Morphologic characteristics and migration rate assessment of barchan dunes in the Southeastern Western Desert of Egypt

Geomorphology ◽  
2016 ◽  
Vol 257 ◽  
pp. 57-74 ◽  
Author(s):  
M.A. Hamdan ◽  
A.A. Refaat ◽  
M. Abdel Wahed
Keyword(s):  
Migration Rate ◽  
Western Desert ◽  
Morphologic Characteristics ◽  
Barchan Dunes ◽  
And Migration

Geomorphology and wind regime of barchans in the Lut Desert (Iran)

2020 ◽  
Author(s):  
Alireza Salehipour Milani ◽  
Nilofar Barkhordari ◽  
Samaneh Shabani ◽  
Ali Mohammadi
Keyword(s):  
Migration Rate ◽  
High Energy ◽  
Morphometric Parameters ◽  
Wind Regime ◽  
The World ◽  
Direction Of Movement ◽  
Length Width ◽  
Barchan Dunes ◽  
And Migration ◽  
Lut Desert

The present research was conducted to determine the morphometry, morphology, and temporal and spatialbehavior of individual barchans in the Lut Desert in Iran. This region is one of the driest places in the world andthere is a little information about the geomorphology of this region, especially on the barchans. Therefore, herein,a total of 391 individual barchan dunes were selected and their morphometric parameters were compared withrespect to the length/width (a/c) ratios (extraordinarily slim to fat barchans), migration rate, direction of movementand influence of wind regime on this landform. The results showed big difference in the morphology, morphometry,and direction and migration rate of barchans between the western and eastern parts of the Lut Desert. The meanmigration rate was about 5.17 m/yr in the study area and ranged between 1.1 and 15.35 m/yr. The annual sand driftpotential was equal to 1053.9 VU in the western part and 803.6VU in the eastern part of the Lut Desert and it wasclassified as high-energy wind environment. The NNW direction (620 VU) in the west as well as the SSW direction(100 VU) had a high effect on the movement of barchans. Their direction of movement ranged from northwest tosoutheast in the western part and from southwest to northeast in the eastern part, which were correlated with thedominant wind directions in these regions. Results of measuring the morphometric parameters of the barchansindicated that mean length, width, height, and maximum length of barchans were equal to 114.5, 179.5, 10.47, and590.2 m, respectively which are relatively high in comparison with data for other barchans studied in some previousresearches in the world. The shape of barchans was classified into slim, normal, pudgy, or fat and extraordinarilyslim. Most of them were slim (166 barchans, 42.5%) and their distribution differed between the eastern and westernparts of the Lut Desert. This can be attributed to local physical situations and wind direction properties.

scholarly journals RS CVn STARS: Photospheric Phenomena and Rotation

1983 ◽  
Vol 71 ◽  
pp. 343-361
Author(s):  
S. Catalano
Keyword(s):  
Migration Rate ◽  
Orbital Motion ◽  
Rotation Period ◽  
Maximum Amplitude ◽  
Activity Level ◽  
Period 2 ◽  
Rs Cvn Stars ◽  
Activity Cycles ◽  
And Migration ◽  
Wave Migration

ABSTRACTThis review presents a summary of observed photospheric phenomena on RS CVn stars: the amplitude, shape, evolution and migration rate of the photometric wave in relation to the rotational and orbital motion.The main points considered are: 1) the activity level (maximum amplitude, short and long timescale variability) versus rotation period; 2) the activity cycles as inferred from changes in the wave migration rate and direction and from the variation of its amplitude; 3) the detection of differential rotation; 4) the connection between the orbital period variation and activity.

Coherency Strain Energy in any Crystal System: Applications to in Situ Observations of Cigm in Calcite

1990 ◽  
Vol 205 ◽  
Author(s):  
R.S. May ◽  
B. Evans
Keyword(s):  
Driving Force ◽  
Migration Rate ◽  
Strain Energy ◽  
Solute Concentration ◽  
Coherency Strain ◽  
Solute Diffusion ◽  
Boundary Orientation ◽  
In Situ Observations ◽  
And Migration

