern Dunes: Volatiles and Geology  

NASA Astrophysics Data System (ADS)

Mars has a vast sea of sand dunes at high northern latitudes known as the north polar erg. These dunes are blanketed with seasonal CO2 frost in the winter and early spring. Sharp dune crests, steep slipfaces and lack of craters suggest that these northern dunes have experienced geologically recent resurfacing. The High Resolution Imaging Science Experiment (HiRISE) on the Mars Reconnaissance Orbiter (MRO) imaged a limited number of sites in the dunes with resolution better than 1 m to look for changes. New HiRISE images show extensive erosion of northern hemisphere dunes associated with seasonal CO2 ice sublimation in the spring. With 2 Mars years of observations we have observed the CO2-ice-free state of the dunes in the first year, frost-covered in late winter, the spring sublimation process, and the ice-free state of the dunes again in the second year. Temporal sequences of images of individual sites were acquired to monitor the sublimation process throughout spring. Ice-free images have been compared between northern summer in MRO year 1 (Mars Year 29) and MRO year 2. New alcoves and aprons are detected on numerous dunes in several sites. In one particular barchan dune field 20% of the dunes show substantial changes and 20% show minor changes. These changes can be traced to locations of early enhanced CO2 ice sublimation. The sublimation activity manifests itself on the dunes as cracks along the dune crest from which dark streaks of sand and dust move down the slipface. The sand travels out onto patterned ground, enabling measurement of the extent of the new aprons, in some cases meters from the dune boundary one year earlier. In order to maintain fresh dunes against such erosion the dune-building processes must still be at work on Mars today. This work was partially supported by JPL/CIT/NASA.

Hansen, Candice; Bridges, N.; Bourke, M.; Byrne, S.; Diniega, S.; Dundas, C.; Herkenhoff, K.; McEwen, A.; Portyankina, G.; Thomas, N.; Colon, C.

2010-10-01

160

First Evidence of Dune Movement on Mars  

NASA Astrophysics Data System (ADS)

Many sand dunes on Mars have pristine morphology, fresh grain flows on avalanche faces and sand streamers extending from barchan horns. This suggests that the saltation threshold for sand is exceeded and dune migration is possible under the current Martian climate. However, sand dune movement has not been observed and there is evidence that many of the dunes may be stabilized or indurated. We report the first evidence for the movement of bodies of windblown sand under current climate conditions on Mars. Repeat images of three sand dunes using the Mars Orbiter Camera were acquired between March 1999 and December 2004. We detected the complete removal of sediment from two small dome dunes in a barchan dune field in the North Polar Sand Sea during this time. The third and largest dome dune (77 m wide) in the sample suite had a slight reduction in size, but dune form remained intact. On Earth, dome dunes are circular to oval low mounds of loose, well-sorted, very fine to medium sand. Slip faces are absent or ephemeral and stand only a meter or so high. That these dunes did not migrate, but were eroded, suggests that they were not in equilibrium. Dome dune morphology is not always as effective as e.g., barchan morphology, for trapping sediment, particularly in locations of high velocity winds. In these situations, the removal of sand downwind can lead to the depletion of the dune. Our data confirms that first; the threshold wind speed for saltation is exceeded under present Martian climate conditions. Second, not all dunes on Mars are stabilized or indurated. Third, dune migration is possible under current Martian conditions; however it is likely to be limited to the smallest barchan and dome dunes (i.e. < 20 m wide).

Bourke, M. C.; Edgett, K. S.

2006-12-01

161

DUNE - a granular flow code  

SciTech Connect

DUNE was designed to accurately model the spectrum of granular. Granular flow encompasses the motions of discrete particles. The particles are macroscopic in that there is no Brownian motion. The flow can be thought of as a dispersed phase (the particles) interacting with a fluid phase (air or water). Validation of the physical models proceeds in tandem with simple experimental confirmation. The current development team is working toward the goal of building a flexible architecture where existing technologies can easily be integrated to further the capability of the simulation. We describe the DUNE architecture in some detail using physics models appropriate for an imploding liner experiment.

Slone, D M; Cottom, T L; Bateson, W B

2004-11-23

162

Quantifying wind blown landscapes using time-series airborne LiDAR at White Sands Dune Field, New Mexico  

NASA Astrophysics Data System (ADS)

Wind blown landscapes are a default geomorphic and sedimentary environment in our solar system. Wind sand dunes are ubiquitous features on the surfaces of Earth, Mars and Titan and prevalent within the aeolian rock records of Earth and Mars. Dunes are sensitive to environmental and climatic changes and a complete understanding of this system promises a unique, robust and quantitative record of paleoclimate extending to the early histories of these worlds. However, our understanding of how aeolian dune landscapes evolve and how the details of the wind are recorded in cross-strata is limited by our lack of understanding of three-dimensional dune morphodynamics related to changing boundary conditions such as wind direction and magnitude and sediment source area. We use airborne LiDAR datasets over 40 km2 of White Sands Dune Field collected from June 2007, June 2008, January 2009, September 2009 and June 2010 to quantify 1) three-dimensional dune geometries, 2) annual and seasonal patterns of erosion and deposition across dune topography, 3) spatial changes in sediment flux related to position within the field, 4) spatial changes in sediment flux across sinuous crestlines and 5) morphologic changes through dune-dune interactions. In addition to measurements, we use the LiDAR data along with wind data from two near-by weather stations to develop a simple model that predicts depositional and stratigraphic patterns on dune lee slopes. Several challenges emerged using time series LiDAR data sets at White Sands Dune Field. The topography upon which the dunes sit is variable and rises by 16 meters over the length of the dune field. In order to compare individual dune geometries across the field and between data sets a base surface was interpolated from local minima and subtracted from the dune topography. Co-registration and error calculation between datasets was done manually using permanent vegetated features within the active dune field and structures built by the national monument as control points. Rapid dune migration rates, particularly at the upwind margin of the field ~6m/yr, result in significant decorrelation between data sets over longer time ranges, which limits the effectiveness of comparing these data sets.

Ewing, R. C.

2011-12-01

163

Dune Succession Predictable patterns of species  

E-print Network

Dune Succession Succession · Predictable patterns of species replacements in an ecological, reproduce rapidly, grow fast PIONEER SPECIES ­ Marram grass on fore dunes · Later species are poorer eruption ­ ex. newly dug pond ­ ex. bare rock after glacier recedes ­ ex. dunes Secondary Succession · Old

Cochran-Stafira, D. Liane

164

Rides et Dunes de Sable Alexandre Valance  

E-print Network

1 Rides et Dunes de Sable Alexandre Valance Institut de Physique de Rennes (IPR), CNRS UMR 6251-linéaire: murissement, saturation Dunes transverses, Barkhanes, Rides éoliennes Sources: · A. Valance: « Dynamique Fluviatile » (Cours M2 Systèmes Complexes, Rennes) · F. Charru et al. : « Ripples and Sand dunes » (Annual

Lucas, Carine - Le Laboratoire de Mathématiques

165

Dune Succession Predictable patterns of species  

E-print Network

1 Dune Succession Succession · Predictable patterns of species replacements in an ecological, reproduce rapidly, grow fast PIONEER SPECIES ­ Marram grass on fore dunes · Later species are poorer eruption ­ ex. newly dug pond ­ ex. bare rock after glacier recedes ­ ex. dunes Secondary Succession · Old

Cochran-Stafira, D. Liane

166

The influence of barchan shape on the moisture and temperature of the dune sand and the diversity of local climate  

NASA Astrophysics Data System (ADS)

The aim of the research was to determine the impact of the barchan shape on moisture and temperature of dune sand in near surface layer. The study was carried out in the spring 2010 on the dune field located 20 km to the north of Laâyoune (Western Sahara). This region is one of the most humid, located in tropical, desert areas, which is associated with the influx of air masses from the Atlantic. Moisture and temperature of the dune sand in near surface layer was analysed on the basis of measurements in different parts of barchans. The studies included also analysis of the physical condition of the atmosphere, meteorological elements within the analyzed dune fields, the grain size distribution and mineral composition of dune sand. Shape of barchans and their orientations were determined on the basis of the detailed topographic survey. The results show important spatial variation in moisture and temperature of dune sand in near surface layer, characterized by very small differences on grain size distribution and mineral composition. It was found that variations in moisture and temperature of dune material were mainly related to the inflow of solar energy. The advection played a lesser role. The main factors affecting the distribution of moisture and temperature of dune sand as well the air surface layer were the aspect and the slope angle of the dunes. Eastern and southern (lee side) parts of the dunes were characterized by several times less moisture than their western and northern parts (stoss side). With the direction of advection from the north-west which occurred during the field studies, there was no evidence of less moisture in the sand of the stoss sides of dunes (despite the greater wind speed intensifying the process of evaporation). It can therefore be assumed that the intensity of sand transport within a dune located in the region with the impact of oceanic air masses depends mainly on the shape and spatial orientation of barchans.

Dluzewski, M.; Zmudzka, E.; Woronko, D.; Biejat, K.

2012-04-01

167

Factors determining desert dune type  

Microsoft Academic Search

While most observers recognize four elemental types of desert dunes (longitudinal, transverse, barchan and star1-3) there is little agreement about which factors determine these types. The angular relationships between the resultant of sand shifting winds and both the crest and principal slipfaces of the elemental types have been discussed qualitatively for many decades. These relationships have been quantified but the

R. J. Wasson; R. Hyde

1983-01-01

168

DUNE: The Dark Universe Explorer  

E-print Network

Understanding the nature of Dark Matter and Dark Energy is one of the most pressing issues in cosmology and fundamental physics. The purpose of the DUNE (Dark UNiverse Explorer) mission is to study these two cosmological components with high precision, using a space-based weak lensing survey as its primary science driver. Weak lensing provides a measure of the distribution of dark matter in the universe and of the impact of dark energy on the growth of structures. DUNE will also include a complementary supernovae survey to measure the expansion history of the universe, thus giving independent additional constraints on dark energy. The baseline concept consists of a 1.2m telescope with a 0.5 square degree optical CCD camera. It is designed to be fast with reduced risks and costs, and to take advantage of the synergy between ground-based and space observations. Stringent requirements for weak lensing systematics were shown to be achievable with the baseline concept. This will allow DUNE to place strong constraints on cosmological parameters, including the equation of state parameter of the dark energy and its evolution from redshift 0 to 1. DUNE is the subject of an ongoing study led by the French Space Agency (CNES), and is being proposed for ESA's Cosmic Vision programme.

A. Refregier; O. Boulade; Y. Mellier; B. Milliard; R. Pain; J. Michaud; F. Safa; A. Amara; P. Astier; E. Barrelet; E. Bertin; S. Boulade; C. Cara; A. Claret; L. Georges; R. Grange; J. Guy; C. Koeck; L. Kroely; C. Magneville; N. Palanque-Delabrouille; N. Regnault; G. Smadja; C. Schimd; Z. Sun

2006-10-03

169

'Endurance Crater's' Dazzling Dunes (false-color)  

NASA Technical Reports Server (NTRS)

As NASA's Mars Exploration Rover Opportunity creeps farther into 'Endurance Crater,' the dune field on the crater floor appears even more dramatic. This false-color image taken by the rover's panoramic camera shows that the dune crests have accumulated more dust than the flanks of the dunes and the flat surfaces between them. Also evident is a 'blue' tint on the flat surfaces as compared to the dune flanks. This results from the presence of the hematite-containing spherules ('blueberries') that accumulate on the flat surfaces.

Sinuous tendrils of sand less than 1 meter (3.3 feet) high extend from the main dune field toward the rover. Scientists hope to send the rover down to one of these tendrils in an effort to learn more about the characteristics of the dunes. Dunes are a common feature across the surface of Mars, and knowledge gleaned from investigating the Endurance dunes close-up may apply to similar dunes elsewhere.

Before the rover heads down to the dunes, rover drivers must first establish whether the slippery slope that leads to them is firm enough to ensure a successful drive back out of the crater. Otherwise, such hazards might make the dune field a true sand trap.

2004-01-01

170

The dune size distribution and scaling relations of barchan dune fields  

E-print Network

Barchan dunes emerge as a collective phenomena involving the generation of thousands of them in so called barchan dune fields. By measuring the size and position of dunes in Moroccan barchan dune fields, we find that these dunes tend to distribute uniformly in space and follow an unique size distribution function. We introduce an analyticalmean-field approach to show that this empirical size distribution emerges from the interplay of dune collisions and sand flux balance, the two simplest mechanisms for size selection. The analytical model also predicts a scaling relation between the fundamental macroscopic properties characterizing a dune field, namely the inter-dune spacing and the first and second moments of the dune size distribution.

Orencio Durán; Veit Schwämmle; Pedro G. Lind; Hans J. Herrmann

2007-01-16

171

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

172

Crescentic Glomerulonephritis and Subepidermal Blisters with Autoantibodies to ?5 and ?6 Chains of Type IV Collagen  

Microsoft Academic Search

We describe a novel autoimmune disease characterized by severe subepidermal bullous eruption and crescentic glomerulonephritis with autoantibodies directed against the noncollagenous domain of the ?5 and ?6 chains of type IV collagen. Biopsy of perilesional skin revealed a subepidermal blister with marked polymorphonuclear infiltrate with linear deposits of IgA and C3. Light microscopy of a kidney biopsy specimen revealed a

Reza F Ghohestani; Sherry L Rotunda; Billy Hudson; William J Gaughan; John L Farber; Guy Webster; Jouni Uitto

2003-01-01

173

As Turkey hosts the northernmost part of the `Fertile Crescent', where  

E-print Network

Magazine R503 As Turkey hosts the northernmost part of the `Fertile Crescent', where humans first combination of geographical factors has provided Turkey with a surprisingly high level of biodiversity. There are forests, shrublands, large rivers, wetlands, and several mountain ranges. Turkey's unique position

Tipple, Brett

174

Kuril Islands tsunami of November 2006: 1. Impact at Crescent City by distant scattering  

E-print Network

Kuril Islands tsunami of November 2006: 1. Impact at Crescent City by distant scattering Z. Kowalik November 2007; published 31 January 2008. [1] A numerical model for the global tsunami computation constructed by Kowalik et al. (2005, 2007a) is applied to the tsunami of November 15, 2006 in the northern

Kowalik, Zygmunt

175

9.4 CLASSIFYING PRECIPITATION EVENTS IN THE FERTILE CRESCENT Jason P. Evans*  

E-print Network

9.4 CLASSIFYING PRECIPITATION EVENTS IN THE FERTILE CRESCENT Jason P. Evans* and Ronald B. Smith (Evans, J.P. et al.,2004) indicated that water vapor contributing to some of these storm events these * Corresponding Author address: Jason P. Evans, Yale University, Dept. of Geology and Geophysics, New Haven, CT

Evans, Jason

176

Peculiar arcuate scotoma in pathologic myopia—optical coherence tomography to detect peripapillary neural tissue loss over the disc crescent  

Microsoft Academic Search

Background: Optical co- herence tomography (OCT) was used to detect peripapillary neural tissue loss (PPNTL) over the disc crescent in pathologic myopia. The retinal neural tissue loss located inside the disc crescent in pathologic myopia is a newly recognized fundus lesion. Methods: Review of ten eyes of ten patients with peripapillary yellowish- white retinal lesions who underwent OCT for evaluation

Tzyy-Chang Ho; Yung-Feng Shih; Szu-Yung Lin; Luke L.-K. Lin; Muh-Shy Chen

2005-01-01

177

01. Northwest Marine Drive (across from the Rose Garden Parkade) 02. West Mall & Crescent Road (near International House)  

E-print Network

Drive (across from the Rose Garden Parkade) 02. West Mall & Crescent Road (near International House) 03. Main Mall & Crescent Road (across from the Flag Pole near Buchanan A) 04. Main Mall & Memorial Road (at Wyman Plaza) 05. Lower Mall between Memorial Road & University Boulevard (near Place Vanier) 06. West

Strynadka, Natalie

178

Summertime View of North Polar Sand Dunes  

NASA Technical Reports Server (NTRS)

10 October 2006 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a suite of dunes in one of the several north polar dune fields. The bright surfaces adjacent to some of the dunes are patches of frost. These dunes spend much of the autumn, winter, and spring seasons covered with carbon dioxide frost. Only in late spring and in summer are the dark windblown sands fully exposed.

Over the course of the 9+ years of the MGS mission, the MOC team has sought evidence that sand dunes may be migrating downwind over time. However, no clear examples of the movement of a whole dune have been identified. On Earth, such movement is typically detectable in air photos of the smallest active dunes over periods of a few years. Owing to the fact that the north polar dunes spend much of each martian year under a cover of frost, perhaps these move much more slowly than their frost-free, terrestrial counterparts. The sand may also be somewhat cemented by ice or minerals, likewise preventing vigorous dune migration in the present environment.

This view covers an area approximately 3 km (1.9 mi) wide and is illuminated by sunlight from the lower left. The dunes are located near 79.8oN, 127.1oW, and the picture was acquired on 11 September 2006.

2006-01-01

179

Size distribution and structure of Barchan dune fields  

E-print Network

Barchans are isolated mobile dunes often organized in large dune fields. Dune fields seem to present a characteristic dune size and spacing, which suggests a cooperative behavior based on dune interaction. In Duran et al. (2009), we propose that the redistribution of sand by collisions between dunes is a key element for the stability and size selection of barchan dune fields. This approach was based on a mean-field model ignoring the spatial distribution of dune fields. Here, we present a simplified dune field model that includes the spatial evolution of individual dunes as well as their interaction through sand exchange and binary collisions. As a result, the dune field evolves towards a steady state that depends on the boundary conditions. Comparing our results with measurements of Moroccan dune fields, we find that the simulated fields have the same dune size distribution as in real fields but fail to reproduce their homogeneity along the wind direction.

Orencio Durán; Veit Schwämmle; Pedro G. Lind; Hans J. Herrmann

2007-01-16

180

Vegetated dune morphodynamics during recent stabilization of the Mu Us dune field, north-central China  

NASA Astrophysics Data System (ADS)

The response of dune fields to changing environmental conditions can be better understood by investigating how changing vegetation cover affects dune morphodynamics. Significant increases in vegetation and widespread dune stabilization over the years 2000-2012 are evident in high-resolution satellite imagery of the Mu Us dune field in north-central China, possibly a lagged response to changing wind strength and temperature since the 1970s. These trends provide an opportunity to study how dune morphology changes with increasing vegetation stabilization. Vegetation expansion occurs mainly by expansion of pre-existing patches in interdunes. As vegetation spreads from interdunes onto surrounding dunes, it modifies their shapes in competition with wind-driven sand movement, primarily in three ways: 1) vegetation anchoring horns of barchans transforms them to parabolic dunes; 2) vegetation colonizes stoss faces of barchan and transverse dunes, resulting in lower dune height and an elongated stoss face, with shortening of barchan horns; and 3) on transverse dunes, the lee face is fixed by plants that survive sand burial. Along each of these pathways of stabilization, dune morphology tends to change from more barchanoid to more parabolic forms, but that transformation is not always completed before full stabilization. Artificial stabilization leads to an extreme case of “frozen” barchans or transverse dunes with original shapes preserved by rapid establishment of vegetation. Observations in the Mu Us dune field emphasize the point that vegetation growth and aeolian sand transport not only respond to external factors such as climate but also interact with each other. For example, some barchans lose sand mass during vegetation fixation, and actually migrate faster as they become smaller, and vegetation growth on a barchan's lower stoss face may alter sand transport over the dune in a way that favors more rapid stabilization. Conceptual models were generalized for the development of vegetation-stabilized dunes, which should be helpful in better understanding of vegetated dune morphology, model verification and prediction, and guiding practical dune stabilization efforts.

Xu, Zhiwei; Mason, Joseph A.; Lu, Huayu

2015-01-01

181

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

182

Dunes of the Frozen North  

NASA Technical Reports Server (NTRS)

19 March 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dark north polar dunes overlying other materials in the north polar region.

Location near: 79.1oN, 228.8oW Image width: 3 km (1.9 mi) Illumination from: lower left Season: Northern Summer

2005-01-01

183

Dunes of the Frozen North  

NASA Technical Reports Server (NTRS)

21 March 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dark north polar dunes overlying other materials in the north polar region.

Location near: 79.1oN, 228.8oW Image width: 3 km (1.9 mi) Illumination from: lower left Season: Northern Summer

2005-01-01

184

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

185

DUNE: The Dark Universe Explorer  

E-print Network

Understanding the nature of Dark Matter and Dark Energy is one of the most pressing issues in cosmology and fundamental physics. The purpose of the DUNE (Dark UNiverse Explorer) mission is to study these two cosmological components with high precision, using a space-based weak lensing survey as its primary science driver. Weak lensing provides a measure of the distribution of dark matter in the universe and of the impact of dark energy on the growth of structures. DUNE will also include a complementary supernovae survey to measure the expansion history of the universe, thus giving independent additional constraints on dark energy. The baseline concept consists of a 1.2m telescope with a 0.5 square degree optical CCD camera. It is designed to be fast with reduced risks and costs, and to take advantage of the synergy between ground-based and space observations. Stringent requirements for weak lensing systematics were shown to be achievable with the baseline concept. This will allow DUNE to place strong constrai...

Réfrégier, A; Mellier, Y; Milliard, B; Pain, R; Michaud, J; Safa, F; Amara, A; Astier, Pierre; Barrelet, E; Bertin, E; Boulade, S; Cara, C; Claret, A; Georges, L; Grange, R; Guy, J; Koeck, C; Kroely, L; Magneville, C; Palanque-Delabrouille, Nathalie; Regnault, N; Smadja, G; Schimd, C; Sun, Z

2006-01-01

186

Extraterrestrial dunes: An introduction to the special issue on planetary dune systems  

E-print Network

Extraterrestrial dunes: An introduction to the special issue on planetary dune systems Mary C on extraterrestrial surfaces are similar to those on Earth, although some have notable differences in bedform scale

Bourke, Mary C.

