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1

Evolution of downsized crescent-shaped dune in wind tunnel experiment  

NASA Astrophysics Data System (ADS)

The migration of a downsized crescent-shaped dune was investigated in a wind tunnel experiment. Quantified upwind influx and vertical oscillation of the sand bed were introduced to modulate the saturation level of the sand flux above the dune surface to affect dune evolution. The evolution was recorded by top-view photography and then abstracted as the evolution of self-defined characteristic quantities using a digital image processing algorithm. The results showed that, in contrast to the case for spanwise quantities, the evolution of streamwise quantities corresponds to a linear increase in the modulation magnitude more positively and in a monotonic and convergent manner. In contrast with quantities on the windward face, the changes in quantities with respect to the horns were nonmonotonic with time and almost uncorrelated with the variation in modulation strength, which reveals the distinctiveness of leeside evolution.

Zhang, Yang; Wang, Yuan; Jia, Pan

2013-09-01

2

Origin of Titan's dunes: noncohesive sand in bidirectional winds or sticky sand in unidirectional winds?  

NASA Astrophysics Data System (ADS)

Eolian dunes occur on Earth, Venus, Mars, and Titan, distinguishing them as one of the more widespread landforms in the solar system. On Earth, unidirectional winds blowing over loose, noncohesive sand produce crescentic-shaped dunes with crests oriented normal to the sand-transport direction (transverse dunes), but roughly half of Earth's large deserts are covered with longer-crested dunes (linear dunes) that are commonly oriented parallel or oblique to the resultant sand-transport vector (longitudinal dunes and oblique dunes, respectively). Such linear dunes form in at least two situations: (1) directionally bimodal winds blowing over loose sand, and (2) unimodal winds blowing over sediment that is vegetated, cohesive, sheltered by upwind topography, or otherwise locally stabilized. This study documents an example (Qaidam Basin, China) where a downwind increase in sediment cohesiveness (due to salt and mud incorporated from the local land surface) causes dunes to change orientation from transverse to longitudinal, and the work presents a compilation of related situations where stabilization of dune sediment has been reported to produce linear dunes. This family of stabilized dunes functions dynamically as self-extending "sand-shadow" or lee dunes. Loose sediment accumulates locally on these dunes, where it becomes stabilized, thereby allowing the dune itself to function as an obstacle that induces subsequent deposition farther downwind. Linear dunes on Titan previously have been interpreted as forming in the first situation listed above: bimodal winds blowing over loose sand. Because Titan's sand is believed to be composed of hydrocarbons or nitriles, however, the hypothesized loose, non-sticky nature of the sand has surprised researchers. In addition, the previous hypothesis of bimodal winds requires that north-south tidal flow be stronger than west-east zonal flow, which also was unexpected. The new hypothesis presented here—that Titan's dunes formed by unidirectional winds blowing over cohesive or sticky sand—resolves these two puzzles, cannot be ruled out with existing observations, and has grossly different implications regarding Titan's sediment properties, surface moisture, and wind regime. Satellite image of dunes in the Qaidam Basin, China. Change in sediment properties causes a change from transverse to longitudinal orientation of the dunes. Transverse dunes are higher in elevation than the longitudinal dunes and composed of noncohesive sand. Longitudinal dunes are cemented with silt, clay, and salt acquired locally.

Rubin, D. M.

2009-12-01

3

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

4

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

5

Membranous nephropathy with crescents.  

PubMed

Membranous nephropathy is a common cause of nephrotic syndrome in adults and can be primary or secondary to systemic lupus erythematosus, chronic infection, or drugs. Rapid decline in renal function in patients with membranous nephropathy may be due to renal vein thrombosis, malignant hypertension, or an additional superimposed destructive process involving the renal parenchyma. Crescents are rare in primary membranous nephropathy and thus suggest another underlying disease process, such as combined membranous and focal or diffuse lupus nephritis. However, in some patients with membranous nephropathy and crescents, the crescentic lesion may be due to a distinct, separate disease process, such as anti-glomerular basement membrane antibodies or anti-neutrophil cytoplasmic antibodies-related pauci-immune glomerulonephritis. Here we describe a case with such renal biopsy findings, review previous reported cases, and discuss possible implications for pathogenesis of the coexistence of these lesions. PMID:21903992

Basford, Amanda Walton; Lewis, Julia; Dwyer, Jamie P; Fogo, Agnes B

2011-09-08

6

Lunar Crescent Visibility.  

National Technical Information Service (NTIS)

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 ...

B. E. Schaefer L. E. Doggett

1994-01-01

7

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

8

Stability of isolated Barchan dunes  

NASA Astrophysics Data System (ADS)

When sand grains are entrained by an air flow over a non-erodible ground, or with limited sediment supply from the bed, they form isolated dunes showing a remarkable crescentic shape with horns pointing downstream. These dunes, known as Barchan dunes, are commonly observed in deserts, with height of a few meters and velocity of a few meters per year (Bagnold 1941). These dunes also exist under water, at a much smaller, centimetric size (Franklin & Charru 2010). Their striking stability properties are not well understood yet. Two phenomena are likely to be involved in this stability: (i) relaxation effects of the sand flux which increases from the dune foot up to the crest, related to grain inertia or deposition, and (ii) a small transverse sand flux due to slope effects and the divergence of the streamlines of the fluid flow. We reproduced aqueous Barchan dunes in a channel, and studied their geometrical and dynamic properties (in particular their shape, velocity, minimum size, and rate of erosion). Using coloured glass beads (see the figure), we were then able to measure the particle flux over the whole dune surface. We will discuss the stability of these dunes in the light of our measurements.

Fourrière, Antoine; Charru, François

2010-11-01

9

Lunar crescent visibility  

NASA Astrophysics Data System (ADS)

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, L. E.; Schaefer, B. E.

1994-02-01

10

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

11

Observations of nearshore crescentic sandbars  

NASA Astrophysics Data System (ADS)

The temporal and spatial variability of crescentic sandbars is analyzed with hourly long-term (months) video observations collected at four barred sites and are qualitatively compared to the temporal and spatial variability predicted by hypotheses underpinning existing approaches and models for crescentic bar formation (edge-wave template model, linear stability analysis, and nonlinear models). The observations, coming from the single barred beaches at Duck (North Carolina, USA) and Miyazaki (Kyushu, Japan), and from the double-barred beaches at the northern Gold Coast (Queensland, Australia) and Noordwijk (Netherlands), show that crescentic sandbar wavelength and amplitude variations over space and time are very common. For instance, at any moment in time, the wavelength of the smallest and longest crescentic bar can differ by a factor of 2. Temporal changes in wavelength and amplitude result from merging and splitting of individual crescents, causing the "final" configuration of a crescentic sandbar system to be very different from the initial configuration. The Gold Coast data indicate that these intrinsically nonlinear interactions are an attempt of the crescentic bar system to self-organize into a more uniform pattern, as splitting is usually confined to the longest crescentic bar observed, whereas merging usually combines the smallest crescentic bars into a longer bar. The observed spatial and temporal crescentic bar behavior contrasts qualitatively with behavior predicted from the edge-wave template model and implies that the predictive skill of linear stability models is limited. Nonlinear models are potentially better suited for a comparison against these field observations; several suggestions to improve these models, and hence to facilitate a data-model comparison, are made.

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

2004-06-01

12

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 ...

13

Dune Formation  

Microsoft Academic Search

Dunes are ubiquitous and exist in many forms in deserts and along coasts. They are a consequence of the wind moving sand grains\\u000a by a mechanism called “saltation”. In order to describe the formation and evolution of dunes one must understand the surface\\u000a flux of sand. Using the equation of motion of turbulent air in the approximation of Jackson and

Hans J. Herrmann

14

The crescentic inverted scarf osteotomy.  

PubMed

A hybrid procedure combining the inverted scarf and crescentic osteotomies is presented. This procedure may serve as a viable modification of the inverted scarf bunionectomy for those surgeons desiring true rotational correction of high intermetatarsal angles. PMID:12567369

O'Brien, Todd

15

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

16

DuneXpress  

Microsoft Academic Search

The DuneXpress observatory will characterize interstellar and interplanetary dust in-situ, in order to provide crucial information\\u000a not achievable with remote sensing astronomical methods. Galactic interstellar dust constitutes the solid phase of matter\\u000a from which stars and planetary systems form. Interplanetary dust, from comets and asteroids, represents remnant material from\\u000a bodies at different stages of early solar system evolution. Thus, studies

Eberhard Grün; Ralf Srama; Nicolas Altobelli; Kathrin Altwegg; James Carpenter; Luigi Colangeli; Karl-Heinz Glassmeier; Stefan Helfert; Hartmut Henkel; Mihaly Horanyi; Annette Jäckel; Sascha Kempf; Markus Landgraf; Neil McBride; Georg Moragas-Klostermeyer; Pasquale Palumbo; Han Scholten; Andre Srowig; Zoltan Sternovsky; Xavier Vo

2009-01-01

17

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

18

Relapsing polychondritis with crescentic glomerulonephritis  

Microsoft Academic Search

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

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

1978-01-01

19

DuneXpress  

NASA Astrophysics Data System (ADS)

The DuneXpress observatory will characterize interstellar and interplanetary dust in-situ, in order to provide crucial information not achievable with remote sensing astronomical methods. Galactic interstellar dust constitutes the solid phase of matter from which stars and planetary systems form. Interplanetary dust, from comets and asteroids, represents remnant material from bodies at different stages of early solar system evolution. Thus, studies of interstellar and interplanetary dust with DuneXpress in Earth orbit will provide a comparison between the composition of the interstellar medium and primitive planetary objects. Hence DuneXpress will provide insights into the physical conditions during planetary system formation. This comparison of interstellar and interplanetary dust addresses directly themes of highest priority in astrophysics and solar system science, which are described in ESA’s Cosmic Vision. The discoveries of interstellar dust in the outer and inner solar system during the last decade suggest an innovative approach to the characterization of cosmic dust. DuneXpress establishes the next logical step beyond NASA’s Stardust mission, with four major advancements in cosmic dust research: (1) analysis of the elemental and isotopic composition of individual interstellar grains passing through the solar system, (2) determination of the size distribution of interstellar dust at 1 AU from 10 - 14 to 10 - 9 g, (3) characterization of the interstellar dust flow through the planetary system, (4) establish the interrelation of interplanetary dust with comets and asteroids. Additionally, in supporting the dust science objectives, DuneXpress will characterize dust charging in the solar wind and in the Earth’s magnetotail. The science payload consists of two dust telescopes of a total of 0.1 m2 sensitive area, three dust cameras totaling 0.4 m2 sensitive area, and a nano-dust detector. The dust telescopes measure high-resolution mass spectra of both positive and negative ions released upon impact of dust particles. The dust cameras employ different detection methods and are optimized for (1) large area impact detection and trajectory analysis of submicron sized and larger dust grains, (2) the determination of physical properties, such as flux, mass, speed, and electrical charge. A nano-dust detector searches for nanometer-sized dust particles in interplanetary space. A plasma monitor supports the dust charge measurements, thereby, providing additional information on the dust particles. About 1,000 grains are expected to be recorded by this payload every year, with 20% of these grains providing elemental composition. During the mission submicron to micron-sized interstellar grains are expected to be recorded in statistically significant numbers. DuneXpress will open a new window to dusty universe that will provide unprecedented information on cosmic dust and on the objects from which it is derived.

Grün, Eberhard; Srama, Ralf; Altobelli, Nicolas; Altwegg, Kathrin; Carpenter, James; Colangeli, Luigi; Glassmeier, Karl-Heinz; Helfert, Stefan; Henkel, Hartmut; Horanyi, Mihaly; Jäckel, Annette; Kempf, Sascha; Landgraf, Markus; McBride, Neil; Moragas-Klostermeyer, Georg; Palumbo, Pasquale; Scholten, Han; Srowig, Andre; Sternovsky, Zoltan; Vo, Xavier

2009-03-01

20

Dynamics of Barchan dunes in a turbulent boundary layer  

NASA Astrophysics Data System (ADS)

When a fluid flow transports a small amount of solid heavy particles on a non-erodible ground, particles form isolated dunes which slowly propagate downstream. Such dunes have been studied experimentally in a channel. Strikingly, particle heaps always form dunes with crescentic shape, similar to that of Barchan dunes in deserts at a much larger scale. Varying the fluid flow and particle properties, it was found that the dune velocity scales as V ˜1/L where L is the dune length, as expected, but does not follow Bagnold's prediction V ˜u*^3 where u* is the friction velocity; some dependence on the particle Reynolds number, and perhaps relaxation effects in the particle flux on the dune surface, have to be considered. PIV measurements show that the fluid velocity does not increase on the lee side of the dune, as predicted by Hunt and co-workers, but slightly decreases because of the sudden increase of roughness. The roughness change also appears to be of particular importance for understanding the variation of the turbulent stresses -?u'v' along the dune.

Charru, Francois; Franklin, Erick

2008-11-01

21

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

Federal Register 2010, 2011, 2012, 2013

...Safety Zone: Crescent City Fourth of July Fireworks Event, Crescent City, CA AGENCY: Coast...support of the Crescent City Fourth of July Fireworks Event on July 4, 2012. This safety...posed by the pyrotechnics used in this fireworks display, the safety zone is...

2012-07-03

22

Morphodynamics of star dunes  

NASA Astrophysics Data System (ADS)

Star dunes are among the biggest and the most impressive dunes in Earth sand seas. Nonetheless, they remain poorly studied, probably because of their apparent complexity. They are massive pyramidal dunes with interlaced arms whose slip faces are oriented in various directions. Being large, they can integrate wind properties over a wide range of time scales. Thus, they are observed for wind regimes with multiple directions, and may result from the amalgamation of dunes or from the development of arms on a well-established dune pattern. In both cases, the roles of wind directional variability and secondary flow have been emphasized but not precisely quantified. Here, we report simulations where the star dune shape results from a a combination of longitudinal dunes, which form the star dune arms. These arms may radiate and so interact with the other dunes in the field. This mass exchange, controlled by the morphodynamics of star dunes arms, must play an important role in the large-scale arrangement of star dunes networks. We first demonstrate that star dune arms orientation maximizes the flux in the direction of crests. This is opposed to the usually admit dunes orientation, which maximizes the sediment transport perpendicular to the crest. Indeed, depending on sand availability, dunes development results from the growth of a wave on a sand bed or from a net transport of sediment, which grows and extends an isolated longitudinal dune over a non-erodible soil. These two different mechanisms lead to two different modes of crests orientation. Then, we show that the propagating arms reach a stationary state characterized by constant width, height and growth rate. These are controlled by the frequency at which the wind changes direction. Arm width and height increase, whereas the propagation speed decreases with a decreasing frequency. These morphodynamics properties are helpful to assess from pattern observation the variability of wind directionality over several time scales.

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

2012-04-01

23

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

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

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

24

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

25

Booming Sand Dunes  

NASA Astrophysics Data System (ADS)

"Booming" sand dunes are able to produce low-frequency sound that resembles a pure note from a music instrument. The sound has a dominant audible frequency (70-105 Hz) and several higher harmonics and may be heard from far distances away. A natural or induced avalanche from a slip face of the booming dune triggers the emission that may last for several minutes. There are various references in travel literature to the phenomenon, but to date no scientific explanation covered all field observations. This thesis introduces a new physical model that describes the phenomenon of booming dunes. The waveguide model explains the selection of the booming frequency and the amplification of the sound in terms of constructive interference in a confined geometry. The frequency of the booming is a direct function of the dimensions and velocities in the waveguide. The higher harmonics are related to the higher modes of propagation in the waveguide. The experimental validation includes quantitative field research at the booming dunes of the Mojave Desert and Death Valley National Park. Microphone and geophone recordings of the acoustic and seismic emission show a variation of booming frequency in space and time. The analysis of the sensor data quantifies wave propagation characteristics such as speed, dispersion, and nonlinear effects and allows the distinction between the source mechanism of the booming and the booming itself. The migration of sand dunes results from a complicated interplay between dune building, wind regime, and precipitation. The morphological and morphodynamical characteristics of two field locations are analyzed with various geophysical techniques. Ground-penetrating radar images the subsurface structure of the dunes and reveal a natural, internal layering that is directly related to the history of dune migration. The seismic velocity increases abruptly with depth and gradually increases with downhill position due to compaction. Sand sampling shows local cementation of sand grains within the discrete layers that explains the increase in velocity and decrease in porosity. The subsurface layering may influence the speed of dune migration and therefore have important consequences on desertification. The positive qualitative and quantitative correlation between the subsurface layering in the dune and the manifestation of the booming sound implies a close relation between environmental factors and the booming emission. In this thesis, the frequency of booming is correlated with the depth of the waveguide and the seismic velocities. The variability on location and season suggests that the waveguide theory successfully unravels the phenomenon of booming sand dunes.

Vriend, Nathalie

26

Dynamics of crescent water wave patterns  

NASA Astrophysics Data System (ADS)

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

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

2005-08-01

27

PEDESTRIAN UNDERPASS AT CRESCENT ROAD AND ROOSEVELT CENTER FROM NORTH. ...  

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

PEDESTRIAN UNDERPASS AT CRESCENT ROAD AND ROOSEVELT CENTER FROM NORTH. NOTE DALE WINLING, 2005 SALLY KRESS TOMPKINS FELLOW, WALKING THROUGH UNDERPASS. - Old Greenbelt, Crescent Road and Southway, Greenbelt, Prince George's County, MD

28

Deformed barchans under alternating flows: Flume experiments and comparison with barchan dunes within Proctor Crater, Mars  

NASA Astrophysics Data System (ADS)

It is generally considered that barchans, isolated crescentic-shaped dunes, develop where wind is unidirectional and the available sand is insufficient to cover the entire dune field; however, Bishop [Bishop, M.A., 2001. Seasonal variation of crescentic dune morphology and morphometry, Strzelecki Simpson desert, Australia. Earth Surface Process and Landforms 26, 783 791.] observed barchans that developed in areas where winds blow seasonally in opposite directions and described a peculiar deformation feature, the “rear slipface,” that is not found in ordinary barchans. Barchans under such bidirectional flows are poorly understood, and it is necessary to study barchans that formed under many different flow conditions. We conducted flume experiments to investigate the deformation of barchans under alternating water flow, and observed new deformation features in addition to rear slipfaces. We conclude that the deformation of barchans can be categorized into four types, one of which shows morphologies similar to barchans within Proctor Crater, Mars. The deformation type depends on the strength of the reverse flow relative to the forward flow and the absolute velocity of the forward flow. Comparison of our results with barchan dunes within Proctor Crater enable us to qualitatively estimate the wind strength and direction related to dune formation on Mars. These results are in agreement with those of Fenton et al. [Fenton, L.K., Toigo, A.D., Richardson, M.I., 2005. Aeolian processes in Proctor Crater on Mars: Mesoscale modeling of dune-forming winds. Journal of Geophysical Research 110 (E6), E06005.].

Taniguchi, Keisuke; Endo, Noritaka

2007-10-01

29

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

2013-05-24

30

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

31

Beach and Dune.  

National Technical Information Service (NTIS)

The flora, vegetation, and microenvironment of beach and dune are sufficiently different to warrant their separate treatment in this chapter. Beach is defined here as the expanse of sandy substrate between mean tide and the foredune or, in the absence of ...

M. G. Barbour A. F. Johnson

1977-01-01

32

Crescentic glomerulonephritis: new aspects of pathogenesis.  

PubMed

This review provides a summary of recent advances in the understanding of crescentic glomerulonephritis, focusing on antineutrophil cytoplasm antibody (ANCA)-associated vasculitis and anti-glomerular basement membrane (anti-GBM) antibody disease. In ANCA-associated vasculitis (AAV), four main conceptual advances are discussed as follows: (1) evidence for the pathogenicity of ANCA, (2) molecular mimicry and the role of infection in AAV, (3) evidence for aberrant T-cell responses and T-cell regulation in AAV, and (4) advances in understanding of genetic predisposition to AAV. In relation to anti-GBM disease we discuss the following: (1) the nature of the Goodpasture autoantigens, (2) T-cell responses and regulation in anti-GBM disease, and (3) human leukocyte antigen and non-human leukocyte antigen genetic associations. PMID:21839369

Tarzi, Ruth M; Cook, H Terence; Pusey, Charles D

2011-07-01

33

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

34

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.

Parteli, Eric J. R.; Duran, Orencio; Tsoar, Haim; Schwammle, Veit; Herrmann, Hans J.

2009-01-01

35

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

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

36

Management of crescentic glomerulonephritis: what are the recent advances?  

PubMed

Crescentic glomerulonephritis (GN) is a life-threatening clinical syndrome characterized by crescents which are morphological manifestations of severe glomerular injury. Immunologically, crescentic GN are classified as anti-glomerular basement membrane nephritis, immune complex-mediated GN and pauci-immune GN. Conventional treatment for crescentic GN mainly consists of corticosteroids, immunosuppressants and plasma exchange. Plasmapheresis is beneficial for patients with Goodpasture's syndrome and those with severe pauci-immune GN. Recently, new therapeutic agents have emerged, such as monoclonal antibodies to T cells, B cells and cytokines (e.g. anti-CD20 antibodies and TNF-? inhibitors) and signal transduction inhibitors, which may provide satisfactory alternatives. However, most of these treatments have only been established in experimental crescentic GN, described in single cases or reported in open-label trials; thus, the safety and efficacy of these agents remain to be investigated via controlled clinical trials. PMID:23689584

Li, Xiao; Chen, Nan

2013-05-08

37

City-swallowing Sand Dunes  

NSDL National Science Digital Library

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

Bell, Trudy E.

2007-06-19

38

Sand Dunes: A Phenomenon Of Wind  

NSDL National Science Digital Library

This webpage from Wayne's Word provides information about the origin of sand dunes, forms of life present there, and the sounds produced by "booming" dunes. Numerous dunes in the United States are described and pictured.

2010-06-29

39

Dune fields in central Western Argentina  

NASA Astrophysics Data System (ADS)

Important accumulations of wind blown sands extend over some sections of plains and pediments. The three dune fields existing in the area are called: Medanos Grandes (great dunes) in the south end of Pie de Palo range between 660 to 750 masl; Las Chacras dune to the southwestern end of Valle Fertil range between 690 to 800 masl; and Mascasin dunes between 450 to 550 masl. These dune fields contain longitudinal, transverse, parabolic, and barchanoid sand dunes with interdune basins.

Suvires, Graciela M.

40

Biogenic crust dynamics on sand dunes  

NASA Astrophysics Data System (ADS)

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

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

2013-02-01

41

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

42

57. VIEW OF CRESCENT ROCK OVERLOOK IN THE DISTANCE FROM ...  

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

57. VIEW OF CRESCENT ROCK OVERLOOK IN THE DISTANCE FROM THE PEAK OF UPPER HAWKSBILL MOUNTAIN (EL. 4,050', HIGHEST POINT IN SHENANDOAH NATIONAL PARK). - Skyline Drive, From Front Royal, VA to Rockfish Gap, VA , Luray, Page County, VA

43

Autoantibodies against myeloid lysosomal enzymes in crescentic glomerulonephritis  

Microsoft Academic Search

Autoantibodies against myeloid lysosomal enzymes in crescentic glomerulonephritis. To investigate the possible association of crescentic glomerulonephritis (CGN) with autoantibodies to myeloid lysosomal enzymes, we tested sera from 35 consecutive patients with CGN without diagnostic immunohistological findings in their renal biopsy for the presence ofantineutrophil cytoplasmic antibodies directed against a 29 kD antigen from azurophilic granules (29 kD-ANCA), against myeloperoxidase (MPO-ANCA)

J W Cohen Tervaert; R Goldschmeding; J D Elema; M van der Giessen; M G Huitema; G K van der Hem; T H The; A E G Kr von dem Borne; C G M Kallenberg

1990-01-01

44

Visibility of the thin lunar crescent: the sociology of an astronomical problem (A case study)  

NASA Astrophysics Data System (ADS)

In the Islamic calendar, a new month starts the day after the first naked-eye sighting of the thin crescent, shortly after a luni-solar conjunction. The crescent can be observed after sunset in the general western direction. As the visibility depends strongly on the atmospheric conditions, the beginning of the Islamic new month cannot be predicted very precisely. Three times a year, because of religious events, officials of Islamic countries decree the beginning of the month on the basis of reports from witnesses who volunteer to watch the thin crescent. In the present study, we confront the dates as decreed by the officials with the astronomical data and criteria of earliest visibility. The data collection consists of 115 dates corresponding to the religious occasions in Algeria between 1963 and 2000. We have found those dates to be largely inconsistent with the astronomical data. The rate of impossible cases (where the crescent was not present at all in the sky, let alone be visible) is about 17.4%. In more than half the cases, one or more of the absolute limits or all-time records of visibility was/were violated. And according to most or all the prediction criteria of visibility, there were about 80% cases in error. We have also found that the error rates versus time correlate well with the sociological changes that occurred in Algeria between 1963 and 2000. Finally, we should emphasize that comparatively to Algeria, the error rates are higher in the Middle-East. These results suggest that the officials must reconsider their approach in the determination of the beginning of the Islamic months.

Guessoum, Nidhal; Meziane, Kiram

2001-06-01

45

Effect of species on dune grass growth  

Microsoft Academic Search

Observations of experimental dunes made over a period of nine years indicate differences in utilizing three different dune species along the North Carolina coast and in the type of dunes produced by them. Ammophila is superior in ease of establishment and rate of sand accumulation but is shortlived. It produces a gently sloping dune. Uniola is difficult to propagate but

W. W. Woodhouse; E. D. Seneca; S. W. Broome

1977-01-01

46

Effect of species on dune grass growth  

Microsoft Academic Search

Observations of experimental dunes made over a period of nine years indicate differences in utilizing three different dune species along the North Carolina coast and in the type of dunes produced by them.Ammophila is superior in ease of establishment and rate of sand accumulation but is shortlived. It produces a gently sloping dune.Uniola is difficult to propagate but is an

W. W. Woodhouse; E. D. Seneca; S. W. Broome

1977-01-01

47

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.

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

2013-01-01

48

Numerical modeling of the wind flow over a transverse dune  

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

49

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

2013-10-04

50

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

51

Predicting vegetation-stabilized dune morphology  

NASA Astrophysics Data System (ADS)

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

Barchyn, T.; Hugenholtz, C.

2012-04-01

52

Nation and Gender in The Eclipse of the Crescent Moon  

Microsoft Academic Search

Summary In this paper I read Géza Gárdonyi's novel, The Eclipse of the Crescent Moon, as a narrative of the Hungarian nation. After surveying the reception of the novel in the past century, pointing out the difficulties Hungarian literary criticism was facing when dealing with The Eclipse, I proceed to read the novel itself as a text that depicts an

Ágnes Györke

2005-01-01

53

Therapeutic effects of prostacyclin analog on crescentic glomerulonephritis of rat  

Microsoft Academic Search

Therapeutic effects of prostacyclin analog on crescentic glomerulonephritis of rat. Prostacyclin (PGI2) is known to have a relaxative action on vascular smooth muscle, an inhibitory action against platelet activation and neutrophil function. Previous studies showed the preventive effects of PGI2 on lupus nephritis and Thy-1 nephritis, although the mechanism has not been clarified. Glomerular endothelial expression of intercellular adhesion molecule-1

Masahiko Kushiro; Kenichi Shikata; Hikaru Sugimoto; Yasushi Shikata; Nobuyuki Miyatake; Jun Wada; Masayuki Miyasaka; Hirofumi Makino

1998-01-01

54

The Muslim Brotherhood and the Emerging ‘Shia Crescent  

Microsoft Academic Search

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

Samuel Helfont

2009-01-01

55

Tsunami Hazard in Crescent City, California from Kuril Islands earthquakes  

NASA Astrophysics Data System (ADS)

On November 15, Crescent City in Del Norte County, California was hit by a series of tsunami surges generated by the M = 8.3 Kuril Islands earthquake causing an estimated 9.7 million (US dollars) in damages to the small boat basin. This was the first significant tsunami loss on US territory since the 1964 Alaska tsunami. The damage occurred nearly 8 hours after the official tsunami alert bulletins had been cancelled. The tsunami caused no flooding and did not exceed the ambient high tide level. All of the damage was caused by strong currents, estimated at 12 to 15 knots, causing the floating docks to be pinned against the pilings and water to flow over them. The event highlighted problems in warning criteria and communications for a marginal event with the potential for only localized impacts, the vulnerability of harbors from a relatively modest tsunami, and the particular exposure of the Crescent City harbor area to tsunamis. It also illustrated the poor understanding of local officials of the duration of tsunami hazard. As a result of the November tsunami, interim changes were made by WCATWC to address localized hazards in areas like Crescent City. On January 13, 2007 when a M = 8.1 earthquake occurred in the Kuril Islands, a formal procedure was in place for hourly conference calls between WCATWC, California State Office of Emergency Services officials, local weather Service Offices and local emergency officials, significantly improving the decision making process and the communication among the federal, state and local officials. Kuril Island tsunamis are relatively common at Crescent City. Since 1963, five tsunamis generated by Kuril Island earthquakes have been recorded on the Crescent City tide gauge, two with amplitudes greater than 0.5 m. We use the MOST model to simulate the 2006, 2007 and 1994 events and to examine the difference between damaging and non-damaging events at Crescent City. Small changes in the angle of the rupture zone results can result in a half meter difference in water heights. We also look at the contribution of fault segments along the Kuril subduction zone using the FACTS server to look at the potentially most damaging source regions for Crescent City. A similar-sized rupture as the November 15 event located further south along the Hokkaido - Honshu area of the subduction zone, is likely to produce a slightly larger amplitude signal with and even greater delay between the first wave arrivals and the largest waves.

Dengler, L.; Uslu, B.; Barberopoulou, A.

2007-12-01

56

Using Overlapping MOC Images to Search for Dune Movement and to Measure Dune Heights  

NASA Astrophysics Data System (ADS)

Overlapping MOC images have been used to search for dune movement and to measure dune heights. No dune movement was found, but dune heights in Proctor and Rabe were measured at 30-100 m. A possible cinder cone in Proctor has also been identified.

Williams, K. K.; Greeley, R.; Zimbelman, J. R.

2003-03-01

57

Kappakoola dunes — aeolian landforms induced by man  

Microsoft Academic Search

The Kappakoola dunes are located on central Eyre Peninsula, in South Australia. These masses of sand stand out from the northwest?southeast trending longitudinal dunes of the regional pattern because they are devoid of vegetation and in detail change in morphology from day to day according to the wind direction. The dunes are demonstrably of recent origin and are developed as

Dianne M. Smith; C. R. Twidale; Jennifer A. Bourne

1975-01-01

58

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

59

Blocking VLA4 Prevents Progression of Experimental Crescentic Glomerulonephritis  

Microsoft Academic Search

Background\\/Aims: Integrins are adhesion molecules of fundamental importance to the recruitment of leucocytes in inflammation. The ?4?1 integrin (VLA-4) is a leucocyte ligand for endothelial vascular cell adhesion molecule-1 (VCAM-1), fibronectin and osteopontin. We addressed the role of VLA-4 in mediating progressive renal injury in vivo using a blocking monoclonal antibody (mAb) in a rat model of crescentic glomerulonephritis. Methods:

Sarah B. Khan; Andrew R. Allen; Gurjeet Bhangal; Jennifer Smith; Roy R. Lobb; H. Terence Cook; Charles D. Pusey

2003-01-01

60

A footprint study of bond initiation in gold wire crescent bonding  

Microsoft Academic Search

The morphological features of the crescent bond footprints on the substrate after peeling the wire off were studied to gain an understanding of the effect of process parameters on the crescent bond formation. In the absence of any ultrasonic energy, metallurgical bonding initiated at the peripheral regions of the crescent bond. The bond strength improved at higher substrate temperatures and

Y. n. Zhou; X. Li; N. J. Noolu

2005-01-01

61

Effects of Harbor Modification on Crescent City, California's Tsunami Vulnerability  

NASA Astrophysics Data System (ADS)

More damaging tsunamis have impacted Crescent City, California in historic times than any other location on the West Coast of the USA. Crescent City's harbor has undergone significant modification since the early 20th century, including construction of several breakwaters, dredging, and a 200 × 300 m2 small boat basin. In 2006, a M w 8.3 earthquake in the Kuril Islands generated a moderate Pacific-wide tsunami. Crescent City recorded the highest amplitudes of any tide gauge in the Pacific and was the only location to experience structural damage. Strong currents damaged docks and boats within the small boat basin, causing more than US 20 million in damage and replacement costs. We examine how modifications to Crescent City's harbor may have affected its vulnerability to moderate tsunamis such as the 2006 event. A bathymetric grid of the basin was constructed based on US Army Corps of Engineers soundings in 1964 and 1965 before the construction of the small boat basin. The method of splitting tsunamis was used to estimate tsunami water heights and current velocities at several locations in the harbor using both the 1964-1965 grid and the 2006 bathymetric grid for the 2006 Kuril event and a similar-sized source along the Sanriku coast of Japan. Model velocity outputs are compared for the two different bathymetries at the tide gauge location and at six additional computational sites in the harbor. The largest difference between the two grids is at the small boat basin entrance, where the 2006 bathymetry produces currents over three times the strength of the currents produced by the 1965 bathymetry. Peak currents from a Sanriku event are comparable to those produced by the 2006 event, and within the boat basin may have been higher. The modifications of the harbor, and in particular the addition of the small boat basin, appear to have contributed to the high current velocities and resulting damage in 2006 and help to explain why the 1933 M w 8.4-8.7 Sanriku tsunami caused no damage at Crescent City.

Dengler, Lori; Uslu, Burak

2011-06-01

62

Formation Mechanisms for Dunes Observed on Titan  

NASA Astrophysics Data System (ADS)

The Cassini spacecraft has discovered massive dune fields on Saturn’s largest moon, Titan. The dunes were observed with the Cassini Synthetic Aperture Radar Imaging (SARS) instrument. The radar instrument operates at a frequency of 13.78 GHz, corresponding to a wavelength 2.2 cm. The resolution for the images examined are ~ 1 pixel = 175 m (varies from image to image). These dunes, or at least what’s visible to radar, through the thick nitrogen Titan atmosphere, seem to be almost exclusively longitudinal dunes (with crests forming parallel to prevailing wind directions). Many unanswered questions remain about these dunes. One goal of this project is to attempt to calculate the heights of these dunes, which has not yet been systematically attempted. We will use radar parallax analyses to calculate the height of the dunes. The Cassini radar determines position based on how long the radar wave took to return to the spacecraft, making an assumption that the surface is a perfect sphere. With changes in height, the time return for radar will change, distorting the image. Looking at these distortions (specifically, the shortening or elongation of the side of a dune) and knowing the inclination angle, we can determine height or depth. We will also use this same method with radar images of the Namib dunes, in southwest Africa, as an Earth analog, to test and determine how accurate our method is. This approach should give useful information on the morphology of the dunes on Titan. Knowing more about the morphology of the dunes can teach us more about the dune’s composition and formation mechanisms.

Vinson, Alec; Hays, C. C.; Lopes-Gautier, R. M.; Mitchell, K. L.; Diniega, S.; Farr, T. G.

2013-01-01

63

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

64

Modeling Megacusps and Dune Erosion  

NASA Astrophysics Data System (ADS)

Megacusps are large, concave, erosional features of beaches, of O(200m) alongshore wavelength, which sometimes occur when rip channel bathymetry is present. It is commonly hypothesized that erosion of the dune and back beach will be greater at the alongshore locations of the megacusp embayments, principally because the beach width is narrower there and larger waves can more easily reach the dune toe (e.g., Short, J. Geol., 1979, Thornton, et al., Mar. Geol., 2007). At present, available field data in southern Monterey Bay provide some support for this hypothesis, but not enough to fully confirm or refute it. This analysis utilizes XBeach, a 2DH nearshore sediment transport model, to test the above hypothesis under a range of wave conditions over several idealized rip-megacusp bathymetries backed by dunes. Model results suggest that while specific wave conditions may result in erosional hot spots at megacusp embayments, other factors such as tides, wave direction, and surf zone bathymetry can often play an equal or stronger role.

