Sulfur Atoms Adsorbed on Cu(100) at Low Coverage: Characterization and Stability against Complexation

DOE PAGES

Walen, Holly; Liu, Da-Jiang; Oh, Junepyo; ...

2017-08-22

By using scanning tunneling microscopy, we characterize the size and bias-dependent shape of sulfur atoms on Cu(100) at low coverage (below 0.1 monolayers) and low temperature (quenched from 300 to 5 K). Sulfur atoms populate the Cu(100) terraces more heavily than steps at low coverage, but as coverage approaches 0.1 monolayers, close-packed step edges become fully populated, with sulfur atoms occupying sites on top of the step. Density functional theory (DFT) corroborates the preferential population of terraces at low coverage as well as the step adsorption site. In experiment, small regions with p(2 × 2)-like atomic arrangements emerge on themore » terraces as sulfur coverage approaches 0.1 monolayer. Using DFT, a lattice gas model has been developed, and Monte Carlo simulations based on this model have been compared with the observed terrace configurations. A model containing eight pairwise interaction energies, all repulsive, gives qualitative agreement. Experiment shows that atomic adsorbed sulfur is the only species on Cu(100) up to a coverage of 0.09 monolayers. There are no Cu–S complexes. Conversely, prior work has shown that a Cu 2S 3 complex forms on Cu(111) under comparable conditions. On the basis of DFT, this difference can be attributed mainly to stronger adsorption of sulfur on Cu(100) as compared with Cu(111).« less

Sulfur Atoms Adsorbed on Cu(100) at Low Coverage: Characterization and Stability against Complexation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Walen, Holly; Liu, Da-Jiang; Oh, Junepyo

By using scanning tunneling microscopy, we characterize the size and bias-dependent shape of sulfur atoms on Cu(100) at low coverage (below 0.1 monolayers) and low temperature (quenched from 300 to 5 K). Sulfur atoms populate the Cu(100) terraces more heavily than steps at low coverage, but as coverage approaches 0.1 monolayers, close-packed step edges become fully populated, with sulfur atoms occupying sites on top of the step. Density functional theory (DFT) corroborates the preferential population of terraces at low coverage as well as the step adsorption site. In experiment, small regions with p(2 × 2)-like atomic arrangements emerge on themore » terraces as sulfur coverage approaches 0.1 monolayer. Using DFT, a lattice gas model has been developed, and Monte Carlo simulations based on this model have been compared with the observed terrace configurations. A model containing eight pairwise interaction energies, all repulsive, gives qualitative agreement. Experiment shows that atomic adsorbed sulfur is the only species on Cu(100) up to a coverage of 0.09 monolayers. There are no Cu–S complexes. Conversely, prior work has shown that a Cu 2S 3 complex forms on Cu(111) under comparable conditions. On the basis of DFT, this difference can be attributed mainly to stronger adsorption of sulfur on Cu(100) as compared with Cu(111).« less

Single crystalline thin films as a novel class of electrocatalysts

DOE PAGES

Snyder, Joshua; Markovic, Nenad; Stamenkovic, Vojislav

2013-01-01

The ubiquitous use of single crystal metal electrodes has garnered invaluable insight into the relationship between surface atomic structure and functional electrochemical properties. But, the sensitivity of their electrochemical response to surface orientation and the amount of precious metal required can limit their use. We present here a generally applicable procedure for producing thin metal films with a large proportion of atomically flat (111) terraces without the use of an epitaxial template. Thermal annealing in a controlled atmosphere induces long-range ordering of magnetron sputtered thin metal films deposited on an amorphous substrate. The ordering transition in these thin metal filmsmore » yields characteristic (111) electrochemical signatures with minimal amount of material and provides an adequate replacement for oriented bulk single crystals. Our procedure can be generalized towards a novel class of practical multimetallic thin film based electrocatalysts with tunable near-surface compositional profile and morphology. Annealing of atomically corrugated sputtered thin film Pt-alloy catalysts yields an atomically smooth structure with highly crystalline, (111)-like ordered and Pt segregated surface that displays superior functional properties, bridging the gap between extended/bulk surfaces and nanoscale systems.« less

Origins of Moiré Patterns in CVD-grown MoS2 Bilayer Structures at the Atomic Scales.

PubMed

Wang, Jin; Namburu, Raju; Dubey, Madan; Dongare, Avinash M

2018-06-21

The chemical vapor deposition (CVD)-grown two-dimensional molybdenum disulfide (MoS 2 ) structures comprise of flakes of few layers with different dimensions. The top layers are relatively smaller in size than the bottom layers, resulting in the formation of edges/steps across adjacent layers. The strain response of such few-layer terraced structures is therefore likely to be different from exfoliated few-layered structures with similar dimensions without any terraces. In this study, the strain response of CVD-grown few-layered MoS 2 terraced structures is investigated at the atomic scales using classic molecular dynamics (MD) simulations. MD simulations suggest that the strain relaxation of CVD-grown triangular terraced structures is observed in the vertical displacement of the atoms across the layers that results in the formation of Moiré patterns. The Moiré islands are observed to nucleate at the corners or edges of the few-layered structure and propagate inwards under both tensile and compressive strains. The nucleation of these islands is observed to happen at tensile strains of ~ 2% and at compressive strains of ~2.5%. The vertical displacements of the atoms and the dimensions of the Moiré islands predicted using the MD simulation are in excellent agreement with that observed experimentally.

Last interglacial (MIS5e) sea-levels and uplift along the north-east Gulf of Aqaba

NASA Astrophysics Data System (ADS)

BAR (KOHN), N.; Stein, M.; Agnon, A.; Yehudai, M.; Lazar, B.; Shaked, Y.

2014-12-01

An uplifted flight of coral reef terraces, extending along the north-east margin of the Gulf of Aqaba (GOA), provides evidence for uplift rates and sea level high stands. GOA fills a narrow and deep tectonic depression lying along the southern sector of the Dead Sea Transform where it meets the Red Sea. This special configuration of the GOA and its latitude turn it into a dependable paleo-sea level monitor, sensitive only to global eustatic changes and local tectonic movements. A sequence of five uplifted coral reef terraces were mapped and characterized on basis of morphology and reef-facies, and their elevation above the present sea level was determined. The fossil reefs studied comprise fringing reefs, some with clear reef-structure that includes a reef flat and a shallow back lagoon. Most outcrops in the study area represent a transgressive sequence in which, during its highest stand, formed fringing reef terraces. We use U-Th ages of fossil corals samples found in growth position at various terraces. Corals from three uplifted reef terraces, R1, R2, and R3 were dated to the last interglacial period particularly to marine isotope stage (MIS) 5e. These ages were achieved from mainly calcitic corals (recrystallized in a freshwater phreatic environment). A few ages were derived from aragonite corals. The three terraces represent three sub-stages within MIS5e: R3 formed during a short standstill at ~130 ka BP; R2 formed during a long and steady standstill between ~128 to ~121 ka BP; and R1 represents a short standstill at ~117 ka BP. Assuming that terrace reef flats represent past sea level high stands, we calculated the coast average uplift rate and constrained the original terraces elevations. The reconstructed eustatic sea level variation during MIS 5e at GOA resembles observations from reef terraces in other locations. Combined, all indicate a significant sea-level rise from the MIS 6 low stand at ~134-130 ka and followed by a long and stable sea level high stand between ~128 to ~121 ka, representing a major reef building period. The long and stable sea level was followed by additional sea-level rise at ~118-116 ka that transgressed over the "stable reefs".

Preparation of atomically flat TiO2(001) surfaces

NASA Astrophysics Data System (ADS)

Wang, Yang; Weitering, Hanno H.; Snijders, Paul C.

2015-03-01

Transition metal oxides with the rutile structure (MO2, M = e.g. Ti, V, or Nb) have highly directional partially occupied t2g orbitals. Some of these orbitals form quasi-1D electronic bands along the rutile c-axis, and Peierls-like ordering phenomena have been observed in VO2 and NbO2. Tailoring the electronic properties of these materials via quantum confinement requires epitaxial growth on suitable substrates such as low index TiO2 surfaces. Because of the high surface energy of rutile TiO2(001), the standard approach of sputtering and annealing usually introduces faceting. Here we demonstrate a facile method to create atomically flat, non-faceted TiO2(001) surfaces. Using scanning tunneling microscopy we observe terraces with a width of approximately 150 nm. Step heights of approximately 0.3 nm are observed, consistent with the c lattice parameter of rutile TiO2. Low energy electron diffraction patterns reveal sharp diffraction spots with an in-plane lattice constant of 0.358 nm which is consistent with a (1x1) ordering of the (001) plane. These TiO2(001) single crystal surfaces can serve as an ideal substrate for further growth of rutile heterostructures. Research sponsored by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division.

Irradiation of amorphous Ta42Si13N45 film with a femtosecond laser pulse

NASA Astrophysics Data System (ADS)

Romano, V.; Meier, M.; Theodore, N. D.; Marble, D. K.; Nicolet, M.-A.

2011-07-01

Films of 260 nm thickness, with atomic composition Ta42Si13N45, on 4″ silicon wafers, have been irradiated in air with single laser pulses of 200 femtoseconds duration and 800 nm wave length. As sputter-deposited, the films are structurally amorphous. A laterally truncated Gaussian beam with a near-uniform fluence of ˜0.6 J/cm2 incident normally on such a film ablates 23 nm of the film. Cross-sectional transmission electron micrographs show that the surface of the remaining film is smooth and flat on a long-range scale, but contains densely distributed sharp nanoprotrusions that sometimes surpass the height of the original surface. Dark field micrographs of the remaining material show no nanograins. Neither does glancing angle X-ray diffraction with a beam illuminating many diffraction spots. By all evidence, the remaining film remains amorphous after the pulsed femtosecond irradiation. The same single pulse, but with an enhanced and slightly peaked fluence profile, creates a spot with flat peripheral terraces whose lateral extents shrink with depth, as scanning electron and atomic force micrographs revealed. Comparison of the various figures suggests that the sharp nanoprotrusions result from an ejection of material by brittle fraction and spallation, not from ablation by direct beam-solid interaction. Conditions under which spallation should dominate over ablation are discussed.

Young Craters on Smooth Plains

NASA Image and Video Library

2000-01-15

This image, from NASA Mariner 10 spacecraft which launched in 1974, shows young craters superposed on smooth plains. Larger young craters have central peaks, flat floors, terraced walls, and radial ejecta deposits.

2D Si island nucleation on the Si(111) surface at initial and late growth stages: On the role of step permeability in pyramidlike growth

NASA Astrophysics Data System (ADS)

Rogilo, D. I.; Fedina, L. I.; Kosolobov, S. S.; Ranguelov, B. S.; Latyshev, A. V.

2017-01-01

Initial and late stages of 2D Si island nucleation and growth (2DNG) on extra-large ( 100 μm) and medium size (1-10 μm) atomically flat Si(111)-(7×7) terraces bordered by step bunches have been studied by in situ REM at T =600-750 °С. At first, the layer-by-layer 2DNG takes place on whole terraces and 2D island concentration dependence on deposition rate R corresponds to critical nucleus size i =1. Continuous 2DNG triggers morphological instabilities: elongated pyramidlike waves and separate pyramids emerge on all terraces at T ≤720 °С and T =750 °С, respectively. Both instabilities arise due to the imbalance of uphill/downhill adatom currents related with large Ehrlich-Schwöbel (ES) barriers and permeability of straight [ 11 bar 2 ] -type step edges. However, the first one is initiated by dominant downhill adatom current to distant sinks: bunches, wave's step edges, and "vacancy" islands emerging on terraces due to 2D island coalescence. As a result, top layer size decreases to the critical terrace width λ where 2DNG takes place. From the analysis of λ ∝ R - χ / 2 scaling at T =650 °C, we have found that i increases from i =2 on a three-layer wave to i =6-8 on a six-layer wave. This authenticates the significance of downhill adatom sink to distant steps related to the step permeability. The second instability type at T >720 °C is related to the raising of uphill adatom current due to slightly larger ES barrier for step-up attachment comparing to the step-down one (EES- 0.9 eV [Phys. Rev. Lett. 111 (2013) 036105]). This leads to "second layer" 2D nucleation on top layers, which triggers the growth of separate pyramids. Because of small difference between ES barriers, net uphill/downhill adatom currents are nearly equivalent, and therefore layer coverage distributions of both instabilities display similar linear slopes.

Correlation between the electrical properties and the interfacial microstructures of TiAl-based ohmic contacts to p-type 4H-SiC

NASA Astrophysics Data System (ADS)

Tsukimoto, S.; Nitta, K.; Sakai, T.; Moriyama, M.; Murakami, Masanori

2004-05-01

In order to understand a mechanism of TiAl-based ohmic contact formation for p-type 4H-SiC, the electrical properties and microstructures of Ti/Al and Ni/Ti/Al contacts, which provided the specific contact resistances of approximately 2×10-5 Ω-cm2 and 7×10-5 Ω-cm2 after annealing at 1000°C and 800°C, respectively, were investigated using x-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). Ternary Ti3SiC2 carbide layers were observed to grow on the SiC surfaces in both the Ti/Al and the Ni/Ti/Al contacts when the contacts yielded low resistance. The Ti3SiC2 carbide layers with hexagonal structures had an epitaxial orientation relationship with the 4H-SiC substrates. The (0001)-oriented terraces were observed periodically at the interfaces between the carbide layers and the SiC, and the terraces were atomically flat. We believed the Ti3SiC2 carbide layers primarily reduced the high Schottky barrier height at the contact metal/p-SiC interface down to about 0.3 eV, and, thus, low contact resistances were obtained for p-type TiAl-based ohmic contacts.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hasegawa, Tomo; Shahed, Syed Mohammad Fakruddin; Sainoo, Yasuyuki

We formed an epitaxial film of CeO{sub 2}(111) by sublimating Ce atoms on Ru(0001) surface kept at elevated temperature in an oxygen ambient. X-ray photoemission spectroscopy measurement revealed a decrease of Ce{sup 4+}/Ce{sup 3+} ratio in a small temperature window of the growth temperature between 1070 and 1096 K, which corresponds to the reduction of the CeO{sub 2}(111). Scanning tunneling microscope image showed that a film with a wide terrace and a sharp step edge was obtained when the film was grown at the temperatures close to the reduction temperature, and the terrace width observed on the sample grown atmore » 1060 K was more than twice of that grown at 1040 K. On the surface grown above the reduction temperature, the surface with a wide terrace and a sharp step was confirmed, but small dots were also seen in the terrace part, which are considerably Ce atoms adsorbed at the oxygen vacancies on the reduced surface. This experiment demonstrated that it is required to use the substrate temperature close to the reduction temperature to obtain CeO{sub 2}(111) with wide terrace width and sharp step edges.« less

Crystal truncation rods from miscut surfaces

DOE PAGES

Petach, Trevor A.; Mehta, Apurva; Toney, Michael F.; ...

2017-05-08

Crystal truncation rods are used to study surface and interface structure. Since real surfaces are always somewhat miscut from a low index plane, it is important to study the effect of miscuts on crystal truncation rods. We develop a model that describes the truncation rod scattering from miscut surfaces that have steps and terraces. We show that nonuniform terrace widths and jagged step edges are both forms of roughness that decrease the intensity of the rods. Nonuniform terrace widths also result in a broad peak that overlaps the rods. We use our model to characterize the terrace width distribution andmore » step edge jaggedness on three SrTiO 3 (001) samples, showing excellent agreement between the model and the data, confirmed by atomic force micrographs of the surface morphology. As a result, we expect our description of terrace roughness will apply to many surfaces, even those without obvious terracing.« less

A New-Type of Long-Range Restructuring of Ordered Metal Surfaces Induced by Lateral Adsorbate Interactions: Iodide on AU(110) Electrodes

DTIC Science & Technology

1994-02-01

separated by monoatomic steps. The direction of the (110) gold rows is evident in the atomic- resolution image of a uniform terrace, shown in Fig. 2A...distinguish between the average surface energy of a gold atom within a (110) terrace and at a monoatomic step (edge) site. The difference between these...having (3 x 2) symmetry (coverage - 0.67), is imaged instead of the substrate, with the iodide arranged in parallel close-packed rows in between the gold

Basal terraces on melting ice shelves

NASA Astrophysics Data System (ADS)

Dutrieux, Pierre; Stewart, Craig; Jenkins, Adrian; Nicholls, Keith W.; Corr, Hugh F. J.; Rignot, Eric; Steffen, Konrad

2014-08-01

Ocean waters melt the margins of Antarctic and Greenland glaciers, and individual glaciers' responses and the integrity of their ice shelves are expected to depend on the spatial distribution of melt. The bases of the ice shelves associated with Pine Island Glacier (West Antarctica) and Petermann Glacier (Greenland) have similar geometries, including kilometer-wide, hundreds-of-meter high channels oriented along and across the direction of ice flow. The channels are enhanced by, and constrain, oceanic melt. New meter-scale observations of basal topography reveal peculiar glaciated landscapes. Channel flanks are not smooth, but are instead stepped, with hundreds-of-meters-wide flat terraces separated by 5-50 m high walls. Melting is shown to be modulated by the geometry: constant across each terrace, changing from one terrace to the next, and greatly enhanced on the ~45° inclined walls. Melting is therefore fundamentally heterogeneous and likely associated with stratification in the ice-ocean boundary layer, challenging current models of ice shelf-ocean interactions.

Craters in an Icy Surface

NASA Image and Video Library

2014-02-26

The crater in the center of this HiRISE image from NASA Mars Reconnaissance Orbiter is unusual because there is a wide, flat bench, or terrace, between the outer rim and the inner section, making it appear somewhat like a bullseye.

Surface reconstruction switching induced by tensile stress of DB steps: From Ba/Si(0 0 1)- 2 × 3 to Ba/Si(0 0 1)-4° off- 3 × 2

NASA Astrophysics Data System (ADS)

Kim, Hidong; Lkhagvasuren, Altaibaatar; Zhang, Rui; Seo, Jae M.

2018-05-01

The alkaline-earth metal adsorption on Si(0 0 1) has attracted much interest for finding a proper template in the growth of high- κ and crystalline films. Up to now on the flat Si(0 0 1) surface with double domains and single-layer steps, the adsorbed Ba atoms are known to induce the 2 × 3 structure through removing two Si dimers and adding a Ba atom per unit cell in each domain. In the present investigation, the Si(0 0 1)-4° off surface with DB steps and single domains has been employed as a substrate and the reconstruction at the initial stage of Ba adsorption has been investigated by scanning tunneling microscopy and synchrotron photoemission spectroscopy. On this vicinal and single domain terrace, a novel 3 × 2 structure rotated by 90° from the 2 × 3 structure has been found. Such a 3 × 2 structure turns out to be formed by adding a Ba atom and a Si dimer per unit cell. This results from the fact that the adsorbed Ba2+ ions with a larger ionic radius relieve tensile stress on the original Si dimers exerted by the rebonded atoms at the DB step.

Differentiating submarine channel-related thin-bedded turbidite facies: Outcrop examples from the Rosario Formation, Mexico

NASA Astrophysics Data System (ADS)

Hansen, Larissa; Callow, Richard; Kane, Ian; Kneller, Ben

2017-08-01

Thin-bedded turbidites deposited by sediment gravity flows that spill from submarine channels often contain significant volumes of sand in laterally continuous beds. These can make up over 50% of the channel-belt fill volume, and can thus form commercially important hydrocarbon reservoirs. Thin-bedded turbidites can be deposited in environments that include levees and depositional terraces, which are distinguished on the basis of their external morphology and internal architecture. Levees have a distinctive wedge shaped morphology, thinning away from the channel, and confine both channels (internal levees) and channel-belts (external levees). Terraces are flat-lying features that are elevated above the active channel within a broad channel-belt. Despite the ubiquity of terraces and levees in modern submarine channel systems, the recognition of these environments in outcrop and in the subsurface is challenging. In this outcrop study of the Upper Cretaceous Rosario Formation (Baja California, Mexico), lateral transects based on multiple logged sections of thin-bedded turbidites reveal systematic differences in sandstone layer thicknesses, sandstone proportion, palaeocurrents, sedimentary structures and ichnology between channel-belt and external levee thin-bedded turbidites. Depositional terrace deposits have a larger standard deviation in sandstone layer thicknesses than external levees because they are topographically lower, and experience a wider range of turbidity current sizes overspilling from different parts of the channel-belt. The thickness of sandstone layers within external levees decreases away from the channel-belt while those in depositional terraces are less laterally variable. Depositional terrace environments of the channel-belt are characterized by high bioturbation intensities, and contain distinctive trace fossil assemblages, often dominated by ichnofabrics of the echinoid trace fossil Scolicia. These assemblages contrast with the lower bioturbation intensities that are recorded from external levee environments where Scolicia is typically absent. Multiple blocks of external levee material are observed in the depositional terrace area where the proximal part of the external levee has collapsed into the channel-belt; their presence characterizes the channel-belt boundary zone. The development of recognition criteria for different types of channel-related thin-bedded turbidites is critical for the interpretation of sedimentary environments both at outcrop and in the subsurface, which can reduce uncertainty during hydrocarbon field appraisal and development.

Tuning metal-insulator transitions in epitaxial V2O3 thin films

NASA Astrophysics Data System (ADS)

Thorsteinsson, Einar B.; Shayestehaminzadeh, Seyedmohammad; Arnalds, Unnar B.

2018-04-01

We present a study of the synthesis of epitaxial V2O3 films on c-plane Al2O3 substrates by reactive dc-magnetron sputtering. The results reveal a temperature window, at substantially lower values than previously reported, wherein epitaxial films can be obtained when deposited on [0001] oriented surfaces. The films display a metal-insulator transition with a change in the resistance of up to four orders of magnitude, strongly dependent on the O2 partial pressure during deposition. While the electronic properties of the films show sensitivity to the amount of O2 present during deposition of the films, their crystallographic structure and surface morphology of atomically flat terraced structures with up to micrometer dimensions are maintained. The transition temperature, as well as the scale of the metal-insulator transition, is correlated with the stoichiometry and local strain in the films controllable by the deposition parameters.

An experimental study of furan adsorption and decomposition on vicinal palladium surfaces using scanning tunneling microscopy

NASA Astrophysics Data System (ADS)

Loui, A.; Chiang, S.

2018-04-01

The intact adsorption and decomposition of furan (C4H4O) on vicinal palladium surfaces with (111)-oriented terraces has been studied by scanning tunneling microscopy (STM) over a range of temperatures. STM images at 225 K show that furan molecules lie flat and prefer to adsorb at upper step edges. At 225 K, furan molecules adsorbed on "narrow" terraces of 20 to 45 Å in width appear to diffuse more readily than those adsorbed on "wide" terraces of 160 to 220 Å. A distinct population of smaller features appears in STM images on "narrow" terraces at 288 K and on "wide" terraces at 415 K and is identified with the C3H3 decomposition product, agreeing with prior studies which demonstrated that furan dissociates on Pd(111) to yield carbon monoxide (CO) and a C3H3 moiety in the 280 to 320 K range. Based on our direct visualization of this reaction using STM, we propose a spatial mechanism in which adsorption of furan at upper step edges allows catalysis of the dissociation, followed by diffusion of the product to lower step edges.

Evidence of the 1762 Arakan and Prior Earthquakes in the Northern Sunda Subduction

NASA Astrophysics Data System (ADS)

Mondal, Dhiman Ranjan

The objective of this dissertation is to understand the seismic hazard associated with Arakan segment of the northern Sunda subduction along SE Bangladesh. In order to do that, it is necessary to document geologic evidence for the 1762 Arakan earthquake and prior events, to help estimate the recurrence interval (repeat time) for that earthquake. Historical records described that the 1762 earthquake caused extensive damage along the Arakan segment of the Sunda subduction system. But the geologic evidence for the earthquake farther north is necessary to better understand its associated seismic hazard to the densely populated nation of Bangladesh. This dissertation presents the results obtained from U/Th dating of the dead and live coral microatolls including their elevations measured by high precision GPS from the Saint Martin's Island, DEM analysis and elevation of terraces from Teknaf coast and fault dislocation modeling based on the data obtained from the Saint Martin's Island and Teknaf. Coral microatolls from Saint Martin's island documents the evidence of the 1762 and prior earthquakes. The U/Th ages documents strong evidence of microatoll die offs related to the 1762 earthquake. The > 2 m elevation difference between the dead microatolls and present-day living corals suggest that the microatolls died due to the coseismic uplift of 1762 Arakan earthquake. This dissertation also provides evidence for two additional earthquakes taking place in 700 and 1140 C.E. which suggests an earthquake recurrence interval of 500 years. Geomorphic studies documented three terraces along the coast of Teknaf. Several marine terraces have been previously documented along the west coast of Myanmar. The youngest of these terraces has been correlated to the coseismic uplift of 1762 Arakan along the Myanmar coast. The terraces along the coast of Teknaf are characterized by flat to semi-flat surfaces followed by sharp topographic rises. DEM (Digital Elevation System) analysis and GPS (Global Positioning System) survey documented 2 to 3 terraces. Among these three, the youngest terrace is possibly linked to the 1762 Arakan Earthquake but the ages have not been verified. Modeling using the data obtained from Saint Martin's Island, Teknaf and other published articles (for the west coast of Teknaf) suggest a fault dipping at 10-15° to the northeast. The result of coseismic slip inversion shows 15-25 m of reverse slip along the Arakan rupture segment, which was accommodated by the upper plate failure. Based on our results from coral microatolls, terraces and the modeling study, this dissertation suggests that this segment of the Arakan collision zone has the potential to cause a future earthquake of Mw > 8 which can produce a devastating effect to the inhabitants of Bangladesh, Myanmar and Eastern India.

Structural deformation at the Flynn Creek impact crater, Tennessee - A preliminary report on deep drilling

NASA Technical Reports Server (NTRS)

Roddy, D. J.

1979-01-01

The geologic and core drilling studies described in the present paper show that the Flynn Creek crater has such distinctive morphological features as a broad flat hummocky floor; large central peak; locally terraced crater walls; uplifted, as well as flat-lying rim segments; and a surrounding ejecta blanket. The major structural features include a shallow depth of total brecciation and excavation as compared with apparent crater diameter; a thin breccia lens underlain by a thin zone of disrupted strata; concentric ring fault zones in inner rim, beneath crater wall, and outer crater floor regions; a large central uplift underlain by a narrow dipping zone of deeply disrupted strata; faulted, folded, brecciated, and fractured rim strata; and uplifted rim strata, which dip away from the crater, and flat-lying rim strata, which terminate as inward dipping rocks.

The initial stages of ZnO atomic layer deposition on atomically flat In0.53Ga0.47As substrates.

PubMed

Skopin, Evgeniy V; Rapenne, Laetitia; Roussel, Hervé; Deschanvres, Jean-Luc; Blanquet, Elisabeth; Ciatto, Gianluca; Fong, Dillon D; Richard, Marie-Ingrid; Renevier, Hubert

2018-06-21

InGaAs is one of the III-V active semiconductors used in modern high-electron-mobility transistors or high-speed electronics. ZnO is a good candidate material to be inserted as a tunneling insulator layer at the metal-semiconductor junction. A key consideration in many modern devices is the atomic structure of the hetero-interface, which often ultimately governs the electronic or chemical process of interest. Here, a complementary suite of in situ synchrotron X-ray techniques (fluorescence, reflectivity and absorption) as well as modeling is used to investigate both structural and chemical evolution during the initial growth of ZnO by atomic layer deposition (ALD) on In0.53Ga0.47As substrates. Prior to steady-state growth behavior, we discover a transient regime characterized by two stages. First, substrate-inhibited ZnO growth takes place on InGaAs terraces. This leads eventually to the formation of a 1 nm-thick, two-dimensional (2D) amorphous layer. Second, the growth behavior and its modeling suggest the occurrence of dense island formation, with an aspect ratio and surface roughness that depends sensitively on the growth condition. Finally, ZnO ALD on In0.53Ga0.47As is characterized by 2D steady-state growth with a linear growth rate of 0.21 nm cy-1, as expected for layer-by-layer ZnO ALD.

One-dimensional model of interacting-step fluctuations on vicinal surfaces: Analytical formulas and kinetic Monte Carlo simulations

NASA Astrophysics Data System (ADS)

Patrone, Paul N.; Einstein, T. L.; Margetis, Dionisios

2010-12-01

We study analytically and numerically a one-dimensional model of interacting line defects (steps) fluctuating on a vicinal crystal. Our goal is to formulate and validate analytical techniques for approximately solving systems of coupled nonlinear stochastic differential equations (SDEs) governing fluctuations in surface motion. In our analytical approach, the starting point is the Burton-Cabrera-Frank (BCF) model by which step motion is driven by diffusion of adsorbed atoms on terraces and atom attachment-detachment at steps. The step energy accounts for entropic and nearest-neighbor elastic-dipole interactions. By including Gaussian white noise to the equations of motion for terrace widths, we formulate large systems of SDEs under different choices of diffusion coefficients for the noise. We simplify this description via (i) perturbation theory and linearization of the step interactions and, alternatively, (ii) a mean-field (MF) approximation whereby widths of adjacent terraces are replaced by a self-consistent field but nonlinearities in step interactions are retained. We derive simplified formulas for the time-dependent terrace-width distribution (TWD) and its steady-state limit. Our MF analytical predictions for the TWD compare favorably with kinetic Monte Carlo simulations under the addition of a suitably conservative white noise in the BCF equations.

Eastern rim of the Chesapeake Bay impact crater: Morphology, stratigraphy, and structure

USGS Publications Warehouse

Poag, C.W.

2005-01-01

This study reexamines seven reprocessed (increased vertical exaggeration) seismic reflection profiles that cross the eastern rim of the Chesapeake Bay impact crater. The eastern rim is expressed as an arcuate ridge that borders the crater in a fashion typical of the "raised" rim documented in many well preserved complex impact craters. The inner boundary of the eastern rim (rim wall) is formed by a series of raterfacing, steep scarps, 15-60 m high. In combination, these rim-wall scarps represent the footwalls of a system of crater-encircling normal faults, which are downthrown toward the crater. Outboard of the rim wall are several additional normal-fault blocks, whose bounding faults trend approximately parallel to the rim wall. The tops of the outboard fault blocks form two distinct, parallel, flat or gently sloping, terraces. The innermost terrace (Terrace 1) can be identified on each profile, but Terrace 2 is only sporadically present. The terraced fault blocks are composed mainly of nonmarine, poorly to moderately consolidated, siliciclastic sediments, belonging to the Lower Cretaceous Potomac Formation. Though the ridge-forming geometry of the eastern rim gives the appearance of a raised compressional feature, no compelling evidence of compressive forces is evident in the profiles studied. The structural mode, instead, is that of extension, with the clear dominance of normal faulting as the extensional mechanism. 

Crater Moreux

NASA Technical Reports Server (NTRS)

1997-01-01

Color image of part of the Ismenius Lacus region of Mars (MC-5 quadrangle) containing the impact crater Moreux (right center); north toward top. The scene shows heavily cratered highlands in the south on relatively smooth lowland plains in the north separated by a belt of dissected terrain, containing flat-floored valleys, mesas, and buttes. This image is a composite of Viking medium-resolution images in black and white and low-resolution images in color. The image extends from latitude 36 degrees N. to 50 degrees N. and from longitude 310 degrees to 340 degrees; Lambert conformal conic projection. The dissected terrain along the highlands/lowlands boundary consists of the flat-floored valleys of Deuteronilus Mensae (on left) and Prontonilus Mensae (on right) and farther north the small, rounded hills of knobby terrain. Flows on the mensae floors contain striae that run parallel to valley walls; where valleys meet, the striae merge, similar to medial moraines on glaciers. Terraces within the valley hills have been interpreted as either layered rocks or wave terraces. The knobby terrain has been interpreted as remnants of the old, densely cratered highland terrain perhaps eroded by mass wasting.

Xe adsorption site distributions on Pt(111), Pt(221) and Pt(531)

NASA Astrophysics Data System (ADS)

Gellman, Andrew J.; Baker, L.; Holsclaw, B. S.

2016-04-01

The ideal structures of the Pt(111), Pt(221) and Pt(531) surfaces expose adsorption sites that can be qualitatively described as terrace sites on Pt(111), both step and terrace sites on Pt(221), and kink sites on Pt(531). The real surface structures of these surfaces can be complicated by imperfections such as misorientation, reconstruction and thermal roughening, all of which will influence their distributions of adsorption sites. Xe adsorption sites on the Pt(111), Pt(221) and Pt(531) surfaces have been probed using both photoemission of adsorbed Xe (PAX) and temperature programmed desorption (TPD) of Xe. Both PAX and Xe TPD are sensitive to the adsorption sites of the Xe and serve as complementary means of assessing the distributions of adsorption sites on these three Pt surfaces. The adsorption of Xe is sufficiently sensitive to detect the presence of residual steps on the Pt(111) surface at a density of 1.5% step atoms per Pt atom. On the Pt(221) surface, PAX and Xe TPD reveal adsorption at both terrace and step sites simultaneously. Although the ideal structure of the Pt(531) surface has no well-defined steps or terraces, Xe adsorption indicates that its adsorption sites are best described as a distribution of both step and kink sites with roughly twice as many steps sites as kinks.

Electronic-Reconstruction-Enhanced Tunneling Conductance at Terrace Edges of Ultrathin Oxide Films.

PubMed

Wang, Lingfei; Kim, Rokyeon; Kim, Yoonkoo; Kim, Choong H; Hwang, Sangwoon; Cho, Myung Rae; Shin, Yeong Jae; Das, Saikat; Kim, Jeong Rae; Kalinin, Sergei V; Kim, Miyoung; Yang, Sang Mo; Noh, Tae Won

2017-11-01

Quantum mechanical tunneling of electrons across ultrathin insulating oxide barriers has been studied extensively for decades due to its great potential in electronic-device applications. In the few-nanometers-thick epitaxial oxide films, atomic-scale structural imperfections, such as the ubiquitously existed one-unit-cell-high terrace edges, can dramatically affect the tunneling probability and device performance. However, the underlying physics has not been investigated adequately. Here, taking ultrathin BaTiO 3 films as a model system, an intrinsic tunneling-conductance enhancement is reported near the terrace edges. Scanning-probe-microscopy results demonstrate the existence of highly conductive regions (tens of nanometers wide) near the terrace edges. First-principles calculations suggest that the terrace-edge geometry can trigger an electronic reconstruction, which reduces the effective tunneling barrier width locally. Furthermore, such tunneling-conductance enhancement can be discovered in other transition metal oxides and controlled by surface-termination engineering. The controllable electronic reconstruction can facilitate the implementation of oxide electronic devices and discovery of exotic low-dimensional quantum phases. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Importance of electronegativity differences and surface structure in molecular dissociation reactions at transition metal surfaces.

PubMed

Crawford, Paul; Hu, P

2006-12-14

The dissociative adsorption of N2 has been studied at both monatomic steps and flat regions on the surfaces of the 4d transition metals from Zr to Pd. Using density functional theory (DFT) calculations, we have determined and analyzed the trends in both straight reactivity and structure sensitivity across the periodic table. With regards to reactivity, we find that the trend in activation energy (Ea) is determined mainly by a charge transfer from the surface metal atoms to the N atoms during transition state formation, namely, the degree of ionicity of the N-surface bond at the transition state. Indeed, we find that the strength of the metal-N bond at the transition state (and therefore the trend in Ea) can be predicted by the difference in Mulliken electronegativity between the metal and N. Structure sensitivity is analyzed in terms of geometric and electronic effects. We find that the lowering of Ea due to steps is more pronounced on the right-hand side of the periodic table. It is found that for the early transition metals the geometric and electronic effects work in opposition when going from terrace to step active site. In the case of the late 4d metals, however, these effects work in combination, producing a more marked reduction in Ea.

In Situ STM Observation of Nonmagnetic Impurity Effect in MBE-grown CeCoIn5 Films

NASA Astrophysics Data System (ADS)

Haze, Masahiro; Torii, Yohei; Peters, Robert; Kasahara, Shigeru; Kasahara, Yuichi; Shibauchi, Takasada; Terashima, Takahito; Matsuda, Yuji

2018-03-01

Local electronic effects in the vicinity of an impurity provide pivotal insight into the origin of unconventional superconductivity, especially when the materials are located on the edge of magnetic instability. In high-temperature cuprate superconductors, a strong suppression of superconductivity and appearance of low-energy bound states are clearly observed near nonmagnetic impurities. However, whether these features are common to other strongly correlated superconductors has not been established experimentally. Here, we report the in situ scanning tunneling microscopy observation of electronic structure around a nonmagnetic Zn impurity in heavy-fermion CeCo(In1-xZnx)5 films, which are epitaxially grown by the state-of-the-art molecular beam epitaxy technique. The films have very wide atomically flat terraces and Zn atoms residing on two different In sites are clearly resolved. Remarkably, no discernible change is observed for the superconducting gap at and around the Zn atoms. Moreover, the local density of states around Zn atoms shows little change inside the c-f hybridization gap, which is consistent with calculations for a periodic Anderson model without local magnetic order. These results indicate that no nonsuperconducting region is induced around a Zn impurity and do not support the scenario of antiferromagnetic droplet formation suggested by indirect measurements in Cd-doped CeCoIn5. These results also highlight a significant difference of the impurity effect between cuprates and CeCoIn5, in both of which d-wave superconductivity arises from the non-Fermi liquid normal state near antiferromagnetic instabilities.

Adsorption of xenon on vicinal copper and platinum surfaces

NASA Astrophysics Data System (ADS)

Baker, Layton

The adsorption of xenon was studied on Cu(111), Cu(221), Cu(643) and on Pt(111), Pt(221), and Pt(531) using low energy electron diffraction (LEED), temperature programmed desorption (TPD) of xenon, and ultraviolet photoemission of adsorbed xenon (PAX). These experiments were performed to study the atomic and electronic structure of stepped and step-kinked, chiral metal surfaces. Xenon TPD and PAX were performed on each surface in an attempt to titrate terrace, step edge, and kink adsorption sites by adsorption energetics (TPD) and local work function differences (PAX). Due to the complex behavior of xenon on the vicinal copper and platinum metal surfaces, adsorption sites on these surfaces could not be adequately titrated by xenon TPD. On Cu(221) and Cu(643), xenon desorption from step adsorption sites was not apparent leading to the conclusion that the energy difference between terrace and step adsorption is minuscule. On Pt(221) and Pt(531), xenon TPD indicated that xenon prefers to bond at step edges and that the xenon-xenon interaction at step edges in repulsive but no further indication of step-kink adsorption was observed. The Pt(221) and Pt(531) TPD spectra indicated that the xenon overlayer undergoes strong compression near monolayer coverage on these surfaces due to repulsion between step-edge adsorbed xenon and other encroaching xenon atoms. The PAX experiments on the copper and platinum surfaces demonstrated that the step adsorption sites have lower local work functions than terrace adsorption sites and that higher step density leads to a larger separation in the local work function of terrace and step adsorption sites. The PAX spectra also indicated that, for all surfaces studied at 50--70 K, step adsorption is favored at low coverage but the step sites are not saturated until monolayer coverage is reached; this observation is due to the large entropy difference between terrace and step adsorption states and to repulsive interactions between xenon atoms adsorbed at step edges (on the platinum surfaces). The results herein provide several novel observations regarding the adsorptive behavior of xenon on vicinal copper and platinum surfaces.

Late Quaternary uplift rate inferred from marine terraces, Muroto Peninsula, southwest Japan: Forearc deformation in an oblique subduction zone

NASA Astrophysics Data System (ADS)

Matsu'ura, Tabito

2015-04-01

Tectonic uplift rates across the Muroto Peninsula, in the southwest Japan forearc (the overriding plate in the southwest Japan oblique subduction zone), were estimated by mapping the elevations of the inner edges of marine terrace surfaces. The uplift rates inferred from marine terraces M1 and M2, which were correlated by tephrochronology with marine isotope stages (MIS) 5e and 5c, respectively, include some vertical offset by local faults but generally decrease northwestward from 1.2-1.6 m ky- 1 on Cape Muroto to 0.3-0.7 m ky- 1 in the Kochi Plain. The vertical deformation of the Muroto Peninsula since MIS 5e and 5c was interpreted as a combination of regional uplift and folding related to the arc-normal offshore Muroto-Misaki fault. A regional uplift rate of 0.46 m ky- 1 was estimated from terraces on the Muroto Peninsula, and the residual deformation of these terraces was attributed to fault-related folding. A mass-balance calculation yielded a shortening rate of 0.71-0.77 m ky- 1 for the Muroto Peninsula, with the Muroto-Misaki fault accounting for 0.60-0.71 m ky- 1, but these rates may be overestimated by as much as 10% given variations of several meters in the elevation difference between the buried shoreline angles and terrace inner edges in the study area. A thrust fault model with flat (5-10° dip) and ramp (60° dip) components is proposed to explain the shortening rate and uplift rate of the Muroto-Misaki fault since MIS 5e. Bedrock deformation also indicates that the northern extension of this fault corresponds to the older Muroto Flexure.

Influence of Terraced area DEM Resolution on RUSLE LS Factor

NASA Astrophysics Data System (ADS)

Zhang, Hongming; Baartman, Jantiene E. M.; Yang, Xiaomei; Gai, Lingtong; Geissen, Viollette

2017-04-01

Topography has a large impact on the erosion of soil by water. Slope steepness and slope length are combined (the LS factor) in the universal soil-loss equation (USLE) and its revised version (RUSLE) for predicting soil erosion. The LS factor is usually extracted from a digital elevation model (DEM). The grid size of the DEM will thus influence the LS factor and the subsequent calculation of soil loss. Terracing is considered as a support practice factor (P) in the USLE/RUSLE equations, which is multiplied with the other USLE/RUSLE factors. However, as terraces change the slope length and steepness, they also affect the LS factor. The effect of DEM grid size on the LS factor has not been investigated for a terraced area. We obtained a high-resolution DEM by unmanned aerial vehicles (UAVs) photogrammetry, from which the slope steepness, slope length, and LS factor were extracted. The changes in these parameters at various DEM resolutions were then analysed. The DEM produced detailed LS-factor maps, particularly for low LS factors. High (small valleys, gullies, and terrace ridges) and low (flats and terrace fields) spatial frequencies were both sensitive to changes in resolution, so the areas of higher and lower slope steepness both decreased with increasing grid size. Average slope steepness decreased and average slope length increased with grid size. Slope length, however, had a larger effect than slope steepness on the LS factor as the grid size varied. The LS factor increased when the grid size increased from 0.5 to 30-m and increased significantly at grid sizes >5-m. The LS factor was increasingly overestimated as grid size decreased. The LS factor decreased from grid sizes of 30 to 100-m, because the details of the terraced terrain were gradually lost, but the factor was still overestimated.

The hydrological response of a small catchment after the abandonment of terrace cultivation. A study case in northwestern Spain

NASA Astrophysics Data System (ADS)

Llorente-Adán, Jose A.; Lana-Renault, Noemí; Galilea, Ianire; Ruiz-Flaño, Purificacion

2015-04-01

Terrace construction for cultivation results in a complete transformation of the hillslopes to a series of flat sectors and almost vertical steps. This strategy, which involves a redistribution of soils and a re-organization of the drainage network, provides fertile soil over steep slopes, improves infiltration and controls overland flow under conditions of intense rainstorms. In Camero Viejo (north-western Iberian ranges) most of the hillslopes are occupied by terraced fields. During the XXth century, rural population declined and agricultural practices were abandoned. In this area, a small catchment (1.9 km2) was monitored in 2012 for studying how the abandonment of agricultural terraces affect water and sediment transfer from the hillslopes to the channels. Terraces occupy 40% of the catchment and are covered by sparse grass and shrubs. The equipment installed in the catchment registers continuously meteorological data, discharge and water table fluctuations. Data on suspended sediment transport is obtained by means of a rising-stage sampler. Here we present the hydrological results corresponding to the years 2012-13 and 2013-14. The hydrological response of the catchment was moderate (annual runoff coefficient < 0.20), which could be in part explained by the high evapotranspiration rates reported in the area. Lows flows were recorded in summer and autumn, when the water reserves of the catchment were dry, and high flows occurred from January, when the catchment became wetter. The shape of the hydrographs, with slow response times, moderate peakflows and long recession limbs suggested a large contribution of subsurface flow, probably favored by deep and well structured soils in the bench terraces. Soil saturation areas were not observed during the study period, suggesting that soil infiltration processes and subsurface flow are important, and that the drainage system of the terraces is probably well maintained. No suspended sediment has been collected so far, confirming the hypothesis that subsurface flow might be a dominant runoff generation process.

Effect of Interaction of the Temperature Field and Supersaturation on the Morphology of the Solid-Vapor Interface in Crystal Growth by Physical Vapor Transport

NASA Technical Reports Server (NTRS)

Grasza, K.; Palosz, W.; Curreri, Peter A. (Technical Monitor)

2002-01-01

An in-situ study of the morphology of the solid-vapor interface during iodine crystal growth was done. The conditions for terrace growth, flat faces formation and retraction, competition between sources of steps, formation of protrusions, surface roughening, and defect overgrowth are demonstrated and discussed.

Secondary succession following logging in the Sitka sprucewestern hemlock forests of southeast Alaska: Implications for wildlife management.

Treesearch

Paul B. Alaback

1984-01-01

Preliminary information on general landscape patterns in southeast Alaska suggests that two major, compositionally distinct vegetation zones can be defined for the closed-forest type: western hemlock-Sitka spruce/Alaska huckleberry/bunchberry on the uplands, and Sitka spruce/devils club-salmonberry on alluvial flats and terraces.Recent clearcuts (0 to 30...

Crater Moreux

NASA Image and Video Library

1998-06-08

Color image of part of the Ismenius Lacus region of Mars (MC-5 quadrangle) containing the impact crater Moreux (right center); north toward top. The scene shows heavily cratered highlands in the south on relatively smooth lowland plains in the north separated by a belt of dissected terrain, containing flat-floored valleys, mesas, and buttes. This image is a composite of Viking medium-resolution images in black and white and low-resolution images in color. The image extends from latitude 36 degrees N. to 50 degrees N. and from longitude 310 degrees to 340 degrees; Lambert conformal conic projection. The dissected terrain along the highlands/lowlands boundary consists of the flat-floored valleys of Deuteronilus Mensae (on left) and Prontonilus Mensae (on right) and farther north the small, rounded hills of knobby terrain. Flows on the mensae floors contain striae that run parallel to valley walls; where valleys meet, the striae merge, similar to medial moraines on glaciers. Terraces within the valley hills have been interpreted as either layered rocks or wave terraces. The knobby terrain has been interpreted as remnants of the old, densely cratered highland terrain perhaps eroded by mass wasting. http://photojournal.jpl.nasa.gov/catalog/PIA00420

The geomorphology of the Chandeleur Island Wetlands

DOE Office of Scientific and Technical Information (OSTI.GOV)

Debusschere, K.; Penland, S.; Westphal, K.

1990-09-01

The Chandeleur Islands represent the largest and oldest transgressive barrier island arc in the northern Gulf of Mexico. Generated by the transgressive submergence of the St. Bernard delta complex, the Chandeleur Islands form the protective geologic framework for one of the richest areas of salt marsh and seagrass flats in Louisiana. The Chandeleur barrier island arc is 60 km long and consists of five individual islands backed by a linear, multiple bar system enclosing a shallow basin floored by extensive seagrass flats. The northern part of the Chandeleur chain is the highest in relief, elevation, width, and habitat diversity. Nonstormmore » morphology is predominantly a combination of continuous dunes and dune terraces. Numerous washover channels and large washover fans extend into the backbarrier environment. Further south, the island width decreases and washover flats and terraces dominate the shoreline morphology In the southernmost section, the island arc is fragmented into a series of small islands and shoals separated by tidal inlets. Between 1984 and 1989, aerial videotape, aerial photographic, and bathymetric surveys were used to map and monitor the geomorphic changes occurring along the shoreline and in backbarrier areas. The aerial videotape mapping surveys focused on the impacts of hurricanes Danny, Elena, and Juan on the geomorphology of the islands. Videotape imagery was acquired in July 1984 and in July (prestorm), August (post-Danny), September (post-Elena), and November (post-Juan) 1985. A coastal geomorphic classification was developed to map the spatial and temporal landscape changes between surveys.« less

Structure sensitivity in the kinetics and the dynamics of CO oxidation over stepped Pd(335) studied by the molecular beam infrared chemiluminescence technique: Determination of working sites during the steady-state reaction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Uetsuka, H.; Watanabe, K.; Kimpara, H.

Kinetics and dynamics of CO oxidation have been studied on a stepped Pd(335) surface at a steady-state condition and compared with those on flat Pd(111). The infrared (IR) chemiluminescence technique was applied to determine where the active catalytic sites are on the Pd(335) surface. Since the vibrational energy state of the product CO{sub 2} is sensitive to the structures of the reaction sites on Pd surfaces, information about the working reaction sites during the steady-state CO oxidation can be obtained from the IR emission spectra of the product CO{sub 2}. The production rate of CO{sub 2} was higher on Pd(335)more » than on Pd(111), indicating that the steps on the surface enhance the catalytic activity for Co oxidation under the steady-state condition. However, the rate data do not necessarily show the real active sites for the CO + O recombination reaction. At a surface temperature of 850 K, the vibrational Boltzmann temperature (T{sub v}) of the product CO{sub 2} on Pd(335) was quite different from (much lower than) that on Pd(111), although the Pd(335) surface has four-atom wide (111) terraces. The lower T{sub v} value on Pd(335) was similar to that on Pd(110)(1 x 1), indicating that a relatively linear activated CO{sub 2} complex was formed. Therefore, during the steady-state CO oxidation on Pd(335), the reaction does not take place on the (111) terrace sites, but mostly on the step sites at 850 K. On the contrary, as the CO coverage increased at a lower surface temperature and at a high CO/O{sub 2} ratio, the T{sub v} values on Pd(335) tend to approach those on Pd(111), indicating that the contribution of the active sites on the steps is decreased and the working reaction sites shift to the (111) terrace sites.« less

Influence of Substrate Bonding and Surface Morphology on Dynamic Organic Layer Growth: Perylenetetracarboxylic Dianhydride on Au(111).

PubMed

Schmidt, Thomas; Marchetto, Helder; Groh, Ullrich; Fink, Rainer H; Freund, Hans-Joachim; Umbach, Eberhard

2018-05-15

We investigated the dynamics of the initial growth of the first epitaxial layers of perylenetetracarboxylic dianhydride (PTCDA) on the Au(111) surface with high lateral resolution using the aberration-corrected spectro-microscope SMART. With this instrument, we could simultaneously study the different adsorption behaviors and layer growth on various surface areas consisting of either a distribution of flat (111) terraces, separated by single atomic steps ("ideal surface"), or on areas with a high density of step bunches and defects ("realistic surface"). The combined use of photoemission electron microscopy, low-energy electron microscopy, and μ-spot X-ray absorption provided a wealth of new information, showing that the growth of the archetype molecule PTCDA not only has similarities but also has significant differences when comparing Au(111) and Ag(111) substrate surfaces. For instance, under otherwise identical preparation conditions, we observed different growth mechanisms on different surface regions, depending on the density of step bunches. In addition, we studied the spatially resolved desorption behavior which also depends on the substrate morphology.

Atom-Scale Mechanisms for Unstable Growth on Patterned GaAs(001)

NASA Astrophysics Data System (ADS)

Tadayyon-Eslami, Tabassom; Kan, Hung-Chih; Calhoun, Lynn; Phaneuf, Ray

2007-03-01

Molecular beam epitaxy on patterned GaAs(001) under standard conditions of temperature (˜600 C), rate (˜ 0.3 nm/s) and flux ratio (As2/Ga˜10:1) leads to a transient instability toward perturbation of the flat surface [1]. Lowering the temperature through approximately 540^oC, roughly coincident with the preroughening temperature changes the mode of this instability [2]; however, as we show in this talk, observations of the As2 flux dependence rule out both preroughening and a reconstructive phase transition as driving the growth mode change. Instead, we find evidence that the change in unstable growth mode can be explained by a competition between decreased adatom collection rate on small terraces and a small anisotropic multi-step Ehrlich-Schwoebel barrier. We relate these effects to the up-down symmetry breaking term which commonly appears in continuum equations for growth. [1] H.-C. Kan, S. Shah, T. Tadayyon-Eslami and R.J. Phaneuf, Phys. Rev. Lett., 92, 146101 (2004). [2] T. Tadayyon-Eslami, H.-C. Kan, L. C. Calhoun and R. J. Phaneuf, Phys. Rev. Lett., 97, 126101 (2006).

Energy of Supported Metal Catalysts: From Single Atoms to Large Metal Nanoparticles

DOE PAGES

James, Trevor E.; Hemmingson, Stephanie L.; Campbell, Charles T.

2015-08-14

It is known that many catalysts consist of late transition metal nanoparticles dispersed across oxide supports. The chemical potential of the metal atoms in these particles correlate with their catalytic activity and long-term thermal stability. This chemical potential versus particle size across the full size range between the single isolated atom and bulklike limits is reported here for the first time for any metal on any oxide. The chemical potential of Cu atoms on CeO 2(111) surfaces, determined by single crystal adsorption calorimetry of gaseous Cu atoms onto slightly reduced CeO 2(111) at 100 and 300 K is shown tomore » decrease dramatically with increasing Cu cluster size. The Cu chemical potential is ~110 kJ/mol higher for isolated Cu adatoms on stoichometric terrace sites than for Cu in nanoparticles exceeding 2.5 nm diameter, where it reaches the bulk Cu(solid) limit. In Cu dimers, Cu’s chemical potential is ~57 kJ/mol lower at step edges than on stoichiometric terrace sites. Since Cu avoids oxygen vacancies, these monomer and dimer results are not strongly influenced by the 2.5% oxygen vacancies present on this CeO 2 surface and are thus considered representative of stoichiometric CeO 2(111) surfaces.« less

Self-diffusion on iridium (100). A structure investigation by field-ion microscopy

NASA Astrophysics Data System (ADS)

Friedl, A.; Schütz, O.; Müller, K.

1992-04-01

An iridium atom was thermally activated for diffusion on the (100) terrace of an Ir tip. The residence sites of the atom between diffusion cycles were recorded by means of a computer-controlled video system which generates a map of all occupied sites. For a field evaporated tip at low temperature this map is a c(2 × 2) grid indicating that only every other fourfold hollow in every other row of an undistor ted (100) surface can be occupied by a diffusing atom. This extraordinary behaviour was already reported by Chen and Tsong [Phys. Rev. Lett. 64 (1990) 3147]. The authors base their interpretation on an exchange diffusion mechanism. As an alternative explanation we propose a local adsorbate induced (2 × 2) reconstruction of the substrate. After heating the same terrace to temperatures above 500 K the residence map of the Ir atom indicates a (1 × 1) structure which, however, contains residues of a c(2 × 2) diffusion pattern: while the diffusion still takes place mainly on a c(2 × 2) sublattice, the diffusion path changes occasionally from one sublattice to the other. This can also be understood by local adsorbate induced distortions.

Temperature-modulated annealing of c-plane sapphire for long-range-ordered atomic steps

NASA Astrophysics Data System (ADS)

Yatsui, Takashi; Kuribara, Kazunori; Sekitani, Tsuyoshi; Someya, Takao; Yoshimoto, Mamoru

2016-03-01

High-quality single-crystalline sapphire is used to prepare various semiconductors because of its thermal stability. Here, we applied the tempering technique, which is well known in the production of chocolate, to prepare a sapphire substrate. Surprisingly, we successfully realised millimetre-range ordering of the atomic step of the sapphire substrate. We also obtained a sapphire atomic step with nanometre-scale uniformity in the terrace width and atomic-step height. Such sapphire substrates will find applications in the preparation of various semiconductors and devices.

Terraced spreading of simple liquids on solid surfaces

NASA Technical Reports Server (NTRS)

Yang, Ju-Xing; Koplik, Joel; Banavar, Jayanth R.

1992-01-01

We have studied the spreading of liquid drops on a solid surface by molecular-dynamics simulations of coexisting three-phase Lennard-Jones systems of liquid, vapor, and solid. We consider both spherically symmetric atoms and diatomic molecules, and a range of interaction strengths. As the attraction between liquid and solid increases we observe a smooth transition in spreading regimes, from partial to complete to terraced wetting. In the terraced case, where distinct monomolecular layers spread with different velocities, the layers are ordered but not solid, with substantial molecular diffusion both within and between layers. The quantitative behavior resembles recent experimental findings, but the detailed dynamics differ. In particular, the layers exhibit an unusual spreading law, where their radii vary in time as R-squared approximately equal to log10t, which disagrees with experiments on polymeric liquids as well as recent calculations.

Modeling right-lateral offset of a Late Pleistocene terrace riser along the Polaris fault using ground based LiDAR imagery

NASA Astrophysics Data System (ADS)

Howle, J. F.; Bawden, G. W.; Hunter, L. E.; Rose, R. S.

