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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, 2014

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

2010-12-27

2

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, 2014

...SHPO) reviewed this project under section 106 of...will be affected by this project. A Historic Properties...for construction and start-up of the Crescent Dunes Solar Energy Project, as selected in the...which authorizes a new program for rapid...

2011-09-29

3

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

2004-01-26

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

Crescent Wars  

NASA Astrophysics Data System (ADS)

Historically, many calendars are based on lunar months, where the start of the month is based on the sighting of the thin crescent Moon in the evening twilight. Yet the problem of predicting (or postdicting) crescent visibility is a difficult task. In modern times, the Islamic calendar is used by more than a billion people, while its utility is abridged by the ambiguities in knowing the dates. As such, I would claim that crescent visibility is the single (nontrivial) astronomical problem that affects the most people. LeRoy Doggett spearheaded an effort to place crescent visibility on a firm observational basis by organizing five Moonwatch campaigns involving thousands of observers spread out across North America. His idea was to collect large numbers of actual observations for direct confrontation with models, and to measure the error rates. This talk will report on his results. The application of the results are broad; frequently in areas of scholarly, historical, social, or military disputes. For example, lunar visibility is vital for dating the Crucifixion, a task contentious among Biblical scholars. Another example is in testing the historicity of the claimed lunar impact reported by Gervase of Canterbury. The meeting will be held in the middle of the Islamic holy month of Ramadan, while in the past two decades the majority of Ramadans have been started based on reported crescent sightings before the time of New Moon.

Schaefer, B. E.

1997-12-01

6

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

7

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

E-print Network

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

Badescu, Viorel; Bolonkin, Alexander A

2007-01-01

8

ON THE CRESCENT'S VISIBILITY  

Microsoft Academic Search

A month in the Islamic lunar calendar begins on the day following the first evening during which the waxing crescent becomes visible. Thus, the central problem in the preparation of Islamic calendars in advance is to formulate the computational procedures for determining the youngest visible phase of the moon. In temperate latitudes, the crescent to start a new lunar month

S. Kamal Abdali

9

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

E-print Network

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

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

2007-07-21

10

Lunar crescent visibility  

Microsoft Academic Search

We report the results of five Moonwatches, in which more than 2000 observers throughout North America attempted to sight the thin lunar crescent. For each Moonwatch we were able to determine the position of the Lunar Date Line (LDL), the line along which a normal observer has a 50% probability of spotting the Moon. The observational LDLs were then compared

L. E. Doggett; B. E. Schaefer

1994-01-01

11

Crescentic ramp turbine stage  

NASA Technical Reports Server (NTRS)

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

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

2007-01-01

12

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

13

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

NASA Astrophysics Data System (ADS)

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

Génois, M.; Courrech Du Pont, S.

2013-12-01

14

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

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

15

Lunar crescent visibility  

NASA Technical Reports Server (NTRS)

We report the results of five Moonwatches, in which more than 2000 observers throughout North America attempted to sight the thin lunar crescent. For each Moonwatch we were able to determine the position of the Lunar Date Line (LDL), the line along which a normal observer has a 50% probability of spotting the Moon. The observational LDLs were then compared with predicted LDLs derived from crescent visibility prediction algorithms. We find that ancient and medieval rules are higly unreliable. More recent empirical criteria, based on the relative altitude and azimuth of the Moon at the time of sunset, have a reasonable accuracy, with the best specific formulation being due to Yallop. The modern theoretical model by Schaefer (based on the physiology of the human eye and the local observing conditions) is found to have the least systematic error, the least average error, and the least maximum error of all models tested. Analysis of the observations also provided information about atmospheric, optical and human factors that affect the observations. We show that observational lunar calendars have a natural bias to begin early.

Doggett, Leroy E.; Schaefer, Bradley E.

1994-01-01

16

Exploring the topography and structure of Saharan linear dunes: Implications for characterizing dunes on Titan  

NASA Astrophysics Data System (ADS)

Tens of thousands of sand dunes encircle the equatorial latitudes of Saturn's moon Titan, as seen by the Cassini Radar and visible-NIR instruments. These are linear in form, comparable in size and morphology to large linear dunes in the Egyptian Sahara. Studies of linear dunes in the Sahara can therefore assist in understanding the characteristics and formation of Titan's dunes. High-resolution topographic profiles of the Egyptian dunes indicate winds draw dune sands into broad stable plinths with steep summits that shift with recent winds. The summits of the Qattaniya Dunes west of Cairo are drawn out into crescents along the dune long axis from dominant, northerly winds on a NNW-trending crestline. Ground penetrating radar surveys show equally spaced layers within the dune, suggesting continuous, regular wind regimes formed the dunes. Larger dunes of the Great Sand Sea south of Siwa Oasis exhibit generally similar topographic profiles and fine layering although numerous flanking features complicate the overall morphology. These analyses can be related to studies of wind pattern effects on Titan's dune forms, residence time of sands within dunes on Titan, and the creation and maintenance of evolved dune forms across Titan. Studies of the effects of morphology and internal structure of these dunes on terrestrial radar remote sensing observations will yield additional information concerning Titan's dunes. Scattering models, for example, seek to explain the radar returns from Titan's dunes based on geometry and sand composition so it is valuable to understand the effects of these parameters on terrestrial dunes.

Farr, T. G.; Heggy, E.; Radebaugh, J.

2011-12-01

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.

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

2012-02-16

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.

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

2012-01-01

21

The sedimentary structure of linear sand dunes  

PubMed

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

Bristow; Bailey; Lancaster

2000-07-01

22

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

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

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

Federal Register 2010, 2011, 2012, 2013, 2014

...Fireworks Event, Crescent City, CA AGENCY: Coast Guard, DHS. ACTION...City Harbor in Crescent City, CA in support of the Crescent City...CFR 1.05-1(g), 6.04-1, 6.04-6, and 160.5; Pub...Fireworks Event, Crescent City, CA. (a) Location. This...

2012-07-03

25

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

Federal Register 2010, 2011, 2012, 2013, 2014

...191, 195; 33 CFR 1.05-1, 6.04-1, 6.04-6, 160.5; Public...in Crescent City Harbor, CA in approximate position 41...05-1(g), 6.04-1, 6.04-6, and 160.5...Harbor, Crescent City, CA. (a) Location. This...

2013-04-23

26

Sand Dunes  

NSDL National Science Digital Library

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

Enright, Rachel

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

Osteopontin expression in human crescentic glomerulonephritis  

Microsoft Academic Search

Osteopontin expression in human crescentic glomerulonephritis.BackgroundOsteopontin is a molecule with diverse biological functions, including cell adhesion, migration, and signaling. The expression of osteopontin has been demonstrated in a number of models of renal injury in association with accumulations of monocyte\\/macrophages, including recent reports of osteopontin expression in glomerular crescents in a rat model of anti-glomerular basement membrane glomerulonephritis.MethodsGlomerular expression of

Kelly L Hudkins; Cecilia M Giachelli; Frank Eitner; William G Couser; Richard J Johnson; Charles E Alpers

2000-01-01

30

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 ...

31

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

32

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

2013-12-02

33

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

34

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

35

Dune Exploration: Mars Allegories  

NASA Astrophysics Data System (ADS)

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

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

2005-12-01

36

Sand Dunes  

NSDL National Science Digital Library

This outdoor activity (on page 2 of the PDF) is a full inquiry investigation into how the amount of moisture in a sand dune relates to the number of plants growing there. Groups of learners will scout at least two locations in a sandy area, count the number and types of plants in contact with a 10 meter line, and then sample the moisture in the top 30 cm of sand in each location, graphing their results to analyze their data. Relates to linked video, DragonflyTV: Sand Dunes.

2012-06-26

37

Caterpillar Dunes  

NASA Technical Reports Server (NTRS)

28 June 2004 Looking somewhat like caterpillars, this April 2004 Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows some of the rounded, wind-eroded sand dune features in a crater in the southern hemisphere near 61.7oS, 160.3oW. For such rounding to occur, the dune sand might need to be somewhat cemented. The picture covers an area about 3 km (1.9 mi) wide and is illuminated by sunlight from the upper left.

2004-01-01

38

First Visibility of the Lunar Crescent  

Microsoft Academic Search

Astronomical observatories are often asked to predict the visibility of the young crescent moon by communities (especially Islamic and Karaite) which use traditional lunar calendars. The SAAO has provided such information for many years, but the early 1990s were a watershed of sorts. Astronomical visibility factors in those years created an unusually severe bias against visibility of the Ramadaan and

J. A. R. Caldwell; C. D. Laney

2000-01-01

39

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

40

Aeolian Dune Deformation in a Multi-Directional Wind Regime, White Sands Dune Field, New Mexico  

NASA Astrophysics Data System (ADS)

Aeolian dunes commonly exist in a multi-directional wind regime. With each constructive wind event, dunes both migrate and deform as a function of the incidence angle of the primary wind to the local brinkline orientation. Can dune shape after many wind events be predicted from the resultant of these wind events? This question was addressed for sinuous crescentic dunes at the White Sands Dune Field, New Mexico, using: (1) a record of wind events from nearby Holloman AFB, and (2) a time-series of LiDAR-derived digital elevation models (DEMs) in which changes in dune shape can be accurately measured. From June 2007 to June 2010, 1,590 wind events occurred in which wind velocity was above the threshold of 18.66 m/s. Based upon the sand-transporting capacity of each wind event, the rose diagram for the overall wind regime shows three modes: (1) a dominant mode from the SW that occurred throughout the year but was most common during the spring, (2) a secondary mode from the N-NE during winter during the passage of frontal weather systems during the summer, and (3) a tertiary mode from the S-SE that occurred primarily during the summer months. From brinkline tracing and difference maps made from DEMs for June 2007, June 2008, January 2009, September 2009, and June 2010, the impact of each component of the wind regime upon dune morphology is evident. Winds from the SW cause dune migration to the NE, and dune crestlines are oriented nearly perpendicular to this wind direction. N-NE winds cause along-crest crabbing of dune sinuosity, accompanied by scour along the northern flank of convex-downwind lee-face segments. S-SE winds cause local crestal reversal and scour of the lee face. Idealized dune cross-strata can be constructed based upon the impact of each wind event. However, beginning with an initial dune shape, subsequent dune shapes in the DEM time-series cannot be predicted using the resultant for the period and its incidence angle with the initial brinkline. Differences between the predicted and the actual dune shape becomes greater with increasing time. It is postulated that each wind event alters dune shape, even if only to a small degree, thereby creating a new antecedent boundary condition to be acted upon by the next wind event.

Pedersen, A.; Kocurek, G.

2013-12-01

41

Lowell's Dunes  

NASA Technical Reports Server (NTRS)

9 December 2004 A century ago, the name Percival Lowell and the planet Mars were intimately linked through his popular writings about canals built by intelligent beings on the fourth planet. Today, a crater in the southern hemisphere of Mars is named for Lowell, who usually observed the planet from a hilltop in Flagstaff, Arizona. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image, acquired in October 2004, shows a portion of a sand dune field in western Lowell Crater. The dunes are located near 51.3oS, 82.5oW. The image covers an area about 3 km (1.9 mi) wide and is illuminated by sunlight from the upper left.

2004-01-01

42

International Federation of Red Cross and Red Crescent Societies  

MedlinePLUS

... Sitemap Go to top The International Federation of Red Cross and Red Crescent Societies (IFRC) is the world's largest humanitarian ... member National Societies . As part of the International Red Cross and Red Crescent Movement, our work is ...

43

First Visibility of the Lunar Crescent  

NASA Astrophysics Data System (ADS)

Astronomical observatories are often asked to predict the visibility of the young crescent moon by communities (especially Islamic and Karaite) which use traditional lunar calendars. The SAAO has provided such information for many years, but the early 1990s were a watershed of sorts. Astronomical visibility factors in those years created an unusually severe bias against visibility of the Ramadaan and Shawwall crescents from the southern half of the continent, relative to North Africa and the Mideast (to an extent not seen since the 1860s!). The perplexity caused by the resulting delay in sightings ultimately led to a much greater level of communication between astronomers and the crescent-watching community. The SAAO began collecting, systematizing, and propagating the astronomical information available on the crescent visibility issue, the current results of which are summarized here. Les communauté (spécialement islamiques et karaïtes) qui utilisent les calendriers lunaires traditionnels, demandent souvent aux observatoires astronomiques de prédire le moment oú le croissant de lune naissant devient visible. Depuis de nombreuses années le SAAO fournit cette information, mais les années 1990 furent une sorte de tournant. Dans ces années-là les facteurs de visibilité astronomiques créèrent une déviation exceptionnellement grave par rapport à la visibilité des croissants du Ramadan et du Shawal sur la moitié sud du continent relative à l'Afrique du Nord et au Moyen-Orient (dans une mesure jamais atteinte depuis les années 1860!). La perplexité due au retard qui en résulta dans la vision du nouveau croissant, conduisit finalement à renforcer la communication entre les astronomes et la communauté des observateurs du croissant. Le SAAO commença à collecter, systématiser et diffuser l'information astronomique disponible sur la question de la visibilité du croissant dont nous résumons ici les résultats actuels.

Caldwell, J. A. R.; Laney, C. D.

2000-12-01

44

33 CFR 80.1152 - Crescent City Harbor, CA.  

Code of Federal Regulations, 2010 CFR

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

2010-07-01

45

33 CFR 80.1152 - Crescent City Harbor, CA.  

Code of Federal Regulations, 2011 CFR

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

2011-07-01

46

Cold DUst around NEarby Stars (DUNES). First results. A resolved exo-Kuiper belt around the solar-like star ?2 Ret  

NASA Astrophysics Data System (ADS)

We present the first far-IR observations of the solar-type stars ? Pav, HR 8501, 51 Peg and ?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 ?m fluxes from ? Pav, HR 8501, and 51 Peg agree with the predicted photospheric fluxes, excluding debris disks brighter than Ldust/Lstar 5 × 10-7 (1? level) around those stars. A flattened, disk-like structure with a semi-major axis of 100 AU in size is detected around ?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. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

Eiroa, C.; Fedele, D.; 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.; Arévalo, 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.

2010-07-01

47

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

48

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

49

Movement of Whole Martian Dunes Difficult to Detect or Confirm  

NASA Technical Reports Server (NTRS)

Dunes on Earth move downwind at different speeds depending upon the local wind conditions, the amount of loose sand available to be transported by wind, the shape and volume of the dunes, and overgrowths of vegetation. Typically, smaller dunes move faster than larger dunes. On Earth, some of the fastest-moving dunes that have been measured (e.g., in the deserts of Peru) move 10 to 30 meters (33 to 100 feet) per year. Small dunes usually have an almost crescent-shape to them, and are known to geologists as barchan dunes.

To look for evidence of dune movement on Mars, the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) has been used to re-visit some areas of known barchan dunes--because these types move the fastest--that were observed by the Mariner 9 orbiter in 1972 and the Viking 1 and 2 orbiters between 1976 and 1980. The picture above, left, shows a MOC high-resolution image taken December 25, 1999. The classic, crescentic shape of the dark barchan dunes can be seen in this picture. The steep slopes, also known as the dune slip faces, on these dunes are facing toward the southwest (north is up in both pictures). Thus, the shape of the dunes indicates that they are moving toward the southwest.

The picture above right shows the MOC image from December 1999 superimposed on a Viking 1 image taken May 27, 1978. During the 11 1/2 Mars years that passed between these two dates, it turns out that no difference can be detected in the position of the dunes seen in the MOC image and the Viking image. The earlier Viking image had a resolution of about 17 meters (56 ft) per pixel, while the MOC image had a resolution of about 3.8 meters (12 ft) per pixel. Although it looks like the dunes didn't move between the Viking and MOC images, this observation is limited by the resolution of the Viking image. It is entirely possible that the dunes have moved as much as 17-20 meters (16-66 ft) and one would not be able to tell by comparing the images. As it is, movement of less than 20 meters (66 ft) in 11 martian years (nearly 22 Earth years) is slower than some dunes of similar size and shape on Earth. Thus, it appears that martian dunes are not 'experiencing' the level of activity commonly reported for some of the modern desert dunes found on Earth. The dune field illustrated in these pictures is located in a western Arabia Terra crater at 1.6oN, 351.6oW. Both the Viking and MOC images are illuminated from the left.

2000-01-01

50

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

51

Nearest neighbor analysis of mega-barchanoid dunes, Ar Rub' al Khali, sand sea: The application of geographical indices to the understanding of dune field self-organization, maturity and environmental change  

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 aeolian systems and proposes an index from which to determine the degree of self-organization (maturity) and possibly relative age, across a variety of spatial scales and planetary contexts. This analogue study examines and compares the geography of crescentic megadune

Mark A. Bishop

2010-01-01

52

The vanishing wheat landraces of the Fertile Crescent  

Technology Transfer Automated Retrieval System (TEKTRAN)

Genetic diversity of wheat landraces constituted a sizable portion of the mega diversity in the Fertile Crescent as a center of origin and of diversity of major crop plants. Following wheat domestication in the Fertile Crescent, early farmers developed diverse wheat landraces, and contributed to the...

53

View of chains of star sand dunes in eastern Algeria from Skylab  

NASA Technical Reports Server (NTRS)

A north-looking oblique view of chains of star sand dunes in eastern Algeria (30.0N, 5.0E) as seen from the Skylab space station in Earth orbit. The low sun angle of about 25 degrees above horizontal enhances the detail in this picture. The field of view at the base of the photograph is approximately 200 kilometers (125 miles). The individual dunes are roughly star-shaped rather than simple crescents which are common in dune fields. In this region the stars are aligned along ridges.

1973-01-01

54

Membranous Nephropathy With MPO-ANCA-Associated Crescentic GN  

PubMed Central

Introduction: Antineutrophil cytoplasmic antibodies (ANCA)-associated glomerulonephritis (GN) is characterized by necrotizing and crescentic GN with paucity of immunoglobulin (Ig) and complement deposition, which is also known as pauci-immune crescentic GN. Membranous nephropathy (MN) is characterized by the formation of subepithelial immune deposit with resultant changes in glomerular basement membrane (GBM), most notably spike formation. Case Presentation: A 48-year-old man presented with marked proteinuria, hypoalbuminemia, and renal dysfunction with positive results for myeloperoxidase (MPO) and ANCA. Renal biopsy revealed crescents and thick GBM with subepithelial spikes along with IgG deposition on immunofluorescent staining. The condition was diagnosed as MN with MPO-ANCA-associated crescentic GN. He was treated with intravenous methylprednisolone and cyclophosphamide. After one-month follow-up, antibody level and renal function did not improve. Conclusions: Coexistence of MN with MPO-ANCA crescentic GN is very rare and should be managed aggressively. PMID:25738112

Kanodia, Kamal; Vanikar, Aruna; Patel, Rashmi; Suthar, Kamlesh; Nigam, Lovelesh; Kute, Vivek; Trivedi, Hargovind

2014-01-01

55

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

56

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

57

Lunar Crescent Detection Based on Image Processing Algorithms  

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

58

Lunar Crescent Detection Based on Image Processing Algorithms  

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

59

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

60

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

61

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

62

53. Roanoke Mountain scenic loop road. View of a crescent ...  

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

53. Roanoke Mountain scenic loop road. View of a crescent overlook looking south-southwest. - Blue Ridge Parkway, Between Shenandoah National Park & Great Smoky Mountains, Asheville, Buncombe County, NC

63

Can a Crescent Mars Ever Be Seen from Earth?  

ERIC Educational Resources Information Center

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

Lamb, John F., Jr.

1990-01-01

64

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

65

Windblown Dunes on the Floor of Herschel Impact Basin  

NASA Technical Reports Server (NTRS)

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

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

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

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

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

1998-01-01

66

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

67

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

68

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

69

A circular piezoelectric transformer with crescent shape input electrodes  

Microsoft Academic Search

For most PZT based piezoelectric materials, the shear mode electromechanical coupling constant is twice as large as the transverse mode coupling. In this study, a new disk type piezoelectric transformer was designed. Crescent shape electrodes at the input side and focused poling direction at the output side on a commercially available PZT disk were designed so that the planar and

Burhanettin KOC; Sedat ALKOY; Kenji UCHINO

1999-01-01

70

The complex origins of domesticated crops in the Fertile Crescent  

Microsoft Academic Search

A combination of genetics and archaeology is revealing the complexity of the relationships between crop plants and their wild ancestors. Archaeobotanical studies are showing that acquisition of the full set of traits observed in domesticated cereals was a protracted process, inter- mediate stages being seen at early farming sites throughout the Fertile Crescent. New genetic data are confirming the multiregional

Terence A. Brown; Martin K. Jones; Wayne Powell; Robin G. Allaby

2008-01-01

71

Virulence of Hessian Fly (Diptera: Cecidomyiidae) in the Fertile Crescent  

Technology Transfer Automated Retrieval System (TEKTRAN)

The Hessian fly, Mayetiola destructor (Say), is an important insect pest of wheat (Triticum spp.) in North Africa, North America, South Europe and North Kazakhstan. Similarly to wheat this pest is believed to originate from West Asia in the Fertile Crescent. To determine the virulence of the Hessian...