Orzech, M.; Reniers, A. J.; Thornton, E. B.

2009-12-01

65

Pauci-immune crescentic glomerulonephritis in limited cutaneous systemic sclerosis.  

PubMed

Pauci-immune necrotizing glomerulonephritis is a form of a rapidly progressive glomerulonephritis that is associated with the anti-neutrophil cytoplasmic antibodies (ANCA). ANCA-associated pauci-immune glomerulonephritis may be secondary to rheumatic diseases. We report on a patient with limited cutaneous systemic sclerosis who presented with subacute onset of nephritic syndrome and renal insufficiency. Her myeloperioxidase ANCA titer was elevated and renal biopsy confirmed pauci-immune crescentic glomerulonephritis, which was stabilized with high-dose glucocorticoid and cyclophosphamide. ANCA-associated necrotizing glomerulonephritis is rarely reported in systemic sclerosis and a systematic review is presented. PMID:22644090

Chan, P T; Mok, C C

2012-05-30

66

Calendars, Crescents and Calculation: The ROG's Islamic Astronomy project  

NASA Astrophysics Data System (ADS)

The Royal Observatory Greenwich (ROG) has acted as a resource centre for mosques in the UK, providing data on the visibility of the new crescent Moon that is essential for determining the beginning of each Islamic month. A series of projects have sought to take advantage of this link, strengthening the connection between the ROG and the British Islamic community and seeking to engage a traditionally 'hard to reach' audience with modern astrophysics. I will describe these activities and offer a brief analysis of their impact.

Massey, R.

2005-12-01

67

Dunes On Titan: Comparison Of The Fensal And Belet Dune Regions Using Multiple Datasets  

Microsoft Academic Search

Titan's equatorial belt hosts large expanses of longitudinal dunes. As the Cassini mission continues, more of them are unveiled by the microwave RADAR, both in the active and passive modes and with an increasing number of viewing geometries. These observations have revealed some variations among dune regions. In particular, we find that the Belet and Fensal dune fields differ in

Alice Le Gall; M. A. Janssen; L. C. Wye; A. G. Hayes; R. D. Lorenz; J. Radebaugh; B. Stiles

2010-01-01

68

SPARC Accelerates Disease Progression in Experimental Crescentic Glomerulonephritis  

PubMed Central

Podocytopenia characterizes many forms of glomerular disease, preceding the development of glomerulosclerosis. While detachment of viable podocytes from the underlying glomerular basement membrane is an important mechanism of podocyte loss, the underlying factors involved remain unclear. Secreted protein acidic and rich in cysteine (SPARC), a matricellular protein with counteradhesive properties, is normally expressed at low levels by the podocyte but is markedly increased following podocyte injury. Accordingly, we elucidate the role of SPARC in mediating experimental crescentic glomerulonephritis by inducing passive nephrotoxic nephritis in SPARC+/+ and SPARC?/? mice. By days 4, 7, and 21 following disease induction, podocyte number is better preserved, glomerulosclerosis is ameliorated, and proteinuria is reduced in SPARC?/? mice as compared with SPARC+/+ littermates. Moreover, the preserved podocyte number in SPARC?/? mice correlates with reduced urinary levels of both nephrin and podocin. To establish a causal role for SPARC in mediating detachment, cultured SPARC+/+ and SPARC?/? podocytes were subjected to mechanical strain as well as trypsin digestion, and detachment assays were performed. While podocytes lacking SPARC were more resistant to stretch-induced detachment, stable re-expression of SPARC restored detachment rates to levels comparable with SPARC+/+ podocytes. Taken together, this study proves that SPARC plays a causal role in mediating podocyte detachment and accelerating glomerulosclerosis in experimental crescentic glomerulonephritis.

Sussman, Amy N.; Sun, Tong; Krofft, Ronald M.; Durvasula, Raghu V.

2009-01-01

69

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

70

A comparison of the crescentic and Mau osteotomies for correction of hallux valgus.  

PubMed

We retrospectively compared crescentic and Mau osteotomies used to treat a total of 39 cases of hallux abductovalgus. Follow-up was possible in 10 of the crescentic cases (mean 228 days) and 24 of the Mau cases (mean 245 days). Preoperatively, the mean first intermetatarsal and hallux abductus angles were 17.5 degrees and 35.4 degrees , respectively, in the crescentic group; and 16.6 degrees and 31.3 degrees , respectively, in the Mau group. Postoperatively, these same radiographic angles were 11.7 degrees and 18.9 degrees , respectively, in the crescentic group; and 9.8 degrees and 12.9 degrees , respectively, in the Mau group, and these differences were not statistically significant. Complications included metatarsus primus elevatus (crescentic 7, Mau 2), lesser metatarsal transfer lesion (crescentic 1, Mau 0), nonunion (crescentic 5, Mau 1), revisional surgery (crescentic 0, Mau 1), and transarticular hardware (crescentic 3, Mau 0). The incidence of complications in the crescentic group was 60%, whereas that in the Mau group was 37.5%; this difference was not statistically significant (P = .276). Analysis by the type of complication revealed statistically significant differences between the crescentic and Mau groups in regard to metatarsus primus elevatus (70% versus 8.3%, P = .001), transarticular hardware (30% versus 0%, P = .02), and nonunion (50% versus 4.2%, P = .006). In conclusion, crescentic and Mau osteotomies satisfactorily corrected the first intermetatarsal and hallux abductus angles in patients that fit our inclusion criteria, although the incidence of postoperative metatarsus primus elevatus, delayed union, and transarticular hardware placement, was higher in the crescentic osteotomy group. Level of Clinical Evidence: 2. PMID:18312917

Hyer, Christopher F; Glover, Jason P; Berlet, Gregory C; Philbin, Terrence M; Lee, Thomas H

71

Cementation in High-Latitude Dunes.  

National Technical Information Service (NTIS)

Cementing of dune sands by carbonates has not been considered to proceed rapidly in high-latitude regions. This study indicates that dunes along the Scotland coast, however, are actively being cemented by carbonates and that this process is quite widespre...

H. H. Roberts W. Ritchie A. Mather

1973-01-01

72

Management of idiopathic crescentic and diffuse proliferative glomerulonephritis: Evidence-based recommendations  

Microsoft Academic Search

Management of idiopathic crescentic and diffuse proliferative glomerulonephritis: Evidence-based recommendations. Idiopathic crescentic glomerulonephritis (GN) often presents with a rapid loss of renal function and pathology showing extensive crescent formation. The disease is caused by different immunopathogenetic mechanisms, pauci-immune, often antineutrophil cytoplasmic antibody (ANCA)-positive microvasculitis, anti-glomerular basement membrane (GBM) antibody disease, and immune complex formation. Historical reviews reveal poor renal prognosis,

Kailash K. Jindal

1999-01-01

73

Glomerular expression of cell-cycle-regulatory proteins in human crescentic glomerulonephritis  

Microsoft Academic Search

To elucidate the mechanism underlying crescentic formation, we assessed the phenotypic characterization and cell-cycle protein\\u000a expression in human crescentic glomerulonephritis (CRGN). Kidney tissue specimens taken from CRGN patients (10 patients with\\u000a pauci-immune type rapidly progressive glomerulonephritis (RPGN), 2 patients with Henoch-Schönlein purpura nephritis, and 1\\u000a patient with IgA nephropathy) were examined immunohistochemically. Most of the cellular components of the crescents

Kosaku Nitta; Shigeru Horita; Kazuho Honda; Keiko Uchida; Teruo Watanabe; Hiroshi Nihei; Michio Nagata

1999-01-01

74

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.

75

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

76

Winds drive dune movement on Mars  

NASA Astrophysics Data System (ADS)

Sand dunes, a common feature on the surface of Mars, can provide a record of recent and past changes. Some dunes near Mars's polar areas have recently been observed to change due to carbon dioxide ice sublimation, but it has not been confirmed whether dunes are still active all over Mars. Winds contribute to dune movement on Earth, but wind tunnel and atmospheric computer simulations have suggested that strong winds would be rare in the current Martian atmosphere. In a new study, Silvestro et al. observe recent dune movement in Mars's tropical regions, which are not affected by seasonal changes in carbon dioxide frost. Focusing on the Arabia Terra and Meridiani regions on Mars, the researchers analyzed images from the High Resolution Science Experiment (HiRISE) camera on board the Mars Reconnaissance Orbiter as well as other sources of data. They measured migration rates of two groups of ripples in the sand in a dune field in Meridiani Planum and found that dunes advanced about 0.4-1 meter in a Martian year.

Balcerak, Ernie

2012-01-01

77

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

78

Conceptual models of the evolution of transgressive dune field systems  

NASA Astrophysics Data System (ADS)

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

A. Hesp, Patrick

2013-10-01

79

Mapping the Stratigraphy of Booming Sand Dunes  

NASA Astrophysics Data System (ADS)

Booming dunes emit a loud rumbling sound after a man-made or natural sand avalanche is generated on the slip face of a large desert dune. The sound consist of one dominant frequency (70 - 105 Hz) with several higher harmonics. A recent publication (Vriend et al., 2007) presented a model of an internal, natural waveguide that propagates the booming emission, amplifies the sound, and sets the booming frequency. The mapping of the subsurface layering, which is necessary for the existence of a waveguide, prompted additional work on the dune structure and stratigraphy. The current work highlights geophysical measurements at Eureka Dunes in Death Valley National Park, CA and Dumont Dunes in the Mojave Desert, CA. Seismic refraction studies indicate strong layering with large velocity jumps across the interfaces. Ground Penetrating Radar (GPR) profiles, at frequencies of 100 MHz and 200 MHz, map out the stratigraphic structure of the dunes. Variations in the near surface layering are able to predict the seasonal variability in booming frequency both quantitatively and qualitatively. The Kirchhoff migrated GPR profiles are superimposed on the local topography obtained with a laser rangefinder. The complex dune structure is resolved to a depth of over 30 meters for the 100 MHz antenna. The GPR profiles of the longitudinal Eureka dune display complex internal structures from old dune crests. Both slopes have slip faces at 30 degrees with parallel layering (< 2m) at the near surface. At the transverse Dumont dune the GPR profile exhibits strong parallel layering on the booming leeward slipface only. The shallower windward face features a remarkable tilted repetitive layering that cuts through the surface. At Dumont Dunes the layering on the leeward face explains the change in booming frequency between 70 - 95 Hertz in the period 2005 - 2008. The tilted layering structure of the shallow windward face prevents the formation of a waveguide and is never able to sustain the booming sound. The Dumont dune progresses slowly, estimated at ~ 1 m/year from correlating satellite images, by forming new slip faces on the leeward face over time. Large precipitation events may cause a new layer to form. Sand sampling provides a quantitative measure on the chemical composition and water content of the layering.

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

2008-12-01

80

Calculation of the separation streamlines of barchans and transverse dunes  

Microsoft Academic Search

We use FLUENT to calculate the wind profile over barchans and transverse dunes. The form of the streamlines of flow separation at the lee side of the dunes is determined for a symmetric barchan dune in three dimensions, and for the height profile of a measured transverse dune field in the Lençóis Maranhenses.

H. J. Herrmann; J. S. Andrade Jr.; V. Schatz; G. Sauermann; E. J. R. Parteli

2005-01-01

81

A large-scale laboratory evaluation of dune erosion models  

Microsoft Academic Search

Simple models for dune erosion are necessary for bridging the gap between event scale predictions and probabilistic forecasts of long term coastal change. 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

M. L. Palmsten; R. A. Holman

2010-01-01

82

New urban forms: the crescents of Bath and Le Corbusier's plan for Rio de Janeiro  

Microsoft Academic Search

This article considers whether formal references in Le Corbusier's work may be traced to the eigtheenth century crescents of Bath and, in particular, Lansdowne Crescent. By exploring this line, it raises the possibility that in the work he produced for the Latin American context, this arch-modernist planner moved beyond the de-contextualized approach for which he is known and explored the

Eloísa Petti Pinheiro

2012-01-01

83

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

84

Involvement of the cytoskeleton in early grey crescent formation in axolotl oocytes  

Microsoft Academic Search

Maturing axolotl oocytes which are treated with protein synthesis inhibitors or which are heat-shocked can be induced to reorganize their cytoplasm and to form an early grey crescent. The maturing axolotl oocyte has been used as a model system to study the role of the cytoskeleton in dorsoventral polarization as visualized by grey crescent formation. Results presented here provide evidence

Jean Gautier; Renée Tencer

1987-01-01

85

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

Microsoft Academic Search

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

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

2008-01-01

86

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

87

Simulations of crescent water wave patterns on finite depth  

NASA Astrophysics Data System (ADS)

A numerical study of the instabilities of Stokes waves on finite depth has been carried out using an efficient fully nonlinear method [D. Clamond and J. Grue, ``A fast method for fully nonlinear water-wave computations,'' J. Fluid Mech. 447, 337 (2001)]. First, attention is given to five-wave instabilities with k0h=O(1), k0 being the wavenumber and h the depth. Both instabilities leading to breaking and instabilities leading to recurrence are studied, yielding considerably different patterns than on infinite depth. Higher-order instabilities are exemplified, for the first time, by simulations of six- and seven-wave instabilities. Simulations of interactions between four- and five-wave instabilities show that a classical modulational instability can destabilize a three-dimensional perturbation causing crescent waves to appear, in accordance with the hypothesis of [M.-Y. Su and A. W. Green, ``Coupled two- and three-dimensional instabilities of surface gravity waves,'' Phys. Fluids 27, 2595 (1984)]. Also, a recurrent five-wave instability can boost the energy in a four-wave instability.

Kristiansen, Ø.; Fructus, D.; Clamond, D.; Grue, J.

2005-06-01

88

Aeolian dune field self-organization – implications for the formation of simple versus complex dune-field patterns  

Microsoft Academic Search

The interpretation of aeolian dune-field patterns as self-organizing complex systems is a new paradigm in which pattern evolution may be addressed. Computer simulations, supported by field and experimental data, indicate that a given wind regime produces a simple dune-field pattern. Dune type and crest orientation are determined by wind regime and pattern ordering occurs through dune–dune interactions over time. Because

Gary Kocurek; Ryan C. Ewing

2005-01-01

89

Solar  

NSDL National Science Digital Library

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

Project, Iowa P.

2004-01-01

90

Monitoring sand dune stabilization along the coastal dunes of Ashdod-Nizanim, Israel, 1945–1999  

Microsoft Academic Search

Temporal changes in the stabilization process along the coastal dunes of Israel were assessed using a series of 23 aerial photographs taken over the period 1944–1999. The stabilization rate was then quantified using a specially developed method for the calculation of sand dune movement and by the calibration of the gray-scale images into vegetation cover maps. An episodic reactivation of

N. Levin; E. Ben-Dor

2004-01-01

91

Dunes On Titan: Comparison Of The Fensal And Belet Dune Regions Using Multiple Datasets  

NASA Astrophysics Data System (ADS)

Titan's equatorial belt hosts large expanses of longitudinal dunes. As the Cassini mission continues, more of them are unveiled by the microwave RADAR, both in the active and passive modes and with an increasing number of viewing geometries. These observations have revealed some variations among dune regions. In particular, we find that the Belet and Fensal dune fields differ in terms of radar albedo and thermal emission. In this paper, we combine different datasets (SAR, radiometry, altimetry, scatterometry and SAR-derived topography) and compare them to an electromagnetic model in order to constrain the compositional and physical properties of the Belet and Fensal dunes. Differences between Fensal and Belet are well explained by various degrees of exposure of Titan's icy crust in the interdune regions (the troughs between the dunes). We find that a significant fraction of the Fensal interdunes must either be clear of sand, thus representing the dune substrate, or covered by icy gravels. This is consistent with VIMS spectra that show an enrichment in water ice in Fensal interdunes (Barnes et al., 2008). Furthermore, in many places in Fensal, dunes remain quite bright on SAR images suggesting that they are thin enough to allow waves to probe the substrate. Both interdune brightness and dune thinning point to the lack of available sediment supply in Fensal. In contrast, sand-sized particles seem abundant at Belet's location where the sand sheet is so thick that even the interdune flats appear radar-dark. The difference in sand supply between Fensal and Belet may be due to different wind regime and/or ground humidity. It may also be related to their respective emplacement: Belet is laying in a deep depression and Fensal dunes encroach on Sinlap's fresh water-ice ejecta blanket. The paper will discuss further the origin of the regional variations among Titan dunes.

Le Gall, Alice; Janssen, M. A.; Wye, L. C.; Hayes, A. G.; Lorenz, R. D.; Radebaugh, J.; Stiles, B.; Cassini RADAR Team

2010-10-01

92

Nearest neighbor methods applied to dune field organization: The Coral Pink Sand Dunes, Kane County, Utah, USA  

NASA Astrophysics Data System (ADS)

Dune fields have recently come to be recognized as self-organizing systems that can be seen progressing from states of disorganization or randomness to uniformity. Dune systems can be highly sensitive to changes in factors, such as climate and sediment transport, that determine system state. Changes in climate and sediment state can take time to work their way through a dune system; this, in turn, leads to spatial heterogeneity in dune field organization. Using the Coral Pink Sand Dunes in southern Utah as a model, this study tests nearest neighbor analysis adapted as a method to objectively identify and characterize differences in two dimensional dune patterns within a dune field and to identify changes in dune patterns over time. Reducing transverse and barchanoid dunes from linear to three-point features in planar space emphasizes the clustering that occurs when dune lengths and wavelengths are more disorganized or random. This clustering may be in response to a system perturbation, such as an influx of sediment, and is reflected in lower nearest neighbor index (R) values. As the system adjusts to the perturbation and moves towards steady state, dune length and spacing increase through migration and coalescing of smaller dunes; the resulting higher R values reflect this move towards greater uniformity in dune pattern. With the organizational states of dune systems recording feedback to changes in extrinsic climate and sediment factors, nearest neighbor analysis provides a proxy measure of system stability.

Wilkins, David E.; Ford, Richard L.

2007-01-01

93

Dunes on Titan observed by Cassini Radar  

NASA Astrophysics Data System (ADS)

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.

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

2008-04-01

94

Two modes of orientation for longitudinal dune deserts  

NASA Astrophysics Data System (ADS)

The shape of dunes depends mainly on wind regimes (alternate magnitude and direction of winds) and the availability of sand. In deserts where winds blow successively in two different directions, dunes are found to be long linear ridges. These linear dunes are the most common dunes on Earth. Indeed, the conditions to their formation are often met because of the succession between summer and winter winds in equatorial deserts, or between day and night winds in coastal deserts. The trend of linear dunes depends on the winds transport capacity and the angle between the two wind directions. When both winds have comparable magnitude and period, dunes are either perpendicular (transverse dunes) or parallel (longitudinal dunes) to the average sand transport direction, respectively for angles between winds smaller or bigger than 90°. When both winds have different magnitude and/or period, dunes orientation is found oblique to the average sand transport direction. Following the pioneering work of Rubin and Hunter, it is widely accepted that linear dune orientation maximizes the orthogonality between the structure and sand fluxes. However, we show in underwater experiments that oblique longitudinal dunes may have two different orientations, depending on the way they grow. These results suggest that in deserts subject to bimodal (and multimodal) wind regimes dune trends depend on initial and limit conditions. Finally, we show that the multiple dune orientations observed within a same field and sometimes on the same structure may not rely on a change of wind regime but can be explained by a unique wind regime.

Courrech du Pont, Sylvain; Narteau, Clément

2013-04-01

95

78 FR 64471 - Crescent Ranger District; Oregon; Withdrawal of Notice for Preparation of an Environmental Impact...  

Federal Register 2010, 2011, 2012, 2013

...Notice for Preparation of an Environmental Impact Statement for the...their intent to prepare an Environmental Impact Statement (EIS...document the project in an environmental assessment. FOR FURTHER...CONTACT: Tim Foley, Team Leader, Crescent Ranger...

2013-10-29

96

Nexus of Terrorism and Drug Trafficking in the Golden Crescent: Afghanistan.  

National Technical Information Service (NTIS)

The nexus of terrorism and drug trafficking in the Golden Crescent region of Southwest Asia and the broader Middle East is Afghanistan. As the region's core state, how Afghanistan builds a strong political and security framework by eliminating safe havens...

L. Taylor

2006-01-01

97

A bilateral crescent and anterior ring pelvic fracture sustained by inadvertently performing the 'splits'  

PubMed Central

A case is presented of a healthy 57 year old female who slipped and fell awkwardly into what is known in athletic terms as the front splits. As a result of her fall she sustained bilateral crescent and superior and inferior rami pelvic fractures. Successful operative fixation was undertaken by a combination of open and percutaneous techniques. To our knowledge this is the first reported case of bilateral crescent fractures, and of a pelvic fracture as a result of this mechanism of injury.

O'Neill, F; Leonard, M; Morris, S

2012-01-01

98

Clinical spectrum and outcome of crescentic glomerulonephritis in children in developing countries  

Microsoft Academic Search

Crescentic glomerulonephritis (CsGN) is an uncommon entity in children. This prospective study was conducted to evaluate the\\u000a aetiology, clinical spectrum and outcome in children with crescentic glomerulonephritis. The single-centre prospective study\\u000a comprised of 22 children with biopsy proven CsGN who had been referred to our institute over the period January 2000 to December\\u000a 2005. These patients were subjected to detailed

Deepak Dewan; Sanjeev Gulati; Raj K. Sharma; Narayan Prasad; Manoj Jain; Amit Gupta; Alok Kumar

2008-01-01

99

Early grey crescent formation experimentally induced by cycloheximide in the axolotl oocyte  

Microsoft Academic Search

The effects of cycloheximide (CH) on grey crescent formation in artificially maturedAmbystoma mexicanum oocytes were determined. CH induced grey crescent formation after a few hours, especially after a 45° to 90° rotation from the vertical animal-vegetal axis. With low concentrations of CH (about 0.5 ng\\/oocyte), meiosis was still able to proceed normally to the stable second metaphase stage, but higher

Simone Grinfeld; Jean-Claude Beetschen

1982-01-01

100

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

101

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

102

[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

103

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

104

Do partially buried dune plants grow in optimal trajectories?  

Microsoft Academic Search

Plant adaptations minimising costs of burial responses are vital in mobile dune ecosystems. Conventionally, the burial responses\\u000a of dune plants have been measured as vertical growth. However, a model developed here shows that growth normal to accumulating\\u000a non-horizontal dune surfaces requires up to 18% less stem production than vertical growth. To determine whether dune plants\\u000a grow with this optimal geometry

M. E. Gilbert; N. W. Pammenter; B. S. Ripley

105

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

106

Considerations for control of house construction in coastal dunes  

Microsoft Academic Search

This study was conducted to determine if maintenance of the integrity of coastal dunes as a form of storm protection should require restrictions on the types of buildings located within the dune zone. A properly built house does not appear to endanger the integrity of the dune to a point where the hazard potential is increased. Active human uses of

Karl F. Nordstrom; James M. McCluskey

1984-01-01

107

Restoration of an ancient dune system enhancing landscape perception  

Microsoft Academic Search

The Doñana National and Natural Parks (SW Spain) present two distinct substrates: the marshes, a silted-up former estuary, and the sands, a Pleistocene detritic formation of gravels, which has been repeatedly covered by dune mantles. The last historical dune-building period occurred during the Little Ice Age (XVI to XIX Centuries) with repeated pulses of dune advance and stability reaching to

Francisco García-Novo; Raquel Fernandez; Lo Faso; Daniel Garcia Sevilla

108

Sub-pixel habitat mapping of a costal dune ecosystem  

Microsoft Academic Search

Bare sand and semi-fixed dunes represent ideal conditions for successionally young slack habitats that support rare species of coastal dune flora. In ecologically significant and large dune systems, such as the Kenfig National Nature Reserve, UK, identification and mapping of favourable (sandy) and unfavourable (scrub-rich) habitats provide baseline information for conservation management. To map this habitat, spectral unmixing of airborne

Neil Stuart Lucas; Sanjeevi Shanmugam; Mike Barnsley

2002-01-01

109

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

110

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.

111

Secondary dune succession on Inhaca Island, Mozambique  

Microsoft Academic Search

Old field succession was studied on coastal dunes supporting tropical evergreen forest on Inhaca Island, Mozambique. Plots of 10×10 m were sited in three early successional stages and in relatively undisturbed forest. Woody species increased in number during succession; leptophylls were most frequent in younger vegetation, whereas microphylls and mesophylls were most frequent in forest. Grasses, shrubs and forbs dominated

B. M. Campbell; C. A. M. Attwell; J. C. Hatton; P. de Jager; J. Gambiza; T. Lynam; F. Mizutani; P. Wynter

1988-01-01

112

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

2004-01-01

113

Coastal aeolian dune development, Sólheimasandur, southern Iceland  

Microsoft Academic Search

A coastal aeolian dune field on the distal parts of Sólheimasandur, southern Iceland is currently undergoing active construction. Ongoing sand deflation in the foreshore is demonstrated by the preservation of sand ridges in the downwind lee of obstacles, while a backshore sandsheet is characterised by actively accumulating long-wavelength wind ripples. The main region of aeolian accumulation is in the immediate

Nigel P. Mountney; Andrew J. Russell

2006-01-01

114

Origin of terrestrial gypsum dunes—Implications for Martian gypsum-rich dunes of Olympia Undae  

Microsoft Academic Search

The Estancia, White Sands, Guadalupe and Cuatrociénegas Dune Fields are among the largest known aeolian gypsum sand-dune accumulations on Earth and occupy closed-drainage basins within the Rio Grande Rift. High sedimentation rates of lacustrine gypsum occur in topographic depressions within the closed basins. The gypsum accumulations result from long-term, complex, interaction between tectonism, climate, and a hydrologic cycle that involves

Anna Szynkiewicz; Ryan C. Ewing; Craig H. Moore; Mihaela Glamoclija; David Bustos; Lisa M. Pratt

2010-01-01

115

[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

116

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

117

Seasonal erosion and restoration of Mars' northern polar dunes.  

PubMed

Despite radically different environmental conditions, terrestrial and martian dunes bear a strong resemblance, indicating that the basic processes of saltation and grainfall (sand avalanching down the dune slipface) operate on both worlds. Here, we show that martian dunes are subject to an additional modification process not found on Earth: springtime sublimation of Mars' CO(2) seasonal polar caps. Numerous dunes in Mars' north polar region have experienced morphological changes within a Mars year, detected in images acquired by the High-Resolution Imaging Science Experiment on the Mars Reconnaissance Orbiter. Dunes show new alcoves, gullies, and dune apron extension. This is followed by remobilization of the fresh deposits by the wind, forming ripples and erasing gullies. The widespread nature of these rapid changes, and the pristine appearance of most dunes in the area, implicates active sand transport in the vast polar erg in Mars' current climate. PMID:21292976

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

2011-02-01

118

Seasonal Erosion and Restoration of Mars’ Northern Polar Dunes  

NASA Astrophysics Data System (ADS)

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

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

2011-02-01

119

Seasonal erosion and restoration of Mars' northern polar dunes  

USGS Publications Warehouse

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

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

2011-01-01

120

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

121

An unusual case of Plasmodium vivax malaria monoinfection associated with crescentic glomerulonephritis: a need for vigilance.  

PubMed

Plasmodium vivax infection is increasingly a major public health burden and the second most frequent human malaria. Higher levels of clinical severity and chloroquine resistance are major factors responsible for such increases. Malarial glomerular injury is uncommon and mainly observed in Plasmodium malariae-infected patients. Occasionally, transient immune complex-mediated glomerulonephritis is associated with Plasmodium falciparum infection. Coexistent crescentic glomerulonephritis and vivax malaria have not previously been reported. We report a fatal case of P. vivax malaria, who presented with acute renal failure. P. vivax monoinfection status was diagnosed with peripheral blood smear and rapid antigen test. Further evaluation for renal failure related to systemic illness and immunological markers were inconclusive. He was treated with antimalarial drugs, hemodialysis, and supportive therapy. Renal biopsy performed for nonrecovering renal failure reveled crescentic glomerulonephritis. This case highlights the need to thoroughly search for malaria-associated crescentic glomerulonephritis using renal biopsy after nonrecovering renal failure. PMID:22806325

Patel, Mohan P; Kute, Vivek B; Gumber, Manoj R; Gera, Dinesh N; Shah, Pankaj R; Patel, Himanshu V; Trivedi, Hargovind L; Vanikar, Aruna V

2012-07-18

122

[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

123

Migration of parabolic dunes at Aberffraw, Anglesey, north Wales  

NASA Astrophysics Data System (ADS)

Aberffraw is a 1-km-wide and 3-km-long transgressive dunefield that extends inland along a northeast-southwest-trending valley from a southwest-facing beach, Traeth Mawr. The prevailing wind is from the southwest, and both the parabolic dunes and the valley within which they lie are sub-parallel to the prevailing wind. The dunefield at Aberffraw includes two foredune ridges and three rows of active compound parabolic dunes. At the landward end is a lake, Llyn Coron, which has been formed by dunes migrating up the valley and damming the river, Afon Ffraw. Between the parabolic dunes are gently sloping interdune areas with a close cropped vegetation. The parabolic dunes at Aberffraw have been migrating inland across the interdune areas. Rates of parabolic dune migration are derived from three sets of aerial photographs taken in 1940, 1982 and 1993. The aerial photographs have been scanned and manipulated in ArcView GIS software. Registration of the aerial photograph to an Ordnance Survey (OS) map was performed using ground control points (GCPs), common fixed features that are identifiable on both the aerial photographs and the baseline map. Attempts to correct for the inherent distortions of aerial photography were made during registration. Standardising the projection of the photographs to a common baseline allows meaningful spatial analysis, and the dune ridges, trailing edges and areas of bare sand were mapped from each photograph as a series of overlays. Rates of dune migration are calculated from the spatial distance between linear trend lines, parallel to the dune crests and perpendicular to the dune migration orientation, applied to sections of dune ridges for 1940 and 1993. Trend lines were only fitted to sections where continuity of dune form was maintained over the given period. The method provides an improved representation of the actual migration rate as it incorporates the whole of the parabolic dune form, and the whole of the compound dune ridge form into the calculation. It effectively measures the centre point or line of a dune or dune ridge as opposed to the variable positions and orientations of the dune crest noses, which represent maximum migration, rather than the mean. Rates of parabolic dune migration range from a minimum of 0 m year -1 to a maximum of 3.6 m year -1, with an average migration rate of 1 m year -1.

Bailey, S. D.; Bristow, C. S.

2004-04-01

124

Barchan dune asymmetry: Observations from Mars and Earth  

NASA Astrophysics Data System (ADS)

Barchan dune asymmetry refers to the extension of one barchan limb downwind. It is a common dune form on Earth and also occurs on Mars and Titan. A new classification of barchan limbs is presented where three types of limb morphology are identified: linear, kinked and beaded. These, along with other dune-scale morphological signatures, are used to identify three of the causes of barchan asymmetry on Mars: bi-directional winds, dune collision and the influence of inclined topography. The potential for specific dune asymmetric morphologies to indicate aspects of the formative wind regime on planetary surfaces is shown. For example, the placement of dune limbs can indicate the general direction and relative strength of formative oblique winds; an extreme barchan limb length may indicate a long duration oblique wind; a kinked limb may be evidence of the passage of a storm; beaded limbs may represent surface-wave instabilities caused by an increase in wind energy parallel to the dune. A preliminary application of these signatures finds evidence for bi-modal winds on Mars. However, these and other morphological signatures of wind direction and relative strength should be applied to planetary landforms with caution as more than one process (e.g., bi-modal winds and collision) may be operating together or sequentially on the dunefield. In addition, analysis should be undertaken at the dunefield scale and not on individual dunes. Finally, morphological data should be acquired from similar-scale dunes within a dunefield. In addition to bi-modal wind regimes on Mars, the frequent parallel alignment of the extended barchan limb to the dune suggests that dune collision is also an important cause of asymmetry on Mars. Some of the more complex dunefield patterns result from a combination of dune collision, limb extension and merging with downwind dunes. Dune asymmetric form does not inhibit dune migration in the Namib Desert or on Mars. Data from the Namib suggest that dune migration rates are similar for symmetric and asymmetric dunes. Further modeling and field studies are needed to refine our understanding of the potential range of limb and dune morphologies that can result from specific asymmetry causes.

Bourke, Mary C.

2010-01-01

125

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

NASA Astrophysics Data System (ADS)

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

Dengler, L.; Uslu, B.

2008-12-01

126

D-penicillamine-induced glomerulonephritis with crescent formation: Remission following drug discontinuation  

PubMed Central

We report a 71-year-old female who presented with rheumatoid arthritis complicated by proteinuria. She had been receiving D-penicillamine (D-Pc) for two years prior to presentation. A urinalysis showed proteinuria and hematuria which disappeared within 3 months after D-Pc was stopped. The renal histological findings showed focal proliferative glomerulonephritis with crescent formation. A total of 10 cases of D-Pc-induced glomerulonephritis with crescent formation without alveolar hemorrhage have previously been reported in the literature. To the best of our knowledge, this is the first case report in which the patient did not require any treatment.

Mokuda, S.; Onishi, M.; Takasugi, K.

2013-01-01

127

Concomitant findings and clinical significance of a fluid crescent between the iliacus muscle and iliac bone on MRI.  

PubMed

BackgroundSome routine magnetic resonance imaging (MRI) examinations show a thin line of fluid signal intensity along the iliac crest ("fluid crescent") between the iliacus muscle and the iliac bone. This fluid crescent has not been described before.PurposeTo evaluate the clinical context and significance of the fluid crescent.Material and MethodsMRI examinations of the abdomen and pelvis performed over 1 year were retrospectively reviewed twice for the presence of a fluid crescent. The relationship between the presence of a fluid crescent and associated abnormal findings, including ascites, iliopsoas compartment, and bone and soft tissue pathologies, was evaluated.ResultsForty-one out of 254 MRI studies (male:female ratio, 136:118; mean age, 42 years) demonstrated a fluid crescent (16%). Thirty-eight of them had associated MRI pathologies: edema of the hip muscles = 24, ascites = 11, iliac bone = 21, and iliopsoas compartment = 7. Correlations between the presence of a fluid crescent and pathological findings were highly significant (P < 0.0001), except for the presence of fluid in the hip joint.ConclusionA fluid crescent is an abnormal MRI finding strongly associated with iliopsoas compartment pathology, ascites, hip muscle edema, and pelvic bone abnormalities. The nature of this fluid crescent is yet to be determined. PMID:23474771

Eshed, Iris; Liberman, Boaz; Inbar, Yael; Amitai, Michal; Portnoy, Orith; Hertz, Marjorie; Apter, Sara

2013-03-10

128

Annual monsoon rains recorded by Jurassic dunes.  