2009-12-01

High resolution (centimeter level) three-dimensional point-cloud imagery of offset glacial outwash deposits were collected by using ground based tripod LiDAR (T-LiDAR) to characterize the cumulative fault slip across the recently identified Polaris fault (Hunter et al., 2009) near Truckee, California. The type-section site for the Polaris fault is located 6.5 km east of Truckee where progressive right-lateral displacement of middle to late Pleistocene deposits is evident. Glacial outwash deposits, aggraded during the Tioga glaciation, form a flat lying ‘fill’ terrace on both the north and south sides of the modern Truckee River. During the Tioga deglaciation melt water incised into the terrace producing fluvial scarps or terrace risers (Birkeland, 1964). Subsequently, the terrace risers on both banks have been right-laterally offset by the Polaris fault. By using T-LiDAR on an elevated tripod (4.25 m high), we collected 3D high-resolution (thousands of points per square meter; ± 4 mm) point-cloud imagery of the offset terrace risers. Vegetation was removed from the data using commercial software, and large protruding boulders were manually deleted to generate a bare-earth point-cloud dataset with an average data density of over 240 points per square meter. From the bare-earth point cloud we mathematically reconstructed a pristine terrace/scarp morphology on both sides of the fault, defined coupled sets of piercing points, and extracted a corresponding displacement vector. First, the Polaris fault was approximated as a vertical plane that bisects the offset terrace risers, as well as bisecting linear swales and tectonic depressions in the outwash terrace. Then, piercing points to the vertical fault plane were constructed from the geometry of the geomorphic elements on either side of the fault. On each side of the fault, the best-fit modeled outwash plane is projected laterally and the best-fit modeled terrace riser projected upward to a virtual intersection in space, creating a vector. These constructed vectors were projected to intersection with the fault plane, defining statistically significant piercing points. The distance between the coupled set of piercing points, within the plane of the fault, is the cumulative displacement vector. To assess the variability of the modeled geomorphic surfaces, including surface roughness and nonlinearity, we generated a suite of displacement models by systematically incorporating larger areas of the model domain symmetrically about the fault. Preliminary results of 10 models yield an average cumulative displacement of 5.6 m (1 Std Dev = 0.31 m). As previously described, Tioga deglaciation melt water incised into the outwash terrace leaving terrace risers that were subsequently offset by the Polaris fault. Therefore, the age of the Tioga outwash terrace represents a maximum limiting age of the tectonic displacement. Using regional age constraints of 15 to 13 kya for the Tioga outwash terrace (Benson et al., 1990; Clark and Gillespie, 1997; James et al., 2002) and the above model results, we estimate a preliminary minimum fault slip rate of 0.40 ± 0.05 mm/yr for the Polaris type-section site.

Magnetization reversal in YIG/GGG(111) nanoheterostructures grown by laser molecular beam epitaxy.

PubMed

Krichevtsov, Boris B; Gastev, Sergei V; Suturin, Sergey M; Fedorov, Vladimir V; Korovin, Alexander M; Bursian, Viktor E; Banshchikov, Alexander G; Volkov, Mikhail P; Tabuchi, Masao; Sokolov, Nikolai S

2017-01-01

Thin (4-20 nm) yttrium iron garnet (Y 3 Fe 5 O 12 , YIG) layers have been grown on gadolinium gallium garnet (Gd 3 Ga 5 O 12 , GGG) 111-oriented substrates by laser molecular beam epitaxy in 700-1000 °C growth temperature range. The layers were found to have atomically flat step-and-terrace surface morphology with step height of 1.8 Å characteristic for YIG(111) surface. As the growth temperature is increased from 700 to 1000 °C the terraces become wider and the growth gradually changes from layer by layer to step-flow regime. Crystal structure studied by electron and X-ray diffraction showed that YIG lattice is co-oriented and laterally pseudomorphic to GGG with small rhombohedral distortion present perpendicular to the surface. Measurements of magnetic moment, magneto-optical polar and longitudinal Kerr effect (MOKE), and X-ray magnetic circular dichroism (XMCD) were used for study of magnetization reversal for different orientations of magnetic field. These methods and ferromagnetic resonance studies have shown that in zero magnetic field magnetization lies in the film plane due to both shape and induced anisotropies. Vectorial MOKE studies have revealed the presence of an in-plane easy magnetization axis. In-plane magnetization reversal was shown to occur through combination of reversible rotation and abrupt irreversible magnetization jump, the latter caused by domain wall nucleation and propagation. The field at which the flip takes place depends on the angle between the applied magnetic field and the easy magnetization axis and can be described by the modified Stoner-Wohlfarth model taking into account magnetic field dependence of the domain wall energy. Magnetization curves of individual tetrahedral and octahedral magnetic Fe 3+ sublattices were studied by XMCD.

Magnetization reversal in YIG/GGG(111) nanoheterostructures grown by laser molecular beam epitaxy

NASA Astrophysics Data System (ADS)

Krichevtsov, Boris B.; Gastev, Sergei V.; Suturin, Sergey M.; Fedorov, Vladimir V.; Korovin, Alexander M.; Bursian, Viktor E.; Banshchikov, Alexander G.; Volkov, Mikhail P.; Tabuchi, Masao; Sokolov, Nikolai S.

2017-12-01

Thin (4-20 nm) yttrium iron garnet (Y3Fe5O12, YIG) layers have been grown on gadolinium gallium garnet (Gd3Ga5O12, GGG) 111-oriented substrates by laser molecular beam epitaxy in 700-1000 °C growth temperature range. The layers were found to have atomically flat step-and-terrace surface morphology with step height of 1.8 Å characteristic for YIG(111) surface. As the growth temperature is increased from 700 to 1000 °C the terraces become wider and the growth gradually changes from layer by layer to step-flow regime. Crystal structure studied by electron and X-ray diffraction showed that YIG lattice is co-oriented and laterally pseudomorphic to GGG with small rhombohedral distortion present perpendicular to the surface. Measurements of magnetic moment, magneto-optical polar and longitudinal Kerr effect (MOKE), and X-ray magnetic circular dichroism (XMCD) were used for study of magnetization reversal for different orientations of magnetic field. These methods and ferromagnetic resonance studies have shown that in zero magnetic field magnetization lies in the film plane due to both shape and induced anisotropies. Vectorial MOKE studies have revealed the presence of an in-plane easy magnetization axis. In-plane magnetization reversal was shown to occur through combination of reversible rotation and abrupt irreversible magnetization jump, the latter caused by domain wall nucleation and propagation. The field at which the flip takes place depends on the angle between the applied magnetic field and the easy magnetization axis and can be described by the modified Stoner-Wohlfarth model taking into account magnetic field dependence of the domain wall energy. Magnetization curves of individual tetrahedral and octahedral magnetic Fe3+ sublattices were studied by XMCD.

Magnetization reversal in YIG/GGG(111) nanoheterostructures grown by laser molecular beam epitaxy

PubMed Central

Krichevtsov, Boris B.; Gastev, Sergei V.; Suturin, Sergey M.; Fedorov, Vladimir V.; Korovin, Alexander M.; Bursian, Viktor E.; Banshchikov, Alexander G.; Volkov, Mikhail P.; Tabuchi, Masao; Sokolov, Nikolai S.

2017-01-01

Abstract Thin (4–20 nm) yttrium iron garnet (Y3Fe5O12, YIG) layers have been grown on gadolinium gallium garnet (Gd3Ga5O12, GGG) 111-oriented substrates by laser molecular beam epitaxy in 700–1000 °C growth temperature range. The layers were found to have atomically flat step-and-terrace surface morphology with step height of 1.8 Å characteristic for YIG(111) surface. As the growth temperature is increased from 700 to 1000 °C the terraces become wider and the growth gradually changes from layer by layer to step-flow regime. Crystal structure studied by electron and X-ray diffraction showed that YIG lattice is co-oriented and laterally pseudomorphic to GGG with small rhombohedral distortion present perpendicular to the surface. Measurements of magnetic moment, magneto-optical polar and longitudinal Kerr effect (MOKE), and X-ray magnetic circular dichroism (XMCD) were used for study of magnetization reversal for different orientations of magnetic field. These methods and ferromagnetic resonance studies have shown that in zero magnetic field magnetization lies in the film plane due to both shape and induced anisotropies. Vectorial MOKE studies have revealed the presence of an in-plane easy magnetization axis. In-plane magnetization reversal was shown to occur through combination of reversible rotation and abrupt irreversible magnetization jump, the latter caused by domain wall nucleation and propagation. The field at which the flip takes place depends on the angle between the applied magnetic field and the easy magnetization axis and can be described by the modified Stoner–Wohlfarth model taking into account magnetic field dependence of the domain wall energy. Magnetization curves of individual tetrahedral and octahedral magnetic Fe3+ sublattices were studied by XMCD. PMID:28685003

Origin of Florida Canyon and the role of spring sapping on the formation of submarine box canyons

USGS Publications Warehouse

Paull, Charles K.; Spiess, Fred N.; Curray, Joseph R.; Twichell, David C.

1990-01-01

Florida Canyon, one of a series of major submarine canyons on the southwestern edge of the Florida Platform, was surveyed using GLORIA, SeaBeam, and Deep-Tow technologies, and it was directly observed during three DSRV Alvin dives. Florida Canyon exhibits two distinct morphologies: a broad V-shaped upper canyon and a deeply entrenched, flat-floored, U-shaped lower canyon. The flat- floored lower canyon extends 20 km into the Florida Platform from the abyssal Gulf. The lower canyon ends abruptly at an ∼3 km in diameter semicircular headwall that rises 750 m with a >60° slope angle to the foot of the upper canyon. The sides of the lower canyon are less steep than its headwall and are characterized by straight faces that occur along preferred orientations and indicate a strong joint control. The upper canyon is characterized by a gently sloping, straight V-shaped central valley cut into a broad terrace. The flat floor of the upper canyon continues as terraces along the upper walls of the lower canyon. On the flanks of the upper canyon, there are five >50-m-deep, >0.5-km-wide, closed sink-hole-like depressions which indicate subsurface dissolution within the platform. The origin of the lower canyon is difficult to explain with traditional models of submarine canyon formation by external physical processes. The movement of ground water, probably with high salinities and reduced compounds along regional joints, may have focused the corrosive force of submarine spring sapping at the head of the lower canyon to produce the canyon's present shape.

Atomic layer deposition overcoating: tuning catalyst selectivity for biomass conversion.

PubMed

Zhang, Hongbo; Gu, Xiang-Kui; Canlas, Christian; Kropf, A Jeremy; Aich, Payoli; Greeley, Jeffrey P; Elam, Jeffrey W; Meyers, Randall J; Dumesic, James A; Stair, Peter C; Marshall, Christopher L

2014-11-03

The terraces, edges, and facets of nanoparticles are all active sites for heterogeneous catalysis. These different active sites may cause the formation of various products during the catalytic reaction. Here we report that the step sites of Pd nanoparticles (NPs) can be covered precisely by the atomic layer deposition (ALD) method, whereas the terrace sites remain as active component for the hydrogenation of furfural. Increasing the thickness of the ALD-generated overcoats restricts the adsorption of furfural onto the step sites of Pd NPs and increases the selectivity to furan. Furan selectivities and furfural conversions are linearly correlated for samples with or without an overcoating, though the slopes differ. The ALD technique can tune the selectivity of furfural hydrogenation over Pd NPs and has improved our understanding of the reaction mechanism. The above conclusions are further supported by density functional theory (DFT) calculations. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A scanning tunnelling microscopy study of C and N adsorption phases on the vicinal Ni(100) surfaces Ni(810) and Ni(911)

NASA Astrophysics Data System (ADS)

Driver, S. M.; Toomes, R. L.; Woodruff, D. P.

2016-04-01

The influence of N and C chemisorption on the morphology and local structure of nominal Ni(810) and Ni(911) surfaces, both vicinal to (100) but with [001] and [ 01 1 bar ] step directions, respectively, has been investigated using scanning tunnelling microscopy (STM) and low energy electron diffraction. Ni(911) undergoes substantial step bunching in the presence of both adsorbates, with the (911)/N surface showing (411) facets, whereas for Ni(810), multiple steps 2-4 layers high are more typical. STM atomic-scale images show the (2 × 2)pg 'clock' reconstruction on the (100) terraces of the (810) surfaces with both C and N, although a second c(2 × 2) structure, most readily reconciled with a 'rumpling' reconstruction, is also seen on Ni(810)/N. On Ni(911), the clock reconstruction is not seen on the (100) terraces with either adsorbate, and these images are typified by protrusions on a (1 × 1) mesh. This absence of clock reconstruction is attributed to the different constraints imposed on the lateral movements of the surface Ni atoms adjacent to the up-step edge of the terraces with a [ 01 1 bar ] step direction.

Large depressions, thickened terraces, and gravitational deformation in the Ebro River valley (Zaragoza area, NE Spain): Evidence of glauberite and halite interstratal karstification

NASA Astrophysics Data System (ADS)

Guerrero, Jesús; Gutiérrez, Francisco; Galve, Jorge P.

2013-08-01

In the studied reach of the Ebro Valley, the terrace and pediment sediments deposited over glauberite- and halite-bearing evaporites show local thickenings (> 50 m) recording dissolution-induced synsedimentary subsidence. Recent data on the lithostratigraphy of the evaporite sequence allow relating the alluvium thickenings with either halite or glauberite dissolution. The alluvium-filled dissolution basin underlying the youngest terraces (T8-T11) is ascribed to halite karstification; the top of a halite unit approximately 75 m thick is situated 40-15 m below the valley bottom. The thickenings of terrace (T1-T7) and pediment sediments are attributed to interstratal glauberite karstification: (1) Coincidence between the elevation range of the terraces and that of the glauberite-rich unit. Glauberite beds reach 30 and 100 m in single-bed and cumulative thickness, respectively. (2) The exposed bedrock underlying thickened alluvium shows abundant subsidence features indicative of interstratal karstification. The most common structure corresponds to hectometer-scale sag basins with superimposed collapses in the central sector of each basin. The subsided bedrock is frequently transformed into dissolution-collapse breccias showing a complete textural gradation, from crackle packbreccias to chaotic floatbreccias and karstic residues. (3) Paleokarst exposures show evidence of karstification confined to specific beds made up of secondary gypsum after precursory glauberite, partly dissolved and partly replaced. Despite the magnitude of the subsidence recorded by the thickened alluvium and unlike nearby tributaries, the terraces show a continuous and parallel arrangement indicating that the fluvial system was able to counterbalance subsidence by aggradation. A number of kilometer-size flat-bottom depressions have been developed in the valley margin, typically next to and inset into thickened terrace and pediment deposits. The subsidence structures exposed in artificial excavations excavated in the bottom of some depressions and the correlation between the altitudinal distribution of these basins and that of the glauberite-rich unit reveal that subsidence related to interstratal glauberite karstification is the main process involved in their genesis. This research ascribes for the first time the thickenings and deformation of specific terrace levels and pediment levels and the development of large karstic depressions to interstratal karstification of exceptionally thick glauberite units.

Three Recipes to Decipher Late Pleistocene Slip Rates of the Chelungpu Thrust (Central Taiwan), based on OSL-dated Folded Terraces

NASA Astrophysics Data System (ADS)

Le Beon, M.; Jaiswal, M.; Ustaszewski, M.; Suppe, J.; Chen, Y.

2009-12-01

Alluvial terraces may be used as markers of the deformation across faults. According to fault-bend folding theory (Suppe, 1983; Fig. 1), the amount of slip recorded since abandonment of a terrace level may be computed in 3 ways by measuring: 1/ terrace heights on the hanging wall relative to the foot wall (h1, h2), 2/ difference in terrace elevation across the fold scarp (Δh), and 3/ width of the fold scarp (WL), heights and scarp width being independent measurements. Contrary to method 3, methods 1 and 2 require knowledge of the subsurface structure of the fault. We aim to use these recipes to determine Late Pleistocene slip rates of the Chelungpu Thrust (CT), one of the most important active faults in the western foothills of Taiwan. It is responsible for the 1999 Mw7.6 Chi-Chi earthquake, which coseismic displacement field was well documented. Yet, the Quaternary activity of CT was examined only at 1 site, located on the southern CT and that yielded a Holocene slip rate of 12.9 ± 4.8 mm/a. Our study area lies on the northern CT, near the town of Hsinshe, where the N-S striking surface rupture of the 1999 earthquake merges into a NE-SW to E-W trending surface fold, and where the largest coseismic displacements are reported. The 3D subsurface geometry of CT has been well imaged (Yue et al, 2005). In Hsinshe area, it shows a N-S to E-W trending fault plane of varying dip with depth, that ramps from a shallow flat detachment. Three main distinct levels of fluvial terraces are discernible on the hanging wall near Hsinshe. They show progressive folding by kink-band migration in relation to the underlying fault geometry, forming a ~50m to ~120m high fold scarp from the lowest (T3) to the highest (T1) terrace level. Detailed morphological analysis using 20m resolution DEM and microtopography will allow us to quantify terrace heights relative to the modern riverbed and scarp heights, as well as to characterize the morphology of Late Pleistocene terrace risers versus tectonic fold scarps. As often as possible, we will implement the 3 recipes to determine the amount of slip undergone by each terrace level. Preliminary estimates based on scarp height (method 2) provide slip of ~700-800m for the highest terrace T1, ~470-530m for T2, and ~250-350m for T3. First results from terrace heights (method 1) are significantly higher and may account for changes in base level that we will be able to quantify. On-going age determination by OSL dating of all terrace levels should provide a detailed history of the deformation across the CT since the Late Pleistocene. Recent ages from T2 and T3 suggest slip rate estimates of ~22 ± 2 mm/a since ~22 ka and of ~17 ± 3 mm/a since ~17 ka.

Geologic map of the Winslow 30’ × 60’ quadrangle, Coconino and Navajo Counties, northern Arizona

USGS Publications Warehouse

Billingsley, George H.; Block, Debra L.; Redsteer, Margaret Hiza

2013-01-01

The Winslow 30’ × 60’ quadrangle encompasses approximately 5,018 km2 (1,960 mi2) within Coconino and Navajo Counties of northern Arizona. It is characterized by gently dipping Paleozoic and Mesozoic strata that dip 1° to 2° northeastward in the southwestern part of the quadrangle and become nearly flat-lying in the northeastern part of the quadrangle. In the northeastern part, a shallow Cenozoic erosional basin developed about 20 million years ago, which subsequently was filled with flat-lying Miocene and Pliocene lacustrine sediments of the Bidahochi Formation, as well as associated volcanic rocks of the Hopi Buttes Volcanic Field. The lacustrine sediments and volcanic rocks unconformably overlie Triassic, Jurassic, and Cretaceous strata. Beginning about early Pliocene time, the Little Colorado River and its tributaries began to remove large volumes of Paleozoic and Mesozoic bedrock from the map area. This erosional development has continued through Pleistocene and Holocene time. Fluvial sediments accumulated episodically throughout this erosional cycle, as indicated by isolated Pliocene(?) and Pleistocene Little Colorado River terrace-gravel deposits on Tucker Mesa and Toltec Divide west of Winslow and younger terrace-gravel deposits along the margins of the Little Colorado River Valley. These gravel deposits suggest that the ancestral Little Colorado River and its valley has eroded and migrated northeastward toward its present location and largely parallels the strike of the Chinle Formation. Today, the Little Colorado River meanders within a 5-km (3-mi) wide valley between Winslow and Leupp, where soft strata of the Chinle Formation is mostly covered by an unknown thickness of Holocene flood-plain deposits. In modern times, the Little Colorado River channel has changed its position as much as a 1.5 km (1 mi) during flood events, but for much of the year the channel is a dry river bed. Surficial alluvial and eolian deposits cover extensive parts of the bedrock outcrops over the entire Winslow quadrangle.

Fully methylated, atomically flat (111) silicon surface

NASA Astrophysics Data System (ADS)

Fidélis, A.; Ozanam, F.; Chazalviel, J.-N.

2000-01-01

The atomically flat hydrogenated (111) silicon surface has been methylated by anodization in a Grignard reagent and the surface obtained characterized by infrared spectroscopy. 100% substitution of the hydrogen atoms by methyl groups is observed. The resulting surface exhibits preserved ordering and superior chemical stability.

Tertiary and Quaternary Research with Remote Sensing Methods

NASA Technical Reports Server (NTRS)

Conel, J. E.

1985-01-01

Problems encountered in mapping the Quaternary section of the Wind River Region using remote sensing methods are discussed. Analysis of the stratigraphic section is a fundamental aspect of the geologic study of sedimentary basins. Stratigraphic analysis of post-Cretaceous rocks in the Wind River Basin encounters problems of a distinctly different character from those involved in studying the pre-Cretaceous section. The interior of the basin is predominantly covered by Tertiary and Quaternary sediments. These rocks, except on the basin margin to the north, are mostly flat lying or gently dipping. The Tertiary section consists of sandstones, siltstones, and tuffaceous sediments, some variegated, but in general poorly bedded and of great lithologic similarity. The Quaternary sediments consist of terrace, fan, and debris tongue deposits, unconsolidated alluvium occupying the bottoms of modern watercourses, deposits of eolian origin and tufa. Terrace and fan deposits are compositionally diverse and reflect the lithologic diversity of the source terranes.

Wetting and spreading at the molecular scale

NASA Technical Reports Server (NTRS)

Koplik, Joel; Banavar, Jayanth R.

1994-01-01

We have studied the microscopic aspects of the spreading of liquid drops on a solid surface by molecular dynamics simulations of coexisting three-phase Lennard-Jones systems of liquid, vapor and solid. We consider both spherically symmetric atoms and chain-like molecules, and a range of interaction strengths. As the attraction between liquid and solid increases we observed a smooth transition in spreading regimes, from partial to complete to terraced wetting. In the terraced case, where distinct monomolecular layers spread with different velocities, the layers are ordered but not solid, with qualitative behavior resembling recent experimental findings, but with interesting differences in the spreading rate.

Detection of a Fermi-level crossing in Si(557)-Au with inverse photoemission

NASA Astrophysics Data System (ADS)

Lipton-Duffin, J. A.; MacLeod, J. M.; McLean, A. B.

2006-06-01

The unoccupied energy bands of the quasi-one-dimensional (1D) Si(557)-Au system have been studied with momentum-resolved inverse photoemission. A band is found that lies (0.4±0.4)eV above the Fermi level at the center of the surface Brillouin zone (Γ¯) . It disperses to higher binding energy, along the Γ Kmacr direction, and crosses the Fermi level at k‖=0.5±0.1Å-1 . The corresponding direction in real space is parallel to both the rows of silicon adatoms and the rows of embedded gold atoms that are distinctive features of this surface reconstruction. The location of the crossing is in good agreement with previously published photoemission data [Altmann , Phys. Rev. B 64, 035406 (2001); Ahn , Phys. Rev. Lett. 91, 196403 (2003)], where two closely spaced bands were found to disperse from the Kmacr zone boundary to lower binding energy and then cross the Fermi level. In addition to the band mentioned above, a band was found that has parabolic dispersion along Γ Kmacr , the direction that is parallel to the rows of embedded gold atoms. The band minimum for the parabolic band lies (0.8±0.4)eV below the vacuum level and it has an effective mass m*=(1.0±0.1)me , where me is the free electron mass. Perpendicular to the rows of gold atoms, as expected for a state with quasi-1D symmetry, it has flat dispersion. This band may be an image state resonance, overlapping the silicon conduction band continuum, and it is spatially localized to the edge of the silicon terraces.

Surface characterization of InP trenches embedded in oxide using scanning probe microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mannarino, Manuel, E-mail: manuel.mannarino@imec.be, E-mail: manuelmannarino@gmail.com; Chintala, Ravi; Vandervorst, Wilfried

2015-12-14

Metrology for structural and electrical analyses at device level has been identified as one of the major challenges to be resolved for the sub-14 nm technology nodes. In these advanced nodes, new high mobility semiconductors, such as III–V compounds, are grown in narrow trenches on a Si substrate. Probing the nature of the defects, the defect density, and the role of processing steps on the surface of such structures are prime metrology requirements. In order to enable defect analysis on a (III–V) surface, a proper sample preparation for oxide removal is of primary importance. In this work, the effectiveness of differentmore » chemical cleanings and thermal annealing procedures is investigated on both blanket InP and oxide embedded InP trenches by means of scanning probe microscopy techniques. It is found that the most effective approach is a combination of an HCl-based chemical cleaning combined with a low-temperature thermal annealing leading to an oxide free surface with atomically flat areas. Scanning tunneling microscopy (STM) has been the preferred method for such investigations on blanket films due to its intrinsic sub-nm spatial resolution. However, its application on oxide embedded structures is non-trivial. To perform STM on the trenches of interest (generally <20 nm wide), we propose a combination of non-contact atomic force microscopy and STM using the same conductive atomic force microscopy tip Our results prove that with these procedures, it is possible to perform STM in narrow InP trenches showing stacking faults and surface reconstruction. Significant differences in terms of roughness and terrace formation are also observed between the blanket and the oxide embedded InP.« less

Long-wave model for strongly anisotropic growth of a crystal step.

PubMed

Khenner, Mikhail

2013-08-01

A continuum model for the dynamics of a single step with the strongly anisotropic line energy is formulated and analyzed. The step grows by attachment of adatoms from the lower terrace, onto which atoms adsorb from a vapor phase or from a molecular beam, and the desorption is nonnegligible (the "one-sided" model). Via a multiscale expansion, we derived a long-wave, strongly nonlinear, and strongly anisotropic evolution PDE for the step profile. Written in terms of the step slope, the PDE can be represented in a form similar to a convective Cahn-Hilliard equation. We performed the linear stability analysis and computed the nonlinear dynamics. Linear stability depends on whether the stiffness is minimum or maximum in the direction of the step growth. It also depends nontrivially on the combination of the anisotropy strength parameter and the atomic flux from the terrace to the step. Computations show formation and coarsening of a hill-and-valley structure superimposed onto a long-wavelength profile, which independently coarsens. Coarsening laws for the hill-and-valley structure are computed for two principal orientations of a maximum step stiffness, the increasing anisotropy strength, and the varying atomic flux.

Pb chains on reconstructed Si(335) surface

NASA Astrophysics Data System (ADS)

Krawiec, Mariusz

2009-04-01

The structural and electronic properties of Si(335)-Au surface decorated with Pb atoms are studied by means of density-functional theory. The resulting structural model features Pb atoms bonded to neighboring Si and Au surface atoms, forming monoatomic chain located 0.2 nm above the surface. The presence of Pb chain leads to a strong rebonding of Si atoms at the step edge. The fact that Pb atoms occupy positions in the middle of terrace is consistent with scanning tunneling microscopy (STM) data and also confirmed by simulated STM images. The calculated band structure clearly shows one-dimensional metallic character. The calculated electronic bands remain in very good agreement with photoemission data.

Structural characterization of oxidized titanium surfaces

NASA Astrophysics Data System (ADS)

Jobin, M.; Taborelli, M.; Descouts, P.

1995-05-01

Oxidized titanium surfaces resulting from various processes have been structurally characterized by means of scanning force microscopy, x-ray photoemission spectroscopy (XPS), x-ray diffraction, and electron energy-loss spectroscopy (EELS) with losses in the 0-100 eV range. It has been found that the surface morphology has a granular structure for electropolished titanium and for titanium evaporated on mica at low substrate temperature (570 K), but changes to flat terraces for the films evaporated at higher temperature (770 K). Angular-dependent XPS has revealed the presence of a Ti2O3 suboxide at the Ti/TiO2 interface for electropolished titanium. Dry oxidation has been performed at 770 and 970 K on both weakly and highly crystallized evaporated titanium films oriented along (0001). In the case of underlying crystallized metallic titanium, the resulting TiO2 films are crystallized with the anatase (004) orientation for oxidation at 770 K and with rutile (200) orientation for oxidation at 970 K. EELS spectra interpreted in terms of the molecular orbitals of a (TiO6)8- cluster show that the local octahedral environment of titanium atoms is preserved on native oxides, even if these oxides are not crystallized.

Nucleation and growth of oxide islands during the initial-stage oxidation of (100)Cu-Pt alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Luo, Langli; Zhou, Guangwen, E-mail: gzhou@binghamton.edu; Kang, Yihong

2015-02-14

The initial-stage oxidation of (100) Cu-Pt alloys has been examined by in situ environmental transmission electron microscopy and ex situ atomic force microscopy (AFM). It is shown that the oxidation proceeds via the nucleation and growth of Cu{sub 2}O islands that show dependence on the alloy composition and oxidation temperature. The kinetic measurements on the oxide nucleation reveal that both the nucleation density and surface coverage of Cu{sub 2}O islands can be promoted by alloying more Pt in the Cu-Pt alloys. Increasing the oxidation temperature above 700 °C results in the growth of large Cu{sub 2}O islands that transits to amore » dendritic growth morphology. The ex situ AFM studies reveal that the nucleation of oxide islands can occur on surface terraces and the subsequent oxide growth depletes local terrace Cu atoms that results in the formation of surface pits.« less

Surface properties of atomically flat poly-crystalline SrTiO3

PubMed Central

Woo, Sungmin; Jeong, Hoidong; Lee, Sang A.; Seo, Hosung; Lacotte, Morgane; David, Adrian; Kim, Hyun You; Prellier, Wilfrid; Kim, Yunseok; Choi, Woo Seok

2015-01-01

Comparison between single- and the poly-crystalline structures provides essential information on the role of long-range translational symmetry and grain boundaries. In particular, by comparing single- and poly-crystalline transition metal oxides (TMOs), one can study intriguing physical phenomena such as electronic and ionic conduction at the grain boundaries, phonon propagation, and various domain properties. In order to make an accurate comparison, however, both single- and poly-crystalline samples should have the same quality, e.g., stoichiometry, crystallinity, thickness, etc. Here, by studying the surface properties of atomically flat poly-crystalline SrTiO3 (STO), we propose an approach to simultaneously fabricate both single- and poly-crystalline epitaxial TMO thin films on STO substrates. In order to grow TMOs epitaxially with atomic precision, an atomically flat, single-terminated surface of the substrate is a prerequisite. We first examined (100), (110), and (111) oriented single-crystalline STO surfaces, which required different annealing conditions to achieve atomically flat surfaces, depending on the surface energy. A poly-crystalline STO surface was then prepared at the optimum condition for which all the domains with different crystallographic orientations could be successfully flattened. Based on our atomically flat poly-crystalline STO substrates, we envision expansion of the studies regarding the TMO domains and grain boundaries. PMID:25744275

Seismic influence in the Quaternary uplift of the Central Chile coastal margin, preliminary results.

NASA Astrophysics Data System (ADS)

Valdivia, D.; del Valle, F.; Marquardt, C.; Elgueta, S.

2017-12-01

In order to quantify the influence of NW striking potentially seismogenic normal faults over the longitudinal variation of the Central Chile Coastal margin uplift, we measured Quaternary marine terraces, which represent the tectonic uplift of the coastal margin. Movement in margin oblique normal faults occurs by co-seismic extension of major subduction earthquakes and has occurred in the Pichilemu fault, generating a 7.0 Mw earthquake after the 2010 8.8 Mw Maule earthquake.The coastal area between 32° and 34° S was selected due to the presence of a well-preserved sequence of 2 to 5 Quaternary marine terraces. In particular, the margin oblique normal NW-trending, SW-dipping Laguna Verde fault, south of Valparaiso (33° S) puts in contact contrasting morphologies: to the south, a flat coast with wide marine terraces is carved in both, Jurassic plutonic rocks and Neogene semi-consolidated marine sediments; to the north, a steeper scarp with narrower marine terraces, over 120 m above the corresponding ones in the southern coast, is carved in Jurassic plutonic rocks.We have collected over 6 months microseimic data, providing information on seismic activity and underground geometry of the Laguna Verde fault. We collected ca. 100 systematic measurements of fringes at the base of paleo coastal scarps through field mapping and a 5 m digital elevation model. These fringes mark the maximum sea level during the terrace's carving.The heights of these fringes range between 0 and 250 masl. We estimate a 0.7 mm/yr slip rate for the Laguna Verde fault based on the height difference between corresponding terraces north- and southward, with an average uplift rate of 0.3 mm/yr for the whole area.NW striking normal faults, besides representing a potential seismic threat to the near population on one of the most densely populated areas of Chile, heavily controls the spatial variation of the coastal margin uplift. In Laguna Verde, the uplift rate differs more than three times northward of the fault.

Controlled epitaxial graphene growth within removable amorphous carbon corrals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Palmer, James; Hu, Yike; Hankinson, John

2014-07-14

We address the question of control of the silicon carbide (SiC) steps and terraces under epitaxial graphene on SiC and demonstrate amorphous carbon (aC) corrals as an ideal method to pin SiC surface steps. aC is compatible with graphene growth, structurally stable at high temperatures, and can be removed after graphene growth. For this, aC is first evaporated and patterned on SiC, then annealed in the graphene growth furnace. There at temperatures above 1200 °C, mobile SiC steps accumulate at the aC corral that provide effective step flow barriers. Aligned step free regions are thereby formed for subsequent graphene growth atmore » temperatures above 1330 °C. Atomic force microscopy imaging supports the formation of step-free terraces on SiC with the step morphology aligned to the aC corrals. Raman spectroscopy indicates the presence of good graphene sheets on the step-free terraces.« less

An Archaeological Reconnaissance of the Over-the-Horizon Radar Project Transmitter Site, Buffalo Flat, Christmas Lake Valley, Lake County, Oregon

DTIC Science & Technology

1986-04-01

intermediate composition. The Fort Rock formation is comprised of four rock types: tuff, diatomite , basaltic agglomerate, and basaltic lava, in descending...location based on bearings on landmarks some distance from the survey area. The property survey established four blocks (areas A, B, C, and D in Figure... physical evidence of prehistoric lake- shores would be evident in the project area in the form of terrace remnants, strand lines, etc. Based on

Modelling hydrological connectivity in semi-arid flat areas: effect of the flow accumulation algorithm on the spatial pattern

NASA Astrophysics Data System (ADS)

López-Vicente, Manuel; Álvarez, Sara

2017-04-01

Much of the water and sediment fluxes in semi-arid landscapes are found to be concentrated in localized pathways. Identifying the location of these pathways is important for management and restoration. This task becomes more complicated in flat areas, such as alluvial terraces, where geomorphic features of concentrated overland flow (rills and ephemeral gullies) are scarce or inexistent. Field identification of sediment delivery pathways as well as depositional areas is also difficult and challenged. The concept of hydrological connectivity (HC) helps us to express the complexity of landscape non-linear responses to rainfall inputs. One of the unsolved issues in overland flow modelling studies is the choice of the right flow accumulation algorithm (FAA). There is an abundant literature on runoff generation under semi-arid conditions, and relating HC and land use management and changes. However, we found a scientific gap in the literature focussed on modelling of HC in flat areas under semi-arid conditions. This study aims to fill in this gap by modelling HC in alluvial terraces (28 ha) in NE Spain under semi-arid conditions (342 mm / year), mainly devoted to rain-fed cereal fields, by using eight FAA. For this purpose, we applied a modified version of the Borselli's index of runoff and sediment connectivity (IC). The study area includes seven fields on flat alluvial terraces, three fields on a gentle slope, small patches of scrubland, and twelve grass buffer strips that are located between each set of fields. Gentle and flat areas (S < 4%) cover 38% of the total surface. A photogrammetry-derived DEM was obtained through a flight, using a photographic camera installed in a professional mapping drone (model eBee by senseFly Ltd.). In order to minimize the effect of the vegetation on the photogrammetry restitution technique, pictures were taken in early spring, before the growth of the cereals. Then, several DEMs were generated independently. For this study, we chose the DEM at 0.5 x 0.5 m of spatial resolution. Before running the IC model, the continuity of the flow path lines throughout the landscape was ensured by removing the local depressions of the DEM with the algorithm of Planchon & Darboux (2001). Taking in mind the low slope of the area, we considered a minimum slope gradient of 0.01 degrees that can be associated with unrealistic sinks or DEM artifices. We run the IC model with the following eight flow accumulation algorithms, without using threshold values for linear flow: four single flow (D8, Rho8, KRA and D-Infinity) and the four multiple flow (MD, BDR, DEMON and TMD). Input working out and GIS calculations were done with three software: QGIS©-64 2.14.0-Essen, SAGA©-64 2.1.2 and ArcGIS© 10.3. As used by many authors, we used the C-RUSLE factor to assess the landscape-weighting factor of the IC model. Simulated HC was validated in the field by identifying the stable, erosion, delivery and sedimentation forms. This study will contribute to hydrological modelling studies in flat and gentle areas and where soil redistribution processes are of low magnitude.

Charge-Dependent Atomic-Scale Structures of High-Index and (110) Gold Electrode Surfaces as Revealed by Scanning Tunneling Microscopy

DTIC Science & Technology

1994-02-01

known gold atomic diameter of 2.89 A. Within a given domain, featuring adjacent terrace strings separated by monoatomic steps, the measured unit-cell...to utilize high-index gold faces in exploring the influence of monoatomic steps and related structural features on surface electrochemical phenomena...110) Gold Electrode Surfaces D1 T IC as Revealed by Scanning Tunneling Microscopy FLECTE MAR 10 19941 by E Xiaoping Gao, Gregory J. Edens, Antoinette

Preparation of atomically flat rutile TiO 2(001) surfaces for oxide film growth

DOE PAGES

Wang, Yang; Lee, Shinbuhm; Vilmercati, P.; ...

2016-01-01

The availability of low-index rutile TiO 2 single crystal substrates with atomically flat surfaces is essential for enabling epitaxialgrowth of rutile transition metal oxide films. The high surface energy of the rutile (001) surface often leads to surface faceting, which precludes the sputter and annealing treatment commonly used for the preparation of clean and atomically flat TiO 2(110) substrate surfaces. In this work, we reveal that stable and atomically flat rutile TiO 2(001) surfaces can be prepared with an atomically ordered reconstructedsurface already during a furnace annealing treatment in air. We tentatively ascribe this result to the decrease in surfacemore » energy associated with the surface reconstruction, which removes the driving force for faceting. Despite the narrow temperature window where this morphology can initially be formed, we demonstrate that it persists in homoepitaxialgrowth of TiO 2(001) thin films. The stabilization of surface reconstructions that prevent faceting of high-surface-energy crystal faces may offer a promising avenue towards the realization of a wider range of high quality epitaxial transition metal oxide heterostructures.« less

Nilosyrtis Mensae

NASA Technical Reports Server (NTRS)

1997-01-01

A color image of part of the Nilosyrtis Mensae region of Mars containing the impact craters Antoniadi and Baldet (south to north) in the lower left corner; north toward top. The scene shows heavily cratered highlands on the south separated from the relatively smooth lowland plains on the northeast corner by a belt of dissected terrain, containing flat-floored valleys, mesas, buttes, and channels. The channels are (left to right) Auqakuh and Huo Hsing Valles; Nili Fossae lie in lower right corner of image.

This image is a composite of Viking medium-resolution images in black and white and low-resolution images in color. The image extends from latitude 20 degrees N. to 40 degrees N. and from longitude 280 degrees to 305 degrees. Mercator projection is used below 30 degrees N.; Lambert projection is used above 30 degrees N.

The dissected terrain along the highlands/lowlands boundary consist of the flat-floored valleys (mensae) and farther north the small, rounded hills of knobby terrain. Flows on the mensa floors contain striae that run parallel to valley walls; where valleys meet, the striae merge, similar to medial moraines on glaciers. Terraces within the valley hills have been interpreted as either layer rocks or wave terraces. The knobby terrain has been interpreted as remnants of the old, densely cratered highland terrain perhaps eroded by mass wasting. Auqakuh and Huo Hsing Valles and Nili Fossae are fretted channels and linear depressions that likely formed by sapping and mass wasting along lines of structural weakness.

Cratering motions and structural deformation in the rim of the Prairie Flat multiring explosion crater

NASA Technical Reports Server (NTRS)

Roddy, D. J.; Ullrich, G. W.; Sauer, F. M.; Jones, G. H. S.

1977-01-01

Cratering motions and structural deformation are described for the rim of the Prairie Flat multiring crater, 85.5 m across and 5.3 m deep, which was formed by the detonation of a 500-ton TNT surface-tangent sphere. The terminal displacement and motion data are derived from marker cans and velocity gages emplaced in drill holes in a three-dimensional matrix radial to the crater. The integration of this data with a detailed geologic cross section, mapped from deep trench excavations through the rim, provides a composite view of the general sequence of motions that formed a transiently uplifted rim, overturned flap, inverted stratigraphy, downfolded rim, and deformed strata in the crater walls. Preliminary comparisons with laboratory experimental cratering and with numerical simulations indicate that explosion craters of the Prairie Flat-type generated by surface and near-surface energy sources tend to follow predictable motion sequences and produce comparable structural deformation. More specifically, central uplift and multiring impact craters with morphologies and structures comparable to Prairie Flat are inferred to have experienced similar deformational histories of the rim, such as uplift, overturning, terracing, and downfolding.

Upper Miocene reef complex of Mallorca, Balearic Islands, Spain

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pomar, L.

1988-02-01

The late Tortonian-Messinian coral reef platform of south Mallorca onlaps a folded middle late Miocene carbonate platform on which progradation of up to 20 km occurs. Vertical sea cliffs (up to 100 m high) superbly show the last 5 km of this progradation and complement the numerous water-well cores from the island interior. The Mallorca reef presents the most complete facies zonation of the Miocene reefs of the western Mediterranean. The reef wall framework is up to 20 m thick and shows (1) erosional reef flat with reef breccia and small corals; (2) spur-and-grove zone with large, massive corals; (3)more » deep buttresses and pinnacles with terraces of branching corals; and (4) deep reef wall with flat, laminar coral colonies, branching red algae, and Halimeda sands.« less

Geology and Thermal History of Mammoth Hot Springs, Yellowstone National Park, Wyoming

USGS Publications Warehouse

Bargar, Keith E.

1978-01-01

Mammoth Hot Springs, located about 8 km inside the north entrance to Yellowstone National Park, consists of nearly 100 hot springs scattered over a score of steplike travertine terraces. The travertine deposits range in age from late Pleistocene to the present. Sporadic records of hot-spring activity suggest that most of the current major springs have been intermittently active since at least 1871. Water moving along the Norris-Mammoth fault zone is heated by partly molten magma and enriched in calcium and bicarbonate. Upon reaching Mammoth this thermal water (temperature about 73?C) moves up through the old terrace deposits along preexisting vertical linear planes of weakness. As the water reaches the surface, pressure is released, carbon dioxide escapes as a gas, and bicarbonate in the water is partitioned into more carbon dioxide and carbonate; the carbonate then combines with calcium to precipitate calcium carbonate, forming travertine. The travertine usually precipitates rapidly from solution and is lightweight and porous; however, dense travertine, such as is found in core from the 113-m research drill hole Y-10 located on one of the upper terraces, forms beneath the surface by deposition in the pore spaces of older deposits. The terraces abound with unusual hot-spring deposits such as terracettes, cones, and fissure ridges. Semicircular ledges (ranging in width from about 0.3 m to as much as 2.5 m), called terracettes, formed by deposition of travertine around slowly rising pools. Complex steplike arrangements of terracettes have developed along runoff channels of some hot springs. A few hot springs have deposited cone-shaped mounds, most of which reach heights of 1-2 m before becoming dormant. However, one long-inactive cone named Liberty Cap attained a height of about 14 m. Fissure ridges are linear mounds of travertine deposited from numerous hot-spring vents along a medial fracture zone. The ridges range in height from about 1 to 6 m and in length from a few meters to nearly 300 m; width at the base of a ridge is equal to or greater than its height. In some places, such as along the northern border of Main Terrace, water from new hot-spring activity becomes ponded behind fissure-ridge barriers or dams and deposits travertine that eventually forms large flat terraces.

Longevity and progressive abandonment of the Rocky Flats surface, Front Range, Colorado

NASA Astrophysics Data System (ADS)

Riihimaki, Catherine A.; Anderson, Robert S.; Safran, Elizabeth B.; Dethier, David P.; Finkel, Robert C.; Bierman, Paul R.

2006-08-01

The post-orogenic evolution of the Laramide landscape of the western U.S. has been characterized by late Cenozoic channel incision of basins and their adjacent ranges. One means of constraining the incision history of basins is dating the remnants of gravel-capped surfaces above modern streams. Here, we focus on an extensive remnant of the Rocky Flats surface between Golden and Boulder, Colorado, and use in situ-produced 10Be and 26Al concentrations in terrace alluvium to constrain the Quaternary history of this surface. Coal and Ralston Creeks, both tributaries of the South Platte River, abandoned the Rocky Flats surface and formed the Verdos and Slocum pediments, which are cut into Cretaceous bedrock between Rocky Flats and the modern stream elevations. Rocky Flats alluvium ranges widely in age, from > 2 Ma to ˜ 400 ka, with oldest ages to the east and younger ages closer to the mountain front. Numerical modeling of isotope concentration depth profiles suggests that individual sites have experienced multiple resurfacing events. Preliminary results indicate that Verdos and Slocum alluvium along Ralston Creek, which is slightly larger than Coal Creek, is several hundred thousand years old. Fluvial incision into these surfaces appears therefore to progress headward in response to downcutting of the South Platte River. The complex ages of these surfaces call into question any correlation of such surfaces based solely on their elevation above the modern channel.

Atomic steps on an ultraflat Si(111) surface upon sublimation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sitnikov, S. V., E-mail: sitnikov@isp.nsc.ru; Latyshev, A. V.; Kosolobov, S. S.

2016-05-15

The kinetics of atomic steps on an ultraflat Si(111) surface is studied by in situ ultrahigh-vacuum reflection electron microscopy at temperatures of 1050–1350°C. For the first time it is experimentally shown that the rate of displacement of an atomic step during sublimation nonlinearly depends on the width of the adjacent terrace. It is established that the atomic mechanism of mass-transport processes at the surface at temperatures higher than 1200°C is controlled by nucleation and the diffusion of surface vacancies rather than of adsorbed Si atoms. The studies make it possible to estimate the activation energy of the dissolution of vacanciesmore » from the surface into the bulk of Si. The estimated activation energy is (4.3 ± 0.05) eV.« less

Reviews Opera: Doctor Atomic DVD: Doctor Atomic Equipment: Digital stopclock with external trigger Book: I Cyborg Book: Flat Earth: The History of an Infamous Idea Book: Mere Thermodynamics Book: CGP revision guides Book: Hiding the Elephant: How Magicians Invented the Impossible Book: Back of the Envelope Physics Web Watch

NASA Astrophysics Data System (ADS)

2009-07-01

WE RECOMMEND Doctor Atomic The new Doctor Atomic opera provkes discussion on ethics I Cyborg The world's first human cyborg shares his life story in I Cyborg Flat Earth: The History of an Infamous Idea Flat Earth gives us a different perspective on creationism Mere Thermodynamics An introductory text on the three laws CGP revision guides This revision guide suits all courses and every pocket Hiding the Elephant: How Magicians Invented the Impossible The mystery of many illusions are solved in this book Back of the Envelope Physics This reference deserves a place on your bookshelf WORTH A LOOK Doctor Atomic The DVD doesn't do justice to the live performance Digital stopclock with external trigger Use these stopclocks when you need an external trigger WEB WATCH Webcasts reach out to an online audience

Physical data of soil profiles formed on late Quaternary marine terraces near Santa Cruz, California

USGS Publications Warehouse

Munster, Jennie; Harden, Jennifer W.

2002-01-01

The marine terraces in and around Santa Cruz, California, represent a set of well-preserved terraces formed as a product of geology, sea level, and climate. A marine terrace begins as a wave cut platform. Eustatic sea level changes, seacliff erosion, and tectonic uplift work together to generate marine terraces. "When a wave-cut platform is raised (due to tectonic activity) above sea level and cliffed by wave action it becomes a marine terrace" (Bradley, 1957, p. 424). During glacial periods, eustatic sea level is estimated to have dropped by 150 meters (Fairbanks, 1989). Cliff retreat measured from aerial photographs between 1930 and 1980 vary from 0.0 to 0.2 m yr–1 (Best and Griggs, 1991). Estimates of uplift rates along the Santa Cruz coastline vary from 0.10 to 0.48 m kyr–1 (Bradley and Griggs, 1976; Weber and others, 1999). Uplift mechanisms include coseismic uplift associated both with a reverse component of slip on the steeply SW dipping Loma Prieta fault in the restraining bend of the San Andreas Fault and a small component of reverse slip on the steeply SE dipping San Gregorio fault (Anderson and Menking 1994). Previous work studying physical properties on these terraces include Pinney and others (in press) and Aniku (1986) and Bowman and Estrada (1980). Sedimentary deposits of the marine terraces are a mixture of terrestrial and marine sediments but generally consist of a sheet of marine deposits overlying the old platform and a wedge of nonmarine deposits banked against the old sea cliff (Bradley, 1957). Bedrock underlying the terraces in the Santa Cruz area is generally either Santa Margarita Sandstone or Santa Cruz Mudstone. The Santa Margarita Sandstone represents an upper Miocene, transgressive, tidally dominated marine-shelf deposit with crossbedded sets of sand and gravel and horizontally stratified and bioturbated invertebrate-fossils beds (Phillips, 1990). The siliceous Santa Cruz Mudstone, of late Miocene age, conformably overlies the Santa Margarita Sandstone. The Santa Cruz Mudstone is a thin to medium-bedded siliceous mudstone with nonsiliceous mudstone and siltstone and minor amounts of sandstone. The siliceous nature implies organic deposition in a quiescent, deep-water environment. Bedrock is mantled by 1–4 meters of medium to coarse-grained regressive beach sediment and fluvial deposits from the Ben Lomond Mountains. Terrace age increases with elevation above sea level, and weathering of primary minerals increases with age. The suite of soils formed on the terraces is referred to as a soil chronosequence. Soil chronosequences, important tools in characterizing natural weathering rates, are defined as a group of soils that differ in age and therefore in duration of weathering but have similar climatic conditions, vegetation, geomorphic position, and parent material (Jenny, 1941; Birkland, 1999). Soils are frequently useful indicators of geomorphic age (Muhs, 1982; Switzer and others, 1988) and are a function of pedogenic and/or eolian processes. Some aspects of soil development can be episodic but when viewed on large time scales can be perceived as continuous (Switzer and others, 1988). The age of the soil may be constrained by the age of the deposit, since soil formation generally commences when deposition has ceased (Birkland, 1999). Dating of the terraces provides an unprecedented opportunity to study weathering and soil-formation rates (Perg and others, 2001; Hanks and others, 1984; Bradley and Griggs, 1976; Bradley and Addicott, 1968; Bradley, 1956). Ages of the terraces recently dated by cosmogenic radionuclide are, starting with the youngest, 65, 92, 137, 139, and 226 k.y. (Perg and others, 2001). However, these ages are much younger than recent radiometric dates on mollusk shells (Muhs, U.S. Geological Survey, personal communication, 2002; Bradley and Addicott, 1968). For this study, soils were sampled on five terraces. Terrace one in the Lighthouse Field along Westcliff in Santa Cruz was the last site selected, and this report contains minimal data on this terrace. Sites on the second, third, and fourth terraces are located in Wilder Ranch, Santa Cruz, California. Site five is on private property north of Wilder Ranch. Careful consideration was taken in selecting field sites, choosing locations in a topographically flat area to avoid effects of erosion, and trying to keep parent material similar. This report contains physical properties of the soil profiles on four of the five marine terraces near Santa Cruz, California, excluding the youngest terrace in all tables except 6 and 7. Data includes field descriptions, bulk density, grain size analyses, weight percent magnetic fraction, and the soil development index. Soil properties are important when trying to understand the chemistry of a given profile or when comparing profiles. Grain size constrains the movement of water in a profile, thus controlling movement of chemicals and weathering rates. Bulk density is a useful property to calculate chemical inventory. Quantifying the magnetic fraction aids in understanding the Fe inventory for these soils. The soil development index is a semi-quantitative way to define the degree of development of a soil profile. This is a useful way to compare development of profiles for this chronosequence or compare the Santa Cruz terraces to a suit of other terraces or another chronosequence.

Ethylene dissociation on flat and stepped Ni(1 1 1): A combined STM and DFT study

NASA Astrophysics Data System (ADS)

Vang, Ronnie T.; Honkala, Karoliina; Dahl, Søren; Vestergaard, Ebbe K.; Schnadt, Joachim; Lægsgaard, Erik; Clausen, Bjerne S.; Nørskov, Jens K.; Besenbacher, Flemming

2006-01-01

The dissociative adsorption of ethylene (C 2H 4) on Ni(1 1 1) was studied by scanning tunneling microscopy (STM) and density functional theory (DFT) calculations. The STM studies reveal that ethylene decomposes exclusively at the step edges at room temperature. However, the step edge sites are poisoned by the reaction products and thus only a small brim of decomposed ethylene is formed. At 500 K decomposition on the (1 1 1) facets leads to a continuous growth of carbidic islands, which nucleate along the step edges. DFT calculations were performed for several intermediate steps in the decomposition of ethylene on both Ni(1 1 1) and the stepped Ni(2 1 1) surface. In general the Ni(2 1 1) surface is found to have a higher reactivity than the Ni(1 1 1) surface. Furthermore, the calculations show that the influence of step edge atoms is very different for the different reaction pathways. In particular the barrier for dissociation is lowered significantly more than the barrier for dehydrogenation, and this is of great importance for the bond-breaking selectivity of Ni surfaces. The influence of step edges was also probed by evaporating Ag onto the Ni(1 1 1) surface. STM shows that the room temperature evaporation leads to a step flow growth of Ag islands, and a subsequent annealing at 800 K causes the Ag atoms to completely wet the step edges of Ni(1 1 1). The blocking of the step edges is shown to prevent all decomposition of ethylene at room temperature, whereas the terrace site decomposition at 500 K is confirmed to be unaffected by the Ag atoms. Finally a high surface area NiAg alloy catalyst supported on MgAl 2O 4 was synthesized and tested in flow reactor measurements. The NiAg catalyst has a much lower activity for ethane hydrogenolysis than a similar Ni catalyst, which can be rationalized by the STM and DFT results.

Method for preparing ultraflat, atomically perfect areas on large regions of a crystal surface by heteroepitaxy deposition

DOEpatents

El Gabaly, Farid; Schmid, Andreas K.

2013-03-19

A novel method of forming large atomically flat areas is described in which a crystalline substrate having a stepped surface is exposed to a vapor of another material to deposit a material onto the substrate, which material under appropriate conditions self arranges to form 3D islands across the substrate surface. These islands are atomically flat at their top surface, and conform to the stepped surface of the substrate below at the island-substrate interface. Thereafter, the deposited materials are etched away, in the etch process the atomically flat surface areas of the islands transferred to the underlying substrate. Thereafter the substrate may be cleaned and annealed to remove any remaining unwanted contaminants, and eliminate any residual defects that may have remained in the substrate surface as a result of pre-existing imperfections of the substrate.

Direct observation for atomically flat and ordered vertical {111} side-surfaces on three-dimensionally figured Si(110) substrate using scanning tunneling microscopy

NASA Astrophysics Data System (ADS)

Yang, Haoyu; Hattori, Azusa N.; Ohata, Akinori; Takemoto, Shohei; Hattori, Ken; Daimon, Hiroshi; Tanaka, Hidekazu

2017-11-01

A three-dimensional Si{111} vertical side-surface structure on a Si(110) wafer was fabricated by reactive ion etching (RIE) followed by wet-etching and flash-annealing treatments. The side-surface was studied with scanning tunneling microscopy (STM) in atomic scale for the first time, in addition to atomic force microscopy (AFM), scanning electron microscopy (SEM), and low-energy electron diffraction (LEED). AFM and SEM showed flat and smooth vertical side-surfaces without scallops, and STM proved the realization of an atomically-flat 7 × 7-reconstructed structure, under optimized RIE and wet-etching conditions. STM also showed that a step-bunching occurred on the produced {111} side-surface corresponding to a reversely taped side-surface with a tilt angle of a few degrees, but did not show disordered structures. Characteristic LEED patterns from both side- and top-reconstructed surfaces were also demonstrated.

26. AERIAL VIEW OF THE ROCKY FLATS PLANT LOOKING NORTHEAST. ...

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

26. AERIAL VIEW OF THE ROCKY FLATS PLANT LOOKING NORTHEAST. IN 1951, A GOOD FRIDAY ISSUE OF THE DENVER POST ANNOUNCED THE ATOMIC ENERGY COMMISSION'S PLANS TO BUILD THE ROCKY FLATS PLANT. UNDER THE HEADLINE 'THERE'S GOOD NEWS TODAY.' POLITICAL LEADERS EXPRESSED GREAT PRIDE IN THE CHOICE OF THE DENVER-BOULDER AREA AS THE SITE FOR AN ATOMIC PLANT AS QUOTED IN THE ROCKY MOUNTAIN NEWS: 'WE ARE PROUD THAT THE AREA HAS BEEN CHOSEN FOR ANOTHER IMPORTANT CONTRIBUTION TO THE NATION'S STRENGTH AND FUTURE SECURITY.' BY THE MID 1970S, PUBLIC OPINION OF THE SITE HAD CHANGED (5/4/78). - Rocky Flats Plant, Bounded by Indiana Street & Routes 93, 128 & 72, Golden, Jefferson County, CO

Assessment of the predisposing factors for shallow landslides activation in terraced areas: the case of the Rupinaro catchment, Liguria (northwestern Italy).