72

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

73

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

74

Sand dunes as migrating strings.  

PubMed

We develop a reduced complexity model for three-dimensional sand dunes, based on a simplified description of the longitudinal and lateral sand transport. The spatiotemporal evolution of a dune migrating over a nonerodible bed under unidirectional wind is reduced to the dynamics of its crest line, providing a simple framework for the investigation of three-dimensional dunes, such as barchan and transverse dunes. Within this model, we derive analytical solutions for barchan dunes and investigate the stability of a rectilinear transverse dune against lateral fluctuations. We show, in particular, that the latter is unstable only if the lateral transport on the dune slip face prevails over that on the upwind face. We also predict the wavelength and the characteristic time that control the subsequent evolution of an unstable transverse dune into a wavy ridge and the ultimate fragmentation into barchan dunes. PMID:23767529

Guignier, L; Niiya, H; Nishimori, H; Lague, D; Valance, A

2013-05-01

75

Vulnerability and fate of a coastal sand dune complex, Rosetta-Idku, northwestern Nile Delta, Egypt  

NASA Astrophysics Data System (ADS)

Types, distribution, and origin of recent sand dunes between Rosetta and Idku, in the western sector of the Nile Delta, Egypt were investigated. Sand samples from the dunes, beach, and seafloor were studied for grain size distribution and mineralogical composition. It has been found that most of the dunes in the study area have been subjected to deterioration and removal due to the construction of buildings and the International Coastal Highway. The remnant constitutes a damaged belt of foredunes that extends from El Bouseily village to the west of Idku town. The dune’s origin is interpreted to be the result of coastal drifting and the subsequent transport of sediments of the former Canopic Nile branch eastward by the predominant longshore current and by aeolian processes. The blown sand grains accumulated to form a belt of coastal sand dunes of original longitudinal and crescentic forms. Urbanization of the coast has severely altered the landscape. The study area is considered vulnerable to the impacts of climate change and the expected rise in sea level. The outcome of potential sea level rise is serious; erosion problems are expected to be exacerbated and vast areas from land and property would be lost. Thus, protection and preservation the remaining dunes in the study area are vital requirements for shore protection.

El Banna, Mahmoud M.

2008-05-01

76

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

77

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

78

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.

79

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

80

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

81

Imperial Sand Dunes  

NSDL National Science Digital Library

The Bureau of Land Management presents the current news, projects, and the geologic and cultural history of the Imperial Sand Dunes at this website. Users can easily search through an abundance of remarkable images of dunes as well as other Californian landscapes. The website offers links to the current rules, regulations, and management plans. Individuals, who will be traveling to the area, can find the weather forecast, an events calendar, and information on volunteering. Visitors can locate archives of Federal Register Notices as well as news releases.

82

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.

83

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

84

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

85

Pauci-immune crescentic glomerulonephritis in the Down's syndrome.  

PubMed

Kidney disease is a rare complication in patients with the Down's syndrome. However, with increased survival, it appears that a growing number of these patients present with glomerulonephritis. Most cases have been reported as case reports and include lesions such as mesangiocapillary glomerulonephritis with hypo-complementemia, crescentic glomerulonephritis with anti-neutrophil cytoplasmic antibodies (ANCA), amyloidosis and immunotactoid glomerulopathy. We report the observation of a 38-year-old man with the Down's syndrome who presented with severe renal failure, proteinuria and microscopic hematuria evolving over two months. There was no history of congenital heart disease or urinary symptoms. Percutaneous renal biopsy revealed fibrous crescents, rupture of Bowman's capsule and peri-glomerular granuloma; there were no deposits on immunofluorescence study. Thoracic computerized tomography scan showed alveolar congestion. The patient tested negative for ANCA. At the time of reporting, the patient is on regular chronic hemodialysis. Our case illustrates a distinct entity that further expands the spectrum of renal disease known to occur in the Down's syndrome. Early detection of the renal disorders may prevent or slow down the progression. PMID:24231490

Cherif, Mejda; Hedri, Hafedh; Ounissi, Mondher; Gergah, Taher; Goucha, Rim; Barbouch, Samia; Abderrahim, Ezzedine; Maiz, Hedi Ben; Kheder, Adel

2013-11-01

86

Martian Dune Field  

NASA Technical Reports Server (NTRS)

This spectacular picture of the Martian landscape by the Viking 1 Lander shows a dune field with features remarkably similar to many seen in the deserts of Earth. The dramatic early morning lighting - 7:30 a.m. local Mars time--reveals subtle details and shading. Taken yesterday (August 3) by the Lander s camera #1, the picture covers 100 , looking northeast at left and southeast at right. Viking scientists have studied areas very much like the one in this view in Mexico and in California (Kelso, Death Valley, Yuma). The sharp dune crests indicate the most recent wind storms capable of moving sand over the dunes in the general direction from upper left to lower right. Small deposits downwind of rocks also indicate this wind direction. Large boulder at left is about eight meters (25 feet) from the spacecraft and measures about one by three meters (3 by 10 feet). The meteorology boom, which supports Viking s miniature weather station, cuts through the picture s center. The sun rose two hours earlier and is about 30 above the horizon near the center of the picture.

1976-01-01

87

Arbuscular Mycorrhizas in Coastal Dunes  

Microsoft Academic Search

Sand dune systems are among the best studied of primary successional sites and have attracted the attention of plant ecologists\\u000a for over a century (Cowles 1899). Surprisingly, the traditional explanation of dune succession overlooks the critical contribution\\u000a of mutualistic fungi that facilitate the invasion of barren areas. In fact, many of the dominant, dune-building plants appear\\u000a to be incapable of

R. Koske; J. Gemma; L. Corkidi; C. Sigüenza; E. Rincón

88

Mars Digital Dune Database  

NASA Astrophysics Data System (ADS)

Currently, there is no comprehensive, global, digital database for dune deposits on Mars. The advent of a series of successful Mars missions, coupled with advances in technology enabling a significant increase in instrument resolution, have provided a large compilation of data covering a wide range of wavelengths for the Martian surface. Given the recent availability of high-resolution data and detailed surficial information returned from orbital and rover missions, it is critical that we update the Mars global information base by creating a digital database of dune deposits that includes this new influx of data. As of spring 2004, the Thermal Emission Imaging System (THEMIS) infrared (IR) coverage of the surface of Mars was 98% for nighttime and 75% for daytime acquired images, forming a data set of global coverage at a resolution not previously possible. The combination of high-resolution and global coverage makes the THEMIS IR data set the logical choice for a planet wide inventory of dune deposits. Data sets of a global scale like those of Mars Orbiter Laser Altimeter (MOLA) and Thermal Emission Spectrometer (TES) will enable rapid and contiguous comparisons with the dune database. Other imagery like that of Mars Orbiter Camera (MOC) will provide very high-resolution, localized visual data for accurate interpretations of morphological characterizations. The dune database will provide researchers with an extensive, comprehensive and stable database for use in a wide-array of global studies. The database will also offer researchers a centralized depository for updating physical parameters with newly validated findings. The initial construction of the database is based upon dune forms or deposits identified, classified and digitized using only THEMIS IR images. These digitized polygons are converted from THEMIS image coordinates to ARCMAP aerographical coordinates, allowing delineation of areal extent of the deposits and preserving relevant THEMIS image information such as Ls, local time, and sun azimuth/angle. The ARCMAP polygons will also retain reference to all THEMIS IR images used in their construction. Where available, THEMIS VIS and/or MOC images will be used to confirm, modify or refine original classifications. In addition to providing an improved resolution for features below the IR image threshold, this secondary examination will also provide a list of cross-referenced THEMIS VIS and MOC images for future investigations. Physical parameters such as wind direction based on slip-face geometry, dune wavelength, elevation, and volume of the deposits will be incorporated into the database on a priority-based schedule. In addition to THEMIS VIS and MOC images, supplemental data sets, such as TES and others, will be used where available to further refine and/or validate existing data on global wind patterns, sediment transport, sources and sinks, and stratigraphic units.

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

2004-12-01

89

Mononuclear cell activation and decreased renal function in IgA nephropathy with crescents  

Microsoft Academic Search

Mononuclear cell activation and decreased renal function in IgA nephropathy with crescents. Our previous immunohistologic studies with monoclonal antibodies (mAb) showed that glomerular and interstitial accumulations of mononuclear cells (MNC) were common features of many types of proliferative glomerulonephritis, especially crescentic glomerulonephritis. The current study examined a series of patients with crescentic IgA disease, since IgA disease in general has

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

1990-01-01

90

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

91

The Golden Crescent: Crossroads of Florida and Georgia  

NSDL National Science Digital Library

Developed by the National Park Service, this site explores the geography and history of "the Golden Crescent," a wide swath of land "along the Atlantic Coast from Savannah to Cape Canaveral and inland towards Tallahassee." The site provides discussion of several "cultural themes" of particular significance to the region, including the mounds and rings left on the landscape by prehistoric peoples, the struggle between colonial empires for control of the territory, the role of Plantation Agriculture, the impact and history of African-Americans, and the region's history as a resort for wealthy tycoons of the gilded age. A Map Room also allows users to locate and read brief descriptions, including travel information, of the National Park sites that coincide with these themes.

92

Sand Furrows: A new surface feature on martian dunes  

NASA Astrophysics Data System (ADS)

Planetary geomorphology is at the forefront of today's Geoscience endeavours. A characteristic of frontier science is the discovery of new landforms and processes. Sand furrows are a new geomorphic feature that has not been previously described. They are ubiquitous and occur on 95% of polar dune images. Furrows are shallow and narrow erosion forms which can extend up to 300 m along a dune surface. Patterns are reminiscent of fluid flow, perhaps even fluvial flow (e.g., sinuosity, braiding and anastomosing) and are often slope-normal. However, furrows also display attributes that defy gravity (e.g., upslope trending flow paths) and they are not associated with terminal deposits. This suggests that the formative fluid is likely to be a pressurised gas. Cryo-venting has been proposed to explain the formation of dark spots and fans in the seasonal ice cap. It has also been linked to the formation of araniform. Here it is proposed to be the process by which aeolian sediment is eroded to form sand furrows. During the Martian spring, basal sublimation of the seasonal CO2 ice cap occurs on dune surfaces. Weaknesses in the ice allow pressurised gas and some dune sediment to be transported through vents to the surface. Furrows are eroded along the gas flow paths as it moves towards the vent. Cryo-venting is therefore identified as a new style of sediment transport on aeolian dunes in our solar system, and one that is, so far, unique to Mars. An estimate of the sand volume eroded from a sample dune during one Mars' spring is geomorphologically significant and is equivalent to that of a small dome dune on Mars (500m^3). The deposits are diffuse and extend into the interdune as well as back onto the source dune. The geomorphic efficacy of cryo-venting as a mechanism of aeolian dune erosion is dependent on the magnitude and frequency of venting, the location of vents and the scale of the source dune. Small dunes may undergo accelerated erosion rates as the ability to intersect vented sediment is reduced by a small surface area.

Bourke, Mary

2013-04-01

93

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

94

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

95

Martian Dunes in Infrared  

NASA Technical Reports Server (NTRS)

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

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

2002-01-01

96

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

97

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

98

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

99

Historical Note/ David Deming, History Editor Crescent Moon Spring: A Disappearing Natural  

E-print Network

Historical Note/ David Deming, History Editor Crescent Moon Spring: A Disappearing Natural Wonder to the shape of the spring, or more precisely, the pond fed by the spring water, which resembles a crescent moon (Figure 1). Currently, the pond is about 200 m long in an east-west direction and about 50 m wide

Jiao, Jiu Jimmy

100

Arabian Nights in America: Hybrid Form and Identity in Diana Abu-Jaber's Crescent  

Microsoft Academic Search

Diana Abu-Jaber's 2003 novel, Crescent, examines the complex position of Arabs and Arab Americans living in the United States with respect to notions of identity by creating a complex hybrid text. Crescent offers characters who face different forms of exile and have to work through fractured, destabilized identities to create for themselves new identities that account for and embrace their

Magali Cornier Michael

2011-01-01

101

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 2010 Available online 29 April 2010 Keywords: Aeolian Dune Mars Venus Titan Earth Aeolian dune fields of planetary dune systems comes from the application of Earth analogs, wind tunnel experiments and modeling

Bourke, Mary C.

102

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

103

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

104

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

2013-09-30

105

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

106

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

107

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

108

Global map of Titan's dune fields  

NASA Astrophysics Data System (ADS)

Introduction Methane is the second major constituent of Titan's atmosphere; but it should be totally removed at least in ten million years by photochemistry in the stratosphere and condensation in the troposphere [1]. The first process produces hydrocarbons which form the haze and can condensate onto the surface. The second process causes methane rains on the surface, which carve channels networks. The loss of methane is possibly balanced by outgassing during cryovolcanic event [2]. But hydrocarbons grains deposited onto the surface cannot be recycled. They may be stored in the dunes [3], which were first seen by SAR (Synthetic Aperture Radar) [4]. We focus our study on the mapping of the dune fields in order to determine their global distribution. The aim is to constrain the amount of hydrocarbon material existing in the dunes, and to relate it to the duration of the methane cycle. Data from the Visual and Infrared Mapping Spectrometer (VIMS) and RADAR instruments onboard Cassini spacecraft can be used to map Titan's surface. Infrared images, which are mainly sensitive to composition and grain size, are very complementary to the microwave measurements which depend mainly on roughness and topography. We used spectral criteria after empirical correction of aerosols to map the distribution of heterogeneous units on Titan [5]. These units are compared with SAR images in overlapping regions. Titan's surface mosaics with VIMS VIMS probes the first ten of microns of the ground in seven narrow atmospheric windows in the 0.88 to 5.11 ?m wavelength range. We built infrared mosaics with cubes sorted by spatial resolution, by keeping cubes corresponding to favorable observing conditions (incidence, emergence, phase and time exposure). Band ratios were computed and combined in false color composite images (red as 1.59/1.27-?m, green as 2.03/1.27-?m and blue as 1.27/1.08-?m). Band ratios are useful to minimize the effect of illuminating conditions and albedo variations [6]. Mosaics of Titan's surface were created using images acquired during 42 flybys from Ta (October 26th 2004) to T42 (March 25th 2008). These images have been integrated into a Geographic Information System (GIS). Global maps of band ratios appear fuzzy at high latitudes due to a low spatial resolution and to the presence of haze and clouds. The unfavorable observing geometry, with high incidence angles, induces a very strong scattering by the aerosols in these regions. On the contrary, equatorial and mid-latitudes regions have been covered at a medium resolution, in better observing conditions. In our color composites, most of Titan surface appears either in brown units, bluish units or bright units. We observed that brown units cover 18% of the whole Titan's surface and are found in equatorial regions. Dark blue units cover roughly 2% of Titan's surface. They are systematically associated with bright terrains and are never found isolated within brown units (Fig. 1a). Dune patterns were first observed in the infrared with VIMS during the closest approach at T4 and T20 flybys [7, 8]. The detailed study of dune fields by [8] shows that dune patterns are found mainly in brown units and interdunes can account for the observed spectral variability. Dunes with Radar SAR dataset We also use the RADAR data in SAR mode, mainly sensitive to roughness, surface topography and dielectric constant variations. It is independent of solar light conditions and of the presence of clouds. We retrieved the radar swaths from Ta to T25 (February 22nd 2007) flybys from the PDS website and reprojected the data using the ISIS2 software. The spatial resolution of the SAR images allows the direct imaging of the dunes. Most of Titan's dunes appear longitudinal and resemble terrestrial dunes, such as the ones found in Namibia [4]. Detailed morphologic analysis was performed in [9], who inferred a dominant wind eastward to account for their formation. Two kinds of dunes have been observed: sand seas and small dunes in low sand supply zones. Most of the aeolian sand deposits are found in sand

Le Corre, L.; Le Mouélic, S.; Sotin, C.; Barnes, J. W.; Brown, R. H.; Baines, K.; Buratti, B.; Clark, R.; Nicholson, P.

2008-09-01

109

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

110

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

111

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

112

Diario Financiero Conferencias y Formacin San Crescente 81, piso 5 Las Condes Metro El Golf Santiago  

E-print Network

Auspician: Diario Financiero Conferencias y Formación San Crescente 81, piso 5 · Las Condes · Metro Diario Financiero. $220.000 Público general. Pases corporativos por inscripciones de más de 5 asistentes

Rudnick, Hugh

113

The evolution of large scale crescentic bars on the northern Gulf of Mexico coast  

Microsoft Academic Search

Airborne bathymetric lidar is used to quantify the properties and evolution of kilometer-scale crescentic bars in the northern Gulf of Mexico between 86.0°W and 86.5°W, a distance of 50km. Repeated lidar surveys in 2004 pre-and-post-Hurricane Ivan, in July 2005 after Hurricane Dennis, and in late 2005 after Hurricane Katrina, in addition to several satellite images, show crescentic bar growth over

Rumana Reaz Arifin; Andrew B. Kennedy

2011-01-01

114

Evaluation of the ameliorative effects of immunosuppressants on crescentic glomerulonephritis in SCG\\/Kj mice  

Microsoft Academic Search

The therapeutic efficacy of immunosuppressants for treating rapidly progressive glomerulonephritis (RPGN) with crescent formation remains controversial. SCG\\/Kj mice spontaneously develop RPGN-like symptoms, characteristic of crescentic glomerulonephritis and systemic small vessel vasculitis, associated with the presence of anti-neutrophil cytoplasmic antibodies (ANCA). We evaluated the “ameliorative”, not prophylactic, effects of immunosuppressive agents, deoxyspergualin (DSG), cyclophosphamide (CYC) and prednisolone (PDN), on RPGN in

Kan Saiga; Minako Yoshida; Iwao Nakamura; Eriko Toyoda; Kazuhiro Tokunaka; Hirohisa Morohashi; Fuminori Abe; Kyuichi Nemoto; Masato Nose

2008-01-01

115

[A systematic analysis of the Ottoman Red Crescent periodical (part II)].  

PubMed

Founded in 1877, the Ottoman Red Crescent Society rendered a lot of important services in military and civil areas in the Ottoman Empire. The Ottoman Red Crescent Society not only gave health services for the soldiers, but it also attempted to obey the international acts signed for the captives and to rescue them together with the countries involved under the supervision of the international Red Cross. In the civilian area, the Ottoman Red Crescent Society also played an active role to meet the casualties' needs, such as food, clothes, and accommodation following natural disasters like earthquake, flood, fire etc. Ottoman Red Crescent Society published a monthly newsletter called Osmanli Hilâl-i Ahmer Mecmuasi to announce its services more effectively to the public since 15 September 1921 (12 Muharrem 1340). The publication of the newsletter continued as Türkiye Hilâl-i Ahmer Mecmuasi after the 15th issue. Starting with the 85th issue on September 15th, 1928 (30 Rebiülevvel 1347) it was printed with Latin alphabet instead of Arabic letters. A brief translation in French and in English exist in the end of each issue. In the second part of this research, news about the Red Crescent Society's organization; financial supports for the Society and, in return, material and financial aids by she Society; local organizations providing aid to the Society; money collected during Bairams; plays and balls arranged by the Society; and the activities of the womens' branch of the Red Crescent Society, are introduced. PMID:14570020

Okutan, Y

2001-01-01

116

Channels on Dunes in Russell Crater  

NASA Technical Reports Server (NTRS)

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

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

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

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

2006-01-01

117

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

118

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

119

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.

Iowa Public Television. Explore More Project

2004-01-01

120

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

121

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

122

[A systematic analysis of the Ottoman Red Crescent periodical (Part III)].  

PubMed

Founded in 1877, the Ottoman Red Crescent Society rendered a lot of important services in military and civil areas in the Ottoman Empire. The Ottoman Red Crescent Society not only gave health services for the soldiers, but it also attempted to obey the international acts signed for the war captives and to rescue them together with the countries involved under the supervision of the international Red Cross. In the civilian area, the Ottoman Red Crescent Society also played an active role to meet the casualties' needs, such as food, clothes, and accommodation following natural disasters like earthquake, flood, fire etc. The Ottoman Red Crescent Society published a monthly newsletter called Osmanli Hilâl-i Ahmer Mecmuasi to announce its services more effectively to the public since 15 September 1921 (12 Muharrem 1340). The publication of the newsletter continued as Türkiye Hilâl-i Ahmer Mecmuas' after the 15th issue. Starting with the 85th issue on September 15th, 1928 (30 Rebiülevvel 1347) it was printed with Latin alphabet instead of Arabic letters. A brief translation in French and in English exist in the end of each issue. In the second part of this research, news about the Red Crescent Society's organization; financial supports for the Society and, in return, material and financial aids by the Society; local organizations providing aid to the Society; money collected during Bairams; plays and balls arranged by the Society; and the activities of the womens' branch of the Red Crescent Society, are introduced. The third and last part of the study deals with the comments of visitors about the Red Crescent Society; and news and activities of the European Red Cross Societies. PMID:17152156

Okutan, Yahya

2002-01-01

123

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

124

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

125

Mean residence time in barchan dunes  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

126

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

2008-10-27

127

[Fertilization and development of axolotl oocytes with already grey crescent experimentally formed during their maturation].  