187

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

188

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

189

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

190

Parabolic dunes in north-eastern Brazil  

E-print Network

In this work we present measurements of vegetation cover over parabolic dunes with different degree of activation along the north-eastern Brazilian coast. We are able to extend the local values of the vegetation cover density to the whole dune by correlating measurements with the gray-scale levels of a high resolution satellite image of the dune field. The empirical vegetation distribution is finally used to validate the results of a recent continuous model of dune motion coupling sand erosion and vegetation growth.

Duran, O; Bezerra, L J C; Herrmann, H J; Maia, L P

2007-01-01

191

Great Kobuk Sand Dunes, Alaska: A Terrestrial Analog Site for Polar, Topographically Confined Martian Dune Fields  

E-print Network

P13B-1369 Great Kobuk Sand Dunes, Alaska: A Terrestrial Analog Site for Polar, Topographically Confined Martian Dune Fields Dinwiddie, C. L.1 ; D. M. Hooper1 ; T. I. Michaels2 ; R. N. Mcginnis1 ; D and Engineering Laboratory, U.S. Army Corps of Engineers, Ft. Wainwright, AK, United States. Martian dune systems

Stillman, David E.

192

Disturbance drives phylogenetic community structure in coastal dune vegetation  

E-print Network

Disturbance drives phylogenetic community structure in coastal dune vegetation Background Coastal dunes are a globally distributed ecosystem characterized by strong internal gradients in disturbance plant community assembly, but their relative importance in coastal dunes is not well elucidated. We

Schierup, Mikkel Heide

193

New Orleans on Parade: Tourism and the Transformation of the Crescent City  

Microsoft Academic Search

New Orleans on Parade tells the story of the Big Easy in the twentieth century. In this urban biography, J. Mark Souther explores the Crescent City's architecture, music, food and alcohol, folklore and spiritualism, Mardi Gras festivities, and illicit sex commerce in revealing how New Orleans became a city that parades itself to visitors and residents alike.\\u000aStagnant between the

J. Mark Souther

2006-01-01

194

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

195

Serum-Starved Adipose-Derived Stromal Cells Ameliorate Crescentic GN by Promoting Immunoregulatory Macrophages  

PubMed Central

Mesenchymal stromal cells (MSCs) derived from adipose tissue have immunomodulatory effects, suggesting that they may have therapeutic potential for crescentic GN. Here, we systemically administered adipose-derived stromal cells (ASCs) in a rat model of anti-glomerular basement membrane (anti-GBM) disease and found that this treatment protected against renal injury and decreased proteinuria, crescent formation, and infiltration by glomerular leukocytes, including neutrophils, CD8+ T cells, and CD68+ macrophages. Interestingly, ASCs cultured under low-serum conditions (LASCs), but not bone marrow-derived MSCs (BM-MSCs), increased the number of immunoregulatory CD163+ macrophages in diseased glomeruli. Macrophages cocultured with ASCs, but not with BM-MSCs, adopted an immunoregulatory phenotype. Notably, LASCs polarized macrophages into CD163+ immunoregulatory cells associated with IL-10 production more efficiently than ASCs cultured under high-serum conditions. Pharmaceutical ablation of PGE2 production, blocking the EP4 receptor, or neutralizing IL-6 in the coculture medium all significantly reversed this LASC-induced conversion of macrophages. Furthermore, pretreating LASCs with aspirin or cyclooxygenase-2 inhibitors impaired the ability of LASCs to ameliorate nephritogenic IgG-mediated renal injury. Taken together, these results suggest that LASCs exert renoprotective effects in anti-GBM GN by promoting the phenotypic conversion of macrophages to immunoregulatory cells, suggesting that LASC transfer may represent a therapeutic strategy for crescentic GN. PMID:23471196

Furuhashi, Kazuhiro; Shimizu, Asuka; Katsuno, Takayuki; Kim, Hangsoo; Saka, Yosuke; Ozaki, Takenori; Sado, Yoshikazu; Imai, Enyu; Matsuo, Seiichi; Maruyama, Shoichi

2013-01-01

196

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

197

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

198

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

199

Size of Suspended Sediment over Dunes  

Technology Transfer Automated Retrieval System (TEKTRAN)

Samples of suspended sediment were collected at four elevations simultaneously over two-dimensional mobile dunes in two mixtures of 0.5 mm sand in a laboratory flume channel. A constant sampling position relative to the dunes was maintained by adjusting the translation rate of the sampling carriage...

200

Evaluation of the void fraction in the crescent-shape moderator cell of the CARR-CNS  

NASA Astrophysics Data System (ADS)

The mathematical model developed in a previous paper is improved in the present paper for analyzing and evaluating the void fraction profiles in the crescent-shape moderator cell of the Cold Neutron Source (CNS) of the China Advanced Research Reactor (CARR) which is now under construction in the China Institute of Atomic Energy (CIAE). The model is then applied to the case of the CARR-CNS with liquid hydrogen as a moderator and the void fraction in the crescent-shape moderator cell of the CARR-CNS is evaluated. The calculation results show that the void fraction in the crescent-shape moderator cell less than 20%. The model and the calculation results will help to obtain insight of the mechanism that controls the void fraction distribution in the crescent-shape moderator cell, and provide theoretical supports for the moderator cell construction.

Li, Liangxing; Li, Huixiong; Kawai, Takeshi; Chen, Tingkuan; Bi, Qincheng

2008-06-01

201

Comparative Impact of Stirring and Shearing in Drug Dissolution Testing with USP Paddle and Crescent-Shaped Spindles  

Microsoft Academic Search

A new crescent-shaped spindle has been proposed to address artefacts found with the USP Paddle spindle. Because of improved stirring and mixing environment within dissolution vessels resulting in improved product-medium interactions, the crescent-shaped spindle provides a more appropriate dissolution test. Diltiazem immediate- (IR) and extended-release (ER) tablets and capsules were used as model drug products to demonstrate that the appropriate

Saeed A. Qureshi

202

Dynamic conversion of solar generated heat to electricity  

Microsoft Academic Search

The effort undertaken during this program led to the selection of the water-superheated steam (850 psig\\/900 F) crescent central receiver as the preferred concept from among 11 candidate systems across the technological spectrum of the dynamic conversion of solar generated heat to electricity. The solar power plant designs were investigated in the range of plant capacities from 100 to 1000

J. C. Powell; E. Fourakis; J. M. Hammer; G. A. Smith; J. C. Grosskreutz; E. McBride

1974-01-01

203

Effect of ground-water recharge on configuration of the water table beneath sand dunes and on seepage in lakes in the sandhills of Nebraska, U.S.A.  

USGS Publications Warehouse

Analysis of water-level fluctuations in about 30 observation wells and 5 lakes in the Crescent Lake National Wildlife Refuge in the sandhills of Nebraska indicates water-table configuration beneath sand dunes in this area varies considerably, depending on the configuration of the topography of the dunes. If the topography of an interlake dunal area is hummocky, ground-water recharge is focused at topographic lows causing formation of water-table mounds. These mounds prevent ground-water movement from topographically high lakes to adjacent lower lakes. If a dune ridge is sharp, the opportunity for focused recharge does not exist, resulting in water-table troughs between lakes. Lakes aligned in descending altitudes, parallel to the principal direction of regional ground-water movement, generally have seepage from higher lakes toward lower lakes. ?? 1986.

Winter, T.C.

1986-01-01

204

Hybrid eolian dunes of William River Dune field, northern Saskatchewan, Canada  

SciTech Connect

A series of northwest-southeast aligned, large-scale (up to 30 m high) eolian dunes, occurring in a confined (600 km/sup 2/) desert area in northern Saskatchewan, Canada, was examined in the field. Observations were made of dune morphology and internal structure, and patterns of sand movement on the dunes were analyzed in relation to wind events during the summer of 1981. Present cross-sectional profiles exhibit steeper northeast slopes, the lower segment of which are intermittently covered by psammophilous grasses. Dune structure is dominated by northeast-dipping accretion laminae. Three /sup 14/C dates from organic material cropping out on the lower southwest slopes reveal that the dunes have migrated as transverse bed forms at rates of roughly 0.5 m/yr during the last few hundred years. However, a progressive increase in height, bulk, and symmetry along the dune axis from northwest to southeast, suggests an along-dune component of sand transport. This view is supported by (1) field measurements of airflow and along-dune sand transport patterns on 2 dunes, and (2) the present-day wind regime (1963-78). Dominated by north-northeast to northeast winds from January to June and by west-southwest winds from July to December, the resultant potential sand transport vector is toward the southeast, virtually identical to the dune axis.

Carson, M.A.; MacLean, P.A.

1985-02-01

205

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

206

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

207

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

208

Late Pleistocene dune activity in the central Great Plains, USA  

Microsoft Academic Search

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

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

209

Seasonal Erosion and Restoration of Mars' Northern Polar Dunes  

Microsoft Academic Search

Despite radically different environmental conditions, terrestrial and martian dunes bear a strong resemblance, indicating that the basic processes of saltation and grainfall (sand avalanching down the dune slipface) operate on both worlds. Here, we show that martian dunes are subject to an additional modification process not found on Earth: springtime sublimation of Mars' CO2 seasonal polar caps. Numerous dunes in

C. J. Hansen; M. Bourke; N. T. Bridges; S. Byrne; C. Colon; S. Diniega; C. Dundas; K. Herkenhoff; A. McEwen; M. Mellon; G. Portyankina; N. Thomas

2011-01-01

210

Barchan and Linear Dunes on Earth and Mars - Comparative Research  

Microsoft Academic Search

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

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

2007-01-01

211

Barchan dune corridors: Field characterization and investigation of control parameters  

E-print Network

Barchan dune corridors: Field characterization and investigation of control parameters H, and the output sand flux of a dune can be computed from the value of its body and horn widths. The dune size direction, in which the dunes have a rather well selected size. Investigating the possible external

Claudin, Philippe

212

Thermoluminescence and radiocarbon dating of Australian desert dunes  

Microsoft Academic Search

Quaternary lithostratigraphic units in continental dunes have been dated at three locations in South Australia by both radiocarbon dating of organic carbon bedded either in dune sands or in deposits correlated with dune building episodes, and by thermoluminescence (TL) sediment dating of the dune sands. It was not possible to date in situ organic carbon and adjacent aeolian quartz particles,

G. J. Gardner; A. J. Mortlock; D. M. Price; M. L. Readhead; R. J. Wasson

1987-01-01

213

Nanofocusing performance of the crescent-shaped cylinder for various surrounding media  

NASA Astrophysics Data System (ADS)

In this work, adjustable broadband light harvesting and field enhancement on the surface of a crescent-shaped cylinder were achieved by considering the surrounding medium in conformal transformation theory. The continuous absorption spectrum shows that the broadband effect is quite robust to the surrounding media. By considering the material properties, we provide a comprehensive discussion of how the material properties of the nanosystem affect the field enhancement and nanofocusing. Furthermore, an optical gain medium is employed to compensate for the absorption losses in the materials. A considerable field enhancement and super-nanofocusing are thus expected. The presented results provide important guidance for optimizing such a nanosystem in experimental studies.

Wu, Hong-Wei; Deng, Yu-Qiang; Zhou, Yu; Dong, Ye-Qing; Fan, Ren-Hao

2014-11-01

214

Hallux rigidus: surgical treatment with the crescentic oblique basilar resection arthroplasty (COBRA).  

PubMed

The treatment of advanced hallux rigidus in an older, more sedentary population with poor bone stock or comorbidities that may make corrective osteotomy, fusion, and implant fixation more problematic has frequently been an issue for orthopedic surgeons. The traditional Keller resection arthroplasty has not fared well because of various problems. Crescentic oblique basilar resection arthroplasty is a viable surgical treatment alternative for older, more sedentary patients who have advanced hallux rigidus with or without hallux valgus. This may also be a good alternative procedure in a more active patient who wishes to avoid fusion of the joint while maintaining some first MTP motion. PMID:19232989

Marks, Richard M

2009-03-01

215

Design and implementation of a hospital information system for the Palestine Red Crescent Society in Lebanon.  

PubMed

A case-mix hospital information system was designed and implemented in Palestine Red Crescent Society hospitals in order to support the network of Palestinian hospitals in Lebanon and to improve the health of refugees in the country. The system is based on routine collection of essential administrative and clinical data for each episode of hospitalization, relying on internationally accepted diagnostic codes. It is a computerized, user-friendly information system that is a stepping-stone towards better hospital management and evaluation of quality of care. It is also a useful model for the development of hospital information systems in Lebanon and in the Near East. PMID:19731791

Rossi, L; Materia, E; Hourani, A; Yousef, H; Racalbuto, V; Venier, C; Osman, M

2009-01-01

216

The Search for Dune Movement on Mars  

NASA Astrophysics Data System (ADS)

Although aeolian processes are active on Mars, questions remain about whether the current wind regime is adequate to cause dune movement. Early studies using Viking images might have detected movement in the northern erg, but that study was limited by image resolution. Since 1997, the Mars Orbiter Camera (MOC) on Mars Global Surveyor has been returning narrow angle (NA) images at resolutions of 1.5-12 m/pixel, and overlapping pairs of these images acquired at sufficiently spaced times can be used to search for dune movement. Whereas most images acquired during the Mapping Phase of the mission were near-nadir looking, images from the Extended and Relay portions of the mission often had look directions off nadir (ROTO images). This geometry causes parallax and complicates the search for dune movement but does not prevent it. Dune locations in MOC (and now THEMIS) images can also be compared to locations in Viking images, but movement would need to be on a larger scale because of the larger pixel sizes of Viking and THEMIS images. Results showing evidence for dune movement or for dune immobility would both be important for understanding the current martian aeolian setting and how it might have changed over time. The MSSS website and a USGS database of potentially overlapping MOC narrow angle images have been used to identify image pairs that could be used to determine whether dunes moved during the time spanned by the images. Of the over 150,000 MOC NA images released, only a small subset are overlapping pairs, and only a subset of those contain dunes. At this time, no definite dune movement has yet been detected, but the study is being expanded to cover more areas on Mars and to include more images as they become available.

Williams, K. K.

2004-12-01

217

Looking Back at 'Purgatory Dune'  

NASA Technical Reports Server (NTRS)

The wheels of NASA's Mars Exploration Rover Opportunity dug more than 10 centimeters (4 inches) deep into the soft, sandy material of a wind-shaped ripple in Mars' Meridiani Planum region during the rover's 446th martian day, or sol (April 26, 2005). Getting the rover out of the ripple, dubbed 'Purgatory Dune,' required more than five weeks of planning, testing, and carefully monitored driving. Opportunity used its navigation camera to capture this look back at the ripple during sol 491 (June 11, 2005), a week after the rover drove safely onto firmer ground. The ripple that became a sand trap is about one-third meter (one foot) tall and 2.5 meters (8 feet) wide.

2005-01-01

218

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

E-print Network

Dune field pattern formation and recent transporting winds in the Olympia Undae Dune Field, north] HighResolution 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

Bourke, Mary C.

219

Sixth International Conference on Aeolian Research, Guelph, Canada. 2006 Barchan dune morphodynamics and linear dune formation on Mars  

E-print Network

Sixth International Conference on Aeolian Research, Guelph, Canada. 2006 Barchan dune morphodynamics and linear dune formation on Mars Mary C. Bourke, Planetary Science Institute, Tucson, mbourke@psi.edu Observations of sand dunes in satellite images indicate a wide variety of dune forms on Mars. Similar to Earth

Bourke, Mary C.

220

Three-dimensional mapping of airflow over dunes  

NASA Astrophysics Data System (ADS)

Similar to the way a river, flowing across Earth's surface, influences sediment transport and shaping of the landscape, coastal winds, which flow over dunes, affect how the dune shapes evolve and how sand is transported along the coast. Wind flow over dunes has been extensively studied, but in most cases, that research has been two-dimensional and focused on straight dunes with smooth slopes and no vegetation or other features that might affect how airflow separates at the crest of the dune.

Balcerak, Ernie

2013-05-01

221

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 occurence 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 consistant with their apparent formation conditions on Earth.

Lee, Pascal; Thomas, Peter C.

1995-01-01

222

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

223

Surgery for hallux valgus with proximal crescentic osteotomy causes variable postoperative pressure patterns.  

PubMed

We prospectively evaluated the results of plantar pressure measurement in 32 patients (43 feet) who had a proximal crescentic osteotomy of the first metatarsal with a modified McBride procedure. The procedure's effectiveness in increasing weightbearing under the first ray, decreasing pressure under the second metatarsal head, and the relationship of radiographic measurements of first metatarsal length and position to postoperative pressure measurements were evaluated. Mean followup was 29 months. Average peak pressure increased postoperatively under the second metatarsal head. Almost identical numbers of feet had first metatarsal elevation (12) or depression (11) greater than 2 mm. Radiographic evidence of first metatarsal elevation, but not shortening, was associated with diminishing peak pressure and pressure-time integral under the first metatarsal head and hallux. Five feet that had first metatarsal elevation greater than 2 mm had new second metatarsal transfer lesions develop. Eleven feet preoperatively and nine feet postoperatively had symptomatic second metatarsal pressure lesions. One lesion persisted, 10 resolved, and eight new lesions developed. Control of the crescentic osteotomy in the sagittal plane was unpredictable despite modification of the surgical technique to plantarly displace the distal segment of the first meta-tarsal. Although average second metatarsal pressure increased postoperatively, there was variability in the correlation of radiographic change and pedobarographic measurements. PMID:16462452

Brodsky, James W; Beischer, Andrew D; Robinson, Andrew H N; Westra, Sjoerd; Negrine, John P; Shabat, Shay

2006-02-01

224

MPO-ANCA associated crescentic glomerulonephritis with numerous immune complexes: case report  

PubMed Central

Background Antineutrophil cytoplasmic antibody (ANCA)-associated crescentic glomerulonephritis (CGN) is a major cause of rapidly progressive glomerulonephritis (RPGN). ANCA-associated CGN is generally classified into pauci-immune RPGN, in which there are few or no immune complexes. Case Presentation A 78-year-old man presented with RPGN after a 7-year course of chronic proteinuria and hematuria with stable renal function. A blood examination showed a high titer of myeloperoxidase (MPO)-ANCA. A renal biopsy showed crescentic glomerulonephritis with abundant subepithelial, intramenbranous and subendothelial deposits by electron microscopy, leading to the diagnosis of ANCA-associated CGN superimposed on type 3 membranoproliferative glomerulonephritis (MPGN). Conclusions This case is unique in that type 3 MPGN and MPO-ANCA-associated CGN coexisted, and no similar case has been reported to date. Because ANCA-associated CGN has a predilection for elderly individuals and primary type 3 MPGN is rarely seen in this age group, coincidental existence appears less likely. This case may confer valuable information regarding the link between immune complex and ANCA-associated CGN. PMID:22656245

2012-01-01

225

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

226

Membranous nephropathy with crescents in a patient with Hashimoto's thyroiditis: a case report.  

PubMed

Membranous nephropathy is a common cause of nephrotic syndrome in adults. It usually occurs secondary to underlying disease processes such as autoimmune disorders, malignancy, infection, and drugs. The presentation of nephrotic syndrome with concomitant precipitous decline in renal function warrants investigation of a coexistent disorder.We report the case of a 30-year-old male who presented with symptoms and signs of hypothyroidism.A diagnosis of Hashimoto's thyroiditis was contemplated based on the presence of high serum levels of antithyroglobulin and antithyroid peroxidase antibodies. Upon initiation of treatment with levothyroxine, patient symptomatology improved; however, the laboratory studies demonstrated continued elevated creatinine, hematuria, and proteinuria, which had not been addressed. Two months following treatment initiation, he had progressive deterioration in renal function and proteinuria. A renal biopsy revealed coexistent necrotizing and crescentic glomerulonephritis and membranous nephropathy.The final diagnosis was necrotizing, crescentic glomerulonephritis with superimposed membranous nephropathy likely secondary to Hashimoto's thyrodiitis.Induction treatment with oral cyclophosphamide and prednisone was started.At the end of 6 months of treatment, there was improvement in renal function and proteinuria and maintenance treatment with azathioprine and low-dose prednisone was initiated. This case highlights the importance of precise and detailed evaluation of patients with autoimmune diseases such as Hashimoto's thyroiditis particularly in the presence of active urine sediment. Proper evaluation and diagnosis of such patients has implications on the prognosis and response to treatment. PMID:25121358

Thajudeen, Bijin; John, Santhosh G; Ossai, Nduka-Obi; Riaz, Irbaz B; Bracamonte, Erika; Sussman, Amy N

2014-08-01

227

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

228

Summary of the DUNE Mission Concept  

E-print Network

The Dark UNiverse Explorer (DUNE) is a wide-field imaging mission concept whose primary goal is the study of dark energy and dark matter with unprecedented precision. To this end, DUNE is optimised for weak gravitational lensing, and also uses complementary cosmolo gical probes, such as baryonic oscillations, the integrated Sachs-Wolf effect, a nd cluster counts. Immediate additional goals concern the evolution of galaxies, to be studied with groundbreaking statistics, the detailed structure of the Milky Way and nearby galaxies, and the demographics of Earth-mass planets. DUNE is a medium class mission consisting of a 1.2m telescope designed to carry out an all-sky survey in one visible and three NIR bands (1deg$^2$ field-of-view) which will form a unique legacy for astronomy. DUNE has been selected jointly with SPACE for an ESA Assessment phase which has led to the Euclid merged mission concept.