NASA Astrophysics Data System (ADS)

Cignetti, Martina; Godone, Danilo; Giordan, Daniele

2017-04-01

The shallow landslides occurrence is strongly correlated with climatic conditions and environmental settings. In the Liguria region (northwestern Italy), the landscape presents an ancient human intervention represented by terraces and, in the last century, by a general overbuilding, both in the few flat areas and in the steep slope hinterland. From the twentieth century, the progressive abandonment of agriculture generated a lack of maintenance of terraced areas, which associated to the urban and the road net development, supported the slope susceptibility to instability. This makes the assessment of the predisposing factors for shallow landslides a multidisciplinary task, combining natural and man-made issues. In this work, we try to define all the main predisposing factors of the Rupinaro catchment (southeast Liguria). We operate starting from a high-resolution Digital Terrain Model (DTM) supplied by an airborne LiDAR survey carried out after the autumn 2014 rainfall events. From this DTM, we mapped a total amount of 96 landslides in the study area. Then, we implemented a classification methodology based on a simple parametric score. In GIS environment we overlaid several layers: i) lithological and hydrogeological map, ii) slope iii) aspect, iv) the land use information, available by the CORINE land cover, and iv) the presence of terraces. Each spatial data was than reclassified according a numerical code. The sum, by raster math, of these factors provided an overall score raster for the entire basin. This method allows the characterization of the entire watershed, gathering all the predisposing factors for the shallow landslides activation. A categorization of the landslides area mapped from the DTM and stored in a vector layer has been made. In particular, we estimated the most frequent code within each landslide polygon, obtaining a representative data of the most influential factors that triggered shallow landslides. The results showed the prevalent occurrence of shallow landslides in correspondence of terraced areas, cultivated by olive grove, with an impervious bedrock, and presenting gently slope and variable exposure from east/west to south. Our approach focuses on the interaction of landslides susceptibility and the land use modifications over time, with more attention over maintenance level of terraces. This methodology represents a starting point for the correct assessment of shallow landslides occurrence factors, capable to generate a susceptibility map of the entire basin, taking in account of the characteristic features of this extremely man-made territory. In order to assess the spatial connectivity of the basin and in addition to highlight the road network and the terraces role in the shallow landslides occurrence, a future comparison of the obtained data with hydrological indexes is planned.

Divorce, Separation, and Housing Changes: A Multiprocess Analysis of Longitudinal Data from England and Wales.

PubMed

Mikolai, Júlia; Kulu, Hill

2018-02-01

This study investigates the effect of marital and nonmarital separation on individuals' residential and housing trajectories. Using rich data from the British Household Panel Survey (BHPS) and applying multilevel competing-risks event history models, we analyze the risk of a move of single, married, cohabiting, and separated men and women to different housing types. We distinguish moves due to separation from moves of separated people and account for unobserved codeterminants of moving and separation risks. Our analysis shows that many individuals move due to separation, as expected, but that the likelihood of moving is also relatively high among separated individuals. We find that separation has a long-term effect on individuals' residential careers. Separated women exhibit high moving risks regardless of whether they moved out of the joint home upon separation, whereas separated men who did not move out upon separation are less likely to move. Interestingly, separated women are most likely to move to terraced houses, whereas separated men are equally likely to move to flats (apartments) and terraced (row) houses, suggesting that family structure shapes moving patterns of separated individuals.

From atoms to steps: The microscopic origins of crystal evolution

NASA Astrophysics Data System (ADS)

Patrone, Paul N.; Einstein, T. L.; Margetis, Dionisios

2014-07-01

The Burton-Cabrera-Frank (BCF) theory of crystal growth has been successful in describing a wide range of phenomena in surface physics. Typical crystal surfaces are slightly misoriented with respect to a facet plane; thus, the BCF theory views such systems as composed of staircase-like structures of steps separating terraces. Adsorbed atoms (adatoms), which are represented by a continuous density, diffuse on terraces, and steps move by absorbing or emitting these adatoms. Here we shed light on the microscopic origins of the BCF theory by deriving a simple, one-dimensional (1D) version of the theory from an atomistic, kinetic restricted solid-on-solid (KRSOS) model without external material deposition. We define the time-dependent adatom density and step position as appropriate ensemble averages in the KRSOS model, thereby exposing the non-equilibrium statistical mechanics origins of the BCF theory. Our analysis reveals that the BCF theory is valid in a low adatom-density regime, much in the same way that an ideal gas approximation applies to dilute gasses. We find conditions under which the surface remains in a low-density regime and discuss the microscopic origin of corrections to the BCF model.

Structure and growth of Bi(110) islands on Si(111)√{3 }×√{3 }-B substrates

NASA Astrophysics Data System (ADS)

Nagase, Kentaro; Kokubo, Ikuya; Yamazaki, Shiro; Nakatsuji, Kan; Hirayama, Hiroyuki

2018-05-01

The structure and growth of ultrathin Bi(110) islands were investigated on a Si(111)√{3 }×√{3 }-B substrate by scanning tunneling microscopy and scanning tunneling spectroscopy (STS). Both even- and odd-layer-height islands nucleated on a one-monolayer-thick wetting layer. The islands preferred the even layer heights over the odd layer heights with an area ratio of 3:1. A weak, long-range corrugation was observed to overlap on the atomic arrangement at the top of the islands. The average distance between the peaks of the corrugation oscillated in accordance with the alternation of even and odd layer heights. Nucleation of single- and double-layer terraces occurred on the islands with even layer heights but not on those with odd layer heights. The unit cell of the single-layer terrace was aligned with that of the underlying even-layer-height island. The inequality in the height preference and the height-dependent oscillation of the corrugation suggested that the even- and odd-layer-height islands possessed different structures. The dominance and stability against terrace nucleation of the even-layer-height islands were consistent with the theoretically predicted stability of the paired layer-stacked black-phosphorus (BP)-like structure for ultrathin Bi(110) films. The alignment of the unit cell at the terrace on the island and STS spectra suggested a BP-like/bulklike/BP-like sandwich structure for the odd-layer-height Bi(110) islands.

Atomically flat platinum films grown on synthetic mica

NASA Astrophysics Data System (ADS)

Tanaka, Hiroyuki; Taniguchi, Masateru

2018-04-01

Atomically flat platinum thin films were heteroepitaxially grown on synthetic fluorophlogopite mica [KMg3(AlSi3O10)F2] by van der Waals epitaxy. Platinum films deposited on a fluorophlogopite mica substrate by inductively coupled plasma-assisted sputtering with oxygen introduction on a synthetic mica substrate resulted in the growth of twin single-crystalline epitaxial Pt(111) films.

Alkylation of Silicon(111) surfaces

NASA Astrophysics Data System (ADS)

Rivillon, S.; Chabal, Y. J.

2006-03-01

Methylation of chlorine-terminated silicon (111) (Si-Cl) is investigated by Infra Red Absorption Spectroscopy (IRAS). Starting from an atomically flat H-terminated Si(111), the surface is first chlorinated by a gas phase process, then methylated using a Grignard reagent. Methyl groups completely replace Cl, and are oriented normal to the surface. The surface remains atomically flat with no evidence of etching.

Hetero-diffusion of Au epitaxy on stepped Ag(110) surface: Study of the jump rate and diffusion coefficient

NASA Astrophysics Data System (ADS)

Benlattar, M.; El koraychy, E.; Kotri, A.; Mazroui, M.

2017-12-01

We have used molecular dynamics simulations combined with an interatomic potential derived from the embedded atom method, to investigate the hetero-diffusion of Au adatom near a stepped Ag(110) surface with the height of one monoatomic layer. The activation energies for different diffusion processes, which occur on the terrace and near the step edge, are calculated both by molecular statics and molecular dynamics simulations. Static energies are found by the drag method, whereas the dynamic barriers are computed at high temperature from the Arrhenius plots. Our numerical results reveal that the jump process requires very high activation energy compared to the exchange process either on the terrace or near the step edge. In this work, other processes, such as upward and downward diffusion at step edges, have also been discussed.

Electron tunneling through atomically flat and ultrathin hexagonal boron nitride

NASA Astrophysics Data System (ADS)

Lee, Gwan-Hyoung; Yu, Young-Jun; Lee, Changgu; Dean, Cory; Shepard, Kenneth L.; Kim, Philip; Hone, James

2011-12-01

Electron tunneling through atomically flat and ultrathin hexagonal boron nitride (h-BN) on gold-coated mica was investigated using conductive atomic force microscopy. Low-bias direct tunneling was observed in mono-, bi-, and tri-layer h-BN. For all thicknesses, Fowler-Nordheim tunneling (FNT) occurred at high bias, showing an increase of breakdown voltage with thickness. Based on the FNT model, the barrier height for tunneling (3.07 eV) and dielectric strength (7.94 MV/cm) of h-BN are obtained; these values are comparable to those of SiO2.

Diffusion on Cu surfaces

NASA Technical Reports Server (NTRS)

Karimi, Majid

1993-01-01

Understanding surface diffusion is essential in understanding surface phenomena, such as crystal growth, thin film growth, corrosion, physisorption, and chemisorption. Because of its importance, various experimental and theoretical efforts have been directed to understand this phenomena. The Field Ion Microscope (FIM) has been the major experimental tool for studying surface diffusion. FIM have been employed by various research groups to study surface diffusion of adatoms. Because of limitations of the FIM, such studies are only limited to a few surfaces: nickel, platinum, aluminum, iridium, tungsten, and rhodium. From the theoretical standpoint, various atomistic simulations are performed to study surface diffusion. In most of these calculations the Embedded Atom Method (EAM) along with the molecular static (MS) simulation are utilized. The EAM is a semi-empirical approach for modeling the interatomic interactions. The MS simulation is a technique for minimizing the total energy of a system of particles with respect to the positions of its particles. One of the objectives of this work is to develop the EAM functions for Cu and use them in conjunction with the molecular static (MS) simulation to study diffusion of a Cu atom on a perfect as well as stepped Cu(100) surfaces. This will provide a test of the validity of the EAM functions on Cu(100) surface and near the stepped environments. In particular, we construct a terrace-ledge-kink (TLK) model and calculate the migration energies of an atom on a terrace, near a ledge site, near a kink site, and going over a descending step. We have also calculated formation energies of an atom on the bare surface, a vacancy in the surface, a stepped surface, and a stepped-kink surface. Our results are compared with the available experimental and theoretical results.

Oxygen content modulation by nanoscale chemical and electrical patterning in epitaxial SrCoO3-δ (0 < δ ≤ 0.5) thin films.

PubMed

Hu, S; Seidel, J

2016-08-12

Fast controllable redox reactions in solid materials at room temperature are a promising strategy for enhancing the overall performance and lifetime of many energy technology materials and devices. Easy control of oxygen content is a key concept for the realisation of fast catalysis and bulk diffusion at room temperature. Here, high quality epitaxial brownmillerite SrCoO2.5 thin films have been oxidised to perovskite (P) SrCoO3 with NaClO. X-ray diffraction, scanning probe microscopy and x-ray photoelectron spectroscopy measurements were performed to investigate the structural and electronic changes of the material. The oxidised thin films were found to exhibit distinct morphological changes from an atomically flat terrace structure to forming small nanosized islands with boundaries preferentially in [100] or [010] directions all over the surface, relaxing the in-plane strain imposed by the substrate. The conductivity, or oxygen content, of each single island is confined by these textures, which can be locally patterned even further with electric poling. The high charging level at the island boundaries indicates a magnified electric capacity of SCO thin films, which could be exploited in future device geometries. This finding represents a new way of oxygen modulation with associated self-assembled charge confinement to nanoscale boundaries, offering interesting prospects in nanotechnology applications.

Oxygen content modulation by nanoscale chemical and electrical patterning in epitaxial SrCoO3-δ (0 < δ ≤ 0.5) thin films

NASA Astrophysics Data System (ADS)

Hu, S.; Seidel, J.

2016-08-01

Fast controllable redox reactions in solid materials at room temperature are a promising strategy for enhancing the overall performance and lifetime of many energy technology materials and devices. Easy control of oxygen content is a key concept for the realisation of fast catalysis and bulk diffusion at room temperature. Here, high quality epitaxial brownmillerite SrCoO2.5 thin films have been oxidised to perovskite (P) SrCoO3 with NaClO. X-ray diffraction, scanning probe microscopy and x-ray photoelectron spectroscopy measurements were performed to investigate the structural and electronic changes of the material. The oxidised thin films were found to exhibit distinct morphological changes from an atomically flat terrace structure to forming small nanosized islands with boundaries preferentially in [100] or [010] directions all over the surface, relaxing the in-plane strain imposed by the substrate. The conductivity, or oxygen content, of each single island is confined by these textures, which can be locally patterned even further with electric poling. The high charging level at the island boundaries indicates a magnified electric capacity of SCO thin films, which could be exploited in future device geometries. This finding represents a new way of oxygen modulation with associated self-assembled charge confinement to nanoscale boundaries, offering interesting prospects in nanotechnology applications.

Habitat use and movement of the endangered Arroyo Toad (Anaxyrus californicus) in coastal southern California

USGS Publications Warehouse

Mitrovich, M.J.; Gallegos, E.A.; Lyren, L.M.; Lovich, R.E.; Fisher, R.N.

2011-01-01

Information on the habitat use and movement patterns of Arroyo Toads (Anaxyrus californicus) is limited. The temporal and spatial characteristics of terrestrial habitat use, especially as it relates to upland use in coastal areas of the species' range, are poorly understood. We present analyses of radiotelemetry data from 40 individual adult toads tracked at a single site in coastal southern California from March through November of 2004. We quantify adult Arroyo Toad habitat use and movements and interpret results in the context of their life history. We show concentrated activity by both male and female toads along stream terraces during and after breeding, and, although our fall sample size is low, the continued presence of adult toads in the floodplain through the late fall. Adult toads used open sandy flats with sparse vegetation. Home-range size and movement frequency varied as a function of body mass. Observed spatial patterns of movement and habitat use both during and outside of the breeding period as well as available climatological data suggest that overwintering of toads in floodplain habitats of near-coastal areas of southern California may be more common than previously considered. If adult toads are not migrating out of the floodplain at the close of the breeding season but instead overwinter on stream terraces in near-coastal areas, then current management practices that assume toad absence from floodplain habitats may be leaving adult toads over-wintering on stream terraces vulnerable to human disturbance during a time of year when Arroyo Toad mortality is potentially highest. ?? 2011 Society for the Study of Amphibians and Reptiles.

Habitat use and movement of the endangered Arroyo Toad (Anaxyrus californicus) in coastal southern California

USGS Publications Warehouse

Gallegos, Elizabeth; Lyren, Lisa M.; Lovich, Robert E.; Mitrovich, Milan J.; Fisher, Robert N.

2011-01-01

Information on the habitat use and movement patterns of Arroyo Toads (Anaxyrus californicus) is limited. The temporal and spatial characteristics of terrestrial habitat use, especially as it relates to upland use in coastal areas of the species' range, are poorly understood. We present analyses of radiotelemetry data from 40 individual adult toads tracked at a single site in coastal southern California from March through November of 2004. We quantify adult Arroyo Toad habitat use and movements and interpret results in the context of their life history. We show concentrated activity by both male and female toads along stream terraces during and after breeding, and, although our fall sample size is low, the continued presence of adult toads in the floodplain through the late fall. Adult toads used open sandy flats with sparse vegetation. Home-range size and movement frequency varied as a function of body mass. Observed spatial patterns of movement and habitat use both during and outside of the breeding period as well as available climatological data suggest that overwintering of toads in floodplain habitats of near-coastal areas of southern California may be more common than previously considered. If adult toads are not migrating out of the floodplain at the close of the breeding season but instead overwinter on stream terraces in near-coastal areas, then current management practices that assume toad absence from floodplain habitats may be leaving adult toads over-wintering on stream terraces vulnerable to human disturbance during a time of year when Arroyo Toad mortality is potentially highest.

Topography of the South Polar Cap and Layered Deposits of Mars: Viking Stereo Grametry at Regional and Local Scales

NASA Technical Reports Server (NTRS)

Schenk, P.; Moore, J.; Stoker, C.

1998-01-01

Layered deposits and residual polar caps on Mars may record the deposition of ice and sediment modulated by periodic climate change. Topographic information relating to layer thicknesses, erosional processes, and formation of dark spirals within these deposits has been sparce or unreliable until the arrival of MOLA in orbit in September 1997. To assist in evaluating these terrains prior to launch and to assess formation and erosion processes in the polar deposits, we have assembled Viking stereo mosaics of the region and have produced the first reliable DEM models of the south polar deposits using automated stereogrammetry tools. Here we report our preliminary topographic results, pending final image pointing updates. The maximum total thickness of the layered deposits in the south polar region is 2.5 km. The thick layered deposits consist of a series of megaterraces. Each terrace is several tens of kilometers wide and is flat or slopes very gently toward the pole. These terraces step downward from a central plateau near the south pole. Terraces are bounded by relatively steep scarps 100-500 meters high that face toward the equator. These scarps correspond to the pattern of dark spirals observed within the residual cap in southern summer, and are interpreted as ice or frost-free surfaces warmed by solar insolation. Several tongue-shaped troughs, with rounded cirquelike heads, are observed near the margins of the deposit. These troughs are 300-600 meters in deep and may be similar to troughs observed in the northern polar deposit.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tang, Chi; Aldosary, Mohammed; Jiang, Zilong

A layer-by-layer epitaxial growth up to 227 atomic layers of ferrimagnetic insulator yttrium iron garnet (YIG) thin films is achieved on (110)-oriented gadolinium gallium garnet substrates using pulsed laser deposition. Atomically smooth terraces are observed on YIG films up to 100 nm in thickness. The root-mean-square roughness is as low as 0.067 nm. The easy-axis lies in the film plane, indicating the dominance of shape anisotropy. For (110)-YIG films, there is well-defined two-fold in-plane anisotropy, with the easiest axis directed along [001]. The Gilbert damping constant is determined to be 1.0 × 10{sup −4} for 100 nm thick films.

Crystal faces of anhydrite (CaSO 4) and their preferential dissolution in aqueous solutions studied with AFM

NASA Astrophysics Data System (ADS)

Shindo, H.; Kaise, M.; Kondoh, H.; Nishihara, C.; Nozoye, H.

Structures of cleaved surfaces of anhydrite were studied with atomic force microscopy (AFM) before and after partial dissolution in aqueous solutions of NH 4Cl and NaHSO 4. Two crystal faces showed atom-resolved images just after cleavage, (100) and (010), of which the former was roughened by the dissolution, while step structures were developed on the latter. After dissolution, steplines ran along the a- and c-axes on the (010) face, while they ran in directions inclined to these axes before. It was revealed that the arrangement of dipoles is a key factor in determining stabilities of step structures on crystal faces. On the terraces, the arrangement of oxygen atoms of the sulfate groups and calcium ions were clearly observed.

Geologic Map of the Round Spring Quadrangle, Shannon County, Missouri

USGS Publications Warehouse

Orndorff, Randall C.; Weary, David J.

2009-01-01

The Round Spring 7.5-minute quadrangle is located in Shannon County, south-central Missouri on the Salem Plateau of the Ozark Plateaus physiographic province. As much as 1,350 feet (ft) of flat-lying to gently dipping Upper Cambrian and Lower Ordovician rocks, mostly dolomite, overlie Mesoproterozoic volcanic rocks. The bedrock is overlain by unconsolidated residuum, colluvium, terrace deposits, and alluvium. Karst features, such as small sinkholes and caves, have formed in the carbonate rocks, and many streams are spring fed. The topography is a dissected karst plain with elevation ranging from 650 ft along the Current River on the eastern edge of the quadrangle to almost 1,200 ft at various places on the ridge tops. The area is mostly forested but contains some farmlands and includes sections of the Ozark National Scenic Riverways of the National Park Service along the Current River. Geologic mapping for this investigation began in the spring of 2001 and was completed in the spring of 2002.

Enhanced chemiluminescence-based detection on gold substrate after electrografting of diazonium precursor-coated gold nanoparticles.

PubMed

Houmed Adabo, Ali; Zeggari, Rabah; Mohamed Saïd, Nasser; Bazzi, Rana; Elie-Caille, Céline; Marquette, Christophe; Martini, Matteo; Tillement, Olivier; Perriat, Pascal; Chaix, Carole; Boireau, Wilfrid; Roux, Stéphane

2016-04-01

Since it was demonstrated that nanostructured surfaces are more efficient for the detection based on the specific capture of analytes, there is a real need to develop strategies for grafting nanoparticles onto flat surfaces. Among the different routes for the functionalization of a surface, the reduction of diazonium salts appears very attractive for the covalent immobilization of nanoparticles because this method does not require a pre-treatment of the surface. For achieving this goal, gold nanoparticles coated by precursor of diazonium salts were synthesized by reduction of gold salt in presence of mercaptoaniline. These mercaptoaniline-coated gold nanoparticles (Au@MA) were successfully immobilized onto various conducting substrates (indium tin oxide (ITO), glassy carbon (GC) and gold electrodes with flat terraces) after addition of sodium nitrite at fixed potential. When applied onto the gold electrodes, such a grafting strategy led to an obvious enhancement of the luminescence of luminol used for the biodetection. Copyright © 2016 Elsevier Inc. All rights reserved.

Exposing high-energy surfaces by rapid-anneal solid phase epitaxy

DOE PAGES

Wang, Y.; Song, Y.; Peng, R.; ...

2017-08-08

The functional design of nanoscale transition metal oxide heterostructures depends critically on the growth of atomically flat epitaxial thin films. Much of the time, improved functionality is expected for heterostructures and surfaces with orientations that do not have the lowest surface free energy. For example, crystal faces with a high surface free energy, such as rutile (001) planes, frequently exhibit higher catalytic activities but are correspondingly harder to synthesize due to energy-lowering faceting transitions. We propose a broadly applicable rapid-anneal solid phase epitaxial synthesis approach for the creation of atomically flat, high surface free energy oxide heterostructures. We also demonstratemore » its efficacy via the synthesis of atomically flat, epitaxial RuO 2(001) films with a superior oxygen evolution activity, quantified by their lower onset potential and higher current density, relative to that of more common RuO 2(110) films.« less

Communication: Two types of flat-planes conditions in density functional theory.

PubMed

Yang, Xiaotian Derrick; Patel, Anand H G; Miranda-Quintana, Ramón Alain; Heidar-Zadeh, Farnaz; González-Espinoza, Cristina E; Ayers, Paul W

2016-07-21

Using results from atomic spectroscopy, we show that there are two types of flat-planes conditions. The first type of flat-planes condition occurs when the energy as a function of the number of electrons of each spin, Nα and Nβ, has a derivative discontinuity on a line segment where the number of electrons, Nα + Nβ, is an integer. The second type of flat-planes condition occurs when the energy has a derivative discontinuity on a line segment where the spin polarization, Nα - Nβ, is an integer, but does not have a discontinuity associated with an integer number of electrons. Type 2 flat planes are rare-we observed just 15 type 2 flat-planes conditions out of the 4884 cases we tested-but their mere existence has implications for the design of exchange-correlation energy density functionals. To facilitate the development of functionals that have the correct behavior with respect to both fractional number of electrons and fractional spin polarization, we present a dataset for the chromium atom and its ions that can be used to test new functionals.

13. AERIAL VIEW OF THE ROCKY FLATS PLANT FROM DIRECTLY ...

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

13. AERIAL VIEW OF THE ROCKY FLATS PLANT FROM DIRECTLY OVERHEAD IN 1954. IN 1950, DOW CHEMICAL COMPANY WAS CHOSEN BY THE ATOMIC ENERGY COMMISSION TO ESTABLISH THE ROCKY FLATS PLANT AS AN ATOMIC BOMB TRIGGER FABRICATION FACILITY. THE CRITERIA FOR SITING SUCH A PLANT INCLUDED A LOCATION WEST OF THE MISSISSIPPI, NORTH OF TEXAS, SOUTH OF THE NORTHERN BORDER OF COLORADO, AND EAST OF UTAH; A DRY MODERATE CLIMATE; A SUPPORTING POPULATION OF AT LEAST 25,000 PEOPLE; AND ACCESSIBILITY FROM LOS ALAMOS, NM, CHICAGO, IL, AND ST. LOUIS, MO. TWENTY-ONE AREAS IN THE UNITED STATES WERE SUGGESTED; SEVEN LOCATIONS WERE SCREENED IN THE DENVER AREA. THIS FOUR-SQUARE MILE AREA WAS SELECTED AND CONSTRUCTION BEGAN IN 1951 (8/31/54). - Rocky Flats Plant, Bounded by Indiana Street & Routes 93, 128 & 72, Golden, Jefferson County, CO

Crystal growth of Bi{sub 2}Te{sub 3} and noble cleaved (0001) surface properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Atuchin, V.V., E-mail: atuchin@thermo.isp.nsc.ru; Functional Electronics Laboratory, Tomsk State University, Tomsk 634050; Golyashov, V.A.

2016-04-15

A high quality Bi{sub 2}Te{sub 3} crystal has been grown by Bridgman method with the use of rotating heat field. The phase purity and bulk structural quality of the crystal have been verified by XRD analysis and rocking curve observation. The atomically smooth Bi{sub 2}Te{sub 3}(0001) surface with an excellent crystallographic quality is formed by cleavage in the air. The chemical and microstructural properties of the surface have been evaluated with RHEED, AFM, STM, SE and XPS. The Bi{sub 2}Te{sub 3}(0001) cleaved surface is formed by atomically smooth terraces with the height of the elemental step of ~1.04±0.1 nm, asmore » estimated by AFM. There is no surface oxidation process detected over a month keeping in the air at normal conditions, as shown by comparative core level photoelectron spectroscopy. - Graphical abstract: A high quality Bi{sub 2}Te{sub 3} crystal has been grown by Bridgman method with the use of rotating heat field and the Bi{sub 2}Te{sub 3}(0001) cleaved surface has been evaluated with RHEED, AFM, STM, SE and XPS. - Highlights: • High-quality Bi{sub 2}Te{sub 3} crystal of 10 mm in diameter and 50 mm long have been grown. • The high-purity cleaved Bi{sub 2}Te{sub 3}(0001) surface has been evaluated by RHEED, AFM, STM and XPS methods. • The Bi{sub 2}Te{sub 3} surface covered by atomically smooth (0001) terraces is chemically stable for a long time.« less

Investigating the landscape of Arroyo Seco—Decoding the past—A teaching guide to climate-controlled landscape evolution in a tectonically active region

USGS Publications Warehouse

Taylor, Emily M.; Sweetkind, Donald S.; Havens, Jeremy C.

2017-05-19

IntroductionArroyo Seco is a river that flows eastward out of the Santa Lucia Range in Monterey County, California. The Santa Lucia Range is considered part of the central California Coast Range. Arroyo Seco flows out of the Santa Lucia Range into the Salinas River valley, near the town of Greenfield, where it joins the Salinas River. The Salinas River flows north into Monterey Bay about 40 miles from where it merges with Arroyo Seco. In the mountain range, Arroyo Seco has cut or eroded a broad and deep valley. This valley preserves a geologic story in the landscape that is influenced by both fault-controlled mountain building (tectonics) and sea level fluctuations (regional climate).Broad flat surfaces called river terraces, once eroded by Arroyo Seco, can be observed along the modern drainage. In the valley, terraces are also preserved like climbing stairs up to 1,800 feet above Arroyo Seco today. These terraces mark where Arroyo Seco once flowed.The terraces were formed by the river because no matter how high they are, the terraces are covered by gravel deposits exactly like those that can be observed in the river today. The Santa Lucia Range, Arroyo Seco, and the Salinas River valley must have looked very different when the highest and oldest terraces were forming. The Santa Lucia Range may have been lower, the Arroyo Seco may have been steeper and wider, and the Salinas River valley may have been much smaller.Arroyo Seco, like all rivers, is always changing. Some-times rivers flow very straight, and sometimes they are curvy. Sometimes rivers are cutting down or eroding the landscape, and sometimes they are not eroding but depositing material. Sometimes rivers are neither eroding nor transporting material. The influences that change the behavior of Arroyo Seco are mountain uplift caused by fault moment and sea level changes driven by regional climate change. When a stream is affected by one or both of these influences, the stream accommodates the change by eroding, depositing, and (or) changing its shape.In the vicinity of Arroyo Seco, the geologically young faulting history is relatively well understood. Geologists have some sense of the most recent faulting event and of the faulting in the recent geologic past. The timing of regional climate changes is also well accepted. In this area, warm climate cycles tend to cause the sea level to rise, and cool climate cycles tend to cause the sea level to fall. If we understand the way the terraces form and their ages in Arroyo Seco, we can draw conclusions about whether faulting and (or) climate contributed to their formation.This publication serves as a descriptive companion to the formal geologic map of Arroyo Seco (Taylor and Sweetkind, 2014) and is intended for use by nonscientists and students. Included is a discussion of the processes that controlled the evolution of the drainage and the formation of the terraces in Arroyo Seco. The reader is guided to well-exposed landscape features in an easily accessible environment that will help nonscientists gain an understanding of how features on a geologic map are interpreted in terms of earth processes.

Atomically Flat Surfaces Developed for Improved Semiconductor Devices

NASA Technical Reports Server (NTRS)

Powell, J. Anthony

2001-01-01

New wide bandgap semiconductor materials are being developed to meet the diverse high temperature, -power, and -frequency demands of the aerospace industry. Two of the most promising emerging materials are silicon carbide (SiC) for high-temperature and high power applications and gallium nitride (GaN) for high-frequency and optical (blue-light-emitting diodes and lasers) applications. This past year Glenn scientists implemented a NASA-patented crystal growth process for producing arrays of device-size mesas whose tops are atomically flat (i.e., step-free). It is expected that these mesas can be used for fabricating SiC and GaN devices with major improvements in performance and lifetime. The promising new SiC and GaN devices are fabricated in thin-crystal films (known as epi films) that are grown on commercial single-crystal SiC wafers. At this time, no commercial GaN wafers exist. Crystal defects, known as screw defects and micropipes, that are present in the commercial SiC wafers propagate into the epi films and degrade the performance and lifetime of subsequently fabricated devices. The new technology isolates the screw defects in a small percentage of small device-size mesas on the surface of commercial SiC wafers. This enables atomically flat surfaces to be grown on the remaining defect-free mesas. We believe that the atomically flat mesas can also be used to grow GaN epi films with a much lower defect density than in the GaN epi films currently being grown. Much improved devices are expected from these improved low-defect epi films. Surface-sensitive SiC devices such as Schottky diodes and field effect transistors should benefit from atomically flat substrates. Also, we believe that the atomically flat SiC surface will be an ideal surface on which to fabricate nanoscale sensors and devices. The process for achieving atomically flat surfaces is illustrated. The surface steps present on the "as-received" commercial SiC wafer is also illustrated. because of the small tilt angle between the crystal "basal" plane and the polished wafer surface. These steps are used in normal SiC epi film growth in a process known as stepflow growth to produce material for device fabrication. In the new process, the first step is to etch an array of mesas on the SiC wafer top surface. Then, epi film growth is carried out in the step flow fashion until all steps have grown themselves out of existence on each defect-free mesa. If the size of the mesas is sufficiently small (about 0.1 by 0.1 mm), then only a small percentage of the mesas will contain an undesired screw defect. Mesas with screw defects supply steps during the growth process, allowing a rough surface with unwanted hillocks to form on the mesa. The improvement in SiC epi surface morphology achievable with the new technology is shown. An atomic force microscope image of a typical SiC commercial epilayer surface is also shown. A similar image of an SiC atomically flat epi surface grown in a Glenn laboratory is given. With the current screw defect density of commercial wafers (about 5000 defects/cm2), the yield of atomically free 0.1 by 0.l mm mesas is expected to be about 90 percent. This is large enough for many types of electronic and optical devices. The implementation of this new technology was recently published in Applied Physics Letters. This work was initially carried out in-house under a Director's Discretionary Fund project and is currently being further developed under the Information Technology Base Program.

Improved metal-insulator-transition characteristics of ultrathin VO2 epitaxial films by optimized surface preparation of rutile TiO2 substrates

NASA Astrophysics Data System (ADS)

Martens, Koen; Aetukuri, Nagaphani; Jeong, Jaewoo; Samant, Mahesh G.; Parkin, Stuart S. P.

2014-02-01

Key to the growth of epitaxial, atomically thin films is the preparation of the substrates on which they are deposited. Here, we report the growth of atomically smooth, ultrathin films of VO2 (001), only ˜2 nm thick, which exhibit pronounced metal-insulator transitions, with a change in resistivity of ˜500 times, at a temperature that is close to that of films five times thicker. These films were prepared by pulsed laser deposition on single crystalline TiO2(001) substrates that were treated by dipping in acetone, HCl and HF in successive order, followed by an anneal at 700-750 °C in flowing oxygen. This pretreatment removes surface contaminants, TiO2 defects, and provides a terraced, atomically smooth surface.

Atomistic simulations of contact area and conductance at nanoscale interfaces.

PubMed

Hu, Xiaoli; Martini, Ashlie

2017-11-09

Atomistic simulations were used to study conductance across the interface between a nanoscale gold probe and a graphite surface with a step edge. Conductance on the graphite terrace was observed to increase with load and be approximately proportional to contact area calculated from the positions of atoms in the interface. The relationship between area and conductance was further explored by varying the position of the contact relative to the location of the graphite step edge. These simulations reproduced a previously-reported current dip at step edges measured experimentally and the trend was explained by changes in both contact area and the distribution of distances between atoms in the interface. The novel approach reported here provides a foundation for future studies of the fundamental relationships between conductance, load and surface topography at the atomic scale.

Effects of Formulated Glyphosate and Adjuvant Tank Mixes on Atomization from Aerial Application Flat Fan Nozzles

DTIC Science & Technology

2012-01-01

Bradley K. Fritz,1 W. Clint Hoffmann,1 and W. E. Bagley2 Effects of Formulated Glyphosate and Adjuvant Tank Mixes on Atomization from Aerial...Application Flat Fan Nozzles REFERENCE: Fritz, Bradley K., Hoffmann, W. Clint, and Bagley, W. E., “Effects of Formulated Glyphosate and Adjuvant Tank Mixes on...factors. Twelve spray-solution treatments were evaluated, ten of which contained a formulated glyphosate product and nine of these con- tained an

Communication: Two types of flat-planes conditions in density functional theory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Xiaotian Derrick; Patel, Anand H. G.; González-Espinoza, Cristina E.

Using results from atomic spectroscopy, we show that there are two types of flat-planes conditions. The first type of flat-planes condition occurs when the energy as a function of the number of electrons of each spin, N{sub α} and N{sub β}, has a derivative discontinuity on a line segment where the number of electrons, N{sub α} + N{sub β}, is an integer. The second type of flat-planes condition occurs when the energy has a derivative discontinuity on a line segment where the spin polarization, N{sub α} – N{sub β}, is an integer, but does not have a discontinuity associated withmore » an integer number of electrons. Type 2 flat planes are rare—we observed just 15 type 2 flat-planes conditions out of the 4884 cases we tested—but their mere existence has implications for the design of exchange-correlation energy density functionals. To facilitate the development of functionals that have the correct behavior with respect to both fractional number of electrons and fractional spin polarization, we present a dataset for the chromium atom and its ions that can be used to test new functionals.« less

Effect of surface morphology on friction of graphene on various substrates

NASA Astrophysics Data System (ADS)

Cho, Dae-Hyun; Wang, Lei; Kim, Jin-Seon; Lee, Gwan-Hyoung; Kim, Eok Su; Lee, Sunhee; Lee, Sang Yoon; Hone, James; Lee, Changgu

2013-03-01

The friction of graphene on various substrates, such as SiO2, h-BN, bulk-like graphene, and mica, was investigated to characterize the adhesion level between graphene and the underlying surface. The friction of graphene on SiO2 decreased with increasing thickness and converged around the penta-layers due to incomplete contact between the two surfaces. However, the friction of graphene on an atomically flat substrate, such as h-BN or bulk-like graphene, was low and comparable to that of bulk-like graphene. In contrast, the friction of graphene folded onto bulk-like graphene was indistinguishable from that of mono-layer graphene on SiO2 despite the ultra-smoothness of bulk-like graphene. The characterization of the graphene's roughness before and after folding showed that the corrugation of graphene induced by SiO2 morphology was preserved even after it was folded onto an atomically flat substrate. In addition, graphene deposited on mica, when folded, preserved the same corrugation level as before the folding event. Our friction measurements revealed that graphene, once exfoliated from the bulk crystal, tends to maintain its corrugation level even after it is folded onto an atomically flat substrate and that ultra-flatness in both graphene and the substrate is required to achieve the intimate contact necessary for strong adhesion.The friction of graphene on various substrates, such as SiO2, h-BN, bulk-like graphene, and mica, was investigated to characterize the adhesion level between graphene and the underlying surface. The friction of graphene on SiO2 decreased with increasing thickness and converged around the penta-layers due to incomplete contact between the two surfaces. However, the friction of graphene on an atomically flat substrate, such as h-BN or bulk-like graphene, was low and comparable to that of bulk-like graphene. In contrast, the friction of graphene folded onto bulk-like graphene was indistinguishable from that of mono-layer graphene on SiO2 despite the ultra-smoothness of bulk-like graphene. The characterization of the graphene's roughness before and after folding showed that the corrugation of graphene induced by SiO2 morphology was preserved even after it was folded onto an atomically flat substrate. In addition, graphene deposited on mica, when folded, preserved the same corrugation level as before the folding event. Our friction measurements revealed that graphene, once exfoliated from the bulk crystal, tends to maintain its corrugation level even after it is folded onto an atomically flat substrate and that ultra-flatness in both graphene and the substrate is required to achieve the intimate contact necessary for strong adhesion. Electronic supplementary information (ESI) available: Sample preparation method, identification of graphene thickness, AFM and FFM measurements. See DOI: 10.1039/c3nr34181j

LiDAR Mapping of Earthquake Uplifted Paleo-shorelines, Southern Wairarapa Coast, North Island, New Zealand

NASA Astrophysics Data System (ADS)

Valenciano, J.; Angenent, J.; Marshall, J. S.; Clark, K.; Litchfield, N. J.

2017-12-01

The Hikurangi subduction margin along the east coast of the North Island, New Zealand accommodates oblique convergence of the Pacific Plate westward beneath the Australian plate at 45 mm/yr. Pronounced forearc uplift occurs at the southern end of the margin along the Wairarapa coast, onshore of the subducting Hikurangi plateau. Along a narrow coastal lowland, a series of uplifted Holocene marine terraces and beach ridges preserve a geologic record of prehistoric coseismic uplift events. In January 2017, we participated in the Research Experience for Undergraduates (REU) program of the NSF SHIRE Project (Subduction at Hikurangi Integrated Research Experiment). We visited multiple coastal sites for reconnaissance fieldwork to select locations for future in-depth study. For the coastline between Flat Point and Te Kaukau Point, we used airborne LiDAR data provided by Land Information New Zealand (LINZ) to create ArcGIS digital terrain models for mapping and correlating uplifted paleo-shorelines. Terrace elevations derived from the LiDAR data were calibrated through the use of Real Time Kinematic (RTK) GPS surveying at one field site (Glenburn Station). Prior field mapping and radiocarbon dating results (Berryman et al., 2001; Litchfield and Clark, 2015) were used to guide our LiDAR mapping efforts. The resultant maps show between four and seven uplifted terraces and associated beach ridges along this coastal segment. At some sites, terrace mapping and lateral correlation are impeded by discontinuous exposures and the presence of landslide debris, alluvial fan deposits, and sand dunes. Tectonic uplift along the southern Hikurangi margin is generated by a complex interaction between deep megathrust slip and shallow upper-plate faulting. Each uplifted Holocene paleo-shoreline is interpreted to represent a single coseismic uplift event. Continued mapping, surveying, and age dating may help differentiate between very large margin-wide megathrust earthquakes (M8.0-9.0+) and smaller, more localized upper-plate thrust events (M7.0-8.0). Both of these earthquake types pose a significant seismic and tsunami hazard for New Zealand residents.

Effects of terracing on soil and water conservation in China: A meta-analysis

NASA Astrophysics Data System (ADS)

Chen, Die; Wei, Wei

2017-04-01

Terracing has long been considered a powerful strategy for soil and water conservation. However, the efficiency is limited by many factors, such as climate, soil properties, topography, land use, population and socioeconomic status. The aim of this critical review was to discuss the effects of terracing on soil and water conservation in China, using a systematic approach to select peer-reviewed articles published in English and Chinese. 46 individual studies were analyzed, involving six terracing structures (level terraces, slope-separated terraces, slope terraces, reverse-slope terraces, fanya juu terraces and half-moon terraces), a wide geographical range (Northeastern China, Southeastern hilly areas, Southwestern mountain areas and Northwestern-central China), and six land use types (forest, crop trees, cropland, shrub land, grassland and bare land) as well as a series of slope gradients ranging from 3° to 35°. Statistical meta-analysis with runoff for 593 observations and sediment for 636 observations confirmed that terracing had a significant effect on water erosion control. In terms of different terrace structures, runoff and sediment reduction were uppermost on slope-separated terraces. Land use in terraces also played a crucial role in the efficiency of conservation, and tree crops and forest were detected as the most powerful land covers in soil and water conservation due to large aboveground biomass and strong root systems below the ground, which directly reduces the pressure of terraces on rainwater redistribution. In addition, a significant positive correlation between slope gradients (3° 15° and 16° 35°) and terracing efficiency on soil and water conservation was observed. This study revealed the effectiveness and variation of terracing on water erosion control on the national scale, which can serve as a scientific basis to land managers and decision-makers.

Investigating the Relationship of Late Pleistocene Terrace Formation and Channel Dynamics within the Texas Gulf Coastal Plain

NASA Astrophysics Data System (ADS)

Ellis, T.; Hassenruck-Gudipati, H. J.; Mohrig, D. C.; Goudge, T. A.

2016-12-01

Terrace formation along coastal rivers is often assumed to be a direct result of punctuated sea-level fall. However, it has been experimentally shown that terraces commonly form under conditions of constant base level fall. In addition, it has been demonstrated that migrating channels in a bedrock system with steady state rock uplift can produce similar looking terraces. The lower Trinity River, in East Texas, is an ideal location to study allogenic (punctuated external forcing) versus autogenic terrace-building mechanisms using lidar measurements and OSL depositional age constraints (Gavin, 2005). To understand paleochannel influence on terrace construction, we measured channel characteristics for 27 preserved segments of paleochannels that are late Pleistocene in age and associated with 27 of 34 measured terraces along about 90 km of the modern river. There is no clear clustering of terrace elevation that might be tied to distinct sea level change events. Rather, the range of mean terrace elevations is indicative of a more constant system transformation. Based on lidar measurements, all paleochannels are larger than the modern channel, suggesting a wetter climate or larger watershed. Channel width measurements are used to quantify these changes in paleoflow discharge. Paleochannel width, radius of curvature and terrace slope measurements are used to characterize the movement of an incising channel. Based upon OSL terrace dates (Gavin, 2005), known global climate variations can be compared to discharge estimates and investigated as a predictor of terrace formation. If terrace formation occurred during distinct intervals of sea level fall, terraces with similar calculated paleoflow discharges are expected to plot along specific downstream elevation profiles. Assuming avulsion-driven terrace formation occurs at locations of higher channel sinuosity, the sinuosity of paleochannels on terraces is compared to the sinuosity of the modern river. Higher paleo-sinuosity would indicate preferential terrace formation at avulsion prone channel bends. Many factors may contribute to terrace formation during sea level fall and as such, we seek correlations between paleochannel morphology and terrace characteristics to distinguish between different terrace forming mechanisms.

A theory of growing crystalline nanorods - Mode I

NASA Astrophysics Data System (ADS)

Du, Feng; Huang, Hanchen

2018-08-01

Nanorods grow in two possible modes during physical vapor deposition (PVD). In mode I, monolayer surface steps dictate the diameter of nanorods. In mode II, multiple-layer surface steps dictate the diameter, which is the smallest possible under physical vapor deposition [5,10]. This paper reports closed-form theories of terrace lengths and nanorod diameter during the growth in mode I, as a function of deposition conditions. The accompanying lattice kinetic Monte Carlo simulations verify these theories. This study reveals that (1) quasi-steady growth exists for each set of nanorod growth conditions, and (2) the characteristic length scales, including terrace lengths and nanorod diameter at the quasi-steady state, depend on the deposition conditions - deposition rate F, substrate temperature T, and incidence angle θ - only as a function of l2D/tan θ, with l2 D = 2(v2 D/Fcosθ) 1/3 as a diffusion-limited length scale and v2D as the atomic diffusion jump rate over monolayer surface steps.

Sea-level history during the Last Interglacial complex on San Nicolas Island, California: implications for glacial isostatic adjustment processes, paleozoogeography and tectonics

USGS Publications Warehouse

Muhs, Daniel R.; Simmons, Kathleen R.; Schumann, R. Randall; Groves, Lindsey T.; Mitrovica, Jerry X.; Laurel, Deanna

2012-01-01

San Nicolas Island, California has one of the best records of fossiliferous Quaternary marine terraces in North America, with at least fourteen terraces rising to an elevation of ~270 m above present-day sea level. In our studies of the lowest terraces, we identified platforms at 38-36 m (terrace 2a), 33-28 m (terrace 2b), and 13-8 m (terrace 1). Uranium-series dating of solitary corals from these terraces yields three clusters of ages: ~120 ka on terrace 2a (marine isotope stage [MIS] 5.5), ~120 and ~100 ka on terrace 2b (MIS 5.5 and 5.3), and ~80 ka (MIS 5.1) on terrace 1. We conclude that corals on terrace 2b that date to ~120 ka were reworked from a formerly broader terrace 2a during the ~100 ka sea stand. Fossil faunas differ on the three terraces. Isolated fragments of terrace 2a have a fauna similar to that of modern waters surrounding San Nicolas Island. A mix of extralimital southern and extralimital northern species is found on terrace 2b, and extralimital northern species are on terrace 1. On terrace 2b, with its mixed faunas, extralimital southern species, indicating warmer than present waters, are interpreted to be from the ~120 ka high sea stand, reworked from terrace 2a. The extralimital northern species on terrace 2b, indicating cooler than present waters, are interpreted to be from the ~100 ka sea stand. The abundant extralimital northern species on terrace 1 indicate cooler than present waters at ~80 ka. Using the highest elevations of the ~120 ka platform of terrace 2a, and assuming a paleo-sea level of +6 m based on previous studies, San Nicolas Island has experienced late Quaternary uplift rates of ~0.25-0.27 m/ka. These uplift rates, along with shoreline angle elevations and ages of terrace 2b (~100 ka) and terrace 1 (~80 ka) yield relative (local) paleo-sea level elevations of +2 to +6 m for the ~100 ka sea stand and -11 to -12 m for the ~80 ka sea stand. These estimates are significantly higher than those reported for the ~100 ka and ~80 ka sea stands on New Guinea and Barbados. Numerical models of the glacial isostatic adjustment (GIA) process presented here demonstrate that these differences in the high stands are expected, given the variable geographic distances between the sites and the former Laurentide and Cordilleran ice sheets. Moreover, the numerical results show that the absolute and differential elevations of the observed high stands provide a potentially important constraint on ice volumes during this time interval and on Earth structure.

Morphology and sediment dynamics of the Capbreton canyon (Bay of Biscay, SW France)

NASA Astrophysics Data System (ADS)

Gaudin, M.; Umr 5805; Ifremer Team

2003-04-01

The Canyon of Capbreton extending in the Bay of Biscay (SW France) is the deepest canyon in the world. Its structure and morphology was studied using new multibeam bathymetry, acoustic imagery and high-resolution seismic data. The canyon head appears only 250 m away from the coast line and runs westward parallel to the north coast of Spain for 160 km due to structural control, then turns northward, widens and abruptly disappears in the continental rise by 3500 m water depth. Its northern margin is flat and progrades clearly westward. Conversely the southern margin is steep and progrades towards the north (i.e. towards the canyon). Down to 800 m water depth, the canyon deeply incises the continental shelf and the axial channel is meandering (sinuosity of 1.9). The canyon shows both major and minor stream beds, perched tributary valleys, nested terraces and abandoned meanders. The terraces have three morphologies: (1) flat, (2) with a raised side or (3) with a horseshoe structure. These morphologies have been interpreted as overbank deposits or nested levees (1 and 2) or as the result of meander abandon (3). Terraces of types (1) and (2) contain mainly fine deposits resulting from decantation of the top of turbulent surges that flow in the canyon. Westward (800 to 2000 m water depth) the main talweg remains sinuous (1.7). On the southern margin, several straight or slightly sinuous S-N tributary valleys are followed by alignments of pockmarks that also indicate a structural control. On the northern margin, a single large tributary valley with a sinuous central talweg, flowing from the upper Aquitaine continental slope, is interpreted as a giant slump scar due to sediment instability. This valley is bordered to the west by a topographic high with sediment waves on the external flank that might be interpreted as a sedimentary levee. The canyon recorded a recent turbidite activity. An 18 cm-thick turbidite was deposited at 650 m water depth by a turbidity current triggered by the storm which affected the French Atlantic coast on 27.12.1999. These present sedimentary processes contribute to maintain the freshness of the canyon morphology. However, the present frequency (in the range of one event every ten years) of gravity processes is too low to explain the incision. This suggests an increased activity when the canyon head was connected to the Adour River (previous to 1310 AD).

Ecosystem services provided by agricultural terraces in semi-arid climates.

NASA Astrophysics Data System (ADS)

Romero-Díaz, Asunción; Díaz-Pereira, Elvira; Boix-Fayos, Carolina; de Vente, Joris

2016-04-01

Since ancient times, agricultural terraces are common features throughout the world, especially on steep slope gradients. Nowadays many terraces have been abandoned or removed and few new terraces are build due to increased mechanisation and intensification of agriculture. However, terraces are amongst the most effective soil conservation practices, reducing the slope gradient and slope length, as well as runoff rate and soil erosion, and without terraces, it would be impossible to cultivate on many hillslopes. Moreover, their scenic interest is undeniable, as in some cases, terraced slopes have even become part of UNESCO World Heritage. In order to highlight the potential benefits, requirements and limitations of terraces, we reviewed different types of sustainable land management practices related to terraces and characterised their implications for provisioning, regulating, supporting, and cultural ecosystem services. We centred our review on terraces in semi-arid environments worldwide, as were documented in the WOCAT (World Overview of Conservation Approaches and Technologies) database. Our results show that the most important ecosystem services provided by terraces relate to regulation of the on-site and off-site effects of runoff and erosion, and maintenance of soil fertility and vegetation cover. The presence of terraces also favours the provision of food, fiber, and clean water. In short, our results stress the crucial environmental, geomorphological and hydrological functions of terraces that directly relate to improving the quality of life of the people that use them. These results highlight the need for renewed recognition of the value of terraces for society, their preservation and maintenance.

Gold atoms and clusters on MgO(100) films; an EPR and IRAS study

NASA Astrophysics Data System (ADS)

Yulikov, M.; Sterrer, M.; Risse, T.; Freund, H.-J.

2009-06-01

Single gold atoms deposited on single crystalline MgO(1 0 0) films grown on Mo(1 0 0) are characterized by electron paramagnetic resonance spectroscopy as well as IR spectroscopy using CO as probe molecules. In this article we describe the first angular dependent measurements to determine the principal hyperfine components of a secondary hyperfine interaction, namely, with 17O of the MgO. The values determined here are in perfect agreement with theoretical expectations and corroborate the previously reported binding mechanism of Au atoms on the oxygen anions of the MgO terrace. The temperature dependent EPR data reveal an onset of Au atom mobility at about 80 K while the formation of Au particles occurs only above 125 K. By an analysis of the EPR line width in combination with STM measurements it is possible to deduce an increase of the interatomic distance above 80 K. The Au/CO complexes show a somewhat smaller temperature stability as compared to the Au atoms. The observed thermal stability is in perfect agreement with theoretical predictions for CO desorption.

Magnetic 4d monoatomic rows on Ag vicinal surfaces

NASA Astrophysics Data System (ADS)

Bellini, V.; Papanikolaou, N.; Zeller, R.; Dederichs, P. H.

2001-09-01

The magnetic properties of 4d monoatomic rows on Ag substrates have been studied by ab initio calculations using the screened Korringa-Kohn-Rostoker (SKKR) Green's function method within density functional theory (DFT) in its local spin density approximation (LSDA). The rows were placed at step-edge (step decoration) and on terrace positions of different vicinal Ag surfaces, i.e., fcc (711), fcc (410), and fcc (221). The results for the magnetic moments are explained in terms of the different coordination numbers of the row atoms and the different hybridization between the rather extended 4d orbitals of the row atoms and the sp-like valence electrons of the Ag substrates. For the fcc (711) vicinal surface, we explore the possibility of antiferromagnetic coupling between the atoms in each row and discuss, by means of total energy calculations, the stability of the antiferromagnetic solutions with respect to the ferromagnetic ones.

Assessment of dry-stone terrace wall degradation with a 3D approach

NASA Astrophysics Data System (ADS)

Djuma, Hakan; Camera, Corrado; Faka, Marina; Bruggeman, Adriana; Hermon, Sorin

2016-04-01

In the Mediterranean basin, terracing is a common element of agricultural lands. Terraces retained by dry-stone walls are used to conserve arable soil, delay erosion processes and retain rainfall runoff. Currently, agricultural land abandonment is widespread in the Mediterranean region leading to terrace wall failure due to lack of maintenance and consequently an increase in soil erosion. The objective of this study is to test the applicability of digital 3D documentation on mountainous agricultural areas for assessing changes in terrace wall geometry, including terrace wall failures and associated soil erosion. The study area is located at 800-1100 m above sea level, in the Ophiolite complex of the Troodos Mountains in Cyprus. Average annual precipitation is 750 mm. Two sites with dry-stone terraces were selected for this study. The first site had a sequence of three terrace walls that were surveyed. The uppermost terrace wall was collapsed at several locations; the middle at few locations; and the lowest was still intact. Three fieldwork campaigns were conducted at this site: during the dry season (initial conditions), the middle and end of the wet season. The second site had one terrace wall that was almost completely collapsed. This terrace was restored during a communal terrace rehabilitation event. Two fieldwork campaigns were conducted for this terrace: before and after the terrace wall restoration. Terrace walls were documented with a set of digital images, and transformed into a 3D point cloud (using web-based services and commercial software - Autodesk 123D catch and Menci Software uMap, respectively). A set of points, registered with the total station and geo-referenced with a GPS, enabled the scaling of the 3D model and aligning the terrace walls within the same reference system. The density (distance between each point) of the reconstructed point clouds is 0.005 m by Umap and 0.025 m by 123D Catch. On the first site, the model analysis identified wall displacements between 3 and 8 cm on 1% of the middle terrace wall. High displacement values (> 8-10 cm) were associated with presence or removal of vegetation and/or data gaps. On the second site, the 3D models indicated that the collapsed terrace had lost a volume of 1.9 m3, which was restored during the communal terrace building event. This digital 3D documentation approach is more economical than laser scanning and it is a promising method for assessment of terrace wall displacement and changes after terrace wall restoration.

Cathodic Corrosion at the Bismuth-Ionic Liquid Electrolyte Interface under Conditions for CO 2 Reduction

DOE PAGES

Medina Ramos, Jonnathan; Zhang, Weiwei; Yoon, Kichul; ...

2018-03-08

Bismuth electrodes undergo distinctive electrochemically induced structural changes in nonaqueous imidazolium ([Im])(+))-based ionic liquid solutions under cathodic polarization. In situ X-ray reflectivity (XR) studies have been undertaken to probe well-ordered Bi (001) films which originally contain a native Bi 2O 3 layer. This oxide layer gets reduced to Bi(0)during the first cyclic voltammetry (CV) scan in acetonitrile solutions containing 1-butyl-3-methylimidazolium ([BMIM](+)) electrolytes. Approximately 60% of the Bi (001) Bragg peak reflectivity is lost during a potential sweep between -1.5 and -1.9 V vs Ag/AgCI due to a similar to 4-10% thinning and a similar to 40% decrease in lateral sizemore » of Bi (001) domains, which are mostly reversed during the anodic scan. Repeated potential cycling enhances the thinning and roughening of the films, suggesting that partial dissolution of Bi ensues during negative polarization. The mechanism of this behavior is understood through molecular dynamics simulations using ReaxFF and density functional theory (DFT) calculations. Both approaches indicate that [Im] + cations bind to the metal surface more strongly than tetrabutylammonium (TBA +) as the potential and the charge on the Bi surface become more negative. ReaxFF simulations predict a higher degree of disorder for a negatively charged Bi (001) slab in the presence of the [Im](+)cations and substantial migration of Bi atoms from the surface. DFT simulations show the formation of Bi center dot center dot center dot[Im] + complexes that lead to the dissolution of Bi atoms from step edges on the Bi (001) surface at potentials between -1.65 and -1.95 V. Bi desorption from a flat terrace requires a potential of approximately -2.25 V. Together, these results suggest the formation of a Bi center dot center dot center dot[Im] + complex through partial cathodic corrosion of the Bi film under conditions (potential and electrolyte composition) that favor the catalytic reduction of CO 2 .« less

Cathodic Corrosion at the Bismuth-Ionic Liquid Electrolyte Interface under Conditions for CO 2 Reduction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Medina Ramos, Jonnathan; Zhang, Weiwei; Yoon, Kichul

Bismuth electrodes undergo distinctive electrochemically induced structural changes in nonaqueous imidazolium ([Im])(+))-based ionic liquid solutions under cathodic polarization. In situ X-ray reflectivity (XR) studies have been undertaken to probe well-ordered Bi (001) films which originally contain a native Bi 2O 3 layer. This oxide layer gets reduced to Bi(0)during the first cyclic voltammetry (CV) scan in acetonitrile solutions containing 1-butyl-3-methylimidazolium ([BMIM](+)) electrolytes. Approximately 60% of the Bi (001) Bragg peak reflectivity is lost during a potential sweep between -1.5 and -1.9 V vs Ag/AgCI due to a similar to 4-10% thinning and a similar to 40% decrease in lateral sizemore » of Bi (001) domains, which are mostly reversed during the anodic scan. Repeated potential cycling enhances the thinning and roughening of the films, suggesting that partial dissolution of Bi ensues during negative polarization. The mechanism of this behavior is understood through molecular dynamics simulations using ReaxFF and density functional theory (DFT) calculations. Both approaches indicate that [Im] + cations bind to the metal surface more strongly than tetrabutylammonium (TBA +) as the potential and the charge on the Bi surface become more negative. ReaxFF simulations predict a higher degree of disorder for a negatively charged Bi (001) slab in the presence of the [Im](+)cations and substantial migration of Bi atoms from the surface. DFT simulations show the formation of Bi center dot center dot center dot[Im] + complexes that lead to the dissolution of Bi atoms from step edges on the Bi (001) surface at potentials between -1.65 and -1.95 V. Bi desorption from a flat terrace requires a potential of approximately -2.25 V. Together, these results suggest the formation of a Bi center dot center dot center dot[Im] + complex through partial cathodic corrosion of the Bi film under conditions (potential and electrolyte composition) that favor the catalytic reduction of CO 2 .« less

Soils of Agricultural Terraces with Retaining Walls in the Mountains of Dagestan

NASA Astrophysics Data System (ADS)

Borisov, A. V.; Korobov, D. S.; Idrisov, I. A.; Kalinin, P. I.