PubMed

Pigmented axolotl coelomic oocytes were induced to form a gray crescent by simultaneous action of a gravity vector and of a heat-shock (36 +/- 0.5 degree C during 10-15 min), according to a previously described method. Those oocytes were subsequently reintroduced into the coelomic cavity of an albino recipient female, which had been previously inseminated. Among fertilized treated oocytes, more than 75% developed into embryos whose dorsal side corresponded to the gray crescent-forming area of the oocyte. It is known that in normally fertilized control eggs, a gray crescent forms just prior to the first cleavage and corresponds in most cases to the dorsal side of the future embryo. Therefore, our results strongly suggest that fertilization is not a primary compulsory step towards effective determination of the future dorsal area in an Amphibian egg, since the required cytoplasmic rearrangements can be elicited much earlier in a maturing oocyte and remain effective during subsequent development. PMID:8044696

Beetschen, J C; Daguzan, C

1993-08-01

128

Timing of frost deposition on Martian dunes: A clue to properties of dune particles?  

NASA Technical Reports Server (NTRS)

Scans were made across the Martian dunes found in images taken at several different times to determine the time history of the dune albedo. Atmospheric contributions were estimated using optical depth data and the brightness of shadows in some images. The data show that the dunes brighten very substantially between L(s) = 10 and 40 deg, depending on the latitude. Bright coverings on dunes form outliers 1 to 5 deg north of the cap edge. Formation of the general cap then sometimes reverses the contrast of the dune field with the surrounding area. Causes for the early deposition of frost on dunes relative to surroundings are discussed.

Thomas, P.

1987-01-01

129

Singing-sand avalanches without dunes  

NASA Astrophysics Data System (ADS)

Singing-sand dunes have attracted curiosity for centuries and are now the subject of controversy. We address here two aspects of this controversy: first the possible link between the frequency heard and the shear rate (for a gravity avalanche on a dune slip-face, scaling as 0.4g/d, with d the ‘mean’ grain diameter), and second, the assumed necessity of a layered dune structure under the avalanche that acts as a resonator. Field recordings of singing dunes over the world reveal that they can present very different spectral characteristics: a dune with polydisperse grains produces a very broad and noisy spectrum, while a dune with sorted grains produces a well-defined frequency. Performing laboratory avalanches on a hard plate with singing-dune sand shows that there is no need for a dune below the sand avalanche to produce the singing sound, and a fortiori neither for the dune's layered structure nor for its particular sound transmission. By sieving the polydisperse grains, the same well-defined frequency is obtained to that of the dune with sorted grains, with the same diameter-frequency relation. The various frequencies heard in the field avalanches match the shear rates not calculated from the average size, but from the various peaks of the grain size distributions.

Dagois-Bohy, S.; Courrech du Pont, S.; Douady, S.

2012-10-01

130

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

2011-05-19

131

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

132

75 FR 70917 - Environmental Impacts Statements; Notice Of Availability  

Federal Register 2010, 2011, 2012, 2013, 2014

...No. 20100444, Final EIS, BLM, NV, Tonopah Solar Energy Crescent Dunes Solar Energy Project, a 7,680-Acre Right-of-Way (ROW) on Public Lands to Construct a Concentrated Solar Thermal Power Plant Facility, Nye County, NV, Wait...

2010-11-19

133

76 FR 7844 - Environmental Impacts Statements; Notice of Availability  

Federal Register 2010, 2011, 2012, 2013, 2014

...No. 20100444, Final EIS, BLM, NV, Tonopah Solar Energy Crescent Dunes Solar Energy Project, a 7,680-Acre Right-of-Way (ROW) on Public Lands to Construct a Concentrated Solar Thermal Power Plant Facility, Nye County, NV,...

2011-02-11

134

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

135

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

136

Strategies to restore fragmented meta-populations of Fertile Crescent wheat landraces  

Technology Transfer Automated Retrieval System (TEKTRAN)

Historically, farmers in the Fertile Crescent (FC) planted diverse assemblages of genotypes (i.e., landraces, LRs) to lower the risk of failure and increase food security because they had limited capacity to control the spatially heterogeneous and temporally unpredictable environment of the FC with ...

137

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

138

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

139

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

PubMed Central

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

Chui, Toco YP; Zhong, Zhangyi; Burns, Stephen A

2011-01-01

140

Ancients' Criterion of Earliest Visibility of the Lunar Crescent - how Good is it  

Microsoft Academic Search

Earliest visibility of the lunar crescent is an important calendrical element. It was needed in all early calendars and remains in use on some lunar calendars today. An astronomical criterion of earliest lunar visibility was therefore evolved quite early, using observations, right from the Babylonian era. Recently, an improved and comprehensive global criterion of earliest visibility, developed by the author,

M. Ilyas

1987-01-01

141

Babylonian Calendar for 20002019 First appearances of the lunar crescent in Babylon computed for 20002019  

E-print Network

1 Babylonian Calendar for 2000­2019 First appearances of the lunar crescent in Babylon computed for 2000­2019 and the equivalent Babylonian dates expressed in the continued Seleucid calendar Mathieu Gregorian calendar date sunset Local Time at Babylon [hr:min] NA1 time from sunset to moonset [time degrees

Ossendrijver, Mathieu

142

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

143

Reorientation Timescales and Pattern Dynamics for Titan's Dunes: Does the Tail Wag the Dog or the Dragon?  

NASA Astrophysics Data System (ADS)

Fields of bedform patterns persist across many orders of magnitude, from cm-scale sub-aqueous current ripples to km-scale aeolian dunes, and form with surprisingly little difference in expression despite a range of formative environments. Because of the remarkable similarity among bedform patterns, extracting information about climate and environment from these patterns is a challenge. For example, crestline orientation is not diagnostic of a particular flow regime; similar patterns form under many different flow configurations. On Titan, these challenges have played out with many attempts to reconcile dune crestline orientation with modeled and expected wind regimes. We propose that thinking about the time-scale of the change in dune orientation, rather than the orientation itself, can provide new insights on the long-term stability of the dune-field patterns and the formative wind regime. In this work, we apply the crestline re-orientation model developed by Werner and Kocurek [Geology, 1997] to the equatorial dune fields of Titan. We use Cassini Synthetic Aperture Radar images processed through a de-noising algorithm recently developed by Lucas et al. [LPSC, 2012] to measure variations in pattern parameters (crest spacing, crest length and defect density, which is the number of defect pairs per total crest length) both within and between Titan's dune fields to describe pattern maturity and identify areas where changes in dune orientation are likely to occur (or may already be occurring). Measured defect densities are similar to Earth's largest linear dune fields, such as the Namib Sand Sea and the Simpson Desert. We use measured defect densities in the Werner and Kocurek model to estimate crestline reorientation rates. We find reorientation timescales varying from ten to a hundred thousand times the average migration timescale (time to migrate a bedform one meter, ~1 Titan year according to Tokano (Aeolian Research, 2010)). Well-organized patterns have the longest reorientation time scales (~105 migration timescales), while the topographically or spatially isolated patches of dunes show the shortest reorientation times (~103 migration timescales). In addition, comparisons between spacing and defect density reveal that the well-organized patterns plot along an expected trend with Earth and Mars' largest, well-organized fields. Patterns on Earth and Mars that have been degraded and broken by environmental change fall off this trend and similarly, so do the isolated dune patterns on Titan fall suggesting changing environmental conditions such as wind regime and/or sediment availability have influenced the dunes on Titan. Crestline orientations in these areas suggest star and crescentic (barchans) morphologies in addition to linear dunes. Our results suggest that Titan's dunes may react to gross bedform transport averaged over orbital timescales, relaxing the requirement that a single modern wind regime is necessary to produce the observed well-organized dune patterns. We find signals of environmental change within the smallest patterns suggesting that the dunes may be recently reoriented or are reorienting to one component of a longer timescale wind regime with a duty cycle that persists over many seasonal cycles.

Ewing, R. C.; Hayes, A. G.; McCormick, C.; Ballard, C.; Troy, S. A.

2012-04-01

144

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

145

Modle statique d'une PEMFC en vue d'une application au Elodie Lechartier  

E-print Network

Modèle statique d'une PEMFC en vue d'une application au pronostic. Elodie Lechartier FEMTO en vue d'une application au pronostic de pile PEMFC, un modèle de comportement obtenu grâce à une to experimental data. MOTS-CLES ­ PEMFC, PHM, modèle, statique. 1. Introduction Dans le contexte actuel où le

Paris-Sud XI, Université de

146

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

NASA Astrophysics Data System (ADS)

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

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

2009-12-01

147

Expanded Geochemical Analysis of the Eocene Crescent Formation, Olympic Peninsula, Washington  

NASA Astrophysics Data System (ADS)

The Coast Range Volcanic Province (Siletzia) of Washington and Oregon formed adjacent to western North America in the early Eocene, and consists of an estimated 250,000 km3 of predominantly tholeiitic flows. In the Crescent Formation, which is locally divided into a submarine lower member and a subaerial upper member, this basaltic flow sequence reaches stratigraphic thicknesses of up to 16 km. A consensus has yet to be reached on the origin of this Large Igneous Province (LIP); proposed mechanisms include slab windows, margin-parallel rifting, and the action of the Yellowstone hotspot. Outcrop evidence for shallow-water depositional environments in the Lower Crescent argues against the member's origin as an abducted portion of oceanic crust, as has also been proposed, and further supports the widely held view that the Upper and Lower Crescent members together represent a nearly continuous eruptive sequence. Rare Earth Element plots for both members display three distinct trends that suggest high and low degrees of both mantle partial melting and fractional crystallization. We also present here what we believe are the first isotopic values for the Lower Crescent (0.512941<143Nd/144Nd<0.512997, 0.703287<87Sr/86Sr<0.703678, 18.907<206Pb/204Pb<19.240, 15.599<207Pb/204Pb<15.661, 38.521<208Pb/204Pb<39.034), which are similar to previous isotopic data collected for the Upper Crescent and suggest a plume component in the mantle source for these rocks.

Haileab, B.; Denny, A.; Harrison, B. K.

2012-12-01

148

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

149

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

150

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

NASA Astrophysics Data System (ADS)

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

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

151

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

152

Great Sand Dunes National Monument and Preserve  

E-print Network

inventory program, the National Park Service (NPS) contracted the Colorado Natural Heritage Program (CNHPGreat Sand Dunes National Monument and Preserve 2003 Vascular Plant Inventory Susan Spackman) in 2001-2004 to conduct a field inventory of vascular plants of Great Sand Dunes National Monument

153

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...

154

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 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 to be the same ...

155

On the dynamics of cartoon dunes  

NASA Astrophysics Data System (ADS)

The spatio-temporal evolution of a downsized model for a barchan dune is investigated experimentally in a narrow water flow channel. We observe a rapid transition from the initial configuration to a steady-state dune with constant mass, shape, velocity, and packing fraction. The development towards the dune attractor is shown on the basis of four different starting configurations. The shape of the attractor exhibits all characteristic features of barchan dunes found in nature, namely a gently inclined windward (upstream) side, crest, brink, and steep lee (downstream) side. The migration velocity is reciprocal to the length of the dune and reciprocal to the square root of the value of its mass. The velocity scaling and the shape of the barchan dune is independent of the particle diameter. For small dunes we find significant deviations from a fixed height-length aspect ratio. Moreover, a particle tracking method reveals that the migration speed of the model dune is one order of magnitude slower than that of the individual particles. In particular, the erosion rate consists of comparable contributions from low energy (creeping) and high energy (saltating) particles. Finally, it is shown that the velocity field of the saltating particles is comparable to the velocity field of the driving fluid.

Groh, Christopher; Rehberg, Ingo; Kruelle, Christof A.

2010-03-01

156

Valles Marineris dune sediment provenance and pathways  

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

157

Reversible acquired tracheobronchomalacia of a combined crescent type and saber-sheath type  

Microsoft Academic Search

A case of tracheobronchomalacia (TBM) in a 71-year-old woman, who had suffered a cough syncope, is reported. It was a combination of both the crescent type (the posterior membranous portion of trachea or bronchus protrudes into the lumen) and the saber-sheath type (the lateral cartilaginous wall of trachea or bronchus protrudes into the lumen). In this patient, acute bronchitis had

Hitoshi Imaizumi; Masamitsu Kaneko; Kazuhisa Mori; Kyoko Yamada; Koji Asakura; Mitsuharu Tamagawa

1995-01-01

158

Design of a Circular Piezoelectric Transformer with Crescent-Shaped Input Electrodes  

Microsoft Academic Search

In this study, a new disk-type piezoelectric transformer design is proposed. The input side of the transformer has a crescent-shaped electrode and the output side has a focused poling direction. The electrodes and poling directions on commercially available piezoelectric ceramic disks were designed so that the planar or shear mode coupling factor (kp or k15) becomes effective rather than the

Burhanettin Koc; Yongkang Gao; Kenji Uchino

2003-01-01

159

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

Microsoft Academic Search

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

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

2003-01-01

160

A GIS Representation of 1964 Tsunami Damage in Crescent City, California  

NASA Astrophysics Data System (ADS)

The March 1964 Alaska tsunami caused major damage in Alaska and also impacted the west coast of North America. Crescent City, California, 3000 km away from the source region, suffered the greatest damage outside Alaska. Twenty-nine blocks of the downtown and harbor areas were inundated and nearly 300 homes and businesses damaged or destroyed. In the aftermath of the tsunami, numerous maps, reports and photographs of the impacts in Crescent City were released, some by engineers and scientists, and much by individuals and the popular press. The Del Norte Historical Society has a large amount of archival material (photographs and eye witness accounts) from the tsunami, much of which has never been thoroughly examined or correlated with other reports. In this study, we assemble all of the available information from these disparate sources into a GIS framework in order to examine the 1964 Crescent City damage in a systematic way and provide a quantitative framework for others who are modeling tsunami impacts. Using ArcGIS 10, old aerial photos, tsunami inundation maps, and photographs were georeferenced to produce GIS layers of 'before and after' Crescent City. Hyperlinks were created to connect photos with their locations in present day. We reference damage to a layer showing Magoon's 1968 map of inundation depth and extent. Structural damage falls into four main groupings: structures floated off of foundations, damage by impact from debris, pressure differences from water infilling structures, and fire. 15 structures were moved off of foundations, all in the direction of the outgoing flow. We also create layers of the structures of the modern city and the predicted tsunami run-up from a Cascadia event. Magoon, Orville T., 1966, Structural Damage by Tsunamis, Proceedings, American Society Civil Engineers, Specialty Conference on Coastal Engineering, Santa Barbara (California), Oct. 1965, pp. 35-68

Velasco Campos, C. J.; Dengler, L. A.

2013-12-01

161

Vegetated linear dunes - chronologically discontinuous archives of several short-term and major dune growth episodes  

NASA Astrophysics Data System (ADS)

Quartz sand dunes cover massive areas defined as arid, making them a potentially important archive of past climates and environments. But, dunes, being highly dynamic and relatively uniform in sedimentological composition, often compromise this potential. Most inland dunes are of the linear type that has a sinuous planar shape. Linear dunes, also associated with active seif dunes, are elongated by oblique cross-(dune) crest deflection of sand grains due to acutely bimodal sand-transporting winds. This prevents formation of long-term and stratigraphically continuous internal dune structure (though fully exposed internal linear dune structures to support this conclusion are rarely found). Therefore, dating of the dune sand by luminescence methods is mainly restricted to the last (re)mobilization phase and cannot track earlier dune growth history. Vegetated linear dunes (VLDs), mainly found in low-latitudes, are characterized by a straight planar shape and a partial shrub cover, and have been proposed to comprise an independent dune type. The stratigraphic cross-section of the VLD includes a sequence of chronologically discontinuous sand units forming the dune core. The accumulation of the units is generally interpreted to pertain to major episodes of strong wind power when sand was available. Possible minor events of sand accumulation are presumed to have been erased by major episodes. The units, often structureless and of similar sedimentological properties can only be discerned by luminescence dating as contacts between units do not necessarily imply chronological boundaries. The VLD core is overlaid by a mantle of sand that while being intermittently morphologically and structurally configured by seasonal winds to depths of several meters, preserves the dune core stratigraphy. Therefore, in a sense, the VLD is a prominent sedimentary body archiving influential short-time and possibly extreme events. Based upon exposed dune stratigraphy, ground-penetrating radar profiling and morphologic analysis, coupled with spatial dense optically stimulated luminescence (OSL) dated full dune cores, the VLD core structure is found to repeat itself in the northwestern Negev (Israel) dunefield, for three time orders, each representing different palaeoclimatic and palaeoenvironmental conditions. Accordingly, a full dune core coring strategy for retrieving luminescence ages which date the major VLD core units is required for adequately dating a vegetated linear dunefield. Exposed sections of VLD cores that reveal the full dune core structure are very important for such dating strategies. The VLD type is suggested to inherently comprise a distinct archive of unique past conditions, mainly since the last glacial. However, further study is required for robust palaeoclimatic interpretation of these archives.

Roskin, Joel

2013-04-01

162

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

163

Dunes  

E-print Network

like a mass of red tapeworms than a bouquet. "Momma and Mr. Tom are your parents." REED/ 4 3 Lizzy was always saying things like that, like Momma wasn't her real mom, even though we have pictures of Momma in the hospital when Lizzy was born. I... protecting you from a stranger who has already seen you naked. I decide that it was probably a man who invented the exam bed, with its metal legs jutting out to the sides, promising cold dis-comfort. Robert smiles the way he does when he wants to have sex...

Reed, Michelle

2006-01-01

164

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

165

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

166

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

167

Laboratory investigation of dune erosion using stereo video  

Microsoft Academic Search

Simple parameterizations of dune erosion are necessary for forecasting erosion potential prior to an oncoming storm. Dune erosion may be parameterized in terms of the elevation of the total water level (composed of surge, tide, and wave runup) above the dune base and period of exposure of the dune to waves. In this work, we test several versions of this

Margaret L. Palmsten; Robert A. Holman

168

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

169

Reestablishing Naturally Functioning Dunes on Developed Coasts.  

PubMed

/ The potential for reestablishing dune habitat is investigated in municipalities in New Jersey, USA, where natural coastal landforms and biota have been eliminated or reduced in extent. Dunes are classified using width, relationship to natural and cultural features, and changes through time, and they are assessed for their value as naturally functioning landforms in developed municipalities. The relationship between size and longevity that exists under natural conditions is altered by human activity. Small dunes on privately owned lots can survive as long as larger dunes in natural areas that are located farther inland, and foredunes repaired using sand fences and earth-moving equipment can survive where they could not under natural conditions.Common beach management practices reduce the ecological values of coastal dunes. Mechanical beach cleaning eliminates incipient dunes, habitat for nesting birds, seed sources for pioneer dune colonizers and food for fauna, and artificially small, stabilized foredunes reduce the variability in microenvironments necessary for biodiversity. Recent initiatives for reducing coastal hazards, protecting nesting birds, and encouraging nature-based tourism provide incentive for the development of a restoration program for beaches and dunes that is compatible with human use. Suggested changes in management practice include restricting or rerouting pedestrian traffic, altering beach-cleaning procedures, using symbolic fences to allow for aeolian transport while preventing trampling of dunes, and eliminating or severely restricting exotic species. Landforms will be more natural in function and appearance but will be more dynamic, smaller and in a different position from those in natural areas. Research needs are specified for ecological, geomorphological, and attitudinal studies to support and inform restoration planning. PMID:10552101

Nordstrom; Lampe; Vandemark

2000-01-01

170

Reproducibility and utility of dune luminescence chronologies  

NASA Astrophysics Data System (ADS)

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

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

2014-02-01

171

Bucillamine-induced membranous nephropathy with crescent formation in a patient with rheumatoid arthritis: case report and literature review.  

PubMed

Bucillamine is a disease-modifying antirheumatic drug that is structurally similar to D-penicillamine. The major renal side effect of bucillamine and D-penicillamine is proteinuria caused by membranous nephropathy (MN). In addition to MN, combined crescent formation has been occasionally reported in D-penicillamine-induced MN, while crescent formation has been rarely reported in bucillamine-treated cases. Here, we describe a 76-year-old female who presented with nephrotic syndrome and rapidly progressive glomerulonephritis. She was receiving bucillamine as initial treatment for recently diagnosed rheumatoid arthritis, and renal biopsy showed MN with crescent formation. To the best of our knowledge, this is the first report of bucillamine-induced MN with crescent formation in the English literature. PMID:25849672

Manabe, Shun; Banno, Mayuko; Nakano, Marie; Fujii, Teruhiro; Fujiwara, Michio; Kita, Yasuhiko; Nitta, Kosaku; Hatano, Michiyasu

2015-01-01

172

Bucillamine-Induced Membranous Nephropathy with Crescent Formation in a Patient with Rheumatoid Arthritis: Case Report and Literature Review  

PubMed Central

Bucillamine is a disease-modifying antirheumatic drug that is structurally similar to D-penicillamine. The major renal side effect of bucillamine and D-penicillamine is proteinuria caused by membranous nephropathy (MN). In addition to MN, combined crescent formation has been occasionally reported in D-penicillamine-induced MN, while crescent formation has been rarely reported in bucillamine-treated cases. Here, we describe a 76-year-old female who presented with nephrotic syndrome and rapidly progressive glomerulonephritis. She was receiving bucillamine as initial treatment for recently diagnosed rheumatoid arthritis, and renal biopsy showed MN with crescent formation. To the best of our knowledge, this is the first report of bucillamine-induced MN with crescent formation in the English literature.