PubMed

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

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

2001-07-01

129

An estimation of the natural value of dune habitats using Empidoidea (Diptera)  

Microsoft Academic Search

The dune landscape along the Belgian coast was evaluated on the basis of its Empidoidea fauna by investigating the faunal composition in different habitat types. The sites selected for sampling were marram dunes, dune grassland, dune slack, scrubby vegetations and three different dune woodlands. White water traps at soil surface level were used to sample five sites from the end

Marc Pollet; Patrick Grootaert

1996-01-01

130

Solar  

Microsoft Academic Search

The dispersion relation for a plasma oscillating in a static magnetic field is derived by the Laplace transform method. The plasma oscillations are found to be unstable in frequency bands around multiples of the gyrofrequency. A numerical application to spot magnetic fields at coronal distances indicates sufficient amplification to make plausible the theory of the origin of solar \\

Hari K. Sen

1952-01-01

131

Ecology, management and monitoring of grey dunes in Flanders  

Microsoft Academic Search

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

Sam Provoost; Carole Ampe; Dries Bonte; Eric Cosyns; Maurice Hoffmann

2004-01-01

132

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

Microsoft Academic Search

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

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

2007-01-01

133

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

Microsoft Academic Search

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

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

2007-01-01

134

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

2013-08-14

135

Renal Progenitor Cells Contribute to Hyperplastic Lesions of Podocytopathies and Crescentic Glomerulonephritis  

PubMed Central

Glomerular injury can involve excessive proliferation of glomerular epithelial cells, resulting in crescent formation and obliteration of Bowman's space. The origin of these hyperplastic epithelial cells in different glomerular disorders is controversial. Renal progenitors localized to the inner surface of Bowman's capsule can regenerate podocytes, but whether dysregulated proliferation of these progenitors contributes to crescent formation is unknown. In this study, we used confocal microscopy, laser capture microdissection, and real-time quantitative reverse transcriptase–PCR to demonstrate that hypercellular lesions of different podocytopathies and crescentic glomerulonephritis consist of three distinct populations: CD133+CD24+podocalyxin (PDX)?nestin? renal progenitors, CD133+CD24+PDX+nestin+ transitional cells, and CD133?CD24?PDX+nestin+ differentiated podocytes. In addition, TGF-? induced CD133+CD24+ progenitors to produce extracellular matrix, and these were the only cells to express the proliferation marker Ki67. Taken together, these results suggest that glomerular hyperplastic lesions derive from the proliferation of renal progenitors at different stages of their differentiation toward mature podocytes, providing an explanation for the pathogenesis of hyperplastic lesions in podocytopathies and crescentic glomerulonephritis.

Angelotti, Maria Lucia; Rizzo, Paola; Dijkman, Henry; Lazzeri, Elena; Mooren, Fieke; Ballerini, Lara; Parente, Eliana; Sagrinati, Costanza; Mazzinghi, Benedetta; Ronconi, Elisa; Becherucci, Francesca; Benigni, Ariela; Steenbergen, Eric; Lasagni, Laura; Remuzzi, Giuseppe; Wetzels, Jack

2009-01-01

136

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

137

Crescentic glomerulonephritis and eosinophilic interstitial infiltrates in a patient with hypereosinophilic syndrome.  

PubMed Central

Crescentic glomerulonephritis with immune complex deposition and acute eosinophilic interstitial nephritis developed in a patient with the hypereosinophilic syndrome. Acute renal failure ensued but was rapidly reversed by high-dose oral prednisone. Confounding factors and unusual findings are described with a review of recent literature. This mode of presentation has not previously been reported. Images Figure 1

Richardson, P.; Dickinson, G.; Nash, S.; Hoffman, L.; Steingart, R.; Germain, M.

1995-01-01

138

Inhibition of protein synthesis elicits early grey crescent formation in the axolotl oocyte  

Microsoft Academic Search

In the axolotl (Ambystoma mexicanum Shaw), it was recently shown that cycloheximide (CH) could induce early grey crescent formation (EGC) in non-activated oocytes, maturing in vitro (Grinfeld and Beetschen 1982). Since it was not proved that EGC was a consequence of protein synthesis inhibition rather than a side-effect of the drug, experiments were performed using microinjections of a quite different

Jean Gautier; Jean-Claude Beetschen

1983-01-01

139

Plasminogen and Plasminogen Activators Protect against Renal Injury in Crescentic Glomerulonephritis  

Microsoft Academic Search

Summary The plasminogen\\/plasmin system has the potential to affect the outcome of inflammatory dis- eases by regulating accumulation of fibrin and other matrix proteins. In human and experimen- tal crescentic glomerulonephritis (GN), fibrin is an important mediator of glomerular injury and renal impairment. Glomerular deposition of matrix proteins is a feature of progressive dis- ease. To study the role of

A. Richard Kitching; Stephen R. Holdsworth; Victoria A. Ploplis; Edward F. Plow; Désiré Collen; Peter Carmeliet; Peter G. Tipping

1997-01-01

140

Morphologic contribution on gross hematuria in mild mesangioproliferative glomerulonephritis without crescents  

Microsoft Academic Search

Summary In order to clarify the pathogenesis of gross hematuria in mild forms of mesangioproliferative glomerulonephritis without crescents, systematic light microscopic, immunohistologic, electron microscopic, and some scanning electron microscopic investigations were carried out on 17 cases of this disease, in part on serial sections. The investigations produced the following results:1.In gross hematuria, erythrocytes pass into Bowman's space in the area

A. Bohle; H. v. Gise; E. Mikeler; J. Rassweiler

1985-01-01

141

Morphology and dynamics of star dunes from numerical modelling  

NASA Astrophysics Data System (ADS)

Star dunes are giant, pyramid-shaped dunes composed of interlaced arms. These arms are marked by sinuous crests and slip faces of various directions. Their radial symmetry and scale suggest that the star dunes form as a result of complex interactions between a multidirectional wind regime and topography. However, despite their ubiquity in modern sand seas, comparatively little is known about their formation and evolution. Here we present a discrete numerical model of star-dune behaviour based on the feedback mechanisms between wind flow and bedform dynamics. Our simulations indicate that the morphology of star dunes results from the combination of individual longitudinal dunes. We find that the arms of the star dunes propagate only under favourable wind regimes. In contrast to dunes that form from an erodible bed, the crests of the propagating arms are oriented such that sand flux is maximized in the direction of arm growth. Our analysis of the simulated three-dimensional structures suggests that the morphodynamics of the arms are controlled by the frequency of wind reorientation, with a high frequency of reorientation leading to smaller arm dimension and high rates of growth. We suggest that arm propagation is an important process of mass exchange in dune fields.

Zhang, Deguo; Narteau, Clément; Rozier, Olivier; Courrech Du Pont, Sylvain

2012-07-01

142

Mars Global Digital Dune Database: MC2-MC29  

USGS Publications Warehouse

Introduction The Mars Global Digital Dune Database presents data and describes the methodology used in creating the database. The database provides a comprehensive and quantitative view of the geographic distribution of moderate- to large-size dune fields from 65? N to 65? S latitude and encompasses ~ 550 dune fields. The database will be expanded to cover the entire planet in later versions. Although we have attempted to include all dune fields between 65? N and 65? S, some have likely been excluded for two reasons: 1) incomplete THEMIS IR (daytime) coverage may have caused us to exclude some moderate- to large-size dune fields or 2) resolution of THEMIS IR coverage (100m/pixel) certainly caused us to exclude smaller dune fields. The smallest dune fields in the database are ~ 1 km2 in area. While the moderate to large dune fields are likely to constitute the largest compilation of sediment on the planet, smaller stores of sediment of dunes are likely to be found elsewhere via higher resolution data. Thus, it should be noted that our database excludes all small dune fields and some moderate to large dune fields as well. Therefore the absence of mapped dune fields does not mean that such dune fields do not exist and is not intended to imply a lack of saltating sand in other areas. Where availability and quality of THEMIS visible (VIS) or Mars Orbiter Camera narrow angle (MOC NA) images allowed, we classifed dunes and included dune slipface measurements, which were derived from gross dune morphology and represent the prevailing wind direction at the last time of significant dune modification. For dunes located within craters, the azimuth from crater centroid to dune field centroid was calculated. Output from a general circulation model (GCM) is also included. In addition to polygons locating dune fields, the database includes over 1800 selected Thermal Emission Imaging System (THEMIS) infrared (IR), THEMIS visible (VIS) and Mars Orbiter Camera Narrow Angle (MOC NA) images that were used to build the database. The database is presented in a variety of formats. It is presented as a series of ArcReader projects which can be opened using the free ArcReader software. The latest version of ArcReader can be downloaded at http://www.esri.com/software/arcgis/arcreader/download.html. The database is also presented in ArcMap projects. The ArcMap projects allow fuller use of the data, but require ESRI ArcMap? software. Multiple projects were required to accommodate the large number of images needed. A fuller description of the projects can be found in the Dunes_ReadMe file and the ReadMe_GIS file in the Documentation folder. For users who prefer to create their own projects, the data is available in ESRI shapefile and geodatabase formats, as well as the open Geographic Markup Language (GML) format. A printable map of the dunes and craters in the database is available as a Portable Document Format (PDF) document. The map is also included as a JPEG file. ReadMe files are available in PDF and ASCII (.txt) files. Tables are available in both Excel (.xls) and ASCII formats.

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

2007-01-01

143

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

2009-10-01

144

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

2010-10-01

145

Analysis of Dark Albedo Features on a Southern Polar Dune Field of Mars  

NASA Astrophysics Data System (ADS)

We observed 20-200 m sized low-albedo seepage-like streaks and their annual change on defrosting polar dunes in the southern hemisphere of Mars, based on the Mars Orbiter Camera (MOC), High Resolution Stereo Camera (HRSC), and High Resolution Imaging Science Experiment (HiRISE) images. The structures originate from dark spots and can be described as elongated or flowlike and, at places, branching streaks. They frequently have another spotlike structure at their end. Their overall appearance and the correlation between their morphometric parameters suggest that some material is transported downward from the spots and accumulates at the bottom of the dune's slopes. Here, we present possible scenarios for: the origin of such streaks, including dry avalanche, liquid CO2, liquid H2O, and gas-phase CO2. Based on their morphology and the currently known surface conditions of Mars, no model interprets the streaks satisfactorily. The best interpretation of only the morphology and morphometric characteristics is only given by the model that implies some liquid water. The latest HiRISE images are also promising and suggest liquid flow. We suggest, with better knowledge of sub-ice temperatures that result from extended polar solar insolation and the heat insulator capacity of water vapor and water ice, future models and measurements may show that ephemeral water could appear and flow under the surface ice layer on the dunes today.

Horváth, András; Kereszturi, Ákos; Bérczi, Szaniszló; Sik, András; Pócs, Tamás; Gánti, Tibor; Szathmáry, Eörs

2009-02-01

146

Analysis of dark albedo features on a southern polar dune field of Mars.  

PubMed

We observed 20-200 m sized low-albedo seepage-like streaks and their annual change on defrosting polar dunes in the southern hemisphere of Mars, based on the Mars Orbiter Camera (MOC), High Resolution Stereo Camera (HRSC), and High Resolution Imaging Science Experiment (HiRISE) images. The structures originate from dark spots and can be described as elongated or flowlike and, at places, branching streaks. They frequently have another spotlike structure at their end. Their overall appearance and the correlation between their morphometric parameters suggest that some material is transported downward from the spots and accumulates at the bottom of the dune's slopes. Here, we present possible scenarios for the origin of such streaks, including dry avalanche, liquid CO(2), liquid H(2)O, and gas-phase CO(2). Based on their morphology and the currently known surface conditions of Mars, no model interprets the streaks satisfactorily. The best interpretation of only the morphology and morphometric characteristics is only given by the model that implies some liquid water. The latest HiRISE images are also promising and suggest liquid flow. We suggest, with better knowledge of sub-ice temperatures that result from extended polar solar insolation and the heat insulator capacity of water vapor and water ice, future models and measurements may show that ephemeral water could appear and flow under the surface ice layer on the dunes today. PMID:19203240

Horváth, András; Kereszturi, Akos; Bérczi, Szaniszló; Sik, András; Pócs, Tamás; Gánti, Tibor; Szathmáry, Eörs

147

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.

148

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.

Holston, Kevin C.

2005-01-01

149

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

PubMed

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

Holston, Kevin C

2005-12-22

150

Sand dune mobilization caused by regional warming in Otintag, China  

Microsoft Academic Search

Remobilization of fixed or semi-fixed sand dunes is the main process of desertification, which is sensitive to climate change. We analyzed 35-year temperature and precipitation data at three meteorological stations in Otintag Sandy Land, and calculated sand dune mobility index by employing the method suggested by Lancaster. In the last 35 years, the regional temperature tended to increase, whereas precipitation,

Baolin Zhang; Xiaoju Lu; Ruilin Luo

2010-01-01

151

Distribution of Sand Dune Successional Species in Monterey Bay  

Microsoft Academic Search

Malkinson et al. (2003) state that the spatial patterns on sand dunes of individual species changed from clustered to regular as succession progressed as the result of the change in relative importance of facilitation and competition. This theory was used to examine the distribution of sand dune succession species in Monterey Bay. We used a quadrat-based approach on randomly selected

David Priestley; Kate Raine; Charlotte Robinson

152

36 CFR 7.80 - Sleeping Bear Dunes National Lakeshore.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 2013-07-01 false Sleeping Bear Dunes National Lakeshore. 7.80 Section...NATIONAL PARK SYSTEM § 7.80 Sleeping Bear Dunes National Lakeshore. (a) Powerless... (c) Bicycling. (1) The Sleeping Bear Heritage Trail, approximately 27...

2013-07-01

153

Morphologic characteristics and development of falling dunes, northeast Kuwait  

Microsoft Academic Search

Falling dunes are the most common aeolian landform in northeast Kuwait. They are associated with the Jal Az-Zor escarpment. Comparison of aerial photographs from 1972 and 1992 indicates that these dunes developed recently. This change in a relatively short period is attributable mainly to drought, intensive land use and availability of sand source linked to surface disturbance. Military activities during

A. Al-Enezi; K. Pye; R. Misak; S. Al-Hajraf

2008-01-01

154

Initiation and variation of the dune fields in semi-arid China – with a special reference to the Hunshandake Sandy Land, Inner Mongolia  

NASA Astrophysics Data System (ADS)

Sedimentary sequences occurring in desert dunes reflect changes in desert systems, and as such may contain signals useful for recognizing spatial and temporal changes of deserts and their response to regional or even global climate fluctuations. Geomorphological and palaeoenvironmental studies within the dune fields of the Asian middle-latitudes have provided some solid evidence for interpreting the history of these sand seas. Using the Hunshandake (Otindag) Sandy Land, a sandy area covered primarily by stabilized dunes and located in the semi-arid zone of eastern Inner Mongolia, China (Fig. 1), as an example, we studied the initiation and variation in the dune landscape in the eastern portion of the desert belt in northern China. On the basis of physical and biochemical indicators in the sediments and OSL chronology, we herein argue that this dune system in the middle latitudes of eastern Asia is much younger than previously assumed and that it has responded sensitively to climate change during the late Quaternary. Geological evidence from the Sandy Land suggests that most of the current dunes are of late Pleistocene or even Holocene age. Palaeosols intercalated in the aeolian sequences and their OSL chronology show that the climate of the Hunshandake was much wetter than today between 9.6 ka and 3 ka. This resulted in stabilization of the dunes in the eastern and central portions of the Sandy Land. Epochs of reworking or stabilization of the dunes are broadly consistent with the fluctuations in northern hemisphere solar radiation although with an obvious time lag. Because the increase rate of annual precipitation was not sufficient to fully stabilize the dunes in more arid part of the region, some active dunes persisted even during this long-lasting wetter epoch. We conclude that periods of Holocene dune stabilization due to palaeosol formation varied along the climate gradients across the various sandy lands of northern China, and in general it began earlier and lasted longer in the east than in the west. The general nature of the sandy lands and their counterparts in the western portion of the desert belt during the LGM and mid-Holocene climate optimum is discussed in comparison with their current states.

Yang, Xiaoping; Wang, Xulong; Liu, Ziting; Li, Hongwei; Ren, Xiaozun; Zhang, Deguo; Ma, Zhibang; Rioual, Patrick; Jin, Xindi; Scuderi, Louis

2013-10-01

155

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

NASA Astrophysics Data System (ADS)

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

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

2012-08-01

156

Spatiotemporal model for the progression of transgressive dunes  

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

157

Sensitivity Analysis of Dune Height Measurements Along Cross-shore Profiles Using a Novel Method for Dune Ridge Extraction  

NASA Astrophysics Data System (ADS)

In barrier islands where communities are subjected to hazards including storm surge and high wave height, coastal dunes offer the first line of defense to property and vital infrastructure. When dunes are over-washed, substantial damage, including complete destruction of buildings and roads can occur. For this reason, dunes are an integral aspect of coastal hazard management. As new, more efficient mapping and analysis technologies evolve, currently used methodologies should be regularly be reexamined in order to ensure the development of the most effective coastal management strategies. Currently, topographical parameters, such as dune height, are usually measured along evenly spaced, shore-perpendicular beach profiles. In previous studies, profile spacing has varied from 20m to over 500m, however, it has been shown that dune height can vary substantially over tens of meters. Profile spacing is a compromise between the resources needed to perform high-resolution measurements and ensuring the capture of meaningful dune features. While it is often clear how the choice of profile spacing will affect the resources needed to perform the analysis, it is often unclear how spacing affects the ability to capture significant dune variation and prevent omission of a narrow dune breach that can open the way for significant flooding. In this study, the structure of alongshore variation in dune height is investigated. The studied dune ridge is located in the Outer Banks, North Carolina, USA and stretches 18km from south of Oregon Inlet (75:31:19W, 35:46:03N) to Rodanthe (75:27:56W, 35:36:31N). The dune ridge is extracted from a 0.5m resolution Digital Elevation Model (DEM) that was interpolated from airborne lidar data using regularized spline with tension. The lidar data was collected in March 2008 by the National Oceanic and Atmospheric Administration. A dune ridge is usually identified as the highest elevation along a shore-perpendicular profile or where ocean-facing slope meets landward-facing slope. In this study, a novel approach for dune ridge extraction is proposed. First, two alongshore end-points of the studied dune ridge are identified using a standard, profile-based method. Then, the dune ridge is traced as the least cost path connecting the two end-points on a cost surface that represents the cumulative penalty for tracing a low elevation path. The cost surface is derived from elevation (i.e., elevation is equal to the cologarithm of the cost). The extracted dune ridge is then sampled at the DEM resolution of 0.5m and analysis of dune ridge height is performed. Statistics on variation in dune height are computed to help understand the sensitivity of dune height measurements to profile spacing and placement. Preliminary results suggest that dune height becomes nearly uncorrelated within 50m and ranges on average nearly a half meter within a five meter window suggesting that dune height measurements are sensitive to profile placement.

Hardin, E.; Mitasova, H.; Overton, M.

2010-12-01

158

Where to dig for gold? - Density segregation inside migrating dunes  

NASA Astrophysics Data System (ADS)

If a fluid streams over an extended area of sand, the grains will self-organize by forming complex structures like ripples or dunes. Below the surface, the inner structure of a dune is determined by the individual fate of the particles. In general, agitated granular matter is known to show de-mixing whenever particles differ in size or density, and indeed size segregation is a well-known feature for dunes, called reverse grading. Here we report results of a recent experimental investigation with two particle species differing not in size but in density. Our experimental setup consists of a stadium-shaped flow channel which is filled with water. Measurements are made with a CCD-camera, placed in front of the straight part, recording side views of the dunes migrating downstream. From an initially prepared triangular heap a rapid relaxation to a steady-state solution is observed with constant mass, shape, and velocity. This attractor exhibits all characteristic features of barchan dunes found in nature, namely a gently inclined windward side, crest, brink, and steep lee face. In addition, if the dune consists of a bi-dense mixture of particles, the heavier particles accumulate at the top of migrating dunes whereas light particles are buried at its bottom. This insight into the sedimentology of dunes composed of different types of sand has, loosely speaking, the implication, that in a dune mixed of gold and sand, gold nuggets are likely to be found at the top of the dune, close to the surface at its crest.

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

2013-06-01

159

Crescent concerns  

Microsoft Academic Search

France is home to approximately five million people of Muslim origin, giving it western Europe's largest Muslim population. Three-quarters of French Muslims trace their origins to just three countries—Algeria, Morocco and Tunisia—but half of today's French Muslim population was born in France. Muslims face considerable difficulties, including poor housing, unemployment and discrimination. Some of these issues are the problems of

SHEREEN EL FEKI

2007-01-01

160

Plasmon hybridization in stacked double crescents arrays fabricated by colloidal lithography.  

PubMed

We apply colloidal lithography to construct stacked nanocrescent dimer structures with an exact vertical alignment and a separation distance of approximately 10 nm. Highly ordered, large arrays of these nanostructures are accessible using nonclose-packed colloidal monolayers as masks. Spatially separated nanocrescent dimers are obtained by application of spatially distributed colloids. The polarization dependent optical properties of the nanostructures are investigated in detail and compared to single crescents. The close proximity of the nanocrescents leads to a coupling process that gives rise to new optical resonances which can be described as linear superpositions of the individual crescents' plasmonic modes. We apply a plasmon hybridization model to explain the spectral differences of all polarization dependent resonances and use geometric arguments to explain the respective shifts of the resonances. Theoretical calculations are performed to support the hybridization model and extend it to higher order resonances not resolved experimentally. PMID:21218827

Vogel, Nicolas; Fischer, Janina; Mohammadi, Reza; Retsch, Markus; Butt, Hans-Jürgen; Landfester, Katharina; Weiss, Clemens K; Kreiter, Max

2011-01-10

161

Crescentic Glomerulonephritis: an update on Pauci-immune and Anti-GBM diseases.  

PubMed

Crescentic glomerulonephritis (GN) in a renal biopsy is a widely accepted "critical diagnosis" in Anatomic Pathology practice. Prompt biopsy evaluation and notification of the referring physician is essential to facilitate rapid therapeutic intervention. The differential diagnostic categories of crescentic GN include pauci-immune GN, anti-glomerular basement membrane (GBM) nephritis and immune complex-mediated GN, distinguished from one another by immunofluorescence and electron microscopic study of the renal biopsy. Immune complex-mediated GN is characterized by abundant glomerular deposits and encompasses several diseases including but not limited to lupus nephritis, cryoglobulinemic GN and immunoglobulin A nephropathy. Pauci-immune GN, with paucity of deposits, correlates closely with antineutrophil cytoplasmic antibody disease due to the identifiable circulating pathogenic antineutrophil cytoplasmic antibody in most patients. Recent studies have identified other antibodies in pauci-immune GN and implicated infectious organisms in triggering autoimmunity in a susceptible host by molecular mimicry of host antigens. Anti-GBM nephritis is a rare but potentially life-threatening autoimmune disease with circulating antibodies against GBM epitopes in ?3 chain of type IV collagen. It is characterized by a linear immunoglobulin G deposition along GBM on immunofluorescence microscopy. Environmental triggers including infections and solvent exposure seem to change the tertiary structure of the type IV collagen ?345 hexamer in GBM, expose neoepitopes, and initiate autoimmunity. Even in light of advances in understanding of pathophysiology and serologic testing, renal biopsy remains the mainstay of diagnosis of crescentic GN. PMID:22313839

Kambham, Neeraja

2012-03-01

162

Serum-starved adipose-derived stromal cells ameliorate crescentic GN by promoting immunoregulatory macrophages.  

PubMed

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

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

2013-03-07

163

Transferred Antigen-Specific TH17 but not TH1 Cells Induce Crescentic Glomerulonephritis in Mice  

PubMed Central

To explore the role of antigen-specific CD4+ T cells in glomerulonephritis, we administered ovalbumin 323–339 peptide conjugated to glomerular-binding polyclonal antibody and induced disease in RAG1?/? mice with CD4+ T cells from OT2 × RAG1?/? mice. These OT2 × RAG1?/? mice have a transgenic T-cell receptor specific for this peptide. When CD4+ T cells were primed in vivo, crescentic glomerulonephritis developed after 21 days in mice given peptide-conjugated glomerular-binding antibody but not unconjugated antibody control. We then investigated the relative roles of TH1 and TH17 cells, using Fab2 fragments of glomerular-binding antibody to exclude a role for antibody in this model. T cells from OT2 × RAG1?/? mice were polarized in vitro, and TH1 or TH17 cell lines were injected into mice that were also given peptide-conjugated Fab2 or unconjugated Fab2 control, giving four experimental groups. After 21 days crescentic glomerulonephritis was seen in mice receiving TH17 cells and peptide-conjugated Fab2 but in none of the other three groups. These results suggest that TH17 but not TH1 cells can induce crescentic glomerulonephritis.

Tulone, Calogero; Giorgini, Angela; Freeley, Simon; Coughlan, Alice; Robson, Michael Gregory

2011-01-01

164

Feasibility of using sand dunes as archives of old air  

NASA Astrophysics Data System (ADS)

Large unaltered samples of the atmosphere covering the past century would complement the history of atmospheric gases obtained from bubbles in ice cores, enabling measurement of geochemically important species such as O2, 14CH4, and 14CO. Sand dunes are a porous media with interstitial air in diffusive contact with the atmosphere, somewhat analogous to the unconsolidated layer of firn atop glaciers. Recent studies have demonstrated the value of firn as an archive of old air [Battle et al., 1996; Bender et al., 1994a]. Unlike firn, sand dunes are incompressible and so remain permeable to greater depths and may extend the firn record into the past century. To evaluate the feasibility of using sand dunes as archives of old air, we drilled 60 m deep test holes in the Algodones Dunes, Imperial Valley, California. The main objective was to see if the air in a sand dune is as old as predicted by a diffusion model, or if the dune is rapidly flushed by advective pumping during windstorms and barometric pressure changes. We dated the air with chlorofluorocarbons and krypton-85, anthropogenic tracers whose atmospheric concentrations are known and have been increasing rapidly in the past half century. These tracer data match the pure diffusion model well, showing that advection in this dune is negligible compared to diffusion as a transport mechanism and that the mean age of the air at 61 m depth is ˜10 years. Dunes therefore do contain old air. However, dunes appear to suffer from two serious drawbacks as archives. Microbial metabolism is evident in elevated CO2 and N2O and depressed CH4 and O2 concentrations in this dune, corrupting the signals of interest in this and probably most dunes. Second, isotopic analyses of N2 and O2 from the dune show that fractionation of the gases occurs due to diffusion of water vapor, complicating the interpretation of the O2 signal beyond the point of viability for an air archive. Sand dunes may be useful for relatively inert gases with large atmospheric concentration changes such as chlorofluorocarbons.

Severinghaus, Jeffrey P.; Keeling, Ralph F.; Miller, Benjamin R.; Weiss, Ray F.; Deck, Bruce; Broecker, Wallace S.

1997-07-01

165

Late Pleistocene dune activity in the central Great Plains, USA  

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

166

Dune migration and slip face advancement in the Rabe Crater dune field, Mars  

NASA Astrophysics Data System (ADS)

Eight overlapping images of a dune slip face in Rabe Crater (35°E, 44°S) from the Mars Global Surveyor Mars Orbiter Camera show changes interpreted to be multiple grainflow events that would indicate present-day sand saltation and dune migration. New occurrences of these features appear sporadically throughout late southern summer and early fall, and then no further changes occur throughout winter. By the following summer the pattern of old streaks had been almost completely covered by new dark streaks. Assuming that this activity is typical from year to year, migration rates are estimated to be on the order of 1-2 cm per martian year, produced by south to southeasterly winds that blow mostly during the southern spring and early summer. This slow migration rate is consistent with a present-day sediment state that is either transport or availability limited.

Fenton, Lori K.

2006-10-01

167

The Role of Algal Mats on Community Succession in Dunes and Dune Slacks  

Microsoft Academic Search

Different kinds of algal communities can live in dune slacks that may become temporarily flooded or remain moist throughout\\u000a the year due to fluctuations in the proximity of the water table (Brown and McLachlan 1990). This chapter focuses on changes\\u000a in the composition of algal communities during periods of flooding and drought, with special emphasis on the hydrological\\u000a characteristics of

G. Vázquez

168

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.

169

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

2013-10-07

170

Effects of sand fences on coastal dune vegetation distribution  

NASA Astrophysics Data System (ADS)

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

Grafals-Soto, Rosana

2012-04-01

171

Sand dunes on the central Delmarva Peninsula, Maryland and Delaware  

USGS Publications Warehouse

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

Denny, Charles Storrow; Owens, James Patrick

1979-01-01

172

Profile measurement and simulation of a transverse dune field in the Lençóis Maranhenses  

Microsoft Academic Search

In this work, we report measurements of the height profile of transverse dunes in the coastal dune field known as “Lençóis Maranhenses”, northeastern Brazil. Our measurements show that transverse dunes with approximately the same height present a variable brink position relative to the crest, in contrast to the case of barchan dunes. Based on our field data, we present a

E. J. R. Parteli; V. Schwämmle; H. J. Herrmann; L. H. U. Monteiro; L. P. Maia

2006-01-01

173

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

Microsoft Academic Search

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

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

2004-01-01

174

Control of Sand Movement on Model Dune by Fence Installation  

NASA Astrophysics Data System (ADS)

Recent desertification has been one of serious environmental issues. It is important to elucidate mechanisms of the sand movement from sand dunes with considering the relations between the dune shape and the turbulent air flow. This relation can be applied to predict and prevent the desertification. In this study, the shape of the dune surface and the erosion rate are measured by the method of laser-sheet visualization. Laser-doppler velocimetry (LDV) has been used for turbulence measurement. Effects of an installed fence on the erosion rate are discussed with emphasis on influences of its position and height. The erosion has been either suppressed or enhanced by the fence. Since there exist two strong erosion areas due to the backflow and wake induced by the fence. In the present experimental conditions, the top of the dune is the most suitable position of the fence for preventing erosion.

Sakamoto, Yusuke; Shimazu, Shota; Tsukahara, Takahiro; Yamamoto, Makoto; Kawaguchi, Yasuo

2010-03-01

175

Addition of Angiotensin II Type 1 Receptor Blocker to CCR2 Antagonist Markedly Attenuates Crescentic Glomerulonephritis  

PubMed Central

The monocyte chemoattractant protein-1 (MCP-1)/CC-chemokine receptor 2 (CCR2) pathway plays a critical role in the development of antiglomerular basement membrane (anti-GBM) nephritis. We recently showed angiotensin II (Ang II) infusion in rats activated MCP-1 and transforming growth factor-?1 (TGF-?1), which in turn induced macrophage infiltration of renal tissues. This study was performed to demonstrate that combination therapy with a CCR2 antagonist (CA) and an Ang II type 1 receptor blocker (ARB) ameliorated renal injury in the anti-GBM nephritis model. An anti-GBM nephritis rat model developed progressive proteinuria and glomerular crescent formation, accompanied by increased macrophage infiltration and glomerular expression of MCP-1, angiotensinogen, Ang II, and TGF-?1. Treatment with CA alone or ARB alone moderately ameliorated kidney injury; however, the combination treatment with CA and ARB dramatically prevented proteinuria and markedly reduced glomerular crescent formation. The combination treatment also suppressed the induction of macrophage infiltration, MCP-1, angiotensinogen, Ang II, and TGF-?1 and reversed the fibrotic change in the glomeruli. Next, primary cultured glomerular mesangial cells (MCs) stimulated by Ang II showed significant increases in MCP-1 and TGF-?1 expression. Furthermore, cocultured model consisting of MCs, parietal epithelial cells, and macrophages showed an increase in Ang II-induced cell proliferation and collagen secretion. ARB treatment attenuated these augmentations. These data suggest that Ang II enhances glomerular crescent formation of anti-GBM nephritis. Moreover, our results demonstrate that inhibition of the MCP-1/CCR2 pathway with a combination of ARB effectively reduces renal injury in anti-GBM nephritis.

Urushihara, Maki; Ohashi, Naro; Miyata, Kayoko; Satou, Ryousuke; Acres, Omar W.; Kobori, Hiroyuki

2011-01-01

176

Platelets are not critical effector cells for the time course of murine passive crescentic glomerulonephritis.  

PubMed

Although platelets are well-known effector cells of inflammatory renal disease, clinical studies were not able to establish platelet inhibition as an effective therapy. Our previous studies using Vasodilator stimulated Phosphoprotein- and P2Y1-deficient mice suggested some early, but no long-term effects of platelets in passive crescentic glomerulonephritis. To define the role of platelets for this disease model, passive crescentic glomerulonephritis was induced in 72 C57Bl/6 mice by intraperitoneal injection of sheep anti-rabbit glomerular basement membrane antibody on 2 consecutive days. Platelets were depleted using anti-glycoprotein Ib? antibodies (p0p3/p0p4) every 4th day. Mice treated with equal amounts of sterile Phosphate buffered solution or rat-IgG served as controls. Blood, urine, and tissues were harvested on days 3 and 28. Renal tissue sections were evaluated after immunostaining using (semi)quantitative and computer-assisted image analysis. Compared to controls, efficient depletion was achieved as indicated by a markedly prolonged bleeding time and a more than 90% reduction in platelet counts (800/nl vs. 42/nl; P?crescentic nephrotoxic nephritis was affected. These data indicate that platelets play a minor role during the time course of this disease model in the mouse. PMID:22779773

Hohenstein, Bernd; Daniel, Christoph; Johnson, Richard J; Amann, Kerstin U; Hugo, Christian P M

2012-07-10

177

Recruitment limitation of native species in invaded coastal dune communities  

Microsoft Academic Search

Recruitment limitation may limit the ability of sites to regenerate after disturbances such as weed invasion and weed management.\\u000a We investigated seed bank constraints and dispersal limitation in coastal dune communities on the east coast of Australia.\\u000a The ability of sites to regenerate naturally following weed removal was assessed in coastal dune communities invaded by the\\u000a invasive alien, bitou bush

Kris French; Tanya J. Mason; Natalie Sullivan

2011-01-01

178

Rip currents, mega-cusps, and eroding dunes  

USGS Publications Warehouse

Dune erosion is shown to occur at the embayment of beach mega-cusps O(200??m alongshore) that are associated with rip currents. The beach is the narrowest at the embayment of the mega-cusps allowing the swash of large storm waves coincident with high tides to reach the toe of the dune, to undercut the dune and to cause dune erosion. Field measurements of dune, beach, and rip current morphology are acquired along an 18??km shoreline in southern Monterey Bay, California. This section of the bay consists of a sandy shoreline backed by extensive dunes, rising to heights exceeding 40??m. There is a large increase in wave height going from small wave heights in the shadow of a headland, to the center of the bay where convergence of waves owing to refraction over the Monterey Bay submarine canyon results in larger wave heights. The large alongshore gradient in wave height results in a concomitant alongshore gradient in morphodynamic scale. The strongly refracted waves and narrow bay aperture result in near normal wave incidence, resulting in well-developed, persistent rip currents along the entire shoreline. The alongshore variations of the cuspate shoreline are found significantly correlated with the alongshore variations in rip spacing at 95% confidence. The alongshore variations of the volume of dune erosion are found significantly correlated with alongshore variations of the cuspate shoreline at 95% confidence. Therefore, it is concluded the mega-cusps are associated with rip currents and that the location of dune erosion is associated with the embayment of the mega-cusp. ?? 2007 Elsevier B.V. All rights reserved.

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

2007-01-01

179

On the transition between 2D and 3D dunes  

Microsoft Academic Search

Sediment transport in sand-bedded alluvial channels is strongly conditioned by bedforms, the planimetric morphology of which can be either two- or three- dimensional. Experiments were undertaken to examine 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

JEREMY G. VENDITTI; MICHAEL CHURCH; SEAN J. BENNETT

2005-01-01

180

Computer simulation of the dynamics of a dune system  

Microsoft Academic Search

The mobile dune system of the Doñana National Park (southwest Spain) covers an area of 100 km2. It is formed by several transverse dune fronts 5–20 m high, lying parallel to the beach, and separated by flat slacks covered by scrub vegetation. Duns move from the beach inland at a rate of 2.5 m per year, burying the slack vegetation

Francisco de Castro

1995-01-01

181

Pathomimie de l'enfant: ? propos d'une observation  

PubMed Central

La pathomimie cutanée se définit comme une maladie factice, provoquée dans un etat de conscience claire par le patient lui-même, au niveau du revêtement cutanéo-muqueux et/ou des phanères. Rare chez l'enfant, il s'agit d'une manifestation psychopathologique potentiellement grave et souvent difficile à prendre en charge. Nous rapportons le cas d'une fillette de 10 ans présentant une pathomimie sous forme de lésions excoriées multiples du visage.

Abilkassem, Rachid; Dini, Nezha; Ourai, Hakim; Kmari, Mohamed; Agadr, Aomar

2013-01-01

182

Soil pH and species diversity in coastal dunes  

Microsoft Academic Search

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

M. Isermann

2005-01-01

183

Acute Kidney Injury due to Crescentic Glomerulonephritis in a Patient with Polycystic Kidney Disease.  