2018-01-01

Soil-archeological studies of agricultural terraces with retaining walls in the area of construction of the Gotsatlinskaya Hydroelectric Power Station in Khunzakh district of the Republic of Dagestan have been performed. The morphogenetic and chemical properties of the anthropogenic soils (Anthrosols) in different parts of the terrace complex are analyzed. It is argued that slope terracing in the mountains ensures the development of thicker soil profiles with pronounced genetic horizons. The soils of agricultural terraces store important information of the paleoenvironmental history and land use. A characteristic feature of the Anthrosols of agricultural terraces is a relatively even distribution of gravelly material of up to 5 cm in diameter in the plow layer. The soils of terraces are characterized by the high variability in their properties within the entire terrace complex and within the particular terraces.

The prevalence of terraced treescapes in analyses of phylogenetic data sets.

PubMed

Dobrin, Barbara H; Zwickl, Derrick J; Sanderson, Michael J

2018-04-04

The pattern of data availability in a phylogenetic data set may lead to the formation of terraces, collections of equally optimal trees. Terraces can arise in tree space if trees are scored with parsimony or with partitioned, edge-unlinked maximum likelihood. Theory predicts that terraces can be large, but their prevalence in contemporary data sets has never been surveyed. We selected 26 data sets and phylogenetic trees reported in recent literature and investigated the terraces to which the trees would belong, under a common set of inference assumptions. We examined terrace size as a function of the sampling properties of the data sets, including taxon coverage density (the proportion of taxon-by-gene positions with any data present) and a measure of gene sampling "sufficiency". We evaluated each data set in relation to the theoretical minimum gene sampling depth needed to reduce terrace size to a single tree, and explored the impact of the terraces found in replicate trees in bootstrap methods. Terraces were identified in nearly all data sets with taxon coverage densities < 0.90. They were not found, however, in high-coverage-density (i.e., ≥ 0.94) transcriptomic and genomic data sets. The terraces could be very large, and size varied inversely with taxon coverage density and with gene sampling sufficiency. Few data sets achieved a theoretical minimum gene sampling depth needed to reduce terrace size to a single tree. Terraces found during bootstrap resampling reduced overall support. If certain inference assumptions apply, trees estimated from empirical data sets often belong to large terraces of equally optimal trees. Terrace size correlates to data set sampling properties. Data sets seldom include enough genes to reduce terrace size to one tree. When bootstrap replicate trees lie on a terrace, statistical support for phylogenetic hypotheses may be reduced. Although some of the published analyses surveyed were conducted with edge-linked inference models (which do not induce terraces), unlinked models have been used and advocated. The present study describes the potential impact of that inference assumption on phylogenetic inference in the context of the kinds of multigene data sets now widely assembled for large-scale tree construction.

Integrating Geomorphic and Social Dynamics in the Analysis of Anthropogenic Landforms: Examining Landscape Evolution of Terrain Modified by Agricultural Terracing

NASA Astrophysics Data System (ADS)

Glaubius, J.; Maerker, M.

2016-12-01

Anthropogenic landforms, such as mines and agricultural terraces, are impacted by both geomorphic and social processes at varying intensities through time. In the case of agricultural terraces, decisions regarding terrace maintenance are intertwined with land use, such as when terraced fields are abandoned. Furthermore, terrace maintenance and land use decisions, either jointly or separately, may be in response to geomorphic processes, as well as geomorphic feedbacks. Previous studies of these complex geomorphic systems considered agricultural terraces as static features or analyzed only the geomorphic response to landowner decisions. Such research is appropriate for short-term or binary landscape scenarios (e.g. the impact of maintained vs. abandoned terraces), but the complexities inherent in these socio-natural systems requires an approach that includes both social and geomorphic processes. This project analyzes feedbacks and emergent properties in terraced systems by implementing a coupled landscape evolution model (LEM) and agent-based model (ABM) using the Landlab and Mesa modeling libraries. In the ABM portion of the model, agricultural terraces are conceptualized using a life-cycle stages schema and implemented using Markov Decision Processes to simulate the changing geomorphic impact of terracing based on human decisions. This paper examines the applicability of this approach by comparing results from a LEM-only model against the coupled LEM-ABM model for a terraced region. Model results are compared by quantify and spatial patterning of sediment transport. This approach fully captures long-term landscape evolution of terraced terrain that is otherwise lost when the life-cycle of terraces is not considered. The coupled LEM-ABM approach balances both environmental and social processes so that the socio-natural feedbacks in such anthropogenic systems can be disentangled.

Molecular transport through capillaries made with atomic-scale precision

NASA Astrophysics Data System (ADS)

Radha, B.; Esfandiar, A.; Wang, F. C.; Rooney, A. P.; Gopinadhan, K.; Keerthi, A.; Mishchenko, A.; Janardanan, A.; Blake, P.; Fumagalli, L.; Lozada-Hidalgo, M.; Garaj, S.; Haigh, S. J.; Grigorieva, I. V.; Wu, H. A.; Geim, A. K.

2016-10-01

Nanometre-scale pores and capillaries have long been studied because of their importance in many natural phenomena and their use in numerous applications. A more recent development is the ability to fabricate artificial capillaries with nanometre dimensions, which has enabled new research on molecular transport and led to the emergence of nanofluidics. But surface roughness in particular makes it challenging to produce capillaries with precisely controlled dimensions at this spatial scale. Here we report the fabrication of narrow and smooth capillaries through van der Waals assembly, with atomically flat sheets at the top and bottom separated by spacers made of two-dimensional crystals with a precisely controlled number of layers. We use graphene and its multilayers as archetypal two-dimensional materials to demonstrate this technology, which produces structures that can be viewed as if individual atomic planes had been removed from a bulk crystal to leave behind flat voids of a height chosen with atomic-scale precision. Water transport through the channels, ranging in height from one to several dozen atomic planes, is characterized by unexpectedly fast flow (up to 1 metre per second) that we attribute to high capillary pressures (about 1,000 bar) and large slip lengths. For channels that accommodate only a few layers of water, the flow exhibits a marked enhancement that we associate with an increased structural order in nanoconfined water. Our work opens up an avenue to making capillaries and cavities with sizes tunable to ångström precision, and with permeation properties further controlled through a wide choice of atomically flat materials available for channel walls.

Maintenance and recovery of agricultural terraces to reduce geo-hydrological hazards: the Santa Giulia in Centaura (Liguria, Italy) and Valstagna (Veneto, Italy) case studies

NASA Astrophysics Data System (ADS)

Giostrella, Paola; Ferrarese, Francesco; Faccini, Francesco; Brandolini, Pierluigi; Lazzeri, Riccardo; Melillo, Massimo; Mozzi, Paolo; Varotto, Mauro; Tarolli, Paolo; Guzzetti, Fausto

2015-04-01

Throughout the World, men have built terraced landscapes to gain ground suitable for cultivation in steep terrain. Beyond the historical and cultural importance of terraced slopes, terraces have played an important role for soil conservation and water management. In many areas, their abandonment has led to more frequent and/or abundant geo-hydrological hazards. We analyse two terraced areas in northern Italy, including (i) the Valstagna prealpine terraces (Veneto) where the Republic of Venice initiated the cultivation of tobacco in 1600, and (ii) the coastal terraces of Santa Giulia di Centaura (Liguria) where terraces host vineyards and olive groves since 2000 years. Using a combination of direct and indirect mapping methods and tools, including LiDAR topographic surveys, the visual interpretation of aerial photographs and the analysis of historical maps, we performed a systematic mapping of the terraces. Using the available maps, we determined statistics for the width, height and extent of stonewalls and we evaluated the historical evolution of the terraces for the past 50 years, considering changes in land use, the expansion of forest, and the changes in the precipitation regime. Finally, through a preliminary cost-benefit analysis, we propose good practices to help the recovery of the terraces in the two study areas.

Evaluation of agricultural best-management practices in the Conestoga River headwaters, Pennsylvania; effects of pipe-outlet terracing on quantity and quality of surface runoff and ground water in a small carbonate-rock basin near Churchtown, Pennsylvania, 1983-89

USGS Publications Warehouse

Lietman, P.L.; Gustafson-Minnich, L. C.; Hall, D.W.

1997-01-01

Terracing effects on surface-runoff and ground- water quantity and quality were investigated by the U.S. Geological Survey, in cooperation with Pennsylvania Department of Environmental Resources, during 1983-89 at a 23.1-acre agricultural site in Lancaster County, Pa., as part of the 1982 Rural Clean Water Program. The site, underlain by carbonate rock, was primarily corn and alfalfa fields; the median slope was 6 percent.Normal precipitation is about 42 inches per year. Average annual runoff was 11 percent and ground- water recharge was 37 percent of precipitation.Runoff quantity, suspended-sediment, and nutrient data, ground-water level and nutrient data, and precipitation-quantity data were collected for 21 months prior to, and 58 months after, pipe-outlet terrace construction. Data were analyzed by use of graphical, regression, covariate, cluster, Mann- Whitney Rank Sum test, and double-mass curvetechniques. Terracing changed runoff characteristics. Storm characteristics were similar throughout the study period. However, after terracing, storms producing less than 0.4 inch of precipitation rarely produced runoff. Total-storm discharge as a function of precipitation did not change significantly throughout the range of runoff-producing storms after terracing. Multiple-discharge peaks on hydrographs before terracing did not occur after terracing when hydrographs reflected the stepwisedraining of each terrace through the pipe outlet. After an initial 2-year period of terrace stabilization, suspended-sediment yield in runoff decreased significantly as a function of runoff. This result was expected because terracing decreased runoff energy, and because terrace ponding allowed time for sediment redeposition. Nitrate plus nitrite yields increased proportionally throughout the range of runoff during the post-terracing period relative to the pre- terracing period. After terracing, a combination of increased soil contact time and increased nitrification caused by wetter soils is believed to have increased nitrate concentrations in runoff. No significant change was found in yields of total nitrogen, ammonia plus organic nitrogen, or total phosphorus relative to runoff before and after terracing. Limited data suggest that fine-sediment particles (less than 0.62 micrometers in diameter), which continued to be discharged from the site, transported most of the phosphorus. Terracing did not significantly change the quantity of recharge to the carbonate aquifer. The mean annual water-table altitude did not change after terracing. Nitrate concentrations of ground water increased significantly at four of the site wells after terracing, probably because of increased contact time of the recharge with nutrient-rich soils in ponded terrace water. Qualitative evidence indicates that large decreases in nutrient requirements and nitrogen applications because of a crop change from corn to alfalfa upgradient of two site wells resulted in either no detectable change or a significant decrease in nitrate concentrations of ground water after terracing.

Conducting LaAlO3/SrTiO3 heterointerfaces on atomically-flat substrates prepared by deionized-water

PubMed Central

Connell, J. G.; Nichols, J.; Gruenewald, J. H.; Kim, D.-W.; Seo, S. S. A.

2016-01-01

We have investigated how the recently-developed water-leaching method for atomically-flat SrTiO3 (STO) substrates affects the transport properties of LaAlO3 (LAO) and STO heterointerfaces. Using pulsed laser deposition at identical growth conditions, we have synthesized epitaxial LAO thin-films on two different STO substrates, which are prepared by water-leaching and buffered hydrofluoric acid (BHF) etching methods. The structural, transport, and optical properties of LAO/STO heterostructures grown on water-leached substrates show the same high-quality as the samples grown on BHF-etched substrates. These results indicate that the water-leaching method can be used to grow complex oxide heterostructures with atomically well-defined heterointerfaces without safety concerns. PMID:27033248

Soil development on a Pleistocene terrace sequence, Boise Valley, Idaho

USGS Publications Warehouse

Othberg, K.L.; McDaniel, P.A.; Fosberg, M.A.

1997-01-01

Study of a sequence of terraces in the western Snake River Plain of Idaho reveals a record of at least seven terraces, the ages of which span the Pleistocene. In the Boise Valley, the youngest terraces are less than -14,500 yr and the oldest terraces are -1.7 Ma. Within this sequence, several relationships exist between soil morphology and terrace chronology. On terraces older than -14,500 yr, argillic horizon development generally increases with terrace age with maximum development occurring in soils of the oldest terraces. CaCO3- and SiO2-cemented duripans are found in soils on terraces that are late middle Pleistocene and older. By virtue of their physical and chemical properties, duripans are very resistant to erosion, and therefore provide stable records of CaCO3 and SiO2 accumulation throughout multiple cycles of loess deposition onto the terrace treads, pedogenesis, and partial erosion. Mean duripan thickness increases with age to a maximum of 0.66 m on the oldest terraces. Our results suggest that a geomorphic surface age of approximately 130,000 yr is required to form the initial plugged horizon that is characteristic of a duripan. CaCO3 and SiO2 accumulation is most rapid in duripans occupying geomorphic surfaces with ages ranging from 130,000 to 300,000 yr. After this, apparent accumulation rates decrease and little additional accumulation of these cementing agents occurs with time.

A geomorphic and tectonic model for the formation of the flight of Holocene marine terraces at Mahia Peninsula, New Zealand

NASA Astrophysics Data System (ADS)

Berryman, Kelvin; Clark, Kate; Cochran, Ursula; Beu, Alan; Irwin, Sarah

2018-04-01

At Table Cape, Mahia Peninsula, North Island, New Zealand, four marine terraces have been uplifted coseismically during the past 3500 years. Detailed facies assessment of the terrace coverbed sequence coupled with identification of modern analogues on the active shore platform were used to infer the process of marine terrace formation and to estimate the timing and amount of past uplift events (earthquakes). The modern platform can be subdivided into seven depositional zones: subtidal, outer platform, intertidal sand pockets, inner platform, high-tide, mid-storm, and storm beach. Terrace coverbeds were characterised from two trenches excavated across the full width of the uplifted terrace sequence. Off-lapping packages of high tidal, mid-storm, and storm beach sediments were most common. Outer platform sediments occurred only rarely near the base of some uplifted shore platforms. Overlying the marine sediments were near-horizontal terrestrial deposits of airfall tephra (on the two highest terraces), subsoil, topsoil, rare wedges of colluvial sediment (slopewash) shed from terrace risers, and an anomalous deposit possibly emplaced by a tsunami. Fifty-one radiocarbon ages, obtained from molluscs in the marine coverbeds, showed a general pattern of seaward-younging across the coastal plain and across each terrace and a less pronounced pattern of decreasing age upward in each coverbed sequence. The distinctive stepped geomorphology of the terraces, the facies and age structure of the terrace deposits and historical earthquake causation of similar terraces elsewhere in New Zealand provided the data to invoke an earthquake-driven model for terrace formation. Marine terrace development following an uplift event involved rapid cutting of a new intertidal shore platform and generally regressive deposition of high-tide to storm beach deposits. Following further uplift, the platform became a geomorphic terrace (above marine influence) and was then mantled by terrestrial sediments. On the two highest terraces at Table Cape, airfall tephras mantling the marine coverbeds provided a minimum age for terrace uplift. The youngest radiocarbon ages from high-tide deposits high in the stratigraphy and near the seaward edge of each terrace provided the best estimates for the timing of uplift. Based on the new radiocarbon ages and the constraining airfall tephra ages, we revised the earthquake ages to 3530-3350, 1810-1730, 1560-1300 and 300-100 cal. YBP. Associated best estimates of the coseismic uplift amounts were 2.1, 1.4, 1.8, and 3.1 m respectively, once we accounted for eustatic sea level changes through the late Holocene.

Relationships between soil parameters and vegetation in abandoned terrace fields vs. non-terraced fields in arid lands (Lanzarote, Spain): An opportunity for restoration

NASA Astrophysics Data System (ADS)

Arévalo, José Ramón; Fernández-Lugo, Silvia; Reyes-Betancort, J. Alfredo; Tejedor, Marisa; Jiménez, Concepción; Díaz, Francisco J.

2017-11-01

Over 90% of terraced fields have been abandoned on the island of Lanzarote in the last 40 years. The present work analyses the effects of abandonment on the soil and vegetation recovery of terraced field agroecosystems by comparing them with adjacent non-terraced fields in Lanzarote, Canary Islands (Spain). This information is necessary to take the appropriate management actions to achieve goals such as soil protection and biodiversity conservation. Results indicate that terraced fields display better soil quality than non-terraced ones, as shown by the significant differences found in parameters such as SAR, exchangeable Na, CaCO3, B content, moisture content or soil depth. Moreover, the terraced fields' plant community has more species similarities with the native plant community when compared with non-terraced areas. Owing to characteristics such as deeper soils, more water capacity, lower salinity and less sodic soils, terraced soils provide better conditions for passive restoration of both soil and vegetation. Therefore, the recovery and maintenance of wall structures and revegetation with native/endemic species are proposed to promote the restoration of native systems and preserve a landscape with cultural and aesthetic value.

Spatio-temporal relation between landslide occurrence and abandoned or not maintained agricultural terraces in the Moldavian Plateau, NE Romania

NASA Astrophysics Data System (ADS)

Ciprian Margarint, Mihai; Santangelo, Michele; Niculita, Mihai; Bucci, Francesco

2016-04-01

Terraced landscapes are one of the most obvious human-shaped landscapes, mainly used to reduce the negative impact of soil erosion due to uncontrolled runoff and shallow landslides occurrence. Nevertheless, as the recent literature emphasizes, these old best practices can transform into a potential hazard for soil degradation, if not appropriately maintained. In Moldavian Plateau (NE Romania), agricultural terraces were built after the 1960s for landslide, soil erosion and runoff control, mainly in connection with construction of reservoirs, for increasing their operation time. Usually, the slope reduction was obtained by construction of cut-off ditches, hillside ditches, intermittent terraces, bench terraces, broad-based terraces, vineyardand orchard terraces. Due to the dry climatic setting, to the lack of hard rocks for construction, and to the generally light earth moving machinery available for construction, terraces are generally characterized by a small escarpment (0.5m to 1m), and a relatively short lateral extension (5 to 40 m). When the terraces were maintained, the backslope was typically covered with grass. When, after the 1990s, the lands were returned to the initial owners, the vegetation cover of the terraces was no more maintained, and the terraces themselves were progressively abandoned, due to lack of funds. Accurate landslide mapping on high resolution LiDAR DEM derived images, allowed to produce geomorphological inventories in 5 test cases, representative of the whole study area. In each inventory, landslides were classified based on type and relative age based on published classification schemes. We investigate the spatial and temporal relation between landslides occurrence and terraces, based on the spatial interactions of landslides of different ages and terraces. Results reveal that terraces were built, both on landslide-free and landslide-bearing slopes, and that frequently landslides and gullies develop on terraced slopes. Reactivations of landslides which were terraced only with the scope of soil erosion control are the most frequent, whereas new landslides also occur, which are generally smaller than 2,000 m^2, and are mostly shallow slides affecting the agricultural layer. We hypothesize that landslides affecting the terraces occur mostly due to the lack of adequate and maintained drainage measures, and as well as of protective measures at the base of the hillslopes to prevent water incision. Our findings provide new input to the study of the relations between agricultural terraces and geomorphological processes, and have direct implications on land management, helping to decipher the critical conditions for landsliding of terraced terrains, which is the base for designing efficient mitigation measurements. Results are relevant because provide a suitable scientific framework to support decisions for a sustainable development of the agricultural communities of these rural areas in the context of a changing climate.

Molecular dynamics simulation studies of ionic liquid electrolytes for electric double layer capacitors

NASA Astrophysics Data System (ADS)

Hu, Zongzhi

Molecular Dynamics (MD) simulation has been performed on various Electric Double Layer Capacitors (EDLCs) systems with different Room Temperature Ionic Liquids (RTILs) as well as different structures and materials of electrodes using a computationally efficient, low cost, united atom (UA)/explicit atom (EA) force filed. MD simulation studies on two 1-butyl-3-methylimidazolium (BMIM) based RTILs, i.e., [BMIM][BF4] and [BMIM][PF6], have been conducted on both atomic flat and corrugated graphite as well as (001) and (011) gold electrode surfaces to understand the correlations between the Electric Double Layer (EDL) structure and their corresponding differential capacitance (DC). Our MD simulations have strong agreement with some experimental data. The structures of electrodes also have a strong effect on the capacitance of EDLCs. MD simulations have been conducted on RTILs of N-methyl-N- propylpyrrolidinium [pyr13] and bis(fluorosulfonyl)imide (FSI) as well as [BMIM][PF6] on both curvature electrodes (fullerenes, nanotube, nanowire) and atomic flat electrode surfaces. It turns out that the nanowire electrode systems have the largest capacitance, following by fullerene systems. Nanotube electrode systems have the smallest capacitance, but they are still larger than that of atomically flat electrode system. Also, RTILs with slightly different chemical structure such as [Cnmim], n = 2, 4, 6, and 8, FSI and bis(trifluoromethylsulfonyl)imide (TFSI), have been examined by MD simulation on both flat and nonflat graphite electrode surfaces to study the effect of cation and anion's chemical structures on EDL structure and DC. With prismatic (nonflat) graphite electrodes, a transition from a bell-shape to a camel-shape DC dependence on electrode potential was observed with increase of the cation alkyl tail length for FSI systems. In contrast, the [Cnmim][TFSI] ionic liquids generated only a camel-shape DC on the rough surface regardless of the length of alkyl tail.

Sedimentary development and correlation of Late Quaternary terraces in the Kyrenia Range, northern Cyprus, using a combination of sedimentology and optical luminescence data

NASA Astrophysics Data System (ADS)

Palamakumbura, Romesh N.; Robertson, Alastair H. F.; Kinnaird, Tim C.; Sanderson, David C. W.

2016-01-01

This study focuses on the younger of a series of Quaternary terraces along the flanks of the Kyrenia Range in northern Cyprus, specifically the Kyrenia (Girne) and the Koupia terraces. The Kyrenia (Girne) terrace is tentatively correlated with oxygen isotope stage 5 (125 Ka), and the Koupia terrace with oxygen isotope stage 3 (<50 Ka). Along the northern flank of the range, the Kyrenia (Girne) terrace deposits (5-20 m above modern sea level) typically begin with a basal lag conglomerate and then pass upwards into shallow-marine calcarenites and then into variable aeolianites, paleosols and fluvial deposits (up to 20 m thick). In contrast, the Koupia terrace (<2 m above modern sea level) consists of aeolianites and shallow-marine calcarenites (up to 8 m thick). The equivalent deposits along the southern flank of the range are entirely non-marine fluvial mud, sands and conglomerates. The marine to continental terrace systems can be tentatively correlated based on mapping, height above modern sea level and sedimentary facies. However, variable preservation and patchy exposure require such correlations to be independently tested. To achieve this, a portable optically stimulated luminescence (OSL) reader was used to determine the luminescence characteristics of the two terrace systems. Luminescence profiles show major differences in luminescence characteristics between the two terrace depositional systems, which can be related to sedimentary processes, provenance and age. These features allow sections in different areas to be effectively correlated. Individual sections show luminescence properties that are generally consistent with an expected up-sequence decrease in age. However, the younger Koupia terrace deposits show higher luminescence intensities compared with the older Kyrenia (Girne) terrace deposits. This can be explained by multiple phases of reworking of the Kyrenia (Girne) terrace deposits, which changed the luminescence characteristics of the sediment. The use of the portable OSL reader is therefore an effective means of correlating Late Quaternary terrace deposits in northern Cyprus and probably also elsewhere.

Unsteady Landscapes: Climatic and Tectonic Controls on Fluvial Terrace Formation

NASA Astrophysics Data System (ADS)

Clubb, F. J.; Mudd, S. M.

2017-12-01

Fluvial terraces are common landforms throughout mountainous regions which represent abandoned remnants of active river systems and their floodplains. The formation of these landforms points to a fundamental unsteadiness in the incision rate of the fluvial network, providing important information on channel response to climatic, tectonic, and base-level forcing, sediment storage and dynamics within mountainous systems, and the relative importance of lateral and vertical incision rates. In his 1877 Report on the Geology of the Henry Mountains, G.K. Gilbert suggested that strath terraces may form due to climatically-driven increase in sediment supply, causing armouring of the channel bed and hindering vertical incision. An alternative hypothesis suggests that strath terraces may be preserved through progressive tectonic uplift or base-level fall. These different formation mechanisms should result in varying distribution of terrace elevations along channels: if terraces are formed through climate-driven variations in sediment supply, we might expect that terrace elevations would be random, whereas progressive fluvial incision should result in a series of terraces with a systematic elevation pattern. Here we test alternative hypotheses for strath terrace formation using a new method for objectively and rapidly identifying terrace surfaces from digital elevation models (DEMs) over large spatial scales. Our new method identifies fluvial terraces using their gradient and elevation compared to the modern channel, thresholds of which are statistically calculated from the DEM and do not need to be set manually by the user. We use this method to extract fluvial terraces for every major river along the coast of California, and quantify their distribution and elevation along the fluvial long profile. Our results show that there is no systematic pattern in terrace elevations despite a well-constrained spatial variation in uplift rates, suggesting that terraces in this region do not reflect the influence of regional tectonics, and may instead be the formed through climatic variations or autogenic fluvial processes.

Processes of Terrace Formation on the Piedmont of the Santa Cruz River Valley During Quaternary Time, Green Valley-Tubac Area, Southeastern Arizona

USGS Publications Warehouse

Lindsey, David A.; Van Gosen, Bradley S.

2010-01-01

In this report we describe a series of stepped Quaternary terraces on some piedmont tributaries of the Santa Cruz River valley in southeastern Arizona. These terraces began to form in early Pleistocene time, after major basin-and-range faulting ceased, with lateral planation of basin fill and deposition of thin fans of alluvium. At the end of this cycle of erosion and deposition, tributaries of the Santa Cruz River began the process of dissection and terrace formation that continues to the present. Vertical cutting alternated with periods of equilibrium, during which streams cut laterally and left thin deposits of channel fill. The distribution of terraces was mapped and compiled with adjacent mapping to produce a regional picture of piedmont stream history in the middle part of the Santa Cruz River valley. For selected tributaries, the thickness of terrace fill was measured, particle size and lithology of gravel were determined, and sedimentary features were photographed and described. Mapping of terrace stratigraphy revealed that on two tributaries, Madera Canyon Wash and Montosa Canyon Wash, stream piracy has played an important role in piedmont landscape development. On two other tributaries, Cottonwood Canyon Wash and Josephine Canyon Wash, rapid downcutting preempted piracy. Two types of terraces are recognized: erosional and depositional. Gravel in thin erosional terraces has Trask sorting coefficients and sedimentary structures typical of streamflood deposits, replete with bar-and-swale surface topography on young terraces. Erosional-terrace fill represents the channel fill of the stream that cuts the terrace; the thickness of the fill indicates the depth of channel scour. In contrast to erosional terraces, depositional terraces show evidence of repeated deposition and net aggradation, as indicated by their thickness (as much as 20+ m) and weakly bedded structure. Depositional terraces are common below mountain-front canyon mouths where streams drop their load in response to abrupt flattening of gradients and expansion of channel banks, and they extend down the piedmont along Josephine Canyon Wash. Gravel in depositional terraces also has sorting coefficients typical of streamflood deposits. Sedimentary features in both types of terraces are consistent with deposition by flash floods in ephemeral streams, suggesting the climate was arid. Bedding and clast armor are weakly developed, clast clusters and imbrication are common, and crossbedding is generally absent. Debris-flow deposits, even near the mountain front, are surprisingly rare. On the tectonically stable piedmont of southeastern Arizona, stream piracy and climate change are the most likely agents of terrace formation. Both piracy and climate change can cause rapid changes in discharge and sediment supply, which initiate cycles of incision, lateral cutting, and aggradation. Increased stream discharge initiates downcutting, but increased sediment supply interrupts downcutting and causes streams to cut laterally and aggrade. At times, on Madera Canyon Wash and Montosa Canyon Wash, stream piracy affected stream discharge and sediment supply, but on Cottonwood Canyon Wash and Josephine Canyon Wash, only climate change could have initiated terrace cutting. Terraces probably formed during extended arid intervals when sparse vegetation and flashy stream discharge combined to increase sediment supply. In most cases, sediment supply was sufficient to promote lateral cutting but not long-term aggradation. Thus, most streams formed erosional terraces. The middle Pleistocene Josephine Canyon Wash formed a depositional terrace because it had a source of abundant unconsolidated sediment.

Uplifting model of the Longmenshan mountain in the eastern margin of Tibetan plateau

NASA Astrophysics Data System (ADS)

Zhang, S.; Ding, R.; Mao, C.

2010-12-01

Longmenshan mountain is a vivid manifestation of the Cenozoic orogenesis in the eastern margin of the Tibetan plateau, and a key to understand the geodynamics of eastward extending of the plateau. Thus the uplift mechanism of Longmenshan mountain became a hot spot issue of geosciences about the Tibetan plateau. Two entirely different hypotheses, i.e., crustal shortening and lower crustal channel flow, were put forward, but the solution is open. Further discussion need our deeper understanding about the uplifting features of the Longmenshan mountain. Fortunately, the uplifting processes were recorded objectively by peneplains and river landforms. We first analysed the peneplains and pediplanes of Longmenshan mountain and its surrounding areas, and surveyed the terraces of Dadu river running across the mountain. Then we studied the uplifting features of the study areas in late Cenozoic time on the basis of landform geometries. Finaly we discussed the possible mechanisms for the uplifting. There are two levels of peneplains whose peneplanations may begin in early Cenozoic time and end at late Miocene when the final fluctuations of elevations were possibly less than one kilometers. The valley of Dadu river is incised into the peneplains and has a staircase of no less than ten levels of terraces. The highest terrace is a strath which was contemporary with the pediplane in the piedmont formed in late Pliocene or in early Pleistocene. Due to their originally flat features, the peneplains and the strath terraces were used as datum planes for judging neotectonic deformations. Since late Miocene, the southeastern side of Longmenshan mountain has been dominated by thrust-faulting with a total vertical displacement of about 4500 m against the Sichuan basin, meantime the northwest side has been maintained flexural uplift with syncline hinge approximately following the Longriba fault. As a landform barrier between Tibetan plateau and Sichuan basin, the crest lines of the mountain are about 500 to 1000 m higher than the hinterland surface on the west side. In a word, Longmenshan mountain has been formed by the combination of eastern-wing thrusting and west-wing flexing which are attested by the deformation of the Tertiary peneplains and the longitudinal profiles of Quaternary strath terraces of Dadu river. The possible mechanisms for the uplifting of the mountain are the fault-bend folding of the upper crust, the upwelling of plastic lower crust , and crustal isostasy induced by surface erosion. In the light of the existence of longitudinal thrust faults or reversely strike-slip fault along the eastern and western wings of Longmenshan mountain, and no finding of longitudinal extensional faults there, fault-bend folding is proposed to be the leading factor.

Time scale for degradation and erosion of archaeological terraces in the Judea Mountains, Israel

NASA Astrophysics Data System (ADS)

Porat, Naomi; Elinson, Rotem; Ben Dor, Eyal; Avni, Yoav; Gadot, Yuval

2017-04-01

The fate of mountain bench terraces which have been abandoned in ancient times is puzzling. On the one hand recently abandoned terraces undergo rapid degradation by walls crumbling, leading to soil being washed by rain water out of breaches in the walls, suggesting that within a short time all soil would be washed down-slope. On the other hand slopes with degraded terraces appear to still retain much soil even though only faint remains of the terraces exist. Moreover, if soil is rapidly eroded down-slope when terraces are no longer maintained, where do subsequent terrace builders find the soil to fill behind the stone walls? These questions were addressed as part of a larger study on the chronology of terraces in the Judea Mountains, Israel. Previous OSL dating of terrace soils in the region showed that the majority of the maintained terraces were constructed during the past 700 years, and only occasionally older ages were obtained for the soil at the very base of these terraces. Concerns were raised that soil erosion caused earlier events of terrace construction to disappear. To check if terraces and soils indeed erode entirely and how long this might take, we selected a relatively smooth hill slope showing small patches of limestone bedrock as well as remains of highly degraded sets of terraces. Three pits were excavated in soils within three different terrace remains down to bedrock, some to a depth of 2 m, and samples for OSL dating were collected from the exposed soil sections. In all three pits the lowermost samples gave ages of 3000-4500 years before the present, possibly the natural soils before any human intervention. However samples from a depth of 35-45 cm gave ages of 350-200 years, providing the last time the soil at that depth was exposed to sunlight. This suggests that the terraces were abandoned in the past 200 years or so and since then degraded. However the thick soil present on most of the slope suggests that after the first stage of rapid degradation the slope reaches equilibrium, probably due to coverage by native shrubs that reduce direct soil erosion, and most of the soil is retained on the slope.

Terraced margins of inflated lava flows on Earth and Mars

NASA Astrophysics Data System (ADS)

Zimbelman, J. R.; Garry, W. B.; Bleacher, J. E.; Crumpler, L. S.

2011-12-01

When fluid basaltic lava flows are emplaced over a shallow regional slope (typically much less than one degree), the lava flows often display impressive characteristics of inflation. Here we describe a distinctive marginal characteristic that is often developed along the margins of endogenously inflated basaltic lava flows; discreet topographic levels of the emplaced lava that are here termed 'terraced margins'. Terraced margins were first noted at the distal end of the Carrizozo lava flow in central New Mexico, where they are particularly well expressed, but terraces have also been observed along some margins of the McCartys lava flow (NM), the distal end of the 1859 Mauna Loa lava flow (HI), and lava flows at Craters of the Moon (ID). Differential Global Positioning System surveys across several terraced margins reveal consistent topographic characteristics: the upper surface of each terrace level is at roughly one half the height of the sheet lobe from which it emerges; when a terrace becomes the source of an additional outbreak, the upper surface of the second terrace is at roughly one half the height of the source terrace; often a subtle topographic depression is present along the contact between a terrace and its source sheet lobe, suggesting that the terrace outflow starts at a level roughly one-third the height of the source lobe; the upper surfaces of both the source sheet lobe and associated terraces are level to within tens of centimeters across length scales of many tens to hundreds of meters, indicative of inflation of all components. The field observations will be used as the constraints for modeling of the inflation and terracing mechanisms, an effort that has only recently started. The multiple imaging data sets now available for Mars have revealed the presence of terraced margins on some lava flows on Mars. Although detailed topographic data are not currently available for the Martian examples identified so far, the presence of terraced margins for lava flows on both Earth and Mars indicates that the terracing mechanism is intimately associated with the lava flow inflation process. This work was supported by grants from the Planetary Geology and Geophysics program of NASA (NNX09AD88G) and the Scholarly Studies program of the Smithsonian Institution.

Uplifted Terraces along the Southeastern Coast of Bangladesh Reveal the Extent of 1762 Earthquake Surface Deformation and Potentially Document Prior Earthquakes

NASA Astrophysics Data System (ADS)

Mondal, D. R.; McHugh, C.; Steckler, M. S.; Seeber, L.; Akhter, S. H.; Mustaque, S.; Knappett, P. S.

2016-12-01

To better understand geohazards for Bangladesh, the surface expression of the 1762 earthquake and previous earthquakes, we surveyed the coast of Teknaf for evidence of uplift with high precision NetR9, RTX GPS. Previous studies by Aung et al. (2006; 2008) and Wang et al. (2013) documented uplifted terraces along the west coast of Myanmar and linked the youngest terrace to the 1762 Arakan earthquake. Previous studies by Mondal et al. (2015) documented 2.5 m uplifted microatoll corals in the Saint Martin anticline, 10 km southwest from the Teknaf coastline, and linked their uplift by U/Th ages to the 1762 earthquake. Along the southeast Bangladesh coastline, we mapped three geomorphic terraces for 70 km from Teknaf to Cox's Bazar. While GPS measured the location and elevation, an optical level (Theodolite) was used to survey across the different terraces from the beach to the Teknaf anticline foothills. The terraces were also characterized by slope analysis using 30 m SRTM DEM to understand the relation between the terrace geomorphology and potential influence from slope aprons derived from the erosion of the anticline. Our results show that the elevation of three terraces is consistent along the coast, and that terrace elevation ranges from 2-5 m, 5 -7 m and 11-13 m for the youngest, intermediate and oldest terrace, respectively. The youngest terrace, previously dated by McHugh et al. (2015) using C-14 from marine shells obtained from the terrace top, is linked to uplift from the 1762 earthquake. Marine fossils are present in the oldest terrace, and we will present the C-14 age results. Results also suggest that the higher terrace is not prominent in those locations where the slope of the anticline aprons is very high, and they are in a close proximity to each other. The present geomorphic evidence suggests that these terraces were uplifted by three paleoearthquakes, and C-14 ages will provide timing for the uplift. Evidence of terrace uplift derived from our GPS survey extends the 1762 surface deformation and megathrust rupture for at least 550 km along the Arakan segment of the Sunda subduction boundary.

External controls on formation and preservation of fluvial terrace staircases in the Southern Pyrenees foreland

NASA Astrophysics Data System (ADS)

Stange, K. M.; van Balen, R. T.; Carcaillet, J.

2012-04-01

The fluvial network of the Southern Pyrenees is an example of transverse drainage systems in young (alpine) mountain belts and it features well preserved fluvial terrace records. Some of the major Southern Pyrenees tributaries, like the Cinca and the Gallego, have been studied previously and have some age controls on their fluvial terrace levels. We extend these records to the largest drainage system of the Southern Pyrenees, the Segre river system, presenting new GIS and field data, as well as exposure ages obtained from in situ produced 10Be cosmogenic nuclides. The terrace staircase of the Segre River is built up by cut and fill type terraces, ranging from 112 to 3 meter above the present-day riverbed. Gravel deposits have commonly thicknesses of 2 to 7 meter over bedrock. Locally they have extensive thicknesses of up to 20 meter and show evidence for the impact of ongoing tectonics (i.e. gypsum doming, tectonic basin) featuring faults and folds as primary features. The terrace record can be subdivided into four groups of terraces that are separated by large incisive steps of about 20 meter: I) old extensive single terrace surfaces (TQ1, ~112m), II) terraces of limited extent preserved as remnant hills (TQ2, ~80m), III) two extensive terrace levels (TQ3 and TQ4, 60-45m), and IV) a well-preserved and extensive lower terrace complex (TQ5-TQ7, 30-3m). The staircase morphology (extent and elevations) of the Segre River shows analogies with other streams of the Southern Pyrenees indicating regional scale causes for the formation of terraces. The terraces TQ1, TQ2,TQ3 and TQ4 have been sampled for in situ produced 10Be cosmogenic nuclides. Our results show preliminary minimum ages of Middle to Late Pleistocene terrace abandonment: TQ1: 274 ka (MIS 9a), TQ2: 135 ka (MIS 5e), TQ3: 106 ka (MIS 5c), and TQ4: 65 ka (MIS 3), and erosion rates of 0.3 cm/ka (TQ1, TQ4), 0.45 cm/ka (TQ3), and 0.73 cm/ka for TQ2. The obtained ages indicate a causal relationship between terrace abandonment (incision) and interglacial periods, and point to a terrace formation (aggradation) related to glacial periods in the Pyrenean headwaters. Sedimentological outcrop observations corroborate a cold-climate based genesis of the terraces and present numerous braided channels, ice rafted boulders and frozen sand clasts. Morphologically, the extensive terraces surfaces point to a more than 4km wide presumably braided river system during formation of TQ1 and TQ2. The longitudinal terraces correlation reveals a downstream diverging trend along the lower reaches (foreland stretch) which is most likely base-level controlled. We link the divergence of the Segre terraces to the downcutting history of the Catalan Coastal Range that borders the Ebro foreland basin to the Mediterranean Sea. The stepped morphology with several topographic levels at the breach record the downcutting history of the Catalan Coastal Range. Our longitudinal Segre terrace profiles point to a base-level of about 200m a.s.l. at the begin of terrace formation at the Segre and indicate gradual incision since at least the Middle Pleistocene. We argue, that the Catalan Coastal Range functioned as a local base-level upstream the sea outlet presumably until the Late Pleistocene. Hence, the preservation of terrace staircases at the Southern Central Pyrenees does not require tectonic uplift (although it can not be excluded) and can be explained by base-level mechanisms, while the terrace formation is climate triggered and the result of glacial-interglacial-cycles in the Pyrenees.

Probing quasi-one-dimensional band structures by plasmon spectroscopy

NASA Astrophysics Data System (ADS)

Lichtenstein, T.; Mamiyev, Z.; Braun, C.; Sanna, S.; Schmidt, W. G.; Tegenkamp, C.; Pfnür, H.

2018-04-01

The plasmon dispersion is inherently related to the continuum of electron-hole pair excitations. Therefore, the comparison of this continuum, as derived from band structure calculations, with experimental data of plasmon dispersion, can yield direct information about the form of the occupied as well as the unoccupied band structure in the vicinity of the Fermi level. The relevance of this statement is illustrated by a detailed analysis of plasmon dispersions in quasi-one-dimensional systems combining experimental electron energy loss spectroscopy with quantitative density-functional theory (DFT) calculations. Si(557)-Au and Si(335)-Au with single atomic chains per terrace are compared with the Si(775)-Au system, which has a double Au chain on each terrace. We demonstrate that both hybridization between Si surface states and the Au chains as well as electronic correlations lead to increasing deviations from the nearly free electron picture that is suggested by a too simple interpretation of data of angular resolved photoemission (ARPES) of these systems, particularly for the double chain system. These deviations are consistently predicted by the DFT calculations. Thus also dimensional crossover can be explained.

Ultra-thin passivating film induced by vinylene carbonate on highly oriented pyrolytic graphite negative electrode in lithium-ion cell

NASA Astrophysics Data System (ADS)

Matsuoka, O.; Hiwara, A.; Omi, T.; Toriida, M.; Hayashi, T.; Tanaka, C.; Saito, Y.; Ishida, T.; Tan, H.; Ono, S. S.; Yamamoto, S.

We investigated the influence of vinylene carbonate, as an additive molecule, on the decomposition phenomena of electrolyte solution [ethylene carbonate (EC)—ethyl methyl carbonate (EMC) (1:2 by volume) containing 1 M LiPF 6] on a highly oriented pyrolytic graphite (HOPG) negative electrode by using cyclic voltammetry (CV) and atomic force microscopy (AFM). Vinylene carbonate deactivated reactive sites (e.g. radicals and oxides at the defects and the edge of carbon layer) on the cleaved surface of the HOPG negative electrode, and prevented further decomposition of the other solvents there. Further, vinylene carbonate induced an ultra-thin film (less than 1.0 nm in thickness) on the terrace of the basal plane of the HOPG negative electrode, and this film suppressed the decomposition of electrolyte solution on the terraces of the basal plane. We consider that this ultra-thin passivating film is composed of a reduction product of vinylene carbonate (VC), and might have a polymer structure. These induced effects might explain how VC improves the life performance of lithium-ion cells.

Crystal-Phase Quantum Wires: One-Dimensional Heterostructures with Atomically Flat Interfaces.

PubMed

Corfdir, Pierre; Li, Hong; Marquardt, Oliver; Gao, Guanhui; Molas, Maciej R; Zettler, Johannes K; van Treeck, David; Flissikowski, Timur; Potemski, Marek; Draxl, Claudia; Trampert, Achim; Fernández-Garrido, Sergio; Grahn, Holger T; Brandt, Oliver

2018-01-10

In semiconductor quantum-wire heterostructures, interface roughness leads to exciton localization and to a radiative decay rate much smaller than that expected for structures with flat interfaces. Here, we uncover the electronic and optical properties of the one-dimensional extended defects that form at the intersection between stacking faults and inversion domain boundaries in GaN nanowires. We show that they act as crystal-phase quantum wires, a novel one-dimensional quantum system with atomically flat interfaces. These quantum wires efficiently capture excitons whose radiative decay gives rise to an optical doublet at 3.36 eV at 4.2 K. The binding energy of excitons confined in crystal-phase quantum wires is measured to be more than twice larger than that of the bulk. As a result of their unprecedented interface quality, these crystal-phase quantum wires constitute a model system for the study of one-dimensional excitons.

Quaternary isotope stratigraphy and paleoclimate of coral reef terraces, Gulf of Aqaba, South Sinai, Egypt

NASA Astrophysics Data System (ADS)

El-Asmar, Hesham M.

Five Quaternary coral reef terraces have been recognized along Sharm ElSheikh-Ras Mohammed coast, of which terraces 'V to II' form a well developed staircase at Um Seed, while recognized separately at Ras Mohammed. Terrace 'I' was only observed as a reef pathches at Sharm ElSheikh-Ras Mohammed road. Terraces 'V to I' exist at elevations of - 1 (b.s.1) to 0 m, 3-6 m, 10-12 m, 15-20 m and 25-35 m (a.s.1), respectively. Uranium series dates of samples representing terraces 'V, IV, III, II and I' show ages grouped as ka, 118-125ka, 200ka, 280-300ka and older 300ka, which are related to isotope stages 1, 5e, 7, 9 and 11, respectively. The variation of δ18O for samples from these terraces show evidence of at least four major warm-wet climatic periods in relationship to high sea level and contemporaneous with the formation of the reef terraces. Faulting affects only the older terraces 'I and II', and along with the occurrence of terrace 'IV' of Last Interglacial age at elevation of 3-6 m suggest that the coastal area has not been subjected to major tectonic activities at least with the last 125 ka.

Evaporation from an Irrigated Terraced Rice Field Evaluated by Using Stable Isotopes: A Case Study in Batad, Philippines

NASA Astrophysics Data System (ADS)

Benavides, P.; Shimada, J.; Kagabu, M.; Loreto, F.; Leong, J.

2013-12-01

Bench terracing is an agricultural technique done by creating a step-like feature, serving as paddies, along the contours of the mountain to make the land more arable. Inundation of the paddies is done in different ways and one way is through a gravity-driven flow mechanism which is observed in Batad. This mechanism involved the flow of water to the next lower terrace in a cascading manner by diverting the water to small canals called spillways. The study aims to detect evaporation of the irrigation water flowing across a continuous terrace using water stable isotopes as tracers. Sampling was done during the planting season to ensure that irrigation water is flowing across the terraces. Samples were taken along the spillways of each terrace. Thirty irrigation water samples from four terraces facing different directions: NE, E, SE and S, and one precipitation sample were analyzed for major ions concentrations and H and O isotope ratios. Stiff and Piper diagrams show that the water samples are of surface and Mg-HCO3 type, implying that the water has juvenile features and has experienced little or no chemical differentiation. Water chemistry does not show any significant trend as the water moves across a terrace. Isotopic compositions range from -51.8‰ to -14.6‰ and from -8.24‰ to -2.39‰ for δ2H and δ18O, respectively. The lowest isotopic compositions are observed mostly in the source waters of the terraces while the highest are at the lowest paddy of the NE-facing terrace. The data plotted in a δ2H-δ18O diagram for each terrace shows linear plots with slopes deviating from the Philippine Meteoric Water Line (PMWL). Highest deviation is observed for the NE-facing terrace with a slope of 6.22, while the lowest is 6.91 from the SE-facing terrace, all of which are significantly lower than the PMWL's slope of 8 (Gerardo-Abaya, 2005). In addition, enrichment in isotopic composition is observed as the water moves away from the source. These findings confirm that evaporation takes place as the water moves across the terrace. Using the Rayleigh distillation equation, the degree of evaporation loss ranges from 23.13% and 24.34% from the SE-facing terrace to 32.50% and 35.80% from the NE-facing terrace for the δ2H and δ18O, respectively. Variations in the results for each terraces can be attributed to the different ambient meteorological conditions during sampling. More sampling is needed to further investigate whether different terrace orientations with similar meteorological conditions can also have an effect with the evaporation.

Anisotropic Dispersion and Partial Localization of Acoustic Surface Plasmons on an Atomically Stepped Surface: Au(788)

NASA Astrophysics Data System (ADS)

Smerieri, M.; Vattuone, L.; Savio, L.; Langer, T.; Tegenkamp, C.; Pfnür, H.; Silkin, V. M.; Rocca, M.

2014-10-01

Understanding acoustic surface plasmons (ASPs) in the presence of nanosized gratings is necessary for the development of future devices that couple light with ASPs. We show here by experiment and theory that two ASPs exist on Au(788), a vicinal surface with an ordered array of monoatomic steps. The ASPs propagate across the steps as long as their wavelength exceeds the terrace width, thereafter becoming localized. Our investigation identifies, for the first time, ASPs coupled with intersubband transitions involving multiple surface-state subbands.

12th US-Japan Seminar: Many Body Quantum Systems from Quantum Gases to Metrology and Information Processing. Held in Madison, Wisconsin on 20-24 September 2015

DTIC Science & Technology

2016-06-03

Ultracold Atoms 5:10 Zelevinsky Ye Inouye High-precision spectroscopy with two-body quantum systems Low entropy quantum gas of polar molecules New limit...12th US-Japan Seminar: Many Body Quantum Systems from Quantum Gases to Metrology and Information Processing Support was provided for The 12th US...Japan Seminar on many body quantum systems which was held in Madison, Wisconsin from September 20 to 24, 2015 at the Monona Terrace Convention Center

An online planning tool for designing terrace layouts

USDA-ARS?s Scientific Manuscript database

A web-based conservation planning tool, WebTERLOC (web-based Terrace Location Program), was developed to provide multiple terrace layout options using digital elevation model (DEM) and geographic information systems (GIS). Development of a terrace system is complicated by the time-intensive manual ...

Linkages of fluvial terrace formation and geometry to Milankovitch-scale climate change revealed by the chronostratigraphy of the Colorado River above Moab, UT, and regional correlations

NASA Astrophysics Data System (ADS)

Jochems, A. P.; Pederson, J. L.

2012-12-01

Fluvial terraces are important markers that contain information about incision, deformation, and climate change in a given landscape. However, our poor understanding of the links between climate drivers and the processes behind terrace formation renders them an imprecise tool. Unresolved issues include the influence of changes in hydrology versus sediment supply in controlling incision or sedimentation, whether terraces truly can be time-correlated across a large watershed or whether this is confounded by transient sediment signals, and the process link between strath/fill terrace form and climate, tectonic, or local valley geometry controls. In terms of the latter issue, terrace type is commonly associated with climate or tectonic controls, and it has been suggested that fill terraces tend to form in bedrock-restricted reaches and strath terraces in broader valleys. We address these problems through detailed chronostratigraphy of Colorado River terraces upstream of Moab, UT, and correlations to similarly well-constrained records near Green River, UT, and eastern Grand Canyon. Along the Colorado profile upstream of Moab, there are four traceable late Pleistocene mainstem terraces we designate as M2, M3y (younger), M3, and M4. Optically stimulated luminescence (OSL) ages indicate sedimentation at 25-20 ka, 50-40 ka, 75-60 ka, and 115-85 ka, respectively, for these deposits. Importantly, results indicate synchronous timing of terrace formation across the Colorado Plateau, ruling out transient sediment signals as a factor. Sedimentation of the M2 and M3 occur during the build-up to and height of glaciations, but the M3y and M4 are instead deposited during episodes of highly variable climate during marine isotope stages (MIS) 3 and 5. Incision notably occurs during interglacials or at least periods of low ice volume. In the Colorado Plateau, we suggest terrace sedimentation is linked to anemic peak flows during full glacial conditions (M2 and M3), but major terrace deposits also form during pulses of dryland tributary sediment loading with markedly different timing (M3y and M4). Conversely, we suggest incision is driven by higher peak flows, such as during the current interglacial. In terms of strath/fill geometry, the spatial patterns of terraces in the study area rule out any simple climate versus tectonic relationship. Rather, local canyon geometry, bedrock resistance, and neotectonics control terrace form. For example, thick (7-13 m) fill terraces are unexpectedly found in broad Professor Valley, whereas thin (2-3 m) strath terraces are found in the canyon upstream. Long-profile survey data show that terraces may exhibit warping on the flanks of the Cache Valley graben and other potentially active salt tectonic features of the Paradox Basin. This and variations in local bedrock properties obfuscate any climate-related information within terrace form itself. In summary, Colorado River terraces were formed in response to glacial-interglacial hydrology changes in the headwaters and also during different periods of increased local sediment loading from the plateau drylands. Terrace form is not simply related to regional climate or tectonics, but instead to variable local valley geometry and neotectonics.

Morphotectonic analysis and 10Be dating of the Kyngarga river terraces (southwestern flank of the Baikal rift system, South Siberia)

NASA Astrophysics Data System (ADS)

Arzhannikova, A.; Arzhannikov, S.; Braucher, R.; Jolivet, M.; Aumaître, G.; Bourlès, D.; Keddadouche, K.

2018-02-01

The formation of the Baikal rift system basins is controlled by active faults separating each basin from the adjacent horsts. The kinematics of these faults is mainly explored through investigation of complex sequences of the fault-intersecting river terraces that record both tectonic and climatic events. This study focuses on the northern margin of the major Tunka basin that develops south-west of Lake Baikal. The development of the basin is controlled by the segmented Tunka fault. We performed a detailed mapping of the Kyngarga river terraces, the best preserved terraces staircase in Baikal rift system, at their intersection with the Tunka fault. In order to decipher the chronology of seismic events and the slip rates along that segment of the fault, key terraces were dated using in situ produced cosmogenic 10Be. We demonstrate that the formation of the terrace staircase occurred entirely during MIS1-MIS2. The obtained data allowed us to estimate the rate of incision at different stages of the terrace staircase formation and the relationship between the vertical and horizontal slip rates along this sub-latitudinal segment of the Tunka fault making respectively 0.8 and 1.12 mm yr- 1 over the past 12.5 ka. Analysis of the paleoseismology and paleoclimate data together with terrace dating provided the possibility to estimate the influence of tectonic and climatic factors on the terrace formation. Our proposed model of the Kyngarga river terrace development shows that the incisions into terraces T3 and T6 were induced by the abrupt climatic warming episodes GI-1 and GI-2, respectively, whereas terraces T5, T4 and T2 were abandoned due to the vertical tectonic displacement along the Tunka fault caused by coseismic ruptures.

Research on Remote Sensing recognition features of Yuan Yang Terraces in Yunnan Province (China)

NASA Astrophysics Data System (ADS)

Xiang, Jie; Chen, Jianping; Lai, ZiLi; Yang, Wei

2016-04-01

Yuan Yang terraces is one of the most famous terraces in China, and it was successfully listed in the world heritage list at the 37th world heritage convention. On the one hand, Yuan Yang terraces retain more soil and water, to reduce both hydrological connectivity and erosion, and to support irrigation. On the other hand, It has the important tourism value, bring the huge revenue to local residents. In order to protect and make use of Yuan Yang terraces better, This study analyzed the spatial distribution and spectral characteristics of terraces:(1) Through visual interpretation, the study recognized the terraces based on the spatial adjusted remote sensing image (2010 Geoeye-1 with resolution of 1m/pix), and extracted topographic feature (elevation, slope, aspect, etc.) based on the digital elevation model with resolution of 20m/pix. The terraces cover a total area of about 11.58Km2, accounted for 24.4% of the whole study area. The terraces appear at range from 1400m to 1800m in elevation, 10°to 20°in slope, northwest to northeast in aspect; (2) Using the method of weight of evidence, this study assessed the importance of different topographic feature. The results show that the sort of importance: elevation>slope>aspect; (3) The study counted the Normalized Difference Vegetation Index (NDVI) changes of terraces throughout the year, based on the landsat-5 image with resolution of 30m/pix. The results show that the changes of terraces' NDVI are bigger than other stuff (e.g. forest, road, house, etc.). Those work made a good preparations for establishing the dynamic remote sensing monitoring system of Yuan Yang terraces.

Dating of river terraces along Lefthand Creek, western High Plains, Colorado, reveals punctuated incision

NASA Astrophysics Data System (ADS)

Foster, Melissa A.; Anderson, Robert S.; Gray, Harrison J.; Mahan, Shannon A.