Manabe, Shun; Banno, Mayuko; Nakano, Marie; Fujii, Teruhiro; Fujiwara, Michio; Kita, Yasuhiko; Nitta, Kosaku; Hatano, Michiyasu

2015-01-01

173

76 FR 47144 - In the Matter of: Jianwei Ding, 51 Bukit Batok Crescent, #0828 Unity Centre, Singapore 658077...  

Federal Register 2010, 2011, 2012, 2013, 2014

...Batok Crescent, 0828 Unity Centre, Singapore 658077, and Registration : 29603-050...and Far Eastron Co. Pte. Ltd., Singapore-based companies that acquired items...scheme whereby he directed activities in Singapore and the United States to obtain the...

2011-08-04

174

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.

175

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.

176

Crescent?shaped slab slides in a submarine canyon system, Arequipa fore?arc basin, off southern Peru  

Microsoft Academic Search

SeaMARC II side?scan imagery and bathymetry, seismic reflection, and free?fall core sampling data reveal the morphology, structure, and hydrology controls on the formation and development of a series of crescent?shaped slab slides along the submarine canyon walls in the Arequipa fore?arc basin off southern Peru. The crescent?shaped slab slides occur in a segment of an approximately 25?km?long canyon course and

Chang Li

1993-01-01

177

'Sharks Teeth' -- Sand Dunes in Proctor Crater  

NASA Technical Reports Server (NTRS)

Sometimes, pictures received from Mars Global Surveyor's Mars Orbiter Camera (MOC) are 'just plain pretty.' This image, taken in early September 2000, shows a group of sand dunes at the edge of a much larger field of dark-toned dunes in Proctor Crater. Located at 47.9oS, 330.4oW, in the 170 km (106 mile) diameter crater named for 19th Century British astronomer Richard A. Proctor (1837-1888), the dunes shown here are created by winds blowing largely from the east/northeast. A plethora of smaller, brighter ripples covers the substrate between the dunes. Sunlight illuminates them from the upper left.

2001-01-01

178

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

179

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

180

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

181

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

182

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

183

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

184

Mean sediment residence time in barchan dunes  

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

185

Green Tea Polyphenol (?)-Epigallocatechin-3-Gallate Restores Nrf2 Activity and Ameliorates Crescentic Glomerulonephritis  

PubMed Central

Crescentic glomerulonephritis (GN) is the most severe form of GN and is associated with significant morbidity and mortality despite aggressive immunotherapy with steroids, cytotoxic drugs, and plasmapheresis. We examined the therapeutic efficacy of the green tea polyphenol (?)-epigallocatechin-3-gallate (EGCG, 50 mg/kg BW/day x3weeks), a potent anti-inflammatory and anti-oxidant agent, on experimental crescentic GN induced in 129/svJ mice by administration of rabbit anti-mouse glomerular basement membrane sera. Routine histology and key molecules involved in inflammatory and redox signaling were studied. EGCG treatment significantly reduced mortality, decreased proteinuria and serum creatinine, and markedly improved renal histology when compared with vehicle-treated mice. The improvements in renal function and histology were accompanied by the restoration of Nrf2 signaling (which was impaired in vehicle-treated mice) as shown by increased nuclear translocation of Nrf2 and cytoplasmic glutamate cysteine ligase catalytic subunit, glutamate cysteine ligase modifier subunit, and glutathione peroxidase. EGCG-treated mice also showed reduction in p-Akt, p-JNK, p-ERK1/2 and p-P38 as well as restoration of PPAR? and SIRT1 levels. Lower dose of EGCG (25 mg/kg BW/day x2 weeks) treatment also significantly decreased proteinuria and serum creatinine, and markedly improved renal histology when compared with vehicle-treated mice. Thus, our data illustrate the efficacy of EGCG in reversing the progression of crescentic GN in mice by targeting multiple signaling and inflammatory pathways as well as countering oxidative stress. PMID:25785827

Zhou, Jason K.; Peng, Ai; Vaziri, Nosratola D.; Mohan, Chandra; Xu, Yan; Zhou, Xin J.

2015-01-01

186

Green tea polyphenol (-)-epigallocatechin-3-gallate restores nrf2 activity and ameliorates crescentic glomerulonephritis.  

PubMed

Crescentic glomerulonephritis (GN) is the most severe form of GN and is associated with significant morbidity and mortality despite aggressive immunotherapy with steroids, cytotoxic drugs, and plasmapheresis. We examined the therapeutic efficacy of the green tea polyphenol (-)-epigallocatechin-3-gallate (EGCG, 50 mg/kg BW/day x3weeks), a potent anti-inflammatory and anti-oxidant agent, on experimental crescentic GN induced in 129/svJ mice by administration of rabbit anti-mouse glomerular basement membrane sera. Routine histology and key molecules involved in inflammatory and redox signaling were studied. EGCG treatment significantly reduced mortality, decreased proteinuria and serum creatinine, and markedly improved renal histology when compared with vehicle-treated mice. The improvements in renal function and histology were accompanied by the restoration of Nrf2 signaling (which was impaired in vehicle-treated mice) as shown by increased nuclear translocation of Nrf2 and cytoplasmic glutamate cysteine ligase catalytic subunit, glutamate cysteine ligase modifier subunit, and glutathione peroxidase. EGCG-treated mice also showed reduction in p-Akt, p-JNK, p-ERK1/2 and p-P38 as well as restoration of PPAR? and SIRT1 levels. Lower dose of EGCG (25 mg/kg BW/day x2 weeks) treatment also significantly decreased proteinuria and serum creatinine, and markedly improved renal histology when compared with vehicle-treated mice. Thus, our data illustrate the efficacy of EGCG in reversing the progression of crescentic GN in mice by targeting multiple signaling and inflammatory pathways as well as countering oxidative stress. PMID:25785827

Ye, Ting; Zhen, Junhui; Du, Yong; Zhou, Jason K; Peng, Ai; Vaziri, Nosratola D; Mohan, Chandra; Xu, Yan; Zhou, Xin J

2015-01-01

187

Transformation from tubulointerstitial nephritis to crescentic glomerulonephritis: an unusual presentation of ANCA-associated renal vasculitis.  

PubMed

A 44-year-old man with acute renal failure and antineutrophil cytoplasmic antibodies (ANCA) positivity was described. The first renal biopsy specimen showed tubulointerstitial nephritis (TIN) with normal glomeruli. However, delayed recovery of renal function with low-dose steroid treatment for TIN prompted a second renal biopsy 1 month later; and the specimen demonstrated a dramatically different morphology, with necrotizing and crescentic glomerulonephritis. Improvement in renal function occurred, together with reduction of ANCA titers, following intensive immunosuppressive therapy. This case illustrates an unusual presentation of TIN in ANCA-associated renal vasculitis. The possible pathogenetic mechanism are discussed. PMID:16538980

Wen, Yao-Ko; Chen, Mei-Ling

2006-01-01

188

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

189

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

190

Predictability of dune activity in real dune fields under unidirectional wind regimes  

NASA Astrophysics Data System (ADS)

We present an analysis of 10 dune fields to test a model-derived hypothesis of dune field activity. The hypothesis suggests that a quantifiable threshold exists for stabilization in unidirectional wind regimes: active dunes have slipface deposition rates that exceed the vegetation deposition tolerance, and stabilizing dunes have the opposite. We quantified aeolian sand flux, slipface geometry, and vegetation deposition tolerance to directly test the hypothesis at four dune fields (Bigstick, White Sands Stable, White Sands Active, and Cape Cod). We indirectly tested the hypothesis at six additional dune fields with limited vegetation data (Hanford, Año Nuevo, Skagen Odde, Salton Sea, Oceano Stable, and Oceano Active, "inverse calculation sites"). We used digital topographic data and estimates of aeolian sand flux to approximate the slipface deposition rates prior to stabilization. Results revealed a distinct, quantifiable, and consistent pattern despite diverse environmental conditions: the modal peak of prestabilization slipface deposition rates was 80% of the vegetation deposition tolerance at stabilized or stabilizing dune fields. Results from inverse calculation sites indicate deposition rates at stabilized sites were near a hypothesized maximum vegetation deposition tolerance (1 m a-1), and active sites had slipface deposition rates much higher. Overall, these results confirm the hypothesis and provide evidence of a globally applicable, simple, and previously unidentified predictor for the dynamics of vegetation cover in dune fields under unidirectional wind regimes.

Barchyn, Thomas E.; Hugenholtz, Chris H.

2015-02-01

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. The 67°N latitude, 62 km2 Great Kobuk Sand Dunes (GKSD) are a terrestrial analog for polar, intercrater sand thermal conductivity, higher wet sand thermal conductivity, infiltration of relatively warm summer

Stillman, David E.

192

Pediatric case of crescentic post-streptococcal glomerulonephritis with myeloperoxidase anti-neutrophil cytoplasmic antibody.  

PubMed

Post-streptococcal glomerulonephritis (PSGN) generally has a good renal prognosis, and immunosuppressive therapies are not needed. However, a few patients present with severe acute kidney injury and extensive crescent formations. The etiology of such patients is not well known, and involvement of anti-neutrophil cytoplasmic antibodies is rarely reported. A 9-year-old girl with rapidly progressive nephritic syndrome was diagnosed with PSGN. A biopsy showed diffuse crescentic glomerulonephritis with immunoglobulin G and C3 deposits; moreover, humps were observed on electron microscopy. After she was administered methylprednisolone pulse therapy and intravenous cyclophosphamide, followed by prednisolone and azathioprine therapy, her urinary abnormalities improved and renal function normalized. However, the myeloperoxidase anti-neutrophil cytoplasmic antibody (MPO-ANCA) titers gradually increased. We speculated that PSGN may be augmented by increased MPO-ANCA levels. Therefore, the patient is currently being treated with losartan, enalapril, azathioprine, and prednisolone. Although the MPO-ANCA titer remains high, urinary findings show mild proteinuria and her renal function has been norma for 18 months since onset. A progressive clinical course and severe histological findings may indicate the involvement of ANCA in deterioration of condition in patients with PSGN. Furthermore, in such cases immunosuppressive therapies should be considered even in pediatric PSGN. PMID:25161112

Kanai, Hiroaki; Sawanobori, Emi; Koizumi, Keiichi; Ohashi, Ryuji; Higashida, Kosuke

2015-04-01

193

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

PubMed Central

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

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

2014-01-01

194

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

195

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

196

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

197

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

198

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

199

Ground-water potentialities in the Crescent Valley, Eureka and Lander Counties, Nevada  

USGS Publications Warehouse

The Crescent Valley is an intermontane basin in Eureka and Lander Counties, just south of the Humboldt River in north-central Nevada. The valley floor, with an area of about 150 square miles, has a shape that more nearly resembles a Y than a crescent, although the valley apparently was named after the arc described by its southern part and northeastern arm. The northwestern arm of the Y extends northward to the small railroad town of Beowawe on the Humboldt River; the northeastern arm lies east of the low Dry Hills. The leg of the Y extends southwestward toward a narrow gap which separates the Crescent Valley from the Carico Lake Valley. The total drainage area of the Crescent Valley-about 700 square miles--includes also the slopes of the bordering mountain ranges: the Shoshone Range to the west, the Cortez Mountains to the east, and the Toiyabe Range to the south. The early history of the Crescent Valley was dominated by mining of silver and gold, centered at Lander in the Shoshone Range and at Cortez and Mill Canyon in the Cortez Mountains, but in recent years the only major mining activity has been at Gold Acres; there open-pit mining of low-grade gold ore has supported a community of about 200. For many years the only agricultural enterprises in the valley were two cattle ranches, but recently addition lands have been developed for the raising of crops in the west-central part of the valley. The average annual precipitation upon the floor of the Crescent Valley is probably less than 7 inches, of which only a little more than 1 inch formally falls during the growing season (from June through September). This is far less than the requirement of any plants of economic value, and irrigation is essential to agricultural development. Small perennial streams rising in the mountains have long been utilized for domestic supply, mining and milling activities of the past, and irrigation, and recently some large wells have been developed for irrigation. In 1956 the total pumpage from wells in the valley was 2,300 acre-feet. The Crescent Valley is a basin in which has accumulated a large volume of sediments that had been eroded and transported by streams from the surrounding mountains. The deepest wells have penetrated only the upper 350 feet of these sediments, which on the basis of the known thickness of sediments in other intermontane basins in central Nevada may be as much as several thousand feet thick. Because this valley fill is saturated practically to the level of the valley floor, the total volume of ground water in storage amounts to millions of acre-feet. In practically all wells drilled to date, the water has been of a quality satisfactory for irrigation and domestic use. The amount of water that can be developed and used perennially is far smaller than the total in storage and is dependent upon the average annual recharge to the ground-water reservoir. This recharge comes principally from streams, fed largely by snowmelt, that drain the higher mountains. The average annum recharge to the valley fill is estimated to be about 13,000 acre-feet. This natural supply, which is largely consumed by native vegetation on the valley floor, constitutes a perennial supply for beneficial use only to the extent that the natural discharge can be reduced. In time, much of the natural discharge, can probably be salvaged, if it is economically feasible to pump ground water after water levels have been lowered as much as 100 feet in the areas that now appear to be favorable for the development of irrigation supplies. In 5 wells in the phreatophyte area, where the water table is within 3-8 feet of the land surface, the trends in water level have paralleled those, in precipitation-downward during the dry years 1952-55, upward in wetter 1956 and 1957, and as high in 1957 as at any time since 1948. In most wells there is also a seasonal fluctuation of 1-3 feet, from a high in the spring to a low in the fall. There is no evi

Zones, Christie Paul

1961-01-01

200

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

201

Lateral migration of linear dunes in the Strzelecki Desert, Australia  

USGS Publications Warehouse

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

Rubin, D.M.

1990-01-01

202

Geology Fieldnotes: Great Sand Dunes National Monument Colorado  

NSDL National Science Digital Library

This article describes the geology of Great Sand Dunes National Monument. The monument is in southern Colorado and contains North America's tallest dunes, which rise over 750 feet high against the Sangre de Cristo Mountains. Great Sand Dunes, containing 30 square miles of dunes, became a national monument in 1932. Features include links to maps, photographs and visitor information as well as a selection of links to related topics.

203

Sand dune movement in the Victoria Valley, Antarctica  

Microsoft Academic Search

We use vertical aerial photographs and LiDAR topographic survey data to estimate dune migration rates in the Victoria Valley dunefield, Antarctica, between 1961 and 2001. Results confirm that the dunes migrated an average of 1.5 m\\/year. These values are consistent with other estimates of dune migration from cold climate deserts and are significantly lower than estimates from warm deserts. Dune migration

Mary C. Bourke; Ryan C. Ewing; David Finnegan; Hamish A. McGowan

2009-01-01

204

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

205

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

206

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

207

Geology Fieldnotes: Sleeping Bear Dunes National Lakeshore, Michigan  

NSDL National Science Digital Library

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

208

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

209

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

210

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"

211

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

E-print Network

Climate and coastal dune vegetation: disturbance, recovery, and succession Thomas E. Miller Æ 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.

212

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

E-print Network

LATE ORDOVICIAN CLIMBING DUNE ASSEMBLAGES : THE SIGNATURE OF GLACIAL OUTBURST? F. GIRARD¹, J ­ Algeria boundary), this presentation aims to describe climbing dunes assemblages (facies, geometries a continental ice-front and a prograding shoreline - climbing dune assemblages in 3 types of sand

Paris-Sud XI, Université de

213

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

214

Barchan dunes morphology dynamics under different environmental conditions  

NASA Astrophysics Data System (ADS)

The aim of this study was to emphasize significance of diversified dynamics of barchans dune morphology. We analyzed and compared barchans found in two dune fields: Kharga (S Egypt) and Tarfaya-Laâyoune (S-Morocco). These dune fields are characterized by significantly different factors responsible for dunes development e.g. textural and mineralogical composition of dune sand, dune sand moisture, air humidity, inter dune vegetation cover. For each investigated dune filed and study period (2008, 2010, 2012 for Kharga and 2007, 2011, 2012 for Tarfaya-Laâyoune dune fields) detailed shape measurement of 20 simple isolated barchans of different dune sizes was made. The ± 10-2 m horizontal and ± 1,5 10-2m vertical accuracy was obtained (1 measuring point per 1m2 on average).In order to compare barchan dunes morphology and to determine depositional and erosional patterns, the 3D models were created. For better understanding of this processes, sand bulk density of barchan surface was measured (1 measuring point per 2m2 on average). The velocity of dunes in relation to dune shape was also analyzed. The results show that the relationship between typically correlated parameters change during movement of the barchans. Most values change by a few percent per year (slip face height, dune base area and dune volume) or by a dozen or so percent per year (windward side length, horns length and width). We obtain good linear relationship (with 0,05 significant level) between slip face height and the dune base area (0,77 < R2 < 0,83), dune volume (0,66 < R2 < 0,72), windward side length (0,58 < R2 < 0,87), horns length (0,71 < R2 < 0,90) or horns width (0,79 < R2 < 0,93). The linear relationship between displacement rate and the morphological parameters is not strong (0,54< R2 < 0,81) for Kharga dune field and (0,41< R2 < 0,66) for Tarfaya-Laâyoune dune field. We noted also good linear relationship between displacement rate and the angle of span of the horns (R2=0,73 on Tarfaya-Laâyoune dune fields). Comparison of shape change of the same barchan made it possible to determine the depositional and erosional zones. The annual changes of surface altitude do not exceed a few percent of the total sand thickness in analyzed zones (more for small dunes). However, we noted important shape differences between barchans of the same slip face height in two investigated dune fields (up to 20% of sand thickness in the same point). We also found a good correlation between barchans shape and bulk density of dune sand. The highest bulk density of the dune sand is noted at the dune horns (up to 1767kg m-3 for Kharga dune field and up to 1644 kg m-3 for Tarfaya-Laâyoune dune field). On the windward (stoss) sides the bulk density of the dune sand depends on barchans shape (slope inclination). The lee sides have the value around 1400 kg m-3. Generally our result show relatively small differences in dune morphology dynamics within the same dune field but much greater between the two analyzed areas.

Dluzewski, M.

2012-04-01

215

Deep crescentic features caused by subglacial boulder point pressure on jointed rock; an example from Virkisjökull, SE Iceland  

NASA Astrophysics Data System (ADS)

A variety of subglacially formed, erosional crescentic features (e.g. crescentic gouges, lunate fractures) have been widely reported on deglaciated bedrock surfaces. They are characterised by a conchoidal fracture that dips in the same direction as the palaeo-ice flow direction, and a steeper fracture that faces against the ice flow. They are generally interpreted as being formed by point pressure exerted by large boulders entrained in basal ice. They are significant in that they record palaeo-ice flow even if shallower glacial striae are obliterated by post-glacial weathering [1, 2, 3]. This contribution reports on deep scallop-shaped, crescentic depressions observed on abraded surfaces of roche moutonnées and whalebacks recently (<10yrs) exposed beneath the actively retreating Virkisjökull, an outlet glacier of the Oraefajökull ice cap in southeast Iceland. The substrate comprises hard rhyolitic rock (relatively rare in Iceland compared to more common basalt and hyaloclastite) with polygonal, columnar jointing. The crescentic depressions at Virkisjökull are cut into smoothed, abraded surfaces festooned with abundant glacial striae. Differences with previously reported crescentic features are: • The scallop-shaped depressions are considerably deeper (5-20 cm); • The steep fracture facing ice flow coincides in all cases with a pre-existing joint that cuts the entire whaleback. The steep joints developed thus before the conchoidal fracture, whilst in reported crescentic features they develop after the conchoidal fracture. We suggest the following formation mechanism. A boulder encased in basal ice exerts continuous pressure on its contact point as it moves across the ice-bedrock contact. This sets up a stress field in the bedrock that does not necessarily exceed the intact rock strength (other crescentic features are rare to absent at Virkisjökull). However, as the stress field migrates (with the transported boulder) and encounters a subvertical, pre-existing joint, stress concentrations build up that do exceed the intact rock strength, resulting in a new (conchoidal) fracture, 'spalling' off a thick, scallop-shaped fragment. The significance of the deep scallop-shaped crescentic depressions is that: • in common with other crescentic features they appear to be robust ice-flow indicators and indicate that former basal ice was rich in coarse, cobble/boulder-sized debris; • they are deeper and represent more significant erosion than previously reported crescentic features; during continuous subglacial erosion they thus (re)introduce a significant roughness on smoothed abraded surfaces, resulting in faster subglacial erosion; • assuming our proposed formation mechanism is correct, they could develop at lower stress (?thinner ice, [3]) than other crescentic features, as they utilise pre-existing weaknesses in the rock. The observations were made as part of the British Geological Survey's Virkisjökull Observatory Project. [1] Gilbert, GK, 1906. Bull. Geo. Soc. Am, v. 17, 303-313. [2] Harris, SE, 1943. J. Geology, v. 51, 244-258. [3] Wintges, T. 1985. J. Glaciology, v. 31, 340-349.