Refregier, Alexandre

2008-01-01

229

Observation of Density Segregation inside Migrating Dunes  

E-print Network

Spatiotemporal patterns in nature, such as ripples or dunes, formed by a fluid streaming over a sandy surface show complex behavior despite their simple forms. Below the surface, the granular structure of the sand particles is subject to self-organization processes, exhibiting such phenomena as reverse grading when larger particles are found on top of smaller ones. Here we report results of an experimental investigation with downscaled model dunes revealing that, if the particles differ not in size but in density, the heavier particles, surprisingly, accumulate in the central core close to the top of the dune. This finding contributes to the understanding of sedimentary structures found in nature and might be helpful to improve existing dating methods for desert dunes.

Christopher Groh; Ingo Rehberg; Christof A. Kruelle

2011-09-18

230

Summary of the DUNE Mission Concept  

E-print Network

The Dark UNiverse Explorer (DUNE) is a wide-field imaging mission concept whose primary goal is the study of dark energy and dark matter with unprecedented precision. To this end, DUNE is optimised for weak gravitational lensing, and also uses complementary cosmolo gical probes, such as baryonic oscillations, the integrated Sachs-Wolf effect, a nd cluster counts. Immediate additional goals concern the evolution of galaxies, to be studied with groundbreaking statistics, the detailed structure of the Milky Way and nearby galaxies, and the demographics of Earth-mass planets. DUNE is a medium class mission consisting of a 1.2m telescope designed to carry out an all-sky survey in one visible and three NIR bands (1deg$^2$ field-of-view) which will form a unique legacy for astronomy. DUNE has been selected jointly with SPACE for an ESA Assessment phase which has led to the Euclid merged mission concept.

Alexandre Refregier; Marian Douspis; the DUNE collaboration

2008-07-25

231

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

232

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

233

Autumn Frost, North Polar Sand Dunes  

NASA Technical Reports Server (NTRS)

Autumn in the martian northern hemisphere began around August 1, 1999. Almost as soon as northern fall began, the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) started documenting the arrival of autumn frost--a precursor to the cold winter that will arrive in late December 1999. The first features to become covered by frost were the sand dunes that surround the north polar ice cap. The dunes seen here would normally appear very dark--almost black--except when covered by frost. Why the dunes begin to frost sooner than the surrounding surfaces is a mystery: perhaps the dunes contain water vapor that emerges from the sand during the day and condenses again at night. This picture shows dunes near 74.7oN, 61.4oW at a resolution of about 7.3 meters (24 feet) per pixel. The area covered is about 3 km (1.9 mi) across and is illuminated from the upper right. The picture appears to be somewhat fuzzy and grainy because the dunes here are seen through the thin haze of the gathering north polar winter hood (i.e., clouds).

1999-01-01

234

Mars Global Digital Dune Database (MGD3): Global dune distribution and wind pattern observations  

USGS Publications Warehouse

The Mars Global Digital Dune Database (MGD3) is complete and now extends from 90°N to 90°S latitude. The recently released south pole (SP) portion (MC-30) of MGD3 adds ?60,000 km2 of medium to large-size dark dune fields and ?15,000 km2 of sand deposits and smaller dune fields to the previously released equatorial (EQ, ?70,000 km2), and north pole (NP, ?845,000 km2) portions of the database, bringing the global total to ?975,000 km2. Nearly all NP dunes are part of large sand seas, while the majority of EQ and SP dune fields are individual dune fields located in craters. Despite the differences between Mars and Earth, their dune and dune field morphologies are strikingly similar. Bullseye dune fields, named for their concentric ring pattern, are the exception, possibly owing their distinctive appearance to winds that are unique to the crater environment. Ground-based wind directions are derived from slipface (SF) orientation and dune centroid azimuth (DCA), a measure of the relative location of a dune field inside a crater. SF and DCA often preserve evidence of different wind directions, suggesting the importance of local, topographically influenced winds. In general however, ground-based wind directions are broadly consistent with expected global patterns, such as polar easterlies. Intriguingly, between 40°S and 80°S latitude both SF and DCA preserve their strongest, though different, dominant wind direction, with transport toward the west and east for SF-derived winds and toward the north and west for DCA-derived winds.

Hayward, Rosalyn; Fenton, Lori; Titus, Timothy N.

2013-01-01

235

Mars Global Digital Dune Database (MGD3): Global dune distribution and wind pattern observations  

NASA Astrophysics Data System (ADS)

The Mars Global Digital Dune Database (MGD3) is complete and now extends from 90°N to 90°S latitude. The recently released south pole (SP) portion (MC-30) of MGD3 adds ˜60,000 km2 of medium to large-size dark dune fields and ˜15,000 km2 of sand deposits and smaller dune fields to the previously released equatorial (EQ, ˜70,000 km2), and north pole (NP, ˜845,000 km2) portions of the database, bringing the global total to ˜975,000 km2. Nearly all NP dunes are part of large sand seas, while the majority of EQ and SP dune fields are individual dune fields located in craters. Despite the differences between Mars and Earth, their dune and dune field morphologies are strikingly similar. Bullseye dune fields, named for their concentric ring pattern, are the exception, possibly owing their distinctive appearance to winds that are unique to the crater environment. Ground-based wind directions are derived from slipface (SF) orientation and dune centroid azimuth (DCA), a measure of the relative location of a dune field inside a crater. SF and DCA often preserve evidence of different wind directions, suggesting the importance of local, topographically influenced winds. In general however, ground-based wind directions are broadly consistent with expected global patterns, such as polar easterlies. Intriguingly, between 40°S and 80°S latitude both SF and DCA preserve their strongest, though different, dominant wind direction, with transport toward the west and east for SF-derived winds and toward the north and west for DCA-derived winds.

Hayward, R. K.; Fenton, L. K.; Titus, T. N.

2014-02-01

236

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

237

A bibliography of dunes: Earth, Mars, and Venus  

NASA Technical Reports Server (NTRS)

Dunes are important depositional landforms and sedimentary environments on Earth and Mars, and may be important on Venus. The similarity of dune forms on Earth and Mars, together with the dynamic similarity of aeolian processes on the terrestrial planets indicates that it is appropriate to interpret dune forms and processes on Mars and Venus by using analog studies. However, the literature on dune studies is large and scattered. The aim of this bibliography is to assist investigators by providing a literature resource on techniques which have proved successful in elucidating dune characteristics and processes on Earth, Mars, and Venus. This bibliography documents the many investigations of dunes undertaken in the last century. It concentrates on studies of inland dunes in both hot and cold desert regions on Earth and includes investigations of coastal dunes only if they discuss matters of general significance for dune sediments, processes, or morphology.

Lancaster, N.

1988-01-01

238

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

239

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

240

Reactivation of Coastal Dunes Documented by Subsurface Imaging of the Great Dune Ridge, Lithuania  

Microsoft Academic Search

BUYNEVICH, I., BITINAS, A. and PUPIENIS, D., 2007. Reactivation of coastal dunes documented by subsurface imaging of the Great Dune Ridge, Lithuania. Journal of Coastal Research, SI 50 (Proceedings of the 9th International Coastal Symposium), 226 - 230. Gold Coast, Australia, ISSN 0749.0208 Large coastal and inland dunefields often consist of multiple generations defined by periods of stability and reactivation.

I. Buynevich; A. Bitinas; D. Pupienis

2007-01-01

241

Membrane Fission Is Promoted by Insertion of Amphipathic Helices and Is Restricted by Crescent BAR Domains  

PubMed Central

Summary Shallow hydrophobic insertions and crescent-shaped BAR scaffolds promote membrane curvature. Here, we investigate membrane fission by shallow hydrophobic insertions quantitatively and mechanistically. We provide evidence that membrane insertion of the ENTH domain of epsin leads to liposome vesiculation, and that epsin is required for clathrin-coated vesicle budding in cells. We also show that BAR-domain scaffolds from endophilin, amphiphysin, GRAF, and ?2-centaurin limit membrane fission driven by hydrophobic insertions. A quantitative assay for vesiculation reveals an antagonistic relationship between amphipathic helices and scaffolds of N-BAR domains in fission. The extent of vesiculation by these proteins and vesicle size depend on the number and length of amphipathic helices per BAR domain, in accord with theoretical considerations. This fission mechanism gives a new framework for understanding membrane scission in the absence of mechanoenzymes such as dynamin and suggests how Arf and Sar proteins work in vesicle scission. PMID:22464325

Boucrot, Emmanuel; Pick, Adi; Çamdere, Gamze; Liska, Nicole; Evergren, Emma; McMahon, Harvey T.; Kozlov, Michael M.

2012-01-01

242

Genetic inhibition of discoidin domain receptor 1 protects mice against crescentic glomerulonephritis.  

PubMed

This study investigated the role of discoidin domain receptor 1 (DDR1), a collagen receptor that displays tyrosine-kinase activity, in the development of glomerulonephritis. Crescentic glomerulonephritis was induced in DDR1-deficient mice and their wild-type (WT) littermates as controls, by injection of alloimmune sheep nephrotoxic serum (NTS). Histological, functional and transcriptomic studies were performed. Glomerulonephritis produced a 17-fold increase of DDR1 expression, predominantly in glomeruli. DDR1 deletion protected NTS-treated mice against glomerular disease (proteinuria/creatininuria 5.5±1.1 vs. 13.2±0.8 g/mmol in WT, crescents 12±2 vs. 24±2% of glomeruli, urea 16±2 vs. 28±5 mM), hypertension (123±11 vs. 157±8 mmHg), and premature death (70 vs. 10% survival) (all P<0.05). Reciprocal stimulation between DDR1 and interleukin-1b expression in vivo and in cultured podocytes suggested a positive feed-back loop between DDR1 and inflammation. In NTS-treated WT mice, administration of DDR1-specific antisense oligodeoxynucleotides decreased DDR1 expression (-56%) and protected renal function and structure, including nephrin expression (4.2±1.4 vs. 0.9±0.4 arbitrary units, P<0.05), compared to control mice receiving scrambled oligodeoxynucleotides. The therapeutic potential of this approach was reinforced by the observation of increased DDR1 expression in glomeruli of patients with lupus nephritis and Goodpasture's syndrome. These results prompt further interest in DDR1 blockade strategies, especially in the treatment of glomerulonephritis. PMID:22751008

Kerroch, Monique; Guerrot, Dominique; Vandermeersch, Sophie; Placier, Sandrine; Mesnard, Laurent; Jouanneau, Chantal; Rondeau, Eric; Ronco, Pierre; Boffa, Jean-Jacques; Chatziantoniou, Christos; Dussaule, Jean-Claude

2012-10-01

243

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

244

The role of dune interactions and wind fluctuations in the selection of dune sizes within barchan fields  

NASA Astrophysics Data System (ADS)

Sand dunes dominate desert morphology. They naturally emerge under strong winds and sufficient sand supply from the interaction between sand transport, topography and hydrodynamics. The fact that dunes are mobile landforms gives a dynamical character to desert geomorphology with potential implications for the surrounding ecosystems. As dune mobility is closely related to dune morphology, in particular its size, the study of the long-term evolution of desert areas requires a better understanding of (1) the factors behind dune size selection and (2) the multi-scale nature of dune morphology. Recently it has been shown that dune size is bounded both at small and large scales by sand transport and hydrodynamics, respectively. The smallest dune size is limited to several meters in length by the existence of the so called "saturation length", i.e. the characteristic length of transport transients. The maximum dune size, in the order of hundreds of meters, is in turn limited by the stabilizing effect of the upper limit of the atmospheric boundary layer. Dune dynamics at both scales is also qualitatively different as elementary dunes emerge from a linear instability, and are thus ubiquitous, while giant dunes seem to result from the coalescence of smaller ones. In consequence, a typical dune field should consist in a roughly continuous hierarchy of dune sizes, with many elementary dunes and very few giant dunes. However, in several cases this is not the correct picture as dune sizes are quite uniform and seems to cluster around an intermediate value that is well above the minimum but much smaller than the maximum one. This points to an alternative selection mechanism different from the simple dune merging. Here, we argue that the combination of dune collisions and wind fluctuations, at least within barchan fields, is able to stop the continuous merging process and select a characteristic dune size in function of local conditions. To that end we use a morphodynamic dune model capable of reproducing the evolution of dune fields for different wind regimes. We find that colliding dunes of very different sizes tend to merge and thus increase the average dune size within the field. In contrast, colliding dunes of comparable sizes tend to redistribute the volume such that both dunes become more equal afterwards, which limits dune growth. In accordance with previous results, we find that dune growth is also limited by wind fluctuations, both in intensity and direction, which lead to the formation of elementary barchans from dune calving. As a result, the balance between those processes contributing to dune growth and those limiting it is able to select a specific, non-trivial dune size. In addition, simulations also suggest that this balance can be unstable in certain conditions and start a positive feedback for dune growth. As collisions with very large dunes have a higher probability of leading to the merging of both dunes, dune growth may continue until it is eventually limited by the size of the atmospheric boundary layer.

Duran Vinent, O.; Parteli, E. J.; Herrmann, H. J.

2012-12-01

245

A Mystery Unraveled: Booming Sand Dunes  

NASA Astrophysics Data System (ADS)

"Booming" sand dunes have intrigued travelers and scientist for centuries. These dunes emit a persistent, low-frequency sound during a slumping event or a natural avalanche on the leeward face of the dune. The sound can last for several minutes and be audible from miles away. The resulting acoustic emission is characterized by a dominant audible frequency (70 - 105 Hz) and several higher harmonics. In the work of Vriend et al. (2007), seismic refraction experiments proved the existence of a multi-layer internal structure in the dune that acts as a waveguide for the acoustic energy. Constructive interference between the reflecting waves enables the amplification and sets the frequency of each boom. A relationship was established that correctly predicts the measured frequency in terms of the thickness (~ 2.0 m) and the seismic body wave velocity of the loose, dry surficial layer (~ 240 m/s) and the substrate half-space (~ 350 m/s). The current work highlights additional measurements and simulations supporting the waveguide model for booming sand dunes. Experiments with ground penetrating radar continuously display the subsurface features which confirm the layered subsurface structure within the dune. Cross-correlation analysis shows that the booming sound propagates at speeds close to the measured body wave velocity. Squeaking sounds, which are generated during the onset of the slide and precede the sustained booming emission, have been found to have distinctly different characteristics. These short bursts of sound are emitted at a lower frequency (50 - 65 Hz) and propagate at a lower propagation speed (125 m/s) than the booming emission. The acoustic and elastic wave propagation in the dune has been simulated with a finite difference code. The interaction between the air and the ground produces a coupling wave along the surface. The reflections in the surficial layer propagate in a dispersive band at a group velocity that is slower than the phase velocity of the layer. Different source mechanisms are used in order to simulate the squeaking and booming emission within the dune. špace{.1in} {\\footnotesize Vriend, N. M., M. L. Hunt, R. W. Clayton, C E. Brennen, K. S. Brantley, and A. Ruiz-Angulo (2007), Solving the mystery of booming sand dunes, Geophys. Res. Lett., 34, L16306, doi:10.1029/2007GL030276.}

Vriend, N. M.; Hunt, M. L.; Clayton, R. W.

2007-12-01

246

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

247

Layers, Landslides, and Sand Dunes  

NASA Technical Reports Server (NTRS)

[figure removed for brevity, see original site]

Released 27 October 2003

This image shows the northern rim of one of the Valles Marineris canyons. Careful inspection shows many interesting features here. Note that the spurs and gullies in the canyon wall disappear some distance below the top of the canyon wall, indicating the presence of some smooth material here that weathers differently from the underlying rocks. On the floor of the canyon, there are remains from a landslide that came hurtling down the canyon wall between two spurs. Riding over the topography of the canyon floor are many large sand dunes, migrating generally from the lower right to upper left.

Image information: VIS instrument. Latitude -14.1, Longitude 306.7 East (53.3 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

248

Dunes on Titan observed by Cassini Radar  

USGS Publications Warehouse

Thousands of longitudinal dunes have recently been discovered by the Titan Radar Mapper on the surface of Titan. These are found mainly within ??30?? of the equator in optically-, near-infrared-, and radar-dark regions, indicating a strong proportion of organics, and cover well over 5% of Titan's surface. Their longitudinal duneform, interactions with topography, and correlation with other aeolian forms indicate a single, dominant wind direction aligned with the dune axis plus lesser, off-axis or seasonally alternating winds. Global compilations of dune orientations reveal the mean wind direction is dominantly eastwards, with regional and local variations where winds are diverted around topographically high features, such as mountain blocks or broad landforms. Global winds may carry sediments from high latitude regions to equatorial regions, where relatively drier conditions prevail, and the particles are reworked into dunes, perhaps on timescales of thousands to tens of thousands of years. On Titan, adequate sediment supply, sufficient wind, and the absence of sediment carriage and trapping by fluids are the dominant factors in the presence of dunes. ?? 2007 Elsevier Inc. All rights reserved.

Radebaugh, J.; Lorenz, R.D.; Lunine, J.I.; Wall, S.D.; Boubin, G.; Reffet, E.; Kirk, R.L.; Lopes, R.M.; Stofan, E.R.; Soderblom, L.; Allison, M.; Janssen, M.; Paillou, P.; Callahan, P.; Spencer, C.; The Cassini Radar Team

2008-01-01

249

Choice of rotation speed (rpm) for bio-relevant drug dissolution testing using a crescent-shaped spindle  

Microsoft Academic Search

Recently a new crescent-shaped spindle has been proposed to address the issues related to poor hydrodynamics of the USP paddle apparatus and its associated artifacts of high variability and lack of bio-relevant results. For improved comparison of drug dissolution characterization, it is highly desirable to conduct testing using common experimental conditions such as spindle rotation speed. A study was conducted

Saeed A. Qureshi

2004-01-01

250

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

251

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

252

Mars global digital dune database and initial science results  

USGS Publications Warehouse

A new Mars Global Digital Dune Database (MGD3) constructed using Thermal Emission Imaging System (THEMIS) infrared (IR) images provides a comprehensive and quantitative view of the geographic distribution of moderate- to large-size dune fields (area >1 kM2) that will help researchers to understand global climatic and sedimentary processes that have shaped the surface of Mars. MGD3 extends from 65??N to 65??S latitude and includes ???550 dune fields, covering ???70,000 km2, with an estimated total volume of ???3,600 km3. This area, when combined with polar dune estimates, suggests moderate- to large-size dune field coverage on Mars may total ???800,000 km2, ???6 times less than the total areal estimate of ???5,000,000 km2 for terrestrial dunes. Where availability and quality of THEMIS visible (VIS) or Mars Orbiter Camera. narrow-angle (MOC NA) images allow, we classify dunes and include dune slipface measurements, which are derived from gross dune morphology and represent the prevailing wind direction at the last time of significant dune modification. For dunes located within craters, the azimuth from crater centroid to dune field centroid (referred to as dune centroid azimuth) is calculated and can provide an accurate method for tracking dune migration within smooth-floored craters. These indicators of wind direction are compared to output from a general circulation model (GCM). Dune centroid azimuth values generally correlate to regional wind patterns. Slipface orientations are less well correlated, suggesting that local topographic effects may play a larger role in dune orientation than regional winds. Copyright 2007 by the American Geophysical Union.

Hayward, R.K.; Mullins, K.F.; Fenton, L.K.; Hare, T.M.; Titus, T.N.; Bourke, M.C.; Colaprete, A.; Christensen, P.R.

2007-01-01

253

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

254

Spatiotemporal model for the progression of transgressive dunes  

E-print Network

Spatiotemporal model for the progression of transgressive dunes H. Yizhaqa, , Y. Ashkenazya , N Transgressive dunes, 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

Ashkenazy, Yossi "Yosef"

255

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

E-print Network

Climate and coastal dune vegetation: disturbance, recovery, and succession Thomas E. Miller Ã? Elise Science+Business Media B.V. 2009 Abstract The sand dune habitats found on barrier islands and other. Foredune, interdune, and backdune habitats common to most coastal dunes have very different vegetation

Miller, Thomas E.

256

LATE ORDOVICIAN CLIMBING DUNE ASSEMBLAGES, THE SIGNATURE OF GLACIAL OUTBURST ?  