2017-10-01

The response of erosional landscapes to Quaternary climate oscillations is recorded in fluvial terraces whose quantitative interpretation requires numerical ages. We investigate gravel-capped strath terraces along the western edge of Colorado's High Plains to constrain the incision history of this shale-dominated landscape. We use 10Be and 26Al cosmogenic radionuclides (CRNs), optically stimulated luminescence (OSL), and thermally transferred OSL (TT-OSL) to date three strath terraces, all beveled in shale bedrock and then deposited upon by Lefthand Creek, which drains the crystalline core of the Front Range. Our study reveals: (i) a long history (hundreds of thousands of years) of fluvial occupation of the second highest terrace, T2 (Table Mountain), with fluvial abandonment at 92 ± 3 ka; (ii) a brief occupation of a narrow and spatially confined terrace, T3, at 98 ± 7 ka; and (iii) a 10-25 thousand year period of cutting and fluvial occupation of a lower terrace, T4, marked by the deposition of a lower alluvial unit between 59 and 68 ka, followed by deposition of an upper alluvial package at 40 ± 3 ka. In conjunction with other recent CRN studies of strath terraces along the Colorado Front Range (Riihimaki et al., 2006; Dühnforth et al., 2012), our data reveal that long periods of lateral planation and fluvial occupation of strath terraces, sometimes lasting several glacial-interglacial cycles, are punctuated by brief episodes of rapid vertical bedrock incision. These data call into question what a singular terrace age represents, as the strath may be cut at one time (its cutting-age) and the terrace surface may be abandoned at a much later time (its abandonment age), and challenge models of strath terraces that appeal to simple pacing by the glacial-interglacial cycles.

52. View from the terrace gardens east to the mansion, ...

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

52. View from the terrace gardens east to the mansion, illustrating the elevation changes created by terracing. View includes the rock garden and the flower garden at the fountain terrace. - Marsh-Billings-Rockefeller National Historical Park, 54 Elm Street, Woodstock, Windsor County, VT

9. View from the terrace gardens east to the mansion, ...

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

9. View from the terrace gardens east to the mansion, illustrating the elevation changes created by terracing. View includes the rock garden and flower garden at the fountain terrace. - Marsh-Billings-Rockefeller National Historical Park, 54 Elm Street, Woodstock, Windsor County, VT

FI-STM study of hydrogen adsorption on Si(100) surface

NASA Astrophysics Data System (ADS)

Hua, Lu; Xiang-dong, Wang; Motai, K.; Hashizume, T.; Sakurai, T.

1992-11-01

Chemisorption of atomic hydrogen on the Si(100)2 × 1 surface has been investigated in detail by using a field ion-scanning tunneling microscope (FI-STM). The results showed that the adsorption geometry changed from the 2 × 1 monohydride phase to the 1 × 1 dihydride phase with increasing exposure of hydrogen. The data of desorption of the hydrogen-saturated Si surface showed that on annealing at 670 K the surface becomes highly disordered: the 1 × 1 dihydride structure is eliminated and the 2 × 1 reconstructed monohydride is also hardly to identify. When the temperature rises to as high as 730 K, the surface is dominated by the 2 × 1 structure with missing dimer rows, and some adatom chains occur on the Si substrate terraces. We attribute the formation of these atomic chains to an epitaxial growth of Si atoms which are formed by the dissociation of SiHx (x = 1, 2, 3 or 4) compounds on the Si surface.

Adsorption of pentacene on (100) vicinal surfaces: role of coordination, surface chemistry and vdWs effects

NASA Astrophysics Data System (ADS)

Matos, Jeronimo; Kara, Abdelkader

2015-03-01

In contrast to low miller index surfaces, vicinal surfaces are characterized by steps and step edges that not only present an interesting atomic landscape for the adsorption organic molecules, but also a unique electronic structure resulting in part from the low coordinated atoms at the step edges. The adsorption of pentacene on the stepped (511), (711), (911) surfaces (respectively 3, 4 and 5-atom wide terraces) of Cu and Ag (coinage transition metals); Pt (reactive transition metal); and Ni (reactive, magnetic transition metal) are studied using density functional theory, in order to investigate the support effects arising from differing surface chemistry. We compare the adsorption energy, adsorption geometry and electronic structure predicted by the PBE functional with those obtained from one of the optimized vdW-DF methods: optB88-vdW. Work supported by the U.S. Department of Energy Basic Energy Science under Contract No. DE-FG02-11ER16243.

Sn nanothreads in GaAs: experiment and simulation

NASA Astrophysics Data System (ADS)

Semenikhin, I.; Vyurkov, V.; Bugaev, A.; Khabibullin, R.; Ponomarev, D.; Yachmenev, A.; Maltsev, P.; Ryzhii, M.; Otsuji, T.; Ryzhii, V.

2016-12-01

The gated GaAs structures like the field-effect transistor with the array of the Sn nanothreads was fabricated via delta-doping of vicinal GaAs surface by Sn atoms with a subsequent regrowth. That results in the formation of the chains of Sn atoms at the terrace edges. Two device models were developed. The quantum model accounts for the quantization of the electron energy spectrum in the self-consistent two-dimensional electric potential, herewith the electron density distribution in nanothread arrays for different gate voltages is calculated. The classical model ignores the quantization and electrons are distributed in space according to 3D density of states and Fermi-Dirac statistics. It turned out that qualitatively both models demonstrate similar behavior, nevertheless, the classical one is in better quantitative agreement with experimental data. Plausibly, the quantization could be ignored because Sn atoms are randomly placed along the thread axis. The terahertz hot-electron bolometers (HEBs) could be based on the structure under consideration.

A change in landscape: Lessons learned from abandonment of ancient Wari agricultural terraces in Southern Peru.

PubMed

Londoño, Ana C; Williams, Patrick Ryan; Hart, Megan L

2017-11-01

Ancient agricultural terrace practices have survived for millennia, sustaining populations through extreme climatic shifts and political regime changes. In arid regions with abrupt relief such as Southern Peru, agricultural terracing is undergoing a resurgence, as has seen revitalization of once abandoned terrace and hydraulic systems. Wari terraces at Cerro Baul provide clues to past cultural practices. They also document sustainable farming practices by using resilient land management techniques which can help combat desertification and degradation of arable lands. Three abandoned Wari terrace systems were mapped using microtopographic methods, the erosion patterns examined, the states of preservation compared, and then the design contrasted with modern terracing practices in the Moquegua Valley. In order to negate the harmful effects of desertification, rehabilitation and reconstruction of these terraces using ancient knowledge and techniques may be necessary. Rehabilitation must be conducted with consideration for preservation of cultural patrimony that may be encountered within the terrace treads or riser structures. With future climatic shifts impacting vulnerable dryland areas more than others, the ability to resiliently respond to these changes may be found in the lessons learned from ancient farming techniques such as the Wari. Copyright © 2017 Elsevier Ltd. All rights reserved.

Morphology of Florida Escarpment chemosynthetic brine seep community sites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Paull, C.K.; Spiess, F.N.; Curray, J.R.

1988-01-01

The Florida Escarpment near 26/sup 0/N was surveyed with Deep-Two, Seabeam, and GLORIA in the area where chemosynthetic communities were discovered via ALVIN in the abyssal Gulf of Mexico. Seabeam bathymetry and GLORIA images indicate that the escarpment is a generally straight cliff with average slopes of about 45/sup 0/ from 2,200 to more than 3,250 m. The escarpment's face is cut by 2-km wide box canyons whose head walls are as steep as the intervening escarpment's face. The shapes of these canyons are difficult to explain with the traditional models of canyon formation. Sidescan sonar images and bottom photographsmore » reveal that the escarpment's face is composed of a series of long, straight bedding-plane terraces which are truncated along nearly vertical orthogonal joints. Exposure of these truncated strata indicate the face of the escarpment is eroded. The contact between the basal escarpment and the flat-lying abyssal hemipelagic sediments is abrupt. Apparently, chemosynthetic communities line extensive sections of the escarpment base where reduced brines seep out into the sea floor. The morphology suggests joints and deep seeps are controlling factors in scarp retreat.« less

Geologic and molluscan evidence for a previously misunderstood late pleistocene, cool water, open coast terrace at Newport Bay, Southern California

USGS Publications Warehouse

Powell, C.L.

2001-01-01

A macro-invertebrate fauna from a 7 m elevation terrace remnant on the front of the Newport Mesa contains 63 mollusks, 58 specifically identified. These taxa represent a mixed death assemblage similar to that seen on rocky terrace platforms at intertidal depths in southern to central California today. The extralimital northern bivalve Macoma inquinala (Carpenter) and gastropods Tectura sp., cf. T. persona (Rathke), and Tegula montereyi (Kiener) suggest slightly cooler water temperatures than present today. These extralimital cool-water taxa, along with the terrace's geomorphic position in the palisades along the front of Newport Mesa, below other mapped terraces, separate it from the well known first terrace and its associated warm-water fauna recognized by previous authors, and suggest a younger age than the first terrace around Newport Bay.

Research on optimal DEM cell size for 3D visualization of loess terraces

NASA Astrophysics Data System (ADS)

Zhao, Weidong; Tang, Guo'an; Ji, Bin; Ma, Lei

2009-10-01

In order to represent the complex artificial terrains like loess terraces in Shanxi Province in northwest China, a new 3D visual method namely Terraces Elevation Incremental Visual Method (TEIVM) is put forth by the authors. 406 elevation points and 14 enclosed constrained lines are sampled according to the TIN-based Sampling Method (TSM) and DEM Elevation Points and Lines Classification (DEPLC). The elevation points and constrained lines are used to construct Constrained Delaunay Triangulated Irregular Networks (CD-TINs) of the loess terraces. In order to visualize the loess terraces well by use of optimal combination of cell size and Elevation Increment Value (EIV), the CD-TINs is converted to Grid-based DEM (G-DEM) by use of different combination of cell size and EIV with linear interpolating method called Bilinear Interpolation Method (BIM). Our case study shows that the new visual method can visualize the loess terraces steps very well when the combination of cell size and EIV is reasonable. The optimal combination is that the cell size is 1 m and the EIV is 6 m. Results of case study also show that the cell size should be at least smaller than half of both the terraces average width and the average vertical offset of terraces steps for representing the planar shapes of the terraces surfaces and steps well, while the EIV also should be larger than 4.6 times of the terraces average height. The TEIVM and results above is of great significance to the highly refined visualization of artificial terrains like loess terraces.

DRIFT POTENTIAL OF TILTED SHIELDED ROTARY ATOMISERS BASED ON WIND TUNNEL MEASUREMENTS.

PubMed

Salah, S Ouled Taleb; Massinon, M; De Cock, N; Schiffers, B; Lebeau, F

2015-01-01

Crop protection is mainly achieved by applying Plant Protection Products (PPP) using hydraulic nozzles, which rely on pressure, to produce a wide droplet size distribution. Because of always increased concerns about drift reduction, a wider range of low drift nozzles, such as air induction nozzles, was adopted in order to reduce the finest part of the spray. While successful for some treatments, the efficiency of coarser sprays is dramatically reduced on small and superhydrophobic target, i.e. at early stage weed control. This may be related to the increased proportion of big bouncing and splashing droplets. On the other hand, Controlled Droplet Application (CDA), using shielded rotary atomizers, stands for an improved control of droplets diameters and trajectories compared to hydraulic nozzles. Unfortunately, these atomizers, because of their horizontal droplet release, are widely recognized to produce more drift than hydraulic nozzles. The present contribution investigates whether the setting of a rotary atomizer 60 degrees forward tilted can reduce drift to acceptable levels in comparison with vertical and 60 degrees forward tilted standard and low drift flat fan nozzles for the same flow rate. In a wind tunnel, the drift potential of a medium spray produced by a tilted shielded rotary atomizer Micromax 120 was benchmarked with that of a flat fan nozzle XR11002 fine spray and that of an anti-drift nozzle Hardi Injet 015 medium spray. Operating parameters were set to apply 0.56 l/min for every spray generator. Vertical drift profiles were measured 2.0 m downward from nozzle axis for a 2 m.s(-1) wind speed. The tilted hydraulic nozzles resulted in a significant drift increase while droplets trajectories are affected by the decrease of the droplet initial vertical speed. Droplets emitted by the shielded rotary atomizer drift due to low entrained air and turbulence. A significant reduction of the cumulative drift was achieved by the rotary atomizer in comparison with flat fan nozzle while still being higher than the anti-drift nozzle. Unfortunately, the drift potential index (DIX) revealed that the cumulative drift reduction may not results in actual drift decrease because of higher drift at higher sampling locations. As a result, the DIX of the shielded rotary atomizer was similar to the standard flat-fan nozzle while the anti-drift nozzle reduced drastically drift as intended. Therefore, the 60 degrees tilted rotary atomizer failed to reach low drift levels as expected despite the reduced span.

2. VIEW IN ROOM 111, ATOMIC ABSORPTION BERYLLIUM ANALYSIS LABORATORY. ...

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

2. VIEW IN ROOM 111, ATOMIC ABSORPTION BERYLLIUM ANALYSIS LABORATORY. AIR FILTERS AND SWIPES ARE DISSOLVED WITH ACIDS AND THE REMAINING RESIDUES ARE SUSPENDED IN NITRIC ACID SOLUTION. THE SOLUTION IS PROCESSED THROUGH THE ATOMIC ABSORPTION SPECTROPHOTOMETER TO DETECT THE PRESENCE AND LEVELS OF BERYLLIUM. - Rocky Flats Plant, Health Physics Laboratory, On Central Avenue between Third & Fourth Streets, Golden, Jefferson County, CO

11. View from the southwest lawn toward the terrace gardens, ...

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

11. View from the southwest lawn toward the terrace gardens, illustrating the grading required to create the terraces. The view includes the flower garden at the fountain terrace, the rock garden, greenhouse and Belvedere. - Marsh-Billings-Rockefeller National Historical Park, 54 Elm Street, Woodstock, Windsor County, VT

53. View from the southwest lawn toward the terrace gardens, ...

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

53. View from the southwest lawn toward the terrace gardens, illustrating the grading required to create the terraces. The view includes the flower garden at the fountain terrace, the rock garden, greenhouse and Belvedere. - Marsh-Billings-Rockefeller National Historical Park, 54 Elm Street, Woodstock, Windsor County, VT

Depositional environments of some Pleistocene coastal terrace deposits, southwestern Oregon - case history of progradational beach and dune sequence.

USGS Publications Warehouse

Hunter, R.E.

1980-01-01

These deposits comprise a basal gravelly unit and 3 overlying sandy units, each with mud beds, a paleosol, or the modern soil in its uppermost part. The gravelly unit is interpreted as a progradational deposit. The main parts of the sandy units are made up of 1) a crossbedded sand facies, the dominant structure in which is medium-scale crossbedding (interpreted as the product of small eolian dunes), and 2) an irregularly bedded sand facies, which is locally pebbly and is dominated by scour-and-fill structures, interpreted as deposits of interdune ephemeral streams, ephemeral ponds, and wet to dry subaerial flats. The mud beds and paleosols represent times of temporary stabilization of the dune field.- from Author

AmeriFlux US-Bn3 Bonanza Creek, 1999 Burn site near Delta Junction

DOE Data Explorer

Randerson, James [University of California, Irvine

2016-01-01

This is the AmeriFlux version of the carbon flux data for the site US-Bn3 Bonanza Creek, 1999 Burn site near Delta Junction. Site Description - The Delta Junction 1999 Burn site is located near Delta Junction, just to the north of the Alaska Range in interior Alaska. All three Delta Junction sites are within a 15-km radius of one another. Composed of a combination of alluvial outwashes, floodplains, and low terraces dissected by glacial streams originating in the nearby Alaska Range. The Donnelly Flats fire burned ~7,600 ha of black spruce (Picea mariana) during June 1999. The boles of the black spruce remained standing 3 years after the fire. 70% of the surface was not covered by vascular plants.

Low-coverage surface diffusion in complex periodic energy landscapes: Analytical solution for systems with symmetric hops and application to intercalation in topological insulators

NASA Astrophysics Data System (ADS)

Gosálvez, Miguel A.; Otrokov, Mikhail M.; Ferrando, Nestor; Ryabishchenkova, Anastasia G.; Ayuela, Andres; Echenique, Pedro M.; Chulkov, Evgueni V.

2016-02-01

This is the first of two papers that introduce a general expression for the tracer diffusivity in complex, periodic energy landscapes with M distinct hop rates in one-, two-, and three-dimensional diluted systems (low-coverage, single-tracer limit). The present report focuses on the analysis of diffusion in systems where the end sites of the hops are located symmetrically with respect to the hop origins (symmetric hops), as encountered in many ideal surfaces and bulk materials. For diffusion in two dimensions, a number of formulas are presented for complex combinations of the different hops in systems with triangular, rectangular, and square symmetry. The formulas provide values in excellent agreement with kinetic Monte Carlo simulations, concluding that the diffusion coefficient can be directly determined from the proposed expressions without performing the simulations. Based on the diffusion barriers obtained from first-principles calculations and a physically meaningful estimate of the attempt frequencies, the proposed formulas are used to analyze the diffusion of Cu, Ag, and Rb adatoms on the surface and within the van der Waals (vdW) gap of a model topological insulator, Bi2Se3 . Considering the possibility of adsorbate intercalation from the terraces to the vdW gaps at morphological steps, we infer that, at low coverage and room temperature, (i) a majority of the Rb atoms bounce back at the steps and remain on the terraces, (ii) Cu atoms mostly intercalate into the vdW gap, the remaining fraction staying at the steps, and (iii) Ag atoms essentially accumulate at the steps and gradually intercalate into the vdW gap. These conclusions are in good qualitative agreement with previous experiments. The companion report (M. A. Gosálvez et al., Phys. Rev. B, submitted] extends the present study to the description of systems that contain asymmetric hops.

Influence of TiO2(110) surface roughness on growth and stability of thin organic films.

PubMed

Szajna, K; Kratzer, M; Wrana, D; Mennucci, C; Jany, B R; Buatier de Mongeot, F; Teichert, C; Krok, F

2016-10-14

We have investigated the growth and stability of molecular ultra-thin films, consisting of rod-like semiconducting para-hexaphenyl (6P) molecules vapor deposited on ion beam modified TiO 2 (110) surfaces. The ion bombarded TiO 2 (110) surfaces served as growth templates exhibiting nm-scale anisotropic ripple patterns with controllable parameters, like ripple depth and length. In turn, by varying the ripple depth one can tailor the average local slope angle and the local step density/terrace width of the stepped surface. Here, we distinguish three types of substrates: shallow, medium, and deep rippled surfaces. On these substrates, 6P sub-monolayer deposition was carried out in ultra-high vacuum by organic molecular beam evaporation (OMBE) at room temperature leading to the formation of islands consisting of upright standing 6P molecules, which could be imaged by scanning electron microscopy and atomic force microscopy (AFM). It has been found that the local slope and terrace width of the TiO 2 template strongly influences the stability of OMBE deposited 6P islands formed on the differently rippled substrates. This effect is demonstrated by means of tapping mode AFM, where an oscillating tip was used as a probe for testing the stability of the organic structures. We conclude that by increasing the local slope of the TiO 2 (110) surface the bonding strength between the nearest neighbor standing molecules is weakened due to the presence of vertical displacement in the molecular layer in correspondence to the TiO 2 atomic step height.

Reaction limited aggregation in surfactant-mediated epitaxy

NASA Astrophysics Data System (ADS)

Wu, Jing; Liu, Bang-Gui; Zhang, Zhenyu; Wang, E. G.

2000-05-01

A theoretical model for reaction limited aggregation (RLA) is introduced to study the effect of a monolayer of surfactant on the formation of two-dimensional islands in heteroepitaxial and homoepitaxial growth. In this model the basic atomic processes are considered as follows. A stable island consists of the adatoms that have exchanged positions with the surfactant atoms beneath them. Movable active adatoms may (a) diffuse on the surfactant terrace, (b) exchange positions with the surfactant atoms beneath them and become island seeds (seed exchange), or (c) stick to stable islands and become stuck but still active adatoms. The rate-limiting step for the formation of a stable island is the seed exchange. Furthermore, a stuck but still active adatom must overcome a sizable potential-energy barrier to exchange positions with the surfactant atom beneath it and become a member of the stable island (aided exchange). The seed exchange process can occur with an adatom or collectively with an addimer. In the case of dimer exchange, the diffusing adatoms on the surfactant terrace can meet and (after exchanging) form stable dimers, which can then become island seeds. Systematic kinetic Monte Carlo simulations and rate-equation analysis of the model are carried out. The key finding of these simulations is that a counterintuitive fractal-to-compact island shape transition can be induced either by increasing deposition flux or by decreasing growth temperature. This major qualitative conclusion is valid for both the monomer and the dimer seed exchanges and for two different substrate lattices (square and triangular, respectively), although there are some quantitative differences in the flux and temperature dependence of the island density. The shape transition observed is contrary to the prediction of the classic diffusion-limited aggregation (DLA) theory, but in excellent qualitative agreement with recent experiments. In rationalizing the main finding, it is crucial to realize that the adatoms stuck to a stable island edge are still active and are surrounded by the surfactant atoms. Therefore, these stuck atoms cannot capture incoming adatoms before they join the island through aided exchange. As a result, an incoming adatom must on average hit the island many times before it finally finds a free edge site to stick to. This search is effectively equivalent to edge diffusion in DLA theory. The stuck adatoms thus act as shields which prevent other mobile adatoms from sticking to the stable islands. This shielding effect, determined by the aided exchange barrier and the density of the mobile adatoms, plays an essential role in inducing the above shape transition in surfactant-mediated epitaxial growth.

Landscapes from the waves—Marine terraces of California

USGS Publications Warehouse

Schulz, Marjorie S.; Lawrence, Corey; Muhs, Daniel; Prentice, Carol S.; Flanagan, Sam

2018-03-08

Many coastlines around the world have stair-step landforms, known as marine terraces. Marine terraces make up a large part of coastal California’s landscape—from San Diego to Crescent City. Find out how these landscapes form, why marine terraces are of interest to scientists, and where you can explore these landscapes.

Chronology of fluvial terrace sequences for large Atlantic rivers in the Iberian Peninsula (Upper Tagus and Duero drainage basins, Central Spain)

NASA Astrophysics Data System (ADS)

Silva, Pablo G.; Roquero, Elvira; López-Recio, Mario; Huerta, Pedro; Martínez-Graña, Antonio M.

2017-06-01

This work analyses the chronology of fluvial terrace sequences of the two most important fluvial basins from central Spain draining to the Atlantic Ocean (Upper Tagus and Duero drainage basins). Both basins evolved under similar Mediterranean climatic conditions throughout the Pleistocene and present comparable number of fluvial terraces (16-17) after excluding the higher terrace levels of the Tagus (T1-T5) entrenched in the Raña surface. These higher ;rañizo terraces; was formed in response to fan-head trenching in this high alluvial piedmont (+220 m) and therefore not properly controlled by Quaternary fluvial downcutting. The study accomplishes the implementation of multiple regression analyses for terrace height-age relationships. To transform relative terrace heights above the present river thalwegs (i.e. +100 m) in numerical ages a ;height-age transference function; has been developed on the basis of preliminary statistical geochronological approaches proposed for Central Spain. The resultant height-age transference function gather 73 published geochronological data for terrace sequences, featuring a 3rd Order Polynomial Function (R2 0.90). This function describes the overall trend of valley downcutting for the last c. 2.3 Ma in Central Spain and is used to assign numerical ages to terrace levels at different relative elevation.

Effects of marsh pond terracing on coastal wintering waterbirds before and after Hurricane Rita.

PubMed

O'Connell, Jessica L; Nyman, John A

2011-11-01

From February to March 2005-2006, we surveyed wintering waterbirds to test effects of terracing on coastal pond use before and after Hurricane Rita. Marsh terracing is intended to slow coastal marsh loss in the Chenier Plain by slowing marsh erosion and encouraging vegetation expansion. Terraces also increase marsh edge in ponds, possibly benefiting waterbirds. We monitored paired terraced and unterraced ponds in three sites within southwestern Louisiana's Chenier Plain. Waterbirds were 75% more numerous in terraced than unterraced ponds. Waterbird richness was similar among ponds when corrected for number of individuals, suggesting terracing increased bird density but did not provide habitat unique from unterraced ponds. Birds were 93% more numerous following Hurricane Rita, mostly due to an influx of migrating waterfowl. Year round residents were similar in number before and after Hurricane Rita. Resident richness did not differ among years after correcting for number of observed individuals. Wading and dabbling foragers were more abundant in terraced ponds and these two guilds represented 74% of birds observed. We detected no difference among ponds for other guilds, i.e., probing, aerial, and diving foragers. Increasing proportion of mash edge increased bird density disproportionately: On average ponds with 10% edge had 6 birds observed and ponds with 30% edge had 16 birds observed. Terraces increased habitat interspersion and were an effective tool for increasing numbers of wintering waterfowl and wading birds. The extent to which terraces were sustainable following hurricane forces is unknown.

Effects of Marsh Pond Terracing on Coastal Wintering Waterbirds Before and After Hurricane Rita

NASA Astrophysics Data System (ADS)

O'Connell, Jessica L.; Nyman, John A.

2011-11-01

From February to March 2005-2006, we surveyed wintering waterbirds to test effects of terracing on coastal pond use before and after Hurricane Rita. Marsh terracing is intended to slow coastal marsh loss in the Chenier Plain by slowing marsh erosion and encouraging vegetation expansion. Terraces also increase marsh edge in ponds, possibly benefiting waterbirds. We monitored paired terraced and unterraced ponds in three sites within southwestern Louisiana's Chenier Plain. Waterbirds were 75% more numerous in terraced than unterraced ponds. Waterbird richness was similar among ponds when corrected for number of individuals, suggesting terracing increased bird density but did not provide habitat unique from unterraced ponds. Birds were 93% more numerous following Hurricane Rita, mostly due to an influx of migrating waterfowl. Year round residents were similar in number before and after Hurricane Rita. Resident richness did not differ among years after correcting for number of observed individuals. Wading and dabbling foragers were more abundant in terraced ponds and these two guilds represented 74% of birds observed. We detected no difference among ponds for other guilds, i.e., probing, aerial, and diving foragers. Increasing proportion of mash edge increased bird density disproportionately: On average ponds with 10% edge had 6 birds observed and ponds with 30% edge had 16 birds observed. Terraces increased habitat interspersion and were an effective tool for increasing numbers of wintering waterfowl and wading birds. The extent to which terraces were sustainable following hurricane forces is unknown.

Timing and process of river and lake terrace formation in the Kyrgyz Tien Shan

NASA Astrophysics Data System (ADS)

Burgette, Reed J.; Weldon, Ray J.; Abdrakhmatov, Kanatbek Ye.; Ormukov, Cholponbek; Owen, Lewis A.; Thompson, Stephen C.

2017-03-01

Well-preserved flights of river and lake terraces traverse an actively deforming rangefront, and form a link between glaciated mountains and a large intermontane lake in the Issyk-Kul basin of the Kyrgyz Tien Shan. We investigated the history and geometry of these lake and river terraces using geologic mapping, surveying, and radiocarbon and terrestrial cosmogenic nuclide dating. A prominent late Pleistocene highstand of the lake occurred over at least the period of 43-25 ka, followed by a period of deep regression and subsequent rise of the lake to the modern sill level in the late Holocene. Major aggradation of the most prominent latest Quaternary river terrace along the Ak-Terek and Barskaun rivers likely started at ∼70-60 ka, coincident to the local last glacial maximum in this region. In contrast to some models of aggradation and incision, the rivers appear to have stayed near the top of the fill for >20 ka, incising subtly below the top of this fill by ∼37 ka, locally. Deep incision likely did not occur until the peak deglaciation in the latest Pleistocene. Older dated terrace surfaces are consistent with one major terrace-forming event per glacial, constant deformation and incision rates, and typical fluvial gradients lower than the modern incising streams. The dating confirms regional terrace correlations for the most prominent late Quaternary terraces, but correlating higher terraces is complicated by spatially varying uplift rates and preferential terrace preservation between basins in the Tien Shan.

[Soft-ridged bench terrace design in hilly loess region].

PubMed

Cao, Shixiong; Chen, Li; Gao, Wangsheng

2005-08-01

Reconfiguration of hillside field into terrace is regarded as one of the key techniques for water and soil conservation in mountainous regions. On slopes exceeding 30 degrees, the traditional techniques of terracing are difficult to apply as risers (i.e., backslopes), and if not reinforced, are so abrupt and easy to collapse under gravity alone, thus damaging the terrace. To improve the reconfiguration of hillside field into terrace, holistic techniques of soft-ridged bench terrace engineering, including revegetation, with trees and planting grasses on riser slopes, were tested between 1997 and 2001 in Xiabiangou watershed of Yan' an, Shaanxi Province. A "working with Nature" engineering approach, riser slopes of 45 degrees, similar to the pre-existing slope of 35 degrees, was employed to radically reduce gravity-erosion. Based on the concepts of biodiversity and the principles of landscape ecology, terrace benches, bunds, and risers were planted with trees, shrubs, forage grasses, and crops, serving to generate a diverse array of plants, a semi-forested area, and to stabilize terrace bunds. Soft-ridged bench terrace made it possible to significantly reduce hazards arising from gravity erosion, and reduce the costs of individual bench construction and maintenance by 24.9% and 55.5% of the costs under traditional techniques, respectively. Such a construction allowed an enrichment and concentration of nutrients in the soils of terrace bunds, providing an ideal environment for a range of plants to grow and develop. The terrace riser could be planted with drought-resistant plants ranging from forage grasses to trees, and this riser vegetation would turn the exposed bunds and risers existing under traditional techniques into plant-covered belts, great green ribbons decorating farmland and contributing to the enhancement of the landscape biology.

The Extraction of Terrace in the Loess Plateau Based on radial method

NASA Astrophysics Data System (ADS)

Liu, W.; Li, F.

2016-12-01

The terrace of Loess Plateau, as a typical kind of artificial landform and an important measure of soil and water conservation, its positioning and automatic extraction will simplify the work of land use investigation. The existing methods of terrace extraction mainly include visual interpretation and automatic extraction. The manual method is used in land use investigation, but it is time-consuming and laborious. Researchers put forward some automatic extraction methods. For example, Fourier transform method can recognize terrace and find accurate position from frequency domain image, but it is more affected by the linear objects in the same direction of terrace; Texture analysis method is simple and have a wide range application of image processing. The disadvantage of texture analysis method is unable to recognize terraces' edge; Object-oriented is a new method of image classification, but when introduce it to terrace extracting, fracture polygons will be the most serious problem and it is difficult to explain its geological meaning. In order to positioning the terraces, we use high- resolution remote sensing image to extract and analyze the gray value of the pixels which the radial went through. During the recognition process, we firstly use the DEM data analysis or by manual selecting, to roughly confirm the position of peak points; secondly, take each of the peak points as the center to make radials in all directions; finally, extracting the gray values of the pixels which the radials went through, and analyzing its changing characteristics to confirm whether the terrace exists. For the purpose of getting accurate position of terrace, terraces' discontinuity, extension direction, ridge width, image processing algorithm, remote sensing image illumination and other influence factors were fully considered when designing the algorithms.

Soil nitrogen accretion along a floodplain terrace chronosequence in northwest Alaska: Influence of the nitrogen-fixing shrub Shepherdia canadensis

USGS Publications Warehouse

Rhoades, Charles; Binkley, Dan; Oskarsson, Hlynur; Stottlemyer, Robert

2008-01-01

Nitrogen enters terrestrial ecosystems through multiple pathways during primary succession. We measured accumulation of total soil nitrogen and changes in inorganic nitrogen (N) pools across a 300-y sequence of river terraces in northwest Alaska and assessed the contribution of the nitrogen-fixing shrub Shepherdia canadensis. Our work compared 5 stages of floodplain succession, progressing from a sparsely vegetated silt cap to dense shrubby vegetation, balsam poplar-dominated (Populus balsamifera) and white spruce-dominated (Picea glauca) mixed forests, and old-growth white spruce forest. Total soil N (0–30 cm depth) increased throughout the age sequence, initially by 2.4 g N·m−2·y−1 during the first 120 y of terrace development, then by 1.6 g N·m−2·y−1 during the subsequent 2 centuries. Labile soil N, measured by anaerobic incubation, increased most rapidly during the first 85 y of terrace formation, then remained relatively constant during further terrace development. On recently formed terraces, Shepherdia shrubs enriched soil N pools several-fold compared to soil beneath Salix spp. shrubs or intercanopy sites. Total and labile soil N accretion was proportional to Shepherdia cover during the first century of terrace development, and mineral soil δ15N content indicated that newly formed river terraces receive substantial N through N-fixation. About half the 600 g total N·m−2 accumulated across the river terrace chronosequence occurred during the 120 y when S. canadensis was dominant. Sediment deposited by periodic flooding continued to add N to terrace soils after the decline in Shepherdia abundance and may have contributed 25% of the total N found in the floodplain terrace soils.

Including Deposition Rate in Models of Cosmogenic Nuclide Accumulation in Fluvial Sediments to Improve Terrace Abandonment Ages

NASA Astrophysics Data System (ADS)

Norton, K. P.; Wang, N.; Van Dissen, R. J.; Little, T.

2017-12-01

Fluvial sediments are archives of the erosional, transport, and depositional processes occurring in the catchment. Terraces become robust markers for geomorphic analysis if their time of abandonment can be determined. Methods such as OSL can determine burial ages for fine grained sediments within the terrace fill but may not be directly related to the terrace abandonment age. Cosmogenic nuclides can be used to determine exposure ages for geologically young terraces but the surface being dated may have been subsequently eroded and the material itself may have been deposited with an inherited nuclide concentration. To deal with this problem, many researchers collect multiple samples with depth to model the depth-dependent nuclide concentration to help constrain inheritance and post-depositional erosion. It is often, however, assumed that the entire sediment pile accumulated instantaneously. In this submission, we present the results of a depth profile model that incorporates sediment accumulation rate to improve terrace age estimates. We test this model on fault-offset river terraces near Kaikoura, New Zealand. We measured depth profiles of OSL ages and cosmogenic nuclide concentrations of two late Quaternary terraces that are offset by up to 800 m across the Kekerengu Fault. OSL ages and dated tephras in the overlying loess provide minimum age constraints for both terraces while OSL ages of fine-grained sediments within the fill provide depositional ages. The predicted sedimentation rates for the terraces are as high as 0.5m/yr, consistent with geologically instantaneous deposition. Modelled abandonment ages from cosmogenic nuclides for the terraces are consistent with OSL and tephra constraints at 9.7 +/- 3.8 ka and 30.4 +/- 2.1 ka, respectively. These terrace abandonment ages yield dextral slip rates of 18.5-20.5 mm/yr and 25-28 mm/yr, respectively, consistent with the rapid slip rate on the adjacent Hope Fault.

Dating of river terraces along Lefthand Creek, western High Plains, Colorado, reveals punctuated incision

USGS Publications Warehouse

Foster, Melissa A.; Anderson, Robert S.; Gray, Harrison J.; Mahan, Shannon

2017-01-01

The response of erosional landscapes to Quaternary climate oscillations is recorded in fluvial terraces whose quantitative interpretation requires numerical ages. We investigate gravel-capped strath terraces along the western edge of Colorado's High Plains to constrain the incision history of this shale-dominated landscape. We use ¹⁰Be and ²⁶Al cosmogenic radionuclides (CRNs), optically stimulated luminescence (OSL), and thermally transferred OSL (TT-OSL) to date three strath terraces, all beveled in shale bedrock and then deposited upon by Lefthand Creek, which drains the crystalline core of the Front Range. Our study reveals: (i) a long history (hundreds of thousands of years) of fluvial occupation of the second highest terrace, T2 (Table Mountain), with fluvial abandonment at 92 ± 3 ka; (ii) a brief occupation of a narrow and spatially confined terrace, T3, at 98 ± 7 ka; and (iii) a 10–25 thousand year period of cutting and fluvial occupation of a lower terrace, T4, marked by the deposition of a lower alluvial unit between 59 and 68 ka, followed by deposition of an upper alluvial package at 40 ± 3 ka. In conjunction with other recent CRN studies of strath terraces along the Colorado Front Range (Riihimaki et al., 2006; Dühnforth et al., 2012), our data reveal that long periods of lateral planation and fluvial occupation of strath terraces, sometimes lasting several glacial-interglacial cycles, are punctuated by brief episodes of rapid vertical bedrock incision. These data call into question what a singular terrace age represents, as the strath may be cut at one time (its cutting-age) and the terrace surface may be abandoned at a much later time (its abandonment age), and challenge models of strath terraces that appeal to simple pacing by the glacial-interglacial cycles.

A postglacial chronology for some alluvial valleys in Wyoming

USGS Publications Warehouse

Leopold, Luna Bergere; Miller, John P.

1954-01-01

Alluvial terraces were studied in several major river basins in eastern Wyoming. Three terraces are present along nearly all the streams and large tributaries. There are several extensive dissected erosion surfaces in the area, but these are much older than, and stand well above, the recent alluvial terraces with which this report is concerned.The three alluvial terraces stand respectively about 40, 10, and 5 feet above the present streams. The uppermost and oldest is a fill terrace comprised of three stratigraphic units of varying age. The oldest unit is Pleistocene and the youngest unit postdates the development of a soil zone, or paleosol, which is characterized by strong accumulation of calcium carbonate and gypsum. This paleosol is an important stratigraphic marker. The middle terrace is generally a cut terrace and is developed on the material making up the youngest alluvium of the high terrace. The lowest is a fill terrace, the surface of which is only slightly higher than the present flood plain.The oldest terrace can tentatively be traced into mountain valleys of the Bighorn Range on the basis of discontinuous remnants. The terrace remnants occur far upstream from the youngest moraine in the valleys studied. On this basis, the terrace sequence is considered to postdate the last Wisconsin ice in the Bighorn Mountains. The paleosol is tentatively correlated with Altithermal time, called in Europe the Climatic Optimum. The terrace sequence is very similar to that suggested by various workers in the southwestern United States.Two streams, Clear Creek and the Powder River, deposited comparable silty alluvium, the surface of which now comprises the highest alluvial terrace. The gradients of these former flood plains differed markedly between the two streams despite the comparability in size of material deposited. This difference in gradient is believed to have required different relative contributions of water from mountain and plain areas than now exist.Knowledge of Recent physiographic history of the area is the basis of determining the relative ages of some gully features. Certain vertical-walled channels or arroyos that might appear to be attributable to postsettlement grazing or other man-induced influences are shown to be Recent but pre-Columbian in age. Such differentiation in age of erosion features is necessary for proper understanding of present-day soil erosion problems.

Multiple paths to straths: A review and reassessment of terrace genesis

NASA Astrophysics Data System (ADS)

Schanz, Sarah A.; Montgomery, David R.; Collins, Brian D.; Duvall, Alison R.

2018-07-01

Strath terraces, an important tool in tectonic geomorphology, have been attributed to climatic, tectonic, volcanic, and human activity, yet the pathways connecting external forcings to the channel response leading to terrace formation are highly variable and complex. To better understand variability and controls on the pathways between forcing and terrace formation, we created a comprehensive database of 421 strath terraces from peer-reviewed literature and noted the strath age and rock type, the ascribed forcing (climate, tectonics, volcanoes, or humans) or whether the cause was unascribed, and the pathway between forcing and strath incision or planation. Study authors identify climate, tectonics, volcanoes, and humans as the forcing for 232 (55%), 20 (5%), 8 (2%), and 5 (1%) strath terraces in our compilation respectively. A forcing was not identified for the remaining 156 (37%) terraces. Strath terraces were dated using 14 different methods: 71% of terraces in our database are dated using methods, such as radiocarbon and optically stimulated luminescence, that date planation and give a maximum age of incision; 16% of terraces are dated with methods that give a minimum age of incision; and 14% use a variety of methods for which a generalization about incision age cannot be made. That the majority of terrace studies use planation ages to understand terrace formation highlights the necessity of knowing the relative timescales of incisional and planation phases, which has so far been quantified in only a handful of studies. In general, rivers in arid regions plane straths in interglacial periods when discharge and sediment transport capacity increase, whereas temperate rivers plane in glacial or interglacial periods when sediment supply increases. Heterogeneities in rock strength between watersheds further control how sediment is produced and when straths are planed. Globally, these regional and watershed controls result in strath planation and incision during all parts of the glacial cycle. Terraces with no identified forcing in our database reach a maximum frequency during the late Holocene (4 kya-present) and could potentially be explained by regional deforestation and increased anthropogenic fire frequency, regionally active tectonics, and climate fluctuations. Deforestation and fires, by reducing the supply of wood to streams, decrease instream sediment retention and could convert alluvial channels to bedrock, thus promoting strath incision. The regional and watershed controls on strath formation highlighted in our database, as well as the possibility of anthropogenic forcings on strath terrace formation in the late Holocene, illustrate the importance of explicitly establishing the pathway between forcing and strath terrace formation in order to accurately interpret the cause of strath formation.

Effects of soil and water conservation on crop productivity: Evidences from Anjenie watershed, Ethiopia

NASA Astrophysics Data System (ADS)

Adgo, Enyew; Teshome, Akalu

2014-05-01

Widespread soil and water conservation activities have been implemented in many parts of eastern Africa to control soil erosion by water and improve land productivity for the last few decades. Following the 1974 severe drought, soil and water conservation became more important to Ethiopia and the approach shifted to watershed based land management initiatives since the 1980s. To capture long-term impacts of these initiatives, a study was conducted in Anjenie Watershed of Ethiopia, assessing fanya juu terraces and grass strips constructed in a pilot project in 1984, and which are still functional nearly 30 years later. Data were collected from government records, field observations and questionnaire surveys administered to 60 farmers. Half of the respondents had terraced farms in the watershed former project area (with terrace technology) and the rest were outside the terraced area. The crops assessed were teff, barley and maize. Cost-benefit analyses were used to determine the economic benefits with and without terraces, including gross and net profit values, returns on labour, water productivity and impacts on poverty. The results indicated that soil and water conservation had improved crop productivity. The average yield on terraced fields was 0.95 t ha-1 for teff (control 0.49), 1.86 t ha-1 for barley (control 0.61), and 1.73 t ha-1 for maize (control 0.77). The net benefit was significantly higher on terraced fields, recording US 20.9 (US -112 control) for teff, US 185 (US -41 control) for barley and US -34.5 (US - 101 control) ha-1 yr-1 for maize. The returns on family labour were 2.33 for barley, 1.01 for teff, and 0.739 US per person-day for maize grown on terraced plots, compared to US 0.44, 0.27 and 0.16 per person-day for plots without terraces, respectively. Using a discount rate of 10%, the average net present value (NPV) of barley production with terrace was found to be about US 1542 over a period of 50 years. In addition, the average financial internal rate of return (FIRR) was 301%. Other long-term impacts of terracing included farmers' growing of maize on terraced fields as a result of water conservation. Currently, farmers also grow barley on terraced fields for two crop seasons per year unlike the experiences on farms without terraces. Household incomes and food security had improved and soil erosion drastically reduced. Many farmers had adopted terracing doubling the original area under the soil conservation pilot project and consequently improving environmental conservation in the watershed.

Living terraced landscapes: Exploring the viability of mountain terraced vineyards in Cyprus

NASA Astrophysics Data System (ADS)

Zoumides, Christos; Giannakis, Elias; Bruggeman, Adriana; Camera, Corrado

2017-04-01

Dry-stone terracing is an intensive cultivation practice that has been implemented for centuries in the Mediterranean region. The Troodos Ophiolite Complex on the island of Cyprus covers an area of 2332 km2 with 31% mean slope gradient, and consists of 140 small communities with a total population of around 50,000 inhabitants. Agriculture is practiced on dry-stone terraces with narrow (1-3 m) to medium-base (3-6 m) bench, constructed by cutting and filling in slopes with gradient between 20 and 40%. The main crop grown on terraces is wine grapes. However, many of the vineyards on terraced hillsides are being gradually abandoned and dry-stone walls remain unmaintained, causing a domino effect of collapsing terraces and leading to soil erosion and sedimentation of downstream infrastructure. The main reasons for the gradual decline of terraced landscapes are the ageing of farming population, the depopulation and marginalization of Troodos communities, the small size of agricultural plots, the high cost of labour and the loss of know-how on dry-stone wall maintenance. Despite these socio-economic issues, policy reforms, especially after the accession of Cyprus to the European Union in 2004, have created new challenges and opportunities, and have focused on improving the viniculture's quality rather than quantity. The new appellation of origin launched in 2007 that define where the wine-grapes are grown, as well as the incentives to create small regional wineries, helped maintain the population of some communities and the vine cultivations on dry-stone terraces. The aim of this study is to analyse the determinants of success or failure in sustaining the terraced vineyards in Cyprus. More precisely, the study explores the characteristics that determine the investment (or not) in terrace maintenance and analyses the interlinkages between farming practices and business strategies. The analysis is based on grape and wine production cost data that is acquired by interviews conducted with winery managers as well as individual farmers, in both maintained and non-maintained terraced vineyards. Preliminary results indicate that the income of farms with well-maintained terraces is not solely derived from grape growing, but also from product differentiation and off-farm activities, such as recreational tourism. On the other hand, farmers with poorly maintained terraces seem not capable to exploit niche market opportunities that generate added value. From a policy perspective, the preservation of terraced landscapes can be supported through targeted measures that aim at improving the quality of vinicultural products, as well as better marketing strategies and consumer awareness of the importance of wine produced on mountain terraces. This study has received funding from the EU FP7 RECARE Project (GA 603498).

Nonmonotonic velocity dependence of atomic friction.

PubMed

Reimann, Peter; Evstigneev, Mykhaylo

2004-12-03

We propose a theoretical model for friction force microscopy experiments with special emphasis on the realistic description of dissipation and inertia effects. Its main prediction is a nonmonotonic dependence of the friction force upon the sliding velocity of the atomic force microscope tip relative to an atomically flat surface. The region around the force maximum can be approximately described by a universal scaling law and should be observable under experimentally realistic conditions.

Off-axis silicon carbide substrates

DOEpatents

Edgar, James; Dudley, Michael; Kuball, Martin; Zhang, Yi; Wang, Guan; Chen, Hui; Zhang, Yu

2014-09-02

A method of epitaxial growth of a material on a crystalline substrate includes selecting a substrate having a crystal plane that includes a plurality of terraces with step risers that join adjacent terraces. Each terrace of the plurality or terraces presents a lattice constant that substantially matches a lattice constant of the material, and each step riser presents a step height and offset that is consistent with portions of the material nucleating on adjacent terraces being in substantial crystalline match at the step riser. The method also includes preparing a substrate by exposing the crystal plane; and epitaxially growing the material on the substrate such that the portions of the material nucleating on adjacent terraces merge into a single crystal lattice without defects at the step risers.

Interfacial nanobubbles on atomically flat substrates with different hydrophobicities.

PubMed

Wang, Xingya; Zhao, Binyu; Ma, Wangguo; Wang, Ying; Gao, Xingyu; Tai, Renzhong; Zhou, Xingfei; Zhang, Lijuan

2015-04-07

The dependence of the morphology of interfacial nanobubbles on atomically flat substrates with different wettability ranges was investigated by using PeakForce quantitative nanomechanics. Interfacial nanobubbles were formed and imaged on silicon nitride (Si3N4), mica, and highly ordered pyrolytic graphite (HOPG) substrates that were partly covered by reduced graphene oxide (rGO). The contact angles and sizes of those nanobubbles were measured under the same conditions. Nanobubbles with the same lateral width exhibited different heights on the different substrates, with the order Si3N4≈mica>rGO>HOPG, which is consistent with the trend of the hydrophobicity of the substrates. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Structure of Boron Nitride Nanotubes: Tube Closing Vs. Chirality

NASA Technical Reports Server (NTRS)

Srivastava, Deepak; Menon, Madhu

1998-01-01

The structure of boron nitride nanotubes is investigated using a generalized tight-binding molecular dynamics method. It is shown that dynamic relaxation results in a wavelike or "rippled" surface in which the B atoms rotate inward and the N atoms move outward, reminiscent of the surface relaxation of the III-V semiconductors. More importantly, the three different morphologies of the tube closing with flat, conical and amorphous ends, as observed in experiments, are shown to be directly related to the tube chiralities. The abundance of flat end tubes observed in experiments is, thus, shown to be an indication of the greater stability of "zig-zag" BN tubes over the "arm-chair" tubes under experimental conditions.

The Meaning of Terrace as Social Interaction Place in Vertical Kampung

NASA Astrophysics Data System (ADS)

Sihombing, Antony; Gumay Poetri, Nurul

2018-01-01

The pros and cons of vertical housing development in Jakarta make me intend to raise the issue of the vertical kampung. In the kampung, there are social spaces where people interact to create a culture of rukun and gotong-royong. It is the terrace which become a container of social interaction. The purpose of this study is to reveal the meaning of the terrace in social interaction in the vertical kampung and its influence when the terrace room is not presented in the vertical kampung. The lost meaning of kampung when terrace is not presented in vertical kampung can be known through cognitive maps. Cognitive maps are the methodologies used to gain a human perception or view of life experiences in a particular place. This study involved several families in West Jatinegara Rusunawa to find out how people looked at the terrace in their life while in Kampung Pulo. Based on the cognitive maps method that has been done by the respondents, the terrace referred to by the villagers is an open space where people can see and interact with each other. Social space in the form of terraces which is needed by the kampung dweller, in fact is not a terrace house which is used as a place to receive guests and as a barrier between the fence and the body of the house.

Modeling runoff and sediment yield from a terraced watershed using WEPP

Treesearch

Mary Carla McCullough; Dean E. Eisenhauer; Michael G. Dosskey

2008-01-01

The watershed version of WEPP (Water Erosion Prediction Project) was used to estimate 50-year runoff and sediment yields for a 291 ha watershed in eastern Nebraska that is 90% terraced and which has no historical gage data. The watershed has a complex matrix of elements, including terraced and non-terraced subwatersheds, multiple combinations of soils and land...

Timing of Quaternary Marine Terrace Formation and Uplift Rates in the Eastern Pontides, NE Turkey

NASA Astrophysics Data System (ADS)

Softa, M.; Spencer, J. Q. G.; Emre, T.; Sözbilir, H.; Turan, M.

2016-12-01

Quaternary records of marine terraces formation are indispensable tool for the better understanding sea-level changes in the coastal region of Pontides. Time of the marine terraces with linked to date of the depositional of its are very crucial to know for active tectonic evolution in this study area. The ages of the marine terraces are not well known in the coastal region of Trabzon and Rize. In the coastal region of eastern Pontides, we have identified three marine terrace levels. Using the optically stimulated dating we show that these three sedimentation period were formed during the at 8.3 ± 2.5 ka, 42 ± 1.8 ka and 78.3 ± 6.1 ka. These ages correspond to marine isotopic stages (MIS) or substages (MISS) 1, 3 and 5a sea level, respectively. The apparent vertical movement is ranging from 1.0 mm/yr to 0.59 mm/yr that obtained from marine terraces in the northeastern of Pontides. We will present timing of the marine terrace formation and vertical movement in the coastal region of Trabzon and Rize. Key words: OSL dating, vertical movement, marine terraces, active tectonic, eastern Pontides.

Improving catalytic selectivity through control of adsorption orientation

NASA Astrophysics Data System (ADS)

Pang, Simon H.

In this thesis, we present an investigation, starting from surface science experiments, leading to design of supported catalysts, of how adsorption orientation can be used to affect reaction selectivity of highly functional molecules. The surface chemistry of furfuryl alcohol and benzyl alcohol and their respective aldehydes was studied on a Pd(111) single-crystal surface under ultra-high vacuum conditions. Temperature-programmed desorption experiments showed that synergistic chemistry existed between the aromatic ring and the oxygen-containing functional group, each allowing the other to participate in reaction pathways that a monofunctional molecule could not. Most important of these was a deoxygenation reaction that occurred more readily when the surface was crowded by the highest exposures. High-resolution electron energy loss spectroscopy revealed that at these high exposures, molecules were oriented upright on the surface, with the aromatic function extending into vacuum. In contrast, at low exposures, molecules were oriented flat on the surface. The upright adsorption geometry was correlated with deoxygenation, whereas the flat-lying geometry was correlated with decarbonylation. The insight gained from surface science experiments was utilized in catalyst design. Self-assembled monolayers of alkanethiolates were used to systematically reduce the average surface ensemble size, and the reaction selectivity was tracked. When a sparsely-packed monolayer was used, such as one formed by 1-adamantanethiol, the reactant furfural was still able to lie flat on the surface and the reaction selectivity was similar to that of the uncoated catalyst. However, when a densely-packed monolayer, formed by 1-octadecanethiol, was used, furfural was not able to adsorb flat on the surface and instead adopted an upright conformation, leading to a drastic increase in aldehyde hydrogenation and hydrodeoxygenation reaction selectivity. Using an even higher sulfur coverage from a monolayer formed by 1,2-benzenedithiol, we determined that hydrodeoxygenation selectively occurred on catalyst particle steps and edges from an upright structure, whereas decarbonylation occurred on particle terraces from a flat-lying structure. Control of furfural adsorption orientation was also achieved through the use of NiCu bimetallic catalysts. The aromatic furan ring was repelled from surface Cu, leading to an upright structure. However, under hydrogenation conditions, Ni tended to be near the surface of thin films and catalysts, leading to less dramatic selectivity enhancement. The presence of a 1-octadecanethiol monolayer kinetically stabilized the surface termination, allowing Cu to remain at the surface.

Long-term indigenous soil conservation technology in the Chencha area, southern Ethiopia: origin, characteristics, and sustainability.

PubMed

Engdawork, Assefa; Bork, Hans-Rudolf

2014-11-01

The purpose of this study is to examine the origin, development, and characteristics of terraces (kella), plus their potentials and determinants for sustainable use in the Chencha-Dorze Belle area of southern Ethiopia. Field surveys were conducted to determine the various parameters of the indigenous terraces and in order to collect samples for radiocarbon dating. To identify farmers' views of the terrace systems, semi-structured interviews and group discussions were also carried out. Terraces were built and used-as radiocarbon dating proves-at least over the last 800 years. The long-term continued usage of the indigenous terraces is the result of social commitments, the structural features of the terraces, and the farmers' responses to the dynamics of social and cultural circumstances. We dubbed that the terraces are a success story of fruitful environmental management over generations. Thus, a strong need is to preserve and develop this important cultural heritage and example of sustainable land use.

LN2 spray droplet size measurement via ensemble diffraction technique

NASA Technical Reports Server (NTRS)

Saiyed, N. H.; Jurns, J.; Chato, David J.

1991-01-01

The size of subcooled liquified nitrogen droplets are measured with a 5 mW He-Ne laser as a function of pressure difference (delta P) across flat spray and full cone pressure atomizing nozzles. For delta P's of 3 to 30 psid, the spray sauter mean diameter (SMD) ranged between 250 to 50 microns. The pressure range tested is representative of those expected during cryogenic fluid transfer operations in space. The droplet sizes from the flat spray nozzles were greater than those from the full cone nozzle. A power function of the form, SMD varies as delta P(exp a), describes the spray SMD as a function of the delta P very well. The values of a were -0.36 for the flat spray and -0.87 for the full cone. The reduced dependence of the flat spray SMD on the delta P was probably because of: (1) the absence of a swirler that generates turbulence within the nozzle to enhance atomization, and (2) a possible increase in shearing stress resulting from the delayed atomization due to the absence of turbulence. The nitrogen quality, up to 1.5 percent is based on isenthalpic expansion, did not have a distinct and measurable effect on the spray SMD. Both bimodal and monomodal droplet size population distributions were measured. In the bimodal distribution, the frequency of the first mode was much greater than the frequency of the second mode. Also, the frequency of the second mode was low enough such that a monomodal approximation probably would give reasonable results.

Quantification of the effect of terrace maintenance on soil erosion: two seasons of monitoring experiments in Cyprus

NASA Astrophysics Data System (ADS)

Camera, Corrado; Djuma, Hakan; Zoumides, Christos; Eliades, Marinos; Charalambous, Katerina; Bruggeman, Adriana

2017-04-01

In the Mediterranean region, rural communities in topographically challenging sites have converted large areas into dry-stone terraces, as the only way to develop sustainable agriculture. Terraces allow softening the steep mountainous slopes, favoring water infiltration and reducing water runoff and soil erosion. However, population decrease over the past 30 years has led to a lack of maintenance of the terraces and the onset of a process of land degradation. The objective of this study is the quantification of the effect of terrace maintenance on soil erosion. We selected two terraces - A and B, 11 and 14 m long, respectively - for monitoring purposes. They are located in a small catchment (10,000 m2) in the Troodos Mountains of Cyprus, at an elevation of 1,300 m a.s.l., and cultivated with vineyards, which is the main agricultural land use of the region. We monitored soil erosion by means of sediment traps, which are installed along 1-m long sections of terrace. We monitored four sections on terrace A and seven on terrace B. During the first monitoring season (winter 2015/16), on terrace A the traps caught sediment of two collapsed and two standing sections of dry-stone wall. The catchment areas of one set of traps (degraded and non-degraded) were closed by a 1x4-m2 plot, to relate erosion rates to a known draining area. On terrace B the traps were all open and caught four collapsed and three standing sections. Also, we installed a weather station (5-minute rainfall, temperature, and relative humidity) and 15 soil moisture sensors, to relate soil erosion processes with climate and (sub)surface hydrology. From the open traps, we observed that soil loss is on average 8 times higher from degraded terrace sections than from standing, well maintained sections, which in our case study corresponds to an 87% reduction of soil loss due to terrace maintenance. If we compare data from the two closed plots, we obtain a much higher soil loss ratio (degraded/standing) of 56, which corresponds to a soil loss reduction of 98%. From the closed plots, we derived an erosion rate of 2.8 t ha-1 y-1 for degraded terraces and 0.05 t ha-1 y-1 for well-maintained terraces. Also, soil moisture monitoring confirmed that standing terraces favor surface water infiltration. For the second season (winter 2016/17), given the differences in results between open and closed traps and therefore the difficulty in consistently upscaling the results, we modified the monitoring design. The 11 traps were kept, all open, but the comparison between maintained and degraded areas is carried out on a sub-catchment basis, rather than on a section basis. We restored the whole sub-catchment of terrace A (≈480-m2) to be considered the maintained treatment of our experiment and kept the sub-catchment of terrace B (≈600-m2) in degraded conditions. To obtain the sub-catchment erosion rate, the sediment collected in the traps is averaged on running meter of wall and integrated on the wall length. This research is supported by the European Union's FP7 RECARE Project (GA 603498).