Krabbendam, M.; Bradwell, T.; Everest, J.

2012-04-01

216

Variation of bee communities on a sand dune complex in the Great Basin: Implications for sand dune conservation  

Technology Transfer Automated Retrieval System (TEKTRAN)

Sand dunes across the Mojave and Great Basin Deserts house rich bee communities. The pollination services these bees provide can be vital in maintaining the diverse, and often endemic, dune flora. These dune environments, however, are threatened by intense off-highway vehicle (OHV) use. Conservati...

217

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

218

Dune Succession Predictable patterns of species  

E-print Network

1 Dune Succession Succession · Predictable patterns of species replacements in an ecological colonizers but better competitors, can make do with lower resource levels, eventually outcompete early species ­ Sand cherry, Cottonwoods Two Types of Succession · Primary · Secondary Primary Succession

Cochran-Stafira, D. Liane

219

Dune Succession Predictable patterns of species  

E-print Network

Dune Succession Succession · Predictable patterns of species replacements in an ecological colonizers but better competitors, can make do with lower resource levels, eventually outcompete early species ­ Sand cherry, Cottonwoods Two Types of Succession · Primary · Secondary Primary Succession

Cochran-Stafira, D. Liane

220

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

221

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.

222

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

223

Particle dynamics of a cartoon dune  

NASA Astrophysics Data System (ADS)

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.

Groh, Christopher; Rehberg, Ingo; Kruelle, Christof A.

2010-06-01

224

Diffusion au sommet d'une  

E-print Network

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

Ramond, Thierry

225

Probabilistic assessment of beach and dune changes  

USGS Publications Warehouse

The recent availability of spatially-dense airborne lidar data makes assessment of the vulnerability of beaches and dunes to storm impacts practical over long reaches of coast. As an initial test, elevations of the tops (D high) and bases (Dlow) of foredune ridges along a 55-km reach on the northern Outer Banks, NC were found to have considerable spatial variability suggesting that different parts of the barrier island would respond differently to storms. Comparing statistics of storm wave runup to D high and Dlow, we found that net erosion due to overwash and dune retreat should be greatest at the northern and southern ends of the study area and least in the central section. This predicted spatial pattern of storm-induced erosion is similar to the spatial pattern of long-term erosion of the shoreline which may be controlled by additional processes (such as gradients in longshore transport) as well as the cross-shore processes considered here. However, consider feedback where at erosional hot spots there is a deficit of sand (caused by gradients in longshore transport) which lead to lower dunes and enhanced erosional cross-shore processes, such as overwash. Hence, the erosional hot spots would be exacerbated, further increasing the vulnerability of the beach and dunes to net erosion.

Sallenger, A.H., Jr.; Stockdon, H.; Haines, J.; Krabill, W.; Swift, R.; Brock, J.

2004-01-01

226

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

227

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

228

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

229

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

230

Multiple origins of linear dunes on Earth and Titan  

USGS Publications Warehouse

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

Rubin, David M.; Hesp, Patrick A.

2009-01-01

231

Climate change in the Fertile Crescent and implications of the recent Syrian drought.  

PubMed

Before the Syrian uprising that began in 2011, the greater Fertile Crescent experienced the most severe drought in the instrumental record. For Syria, a country marked by poor governance and unsustainable agricultural and environmental policies, the drought had a catalytic effect, contributing to political unrest. We show that the recent decrease in Syrian precipitation is a combination of natural variability and a long-term drying trend, and the unusual severity of the observed drought is here shown to be highly unlikely without this trend. Precipitation changes in Syria are linked to rising mean sea-level pressure in the Eastern Mediterranean, which also shows a long-term trend. There has been also a long-term warming trend in the Eastern Mediterranean, adding to the drawdown of soil moisture. No natural cause is apparent for these trends, whereas the observed drying and warming are consistent with model studies of the response to increases in greenhouse gases. Furthermore, model studies show an increasingly drier and hotter future mean climate for the Eastern Mediterranean. Analyses of observations and model simulations indicate that a drought of the severity and duration of the recent Syrian drought, which is implicated in the current conflict, has become more than twice as likely as a consequence of human interference in the climate system. PMID:25733898

Kelley, Colin P; Mohtadi, Shahrzad; Cane, Mark A; Seager, Richard; Kushnir, Yochanan

2015-03-17

232

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

233

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

234

Dune Field in a Southern Highlands Crater  

NASA Technical Reports Server (NTRS)

[figure removed for brevity, see original site]

Released 5 September 2003

Dark dunes sit on a rough, eroding sedimentary surface in the floor of an 83 km diameter crater. This crater is one of dozens in Noachis Terra, in the southern highlands of Mars, to have both dark dunes and an eroding surface. Note how the dunes seem to ignore the underlying rough surface in some cases, while in other places the dunes seem to have wrapped themselves around sharp knobs.

Image information: VIS instrument. Latitude -40.5, Longitude 34.6 East (325.4 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.

2003-01-01

235

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

236

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

237

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

238

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

239

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

240

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

241

Identification of Optic Disc Elevation and the Crescent Sign Using Point-of-Care Ocular Ultrasound in Children.  

PubMed

Point-of-care ocular ultrasound has been used to detect papilledema. In previous studies, investigators have evaluated only optic nerve sheath diameter as a screen for increased intracranial pressure. In this series of 4 children, we demonstrate 2 additional optic nerve abnormalities using point-of-care ocular ultrasound: optic disc elevation and the crescent sign. Assessing the optic nerve for each of these 3 findings may assist the examiner in detecting papilledema. PMID:25831036

Marchese, Ronald F; Mistry, Rakesh D; Scarfone, Richard J; Chen, Aaron E

2015-04-01

242

A three-step scheme for gray crescent formation in the rotated axolotl oocyte.  

PubMed

It has been shown that various inhibitors of protein synthesis can elicit the precocious appearance of a gray crescent (GC) in in vitro maturing, nonactivated Ambystoma mexicanum oocytes. However, evidence has now been obtained that these treatments fail to induce GC formation when the oocytes are enucleated before initiation of maturation. The ability to form a GC is reestablished in enucleated oocytes by the injection of nucleoplasm from a normal oocyte, either before or after the injection of the inhibitor. In the latter case, the GC appears very rapidly, even though protein synthesis is at about 1/10th that of the control enucleated oocyte, after treatment with diphtheria toxin (final concentration 10(-8) M) as an inhibitor. One or several nuclear factors, in conjunction with inhibition of protein synthesis, are therefore essential for early symmetrization. The corrective nuclear factor is already present in the germinal vesicle of young oocytes, at the very beginning of vitellogenesis. It is not species specific, since enucleated axolotl oocytes can be symmetrized with Pleurodeles or even Xenopus oocyte nucleoplasm. Moreover, it has been shown that the nuclear-cytoplasmic interaction is possible only when cytoplasmic maturation has been proceeding for at least 10 hr after exposure to progesterone (at 18 degrees C). A three-step process as a prerequisite of GC formation in the oocyte is proposed: Cytoplasmic maturation must proceed till a reactive state is attained, allowing interactions with nuclear factors; Nuclear factor(s) interact(s) with matured cytoplasm; Inhibition of protein synthesis triggers GC formation. Sequence of steps 2 and 3 can be experimentally inverted but must always be preceded by step 1. Since a sharp reduction in amino acid incorporation has also been found in normally fertilized eggs just prior to GC formation, it is suggested that the scheme described above could be also applicable to normal symmetrization in this model system. PMID:4007261

Gautier, J; Beetschen, J C

1985-07-01

243

Origin of the late quaternary dune fields of northeastern Colorado  

USGS Publications Warehouse

Stabilized eolian deposits, mostly parabolic dunes and sand sheets, cover much of the landscape of northeastern Colorado and adjacent parts of southwestern Nebraska in four geographically distinct dune fields. Stratigraphic and soil-geomorphic relations and accelerator radiocarbon dating indicate that at least three episodes of eolian sand movement occurred between 27 ka and 11 ka, possibly between 11 ka and 4 ka, and within the past 1.5 ka. Thus, eolian sand deposition took place under both glacial and interglacial climatic conditions. In the youngest episodes of eolian sand movement, Holocene parabolic dunes partially buried Pleistocene sand sheet deposits. Late Holocene sands in the Fort Morgan and Wray dune fields, to the south of the South Platte River, have trace element ratios that are indistinguishable from modern South Platte River sands, but different from Ogallala Formation bedrock, which has previously been cited as the main source of dune sand on the Great Plains. Sands in the Greeley dune field, to the north of the South Platte River, have trace element concentrations that indicate a probable Laramie Formation source. Measurements of parabolic dunes indicate paleowinds from the northwest in all dune fields, in good agreement with resultant drift directions calculated for nearby weather stations. Thus, paleowinds were probably not significantly different from present-day winds, and are consistent with a South Platte River source for the Fort Morgan and Wray dune fields, and a Laramie Formation source for the Greeley dune field. Sand accumulated downwind of the South Platte River to form the Fort Morgan dune field. In addition, sand was also transported farther downwind over the upland formed by the calcrete caprock of the Ogallala Formation, and deposited in die lee of the upland on the southeast side. Because of high wind energy, the upland itself served as a zone of sand transport, but little or no sand accumulation took place on this surface. These studies, which demonstrate the importance of fluvial-source sediments for dune fields in Colorado, may be applicable to other dune fields in North America. Because modern drift potentials in northeastern Colorado are among the highest in the world, the present stability of dunes in the region may be in part a function of the dunes being supply-limited rather than solely transport-limited. Extensive (??? 7700 km2) late Holocene dunes document that eolian sand in northeastern Colorado is very sensitive to small changes in climate or fluvial source conditions.

Muhs, D.R.; Stafford, T.W.; Cowherd, S.D.; Mahan, S.A.; Kihl, R.; Maat, P.B.; Bush, C.A.; Nehring, J.

1996-01-01

244

Linear Dunes and Playas, Simson Desert, South Australia, Australia  

NASA Technical Reports Server (NTRS)

This image of abstract shapes is comprised numerous subparallel, very long, orange colored linear dunes and patchy grey dry lakes (playas). The dunes are aligned north to south in the great central basin of Astralia (27.0S, 138.0E). The regularity of the dunes is created by the winds blowing from the south. As the dunes advance, jaged edges on the south side of each dry lake are formed while the north side is eroded smooth by the wind and water.

1991-01-01

245

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

246

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

247

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

Federal Register 2010, 2011, 2012, 2013, 2014

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

2011-11-04

248

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

Federal Register 2010, 2011, 2012, 2013, 2014

...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

249

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.

250

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

251

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

252

Origin of the late Quaternary dune fields of northeastern Colorado  

NASA Astrophysics Data System (ADS)

Stabilized eolian deposits, mostly parabolic dunes and sand sheets, cover much of the landscape of northeastern Colorado and adjacent parts of southwestern Nebraska in four geographically distinct dune fields. Stratigraphic and soil-geomorphic relations and accelerator radiocarbon dating indicate that at least three episodes of eolian sand movement occurred between 27 ka and 11 ka, possibly between 11 ka and 4 ka, and within the past 1.5 ka. Thus, eolian sand deposition took place under both glacial and interglacial climatic conditions. In the youngest episodes of eolian sand movement, Holocene parabolic dunes partially buried Pleistocene sand sheet deposits. Late Holocene sands in the Fort Morgan and Wray dune fields, to the south of the South Platte River, have trace element ratios that are indistinguishable from modern South Platte River sands, but different from Ogallala Formation bedrock, which has previously been cited as the main source of dune sand on the Great Plains. Sands in the Greeley dune field, to the north of the South Platte River, have trace element concentrations that indicate a probable Laramie Formation source. Measurements of parabolic dunes indicate paleowinds from the northwest in all dune fields, in good agreement with resultant drift directions calculated for nearby weather stations. Thus, paleowinds were probably not significantly different from present-day winds, and are consistent with a South Platte River source for the Fort Morgan and Wray dune fields, and a Laramie Formation source for the Greeley dune field. Sand accumulated downwind of the South Platte River to form the Fort Morgan duen field. In addition, sand was also transported farther downwind over the upland formed by the calcrete caprock of the Ogallala Formation, and deposited in the lee of the upland on the southeast side. Because of high wind energy, the upland itself served as a zone of sand transport, but little or no sand accumulation took place on this surface. These studies, which demonstrate the importance of fluvial-source sediments for dune fields in Colorado, may be applicable to other dune fields in North America. Because modern drift potentials in northeastern Colorado are among the highest in the world, the present stability of dunes in the region may be in part a function of the dunes being supply-limited rather than solely transport-limited. Extensive (˜ 7700 km 2) late Holocene dunes document that eolian sand in northeastern Colorado is very sensitive to small changes in climate or fluvial source conditions.

Muhs, Daniel R.; Stafford, Thomas W.; Cowherd, Scott D.; Mahan, Shannon A.; Kihl, Rolf; Maat, Paula B.; Bush, Charles A.; Nehring, Jennifer

1996-09-01

253

Titan dune heights retrieval by using Cassini Radar Altimeter  

NASA Astrophysics Data System (ADS)

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

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

2014-02-01

254

Relating climate and sand transport to incipient dune development.  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

255

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

256

Bifurcation analysis of the transition of dune shapes under a unidirectional wind.  

PubMed

A bifurcation analysis of dune shape transition is made. By use of a reduced model of dune morphodynamics, the Dune Skeleton model, we elucidate the transition mechanism between different shapes of dunes under unidirectional wind. It was found that the decrease in the total amount of sand in the system and/or the lateral sand flow shifts the stable state from a straight transverse dune to a wavy transverse dune through a pitchfork bifurcation. A further decrease causes wavy transverse dunes to shift into barchans through a Hopf bifurcation. These bifurcation structures reveal the transition mechanism of dune shapes under unidirectional wind. PMID:22587286

Niiya, Hirofumi; Awazu, Akinori; Nishimori, Hiraku

2012-04-13

257

Tour of Park Geology: Sand Dunes  

NSDL National Science Digital Library

This Park Geology site provides links to tours of individual National Parks, Monuments, and Recreation Areas with sand dunes. Where appropriate for each park, links are provided to maps, photographs, geologic research, related links, visitor information, and teacher features (resources for teaching geology with National Park examples). The list includes places such as Death Valley and Mojave National Preserve, along with less well-known areas such as the Pictured Rocks National Lakeshore in Michigan and the Wright Brothers National Memorial in North Carolina.

258

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 is to be found in the nature of central or normal projections (photography is basically a central projection

Stachel, Hellmuth

259

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

260

Biogenic crust dynamics on sand dunes Shai Kinast,1  

E-print Network

]. Their stability is strongly affected by the degree of vegetation coverage. High coverage reduces the wind power crust and vegetation coverage. As the precipitation increases, the dunes are gradually sta- bilized-Gurion University, Beer Sheva, 84105, Israel (Dated: July 3, 2012) Sand dunes are often covered by vegetation

Ashkenazy, Yossi "Yosef"

261

Effect of Bentonite on Permeability of Dune Sand  

Microsoft Academic Search

A compacted mixture of bentonite with sand has been used to form barrier of fluids, in absence of impervious natural soils. This paper focuses on the permeability behavior of dune sand\\/bentonite mixtures. Results of laboratory investigations are presented to show the influence of bentonite on permeability of dune sand. One dimensional consolidation and falling head permeability tests were conducted to

N. K. Ameta; Abhay Shivaji Wayal

262

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

263

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

264

Particle tracking and mean residence time in barchan dunes  

NASA Astrophysics Data System (ADS)

We analyze sediment particles motions in steady-state barchan dunes by tracking individual cells of a 3-D cellular automaton dune model. The overall sediment flux may be decomposed into advective and dispersive fluxes to estimate the relative contribution of the underlying physical processes to the barchan dune shape. The net lateral sediment transport from the center to the horns indicates that dispersion on the stoss slope is more efficient than avalanches on the lee slope. The combined effect of these two antagonistic dispersive processes restricts the lateral mixing of sediment particles in the central region of barchan dunes. Then, for different flow strength and dune size, we find that the mean residence time of sediment particles in barchan dunes is equal to the surface of the central longitudinal dune slices divided by the input sand flux. We infer that this central slice contains most of the relevant information about barchan dune morphodynamics. Finally, we initiate a discussion about sediment transport and memory in presence of bedforms using the advantages of the particle tracking technique.

Zhang, Deguo; Narteau, Clement; Rozier, Olivier

2013-04-01

265

Origin of the late Quaternary dune fields of northeastern Colorado  

Microsoft Academic Search

Stabilized eolian deposits, mostly parabolic dunes and sand sheets, cover much of the landscape of northeastern Colorado and adjacent parts of southwestern Nebraska in four geographically distinct dune fields. Stratigraphic and soil-geomorphic relations and accelerator radiocarbon dating indicate that at least three episodes of eolian sand movement occurred between 27 ka and 11 ka, possibly between 11 ka and 4

Daniel R. Muhs; Thomas W. Stafford; Scott D. Cowherd; Shannon A. Mahan; Rolf Kihl; Paula B. Maat; Charles A. Bush; Jennifer Nehring

1996-01-01

266

tude et ralisation oriente objet d'une cellule minimale  

E-print Network

Étude et réalisation orientée objet d'une cellule minimale Hiep Minh Phan Année académique 2010 cellule vivante, de nombreux logiciels sont créés afin de pouvoir tester et vérifier différentes'implémentation d'une cellule minimale à l'aide de modèles spatiaux 2D. Misant sur une grande flexibilité et

Libre de Bruxelles, Université

267

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

268

36 CFR 7.88 - Indiana Dunes National Lakeshore.  

Code of Federal Regulations, 2014 CFR

...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

269

36 CFR 7.80 - Sleeping Bear Dunes National Lakeshore.  

Code of Federal Regulations, 2013 CFR

... 1 2013-07-01 2013-07-01 false Sleeping Bear Dunes National Lakeshore. 7.80 Section 7.80 Parks, Forests...AREAS OF THE NATIONAL PARK SYSTEM § 7.80 Sleeping Bear Dunes National Lakeshore. (a) Powerless flight. The...

2013-07-01

270

36 CFR 7.80 - Sleeping Bear Dunes National Lakeshore.  

Code of Federal Regulations, 2011 CFR

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

2011-07-01

271

36 CFR 7.80 - Sleeping Bear Dunes National Lakeshore.  

Code of Federal Regulations, 2012 CFR

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

2012-07-01

272

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

273

36 CFR 7.80 - Sleeping Bear Dunes National Lakeshore.  

Code of Federal Regulations, 2010 CFR

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

2010-07-01

274

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

275

36 CFR 7.80 - Sleeping Bear Dunes National Lakeshore.  

Code of Federal Regulations, 2014 CFR

... 1 2014-07-01 2014-07-01 false Sleeping Bear Dunes National Lakeshore. 7.80 Section 7.80 Parks, Forests...AREAS OF THE NATIONAL PARK SYSTEM § 7.80 Sleeping Bear Dunes National Lakeshore. (a) Powerless flight. The...

2014-07-01

276

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

277

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

278

Narrowing the gap between real and simulated barchan dune dynamics  

NASA Astrophysics Data System (ADS)

There are a growing number of computer simulation models capable of reproducing many of the morphological characteristics and dynamics of real barchan sand dunes. While these models offer tremendous insight and opportunities to develop hypotheses, there is a relative paucity of empirical observations to use as a basis for validation. To address this issue we present empirical observations of barchan dune dynamics using high-resolution, multi-temporal satellite imagery from locations in Peru, Namibia, and Mauritania. We highlight the response of barchan dunes to collisions, wind direction variability, interactions with bedrock topography, and depletion of sediment supply. First, we document the process of dunes emerging from the slipfaces of barchan dunes. In the past, this process was only observed in numerical models or interpreted from single-date imagery. We also show that collisions can result in calving or shedding of dunes from the horns. Second, we present the first empirical evidence of barchans changing into dome and "wedge" dunes under the influence of bimodal winds. Third, we show that barchans break down when they encounter uphill topography. However, they can re-form in the lee of a bedrock obstacle if sediment supply is sufficient. Finally, we show that, in the absence of collisions, small barchans can disappear quickly when they lose upwind sediment supply. Altogether, our observations add to the empirical record of barchan dune dynamics and are useful for evaluating the behaviour of numerical models.

Hugenholtz, C.; Barchyn, T. E.