E-print Network

1 LATE ORDOVICIAN CLIMBING DUNE ASSEMBLAGES, THE SIGNATURE OF GLACIAL OUTBURST ? F. GIRARD1, J, stoss-depositional 2D or 3D dunes. Based on data of outcrops from the paraglacial successions to describe climbing dunes assemblages (facies, geometries and depositional model), and to relate them

Paris-Sud XI, Université de

257

Modeling emergent large-scale structures of barchan dune fields  

E-print Network

Modeling emergent large-scale structures of barchan dune fields S. Worman , A.B. Murray , R, barchan dunes typically exist as members of larger fields that display strik- ing, enigmatic structures that cannot be readily explained by examining the dynamics at the scale of single dunes, or by appealing

Claudin, Philippe

258

Thermoluminescence dating on gypseous dunes of Lake Amadeus, central Australia  

Microsoft Academic Search

The formation of shoreline gypseous dunes is a major event in the Quaternary history of many playas in central Australia. The dunes probably were formed during a period of high regional water table when abundant gypsum was deposited in a near?shore groundwater seepage zone and deflated on to the shoreline dunes. Ten samples from two sites at Lake Amadeus, a

X. Y. Chen; J. R. Prescott; J. T. Hutton

1990-01-01

259

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

260

Exploring inner structure of Titan's dunes from Cassini Radar observations  

NASA Astrophysics Data System (ADS)

Linear dunes discovered in the equatorial regions of Titan by the Cassini-Huygens mission are morphologically very similar to many terrestrial linear dune fields. These features have been compared with terrestrial longitudinal dune fields like the ones in Namib desert in western Africa. This comparison is based on the overall parallel orientation of Titan's dunes to the predominant wind direction on Titan, their superposition on other geomorphological features and the way they wrap around topographic obstacles. Studying the internal layering of dunes has strong implications in understanding the hypothesis for their origin and evolution. In Titan's case, although the morphology of the dunes has been studied from Cassini Synthetic Aperture Radar (SAR) images, it has not been possible to investigate their internal structure in detail as of yet. Since no radar sounding data is available for studying Titan's subsurface yet, we have developed another technique to examine the inner layering of the dunes. In this study, we utilize multiple complementary radar datasets, including radar imaging data for Titan's and Earth's dunes and Ground Penetrating Radar (GPR)/radar sounding data for terrestrial dunes. Based on dielectric mixing models, we suggest that the Cassini Ku-band microwaves should be able to penetrate up to ~ 3 m through Titan's dunes, indicating that the returned radar backscatter signal would include contributions from both surface and shallow subsurface echoes. This implies that the shallow subsurface properties can be retrieved from the observed radar backscatter (?0). In our analysis, the variation of the radar backscatter as a function of dune height is used to provide an insight into the layering in Titan's dunes. We compare the variation of radar backscatter with elevation over individual dunes on Titan and analogous terrestrial dunes in three sites (Great Sand Sea, Siwa dunes and Qattaniya dunes) in the Egyptian Sahara. We observe a strong, positive correlation between the backscatter and elevation along dune profile for the larger, older dunes in the Great Sand Sea in south-western Egypt and Siwa dune field in north-western Egypt, as opposed to the weak negative correlation exhibited by the smaller, younger Qattaniya dunes in north-eastern Egypt. This result is reinforced by our GPR survey on a large dune in the Siwa dune field and a smaller dune in the Qattaniya dune field. Our GPR data suggest the internal structure of larger dunes to consist of greater number of layers/cross-strata than smaller ones in the first 8 meters of the subsurface, which corresponds to the radar penetration depth at (0.8-1.2) GHz. Dunes on Titan exhibit backscatter-height dependency similar to the smaller Qattaniya dunes. In particular, the Shangri-La and Belet dunes on Titan exhibit a significantly stronger, negative correlation for the backscatter-height dependency compared to the Fensal and Aztlan dunes, suggesting a difference in the internal layering, relative ages and formation history of these dunes on Titan.

Sharma, P.; Heggy, E.; Farr, T. G.

2013-12-01

261

A free cellular model of dune dynamics: Application to El Fangar spit dune system (Ebro Delta, Spain)  

NASA Astrophysics Data System (ADS)

Currently, dune field surveying is employed to assess dune net volume changes and their accretion and erosion patterns. In dune fields with complex sediment sources and sink interactions such as El Fangar Spit (Ebro Delta, Spain), it is difficult to establish the sediment input and output with only net volume changes estimated by dune field surveying. This work presents a free dune dynamic cellular model that incorporates algorithms that introduce wind data into the erosion and transport processes. The model can be applied to dune systems with variable wind regime. A calibration methodology based on the morphological reproduction of the observed dune field evolution is proposed. The model and the calibration methodology is applied to a region of El Fangar dune system surveyed with DGPS on 15th and 18th April 2012. The difference between the final measured dune state and the best morphological reproduction obtained with the model is employed to estimate the sediment flux. This operation yields an output sand flux of 98.8 m3 and an input of 292.6 m3. This algorithm could have a great impact on the study of complex dune systems where the dunes act as sinks and sources of beach sediments and in the characterization of the beach-dune interactions.

Barrio-Parra, Fernando; Rodríguez-Santalla, Inmaculada

2014-01-01

262

Dune Morphology and Substrate Dependence on Titan  

NASA Astrophysics Data System (ADS)

We are using Cassini's Visual and Infrared Mapping Spectrometer (VIMS) to study Titan's sand. Specifically, we are constraining the sand's composition, the precise composition of which is still unknown. Water ice has been ruled out, leaving atmospherically-derived hydrocarbons as the best fit. The means of constraint involved spectrally unmixing images of Titan's dunes. We selected our spectral endmembers using high resolution VIMS IR images (noodle maps), specifically from T20. We have 5 spectral endmembers, labeled by color from VIMS IR maps: dark brown, dark blue, Xanadu bright, equatorially bright, and 5- micron bright. We set up a linear model to test on mixed substrate pixels from the northern Fensal sand dunes. Our model assumes some percent dark brown (sand) and some percent one other endmember. The product is a substrate map of Titan's dune fields, which we will compare with RADAR maps of the same area. Our results will determine if substrate type plays a role in dune morphology and location.

Vixie, Graham; Barnes, Jason; Radebaugh, Jani

2010-10-01

263

Beaches, Dunes, and Barrier Islands. Habitat Pac.  

ERIC Educational Resources Information Center

The materials in this educational packet are designed for use with students in grades 4 through 7. They consist of a leader overview, teaching guides and student data sheets for three activities, and a poster. The leader overview describes the nature of beaches, dunes, and barrier islands, tracing their development, settlement, and management and…

Fish and Wildlife Service (Dept. of Interior), Washington, DC.

264

Particle dynamics of a cartoon dune  

E-print Network

The spatio-temporal evolution of a downsized model for a desert dune is observed experimentally in a narrow water flow channel. A particle tracking method reveals that the migration speed of the model dune is one order of magnitude smaller than that of individual grains. In particular, the erosion rate consists of comparable contributions from creeping (low energy) and saltating (high energy) particles. The saltation flow rate is slightly larger, whereas the number of saltating particles is one order of magnitude lower than that of the creeping ones. The velocity field of the saltating particles is comparable to the velocity field of the driving fluid. It can be observed that the spatial profile of the shear stress reaches its maximum value upstream of the crest, while its minimum lies at the downstream foot of the dune. The particle tracking method reveals that the deposition of entrained particles occurs primarily in the region between these two extrema of the shear stress. Moreover, it is demonstrated that the initial triangular heap evolves to a steady state with constant mass, shape, velocity, and packing fraction after one turnover time has elapsed. Within that time the mean distance between particles initially in contact reaches a value of approximately one quarter of the dune basis length.

Christopher Groh; Ingo Rehberg; Christof A. Kruelle

2009-11-04

265

Moving dunes on the Google Earth  

E-print Network

Several methods exist for surveying the dunes and estimate their migration rate. Among methods suitable for the macroscopic scale, the use of the satellite images available on Google Earth is a convenient resource, in particular because of its time series. Some examples of the use of this feature of Google Earth are here proposed.

Sparavigna, Amelia Carolina

2013-01-01

266

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

267

Morphodynamic modeling of aeolian dunes: Review and future plans  

NASA Astrophysics Data System (ADS)

Sand dunes are ubiquitous in deserts, on coasts, on the sea bottom, and on the surface of Mars, Venus and Titan. The quantitative understanding of dune dynamics is thus of relevance for a broad range of physical, geological and planetary sciences. A morphodynamic model for dunes, which combines an analytical description of the average turbulent wind field over the topography with a continuum saltation model, has proven successful to quantitatively reproduce the shape of aeolian dunes of different types. We present a short review on the physics of dune formation and the model development, as well as some future plans for further developments and applications.

Parteli, E. J. R.; Kroy, K.; Tsoar, H.; Andrade, J. S.; Pöschel, T.

2014-10-01

268

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

269

Seasonal erosion and restoration of Mars' northern polar dunes  

USGS Publications Warehouse

Despite radically different environmental conditions, terrestrial and martian dunes bear a strong resemblance, indicating that the basic processes of saltation and grainfall (sand avalanching down the dune slipface) operate on both worlds. Here, we show that martian dunes are subject to an additional modification process not found on Earth: springtime sublimation of Mars' CO 2 seasonal polar caps. Numerous dunes in Mars' north polar region have experienced morphological changes within a Mars year, detected in images acquired by the High-Resolution Imaging Science Experiment on the Mars Reconnaissance Orbiter. Dunes show new alcoves, gullies, and dune apron extension. This is followed by remobilization of the fresh deposits by the wind, forming ripples and erasing gullies. The widespread nature of these rapid changes, and the pristine appearance of most dunes in the area, implicates active sand transport in the vast polar erg in Mars' current climate.

Hansen, C.J.; Bourke, M.; Bridges, N.T.; Byrne, S.; Colon, C.; Diniega, S.; Dundas, C.; Herkenhoff, K.; McEwen, A.; Mellon, M.; Portyankina, G.; Thomas, N.

2011-01-01

270

Seasonal Erosion and Restoration of Mars’ Northern Polar Dunes  

NASA Astrophysics Data System (ADS)

Despite radically different environmental conditions, terrestrial and martian dunes bear a strong resemblance, indicating that the basic processes of saltation and grainfall (sand avalanching down the dune slipface) operate on both worlds. Here, we show that martian dunes are subject to an additional modification process not found on Earth: springtime sublimation of Mars’ CO2 seasonal polar caps. Numerous dunes in Mars’ north polar region have experienced morphological changes within a Mars year, detected in images acquired by the High-Resolution Imaging Science Experiment on the Mars Reconnaissance Orbiter. Dunes show new alcoves, gullies, and dune apron extension. This is followed by remobilization of the fresh deposits by the wind, forming ripples and erasing gullies. The widespread nature of these rapid changes, and the pristine appearance of most dunes in the area, implicates active sand transport in the vast polar erg in Mars’ current climate.

Hansen, C. J.; Bourke, M.; Bridges, N. T.; Byrne, S.; Colon, C.; Diniega, S.; Dundas, C.; Herkenhoff, K.; McEwen, A.; Mellon, M.; Portyankina, G.; Thomas, N.

2011-02-01

271

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

272

Changes of Bulgarian Coastal Dune Landscape under Anthropogenic Impact  

NASA Astrophysics Data System (ADS)

At one time large sand dune formations were widely distributed along the Bulgarian coast. However, due to increased urbanization in the coastal zone, the areas of total dune landscape has been constantly reduced. Dunes presently comprise only 10% of the entire 412 km long coastline of Bulgaria: they embrace a total length of 38.57 km and a total area of 8.78 km2 Important tasks in dune protection are identification of landscape changes for a certain period of time and accurate delineation of sand dune areas. The present research traces sand dune changes along the Bulgarian Black Sea coast over a 27 year period (1983-2010). This period includes also the time of expanded tourist boom and overbuilding of the coastal zone, and respectively presents the largest dune changes and reductions. Based on the landscape change analyst in GIS environment the study also aims to explore the importance of different natural and human factors in driving the observed dune alterations and destruction. To detect and assess dune changes during the last 3 decades, we used data for sand dunes derived from several sources at different time periods in order to compare changes in shoreline positions, dune contours and areas: i) Topographic maps in 1:5,000 scale from 1983; ii) Modern Very High Resolution orthophotographs from 2006 and 2010; iii) QuickBird Very High Resolution satellite images from 2009; iv) Statistical information for population and tourist infrastructure is also used to consider the influence of human pressure and hotel developments on the dune dynamics. In addition, for more detailed description and visualization of main dune types, digital photos have been taken at many parts of the Bulgarian coast. The study was performed in GIS environment. Based on the results obtained the dunes along the Bulgarian coast were divided into three main groups with relation to the general factors responsible for their alterations: i) Dunes that have decreased in result of shoreline retreat and erosion of the beach itself. Typically dunes are located behind sand beaches and they are part of the beach-dune systems. Such type of dune reduction could be driven by combination of many factors, both natural ones (such as severe storms, erosion, heavy rains or flooding) and human impacts (large number of installed coast-protection structures along the coast, which interrupt the sediment transport, create new sedimentary deficit and generate erosion). During the recent years most of the Bulgarian beaches have progressively eroded and their areas have significantly been decreased. ii) Dunes that have been reduced/damaged and lost due to expanded tourist and housing infrastructures/developments and due to afforestaion activities. The principal sources of human impacts on sand dunes in Bulgaria are rapid coastal urbanization over the recent years (i.e., hotel and residential constructions, roads, parking structures, and other related infrastructure), unregulated camping and "temporary" constructions on the dunes, a lax regulatory environment that tolerates the re-zoning of protected sand dunes to "agricultural" areas. At most recreational sites there were wide coastal dunes, which however have been destroyed during tourist constructions. Such are dunes at the most famous Bulgarian sea resorts of Golden Sands and Sunny Beach in the areas of Varna and Nessebar. As a consequence, major areas along the Bulgarian coast were completely urbanized by hotels and other infrastructures and large sand dune systems were damaged. iii) Dunes located at still undeveloped coastal sections: yet they are naturally preserved and unthreatened by human pressure boom. These are just a few dune sites: at the northernmost portion of the Bulgarian coast (in the area of Durankulak), at the central part in the region of the largest Bulgarian river, Kamchia River, and along the southernmost coastline (in the area of Veleka River). Although sand dunes in Bulgaria are protected areas and national reserves they have been exposed to large anthropogenic pressure in particu

Palazov, A.; Young, R.; Stancheva, M.; Stanchev, H.

2012-04-01

273

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

274

Moderate to severe hallux valgus deformity: correction with proximal crescentic osteotomy and distal soft-tissue release  

Microsoft Academic Search

Between 1991 and 1995, 96 patients (114 feet) were treated with a proximal crescentic metatarsal osteotomy and distal soft-tissue\\u000a procedure for moderate to severe hallux valgus deformity [intermetatarsal (IM) angle > 15, or hallux valgus (HV) angle >\\u000a 30]. At an average follow-up of 26 months, 8 men and 62 women (86 feet) with a mean age of 53.2 years

R. Zettl; H.-J. Trnka; M. Easley; M. Salzer; P. Ritschl

2000-01-01

275

The Duffy antigen receptor for chemokines is up-regulated during acute renal transplant rejection and crescentic glomerulonephritis1  

Microsoft Academic Search

The Duffy antigen receptor for chemokines is up-regulated during acute renal transplant rejection and crescentic glomerulonephritis.BackgroundRecruitment of leukocytes during immune responses requires the coordinate expression of adhesion molecules in concert with chemokines and their receptors. The Duffy antigen receptor for chemokines (DARC) binds multiple chemokines and is expressed on postcapillary venules in the normal kidney. The chemokine receptor CCR5, which

Stephan Segerer; Heinz Regele; Matthias Mack; Renate Kain; Jean-Pierre Cartron; Yves Colin; Dontscho Kerjaschki; Detlef Schlöndorff

2000-01-01

276

Anti-neutrophil cytoplasmic (ANCA) and anti-glomerular basement membrane (GBM) autoantibodies in necrotizing and crescentic glomerulonephritis  

Microsoft Academic Search

Anti-neutrophil cytoplasmic autoantibodies (ANCA) and anti-glomerular basement membrane (GBM) necrotizing and crescentic glomerulonephritis\\u000a are aggressive and destructive glomerular diseases that are associated with and probably caused by circulating ANCA and anti-GBM\\u000a antibodies. These necrotizing lesions are manifested by acute nephritis and deteriorating kidney function often accompanied\\u000a by distinctive clinical features of systemic disease. Prompt diagnosis requires clinical acumen that allows

Sofia Lionaki; J. Charles Jennette; Ronald J. Falk

2007-01-01

277

From landform to process: Morphology and formation of lake-bed barchan dunes, Makgadikgadi, Botswana  

NASA Astrophysics Data System (ADS)

A suite of crescentic landforms is visible from remotely sensed imagery within the Ntwetwe panPan in the Makgadikgadi basin, Botswana. We investigate the most distinct of these landforms using morphometric measurements, sedimentary data and Optically Stimulated Luminescence (OSL) signal analysis. Comparative analysis with previously published barchan morphological data sets suggest the Ntwetwe features fall within the spectrum of morphometric parameters found in a range of barchan dunefields from around the world. There is currently insufficient comparative morphometric data from sub-aqueous dunefields to be able to distinguish the particular formative environment of the dune. OSL signal analyses however, support the hypothesis of Grove (1969) [Grove, A.T., 1969. Landforms and climatic change in the Kalahari and Ngamiland. Geographical Journal, 135: 191-212] that the last deposition of the sediments within the Ntwetwe forms was most likely aeolian in origin. Luminescence signal analysis is employed to investigate potential transport and bleaching environments of the sediments forming the features, but results in this case do not shed further light on the formative conditions of these enigmatic landforms.

Burrough, Sallie L.; Thomas, David S. G.; Bailey, Richard M.; Davies, Lauren

2012-08-01

278

[Notes on the Indian Red Crescent aid and Dr. Ensari's contributions before the decline of the Ottoman Empire].  

PubMed

This article deals with the Indian Red Crescent aids and Dr. Ahmed Ensari's role in this activity during the wars in the early 20th century that led the Ottoman Empire to dismantle. The Indian Red Crescent presided by Dr. Ensari sent a medical team and sanitary material for the Ottomans battered during the war in Tripoli (1911) and the succeeding war at the Balkans (1912). The article also deals with the meetings of the above-mentioned medical team with the Ottoman statesmen and dignitaries; its success at the Tripoli front and its projects concerning the Ottoman immigrants from the Balkan region. The humanitarian aids of the Indian Red Crescent continued afterwards, especially during the World War II (1914-1918) and the War of Independence (1919-1922). On their return to India, Dr. Ensari and the members of the team held a series of meetings and spoke of their activities to the people in their country. They tried to spread their sympathy for the Ottoman-Turkish people even to the outposts of India. This article is an attempt to describe the sympathy of this brother nation (Pakistan of today) proved by their aids and support far away from their borders. PMID:17152149

Izgöer, Ahmet Zeki

2002-01-01

279

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

280

Viscous liquid flow on Martian dune slopes  

E-print Network

The observed temporary dark streaks on some dune slopes on Mars may be due to thin sheets of water (or some other liquid) trickling downhill. This note corrects conceptual errors in a previous paper (M\\"{o}hlmann and Kereszturi 2010, Icarus 207, 654-658) which affect the velocity profile of such flows, and produce over-estimates of their depths and mass fluxes by factors of almost two.

Dobrovolskis, Anthony R

2014-01-01

281

Viscous liquid flow on Martian dune slopes  

NASA Astrophysics Data System (ADS)

The observed temporary dark streaks on some dune slopes on Mars may be due to thin sheets of water (or some other liquid) trickling downhill. This note corrects conceptual errors in a previous paper (Möhlmann and Kereszturi, 2010, Icarus207, 654-658) which affect the velocity profile of such flows, and produce over-estimates of their depths and mass fluxes by factors of almost two.

Dobrovolskis, Anthony R.

2014-12-01

282

Southern high latitude dune fields on Mars: Morphology, aeolian inactivity, and climate change  

Microsoft Academic Search

In a study area spanning the martian surface poleward of 50° S., 1190 dune fields have been identified, mapped, and categorized based on dune field morphology. Dune fields in the study area span ? 116400km2, leading to a global dune field coverage estimate of ?904000km2, far less than that found on Earth. Based on distinct morphological features, the dune fields

Lori K. Fenton; Rosalyn K. Hayward

2010-01-01

283

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

E-print Network

Modelling Desert Dune Fields Based on Discrete Dynamics STEVEN R. BISHOPa, *, HIROSHI MOMIJIb is developed to model the dynamics of sand dunes. The physical processes display strong non-linearity that has features we monitor morphology, dune growth, dune migration and spatial patterns within a dune field

284

Dunes on Mars, `Venus', Earth, and subaqueous ripples: a scaling law for their elementary size  

E-print Network

Dunes on Mars, `Venus', Earth, and subaqueous ripples: a scaling law for their elementary size P@pmmh.espci.fr Dunes and bedforms are observed in considerably di- verse environments: aeolian dunes of sand as well as snow, dunes under water, but also dunes on Mars or Titan. Summarising our work published in [1], we

Claudin, Philippe

285

Annual monsoon rains recorded by Jurassic dunes.  

PubMed

Pangaea, the largest landmass in the Earth's history, was nearly bisected by the Equator during the late Palaeozoic and early Mesozoic eras. Modelling experiments and stratigraphic studies have suggested that the supercontinent generated a monsoonal atmospheric circulation that led to extreme seasonality, but direct evidence for annual rainfall periodicity has been lacking. In the Mesozoic era, about 190 million years ago, thick deposits of wind-blown sand accumulated in dunes of a vast, low-latitude desert at Pangaea's western margin. These deposits are now situated in the southwestern USA. Here we analyse slump masses in the annual depositional cycles within these deposits, which have been described for some outcrops of the Navajo Sandstone. Twenty-four slumps, which were generated by heavy rainfall, appear within one interval representing 36 years of dune migration. We interpret the positions of 20 of these masses to indicate slumping during summer monsoon rains, with the other four having been the result of winter storms. The slumped lee faces of these Jurassic dunes therefore represent a prehistoric record of yearly rain events. PMID:11452305

Loope, D B; Rowe, C M; Joeckel, R M

2001-07-01

286

Dune Morphology and Substrate Dependence on Titan  

NASA Astrophysics Data System (ADS)

We are using Cassini's Visual and Infrared Mapping Spectrometer (VIMS) to study Titan's sand. Specifically, we are constraining the sand's composition, the precise composition of which is still unknown. Water ice has been ruled out, leaving atmospherically-derived hydrocarbons as the best fit. We spectrally unmixed chosen pixels, each representing one unique composition, to determine the composition of Titan's equatorial sand seas. We selected our spectral endmembers using high resolution VIMS IR images (noodle maps), specifically from T20. We have 5 spectral endmembers, labeled by color from VIMS IR maps: dark brown, dark blue, Xanadu bright, equatorially bright, and 5-micron bright. The exact superposition of spectral endmembers of the sand's composition remains the subject of further study. We set up a linear model to test on mixed substrate pixels from the T20 flyby of Cassini over the northern Fensal sand dunes. Our model assumes some percent dark brown (sand) and some percent one other endmember. The product is a substrate map of Titan's dune fields, which we will compare with RADAR maps of the same area. Our results will determine if substrate type plays a role in dune morphology and location.