PubMed

Polycystic kidney disease is an inherited condition, characterized by the development of cysts in the kidney, as well as in other organs. Patients with polycystic kidney can suffer from the same causes of acute kidney injury as the general population. Nephritic syndrome is an uncommon cause of acute kidney injury in the general population and less common in patients with polycystic kidney disease. We report the second case of crescentic glomerulonephritis, causing acute kidney injury, in a patient with polycystic kidney disease. PMID:23914203

Maggard, Reuben; Makary, Raafat; Monteiro, Carmela L; James, Leighton R

2013-07-11

184

Barchan dune corridors: Field characterization and investigation of control parameters  

NASA Astrophysics Data System (ADS)

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.

Elbelrhiti, H.; Andreotti, B.; Claudin, P.

2008-06-01

185

Effects of topography on the dune forming winds on Titan  

NASA Astrophysics Data System (ADS)

Cassini 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. 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. One can find examples of dunes on Earth that fit several wind regimes. To date only one GCM, that of Tokano (2008, 2010), 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 (Friedson et al. 2009), is unable to reproduce the fast westerlies. 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: Tokano, T. 2008. Icarus 194, 243-262. Tokano, T. 2010. Aeolian Research 2, 113-127. Friedson, J. et al. 2009. Planet. Sp. Sci., 57, 1931-1949.

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

2013-10-01

186

An analysis of the current stability of the Dune Field at Great Sand Dunes National Monument using temporal TM imagery (1984–1998)  

Microsoft Academic Search

Research conducted at the Great Sand Dunes National Monument (37°46.5?N, 105°32.5?W) thus far has focused on dune composition in order to explain formation, dune migration to monitor aeolian processes, and dune extent to detect encroachment in the eastern periphery, a region that contains several visitor services. These studies used a series of field techniques in conjunction with aerial photography; however,

Jason R. Janke

2002-01-01

187

Dwelling in the Dunes: Traditional Use of the Dune Shacks of the Peaked Hill Bars Historic District, Cape Cod.  

National Technical Information Service (NTIS)

This ethnographic report provides a picture of the traditions and cultural patterns of the dune dwellers living in shacks in the Peaked Hill Bars Historic District, Cape Cod National Seashore, Massachusetts. The report describes the seasonal settlement of...

R. J. Wolfe

2005-01-01

188

Internal Structure of a Star Dune Imaged Using Ground-Penetrating Radar  

NASA Astrophysics Data System (ADS)

The Coral Pink Sand Dunes, located in far southwestern Kane County,Utah, is the site of an onging investigation into factors influencing dune field development. This elongate dune field (11 km by ~1.2 km) includes bedforms ranging along a continuum from stabilized sand sheets and vegetated parabolic dune forms to fully active transverse dunes and barchanoid ridges. This paper presents the results of our ground-penetrating radar (GPR) reconnaissance transects across a small star dune in the south central (active) portion of the dune field. GPR data (100 MHz, 1.0-meter offset, 0.5-meter step) were collected from four transects bracketing the star dune and provide radar imagery of the sedimentary structure of four arms of the dune and underlying bedrock. Processing of the GPR data consisted of a few steps, including dewowing and bandpass filtering, migration, and topographic correction. Results from data migration were mixed but overall did not appear to improve the imagery. Interpretations are made primarily from the unmigrated data cross-checked against the migrated dataset. Depth to bedrock ranges from 0 meters in the surrounding interdune serirs to 25 meters under the star dune crest. The shallow nature of the dune sands and a lack of major cross-stratification revealed in the cross sections suggest these dunes are still accumulating sand and respond quickly to changes in wind direction. The orientation of the foresets in the peak and main transverse dune arm imply the dune is presently responding to a southwesterly windflow. Southeasterward dipping foresets in three smaller (minor) arms longitudinal to the transverse dune possibly reflect modification of windflow around the main dune body. Comparison of aerial photography of the area from 1955 and 1960 with that of 1997 indicate the star dune formed through capture of another, smaller dune that merged from the southwest. The SE dipping foresets in the minor arms appear to reflect this capture, and so preserve both dune movement as well as windflow modification.

Wilkins, D. E.; Ford, R. L.; Clement, W. P.

2002-12-01

189

Pauci-immune necrotizing crescentic glomerulonephritis with crescentic and full moon extracapillary proliferation: clinico-pathologic correlation and follow-up study.  

PubMed

The prognostic value of the type and extent of extracapillary proliferation (ECP) in pauci-immune necrotizing crescentic glomerulonephitis (PIGN) was evaluated in this study. In 141 PIGN cases, all glomeruli with ECP were grouped according to type (cellular, fibrocellular and fibrous) and extent of the lesions in Bowman's space; (segmental, semicircumferential and circumferential, which might be termed full moon-FM). Cases with cellular and fibrous lesions involving ? 50% of glomeruli with ECP were classified as cellular and fibrous groups, respectively, while the remaining cases were classified as fibrocellular. Cases with segmental and circumferential (FM glomerulus) lesions involving ? 50% of glomeruli with ECP were classified as ECPI and ECPIII (FM) groups, respectively, while the rest were classified as ECPII. All the cases were classified according to Berden et al. Significant results were only nearly obtained for the FM group, including the need for dialysis. The Cox regression model revealed a 2.6-fold risk for FM cases regarding dialysis requirement. We propose that the percentage of FM glomeruli should be noted in the pathology report, and cases with more than 50% of FM glomeruli (FM group) should be identified in the group with increased risk of dialysis requirement. Our series also suggests that classification according to Berden et al. is of clinical relevance. PMID:23246377

Unlu, Mehtat; Kiremitci, Saba; Ensari, Arzu; Ozluk, Yasemin; Kilicaslan, Isin; Ozdemir, Binnaz Handan; Ates, Deniz; Ertoy Baydar, Dilek; Gonul, Ipek Isik; Memis, Leyla; Sarsik, Banu; Sen, Sait; Akkaya, Bahar; Orhan, Diclehan; Gonlusen, Gulfiliz; Ellidokuz, Hulya; Ada, Sibel; Cavdar, Caner; Akagun, Tulin; Kamali, Sevil; Aksu, Kenan; Yazisiz, Veli; Paydas, Saime; Soylu, Alper; Sarioglu, Sulen

2012-12-14

190

[A case of crescentic poststreptococcal acute glomerulonephritis (PSAGN) accompanied by membranous nephropathy].  

PubMed

In 2010, a 71-year-old man was referred to our hospital because of mild proteinuria and hematuria. At that time, he had been asymptomatic. Three months later he noticed macroscopic hematuria, followed by general malaise, and then anorexia. He was admitted for acute kidney injury (serum creatinine 2.7 mg/dL), marked proteinuria (4.35 g/gCr), and elevated C-reactive protein (7.21 mg/dL). Some vesicles were noted on the soft palate, and a throat culture yielded a growth of group A beta-hemolytic streptococci. Antistreptolysin O and antistreptokinase titers were elevated, but serum complement levels were within normal limits. Antineutrophil cytoplasmic antibodies (ANCA) directed against elastase and bactericidal permeability increasing protein (BPI)were positive. The renal function and inflammation did not improve despite oral antibiotic therapy. Pathological examination of a renal biopsy specimen revealed diffuse crescent formation, numerous subepithelial dome-shaped deposits (humps), and prominent endocapillary proliferation. Furthermore, a focal and segmental spike appearance was seen, with deposits smaller than humps. There was a striking clinical improvement after steroid pulse therapy followed by oral prednisolone. The features of this case strongly suggest crescentic PSAGN accompanied by pre-existing membranous nephropathy. PMID:23819387

Matsuda, Jun; Nagayama, Ikue; Yamaguchi, Yoshito; Itano, Seiji; Mori, Daisuke; Imakita, Natsuko; Takeji, Masanobu; Yamauchi, Atsushi

2013-01-01

191

Amphiphilic crescent-moon-shaped microparticles formed by selective adsorption of colloids.  

PubMed

We use a microfluidic device to prepare monodisperse amphiphilic particles in the shape of a crescent-moon and use these particles to stabilize oil droplets in water. The microfluidic device is comprised of a tapered capillary in a theta (?) shape that injects two oil phases into water in a single receiving capillary. One oil is a fluorocarbon, while the second is a photocurable monomer, which partially wets the first oil drop; silica colloids in the monomer migrate and adsorb to the interface with water but do not protrude into the oil interface. Upon UV-induced polymerization, solid particles with the shape of a crescent moon are formed; removal of fluorocarbon oil yields amphiphilic particles due to the selective adsorption of silica colloids. The resultant amphiphilic microparticles can be used to stabilize oil drops in a mixture of water and ethanol; if they are packed to sufficient surface density on the interface of the oil drop, they become immobilized, preventing direct contact between neighboring drops, thereby providing the stability. PMID:21417254

Kim, Shin-Hyun; Abbaspourrad, Alireza; Weitz, David A

2011-03-21

192

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

193

Monitoring of desert dune topography by multi angle sensors  

NASA Astrophysics Data System (ADS)

Nowadays, the sandy desert is rapidly expanding world widely and results in a lot of risks in the socio-econimical aspects as well as the anthropogenic activities. For example, the increasing occurrences of mineral dust storm which presumably originated from the sandy deserts in northwest China become a serious threat in human activities as well as public health over Far East Asian area as the interpretation by the MODIS analysis (Zhang et al., 2007) and the particle trajectory simulation with HYSPLYT (HYbrid Single-Particle Lagrangian Integrated Trajectory) (Kim et al., 2011) identified. Since the sand dune activity has been recognized as an essential indicator of the progressive desertification, it is important to establish the monitoring method for the variations of topographic properties by the dune activities such as local roughness. Thus it will provide the crucial data about the extent and the transition of sandy desert. For example, it is well known the aerodynamic roughness lengths Zo which can be driven from the specialized sensor such as POLDER (POLarization and Directionality of the Earth's Reflectances) is essential to understand desert dune characteristics. However, for the multi temporal observation of dune fields, the availability of data set to extract Zo is limited. Therefore, we employed MISR (Multi angle imaging Spectro Radiometer) image sequence to extract multi angle topographic parameters such as NDAI (Normalized Difference Angular Index) or the variation of radiance with the viewing geometry which are representing the characteristics of target desert topography instead of Zo. In our approach, NDAI were expanded to the all viewing angles and then compared over the target sandy desert and the surrounding land covers. It showed very strong consistencies according to the land cover type and especially over the dynamic dune fields. On the other hands, the variation of NDAIs of sandy desert combining with the metrological observations were examined and showed a correlation between the intensities sand dune activities and the surface wind conditions. In conclusion, we proved that the trace of the sandy desert boundaries for long observation period is feasible with the multi angle orbital sensor observation by investigating the expanded NDAIs from various sample sand dune fields. However, it is quite uncertain whether the consistency of MISR NDAIs over sandy deserts originated from the aeolian micro structures, the reflectance of sand or the aspect angle of dune morphology. Therefore, in the next stage, the local roughness properties extracted from MISR data analysis will be compared with the topographic information from high resolution stereo satellite imagery such as ALOS PRISM (Panchromatic Remote-sensing Instrument for Stereo Mapping). Consequently it will correctly evaluate the suitability of multi angle observation parameters as a dune activity indicator.

Yun, J.; Kim, J.; Choi, Y.; Yun, H.

2011-12-01

194

Long-term observations of clinicopathological characteristics and outcome of Japanese patients with pauci-immune crescentic glomerulonephritis.  

PubMed

BACKGROUND: The clinicopathological characteristics and outcome with pauci-immune crescentic glomerulonephritis (CreGN) are presumed to vary over time. We examined the characteristics and outcome of Japanese patients with CreGN according to the treatment periods. PATIENTS AND METHODS: From 1968 to 2011, we examined a total of 102 patients diagnosed with pauci-immune CreGN by renal biopsy. The patients were divided into three groups according to the treatment periods-Group I (1968-1988, n = 18), Group II (1989-2001, n = 37; when the nationwide survey of rapidly progressive glomerulonephritis [RPGN] was performed in Japan), and Group III (2002-2011, n = 47; after publication of the Japanese guideline for RPGN). RESULTS: There were no significant differences in blood pressure, renal function or anti-neutrophil cytoplasmic antibody titer between groups. On the other hand, the rate of crescent formation and degree of interstitial inflammatory cell infiltration were decreased in Group III. Serum creatinine (<3.0, 3.0-6.0, ?6.0 mg/dL) and crescent formation (<30, 30-50, 50-80, ?80 %) were significant renal prognostic factors in Group III [serum creatinine: hazard ratio (HR) 4.79, 95 % confidence interval (CI) 1.43-16.1, P = 0.011; crescent formation: HR 2.86, 95 % CI 1.06-7.73, P = 0.039]. Furthermore, renal survival rate of patients with crescent formation <50 % and patient survival rate of patients with serum creatinine <3 mg/dL were improved in Group III. CONCLUSION: Patients with CreGN were diagnosed in the early phase of crescent formation and outcome has improved in recent years. PMID:23572289

Kitagawa, Kiyoki; Furuichi, Kengo; Shinozaki, Yasuyuki; Toyama, Tadashi; Kitajima, Shinji; Hara, Akinori; Iwata, Yasunori; Sakai, Norihiko; Kaneko, Shuichi; Wada, Takashi

2013-04-10

195

Immature stages of the Brazilian crescent butterfly Ortilia liriope (Cramer) (Lepidoptera: Nymphalidae).  

PubMed

We provide the first information on the morphology of the immature stages (egg, larva, and pupa), oviposition and larval behavior, and host plant, for the Brazilian crescent butterfly Ortilia liriope (Cramer), based on material from Santarém Municipality, Pará State, Northern Brazil. Females of O. liriope lay eggs in clusters. After hatching, larvae eat the exochorion and remain gregarious in all but the final instar. The host plant recorded in the study site is Justicia sp. (Acanthaceae). Despite the scarcity of data on the immature stages of Neotropical Melitaeini, we can already say that some morphological and behavioral traits observed in the immature stages of O. liriope are also present in all known genera in this tribe. PMID:21710028

Silva, P L; Oliveira, N P; Barbosa, E P; Okada, Y; Kaminski, L A; Freitas, A V L

196

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

NASA Astrophysics Data System (ADS)

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

Kochemasov, G. G.

2008-09-01

197

DUst around NEarby Stars (DUNES): description of the project and results  

NASA Astrophysics Data System (ADS)

DUNES is an Open Time Key Programme of the Herschel Space Observatory aimed at detecting and studying cold dusty --debris-- discs, i.e. Kuiper-belt analogues, around FGK stars of the solar neighbourhood, in a volume-limited sample of 133 stars. The sensitivity and wavelengths of the two instruments used, namely PACS (70, 100, and 160 ?m) and SPIRE (250, 350, and 500 ?m) are the appropriate ones for these tasks. Debris discs are the result of collisions of planetesimals formed at early stages of the star formation episode, when the star is younger than about 30 Myr, and the discs, so-called protoplanetary, are composed of gas and dust. The whole sample is already observed and the team is currently analysing the data. We outline here some of the main results we have found.

Montesinos, B.; Eiroa, C.; Dunes Team

2013-05-01

198

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

199

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

200

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

201

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

Microsoft Academic Search

Large expanses of linear dunes cover Titan’s equatorial regions. As the Cassini mission continues, more dune fields are becoming unveiled and examined by the microwave radar in all its modes of operation (SAR, radiometry, scatterometry, altimetry) and with an increasing variety of observational geometries. In this paper, we report on Cassini’s radar instrument observations of the dune fields mapped through

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

2011-01-01

202

Soil nutrients are not responsible for arrested succession in disturbed coastal dune forest  

Microsoft Academic Search

Coastal dune forest succession frequently proceeds via the Acacia karroo pathway, but may become arrested. We examine whether soil fertility arrests forest succession in A. karroo stands in coastal dune forest in KwaZulu-Natal province, South Africa. We examined soil fertility of A. karroo stands, the adjacent forest, and forested dune slacks at Cape Vidal, and four rehabilitating A. karroo stands

L. J. Boyes; M. E. Griffiths; A. D. Manson; M. J. Lawes

2010-01-01

203

Lunette dunes in the northeast Cape, South Africa, as geomorphic indicators of palaeoenvironmental change  

Microsoft Academic Search

Three lunette dunes occur on the southern shore of a pan on the farm Buffelsfontein above the Great Escarpment in the northeastern part of the Eastern Cape Province, South Africa. The two inner lunettes are formed of silt and clay, and the third of fine sand. The location of these dunes is anomalous as lunette dunes are rare in the

M. E. Marker; P. J. Holmes

1995-01-01

204

Rare earth elements of the Altar Desert dune and coastal sands, Northwestern Mexico  

Microsoft Academic Search

Twenty-one surficial sand samples from the Altar Desert coastal and desert dune systems were analysed for rare earth elements (REE) content. This was done to observe the provenance signatures for four strategic dune localities near the Colorado River Delta, the El Pinacate dune fields, and the beaches of the north of the Gulf of California in the state of Sonora,

Juan José Kasper-Zubillaga; Beatriz Acevedo-Vargas; Ofelia Morton Bermea; Glicinia Ortiz Zamora

2008-01-01

205

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

206

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

Microsoft Academic Search

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

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

2010-01-01

207

Development of a Late Quaternary Marine Terraced Landscape during On-Going Tectonic Contraction, Crescent City Coastal Plain, California  

Microsoft Academic Search

The Crescent City coastal plain is a low-lying surface of negligible relief that lies on the upper plate of the Cascadia subduction zone in northernmost California. Whereas coastal reaches to the north in southern Oregon and to the south near Cape Mendocino contain flights of deformed marine terraces from which a neotectonic history can be deduced, equivalent terraces on the

Michael Polenz; Harvey M. Kelsey

1999-01-01

208

Similarities of Tritonian guttae and Martian dark dune spots  

NASA Astrophysics Data System (ADS)

Dark spots with bright halo near the edge of the Triton's photographed south polar cap and Martian Dark Dune Spots (DDS) sometimes with bright halo, found at the Martian circumpolar regions show striking morphological similarities which may imply similar formative processes.

Hargitai, H. I.

2012-09-01

209

Alphabetisation conscientisante comme base d'une education permanente  

NASA Astrophysics Data System (ADS)

D'après la pratique et les enseignements vécus, nous pensons qu'une alphabétisation fonctionnelle et conscientisante est susceptible de constituer la base d'une éducation permanente (life long education), à condition que: Une philosophie et une anthropologie de la libération de l'homme soient le fondement de 1'alphabétisation;

Ndimurukundo, Nicephore

1994-05-01

210

SIMULTANEOUS SIDE BY SIDE VARIABILITY OF SEDIMENT CONCENTRATION OVER DUNES  

Technology Transfer Automated Retrieval System (TEKTRAN)

A series of laboratory experiments were conducted in a laboratory flume to characterize the lateral variations of suspended sediment over dunes. Forty experimental runs were made using flow depths of 0.33 and 0.13 m in a 1.2 m wide flume channel. The Froude number was 0.5 and the median diameter of...

211

A parameterization of flow separation over subaqueous dunes  

NASA Astrophysics Data System (ADS)

Flow separation plays a key role in the development of dunes, and modeling the complicated flow behavior inside the flow separation zone requires much computational effort. To make a first step toward modeling dune development at reasonable temporal and spatial scales, a parameterization of the shape of the flow separation zone over two-dimensional dunes is proposed herein, in order to avoid modeling the complex flow inside the flow separation zone. Flow separation behind dunes, with an angle-of-repose slip face, is characterized by a large circulating leeside eddy, where a separation streamline forms the upper boundary of the recirculating eddy. Experimental data of turbulent flow over two-dimensional subaqueous bed forms are used to parameterize this separation streamline. The bed forms have various heights and height to length ratios, and a wide range of flow conditions is analyzed. This paper shows that the shape of the flow separation zone can be approximated by a third-order polynomial as a function of the distance away from the flow separation point. The coefficients of the polynomial can be estimated, independent of flow conditions, on the basis of bed form shape at the flow separation point and a constant angle of the separation streamline at the flow reattachment point.

Paarlberg, Andries J.; Dohmen-Janssen, C. Marjolein; Hulscher, Suzanne J. M. H.; Termes, Paul

2007-12-01

212

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

213

Comment on ``Minimal size of a barchan dune''  

Microsoft Academic Search

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, Durán, and Herrmann [Phys. Rev. E 75, 011301 (2007)] predicts

B. Andreotti; P. Claudin

2007-01-01

214

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

215

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

216

Predicting flooding probability for beach\\/dune systems  

Microsoft Academic Search

The determination of the risk from flooding that shorefront communities face is an important component of coastal management that has not been resolved successfully. Wave runup offers one way of quantifying the risk of coastal flooding that results from overtopping by storm waves. The calculation of runup probabilities uses wave frequency analysis and an average beach\\/dune profile for a given

Paul A. Garès

1990-01-01

217

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...

218

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

219

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

220

Dunes, turbulent eddies, and interfacial exchange with permeable sediments  

Microsoft Academic Search

Interfaces between a water column and underlying porous media are ubiquitous in nature. Turbulent flow over an irregular interface separating a water column and underlying porous media drives advective-fluid exchange between the two domains. We investigate the dynamics of this coupled system for unidirectional flow in the water column and a triangular interface modeled on dunes. Numerical simulations solve the

M. Bayani Cardenas; John L. Wilson

2007-01-01

221

Amelioration of Crescentic Glomerulonephritis by RhoA Kinase Inhibitor, Fasudil, through Podocyte Protection and Prevention of Leukocyte Migration  

PubMed Central

The small GTPase RhoA is activated by the angiotensin II (AngII) type 1 receptor (AT1R), which is part of the local renin-angiotensin system that is involved in podocyte injury preceding glomerular crescent formation. We demonstrated previously that inhibition of AT1R protects against crescentic glomerular injury in Fc receptor-deficient mice (??/?) with anti-glomerular basement membrane antibody-induced glomerulonephritis (anti-GBM GN). Here, we hypothesized that the RhoA kinase inhibitor, fasudil, attenuates AT1R-dependent crescentic GN. We examined anti-GBM GN in ??/? mice with or without fasudil treatment, and further investigated the underlying mechanisms in cultured differentiated podocytes and leukocytes. Fasudil markedly attenuated crescentic GN with a significant decrease in proteinuria and hematuria, infiltration of T cells and monocytes/macrophages as well as their local proliferation, and preservation of podocyte-specific proteins, including WT-1 and nephrin, in glomeruli. In vitro studies showed that AngII induced the down-regulation of both nephrin and WT-1 expression in podocytes, which was reversed by fasudil in a dose-dependent manner. Additionally, fasudil blocked the AngII-induced migration of both macrophages and T cells. Furthermore, we also examined lipopolysaccharide-induced nephrotic syndrome in severe combined immunodeficiency disease mice and found that fasudil failed to block the development of proteinuria because of a B7-1-dependent podocyte injury. In conclusion, fasudil treatment prevents crescent formation and disease progression in anti-GBM GN by preventing AngII-induced podocyte injury and leukocyte migration.

Hidaka, Teruo; Suzuki, Yusuke; Yamashita, Michifumi; Shibata, Terumi; Tanaka, Yuichi; Horikoshi, Satoshi; Tomino, Yasuhiko

2008-01-01

222

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

223

Pressure Fluctuation Caused by Dune Structures in Hydraulic Solid Transport Pipe Flow  

NASA Astrophysics Data System (ADS)

This paper presents an experimental investigation on flow pressure fluctuation caused by dune formation during hydraulic solid transportation in horizontal pipelines. Digital photography was employed to study the morphologic characteristics of sand bed transportation with corresponding time based pressure measurement obtained using a pressure transducer. Combined, these experimental results characterized the interaction between dune formation and flow pressure fluctuation. With dune structures formed, significant pressure fluctuation was detected. These measurements combined with previous studies on dune flow field contribute to the fundamental insights into the physics of dune mode hydraulic solid transport flow in a closed conduit.

Wang, L.; Goharzadeh, A.; Rodgers, P.

2011-09-01

224

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

Microsoft Academic Search

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

Kevin C. Holston

2005-01-01

225

Carbimazole-induced, ANCA-associated, crescentic glomerulonephritis: case report and literature review.  

PubMed

Anti-neutrophil cytoplasmic antibodies (ANCA)-associated vasculitis is a rare complication of antithyroid drug use that was first described with propylthiouracil. We describe an ANCA-associated rapidly progressive glomerulonephritis in a patient treated with carbimazole during 6 months for Graves disease that resulted in end-stage renal disease. A 66-year-old man treated with carbimazole for Graves disease was admitted for macroscopic hematuria and edema of the lower extremities. Laboratory work-up showed elevated serum creatinine (435 ?mol/L), mixed hematuria, nephrotic range proteinuria, and a low positive c-ANCA titer with proteinase-3 specificity. Renal biopsy showed necrotizing, crescentic, pauci-immune glomerulonephritis. Carbimazole was discontinued and hemodialysis was initiated as well as high-dose glucocorticoids and pulses of intravenous cyclophosphamide. Despite immunosuppressive treatment, the patient remained dialysis-dependent at 6 months after diagnosis. Graves disease remained in remission after carbimazole withdrawal. ANCA-associated vasculitis manifesting as glomerulonephritis is a potential adverse effect of all antithyroid drugs. Although prognosis is usually good, end-stage renal disease may ensue in rare cases. Physicians should have a high index of suspicion in patients receiving antithyroid drugs who present with symptoms or signs suggestive of progressive renal disease. PMID:23343442

Mavrakanas, Thomas A; Bouatou, Yassine; Samer, Caroline; de Seigneux, Sophie; Meyer, Patrick

2013-01-24

226

Modified crescentic proximal metatarsal osteotomy and distal soft tissue procedures in hallux valgus.  

PubMed

The results of a modified crescentic proximal metatarsal osteotomy and distal soft tissue procedures for patients with symptomatic, incongruent, metatarsophalangeal joint, hallux valgus deformity were reviewed. Forty-nine feet of 41 patients were evaluated. All of the patients were male military personnel of different ranks, and their mean age was 23 years (range, 20-43 years). The mean follow-up period was 25 months (range, 10-60 months). The patients were evaluated according to the American Orthopedic Foot and Ankle Society forefoot scoring system. The mean preoperative score was 54.4, and the mean postoperative score was 95.4. The mean hallux valgus angle was 39.4 degrees before surgery and 12.8 degrees after surgery (26.6 degrees correction); the mean intermetatarsal angle was 15.9 degrees before surgery and 7.1 after surgery (8.8 degrees correction). A total of 93.8% of the patients were satisfied with the results of the procedure. Complications included delayed union in one case and superficial wound infections in two cases. We also emphasize small modifications performed while shifting the metatarsal shaft laterally and compare the results of our study with those of similar studies. PMID:17256694

Baykal, Barbaros; Kirdemir, Vecihi; Ate?alp, A Sabri; Bek, Dogan; Tercan, Volkan

2006-12-01

227

Rhino-orbitocerebral mucormycosis in a patient with idiopathic crescentic glomerulonephritis.  

PubMed

Mucormycosis, caused by mucorales, is an acute, rapidly progressive infection associated with high mortality. Rhino-orbitocerebral infection is the most common variant and is generally seen in association with immune deficiency syndromes. Prompt medical treatment of this infection and debridement decreases the mortality rate. We describe a 47-year-old man with crescentic glomerulonephritis on maintenance prednisolone therapy. He had earlier received steroid and cyclophosphamide pulse therapies. Renal functions improved following immunosuppressive treatment. In the third month of maintenance therapy, he presented to us with left-sided facial swelling and bloody nasal discharge. He had high blood sugar and acidic blood pH (ketoacidosis), probably due to steroid therapy. Magnetic resonance imaging of the head and sinuses showed inflammation and mass in the ethmoid sinus and nose with partial septal destruction, proptosis, global destruction of the left eye, brain infarction and carotid artery obliteration. Endoscopic biopsy of the sinuses revealed severe tissue necrosis. Samples of nasal discharge and biopsy tissue showed aseptate hyphae on light microscopy and culture, compatible with Rhizopus. The patient was treated with amphotericin B and multiple wound debridements along with ethmoidectomy and enucleation of the left eye. He was discharged in good general condition but with mild right hemiparesis. On follow-up examination at one year, there were no signs of fungal infection or renal dysfunction. PMID:23816728

Sanavi, Suzan; Afshar, Reza; Afshin-Majd, Siamak

2013-07-01

228

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

NASA Astrophysics Data System (ADS)

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 Pacific with spatial resolution of one minute. Numerical results are compared to sea level data collected by Pacific DART buoys. The tide gauge at Crescent City (CC) recorded an initial tsunami wave of about 20 cm amplitude and a second larger energy packet arriving 2 hours later. The first energy input into the CC harbor was the primary (direct) wave traveling over the deep waters of the North Pacific. Interactions with submarine ridges and numerous seamounts located in the tsunami path were a larger source of tsunami energy than the direct wave. Travel time for these amplified energy fluxes is longer than for the direct wave. Prime sources for the larger fluxes at CC are interactions with Koko Guyot and Hess Rise. Tsunami waves travel next over the Mendocino Escarpment where the tsunami energy flux is concentrated owing to refraction and directed toward CC. Local tsunami amplification over the shelf break and shelf are important as well. In many locations along the North Pacific coast, the first arriving signal or forerunner has lower amplitude than the main signal, which often is delayed. Understanding this temporal distribution is important for an application to tsunami warning and prediction. As a tsunami hazard mitigation tool, we propose that along with the sea level records (which are often quite noisy), an energy flux for prediction of the delayed tsunami signals be used.

Kowalik, Z.; Horrillo, J.; Knight, W.; Logan, Tom

2008-01-01

229

Aeolian Dunes as Evidence for Explosive Volcanism in the Tharsis Region of Mars  

NASA Astrophysics Data System (ADS)

Two transverse dune fields occur among Late Amazonian volcanic and aeolian landforms in southwestern Tharsis, Mars. The first is located ˜70 km northwest of Biblis Patera, around 5°N, 125°W. The second is located about 500 km northwest of Arsia Mons, at 2°S, 130°W. The latter is the largest dune field thus far documented to occur in the equatorial latitudes of Mars. Unlike other dunes on the planet, both dune fields in Tharsis have low thermal inertias (<2.7 × 10 -3cal cm -2sec -0.5K -1) and high albedos (˜0.26) that are indistinct from their surrounding terrain. Both dune fields have superposed features, such as impact craters, lava flows, smooth-surfaced units, and bright wind streaks. The dune fields therefore appear to be inactive and mantled by fine-grained material (i.e., particles <60 ?m). To form, aeolian dunes require a supply of sand. On Earth, most dune sands are supplied by fluvial and littoral processes, but this is not the case in Tharsis on Mars. Because they are superposed on a Late Amazonian surface, the climate is assumed to have been hyper-arid throughout the time that the dunes have existed. Under these conditions, the only plausible source for quantities of sediment sufficient to form transverse dune fields is explosive volcanism. Therefore, the two dune fields in Tharsis are evidence that explosive volcanism has occurred in this region in the Late Amazonian Epoch.

Edgett, Kenneth S.

1997-11-01

230

Sticky dunes in a wet desert: Formation, stabilisation and modification of the Australian desert dunefields  

NASA Astrophysics Data System (ADS)

Independent dating evidence and dune morphology indicate great stability of the Australian dunefields. Most dunefields have seen only minor superficial modification since they were formed, up to 1 million years ago, despite quite large changes in climate conditions. This stability may be partly due to the relatively dense vegetation cover on Australian dunes under the marginally arid climate. But new studies, supported by many older observations, suggest that 'sticky' dunes (where sand grains are bonded or cemented) may form under a broader range of wind climates than widely thought and have greater resistance to reworking. New mapping of the Australian continental dunefields from satellite imagery shows a previously unrecognised diversity of dune morphologies. Dune orientation, continuity, connectedness, crest planform, crest sharpness, spacing and setting all show patterns of variation over the continent. These are consistent with the overall low sand supply and variable wind climate that contribute to the dominance of longitudinal dunes but also with only superficial modification of the dunes after their initial formation. The longevity of the dunes is likely also partly due to the stabilisation of dune sand by pedogenesis: the bonding of sand by pedogenic calcium carbonate, gypsum, silica and translocated clays. The extremely low mobility of the sand dunes has led to preservation of dunes of great age, with stacked accretionary units and multiple palaeosols.

Hesse, Paul

2011-11-01

231

Why do active and stabilized dunes coexist under the same climatic conditions?  

PubMed

Sand dunes can be active (mobile) or stable, mainly as a function of vegetation cover and wind power. However, there exists as yet unexplained evidence for the coexistence of bare mobile dunes and vegetated stabilized dunes under the same climatic conditions. We propose a model for dune vegetation cover driven by wind power that exhibits bistabilty and hysteresis with respect to the wind power. For intermediate wind power, mobile and stabilized dunes can coexist, whereas for low (or high) wind power they can be fixed (or mobile). Climatic change or human intervention can turn active dunes into stable ones and vice versa; our model predicts that prolonged droughts with stronger winds can result in dune reactivation. PMID:17501612

Yizhaq, Hezi; Ashkenazy, Yosef; Tsoar, Haim

2007-05-02

232

Wind deposition of mud aggregates and their role in development of lamellae in the Fair Oaks Dunes, Indiana  

Microsoft Academic Search

Three parabolic dunes from the Fair Oaks Dune field in northern Indiana were excavated, in order to study the properties and genesis of lamellae. Reddish lamellae with sharp upper boundaries and diffuse lower boundaries are intercalated with yellowish sand layers within the upper 3–5 m of each dune. The thicknesses of the lamellae decrease from >2 cm in the east (Winamac dune)

Zoran Kilibarda; Erin Argyilan; Joe Blockland

2008-01-01

233

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

234

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

SciTech Connect

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

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

2011-12-15

235

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

236

End-Stage Renal Failure due to Crescentic Glomerulonephritis in a Patient with Behçet’s Syndrome  

Microsoft Academic Search

We report a rare case of a patient with Behçet’s syndrome who developed end-stage renal failure due to crescentic glomerulonephritis (GN). A 20-year-old male patient had suffered from uveitis, aphthous mouth ulcers and genital ulceration for the past 7 years. His renal function rapidly deteriorated and renal biopsy specimens obtained when his serum creatinine level was 3 mg\\/dl showed diffuse

Takanobu Sakemi; Tomiyoshi Yoshiyuki; Yuji Ikeda; Noriaki Suzuki; Kohei Nagasawa

1998-01-01

237

Endoscopic crescentic fold disease of the sigmoid colon: the clinical and histopathological spectrum of a distinctive endoscopic appearance  

Microsoft Academic Search

In this paper we describe an endoscopic appearance of the sigmoid colon characterised by mucosal swelling, erythema and haemorrhage strictly localised to the crescentic mucosal folds. In a 5-year period these changes were seen in 34 (1.42%) of 2380 colonoscopies and fibreoptic sigmoidoscopies. The majority of patients were middle-aged or elderly. Diverticular disease was present in most (82%) but the

S. Gore; N. A. Shepherd; S. P. Wilkinson

1992-01-01

238

Role of integrin-linked kinase in epithelial-mesenchymal transition in crescent formation of experimental glomerulonephritis  

Microsoft Academic Search

Background. Glomerular parietal epithelial- mesenchymal transition (EMT) is a key event in crescent formation of glomerulonephritis (GN). Integrin-linked kinase (ILK) is an integrin cytoplasmic-binding protein that has been implicated in the regulation of cell adhesion, extracellular matrix organization and EMT. Transforming growth factor-b (TGF-b) is involved in the induction and progression of EMT in several tissues. Methods. To investigate whether

Maki Shimizu; Shuji Kondo; Maki Urushihara; Masanori Takamatsu; Katsuyoshi Kanemoto; Michio Nagata; Shoji Kagami

2006-01-01

239

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

240

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

NASA Astrophysics Data System (ADS)

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 dunes, 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.