Surface topography and electrical properties in Sr2FeMoO6 films studied at cryogenic temperatures

NASA Astrophysics Data System (ADS)

Angervo, I.; Saloaro, M.; Mäkelä, J.; Lehtiö, J.-P.; Huhtinen, H.; Paturi, P.

2018-03-01

Pulsed laser deposited Sr2FeMoO6 thin films were investigated for the first time with scanning tunneling microscopy and spectroscopy. The results confirm atomic scale layer growth, with step-terrace structure corresponding to a single lattice cell scale. The spectroscopy research reveals a distribution of local electrical properties linked to structural deformation in the initial thin film layers at the film substrate interface. Significant hole structure giving rise to electrically distinctive regions in thinner film also seems to set a thickness limit for the thinnest films to be used in applications.

TerraceM: A Matlab® tool to analyze marine terraces from high-resolution topography

NASA Astrophysics Data System (ADS)

Jara-Muñoz, Julius; Melnick, Daniel; Strecker, Manfred

2015-04-01

To date, Light detection and ranging (LiDAR), high- resolution topographic data sets enable remote identification of submeter-scale geomorphic features bringing valuable information of the landscape and geomorphic markers of tectonic deformation such as fault-scarp offsets, fluvial and marine terraces. Recent studies of marine terraces using LiDAR data have demonstrated that these landforms can be readily isolated from other landforms in the landscape, using slope and roughness parameters that allow for unambiguously mapping regional extents of terrace sequences. Marine terrace elevation has been used since decades as geodetic benchmarks of Quaternary deformation. Uplift rates may be estimated by locating the shoreline angle, a geomorphic feature correlated with the high-stand position of past sea levels. Indeed, precise identification of the shoreline-angle position is an important requirement to obtain reliable tectonic rates and coherent spatial correlation. To improve our ability to rapidly assess and map different shoreline angles at a regional scale we have developed the TerraceM application. TerraceM is a Matlab® tool that allows estimating the shoreline angle and its associated error using high-resolution topography. For convenience, TerraceM includes a graphical user interface (GUI) linked with Google Maps® API. The analysis starts by defining swath profiles from a shapefile created on a GIS platform orientated orthogonally to the terrace riser. TerraceM functions are included to extract and analyze the swath profiles. Two types of coastal landscapes may be analyzed using different methodologies: staircase sequences of multiple terraces and rough, rocky coasts. The former are measured by outlining the paleo-cliffs and paleo-platforms, whereas the latter are assessed by picking the elevation of sea-stack tops. By calculating the intersection between first-order interpolations of the maximum topography of swath profiles we define the shoreline angle in staircase terraces. For rocky coasts, the maximum stack peaks for a defined search ratio as well as a defined inflection point on the adjacent main cliff are interpolated to calculate the shoreline angle at the intersection with the cliff. Error estimates are based on the standard deviation of the linear regressions. The geomorphic age of terraces (Kt) can be also calculated by the linear diffusion equation (Hanks et al., 1989), with a best-fitting model found by minimizing the RMS. TerraceM has the ability to efficiently process several profiles in batch-mode run. Results may be exported in various formats, including Google Earth and ArcGis, basic statistics are automatically computed. Test runs have been made at Santa Cruz, California, using various topographic data sets and comparing results with published field measurements (Anderson and Menking, 1994). Repeatability was evaluated using multiple test runs made by students in a classroom setting.

Universal aspects of adhesion and atomic force microscopy

NASA Technical Reports Server (NTRS)

Banerjea, Amitava; Smith, John R.; Ferrante, John

1990-01-01

Adhesive energies are computed for flat and atomically sharp tips as a function of the normal distance to the substrate. The dependence of binding energies on tip shape is investigated. The magnitudes of the binding energies for the atomic force microscope are found to depend sensitively on tip material, tip shape and the sample site being probed. The form of the energy-distance curve, however, is universal and independent of these variables, including tip shape.

Atomically resolved scanning force studies of vicinal Si(111)

NASA Astrophysics Data System (ADS)

Pérez León, Carmen; Drees, Holger; Wippermann, Stefan Martin; Marz, Michael; Hoffmann-Vogel, Regina

2017-06-01

Well-ordered stepped semiconductor surfaces attract intense attention owing to the regular arrangements of their atomic steps that makes them perfect templates for the growth of one-dimensional systems, e.g., nanowires. Here, we report on the atomic structure of the vicinal Si (111 ) surface with 10∘ miscut investigated by a joint frequency-modulation scanning force microscopy (FM-SFM) and ab initio approach. This popular stepped surface contains 7 ×7 -reconstructed terraces oriented along the Si (111 ) direction, separated by a stepped region. Recently, the atomic structure of this triple step based on scanning tunneling microscopy (STM) images has been subject of debate. Unlike STM, SFM atomic resolution capability arises from chemical bonding of the tip apex with the surface atoms. Thus, for surfaces with a corrugated density of states such as semiconductors, SFM provides complementary information to STM and partially removes the dependency of the topography on the electronic structure. Our FM-SFM images with unprecedented spatial resolution on steps coincide with the model based on a (7 7 10 ) orientation of the surface and reveal structural details of this surface. Two different FM-SFM contrasts together with density functional theory calculations explain the presence of defects, buckling, and filling asymmetries on the surface. Our results evidence the important role of charge transfers between adatoms, restatoms, and dimers in the stabilisation of the structure of the vicinal surface.

Identifying the source of fluvial terrace deposits using XRF scanning and Canonical Discriminant Analysis: A case study of the Chihshang terraces, eastern Taiwan

NASA Astrophysics Data System (ADS)

Chang, Queenie; Lee, Jian-Cheng; Hunag, Jyh-Jaan; Wei, Kuo-Yen; Chen, Yue-Gau; Byrne, Timothy B.

2018-05-01

The source of fluvial deposits in terraces provides important information about the catchment fluvial processes and landform evolution. In this study, we propose a novel approach that combines high-resolution Itrax-XRF scanning and Canonical Discriminant Analysis (CDA) to identify the source of fine-grained fluvial terrace deposits. We apply this approach to a group of terraces that are located on the hanging wall of the Chihshang Fault in eastern Taiwan with two possible sources, the Coastal Range on the east and the Central Range on the west. Our results of standard samples from the two potential sources show distinct ranges of canonical variables, which provided a better separation ability than individual chemical elements. We then tested the possibility of using this approach by applying it to several samples with known sediment sources and obtain positive results. Applying this same approach to the fine-grained sediments in Chihshang terraces indicates that they are mostly composed of Coastal Range material but also contain some inputs from the Central Range. In two lowest terraces T1 and T2, the fine-grained deposits show significant Central Range component. For terrace T4, the results show less Central Range input and a trend of decreasing Central Range influences up section. The Coastal Range material becomes dominant in the two highest terraces T7 and T10. Sediments in terrace T5 appear to have been potentially altered by post-deposition chemical alteration processes and are not included in the analysis. Our results show that the change in source material in the terraces deposits was relatively gradual rather than the sharp changes suggested by the composition of the gravels and conglomerates. We suggest that this change in sources is related to the change in dominant fluvial processes that controlled by the tectonic activity.

[Ecosystem services of Chongyi Hakka Terraces].

PubMed

Miao, Jian Qun; Wang, Zhi Qiang; Yang, Wen Ting; Sun, Song; Huang, Guo Qin

2017-05-18

An economic evaluation of the main ecosystem services of Chongyi Hakka Terraces can help to demonstrate the contributions of the terrace system to Hakka society, on the basis of which the protection of Hakka Terrace system could be undertaken by the local government. In view of the social and economic characteristics of Chongyi Hakka Terrace ecosystem and its location, an index system was established to evaluate the service function, and a qualitative analysis was conducted for these functions and their importance. Besides, based on the data collected in 2014, with a combination of physical quality and economic value, a quantitative analysis was carried out for its nine ser-vice indicators. The findings were as follows: firstly, among the nine evaluation indicators, the phy-sical quality and the economic value of soil conservation both ranked the highest, the former being 76457 kg·hm -2 and the latter 105033 yuan·hm -2 , accounting respectively for 72.2% and 30.0% of the total mass and total value of the Hakka Terrace ecosystem. Secondly, the unique service functions of Hakka Terrace ecosystem could be embodied in its cultural heritage and landscape, the corresponding economic values reaching up to 100000 yuan·hm -2 and 46333 yuan·hm -2 respectively, ranking the second and third highest among the nine indicators. Thirdly, the agricultural pro-ducts from the Hakka Terrace were vital welfare for the local residents, but their physical quality and the economic value only accounted for 6.1% and 10.4% of its total mass and total value respectively. As a result, the service functions of the Hakka Terrace ecosystem would be dramatically undervalued with respect to agricultural products only. These economic figures could reveal the huge contributions which the Hakka Terrace ecosystem had made to the society, not only raising awareness of the necessity to preserve the agricultural heritage by the administrators and the public, but also providing efficient data support for the government when making ecological compensation criteria for the Hakka Terrace system.

26Al - 10Be cosmogenic nuclide isochron burial dating in combination with luminescence dating of two Danube terraces

NASA Astrophysics Data System (ADS)

Neuhuber, Stephanie; Braumann, Sandra; Lüthgens, Christopher; Fiebig, Markus; Häuselmann, Philipp; Schäfer, Jörg

2016-04-01

The Quaternary sediment record in the Vienna Basin is influenced by two main factors: (1) the tectonic development of a pull apart basin along a sinistral strike slip fault system between the Eastern Alps and the West Carpathians and by (2) strongly varying sediment supply during the Plio- and Pleistocene. From the Late Pannonian (8.8 Ma) onward a large-scale regional uplift (Decker et al., 2005) controls terrace formation in the Vienna Basin. The main sediment supply into the Vienna Basin originates from the Danube, and subordinately from tributaries to the south such as Piesting, Fischa, Leitha and from the north by the river March. Today the Danube forms a large floodplain that is bordered to the north by one large Pleistocene terrace, the Gänserndorf Terrace that is situated 17 m above todays water level. Farther to the east a smaller terrace, the Schlosshof Terrace, reaches 25 m above todays water level. These terrace levels are tilted by movement of underlying blocks (Peresson, 2006). Both, the Schlosshof and Gänserndorf terraces consist of successions of up to 2 m thick gravel beds with intercalated sand layers or -lenses that may locally reach thicknesses up to 0.8 m. At each terrace one gavel pit was selected to calculate the time of terrace deposition by luminescence dating in combination with 26Al/10Be cosmogenic nuclide isochrone dating (Balco and Rovery, 2008). Five quartz stones from the base of each terrace were physically and chemically processed to obtain Al and Be oxides for Acceleration Mass Spectrometry. Sand samples for luminescence dating were taken above the cosmogenic nuclide samples from the closest suitable sand body. Decker et al., 2005. QSR 24, 307-322 Peresson, 2006 Geologie der österreichischen Bundesländer Niederösterreich 255-258 Balco and Rovey, 2008. AJS 908, 1083-1114 Thanks to FWF P 23138-N19, OMAA 90öu17

Surface structure of micro-diamond from ultrahigh-pressure felsic granulite, Bohemian Massif: AFM study of growth and resorption phenomena

NASA Astrophysics Data System (ADS)

Kotková, J.; Klapetek, P.

2012-04-01

Morphology, associated phases and retrogression phenomena of in-situ microdiamonds formed at extreme pressures in ultrahigh-pressure metamorphic terranes represent excellent tools to study character of diamond-forming media at great depths. Well-preserved microdiamonds discovered recently along with coesite in ultrahigh-pressure granulites of the north Bohemian crystalline basement, European Variscan belt (Kotková et al., 2011), provide unique material for such investigations. The diamonds are enclosed in major granulite phases, i.e. garnet both in felsic and intermediate lithologies and in kyanite in the felsic sample, as well as in zircon. Transmitted and reflected light microscopy of the felsic granulite sample, with peak mineral assemblage garnet, kyanite, feldspar and quartz, revealed presence of numerous, 5-20 μm-sized, perfectly preserved diamond crystals enclosed in kyanite grains. In contrast, diamonds within garnet are rare, can reach up to 30 μm in size, and graphite rims as well as polycrystalline graphite aggregates possibly representing complete diamond retrogression are common. We applied atomic force microscopy to study in-situ crystal morphology and surface microtopographic features, representing clues to the conditions and mechanisms of crystal formation as well as diamond resorption and retrogression. Both diamond enclosed in garnet and in kyanite of the felsic granulite occur exclusively as single crystals. The crystals have octahedral crystal shapes with straight but rounded edges and rounded corners. Concentric triangular terraces delimiting a flat triangular table on crystal scale and small micron-sized negatively oriented downward-pointing trigons developed on the octahedron crystal faces. Higher magnification reveals presence of discontinuous elongate hillocks oriented parallel to the octahedron face edge with positively oriented trigons. We suggest that the large-scale triangular terraces represent growth features. In contrast, the rounding of crystal edges and corners and development of negative trigons reflect diamond resorption. According to experimental works, such features are attributed to high temperature resorption, i.e. oxidation above ~ 950°C due to interaction with CO2 and/or H2O-bearing fluids (or fluid-bearing melts). Our results are consistent with presence of supercritical C-O-H fluid in the rocks in subduction zones documented from other ultrahigh-pressure metamorphic terranes, the resorption morphology corresponding rather to the interaction with water-rich than CO2-rich fluids. Kotková J., ÓBrien P., Ziemann M. (2011): Diamond and coesite discovered in Saxony-type granulite: Solution to the Variscan garnet peridotite enigma. Geology, 39, 7, 667-670.

Microstructural dependency of optical properties of m-plane InGaN multiple quantum wells grown on 2° misoriented bulk GaN substrates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tang, Fengzai; Barnard, Jonathan S.; Zhu, Tongtong

A non-polar m-plane structure consisting of five InGaN/GaN quantum wells (QWs) was grown on ammonothermal bulk GaN by metal-organic vapor phase epitaxy. Surface step bunches propagating through the QW stack were found to accommodate the 2° substrate miscut towards the -c direction. Both large steps with heights of a few tens of nanometres and small steps between one and a few atomic layers in height are observed, the former of which exhibit cathodoluminescence at longer wavelengths than the adjacent m-plane terraces. This is attributed to the formation of semi-polar facets at the steps on which the QWs are shown tomore » be thicker and have higher Indium contents than those in the adjacent m-plane regions. Discrete basal-plane stacking faults (BSFs) were occasionally initiated from the QWs on the main m-plane terraces, but groups of BSFs were frequently observed to initiate from those on the large steps, probably related to the increased strain associated with the locally higher indium content and thickness.« less

Surface step terrace tuned microstructures and dielectric properties of highly epitaxial CaCu3Ti4O12 thin films on vicinal LaAlO3 substrates

PubMed Central

Yao, Guang; Gao, Min; Ji, Yanda; Liang, Weizheng; Gao, Lei; Zheng, Shengliang; Wang, You; Pang, Bin; Chen, Y. B.; Zeng, Huizhong; Li, Handong; Wang, Zhiming; Liu, Jingsong; Chen, Chonglin; Lin, Yuan

2016-01-01

Controllable interfacial strain can manipulate the physical properties of epitaxial films and help understand the physical nature of the correlation between the properties and the atomic microstructures. By using a proper design of vicinal single-crystal substrate, the interface strain in epitaxial thin films can be well controlled by adjusting the miscut angle via a surface-step-terrace matching growth mode. Here, we demonstrate that LaAlO3 (LAO) substrates with various miscut angles of 1.0°, 2.75°, and 5.0° were used to tune the dielectric properties of epitaxial CaCu3Ti4O12 (CCTO) thin films. A model of coexistent compressive and tensile strained domains is proposed to understand the epitaxial nature. Our findings on the self-tuning of the compressive and tensile strained domain ratio along the interface depending on the miscut angle and the stress relaxation mechanism under this growth mode will open a new avenue to achieve CCTO films with high dielectric constant and low dielectric loss, which is critical for the design and integration of advanced heterostructures for high performance capacitance device applications. PMID:27703253

Surface step terrace tuned microstructures and dielectric properties of highly epitaxial CaCu3Ti4O12 thin films on vicinal LaAlO3 substrates

NASA Astrophysics Data System (ADS)

Yao, Guang; Gao, Min; Ji, Yanda; Liang, Weizheng; Gao, Lei; Zheng, Shengliang; Wang, You; Pang, Bin; Chen, Y. B.; Zeng, Huizhong; Li, Handong; Wang, Zhiming; Liu, Jingsong; Chen, Chonglin; Lin, Yuan

2016-10-01

Controllable interfacial strain can manipulate the physical properties of epitaxial films and help understand the physical nature of the correlation between the properties and the atomic microstructures. By using a proper design of vicinal single-crystal substrate, the interface strain in epitaxial thin films can be well controlled by adjusting the miscut angle via a surface-step-terrace matching growth mode. Here, we demonstrate that LaAlO3 (LAO) substrates with various miscut angles of 1.0°, 2.75°, and 5.0° were used to tune the dielectric properties of epitaxial CaCu3Ti4O12 (CCTO) thin films. A model of coexistent compressive and tensile strained domains is proposed to understand the epitaxial nature. Our findings on the self-tuning of the compressive and tensile strained domain ratio along the interface depending on the miscut angle and the stress relaxation mechanism under this growth mode will open a new avenue to achieve CCTO films with high dielectric constant and low dielectric loss, which is critical for the design and integration of advanced heterostructures for high performance capacitance device applications.

Surface step terrace tuned microstructures and dielectric properties of highly epitaxial CaCu3Ti4O12 thin films on vicinal LaAlO3 substrates.

PubMed

Yao, Guang; Gao, Min; Ji, Yanda; Liang, Weizheng; Gao, Lei; Zheng, Shengliang; Wang, You; Pang, Bin; Chen, Y B; Zeng, Huizhong; Li, Handong; Wang, Zhiming; Liu, Jingsong; Chen, Chonglin; Lin, Yuan

2016-10-05

Controllable interfacial strain can manipulate the physical properties of epitaxial films and help understand the physical nature of the correlation between the properties and the atomic microstructures. By using a proper design of vicinal single-crystal substrate, the interface strain in epitaxial thin films can be well controlled by adjusting the miscut angle via a surface-step-terrace matching growth mode. Here, we demonstrate that LaAlO 3 (LAO) substrates with various miscut angles of 1.0°, 2.75°, and 5.0° were used to tune the dielectric properties of epitaxial CaCu 3 Ti 4 O 12 (CCTO) thin films. A model of coexistent compressive and tensile strained domains is proposed to understand the epitaxial nature. Our findings on the self-tuning of the compressive and tensile strained domain ratio along the interface depending on the miscut angle and the stress relaxation mechanism under this growth mode will open a new avenue to achieve CCTO films with high dielectric constant and low dielectric loss, which is critical for the design and integration of advanced heterostructures for high performance capacitance device applications.

Ab Initio calculation on magnetism of monatomic Fe nanowire on Au (111) surface

NASA Astrophysics Data System (ADS)

Yasui, Takashi; Nawate, Masahiko

2010-01-01

The magnetic anisotropy of the one-dimensional monatomic Fe wire on the Au (111) texture has been theoretically analyzed using Wien2k flamework. The model simulates experimentally observed ferromagnetic Fe monatomic wire self-organized along the terrace edge of the Au (788) plane, which exhibits the magnetizaiton perpendicular both the wire and Au plane. In the case of the model consisting the one-dimensional Fe wire placed on the Au (111) plane with the Au lattice cite, no significant anisotropy is resulted by the calculation. On the other hand, the model where the Fe wire is formed along the Au terrace like step indicates the anisotropy of which easy direction is along the wire, resulting in differenct direction from the experiment. When we introduce the disorder in the Fe wire array, the easy direction changes. As for the model that the every other Fe atoms are slightly closer to the Au step (approx 0.0091 nm) the easy direction turns to be perpendicular to the wire and parallel to the Au plane, that is, the dislocation direction. The disorder in the Fe wire seems to play significant roll in the anisotropy.

Evolution of soils on quaternary reef terraces of Barbados, West Indies

USGS Publications Warehouse

Muhs, D.R.

2001-01-01

Soils on uplifted Quaternary reef terraces of Barbados, ???125,000 to ???700,000 yr old, form a climo-chronosequence and show changes in physical, chemical, and mineralogical properties with terrace age. Parent materials are dust derived from the Sahara, volcanic ash from the Lesser Antilles island arc, and detrital carbonate from the underlying reef limestone. Although some terrace soils are probably eroded, soils or their remnants are redder and more clay-rich with increasing terrace age. Profile-average Al2O3 and Fe2O3 content increases with terrace age, which partially reflects the increasing clay content, but dithionite-extractable Fe also increases with terrace age. Profile-average K2O/TiO2, Na2O/TiO2, and P2O5/TiO2 values decrease with terrace age, reflecting the depletion of primary minerals. Average SiO2/Al2O3 values also decrease with terrace age and reflect not only loss of primary minerals but also evolution of secondary clay minerals. Although they are not present in any of the parent materials, the youngest terrace soils are dominated by smectite and interstratified kaolinite-smectite, which gradually alter to relatively pure kaolinite over ???700,000 yr. Comparisons with other tropical islands, where precipitation is higher and rates of dust fall may be lower, show that Barbados soils are less weathered than soils of comparable age. It is concluded that many soil properties in tropical regions can be potentially useful relative-age indicators in Quaternary stratigraphic studies, even when soils are eroded or changes in soil morphology are not dramatic. ?? 2001 University of Washington.

Revised history of the great Kanto earthquakes from the ages of Holocene marine terraces

NASA Astrophysics Data System (ADS)

Komori, J.; Shishikura, M.; Ando, R.; Yokoyama, Y.; Miyairi, Y.

2017-12-01

The Sagami Trough, where the Philippine Sea Plate subducts beneath the continental plate of the Japanese Archipelago, is considered to be a typical example where characteristic earthquakes repeat. Previous studies in some decades claimed that approximate M8 interplate earthquakes, called Genroku type earthquakes, occur with the interval of 2,000―2,700 years. In this study, we measured the emergence ages of the marine terraces in the Chikura lowland, which lies to the southeast of the Boso Peninsula, to reevaluate the history of the great earthquake over the past 10,000 years. The dates of the marine terraces are measured via radiocarbon dating of shell fossils obtained from the marine deposits. The sampling method employed in this study collects core samples using a dense and systematic drilling survey, which increased the reliability when correlating shell fossils with marine terraces. Moreover, we explored the surface profiles of the terraces with detailed digital elevation model (DEM) data obtained using LiDAR. The maximum emergence ages of the marine terraces were dated at 6300 cal yBP, 3000 cal yBP, and 2200 cal yBP from the top terrace excepting the lowest terrace (which was estimated at AD1703). In addition, another previously unrecognized terrace was detected between the highest and the second terrace in both the dating and the geomorphological analyses and was dated at 5800 cal yBP. The newly obtained ages are nearly a thousand of years younger than previously estimated ages; consequently, the intervals of the great earthquakes that occurred along the Sagami Trough are estimated to be much shorter and more varied than those of previous estimations. This result indicates that the temporal pattern of the large earthquakes occur along the Sagami Trough does not follow a characteristic pattern as previously considered.

Coastal geomorphic conditions and styles of storm surge washover deposits from Southern Thailand

NASA Astrophysics Data System (ADS)

Phantuwongraj, Sumet; Choowong, Montri; Nanayama, Futoshi; Hisada, Ken-Ichiro; Charusiri, Punya; Chutakositkanon, Vichai; Pailoplee, Santi; Chabangbon, Akkaneewut

2013-06-01

The characteristics of tropical storm washover deposits laid down during the years 2007 to 2011 along the southern peninsular coast of the Gulf of Thailand (GOT) were described in relation to their different geomorphic conditions, including perched fan, washover terrace and sheetwash lineations preserved behind the beach zone within 100 m of the shoreline. As a result, washover terrace and sheetwash lineations were found where the beach configuration was uniform and promoted an unconfined flow. Non-uniform beach configurations that promoted a confined flow resulted in a perched fan deposit. Washover sediments were differentiated into two types based on sedimentary characteristics, including (i) a thick-bedded sand of multiple reverse grading layers and (ii) a medium-bedded sand of multiple normal grading layers. In the case of thick-bedded washover deposits, the internal sedimentary structures were characterized by the presence of sub-horizontal bedding, reverse grading, lamination, foreset bedding and wavy bedding, whereas, horizontal bedding, normal grading, and dunes were the dominant structures in the medium-bedded washover sand. Rip-up clasts were rare and recognized only in the washover deposits in the bottom unit, which reflects the condition when a mud supply was available. All washover successions were found in the landward inclined-bedding with a basal sharp contact. A high elevated beach ridge associated with a large swale at the backshore proved suitable for a thick-bedded washover type, whereas a small beach ridge with uniformly flat backshore topography promoted a medium-bedded washover sediment.

Uranium series ages of corals from the upper Pleistocene Mulege terrace, Baja California Sur, Mexico

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ashby, J.R.; Ku, T.L.; Minch, J.A.

1987-02-01

Specimens of Porites californica contained in the sediments of upper Pleistocene, +12-m marine terrace deposits developed on the east coast of the Baja California (Mexico) peninsula at Mulege have yielded /sup 239/Th//sup 234/U dates of 124 +/- 5 and 144 +/- 7 ka (+/- 1 sigma). These dates can be assigned to the well-documented late Pleistocene oxygen-isotope stage 5e high sea stand. Differences between the eustatic and present elevations of this terrace indicate average uplift rates since terrace formation of approximately 4 to 5 cm/1000 yr, indicating a relative stability and lack of major vertical deformation since the late Pleistocene.more » This terrace in the Mulege area can now be correlated with other marine terraces throughout the Baja California peninsula and southern California.« less

Consequences of Common Topological Rearrangements for Partition Trees in Phylogenomic Inference.

PubMed

Chernomor, Olga; Minh, Bui Quang; von Haeseler, Arndt

2015-12-01

In phylogenomic analysis the collection of trees with identical score (maximum likelihood or parsimony score) may hamper tree search algorithms. Such collections are coined phylogenetic terraces. For sparse supermatrices with a lot of missing data, the number of terraces and the number of trees on the terraces can be very large. If terraces are not taken into account, a lot of computation time might be unnecessarily spent to evaluate many trees that in fact have identical score. To save computation time during the tree search, it is worthwhile to quickly identify such cases. The score of a species tree is the sum of scores for all the so-called induced partition trees. Therefore, if the topological rearrangement applied to a species tree does not change the induced partition trees, the score of these partition trees is unchanged. Here, we provide the conditions under which the three most widely used topological rearrangements (nearest neighbor interchange, subtree pruning and regrafting, and tree bisection and reconnection) change the topologies of induced partition trees. During the tree search, these conditions allow us to quickly identify whether we can save computation time on the evaluation of newly encountered trees. We also introduce the concept of partial terraces and demonstrate that they occur more frequently than the original "full" terrace. Hence, partial terrace is the more important factor of timesaving compared to full terrace. Therefore, taking into account the above conditions and the partial terrace concept will help to speed up the tree search in phylogenomic inference.

Mechanisms of protein and virus crystal growth: An atomic force microscopy study of canavalin and STMV crystallization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Land, T.A.; De Yoreo, J.J.; Malkin, A.J.

1996-05-01

The evolution of surface morphology and step dynamics during growth of rhombohedral crystals of the protein canavalin and crystals of the cubic satellite tobacco mosaic virus (STMV) have been investigated for the first time by in situ atomic force microscopy. These two crystals were observed to grow by very different mechanisms. Growth of canavalin occurs on complex vicinal hillocks formed by multiple, independently acting screw dislocations. Small clusters were observed on the terraces. STMV on the other hand, was observed to grow by 2D nucleation of islands. No dislocations were found on the crystal. The results are used to determinemore » the growth mechanisms and estimate the fundamental materials parameters. The images also illustrate the important mechanism of defect incorporation and provide insight to the processes that limit the growth rate and uniformity of these crystals.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Muslimov, A. E., E-mail: amuslimov@mail.ru; Butashin, A. V.; Kanevsky, V. M.

The (001) cleavage surface of vanadium pentoxide (V{sub 2}O{sub 5}) crystal has been studied by scanning tunneling spectroscopy (STM). It is shown that the surface is not reconstructed; the STM image allows geometric lattice parameters to be determined with high accuracy. The nanostructure formed on the (001) cleavage surface of crystal consists of atomically smooth steps with a height multiple of unit-cell parameter c = 4.37 Å. The V{sub 2}O{sub 5} crystal cleavages can be used as references in calibration of a scanning tunneling microscope under atmospheric conditions both along the (Ñ…, y) surface and normally to the sample surfacemore » (along the z axis). It is found that the terrace surface is not perfectly atomically smooth; its roughness is estimated to be ~0.5 Å. This circumstance may introduce an additional error into the microscope calibration along the z coordinate.« less

Sulfur-induced structural motifs on copper and gold surfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Walen, Holly

The interaction of sulfur with copper and gold surfaces plays a fundamental role in important phenomena that include coarsening of surface nanostructures, and self-assembly of alkanethiols. Here, we identify and analyze unique sulfur-induced structural motifs observed on the low-index surfaces of these two metals. We seek out these structures in an effort to better understand the fundamental interactions between these metals and sulfur that lends to the stability and favorability of metal-sulfur complexes vs. chemisorbed atomic sulfur. The experimental observations presented here—made under identical conditions—together with extensive DFT analyses, allow comparisons and insights into factors that favor the existence ofmore » metal-sulfur complexes, vs. chemisorbed atomic sulfur, on metal terraces. We believe this data will be instrumental in better understanding the complex phenomena occurring between the surfaces of coinage metals and sulfur.« less

Role of codeposited impurities during growth. I. Explaining distinctive experimental morphology on Cu(0 0 1)

NASA Astrophysics Data System (ADS)

Hamouda, Ajmi Bh.; Sathiyanarayanan, Rajesh; Pimpinelli, Alberto; Einstein, T. L.

2011-01-01

A unified explanation of the physics underlying all the distinctive features of the growth instabilities observed on Cu vicinals has long eluded theorists. Recently, kinetic Monte Carlo studies showed that codeposition of impurities during growth could account for the key distinctive experimental observations [Hamouda , Phys. Rev. BPLRBAQ0556-280510.1103/PhysRevB.77.245430 77, 245430 (2008)]. To identify the responsible impurity atom, we compute the nearest-neighbor binding energies (ENN) and terrace diffusion barriers (Ed) for several candidate impurity atoms on Cu(0 0 1) using DFT-based VASP. Our calculations show that codeposition (with Cu) of midtransition elements, such as Fe, Mn, and W, could—in conjunction with substantial Ehrlich-Schwoebel barriers—cause the observed instabilities; when the experimental setup is considered, W emerges to be the most likely candidate. We discuss the role of impurities in nanostructuring of surfaces.

Magneto-optical rotation in cavity QED with Zeeman coherence

NASA Astrophysics Data System (ADS)

Sun, Hui; Jia, Xiaohua; Fan, Shuangli; Zhang, Hongjun; Guo, Hong

2018-06-01

We investigate theoretically the magneto-optical rotation in cavity QED system with atomic Zeeman coherence, which is established via coherent population trapping. Owing to Zeeman coherence, the ultranarrow transmission spectrum less than 1 MHz with gain can be achieved with a flat-top Faraday rotation angle. By controlling the parameters appropriately, the input probe components within the flat-top regime rotate with almost the same angle, and transmit through the cavity perpendicularly to the other components outside the flat-top regime. The concepts discussed here provide an important tool for perfect ultranarrow Faraday optical filter and quantum information processing.

Study on high-resolution representation of terraces in Shanxi Loess Plateau area

NASA Astrophysics Data System (ADS)

Zhao, Weidong; Tang, Guo'an; Ma, Lei

2008-10-01

A new elevation points sampling method, namely TIN-based Sampling Method (TSM) and a new visual method called Elevation Addition Method (EAM), are put forth for representing the typical terraces in Shanxi loess plateau area. The DEM Feature Points and Lines Classification (DEPLC) put forth by the authors in 2007 is perfected for depicting the main path in the study area. The EAM is used to visualize the terraces and the path in the study area. 406 key elevation points and 15 feature constrained lines sampled by this method are used to construct CD-TINs which can depict the terraces and path correctly and effectively. Our case study shows that the new sampling method called TSM is reasonable and feasible. The complicated micro-terrains like terraces and path can be represented with high resolution and high efficiency successfully by use of the perfected DEPLC, TSM and CD-TINs. And both the terraces and the main path are visualized very well by use of EAM even when the terrace height is not more than 1m.

Seventeenth-century uplift in eastern Hokkaido, Japan

USGS Publications Warehouse

Atwater, B.F.; Furakawa, R.; Hemphill-Haley, E.; Ikeda, Y.; Kashima, K.; Kawase, K.; Kelsey, H.M.; Moore, A.L.; Nanayama, F.; Nishimura, Y.; Odagiri, S.; Ota, Y.; Park, S.-C.; Satake, K.; Sawai, Y.; Shimokawa, K.

2004-01-01

Shores of eastern Hokkaido rose by perhaps 1 m a few centuries ago. The uplifted area extended at least 50 km along the southern Kuril Trench. It included the estuaries Akkeshi-ko and Hichirippu, on the Pacific coast, and Fu??ren-ko and Onneto??, which open to the Okhotsk Sea. At each estuary, intertidal and subtidal flats rose with respect to tide level; wetland plants colonized the emerging land; and peaty wetland deposits thereby covered mud and sand of the former flats. Previous work at Akkeshi-ko and Onneto?? showed that such emergence occurred at least three times in the past 3000 years. Volcanic-ash layers date the youngest emergence to the seventeenth century AD. New evidence from Akkeshi-ko, Hichirippu and Fu??ren-ko clarifies the age and amount of this youngest emergence. Much of it probably dates from the century's middle decades. Some of the newly emerged land remained above high tides into the middle of the eighteenth century or later. The emergence in the last half of the seventeenth century probably exceeded 0.5 m (inferred from stratigraphy and diatom palaeoecology) without far exceeding 1 m (estimated by comparing seventeenth- and eighteenth-century descriptions of Akkeshi-ko). The stratigraphy and palaeoecology of the emergence are better explained by tectonic uplift than by bay-mouth blockage, tidal-flat accretion or sea-level fall. Eastern Hokkaido needs occasional uplift, moreover, to help reconcile its raised marine terraces with its chronic twentieth-century subsidence. Because it took place above forearc mantle, eastern Hokkaido's seventeenth-century uplift probably lacks analogy with coseismic uplift that occurs above typical plate-boundary ruptures at subduction zones.

Consequences of Common Topological Rearrangements for Partition Trees in Phylogenomic Inference

PubMed Central

Minh, Bui Quang; von Haeseler, Arndt

2015-01-01

Abstract In phylogenomic analysis the collection of trees with identical score (maximum likelihood or parsimony score) may hamper tree search algorithms. Such collections are coined phylogenetic terraces. For sparse supermatrices with a lot of missing data, the number of terraces and the number of trees on the terraces can be very large. If terraces are not taken into account, a lot of computation time might be unnecessarily spent to evaluate many trees that in fact have identical score. To save computation time during the tree search, it is worthwhile to quickly identify such cases. The score of a species tree is the sum of scores for all the so-called induced partition trees. Therefore, if the topological rearrangement applied to a species tree does not change the induced partition trees, the score of these partition trees is unchanged. Here, we provide the conditions under which the three most widely used topological rearrangements (nearest neighbor interchange, subtree pruning and regrafting, and tree bisection and reconnection) change the topologies of induced partition trees. During the tree search, these conditions allow us to quickly identify whether we can save computation time on the evaluation of newly encountered trees. We also introduce the concept of partial terraces and demonstrate that they occur more frequently than the original “full” terrace. Hence, partial terrace is the more important factor of timesaving compared to full terrace. Therefore, taking into account the above conditions and the partial terrace concept will help to speed up the tree search in phylogenomic inference. PMID:26448206

When is a terrace not a terrace? The importance of understanding landscape evolution in studies of terraced agriculture.

PubMed

Ferro-Vázquez, C; Lang, C; Kaal, J; Stump, D

2017-11-01

Before the invention of modern, large-scale engineering projects, terrace systems were rarely built in single phases of construction, but instead developed gradually, and could even be said to have evolved. Understanding this process of landscape change is therefore important in order to fully appreciate how terrace systems were built and functioned, and is also pivotal to understanding how the communities that farmed these systems responded to changes; whether these are changes to the landscape brought about by the farming practices themselves, or changes to social, economic or climatic conditions. Combining archaeological stratigraphy, soil micromorphology and geochemistry, this paper presents a case-study from the historic and extensive terraced landscape at Konso, southwest Ethiopia, and demonstrates - in one important river valley at least - that the original topsoil and much of the subsoil was lost prior to the construction of hillside terraces. Moreover, the study shows that alluvial sediment traps that were built adjacent to rivers relied on widespread hillside soil erosion for their construction, and strongly suggests that these irrigated riverside fields were formerly a higher economic priority than the hillside terraces themselves; a possibility that was not recognised by numerous observational studies of farming in this landscape. Research that takes into account how terrace systems change through time can thus provide important details of whether the function of the system has changed, and can help assess how the legacies of former practices impact current or future cultivation. Copyright © 2017 Elsevier Ltd. All rights reserved.

Evaluation of Light Detection and Ranging (LIDAR) for measuring river corridor topography

USGS Publications Warehouse

Bowen, Z.H.; Waltermire, R.G.

2002-01-01

LIDAR is relatively new in the commercial market for remote sensing of topography and it is difficult to find objective reporting on the accuracy of LIDAR measurements in an applied context. Accuracy specifications for LIDAR data in published evaluations range from 1 to 2 m root mean square error (RMSEx,y) and 15 to 20 cm RMSEz. Most of these estimates are based on measurements over relatively flat, homogeneous terrain. This study evaluated the accuracy of one LIDAR data set over a range of terrain types in a western river corridor. Elevation errors based on measurements over all terrain types were larger (RMSEz equals 43 cm) than values typically reported. This result is largely attributable to horizontal positioning limitations (1 to 2 m RMSEx,y) in areas with variable terrain and large topographic relief. Cross-sectional profiles indicated algorithms that were effective for removing vegetation in relatively flat terrain were less effective near the active channel where dense vegetation was found in a narrow band along a low terrace. LIDAR provides relatively accurate data at densities (50,000 to 100,000 points per km2) not feasible with other survey technologies. Other options for projects requiring higher accuracy include low-altitude aerial photography and intensive ground surveying.

Desert agricultural terrace systems at EBA Jawa (Jordan) - Layout, water availability and efficiency

NASA Astrophysics Data System (ADS)

Meister, Julia; Krause, Jan; Müller-Neuhof, Bernd; Portillo, Marta; Reimann, Tony; Schütt, Brigitta

2016-04-01

Located in the arid basalt desert of northeastern Jordan, the Early Bronze Age (EBA) settlement of Jawa is by far the largest and best preserved archaeological EBA site in the region. Recent surveys in the close vicinity revealed well-preserved remains of three abandoned agricultural terrace systems. In the presented study these archaeological features are documented by detailed mapping and the analysis of the sediment records in a multi-proxy approach. To study the chronology of the terrace systems optically stimulated luminescence (OSL) is used. In order to evaluate the efficiency of the water management techniques and its impact on harvest yields, a crop simulation model (CropSyst) under today's climatic conditions is applied, simulating crop yields with and without (runoff) irrigation. In order to do so, a runoff time series for each agricultural terrace system and its catchment is generated, applying the SCS runoff curve number method (CN) based on rainfall and soil data. Covering a total area of 38 ha, irrigated terrace agriculture was practiced on slopes, small plateaus, and valleys in the close vicinity of Jawa. Floodwater from nearby wadis or runoff from adjacent slopes was collected and diverted via surface canals. The terraced fields were arranged in cascades, allowing effective water exploitation through a system of risers, canals and spillways. The examined terrace profiles show similar stratigraphic sequences of mixed unstratified fine sediments that are composed of small-scale relocated sediments with local origin. The accumulation of these fines is associated with the construction of agricultural terraces, forcing infiltration and storage of the water within the terraces. Two OSL ages of terrace fills indicate that the construction of these terrace systems started as early as 5300 ± 300 a, which fits well to the beginning of the occupation phase of Jawa at around 3.500 calBC, thus making them to the oldest examples of its kind in the Middle East known to date. The results for simulating yields of different crops and under different irrigation scenarios showed that simulated mean grain yields were greater under supplemental irrigation. Thereby, yields usually increase considerably with increasing catchment size and thus (runoff) irrigation. Moreover, there is a significant decrease of crop failures under irrigation. Overall, these agricultural terrace systems seem to have been very efficient and their construction required a good understanding of the local climate, hydrology, geomorphology & pedology.

Atomic-scale and pit-free flattening of GaN by combination of plasma pretreatment and time-controlled chemical mechanical polishing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Deng, Hui; Endo, Katsuyoshi; Yamamura, Kazuya, E-mail: yamamura@upst.eng.osaka-u.ac.jp

2015-08-03

Chemical mechanical polishing (CMP) combined with atmospheric-pressure plasma pretreatment was applied to a GaN (0001) substrate. The irradiation of a CF{sub 4}-containing plasma was proven to be very useful for modifying the surface of GaN. When CMP was conducted on a plasma-irradiated surface, a modified layer of GaF{sub 3} acted as a protective layer on GaN by preventing the formation of etch pits. Within a short duration (8 min) of CMP using a commercially available CeO{sub 2} slurry, an atomically flat surface with a root mean square (rms) roughness of 0.11 nm was obtained. Moreover, etch pits, which are inevitably introduced inmore » conventional CMP, could not be observed at the dislocation sites on the polished GaN surface. It was revealed that CMP combined with the plasma pretreatment was very effective for obtaining a pit-free and atomically flat GaN surface.« less

Uplift rates of the marine terraces in the south coast of Japan deduced from in situ cosmogenic 10Be and 26Al

NASA Astrophysics Data System (ADS)

Yokoyama, Y.; Nagano, G.; Nakamura, A.; Maemoku, H.; Miyairi, Y.; Matsuzaki, H.

2015-12-01

Marine terraces are low-relief platforms located along coastal areas. They are formed by waves action with the changes in the relative sea level (RSL) that is affected by combined effects of the eustatic sea level (ESL) and the tectonic movements (e.g. uplift, subsidence and isostatic effect). Therefore, determining the ages and the elevations of the marine terraces allows us to reconstruct the ESL and/or the tectonic history of the study area. The Kii Peninsula and the southern coast of the Shikoku Island are located along the Nankai Trough where the Philippine Sea Plate is subducting under the Eurasian plate. There exist relatively well-preserved marine terraces along the coastal line with the elevation of ca. 50 -100 m. Because of this unique tectonic setting, the terraces are regarded as the suitable counterparts to reconstruct uplift history of the south coast of Japan. However, the ages of these terraces are poorly understood due to the lack of the ash layers that is suitable for the tephrochronology. In this study, we determine the age of the marine terraces using terrestrial in-situ cosmogenic radionuclides (TCN), 10Be and 26Al. This is the first age estimation of the marine terraces in Japan using TCN, allowing us to determine the uplift rates and the seismic history of the region.

Geology and ground-water hydrology of the Angostura irrigation project, South Dakota, with a section on the mineral quality of the waters

USGS Publications Warehouse

Littleton, Robert T.; Swenson, Herbert A.

1949-01-01

The lands to be irrigated from water stored in the Angostura Reservoir are situated on the lover of two terraces along the southeast side of the Cheyenne River in northeastern Fall River County and on the terrace known as Harrison Plat in southeastern Custer County, S. Dak. The terrace deposits are composed of relatively permeable sands and gravels that rest on a shale bedrock platform. The terrace surfaces are mantled in part by slope wash derived from higher shale slopes and by wind-blown sand. Ground water occurs under water-table conditions in the river alluvium and in terraces above the river. Although the zone of saturation in the terrace deposits is 6enerally thin, it is essentially continuous in the area southeast of the river, and the water issues as springs in the terrace faces along the inner valley of the river and along the valleys of tributary streams cuttin6 back into the terraces. A zone of saturation is present only in part of the Harrison Plat area, and it extends to the terrace face only along Cottonwood Creek. Wells in the unconsolidated mantle rock supply water for domestic and stock purposes, but yields are small. Abundant supplies of artesian water are available at depths ranging up to 3,000 feet but are not now utilized except at the extreme western end of the area where the bedrock aquifer is close below the surface. The effect of applying irrigation water on the terrace lands will depend on the character of the underlying material and on the measures taken to forestall waterlogging and other undesirable effects. Terrace areas that are mantled by slope wash will be especially susceptible to waterlogging, as will valley-bottom areas mantled by colluvium that are adjacent to irrigated terracea. Periodic measurements of water levels in observation wells will give warning of potential waterlogging in time to permit taking preventive measures. Analyses of samples of both ground water and surface water indicate a high mineral content. In general, samples from the Cheyenne River are higher in total dissolved solids and lower in percent sodium than the ground water.

Terrace aggradation during the 1978 flood on Powder River, Montana, USA

USGS Publications Warehouse

Moody, J.A.; Meade, R.H.

2008-01-01

Flood processes no longer actively increase the planform area of terraces. Instead, lateral erosion decreases the area. However, infrequent extreme floods continue episodic aggradation of terraces surfaces. We quantify this type of evolution of terraces by an extreme flood in May 1978 on Powder River in southeastern Montana. Within an 89-km study reach of the river, we (1) determine a sediment budget for each geomorphic feature, (2) interpret the stratigraphy of the newly deposited sediment, and (3) discuss the essential role of vegetation in the depositional processes. Peak flood discharge was about 930??m3 s- 1, which lasted about eight??days. During this time, the flood transported 8.2??million tons of sediment into and 4.5??million tons out of the study reach. The masses of sediment transferred between features or eroded from one feature and redeposited on the same feature exceeded the mass transported out of the reach. The flood inundated the floodplain and some of the remnants of two terraces along the river. Lateral erosion decreased the planform area of the lower of the two terraces (~ 2.7??m above the riverbed) by 3.2% and that of the higher terrace (~ 3.5??m above the riverbed) by 4.1%. However, overbank aggradation, on average, raised the lower terrace by 0.16??m and the higher terrace by 0.063??m. Vegetation controlled the type, thickness, and stratigraphy of the aggradation on terrace surfaces. Two characteristic overbank deposits were common: coarsening-upward sequences and lee dunes. Grass caused the deposition of the coarsening-upward sequences, which had 0.02 to 0.07??m of mud at the base, and in some cases, the deposits coarsened upwards to coarse sand on the top. Lee dunes, composed of fine and very fine sand, were deposited in the wake zone downstream from the trees. The characteristic morphology of the dunes can be used to estimate some flood variables such as suspended-sediment particle size, minimum depth, and critical shear velocity. Information about depositional processes during extreme floods is rare, and therefore, the results from this study aid in interpreting the record of terrace stratigraphy along other rivers.

Do agricultural terraces and forest fires recurrence in Mediterranean afforested micro-catchments alter soil quality and soil nutrient content?

NASA Astrophysics Data System (ADS)

E Lucas-Borja, Manuel; Calsamiglia, Aleix; Fortesa, Josep; García-Comendador, Julián; Gago, Jorge; Estrany, Joan

2017-04-01

Bioclimatic characteristics and intense human pressure promote Mediterranean ecosystems to be fire-prone. Afforestation processes resulting from the progressive land abandonment during the last decades led to greater biomass availability increasing the risk of large forest fires. Likewise, the abandonment and lack of maintenance in the terraced lands constitute a risk of land degradation in terms of soil quantity and quality. Despite the effects of fire and the abandonment of terraced lands on soil loss and physico-chemical properties are identified, it is not clearly understood how wildfires and abandonment of terraces affect soil quality and nutrients content. Microbiological soil parameters and soil enzymes activities are biomarkers of the soil microbial communitýs functional ability, which potentially enables them as indicators of change, disturbance or stress within the soil community. The objective of this study was to investigate the effects of terracing (abandoned and non-abandoned) on the soil enzyme activities, microbiological soil parameters and soil nutrients dynamics in three Mediterranean afforested micro-catchments (i.e., < 2 ha) under different forest fire recurrence in the last 20 years; i.e., unburned areas, burned once and burned twice. The combination of the presence of terraces and the recurrence of forest fire, thirty-six plots of 25 m2 were sampled along the these three micro-catchments collecting four replicas at the corners of each plot. The results elucidated how non-terraced and unburned plots presented the highest values of soil respiration rate and extracellular soil enzymes. Differences between experimental plots with different forest fire recurrence or comparing terraced and unburned plots with burned plots were weaker in relation to biochemical and microbiological parameters. Soil nutrient content showed an opposite trend with higher values in terraced plots, although differences were weaker. We conclude that terraced landscapes present poorer soil quality parameters due to land abandonment and the lack of terraced management. In addition, forest fire recurrence exacerbates soil degradation processes due to the direct effects on vegetation and soil properties.

Terrace Layout Using a Computer Assisted System

USDA-ARS?s Scientific Manuscript database

Development of a web-based terrace design tool based on the MOTERR program is presented, along with representative layouts for conventional and parallel terrace systems. Using digital elevation maps and geographic information systems (GIS), this tool utilizes personal computers to rapidly construct ...

Ripple formation on atomically flat cleaved Si surface with roughness of 0.038 nm rms by low-energy Ar{sup 1+} ion bombardment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pahlovy, Shahjada A.; Mahmud, S. F.; Yanagimoto, K.

The authors have conducted research regarding ripple formation on an atomically flat cleaved Si surface by low-energy Ar{sup +} ion bombardment. The cleaved atomically flat and smooth plane of a Si wafer was obtained by cutting vertically against the orientation of a Si (100) wafer. Next, the cleaved surface was sputtered by a 1 keV Ar{sup +} ion beam at ion-incidence angles of 0 deg., 60 deg., 70 deg., and 80 deg. The results confirm the successful ripple formation at ion-incidence angles of 60 deg. - 80 deg. and that the wavelength of the ripples increases with the increase ofmore » the ion-incidence angle, as well as the inverse of ion doses. The direction of the ripple also changes from perpendicular to parallel to the projection of the ion-beam direction along the surface with the increasing ion-incidence angle. The authors have also observed the dose effects on surface roughness of cleaved Si surface at the ion-incidence angle of 60 deg., where the surface roughness increases with the increased ion dose. Finally, to understand the roughening mechanism, the authors studied the scaling behavior, measured the roughness exponent {alpha}, and compared the evolution of scaling regimes with Cuerno's one-dimensional simulation results.« less

Quantification of surface uplift by using paleo beach deposits (Oman, Northern Indian Ocean)

NASA Astrophysics Data System (ADS)

Hoffmann, Gösta; Schneider, Bastian; Monschau, Martin; Mechernich, Silke

2017-04-01

The study focusses on a coastal area along the Arabian Sea in Oman. Here, a staircase of marine terraces is seen as geomorphological evidence suggesting sub-recent uplift of a crustal block in the northeast of the Arabian Peninsula. The erosional terraces are cut into Paleocene to Early Eocene limestone formations. These limestone formations are underlain by allochtonous ophiolites. We mapped the terraces over a distance of 60 km and identified at least 8 terrace levels in elevations up to 350 m above present sea level. The uppermost terraces are erosional, whereas the lower ones are depositional in style. Mollusc and coral remains as well as beach-rock are encountered on the terrace surfaces. The formations are dissected by NW-SE trending faults. Some of the terraces are very pronounced features in the landscape and easy to trace, others are partly eroded and preserved as remnants only. The deposit along the shoreline angle act as a datum making use of the fact that the rocks formed in a defined horizontal level which is the paleo-sea level. Hence, any offset from the primary depositional level is evidence for neotectonic movements. We utilise differential GPS to map the elevation of beachrock deposits. Age constraints on terrace formation is derived by sampling the beachrock deposits and dating using cosmogenic nuclii. The results indicate ongoing uplift in the range of less than a millimetre per year. The uplift is differential as the terraces are tilted. We mapped oblique normal and strike-slip faults in the younger terraces. We hypothesise that the mechanism responsible for the uplift is not tectonics but driven by the serpentinisation of the ophiolite that underlie the limestone formations. One process during the serpentinisation is the hydration of the mantle rocks which is responsible for a decrease in density. The resulting buoyancy and significant solid volume increase lead to the observed deformation including uplift.

The interaction of prehistoric human settlement, sea level change and tectonic uplift of the Coastal Range, eastern Taiwan

NASA Astrophysics Data System (ADS)

Yang, H.; Chen, W. S.

2017-12-01

The late Cenozoic mountain belt of Taiwan, resulting from the collision between the Eurasian and Philippine Sea plates, is known for its rapid tectonic uplift. As postglacial sea level rose ca. 15,000 yr ago, the eastern coast of Taiwan, due to the rapid tectonic uplift rate, displayed a totally different scenario comparing with most of the coastal plains around the world. At the beginning of postglacial era, the sea level rising rate was greater than the tectonic uplift rate which induced the original piedmont alluvial fan or coastal plain to be overwhelmed by sea water rapidly. Around 13.5 ka, the tectonic uplift rate caught up with the sea level rising and broad wave-cut platform formed. The approximation of tectonic uplift and sea level rising rates was lasting from 13.5 to 5ka, but shoreline progradation may have been enhanced by increased slope erosion which resulted in the alluvial fan forming at the later time of this period. As soon as the eustasy stabilized, the landmass continued to uplift which might have enhanced the river incising and wave erosion rapidly. Therefore the topographic expression along the eastern fringing of Coastal Range forms extended alluvial-fan, stream, and marine terraces and are covered by late Holocene colluvium and marine deposits. 88 archaeological sites were chosen in this study based on surface survey where the archaeological chronology of cultural stage is established primarily through examining pottery series and associated manual excavation. It is interesting that most of the archaeological sites were located on the alluvial fan although the Holocene marine terraces have formed after 5ka. There are no clear evidences to support a shore-oriented settlement, but the abundant alluvial depositional structures observed from the overlaying formation reveals the stream depositional system was still active at this time. If the Neolithic people wanted to come to the "new born" coastal region for the abundant ocean resources, they have to face the flat marine terraces should be still situated in inter-tidal or shallow sub-tidal zone and the alluvial fan where river began to incise might be a better choice for habitation.

The evolution of crop cultivation and paleoenvironment in the Longji Terraces, southern China: Organic geochemical evidence from paleosols.

PubMed

Jiang, Yongjian; Li, Shijie; Chen, Wei; Cai, Desuo; Liu, Yan

2017-11-01

The Longji ancient agricultural terraces in the Longji Mountain area (Guilin, southern China), which still remain in use, are famous for their magnificent terraced landscape with a mix of ecosystem and human inhabitation. Previous research has revealed the genesis and preliminary paleoenvironmental record of the agricultural terraces, but little is known about variations in crop cultivation over time. In this study, organic geochemical analyses and radiocarbon dating of an aggradational cultivated soil from a terrace profile were used to explore crop type variation and relevant paleoenvironmental change during the period of cultivation on the Longji Terraces. Hydroponic farming with rice (C 3 ) planting has been the dominant cultivation mode since the initial construction of the terraces. Warm-dry climate contributed to the growth of drought-tolerant crop (C 4 ) cultivation in the late 15th century. Temperature deterioration during the Little Ice Age had a negative impact on dry and hydroponic farming activities from the late 15th century to the late 19th century, while climate warming after the Little Ice Age promoted the redevelopment of hydroponic farming. Copyright © 2016 Elsevier Ltd. All rights reserved.

Evaluation of nekton use and habitat characteristics of restored Louisiana marsh

USGS Publications Warehouse

Thom, C.S.B.; Peyre, M.K.G.L.; Nyman, J.A.

2004-01-01

Marsh terracing and coconut fiber mats are two wetland restoration techniques implemented at Sabine National Wildlife Refuge, Louisiana, USA. Using nekton as an indicator of habitat quality, nekton community assemblages were compared between terraced, coconut-matted, unmanaged marsh (restoration goal), and open water (pre-restoration) habitats. Using a throw trap and a 3 m ?? 2 m straight seine, 192 nekton samples were collected over four dates in 2001 and 2002 at all habitats. Nekton abundance was similar at unmanaged marsh (restoration goal), coconut mat, and terrace edge, and significantly higher than at open water (pre-restoration) sites (P < 0.05). Coconut-matted habitat and unmanaged marsh edges had significantly higher numbers of benthic dependent species than terrace edges (P < 0.05), potentially because of differences in substrate. Terraced sites had lower organic matter and siltier substrate as compared to unmanaged marsh sites. At Sabine NWR, terracing increased nekton use as compared to pre-restoration conditions (open water samples) by providing marsh edge habitat, but failed to support a nekton community similar to unmanaged marsh (restoration goals) or coconut-matted sites. Future restoration projects may evaluate the combined use of coconut mats with terracing projects in order to enhance habitat for benthic dependent nekton.