Vixie, Graham D.; Barnes, J. W.; Radebaugh, J.

2010-10-01

287

Particle dynamics of a cartoon dune  

E-print Network

The spatio-temporal evolution of a downsized model for a desert dune is observed experimentally in a narrow water flow channel. A particle tracking method reveals that the migration speed of the model dune is one order of magnitude smaller than that of individual grains. In particular, the erosion rate consists of comparable contributions from creeping (low energy) and saltating (high energy) particles. The saltation flow rate is slightly larger, whereas the number of saltating particles is one order of magnitude lower than that of the creeping ones. The velocity field of the saltating particles is comparable to the velocity field of the driving fluid. It can be observed that the spatial profile of the shear stress reaches its maximum value upstream of the crest, while its minimum lies at the downstream foot of the dune. The particle tracking method reveals that the deposition of entrained particles occurs primarily in the region between these two extrema of the shear stress. Moreover, it is demonstrated that...

Groh, Christopher; Kruelle, Christof A

2009-01-01

288

The effects of psammophilous plants on sand dune dynamics  

E-print Network

Psammophilous plants are special plants that flourish in sand moving environments. There are two main mechanisms by which the wind affects these plants: (i) sand drift exposes roots and covers branches--the exposed roots turn into new plants and the covered branches turn into new roots; both mechanisms result in an enhanced growth rate of the psammophilous plant cover of the dunes; (ii) strong winds, often associated with sand movement, tear branches and seed them in nearby locations, resulting in new plants and an enhanced growth rate of the psammophilous plant cover of the dunes. Despite their important role in dune dynamics, to our knowledge, psammophilous plants have never been incorporated into mathematical models of sand dunes. Here, we attempt to model the effects of these plants on sand dune dynamics. We construct a set of three ordinary differential equations for the fractions of surface cover of regular vegetation, biogenic soil crust and psammophilous plants. The latter reach their optimal growth under (i) specific sand drift or (ii) specific wind power. We show that psammophilous plants enrich the sand dune dynamics. Depending on the climatological conditions, it is possible to obtain one, two, or three steady dune states. The activity of the dunes can be associated with the surface cover--bare dunes are active, and dunes with significant cover of vegetation, biogenic soil crust, or psammophilous plants are fixed. Our model shows that under suitable precipitation rates and wind power, the dynamics of the different cover types is in accordance with the common view that dunes are initially stabilized by psammophilous plants that reduce sand activity, thus enhancing the growth of regular vegetation that eventually dominates the cover of the dunes and determines their activity.

Golan Bel; Yosef Ashkenazy

2013-08-30

289

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

290

Submarine sand dunes and sedimentary environments in Oceanographer Canyon.  

USGS Publications Warehouse

Reveals an extensive field of large sand dunes on the canyon floor. The dunes are medium to coarse sand, are oriented across the axis, and the largest of them are as high as 3m and have wavelengths up to 15m. Their asymmetry, grain size, and height suggest that they are formed by axial currents flowing up- and downcanyon and that the largest dunes require flows of at least 70 cm/sec.-from Authors

Valentine, P.C.; Cooper, R.A.; Uzmann, J.R.

1984-01-01

291

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

292

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

293

Sand dune materials and polar layered deposits on Mars  

NASA Technical Reports Server (NTRS)

The possible place of sand in the Martian polar layered deposits is examined. The erosional features in layered deposits and the morphologic relationship of dunes and the layered deposits are discussed. The colors of the polar dunes are shown to be similar to the colors of dunes at other latitudes, suggesting that the polar dunes can be explained without any special or exotic mechanism. Consideration is given to mixing and segregation of materials by eolian processes observed on Mars, showing that sand was probably carried to the polar regions during part of the formation of the layered deposits.

Thomas, Peter; Weitz, Catherine

1989-01-01

294

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

295

A COMPARATIVE ANALYSIS OF BARCHAN DUNES IN THE INTRA-CRATER DUNE FIELDS AND THE NORTH POLAR SAND SEA. M.C. Bourke1  

E-print Network

A COMPARATIVE ANALYSIS OF BARCHAN DUNES IN THE INTRA-CRATER DUNE FIELDS AND THE NORTH POLAR SAND@nasm.si.edu. Introduction: Martian sand dunes have the poten- tial 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 to- wards

Bourke, Mary C.

296

76 FR 10915 - Minor Boundary Revision at Indiana Dunes National Lakeshore  

Federal Register 2010, 2011, 2012, 2013

...Service Minor Boundary Revision at Indiana Dunes National Lakeshore AGENCY: National Park...9(c)(1), the boundary of Indiana Dunes National Lakeshore in the State of Indiana...depicted on a map entitled ``Indiana Dunes National Lakeshore, Proposed...

2011-02-28

297

76 FR 19304 - Endangered and Threatened Wildlife and Plants; Endangered Status for Dunes Sagebrush Lizard  

Federal Register 2010, 2011, 2012, 2013

...Wildlife and Plants; Endangered Status for Dunes Sagebrush Lizard AGENCY: Fish and Wildlife...December 14, 2010, proposed rule to list the dunes sagebrush lizard (Sceloporus arenicolus...period for the proposed rule to list the dunes sagebrush lizard (Sceloporus...

2011-04-07

298

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

Federal Register 2010, 2011, 2012, 2013

...Plan and Draft Environmental Assessment; Dunes Sagebrush Lizard, Texas AGENCY: Fish...the draft Texas Conservation Plan for the Dunes Sagebrush Lizard (TCP). The draft TCP...Service (Service) and the Applicant for the dunes sagebrush lizard (Sceloporus...

2011-10-06

299

77 FR 11061 - Endangered and Threatened Wildlife and Plants; Proposed Endangered Status for the Dunes Sagebrush...  

Federal Register 2010, 2011, 2012, 2013

...Plants; Proposed Endangered Status for the Dunes Sagebrush Lizard AGENCY: Fish and Wildlife...2010, proposed endangered status for the dunes sagebrush lizard (Sceloporus arenicolus...a signed conservation agreement for the dunes sagebrush lizard in Texas. We are...

2012-02-24

300

Airborne gamma-ray spectrometer and magnetometer survey, Crescent quadrangle (Oregon). Volume II. Final report  

SciTech Connect

Seventeen uranium anomalies meet the minimum statistical requirements as defined in Volume I. These anomalies are listed and are shown on the Uranium Anomaly Interpretation Map. Potassium (%K), equivalent Uranium (ppM eU), equivalent Thorium (ppM eT), eU/eT, eU/K, eT/K, and magnetic Pseudo Contour Maps are presented in Appendix E. Stacked Profiles showing geologic strip maps along each flight-line, together with sensor data, and ancillary data are presented in Appendix F. All maps and profiles were prepared on a scale of 1:250,000, but have been reduced to 1:500,000 for presentation in Volume II. Anomaly No. 1 is over Pliocene-Pleistocene basalt and andesite (Qtba). Anomaly No. 2 is over the contact zone between rhyolitic rocks of the John Day formation (Tmor) and Quaternary alluvium (Qal). Anomaly No. 3 is over the contact area between Tertiary silicic ash-flow tuff (Tat) and Quaternary alluvium (Qal). Anomalies No. 4, No. 5, No. 6 are over Recent pumice and ash-flow deposits (Qrp). Anomalies No. 7, No. 8, No. 9, and No. 10 are over Pliocene/Pleistocene basalt (Qtb). Anomaly No. 11 is over the contact area between Pliocene basalt (Tpb), and Pliocene/Pleistocene basalt (Qtb). Anomaly No. 12 is over Quaternary terrace deposits (Qpn). Anomalies No. 13, and No. 14 are over Pleistocene basalt (Tpb). Anomaly No. 15 is over tuffaceous sedimentary rocks (Ts). Anomaly No. 16, the largest in the quadrangle, is over tuffaceous sedimentary rocks (Ts), dune sands (Qd), silicic vent rocks (Tvs), and Quaternary lacustrine rocks (Q1). Anomaly No. 17 is over silicic vent rocks and Quaternary lacustrine sediments (Q1).

Not Available

1981-01-01

301

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

302

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

NASA Astrophysics Data System (ADS)

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 of dune crest length, spacing, defect density, and orientation indicates that the pattern is complex, representing two constructional generations of dunes. The oldest and best-organized generation forms the primary crestlines and is transverse to circumpolar easterly winds. Gross bed form-normal analysis of the younger pattern of crestlines indicates that it emerged with both circumpolar easterly winds and NE winds and is reworking the older pattern. Mapping of secondary flow fields over the dunes indicates that the most recent transporting winds were from the NE. The younger pattern appears to represent an influx of sediment to the dune field associated with the development of the Olympia Cavi reentrant, with NE katabatic winds channeling through the reentrant. A model of the pattern reformation based upon the reconstructed primary winds and resulting secondary flow fields shows that the development of the secondary pattern is controlled by the boundary condition of the older dune topography.

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

2010-08-01

303

Mars Global Digital Dune Database: MC2-MC29  

USGS Publications Warehouse

Introduction The Mars Global Digital Dune Database presents data and describes the methodology used in creating the database. The database provides a comprehensive and quantitative view of the geographic distribution of moderate- to large-size dune fields from 65? N to 65? S latitude and encompasses ~ 550 dune fields. The database will be expanded to cover the entire planet in later versions. Although we have attempted to include all dune fields between 65? N and 65? S, 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) or Mars Orbiter Camera narrow angle (MOC NA) images allowed, we classifed dunes and included dune slipface measurements, which were derived from gross dune morphology and represent the prevailing wind direction at the last time of significant dune modification. For dunes located within craters, the azimuth from crater centroid to dune field centroid was calculated. Output from a general circulation model (GCM) is also included. In addition to polygons locating dune fields, the database includes over 1800 selected Thermal Emission Imaging System (THEMIS) infrared (IR), 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 a series of ArcReader projects 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 ArcMap projects. The ArcMap projects allow fuller use of the data, but require ESRI ArcMap? software. Multiple projects were required to accommodate the large number of images needed. A fuller description of the projects can be found in the Dunes_ReadMe file and the ReadMe_GIS file in the Documentation folder. For users who prefer to create their own projects, the data is available in ESRI shapefile and geodatabase formats, as well as the open Geographic 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. ReadMe files are available in PDF and ASCII (.txt) files. Tables are available in both Excel (.xls) and ASCII formats.

Hayward, Rosalyn K.; Mullins, Kevin F.; Fenton, L.K.; Hare, T.M.; Titus, T.N.; Bourke, M.C.; Colaprete, Anthony; Christensen, P.R.

2007-01-01

304

Aeolian Processes of the Pismo-Oceano Dune Complex, California  

NASA Astrophysics Data System (ADS)

The Pismo Dunes are located approximately 250 km northwest of Los Angeles and consist of 90 km2 of transverse, parabolic and paleodunes. The Pismo Dunes are one of the largest dune complexes on the west coast and are the largest remaining south of San Francisco Bay, but despite their size, relatively few process morphology studies have focused on their form and history. Specifically, the dune field includes 12 km2 of actively migrating transverse dune ridges advancing onshore in three distinct phases separated by small depressions easily indentified using a LiDAR-generated elevation model. An early field investigation by Tchakerian (1983) revealed a uniform increase in slip face heights and crestline wavelengths inland with no apparent change in grain size. Measurement of recent aerial imagery shows variable migration rates throughout the dunes and wavelengths between 30 and 100 m closest to the beach, in the second ridge between 50 and 140 m, and from 70 to 250 m furthest inland. During El Niño and La Niña periods, westerly winds advance onshore nearly perpendicular to the crestlines, fueling episodic migration of the dune field. It is hypothesized that particularly strong ENSO periods may have led to the development of distinct dune phases with separating depressions and the development of defects along the dune crest. Defects associated with the wakes of incipient vegetation and inter-dune depressions are conspicuous and widespread, though localized and variable through time and space. Aerial imagery taken in September 1994 shows a wider, more even distribution of defects across the dune field than currently visible. The signal is, however, complicated by the closure of the dune field to oversand vehicles in 1982. The closure of much of the complex to vehicular traffic in 1982 may play a role, as Tchakerian's crestline wavelength measurements were far smaller than those obtained for this study while maintaining a likewise increase between phases. At a decadal scale, excessive vehicular traffic may have impeded the transition of emergent, defect-ridden dune forms into mature transverse ridges. Despite the astounding lack to studies focusing on the Pismo Dunes, the complex presents multiple opportunities for inquiry regarding climatic control on dune field evolution, defect law and complex landform pattern development, and long-term anthropogenic alteration of coastal process morphology.

Barrineau, C. P.; Tchakerian, V.; Houser, C.

2012-12-01

305

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

306

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

307

Space Radar Image of Namibia Sand Dunes  

NASA Technical Reports Server (NTRS)

This spaceborne radar image shows part of the vast Namib Sand Sea on the west coast of southern Africa, just northeast of the city of Luderitz, Namibia. The magenta areas in the image are fields of sand dunes, and the orange area along the bottom of the image is the surface of the South Atlantic Ocean. The region receives only a few centimeters (inches) of rain per year. In most radar images, sandy areas appear dark due to their smooth texture, but in this area the sand is organized into steep dunes, causing bright radar reflections off the dune 'faces.' This effect is especially pronounced in the lower center of the image, where many glints of bright radar reflections are seen. Radar images of this hyper-arid region have been used to image sub-surface features, such as abandoned stream courses. The bright green features in the upper right are rocky hills poking through the sand sea. The peninsula in the lower center, near Hottentott Bay, is Diaz Point; Elizabeth Point is south of Diaz Point. This image was acquired by Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) onboard the space shuttle Endeavour on April 11, 1994. The image is 54.2 kilometers by 82.2 kilometers (33.6 miles by 51.0 miles) and is centered at 26.2 degrees South latitude, 15.1 degrees East longitude. North is toward the upper left. The colors are assigned to different radar frequencies and polarizations of the radar as follows: red is L-band, horizontally transmitted and received; green is L-band, horizontally transmitted, vertically received; and blue is C-band, horizontally transmitted, horizontally received. SIR-C/X-SAR, a joint mission of the German, Italian, and United States space agencies, is part of NASA's Mission to Planet Earth.

1994-01-01

308

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

309

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

310

Services la vie tudiante ORGANISATION D'UNE ACTIVIT TUDIANTE  

E-print Network

Services à la vie étudiante ORGANISATION D'UNE ACTIVIT� �TUDIANTE Premières étapes 1 Pour le financement de projets pertinents à votre domaine d'études. Exemple : l'organisation d nombre d'étudiants de la communauté universitaire. Exemple : l'organisation d'une sortie socioculturelle

Vellend, Mark

311

Morphology and dynamics of star dunes from numerical modelling  

NASA Astrophysics Data System (ADS)

Star dunes are giant pyramidal dunes composed of interlaced arms with sinuous crests and slip faces oriented in various directions. The radial symmetry and the size of the pattern seem to illustrate a high degree of complexity between multidirectional wind regime and topography. However, compared to other dune types, little is known about the formation and the evolution of star-dunes, which are ubiquitous in modern sand seas. Here, using a discrete model based on feedback mechanisms between flow and bedform dynamics, we show that star dune morphology results from a combination of longitudinal dunes produced by primary winds. Depending on the wind regime, star dune arms may radiate or not. In opposition to the bedform alignment on an erodible bed, the crest of the propagating arms have an orientation that maximises the sand flux in the direction of arm growth. This behaviour is described by an analytical solution when taking arm aspect ratios into account. Thanks to the 3D sedimentary structures produced by the model, we also find that arm morphodynamics is controlled by the frequency of wind reorientation. When this frequency increases, arm dimensions decreases and growth rate increases. We suggest that this arm propagation is an important mass exchange process in dune fields.

Narteau, C.; Courrech Du Pont, S.; Zhang, D.; Rozier, O.

2012-12-01

312

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

313

Model for the genesis of coastal dune fields with vegetation  

NASA Astrophysics Data System (ADS)

Vegetation greatly affects the formation and dynamics of dune fields in coastal areas. In the present work, we use dune modeling in order to investigate the genesis and early development stages of coastal dune fields in the presence of vegetation. The model, which consists of a set of coupled equations for the turbulent wind field over the landscape, the saltation flux and the growth of vegetation cover on the surface, is applied to calculate the evolution of a sand patch placed upwind of a vegetated terrain and submitted to unidirectional wind and constant sand influx. Different dune morphologies are obtained, depending on the characteristic rate of vegetation growth relative to wind strength: barchans, transverse dunes with trailing ridges, parabolic dunes and vegetated, alongshore sand barriers or foredunes. The existence of a vegetation-free backshore is found to be important for the nucleation timescale of coastal dune generations. The role of the sand influx and of the maximum vegetation cover density for the dune shape is also discussed.

de M. Luna, Marco C. M.; Parteli, Eric J. R.; Durán, Orencio; Herrmann, Hans J.

2011-06-01

314

36 CFR 7.80 - Sleeping Bear Dunes National Lakeshore.  

...2014-07-01 2014-07-01 false Sleeping Bear Dunes National Lakeshore. 7.80 Section...NATIONAL PARK SYSTEM § 7.80 Sleeping Bear Dunes National Lakeshore. (a) Powerless... (c) Bicycling. (1) The Sleeping Bear Heritage Trail, approximately 27...

2014-07-01

315

36 CFR 7.80 - Sleeping Bear Dunes National Lakeshore.  

Code of Federal Regulations, 2012 CFR

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

2012-07-01

316

36 CFR 7.80 - Sleeping Bear Dunes National Lakeshore.  

Code of Federal Regulations, 2011 CFR

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

2011-07-01

317

36 CFR 7.80 - Sleeping Bear Dunes National Lakeshore.  

Code of Federal Regulations, 2010 CFR

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

2010-07-01

318

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. 7.80 Section...NATIONAL PARK SYSTEM § 7.80 Sleeping Bear Dunes National Lakeshore. (a) Powerless... (c) Bicycling. (1) The Sleeping Bear Heritage Trail, approximately 27...

2013-07-01

319

36 CFR 7.88 - Indiana Dunes National Lakeshore.  

Code of Federal Regulations, 2011 CFR

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

2011-07-01

320

Holocene eolian activity in the Minot dune field, North Dakota  

USGS Publications Warehouse

Stabilized eolian sand is common over much of the Great Plains region of the United States and Canada, including a subhumid area of ??? 1500 km2 near Minot, North Dakota. Eolian landforms consist of sand sheets and northwest-trending parabolic dunes. Dunes and sand sheets in the Minot field are presently stabilized by a cover of prairie grasses or oak woodland. Stratigraphic studies and accelerator mass spectrometry radiocarbon dating of paleosols indicate at least two periods of eolian sand movement in the late Holocene. Pedologic data suggest that all of the dune field has experienced late Holocene dune activity, though not all parts of the dune field may have been active simultaneously. Similar immobile element (Ti, Zr, La, Ce) concentrations support the interpretation that eolian sands are derived from local glaciofluvial and glaciolacustrine sediments. However, glaciolacustrine and glaciofluvial source sediments have high Ca concentrations from carbonate minerals, whereas dune sands are depleted in Ca. Because noneolian-derived soils in the area are calcareous, these data indicate that the Minot dune field may have had extended periods of activity in the Holocene, such that eolian abrasion removed soft carbonate minerals. The southwest-facing parts of some presently stabilized dunes were active during the 1930s drought, but were revegetated during the wetter years of the 1940s. These observations indicate that severe droughts accompanied by high temperatures are the most likely cause of Holocene eolian activity.

Muhs, D.R.; Stafford, T.W., Jr.; Been, J.; Mahan, S.A.; Burdett, J.; Skipp, G.; Rowland, Z.M.

1997-01-01

321

36 CFR 7.88 - Indiana Dunes National Lakeshore.  

Code of Federal Regulations, 2012 CFR

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

2012-07-01

322

36 CFR 7.88 - Indiana Dunes National Lakeshore.  

...Property 1 2014-07-01 2014-07-01 false Indiana Dunes National Lakeshore. 7.88 Section 7.88 Parks, Forests...REGULATIONS, AREAS OF THE NATIONAL PARK SYSTEM § 7.88 Indiana Dunes National Lakeshore. (a) Fishing. Unless...

2014-07-01

323

36 CFR 7.88 - Indiana Dunes National Lakeshore.  

Code of Federal Regulations, 2010 CFR

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

2010-07-01

324

36 CFR 7.88 - Indiana Dunes National Lakeshore.  

Code of Federal Regulations, 2013 CFR

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

2013-07-01

325

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, the similarity of millipede assemblages on the two chrono- sequences to those on three sets of reference sites farther away. Key words: coastal dune forests, millipedes, regeneration, rehabilitation, succession

Pretoria, University of

326

Dunes, Boxcars, and Ball Jars: Mining the Great Lakes Shores  

NSDL National Science Digital Library

Spreadsheets Across the Curriculum module/Geology of National Parks course. Students estimate the volume of sand in Hoosier Slide, a large dome-shaped dune quarried away in the 1920s from what is now Indiana Dunes National Lakeshore. They also estimate the number of boxcars to carry the sand, and the number of Ball jars produced from it.