Prestrud Anderson, Suzanne; Anderson, Robert S.

1990-06-01

241

Dunes and microdunes on Venus: Why were so few found in the Magellan data?  

NASA Astrophysics Data System (ADS)

A search through cycle 1, 2, and 3 Magellan radar data covering 98% of the surface of Venus revealed very few dunes. Only two possible dune fields and several areas that may contain microdunes smaller than the resolution of the images (75 m) were identified. The Aglaonice dune field was identified in the cycle 1 images by the specular returns characteristic of dune faces oriented perpendicular to the radar illumination. Cycle 1 and 2 data of the Fortuna-Meshkenet dune field indicate that there has been no noticeable movement of the dunes over an 8-month period. The dunes, which are oriented both parallel and perpendicular to the radar illumination, appear to be dark features on a brighter substrate. Bright and dark patches that were visible in either cycle 1 or 2 data, but not both, allowed identification of several regions in the southern part of Venus that may contain microdunes. The microdunes are associated with several parabolic crater deposits in the region and are probably similar to those formed in wind tunnel experiments under Venus-like conditions. Bragg scattering and/or subpixel relfections from the near-normal face on asymmetric microdunes may account for these bright and dark patches. Look-angle effects and the lack of sufficient sand-size particles seem to be most likely reasons so few dunes were identified in Magellan data. Insufficient wind speeds, thinness of sand cover, and difficulty in identifying isolated dunes may also be contributors to the scarcity of dunes.

Weitz, Catherine M.; Plaut, Jeffrey J.; Greeley, Ronald; Saunders, R. Steven

1994-11-01

242

Soil Processes and Salt Dynamics in Dune Soils  

Microsoft Academic Search

In Chapter 5 (this volume), we described the soil pattern and characteristics of the sand dune ecosystem of Nizzana. In the\\u000a following, we will reconstruct the formation of the main soils, their weathering and brownification, their aggregation and\\u000a crust formation, their humus accumulation and carbonate accumulation being some of the main soil processes. However, our special\\u000a interest will be on

P. Felix-Henningsen; B. Rummel; H.-P. Blume

243

Comment on "Minimal size of a barchan dune".  

PubMed

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, Durán, 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 cannot 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 Planet. Sci. Lett. 252, 30 (2006)]. They instead propose that Martian dunes, composed of large grains (500 microm), were formed in the past under very strong winds. We emphasize that this saltating grain size, estimated from thermal diffusion measurements, is far from straightforward. Moreover, the microscopic photographs taken by the rovers on Martian Aeolian bedforms show a grain size of 87+/-25 microm together with hematite spherules at millimeter scale. As those so-called "blueberries" cannot be entrained more frequently than a few hours per century, we conclude that the saltating grains on Mars are the small ones, which gives a second strong argument against the model of Parteli. PMID:18233886

Andreotti, B; Claudin, P

2007-12-21

244

Seasonality of mycorrhizae in coastal sand dunes of Baja California  

Microsoft Academic Search

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

Concepción Sigüenza; Ileana Espejel; Edith B. Allen

1996-01-01

245

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

246

Runoff and Erosion Processes Within a Dune System  

Microsoft Academic Search

The occurrence of surface runoff processes is often regarded by geomorphologists or hydrologists as irrelevant within sandy\\u000a areas and dune systems, due to the very high infiltration rates of sand. The presumed lack of runoff processes has been mentioned\\u000a several times in the case of the northwestern Negev sand field (Hillel and Tadmor 1962; Tsoar and Zohar 1985; Tsoar and

G. J. Kidron; A. Yair

247

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

248

Predicting flooding probability for beach\\/dune systems  

Microsoft Academic Search

The determination of the risk from flooding that shorefront communities face is an important component of coastal management\\u000a that has not been resolved successfully. Wave runup offers one way of quantifying the risk of coastal flooding that results\\u000a from overtopping by storm waves. The calculation of runup probabilities uses wave frequency analysis and an average beach\\/dune\\u000a profile for a given

Paul A. Garès

1990-01-01

249

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

PubMed Central

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

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

2012-01-01

250

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

251

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

252

Possibility of star (pyramid) dune development in the area of bimodal wind regime  

NASA Astrophysics Data System (ADS)

Star (pyramid) dunes are the largest aeolian landforms. They can occur in three types - simple, complex and compound. Development of this type of dunes is usually connected with multidirectional or complex wind regimes. The aim of this study was to verify a hypothesis that the star dunes can also develop by a bimodal wind regime and by local modifications of nearsurface wind flow directions. Field study was performed on Erg Chebbi, in southern Morocco. Several star and transverse dunes were selected for the study of their shape. The star dunes were analysed concerning their type and position in the dune field. This erg contains all of three types of star dunes together with transverse dunes. The regional wind data show that there are two dominant wind directions - NE (Chergui) and SW (Saheli). To determine the difference in shape of star dunes, we performed topographic surveying by GPS RTK. The results allowed to create 3D models of star dunes. The models were used to determine metric characteristics of star dunes, including area of dune basis, volume, and slope angles. On the basis of 3D models, primary, secondary and, on the compound dunes, tertiary arms were determined. Primary arms on each type of star dunes, as well as crestlines of transverse dunes, have dominant orientation NW-SE, perpendicular to two dominant wind directions. This clearly confirms that star dunes of Erg Chebbi develop by a bimodal wind regime In contrast to primary arms, subsidiary (secondary and tertiary) arms are not connected to general wind regime. The secondary arms of star dunes occur to be differentially developer. There are more subsidiary arms on SW sides in comparison to the E sides of the dunes where inclination of slopes is constant. It can be therefore inferred that sand has been supplied predominantly from SW direction. This is supported by distribution of the dunes on the erg. Most compound star dunes compose a chain along the E margin of the erg. Comparison of compound star dunes located in E and W parts of the erg allow inferring that there must have been differences in supply of the aeolian sand. Eastern slopes of compound star dunes developed in the W part of the erg are inclined 10-15°. This shows that significant delivery of the sand must have occurred also from NE. Eastern slopes of compound star dunes located in the E part of the erg are inclined 20-30°. It can be therefore inferred that they have functioned mainly as lee slopes and the sand was delivery from SW. This proves that location of the dunes within the erg plays a significant role in shaping wind directions responsible for delivery of the sand. Orientation of subsidiary arms does not show any relationship with general wind regime, which leads to conclusion that the subsidiary arms develop due to local diversified regime of nearsurface wind flow. This is governed by barriers such as the star dunes themselves and not by other topographic obstacles.

Biejat, K.

2012-04-01

253

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

254

Changes to dunes caused by 4WD vehicle tracks in beach camping areas of Fraser Island  

Microsoft Academic Search

Although dunes are known to have very low tolerance to human disturbance and provide irreplaceable ecosystem services (e.g. erosion co ntrol, critical habitat and nesting sites), in dunes serve as campsites for large numbers of people (~ 90,000 p.a.) on the ocean-exposed shores of Fraser Island, Australia. On the island, camp sites are located in the established dunes and can

Thomas A. Schlacher; Luke M. C. Thompson

255

Changes in landscape and vegetation of coastal dunes in northwest Europe: a review  

Microsoft Academic Search

In coastal dunes, landscape changes are a rule, rather than an exception. This paper gives an overview of changes in landscape\\u000a and vegetation with a focus on the past century. The history of dunes is characterised by phases of sand drift, alternated\\u000a with geomorphological stability. The historical development of dune woodland during these stable phases has been documented\\u000a for sites

Sam Provoost; M. Laurence M. Jones; Sally E. Edmondson

2011-01-01

256

Lichens as indicators of a perturbation\\/stability gradient in the Asperillo dunes, SW spain  

Microsoft Academic Search

In the asperillo dune system, Southwest Spain, lichen vegetation covering the dune sand, has a low species diversity but is\\u000a an important component of the perennial vegetation, providing stability, nutrients, and moisture to the soil layer. The Asperillo\\u000a dunes harbour (1) natural ecosystems, (2) disturbed systems affected by forestry activities where the natural vegetation is\\u000a eliminated, and (3) pine forest

J. B. Gallego Fernández; M. C. Díaz Barradas

1997-01-01

257

Holocene dune-sourced alluvial fans in the Nebraska Sand Hills  

Microsoft Academic Search

The large, stabilized dunes of the Nebraska Sand Hills are in a phase of degradation. The deposition of small-scale alluvial fans composed of well-sorted, fine- to medium-grained sand occurs when sand is transported via gullies on the lee side of large barchanoid-ridge dunes during infrequent, intense summer rain storms (>5 cm\\/h). The hydraulic conductivity of the dune sand itself is

Mark R. Sweeney; David B. Loope

2001-01-01

258

La perception d’une discipline scolaire par les elèves. Représentation et effets identitaires  

Microsoft Academic Search

Résumé  La perception d’une discipline par les élèves est abordée comme relevant d’une construction visant à donner un sens à leur\\u000a réalité scolaire quotidienne et ne se réalisant donc pas indépendamment des conditions sociales de son élaboration, ni des\\u000a significations sociales attribuées à cette discipline et à ses contenus. Les résultats d’une enquête mennée en France auprès\\u000a d’élèves de niveau Collège

Michel Chambon

1990-01-01

259

Accelerated Dune Migration and Aeolian Transport During El Niño Events along the NE Brazilian Coast  

Microsoft Academic Search

MAIA, L.P.; FREIRE, G.S.S., and LACERDA, L.D., 2005. Accelerated dune migration and aeolian transport during El Nino events along the NE Brazilian coast. Journal of Coastal Research, 21(6), 1121-1126. West Palm Beach (Flor- ida), ISSN 0749-0208. Dune migration response to regional inter-annual climate variability in Ceara ´ , Northeastern Brazil was investigated. Dunes along the study area are mainly barchans

L. P. Maia; G. S. S. Freire; L. D. Lacerda

2005-01-01

260

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

NASA Astrophysics Data System (ADS)

Large expanses of linear dunes cover Titan's equatorial regions. As the Cassini mission continues, more dune fields are becoming unveiled and examined by the microwave radar in all its modes of operation (SAR, radiometry, scatterometry, altimetry) and with an increasing variety of observational geometries. In this paper, we report on Cassini's radar instrument observations of the dune fields mapped through May 2009 and present our key findings in terms of Titan's geology and climate. We estimate that dune fields cover ˜12.5% of Titan's surface, which corresponds to an area of ˜10 million km 2, roughly the area of the United States. If dune sand-sized particles are mainly composed of solid organics as suggested by VIMS observations (Cassini Visual and Infrared Mapping Spectrometer) and atmospheric modeling and supported by radiometry data, dune fields are the largest known organic reservoir on Titan. Dune regions are, with the exception of the polar lakes and seas, the least reflective and most emissive features on this moon. Interestingly, we also find a latitudinal dependence in the dune field microwave properties: up to a latitude of ˜11°, dune fields tend to become less emissive and brighter as one moves northward. Above ˜11° this trend is reversed. The microwave signatures of the dune regions are thought to be primarily controlled by the interdune proportion (relative to that of the dune), roughness and degree of sand cover. In agreement with radiometry and scatterometry observations, SAR images suggest that the fraction of interdunes increases northward up to a latitude of ˜14°. In general, scattering from the subsurface (volume scattering and surface scattering from buried interfaces) makes interdunal regions brighter than the dunes. The observed latitudinal trend may therefore also be partially caused by a gradual thinning of the interdunal sand cover or surrounding sand sheets to the north, thus allowing wave penetration in the underlying substrate. Altimetry measurements over dunes have highlighted a region located in the Fensal dune field (˜5° latitude) where the icy bedrock of Titan is likely exposed within smooth interdune areas. The hemispherical assymetry of dune field properties may point to a general reduction in the availability of sediments and/or an increase in the ground humidity toward the north, which could be related to Titan's asymmetric seasonal polar insolation. Alternatively, it may indicate that either the wind pattern or the topography is less favorable for dune formation in Titan's northern tropics.

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

261

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

NASA Astrophysics Data System (ADS)

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

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

2010-11-01

262

Dunes on Saturn's moon Titan as revealed by the Cassini Mission  

NASA Astrophysics Data System (ADS)

Dunes on Titan, a dominant landform comprising at least 15% of the surface, represent the end product of many physical processes acting in alien conditions. Winds in a nitrogen-rich atmosphere with Earth-like pressure transport sand that is likely to have been derived from complex organics produced in the atmosphere. These sands then accumulate into large, planet-encircling sand seas concentrated near the equator. Dunes on Titan are predominantly linear and similar in size and form to the large linear dunes of the Namib, Arabian and Saharan sand seas. They likely formed from wide bimodal winds and appear to undergo average sand transport to the east. Their singular form across the satellite indicates Titan's dunes may be highly mature, and may reside in a condition of stability that permitted their growth and evolution over long time scales. The dunes are among the youngest surface features, as even river channels do not cut through them. However, reorganization time scales of large linear dunes on Titan are likely tens of thousands of years. Thus, Titan's dune forms may be long-lived and yet be actively undergoing sand transport. This work is a summary of research on dunes on Titan after the Cassini Prime and Equinox Missions (2004-2010) and now during the Solstice Mission (to end in 2017). It discusses results of Cassini data analysis and modeling of conditions on Titan and it draws comparisons with observations and models of linear dune formation and evolution on Earth.

Radebaugh, Jani

263

Can beach dune ridges of the Texas Gulf Coast preserve climate signals?  

NASA Astrophysics Data System (ADS)

A study of the evolution of North Padre Island (southern Texas Gulf Coast) dunes was carried out using LIDAR topographic data, dune vibracores through the center of the dunes, and grab samples of shoreface sand at four locations along a cross-shore profile. Grain-size analyses of the vibracores show vertical variations in shoreface sand deposition over decimeter depth intervals. A dune ridge growth model is introduced that describes the dune vertical accretion rate as a function of island progradation and freshwater lens expansion. This model allows indirect dating of the dune core samples based on a known island progradation rate (1 m/year), and height and spacing of the dunes calculated from the topographic data. A sand provenance model is also proposed that links the sand deposition in the dunes with sand sourced from various depths along the shoreface profile, depending on storm activity. We present evidence linking the changes in storm-sand deposition in the dune cores with yearly climatic fluctuations in the Gulf of Mexico associated with landfalling tropical storm activity in the period from 1942-1965. This record of storm-induced sand variability is negatively correlated with El Niño-Southern Oscillation (Pacific) sea surface temperature variability, and positively correlated with North Atlantic decadal sea surface temperature variability.

Garrison, James R.; Mestas-Nuñez, Alberto M.; Williams, Joshua R.; Lumb, Luz M.

2012-06-01

264

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

USGS Publications Warehouse

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

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

2013-01-01

265

Quantitative analysis of the long- and short-arm crescentic shelf bunionectomy osteotomies in fresh cadaveric matched pair specimens.  

PubMed

Two variations of crescentic shelf osteotomies have been described for the treatment of moderate to severe hallux abductovalgus: a short arm and a long arm. This study tested the hypothesis that the short-arm osteotomy will have a greater moment to failure and angular stiffness than the long arm. Eighteen first metatarsal specimens were dissected from 9 matched pairs of fresh frozen cadaveric specimens. One metatarsal from each pair received a short-arm osteotomy, whereas the other received a long-arm osteotomy. Each osteotomy was fixed with 2 screws. The short arm was fixed with 1 oblique screw and 1 dorsal-to-plantar screw. The long arm was fixed with 2 dorsal-to-plantar screws: 1 at the proximal aspect and 1 at the distal aspect of the shelf. Each specimen was loaded in a materials testing machine to measure moment to failure and angular stiffness. The base of the first metatarsal was potted and load applied to the plantar aspect of the metatarsal head at a constant rate until failure of the osteotomy. The mean maximum moment to failure of the short arm was significantly greater than the long arm (2.04 ± 0.96 Newton meter [Nm] vs. 1.48 ± 0.67 Nm, P = .03). The mean angular stiffness was significantly greater for short arm versus long arm (23.8 ± 19.11 Nm/radian vs. 0.98 ± 9.08 Nm/radian, P = .01). We report statistically significant data supporting the short-arm crescentic shelf osteotomy to have a greater moment to failure and angular stiffness compared with the long-arm crescentic shelf osteotomy. PMID:21353999

Gocke, Sean P; Rottier, Francis J; Havey, Robert M; Renner, Susan M; Patwardhan, Avinash G; Carandang, Gerard

266

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

USGS Publications Warehouse

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

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

2012-01-01

267

Remote sensing and spatial analysis of aeolian sand dunes: A review and outlook  

NASA Astrophysics Data System (ADS)

For more than four decades remote sensing images have been used to document and understand the evolution of aeolian sand dunes. Early studies focused on mapping and classifying dunes. Recent advances in sensor technology and software have allowed investigators to move towards quantitative investigation of dune form evolution and pattern development. These advances have taken place alongside progress in numerical models, which are capable of simulating the multitude of dune patterns observed in nature. The potential to integrate remote sensing (RS), spatial analysis (SA), and modeling to predict the future changes of real-world dune systems is steadily becoming a reality. Here we present a comprehensive review of significant recent advances involving RS and SA. Our objective is to demonstrate the capacity of these technologies to provide new insight on three important research domains: (1) dune activity, (2) dune patterns and hierarchies, and (3) extra-terrestrial dunes. We outline how several recent advances have capitalized on the improved spatial and spectral resolution of RS data, the availability of topographic data, and new SA methods and software. We also discuss some of the key research challenges and opportunities in the application of RS and SA dune field, including: the integration of RS data with field-based measurements of vegetation cover, structure, and aeolian transport rate in order to develop predictive models of dune field activity; expanding the observational evidence of dune form evolution at temporal and spatial scales that can be used to validate and refine simulation models; the development and application of objective and reproducible SA methods for characterizing dune field pattern; and, expanding efforts to quantify three-dimensional topographic changes of dune fields in order to develop improved understanding of spatio-temporal patterns of erosion and deposition. Overall, our review indicates a progressive evolution in the way sand dunes are studied: whereas traditional field studies of airflow and sand transport can clarify event-based process-form interactions, investigators are realizing a synoptic perspective is required to address the response of dune systems to major forcings. The integration and evolution of the technologies discussed in this review are likely to form a foundation for future advances in aeolian study.

Hugenholtz, Chris H.; Levin, Noam; Barchyn, Thomas E.; Baddock, Matthew C.

2012-03-01

268

How much liquid water was there on Martian dunes?  

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

269

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

NASA Astrophysics Data System (ADS)

On 10th March 2008, the high energy storm Johanna hit the French Atlantic coast, generating severe dune erosion on Vougot Beach (Brittany, France). In this paper, the recovery of the dune of Vougot Beach is analysed through a survey of morphological changes and hydrodynamic conditions. Data collection focused on the period immediately following storm Johanna until July 2010, i.e. over two and a half years. Results showed that the dune retreated by a maximum of almost 6 m where storm surge and wave attack were the most energetic. Dune retreat led to the creation of accommodation space for the storage of sediment by widening and elevating space between the pre- and post-storm dune toe, and reducing impacts of the storm surge. Dune recovery started in the month following the storm event and is still ongoing. It is characterised by the construction of "secondary" embryo dunes, which recovered at an average rate of 4-4.5 cm per month, although average monthly volume changes varied from - 1 to 2 m3.m- 1. These embryo dunes accreted due to a large aeolian sand supply from the upper tidal beach to the existing foredune. These dune-construction processes were facilitated by growth of vegetation on low-profile embryo dunes promoting backshore accretion. After more than two years of survey, the sediment budget of the beach/dune system showed that more than 10,000 m3 has been lost by the upper tidal beach. We suggest that seaward return currents generated during the storm of 10th March 2008 are responsible for offshore sediment transport. Reconstitution of the equilibrium beach profile following the storm event may therefore have generated cross-shore sediment redistribution inducing net erosion in the tidal zone.

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

2012-02-01

270

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

NASA Astrophysics Data System (ADS)

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

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

2010-05-01

271

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

NASA Astrophysics Data System (ADS)

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

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

272

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

Microsoft Academic Search

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

S. Shanmugam; M. Barnsley

273

Remotely sensed dune celerity and sand flux measurements of the world's fastest barchans (Bodélé, Chad)  

NASA Astrophysics Data System (ADS)

Quantifying sand flux with field measurements is an expensive and time-consuming process. We here present an alternative approach using the COSI-Corr software package for Earth surface deformation detection. Using pairs of ASTER satellite images, we detected dune migration in the Bodélé depression of northern Chad over time intervals of one month to 6.5 years. The displacement map can be used to automatically distinguish dunes from interdunes, which is a crucial step towards calculating sand flux. We interpolated a surface between the interdune areas and subtracted it from a digital elevation model, thus obtaining dune heights and volumes. Multiplying height with celerity yields a pixel-by-pixel estimate of the sand flux. We applied this method to large diatomite dunes in the Bodélé, confirming that these are some of the world's fastest moving barchans. Plotting dune height against inverse celerity reveals sand flux at the dune crest of >200 m3/m/yr. Average dune sand flux values for the eastern and western Bodélé are 76 and 99 m3/m/yr, respectively. The contribution of the dunes to the total area-averaged sand flux is 24-29 m3/m/yr, which is ~10% of the saltation flux determined by previously published field measurements.

Vermeesch, Pieter; Drake, Nick

2008-12-01

274

Response of sand dunes to variations in tidal flow: Fraser Estuary, Canada  

Microsoft Academic Search

The morphology of dunes in rivers and estuaries often lags behind changes in river discharge and neap-spring tides. This study extends previous research by examining the response of large subtidal dunes in the Fraser Estuary, Canada, to changing flow conditions over a semidiurnal tidal cycle. An acoustic Doppler current profiler (ADCP) is used to measure three-dimensional velocity profiles and estimate

Ray Kostaschuk; Jim Best

2005-01-01

275

A Beach and Dune Community. 4-H Marine Science. Member's Guide. Activity I. MSp 1.  

ERIC Educational Resources Information Center

|The investigation in this booklet is designed to provide 4-H members with opportunities to identify common plants and animals found on beaches and sand dunes and to determine the role of the plants and animals in this community. Learners are provided with a picture of a hypothetical beach and sand dune and a list of organisms (included in the…

Auburn Univ., AL. Cooperative Extension Service.

276

Remobilization of southern African desert dune systems by twenty-first century global warming.  

PubMed

Although desert dunes cover 5 per cent of the global land surface and 30 per cent of Africa, the potential impacts of twenty-first century global warming on desert dune systems are not well understood. The inactive Sahel and southern African dune systems, which developed in multiple arid phases since the last interglacial period, are used today by pastoral and agricultural systems that could be disrupted if climate change alters twenty-first century dune dynamics. Empirical data and model simulations have established that the interplay between dune surface erodibility (determined by vegetation cover and moisture availability) and atmospheric erosivity (determined by wind energy) is critical for dunefield dynamics. This relationship between erodibility and erosivity is susceptible to climate-change impacts. Here we use simulations with three global climate models and a range of emission scenarios to assess the potential future activity of three Kalahari dunefields. We determine monthly values of dune activity by modifying and improving an established dune mobility index so that it can account for global climate model data outputs. We find that, regardless of the emission scenario used, significantly enhanced dune activity is simulated in the southern dunefield by 2039, and in the eastern and northern dunefields by 2069. By 2099 all dunefields are highly dynamic, from northern South Africa to Angola and Zambia. Our results suggest that dunefields are likely to be reactivated (the sand will become significantly exposed and move) as a consequence of twenty-first century climate warming. PMID:15988522

Thomas, David S G; Knight, Melanie; Wiggs, Giles F S

2005-06-30

277

Preliminary observations on managing and reclaiming frontal dunes within the Durban municipal area  

Microsoft Academic Search

The Bluff dunes, located within the Durban (South Africa) municipal area, have become increasingly degraded as a consequence of human pressures over the last quarter century. The resulting localised wind-blown sand pollution of roads and storm drains necessitated a dune reclamation project involving a multi-disciplinary team of Parks managers and engineers. An effective solution was provided by a combination of

G. R. Nichols

1996-01-01

278

Foraging behaviour of donkeys grazing in a coastal dune area in temperate climate conditions  

Microsoft Academic Search

A small herd of donkeys was introduced in a coastal dune reserve ‘Houtsaegerduinen’ (ca. 80ha) in Belgium, in order to slow down expansion of dominant grass and shrub species. The Houtsaegerduinen is a nutrient poor scrub-dominated dune system with a spatially heterogeneous vegetation pattern. Different aspects of the grazing behaviour (grazing time, bite rate, habitat use, diet composition) of the

Indra Lamoot; Julie Callebaut; Else Demeulenaere; Charlotte Vandenberghe; Maurice Hoffmann

2005-01-01

279

A Dune Simulation Wind Tunnel for Studies of Lee Face Processes  

Microsoft Academic Search

Sand is deposited on the lee slope of dunes by grainfall, avalanching (grainflow), and wind ripple migration. These processes play major roles in the formation of aeolian cross strata. Grainfall is produced by saltating grains that are blown over the dune crest and fall on the lee slope. Avalanching occurs when sand on the lee slope fails and the resulting

K. Cupp; N. Lancaster; W. G. Nickling

2004-01-01

280

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

Microsoft Academic Search

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

J. Anthony Stallins; Albert J. Parker

2003-01-01

281

Dune Retreat and Shoreline Change on the Outer Banks of North Carolina  

NASA Astrophysics Data System (ADS)

Barrier islands are popular recreational areas of economic importance that are constantly changing. Costly efforts are made to maintain beaches and stabilize dunes within this dynamic environment. We examine one year of coastal change along the barrier islands of the North Carolina Outer Banks. LIDAR data collected in September of 1997 and 1998 along a 175 km stretch of the Atlantic coast of the North Carolina Outer Banks provide the basis for quantitative determination of changes in beach morphology. The survey of 1998 was conducted a few days after the passage of Hurricane Bonnie. Hurricane Bonnie provided a unique opportunity to study factors that influence coastal change because after making landfall it traveled roughly parallel to the coastline, causing relatively uniform storm conditions along a long reach of coast. During the one-year study interval, beach widths throughout the study region tended to decrease. We determined the maximum dune retreat for each 1 m bin of 1997 beach width in different parts of the Outer Banks. Maximum dune retreat was greatest for beach widths of approximately 20 m and for dune base elevations less than 4.0 m. For comparable beach widths, maximum dune retreat increased from south to north. The undeveloped natural beaches of the Core Banks experienced relatively little change in beach width, dune height and dune base position. The greatest morphological changes occurred on Ocracoke Island and Hatteras Island where the dunes had been stabilized and the beaches had been artificially maintained.

Burroughs, S. M.; Tebbens, S. F.

2005-12-01

282

Comparing the Effectiveness of Ground-Penetrating Radar in Imaging Siliciclastic And Mafic- Volcaniclastic Dune Sands  

NASA Astrophysics Data System (ADS)

Experiments using ground-penetrating radar (GPR) systems in two, different dune sediment environments allow comparisons of the relative effectiveness of subsurface imaging and feature detection. One experiment was carried out in the Coral Pink Sand Dunes (CPSD) in southern Utah, and a second in the Grand County Off Road Vehicle area in Moses Lake (ML), Washington. Both experiments used a MALA GPR system with 500MHz antenna and similar data sampling and acquisition parameters. The dunes at the CPSD site are comprised of nearly pure, very well sorted quartz sands. These sharply contrast with dunes at the ML site which are comprised of basalt-rich (up to 80%) sands. The ML site was selected as a terrestrial analog to Martian dunes that have been shown in other studies to have a similar mineralogy. As with other quartz dune studies, radar images gathered at the CPSD site clearly show cross-bedding structures and were able to identify the bedrock/dune interface as well as the locally shallow water table. The imagery collected at the ML site was not as clear, but some dune structures, ash beds, and water are visible in the imagery. We propose that thee higher basalt content at the ML sites results in greater signal loss than in the siliciclastic sands at the CPSD site. The reduced signal transmissivity in the mafic sands may have implications for selection of GPR instrumentation in future Mars investigations.

Wilkins, D. E.; Clement, W.

2007-12-01

283

Aeolian Dunes as Evidence for Explosive Volcanism in the Tharsis Region of Mars  

Microsoft Academic Search

Two transverse dune fields occur among Late Amazonian volcanic and aeolian landforms in southwestern Tharsis, Mars. The first is located ?70 km northwest of Biblis Patera, around 5°N, 125°W. The second is located about 500 km northwest of Arsia Mons, at 2°S, 130°W. The latter is the largest dune field thus far documented to occur in the equatorial latitudes of

Kenneth S. Edgett

1997-01-01

284

Direct seeding of grass species for sand dune stabilization on the mid-Atlantic sea coast  

Microsoft Academic Search

The stabilization of moving sand dunes at Provincetown, Massachusetts, depends, to a large degree, upon the environmental factors of wind, temperature and rainfall. Direct seedings of grasses for the purpose of stilling these moving dunes can be wiped out totally by the severe northeast and northwest winds which occur in the very early spring. In this study, 9 different mulches

J. M. Zak

1977-01-01

285

The effect of sparse vegetation on the transport of dune sand by wind  

Microsoft Academic Search

The precise effect of a sparse plant cover on the transport of dune sand by wind is a critical factor in understanding the morphology, evolution and global distribution of aeolian dunes1-3. It is also of considerable practical importance in sand stabilization, rehabilitation and restoration ecology. Here I report the first detailed experimental quantification of this effect using living plants in

Ralf Buckley

1987-01-01

286

Population ecology on an environmental gradient: Cakile edentula on a sand dune  

Microsoft Academic Search

A naturally-occurring sand dune population of the annual plant Cakile edentula (Brassicaceae) was studied for two years. The plants grew along an environmental gradient stretching from open sand beach (seaward) to densely vegetated dunes (landward). Survivorship and reproductive output were estimated from plants in permanent quadrats. The dispersal of seeds was documented by sifting fruits from the sand substrate at

Paul A. Keddy

1982-01-01

287

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

Microsoft Academic Search

Analytical models to calculate notch development and subsequent mass 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 using elementary engineering statics and soil mechanics. An empirical transport coefficient in the model describing the notch

Li H. Erikson; Magnus Larson; Hans Hanson

2007-01-01

288

Very large dune formation along the Ebro outer continental shelf (Western Mediterranean)  

Microsoft Academic Search

Large and very large subaqueous dunes have been observed in a number of outer shelf regions around the world, tipically developing on fossil sand bodies and ridges. Dunes observed on outer shelves usually display large dimensions with maximum wavelength reaching up to 500 m and heights up to 20 m. Forcing mechanisms able to induce their formation have been described

Claudio Lo Iacono; Jorge Guillén; Pere Puig; Marta Ribó; Maria Ballesteros; Albert Palanques; Marcelli Farrán; Juan Acosta

2010-01-01

289

Coupling the dynamics of boundary layers and evolutionary dunes.  

PubMed

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

Ortiz, Pablo; Smolarkiewicz, Piotr K

2009-04-20

290

Morphological thresholds for the definition of the vulnerability of coastal dunes in northern Italy  

NASA Astrophysics Data System (ADS)

The Emilia Romagna coastline is located in northern Italy, facing the Adriatic Sea. It is characterised by natural areas with dunes and urbanised zones. This work only relates with natural areas in order to define storm thresholds able to generate morphological changes on coastal dunes. The main morphological impact is related to the dune system only, generating dune frontal erosion and/or overtopping and dune destruction. The chosen indicator of this morphological impact is the Dune Stability Factor (DSF, Fig. 1) that describes the most probable effect of a storm on the dune system and was the factor consequently used to define wave height and surge levels able to generate significant morphological changes. The methodology used for identifying the threshold includes three important dynamic factors (waves, tide and surge) plus detailed topographic information. The contribution of the sea elevation to inundation/damages was analysed using surge and tidal levels, while the contribution of storms was included into the run-up computation (max Water Level=tide+surge+run-up). Waves, tide and surge levels were extracted from literature considering three “worst” scenarios where a storm with 1, 10 and 100 years return period occurs at the same time as a surge with the same return periods and at the same time as a high spring tide of +0.45m above MSL. The computed max WL was used to calculate the DSF and to define vulnerability categories along the coastline. If the DSF ? 20% the dune is considered vulnerable to complete removal and erosion. If DSF is between 20% and 75% the dune is considered vulnerable to frontal erosion. Finally, if DSF is above 75% the dune is not believed to be vulnerable. To define the DSF percentage values listed above, a comparison was made between measured profiles before and after registered storms. There are some exceptions that do not show a correspondence with the percentages defined above but in general there is a good agreement between the DSF-predicted vulnerability and the observed erosion (70%/90%). The analysis of the morphological impact along natural areas reveals that the joint occurrence of the 1-yr return period wave+the 1-yr return period surge+high spring tide leads to dune erosion and overtopping. This conclusion derives from the analysis of the results of the DSF computation that shows how 60% of the whole studied profiles are damaged by the sea state described above. Figure 1: Dune Stability Factor = (A_dunefoot/A_hmax)*100 where A_dunefoot is the dune cross-sectional area, A_hmax is the cross sectional area calculated between the max water level (for each scenario) and the dune crest

Armaroli, C.; Ciavola, P.; Masina, M.

2009-12-01

291

A Case of Elderly-Onset Crescentic Henoch-Sch?nlein Purpura Nephritis with Hypocomplementemia and Positive MPO-ANCA  

PubMed Central

Henoch-Schönlein purpura (HSP) is common in childhood and often self-limiting. There have been limited studies on elderly-onset HSP nephritis (HSPN). A 76-yr-old man was transferred to our hospital with a 1-month history of oliguria, abdominal pain, edema and palpable purpura in the legs. Three months ago, he was admitted to another hospital with jaundice, and consequently diagnosed with early common bile duct cancer. The patient underwent a Whipple's operation. Antibiotics were administrated because of leakage in the suture from the surgery. However, he showed progressive renal failure with edema and purpura in the legs. Laboratory investigations showed serum creatinine 6.4 mg/dL, 24-hr urine protein 8,141 mg/day, myeloperoxidase anti-neutrophil cytoplasmic antibodies (MPO-ANCA) 1:40 and C3 below 64.89 mg/dL. Renal biopsy showed crescentic glomerulonephritis, as well as mesangial and extracapillary Ig A deposition. We started steroid therapy and hemodialysis, but he progressed to end-stage renal failure and he has been under maintenance hemodialysis. We describe elderly onset HSPN with MPO-ANCA can be crescentic glomerulonephritis rapidly progressed to end stage renal failure.

Yu, Jung-Hee; Lee, Jae Eun; Kim, Hyang; Kim, Kyungeun; Jang, Ki-Seok; Park, Moon Hyang

2012-01-01

292

[The relationships of rapidly progressive glomerulonephritis (RPGN), crescentic glomerulonephritis and vasculitis: the clinical, histopathological and therapeutic considerations].  

PubMed

Rapidly progressive glomerulonephritis (RPGN) is a rare but severe condition, with a particular poor outcome in the absence of aggressive therapy. Our study describes all RPGN consecutive cases treated during the 1994-1995 period, with special interest in revealing negative prognostic features at presentation and the optimum therapeutic strategy. 14 (20% of all ARF for the same period) cases were classified as RPGN. Although rare (30%), extrarenal symptoms were related with a more unfavourable course. Creatinine clearance at presentation was not a reliable prognostic factor in our study. ANCA was found in 86% of our patients (p-ANCA/c-ANCA = 2/1), and therapeutic success was associated with ANCA disappearance. Crescentic glomerulonephritis was seen in 93% of all cases 77% of which were type III, pauciimune, ANCA positive. Vasculitic lesions and fibrous crescents, but not % of glomerular circumference or % of affected glomeruli were also related with a poor prognosis. Only 43% of our RPGN cases survived with a normal renal function. i.v. metil-prednisolone (at presentation, as soon as possible) followed by i.v. cyclophosphamide up to six months was the best therapeutic regimen, with no important side-effects. PMID:9455438

Covic, A; Marian, D; Florea, L; Mititiuc, I; C?runtu, I; Cotu?iu, C; Covic, M

293

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

NSDL National Science Digital Library

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

Rodbell, Donald T.