Two C++ Libraries for Counting Trees on a Phylogenetic Terrace.

PubMed

Biczok, R; Bozsoky, P; Eisenmann, P; Ernst, J; Ribizel, T; Scholz, F; Trefzer, A; Weber, F; Hamann, M; Stamatakis, A

2018-05-08

The presence of terraces in phylogenetic tree space, that is, a potentially large number of distinct tree topologies that have exactly the same analytical likelihood score, was first described by Sanderson et al. (2011). However, popular software tools for maximum likelihood and Bayesian phylogenetic inference do not yet routinely report, if inferred phylogenies reside on a terrace, or not. We believe, this is due to the lack of an efficient library to (i) determine if a tree resides on a terrace, (ii) calculate how many trees reside on a terrace, and (iii) enumerate all trees on a terrace. In our bioinformatics practical that is set up as a programming contest we developed two efficient and independent C++ implementations of the SUPERB algorithm by Constantinescu and Sankoff (1995) for counting and enumerating trees on a terrace. Both implementations yield exactly the same results, are more than one order of magnitude faster, and require one order of magnitude less memory than a previous 3rd party python implementation. The source codes are available under GNU GPL at https://github.com/terraphast. Alexandros.Stamatakis@h-its.org. Supplementary data are available at Bioinformatics online.

High-Resolution Geologic Mapping of Martian Terraced Fan Deposits

NASA Astrophysics Data System (ADS)

Wolak, J. M.; Patterson, A. B.; Smith, S. D.; Robbins, N. N.

2018-06-01

This abstract documents our initial progress (year 1) mapping terraced fan features on Mars. Our objective is to investigate the role of fluids during fan formation and produce the first high-resolution geologic map (1:18k) of a terraced fan.

Matter-wave propagation in optical lattices: geometrical and flat-band effects

DOE PAGES

Metcalf, Mekena; Chern, Gia-Wei; Di Ventra, Massimiliano; ...

2016-03-17

Here we report that the geometry of optical lattices can be engineered allowing the study of atomic transport along paths arranged in patterns that are otherwise difficult to probe in the solid state. A question feasible to atomic systems is related to the speed of propagation of matter-waves as a function of the lattice geometry. To address this issue, we have investigated theoretically the quantum transport of non-interacting and weakly-interacting ultracold fermionic atoms in several 2D optical lattice geometries. We find that the triangular lattice has a higher propagation velocity compared to the square lattice, and the cross-linked square latticemore » has an even faster propagation velocity. The increase results from the mixing of the momentum states which leads to different group velocities in quantum systems. Standard band theory provides an explanation and allows for a systematic way to search and design systems with controllable matter-wave propagation. Moreover, the presence of a flat band such as in a two-leg ladder geometry leads to a dynamical density discontinuity due to its localized atoms. Lastly, we discuss possible realizations of those dynamical phenomena.« less

Uranium-Series Ages of Marine Terrace Corals from the Pacific Coast of North America and Implications for Last-Interglacial Sea Level History

USGS Publications Warehouse

Muhs, D.R.; Kennedy, G.L.; Rockwell, T.K.

1994-01-01

Few of the marine terraces along the Pacific coast of North America have been dated using uranium-series techniques. Ten terrace sequences from southern Oregon to southern Baja California Sur have yielded fossil corals in quantities suitable for U-series dating by alpha spectrometry. U-series-dated terraces representing the ???80,000 yr sea-level high stand are identified in five areas (Bandon, Oregon; Point Arena, San Nicolas Island, and Point Loma, California; and Punta Banda, Baja California); terraces representing the ???125,000 yr sea-level high stand are identified in eight areas (Cayucos, San Luis Obispo Bay, San Nicolas Island, San Clemente Island, and Point Loma, California; Punta Bands and Isla Guadalupe, Baja California; and Cabo Pulmo, Baja California Sur). On San Nicolas Island, Point Loma, and Punta Bands, both the ???80,000 and the ???125,000 yr terraces are dated. Terraces that may represent the ???105,000 sea-level high stand are rarely preserved and none has yielded corals for U-series dating. Similarity of coral ages from midlatitude, erosional marine terraces with coral ages from emergent, constructional reefs on tropical coastlines suggests a common forcing mechanism, namely glacioeustatically controlled fluctuations in sea level superimposed on steady tectonic uplift. The low marine terrace dated at ???125,000 yr on Isla Guadalupe, Baja California, presumed to be tectonically stable, supports evidence from other localities for a +6-m sea level at that time. Data from the Pacific Coast and a compilation of data from other coasts indicate that sea levels at ???80,000 and ???105,000 yr may have been closer to present sea level (within a few meters) than previous studies have suggested.

Ages of Quaternary Rio Grande terrace-fill deposits, Albuquerque area, New Mexico

USGS Publications Warehouse

,; Mahan, Shannon; Stone, Byron D.; Shroba, Ralph R.

2007-01-01

Results from luminescence dating on 13 samples from the Albuquerque area show that major-drainage fluvial deposits represent significant periods of aggradation that formed paired, correlatable terraces on the east and west margins of the Rio Grande valley . The youngest terrace fills (Primero Alto) formed during late Pleistocene as a result of streamflow variations with climate cooling during Marine Oxygen-Isotope Stage 3; our ages suggest aggradation of the upper part of the fill occurred at about 47–40 ka . Deposits of the second (Segundo Alto) terraces reached maximum height during climate cooling in the early part of Marine Oxygen-Isotope Stage 5 as late as 90–98 ka (based on dated basalt flows) . Our luminescence ages show considerable scatter and tend to be younger (range from 63 ka to 162 ka) . The third (Tercero Alto) and fourth (Cuarto Alto) terraces are dated on the basis of included volcanic tephra. Tercero Alto terrace-fill deposits contain the Lava Creek B tephra (639 ka), and Cuarto Alto terrace-fill deposits contain tephra of the younger Bandelier Tuff eruption (1 .22 Ma), the Cerro Toledo Rhyolite (1 .47 Ma), and the older Bandelier Tuff eruption (1 .61 Ma). These periods of aggradation culminated in fluvial terraces that are preserved at maximum heights of 360 ft (Cuarto Alto), 300 ft. (Tercero Alto), 140 ft (Segundo Alto), and 60 ft. (Primero Alto) above the modern floodplain. Despite lithologic differences related to local source-area contributions, these terracefill deposits can be correlated across the Rio Grande and up- and down-valley for tens of miles based on maximum height of the terrace above the modern floodplain.

Using OSL to decipher past soil history in archaeological terraces, Judea Highlands, Israel

NASA Astrophysics Data System (ADS)

Porat, Naomi; Gadot, Yuval; Davidovich, Uri; Avni, Yoav; Avni, Gideon; Golan, Dani

2015-04-01

Archaeological terraces are the most prominent feature of the agricultural sphere in the hilly landscape throughout the Mediterranean. Using terrace walls for the artificial creation of arable plots of land was a major technological innovation that has completely altered the natural terrain. As such, the dating of these simply built features is of upmost importance. Archaeological excavations and OSL dating of the soil infill of terraces were carried out in three excavation areas at Mt. Eitan in the Judea Highlands, Israel. Previous survey showed that Mt. Eitan was settled continuously at least from the Middle Bronze Age (ca 3800 years ago) and until modern times. The OSL ages shows that all extant terraces were constructed in the past 550-200 years, in the Ottoman period. Older ages are limited only to the base of a few terraces, and they range from the Roman Period (ca 1800 years ago) to Mamluk times (ca 700 years ago). Many of the soil samples contain quartz grains with older ages, indicating incomplete bleaching of the sediment at the time of terrace construction. We used the finite mixture model to find out if there are distinct age clusters to these poorly bleached grains. Analyses were carried out on a compilation of all measured De values (small aliquots) from the entire study area, and for each area separately. Results show that the unbleached grains cluster into only a few periods and highlight four synchronous episodes of terrace building in the past 800 years. The Roman and Early Islamic periods are also represented, even in area where soils with such ages were not found. The unbleached grains preserve older episodes of terrace building no longer represented in the landscape.

Lithologic controls on valley width and strath terrace formation

NASA Astrophysics Data System (ADS)

Schanz, Sarah A.; Montgomery, David R.

2016-04-01

Valley width and the degree of bedrock river terrace development vary with lithology in the Willapa and Nehalem river basins, Pacific Northwest, USA. Here, we present field-based evidence for the mechanisms by which lithology controls floodplain width and bedrock terrace formation in erosion-resistant and easily friable lithologies. We mapped valley surfaces in both basins, dated straths using radiocarbon, compared valley width versus drainage area for basalt and sedimentary bedrock valleys, and constructed slope-area plots. In the friable sedimentary bedrock, valleys are 2 to 3 times wider, host flights of strath terraces, and have concavity values near 1; whereas the erosion-resistant basalt bedrock forms narrow valleys with poorly developed, localized, or no bedrock terraces and a channel steepness index half that of the friable bedrock and an average channel concavity of about 0.5. The oldest dated strath terrace on the Willapa River, T2, was active for nearly 10,000 years, from 11,265 to 2862 calibrated years before present (cal YBP), whereas the youngest terrace, T1, is Anthropocene in age and recently abandoned. Incision rates derived from terrace ages average 0.32 mm y- 1 for T2 and 11.47 mm y- 1 for T1. Our results indicate bedrock weathering properties influence valley width through the creation of a dense fracture network in the friable bedrock that results in high rates of lateral erosion of exposed bedrock banks. Conversely, the erosion-resistant bedrock has concavity values more typical of detachment-limited streams, exhibits a sparse fracture network, and displays evidence for infrequent episodic block erosion and plucking. Lithology thereby plays a direct role on the rates of lateral erosion, influencing valley width and the potential for strath terrace planation and preservation.

Spatial patterns of (137)Cs inventories and soil erosion from earth-banked terraces in the Yimeng Mountains, China.

PubMed

Zhang, Yunqi; Long, Yi; An, Juan; Yu, Xingxiu; Wang, Xiaoli

2014-10-01

The Yimeng Mountains is one of China's most susceptible regions to soil erosion. In this region, slopes are composed of granite- or gneiss-derived soils that are commonly cultivated using earth-banked terraces. Based on the (137)Cs measurement for nine reference cores, the present study analysed the spatial patterns of (137)Cs inventory and soil erosion using 105 sampling points in a seven-level earth-banked terrace system. The mean (137)Cs inventory, standard deviation, coefficient of variation, and allowable error for the nine reference cores were 987 Bq m(-2), 71 Bq m(-2), 7%, and 6%, respectively, values that may reflect the heterogeneity of the initial (137)Cs fallout deposit. Within each terrace, the (137)Cs inventory generally increases from the rear edge to the front edge, accompanied by a decrease in the erosion rate. This results from planation by tillage and rainfall runoff during the development of the earth-banked terraces. Across the entire seven-level terrace system, (137)Cs inventories decrease from the highest terrace downwards, but increase in the lower terraces, whereas erosion rate displays the opposite trend. These trends are the result of the combined effects of the earth-bank segmented hillslope, the limited protection of the earth banks, and rainfall runoff in combination with tillage. The high coefficients of variation of (137)Cs inventories for the 21 sampling rows, with a mean value of 44%, demonstrate the combined effects of variations in original microtopography, anthropogenic disturbance, the incohesive soils weathered from underlying granite, and the warm climate. Although earth-banked terraces can reduce soil erosion to some extent, the estimated erosion rates for the study area are still very high. Copyright © 2014 Elsevier Ltd. All rights reserved.

Wetting of flat gradient surfaces.

PubMed

Bormashenko, Edward

2018-04-01

Gradient, chemically modified, flat surfaces enable directed transport of droplets. Calculation of apparent contact angles inherent for gradient surfaces is challenging even for atomically flat ones. Wetting of gradient, flat solid surfaces is treated within the variational approach, under which the contact line is free to move along the substrate. Transversality conditions of the variational problem give rise to the generalized Young equation valid for gradient solid surfaces. The apparent (equilibrium) contact angle of a droplet, placed on a gradient surface depends on the radius of the contact line and the values of derivatives of interfacial tensions. The linear approximation of the problem is considered. It is demonstrated that the contact angle hysteresis is inevitable on gradient surfaces. Electrowetting of gradient surfaces is discussed. Copyright © 2018 Elsevier Inc. All rights reserved.

The effect of process parameters on Twin Wire Arc spray pattern shape

DOE PAGES

Hall, Aaron Christopher; McCloskey, James Francis; Horner, Allison Lynne

2015-04-20

A design of experiments approach was used to describe process parameter—spray pattern relationships in the Twin Wire Arc process using zinc feed stock in a TAFA 8835 (Praxair, Concord, NH, USA) spray torch. Specifically, the effects of arc current, primary atomizing gas pressure, and secondary atomizing gas pressure on spray pattern size, spray pattern flatness, spray pattern eccentricity, and coating deposition rate were investigated. Process relationships were investigated with the intent of maximizing or minimizing each coating property. It was determined that spray pattern area was most affected by primary gas pressure and secondary gas pressure. Pattern eccentricity was mostmore » affected by secondary gas pressure. Pattern flatness was most affected by primary gas pressure. Lastly, coating deposition rate was most affected by arc current.« less

The effect of process parameters on Twin Wire Arc spray pattern shape

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hall, Aaron Christopher; McCloskey, James Francis; Horner, Allison Lynne

A design of experiments approach was used to describe process parameter—spray pattern relationships in the Twin Wire Arc process using zinc feed stock in a TAFA 8835 (Praxair, Concord, NH, USA) spray torch. Specifically, the effects of arc current, primary atomizing gas pressure, and secondary atomizing gas pressure on spray pattern size, spray pattern flatness, spray pattern eccentricity, and coating deposition rate were investigated. Process relationships were investigated with the intent of maximizing or minimizing each coating property. It was determined that spray pattern area was most affected by primary gas pressure and secondary gas pressure. Pattern eccentricity was mostmore » affected by secondary gas pressure. Pattern flatness was most affected by primary gas pressure. Lastly, coating deposition rate was most affected by arc current.« less

Surface atomic structure of alloyed Mn 5Ge 3(0 0 0 1) by scanning tunneling microscopy

NASA Astrophysics Data System (ADS)

Kim, Howon; Jung, Goo-Eun; Yoon, Jong Keon; Chung, Kyung Hoon; Kahng, Se-Jong

Surface atomic structure of Mn 5Ge 3(0 0 0 1) is studied by scanning tunneling microscopy. Hexagonal honeycomb ordering is observed at high energy levels, ∣ E - EF∣ ˜ 1.2 eV, on the flat regions of three-dimensional Mn 5Ge 3 islands. At low energy levels, ∣ E - EF∣ ˜ 0.5 eV, however, atomic images exhibit dot-array and ring-array structures, which show complete and partial contrast inversion, compared to the honeycomb ordering. Experimental observations are discussed on the basis of possible atomic models.

Enhancement of magnetocaloric effect in the Gd 2Al phase by Co alloying

DOE PAGES

Huang, Z. Y.; Fu, H.; Hadimani, R. L.; ...

2014-11-14

We observe that Cu clusters grow on surface terraces of graphite as a result of physical vapor deposition in ultrahigh vacuum. We show that the observation is incompatible with a variety of models incorporating homogeneous nucleation and high level calculations of atomic-scale energetics. An alternative explanation, ion-mediated heterogeneous nucleation, is proposed and validated, both with theory and experiment. This serves as a case study in identifying when and whether the simple, common observation of metal clusters on carbon-rich surfaces can be interpreted in terms of homogeneous nucleation. We describe a general approach for making system-specific and laboratory-specific predictions.

Determining whether metals nucleate homogeneously on graphite: A case study with copper

DOE PAGES

Appy, David; Lei, Huaping; Han, Yong; ...

2014-11-05

In this study, we observe that Cu clusters grow on surface terraces of graphite as a result of physical vapor deposition in ultrahigh vacuum. We show that the observation is incompatible with a variety of models incorporating homogeneous nucleation and calculations of atomic-scale energetics. An alternative explanation, ion-mediated heterogeneous nucleation, is proposed and validated, both with theory and experiment. This serves as a case study in identifying when and whether the simple, common observation of metal clusters on carbon-rich surfaces can be interpreted in terms of homogeneous nucleation. We describe a general approach for making system-specific and laboratory-specific predictions.

Soil water management practices (terraces) helped to mitigate the 2015 drought in Ethiopia.

PubMed

Kosmowski, Frédéric

2018-05-31

While the benefits of soil water management practices relative to soil erosion have been extensively documented, evidence regarding their effect on yields is inconclusive. Following a strong El-Niño, some regions of Ethiopia experienced major droughts during the 2015/16 agricultural season. Using the propensity scores method on a nationally representative survey in Ethiopia, this study investigates the effect of two widely adopted soil water management practices - terraces and contour bunds - on yields and assesses their potential to mitigate the effects of climate change. It is shown that at the national level, terraced plots have slightly lower yields than non-terraced plots. However, data support the hypothesis that terraced plots acted as a buffer against the 2015 Ethiopian drought, while contour bunds did not. This study provides evidence that terraces have the potential to help farmer deal with current climate risks. These results can inform the design of climate change adaptation policies and improve targeting of soil water management practices in Ethiopia.

Soil chemistry and mineralogy of the Santa Cruz coastal terraces

USGS Publications Warehouse

Pinney, Colin; Aniku, Jacob; Burke, Raymond; Harden, Jennifer; Singer, Michael; Munster, Jennie

2002-01-01

Marine terraces in the central coast of California provide an opportunity to study a soil chronosequence in which similar materials (beach deposits) have been weathered under similar slope, climatic, and vegetation conditions during the Quaternary. The terraces between Santa Cruz and Año Nuevo, California, have been studied for decades and are thought to be one of the best example of marine terraces in California {Lawson (1893), Wilson (1907); Branner and others (1909), Rode (1930) Page and Holmes (1945), Alexander (1953), Bradley (1956, 1957, 1958, and 1965), Bradley and Addicott (1968), Clark (1966 and 1970), Jahns and Hamilton (1971), Lajoie and others (1972), Bradley and Griggs (1976). Hanks and others (1986), Aniku (1986), Fine and others (1988), Anderson (1990 and 1994), and Rosenbloom and Anderson (1994).} Here we report morphological, chemical, physical, and mineralogical data for the soils that were formed in deposits on the Santa Cruz marine terraces in order to examine soil characteristics as a function of increasing terrace age.

Terrace width variations in complex Mercurian craters and the transient strength of cratered Mercurian and lunar crust

NASA Technical Reports Server (NTRS)

Leith, Andrew C.; Mckinnon, William B.

1991-01-01

The effective cohesion of the cratered region during crater collapse is determined via the widths of slump terraces of complex craters. Terrace widths are measured for complex craters on Mercury; these generally increase outward toward the rim for a given crater, and the width of the outermost major terrace is generally an increasing function of crater diameter. The terrace widths on Mercury and a gravity-driven slump model are used to estimate the strength of the cratered region immediately after impact (about 1-2 MPa). A comparison with the previous study of lunar complex craters by Pearce and Melosh (1986) indicates that the transient strength of cratered Mercurian crust is no greater than that of the moon. The strength estimates vary only slightly with the geometric model used to restore the outermost major terrace to its precollapse configuration and are consistent with independent strength estimates from the simple-to-complex crater depth/diameter transition.

Oxidation-driven surface dynamics on NiAl(100)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qin, Hailang; Chen, Xidong; Li, Liang

Atomic steps, a defect common to all crystal surfaces, can play an important role in many physical and chemical processes. However, attempts to predict surface dynamics under nonequilibrium conditions are usually frustrated by poor knowledge of the atomic processes of surface motion arising from mass transport from/to surface steps. Using low-energy electron microscopy that spatially and temporally resolves oxide film growth during the oxidation of NiAl(100) we demonstrate that surface steps are impermeable to oxide film growth. The advancement of the oxide occurs exclusively on the same terrace and requires the coordinated migration of surface steps. The resulting piling upmore » of surface steps ahead of the oxide growth front progressively impedes the oxide growth. This process is reversed during oxide decomposition. The migration of the substrate steps is found to be a surface-step version of the well-known Hele-Shaw problem, governed by detachment (attachment) of Al atoms at step edges induced by the oxide growth (decomposition). As a result, by comparing with the oxidation of NiAl(110) that exhibits unimpeded oxide film growth over substrate steps, we suggest that whenever steps are the source of atoms used for oxide growth they limit the oxidation process; when atoms are supplied from the bulk, the oxidation rate is not limited by the motion of surface steps.« less

Oxidation-driven surface dynamics on NiAl(100)

DOE PAGES

Qin, Hailang; Chen, Xidong; Li, Liang; ...

2014-12-29

Atomic steps, a defect common to all crystal surfaces, can play an important role in many physical and chemical processes. However, attempts to predict surface dynamics under nonequilibrium conditions are usually frustrated by poor knowledge of the atomic processes of surface motion arising from mass transport from/to surface steps. Using low-energy electron microscopy that spatially and temporally resolves oxide film growth during the oxidation of NiAl(100) we demonstrate that surface steps are impermeable to oxide film growth. The advancement of the oxide occurs exclusively on the same terrace and requires the coordinated migration of surface steps. The resulting piling upmore » of surface steps ahead of the oxide growth front progressively impedes the oxide growth. This process is reversed during oxide decomposition. The migration of the substrate steps is found to be a surface-step version of the well-known Hele-Shaw problem, governed by detachment (attachment) of Al atoms at step edges induced by the oxide growth (decomposition). As a result, by comparing with the oxidation of NiAl(110) that exhibits unimpeded oxide film growth over substrate steps, we suggest that whenever steps are the source of atoms used for oxide growth they limit the oxidation process; when atoms are supplied from the bulk, the oxidation rate is not limited by the motion of surface steps.« less

New Quaternary geochronometric constraints on river incision in the Virginia Piedmont: Relative contributions of climate, base-level fall, knickpoint retreat, and active tectonics

NASA Astrophysics Data System (ADS)

Malenda, Helen Fitzgerald

River terraces are fluvial landforms that represent flood plains abandoned through river incision and, when accurately correlated and dated, can serve as paleogeodetic markers, indicating the elevation and location of past channels and the subsequent fluvial and tectonic processes shaping the landscape. Fluvial terraces are most useful when the incision processes that caused their abandonment and formation are better understood. This thesis studies river incision reconstructed from fluvial terraces of the South Anna River in the central Virginia Piedmont, USA. The South Anna River flows directly above an active fault, on which large, but infrequent seismic events have occurred, and the most recent event was the 23 August 2011 Mineral earthquake. Two conceptual incision models are tested to better understand the fluvial response to active tectonics in this region: 1) spatially-uniform vertical incision and 2) diachronous horizontal knickpoint retreat. Here, terraces and incision were evaluated in the context of a 1:24,000 scale surficial map of alluvial deposits, optically stimulated luminescence (OSL) and infrared luminescence (IRSL) geochronology, and knickpoint celerity modeling. The South Anna River and its tributaries traverse across the geologic, topographic and structural grain of central Virginia Piedmont, USA, a region known for Late Cenozoic base-level fall, high amplitude climate changes, and historic seismicity. Litho- and pedostratigraphically correlative deposits are found to form five groups of terraces (Qt1-Qt5) with similar, but not exact relative elevations above modern channel. Within these groups, the terraces have similar OSL/IRSL ages that do not systematically decrease in age upstream towards knickpoint in the modern channel. Similarly, the modeled rate of knickpoint retreat through the South Anna channel of ~7-14km/Ma is too slow to explain the time-transgressive OSL/IRSL dates for any terrace group. Terrace formation by knickpoint migration and horizontal floodplain abandonment is rejected as a dominant process in terrace formation, in favor of more spatially-uniform vertical incision. In this landscape, the OSL/IRSL results suggest that flood plains are widened and then are abandoned and become terraces as the South Anna channel responds to climatically-driven unsteady changes in discharge and sediment yield. The complex age-elevation relationships of terraces proximal to epicenter of the 23 August 2011 Mineral earthquake argue for a terrace correlation that allows for rock uplift consistent with the co-seismic response of the 2011 Mineral earthquake.

Implementing automatic LiDAR and supervised mapping methodologies to quantify agricultural terraced landforms at landscape scale: the case of Veneto Region

NASA Astrophysics Data System (ADS)

Eugenio Pappalardo, Salvatore; Ferrarese, Francesco; Tarolli, Paolo; Varotto, Mauro

2016-04-01

Traditional agricultural terraced landscapes presently embody an important cultural value to be deeply investigated, both for their role in local heritage and cultural economy and for their potential geo-hydrological hazard due to abandonment and degradation. Moreover, traditional terraced landscapes are usually based on non-intensive agro-systems and may enhance some important ecosystems services such as agro-biodiversity conservation and cultural services. Due to their unplanned genesis, mapping, quantifying and classifying agricultural terraces at regional scale is often critical as far as they are usually set up on geomorphologically and historically complex landscapes. Hence, traditional mapping methods are generally based on scientific literature and local documentation, historical and cadastral sources, technical cartography and aerial images visual interpretation or, finally, field surveys. By this, limitations and uncertainty in mapping at regional scale are basically related to forest cover and lack in thematic cartography. The Veneto Region (NE of Italy) presents a wide heterogeneity of agricultural terraced landscapes, mainly distributed within the hilly and Prealps areas. Previous studies performed by traditional mapping method quantified 2,688 ha of terraced areas, showing the higher values within the Prealps of Lessinia (1,013 ha, within the Province of Verona) and in the Brenta Valley (421 ha, within the Province of Vicenza); however, terraced features of these case studies show relevant differences in terms of fragmentation and intensity of terraces, highlighting dissimilar degrees of clusterization: 1.7 ha on one hand (Province of Verona) and 1.2 ha per terraced area (Province of Vicenza) on the other one. The aim of this paper is to implement and to compare automatic methodologies with traditional survey methodologies to map and assess agricultural terraces in two representative areas of the Veneto Region. Testing different Remote Sensing analyses such as LiDAR topography survey and visual interpretation from aerial orthophotos (RGB+NIR bands) we performed a territorial analysis in the Lessinia and Brenta Valley case studies. Preliminary results show that terraced feature extraction by automatic LiDAR survey is more efficient both in identifying geometries (walls and terraced surfaces) and in quantifying features under the forest canopy; however, traditional mapping methodology confirms its strength by matching different methods and different data such as aerial photo, visual interpretation, maps and field surveys. Hence, the two methods here compared represent a cross-validation and let us to better know the complexity of this kind of landscape.

Experimental Investigation of the Formation of Complex Craters

NASA Astrophysics Data System (ADS)

Martellato, E.; Dörfler, M. A.; Schuster, B.; Wünnemman, K.; Kenkmann, T.

2017-09-01

The formation of complex impact craters is still poorly understood, because standard material models fail to explain the gravity-driven collapse at the observed size-range of a bowl-shaped transient crater into a flat-floored crater structure with a central peak or ring and terraced rim. To explain such a collapse the so-called Acoustic Fluidization (AF) model has been proposed. The AF assumes that heavily fractured target rocks surrounding the transient crater are temporarily softened by an acoustic field in the wake of an expanding shock wave generated upon impact. The AF has been successfully employed in numerous modeling studies of complex crater formation; however, there is no clear relationship between model parameters and observables. In this study, we present preliminary results of laboratory experiments aiming at relating the AF parameters to observables such as the grain size, average wave length of the acoustic field and its decay time τ relative to the crater formation time.

A process-based algorithm for simulating terraces in SWAT

USDA-ARS?s Scientific Manuscript database

Terraces in crop fields are one of the most important soil and water conservation measures that affect runoff and erosion processes in a watershed. In large hydrological programs such as the Soil and Water Assessment Tool (SWAT), terrace effects are simulated by adjusting the slope length and the US...

Exploring the spatial heterogeneity of terraced landscapes using LiDAR: the Slope Local Length of Auto-Correlation (SLLAC).

NASA Astrophysics Data System (ADS)

Sofia, Giulia; Marinello, Francesco; Tarolli, Paolo

2014-05-01

Terraces represent an outstanding example that displays centuries of a ubiquitous human-Earth interaction, in a very specific and productive way, and they are a significant part of numerous local economies. They, in fact, optimise the local resources for agricultural purposes, but also exploit marginal landscapes, expanding local populations. The ubiquity, variety, and importance of terraces have motivated studies designed to understand them better both as cultural and ecological features, but also as elements that can deeply influence runoff generation and propagation, contributing to local instabilities, and triggering or aggravating land degradation processes. Their vulnerability in the face of fast-growing urban settlements and the changes in agricultural practices is also well known, prompting protection measures strongly supported by local communities, but also by national and international projects. This work explores the spatial heterogeneity of terraced landscapes, identifying a proper indicator able to discriminate a terraced landscape respect to a more natural one. Recognizing and characterizing terraced areas can offer important multi-temporal insights into issues such as agricultural sustainability, indigenous knowledge systems, human-induced impact on soil degradation or erosive and landslide processes, geomorphological and pedologic processes that influence soil development, and climatic and biodiversity changes. More in detail, the present work introduces a new morphological indicator from LiDAR, effectively implementable for the automatic characterization of terraced landscapes. For the study, we tested the algorithm for environments that differ in term of natural morphology and terracing system. Starting from a LiDAR Digital Terrain Models (DTM), we considered the local auto-correlation (~local self-similarity) of the slope, calculating the correlation between a slope patch and its surrounding areas. We define the resulting map as the "Slope Local Length of Auto-Correlation", or SLLAC map. The SLLAC map texture is characterized by the presence of peculiar elongated fibers that change depending on the landscape morphology, and on the type of terracing system. The differences in texture can be measured, and they can be used to discriminate terraced areas from more natural ones. Given the raising importance of these landscapes, the proposed procedure can offer an important and promising tool to explore the spatial heterogeneity of terraced sites.

Tectonic influences on the preservation of marine terraces: Old and new evidence from Santa Catalina Island, California

USGS Publications Warehouse

Schumann, R. Randall; Minor, Scott A.; Muhs, Daniel R.; Groves, Lindsey T.; McGeehin, John P.

2012-01-01

The California Channel Islands contain some of the best geologic records of past climate and sea-level changes, recorded in uplifted, fossil-bearing marine terrace deposits. Among the eight California Channel Islands and the nearby Palos Verdes Hills, only Santa Catalina Island does not exhibit prominent emergent marine terraces, though the same terrace-forming processes that acted on the other Channel Islands must also have occurred on Santa Catalina. We re-evaluated previous researchers' field evidence and examined new topographic, bathymetric, and stream-profile data in order to find possible explanations for the lack of obvious marine terrace landforms or deposits on the island today. The most likely explanation is associated with the island's unresolved tectonic history, with evidence for both recent uplift and subsidence being offered by different researchers. Bathymetric and seismic reflection data indicate the presence of submerged terrace-like landforms from a few meters below present sea level to depths far exceeding that of the lowest glacial lowstand, suggesting that the Catalina Island block may have subsided, submerging marine terraces that would have formed in the late Quaternary. Similar submerged marine terrace landforms exist offshore of all of the other California Channel Islands, including some at anomalously great depths, but late Quaternary uplift is well documented on those islands. Therefore, such submarine features must be more thoroughly investigated and adequately explained before they can be accepted as definitive evidence of subsidence. Nevertheless, the striking similarity of the terrace-like features around Santa Catalina Island to those surrounding the other, uplifting, Channel Islands prompted us to investigate other lines of evidence of tectonic activity, such as stream profile data. Recent uplift is suggested by disequilibrium stream profiles on the western side of the island, including nickpoints and profile convexities. Rapid uplift is also indicated by the island's highly dissected, steep topography and abundant landslides. A likely cause of uplift is a restraining bend in the offshore Catalina strike-slip fault. Our analysis suggests that Santa Catalina Island has recently experienced, and may still be experiencing, relatively rapid uplift, causing intense landscape rejuvenation that removed nearly all traces of marine terraces by erosion. A similar research approach, incorporating submarine as well as subaerial geomorphic data, could be applied to many tectonically active coastlines in which a marine terrace record appears to be missing.

Mass movements and infiltration on abandoned terraces in the Iberian Range, Northern Spain

NASA Astrophysics Data System (ADS)

Arnáez, José; Lana-Renault, Noemí; Ruiz-Flaño, Purificación; Pascual, Nuria; Lasanta, Teodoro

2017-04-01

Terraced slopes were one of the most common agricultural landscapes in mountain areas of the Mediterranean region. Built to ensure agricultural production, terraces have acted as an effective soil conservation system at both slope and catchment scale. Demographic and socioeconomic changes in the last 60 years in the Mediterranean mountains have led to the abandonment of terraces. The consequent lack of maintenance of such agricultural structures has triggered diverse erosion processes. At the beginning of the 20th century, the upper valleys of the Leza, Jubera and Cidacos rivers, in the Iberian range (northern Spain), held more than 10,000 inhabitants and a cultivated area of 21,021 ha, of which 13,274 ha were farming terraces (63% of the agricultural space). At present, these terraces are abandoned. The most common erosion processes on the walls of abandoned terraces are stone collapses, which leave the riser completely unprotected, and small mass movements. A total amount of 240 terrace failures with mass movement were identified in the 53 studied plots, which means an average number of 4.5 per plot and 10.6 per 100 m of wall. At plot scale, the average volume of debris was 15.1 m3 (33.1 m3 for every 100 m of wall). Soil infiltration capacity and the way the water flows downslope may be the main triggers for mass movements. Rainfall simulations carried out in the study area showed an average infiltration coefficient above 75%. Infiltration coefficients were higher on concave hillslopes (above 85%), probably because the plots in these sectors were intensively tilled in the past, with plowed and permeable anthropogenic soils. The infiltrated water becomes a destabilizing factor for the terrace wall. The lack of deep percolation due to a more impermeable substrate (e.g., the original soil of the slope) favours the accumulation of water within the artificial soil, behind the stone wall. The increasing weight of the material can cause the activation of mass movements. The information obtained can be useful to identify the sectors prone to soil erosion due to terrace failure, and thus help to preserve terraces more efficiently. Acknowledgement This research was supported by the ESPAS project (CGL2015-65569-R, funded by the MINECO-FEDER)

Scanning tuneeling microscopy studies of fivefold surfaces of icosahedral Al-Pd-Mn quasicrystals and of thin silver films on those surfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Unal, Baris

2008-01-01

The present work in this dissertation mainly focuses on the clean fivefold surfaces of i-Al-Pd-Mn quasicrystals as well as the nucleation and growth of Ag films on these surfaces. In addition, Ag film growth on NiAl(110) has been explored in the frame of this dissertation. First, we have investigated the equilibration of a fivefold surface of icosahedral Al-Pd-Mn quasicrystal at 900-915 K and 925-950 K, using Omicron variable temperature scanning tunneling microscope (STM). Annealing at low temperatures resulted in many voids on some terraces while the others were almost void-free. After annealing at 925-950K, void-rich terraces became much rarer. Ourmore » STM images suggest that through growth and coalescence of the voids, a different termination becomes exposed on host terraces. All of these observations in our study indicate that even after the quasicrystalline terrace-step structure appears, it evolves with time and temperature. More specifically, based on the STM observations, we conclude that during the annealing a wide range of energetically similar layers nucleate as surface terminations, however, with increasing temperature (and time) this distribution gets narrower via elimination of the metastable void-rich terraces. Next, we have examined the bulk structural models of icosahedral Al-Pd-Mn quasicrystal in terms of the densities, compositions and interplanar spacings for the fivefold planes that might represent physical surface terminations. In our analyses, we mainly have focused on four deterministic models which have no partial or mixed occupancy but we have made some comparisons with an undeterministic model. We have compared the models with each other and also with the available experimental data including STM, LEED-IV, XPD and LEIS. In all deterministic models, there are two different families of layers (a pair of planes), and the nondeterministic model contains similar group of planes. These two families differ in terms of the chemical decoration of their top planes. Hence, we name them as Pd +(with Pd) and Pd-(without Pd). Based on their planer structure and the step height, it can be said that these two families can be viable surface terminations. However, besides the Pd content, these two sets differ in terms of relative densities of their top planes as well as the gap separating the layer from the nearest atomic plane. The experimental data and other arguments lead to the conclusion that the Pd- family is favored over the Pd +. This has an important implication on the interpretation of local motifs seen in the high resolution STM images. In other words, the dark stars are not formed by cut-Bergmans rather they are formed by cut-Mackays.« less

Spatial analysis of fluvial terraces in GRASS GIS accessing R functionality

NASA Astrophysics Data System (ADS)

Józsa, Edina

2017-04-01

Terrace research along the Danube is a major topic of Hungarian traditional geomorphology because of the socio-economic role of terrace surfaces and their importance in paleo-environmental reconstructions. Semi-automated mapping of fluvial landforms from a coherent digital elevation dataset allow objective analysis of hydrogeomorphic characteristics with low time and cost requirements. New results obtained with unified GIS-based algorithms can be integrated with previous findings regarding landscape evolution. The complementary functionality of GRASS GIS and R provides the possibility to develop a flexible terrain analysing tool for the delineation and quantifiable analysis of terrace remnants. Using R as an intermediate analytical environment and visualisation tool gives great added value to the algorithm, while GRASS GIS is capable of handling the large digital elevation datasets and perform the demanding computations to prepare necessary raster derivatives (Bivand, R.S. et al. 2008). The proposed terrace mapping algorithm is based on the work of Demoulin, A. et al. (2007), but it is further improved in the form of GRASS GIS script tool accessing R functionality. In the first step the hydrogeomorphic signatures of the given study site are explored and the area is divided along clearly recognizable structural-morphological boundaries.The algorithm then cuts up the subregions into parallel sections in the flow direction and determines cells potentially belonging to terrace surfaces based on local slope characteristics and a minimum area size threshold. As a result an output report is created that contains a histogram of altitudes, a swath-profile of the landscape, scatter plots to represent the relation of the relative elevations and slope values in the analysed sections and a final plot showing the longitudinal profile of the river with the determined height ranges of terrace levels. The algorithm also produces a raster map of extracted terrace remnants. From this dataset it is possible to interpolate a new digital elevation model approximating the former terraced valley surface using the Ordinary Kriging method (Troiani, F. and Della Seta, M. 2011). The applicability of the algorithm was tested on the northern foreland of Gerecse Mountains, an antecedent valley section of the Danube, with terrace remnants expected in 6 to 8 altitude ranges. Methodological issues arising from determining the optimal threshold values were explored using an artificial hillslope model, while the terrace profiles and terrace-top surfaces raster generated from the digital elevation model were validated with the previous findings of traditional geomorphological surveys. This research was supported by the Human Capacities Grant Management Office and the Hungarian Ministry of Human Capacities in the framework of the NTP-NFTÖ-16 project. References: Bivand, R.S. et al. (2008). Applied Spatial Data Analysis with R. New York: Springer. 378 p. Demoulin, A. et al. (2007). An automated method to extract fluvial terraces from digital elevation models: The Vesdre valley, a case study in eastern Belgium. - Geomorphology 91 (1-2): 51-64. Troiani, E. and Della Seta, M. (2011). Geomorphological response of fluvial and coastal terraces to Quaternary tectonics and climate as revealed by geostatistical topographic analysis. - Earth Surface Processes and Landforms 36: 1193-1208.

Post-eruptive Submarine Terrace Development of Capelinhos, Azores

NASA Astrophysics Data System (ADS)

Zhongwei Zhao, Will; Mitchell, Neil; Quartau, Rui; Tempera, Fernando; Bricheno, Lucy

2017-04-01

Erosion of the coasts of volcanic islands by waves creates shallow banks, but how erosion proceeds with time to create them and how it relates to wave climate is unclear. In this study, historical and recent marine geophysical data collected around the Capelinhos promontory (western Faial Island, Azores) offer an unusual opportunity to characterize how a submarine terrace developed after the eruption. The promontory was formed in 1957/58 during a Surtseyan eruption that terminated with extensive lava forming new rocky coastal cliffs. Historical measurements of coastline position are supplemented here with coastlines measured from 2004 and 2014 Google Earth images in order to characterize coastline retreat rate and distance for lava- and tephra-dominated cliffs. Swath mapping sonars were used to characterize the submarine geometry of the resulting terrace (terrace edge position, gradient and morphology). Limited photographs are available from a SCUBA dive and drop-down camera deployments to ground truth the submarine geomorphology. The results reveal that coastal retreat rates have decreased rapidly with the time after the eruption, possibly explained by the evolving resistance to erosion of cliff base materials. Surprisingly, coastline retreat rate decreases with terrace width in a simple inverse power law with terrace width. We suspect this is only a fortuitous result as wave attenuation over the terrace will not obviously produce the variation, but nevertheless it shows how rapidly the retreat rate declines. Understanding the relationship between terrace widening shelf and coastal cliff retreat rate may be more widely interesting if they can be used to understand how islands evolve over time into abrasional banks and guyots.

Quaternary fans and terraces in the Khumbu Himal south of Mount Everest: their characteristics, age and formation

USGS Publications Warehouse

Barnard, P.L.; Owen, L.A.; Finkel, R.C.

2006-01-01

Large fans and terraces are frequent in the Khumbu Himal within the high Himalayan valleys south of Mt. Everest. These features are composed of massive matrix- and clast-supported diamicts that were formed from both hyperconcentrated flows and coarse-grained debris flows. Cosmogenic radionuclide (CRN) exposure ages for boulders on fans and terraces indicate that periods of fan and terrace formation occurred at c. 16, c. 12, c. 8, c. 4 and c. 1.5 ka, and are broadly coincident with the timing of glaciation in the region. The dating precision is insufficient to resolve whether the surfaces formed before, during or after the correlated glacial advance. However, the sedimentology, and morphostratigraphic and geomorphological relationships suggest that fan and terrace sedimentation in this part of the Himalaya primarily occurs during glacier retreat and is thus paraglacial in origin. Furthermore, modern glacial-lake outburst floods and their associated deposits are common in the Khumbu Himal as the result of glacial retreat during historical times. We therefore suggest that Late Quaternary and Holocene fan and terrace formation and sediment transfer are probably linked to temporal changes in discharge and sediment load caused by glacier oscillations responding to climate change. The timing of major sedimentation events in this region can be correlated with fans and terraces in other parts of the Himalaya, suggesting that major sedimentation throughout the Himalaya is synchronous and tied to regional climatic oscillations. Bedrock incision rates calculated from strath terrace ages average c. 3.9 mm a−1, suggesting that the overall rate of incision is set by regional uplift.

Terrace effects on soil erosion processes in a watershed of the loess plateau

USDA-ARS?s Scientific Manuscript database

Terraces in crop fields are one of the most important soil and water conservation measures that affect runoff and erosion processes in a watershed. In this paper, terrace effects on soil erosion and sediment transport in the upstream and middle sections of the Weihe River basin in the Loess Plateau ...

MOLA Topographic Evidence for a Massive Noachian Ocean on Mars

NASA Technical Reports Server (NTRS)

Parker, T. J.; Grant, J. A.; Anderson, F. S.; Franklin, B. J.

2002-01-01

If the topographic terraces described are coastal, an ocean upwards of 5 to 7 km deep would be required by the maximum elevation of terraces identified south of Elysium Planitia. The highest terrace identified to date is at 2200 m elevation. Additional information is contained in the original extended abstract.

Cryoplanation terraces of interior and western Alaska

NASA Technical Reports Server (NTRS)

Reger, R. D.

1993-01-01

Cryoplanation terraces are step- or table like residual landforms consisting of a nearly horizontal bedrock surface covered by a thin veneer of rock debris and bounded by ascending or descending scarps or both. Among examples studied, rubble-covered scarps range in height from 3 to 76 m and slope from 9 deg to 32 deg; nearly vertical scarps exist where bedrock is exposed or thinly buried. Simple transverse nivation hollows, which are occupied by large seasonal snow banks, commonly indent the lower surfaces of sharply angular ascending scarps. Terrace treads slope from 1 deg to 10 deg and commonly cut across bedrock structures such as bedding, rock contacts, foliation, joints, faults, and shear zones. Debris on terrace treads is generally 0.8-2.5 m thick. Permafrost table is generally present from 0.5 to 2 m below the tread surface. Permafrost is shallowest in the floors of nivation hollows and deepest in the well-drained margins of terrace treads. Side slopes of cryoplanation terraces are shallowly buried bedrock surfaces that are littered with a variety of mass-movement deposits.

Hillslope terracing effects on the spatial variability of plant development as assessed by NDVI in vineyards of the Priorat region (NE Spain).

PubMed

Martínez-Casasnovas, José A; Ramos, María Concepción; Espinal-Utgés, Sílvia

2010-04-01

The availability of heavy machinery and the vineyard restructuring and conversion plans of the European Union Common Agricultural Policy (Commission Regulation EC no. 1227/2000 of 31 May 2000) have encouraged the restructuring of many vineyards on hillslopes of Mediterranean Europe, through the creation of terraces to favor the mechanization of agricultural work. Terrace construction requires cutting and filling operations that create soil spatial variability, which affects soil properties and plant development. In the present paper, we study the effects of hillslope terracing on the spatial variability of the normalized difference vegetation index (NDVI) in fields of the Priorat region (NE Spain) during 2004, 2005, and 2006. This index was computed from high-resolution remote sensing data (Quickbird-2). Detailed digital terrain models before and after terrace construction were used to assess the earth movements. The results indicate that terracing by heavy machinery induced high variability on the NDVI values over the years, showing significant differences as effect of the cut and fill operations.

1.5% root-mean-square flat-intensity laser beam formed using a binary-amplitude spatial light modulator.

PubMed

Liang, Jinyang; Kohn, Rudolph N; Becker, Michael F; Heinzen, Daniel J

2009-04-01

We demonstrate a digital micromirror device (DMD)-based optical system that converts a spatially noisy quasi-Gaussian to an eighth-order super-Lorentzian flat-top beam. We use an error-diffusion algorithm to design the binary pattern for the Texas Instruments DLP device. Following the DMD, a telescope with a pinhole low-pass filters the beam and scales it to the desired sized image. Experimental measurements show a 1% root-mean-square (RMS) flatness over a diameter of 0.28 mm in the center of the flat-top beam and better than 1.5% RMS flatness over its entire 1.43 mm diameter. The power conversion efficiency is 37%. We develop an alignment technique to ensure that the DMD pattern is correctly positioned on the incident beam. An interferometric measurement of the DMD surface flatness shows that phase uniformity is maintained in the output beam. Our approach is highly flexible and is able to produce not only flat-top beams with different parameters, but also any slowly varying target beam shape. It can be used to generate the homogeneous optical lattice required for Bose-Einstein condensate cold atom experiments.

Mechanism of formation of the response of a hydrogen gas sensor based on a silicon MOS diode

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gaman, V. I.; Balyuba, V. I.; Gritsyk, V. Yu.

2008-03-15

Experimental data on the dependence of the flat-band voltage and relaxation time for the capacitance of the space-charge region in an MOS diode (Pd-SiO{sub 2}-n-Si) on the hydrogen concentration in a hydrogen/air gaseous mixture are discussed. It is assumed that variation in the flat-band voltage U{sub fb} in an MOS structure with the thickness d = 369 nm subjected to a hydrogen/air gaseous mixture can be accounted for by the formation of dipoles in the Pd-SiO{sub 2} gap due to polarization of hydrogen atoms (H{sub a}). An analytical expression describing the dependence of variation in the flat-band voltage {Delta}U{sub fb}more » on the hydrogen concentration n{sub H{sub 2}} was derived. In MOS structures with d {<=} 4 nm (or MOS diodes), the value of {Delta}U{sub fb} is mainly controlled by passivation of the centers responsible for the presence of the surface acceptor-type centers at the SiO{sub 2}-n-Si interface by hydrogen atoms. Analytical expressions describing the dependences of {Delta}U{sub fb} and the capacitance relaxation time in the space-charge region on n{sub H{sub 2}} are derived. The values of the density of adsorption centers and the adsorption heat for hydrogen atoms at the Pd-SiO{sub 2} and SiO{sub 2}-n-Si interfaces are found.« less

Mechanism of formation of the response of a hydrogen gas sensor based on a silicon MOS diode

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gaman, V. I.; Balyuba, V. I.; Gritsyk, V. Yu.

2008-03-15

Experimental data on the dependence of the flat-band voltage and relaxation time for the capacitance of the space-charge region in an MOS diode (Pd-SiO{sub 2}-n-Si) on the hydrogen concentration in a hydrogen/air gaseous mixture are discussed. It is assumed that variation in the flat-band voltage U{sub fb} in an MOS structure with the thickness d = 369 nm subjected to a hydrogen/air gaseous mixture can be accounted for by the formation of dipoles in the Pd-SiO{sub 2} gap due to polarization of hydrogen atoms (H{sub a}). An analytical expression describing the dependence of variation in the flat-band voltage {delta}U{sub fb}more » on the hydrogen concentration n{sub H2} was derived. In MOS structures with d {<=} 4 nm (or MOS diodes), the value of {delta}U{sub fb} is mainly controlled by passivation of the centers responsible for the presence of the surface acceptor-type centers at the SiO{sub 2}-n-Si interface by hydrogen atoms. Analytical expressions describing the dependences of {delta}U{sub fb} and the capacitance relaxation time in the space-charge region on n{sub H2} are derived. The values of the density of adsorption centers and the adsorption heat for hydrogen atoms at the Pd-SiO{sub 2} and SiO{sub 2}-n-Si interfaces are found.« less

Ages and potential drivers of fluvial fill terrace formation in the southern-central Andes, NW Argentina

NASA Astrophysics Data System (ADS)

Tofelde, S.; Savi, S.; Wickert, A. D.; Wittmann, H.; Alonso, R. N.; Strecker, M. R.; Schildgen, T. F.

2015-12-01

Fluvial fill terraces record changes in past sediment to water discharge ratios. Across the world, fill terrace formation in glaciated catchments has been linked to variable sediment production and river discharge over glacial-interglacial cycles. However, pronounced fill terraces far from major glaciers and ice sheets have the potential to record a different set of climate forcings. So far, little is known about how changes in global climate on multi-millenial timescales affected the rainfall patterns in the interior of South America, or how those changes might be reflected in the landscape. Nonetheless, several studies in the Central Andes have linked terrace formation to precessionally-controlled changes in precipitation. In this study, we investigate the timing of fluvial fill terrace planation and abandonment in the Quebrada del Toro, an intermontane basin located in the Eastern Cordillera of the southern-central Andes in NW Argentina. Fluvial fills in the valley reach more than 100 m above the current river level. Within the fills, we observe a minimum of 5 terrace levels with pronounced differences in their extent and preservation. These fills document successive episodes of incision, punctuated by periods of lateral planation and possible partial re-filling. The filling and re-incision has previously been associated with tectonic activity in the basin, but the potential superposed role of climate cycles in forming terraces has not been considered. We sampled four CRN (10Be) depth profiles to date the abandonment of the broadest terrace surfaces, least affected by later overwash and erosion. The ages fall within the late Pleistocene (~ 80 ka to 400 ka). While the presence of inflationary soils beneath desert pavements make precise age determinations difficult, our preliminary calculations suggest a potential link to orbital eccentricity (~100 kyr) cycles, pointing to a different timescale of landscape response to climate forcing compared to previous studies.

Modelling and simulation of Holocene marine terrace development in Boso Peninsula, central Japan

NASA Astrophysics Data System (ADS)

Noda, Akemi; Miyauchi, Takahiro; Sato, Toshinori; Matsu'ura, Mitsuhiro

2018-04-01

In the southern part of Boso Peninsula, central Japan, we can observe a series of well-developed Holocene marine terraces. We modeled the development of these marine terraces by considering sea-level fluctuation and steady land uplift. The evolution of coastal landform is generally described as follows: altitude change = - erosion + deposition - sea-level rise + land uplift. In this study, the erosion rate is supposed to be proportional to the dissipation rate of wave energy, and the deposition rate of eroded materials to decay exponentially as they are transported seaward. The rate of sea-level rise is given by the time derivative of a sea-level curve obtained from the sediment core records of oxygen isotope ratios. Steady plate subduction generally brings about steady crustal uplift/subsidence independently of earthquake occurrence, and so the land-uplift rate is regarded as time independent on a long-term average. Our simulation results show that a pair of sea cliff and abrasion platform is efficiently formed about a stationary point of the sea-level curve. The Holocene sea-level curve has four peaks and three troughs, and so basically seven terraces are formed one by one during the past 10,000 yr. However, when the land-uplift rate is low, most of the terraces formed at older times sink in the sea. When the land-uplift rate is high, the overlap and/or reverse of older and younger terraces occur frequently, and so the correspondence between the age and present altitude of terraces is not necessarily one-to-one. Taking the land-uplift rate to be 3-4 mm/yr, we can reproduce a series of well-developed Holocene marine terraces in Boso Peninsula independently of coseismic uplifts. From these simulation results, we may conclude that the Holocene marine terraces in Boso Peninsula were developed as a result of the composite process of sea-level fluctuation and steady coastal uplift.

Growth of two-dimensional Ge crystal by annealing of heteroepitaxial Ag/Ge(111) under N2 ambient

NASA Astrophysics Data System (ADS)

Ito, Koichi; Ohta, Akio; Kurosawa, Masashi; Araidai, Masaaki; Ikeda, Mitsuhisa; Makihara, Katsunori; Miyazaki, Seiichi

2018-06-01

The growth of a two-dimensional crystal of Ge atoms on an atomically flat Ag(111) surface has been demonstrated by the thermal annealing of a heteroepitaxial Ag/Ge structure in N2 ambient at atmospheric pressure. The surface morphology and chemical bonding features of heteroepitaxial Ag(111) grown on wet-cleaned Ge(111) after annealing at different temperatures and for various times have been systematically investigated to control the surface segregation of Ge atoms and the planarization of the heteroepitaxial Ag(111) surface.

Tectonic geomorphology and paleoseismology of strike-slip faults in Jamaica: Implications for distribution of strain and seismic hazard along the southern edge of the Gonave microplate

NASA Astrophysics Data System (ADS)

Koehler, R. D.; Mann, P.; Brown, L. A.

2009-12-01

The east-west, left lateral strike-slip fault system forming the southern edge of the Gonave microplate crosses the110-km-long and 70-km-wide island of Jamaica. GPS measurements in the northeastern Caribbean are supportive of the microplate interpretation and indicate that ~ half of the Caribbean-North America left-lateral plate motion (8-14 mm/yr) is carried by the Plantain Garden (PGFZ) and associated faults in Jamaica. We performed Neotectonic mapping of the Plantain Garden fault along the southern rangefront of the Blue Mountains and conducted a paleoseismic study of the fault at Morant River. Between Holland Bay and Morant River, the fault is characterized by a steep, faceted, linear mountain front, prominent linear valleys and depressions, shutter ridges, and springs. At the eastern end of the island, the PGFZ is characterized by a left-stepping fault geometry that includes a major, active hot spring. The river cut exposure at Morant River exposes a 1.5-m-wide, sub-vertical fault zone juxtaposing sheared alluvium and faulted Cretaceous basement rocks. This section is overlain by an, unfaulted 3-m-thick fluvial terrace inset into a late Pleistocene terrace that is culturally modified. Upward fault terminations indicate the occurrence of three paleoearthquakes that occurred prior to deposition of the flat lying inset terrace around 341-628 cal yr BP. At this time, our radiocarbon results suggest that we can rule out the PGFZ as the source of the 1907 Kingston earthquake 102 years ago, as well as, the 1692 event that destroyed Port Royal 317 years ago and produced a major landslide at Yallahs. Pending OSL ages will constrain the age of the penultimate and most recent ruptures. Gently to steeply dipping rocks as young as Pliocene exposed in roadcuts within the low coastal hills south of and parallel to the Plantain Garden fault may indicate active folding and blind thrust faulting. These structures are poorly characterized and may accommodate an unknown amount of oblique strain. Reconnaissance mapping was also performed along the South Coast fault in south-central Jamaica north of Portland Ridge, and along the Crawle River-Rio Minho fault near Frankfield in the Central Inlier. The absence of fault scarps or other tectonic geomorphic features across fluvial terraces of the Milk and Minho Rivers indicate that the South Coast fault has not been active in Holocene time. Left laterally offset streams, linear valleys, and saddles support active faulting along the east-west Crawle River-Rio Minho fault that is roughly collinear with the western extension of the Plantain Garden fault.