Module by: Tiffany Roberts, University of South Florida Cover Page by: Len Vacher and Denise Davis, University of South Florida

327

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

328

The effects of psammophilous plants on sand dune dynamics  

E-print Network

Psammophilous plants are special plants that flourish in sand moving environments. There are two main mechanisms by which the wind affects these plants: (i) sand drift exposes roots and covers branches--the exposed roots turn into new plants and the covered branches turn into new roots; both mechanisms result in an enhanced growth rate of the psammophilous plant cover of the dunes; (ii) strong winds, often associated with sand movement, tear branches and seed them in nearby locations, resulting in new plants and an enhanced growth rate of the psammophilous plant cover of the dunes. Despite their important role in dune dynamics, to our knowledge, psammophilous plants have never been incorporated into mathematical models of sand dunes. Here, we attempt to model the effects of these plants on sand dune dynamics. We construct a set of three ordinary differential equations for the fractions of surface cover of regular vegetation, biogenic soil crust and psammophilous plants. The latter reach their optimal growth u...

Bel, Golan

2013-01-01

329

Strength analysis of CARR-CNS with crescent-shape moderator cell and helium sub-cooling jacket covering cell  

NASA Astrophysics Data System (ADS)

The new type of the moderator cell was developed for the cold neutron source (CNS) of the China Advanced Research Reactor (CARR) which is now being constructed at the China Institute of Atomic Energy in Beijing. A crescent-shape moderator cell covered by the helium sub-cooling jacket is adopted. The structure of the moderator cell is optimized by the stress FEM analysis. A crescent-shape would help to increase the volume of the moderator cell for fitting it to the four cold neutron guide tubes, even if liquid hydrogen, not liquid deuterium, was used as a cold moderator. The helium sub-cooling jacket covering the moderator cell removes the nuclear heating of the outer shell wall of the cell. It contributes to reduce the void fraction of liquid hydrogen in the outer shell of the moderator cell. Such a type of a moderator cell is suitable for the CNS with higher nuclear heating. The cold helium gas flows down first into the helium sub-cooling jacket and then flows up to the condenser. The theory of the self-regulation suitable to the thermo-siphon type of the CNS is also applicable and validated.

Yu, Qingfeng; Feng, Quanke; Kawai, Takeshi; Shen, Feng; Yuan, Luzheng; Cheng, Liang

2005-12-01

330

Toll-Like Receptor 4 Stimulation Triggers Crescentic Glomerulonephritis by Multiple Mechanisms Including a Direct Effect on Renal Cells  

PubMed Central

A role for toll-like receptor 4 (TLR4) has been suggested in previous studies of glomerulonephritis, but the complex integration of these effects has not been explored. To separate effects on the innate and adaptive immune responses, we use the autologous nephrotoxic nephritis model with two disease induction protocols. First, we give a TLR4 ligand at the time of immunization and show the effects are mediated via TLR4 by comparing wild-type and TLR4-deficient mice. In wild-type mice histological measures of disease and serum creatinine are all at least twice as high as TLR4-deficient mice, due to an enhanced immune response to the nephritogenic sheep IgG. Second, we stimulate TLR4 later in the course of disease development and construct four groups of bone marrow chimeric or sham chimeric mice to study the role of TLR4 on bone marrow or renal cells. The most striking finding is that renal cell TLR4 stimulation increases glomerular crescent formation, with a mean of 21% and 25% in the two groups of mice with renal cell TLR4 compared with 0.1% and 0.6% in the two groups without, with differences mirrored by changes in serum creatinine. These findings, in a single disease model, illustrate that TLR4 stimulation triggers crescentic glomerulonephritis by effects on both the adaptive and innate immune response, with a crucial direct effect on renal cells. PMID:20566738

Giorgini, Angela; Brown, Heather J.; Sacks, Steven H.; Robson, Michael G.

2010-01-01

331

Late Pleistocene dune activity in the central Great Plains, USA  

NASA Astrophysics Data System (ADS)

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 CO 2 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.

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

2011-12-01

332

Role of amino acid transporter LAT2 in the activation of mTORC1 pathway and the pathogenesis of crescentic glomerulonephritis.  

PubMed

Molecular mechanisms and signaling pathways leading to cellular proliferation and lesion formation in the crescentic glomerulonephritis (CGN) remain elusive. In the present study we have explored a potential role of the mammalian target of rapamycin complex 1 (mTORC1) signaling pathway and amino acid transporter (LAT) in the pathogenesis of CGN. Immunohistochemistry and western blot analysis of glomeruli isolated from a rat model of CGN revealed that activation of mTORC1 preceded crescent formation in glomerular parietal epithelial cells (PECs) and podocytes. Daily treatment of rats with the mTOR inhibitor everolimus just after induction of CGN was not beneficial and instead led to increased cellular necrosis of PECs. However, daily treatment starting 7 days after the onset of CGN was beneficial and maintained intact glomeruli. Out of three forms of L-type neutral amino acid transporters (LAT1-LAT3) studied here, only LAT2 was found to be upregulated in the PECs and podocytes in advance of the crescent formation as well as in the crescent lesion itself. Cell culture study revealed that plasma membrane expression of LAT2 markedly stimulated mTORC1 signaling pathway, which was significantly abrogated by coexistence of LAT inhibitor. Finally, LAT inhibitor significantly abrogated development of crescent formation of CGN on day 7. Our data suggest that LAT2 may have a pivotal role in the pathogenesis of CGN by activating the mTORC1 pathway in the glomerular epithelial cells. PMID:21403644

Kurayama, Ryota; Ito, Noriko; Nishibori, Yukino; Fukuhara, Daisuke; Akimoto, Yoshihiro; Higashihara, Eiji; Ishigaki, Yasuhito; Sai, Yoshimichi; Miyamoto, Ken-ichi; Endou, Hitoshi; Kanai, Yoshikatstu; Yan, Kunimasa

2011-07-01

333

Equinoctial Activity Over Titan Dune Fields Revealed by Cassini/vims  

NASA Astrophysics Data System (ADS)

Titan, the largest satellite of Saturn, is the only satellite in the solar system with a dense atmosphere. The close and continuous observations of Titan by the Cassini spacecraft, in orbit around Saturn since July 2004, bring us evidences that Titan troposphere and low stratosphere experience an exotic, but complete meteorological cycle similar to the Earth hydrological cycle, with hydrocarbons evaporation, condensation in clouds, and rainfall. Cassini monitoring campaigns also demonstrate that Titan's cloud coverage and climate vary with latitude. Titan's tropics, with globally weak meteorological activity and widespread dune fields, seem to be slightly more arid than the poles, where extensive and numerous liquid reservoirs and sustained cloud activity have been discovered. Only a few tropo-spheric clouds have been observed at Titan's tropics during the southern summer. As equinox was approaching (in August 2009), they occurred more frequently and appeared to grow in strength and size. We present here the observation of intense brightening at Titan's tropics, very close to the equinox. These detections were conducted with the Visual and Infrared Mapping Spectrometer (VIMS) onboard Cassini. We will discuss the VIMS images of the three individual events detected so far, observed during the Titan's flybys T56 (22 May 2009), T65 (13 January 2010) and T70 (21 June 2010). T56, T65 and T70 observations show an intense and transient brighten-ing of large regions very close to the equator, right over the extensive dune fields of Senkyo, Belet and Shangri-La. They all appear spectrally and morphologically different from all transient surface features or atmospheric phenomena previously reported. Indeed, these events share in particular a strong brightening at wavelengths greater than 2 ?m (especially at 5 ?m), making them spectrally distinct from the small tropical clouds observed before the equinox and the large storms observed near the equator in September and October 2010. In this paper, we will discuss the possibility that these singular events may have occurred very close to the surface, having a strong link with the underlying dune fields. Radiative transfer calculations indeed show that these singular brightenings are due to the transient appearance of an additional atmospheric layer, confined at very low altitudes and loaded with few but large particles. Gathering all the observational and modeling constraints, we conclude that the most probable explanation for these events is the local and transient occurrence of huge sand storms, directly originating from the underlying dune fields. We will also discuss the possible implications of the equinoctial occurrence of such events for Titan's tropical wind regimes and for the present-day activity of equatorial dunes.

Rodriguez, S.; Le Mouelic, S.; Barnes, J. W.; Hirtzig, M.; Rannou, P.; Sotin, C.; Brown, R. H.; Bow, J.; Vixie, G.; Cornet, T.; Bourgeois, O.; Narteau, C.; Courrech Du Pont, S.; Le Gall, A.; Reffet, E.; Griffith, C. A.; Jaumann, R.; Stephan, K.; Buratti, B. J.; Clark, R. N.; Baines, K. H.; Nicholson, P. D.; Coustenis, A.

2012-12-01

334

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

335

Vegetation controls on the maximum size of coastal dunes  

PubMed Central

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 coevolution 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 timescale 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 landward and thus leads to larger foredunes. In this scenario, plants play a much more active role in modifying their habitat and altering coastal vulnerability than previously thought. PMID:24101481

Durán, Orencio; Moore, Laura J.

2013-01-01

336

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

337

Vegetation controls on the maximum size of coastal dunes.  

PubMed

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 coevolution 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 timescale 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 landward and thus leads to larger foredunes. In this scenario, plants play a much more active role in modifying their habitat and altering coastal vulnerability than previously thought. PMID:24101481

Durán, Orencio; Moore, Laura J

2013-10-22

338

Effects of sand fences on coastal dune vegetation distribution  

NASA Astrophysics Data System (ADS)

Sand fences are important human adjustments modifying the morphology of developed shores. The effects of sand fences on sediment transport and deposition in their initial stages have been well studied, but little is known about the effect of deteriorated sand fences that have become partially buried low scale barriers within the dune, potentially benefiting vegetation growth by protecting it from onshore stress. Data on vegetation, topography and fence characteristics were gathered at three dune sites in Ocean City, New Jersey on September 2007 and March 2008 to evaluate the effect of fences within the dune on vegetation distribution. Variables include: distance landward of dune toe, degree of sheltering from onshore stressors, net change in surface elevation (deposition or erosion), vegetation diversity and density, presence of remnant fence, and distance landward of fence. Results for the studied environment reveal that 1) vegetation diversity or density does not increase near remnant fences because most remnants are lower than average vegetation height and can not provide shelter; but 2) vegetation distribution is related to topographic variables, such as degree of sheltering, that are most likely the result of sand accretion caused by fence deployment. Fence deployment that prioritizes the creation of topographically diverse dunes within a restricted space may increase the diversity and density of the vegetation, and the resilience and value of developed dunes. Managers should consider the benefits of using sand fences on appropriately wide beaches to create a protective dune that is also diverse, functional and better able to adapt to change.

Grafals-Soto, Rosana

2012-04-01

339

Absolute dune ages and implications for the time of formation of gullies in Nirgal Vallis, Mars  

Microsoft Academic Search

Transverse dunes cover the valley floor of Nirgal Vallis, a 670 km long valley network at 318°E and 29°S. The dunes are superposed by small undeformed impact craters, which implies that the dunes are inactive under present atmospheric conditions. The last active phase of dune movement (absolute age) can be determined by crater size frequency distributions. The derived absolute ages

D. Reiss; S. van Gasselt; G. Neukum; R. Jaumann

2004-01-01

340

Implications of Dune Pattern Analysis for Titan's Surface History Christopher Jon Savage  

E-print Network

Implications of Dune Pattern Analysis for Titan's Surface History Christopher Jon Savage A thesis Reserved #12;ABSTRACT Implications of Dune Pattern Analysis for Titan's Surface History Christopher Jon Savage Department of Geological Sciences, BYU Master of Science Analyzing dune parameters such as dune

Seamons, Kent E.

341

A comparison of methods used to estimate the height of sand dunes on Mars  

E-print Network

A comparison of methods used to estimate the height of sand dunes on Mars M.C. Bourke a,b,, M bodies is difficult. We assess four methods that can be used to estimate the height of aeolian dunes of which were not previously available for dunes on Mars. They include dune height, width, length, surface

Bourke, Mary C.

342

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 to a turbulent shear flow predicts that the wavelength at which the bed destabilises to form dunes should scale in water (subaqueous ripples), in air (aeolian dunes and fresh snow dunes), in a high pressure CO2 wind

Claudin, Philippe

343

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 role of the free surface, we evidence that river dunes can not form from a linear instability. Finally, we discuss a non-linear criterion for the selection of the size of dunes and mega-dunes. 1 A VERY

Claudin, Philippe

344

Age and Paleoclimatic Significance of Holocene Sand Dunes in Northeastern Colorado  

Microsoft Academic Search

Stabilized parabolic sand dunes are extensive in northeastern Colorado and adjacent southwestern Nebraska and suggest that precipitation was lower when the dunes were formed than it is now. Orientations of the parabolic dunes indicate a paleowind from the northwest. Soils developed on these dunes are Ustic Torripsamments with A\\/AC\\/C profiles that have morphological and textural properties similar to soils on

Daniel R. Muhs

1985-01-01

345

Two modes for dune orientation -Supplementary information Sylvain Courrech du Pont,1,  

E-print Network

Two modes for dune orientation - Supplementary information Sylvain Courrech du Pont,1, Cl flux over a linear dune 1 B. Bed Instability 2 C. Dune fingering 4 D. Wind speed-up 5 E. Discussion 6 II. Experiments 9 A. Dunes underwater 9 B. Experimental setup 10 C. Orientation, amplitude

Narteau, Clément

346

Sleeping Bear Dunes National Park Service U.S. Department of the Interior  

E-print Network

Sleeping Bear Dunes National Park Service U.S. Department of the Interior Sleeping Bear Dunes National Lakeshore Sleeping Bear Dunes National Lakeshore was established in 1970 to preserve its many outstanding natural features. The National Park Service protects the forests, beaches, dunes, and ancient

Isaacs, Rufus

347

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

E-print Network

Invasive grasses, climate change, and exposure to storm-wave overtopping in coastal dune ecosystems result in increased risk of flooding in coastal areas. In the Pacific Northwest (USA), coastal dunes and reducing dune height. Here we quantify the relative exposure to storm-wave induced dune overtopping posed

348

Adaptation with gene flow across the landscape in a dune sunflower  

E-print Network

Adaptation with gene flow across the landscape in a dune sunflower ROSE L. ANDREW,* KATHERINE L in active sand dunes and adjacent non-dune habitat, using landscape genetics approaches, such as circuit resistance owing to patchy and unfavourable habitat in the dunes would contribute to divergence. Instead, we

Rieseberg, Loren

349

An efficient implementation of an adaptive and parallel grid in DUNE  

E-print Network

An efficient implementation of an adaptive and parallel grid in DUNE Adrian Burri, Andreas Dedner-Herder-Str. 10, D-79104 Freiburg i. Br., Germany Email: alugrid@mathematik.uni-freiburg.de, DUNE website: http://dune and parallel grid (ALUGrid) within the Distributed and Unified Numerics Environment DUNE. A generalization

Ohlberger, Mario

350

Dating of Sand Dunes Using Cosmogenic Chlorine-36: An Example From the Nebraska Sand Hills, USA  

E-print Network

Dating of Sand Dunes Using Cosmogenic Chlorine-36: An Example From the Nebraska Sand Hills, USA- ing sand dunes based on the accumulation of cosmogenic chlorine-36 in sand grains. The concen- tration of chlorine-36 in a stable sand dune primarily depends on the length of time the dune has been exposed

Zreda, Marek

351

Interdisciplinary research produces results in understanding planetary dunes  

USGS Publications Warehouse

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.

2012-01-01

352

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

353

The difficulty in considering modifiable pathology risk factors in children with IgA nephropathy: crescents and timing of renal biopsy.  

PubMed

The need for an early diagnosis of primary IgA nephropathy (IgAN) is particularly felt in children since they have a long life expectancy. However, IgAN has a slowly progressive course and renal function can even remain unchanged for decades. The long-term predictive value of modifiable risk factors, such as proteinuria and proliferative/inflammatory lesion at renal biopsy, remains unknown. Interest has focused on crescents, which represent a clear risk factor for renal vasculitides. A number of rare cases of extracapillary IgAN involving >40 % of glomeruli have been reported, but in most cases of IgAN crescents involve <10 % of glomeruli. The long-term effect of small non-circumferential crescents detected by chance or without a clinical picture of progressive IgAN is still unknown. The Oxford study failed to find a predictive value of crescents in either children or adults, and these results were confirmed by the recent VALIGA study on 1,147 patients with IgAN (174 children). A recent study reports a correlation between the time elapsed from the diagnosis of urinary abnormalities and renal biopsy which suggests that crescents are associated with disease onset and then likely undergo a healing process into sclerotic lesions, which are commonly detected in biopsies performed years after onset. The authors of this study propose that primary IgAN may have similarities with Henoch-Schoenlein purpura nephritis, which presents with acute glomerular damage, mesangial proliferation, endocapillary leucocyte infiltration and crescent formations, and that these lesions can undergo resolution with sclerotic healing. This hypothesis is highly suggestive of the silent progression of several cases of IgAN without clear clinical changes, stressing once more the need for a combined clinical and pathological evaluation of children with IgAN that considers both the underlying pathogenetic event and its possible evolution. PMID:25318618

Coppo, Rosanna; Davin, Jean-Claude

2015-02-01

354

An analysis of the moon's surface using reflected illumination from the earth during a waning crescent lunar phase  

NASA Technical Reports Server (NTRS)

There have been many articles written concerning the lunar after-glow, the spectacular reflection from the moon's surface, and the possible observation of luminescence on the dark side of the moon. The researcher, using a 600 mm cassegrain telescope lense and Kodak 400 ASA T-Max film, photographed the crescent moon whose dark side was clearly visible by the reflected light from earth. The film was digitized to a Perkin-Elmer 1010M microdensitometer for enhancement and enlargement. The resulting pictures indicate a completely different land pattern formation than observed during a full moon. An attempt is made to analyze the observed structures and to compare them to the pictures observed during the normal full moon. There are boundaries on the digitized dark section of the moon that can be identified with structures seen during the normal full moon. But, these variations do change considerably under enhancement.

Hammond, Ernest C., Jr.; Linton-Petza, Maggie

1989-01-01

355

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

PubMed Central

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.

2014-01-01

356

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

357

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

358

Aerial view of old station and sand dunes looking east ...  

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

Aerial view of old station and sand dunes looking east from tower of newer station. - Vermilion Life Saving Station, Shore of Lake Superior, 10 miles west of Whitefish Point, Paradise, Chippewa County, MI

359

25. Wide view from the dune to the southeast, showing ...  

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

25. Wide view from the dune to the southeast, showing from right to left, surf, beach, bluff, stilwell Hall. - Fort Ord, Soldiers' Club, California State Highway 1 near Eighth Street, Seaside, Monterey County, CA

360

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

361

Documentation of Recent Surface Winds on Martian Sand Dunes  

NASA Astrophysics Data System (ADS)

Images from the High Resolution Imaging Science Experiment (HiRISE) are of sufficient resolution to record wind ripple patterns on the surfaces of sand dunes present across the surface of Mars. We are in the early stages of an investigation to map the ripple orientations preserved on Martian sand dunes, in order to evaluate the recent wind flow over the dunes, and compare that wind flow pattern to the winds documented over terrestrial sand dunes. HiRISE image ESP_025645_1455 covers a sand dune field on the floor of a 20-km-diameter unnamed impact crater in the Terra Cimmeria region of the southern highlands, east of the Hellas impact basin. This image is centered at 34.23 S latitude, 138.437 E longitude with 25 cm/pixel resolution, and was taken on Jan 25 of 2012 during northern spring (Ls = 57.4). Using ArcGIS, lines were drawn across three ripples perpendicular to the ripple crests, avoiding places where complex ripple patterns suggest more than one recent wind direction. The length of the lines provides a measure of ripple wavelength, and the line orientation gives azimuth (with a 180 degree absolute ambiguity). The barchan-like shape of some dunes, including occasional slip faces, suggest sand driving winds were from the southwest, although dune asymmetries indicate the wind regime likely was much more complex than a unimodal wind. Measurements of ripple orientations are being collected from dune locations across the planet, which should provide new constraints for the modeling of recent Martian winds. This work was supported by NASA MDAP grant NNX12AJ38G.

Zimbelman, J. R.; Johnson, M. B.

2013-12-01

362

Simulation model of erosion and deposition on a barchan dune  

NASA Technical Reports Server (NTRS)

Erosion and deposition over a barchan dune near the Salton Sea, California, are modeled by bookkeeping the quantity of sand in saltation following streamlines of transport. Field observations of near surface wind velocity and direction plus supplemental measurements of the velocity distribution over a scale model of the dune are combined as input to Bagnold type sand transport formulas corrected for slope effects. A unidirectional wind is assumed. The resulting patterns of erosion and deposition compare closely with those observed in the field and those predicted by the assumption of equilibrium (downwind translation of the dune without change in size or geometry). Discrepancies between the simulated results and the observed or predicted erosional patterns appear to be largely due to natural fluctuations in the wind direction. The shape of barchan dunes is a function of grain size, velocity, degree of saturation of the oncoming flow, and the variability in the direction of the oncoming wind. The size of the barchans may be controlled by natural atmospheric scales, by the age of the dunes, or by the upwind roughness. The upwind roughness can be controlled by fixed elements or by sand in the saltation. In the latter case, dune scale is determined by grain size and wind velocity.