294

Short-term changes in mobile dunes at Port Alfred, South Africa  

NASA Astrophysics Data System (ADS)

Development along the western beachfront of Port Alfred, which is situated along a sandy shoreline, increased markedly in the 1960s as the coastal town became a popular holiday resort. This development included the removal of coastal vegetation, which resulted in the destabilization of dunes and migration of sand westerly onto the road, West Beach parking lot, and lawns of the cabanas. Sand traps were constructed to collect sand blowing across the dunes over set periods, and the net sand movement along the mobile dune belt was calculated using Hunter's equation. The dunes show an easterly movement of sand at a rate of 3.5 m/yr, which is comparable with figures recorded along other areas of this coastline. Considering the wind regime and amount of sand movement along this coast, it is inappropriate to clear vegetation and develop within the dune region.

Lubke, Roy A.; Sugden, Jean

1990-03-01

295

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

NASA Astrophysics Data System (ADS)

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

Barchyn, Thomas E.; Hugenholtz, Chris H.

2013-11-01

296

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

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

297

West coast dune plumes: Climate driven contrasts in dunefield morphogenesis along the western and southern South African coasts  

Microsoft Academic Search

This study examines two major late Quaternary coastal dune systems situated in the southwestern-most extremity of Africa. The False Bay and Duinefontyn dune plumes formed in close proximity, but under contrasting oceanographic regimes (warm Agulhas and cold Benguela oceanic current systems respectively). The False Bay and Duinefontyn dune plumes have hitherto lacked the objective, numerical chronology required to realize their

David L. Roberts; Mark D. Bateman; Colin V. Murray-Wallace; Andrew S. Carr; Peter J. Holmes

2009-01-01

298

Functions of biological soil crusts on central European inland dunes: Water repellency and pore clogging influence water infiltration  

Microsoft Academic Search

Biological soil crusts play a key role for hydrological processes in many open landscapes. They seal and stabilize the topsoil and promote surface run-off. Three crust types were identified on two inland dunes in Brandenburg, North-East Germany: A natural, active dune, located in a former military training area near Lieberose, and an artificial dune, which was constructed in 2001 and

Thomas Fischer; Roland Spröte; Maik Veste; Wolfgang Wiehe; Philipp Lange; Oliver Bens; Thomas Raab; Reinhard F. Hüttl

2010-01-01

299

An unusual climbing dune, Big Hellfire Pass, Stewart Island, New Zealand: exploration through environment, vegetation and trait patterns  

Microsoft Academic Search

Big Hellfire Dune on the western coast of Stewart Island\\/Rakiura, New Zealand, is an unusual dune climbing 220 m in altitude on the Ruggedy Range, to dissipate on the leeward side of Hellfire Pass. To record vegetation and environmental characters we ran six transects parallel to the coast, at 50-m altitudinal intervals up the dune. Topography reflected substrate and sand

AL Murphy; RB Silberbauer; RE Streeter; Smiley; AR Smith; S Darling; PR van Essen; GL Rapson

2012-01-01

300

The timing of climbing dune formation in southwestern Niger: fluvio-aeolian interactions and the rôle of sand supply  

Microsoft Academic Search

Contemporary gully erosion has exposed sections in a climbing dune which is banked up against ferricrete terraces along the southern bank of the Niger River in southwestern Niger. The main sand transport direction in this area is from northeast to southwest, and the immediate source of the dune sand is the Niger River. Dune stratigraphy contains evidence of episodic, fluvially

Helen M Rendell; Michèle L Clarke; Andrew Warren; Adrian Chappell

2003-01-01

301

Solar Diameter Evaluation from 1999 Eclipse Observations  

NASA Astrophysics Data System (ADS)

Solar eclipse observations allow for monitoring the solar diameter within time-frames ranging from several to hundreds of years. To determine the solar diameter on August 11 1999 the expedition of Kyiv Taras Shevchenko University to Romania performed photoelectric observations of the total solar eclipse within the shadow path near its northern and southern edges. The light curves of eclipse were obtained at each of six observational sites in visible and near-infrared light. They were UTC-timed and calibrated against the full Sun disk luminosity. To obtaine the angular diameter of the Sun from the light curves observed a theoretical light curve was simulated to relate solar limb darkening function in question with the luminosity of the solar crescent. Lunar limb irregularities and chromosphere light were also taken into account. The least squares method was used to fit the theoretical light curve to each of the observed ones the solar semidiameter being one of the best-fit parameters. Solar semidiameter estimates were obtained at each of the observational sites. The average value of the solar semidiameter estimations obtained is considered to be the final solar semidiameter estimate

Danylevsky, Vassyl; Danylevsky, V.; Kryvodubskyj, V.; Molotaj, O.; Taranukha, Yu.; Tel'Nyuk-Adamchuk, V.

302

Solar Diameter Evaluation from 1999 Eclipse Observations  

NASA Astrophysics Data System (ADS)

Solar eclipse observations allow for monitoring the solar diameter within time-frames ranging from several to hundreds of years. To determine the solar diameter on August 11 1999 the expedition of Kyiv Taras Shevchenko University to Romania performed photoelectric observations of the total solar eclipse within the shadow path near its northern and southern edges. The light curves of eclipse were obtained at each of six observational sites in visible and near-infrared light. They were UTC-timed and calibrated against the full Sun disk luminosity. To obtaine the angular diameter of the Sun from the light curves observed a theoretical light curve was simulated to relate solar limb darkening function in question with the luminosity of the solar crescent. The least squares method was used to fit the theoretical light curve to each of the observed ones the solar semidiameter being one of the best-fit parameters. Lunar limb irregularities and chromosphere light were also taken into account. Solar semidiameter estimates were obtained at each of the observational sites. The average value of the solar semidiameter estimations obtained is considered to be the final solar semidiameter estimate.

Buromsky, Mykola; Danylevsky, Vassyl; Kryvodubskyj, Valerij; Molotaj, Oleksandr; Taranukha, Yury; Tel'Nyuk-Adamchuk, Volodymyr

303

Solar Diameter Evaluation from 1999 Eclipse Observations  

NASA Astrophysics Data System (ADS)

Solar eclipse observations allow for monitoring the solar diameter within time-frames ranging from several to hundreds of years. To determine the solar diameter on August 11 1999 the expedition of Kyiv Taras Shevchenko University to Romania performed photoelectric observations of the total solar eclipse within the shadow path near its northern and southern edges. The light curves of eclipse were obtained at each of six observational sites in visible and near-infrared light. They were UTC-timed and calibrated against the full Sun disk luminosity. To obtaine the angular diameter of the Sun from the light curves observed a theoretical light curve was simulated to relate solar limb darkening function in question with the luminosity of the solar crescent. Lunar limb irregularities and chromosphere light were also taken into account. The least squares method was used to fit the theoretical light curve to each of the observed ones the solar semidiameter being one of the best-fit parameters. Solar semidiameter estimates were obtained at each of the observational sites. The average value of the solar semidiameter estimations obtained is considered to be the final solar semidiameter estimate.

Buromsky, Mykola; Danylevsky, Vassyl; Kryvodubskyj, Valeryj; Molotaj, Oleksandr; Taranukha, Yury; Tel'Nyuk-Adamchuk, Volodymyr

304

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

PubMed

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

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

2011-03-14

305

Changing Climate and Wind Patterns Revealed in Indiana's Fair Oaks Dunes  

NASA Astrophysics Data System (ADS)

Fair Oak Dunes (FOD) cover over 1100 square miles in north-central Indiana. Careful study of dune morphology reveals three types of dunes in regards to their size. The first order forms are compound parabolic dunes that reach over five miles in length and have the apex of parabola pointing in a southwesterly direction. The spacing between these dunes is three to five miles. The second order dune ridges are compound parabolic dunes that range in size from one to three miles in length with spacing of about one mile between the ridges. Both, the second order and the third order dunes have the apex of parabola pointing in northeasterly direction, opposite of the first order dunes. The third order dune ridges are simple parabolic dunes that reach up to half mile in length and are 25 to 30 feet tall in western part to over 45 feet in the eastern part of the FOD. All dunes are fixed by lush vegetation. Preliminary grain size analyses indicate that north part of FOD has coarser sand (0.283 mm) than southern part (0.197 mm), while eastern part (0.271 mm) is coarser than the western part (0.223 mm). This grain size distribution is in accordance with initial interpretation of dune morphology. Strong northeasterly winds associated with anticyclone were prevalent in early dune formation about 14,000 years ago near the end of last glacial. The finest particles were blown south and southwest from the source area which was north and east of the present dunes. Cyclonic southwesterly winds become dominant in Holocene and caused a reworking of the original large dunes into smaller forms as well as removal of some of the finest particles back to the original source to the northeast. Limited vertical dune profiles indicate that below the 5 feet of bioturbated surface layer are alternating light layers (3 to 5 inch thick) and dark laminae (1-2 inches thick). Dark laminae consist of quartz grains with `hairy' surfaces covered with reddish iron oxides or clays. They contain twice as much silt fraction and are more indurated and resistant to weathering than light layers separating them. Are these alternating layers depositional or postdepositional structures? Depositional origin would indicate episodes of drier climate and strong winds creating light, coarser layers while dark laminae would be indication of wet climate and weak winds transporting only dust particles. Postdepositional origin would indicate formation of "dissipation structures" created by soil water translocation of fines during humid climate. Many of the questions about timing of original dunes and their later transformation as well as timing of dark laminae and light layers within the dunes will hopefully be answered by OSL dating.

Kilibarda, Z.

2004-12-01

306

Formation of Linear Dunes and Other Secrets of the Simpson Desert, Australia  

NASA Astrophysics Data System (ADS)

It is estimated that linear dunes represent 40 percent of all dunes on Earth. Linear dunes have also been found on every terrestrial planet with an appreciable atmosphere, including Mars, Venus and Titan. Remarkably, however, despite how prevalent they are very little is known about their formation, chronology and their interaction with adjacent sediment sources. There are two basic hypotheses regarding the origin of linear dunes. The "wind rift" concept suggests that linear dunes are swept together from local material. In this model wind moves across the surface as horizontal vortices scouring or channeling out alluvial sand deposits [Pell et al., 1999; 2000]. The linear nature of the dunes is attributed to the parallel direction of the vortices. In the "depositional" concept sand is thought to come from a few depositional sources which can then be transported great distances. In this model linear dunes are a result of bidirectional winds that blow the sand together from either direction [Wopfner and Twidale, 2001]. Recently we began a series of studies in the Simpson Desert of Australia to tests these competing hypotheses. The Simpson Desert is located in the Lake Eyre basin and borders the Northwest Territory, Queensland and South Australia. Typically the area receives less than 150 mm (6 inches) of rain annually, and the rivers that drain into the Simpson Desert terminate in a series of floodout deposits where the flood waters simply debouch into the desert and seep into the sand leaving behind fresh sediment deposits. There is evidence indicating that these alluvial sediments are subsequently reworked into new dunes [Hollands et al., 2006]; however, the mechanism and timing of these processes is poorly understood. Using Differential Global Positioning System (DGPS) equipment we conducted a series of topographic surveys of linear dunes located in the western and southern parts of the Simpson Desert. Several of these dunes were staked so that we can monitor changes in dune morphometry over time. Results of the DGPS survey were also compared to Shuttle Radar Topographic Mission (SRTM) data as a way of verifying the accuracy of these data so that dune morphometry can be studied in a more systematic way. Our results will help us to better understand how linear dunes form and the environmental conditions necessary to generate them on Earth and on other terrestrial planets.

Craddock, R. A.; Hutchinson, M. F.; Tooth, S.; Maxwell, T. A.; Stein, J. A.; Howard, A. D.; Irwin, R. P.; Wilson, S.

2006-12-01

307

Flood-formed dunes in Athabasca Valles, Mars: morphology, modeling, and implications  

NASA Astrophysics Data System (ADS)

Estimates of discharge for martian outflow channels have spanned orders of magnitude due in part to uncertainties in floodwater height. A methodology of estimating discharge based on bedforms would reduce some of this uncertainty. Such a methodology based on the morphology and granulometry of flood-formed (`diluvial') dunes has been developed by Carling (1996b, in: Branson, J., Brown, A.G., Gregory, K.J. (Eds.), Global Continental Changes: The Context of Palaeohydrology. Geological Society Special Publication No. 115, London, UK, 165-179) and applied to Pleistocene flood-formed dunes in Siberia. Transverse periodic dune-like bedforms in Athabasca Valles, Mars, have previously been classified both as flood-formed dunes and as antidunes. Either interpretation is important, as they both imply substantial quantities of water, but each has different hydraulic implications. We undertook photoclinometric measurements of these forms, and compared them with data from flood-formed dunes in Siberia. Our analysis of those data shows their morphology to be more consistent with dunes than antidunes, thus providing the first documentation of flood-formed dunes on Mars. Other reasoning based on context and likely hydraulics also supports the bedforms' classification as dunes. Evidence does not support the dunes being aeolian, although a conclusive determination cannot be made with present data. Given the preponderance of evidence that the features are flood-formed instead of aeolian, we applied Carling's (1996b, in: Branson, J., Brown, A.G., Gregory, K.J. (Eds.), Global Continental Changes: The Context of Palaeohydrology. Geological Society Special Publication No. 115, London, UK, 165-179) dune-flow model to derive the peak discharge of the flood flow that formed them. The resultant estimate is approximately 2×106 m3/s, similar to previous estimates. The size of the Athabascan dunes' in comparison with that of terrestrial dunes suggests that these martian dunes took at least 1-2 days to grow. Their flattened morphology implies that they were formed at high subcritical flow and that the flood flow that formed them receded very quickly. Currently at: Earth Surface Dynamics Program, U.S. Geological Survey, MS 906, National Center, 12201 Sunrise Valley Drive, Reston, VA 20192, USA.

Burr, Devon M.; Carling, Paul A.; Beyer, Ross A.; Lancaster, Nicholas

2004-09-01

308

Etude numerique du sillage tourbillonnaire d'une eolienne  

NASA Astrophysics Data System (ADS)

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

Sibuet Watters, Christophe

309

Wind may have driven avalanches on Martian dunes  

NASA Astrophysics Data System (ADS)

In the sand dunes in the north polar sand sea of Mars, sand avalanches that appear as wedge-shaped alcoves can be seen above fan-shaped deposits. The avalanches, which are typically several meters across, are currently actively forming, with new alcoves showing up in recent images taken in consecutive Mars years. Some scientists have proposed that these sand avalanches occur when frozen carbon dioxide (CO2) sublimates, triggering the downslope flow (mass wasting) of sand grains and rock that had been lying on top of the CO2 frost. However, Horgan and Bell now suggest that these alcoves may actually have been formed by wind-driven movement of sand, not by CO2 sublimation.

Balcerak, Ernie

2012-07-01

310

Water resources of Sleeping Bear Dunes National Lakeshore, Michigan  

USGS Publications Warehouse

Sleeping Bear Dunes National Lakeshore in a water-rich area. It borders Lake Michigan and several small streams flow through the park to the lake. Small lakes are numerous within the park and near its boundaries. Ground water is available at most places in the park and wells yield as much as 100 gallons per minute. Water from streams, lakes, wells, and springs is of good quality. Dissolved solids range from 35 to 180 mg/L in lakes, from 145 to 214 mg/L in streams, and from 136 to 468 mg/L in groundwater. Analyses of samples for pesticides and trace metals indicate that no pesticides are present in the water, and that concentrations of trace metals do not exceed recommended drinking-water standards. Surface and ground water are available in sufficient quantity in most areas of the park for the development of water supplies for visitor 's centers, campgrounds, picnic areas, and other park facilities. (USGS)

Handy, A. H.; Stark, J. R.

1984-01-01

311

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

NASA Astrophysics Data System (ADS)

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

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

2011-08-01

312

Sorting out abrasion in a gypsum dune field  

NASA Astrophysics Data System (ADS)

Grain size distributions in eolian settings are the result of both sorting and abrasion of grains by saltation. The two are tightly coupled because mobility of particles determines abrasion rate, while abrasion affects the mobility of particles by changing their mass and shape; few field studies have examined this quantitatively. We measured grain size and shape over a 9 km transect downwind of a line sediment source at White Sands National Monument, a gypsum dune field. The sediment source is composed of rodlike (elongate), coarse particles whose shapes appear to reflect the crystalline structure of gypsum. Dispersion in grain size decreases rapidly from the source. Coarse particles gradually become less elongate, while an enrichment of smaller, more elongate grains is observed along the transect. Transport calculations confirm that White Sands is a threshold sand sea in which (1) the predominant particle diameter reflects grains transported in saltation under the dune-forming wind velocity and (2) smaller, elongate grains move in suspension under this dominant wind. Size-selective transport explains first-order trends in grain size; however, abrasion changes the shape of saltating grains and produces elongate, smaller grains that are spallation and breaking products of larger particles. Both shape and size changes saturate 5-6 km downwind of the source. As large particles become more equant, abrasion rates slow down because protruding regions have been removed. Such asymptotic behavior of shape and abrasion rate has been observed in theory and experiment and is likely a generic result of the abrasion process in any environment.

Jerolmack, Douglas J.; Reitz, Meredith D.; Martin, Raleigh L.

2011-06-01

313

Nucléation, ascension et éclatement d'une bulle de champagne  

NASA Astrophysics Data System (ADS)

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

Liger-Belair, G.

2006-03-01

314

Nourishment of perched sand dunes and the issue of erosion control in the Great Lakes  

NASA Astrophysics Data System (ADS)

Although limited in coverage, perched sand dunes situated on high coastal bluffs are considered the most prized of Great Lakes dunes. Grand Sable Dunes on Lake Superior and Sleeping Bear Dunes on Lake Michigan are featured attractions of national lakeshores under National Park Service management. The source of sand for perched dunes is the high bluff along their lakeward edge. As onshore wind crosses the bluff, flow is accelerated upslope, resulting in greatly elevated levels of wind stress over the slope brow. On barren, sandy bluffs, wind erosion is concentrated in the brow zone, and for the Grand Sable Bluff, it averaged 1 m3/yr per linear meter along the highest sections for the period 1973 1983. This mechanism accounts for about 6,500 m3 of sand nourishment to the dunefield annually and clearly has been the predominant mechanism for the long-term development of the dunefield. However, wind erosion and dune nourishment are possible only where the bluff is denuded of plant cover by mass movements and related processes induced by wave erosion. In the Great Lakes, wave erosion and bluff retreat vary with lake levels; the nourishment of perched dunes is favored by high levels. Lake levels have been relatively high for the past 50 years, and shore erosion has become a major environmental issue leading property owners and politicians to support lake-level regulation. Trimming high water levels could reduce geomorphic activity on high bluffs and affect dune nourishment rates. Locally, nourishment also may be influenced by sediment accumulation associated with harbor protection facilities and by planting programs aimed at stabilizing dunes.

Marsh, William M.

1990-09-01

315

Characteristics and outcome of crescentic glomerulonephritis in patients with both antineutrophil cytoplasmic antibody and anti-glomerular basement membrane antibody.  

PubMed

A subset of patients with crescentic glomerulonephritis (CGN) is characterized serologically by the presence of antineutrophil cytoplasmic antibody (ANCA) and anti-glomerular basement membrane antibody (anti-GBM) called "double positive" disease. The clinical significance of the occurrence of both antibodies is not clear. This study aims to describe the clinical and histologic characteristics and outcomes of CGN in a US cohort of double positive (DP) patients and compare them to patients with anti-GBM disease only or ANCA only (ANCA-associated vasculitis (AAV)). Renal biopsies with a diagnosis of CGN with either pauci-immune or linear immunofluorescence were selected and classified as AAV, anti-GBM disease, or DP based on serologic testing at the time of biopsy. Data on demographics, clinical presentation, treatment, and outcome were obtained by chart review. Six patients with anti-GBM disease, 9 with DP disease, and 18 AAV patients matched for year of diagnosis with DP were identified. Extrarenal disease manifestations were more prominent in the DP patients. The DP patients had severe renal dysfunction at presentation with eight of nine patients requiring dialysis at presentation. Renal biopsy findings of DP patients were similar to anti-GBM disease with majority of glomeruli showing cellular crescents. Eighty-nine percent of patients were treated with immunosuppressive therapy and 78 % with plasmapheresis. At 1 year, all nine DP patients reached end-stage renal disease. We conclude that the DP patients share extrarenal manifestations similar to AAV patients while the renal manifestations resemble anti-GBM patients clinically and histologically. The renal prognosis of DP patients remains poor despite treatment. PMID:23624587

Srivastava, A; Rao, G K; Segal, P E; Shah, M; Geetha, D

2013-04-28

316

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

NASA Astrophysics Data System (ADS)

Preservation and effective management of highly dynamic coastal features located in areas under development pressures requires in-depth understanding of their evolution. Modern geospatial technologies such as lidar, real time kinematic GPS, and three-dimensional GIS provide tools for efficient acquisition of high resolution data, geospatial analysis, feature extraction, and quantification of change. These techniques were applied to the Jockey's Ridge, North Carolina, the largest active dune field on the east coast of the United States, with the goal to quantify its deflation and rapid horizontal migration. Digitized contours, photogrammetric, lidar and GPS point data were used to compute a multitemporal elevation model of the dune field capturing its evolution for the period of 1974- 2004. In addition, peak elevation data were available for 1915 and 1953. Analysis revealed possible rapid growth of the dune complex between 1915-1953, followed by a slower rate of deflation that continues today. The main dune peak grew from 20.1 m in 1915 to 41.8 m in 1953 and has since eroded to 21.9 m in 2004. Two of the smaller peaks within the dune complex have recently gained elevation, approaching the current height of the main dune. Steady annual rate of main peak elevation loss since 1953 suggests that increase in the number of visitors after the park was established in 1974 had little effect on the rate of dune deflation. Horizontal dune migration of 3-6 m/yr in southerly direction has carried the sand out of the park boundaries and threatened several houses. As a result, the south dune section was removed and the sand was placed at the northern end of the park to serve as a potential source. Sand fencing has been an effective management strategy for both slowing the dune migration and forcing growth in dune elevation. Understanding the causes of the current movements can point to potential solutions and suggest new perspectives on management of the dune as a tourist attraction and as a recreation site, while preserving its unique geomorphic character and dynamic behavior.

Mitasova, Helena; Overton, Margery; Harmon, Russell S.

2005-12-01

317

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

EPA Science Inventory

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

318

Barrier Dune System along the Outer Banks of North Carolina: A Reappraisal  

Microsoft Academic Search

Barrier dune development has been encouraged by man along the Outer Banks of North Carolina to stabilize the barrier islands. This modification of a delicately balanced natural system is leading to severe adjustments in both geological and ecological processes.

Robert Dolan

1972-01-01

319

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

NASA Astrophysics Data System (ADS)

The movement of sand dunes in the desert is an emergent process; the overall movement of a dune is influenced both by the random interactions among individual sand particles and by the process of wind adding and subtracting sand. People often misconstrued emergent processes as deterministic processes containing central causality. I present a case study of how one person, an adult, who was not an expert in physics, articulated and refined her explanation of the movement of sand dunes. She began with centralized causality but ended with an explanation containing the cogent emergent ideas. This case study is noteworthy in exemplifying the dynamic process of generating an explanation. The interviewee went through four different explanations at three different levels (macro, micro and mid-level) and concluded with an explanation that simultaneously addressed the movement of sand dunes at all three levels.

Barth-Cohen, Lauren

2010-10-01

320

The Enigmatic Longevity of Granular Materials on Mars: The Case for Geologically Episodic Dune Formation  

NASA Astrophysics Data System (ADS)

Processes mitigating sand attrition are ultimately defeated by the vast time available on Mars. Sand longevity results from long-term climatic cycling. Dune fields undergo relatively brief periods of activity, then lapse into protracted periods of aeolian stasis.

Marshall, J.

1999-03-01

321

Geophysical Mars Analog Studies of Multiphase Water in the Great Kobuk Sand Dunes, Northwestern Alaska  

NASA Astrophysics Data System (ADS)

Late-winter GPR and CCR geophysical surveys of high-latitude, slowly migrating sand dunes were highly effective at mapping geology and the hydrocryophere. Such instruments should be regularly included in rover payloads.

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

2011-03-01

322

Dune Scrub Communities and Their Correlation with Environmental Factors at Point Reyes National Seashore, California.  

National Technical Information Service (NTIS)

Dune scrub vegetation characterized by three soft-leaved shrubs, Haplopappus ericoides, Lupinus arboreaus and Lupinus chamissonis, was sampled at Point Reyes National Seashore (PRNS), Marin County, California, using the Braun-Blanquet releve method. Eight...

B. Holton A. F. Johnson

1979-01-01

323

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

National Technical Information Service (NTIS)

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

2003-01-01

324

The impact of devegetated dune fields on North American climate during the late Medieval Climate Anomaly  

NASA Astrophysics Data System (ADS)

During the Medieval Climate Anomaly, North America experienced severe droughts and widespread mobilization of dune fields that persisted for decades. We use an atmosphere general circulation model, forced by a tropical Pacific sea surface temperature reconstruction and changes in the land surface consistent with estimates of dune mobilization (conceptualized as partial devegetation), to investigate whether the devegetation could have exacerbated the medieval droughts. Presence of devegetated dunes in the model significantly increases surface temperatures, but has little impact on precipitation or drought severity, as defined by either the Palmer Drought Severity Index or the ratio of precipitation to potential evapotranspiration. Results are similar to recent studies of the 1930s Dust Bowl drought, suggesting bare soil associated with the dunes, in and of itself, is not sufficient to amplify droughts over North America.

Cook, B. I.; Seager, R.; Miller, R. L.

2011-07-01

325

[Ecological adaptability of Pennisetum centrasiaticum clones on farmland-sand dune ecotone of Keerqin sandy land].  

PubMed

The individual growth, morphology and population biomass of Pennisetum centrasiaticum clones at two different habitats of farmland-sand dune ecotone on Keerqin sandy land of Inner Mongolia were compared in this study. P. centrasiaticum clones had significant morphological plasticity and different biomass distribution pattern at different habitats. Compared with P. centrasiaticum clones on semi-fixed sand dunes, those on farmland-sand dune transitive zone had a greater leaf elongation, longer rhizomes and internodes, more adventitious buds, larger amount of biomass, and deeper distribution of underground biomass, which were closely associated with the loose texture of the upper soil and the rather favorable water condition of the lower soil. It is believed that the population can well adapt itself to the farmland-sand dune ecotone habitats, and thus, play an important role in fixing mobile sand in succession of arenaceous vegetation. PMID:11962318

Chen, Shiping; Gao, Yubao; Ren, Anzhi; Liang, Yu; Liu, Shuang; Liu, Ning

2002-01-01

326

Dynamic dune management, integrating objectives of nature development and coastal safety: Examples from the Netherlands  

NASA Astrophysics Data System (ADS)

This paper discusses and compares results of management interventions to remobilise dunes and obtain more autonomous changes in foredunes resulting from a change in coastal defence policy. In recent decades, nature conservation managers tried to restore aeolian dynamics and dune mobility landward of foredunes to maintain threatened, rare pioneer species. Results indicate that destabilisation activities yielded an important increase of blowing sand and its effects on ecology but with a limited effect on the desired integral remobilization of dunes. Roots remaining in the sand after removal of vegetation and soil is one of the main problems. Follow up removal of roots for 3 to 5 years seems to be essential, but it is not clear whether the dunes will remain mobile in the long term.

Arens, Sebastiaan M.; Mulder, Jan P. M.; Slings, Quirinus L.; Geelen, Luc H. W. T.; Damsma, Petra

2013-10-01

327

Creating dune landscapes for nature and housing - how to assess the designs?  

NASA Astrophysics Data System (ADS)

Over the last decades landscape and nature organisations in The Netherlands initiated discussions about safeguarding characteristic historical landscapes, as well as improving nature and landscape quality. In these discussions they were supported by Dutch government agencies and newspapers. As a consequence, architects, landscape architects and building firms in the Netherlands try to upgrade the quality of houses and build-up areas by creating special landscape settings. Dunes are one of the landscapes that appeal to the designers, and several projects make use of dunes to create a quality living environment. Also nature manager construct dunes in what is called 'new nature'. This contribution evaluates several projects creating dune landscapes. Criteria for the evaluation are: - the subsequent geomorphology, - the materials used for construction, - the resulting internal structure, - the soil profile, - the relationship with the vegetation, - the historical integrity of the location. These examples indicate that engaging earth-scientific knowhow would substantially improve the authenticity of the designs.

van den Ancker, J.; Jungerius, P. D.; Hartman, J.

2012-04-01

328

Quantifying landscape-ecological succession in a coastal dune system using sequential aerial photography and GIS  

Microsoft Academic Search

Summary  This contribution presents an attempt to measure the path of habitat and vegetation succession in a coastal dune system (Kenfig\\u000a Burrows, South Wales) using remote sensing and GIS. The loss of slack habitats associated with the continuing stabilization\\u000a of this dune system is a major cause for concern. These habitats support a range of plant species, including the rare fen

2002-01-01

329

Construction d'une échelle d'attachement au lieu de travail : une démarche exploratoire  

Microsoft Academic Search

Notre article présente les résultats d'une série de cinq études visant la construction et la validation d'une échelle d'attachement au lieu de travail (ÉALT). S'appuyant sur la Théorie de l'attachement au lieu (Place attachment) définie par Shumaker et Taylor (1983) et concevant l'attachement au lieu de travail comme un lien affectif résultant de l'interaction dynamique entre une personne et son

Liliane Rioux

2006-01-01

330

Spatial Distribution of Soil Nematode Communities in Stable and Active Sand Dunes of Horqin Sandy Land  

Microsoft Academic Search

To explore the ecological significance of artificial plantation and the restoration process in sand dune ecosystems, the spatial distribution of soil nematode communities in stable and active sand dunes were investigated in northeastern Inner Mongolia, China. Soil nematode community structure and composition at five soil depths (0–5 cm, 5–10 cm, 10–20 cm, 20–40 cm, and 40–60 cm) and three slope positions (windward slope, top slope,

Xiaoke Zhang; Xiwen Dong; Wenju Liang

2010-01-01

331

Spatial indicators of plant community assembly from a 453-year sand-dune chronosequence  

Microsoft Academic Search

Background: We explored evidence for spatial patterning in vegetation across a sand-dune chronosequence spanning 453 years of primary succession to test for indications of a temporal signature of niche versus neutral processes during community assembly.Methods: The study was conducted on a series of dune-capped beach ridges located in Wilderness State Park in Emmet County of northern Lower Michigan, United States

Jennifer M. Waugh; Lonnie W. Aarssen

2011-01-01

332

Arbuscular mycorrhizae in a tropical sand dune ecosystem on the Gulf of Mexico  

Microsoft Academic Search

Root samples of 37 species distributed on the beach and along a successional gradient (from mobile to stabilized areas) in\\u000a a tropical sand dune system on the Gulf of Mexico showed that 97% of the species were mycorrhizal. The mycorrhizal inoculum\\u000a potential of the sand from several dune areas was compared using two different bioassays. Firstly, the field rate of

Lea Corkidi; Emmanuel Rincón

1997-01-01

333

Étude par simulation numérique de l'annihilation en surface d'une dislocation coin  

Microsoft Academic Search

Nous avons étudié par simulation numérique à l'échelle atomique la stabilité d'une dislocation coin, de plan de glissement proche et parallèle à une surface libre. La même étude à été conduite pour le débris idéalisé d'annihilation d'une telle dislocation : une cavité de longueur infinie, de section rectangulaire et de profondeur variable, créée par élimination partielle d'atomes appartenant à deux

P. Geysermans; V. Pontikis

2003-01-01

334

The role of archaeophytes and neophytes in the Dutch coastal dunes  

Microsoft Academic Search

The position of alien plant species in the Dutch coastal dune vegetation is evaluated considering 12 archaeophytes and 20\\u000a neophytes (including one moss), all of widespread occurrence in the coastal area of the Netherlands. Almost all archaeophytes\\u000a have become part of natural vegetation types. Open scrub communities, in particular Hippophae rhamnoides-Sambucus nigra scrub at the leeside of the outer dunes,

Eduard J. Weeda

2010-01-01

335

Atlantic storminess and historical sand drift in Western Europe: implications for future management of coastal dunes  

Microsoft Academic Search

Historical records of sand drift and dune-building along the coastline of Western Europe provide insights into the natural\\u000a processes of sand dune accretion and both the impacts of, and human responses to, sand incursions. The analysis of documentary\\u000a records, instrumental data and proxy records over the last 1,000 years indicates that this period, which included the Little\\u000a Ice Age (AD 1570–1900),

Michèle L. Clarke; Helen M. Rendell

2011-01-01

336

Microbiotic crust control of runoff generation on sand dunes in the Negev Desert  

Microsoft Academic Search

The general belief that dune sands in arid regions are not likely to generate runoff and that runoff necessitates wet conditions is examined. Runoff generation was measured within an arid dune field in the western Negev Desert, Israel, during 1990–1994 on 16 plots (1.2–6.6 m2), constructed along a continuum of crust-covered crust. The relationships between chlorophyll a and carbohydrates of

Giora J. Kidron; Aaron Yair; Ahuva Vonshak; Aharon Abeliovich

2003-01-01

337

Impact of anthropogenic disturbances on beetle communities of French Mediterranean coastal dunes  

Microsoft Academic Search

In coastal dunes, influenced by anthropogenic activities such as tourism, it is important to determine the relative influence\\u000a of environmental factors at different spatial scales to evaluate the sensitivity of local communities to disturbances. We\\u000a analyzed beetle communities of 14 dunes of the French Mediterranean coast: four in the relatively preserved Camargue area,\\u000a and ten in the Var department, where

Vincent Comor; Jérôme Orgeas; Philippe Ponel; Christiane Rolando; Yannick R. Delettre

2008-01-01

338

Aeolian Dunes as Evidence for Explosive Volcanism in the Tharsis Region of Mars  

Microsoft Academic Search

Two transverse dune fields occur among Late Amazonian volcanic and aeolian landforms in southwestern Tharsis, Mars. The first is located ~70 km northwest of Biblis Patera, around 5 degN, 125 degW. The second is located about 500 km northwest of Arsia Mons, at 2 degS, 130 degW. The latter is the largest dune field thus far documented to occur in

Kenneth S. Edgett

1997-01-01

339

Assessing the engineering properties of concrete made with fine dune sands: an experimental study  

Microsoft Academic Search

Sand dunes cover an area of 16.6% of the total area of Egypt. This paper presents the results of an extensive laboratory testing\\u000a that was carried out to determine the engineering properties of concrete. The concrete fine aggregate is fine dune sands obtained\\u000a from three sites in the Kharga Oasis, Western Desert, Egypt. All samples were classified as poorly graded

El-Sayed Sedek Abu Seif; Abu Seif

340

Optically stimulated luminescence dating of aeolian sand in the otindag dune field and holocene climate change  

USGS Publications Warehouse

The dune system in Otindag sand field of northern China is sensitive to climate change, where effective moisture and related vegetation cover play a controlling role for dune activity and stability. Therefore, aeolian deposits may be an archive of past environmental changes, possibly at the millennial scale, but previous studies on this topic have rarely been reported. In this study, thirty-five optically stimulated luminescence (OSL) ages of ten representative sand-paleosol profiles in Otindag sand field are obtained, and these ages provide a relatively complete and well-dated chronology for wet and dry variations in Holocene. The results indicate that widespread dune mobilization occurred from 9.9 to 8.2 ka, suggesting a dry early Holocene climate. The dunes were mainly stabilized between 8.0 and 2.7 ka, implying a relatively wet climate, although there were short-term penetrations of dune activity during this wet period. After ???2.3 ka, the region became dry again, as inferred from widespread dune activity. The "8.2 ka" cold event and the Little Ice Age climatic deterioration are detected on the basis of the dune records and OSL ages. During the Medieval Warm Period and the Sui-Tang Warm Period (570-770 AD), climate in Otindag sand field was relatively humid and the vegetation was denser, and the sand dunes were stabilized again. These aeolian records may indicate climate changes at millennial time scale during Holocene, and these climatic changes may be the teleconnection to the climate changes elsewhere in the world. ?? Science in China Press and Springer-Verlag GmbH 2008.