2011-12-01

279

The effects of psammophilous plants on sand dune dynamics  

NASA Astrophysics Data System (ADS)

Mathematical models of sand dune dynamics have considered different types of sand dune cover. However, despite the important role of psammophilous plants (plants that flourish in moving-sand environments) in dune dynamics, the incorporation of their effects into mathematical models of sand dunes remains a challenging task. Here we propose a nonlinear physical model for the role of psammophilous plants in the stabilization and destabilization of sand dunes. There are two main mechanisms by which the wind affects these plants: (i) sand drift results in the burial and exposure of plants, a process that is known to result in an enhanced growth rate, and (ii) strong winds remove shoots and rhizomes and seed them in nearby locations, enhancing their growth rate. Our model describes the temporal evolution of the fractions of surface cover of regular vegetation, biogenic soil crust, and psammophilous plants. The latter reach their optimal growth under either (i) specific sand drift or (ii) specific wind power. The model exhibits complex bifurcation diagrams and dynamics, which explain observed phenomena, and it predicts new dune stabilization scenarios. Depending on the climatological conditions, it is possible to obtain one, two, or, predicted here for the first time, three stable dune states. Our model shows that the development of the different cover types depends on the precipitation rate and the wind power and that the psammophilous plants are not always the first to grow and stabilize the dunes.

Bel, Golan; Ashkenazy, Yosef

2014-07-01

280

cologie et conservation d'une steppe mditerranenne  

E-print Network

�cologie et conservation d'une steppe méditerranéenne La plaine de Crau Laurent Tatin, Axel Wolff des coussouls de Crau. Les paysages des steppes marquent les esprits, à l'évocation de celles du plus singulières au monde. En France, entre la Camargue et les Alpilles, une steppe d'une rare richesse

Canet, Léonie

281

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

282

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

283

Large-eddy simulation of unidirectional turbulent flow over dunes  

NASA Astrophysics Data System (ADS)

We performed large eddy simulation of the flow over a series of two- and three-dimensional dune geometries at laboratory scale using the Lagrangian dynamic eddy-viscosity subgrid-scale model. First, we studied the flow over a standard 2D transverse dune geometry, then bedform three-dimensionality was imposed. Finally, we investigated the turbulent flow over barchan dunes. The results are validated by comparison with simulations and experiments for the 2D dune case, while the results of the 3D dunes are validated qualitatively against experiments. The flow over transverse dunes separates at the dune crest, generating a shear layer that plays a crucial role in the transport of momentum and energy, as well as the generation of coherent structures. Spanwise vortices are generated in the separated shear; as they are advected, they undergo lateral instabilities and develop into horseshoe-like structures and finally reach the surface. The ejection that occurs between the legs of the vortex creates the upwelling and downdrafting events on the free surface known as "boils". The three-dimensional separation of flow at the crestline alters the distribution of wall pressure, which may cause secondary flow across the stream. The mean flow is characterized by a pair of counter-rotating streamwise vortices, with core radii of the order of the flow depth. Staggering the crestlines alters the secondary motion; two pairs of streamwise vortices appear (a strong one, centred about the lobe, and a weaker one, coming from the previous dune, centred around the saddle). The flow over barchan dunes presents significant differences to that over transverse dunes. The flow near the bed, upstream of the dune, diverges from the centerline plane; the flow close to the centerline plane separates at the crest and reattaches on the bed. Away from the centerline plane and along the horns, flow separation occurs intermittently. The flow in the separation bubble is routed towards the horns and leaves the dune at the tips. Barchan dunes induce two counter-rotating streamwise vortices, along each of the horns, which direct high-momentum fluid toward the symmetry plane and low-momentum fluid near the bed away from the centerline.

Omidyeganeh, Mohammad

284

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

285

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 Stephen Moysey, Marek Zreda and Jim Goeke The large-scale mobility of sand dunes in continental dune of these landforms. Traditional methods for dating sand dunes, e.g. stratigraphic and radiocarbon dating

Zreda, Marek

286

Speculation on Martian north polar wind circulation and the resultant orientations of polar sand dunes  

Microsoft Academic Search

When seen at frost cap minimum, Martian north polar erg dunes north of 80 deg N record east winds, while those south of that latitude record west winds. Many of the transverse dunes are considered to be reversing dunes, and dunes in the two fields may have reversed at least once during the lifetime of the Viking Orbiters. It is

A. W. Ward; K. B. Doyle

1983-01-01

287

Holocene environmental changes in the Whitefish Dunes Area, Door Peninsula, Northern Lake Michigan Basin, USA  

Microsoft Academic Search

A two meter sediment core taken from an inter-dune pond in Whitefish Dunes State Park, Door Peninsula, Wisconsin, provides a record of paleoenvironmental changes in the area from approximately 3600 RCYBP to 5100 RCYBP. The hydrology of the Whitefish Dunes pond is now apparently dependent on ground water recharge from local precipitation that infiltrates into the dunes and from Clark

Barry B. Miller; J. S. Tevesz; John S. Carney

1998-01-01

288

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

E-print Network

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

Thaxton, Christopher S.

289

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

290

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

291

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

292

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.

293

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

294

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

295

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

296

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

297

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

298

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

299

Great Sand Dunes National Monument and Preserve  

NSDL National Science Digital Library

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

300

Field and Laboratory Investigations of Coastal Dune Morphodynamics  

NASA Astrophysics Data System (ADS)

Coastal dunes are important features along many coastlines, owing to their role in sediment budgets, their use as ecologically unique habitat, and their ability to protect onshore resources from wave attack. Skillful predictions of the erosion and overtopping rates of these features are needed to quantify coastal vulnerability during major storm events. Knowledge of post-storm recovery and subsequent dune growth rates is critical to developing quantitative sediment budgets and ultimately for predicting future shoreline positions. We have been conducting both long-term field and large-scale laboratory studies to improve our understanding of dune morphodynamics and will present results of dune behavior, including various feedback mechanisms, at scales ranging from individual storm events to decadal trends. A large-scale physical model study of dune erosion was recently performed at Oregon State University's O.H. Hinsdale Wave Research Laboratory producing a comprehensive, near prototype-scale data set of hydrodynamics, sediment transport, and morphological evolution during extreme dune erosion events. The laboratory moveable bed beach/dune system was brought to equilibrium with pre-storm random wave conditions. It was subsequently subjected to attack from steadily increasing water levels and offshore wave heights simulating a natural storm surge hydrograph. 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. Initial results suggest strong feedbacks between the evolution of the foreshore profile during the storm and episodic dune slumping events. Beach topographic data have been collected quarterly along southwest Washington and northwest Oregon since 1997 resolving the seasonal to interannual morphological variability of a nearly 160-km long high-energy dissipative coastline. Major climate events (such as El Ninos) cause region-wide dune erosion/scarping due to high water levels and increased storminess. However, subsequent dune recovery rates have been variable and appear linked to variations in short-term shoreline change rates and sediment budgets. At interannual scale regions of high shoreline progradation rates experience relatively high dune growth rates. At longer time scales, overall dune morphology is again linked to shoreline change rates but with the highest foredune ridges occurring in areas of relative stable shorelines at decadal scale.

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

2007-12-01

301

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

302

Interactions between mycorrhizal colonization and plant life forms along the successional gradient of coastal sand dunes in the eastern Mediterranean, Turkey  

Microsoft Academic Search

The mycorrhizal status of dune plant species in relation to their plant life forms was surveyed along a successional gradient of sand dune on the southern Mediterranean coast of Turkey. Roots of 64 dune plant species belonging to 30 families were collected from sand dune communities at four different successional stages: embryonic dunes (ED), mobile dunes (MD), fixed dunes (FD),

Halil Çakan; Çi?dem Karata?

2006-01-01

303

Ideal Microhabitats on Mars: The Astrobiological Potential of Polar Dunes  

Microsoft Academic Search

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

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

2009-01-01

304

Ideal Microhabitats on Mars: The Astrobiological Potential of Polar Dunes  

NASA Astrophysics Data System (ADS)

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

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

2009-03-01

305

Methane storms as a driver of Titan's dune orientation  

E-print Network

Titan's equatorial regions are covered by eastward propagating linear dunes. This direction is opposite to mean surface winds simulated by Global Climate Models (GCMs), which are oriented westward at these latitudes, similar to trade winds on Earth. Different hypotheses have been proposed to address this apparent contradiction, involving Saturn's gravitational tides, large scale topography or wind statistics, but none of them can explain a global eastward dune propagation in the equatorial band. Here we analyse the impact of equinoctial tropical methane storms developing in the superrotating atmosphere (i.e. the eastward winds at high altitude) on Titan's dune orientation. Using mesoscale simulations of convective methane clouds with a GCM wind profile featuring superrotation, we show that Titan's storms should produce fast eastward gust fronts above the surface. Such gusts dominate the aeolian transport, allowing dunes to extend eastward. This analysis therefore suggests a coupling between superrotation, tro...

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

2015-01-01

306

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

307

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

308

Nutrient deficiency in dune slack pioneer vegetation: a review  

Microsoft Academic Search

A review of results of fertilization experiments in wet dune slacks is presented. In most cases the above-ground biomass appeared\\u000a to be limited by nitrogen availability. Primary phosphorus limitation was assessed only once in a dune slack where sod cutting\\u000a had been applied very recently. In most other case studies phosphorus limits biomass production after nitrogen deficiency\\u000a was lifted. Potassium

E. J. Lammerts; A. P. Grootjans

1997-01-01

309

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

310

Holocene history of the Great Kobuk Sand Dunes, Northwestern Alaska  

NASA Astrophysics Data System (ADS)

Located just north of the Arctic Circle, the Great Kobuk Sand Dunes (GKSD) are an inland dune field that is closely surrounded by boreal forest. The history of the GKSD tells us about changes in aridity, a climatic parameter whose history is poorly understood at high latitudes. Vegetated dunes in several states of geomorphic preservation surround the active dune field today, evidencing a complex history of Holocene activity. Small lakes in the forest bordering the dunes accumulate wind-blown sand. We use 14C-dated, lake-sediment cores to reconstruct a continuous history of sand influx over the last 8000 yr. The validity of this record is supported by limiting ages obtained from stratigraphic sections within the dune field. The extent of the GKSD underwent a fluctuating shrinkage coincident with Neoglaciation. This downsizing trend was interrupted by periods of increased sand deposition into lakes occurring 4800-4200, 3300-2600, 1300-700, and 300-100 calendar years ago. Aridity in the Kobuk valley during the Holocene probably was controlled by the frequency of North Pacific storms entering the region in late summer. Our results describe the first continuous history of changing moisture balance for central Beringia during the Holocene and comprise a baseline against which future records of climatic and ecological change in this region can be compared.

Mann, D. H.; Heiser, P. A.; Finney, B. P.

2002-02-01

311

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

2007-07-10

312

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

2008-07-24

313

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

Microsoft Academic Search

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

JANE L. PORSYTH; ERNEST S. HAMILTON

314

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

315

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

2013-07-12

316

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

317

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

318

Titan's Yin-yang equator: dunes and Xanadu  

NASA Astrophysics Data System (ADS)

Two of Titan's most enigmatic geomorphological features, the dark dunes and the bright Xanadu terrain, encircle Titan's equator. They may bracket the time frame for persistence of surface features on Titan, so understanding their ages is important for evaluating Titan's surface history. Dunes, covering nearly 20% of Titan's surface, are rarely cut by other features and are thus among the youngest on Titan. Pattern analysis reveals current wind strengths and directions and contains information about past wind and sediment supply conditions. In contrast, the rugged Xanadu terrain contains the highest density of likely impact craters of any region on Titan, and thus is among the oldest terrains. Some of the most well-evolved river drainages on Titan are present in Xanadu, and reflect widespread and persistent precipitation and erosion, begun in the distant past and extending perhaps to the present day. As we broaden our vision beyond the study of individual geomorphic features, we seek to find a spatial and temporal connection between them. Dunes abut Xanadu on nearly all sides, and the presence of Xanadu affects the pattern of dunes for many hundreds of kilometers. Yet if dunes are younger than Xanadu and active, it is not clear why they do not invade its topographically subdued margins - perhaps sands are actively removed from the margins of Xanadu by fluvial processes. These processes, however, do not create dune-carving drainages, blur the dune structures or form obvious sand sinks. Piecing together the related evolution of these morphologically disparate yet spatially linked features is critical for creating a viable relative geological time scale for Titan.

Radebaugh, Jani; Lorenz, Ralph; Savage, Chris

2010-04-01

319

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

320

The Mediterranean Coastal Dunes in Egypt: An Endangered Landscape  

NASA Astrophysics Data System (ADS)

The Mediterranean coast in Egypt extends almost 900 km, the major part of which is bordered by sand dunes of different natures and types. Along the coastline between Alexandria and El-Alamein, a distance of some 100 km, the sand dunes represent a particular landscape with special characteristics and features, and consequently plants with particular attributes. In this area, the belt of sand dunes has developed immediately south of the shore and these dunes may rise up to 10 m in height and extend about 0·5-1·5 km inland from the shore. These dunes are famous as a habitat for the fig (Ficus carica L.) cultivation depending on the irregular rainfall. They also represent a landing station and a cross-road for birds such as quail migrating from Europe in the north. In the past, summer resort areas were confined to limited areas with few people, these same areas support the growth of some important plant species, for example, sand binders, medicinal and range plants. For more than two decades, there has been considerable socio-economic change and an open-door policy in the economy of the country has been adopted. One of the consequences of this change is that a great part of the coastal dune belt west of Alexandria till El-Alamein, has been subjected to destruction, due to the continuous construction of summer resort villages. These were built at a distance of about 100 m of the shoreline, extending 400-600 m inland and a breadth of 400 m or more along the shoreline. The area already covered by the dunes is now almost occupied by new buildings, gardens and other infrastructure. The consequences of these human activities are numerous and include impacts on the soil, water resources, the flora and the fauna, migrating birds, trends of the indigenous people, and the cultural environment. The present paper gives a concise environmental setting of the dune belt before the advent of the new activities, and the socio-economic and political attitudes which threaten the dunes. The ecological consequences of the recent human activities and recommendations are presented.

Batanouny, K. H.

1999-08-01

321

A constitutive relationship between mean and local eolian dune migration  

NASA Astrophysics Data System (ADS)

How can eolian dune fields achieve alignment to a wind regime if every sediment transporting wind event displaces curved bedform crests unequally? Gross bedform-normal transport and alignment is a kinematic model that describes how bedforms are oriented and migrate in response to a dominant and subordinate sediment-transport vector. The local bedform normal model describes how eolian dune crests deform non-uniformly in response to a singular sediment-transporting wind event. Bedform crest alignment to sediment transporting wind events is the conceptual underpinning that predicts what fraction of the sediment flux goes into bedform migration in both models. By embracing this geometric commonality we reconcile the two models. The new kinematic model yields a constitutive relationship between mean and local dune crest orientation and kinematics for a statistically steady wind regime. The new kinematic model is applied to calculate mean and directional variation in sediment flux at the White Sands dune field, NM, using meteorological data. The model results are compared to observed dune migration and orientation imaged in a time series of DEMs built from a time series of airborne LiDAR surveys.

Swanson, T.; Mohrig, D. C.; Kocurek, G.

2013-12-01

322

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

323

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

324

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

E-print Network

Crescent as a Result of Global Warming J. P. EVANS Department of Geology and Geophysics, Yale University of global warming. Regional climate model [fifth-generation Pennsylvania State University­National Cen- ter watershed. Growing acceptance of the reality of global warming has recently led to an increase

Evans, Jason

325

RESEARCH ARTICLE The scale of genetic differentiation in the Dunes Sagebrush-Lizard  

E-print Network

RESEARCH ARTICLE The scale of genetic differentiation in the Dunes Sagebrush-Lizard (Sceloporus+Business Media B.V. 2008 Abstract The Dunes Sagebrush-Lizard (Sceloporus are- nicolus) is a North American

Zamudio, Kelly R.

326

36 CFR 28.3 - Boundaries: The Community Development District; The Dune District; The Seashore District.  

Code of Federal Regulations, 2010 CFR

...2010-07-01 false Boundaries: The Community Development District; The Dune District...Provisions § 28.3 Boundaries: The Community Development District; The Dune District...headquarters. There are three districts: The Community Development District, the Seashore...

2010-07-01

327

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

Code of Federal Regulations, 2012 CFR

...Evaluation of sand dunes in mapping coastal flood hazard areas. 65.11 Section 65...INSURANCE AND HAZARD MITIGATION National Flood Insurance Program IDENTIFICATION AND...Evaluation of sand dunes in mapping coastal flood hazard areas. (a) General...

2012-10-01

328

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

Code of Federal Regulations, 2010 CFR

...Evaluation of sand dunes in mapping coastal flood hazard areas. 65.11 Section 65...INSURANCE AND HAZARD MITIGATION National Flood Insurance Program IDENTIFICATION AND...Evaluation of sand dunes in mapping coastal flood hazard areas. (a) General...

2010-10-01

329

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

Code of Federal Regulations, 2011 CFR

...Evaluation of sand dunes in mapping coastal flood hazard areas. 65.11 Section 65...INSURANCE AND HAZARD MITIGATION National Flood Insurance Program IDENTIFICATION AND...Evaluation of sand dunes in mapping coastal flood hazard areas. (a) General...

2011-10-01

330

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

Code of Federal Regulations, 2014 CFR

...Evaluation of sand dunes in mapping coastal flood hazard areas. 65.11 Section 65...INSURANCE AND HAZARD MITIGATION National Flood Insurance Program IDENTIFICATION AND...Evaluation of sand dunes in mapping coastal flood hazard areas. (a) General...

2014-10-01

331

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

Code of Federal Regulations, 2013 CFR

...Evaluation of sand dunes in mapping coastal flood hazard areas. 65.11 Section 65...INSURANCE AND HAZARD MITIGATION National Flood Insurance Program IDENTIFICATION AND...Evaluation of sand dunes in mapping coastal flood hazard areas. (a) General...

2013-10-01

332

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

333

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

334

Examining variability in preserved topography of linear dunes on a salt substrate  

NASA Astrophysics Data System (ADS)

Linear dunes in the Norphlet sandstone in the Gulf of Mexico were developed on the underlying Louann salt layer during the Late Jurassic as they subsided into the salt substrate. The carbonate Smackover Formation overlies the Norphlet dunes as a result of a marine transgression. Despite the rapid marine deposition, the dunes show variability in their preserved dune-surface topography that indicates time between termination of the local dune development and overall marine transgression. We performed physical experiments and created a mathematical model to understand dune and salt deformation and to determine the time scale controls on the final topography. Our results indicate that the ratio of sand to salt thickness governs the amount and rate of subsidence, thus affecting the final dune topography. However, dune spacing and/or experimental scale also controls subsidence rates. Varying amounts of friction with either tank walls or neighboring dunes can alter the flow rate of salt, which affects the rate at which the dune can subside. Linear dune migration also creates an age gradient that gives way to a gradient in relief of the preserved dunes. Older upwind portions of dunes were likely able to fully subside before the marine transgression, whereas the more recently deposited downwind dune tips still had high relief at the time of marine deposition. We conclude that preserved dunes that are downwind, over thin salt, and/or closely spaced have higher relief, and dunes that are upwind, over thick salt, and/or sparsely spaced have less relief. Seismic data from the Gulf of Mexico corroborates our results.;

Piliouras, A.; Kim, W.; Kocurek, G.; Mohrig, D. C.; Kopp, J.

2012-12-01

335

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

336

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

337

Aeolian dunes as ground truth for atmospheric modeling on Mars  

USGS Publications Warehouse

Martian aeolian dunes preserve a record of atmosphere/surface interaction on a variety of scales, serving as ground truth for both Global Climate Models (GCMs) and mesoscale climate models, such as the Mars Regional Atmospheric Modeling System (MRAMS). We hypothesize that the location of dune fields, expressed globally by geographic distribution and locally by dune centroid azimuth (DCA), may record the long-term integration of atmospheric activity across a broad area, preserving GCM-scale atmospheric trends. In contrast, individual dune morphology, as expressed in slipface orientation (SF), may be more sensitive to localized variations in circulation, preserving topographically controlled mesoscale trends. We test this hypothesis by comparing the geographic distribution, DCA, and SF of dunes with output from the Ames Mars GCM and, at a local study site, with output from MRAMS. When compared to the GCM: 1) dunes generally lie adjacent to areas with strongest winds, 2) DCA agrees fairly well with GCM modeled wind directions in smooth-floored craters, and 3) SF does not agree well with GCM modeled wind directions. When compared to MRAMS modeled winds at our study site: 1) DCA generally coincides with the part of the crater where modeled mean winds are weak, and 2) SFs are consistent with some weak, topographically influenced modeled winds. We conclude that: 1) geographic distribution may be valuable as ground truth for GCMs, 2) DCA may be useful as ground truth for both GCM and mesoscale models, and 3) SF may be useful as ground truth for mesoscale models. Copyright 2009 by the American Geophysical Union.