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

1977-01-01

363

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

364

Barchan dune corridors: field characterization and investigation of control parameters  

E-print Network

The structure of the barchan field located between Tarfaya and Laayoune (Atlantic Sahara, Morocco) is quantitatively investigated and compared to that in La Pampa de la Joya (Arequipa, Peru). On the basis of field measurements, we show how the volume, the velocity and the output sand flux of a dune can be computed from the value of its body and horn widths. The dune size distribution is obtained from the analysis of aerial photographs. It shows that these fields are in a statistically homogeneous state along the wind direction and present a `corridor' structure in the transverse direction, in which the dunes have a rather well selected size. Investigating the possible external parameters controlling these corridors, we demonstrate that none among topography, granulometry, wind and sand flux is relevant. We finally discuss the dynamical processes at work in these fields (collisions and wind fluctuations), and investigate the way they could regulate the size of the dunes. Furthermore we show that the overall sand flux transported by a dune field is smaller than the maximum transport that could be reached in the absence of dunes, i.e. in saltation over the solid ground.

Hicham Elbelrhiti; Bruno Andreotti; Philippe Claudin

2006-09-06

365

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

Microsoft Academic Search

Contrasting wind, sediment and frost precipitation regimes contribute to different dune scale and form on Mars. Isolated barchans in the NPSS are smaller but assume a classic barchan form. Intra-crater barchans are larger and more variable in form.

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

2004-01-01

366

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

NASA Astrophysics Data System (ADS)

Contrasting wind, sediment and frost precipitation regimes contribute to different dune scale and form on Mars. Isolated barchans in the NPSS are smaller but assume a classic barchan form. Intra-crater barchans are larger and more variable in form.

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

2004-03-01

367

Role of amino acid transporter LAT2 in the activation of mTORC1 pathway and the pathogenesis of crescentic glomerulonephritis  

Microsoft Academic Search

Molecular mechanisms and signaling pathways leading to cellular proliferation and lesion formation in the crescentic glomerulonephritis (CGN) remain elusive. In the present study we have explored a potential role of the mammalian target of rapamycin complex 1 (mTORC1) signaling pathway and amino acid transporter (LAT) in the pathogenesis of CGN. Immunohistochemistry and western blot analysis of glomeruli isolated from a

Ryota Kurayama; Noriko Ito; Yukino Nishibori; Daisuke Fukuhara; Yoshihiro Akimoto; Eiji Higashihara; Yasuhito Ishigaki; Yoshimichi Sai; Ken-ichi Miyamoto; Hitoshi Endou; Yoshikatstu Kanai; Kunimasa Yan

2011-01-01

368

Modeling the large-scale structure of a barchan dune field  

E-print Network

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: (1) Dunes exchange sand through the fluxes that leak from the downwind side of each dune and are captured on their upstream sides; (2) when dunes become sufficiently large, small dunes are born on their downwind sides (`calving'); and (3) 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.

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

2013-03-07

369

Large Eddy Simulation of Flow and Sediment Transport over Dunes  

NASA Astrophysics Data System (ADS)

Understanding the nature of flow over bedforms has a great importance in fluvial and coastal environments. For example, a bedform is one source of energy dissipation in water waves outside the surf zone in coastal environments. In rivers, the migration of dunes often affects the stability of the river bed and banks. In general, when a fluid flows over a sediment bed, the sediment transport generated by the interaction of the flow field with the bed results in the periodic deformation of the bed in the form of dunes. Dunes generally reach an equilibrium shape, and slowly propagate in the direction of the flow, as sand is lifted in the high shear regions, and redeposited in the separated flow areas. Different numerical approaches have been used in the past to study the flow and sediment transport over bedforms. In most research works, Reynolds Averaged Navier Stokes (RANS) equations are employed to study fluid motions over ripples and dunes. However, evidences suggests that these models can not represent key turbulent quantities in unsteady boundary layers. The use of Large Eddy Simulation (LES) can resolve a much larger range of smaller scales than RANS. Moreover, unsteady simulations using LES give vital turbulent quantities which can help to study fluid motion and sediment transport over dunes. For this steady, we use a three-dimensional, non-hydrostatic model, OpenFOAM. It is a freely available tool which has different solvers to simulate specific problems in engineering and fluid mechanics. Our objective is to examine the flow and sediment transport from numerical stand point for bed geometries that are typical of fixed dunes. At the first step, we performed Large Eddy Simulation of the flow over dune geometries based on the experimental data of Nelson et al. (1993). The instantaneous flow field is investigated with special emphasis on the occurrence of coherent structures. To assess the effect of bed geometries on near bed turbulence, we considered different dune geometries based on dune height and wave length. We will also examine the role of near bed turbulence on sediment transport over dunes. For validation, profiles of velocities, turbulent intensities, and sediment transport calculated by the numerical model will be compared with available experimental measurements.

Agegnehu, G.; Smith, H. D.

2012-12-01

370

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

371

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. Using meso-scale simulations of convective methane clouds [3, 4] with a GCM wind profile featuring the super-rotation [5, 6], we show that Titan's storms should produce fast eastward gust fronts above the surface (see Figure 1). Such gusts dominate the aeolian transport. Using GCM wind roses and analogies with terrestrial dune fields as the Rub' al-Khali desert, we show that under these conditions Titan's dune growth occurs eastward (see Figure 2). Moreover, we explain other features of Titan's dunes (i.e. divergence from the equator, size and spacing). This analysis therefore reveals an unexpected coupling between super-rotation, tropical storms and dune formation on Titan, and has implications for the understanding of terrestrial dunes. References: [1] Lorenz et al. (2006) Science [2] Lorenz & Radebaugh (2009) Geophysical Research Letter [3] Barth & Rafkin (2007) Geophysical Research Letter [4] Barth & Rafkin (2010) Icarus [5] Charnay & Lebonnois (2012) Nature Geoscience [6] Lebonnois et al. (2012) Icarus Development of a methane storm with formation of a gust front. Colorbar corresponds to the mixing ratio of condensed methane (in g/kg) Resultant drift direction obtained by combining the GCM sand flux roses with the impact of one gust front every equinox at any location.

Charnay, B.; Barth, E. L.; Rafkin, S. C.; Narteau, C.; Lebonnois, S.; Rodriguez, S.

2013-12-01

372

Differing Abundances of Gypsum in the Primary and Secondary Dunes of the Martian Dune Field Olympia Undae  

NASA Astrophysics Data System (ADS)

We report on a compositional study in Olympia Undae, located around the polar cap of Mars. Gypsum has been detected throughout the sand sea but with a decline in abundance westward (Langevin et al., 2005). Dune crests are the regions of highest apparent gypsum concentration in CRISM images. Olympia Undae consists of primary dunes formed transverse to circumpolar easterly winds and secondary dunes which lie almost orthogonal to the primary dunes (Ewing et al. 2010). METHODS: We examined a number of CRISM and HiRISE images across the dune field. We focused our preliminary study on FRT0000C31A and FRT0000C2FC, which exhibited the best spectral signatures. Gypsum was identified in CRISM images by its unique 1.45/1.49/1.54 ?m triplet, ~1.94-1.95 ?m band, 2.22/2.27 ?m doublet and 2.49 ?m band with a 2.42 ?m shoulder. Spectra were acquired from regions of interest (ROIs) created along the crests of primary dunes and the low-relief crests of the secondary dunes (Fig. 1). FINDINGS: CRISM spectra of primary and secondary dune crest ROIs from FRT0000C2FC are compared with a gypsum-rich unit in FRT0000CA5C (Fig. 2). The I/F of gypsum-bearing regions is much darker than pure gypsum indicating a mixture composition containing darker components. The depth of the ~1.95 ?m hydration band is ~20-30% stronger for primary dune crests relative to the secondaries, which suggests a similar relationship among the gypsum abundance of these features, assuming similar components and grain sizes. Semi-quantitative analyses are underway to measure this in more detail. Continuing studies are planned with additional images as well. Figure 1 A map-projected view of CRISM image FRT0000C2FC with ROI locations for the primary (P) and secondary (S) dune crests marked. Figure 2 CRISM I/F spectra of gypsum-bearing units in Olympia Undae compared with laboratory reflectance spectra of minerals.

Szumila, I. T.; Bishop, J. L.; Fenton, L. K.; Brown, A. J.

2012-12-01

373

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

374

Parabolic dune reactivation and migration at Napeague, NY, USA: Insights from aerial and GPR imagery  

NASA Astrophysics Data System (ADS)

Observations from mapping since the 19th century and aerial imagery since 1930 have been used to study changes in the aeolian geomorphology of coastal parabolic dunes over the last ~ 170 years in the Walking Dune Field, Napeague, NY. The five large parabolic dunes of the Walking Dune Field have all migrated across, or are presently interacting with, a variably forested area that has affected their migration, stabilization and morphology. This study has concentrated on a dune with a particularly complex history of stabilization, reactivation and migration. We have correlated that dune's surface evolution, as revealed by aerial imagery, with its internal structures imaged using 200 MHz and 500 MHz Ground Penetrating Radar (GPR) surveys. Both 2D (transect) and high-resolution 3D GPR imagery image downwind dipping bedding planes which can be grouped by apparent dip angle into several discrete packages of beds that reflect distinct decadal-scale episodes of dune reactivation and growth. From aerial and high resolution GPR imagery, we document a unique mode of reactivation and migration linked to upwind dune formation and parabolic dune interactions with forest trees. This study documents how dune-dune and dune-vegetation interactions have influenced a unique mode of blowout deposition that has alternated on a decadal scale between opposite sides of a parabolic dune during reactivation and migration. The pattern of recent parabolic dune reactivation and migration in the Walking Dune Field appears to be somewhat more complex, and perhaps more sensitive to subtle environmental pressures, than an idealized growth model with uniform deposition and purely on-axis migration. This pattern, believed to be prevalent among other parabolic dunes in the Walking Dune Field, may occur also in many other places where similar observational constraints are unavailable.

Girardi, James D.; Davis, Dan M.

2010-02-01

375

Insights from a Geophysical and Geomorphological Mars Analog Field Study at the Great Kobuk Sand Dunes, Northwestern Alaska  

Microsoft Academic Search

Terrestrial dune systems are used as natural analogs to improve understanding of the processes by which planetary dunes form and evolve. Selected terrestrial analogs are often warm-climate dune fields devoid of frozen volatiles, but cold-climate dunes offer a better analog for polar dunes on Mars. The cold-climate Great Kobuk Sand Dunes (GKSD) of Kobuk Valley National Park, Alaska, are a

R. N. McGinnis; C. L. Dinwiddie; D. Stillman; K. Bjella; D. M. Hooper; R. E. Grimm

2010-01-01

376

Dunes and Clouds in False Color  

NASA Technical Reports Server (NTRS)

[figure removed for brevity, see original site]

The theme for the weeks of 1/17 and 1/24 is the north polar region of Mars as seen in false color THEMIS images. Ice/frost will typically appear as bright blue in color; dust mantled ice will appear in tones of red/orange.

The small greenish features in this image are sand dunes. The white feature on the right side is likely an ice cloud.

Image information: VIS instrument. Latitude 84.6, Longitude 203.1 East (156.9 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

377

Blue Polar Dunes In False Color  

NASA Technical Reports Server (NTRS)

[figure removed for brevity, see original site]

The theme for the weeks of 1/17 and 1/24 is the north polar region of Mars as seen in false color THEMIS images. Ice/frost will typically appear as bright blue in color; dust mantled ice will appear in tones of red/orange.

The small dunes in this image are 'bluer' than the rest of the layered ice/dust units to the left.

Image information: VIS instrument. Latitude 84.5, Longitude 206.6 East (153.4 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

378

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}...

Luna, Marco Cesar M de M; Herrmann, Hans J

2011-01-01

379

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...

Refregier, Alexandre

2008-01-01

380

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

381

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

382

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

383

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

384

The Herschel DUNES Open Time Key Programme  

NASA Technical Reports Server (NTRS)

We will use the unique photometric capabilities provided by Herschel to perform a deep and systematic survey for faint, cold debris disks around nearby stars. Our sensitivity-limited Open Time Key Programme (OTKP) aims at finding and characterizing faint extrasolar analogues to the Edgeworth-Kuiper Belt (EKB) in an unbiased, statistically significant sample of nearby FGK main-sequence stars. Our target set spans a broad range of stellar ages (from 0.1 to 10 Gyr) and is volume-limited (distances < 20 pc). All stars with known extrasolar planets within this distance are included; additionally, some M- and A-type stars will be observed in collaboration with the Herschel DEBRIS OTKP, so that the entire sample covers a decade in stellar mass, from 0.2 to 2 solar masses. We will perform PACS and SPIRE photometric observations covering the wavelength range from 70 to 500 microns. The PACS observations at 100 microns have been designed to detect the stellar photospheres down to the confusion limit with a signal-to-noise ratio > 5. The observations in the other Herschel bands will allow us to characterize, model, and constrain the disks. As a result, it will be possible for us to reach fractional dust luminosities of a few times 10-7, close to the EKB level in the Solar System. This will provide an unprecedented lower limit to the fractional abundance of planetesimal systems and allow us to assess the presence of giant planets, which would play dynamical roles similar to those played by Jupiter and Neptune in the Solar System. The proposed observations will provide new and unique evidence for the presence of mature planetary systems in the solar neighbourhood and, in turn, will address the universality of planet/planetary system formation in disks around young stars.

Danchi, William C.

2009-01-01

385

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

386

Effects of Trampling Limitation on Coastal Dune Plant Communities  

NASA Astrophysics Data System (ADS)

Sandy coastlines are sensitive ecosystems where human activities can have considerable negative impacts. In particular, trampling by beach visitors is a disturbance that affects dune vegetation both at the species and community level. In this study we assess the effects of the limitation of human trampling on dune vegetation in a coastal protected area of Central Italy. We compare plant species diversity in two recently fenced sectors with that of an unfenced area (and therefore subject to human trampling) using rarefaction curves and a diversity/dominance approach during a two year study period. Our results indicate that limiting human trampling seems to be a key factor in driving changes in the plant diversity of dune systems. In 2007 the regression lines of species abundance as a function of rank showed steep slopes and high Y-intercept values in all sectors, indicating a comparable level of stress and dominance across the entire study site. On the contrary, in 2009 the regression lines of the two fenced sectors clearly diverge from that of the open sector, showing less steep slopes. This change in the slopes of the tendency lines, evidenced by the diversity/dominance diagrams and related to an increase in species diversity, suggests the recovery of plant communities in the two fences between 2007 and 2009. In general, plant communities subject to trampling tended to be poorer in species and less structured, since only dominant and tolerant plant species persisted. Furthermore, limiting trampling appears to have produced positive changes in the dune vegetation assemblage after a period of only two years. These results are encouraging for the management of coastal dune systems. They highlight how a simple and cost-effective management strategy, based on passive recovery conservation measures (i.e., fence building), can be a quick (1-2 years) and effective method for improving and safeguarding the diversity of dune plant communities.

Santoro, Riccardo; Jucker, Tommaso; Prisco, Irene; Carboni, Marta; Battisti, Corrado; Acosta, Alicia T. R.

2012-03-01

387

Effects of trampling limitation on coastal dune plant communities.  

PubMed

Sandy coastlines are sensitive ecosystems where human activities can have considerable negative impacts. In particular, trampling by beach visitors is a disturbance that affects dune vegetation both at the species and community level. In this study we assess the effects of the limitation of human trampling on dune vegetation in a coastal protected area of Central Italy. We compare plant species diversity in two recently fenced sectors with that of an unfenced area (and therefore subject to human trampling) using rarefaction curves and a diversity/dominance approach during a two year study period. Our results indicate that limiting human trampling seems to be a key factor in driving changes in the plant diversity of dune systems. In 2007 the regression lines of species abundance as a function of rank showed steep slopes and high Y-intercept values in all sectors, indicating a comparable level of stress and dominance across the entire study site. On the contrary, in 2009 the regression lines of the two fenced sectors clearly diverge from that of the open sector, showing less steep slopes. This change in the slopes of the tendency lines, evidenced by the diversity/dominance diagrams and related to an increase in species diversity, suggests the recovery of plant communities in the two fences between 2007 and 2009. In general, plant communities subject to trampling tended to be poorer in species and less structured, since only dominant and tolerant plant species persisted. Furthermore, limiting trampling appears to have produced positive changes in the dune vegetation assemblage after a period of only two years. These results are encouraging for the management of coastal dune systems. They highlight how a simple and cost-effective management strategy, based on passive recovery conservation measures (i.e., fence building), can be a quick (1–2 years) and effective method for improving and safeguarding the diversity of dune plant communities. PMID:22302225

Santoro, Riccardo; Jucker, Tommaso; Prisco, Irene; Carboni, Marta; Battisti, Corrado; Acosta, Alicia T R

2012-03-01

388

Sand Dunes of Nili Patera in 3-D  

NASA Technical Reports Server (NTRS)

The most exciting new aspect of the Mars Global Surveyor (MGS) Extended Mission is the opportunity to turn the spacecraft and point the Mars Orbiter Camera (MOC) at specific features of interest. Opportunities to point the spacecraft come about ten times a week. Throughout the Primary Mission (March 1999 - January 2001), nearly all MGS operations were conducted with the spacecraft pointing 'nadir'--that is, straight down. A search for the missing Mars Polar Lander in late 1999 and early 2000 demonstrated that pointing the spacecraft could allow opportunities for MOC to see things that simply had not entered its field of view during typical nadir-looking operations, and to target areas previously seen in a nadir view so that stereo ('3-D') pictures could be derived.

One of the very first places photographed by the MOC at the start of the Mapping Mission in March 1999 was a field of dunes located in Nili Patera, a volcanic depression in central Syrtis Major. A portion of this dune field was shown in a media release on March 11, 1999, 'Sand Dunes of Nili Patera, Syrtis Major'. Subsequently, the image was archived with the NASA Planetary Data System, as shown in the Malin Space Science Systems MOC Gallery. On April 24, 2001, an opportunity arose in which the MGS could be pointed off-nadir to take a new picture of the same dune field. By combining the nadir view from March 1999 and the off-nadir view from April 2001, a stereoscopic image was created. The anaglyph shown here must be viewed with red (left-eye) and blue (right-eye) '3-D' glasses. The dunes and the local topography of the volcanic crater's floor stand out in sharp relief. The images, taken more than one Mars year apart, show no change in the shape or location of the dunes--that is, they do not seem to have moved at all since March 1999.

2001-01-01

389

Defrosting Polar Dunes--Changes Over a 26-Day Period  

NASA Technical Reports Server (NTRS)

As the retreat of the south polar winter frost cap became visible in June 1999, high resolution images from the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) began to show dark spots forming on the surfaces of frost-covered sand dunes. Immediately, the MOC science team began to plan to observe several dune fields more than once, should that opportunity arise, so that the evolution of these dark spots could be documented and studied. Such work will eventually lead to abetter understanding of how the martian polar caps retreat as winter ends and spring unfolds in each hemisphere.

MGS is in a polar orbit, which means that, unlike many other places on Mars, the spacecraft has more opportunities to take pictures of the same place. Dune fields near 87o latitude can be repeatedly viewed; dunes near the equator are not likely to be photographed more than once during the entire MGS mission.

The pictures presented here show changes on a set of nearly pear-shaped sand dunes located on the floor of an unnamed crater at 59oS, 353oW. The picture on the left shows the dunes as they appeared on June 19, 1999, the picture on the right shows the same dunes on July 15, 1999. The dark spots in the June 19picture--indicating areas where frost has sublimed away--became larger by July 15th. In addition, new spots had appeared as of mid-July. If possible, these dunes will be photographed by MOC again in mid-August and each month until the frost is gone.

The pictures shown in (B) (above) are expanded views of portions of the pictures in (A). The 200 meter scale bar equals 656 feet; the 100 meter bar is 328 feet (109 yards) long. All images are illuminated from the upper left; north is toward the upper right.

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

390

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 about flow and sediment dynamics over high-angle (~30°) dunes, however little is known about low

Venditti, Jeremy G.

391

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

392

Laboratory investigation of beach scarp and dune recession due to notching and subsequent failure  

E-print Network

Laboratory investigation of beach scarp and dune recession due to notching and subsequent failure of dunes are presented. The notch evolution model is based on a transport equation for sediment from the dune and the sediment volume conservation equation, whereas the models of mass failure are derived

US Army Corps of Engineers

393

Global mapping and characterization of Titan's dune fields with Cassini: Correlation between RADAR and VIMS observations  

E-print Network

Global mapping and characterization of Titan's dune fields with Cassini: Correlation between RADAR dunes have been observed in the equatorial regions of Titan, Saturn's largest moon. As the Cassini-resolution coverage of Titan's surface increases, revealing new dune fields and allowing refinements

Narteau, Clément

394

The Use of Terrestrial Laser Scanning (TLS) in Dune Ecosystems: The Lessons Learned  

E-print Network

The Use of Terrestrial Laser Scanning (TLS) in Dune Ecosystems: The Lessons Learned Rusty A. Feagin of terrestrial laser scanning (TLS) in dune ecosystems: the lessons learned. Journal of Coastal Research, 30 terrestrial laser scanning (TLS) to quantify sand dune geomorphology. As an example of the use of TLS, we

395

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 22 March 2010; published 23 April 2010. [1] Multiple occurrences of "wall dunes" are found several kilometers above the Valles Marineris canyon floor. Dune slip face orientation and bed form morphologies

Perfect, Ed

396

Shrubs as ecosystem engineers in a coastal dune: influences on plant populations, communities and ecosystems  

E-print Network

Shrubs as ecosystem engineers in a coastal dune: influences on plant populations, communities the landscape? Location: Coastal hind-dune system, Bodega Head, northern California. Methods: In each of 4 years ­ Ericameria ericoides and the nitrogen-fixing Lupinus chamissonis ­ with those in adjacent open dunes. Results

Cushman, J. Hall

397

Mars Global Digital Dune Database and initial science results Rosalyn K. Hayward,1  

E-print Network

Mars Global Digital Dune Database and initial science results Rosalyn K. Hayward,1 Kevin F. Mullins 20 November 2007. [1] A new Mars Global Digital Dune Database (MGD3 ) constructed using Thermal of the geographic distribution of moderate- to large-size dune fields (area >1 km2 ) that will help researchers

Bourke, Mary C.