AbstractIn situ observations of CIGM in CaCO3 bicrystals with a SrCO3 solute source were made. The change in boundary orientation and migration rate were compared with solute concentration. The liquid film model for coherency strain Induced migration was generalized to any non-cubic system and applied to CaCO3-SrCO3. The coherent layer was modeled as a thin film on an infinite half-space. The strain energy was found from solution of the Hooke's law expressions transformed to the appropriate coordinate system. For triclinic or monoclinic films the strain tensor was found by an eigenvector decomposition of the transformation matrix that defined the lattice parameter change with composition. High anisotropy of Vegard's law constants for CaCO3-SrCO3 caused (111) to have the lowest coherency strain per unit solute. Surfaces perpendicular to (111) in coherent equilibria were predicted to have half the solute concentration and three times the migration driving force of those perpendicular to (111). However, no correlation between solute concentration and boundary orientation was observed. Ambiguous and contradictory evidence for a relationship between solute concentration, boundary orientation, and migration rate was found. The self-stress state of a grain boundary in a solute diffusion field may be better modelled as hydrostatic rather than plane stress. Hydrostatic compression may interact with the boundary excess volume and cause a PV driving force for migration. Predictions based on coherent equilibrium at a surface have not been tested for that geometry in calcite; they should be tested before they are applied to grain boundaries.

EUS-guided gold fiducial placement and migration rate

2014 ◽  
Vol 80 (3) ◽  
pp. 533-534 ◽  
Author(s):  
Lorenzo Fuccio ◽  
Gabriele Lami ◽  
Alessandra Guido ◽  
Carlo Fabbri
Keyword(s):  
Migration Rate ◽  
And Migration

Subaqueous barchan dunes in turbulent shear flow. Part 1. Dune motion

2011 ◽  
Vol 675 ◽  
pp. 199-222 ◽  
Author(s):  
E. M. FRANKLIN ◽  
F. CHARRU
Keyword(s):  
Erosion Rate ◽  
Friction Velocity ◽  
Turbulent Channel Flow ◽  
Minimum Size ◽  
Turbulent Shear ◽  
Turbulent Shear Flow ◽  
Rate Minimum ◽  
Flow Part ◽  
Barchan Dunes ◽  
And Migration

Experiments are reported on the formation and migration of isolated dunes in a turbulent channel flow. These dunes have a very robust crescentic shape with horns pointing downstream, very similar to that of the barchan dunes observed in deserts at a much larger scale. Their main geometrical and dynamical properties are studied in detail, for four types of grains: the conditions for their formation, their morphology, the threshold shear stress for their motion, their velocity, erosion rate, minimum size and the longitudinal stripes of grains hollowed by fluid streaks in the boundary layer. In particular, the law for the dune velocity is found to involve two dimensionless parameters, the Shields number and the sedimentation Reynolds number, in contrast with predictions based on classical laws for particle transport. As the dune migrates, its size slowly decreases because of a small leakage of particles at the horn tips, and the erosion law is given. A minimum size is evidenced, which is shown to increase with the friction velocity and scale with a settling length.

scholarly journals Caffeic Acid Reduces the Viability and Migration Rate of Oral Carcinoma Cells (SCC-25) Exposed to Low Concentrations of Ethanol

2014 ◽  
Vol 15 (10) ◽  
pp. 18725-18741 ◽  
Author(s):  
Arkadiusz Dziedzic ◽  
Robert Kubina ◽  
Agata Kabała-Dzik ◽  
Robert Wojtyczka ◽  
Tadeusz Morawiec ◽  
...  
Keyword(s):  
Caffeic Acid ◽  
Migration Rate ◽  
Carcinoma Cells ◽  
Oral Carcinoma ◽  
Low Concentrations ◽  
And Migration

scholarly journals Photobiomodulation Effects of Single Near-Infrared (825 nm), Green (525 nm) and Combination of Wavelengths on Adipose-Derived Mesenchymal Stem Cell Physiology

2021 ◽  
Author(s):  
Anine Crous ◽  
Madeleen Jansen Rensburg ◽  
Heidi Abrahamse
Keyword(s):  
Migration Rate ◽  
Near Infrared ◽  
Cell Concentration ◽  
Cell Metabolism ◽  
Cell Physiology ◽  
Intracellular Ros ◽  
Infra Red ◽  
Measurement Cell ◽  
And Migration

Abstract Photobiomodulation (PBM) has been used as a bio stimulatory tool for adipose-derived mesenchymal stem cells (ADMSCs). The goal of this in vitro research was to examine the effects of combined and/or single applications of near infra-red (NIR) and green PBM using 5 J/cm2 on ADMSCs. The results indicated that the viability of ADMSCs are not affected by single or combined wavelengths of 525 and 825 nm at 5 J/cm2. However, PBM significantly stimulated cell metabolism seen by an increase in proliferation, it also upregulated intracellular ROS and MMP using 825 nm and 525 nm wavelengths. The combined wavelength irradiation mimicked results found for 825 nm during ATP measurement, cell concentration and migration rate, however significant MMP stimulation and increased ROS production was achieved. In conclusion, results indicate that the combination wavelengths of 525 and 825 nm can be used in the expansion and differentiation of ADMSCs for regenerative purposes.

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