Zhou, Y. L.; Lu, H. Y.; Mason, J.; Miao, X. D.; Swinehart, J.; Goble, R.

2008-01-01

341

Impact of dumped sediments on subaqueous dunes, outer Weser Estuary, German Bight, southeastern North Sea  

NASA Astrophysics Data System (ADS)

The impact of dredge spoil disposal on asymmetrical large-scale dunes has been studied at a disposal site in a shallow subtidal area of the outer Weser Estuary (German Bight, southeastern North Sea). Between June and December 1998, this site was used for the disposal of ~3×106 m3 dredge spoil. Repeated bathymetric surveys with a multibeam echosounder system reveal that the artificial supply of sediment provoked significant morphological changes in the dune field, including the infill of dune troughs and even the complete burial of individual dunes. However, even completely buried dunes began to regenerate within a few months. In addition, slow migration of the dunes toward the open sea was observed, indicating net seaward sediment transport in the survey area. Since the dumped sediment does not appear to have a persistent effect on the bedforms and, in all likelihood, will be exported from the estuarine system on medium- to long-term timescales, the investigated area constitutes a suitable disposal site.

Wienberg, Claudia; Hebbeln, Dierk

2005-02-01

342

Photoclinometry, Morphometry, and Spectroscopy of Titan's Sand Dunes from Cassini/VIMS  

NASA Astrophysics Data System (ADS)

We present results from recent Cassini Visual and Infrared Mapping Spectrometer (VIMS) observations of the sand seas that cover Titan's equatorial region. High-resolution (~500 m/pixel) spectral mapping from the T20 Titan flyby on 2006 October 20 shows the dunes. The dunes themselves, and presumably therefore the sand of which they are comprised, are dark in all of Titan's spectral windows. The spectrum best matches organic material, but a small water-ice component cannot be ruled out. Thus the sand particles cannot be pure water ice but could still be mostly ice by volume but coated by an organic rind at least several microns thick. The dunes are separated by interdunes in some places, but are continuous in others. Where interdunes exist, we are able to map the extent of the substrate units. Where no interdunes exist, we use photoclinometry to ascertain crest-trough-crest heights of between 30 and 70 meters. Dune separations in the T20 observations are just over 2 kilometers from crest to crest; the dunes' orientations are predominantly east-west, but with variations of up to 10 degrees in either direction. A properly designed future VIMS observation would be capable of gathering a resolved profile of the dune slopes to ascertain wind direction and present activity status.

Barnes, J. W.; Brown, R. H.; Soderblom, L. A.; Sotin, C.; Jaumann, R.; Le Mouelic, S.; Rodriguez, S.; Beyer, R. A.; Buratti, B. J.; Pitman, K.; Baines, K. H.; Nicholson, P. D.

2007-12-01

343

A 45-year time series of Saharan dune mobility from remote sensing  

NASA Astrophysics Data System (ADS)

Decadal trends in the aeolian dust record of the Sahara affect the global climate system and the nutrient budget of the Atlantic Ocean. One proposed cause of these trends are changes in the frequency and intensity of dust storms, which have hitherto been hard to quantify. Because sand flux scales with the cube of wind speed, dune migration rates can be used as a proxy for storminess. Relative changes in the storminess of the Sahara can thus be monitored by tracking the migration rates of individual sand dunes over time. The Bodélé Depression of northern Chad was selected as a target area for this method, because it is the most important point-source of aeolian dust on the planet and features the largest and fastest dunes on Earth. A collection of co-registered Landsat, SPOT, and ASTER scenes, combined with declassified American spy satellite images was used to construct a 45 year record of dune migration in the Bodélé Depression. One unexpected outcome of the study was the observation of binary dune interactions in the imagery sequence, which reveals that when two barchan dunes collide, a transfer of mass occurs so that one dune appears to travel through the other unscathed, like a solitary wave. This confirms a controversial numerical model prediction and settles a decade-old debate in aeolian geomorphology. The COSI-Corr change detection method was used to measure the dune migration rates from 1984 until 1987, 1990, 1996, 2000, 2003, 2005, 2007, 2008, 2009, and 2010. An algorithm was developed to automatically warp the resulting displacement fields back to a common point in time. Thus, individual image pixels of a dune field were tracked over time, allowing the extraction of a time series from the co-registered satellite images without further human intervention. The automated analysis was extended further back into the past by comparison of the 1984 image with declassified American spy satellite (Corona) images from 1965 and 1970. Due to the presence of specks of dust as well as image distortions caused by shrinking of the photographic film, it was not possible to automatically measure the dune displacements of these scenes with COSI-Corr. Instead, the image was georeferenced and coregistered to the 1984 Landsat imagery by third order polynomial fits to 531 tie points, and the displacements of ten large barchan dunes were measured by hand. Thanks to the 19-year time lapse between the two images used for these 'analog' measurements, their precision is better than 5%, which is comparable with that of the automated COSI-Corr analysis. The resulting dune celerities are identical to the automated measurements, which themselves show little or no temporal variability over the subsequent 26 years. The lack of any trend in the time series of dune celerity paints a picture of remarkably stable dune mobility over the past 45 years. None of the distributions fall outside the overall average of 25m/yr. The constant dune migration rates resulting from our study indicate that there has been no change in the storminess of the Sahara over the past 45 years. The observed dust trends are therefore caused by changes in vegetation cover, which in turn reflect changes in precipitation and land usage. This work highlights the importance of the hyper-arid Bodélé Depression, which provides a steady but finite supply of aeolian dust to the atmosphere without which nutrient fluxes and terrestrial albedo would be more variable than they are today.

Vermeesch, P.

2012-04-01

344

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

NASA Astrophysics Data System (ADS)

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

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

2003-12-01

345

Solar energy  

Microsoft Academic Search

Water pumps, solar power stations, air conditioners, fresh-water stills, solar homes, solar cookers, fruit driers, devices for (low temperature) steaming of reinforced concrete members, solar refrigerators, solar hothouses, welding and melting of metals presents a far from complete list of the devices and areas of the possible broad use of solar energy. The first plant of solar equipment is to

G. Y. Umarov; A. A. Yershov

1975-01-01

346

Simulated impact of sea level rise on phreatic level and vegetation of dune slacks in the Voorne dune area (The Netherlands)  

Microsoft Academic Search

Effects of sea level rise and different coastline management options on the phreatic level in a coastal dune area are calculated, using a scenario with 60 cm sea level rise in the course of the next century, resulting from global climatic changes. Changes in the phreatic level - both lowering and rising - are evaluated for their effects on the

V. Noest

1991-01-01

347

Clinical and histological outcome predictors in renal limited pauci-immune crescentic glomerulonephritis: a single centre experience.  

PubMed

Renal-limited vasculitis is a pauci-immune crescentic glomerulonephritis with no signs of systemic involvement, representing one of the most common causes of rapidly progressive glomerulonephritis. The study aims to examine clinical and histological features in twenty-four patients with RLV diagnosed by the Nephrology Department of Sapienza University of Rome, Italy, evaluating the role of these parameters in predicting renal survival. Patients details, clinical and histological features and outcomes were recorded at the time of renal biopsy and over a mean follow-up period of 36±6 months. In our study, serum creatinine at presentation was significantly higher in patients who had a poor outcome than in those who survived with independent renal function (6.3±2.47 mg/dl vs 2.84±2.01 mg/dl, P= 0.002). The presence of C3c was found in the area of glomerular fibrinoid necrosis and in small arteries and arterioles with fibrinoid necrosis in 17 patients (P= 0.018). In conclusion, serum creatinine at presentation and focal C3c depositions in areas of glomerular and arteriolar fibrinoid necrosis were the best determinants of poor renal outcome, maybe underlining the pathogenic role of alternative pathway activation of complement system but also demonstrating the focal distribution of necrotizing lesions. PMID:22507343

Gigante, A; Salviani, C; Giannakakis, K; Rosato, E; Barbano, B; Moroso, A; Gasperini, M L; Nofroni, I; Salsano, F; Cianci, R; Pugliese, F

348

[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

349

Hydrodynamic significance of variable ripple morphology across deep-water barchan dunes in the Faroe–Shetland Channel  

Microsoft Academic Search

A combination of high-resolution (30 kHz) sidescan sonar and seafloor photography has been used to image barchan dunes and sand ripples in the Faroe–Shetland Channel. The barchan dunes display body lengths and horn-to-horn widths of up to 120 m, and the horns point downcurrent to the southwest. The seafloor surrounding the dunes is variable, with gravel patches, sand with gravel

Russell B Wynn; Douglas G Masson; Brian J Bett

2002-01-01

350

Population dynamics of some major woody species in relation to long-term succession on the dunes of Voorne  

Microsoft Academic Search

This study is a follow-up of medium-term succession studies based on a vegetation map, scale 1:2 500, of the dunes near Oostvoorne made in 1959 and 1980. The area has a marked zonation with partly very young dunes and inner dunes at a distance of >1 200 m from the beach which are 800 yr old. The overall succession trend

Eddy van der Maarel; Nick de Cock; Ernie de Wildt

1985-01-01

351

The Holocene History of the White Sands Dune Field and the influences of Climate on Eolian Deflation and Playa Lakes  

Microsoft Academic Search

White Sands National Monument is the largest gypsum dune field in the world. The dunes have formed downwind of a 20-m-deep, 19-km-wide deflation basin containing large playa lakes. Today, the gypsum sand is derived from the edge of the deflation basin, next to the dune field, rather than the alkali flat and playa lakes where gypsum crystals are forming. Three

R. P. Langford

2001-01-01

352

The sand dunes and their vegetation along the Mediterranean coast of France. Their likely response to climatic change  

Microsoft Academic Search

The Golfe du Lion is mainly bordered by low and narrow sand dunes. Since about four decades, 1\\/3 of its shoreline has been receding, while 1\\/3 has been prograding and another 1\\/3 is stable. Several types of dunes may be described mainly depending on storms, high wind frequencies and sand grain size. Vegetation on dune system is distributed along a

Jean-Jacques Corre

1991-01-01

353

Seasonal Tes and Moc Observations of The Russell Crater Dune Field: Recent Surface Runoff On A Dune Slope Within The Last Martian Year?  

NASA Astrophysics Data System (ADS)

Rill erosion on a dune slope in the Russell Crater dune field was detected on the high resolution Mars Orbiter Camera (MOC)-NA image M1901170 at 54.5S and 347.3W. Identical erosion features occur on dunes in the Green Crater at 53.0S and 8.2W. The identified erosional morphology differs from previously observed gully erosion [1] elsewhere on Mars. Seasonal observations indicate that the extremely fresh appearing erosion might be caused by recent surface runoff within the last Martian year. The erosional features in the Russell Crater dune field are located on a 350 m high dune slope with a dip of about 8. The erosion starts in small alcoves in a den- dritic pattern at the dune crest and merges after a short distance into main channels, which have a parallel pattern following the slope topography. In contrast to all other observed gullies on Mars they run out and abruptly end at the dune base without a de- positional apron. The morphological forms show strong affinity to rill erosion on Earth [2], except from the lack of an apron. The morphology of the rills indicates that over- land flow caused the erosion. The image was acquired in mid autumn at LS 50. The very fresh appearing rills suggest that the erosion took place by a defrosting process between late winter and mid spring indicated by seasonal observations of TES albedo and temperature data [3]. The temperature increases from 148K in winter up to an ob- served maximum temperature of 276K (near the water ice sublimation temperature) in mid spring. In the same time period the albedo decreases from 0.3 to 0.1. We favour an erosion process by liquid water: the rills are located in absolute elevations of about 200 m and the retreat of the south polar cap leads to an increase of the atmospheric pressure in the southern spring [4, 5] which could allow liquid water to be stable in this region [6]. The lack of a depositional apron may be caused by compaction of the dust material with potentially simultaneous sublimation of the fluid. References: [1] Malin and Edgett, 2000, Science, 288, 2330-2335. [2] Higgins, 1990, Groundwater Geomorphology, Boulder, Colorado, Geological Society of America Special Paper 252, 139-155. [3] Reiss and Jaumann, 2002, LPSC. [4] Hess S.L., 1979, JGR, 84, 2923-2927. [5] Houben et al., 1997, JGR, 102, 9069-9083. [6] Haberle et al., 2001, JGR, 106, 23317-23326.

Reiss, D.; Jaumann, R.

354

Luminescence dating of Holocene dune complexes along the shore of northern France (Picardy)  

NASA Astrophysics Data System (ADS)

The Holocene dune and peat complexes along the shore of northern France (Picardy) had already been studied in detail by Meurisse et al. (2005) and Meurisse-Fort (2009). Information about the palaeodevelopment of those dune fields is hence given due to existing 14C data as well as by sedimentological and morphological analyses. Due to the results from radiocarbon dating, different types of aeolian bodies could be correlated along the Picardy coastline and a regional stratigraphic sequence could be established (Meurisse-Fort, 2009). The aim of the ongoing study is to get a higher chronological resolution for the different phases of dune activity in Picardy by luminescence dating what is a powerful tool to determine the time of last sunlight exposure of grains before burial (this information yields important information about dune movement). Samples for OSL dating were taken from dune bodies located in Tardinghen, Hardelot, Saint-Frieux and Saint-Gabriel. For dating, a single aliquot regenerative dose (SAR) protocol (Murray & Wintle 2003) is applied to coarse grained quartz. First tests concerning the signal intensity, the purity of the quartz OSL signal and the bleaching properties showed that quartz OSL dating works well for the dunes of the northern France coastline. The new luminescence ages will help to better unravel the phases of sand dune activity and stabilisation mainly controlled by climate changes and human impact. References: Meurisse, M., Van Vliet-Lanoë, B., Talon, B. & Recourt, P. (2005): Complexes dunaires et tourbeux holocènes du littoral du Nord de la France. - Geoscience, 337 : 675-684. Meurisse-Fort, M. (2009): Enregistrement haute résolution des massifs dunaires ; Manche, mer du Nord et Atlantique - Le rôle des tempêtes. Thèse de Doctorat soutenue en juin 2007, Université de Lille1. Coll. Recherches - Sciences (Sciences de la Terre). EPU-Publibook (ed.), Paris, 310 pp. Murray, A.S. & Wintle, A.G. (2003): The single aliquot regenerative dose protocol: potential for improvements in reliability. - Radiat. Meas., 37: 377-381.

Lauer, Tobias; Frechen, Manfred; Meurisse-Fort, Murielle; Gosselin, Guillaume; van Vliet-Lanoë, Brigitte

2010-05-01

355

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

NASA Astrophysics Data System (ADS)

Although aeolian landforms are pervasive on Mars, evidence for contemporary activity has been limited. The next major campaign for the Mars Exploration Rover “Opportunity” is the investigation of the ˜20 km diameter Endeavor crater, ˜6 km to southeast of the rover's position as of December 2010. We present evidence from orbital imagery that eight aeolian bed forms (˜14,000 m2) in Endeavor crater have been active within the past decade (2001-2009), at a spatial scale that should be directly observable by Opportunity from the crater rim. Two dunes appear to show translational migration (˜10-20 m), but all dunes indicate erosion to be the dominant process with up to 100% sediment removal. Thermophysical properties of these dunes are consistent with very fine to fine sand sizes, the particle sizes most easily moved by the Martian atmosphere. The dunes that show the most surface change have a rippled appearance without well-defined slip faces. Based on their morphology (elliptical shape), we classify them as dome dunes. Mesoscale atmospheric modeling is employed to provide insight into the atmospheric forcing of this aeolian system. The major wind regimes from modeling are consistent with observations of wind streaks, sand streamers, ripples, and slip faces of regional dune fields although modeled wind speeds are insufficient to move sand. The translation and erosion of these dunes constitutes the largest contemporary movement of sand-sized sediment reported on Mars to date and demonstrates that Endeavor crater has been subject to wind profiles exceeding the threshold velocity at the surface (daily/seasonally and/or episodically) in the recent past.

Chojnacki, Matthew; Burr, Devon M.; Moersch, Jeffrey E.; Michaels, Timothy I.

2011-04-01

356

The utility of desert sand dunes as Quaternary chronostratigraphic archives: evidence from the northeast Rub' al Khali  

NASA Astrophysics Data System (ADS)

The distributions of optically stimulated luminescence (OSL) ages from dunes are affected by palaeoenvironmental changes, complex dune dynamics and sampling strategy. Extracting the relative importance of these factors when interpreting discontinuous OSL chronologies from sand dunes has proven difficult, and is particularly hindered in contexts where the internal sedimentary structures of dunes are not visible. In this study samples for OSL dating were taken from three major dune exposures in the Rub' al Khali, United Arab Emirates, each showing clear internal structure, with the aim of addressing these problems. Specific objectives were to assess how ages of individual sedimentary units represent dune accumulation as a whole, and how the dune record in turn reflects known past environmental changes. Final ages were calculated using the OxCal software package, by incorporating the known relative stratigraphy through the application of Bayesian methods. The results show that stratigraphy alone is not sufficient at these sites to guide OSL sampling; that is, chrono- and lithostratigraphic boundaries do not necessarily coincide. Where chronological hiatuses are present, internal sediment stratigraphy can be a useful tool in identifying potential problems of under-sampling the full dune record. The implications of these findings for reconstructing Quaternary climates from dune chronologies are considered.

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

2013-10-01

357

Palaeoclimate interpretations of Late Pleistocene vegetated linear dune mobilization episodes: evidence from the northwestern Negev dunefield, Israel  

NASA Astrophysics Data System (ADS)

The northern Sinai - northwestern (NW) Negev erg stretches east out of the Nile Delta that is believed to be the erg's sand source. The vegetated linear dune (VLD) field of the NW Negev Desert, situated at the downwind eastern end of the erg, constitutes an ideal setting for dating and interpreting its Late Quaternary dune encroachment episodes. This study builds upon the results of Roskin et al. (Age, origin and climatic controls on vegetated linear dunes in the northwestern Negev Desert (Israel), Quaternary Science Reviews 30 (2011), 1649-1674) that presented the stratigraphy of 35 sections and 97 optically stimulated luminescence (OSL) ages from the NW Negev dunefield. Here we analyze Late Pleistocene dune mobilizations and stabilizations and interpret their palaeoclimatic controls in light of regional and global dune ages, sediment records and proxies. While initial dune encroachment into, and stabilization in, the NW Negev took place during the Last Glacial Maximum (LGM) at ~23-18 ka, spatial and statistical analyses of the OSL dataset suggest that since the LGM, Negev dune activity was concentrated in two significant mobilization-stabilization episodes: a main episode at ~16-13.7 ka and a minor one at ~12.4-11.6 ka when the dunes reached their maximum spatial extent and stabilized. These episodes include rapid dune encroachment and accretion events and coincide with the Heinrich 1 and Younger Dryas cold events, respectively. The Late Pleistocene sand-transporting winds were characterized by a westerly direction that resulted in west-east VLD elongation. Dune mobilizations may have occurred in response to wintertime East Mediterranean cyclonic systems that brought storms of rainfall and strong winds. The rapid dune mobilization events and their concurrence with the Heinrich 1 and Younger Dryas cold events suggest a more global control. Despite the rainfall, the elongating VLDs were probably sparsely vegetated because of the high wind power; their stabilization resulted from a decrease in storminess, with the onset of a more arid Holocene climate. Other global low-latitude dune mobilizations and stabilizations are concentrated at the end of the Late Pleistocene, leading us to suggest that these were also controlled mainly by global cold-events and subsequent changes in windiness. The recurring discontinuous aeolian sedimentation pattern found in OSL-dated VLDs provides new and important chronological and sedimentological insight into prominent dune mobilization and stabilization processes. The suggested link between global drops in cold-event windiness and low-latitude dune stabilization episodes emphasizes the prevalence of winds over aridity regarding major dune mobilizations for low-latitude dunes, even if vegetated.

Roskin, J.; Tsoar, H.; Porat, N.; Blumberg, D. G.

2012-04-01

358

Oceanobacillus chungangensis sp. nov., isolated from a sand dune.  

PubMed

A Gram-stain-positive, spore-forming, rod-shaped, motile, strictly aerobic bacterial strain, designated CAU 1051(T), was isolated from a sand dune and its taxonomic position was investigated using a polyphasic approach. Strain CAU 1051(T) grew optimally at pH 5.0 and 30 °C. NaCl was not required for growth but up to 10.0?% (w/v) NaCl was tolerated. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain CAU 1051(T) formed a distinct lineage within the genus Oceanobacillus and was most closely related to Oceanobacillus profundus CL-MP28(T), Oceanobacillus caeni S-11(T), and Oceanobacillus picturae LMG 19492(T) (96.8?%, 95.6?% and 95.3?% similarity, respectively). DNA-DNA reassociation analysis showed that strain CAU 1051(T) displayed 28.2±0.7?% relatedness to O. profundus KCTC 13625(T). Strain CAU 1051(T) contained MK-7 as the only isoprenoid quinone and anteiso-C15?:?0 as the major fatty acid. The cell wall peptidoglycan of strain CAU 1051(T) contained meso-diaminopimelic acid. The polar lipids were composed of diphosphatidylglycerol, phosphatidylglycerol, six unidentified phospholipids, an unidentified glycolipid, and six unidentified polar lipids. The major whole-cell sugars were glucose and ribose. The DNA G+C content was 36.3 mol%. On the basis of phenotypic data and phylogenetic inference, strain CAU 1051(T) represents a novel species of the genus Oceanobacillus for which the name Oceanobacillus chungangensis sp. nov. is proposed. The type strain is CAU 1051(T) (?=?KCTC 33035(T)?=?CCUG 63270(T)). PMID:23625258

Lee, Dong Chae; Kang, Hyeonji; Weerawongwiwat, Veeraya; Kim, Beomjoon; Choi, Young-Wan; Kim, Wonyong

2013-04-26

359

Experimental restoration of native vegetation in Indiana Dunes National Lakeshore  

USGS Publications Warehouse

We investigated the effects of prescribed fire, herbicide treatment, and sod removal on the eradication of exotic grasses and the establishment of native plant species in 24 experimental restoration plots in three razed residential sites within the boundary of Indiana Dunes National Lakeshore. During 1992-1995, herbicide treatment and sod removal decreased the combined cover of Poa pratensis (Kentucky blue grass) and Agropyron repens (quackgrass) significantly (from 82% to 13%, and 85% to 8%, respectively), whereas fire did not suppress such exotic lawn grasses. In 1993, several opportunistic species, represented by Cyperus spp. (umbrella sedges), Digitaria sanguinalis (crab grass), and Ambrosia artemisiifolia (common ragweed), filled the gaps left by the removal of lawn grasses. For the same period, Detrended Correspondence Analysis revealed a clear vegetation divergence between the control-fire plots and the herbicide-sod removal plots. While Poa pratensis and Agropyron repens continued to dominate the control and fire plots, the planted native species, represented by Schizachyrium scoparium (little blue-stem), Sorghastrum nutans (Indian grass), Rudbeckia hirta (black-eyed susan), and Monarda punctata (horsemint), began to dominate in the herbicide and sod removal plots from 1994. In both herbicide and sod removal plots, the ground cover of grasses (68%) was much higher than the forbs (10%). The herbicide plots, where exotic species were removed but nitrogen-rich top soils were not removed, showed a higher diversity of planted native species than the sod removal plots (where both exotic species and top soils were removed) and the control-fire plots (where neither was removed). This finding suggests that an optimum but not excessive concentration of soil nitrogen is needed to support a maximum species diversity in such infertile substrate as sandy soil. In addition, the decrease in potassium in all plots, regardless of treatment, suggests that potassium may become a limiting factor for our restored native vegetation.

Choi, Young D.; Pavlovic, Noel B.

1998-01-01

360

Linking marine resources to ecotonal shifts of water uptake by terrestrial dune vegetation.  

PubMed

As evidence mounts that sea levels are rising, it becomes increasingly important to understand the role of ocean water within terrestrial ecosystem dynamics. Coastal sand dunes are ecosystems that occur on the interface of land and sea. They are classic ecotones characterized by zonal distribution of vegetation in response to strong gradients of environmental factors from the ocean to the inland. Despite the proximity of the dune ecosystem to the ocean, it is generally assumed that all vegetation utilizes only freshwater and that water sources do not change across the ecotone. Evidence of ocean water uptake by vegetation would redefine the traditional interpretation of plant-water relations in the dune ecosystem and offer new ideas for assessing maritime influences on function and spatial distribution of plants across the dune. The purpose of this study was to identify sources of water (ocean, ground, and rain) taken up by vegetation using isotopic analysis of stem water and to evaluate water uptake patterns at the community level based on the distribution and assemblage of species. Three coastal dune systems located in southern Florida, USA, and the Bahamian bank/platform system were investigated. Plant distributions across the dune were zonal for 61-94% of the 18 most abundant species at each site. Species with their highest frequency on the fore dune (nearest the ocean) indicate ocean water uptake as evidenced by delta 18O values of stem water. In contrast, species most frequent in the back dune show no evidence of ocean water uptake. Analysis of species not grouped by frequency, but instead sampled along a transect from the ocean toward the inland, indicates that individuals from the vegetation assemblage closest to the ocean had a mixed water-harvesting strategy characterized by plants that may utilize ocean, ground-, and/or rainwater. In contrast, the inland vegetation relies mostly on rainwater. Our results show evidence supporting ocean water use by dune vegetation and demonstrate an exciting relationship between seawater and ecotonal shifts in plant function of a terrestrial ecosystem. PMID:16995639

Greaver, Tara L; Sternberg, Leonel L da S

2006-09-01

361

Assessing significant geomorphic changes and effectiveness of dynamic restoration in a coastal dune ecosystem  

NASA Astrophysics Data System (ADS)

A shift from restoring coastal dunes as stabilized landscapes toward more morphodynamic ecosystems is underway. This paper uses results from a recent case study where invasive vegetation was removed from a coastal dune complex in western Canada as a first step in a dynamic ecosystem restoration project. Spatial statistical methods, used in the natural sciences to quantify patterns of significant spatial-temporal changes, are reviewed and the local Moran's Ii spatial autocorrelation statistic is explored for detecting and assessing significant changes. Cluster maps of positive (depositional) and negative (erosional) changes were used to derive statistically significant volumetric changes within discrete geomorphic units (beach, foredune, transgressive dune) over one year following vegetation removal. All units experienced net increases in sediment budgets compared to a pre-restoration surface. The beach experienced the highest episodic erosion and volumetric change and greatest net annual sediment budget. Compared to the beach, the annual sediment budget of the foredune was 19% whereas the transgressive dune was 33%. The foredune recovered rapidly to initial erosion during restoration and subsequent natural events with consistently positive sediment volumes and attained a form similar to that pre-restoration. Aeolian deflation and sand bypassing through the foredune was greatest in the two months following vegetation removal and peak accretion in the transgressive dune resulted from depositional lobes extending from the foredune, smaller dunes migrating within the complex, and growth of a precipitation ridge along the eastern margin. Several methodological and logistical considerations for detecting significant change in dynamic dune landscapes are discussed including sampling strategy design, data normalization and control measures, and incorporating uncertainty and inherent spatial relations within acquired datasets to ensure accuracy and comparability of results. Generally underutilized in coastal geomorphology, spatial autocorrelation methods (e.g., local Moran's Ii) are recommended over spatially uniform threshold approaches for the ability to detect local change processes and explore hypotheses on spatial-temporal dynamics. Finally, several key geomorphic indicators, that are believed to aid in re-establishing ecological conditions and processes that favor more resilient and natural dune ecosystems, are identified for assessing the effectiveness of dynamic restoration projects including: increased aeolian activity, enlarged active sand surface area, positive sediment budgets, increased dune morphodynamics, improved geomorphic diversity, and enhanced geomorphic resilience. Although limited in temporal scope, the case study results show that the initial phase of the restoration treatment was effective in enhancing all indicators except for increasing sand surface area. Given decadal scale observations of climatic changes and longer-term eco-geomorphic trajectory toward stabilization in the region, however, it is unlikely that the geomorphic effectiveness of this restoration effort will continue without continued frequent treatment interventions.

Walker, Ian J.; Eamer, Jordan B. R.; Darke, Ian B.

2013-10-01

362

Aeolian processes in Proctor Crater on Mars: Mesoscale modeling of dune-forming winds  

NASA Astrophysics Data System (ADS)

Both atmospheric modeling and spacecraft imagery of Mars are now of sufficient quality that the two can be used in conjunction to acquire an understanding of regional- and local-scale aeolian processes on Mars. We apply a mesoscale atmospheric model adapted for use on Mars (the Mars MM5) to Proctor Crater, a 150 km diameter crater in the southern highlands. Proctor Crater contains numerous aeolian features that indicate wind direction, including a large dark dune field with reversing transverse and star dunes containing three different slipface orientations, small and older bright bedforms that are most likely transverse granule ripples, and seasonally erased dust devil tracks. Results from model runs spanning a Martian year, with a horizontal grid spacing of 10 km, predict winds aligned with two of the three dune slipfaces as well as spring and summer winds matching the dust devil track orientations. The primary (most prevalent) dune slipface orientation corresponds to a fall and winter westerly wind created by geostrophic forces. The tertiary dune slipface orientation is caused by spring and summer evening katabatic flows down the eastern rim of the crater, influencing only the eastern portion of the crater floor. The dunes are trapped in the crater because the tertiary winds, enhanced by topography, counter transport from the oppositely oriented primary winds, which may have originally carried sand into the crater. The dust devil tracks are caused by light spring and summer westerly winds during the early afternoon caused by planetary rotation. The secondary dune slipface orientation is not predicted by model results from either the Mars MM5 or the Geophysical Fluid Dynamics Laboratory Mars general circulation model. The reason for this is not clear, and the wind circulation pattern that creates this dune slipface is not well constrained. The Mars MM5 model runs do not predict stresses above the saltation threshold for dune sand of the appropriate size and composition. As with previous work, the calculated wind velocities are too low, which may be caused by too large of a grid spacing.

Fenton, Lori K.; Toigo, Anthony D.; Richardson, Mark I.

2005-06-01

363

A Dune Simulation Wind Tunnel for Studies of Lee Face Processes  

NASA Astrophysics Data System (ADS)

Sand is deposited on the lee slope of dunes by grainfall, avalanching (grainflow), and wind ripple migration. These processes play major roles in the formation of aeolian cross strata. Grainfall is produced by saltating grains that are blown over the dune crest and fall on the lee slope. Avalanching occurs when sand on the lee slope fails and the resulting grainflow will deposit tongues of sand downslope. Lee slope deposits are often preserved in the rock record and an understanding of the conditions that produce them as well as avalanche frequency and magnitude could provide important information about dune morphology, sediment flux and availability, air flow, and the environment of deposition. Despite their importance there have been very few studies of grainfall and avalanching because the lee slope of dunes is a very fragile and easily disturbed environment. Designing research strategies to study these processes presents significant technical challenges. To overcome these obstacles construction and testing of a dune simulation wind tunnel was recently completed as a joint project between the Wind Erosion Laboratory, Department of Geography, University of Guelph and the Desert Research Institute. This wind tunnel contains a small, but true-scale sand dune that is 8.5 m long, 1.2 m high, and 1 m wide and is capable of producing wind speeds of 16 m/s at 30cm above the dune crest. The wind tunnel provides an opportunity to study lee slope processes in a well-constrained environment by controlling wind speeds and direction, dune geometry and composition, and allows for extensive instrumentation and close observation of depositional processes. Preliminary experiments in the dune simulation wind tunnel indicate that avalanche frequency is predictable: increased wind speeds resulted in more frequent avalanches. Avalanches commonly originate in the mid-lee slope region at or near the point of reattachment of the return cell caused by flow separation at the crest. Downslope saltation and/or reptation on the lee slope surface appear to slow at the point of reattachment and appears to be an important factor in the location of avalanche origination. Preliminary measurements of the distribution of sediment deposited by grainfall at three different wind speeds suggest a possible depositional bulge in the mid-lee slope region. Research supported by NSF EAR-0207833

Cupp, K.; Lancaster, N.; Nickling, W. G.

2004-12-01

364

Dune Retreat and Shoreline Change on the Outer Banks, North Carolina, 1997-1998  

NASA Astrophysics Data System (ADS)

LIDAR data were collected in late September of 1997 and 1998 along a 175 km stretch of the Atlantic coast of the Outer Banks, North Carolina between Cape Lookout and Oregon Inlet. These data, available from NOAA, provide the basis for quantitative determination of the changes in beach morphology during this one-year interval. There had been no recent large storms preceding the 1997 data collection. The 1998 data were collected 4 days and 10 days after Hurricane Bonnie. Beaches east and north of Ocracoke Inlet have been stabilized and maintained since the 1930s while beaches to the south and west have been left in their natural state. We examine shoreline perpendicular profiles, taken every 20 m along the shoreline, that extend from an onshore baseline to the shoreline. Using these profiles, we determine horizontal shoreline position and, for the most seaward dune, dune height and the position and elevation of the dune base. These parameters change between 1997 and 1998 due to changes in beach morphology. For locations where the 1997 beach width was wider than approximately 20 m, there is a nonlinear relationship between the 1997 beach width and the associated maximum dune retreat. This relationship varies from south to north. Greater maximum dune retreats are found for comparable beach widths north of Ocracoke Inlet, the region where beaches have been actively maintained.

Burroughs, S. M.; Tebbens, S. F.

2005-05-01

365

Adaptation with gene flow across the landscape in a dune sunflower.  

PubMed

Isolation by adaptation increases divergence at neutral loci when natural selection against immigrants reduces the rate of gene flow between different habitats. This can occur early in the process of adaptive divergence and is a key feature of ecological speciation. Despite the ability of isolation by distance (IBD) and other forms of landscape resistance to produce similar patterns of neutral divergence within species, few studies have used landscape genetics to control for these other forces. We have studied the divergence of Helianthus petiolaris ecotypes living in active sand dunes and adjacent non-dune habitat, using landscape genetics approaches, such as circuit theory and multiple regression of distance matrices, in addition to coalescent modelling. Divergence between habitats was significant, but not strong, and was shaped by IBD. We expected that increased resistance owing to patchy and unfavourable habitat in the dunes would contribute to divergence. Instead, we found that landscape resistance models with lower resistance in the dunes performed well as predictors of genetic distances among subpopulations. Nevertheless, habitat class remained a strong predictor of genetic distance when controlling for isolation by resistance and IBD. We also measured environmental variables at each site and confirmed that specific variables, especially soil nitrogen and vegetation cover, explained a greater proportion of variance in genetic distance than did landscape or the habitat classification alone. Asymmetry in effective population sizes and numbers of migrants per generation was detected using coalescent modelling with Bayesian inference, which is consistent with incipient ecological speciation being driven by the dune habitat. PMID:22429200

Andrew, Rose L; Ostevik, Katherine L; Ebert, Daniel P; Rieseberg, Loren H

2012-03-19

366

[Spatial distribution patterns of dry sand layer on windward slope of dunes in Horqin Sand Land].  