398

38 BULLETIN O F THE UNITED STATES FISH COMMISSION. 11.-HOW TO QTBENGTHENTHE DUNES.*  

E-print Network

38 BULLETIN O F THE UNITED STATES FISH COMMISSION. 11.-HOW TO QTBENGTHENTHE DUNES.* B y 6. ROECK. Iu au article on the formation of the dunes, in No; 33 of the Deutsolie lf art can do nothing or but little to resist the force of the shifting dune." This often

399

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

...2014-10-01 false Evaluation of sand dunes in mapping coastal flood hazard areas...AREAS § 65.11 Evaluation of sand dunes in mapping coastal flood hazard areas...NFIP, FEMA will consider storm-induced dune erosion potential in its...

2014-10-01

400

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 to the Jockey's Ridge, North Carolina, the largest active dune field on the east coast of the United States, lidar and GPS point data were used to compute a multitemporal elevation model of the dune field

Mitasova, Helena

401

The role of streamline curvature in sand dune dynamics: evidence from field and wind tunnel measurements  

Microsoft Academic Search

Field measurements on an unvegetated, 10 m high barchan dune in Oman are compared with measurements over a 1:200 scale fixed model in a wind tunnel. Both the field and wind tunnel data demonstrate similar patterns of wind and shear velocity over the dune, confirming significant flow deceleration upwind of and at the toe of the dune, acceleration of flow

Giles F. S. Wiggs; Ian Livingstone; Andrew Warren

1996-01-01

402

The Great Sand Dunes Ecosystem Elk and Bison Carrying Capacity Model: Description and Scenario Results  

E-print Network

1 The Great Sand Dunes Ecosystem Elk and Bison Carrying Capacity Model: Description and Scenario studying the Sand Dunes ecosystem in the past decade. The information they have gathered has been.S. Geological Survey, and Great Sand Dunes National Park and Preserve for providing funding to support

Boone, Randall B.

403

A 3 km atmospheric boundary layer on Titan indicated by dune spacing and Huygens data  

E-print Network

Note A 3 km atmospheric boundary layer on Titan indicated by dune spacing and Huygens data Ralph D a b s t r a c t Some 20% of Titan's surface is covered in large linear dunes that resemble parameter limiting the growth of giant dunes, namely the boundary layer thickness (Andreotti et al., 2009

Claudin, Philippe

404

Sand dune dynamics and climate change: A modeling H. Yizhaq,1  

E-print Network

Sand dune dynamics and climate change: A modeling approach H. Yizhaq,1 Y. Ashkenazy,1 and H. Tsoar2] We provide several examples for the coexistence of active and fixed sand dunes under similar climatic conditions, namely, with respect to wind power and precipitation rate. A model is developed for dune

Ashkenazy, Yossi "Yosef"

405

The Holocene 14,2 (2004) pp. 209217 Late-Holocene dune activity linked to  

E-print Network

The Holocene 14,2 (2004) pp. 209­217 Late-Holocene dune activity linked to hydrological drought) Received 27 August 2002; revised manuscript accepted 17 December 2002 Abstract: Dune elds of the Great-Holocene aeolian activity in the Nebraska Sand Hills, the largest dune eld on the Great Plains of North America

Loope, David B.

406

Florida (Pensacola Beach) dune restoration Project General Project DescriPtion  

E-print Network

Florida (Pensacola Beach) dune restoration Project General Project DescriPtion The project equipment has inhibited plant growth and prevented the natural seaward expansion of the dunes since June 2010. The primary dunes are the first natural line of defense for coastal Florida to prevent the loss

407

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

E-print Network

dunes PHOEBE L. ZARNETSKE,1, ERIC W. SEABLOOM,2 AND SALLY D. HACKER 1 1 Department of Zoology, Oregon may have knock-on effects on non-target native species and ecosystems. For example, coastal dunes arenaria and Ammophila breviligulata. These invasive grasses have converted open, low-lying sand dunes

408

A generic grid interface for parallel and adaptive scientific Part II: implementation and tests in DUNE  

E-print Network

and tests in DUNE P. Bastian1 M. Blatt1 A. Dedner2 C. Engwer1 R. Kl¨ofkorn2 R. Kornhuber4 M. Ohlberger3 O performance losses. The imple- mentation is realized as part of the software environment DUNE [10]. Numerical, 65Y05, 68U20 Key words: DUNE, hierarchical grids, software, abstract interface, generic programming

Bastian, Peter

409

SIMULATION OF THE EFFECT OF WIND SPEEDUP IN THE FORMA-TION OF TRANSVERSE DUNE FIELDS  

E-print Network

SIMULATION OF THE EFFECT OF WIND SPEEDUP IN THE FORMA- TION OF TRANSVERSE DUNE FIELDS HIROSHI 21 February 2000; Accepted 25 February 2000 ABSTRACT A computer simulation model for transverse-dune distinct problems were found regarding the cross-sectional dune shape, namely

410

Marine and River Dune Dynamics -1-3 April 2008 -Leeds, United Kingdom 1 INTRODUCTION  

E-print Network

Marine and River Dune Dynamics - 1-3 April 2008 - Leeds, United Kingdom 315 1 INTRODUCTION Bedload for the growth of bedload sheets. Bedload sheets are widely thought to be the a pre- cursor to gravel dune process required for dune growth. This can only happen in flows well in ex- cess of the critical threshold

Venditti, Jeremy G.

411

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 storms and to predict which dune species might be appropriate for resto- ration after storm damage across dune zones. This predic- tion was tested with six plant species that differed in their storm response

Miller, Thomas E.

412

Reply to "Comment on `Minimal size of a barchan dune' " E. J. R. Parteli,1  

E-print Network

Reply to "Comment on `Minimal size of a barchan dune' " E. J. R. Parteli,1 O. Durán,2 and H. J. Rev. E 75, 011301 2007 . We show that the equations of the dune model used in our calcula- tions are self-consistent and effectively lead to a dependence of the minimal dune size on the wind speed through

Claudin, Philippe

413

Morphodynamics of small-scale superimposed sand waves over migrating dune bed forms  

E-print Network

Morphodynamics of small-scale superimposed sand waves over migrating dune bed forms Jeremy G migrating dunes are examined using data drawn from laboratory experiments. We refer to the superimposed classified as ripples, dunes, or bars. Within the experiments, the sheets formed downstream

Venditti, Jeremy G.

414

Geologic Influences on Groundwater Flow to Inter-Dune Wetlands, Southeastern Virginia  

E-print Network

Geologic Influences on Groundwater Flow to Inter-Dune Wetlands, Southeastern Virginia Matthew center, and mantle the long inter-dune swales near the ocean shore. The appearance and subsequent disappearance of redoximorphic wetland soil features in the young, sandy soils of the inter-dune swales here may

Darby, Dennis

415

DUNE-FEM. A general purpose discretization toolbox for parallel and adaptive scientific  

E-print Network

DUNE-FEM. A general purpose discretization toolbox for parallel and adaptive scientific computing Andreas Dedner, Robert Kl¨ofkorn, Martin Nolte, Mario Ohlberger Abstract DUNE-FEM is a free discretization toolbox for parallel and adaptive sci- entific computing based on DUNE. The implementation

416

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

E-print Network

Cassini SAR, radiometry, scatterometry and altimetry observations of Titan's dune fields A. Le Gall observations Geological processes a b s t r a c t Large expanses of linear dunes cover Titan's equatorial regions. As the Cassini mission continues, more dune fields are becoming unveiled and examined

Mojzsis, Stephen J.

417

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 photogrammetric methods to the study and management of dynamic dune systems. Two sets of panchromatic

Brown, Daniel G.

418

Quaternary Science Reviews 23 (2004) 11731182 Optical and radiocarbon ages of stacked paleosols and dune sands  

E-print Network

and dune sands in the Nebraska Sand Hills, USA R.J. Goble*, Joseph A. Mason, David B. Loope, James B In the episodically active eolian dune fields of the Great Plains, buried soils provide crucial evidence for periods of time during which the dunes were grass- covered and immobile (e.g. Ahlbrandt et al., 1983; Loope et al

Loope, David B.

419

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 forestsI' a known-aged series of stands representative or coastal dune ["orest suceesslun. A survey of the millipede-specific millipede COIII III unity variables on rehabilitating dunes with those recorded in relatively undisturbed d

Pretoria, University of

420

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

421

Southern high latitude dune fields on Mars: Morphology, aeolian inactivity, and climate change  

USGS Publications Warehouse

In a study area spanning the martian surface poleward of 50?? S., 1190 dune fields have been identified, mapped, and categorized based on dune field morphology. Dune fields in the study area span ??? 116400km2, leading to a global dune field coverage estimate of ???904000km2, far less than that found on Earth. Based on distinct morphological features, the dune fields were grouped into six different classes that vary in interpreted aeolian activity level from potentially active to relatively inactive and eroding. The six dune field classes occur in specific latitude zones, with a sequence of reduced activity and degradation progressing poleward. In particular, the first signs of stabilization appear at ???60?? S., which broadly corresponds to the edge of high concentrations of water-equivalent hydrogen content (observed by the Neutron Spectrometer) that have been interpreted as ground ice. This near-surface ground ice likely acts to reduce sand availability in the present climate state on Mars, stabilizing high latitude dunes and allowing erosional processes to change their morphology. As a result, climatic changes in the content of near-surface ground ice are likely to influence the level of dune activity. Spatial variation of dune field classes with longitude is significant, suggesting that local conditions play a major role in determining dune field activity level. Dune fields on the south polar layered terrain, for example, appear either potentially active or inactive, indicating that at least two generations of dune building have occurred on this surface. Many dune fields show signs of degradation mixed with crisp-brinked dunes, also suggesting that more than one generation of dune building has occurred since they originally formed. Dune fields superposed on early and late Amazonian surfaces provide potential upper age limits of ???100My on the south polar layered deposits and ???3Ga elsewhere at high latitudes. No craters are present on any identifiable dune fields, which can provide a lower age limit through crater counting: assuming all relatively stabilized dune fields represent a single noncontiguous surface of uniform age, their estimated crater retention age is dune field (94km2) has a crater retention age dune fields in the largest basins (Hellas and Argyre Planitiae) are consistent with the previously proposed idea that dune sands are not typically transported far from their source regions on Mars. ?? 2009 Elsevier B.V.

Fenton, L.K.; Hayward, R.K.

2010-01-01

422

Definition and origin of the dune-field pattern at White Sands, New Mexico  

NASA Astrophysics Data System (ADS)

A LiDAR-derived digital elevation model (DEM) of a representative portion of the White Sands Dune Field, New Mexico, allows for characterization of an unprecedented range of dune-field parameters and serves as a basis for pattern analysis. Dune-field parameters were measured and statistically analyzed for populations of dunes selected at random and occurring along transects. Populations sampled by these two different methods are comparable, but highlight the sensitivity of transect placement in a dune field that has pattern heterogeneity. Based upon coefficients of variation, pattern emerges at White Sands primarily because of a strong fabric of crestline orientation, and secondarily because of the regularity of spacing between dunes of similar shape as defined by sinuosity, height and length. Linear regression of dune parameters shows that dune geometric relationships vary primarily with crestline length, but there is little correlation between other parameters, including dune spacing and height. This result highlights the sensitivity of identifying topographic heterogeneity in a LiDAR-derived DEM, given that mean ratios conform to global averages. Stripping off the dunes in Matlab shows a terraced surface, which is interpreted to represent paleo-shorelines formed during relative still stands in the overall retreat of Lake Otero. Elevated bands of higher, more closely spaced dunes occur just leeward of the paleo-shorelines. A revised model for the White Sands Dune Field consists of the basinward progradation of successive dune-field segments. Each segment is associated with a paleo-shoreline, and consists of an upwind dune ridge, represented by the elevated bands, and a leeward dune field.

Baitis, Elke; Kocurek, Gary; Smith, Virginia; Mohrig, David; Ewing, Ryan C.; Peyret, A.-P. B.

2014-12-01

423

Hydrology of Coastal Dune Lakes in Walton County, FL  

Microsoft Academic Search

The Choctawhatchee Basin coastal dune lakes are a unique feature of the Florida Panhandle. They are predominantly freshwater bodies, with intermittent connections to the Gulf of Mexico. Rapid residential development in the surrounding watersheds has raised concerns regarding water quality within the lakes, specifically increasing nutrient levels. This paper reports on hydrologic and water quality assessments of three of these

J. W. Jawitz; J. Bhadha

2008-01-01

424

Discussion. Cemented horizon in subarctic Alaskan sand dunes.  

USGS Publications Warehouse

Exception is taken to the conclusions (M.A. 84M/4465) concerning the distribution, age and origin of the cementing materials of carbonate crusts in the eaeolian sand deposits of the dune field in the central Kobuk Valley. (Following abstract)-M.S.

Galloway, J.P.; Koster, E.A.; Hamilton, T.D.

1985-01-01

425

Active Processes on Mars: Dry Ice and Dunes  

NASA Astrophysics Data System (ADS)

Icy volatiles on Mars are responsible for geomorphic changes on dunes, taking place in today's climate. Both north and south polar regions show sediment transport in the spring, associated with sublimation of seasonal ice. Using HiRISE, the High Resolution Imaging Science Experiment, on the Mars Reconnaissance Orbiter (MRO), we explore possible mechanisms.

Hansen, C. J.; Diniega, S.; Dundas, C.; McEwen, A.; Portyankina, G.; Thomas, N.; Byrne, S.

2011-10-01

426

Rabbit grazing and species diversity in a dune area  

Microsoft Academic Search

Summary The relation between density of rabbit populations and plant species diversity is discussed. In the dunes of the Dutch Frisian Island of Schiermonnikoog, the rabbit grazing pressure has been quantified on the basis of traces of recent grazing activity. Moderate grazing turned out to bring about maximal species richness. Current changes in grazing pressure (either decrease or increase) can

H. J. Zeevalking; L. F. M. Fresco

1977-01-01

427

Population biology of salt marsh and sand dune annuals  

Microsoft Academic Search

Annuals represent a significant component of the vegetation of coastal salt marshes and sand dunes. From many points of view, the two habitats might appear to have little in common. Yet both are characterized by episodes of low water potential, marked spatial and temporal heterogeneity and a zonation which, within certain limits, reflects successional change.

A. R. Watkinson; A. J. Davy

1985-01-01

428

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

429

Analysis of Coastal Dunes: A Remote Sensing and Statistical Approach.  

ERIC Educational Resources Information Center

Remote sensing analysis and statistical methods were used to analyze the coastal dunes of Plum Island, Massachusetts. The research methodology used provides an example of a student project for remote sensing, geomorphology, or spatial analysis courses at the university level. (RM)

Jones, J. Richard

1985-01-01

430

Low-flying Helicopter Scanning Great Sand Dunes National Park  

USGS Multimedia Gallery

Citizens and visitors should not be alarmed if they witness a low-flying helicopter, with a large wire-loop contraption hanging from a cable underneath, flying over the Great Sand Dunes National Park in the next couple of weeks. Starting on or about Monday, Oct. 10, and lasting for one to two weeks...

431

Internal structure of the aeolian sand dunes of El Fangar spit, Ebro Delta (Tarragona, Spain)  

NASA Astrophysics Data System (ADS)

This paper presents an analysis of the dune field dynamics of El Fangar Spit in the Ebro Delta (Spain), associating it with the internal structure of dunes carried out with ground-penetrating radar and supported by data from topographic DGPS. These analyses are of great importance to ascertain the state of the internal structure of dunes as an important element in their stability and, therefore in their evolution. The internal structure shows accretion and progradation sequences of dunes over beach deposits, which depend on dune morphology (height, crest orientation) and location, as well as the processes acting on them.

Rodríguez Santalla, Inmaculada; Sánchez García, María José; Montoya Montes, Isabel; Gómez Ortiz, David; Martín Crespo, Tomas; Serra Raventos, Jordi

2009-03-01

432

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

433

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

434

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 ...

435

Shallow ground-water flow, water levels, and quality of water, 1980-84, Cowles Unit, Indiana Dunes National Lakeshore  

Microsoft Academic Search

The Cowles Unit of Indiana Dunes National Lakeshore in Porter County, northwest Indiana, contains a broad dune-beach complex along the southern shoreline of Lake Michigan and a large wetland, called the Great Marsh, that occupies the lowland between the shoreline dunes and an older dune-beach complex farther inland. Water levels and water quality in the surficial aquifer were monitored from

D. A. Cohen; R. J. Shedlock

1986-01-01

436

The effect of wind speedup in the formation of transverse dune fields Hiroshi Momiji *, **, Ricardo CarreteroGonz'alez***,  

E-print Network

The effect of wind speedup in the formation of transverse dune fields Hiroshi Momiji *, **, Ricardo September 1999) Abstract A computer simulation model for transverse­dune­field dynamics, corresponding regarding the cross­sectional dune shape, namely the erosion in the lee of dunes and the steepness

437

When dunes move together, structure of deserts emerges Mathieu Genois, Pascal Hersen, and Sylvain Courrech du Pont  

E-print Network

When dunes move together, structure of deserts emerges Mathieu G´enois, Pascal Hersen, and Sylvain shaped barchan dunes are highly mobile dunes that are usually presented as a proto- typical model of sand dunes. Although they have been theoretically shown to be unstable when considered separately, it is well

Paris-Sud XI, Université de

438

PUBLISHED ONLINE: 24 JUNE 2012 | DOI: 10.1038/NGEO1503 Morphology and dynamics of star dunes from  

E-print Network

dunes from numerical modelling Deguo Zhang1 , Clément Narteau1 *, Olivier Rozier1 and Sylvain Courrech du Pont2 * Star dunes are giant, pyramid-shaped dunes composed of interlaced arms. These arms suggest that the star dunes form as a result of complex interactions between a multidirectional wind

Narteau, Clément

439

JOURNAL OF GEOPHYSICAL RESEARCH, VOL. ???, XXXX, DOI:10.1029/, The effects of psammophilous plants on sand dune1  

E-print Network

on sand dune1 dynamics2 Golan Bel, 1 Yosef Ashkenazy, 1 Corresponding author: G. Bel, Department, 2014, 2:29pm D R A F T #12;X - 2 BEL AND ASHKENAZY: PSAMMOPHILOUS PLANTS - SAND DUNE DYNAMICS Abstract. Mathematical models of sand dune dynamics have considered3 different types of sand dune cover. However, despite

Ashkenazy, Yossi "Yosef"

440

JOURNAL OF GEOPHYSICAL RESEARCH, VOL. ???, XXXX, DOI:10.1002/, The effects of psammophilous plants on sand dune1  

E-print Network

on sand dune1 dynamics2 Golan Bel, 1 Yosef Ashkenazy, 1 Corresponding author: G. Bel, Department, 2014, 7:28am D R A F T #12;X - 2 BEL AND ASHKENAZY: PSAMMOPHILOUS PLANTS - SAND DUNE DYNAMICS Abstract. Mathematical models of sand dune dynamics have considered3 different types of sand dune cover. However, despite

Ashkenazy, Yossi "Yosef"

441

Marine litter in Mediterranean sandy littorals: Spatial distribution patterns along central Italy coastal dunes.  

PubMed

Sandy shores are generally considered important sinks for marine litter and the presence of this litter may represent a serious threat to biotic communities and dune integrity mostly due to cleaning activities carried out through mechanical equipment. In spring (April-May) 2012 we sampled 153 2×2m random plots to assess the spatial distribution patterns of litter on Central Italy sandy shores. We analysed the relationship between the presence of litter and coastal dune habitats along the sea-inland gradient. Our results showed that the most frequent litter items were plastic and polystyrene. Differences of marine litter spatial distribution were found between upper beach and fore dune habitats and fixed dune habitats: embryo dune and mobile dune habitats show the highest frequency of litter, but, surprisingly, marine litter did not impact fixed dune habitats, these possibly acting as a natural barrier protecting the inner part of the coast from marine litter dispersion. PMID:25455823

Poeta, Gianluca; Battisti, Corrado; Acosta, Alicia T R

2014-12-15

442

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

443

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

444

Soil development in OSL dated sandy dune substrates under Quercus robur Forest (Netherlands)  

NASA Astrophysics Data System (ADS)

Coastal dune landscapes are very dynamic. The present distribution of vegetation and soil is the result of over 2000 years of natural processes and human management. The initial soil development was controlled by an increase of the organic matter content, which consisted mainly of decomposed roots of grasses (rhizomull), and a decrease of the soil pH to 3-4 by decalcification. This stage was followed by the development of a deciduous forest, which was dominated by Quercus robur. Since 1600 AD, a large part of the deciduous forest that dominated the east side of the coastal dune landscape transferred in expensive residential areas and urbanizations. Nevertheless some parts of the oak forest belt remained. The present forest soils are acid and the controlling soil processes are leaching of sesquioxides and storage of organic matter in mormoder humus forms. The sustainability of ecosystems is closely related to the quality of the humus form, controlling nutrient cycling and water supply. Therefore, improve of knowledge of humus form development and properties is important. We applied soil micromorphology and pyrolysis-gas chromatography/mass spectrometry (GC/MS) to investigate more details of humus form development at two locations (Duivendrift and Hoek van Klaas) in the