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

2009-01-01

338

Orographic forcing of dune forming winds on Titan  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

339

Observations Regarding Small Eolian Dunes and Large Ripples on Mars  

NASA Technical Reports Server (NTRS)

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

Edgett, Kenneth S.

2001-01-01

340

Observations regarding small eolian dunes and large ripples on Mars  

NASA Astrophysics Data System (ADS)

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

Edgett, K. S.

2001-11-01

341

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

Federal Register 2010, 2011, 2012, 2013, 2014

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

2011-09-15

342

Dynamique d'une bulle cylindrique de cavitation : tude analytique et validation de la mthode  

E-print Network

présente sous la forme d'une bulle de cavitation cylindrique de rayon Rb se trouvant à l'intérieur d'une goutte cylindrique d'eau de rayon Rg , elle-même sous pression d'une atmosphère d'air, comme schématisé temps de collapse en fonction de correspond- ant au ratio entre le rayon maximum de la bulle et le

343

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

344

On the transition between 2D and 3D dunes JEREMY G. VENDITTI*1  

E-print Network

On the transition between 2D and 3D dunes JEREMY G. VENDITTI*1 , MICHAEL CHURCH* and SEAN J the processes that transform the bed configuration from two-dimensional (2D) dunes to three- dimensional (3D) dunes. A narrowly graded, 500 lm size sand was subjected to a 0Æ15 m deep, non-varying mean flow ranging

Venditti, Jeremy G.

345

Morphological barrier island changes and recovery of dunes after Hurricane Dennis, St. George Island, Florida  

E-print Network

Morphological barrier island changes and recovery of dunes after Hurricane Dennis, St. George September 2009 Keywords: Dune recovery LiDAR Overwash Hurricane Dennis Barrier island During the summer of the barrier island are analyzed, along with the short-term post-storm recovery of secondary dunes. Results

Fagherazzi, Sergio

346

Solving the mystery of booming sand dunes Nathalie M. Vriend,1  

E-print Network

Solving the mystery of booming sand dunes Nathalie M. Vriend,1 Melany L. Hunt,1 Robert W. Clayton,2 of a large dune. The sound is remarkable because it is composed of one dominant audible frequency (70 to 105 Hz) plus several higher harmonics. This study challenges earlier reports that the dunes' frequency

Martin, Alain

347

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

348

Dynamics of unusual debris flows on Martian sand dunes Hideaki Miyamoto,1,2  

E-print Network

Dynamics of unusual debris flows on Martian sand dunes Hideaki Miyamoto,1,2 James M. Dohm,3 Victor 9 June 2004; published 8 July 2004. [1] Gullies that dissect sand dunes in Russell impact crater a surface layer of interstitial ice within the dune deposits to several centimeters depth. INDEX TERMS: 1824

Bourke, Mary C.

349

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

350

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

351

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.

352

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

353

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.

354

AlAbAmA Dune RestoRAtion PRoject General Project DescriPtion  

E-print Network

AlAbAmA Dune RestoRAtion PRoject General Project DescriPtion The cities of Gulf Shores and Orange miles of dune habitat. This restoration project will result in the formation of a partnership, the Coastal Alabama Dune Restoration Cooperative (CADRC), to restore natural resources that were injured

355

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.

356

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 Licence #12;iv Abstract It is increasingly obvious that dunes with low-angle lee-sides (

Venditti, Jeremy G.

357

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.

2004-01-01

358

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

359

INITIATION AND DEVELOPMENT OF SAND DUNES IN RIVER CHANNELS Jeremy George Venditti  

E-print Network

INITIATION AND DEVELOPMENT OF SAND DUNES IN RIVER CHANNELS by Jeremy George Venditti B in the experiments. The 2D bedforms initiated by the Kelvin-Helmholtz instability developed into dune features that grew exponentially towards equilibrium dimensions. Dune heights and lengths increased with flow

Venditti, Jeremy G.

360

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

361

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

362

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.

363

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

364

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.

365

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

E-print Network

Sand dune mobility under climate change in the Kalahari and Australian deserts Y. Ashkenazy & H.V. 2011 Abstract Vegetation cover on sand dunes mainly depends on wind power (drift potential--DP) and precipitation. When this cover decreases below a minimal percentage, dunes will start moving. It is therefore

Ashkenazy, Yossi "Yosef"

366

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

367

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.

368

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

369

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"

370

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.

371

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

E-print Network

The fluid dynamics of river dunes: A review and some future research directions Jim Best Earth; revised 14 October 2005; accepted 20 October 2005; published 21 December 2005. [1] Dunes are present, and deposition within many rivers. Progress in understanding the fluid dynamics associated with alluvial dunes

Venditti, Jeremy G.

372

Late Pleistocene and Holocene dune activity and wind regimes in the western Sahara Desert of Mauritania  

Microsoft Academic Search

The western Sahara Desert in Mauritania is dominated by extensive sand seas consisting largely of linear dunes. Analyses of Landsat images, geomorphic and stratigraphic studies, and optically stimulated luminescence dating of dunes in the Azefal, Agneitir, and Akchar sand seas provide evidence that three main generations of dunes were formed during the periods 25 15 ka (centered around the Last

Nicholas Lancaster; Gary Kocurek; Ashok Singhvi; V. Pandey; Max Deynoux; Jean-Francois Ghienne; Khalidou Lô

2002-01-01

373

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

374

[Formation of the gray crescent, induced in axolotl oocytes during maturation, depends on factors of nuclear origin].  

PubMed

Inhibitors of protein synthesis caN elicit the precocious appearance of a grey crescent (GC) in in vitro maturing Ambystoma mexicanum oocytes. This treatment however fails to induce GC formation when the oocytes are enucleated before initiation of maturation. The ability to form a GC is reestablished in enucleated oocytes by the injection of nucleoplasm from a normal oocyte, either before or after injection of the inhibitor. In the latter case, the GC appears even though the protein synthesis level is already about one-tenth that of the control enucleated oocytes. One or several nuclear factors, in conjunction with protein synthesis inhibition, are therefore essential for the early symmetry reaction. The corrective nuclear factor is already present in the germinal vesicle of young oocytes at the very beginning of vitellogenesis. It is not species-specific and enucleated axolotl oocytes can be symmetrized with Pleurodeles or even Xenopus oocyte nucleoplasm. The interaction between nuclear factor(s) and cytoplasm is possible only when cytoplasmic maturation has occurred. PMID:6412990

Gautier, J; Beetschen, J C

1983-01-01

375

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

PubMed Central

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

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

2014-01-01

376

Solar collection  

SciTech Connect

This report contains summaries and pictures of projects funded by the Appropriate Technology Small Grants Program which include the following solar technologies: solar dish; photovoltaics; passive solar building and solar hot water system; Trombe wall; hot air panel; hybrid solar heating system; solar grain dryer; solar greenhouse; solar hot water workshops; and solar workshops.

Cole, S.L.

1984-08-01

377

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

378

Vegetative control of inland sand dunes in the Pacific Northwest  

Microsoft Academic Search

Mammoth wildrye, Elymus giganteus Vahl. was found, after exhaustive tests using a large number of native and some exotic perennial herbaceous and woody plants, to be most effective for inland sand dune control. A superior strain selected for its vigor and rapid vegetative growth was named `Volga,' released, and registered in 1964. It is propagated vegetatively. Under irrigation and with

J. L. Schwendiman

1977-01-01

379

Vegetative control of inland sand dunes in the Pacific Northwest  

Microsoft Academic Search

Mammoth wildrye,Elymus giganteus Vahl. was found, after exhaustive tests using a large number of native and some exotic perennial herbaceous and woody plants, to be most effective for inland sand dune control. A superior strain selected for its vigor and rapid vegetative growth was named ‘Volga,’ released, and registered in 1964. It is propagated vegetatively. Under irrigation and with fertiliter,

J. L. Schwendiman

1977-01-01

380

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

381

Coniferous afforestation increases soil carbon in maritime sand dunes  

Microsoft Academic Search

Afforestation of grasslands can increase C sequestration and provide additional economic and environmental benefits. Pine plantations, however, have often been found to deplete soil organic C and trigger detrimental effects on soils. We examined soil characteristics under a 45-year-old Pinus radiata stand and under adjacent grassland on maritime dunes in temperate Argentina. Soil under the pine plantation had greater soil

Nilda M. Amiotti; Pablo Zalba; Adrian Ares; Javier M. Rossi

2012-01-01

382

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

383

Vetiver System for Sand Dune Stabilization A Vietnamese Experience  

Microsoft Academic Search

Sand dunes occupy more than 70,000 ha along the coast of Central Vietnam, being the sources of such natural disasters as sand storm, sand flow\\/flash flood etc., that eat either slowly or catastrophically villages and fields. This has been surveyed by a team of geologists from the Research Institute of Geology and Mineral Resources (RIGMR), who also looked for remedial

384

Coastal sand dune stabilization in the Pacific Northwest  

Microsoft Academic Search

Coastal dunes are stabilized in three stages: (1) The initial stage uses sand-stilling grasses established vegetatively. For this purpose, European beachgrass, Ammophila arenaria (L.) Link., is most used, followed by American beachgrass, A. breviligulata Fern., or American dunegrass, Elymus mollis Trin. Large solid plantings must be made with the spacing and number of plants per hill adjusted to the site

J. L. Schwendiman

1977-01-01

385

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

E-print Network

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

Reiners, Peter W.

386

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...

387

Lateral variations in suspended sediment concentration over dunes  

Technology Transfer Automated Retrieval System (TEKTRAN)

The magnitude of the lateral variations in the concentration of suspended sediment over dunes in an alluvial sand-bed channel are poorly known. Characterizing the lateral distributions of suspended sediment is important for understanding its causes and for accurate measurement of the rate of sedim...

388

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

389

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

390

SPATIAL VARIATIONS IN SUSPENDED SEDIMENT TRANSPORT OVER DUNES  

Technology Transfer Automated Retrieval System (TEKTRAN)

The magnitude of the lateral variations in the concentration of suspended sediment over dunes in an alluvial sand-bed channel are poorly known. Characterizing the lateral distributions of suspended sediment is important for understanding its causes and for accurate measurement of the rate of sedim...

391

Modlisation d'une srie financire par mouvement Brownien  

E-print Network

Brownien frac- tionnaire fBm (fractional Brownian motion) qui est caractérisé par son in- dice de Hurst HModélisation d'une série financière par mouvement Brownien multi-fractionnaire parcimonieux Pierre In this work we introduce sparse modelling for fractal like pro- cesses. We recall the stream which has leaded

Paris-Sud XI, Université de

392

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

393

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

394

Volcaniclastic dunes from the 2006 deposits of Tungurahua volcano, Ecuador  

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

395

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"

396

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

397

Recent aeolian dune change on Mars M.C. Bourke a,b,, K.S. Edgett c  

E-print Network

Recent aeolian dune change on Mars M.C. Bourke a,b,, K.S. Edgett c , B.A. Cantor c a Planetary 2007 Abstract 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

Bourke, Mary C.

398

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

399

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"

400

Ground-penetrating radar (GPR) for imaging stratigraphic features and groundwater in sand dunes  

NASA Astrophysics Data System (ADS)

In this work, the internal structures of some sand dunes from the Eastern Province of Saudi Arabia, and Moreton Island in Australia have been visualized using the GPR technique. The depth of penetration that was achieved is limited (less than 35 m using a 100-MHz antenna, and approximately 9 m using a 500-MHz antenna), but the excellent spatial resolution has made it possible to clearly identify internal dune bedding features such as cross-laminations. It is shown that a radargram of a sand dune can be interpreted to provide clues about the evolutional history of the dune. The groundwater table inside a dune, when present, is shown to be detectable using GPR provided the appropriate antenna frequency is used. Also, discrete wetting fronts and preferential flow paths have been visualized in dunes that have become saturated after episodes of rain, indicating that internal groundwater movement in dunes appears to be controlled by stratigraphic features.

Harari, Zaki

1996-11-01

401

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

402

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

403

Dispersal by cattle of salt-marsh and dune species into salt-marsh and dune communities  

Microsoft Academic Search

Seed dispersal via ingestion and defecation by large herbivores (endozoochory) plays a potentially important role in structuring plant communities. In the present study we tested whether cattle disperse seeds between different plant communities in a heterogeneous coastal habitat. We surveyed the seed contents of cattle dung collected from two habitat types within a grazing system, one in dunes and the

J. P. Bakker; L. Gálvez Bravo; A. M. Mouissie

2008-01-01

404

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

405

Synthesis of various ionospheric convection patterns for IMF BY-dominated periods: Split crescent cells, exchange cells, and theta aurora formation  

Microsoft Academic Search

When the dawn-to-dusk component of the interplanetary magnetic field (IMF BY) is dominant, ionospheric convection exhibits a distorted two-cell pattern with its dawn-dusk and interhemispheric asymmetries regulated by the IMF BY polarity. For BY > 0, the convection in the Northern (Southern) Hemisphere usually consists of a relatively round cell on the duskside (dawnside) and a crescent-shaped cell on the

Masakazu Watanabe; George J. Sofko

2008-01-01

406

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

407

Population-based resequencing reveals that the flowering time adaptation of cultivated barley originated east of the Fertile Crescent.  

PubMed

Gene resequencing and association analysis present new opportunities to study the evolution of adaptive traits in crop plants. Here we apply these tools to an extensive set of barley accessions to identify a component of the molecular basis of the flowering time adaptation, a trait critical to plant survival. Using an association-based study to relate variation in flowering time to sequence-based polymorphisms in the Ppd-H1 gene, we identify a causative polymorphism (SNP48) that accounts for the observed variation in barley flowering time. This polymorphism also shows latitude-dependent geographical distribution, consistent with the expected clinal variation in phenotype with the nonresponsive form predominating in the north. Networks, genealogies, and phylogenetic trees drawn for the Ppd-H1 haplotypes reveal population structure both in wild barley and in domesticated barley landraces. The spatial distribution of these population groups indicates that phylogeographical analysis of European landraces can provide information relevant to the Neolithic spread of barley cultivation and also has implications for the origins of domesticated barley, including those with the nonresponsive ppd-H1 phenotype. Haplotypes containing the nonresponsive version of SNP48 are present in wild barley accessions, indicating that the nonresponsive phenotype of European landraces originated in wild barley. The wild accessions whose nonresponsive haplotypes are most closely similar to those of landraces are found in Iran, within a region suggested as an area for domestication of barley east of the Fertile Crescent but which has previously been thought to have contributed relatively little to the diversity of European cultivars. PMID:18669581

Jones, Huw; Leigh, Fiona J; Mackay, Ian; Bower, Mim A; Smith, Lydia M J; Charles, Michael P; Jones, Glynis; Jones, Martin K; Brown, Terence A; Powell, Wayne

2008-10-01

408

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 coastal dune area of the Amsterdamse Waterleidingduinen (near Haarlem, the Netherlands). However, to understand forest soil development, including the organic matter composition in the humus form, the age of the substrate and the forest is required. Therefore, we used tradition techniques as pollen analysis and radiocarbon dating but also the recently introduced optical stimulated luminescence (OSL) dating technique. OSL dating works excellent for aeolian sandy deposits with a high percentage of quartz grains. The OSL age is defined as the time after the last bleaching by solar radiation of mineral grains. Or in other words, the start of a stable period without sand drifting. In the Ah horizons we observed palynological traces of a former dune landscape with grasses and typical dune land shrubs. The F and H horizons were dominated by Quercus pollen. In thin sections we found that in the upper part of the F horizons the soil skeleton was formed by leaf litter fragments that were fragmented and decomposed by fungi and micro arthropods. The soil skeleton of the lower part of the F horizons consisted of a mixture of leaf litter fragments and (dead) root fragments. In this part of the profile, fungi and micro arthropods were also responsible for the physical and chemical organic matter decomposition. The soil skeleton of the Ah horizons was formed by mineral grains in which small sized organic aggregates occurred. These aggregates may have four possible sources: (1) sinsedimentary aggregates, involved in sand drifting, (2) fecal relicts from decomposed (older) roots of a former dune land vegetation, (2) fecal relicts from decomposed (younger) roots of the forest and its understory, and (3) infiltrated parts of fecal pallets from the overlying F horizons. The calibrated radiocarbon dates of organic matter from the upper 5 cm of the Ah horizons go back to around 1960 AD. This points to a 45 year period for the development of the ectorganic horizons, assuming that fresh organic matter did not ‘contaminate' the radiocarbon dating. The OSL the ages of quartz grains from the upper 5 cm of the Ah horizons indicate landscape stabilization around 1800AD implying that two centuries were available for vegetation and soil development. There seems to be a significant difference between the OSL and 14C ages of the top of the Ah horizon. The OSL dates are very reliable. They indicate the correct time of the transformation of drift sand into stable, vegetated landscape. The pollen spectra of the Ah horizon show traces of dune grass and shrub landscape, but probably these pollen grains originate from sinsedimentary organic aggregates. And during the juvenile phase of a quercus forest, the quercus pollen production is very low and other wind pollinated grains from dune grasses

van Mourik, J. M.; Nierop, Ir. K.; Verstraten, J. M.

2009-04-01

409

DuneXpress: dust astronomy with Dune and ConeXpress  

NASA Astrophysics Data System (ADS)

We present a mission scenario to implement the Cosmic Dune mission concept (Cosmic dust measurements near Earth) using the ConeXpress platform developed by Dutch Space. We discuss the different strategies for the instrument integration on-board the platform and present a preliminary mission design. Goal of the mission is to reach the Sun-Earth Lagrange point L2. As ConeXpress is propelled with ion engines, a mission design inspired from the Smart 1 mission is developed. The ConeXpress spacecraft benefits of launch opportunities as secondary payload on-board an Ariane 5 rocket and is injected into a classical geostationary transfer orbit (GTO). Starting from this parking orbit, the mission scenario is divided in 3 phases. The first phase consists in raising the orbit perigee as quick as possible up to 20000 km to minimize the spacecraft exposure to the Van Allen radiation belt. During the second phase, the perigee altitude is kept constant, while the apogee altitude is raised up to the Moon's orbit distance. The third phase consists in a Moon swing-by, which injects the spacecraft into a Halo orbit around the Lagrange point L2.

Altobelli, N.; Lera, S.; Srama, R.; Vo, X.; de Kam, J.; Gruen, E.

410

Laboratory Analyses Of Basaltic Dunes In The Ka'u Desert Of Hawaii And Implications For Understanding Dark Dunes On Mars  

NASA Astrophysics Data System (ADS)

Dark dunes are the dominant aeolian bedforms on Mars and consist of ancient volcanic ashes and reworked basaltic lavas. Basaltic dunes are rare on Earth and only occur in limited areas, such Hawaii. Because the Hawaiian dunes are composed of reworked basaltic sediments transported by eolian processes, they are a promising subject matter of analogy studies. Samples of dark dune sands, ash, and tephra collected in Hawaii's Ka'u Desert were collected during field trips in summer 2009 and 2010. They were analyzed by a variety of laboratory methods, including spectral, microscope, and microprobe investigations, in order examine their detailed mineralogical composition and constitution. We then compared the results to the eolian dunes on Mars. Sand samples were collected from three different dark dunes in Ka'u Desert: a large, vegetated, parabolic dune, a falling dune, and a large climbing dune. Tephra from the phreatic eruption that began in March 2008 was collected over a two year period using sample collectors placed at different locations downwind of Kilauea caldera. Analyses of these samples allow us to determining the initial composition, grain shape, and grain size of probable source materials. The visible and near-infrared reflectance spectra of the samples were acquired for the 0.5 to 2.5µm range. The overall spectral shape of the dune sand samples indicates a mineralogical correlation between Martian and terrestrial dune sands indicating a similar volcanic origin of the sediments. The spectra of the Hawaiian samples reveal some aqueous alteration, which is probably related to hydrated amorphous silica. Initial microscope and microprobe analyses reveal a high amount of volcanic glass and rock fragments in the samples, followed by olivine, feldspars, and pyroxene. Vitric particles that dominate the majority of the dune samples indicate in situ material accumulation following larger phreatic eruptions. The top coarse-grained layer of the climbing dune comprises a higher amount of rock fragments, indicating that these sands originate from reworked lava and were deposited in a subsequent dune formation phase (see also Craddock et al., this conference). We will present the comparison of Martian, terrestrial and library spectra, determine grain shape and grain size, and propose possible sediment sources, transport mechanisms, and development of the dune material.

Tirsch, D.; Craddock, R. A.; Nanson, G.; Tooth, S.; Langhans, M.