PubMed

An observation was conducted on the thickness of dry sand layer on the windward slope of mobile and fixed dunes in west Horqin Sand Land, with the spatial distribution of the dry sand layer analyzed. Most of the dry sand layer had a thickness of 5-15 cm, and 92.0% and 98.6% of the mobile and fixed dunes had the dry sand layer with this thickness, respectively. Sand-fixing plants affected the thickness and the spatial distribution of the dry sand layer. There was an obvious spatial difference in the thickness of the dry sand layer on mobile dunes, being much thicker in the upper west areas while much thinner in the lower east areas. The thickness of the dry sand layer varied from 0 to 40 cm, with an average of 9.58 +/- 3.95 cm, and the CV was 41%. The variogram of the spatial distribution of dry sand layer on mobile dunes was expressed as spherical model, with a moderate spatial correlation. In contrast, the thickness of dry sand layer on fixed dunes showed obvious homogeneity, and had less spatial difference. The thickness of the dry sand layer ranged from 0 to 20 cm, with an average of 10.91 +/- 1.70 cm, and the CV was only 16%. PMID:22803448

Zong, Qin; Lamusa, A; Luo, Yong-Ming; Niu, Cun-Yang; Chen, Xue-Feng; Wang, Hai-Yang

2012-04-01

367

Crescent Lake Dam Project.  

National Technical Information Service (NTIS)

Though some people might consider Oregon to be less arid than the majority of western states, Washington being another notable exception, in fact all the land east of the Cascade Mountain Range in both Oregon and Washington qualifies as part of the region...

T. R. Linenberger

1999-01-01

368

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

2008-07-31

369

Multiple dust sources in the Sahara Desert: The importance of sand dunes  

NASA Astrophysics Data System (ADS)

We determine the current sources of dust in the Sahara Desert using quantitative correlation between the number of days with dust storms (NDS), derived from remote-sensing data of high temporal resolution, with the distribution of the soil types and geomorphic units. During 2006-8 the source of over 90% of the NDS was found to be sand dunes, leptosols, calcisols, arenosols, and rock debris. In contrast to previous studies, only few dust storms originated from playas and dry lake beds. Land erodibility was estimated by regressing the NDS to the number of days with high-speed wind events, and was found to be high for sand dunes. Clay and fine-silt grains and aggregates are scarce in sand dunes, which most likely produce dust particles through aeolian abrasion of sand grains. Thus, saltating sand grains impacting clay aggregates on playa surfaces cannot be the sole process for generating dust in the Sahara.

Crouvi, Onn; Schepanski, Kerstin; Amit, Rivka; Gillespie, Alan R.; Enzel, Yehouda

2012-07-01

370

The impact of Acacia saligna invasion on Italian coastal dune EC habitats.  

PubMed

Alien species can represent a threat to several ecosystems because they can alter species relationships and ecosystem function. In Italy, Acacia saligna is a major invader and it forms dense stands in coastal environments. We analyze the impact of A. saligna in Italian Mediterranean dune systems. We randomly sampled coastal dune vegetation and investigated its floristic composition with ordination techniques. We compared species richness in invaded and non-invaded plots with rarefaction curves and analyzed the frequency of focal and ruderal species. A. saligna invaded Mediterranean scrub (habitats 2250* and 2260) and coastal Pinus dune wood (habitat 2270*) and it is particularly prevalent in sunny areas of habitat 2270*. We observed an increase in ruderal species and a decrease in focal species in the invaded plots of habitat 2270*. We suggest that more open and disturbed areas are more prone to A. saligna invasion. PMID:23932256

Del Vecchio, Silvia; Acosta, Alicia; Stanisci, Angela

2013-07-17

371

The sand seas of Titan: Cassini RADAR observations of longitudinal dunes.  

PubMed

The most recent Cassini RADAR images of Titan show widespread regions (up to 1500 kilometers by 200 kilometers) of near-parallel radar-dark linear features that appear to be seas of longitudinal dunes similar to those seen in the Namib desert on Earth. The Ku-band (2.17-centimeter wavelength) images show approximately 100-meter ridges consistent with duneforms and reveal flow interactions with underlying hills. The distribution and orientation of the dunes support a model of fluctuating surface winds of approximately 0.5 meter per second resulting from the combination of an eastward flow with a variable tidal wind. The existence of dunes also requires geological processes that create sand-sized (100- to 300-micrometer) particulates and a lack of persistent equatorial surface liquids to act as sand traps. PMID:16675695

Lorenz, R D; Wall, S; Radebaugh, J; Boubin, G; Reffet, E; Janssen, M; Stofan, E; Lopes, R; Kirk, R; Elachi, C; Lunine, J; Mitchell, K; Paganelli, F; Soderblom, L; Wood, C; Wye, L; Zebker, H; Anderson, Y; Ostro, S; Allison, M; Boehmer, R; Callahan, P; Encrenaz, P; Ori, G G; Francescetti, G; Gim, Y; Hamilton, G; Hensley, S; Johnson, W; Kelleher, K; Muhleman, D; Picardi, G; Posa, F; Roth, L; Seu, R; Shaffer, S; Stiles, B; Vetrella, S; Flamini, E; West, R

2006-05-01

372

Impact of atmospheric circulation patterns on coastal dune dynamics, NW Spain  

NASA Astrophysics Data System (ADS)

Dunes in temperate latitudes have experienced a significant stabilization in recent times, essentially as a consequence of the expansion of dense vegetation cover. Yet, the causes for this gradual stabilization as well as the causes promoting antecedent aeolian mobilization remain poorly understood. The Traba coastal dune field, located in NW Spain, was examined to explore the causes inducing aeolian activity and subsequent stabilization since 1940. Morphological changes were identified through the combination of aerial photographs and geophysical techniques. Local wind field regimes were simulated using a regional climate model to obtain the variability of the most relevant modes of atmospheric circulation in the North Atlantic and European regions; North Atlantic Oscillation (NAO), Eastern Atlantic (EA) and Scandinavian (SCAND). This allows us to identify the impact of these circulation modes over dune dynamics. Results document an episode of aeolian activity during the 1950s followed by a gradual stabilization and fixation of the dune coincident with a decrease on storm and wind intensity. Yet, aeolian sand movement remained active in small areas (blowouts), occurring mainly during the summer. NE winds associated with a negative phase of the EA explain the movement of sand within the dune field under favorable conditions of sand supply. On the other hand, sand supply to the dune field from the beach was promoted by NW winds coincident with the summer negative phase of NAO. During winter, the negative NAO favored frequent SW winds associated with the passage of intense storms, which in turn explain sand remobilization from the beach making sediment available for the NW winds to blow inland. With this work, it is proven that to understand past and future aeolian activity requires critical consideration of the variability and impact of the two principal modes of atmospheric circulation in the North Atlantic (NAO and EA). The SCAND mode explaining a lower percentage of the local wind field variability was also included to achieve higher significance levels of explained variance.

González-Villanueva, R.; Costas, S.; Pérez-Arlucea, M.; Jerez, S.; Trigo, R. M.

2013-03-01

373

The Fate of Threatened Coastal Dune Habitats in Italy under Climate Change Scenarios  

PubMed Central

Coastal dunes worldwide harbor threatened habitats characterized by high diversity in terms of plant communities. In Italy, recent assessments have highlighted the insufficient state of conservation of these habitats as defined by the EU Habitats Directive. The effects of predicted climate change could have dramatic consequences for coastal environments in the near future. An assessment of the efficacy of protection measures under climate change is thus a priority. Here, we have developed environmental envelope models for the most widespread dune habitats in Italy, following two complementary approaches: an “indirect” plant-species-based one and a simple “direct” one. We analyzed how habitats distribution will be altered under the effects of two climate change scenarios and evaluated if the current Italian network of protected areas will be effective in the future after distribution shifts. While modeling dune habitats with the “direct” approach was unsatisfactory, “indirect” models had a good predictive performance, highlighting the importance of using species’ responses to climate change for modeling these habitats. The results showed that habitats closer to the sea may even increase their geographical distribution in the near future. The transition dune habitat is projected to remain stable, although mobile and fixed dune habitats are projected to lose most of their actual geographical distribution, the latter being more sensitive to climate change effects. Gap analysis highlighted that the habitats’ distribution is currently adequately covered by protected areas, achieving the conservation target. However, according to predictions, protection level for mobile and fixed dune habitats is predicted to drop drastically under the climate change scenarios which we examined. Our results provide useful insights for setting management priorities and better addressing conservation efforts to preserve these threatened habitats in future.

Prisco, Irene; Carboni, Marta; Acosta, Alicia T. R.

2013-01-01

374

Cryptobiotic crusts of a seasonally inundated Dune–Pan system at Edwards Air Force Base, Western Mojave Desert, California  

Microsoft Academic Search

Cryptobiotic crusts are a dominant component of an area of dunes and pans situated on Pleistocene Lake Thompson bed at Edwards Air Force Base (EAFB), California. Crusts cover about 50% of the surface area; upland crusts cover 80% of the dunes, aquatic remnant crusts cover about 20% of the pans. The biomass of the crusts is about twice the maximum

William N. Brostoff

2002-01-01

375

Quantifying off-highway vehicle impacts on density and survival of a threatened dune-endemic plant  

Microsoft Academic Search

Off-highway vehicle (OHV) recreation impacts species and ecosystems around the world, and is particularly prevalent in the United States. Our study examines the impact of OHVs on one of several species restricted within the United States to the Algodones Dunes, California. This dune system attracts many OHV enthusiasts annually, and interest in determining the impact of OHVs on Astragalus magdalenae

Jeremiah D. Groom; Lloyd B. McKinney; Lianne C. Ball; Clark S. Winchell

2007-01-01

376

Quantifying roughness density of vegetation and nebkha dunes in the Chihuahuan Desert, New Mexico, USA using terrestrial laser scanning  

NASA Astrophysics Data System (ADS)

The roughness density and patterning of vegetation and nebkha dune elements in semi-arid environments has important implications for aeolian sediment transport. These individual elements often form complex spatial patterns, which are traditionally quantified as a single density or lambda value based on mean shrub height, breath and number of elements within a defined surface area. Measurements of height and width are undertaken using traditional surveying techniques or based on remote sensing imagery analysis, which are limited in their ability to capture the true frontal area of vegetation and dune elements, as well as the relationship between solid and flexible frontal area components. Here we use terrestrial laser scanning (TLS) to quantify three-dimensional plant and dune distributions, determining height and width values for individual elements in three different vegetation communities at the Jornada Experimental Range in the Chihuahuan Desert, New Mexico, USA. These communities include a creosote vegetated surface without dunes, an incipient mesquite nebkha dune environment and a mature mesquite nebkha dune site. TLS measurements compare well to manual measurements using DGPS and survey levels, but have the advantage that larger areas can be systematically quantified more efficiently. More importantly, TLS derived surface, dune and vegetation DEMs enable us to accurately characterise individual dune and shrub frontal areas under different wind directions, improving traditional lambda calculations.

Nield, J. M.; Gillies, J. A.; Nickling, W. G.

2012-04-01

377

LONG-DISTANCE WANDERING AND MATING BY THE DANCING WHITE LADY SPIDER (LEUCORCHESTRIS ARENICOLA) (ARANEAE, SPARASSIDAE) ACROSS NAMIB DUNES  

Microsoft Academic Search

Adult males of the Dancing White Lady Spider (Leucorchestris arenicola, Araneae, Spar- assidae) occurring in the dunes of the Namib Desert, Namibia, frequently wander far out of their 3m radius territories on dark nights. They move across bare dune slopes in search of mating opportunities and subsequently return to their burrows. In the current study, I describe the long-distance movements

Joh R. Henschel

2002-01-01

378

Changes in area of grasslands on the dunes between richards bay and the mfolozi river, 1937 to 1974  

Microsoft Academic Search

Grasslands on the dunes between Richards Bay and the Mfolozi river have diminished rapidly during the last 34 years (1937 : 2 829 ha, 32%; 1974 : 399 ha, 4,8% of study area). They have been replaced by Acacia karroo Woodland, Secondary Dune Scrub and plantations of Eucalyptus spp. and Pinus spp. The changes are due to measures adopted by

P. J. Weisser

1978-01-01

379

To live or to survive in Doñana dunes: Adaptive responses of woody species under a Mediterranean climate  

Microsoft Academic Search

The Dune System of Doñana National Park (SW Spain) exhibit a mosaic of environmental characteristics, with different plant communities, all under the same Mediterranean climate, creating an interesting field laboratory for the study of plant responses to stressing conditions. Fourteen woody plant populations were selected, belonging to either xerophytic or hygrophytic plant communities on stabilised dunes, where topography causes differences

M. Zunzunegui; M. C. Díaz Barradas; F. Ain-Lhout; A. Clavijo; F. García Novo

2005-01-01

380

The Holocene History of the White Sands Dune Field and the influences of Climate on Eolian Deflation and Playa Lakes  

NASA Astrophysics Data System (ADS)

White Sands National Monument is the largest gypsum dune field in the world. The dunes have formed downwind of a 20-m-deep, 19-km-wide deflation basin containing large playa lakes. Today, the gypsum sand is derived from the edge of the deflation basin, next to the dune field, rather than the alkali flat and playa lakes where gypsum crystals are forming. Three erosional shorelines mark wetter episodes when playa lakes formed in the deflation basin. The youngest shoreline is forming today around Lake Lucero playa. The oldest shoreline, termed L1 is degraded and probably formed at the Pleistocene-Holocene transition. Deflation from the L1 to the L2 shoreline cut through Pleistocene bedded evaporites and probably marks initiation of the dune field. This event was before 5,840 years BP, based on radiocarbon in a lake dammed by the dunes. This reinforces an evolving consensus that episodes of deflation have characterized desert basins in the southwestern United States. Regional deflation events have been dated at 7,000 years and 4,000 years BP. The shorelines in the deflation basin imply that the White Sands dune field was created in short episodes and the modern dune field may not represent conditions active during expansion of the dune sea. >http://www.geo.utep.edu/Faculty_Staff/langford.html

Langford, R. P.

2001-12-01

381

Grain size, mineralogical and geochemical studies of coastal and inland dune sands from El Vizcaíno Desert, Baja California Peninsula, Mexico  

Microsoft Academic Search

A sedimentological, petrological and geochemical research work was carried out in order to fi nd out the origin and provenance of coastal and inland desert dunes from El Vizcaíno Desert, northwestern Mexico. Fifty four sand samples were collected from the windward, crest and slip face of coastal and desert dunes (barchan, transverse, aeolian sand sheets). Onshore winds generates fi ne,

Juan José Kasper-Zubillaga; Hugo Zolezzi-Ruiz

2007-01-01

382

Denivation Features of Polar Dunes: An Earth Analogue for Morphological Indicators of Solid Water on Mars  

NASA Astrophysics Data System (ADS)

The identification of sources of water on Mars will be critical to the successful exploration of the planet and the establishment of a permanent presence by humans. While the Martian polar ice caps contain up to 70% water by mass, the extreme climate of these regions means that they may not be suitable for habitation. As a result, other sites must be identified where access to water is possible. Recent evidence has emerged that suggests sand dunes on Mars may contain 40-50% water by mass (Bourke 2005). In this paper, we present niveo-aeolian features observed in the sand dunes of the Victoria Valley, Antarctica, which have long been considered an Earth analogue for those on Mars (Morris et al. 1972). These features include cornices of permafrosted sand in dune-crest deflation hollows, exposed erosion resistant frozen water and sand lenses, wet sand flows and seeps. We also report on the morphological characteristics of sand sink holes which form in chains above layers of buried, melting and/or sublimating snow. This process is apparently reliant on the melting of inter-grain ice bonds and subsequent formation of a dry mobile sand layer on the dune surface. These micro-morphological features associated with summertime denivation of the Victoria Valley sand dunes, which are 5 to 10 m high and several hundred meters in crest length, are too small to identify on air photographs, satellite imagery and LIDAR DEMS of these transverse barchanoid ridges. However, on Mars where sand dunes are 1 to 2 orders of magnitude larger, these features may be identifiable if solid water exists within them, as suggested by Bourke (2005). Perhaps of greater importance, they may indicate the presence of buried palaeo-snow layers which have been preserved beneath the erosion resistant permafrosted sand dunes on Mars. We believe that the formation and subsequent exposure of these snow layers is the primary cause of the denivation features present in the polar dunes of the Victoria Valley, Antarctica. References: Bourke, M.C. 2005: Water on Mars. The Halstead Lecture, British Association for the Advancement of Science, Trinity College, Dublin, September 2005. Morris, E.C., Mutch, T.A. and Holt, H.E. 1972: Atlas of geologic features in the Dry Valleys of South Victoria Land, Antarctica: Possible analogs of Martian surface features. Interagency report: Astrogeology 52. Prepared under NASA contract L-9718 by the Geological Survey.

McGowan, H. A.; Neil, D.

2005-12-01

383

Stratigraphy of Back-Barrier Coastal Dunes, Northern North Carolina and Southern Virginia  

Microsoft Academic Search

HAVHOLM, K.G.; AMES, D.V.; WHITTECAR, G.R.; WENELL, B.A.; RIGGS, S.R.; JOL, H.M.; BERGER, G.W., and HOLMES, M.A., 2004. Stratigraphy of back-barrier coastal dunes, northern North Carolina and southern Virginia. Journal of Coastal Research, 20(4), 980-999. West Palm Beach (Florida). ISSN 0749-0208. Ground penetrating radar studies of four representative active back-barrier dunes, combined with radiocarbon and photon-stimulated-luminescence dating techniques and soils

K. G. Havholm; D. V. Ames; G. R. Whittecar; B. A. Wenell; S. R. Riggs; H. M. Jol; G. W. Berger; M. A. Holmes

2004-01-01

384

Heterogeneity in Mantle Sources for Eocene Basalts in Washington: Trace Element and Sr-Nd Isotopic Evidence from the Crescent and Teanaway Basalts  

NASA Astrophysics Data System (ADS)

Two roughly contemporaneous episodes of voluminous, dominantly basaltic magmatism occurred in Washington State during the Eocene. The more westward episode, represented by the ~53-45 Ma Crescent Formation, consists of up to 20 km of submarine and subaerial basalts erupted in rift basins along the continental margin. The more eastward episode, represented by the ~47 Ma Teanaway Group, comprises a dike swarm and associated eruptive rocks that are of uncertain tectonic affinity. In this study we present trace element and isotopic data to characterize the mantle sources of these rocks and attempt to discern factors responsible for differences between these sources. Crescent basalts (La/YbN = 1.34-4.02; avg. Zr/Hf = 35.6±1.3) and Teanaway basalts (La/YbN = 1.10-3.83; avg. Zr/Hf = 35.8±2.2) have similar REE patterns and immobile TE ratios. However, the Teanaway samples show greater enrichment in incompatible trace elements (Cs>Pb>Ba>Rb~Th>U>Yb>Y>Zr~Hf) and on spidergrams display subduction signatures (e.g., HFSE depletions) not seen in the Crescent data. Teanaway samples also have more evolved isotopic compositions (?Nd = +4.4 to +1.1; 87Sr/86Sri = 0.704132 to 0.707093) than Crescent samples (?Nd = +7.2 to +5.3; 87Sr/86Sri = 0.703110 to 0.704616 but Sr ratios > 0.7040 probably reflect seawater alteration or disturbance associated with low grade metamorphism). On a Sr-Nd isotopic diagram the Teanaway samples deviate from the mantle array, defining a trend toward higher 87Sr/86Sr with minimal variation in ?Nd. The trajectory of this trend suggests involvement of an end member that is distinct from the "crustal component" in other Tertiary igneous rocks from the region. In addition, the highest 87Sr/86Sr Teanaway sample is also the most primitive (highest Mg#, Ni, Sr), which argues against an origin involving simple progressive crustal contamination. We suggest instead that the more evolved isotopic character of the Teanaway basalts (as well as their TE enrichments) reflects derivation from mantle that had been metasomatized during earlier episodes of subduction. Four Teanaway dikes from the eastern side of the swarm define a 170 Ma Rb-Sr isochron, which if not an artifact of mixing, implies that the history of mantle modification in this region extends back to the Mesozoic. The Crescent basalts, having formed outboard of the subduction zone, may provide insight into the nature of the mantle prior to such metasomatism.

Tepper, J. H.; Nelson, B. K.; Clark, K.; Barnes, R. P.

2008-12-01

385

Spatial heterogeneity of soil properties and vegetation–soil relationships following vegetation restoration of mobile dunes in Horqin Sandy Land, Northern China  

Microsoft Academic Search

Quantitative methods were used to examine soil properties and their spatial heterogeneity in a 0-year fenced mobile dune (MD0),\\u000a an 11-year fenced mobile dune (MD11) and a 20-year fenced mobile dune (MD20) in Horqin Sandy Land, Northern China. The objective\\u000a of the study was to assess the effect of vegetation restoration on heterogeneity of soil properties in sand dunes and

Xiaoan Zuo; Xueyong Zhao; Halin Zhao; Tonghui Zhang; Yirui Guo; Yuqiang Li; Yingxin Huang

2009-01-01

386

Diversity of arbuscular mycorrhizal fungi along a sand dune stabilization gradient: A case study at Praia da Joaquina, Ilha de Santa Catarina, South Brazil  

Microsoft Academic Search

Species diversity of arbuscular mycorrhizal fungi (AMF) was assessed along a dune stabilization gradient (embryonic dune,\\u000a foredune and fixed dune) at Praia da Joaquina, Ilha de Santa Catarina. The dunes were chosen as a case study to assess whether\\u000a diversity and mycorrhizal inoculum potential (MIP) increase along the gradient. Ten soil samples were collected from each\\u000a stage and pooled, and

Analia S. Cordoba; Margarida M. de Mendonça; Sidney L. Stürmer; Paul T. Rygiewicz

2001-01-01

387

Activation history of the Hutchinson dunes in east-central Kansas, USA during the past 2200 years  

NASA Astrophysics Data System (ADS)

This paper presents data for the Hutchinson dunes, the third and southernmost of three dunefields that collectively span a 400 km north-south transect of the eastern Great Plains. Optically stimulated luminescence dating was used to create a new, high temporal- and spatial-resolution chronology of dunefield activity, which spans the last 2200 years. Ages indicate that three major episodes of dune activity occurred ˜2100-1800, ˜1000-900, and after ˜600 years ago, especially within the past 420-70 years. Dune activity ˜1000-900 years ago correlates to the height of the Medieval Climatic Anomaly. Widespread dune activity during the past 600 years, which peaked ˜320 and ˜200 years ago, correlates with the coolest periods of the Little Ice Age. Dune activity in the Hutchinson dunes during the Medieval Climatic Anomaly correlates well with available proxy data and dune records from the region, including other eastern-margin dunefields, and suggests that one or more severe droughts were occurring throughout most of the Great Plains at this time. Dune activity during the Little Ice Age, unlike that of the Medieval Climatic Anomaly, does not correlate with other eastern margin dunefields, but does with those in western Kansas, Colorado, Oklahoma, and Texas and with other regional proxies. This pattern suggests that Little Ice Age droughts, unlike those associated with the Medieval Climatic Anomaly, were less intense and/orgeographically limited. Little Ice Age droughts, though, were still significant as evidenced by the migration of large dune forms in the Hutchinson dunes at this time.

Halfen, Alan F.; Johnson, William C.; Hanson, Paul R.; Woodburn, Terri L.; Young, Aaron R.; Ludvigson, Gregory A.

2012-08-01

388

A wind tunnel simulation of the effects of stoss slope on the lee airflow pattern over a two-dimensional transverse dune  

Microsoft Academic Search

Secondary airflow plays an important role in dune formation and development. The lee airflow pattern over transverse dunes is important in determining the shape, alignment, and spacing of dunes and is influenced significantly by the lee slope angle. In this paper we present the results of scaled wind tunnel simulations of the effects of stoss slope on the mean lee

Zhibao Dong; Guangqiang Qian; Wanyin Luo; Hongtao Wang

2007-01-01

389

Aeolian sand as a tool for understanding Mars: Thermal infrared remote sensing of volcaniclastic Mars-analog sand dunes in Christmas Lake Valley, Oregon, U.S.A  

Microsoft Academic Search

INTRODUCTION: On Earth, aeolian sand dunes are used as tools of scientific inquiry. Holocene and Pleistocene dunes preserve clues about Quaternary climate variations and human activities ranging from Ice Age hunting practices to Twentieth Century warfare. Modern dunes contain the sedimentary textures and structures necessary for interpreting ancient sandstones, and they provide natural laboratories for investigation of aeolian physics and

Kenneth S. Edgett

1996-01-01

390

Vegetation changes associated with barrier-dune construction on the outer banks of North Carolina  

Microsoft Academic Search

Manmade dunes are used to stabilize the barrier islands of the mid-Atlantic coast of the United States so that they are more amenable to development. Although this strategy has stabilized extensive sections of the barrier-island substrate, it has also caused significant ecological changes. The rate and pattern of the resulting vegetation changes along the Outer Banks of North Carolina were

P. Michael Schroeder; Robert Dolan; Bruce P. Hayden

1977-01-01

391

Barrier Dune System along the Outer Banks of North Carolina: A Reappraisal.  

PubMed

Barrier dune development has been encouraged by man along the Outer Banks of North Carolina to stabilize the barrier islands. This modification of a delicately balanced natural system is leading to severe adjustments in both geological and ecological processes. PMID:17791917

Dolan, R

1972-04-21

392

The physicochemistry of some dune ponds on the Outer Banks, North Carolina  

Microsoft Academic Search

A survey of the chemical composition of five coastal dune ponds on the Outer Banks, North Carolina, showed the ponds to be more similar to underlying groundwater than to dilute seawater or average river water. With a mean total ionic content of 3.14 mmol l?1 the ponds were decidedly fresh. Variations in chemistry between the ponds resulted from physiographic association

George W. Kling

1986-01-01

393

Dune Retreat and Shoreline Change on the Outer Banks of North Carolina  

Microsoft Academic Search

Barrier islands are popular recreational areas of economic importance that are constantly changing. Costly efforts are made to maintain beaches and stabilize dunes within this dynamic environment. We examine one year of coastal change along the barrier islands of the North Carolina Outer Banks. LIDAR data collected in September of 1997 and 1998 along a 175 km stretch of the

S. M. Burroughs; S. F. Tebbens

2005-01-01

394

Holocene storm surge signatures in the coastal dunes of the western Netherlands  

Microsoft Academic Search

On five different sites along the central Netherlands' coast one or more sequences of shell deposits in the dunes have been observed. They are believed to be the result of storm surge activity on the foreshore, either through swash or overwash action, and of subsequent preservation due to aeolian coverage of a basically sedimentary coastal system. Through their stratigraphical positions

S. Jelgersma; M. J. F. Stive; L. van der Valk

1995-01-01

395

A 45-year time series of dune mobility indicating constant windiness over the central Sahara  

NASA Astrophysics Data System (ADS)

Although evidence is mounting that links global warming to changes in atmospheric dynamics over the Atlantic realm, similar studies over the African continent are lacking. And even if such models would exist, it would be difficult to verify their validity due to the paucity of meteorological observations and anemometers in the central Sahara. A pragmatic way around this problem is to monitor barchan dune velocity as a proxy for the windiness of desert areas. Dune migration rates are a measure of the amount of work done by the wind which does not require field measurements but can be observed from space instead. This paper presents a novel application of the remote sensing tool COSI-Corr for the construction of time series of dune mobility from sequences of optical satellite imagery. The technique has been applied to the Bodélé Depression in northern Chad, to demonstrate that dune migration rates in the central Sahara have been remarkably constant for nearly half a century, leading us to conclude that wind velocities have not changed more than 0.2% per year over that period. It is therefore unlikely that the frequency and intensity of dust storms originating from this ‘hot spot’ has significantly changed over the past decades either.

Vermeesch, P.; Leprince, S.

2012-07-01

396

Soil seed banks, habitat heterogeneity, and regeneration strategies in a Mediterranean coastal sand dune  

Microsoft Academic Search

This study investigated the effects of microhabitat characteristics on soil seed bank structure, regeneration strategies, and plant composition in a Mediterranean coastal sand dune in Israel. Three different microhabitats were selected: (a) open patches between shrubs, (b) shrub understorey, and (c) open, disturbed patches in pedestrian trails. In each microhabitat two types of sampling plots were established: (a) seed- ling

MARCELO STERNBERG; SHUNLI L. YU

2004-01-01

397

Establishment of woody plants for secondary and tertiary dune stabilization along the mid-Atlantic coast  

Microsoft Academic Search

Secondary and tertiary sand dunes along the Atlantic coast were originally covered with dense vegetation, including trees and shrubs. Most of this vegetation has been destroyed by various forms of development. The objective of this study was to evaluate the effects of various establishment techniques on the survival and growth of native and naturalized woody plants for secondary and tertiary

W. C. Sharp; V. B. Hawk

1977-01-01

398

Soil water and temperature patterns in an arid desert dune sand  

Microsoft Academic Search

Under arid natural conditions, soil water content governs and limits the number and size of perennial plant species. Thus, plant-available soil water is the main constraint for sustainable control of desert encroachment. To evaluate possibilities for re-vegetation of bare sand surfaces, soil water and temperature patterns for typical sand dunes in a desert climate were investigated. Bare and vegetated soil

Ronny Berndtsson; Kanichi Nodomi; Hiroshi Yasuda; Thomas Persson; Heshen Chen; Kenji Jinno

1996-01-01

399

Spatial characterization, resolution, and volumetric change of coastal dunes using airborne LIDAR: Cape Hatteras, North Carolina  

Microsoft Academic Search

The technological advancement in topographic mapping known as airborne Light Detection and Ranging (LIDAR) allows researchers to gather highly accurate and densely sampled coastal elevation data at a rapid rate. The problem is to determine the optimal resolutions at which to represent coastal dunes for volumetric change analysis. This study uses digital elevation models (DEM) generated from LIDAR data and

Jason W. Woolard; Jeffrey D. Colby

2002-01-01

400

Climate-driven changes in tropical cyclone intensity shape dune activity on Earth's largest sand island  

Microsoft Academic Search

I use historical aerial photos and detailed climatic time series to show the geomorphological consequences of a dramatic decrease in tropical cyclone frequency and intensity in eastern Australia since the early 1980s, leading to rapid dune stabilization on the Earth's largest sand island and a World Heritage Site, Fraser Island, Australia. Climate warming is generally expected to increase the intensity

Noam Levin

2010-01-01

401

ETUDE D'UNE COUTUME EN SOMALIE LA CIRCONCISION ET L'INFIBULATION DES FILLES  

Microsoft Academic Search

RESUME La circoncision et l'infi bu l ation des femmes est une p ratique courante dans plusieurs pays africains. Les a u t e u rs rap p o rtent les résultats d'une enquête menée auprès de la population locale somalienne lors de leur participation dans l'opération \\

BEN FREDJ

1995-01-01

402

Application of the ERICA Integrated Approach to the Drigg coastal sand dunes.  

PubMed

The EC-funded project 'Environmental Risks from Ionising Contaminants: Assessment and Management' (ERICA) developed an 'Integrated Approach' for assessing the impact of ionising radiation on ecosystems. This paper presents the application of the ERICA Integrated Approach, supported by a software programme (the ERICA Tool) and guidance documentation, to an assessment of the Drigg coastal sand dunes (Cumbria, UK). Targeted sampling provided site-specific data for sand dune biota, including amphibians and reptiles. Radionuclides reported included (90)Sr, (99)Tc, (137)Cs, (238)Pu, (239+240)Pu and (241)Am. Site-specific data were compared to predictions derived using the ERICA Tool. Some under- and over-predictions of biota activity concentrations were identified but can be explained by the specific ecological characteristics and contamination mechanism of the dunes. Overall, the results indicated no significant impact of ionising radiation on the sand dune biota and the Integrated Approach was found to be a flexible and effective means of conducting a radiation impact assessment. PMID:18450343

Wood, M D; Marshall, W A; Beresford, N A; Jones, S R; Howard, B J; Copplestone, D; Leah, R T

2008-05-01

403

Factors influencing seed germination of Cyperus capitatus, inhabiting the moving sand dunes in southern Europe  

Microsoft Academic Search

Cyperus capitatus Vandelli (Cyperaceae) is distributed in coastal sandy habitats and mobile dunes of south Europe. Its seed germination ecology is not known, despite its potential to be used in re-vegetation projects. Laboratory experiments were conduced to assess the effects of salinity, light regime, cold stratification and burial on seed germination of this species. Overall, increasing salinity delayed germination, increased

S. Redondo-Gómez; L. Andrades-Moreno; R. Parra; E. Mateos-Naranjo; A. M. Sánchez-Lafuente

2011-01-01

404

Habitat use of ponies and cattle foraging together in a coastal dune area  

Microsoft Academic Search

Grazing by large ungulates has been chosen as a management tool in scrub-dominated dune reserves at the Belgian coast. Due to morphological and physiological differences between cattle and ponies, differences in foraging behaviour and habitat use are expected, and these may result in a different impact on the spatially heterogeneous and nutrient-limited ecosystem. Grazing behaviour and habitat use of Shetland

Indra Lamoot; Carolien Meert; Maurice Hoffmann

2005-01-01

405

Association of arbuscular mycorrhizal fungi with plants of coastal sand dunes of west coast of India  

Microsoft Academic Search

An inventory of arbuscular mycorrhizal (AM) fungal status of 28 plant species belonging to 14 families established on the coastal sand dunes of southwest coast of India was performed. Roots of 23 plant species were colonized by AM fungi, whereas the rhizosphere of only 20 plant species possessed AM fungal spores. Canavalia cathartica had the highest root colonization (83%) by

K. R. BEENA; A. B. ARUN; N. S. RAVIRAJA; K. R. SRIDHAR

406

Do season and habitat influence the behaviour of Haflin- ger mares in a coastal dune area?  

Microsoft Academic Search

This study was performed to gain more knowledge about the behaviour and habitat use of Haflinger mares, free-ranging in a low-productivity dune area. Detailed data on these animals' time budgets were collected over a full year, through the focal animal observation technique. On average the Haflinger horses spent 68 % of the daytime grazing, 18 % resting and 8 %

Indra Lamoot; Maurice Hoffmann

2004-01-01

407

The Enigmatic Longevity of Granular Materials on Mars: The Case for Geologically Episodic Dune Formation  

Microsoft Academic Search

Martian sand dunes are concentrated in vast sand seas in the circumpolar belt of the planet's northern hemisphere, but they are also pervasive over the whole planet. Their occurrence is to be expected on a super-arid planetary surface subjected to boundary layer drag from a continually active atmosphere. Whilst their occurrence is to be expected, their survival is enigmatic. But

J. Marshall

1999-01-01

408

Enhancing the Internationalisation of Distance Education in the Biological Sciences: The DUNE Project and Genetic Engineering.  

ERIC Educational Resources Information Center

Describes the Distance Educational Network of Europe (DUNE) project that aims at enhancing the development of distance education in an international context. Highlights issues relating to the delivery of distance-learning courses in a transnational forum. Describes the genetic engineering course that aims at explaining the core techniques of…

Leach, C. K.; And Others

1997-01-01

409

Abiotic conditions and plant cover differentially affect microbial biomass and community composition on dune gradients  

Microsoft Academic Search

Dune systems are characterized by strong gradients of physical stress, with blowing sand and salt spray decreasing with distance from the ocean, and soil nutrients increasing. In this study we ask how soil microbial community composition and biomass change along transects away from the ocean, and whether these changes are regulated by abiotic stress or by resource availability. We collected

T. K. Rajaniemi; V. J. Allison

2009-01-01

410

The Lumbricidae of a dune-machair soil gradient in Tiree, Argyll  

Microsoft Academic Search

1. 1. The geographical and ecological distribution of the Lumbricidae in the Hebrides has already been described in broad terms. Here the distribution in a particular dune-machair system is described in detail.2. 2. The survey area at the Reef (near Baugh), Tiree is described, and the main ecological discontinuities outlined. The six sampling stations of a transect from the shore

J. Morton Boyd

1957-01-01

411

LASIUS PSAMMOPHILUS SEIFERT AND FORMICA CINEREA MAYR (HYMENOPTERA: FORMICIDAE) ON SAND DUNES: CONFLICTS AND COEXISTENCE  

Microsoft Academic Search

Lasius psammophilus Seifert and Formica cinerea Mayr can both be found on sand dunes in high densities. Sometimes they even nest in each other's immediate neigh- bourhood, which implies the possibility of conflicts, and the existence of mechanisms for avoiding contest competiti