2010-12-01

411

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

412

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

NASA Astrophysics Data System (ADS)

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

Benaafi, Mohammed; Abdullatif, Osman

2014-05-01

413

Debris-flow benches: Dune-contact deposits record paleo-sand dune positions in north Panamint Valley, Inyo County, California  

SciTech Connect

Debris flows debouching onto the alluvial fan at the north end of Panamint Valley, California, have been episodically impounded behind sand dunes, resulting in boulder-strewn, nearly flat topped deposits in irregular basins upslope of the dune, whose upper surface is higher than the adjacent fan surface. Upslope migration of the dune field over and beyond these deposits eventually leaves them as debris-flow benches rising above the general fan surface. These features are therefore dune-contact forms, analogous to ice-contact forms such as kame terraces, in that both involve deposition against ephemeral barriers. Benches punctuate the alluvial-fan surface for 5 km downfan from the modern dune field. Clast seismic velocities of boulders on these benches indicate that bench ages increase monotonically with distance from the present dunes, implying that the dune field has migrated up the fan. Because the oldest bench is below the altitude of the highest pluvial lake shoreline in Panamint Valley (Gale Stage, ca. 50 ka) and slightly above the latest lakeshore (I Stage, ca. 14 ka), it seems likely that the dunes originated near the shore of the latest lake and have moved upfan at an average rate of 0.8 m/yr.

Anderson, S.P. (Univ., of California, Berkeley (USA)); Anderson, R.S. (Univ. of California, Santa Cruz (USA))

1990-06-01

414

Mesure par interférométrie laser du mouvement d'une particule proche d'une paroi  

NASA Astrophysics Data System (ADS)

An experimental technique based on laser interferometry is used to obtain the displacement of a sphere towards a plane wall in a viscous fluid : it consists in inserting the sphere in an interferometric system, in such a way that the displacement of the sphere changes the state of interference. An important feature of the setup is that the shape, the roughness, and the positioning of the sphere in the optical path are relatively uncritical. The spheres used in the experiment are bearing balls, 4 and 5 × 10^{-3} m in diameter. The accuracy on the sphere displacement is of the order of 2 × 10^{-8} m. The interference signal is digitalized and stored in a microcomputer. The data are then processed to yield the friction coefficient f^T_zz of the sphere in its motion very close to the wall. The variation of f^T_zz with the non-dimensional gap \\varepsilon (ratio of the gap to the sphere radius) show three regions: (i) One in which a is small but at least 10 times larger than the non-dimensional rugosity (ratio of the scale of rugosity to the sphere radius) ; there is then a very good agreement with the result valid for a smooth sphere f^T_zz = 1/\\varepsilon from lubrication theory. (ii) When \\varepsilon decreases to the order of the non-dimensional rugosity, the friction coefficient is then smaller than 1/\\varepsilon. The technique thus opens a way to study the effects of rugosity in hydrodynamics. (iii) The technique allows to measure gaps of the order of 10^{-8} m and could thus be used in future studies of short ranges forces. On utilise une technique expérimentale basée sur l'interférométrie laser pour déterminer le déplacement d'une sphère s'approchant d'une paroi plane dans un fluide visqueux: la technique consiste à insérer la sphère dans un système interférométrique, de façon que son déplacement change l'état d'interférence détecté. Une particularité importante du montage utilisé est que la forme, l'état de surface, le positionnement, et l'alignement de la sphère dans le montage optique sont relativement peu critiques. Les sphères utilisées sont des billes de roulements à billes, de 4 et 5 × 10^{-3} m de diamètre. La précision sur le déplacement de la sphère est de l'ordre de 2 × 10^{-8} m. Le signal d'interférence est digitalisé et stocké dans un micro-ordinateur. Le traitement des données permet alors d'obtenir le coefficient de frottement f^T_zz de la sphère en mouvement tout près de la paroi. La variation de f^T_zz avec l'intervalle sans dimension \\varepsilon (rapport de l'intervalle entre la sphère et la paroi au rayon de la sphère) permet de distinguer trois régions: (i) Une région où \\varepsilon est petit mais au moins 10 fois plus grand que la rugosité non dimensionnelle (rapport de l'échelle de la rugosité au rayon de la sphère) ; le résultat expérimental est alors en très bon accord avec la formule f^T_zz = 1/\\varepsilon démontrée en théorie de la lubrification, formule valable pour une sphère lisse. (ii) Lorsque \\varepsilon décroît pour devenir de l'ordre de grandeur de la rugosité non dimensionnelle, le coefficient de frottement est alors inférieur à Il E. La technique ouvre ainsi une nouvelle voie à l'étude des effets de rugosité en hydrodynamique. (iii) La technique permet de mesurer des intervalles de l'ordre de 10^{-8} m et pourrait ainsi être utilisée dans l'étude des forces à courte portée.

Assou, Y.; Joyeux, D.; Azouni, A.; Feuillebois, F.

1991-02-01

415

Valles Marineris Dune Fields as Seen From the HiRISE, CTX and THEMIS Cameras  

NASA Astrophysics Data System (ADS)

Dune fields on Mars offer an opportunity to investigate the nature of eroded sediments and their interactions with the atmosphere. We examined 20 dune fields in Valles Marineris (VM) from the Mars Global Digital Dune Database [Hayward et al., 2007] to identify significant trends in composition, thermophysical properties, morphology and origin. Dune fields were examined in terms of: slopes, albedo, dust index, thermal inertia and the corresponding derived particle size. We have used image data from the Mars Reconnaissance Orbiter (MRO) instruments CTX [McEwen et al., 2006] and HiRISE [Malin et al., 2007] to establish geologic context for the dune fields, and in particular, to examine their relationships to neighboring geologic units. In general, VM dune fields display greater topographic relief and closer proximity to their inferred source regions than is typical for dune fields elsewhere on Mars. These dunes have a relatively high TES-derived thermal inertia mean value (394 Jm-2K-1 s-1/2, units hereafter assumed), which corresponds to ~1000 ?m grains [Pelkey et al., 2001] or very coarse sand sizes. In contrast, typical non-VM dunes have a lower thermal inertia value of ~250, corresponding to ~350 ?m grains. To investigate this more closely, high-resolution THEMIS-derived thermal inertia maps were created [Putzig et al., 2004]. CTX and HiRISE visible images revealed that bedrock outcrops are commonly found within dune fields, erroneously elevating the TES thermal inertia values over the ~3x5-km TES footprint. However, even after excluding intra-dune outcrop areas using higher-resolution THEMIS data, several VM dune fields have anomalously high thermal inertia values (>500) compared with non-VM dune fields. It is possible that the high thermal inertia values are indicative of indurated (fossilized) dune surfaces, rather than large individual grain sizes. Coprates Chasma contains a concentration of 6 dune fields both within the main chasm and in depressions to the south. The southern fields are comprised of isolated barchanoid dunes, in close proximity to or atop wall material that has been deposited by mass wasting. In the main chasm, previously unidentified barchans composed of large grain sizes, as inferred from THEMIS thermal inertia, are found in CTX images within spur and gully wall units 2-3 km above the canyon floor. TES spectrum of these dunes indicates a basaltic composition, suggesting that the nearby wall units, also thought to be of a basaltic composition [McEwen et al., 1999], could be the source of the dune sediments. Future MRO observations of this area may resolve whether these dune sediments are locally derived. Ganges Chasma has the highest concentration of dunes in VM, including the largest (~6000 km2) non-polar dune field on Mars. These dunes are found surrounding the sulfate-bearing Ganges Mensa and other layered deposits. In one example, a light-toned yardang containing CRISM-detected hydrated sulfates [Pelkey et al., 2007] has shed fans of fine-grained material, contributing sediment to the area. Dune slipface orientation would suggest a dominant wind direction blowing to the west at the last time of dunes activity. This corresponds with the more recent deposit of lighter-toned material down-wind and atop the dark-toned sand sheets, as observed in HiRISE and THEMIS thermal inertia images. These lighter-toned materials, inferred to be composed of sulfate grains (~350 ?m), form bright ripples which gradually disappear away from the yardang. Whether these sulfates constitute a significant percentage of the dune composition is currently under investigation.

Chojnacki, M.; Moersch, J. E.

2008-12-01

416

Reconstruction d’une Carbonisation du Pouce par Lambeau Chinois  

PubMed Central

Summary La main en tant qu’organe majeur de la préhension peut être le siège de brûlures graves qui compromettent sa fonction. Bien qu’elle ne représente que 2% de la surface corporelle la brûlure de la main est grave et difficile à traiter, vu la vulnérabilité et la complexité de son appareil locomoteur. Nous rapportons dans ce travail le cas d’un patient victime d’une carbonisation de la main. Huit mois après le parage et la couverture par lambeau inguinal, le patient bénéficie d’une reconstruction du pouce par lambeau chinois associé à une greffe osseuse. Le résultat s’est avéré satisfaisant. Le lambeau chinois prouve par son apport vasculaire et par sa facilité technique qu’il est un moyen très intéressant dans la reconstruction du pouce - ou des doigts en général - surtout dans un contexte de brûlure. PMID:21991226

Khales, A.; Achbouk, J.A.; Moussaoui, A.; Belmir, R.; Tourabi, K.; Oufkir, A.; Ihrai, H.

2010-01-01

417

Soins primaires des personnes victimes d’une lésion médullaire  

PubMed Central

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

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

2012-01-01

418

Urinary Thrombin: A Novel Marker of Glomerular Inflammation for the Diagnosis of Crescentic Glomerulonephritis (Prospective Observational Study)  

PubMed Central

Background Crescentic glomerulonephritis (CresGN), an uncommon rapidly progressive disease, is characterized by severe glomerular inflammation with fibrin deposition. The lack of specific CresGN biomarkers delays diagnosis and threatens life. Because fibrin deposits in CresGN glomeruli indicate thrombin generation, we hypothesized that thrombin is excreted in urine and is a specific CresGN biomarker. Methods We measured urinary thrombin activity in 200 untreated patients (17 with CresGN, 183 with primary glomerulonephritis) and controls (8 patients with healed CresGN, 11 with nephrosclerosis, and 10 with tubulointerstitial nephritis, and 66 healthy volunteers). CresGN types included 15 pauci-immune and 2 immune complex. We assessed the diagnostic accuracy of thrombinuria in 169 patients with hematuria and proteinuria. Renal biopsy tissues were immunostained for tissue factor and fibrin. We analyzed the relationship of thrombinuria to plasma thrombin-antithrombin complex, hematuria, proteinuria, glomerular filtration rate, glomerular fibrin deposition, antineutrophil cytoplasmic antibodies (ANCAs), and C-reactive protein (CRP). We studied changes in thrombin activities after glucocorticoid treatment in 12 patients with thrombinuria. Results The highest thrombinuria occurrence was in CresGN (70.6%), followed by membranoproliferative glomerulonephritis (41.7%), IgA nephropathy (9.2%), and acute glomerulonephritis (0%). More than 75% of patients with nonproliferative glomerulonephritis manifested no thrombinuria. No controls had thrombinuria. Thrombinuria showed high CresGN specificity (90.1%) and moderate sensitivity (70.6%) and was detected in 4 of 7 patients with ANCA-negative CresGN. In CresGN, thrombinuria was associated with fibrin deposition in glomerular extracapillary tissue, where monocytes/macrophages expressed tissue factor. Thrombinuria in CresGN was unrelated to plasma thrombin-antithrombin complex, hematuria, proteinuria, glomerular filtration rate, and CRP. After glucocorticoid treatment, thrombinuria in patients with CresGN rapidly disappeared but proteinuria and hematuria persisted. Conclusions Thrombinuria was specific for glomerular inflammation, was unaffected by systemic inflammation or coagulation, and demonstrated good diagnostic accuracy for CresGN including ANCA-negative cases. Thrombinuria measurement may provide risk-free diagnosis and screening for CresGN. PMID:25742509

Kitamoto, Yasunori; Arizono, Kenji; Fukui, Hiroyoshi; Tomita, Kimio; Kitamura, Hiroshi; Taguma, Yoshio; Imamura, Takahisa

2015-01-01

419

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

Microsoft Academic Search

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

Elen Gwenllian Richards; Helene Burningham

2011-01-01

420

Article original Utilisation d'une chambre de transpiration portable  

E-print Network

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

Paris-Sud XI, Université de

421

Soins des patients atteints d’une mucoviscidose  

Microsoft Academic Search

RésuméLa mucoviscidose, la maladie pédiatrique autosomique héréditaire la plus fréquente, n’atteint plus uniquement des enfants, car son traitement moderne a permis aux patients de vivre plus longtemps avec une meilleure qualité de vie. Voici plus de 16 ans, l’identification du gène responsable et de la mutation la plus fréquente, ?F508, a suscité l’espoir général d’une guérison rapide de cette maladie.

Birgitta Strandvik

2006-01-01

422

Archaeology and holocene sand dune stratigraphy on Chatham Island  

Microsoft Academic Search

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

B. G. McFadgen

1994-01-01

423

Evidence for sensitivity of dune wetlands to groundwater nutrients.  

PubMed

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

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

2014-08-15

424

Diurnal emissivity dynamics in bare versus biocrusted sand dunes.  

PubMed

Land surface emissivity (LSE) in the thermal infrared depends mainly on the ground cover and on changes in soil moisture. The LSE is a critical variable that affects the prediction accuracy of geophysical models requiring land surface temperature as an input, highlighting the need for an accurate derivation of LSE. The primary aim of this study was to test the hypothesis that diurnal changes in emissivity, as detected from space, are larger for areas mostly covered by biocrusts (composed mainly of cyanobacteria) than for bare sand areas. The LSE dynamics were monitored from geostationary orbit by the Spinning Enhanced Visible and Infrared Imager (SEVIRI) over a sand dune field in a coastal desert region extending across both sides of the Israel-Egypt political borderline. Different land-use practices by the two countries have resulted in exposed, active sand dunes on the Egyptian side (Sinai), and dunes stabilized by biocrusts on the Israeli side (Negev). Since biocrusts adsorb more moisture from the atmosphere than bare sand does, and LSE is affected by the soil moisture, diurnal fluctuations in LSE were larger for the crusted dunes in the 8.7 ?m channel. This phenomenon is attributed to water vapor adsorption by the sand/biocrust particles. The results indicate that LSE is sensitive to minor changes in soil water content caused by water vapor adsorption and can, therefore, serve as a tool for quantifying this effect, which has a large spatial impact. As biocrusts cover vast regions in deserts worldwide, this discovery has repercussions for LSE estimations in deserts around the globe, and these LSE variations can potentially have considerable effects on geophysical models from local to regional scales. PMID:25437760

Rozenstein, Offer; Agam, Nurit; Serio, Carmine; Masiello, Guido; Venafra, Sara; Achal, Stephen; Puckrin, Eldon; Karnieli, Arnon

2015-02-15

425

Coastal sand dune stabilization in the Pacific Northwest  

Microsoft Academic Search

Coastal dunes are stabilized in three stages: (1) The initial stage uses sand-stilling grasses established vegetatively. For this purpose, European beachgrass,Ammophila arenaria (L.) Link., is most used, followed by American beachgrass,A. breviligulata Fern., or American dunegrass,Elymus mollis Trin. Large solid plantings must be made with the spacing and number of plants per hill adjusted to the site conditions. Plantings, using

J. L. Schwendiman

1977-01-01

426

Sargassum as a Natural Solution to Enhance Dune Plant Growth  

Microsoft Academic Search

Many beach management practices focus on creating an attractive environment for tourists, but can detrimentally affect long-term\\u000a dune integrity. One such practice is mechanical beach raking in which the wrack line is removed from the beach front. In Texas,\\u000a Sargassum fluitans and natans, types of brown alga, are the main components of wrack and may provide a subsidy to the

Amy Williams; Rusty Feagin

2010-01-01

427

Détection et caractérisation optiques d'une nanoparticule métallique isolée  

NASA Astrophysics Data System (ADS)

La détection optique d'une nanoparticule métallique unique par une nouvelle technique de microscopie par modulation spatiale est décrite. Dans le cas d'un nano-objet de métal noble, la mesure quantitative de son spectre d'absorption au voisinage de la résonance plasmon de surface et sa comparaison précise à un modèle théorique permettent une identification optique complète de l'objet étudié: taille, forme et orientation sur la surface sont déterminées.

Del Fatti, N.; Muskens, O.; Vallée, F.; Huntzinger, J. R.; Billaud, P.; Broyer, M.

2006-10-01

428

valuation d'une architecture de stockage RDF distribue  

E-print Network

�valuation d'une architecture de stockage RDF distribuée Maeva Antoine1 , Françoise Baude1 distribuée, entre autres de type pair-à-pair, pour pouvoir passer à l'échelle. Un système de stockage RDF existe actuellement une douzaine de benchmarks pour le RDF, mais aucun d'entre eux ne se présente comme

Paris-Sud XI, Université de

429

The focal plane instrumentation for the DUNE mission  

E-print Network

DUNE (Dark Universe Explorer) is a proposed mission to measure parameters of dark energy using weak gravitational lensing The particular challenges of both optical and infrared focal planes and the DUNE baseline solution is discussed. The DUNE visible Focal Plane Array (VFP) consists of 36 large format red-sensitive CCDs, arranged in a 9x4 array together with the associated mechanical support structure and electronics processing chains. Four additional CCDs dedicated to attitude control measurements are located at the edge of the array. All CCDs are 4096 pixel red-enhanced e2v CCD203-82 devices with square 12 $\\mu$m pixels, operating from 550-920nm. Combining four rows of CCDs provides a total exposure time of 1500s. The VFP will be used in a closed-loop system by the spacecraft, which operates in a drift scan mode, in order to synchronize the scan and readout rates. The Near Infrared (NIR) FPA consists of a 5 x 12 mosaic of 60 Hawaii 2RG detector arrays from Teledyne, NIR bandpass filters for the wavelength bands Y, J, and H, the mechanical support structure, and the detector readout and signal processing electronics. The FPA is operated at a maximum temperature of 140 K for low dark current of 0.02e$-$/s. Each sensor chip assembly has 2048 x 2048 square pixels of 18 $\\mu$m size (0.15 arcsec), sensitive in the 0.8 to 1.7 $\\mu$m wavelength range. As the spacecraft is scanning the sky, the image motion on the NIR FPA is stabilized by a de-scanning mirror during the integration time of 300 s per detector. The total integration time of 1500 seconds is split among the three NIR wavelengths bands. DUNE has been proposed to ESA's Cosmic Vision program and has been jointly selected with SPACE for an ESA Assessment Phase which has led to the joint Euclid mission concept.

Jeff Booth; Mark Cropper; Frank Eisenhauer; Alexandre Refregier; the DUNE collaboration

2008-07-25

430

A non-monotone conservation law for dune morphodynamics  

E-print Network

We investigate a non-local non linear conservation law, first introduced by A.C. Fowler to describe morphodynamics of dunes, see \\cite{Fow01, Fow02}. A remarkable feature is the violation of the maximum principle, which allows for erosion phenomenon. We prove well-posedness for initial data in $L^2$ and give explicit counterexample for the maximum principle. We also provide numerical simulations corroborating our theoretical results.

Alibaud, Nathaël; Isèbe, Damien

2007-01-01

431

Comment on "Minimal size of a barchan dune"  

E-print Network

It is now an accepted fact that the size at which dunes form from a flat sand bed as well as their `minimal size' scales on the flux saturation length. This length is by definition the relaxation length of the slowest mode toward equilibrium transport. The model presented by Parteli, Duran and Herrmann [Phys. Rev. E 75, 011301 (2007)] predicts that the saturation length decreases to zero as the inverse of the wind shear stress far from the threshold. We first show that their model is not self-consistent: even under large wind, the relaxation rate is limited by grain inertia and thus can not decrease to zero. A key argument presented by these authors comes from the discussion of the typical dune wavelength on Mars (650 m) on the basis of which they refute the scaling of the dune size with the drag length evidenced by Claudin and Andreotti [Earth Pla. Sci. Lett. 252, 30 (2006)]. They instead propose that Martian dunes, composed of large grains (500 micrometers), were formed in the past under very strong winds. We show that this saltating grain size, estimated from thermal diffusion measurements, is not reliable. Moreover, the microscopic photographs taken by the rovers on Martian aeolian bedforms show a grain size of 87 plus or minus 25 micrometers together with hematite spherules at millimetre scale. As those so-called ``blueberries'' can not be entrained by reasonable winds, we conclude that the saltating grains on Mars are the small ones, which gives a second strong argument against the model of Parteli et al.

B. Andreotti; P. Claudin

2007-05-24

432

The focal plane instrumentation for the DUNE mission  

E-print Network

DUNE (Dark Universe Explorer) is a proposed mission to measure parameters of dark energy using weak gravitational lensing The particular challenges of both optical and infrared focal planes and the DUNE baseline solution is discussed. The DUNE visible Focal Plane Array (VFP) consists of 36 large format red-sensitive CCDs, arranged in a 9x4 array together with the associated mechanical support structure and electronics processing chains. Four additional CCDs dedicated to attitude control measurements are located at the edge of the array. All CCDs are 4096 pixel red-enhanced e2v CCD203-82 devices with square 12 $\\mu$m pixels, operating from 550-920nm. Combining four rows of CCDs provides a total exposure time of 1500s. The VFP will be used in a closed-loop system by the spacecraft, which operates in a drift scan mode, in order to synchronize the scan and readout rates. The Near Infrared (NIR) FPA consists of a 5 x 12 mosaic of 60 Hawaii 2RG detector arrays from Teledyne, NIR bandpass filters for the wavelength ...

Booth, Jeff; Eisenhauer, Frank; Refregier, Alexandre

2008-01-01