Morphological evidence and direct estimates of rapid melting beneath Totten Glacier Ice Shelf, East Antarctica

NASA Astrophysics Data System (ADS)

Greenbaum, Jamin; Schroeder, Dustin; Grima, Cyril; Habbal, Feras; Dow, Christine; Roberts, Jason; Gwyther, David; van Ommen, Tas; Siegert, Martin; Blankenship, Donald

2017-04-01

Totten Glacier drains at least 3.5 meters of eustatic sea level potential from marine-based ice in the Aurora Subglacial Basin (ASB) in East Antarctica, more than the combined total of all glaciers in West Antarctica. Totten Glacier has been the most rapidly thinning glacier in East Antarctica since satellite altimetry time series began and the nature of the thinning suggests that it is driven by enhanced basal melting due to ocean processes. While grounded ice thinning rates have been steady, recent work has shown that Totten's floating ice shelf may not have the same thinning behavior; as a result, it is critical to observe ice shelf and cavity boundary conditions and basal processes to understand this apparent discrepancy. Warm Modified Circumpolar Deep Water (MCDW), which has been linked to glacier retreat in West Antarctica, has been observed in summer and winter on the nearby Sabrina Coast continental shelf and deep depressions in the seafloor provide access for MCDW to reach the ice shelf cavity. Given its northern latitude, numerical ice sheet modeling indicates that Totten Glacier may be prone to retreat caused by hydrofracture in a warming climate, so it is important to understand how intruding MCDW is affecting thinning of Totten Glacier's ice shelf. Here we use post-processed, focused airborne radar observations of the Totten Glacier Ice Shelf to delineate multi-km wide basal channels and flat basal terraces associated with high basal reflectivity and specularity (flatness) anomalies and correspondingly large ice surface depressions that indicate active basal melting. Using a simple temperature-attenuation model, and basal roughness corrections, we present basal melt rates associated with the radar reflection and specularity anomalies and compare them to those derived from numerical ocean circulation modeling and an ice flow divergence calculation. Sub-ice shelf ocean circulation modeling and under-ice robotic observations of Pine Island Glacier Ice Shelf in West Antarctica and the Petermann Glacier Ice Shelf in Greenland have shown that basal terraces associated with large basal channels are an indication of rapidly melting ice shelves. In this context, these new results identify an East Antarctic example of rapid basal melting processes and demonstrate that airborne radar can be used to identify basal characteristics and processes relevant to ice shelf stability.

Comparative Study of the Binding of Concanavalin A to Self-Assembled Monolayers Containing a Thiolated α-Mannoside on Flat Gold and on Nanoporous Gold

PubMed Central

Pandey, Binod; Tan, Yih Horng; Fujikawa, Kohki; Demchenko, Alexei V.

2013-01-01

We have prepared SAMs containing 8-mercaptooctyl α-D-mannopyranoside, either as a single component or in mixed SAMs with n-octanethiol on flat gold surfaces and on nanoporous gold. Electrochemical impedance spectroscopy showed that the mixed SAMs on flat gold surfaces showed the highest Con A binding near 1:9 solution molar ratio of thiolatedα-mannoside to n-octanethiol whereas those on NPG showed the highest response at 1:19 solution molar ratio of thiolated α-mannoside to n-octanethiol. Atomic force microscopy was employed to image the monolayers, and also to image the bound Con A protein. PMID:23519474

ESR dating marine terraces along the Mediterranean coast of the Antakya Graben, SE Turkey: Sea level change and tectonic implications

NASA Astrophysics Data System (ADS)

Tari, Ufuk; Tüysüz, Okan; Blackwell, Bonnie; Genç, Ş. Can; İmren, Caner; Florentin, Jonathan A.; Skinner, Anne

2015-04-01

In southeastern Turkey, NE-trending Antakya Graben forms an asymmetric depression filled by Pliocene marine siliciclastic sediment, Pleistocene to Recent fluvial terrace sediment and alluvium. A multi-segmented, dominantly sinistral fault lying along the graben possibly connects the Cyprus Arc in the west to the Amik Triple Junction on the Dead Sea Fault (DSF) in the east. Normal faults, bounding the southeastern margin caused the graben to tilt southeastward and these faults are younger than the sinistral ones. Westward escape of the continental İskenderun Block along the sinistral faults belonging to the DSF in the east and to the Eastern Anatolian Fault in the north caused Antakya Graben to open since Pliocene. In the later stages of this opening, normal faults developed along the southeastern of the graben, leading to differential uplift of the Mediterranean coastal terraces. Tectonic uplift coupled with sea level fluctuations has produced several stacked marine terraces at elevations ranging from 0.25 m to 180 m above current sea level along the Mediterranean coast. In this study we dated these terrace deposits by using electron spin resonance (ESR) method. In the NW part of the graben, terraces at 30 m above mean sea level (amsl) yield 63±8 ka and correlate with Marine Isotope Stage (MIS) 4. Older units dating to MIS 7 and 5 likely were being eroded to supply some fossils found in this terrace. On the 45 m amsl terrace dates to 114±7 ka, which is the MIS 5d/5e boundary. Terrace deposits at 105 m amsl belong to MIS 5c boundary at 91±13 ka. At Samandağ site at 39 m amsl, molluscs deposited in a large tidal channel indicate MIS 5d/5e boundary at 116 ± 5 ka. Contemporary sediments are seen in different elevations in the SE part of the graben. The youngest samples suggest an age 14±1 ka in the late MIS 2 for the slump topping the 8 m amsl terrace. At the 50 m amsl terrace dates to 89±5 ka and correlate with MIS 5a/5c. Here 180 m amsl terrace gave a preliminary age of 398 ± 24 ka, correlating with MIS 11. These data support that differential uplifting occurred in the Antakya Graben during the Quaternary and eustatic sea level changes in the Mediterranean have controlled the morphological evolution of the region. Uplift on the Mediterranean coast probably still continues, since the Paleolithic Merdivenli Cave sits at ~ 50 m amsl and the Middle Paleolithic Üçağızlı Cave sits at ~ 20 m amsl, and the ancient harbour, Seleucia Pierria now sits above sea level.

Wrinkle-free atomically thin CdS nanosheets for photocatalytic hydrogen evolution

NASA Astrophysics Data System (ADS)

Pan, Ziwei; Li, Junnan; Zhou, Kebin

2018-05-01

Two-dimensional (2D) nanosheets of atomic thickness have attracted extensive research interest recently. In this work, atomically thin (0.7 nm) flat CdS (F-CdS) nanosheets of several tens of micrometers in lateral size were synthesized by a solvent-thermal method. The as-synthesized F-CdS could maintain flat morphology well in solution, while irreversible wrinkles could be generated after drying, forming wrinkled CdS (W-CdS) samples. It was revealed that the formation of wrinkles could reduce light absorbance, narrow the band gap, move down the conduction band position and accelerate electron–hole recombination. As photocatalysts, the F-CdS achieved a photocatalytic H2 evolution rate of 138.7 mmol g‑1 h‑1 without any co-catalyst under visible light, which was much higher than that of the W-CdS sample (with an H2 evolution rate of only 52.8 mmol g‑1 h‑1). This work demonstrates that great attention should be paid to the wrinkles in 2D materials as photocatalysts.

Effect of Pd surface structure on the activation of methyl acetate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Lijun; Xu, Ye

2011-01-01

The activation of methyl acetate (CH3COOCH3; MA) has been studied using periodic density functional theory calculations to probe the effect of Pd surface structure on the selectivity in MA activation. The adsorption of MA, dehydrogenated derivatives, enolate (CH2COOCH3; ENL) and methylene acetate (CH3COOCH2; MeA), and several dissociation products (including acetate, acetyl, ketene, methoxy, formaldehyde, CO, C, O, and H); and C-H and C-O (mainly in the RCO-OR position) bond dissociation in MA, ENL, and MeA, are calculated on Pd(111) terrace, step, and kink; and on Pd(100) terrace and step. The adsorption of most species is not strongly affected between (111)-more » to (100)-type surfaces, but is clearly enhanced by step/kink compared to the corresponding terrace. Going from terrace to step edge and from (111)- to (100)-type surfaces both stabilize the transition states of C-O bond dissociation steps. Going from terrace to step edge also stabilizes the transition states of C-H bond dissociation steps, but going from (111)- to (100)-type surfaces does not clearly do so. We propose that compared to the Pd(111) terrace, the Pd(100) terrace is more selective for C-O bond dissociation that is desirable for alcohol formation, whereas the Pd step edges are more selective for C-H bond dissociation.« less

Modeling stream-bank erosion in the Southern Blue Ridge Mountains

Treesearch

James C. Rogers; David S. Leigh

2013-01-01

Deforestation, followed by soil erosion and subsequent deposition of alluvium in valleys, played a critical role in the formation of historical terraces in much of the Southern Blue Ridge Mountains. Such terraces add a significant amount of sediment to the tributaries of the region as streams laterally erode the terrace banks. This study examined the contribution of...

Laser-Induced Fluorescence and Performance Analysis of the Ultra-Compact Combustor

DTIC Science & Technology

2008-06-01

fiber as a sealant. .............................................................................................. 68  Figure 37. A view of AFIT’s flat...ratio cm Centimeters CO Carbon Monoxide CO2 Carbon Dioxide Cp Constant-pressure specific heat CxHy General formula of a hydrocarbon C2H4...Standard liters per minute T Temperature, thrust U Combustor inlet velocity v Velocity x Number of carbon atoms y Number of hydrogen atoms (A-X) OH

U-series ages of solitary corals from the California coast by mass spectrometry

USGS Publications Warehouse

Stein, Martin; Wasserburg, G.J.; Lajoie, K.R.; Chen, J.-H.

1991-01-01

The purpose of this study is to evaluate the feasibility of dating fossil solitary corals from Pleistocene marine strandlines outside tropical latitudes using the recently developed high sensitivity, high-precision U-series technique based on thermal-ionization mass-spectrometry (TIMS). The TIMS technique is much more efficient than conventional a spectrometry and, as a result, multiple samples of an individual coral skeleton, or different specimens from the same bed can be analyzed. Detached and well-rounded fossil specimens of the solitary coral Balanophyllia elegans were collected from relict littoral deposits on emergent marine terraces along the California coast at Cayucos terrace (elevation 8 m, previously dated at 124 and 117 Ky by ?? counting), Shell Beach terrace (elevation about 25 m, previously undated), Nestor terrace, San Diego (elevation 23 m, previously dated at 131 to 109 Ky ), Bird Rock terrace, San Diego ( elevation 8 m, previously dated at 81 Ky ). Attached living specimens were collected from the intertidal zone on the modern terrace at Moss Beach. Concentrations of 232Th in both living and fossil specimens are much higher than in reef-building corals (12 to 624 pmol/g vs. 0.1 to 1.6 pmol/g, respectively). However, because 230Th/232Th in Balanophyllia elegans are very low (2.22 ?? 10-3 to 4.33 ?? 10-4), the high 232Th concentrations have negligible effect on the 230Th-234U dates. The high 232Th concentration in the living specimen (33.1 pmol/g) indicates that a significant amount of 232Th is incorporated in the aragonitic skeleton during growth, or attached to clay-sized silicates trapped in the skeletal material. The calculated initial 234U activities in the fossil specimens of Balanophyllia elegans are higher than the 234U activity in modern seawater or in the modern specimen. The higher initial activities could possibly reflect the influx of 234U-enriched continental water into Pleistocene coastal waters, or it could reflect minor diagenetic alteration, a persistent and fundamental problem in dating all corals. Samples from a compound specimen from the Cayucos terrace were subjected to different preparation procedures. Samples prepared by a standard acid washing procedure yielded 230Th-234U ages of 125, 123, and 122 Ky, whereas samples prepared by an abbreviated procedure without acid washing yield significantly lower ages of 113 and 112 Ky. Two other specimens from the same bed yielded 230Th-234U ages of 118 and 115 Ky. Also, two specimens from a stratigraphically higher bed yielded ages of 120 and 117 Ky, and three specimens from a lower bed yield ages of 115, 113, and 101 Ky. Nine of the twelve ages of the treated samples from the Cayucos terrace range from 125 to 113 Ky. However, the ages do not follow the stratigraphie order. Two possible interpretations are ( 1 ) the age of the terrace deposit is 125 Ky and all younger ages reflect variable diagenetic alteration or (2) the age of the terrace is 125 to 113 Ky and the ages reflect sediment reworking over a period of 12 Ky. Three specimens from a single bed on the Shell Beach terrace yield ages of 126, 122, and 121 Ky, similar to the older ages from Cayucos. The ages of solitary corals from the Cayucos and Shell Beach terraces are similar to ages of reef-building corals from terraces at numerous tropical localities. These are correlated with the last interglacial sea-level highstand, which probably stood 2 to 10 m above present sea level. The youngest ages and present elevations of the Cayucos and Shell Beach terraces yield tectonic uplift rates of 0.01 and 0.15 m/Ky, respectively, assuming the original elevation of each terrace was 7 m. Four specimens from the basal gravel on the Nestor terrace yielded ages of 145, 143, 137, and 133 Ky. The three oldest ages, however, are older than that associated with the last interglacial. The possible explanations for these older ages are ( 1 ) diagenic alteration or ( 2 ) the Nestor terrace deposits reflect in s

Geohydrology of the alluvial and terrace deposits of the North Canadian River from Oklahoma City to Eufaula Lake, central Oklahoma

USGS Publications Warehouse

Havens, J.S.

1989-01-01

This investigation was undertaken to describe the geohydrology of the alluvial and terrace deposits along the North Canadian River between Lake Overholser and Eufaula Lake, an area of about 1,835 square miles, and to determine the maximum annual yield of ground water. A 1982 water-level map of the alluvial and terrace aquifer was prepared using field data and published records. Data from test holes and other data from the files of the U.S. Geological Survey and the Oklahoma Water Resources Board were used to establish the approximate thickness of the alluvial and terrace deposits. The North Canadian River from Lake Overholser, near Oklahoma City, to Eufaula Lake is paralleled by a 2- to 3-mile wide band of alluvium. Scattered terrace deposits on either side of the alluvium reach an extreme width of 8 miles. Rocks of Permian age bound the alluvial and terrace deposits from the west to the midpoint of the study area; Pennsylvanian rocks bound the alluvial and terrace deposits from that point eastward. Three major aquifers are present in the study area: the alluvial and terrace aquifer, consisting of alluvium and terrace deposits of Quaternary age in a narrow band on either side of the North Canadian River; the Garber-Wellington aquifer of Permian age, consisting of an upper unconfined zone and a lower confined zone separated by relatively impermeable shales; and the Ada-Vamoosa aquifer of Pennsylvanian age. At locations were the alluvial and terrace aquifer overlies either of the other aquifers, there is hydraulic continuity between the alluvial and terrace aquifer and the other aquifers, and water levels are the same. Most large-scale municipal and industrial pumping from the Garber-Wellington aquifer is from the lower zone and has little discernible effect upon the alluvial and terrace aquifer. The total estimated base flow of the North Canadian River for the studied reach is 264 cubic feet per second. Evapotranspiration from the basin in August is about 60 cubic feet per second for the North Canadian River from Lake Overholser to a measuring station above Eufaula Lake. Estimated recharge rates to the alluvial and terrace aquifer in the basin range from 1.7 inches at the west edge of the study area to 7.0 inches at the east edge. Total permitted withdrawal from the aquifer, according to records of the Oklahoma Water Resources Board, ranged from 2,107 acre-feet per year in 1942 to about 21,415 acre-feet per year in 1982. Simulations of the alluvial and terrace aquifer from Lake Overholser to Eufaula Lake were made using a finite-difference model developed by McDonald and Harbaugh (1984). The area of the aquifers was subdivided into a finite-difference grid having 30 rows and 57 columns with cells measuring 1 mile in the north-south direction and 2 miles in the east-west direction. The model was calibrated in two steps: A steady-state calibration simulated head distribution prior to extensive pumping of the aquifer in 1942, and a transient calibration simulated head distribution after extensive pumpage. The final horizontal hydraulic conductivity used for the alluvial and terrace aquifer was 0.0036 feet per second (310 feet per day) at all locations. The recharge rate for the alluvial and terrace aquifer ranged from 1.7 inch per year in the west to 7.0 inches per year in the east, and averaged about 3.3 inches per year. A specific yield of 15 percent was used for the transient simulation. Permitted pumpage for 1942 through 1982 was used in the digital model to estimate the annual volume of water in storage in the alluvial and terrace aquifer for the years for this time period. The 1982 permitted pumpage rates were used for projections for 1983 to 2020. The estimated volume of water in storage was 1,940,000 acre-feet in 1982. Because the estimated recharge rate is equal to the allowed pumpage rate in 1982, the projected volume of water in storage in both 1993 and 2020 was 1,890,000 acre-feet.

Structural characterization of bulk GaN crystals grown under high hydrostatic pressure

NASA Astrophysics Data System (ADS)

Liliental-Weber, Zuzanna; Kisielowski, C.; Ruvimov, S.; Chen, Y.; Washburn, J.; Grzegory, I.; Bockowski, M.; Jun, J.; Porowski, S.

1996-09-01

This paper describes TEM characterization of bulk GaN crystals grown at 1500-1800Kin the form of plates from a solution of atomic nitrogen in liquid gallium under high nitrogen pressure (up to 20 kbars). The x-ray rocking curves for these crystals were in the range of 20-30 arc-sec. The plate thickness along the c axis was about 100 times smaller than the nonpolar growth directions. A substantial difference in material quality was observed on the opposite sides of the plates normal to the c direction. On one side the surface was atomically flat, while on the other side the surface was rough, with pyramidal features up to 100 nm high. The polarity of the crystals was determined using convergent-beam electron diffraction. The results showed that, regarding the long bond between Ga and N along the c-axis, Ga atoms were found to be closer to the flat side of the crystal, while N atoms were found to be closer to the rough side. Near the rough side, within 1/10 to 1/4 of the plate thickness, there was a high density of planar defects (stacking faults and dislocation loops decorated by Ga/void precipitates). A model explaining the defect formation is proposed.

Traceable atomic force microscopy of high-quality solvent-free crystals of [6,6]-phenyl-C{sub 61}-butyric acid methyl ester

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lazzerini, Giovanni Mattia; Yacoot, Andrew; Paternò, Giuseppe Maria

2016-02-01

We report high-resolution, traceable atomic force microscopy measurements of high-quality, solvent-free single crystals of [6,6]-phenyl-C61-butyric acid methyl ester (PCBM). These were grown by drop-casting PCBM solutions onto the spectrosil substrates and by removing the residual solvent in a vacuum. A home-built atomic force microscope featuring a plane mirror differential optical interferometer, fiber-fed from a frequency-stabilized laser (emitting at 632.8 nm), was used to measure the crystals' height. The optical interferometer together with the stabilized laser provides traceability (via the laser wavelength) of the vertical measurements made with the atomic force microscope. We find that the crystals can conform to the surfacemore » topography, thanks to their height being significantly smaller compared to their lateral dimensions (namely, heights between about 50 nm and 140 nm, for the crystals analysed, vs. several tens of microns lateral dimensions). The vast majority of the crystals are flat, but an isolated, non-flat crystal provides insights into the growth mechanism and allows identification of “molecular terraces” whose height corresponds to one of the lattice constants of the single PCBM crystal (1.4 nm) as measured with X-ray diffraction.« less

Statistical analyses of soil properties on a quaternary terrace sequence in the upper sava river valley, Slovenia, Yugoslavia

USGS Publications Warehouse

Vidic, N.; Pavich, M.; Lobnik, F.

1991-01-01

Alpine glaciations, climatic changes and tectonic movements have created a Quaternary sequence of gravely carbonate sediments in the upper Sava River Valley, Slovenia, Yugoslavia. The names for terraces, assigned in this model, Gu??nz, Mindel, Riss and Wu??rm in order of decreasing age, are used as morphostratigraphic terms. Soil chronosequence on the terraces was examined to evaluate which soil properties are time dependent and can be used to help constrain the ages of glaciofluvial sedimentation. Soil thickness, thickness of Bt horizons, amount and continuity of clay coatings and amount of Fe and Me concretions increase with soil age. The main source of variability consists of solutions of carbonate, leaching of basic cations and acidification of soils, which are time dependent and increase with the age of soils. The second source of variability is the content of organic matter, which is less time dependent, but varies more within soil profiles. Textural changes are significant, presented by solution of carbonate pebbles and sand, and formation is silt loam matrix, which with age becomes finer, with clay loam or clayey texture. The oldest, Gu??nz, terrace shows slight deviation from general progressive trends of changes of soil properties with time. The hypothesis of single versus multiple depositional periods of deposition was tested with one-way analysis of variance (ANOVA) on a staggered, nested hierarchical sampling design on a terrace of largest extent and greatest gravel volume, the Wu??rm terrace. The variability of soil properties is generally higher within subareas than between areas of the terrace, except for the soil thickness. Observed differences in soil thickness between the areas of the terrace could be due to multiple periods of gravel deposition, or to the initial differences of texture of the deposits. ?? 1991.

The importance of understanding landscape evolution in studies of terraced agriculture

NASA Astrophysics Data System (ADS)

Ferro-Vazquez, Cruz; Lang, Carol; Kaal, Joeri; Stump, Daryl

2017-04-01

Before the invention of modern, large-scale engineering projects, terrace systems were rarely built in single phases of construction, but instead developed gradually, and could even be said to have evolved. Understanding this process of landscape change is therefore important in order to fully appreciate how terrace systems were built and functioned, and is also pivotal to understand how the communities that farmed these systems responded to changes; whether these are changes to the landscape brought about by the farming practices themselves, or changes to social, economic or climatic conditions. With this aim, we studied the historic and extensive terraced landscape at Konso, southwest Ethiopia, combining archaeological stratigraphy, soil micromorphology and geochemistry. Our results demonstrated that erosion has not only been the trigger for the inception of the Konso terraced system but also the foundation of its productivity: it was engineered for taking advantage of erosion by controlling it, first by harvesting soils that had washed into watercourses within irrigable riverside sediment traps, and then by effectively 'repopulating' the denuded hillsides with new soils through the construction of hillside terraces. From this new perspective, soil erosion has been a necessary enemy which, while managed, has constituted an agronomic resource, the system having initially relied on soil erosion to be productive, and the community having apparently only begun constructing terraces in order to protect the productive alluvial fields that were the legacy of that first phase of erosion. Research that takes into account how terrace systems change through time can thus provide important details of whether the function of the system has changed, and can help assess how the legacies of former practices impact current or future cultivation.

Agronomic Challenges and Opportunities for Smallholder Terrace Agriculture in Developing Countries.

PubMed

Chapagain, Tejendra; Raizada, Manish N

2017-01-01

Improving land productivity is essential to meet increasing food and forage demands in hillside and mountain communities. Tens of millions of smallholder terrace farmers in Asia, Africa, and Latin America who earn $1-2 per day do not have access to peer-reviewed knowledge of best agronomic practices, though they have considerable traditional ecological knowledge. Terrace farmers also lack access to affordable farm tools and inputs required to increase crop yields. The objectives of this review are to highlight the agronomic challenges of terrace farming, and offer innovative, low-cost solutions to intensify terrace agriculture while improving local livelihoods. The article focuses on smallholder farmers in developing nations, with particular reference to Nepal. The challenges of terrace agriculture in these regions include lack of quality land area for agriculture, erosion and loss of soil fertility, low yield, poor access to agricultural inputs and services, lack of mechanization, labor shortages, poverty, and illiteracy. Agronomic strategies that could help address these concerns include intensification of terraces using agro-ecological approaches along with introduction of light-weight, low-cost, and purchasable tools and affordable inputs that enhance productivity and reduce female drudgery. To package, deliver, and share these technologies with remote hillside communities, effective scaling up models are required. One opportunity to enable distribution of these products could be to "piggy-back" onto pre-existing snackfood/cigarette/alcohol distribution networks that are prevalent even in the most remote mountainous regions of the world. Such strategies, practices, and tools could be supported by formalized government policies dedicated to the well-being of terrace farmers and ecosystems, to maintain resiliency at a time of alarming climate change. We hope this review will inform governments, non-governmental organizations, and the private sector to draw attention to this neglected and vulnerable agro-ecosystem in developing countries.

The Pingding segment of the Altyn Tagh Fault (91 °E): Holocene slip-rate determination from cosmogenic radionuclide dating of offset fluvial terraces

DOE PAGES

Meriaux, A. -S.; Van der Woerd, J.; Tapponnier, P.; ...

2012-09-25

Morphochronologic slip-rates on the Altyn Tagh Fault (ATF) along the southern front of the Pingding Shan at ~90.5°E are determined by cosmogenic radionuclide (CRN) dating of seven offset terraces at two sites. The terraces are defined based upon morphology, elevation and dating, together with fieldwork and high-resolution satellite analysis. The majority of the CRN model ages fall within narrow ranges (<2 ka) on the four main terraces (T1, T2, T3 and T3′), and allow a detailed terrace chronology. Bounds on the terrace ages and offsets of 5 independent terraces yield consistent slip-rate estimates. The long-term slip-rate of 13.9 ± 1.1more » mm/yr is defined at the 95% confidence level, as the joint rate probability distribution of the rate derived from each independent terrace. It falls within the bounds of all the rates defined on the central Altyn Tagh Fault between the Cherchen He (86.4°E) and Akato Tagh (~88°E) sites. This rate is ~10 mm/yr less than the upper rate determined near Tura at ~87°E, in keeping with the inference of an eastward decreasing rate due to progressive loss of slip to thrusts branching off the fault southwards but it is greater than the 9 ± 4 mm/yr rate determined at ~90°E by GPS surveys and other geodetic short-term rates defined elsewhere along the ATF. Furthermore, whether such disparate rates will ultimately be reconciled by a better understanding of fault mechanics, resolved transient deformations during the seismic cycle or by more accurate measurements made with either approach remains an important issue.« less

Emergent Marine Terraces in Cebu Island, Philippines and Their Implications for Relative Sea Level Changes in the Late Quaternary

NASA Astrophysics Data System (ADS)

Ramos, N. T.; Sarmiento, K. J. S.; Maxwell, K. V.; Soberano, O. B.; Dimalanta, C. B.

2017-12-01

The remarkable preservation and extensive distribution of emergent marine terraces in the Philippines allow us to study relative sea level changes and tectonic processes during the Late Quaternary. While higher uplift rates and possible prehistoric coseismic events are recorded by emergent coral reefs facing subduction zones, the central Philippine islands are reported to reflect vertical tectonic stability as they are distant from trenches. To constrain the coastal tectonics of the central Philippine region, we studied emergent sea level indicators along the coasts of northern Cebu Island in Tabuelan, San Remigio, and Bogo City. Upper steps of marine terraces were interpreted from IFSAR-derived DEMs, in which at least two and seven steps were identified along the west (Tabuelan) and east (Bogo) coasts, respectively. In Tabuelan, two extensive terrace steps (TPT) were interpreted with TPT1 at 5-13 m above mean sea level (amsl) and TPT2 at 27-44 m amsl. Five to possibly seven terrace steps (BPT) were delineated in Bogo City with elevations from lowest (BPT1) to highest (BPT7) at BPT1: 4-6 m, BPT2: 12-18 m, BPT3: 27-33 m, BPT4: 39-46 m, BPT5: 59-71 m, BPT6: 80-92 m, and BPT7: 103-108 m amsl. These upper terraces are inferred to be Late Pleistocene in age based on an initial MIS 5e age reported for a 5-m-high terrace in Mactan Island. At some sites, even lower and narrower terrace surfaces were observed, consisting of cemented coral rubble that surround eroded and attached corals. These lower carbonate steps, with elevations ranging from 1 to 3 m amsl, further provide clues on relative sea level changes and long-term tectonic deformation across Cebu Island.

Geologic map of the Alley Spring quadrangle, Shannon County, Missouri

USGS Publications Warehouse

Weary, David J.; Orndorff, Randall C.

2012-01-01

The Alley Spring 7.5-minute quadrangle is located in south-central Missouri within the Salem Plateau region of the Ozark Plateaus physiographic province. About 1,990 feet (ft) of flat-lying to gently dipping Lower Paleozoic sedimentary rocks, mostly dolomite, chert, sandstone, and orthoquartzite, overlie Mesoproterozoic volcanic rocks. A small exposure of the volcanic rocks exists near the eastern edge of the quadrangle. Unconsolidated residuum, colluvium, terrace deposits, and alluvium overlie the sedimentary rocks. Karst features, such as sinkholes, caves, and springs, have formed in the carbonate rocks. Many streams are spring fed. Alley Spring, the largest karst spring in the quadrangle, has an average discharge of 81 million gallons per day. The topography is a dissected karst plain with elevation ranging from 630 ft where the Jacks Fork River exits the quadrangle to more than 1,140 ft at numerous places in the northern half of the quadrangle. The most prominent physiographic feature is the valley of the Jacks Fork River. Most of the land in the quadrangle is privately owned and used primarily for grazing cattle and horses and growing timber. A large minority of the land within the quadrangle is publicly owned, either by the Missouri State Forests or by the Ozark National Scenic Riverways of the National Park Service. Geologic mapping for this investigation was conducted in 2003 and 2004.

Sharp transition from ripple patterns to a flat surface for ion beam erosion of Si with simultaneous co-deposition of iron

NASA Astrophysics Data System (ADS)

Zhang, K.; Brötzmann, M.; Hofsäss, H.

2012-09-01

We investigate pattern formation on Si by sputter erosion under simultaneous co-deposition of Fe atoms, both at off-normal incidence, as function of the Fe surface coverage. The patterns obtained for 5 keV Xe ion irradiation at 30° incidence angle are analyzed with atomic force microscopy. Rutherford backscattering spectroscopy of the local steady state Fe content of the Fe-Si surface layer allows a quantitative correlation between pattern type and Fe coverage. With increasing Fe coverage the patterns change, starting from a flat surface at low coverage (< 2×1015 Fe/cm2) over dot patterns (2-8×1015 Fe/cm2), ripples patterns (8-17×1015 Fe/cm2), pill bug structures (1.8×1016 Fe/cm2) and a rather flat surface with randomly distributed weak pits at high Fe coverage (>1.8×1016 Fe/cm2). Our results confirm the observations by Macko et al. for 2 keV Kr ion irradiation of Si with Fe co-deposition. In particular, we also find a sharp transition from pronounced ripple patterns with large amplitude (rms roughness ˜ 18 nm) to a rather flat surface (rms roughness ˜ 0.5 nm). Within this transition regime, we also observe the formation of pill bug structures, i.e. individual small hillocks with a rippled structure on an otherwise rather flat surface. The transition occurs within a very narrow regime of the steady state Fe surface coverage between 1.7 and 1.8×1016 Fe/cm2, where the composition of the mixed Fe-Si surface layer of about 10 nm thickness reaches the stoichiometry of FeSi2. Phase separation towards amorphous iron silicide is assumed as the major contribution for the pattern formation at lower Fe coverage and the sharp transition from ripple patterns to a flat surface.

Oleophobic properties of the step-and-terrace sapphire surface

NASA Astrophysics Data System (ADS)

Muslimov, A. E.; Butashin, A. V.; Kanevsky, V. M.

2017-03-01

Sapphire is widely used in production of optical windows for various devices due to its mechanical and optical properties. However, during operation the surface can be affected by fats, oils, and other organic contaminations. Therefore, it is important to improve the oleophobic properties of sapphire windows. In this study, we investigate the interaction of a supersmooth sapphire surface with oleic acid droplets, which imitate human finger printing. It is established that chemical-mechanical polishing with additional annealing in air, which leads to the formation of an atomically smooth sapphire surface, makes it possible to significantly improve the oleophobic properties of the surface. The results are analyzed using the Ventsel-Deryagin homogeneous wetting model.

Oleophobic properties of the step-and-terrace sapphire surface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Muslimov, A. E., E-mail: amuslimov@mail.ru; Butashin, A. V.; Kanevsky, V. M.

Sapphire is widely used in production of optical windows for various devices due to its mechanical and optical properties. However, during operation the surface can be affected by fats, oils, and other organic contaminations. Therefore, it is important to improve the oleophobic properties of sapphire windows. In this study, we investigate the interaction of a supersmooth sapphire surface with oleic acid droplets, which imitate human finger printing. It is established that chemical–mechanical polishing with additional annealing in air, which leads to the formation of an atomically smooth sapphire surface, makes it possible to significantly improve the oleophobic properties of themore » surface. The results are analyzed using the Ventsel–Deryagin homogeneous wetting model.« less

UHV-TEM-REM Studies of Si(111) Surfaces

NASA Astrophysics Data System (ADS)

Yagi, K.; Yamanaka, A.; Sato, H.; Shima, M.; Ohse, H.; Ozawa, S.; Tanishiro, Y.

Recent progresses of ultra-high vacuum transmission and reflection electron microscope studies of clean Si(111) surfaces are described. Anisotropy of surface atomic steps such as step energy, bunching of steps, are studied. Out of phase boundaries are observed in transmission mode and its energy relative to the step energy is studied. The phase transition between the 1 × 1 and the 7 × 7 structures around 830°C, studied previously is re-examined under various conditions. Contraction strains of the 7 × 7 structure and adatom density on terraces play important role during the transition. Diffuse scattering observed by LEED and RHEED above the transition temperature is not observed in teh TED pattern from a thin film.

An evaluation of uranium-series dating of fossil echinoids from southern California Pleistocene marine terraces

USGS Publications Warehouse

Muhs, D.R.; Kennedy, G.L.

1985-01-01

Fossil sea urchins (Strongylocentrotus) from Pleistocene marine terraces on the southern California Channel Islands have been dated by the uranium-series method in order to test the suitability of echinoids for dating marine terraces. Results indicate that urchin plates and spines do not behave as closed systems with respect to both uranium and thorium. Calculated ages based on these data do not agree with uranium-series ages (120,000 and 127,000 yrs) obtained previously from corals from the same localities. Thus, fossil sea urchins (Strongylocentrotus) are not considered suitable for uraniumseries dating of Pleistocene marine terrace deposits. ?? 1985.

Geomorphic and sedimentary responses of the Bull Creek Valley (Southern High Plains, USA) to Pleistocene and Holocene environmental change

NASA Astrophysics Data System (ADS)

Arauza, Hanna M.; Simms, Alexander R.; Bement, Leland C.; Carter, Brian J.; Conley, Travis; Woldergauy, Ammanuel; Johnson, William C.; Jaiswal, Priyank

2016-01-01

Fluvial geomorphology and stratigraphy often reflect past environmental and climate conditions. This study examines the response of Bull Creek, a small ephemeral creek in the Oklahoma panhandle, to environmental conditions through the late Pleistocene and Holocene. Fluvial terraces were mapped and their stratigraphy and sedimentology documented throughout the course of the main valley. Based on their elevations, terraces were broadly grouped into a late-Pleistocene fill terrace (T3) and two Holocene fill-cut terrace sets (T2 and T1). Terrace systems are marked by similar stratigraphies recording the general environmental conditions of the time. Sedimentary sequences preserved in terrace fills record the transition from a perennial fluvial system during the late glacial period and the Younger Dryas to a semiarid environment dominated by loess accumulation and punctuated by flood events during the middle to late Holocene. The highest rates of aeolian accumulation within the valley occurred during the early to middle Holocene. Our data provide significant new information regarding the late-Pleistocene and Holocene environmental history for this region, located between the well-studied Southern and Central High Plains of North America.

Economic and social activities on ancient Cypriot terraced landscapes.

PubMed

Ridder, Elizabeth; Galletti, Christopher S; Fall, Patricia L; Falconer, Steven E

2017-11-01

We investigate ancient agricultural terraces and their associated social and economic activities across the site complex consisting of the village at Politiko-Troullia and its more extensive associated taskscape. Surface artifact distributions mapped over 12 ha are integrated with evidence excavated from this Bronze Age settlement in central Cyprus. Contrary to expectations, artifact densities do not diminish with distance from the village architecture. In particular, concentrations of Prehistoric Bronze Age ceramics and ground stone artifacts are most pronounced on nearby terraced hillsides. These terraces were not utilized for domestic structures, but for extensive processing of agricultural crops and copper ore. Bronze Age excavated plant remains indicate cultivation of olives, grapes and figs, with wood resources dominated by olive and pine. Larger, non-portable ground stones and gaming stones are associated with communal social and economic activities in open courtyard settings in Politiko-Troullia. This category of ground stone also is particularly common on the terraced hillsides around Troullia, suggesting that similar behaviors occurred beyond village structures. The terraced landscape of Politiko-Troullia exemplifies a multi-faceted taskscape with a range of agricultural, metallurgical and social activities. Copyright © 2016 Elsevier Ltd. All rights reserved.

Ecosystem development on terraces along the Kugururok River, northwest Alaska

USGS Publications Warehouse

Binkley, Dan; Suarez, F.; Stottlemyer, R.; Caldwell, B.

1997-01-01

Riverside terraces along the Kugururok River in the Noatak National Preserve provided an opportunity to study primary succession, considering general trends that apply across all terraces, and unique events that influence individual terraces. The 30-year-old willow/poplar (Salix spp., Populus balsamifera L.) terrace had no trees taller than 1.5 m; the abundant spruce trees were not tall enough to emerge from the canopy height of the willows and poplars, and moose (Alces alces [Clinton]) browsing limited the canopy height of these plants. The 75-year-old poplar/spruce (Picea glauca [Moench] Voss) terrace had a high density of poplars (> 1000/ha) and low density of spruce (125/ha); heavy browsing by moose reduced the density of poplar by about one-half. The removal of the poplar by moose in this stand resulted in sustained increases in growth of individual spruce trees. The 100-year-old younger spruce/poplar terrace had about twice as many spruce trees (1250/ha) as poplar trees (500/ha), and the spruce trees were larger on average than the poplar trees. In the 220+ year-old older spruce/poplar type, only a few poplars remained (about 25/ha), and the number of spruce trees (600/ha) was only half that of the younger stage, either from lower initial spruce density on this terrace, or increased mortality of spruce. The 240+ year-old spruce type was a second-generation forest, characterized by a high density (1950/ha) of small spruce trees, some of which were tilted, indicating discontinuous permafrost. Plant litterfall mass showed no strong trend with terrace age, although N content of litterfall appeared to decline by about 1/3 in the spruce-dominated stages. Fungal biomass increased with ecosystem age, whereas bacterial biomass and microfauna declined. We found no evidence of declining soil N supply in older stages, but fertilization experiments would be needed to determine if N limitation of productivity changed with ecosystem development. We conclude that the general successional trend of increased spruce dominance is robust for this location, but that unique events play important roles in determining tree densities and the timing of the shift in dominance from poplar to spruce. The arrival of moose in the 1970s accelerated dominance by spruce on young terraces.

Morphosedimentary and hydrographic features of the northern Argentine margin: The interplay between erosive, depositional and gravitational processes and its conceptual implications

NASA Astrophysics Data System (ADS)

Preu, Benedict; Hernández-Molina, F. Javier; Violante, Roberto; Piola, Alberto R.; Paterlini, C. Marcelo; Schwenk, Tilmann; Voigt, Ines; Krastel, Sebastian; Spiess, Volkhard

2013-05-01

Bottom currents and their margin-shaping character became a central aspect in the research field of sediment dynamics and paleoceanography during the last decades due to their potential to form large contourite depositional systems (CDS), consisting of both erosive and depositional features. A major CDS at the northern Argentine continental margin was studied off the Rio de la Plata River by means of seismo- and hydro-acoustic methods including conventional and high-resolution seismic, parametric echosounder and single and swath bathymetry. Additionally, hydrographic data were considered allowing jointly interpretation of morphosedimentary features and the oceanographic framework, which is dominated by the presence of the dynamic and highly variable Brazil-Malvinas Confluence. We focus on three regional contouritic terraces identified on the slope in the vicinity of the Mar del Plata Canyon. The shallowest one, the La Plata Terrace (˜500 m), is located at the Brazil Current/Antarctic Intermediate Water interface characterized by its deep and distinct thermocline. In ˜1200 m water depth the Ewing Terrace correlates with the Antarctic Intermediate Water/Upper Circumpolar Deep Water interface. At the foot of the slope in ˜3500 m the Necochea Terrace marks the transition between Lower Circumpolar Deep Water and Antarctic Bottom Water during glacial times. Based on these correlations, a comprehensive conceptual model is proposed, in which the onset and evolution of contourite terraces is controlled by short- and long-term variations of water mass interfaces. We suggest that the terrace genesis is strongly connected to the turbulent current pattern typical for water mass interfaces. Furthermore, the erosive processes necessary for terrace formation are probably enhanced due to internal waves, which are generated along strong density gradients typical for water mass interfaces. The terraces widen through time due to locally focused, partly helical currents along the steep landward slopes and more tabular conditions seaward along the terrace surface. Considering this scheme of contourite terrace development, lateral variations of the morphosedimentary features off northern Argentina can be used to derive the evolution of the Brazil-Malvinas Confluence on geological time scales. We propose that the Brazil-Malvinas Confluence in modern times is located close to its southernmost position in the Quaternary, while its center was shifted northward during cold periods.

Interpreting the paleozoogeography and sea level history of thermally anomalous marine terrace faunas: a case study from the the Last Interglacial Complex of San Clemente Island, California

USGS Publications Warehouse

Muhs, Daniel R.; Groves, Lindsey T.; Schumann, R. Randall

2014-01-01

Marine invertebrate faunas with mixtures of extralimital southern and extralimital northern faunal elements, called thermally anomalous faunas, have been recognized for more than a century in the Quaternary marine terrace record of the Pacific Coast of North America. Although many mechanisms have been proposed to explain this phenomenon, no single explanation seems to be applicable to all localities where thermally anomalous faunas have been observed. Here, we describe one such thermally anomalous fossil fauna that was studied on the second emergent marine terrace at Eel Point on San Clemente Island. The Eel Point terrace complex is a composite feature, consisting of a narrow upper bench (terrace 2a) and a broader lower bench (terrace 2b). Terrace 2b, previously dated from ~128 ka to ~114 ka, was thought to date solely to marine isotope stage (MIS) 5.5, representing the peak of the last interglacial period. Nevertheless, the fauna contains an extralimital northern species and several northward-ranging species, as well as an extralimital southern species and several southward-ranging species. Similar faunas with thermally anomalous elements have also been reported from San Nicolas Island, Point Loma (San Diego County), and Cayucos (San Luis Obispo County), California. U-series dating of corals at those localities shows that the thermally anomalous faunas may be the result of mixing of fossils from both the ~100-ka (cool-water) and the ~120-ka (warm-water) sea level high stands. Submergence, erosion, and fossil mixing of the ~120-ka terraces by the ~100-ka high-sea stand may have been possible due to glacial isostatic adjustment (GIA) effects on North America, which could have resulted in a higher-than-present local sea level stand at ~100 ka. The terrace elevation spacing on San Clemente Island is very similar to that on San Nicolas Island, and we hypothesize that a similar mixing took place on San Clemente Island. Existing fossil records from older terraces elsewhere in California also show thermally anomalous elements, indicating that the scenario presented here for the last interglacial complex may have applicability to much of the marine Quaternary record for the Pacific Coast.

The strategies of local farmers' water management and the eco-hydrological effects of irrigation-drainage engineering systems in world heritage of Honghe Hani Rice Terraces

NASA Astrophysics Data System (ADS)

Gao, Xuan

2017-04-01

Terraces are built in mountainous regions to provide larger area for cultivation,in which the hydrological and geomorphological processes are impacted by local farmers' water management strategies and are modified by manmade irrigation-drainage engineering systems.The Honghe Hani Rice Terraces is a 1300a history of traditional agricultural landscape that was inscribed in the 2013 World Heritage List.The local farmers had developed systematic water management strategies and built perfect irrigation-drainage engineering systems to adapt the local rainfall pattern and rice farming activities.Through field investigation,interviews,combined with Geographic Information Systems,Remote Sensing images and Global Positioning Systems technology,the water management strategies as well as the irrigation-drainage systems and their impacts on eco-hydrological process were studied,the results indicate:Firstly,the local people created and maintained an unique woodcarving allocating management system of irrigating water over hundreds years,which aids distributing water and natural nutrition to each terrace field evenly,and regularly according to cultivation schedule.Secondly,the management of local people play an essential role in effective irrigation-drainage engineering system.A ditch leader takes charge of managing the ditch of their village,keeping ample amount of irrigation water,repairing broken parts of ditches,dealing with unfair water using issues,and so on.Meanwhile,some traditional leaders of minority also take part in.Thus, this traditional way of irrigation-drainage engineering has bringed Hani people around 1300 years of rice harvest for its eco-hydrological effects.Lastly we discuss the future of Honghe Hani Rice Terraces,the traditional cultivation pattern has been influenced by the rapid development of modern civilization,in which some related changes such as the new equipment of county roads and plastic channels and the water overusing by tourism are not totally rely on eco-hydrological engineering rules,which broke the ecosystem stability of agricultural terraces.The current situation of Honghe Hani Rice Terraces heritage cannot completely meets the purpose of sustainability development and appropriate conservation of Honghe Hani Rice Terraces heritage.This study of traditional cultivation pattern can help us to propose rational solutions for future development of terraces heritages. Key words:Honghe Hani Rice Terraces,water management,eco-hydrological effects,heritage conservation

Estimation of terracing characteristics from airborne laser scanning data

NASA Astrophysics Data System (ADS)

Kokalj, Žiga

2015-04-01

Agricultural terraces are a fundamental morphological form of the Slovenian landscape. They are present in all of its diverse geographical regions, from Mediterranean and Dinaric hills and plateaus, Alpine mountains and plains, to Pannonian hills. New systematic research based on mapping aerial orthophotos and historical maps revealed previously unrecorded distribution and extent of terracing. However, the extensive overgrowing of the Slovenian countryside in the past century, when forest cover has grown from 40% to more than 60%, hid many of the terraces under a thick forest canopy. This is especially true for the higher and more remote areas where unfavourable natural conditions have coupled with depopulation processes. In such conditions, the only reasonable technique to observe cultural terraces and other remains of past human activities over large areas is airborne laser scanning. With the country-wide airborne lidar data becoming available, many new possibilities for discovery as well as quantitative analyses are becoming available. We explored manual and semiautomatic approaches to obtain terracing characteristics around representative villages of diverse landscape types. Individual terraces can be described with several attributes, such as riser slope gradient, riser height, tread area, length and width, ratio of length and width, altitude, location of the terrace in the thermal band, distance to the settlement, number and type of trees, distance between trees, and number of vineyard rows. Such characteristics can be derived manually, which can be painstakingly slow, but with relative precisions reaching the order of centimetres and decimetres, or semiautomatically, which is much faster, but with worse precision levels, mainly due to various outliers and errors in processing. The success of attribute derivation is highly dependent on raw lidar data acquisition parameters and processing. Manual interpretation has a distinct advantage of the possibility to explore and manipulate the raw data, i.e. the lidar point cloud, where relevant features that could be removed in the filtering process can still be traced and their exact extents discernible. However, this is only possible for specific and very detailed analyses, while much more of the work has to be done with already processed raster elevation data. Processing has to be tailored specifically with terracing in mind, otherwise typical characteristics, such as riser slope gradient and thread edges can be distorted. We also investigated the role different elevation model visualizations have on the manual interpretation of terraced landscapes and which visualizations can benefit semiautomatic processing.

Quaternary Deformation of Sumba, Indonesia: Evidence from Carbonate Terraces

NASA Astrophysics Data System (ADS)

Dahlquist, M. P.; West, A. J.; Dolan, J. F.

2014-12-01

The Banda Arc of Indonesia remains one of the least understood tectonic domains on the modern Earth. The island of Sumba, located approximately 50 km south of Flores and 120 km north of the Java Trench, northwest of where it transitions into the Timor Trough, lies in a region of tectonic transition and potentially offers insights into regional dynamics. The Banda Arc is volcanically active, but Sumba itself is not volcanic. The northern coast of Sumba is covered in Quaternary coral terraces, with the rest of the island's surface geology composed of Mio-pliocene carbonates and uplifted Late Cretaceous-Oligocene forearc basin and volcanic rocks. The purpose of this study is to remotely map the topographic expression of the coral terraces and use the information gained to better understand deformation on Sumba since their deposition. The ages of the coral terraces, of which many platforms are exposed over significant areas of the island, have been constrained at Cape Luandi in north central Sumba, but uplift rates calculated from those ages may not be representative of the island as a whole. The lateral continuity of these dated terraces can help constrain the extent to which uplift of Sumba is spatially variable. Analysis of the terraces using SRTM digital elevation data with ArcGIS software makes it possible to trace the same terrace platforms over large distances, and shows that the north central part of the island has experienced the most uplift since the deposition of the terraces, forming an anticline with the east limb dipping more steeply than the west. The terraces are not well preserved on the southern half of the island. Exposure of older rocks and lack of terrace preservation, as well as a south-skewed drainage divide suggests the southern half of the island experiences greater exhumation, but this could be driven by climate or other factors and does not necessarily indicate more rapid uplift. Study of Quaternary deformation of Sumba can offer greater understanding of the ongoing collision of the Banda Arc with the Australian continent. A more complete picture of the region may provide insights into seismic hazards as well as the behavior of arc-continent collision systems and active margins in general.

Ridge Minimization of Ablated Morphologies on ITO Thin Films Using Squared Quasi-Flat Top Beam

PubMed Central

Jeon, Jin-Woo; Choi, Wonsuk; Shin, Young-Gwan; Ji, Suk-Young

2018-01-01

In this study, we explore the improvements in pattern quality that was obtained with a femtosecond laser with quasi-flat top beam profiles at the ablated edge of indium tin oxide (ITO) thin films for the patterning of optoelectronic devices. To ablate the ITO thin films, a femtosecond laser is used that has a wavelength and pulse duration of 1030 nm and 190 fs, respectively. The squared quasi-flat top beam is obtained from a circular Gaussian beam using slits with varying x-y axes. Then, the patterned ITO thin films are measured using both scanning electron and atomic force microscopes. In the case of the Gaussian beam, the ridge height and width are approximately 39 nm and 1.1 μm, respectively, whereas, when the quasi-flat top beam is used, the ridge height and width are approximately 7 nm and 0.25 μm, respectively. PMID:29601515

Modeling the erosion risk potential induced by terraces and their condition in a highly dynamic watershed close to the Three-Gorges-Dam

NASA Astrophysics Data System (ADS)

Schönbrodt, S.; Behrens, T.; Imbery, S.; Scholten, T.

2010-03-01

Globally, the Three-Gorges Ecosystem is currently one of the most anthropogenic influenced regions. Due to the Three-Gorges Dam large areas in the upper catchment of the Yangtze and its major tributaries become inundated. Consequently, high land-use dynamic with resettlements, construction of infrastructure, and new land reclamation for smallholder agriculture and cash crops characterize this area. Therefore, ecological impacts are expected in an unforeseeable dimension. Soil loss is one of the major threats and its control an enormous challenge. Even existing erosion control measures like dry-stone walling bench terraces have to be adapted to this new situation in order to keep their effectiveness. In the highly dynamic watershed of the Xiangxi, a first class tributary to the Yangtze, this study aims to assess and predict the spatial and temporal varying dam-caused soil erosion risk potential. Using a multi-level and multi-scale approach this study seeks to develop an integrative data-based methodology for soil erosion assessment by means of GIS-based erosion modeling using relevant digital terrain data, field investigations and remote sensing. The different scales considered cover the Xiangxi watershed (3.100 km²), the highly dynamic backwater area (500 km²), and two micro-scale study sites (3 km² and 88 km²) subject to flooding and high land-use dynamic. Central features of the Xiangxi watershed are steep slopes artificially fractured by terraces. A preliminary erosion survey has shown a strong connection of the frequency and intensity of erosion and the quality of terrace-maintenance. Terraces with wall disorders and technically poor constructed design show higher soil loss and runoff than well-maintained terraces. Their condition is regarded as a driving erosion factor. Therefore, a conceptual Terrace-Condition-Erosion model (TerraCE) was developed in order to assess to what extent soil erosion depends on the quality of terraces. Central aspects are the distance to the inundated area, to the road network, and to the settlements. Four classes of terrace-maintenance are analyzed: well-maintained (20 %), badly-maintained (48 %), partially collapsed (15 %), and completely collapsed (6 %). Unterraced farmland (7 %) is regarded as an extra class. First results of TerraCE indicate that with increasing distance from the highly dynamic inundated area and the main roads the better is the quality of terrace-maintenance with less wall disorders and less soil erosion potential. It is concluded that the construction of infrastructure and the artificially fluctuating water level at the dam lead to a degradation of terraces within close distances to the Xiangxi and the main road network. Terraced farmland that is more remote to the main transportation routes seems to be less influenced by the high land-use dynamic. The mean distance of (a) well-/badly-maintainedand(b)partially-/completely collapsed terraces from the Xiangxi is(a) 613.8 m with SD 318.2 m/474.4 m with SD 291.6 m and (b) 208.6m with SD 292.1 m/127.6 m with SD 81.7 m. In average, unterraced farmland is 261.9 m (SD 286.2 m) located from the new shoreline of the Xiangxi. By combining the model results with DEM-analysis and remote sensing data a high-resolution soil erosion risk model will be computed using spatial regression approaches. It aims to assess the soil erosion as a function of natural factors and anthropogenic impacts in an increasingly complex system. Especially against the background of global change and the increasing demand for water and energy the study aims at enhancing the understanding of the ecological consequences of large dam projects.

Ceramic surfaces, interfaces and solid-state reactions

NASA Astrophysics Data System (ADS)

Heffelfinger, Jason Roy

Faceting, the decomposition of a surface into two or more surfaces of different orientation, is studied as a function of annealing time for ceramic surfaces. Single-crystals of Alsb2Osb3\\ (alpha-Alsb2Osb3 or corundum structure) are carefully prepared and characterized by atomic force microscopy, scanning electron microscopy and transmission electron microscopy. The mechanisms by which the originally smooth vicinal surface transforms into either a hill-and-valley or a terrace-and-step structure have been characterized. The progression of faceting is found to have a series of stages: surface smoothing, nucleation and growth of individual facets, formation of facet domains, coalescence of individual and facet domains and facet coarsening. These stages provide a model for the mechanisms of how other ceramic surfaces may facet into hill-and-valley and terrace-and-step surface microstructures. The well characterized Alsb2Osb3 surfaces provide excellent substrates by which to study the effect of surface structure on thin-film growth. Pulsed-laser deposition was used to grow thin films of yttria stabilized zirconia (YSZ) and Ysb2Osb3 onto annealed Alsb2Osb3 substrates. The substrate surface structure, such as surface steps and terraces, was found to have several effects on thin-film growth. Thin-films grown onto single-crystal substrates serve as a model geometry for studying thin-film solid-state reactions. Here, the reaction sequence and orientation relationship between thin films of Ysb2Osb3 and an Alsb2Osb3 substrate were characterized for different reaction temperatures. In a system were multiple reaction phases can form, the yttria aluminum monoclinic phase (YAM) was found to form prior to formation of other phases in this system. In a second system, a titanium alloy was reacted with single crystal Alsb2Osb3 in order to study phase formation in an intermetallic system. Both Tisb3Al and TiAl were found to form as reaction products and their orientation relationships with the Alsb2Osb3 are discussed.

Digital data sets that describe aquifer characteristics of the Enid isolated terrace aquifer in northwestern Oklahoma

USGS Publications Warehouse

Becker, C.J.; Runkle, D.L.; Rea, Alan

1997-01-01

ARC/INFO export and nonproprietary format files The data sets in this report include digitized aquifer boundaries and maps of hydraulic conductivity, recharge, and ground-water level elevation contours for the Enid isolated terrace aquifer in northwestern Oklahoma. The Enid isolated terrace aquifer covers approximately 82 square miles and supplies water for irrigation, domestic, municipal, and industrial use for the City of Enid and western Garfield County. The Quaternary-age Enid isolated terrace aquifer is composed of terrace deposits that consist of discontinuous layers of clay, sandy clay, sand, and gravel. The aquifer is unconfined and is bounded by the underlying Permian-age Hennessey Group on the east and the Cedar Hills Sandstone Formation of the Permian-age El Reno Group on the west. The Cedar Hills Sandstone Formation fills a channel beneath the thickest section of the Enid isolated terrace aquifer in the midwestern part of the aquifer. All of the data sets were digitized and created from information and maps in a ground-water modeling thesis and report of the Enid isolated terrace aquifer. The maps digitized were published at a scale of 1:62,500. Ground-water flow models are numerical representations that simplify and aggregate natural systems. Models are not unique; different combinations of aquifer characteristics may produce similar results. Therefore, values of hydraulic conductivity and recharge used in the model and presented in this data set are not precise, but are within a reasonable range when compared to independently collected data.

Structure disorder degree of polysilicon thin films grown by different processing: Constant C from Raman spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Quan, E-mail: wangq@mail.ujs.edu.cn; State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000; Zhang, Yanmin

2013-11-14

Flat, low-stress, boron-doped polysilicon thin films were prepared on single crystalline silicon substrates by low pressure chemical vapor deposition. It was found that the polysilicon films with different deposition processing have different microstructure properties. The confinement effect, tensile stresses, defects, and the Fano effect all have a great influence on the line shape of Raman scattering peak. But the effect results are different. The microstructure and the surface layer are two important mechanisms dominating the internal stress in three types of polysilicon thin films. For low-stress polysilicon thin film, the tensile stresses are mainly due to the change of microstructuremore » after thermal annealing. But the tensile stresses in flat polysilicon thin film are induced by the silicon carbide layer at surface. After the thin film doped with boron atoms, the phenomenon of the tensile stresses increasing can be explained by the change of microstructure and the increase in the content of silicon carbide. We also investigated the disorder degree states for three polysilicon thin films by analyzing a constant C. It was found that the disorder degree of low-stress polysilicon thin film larger than that of flat and boron-doped polysilicon thin films due to the phase transformation after annealing. After the flat polysilicon thin film doped with boron atoms, there is no obvious change in the disorder degree and the disorder degree in some regions even decreases.« less

Single d-metal atoms on F(s) and F(s+) defects of MgO(001): a theoretical study across the periodic table.

PubMed

Neyman, Konstantin M; Inntam, Chan; Matveev, Alexei V; Nasluzov, Vladimir A; Rösch, Notker

2005-08-24

Single d-metal atoms on oxygen defects F(s) and F(s+) of the MgO(001) surface were studied theoretically. We employed an accurate density functional method combined with cluster models, embedded in an elastic polarizable environment, and we applied two gradient-corrected exchange-correlation functionals. In this way, we quantified how 17 metal atoms from groups 6-11 of the periodic table (Cu, Ag, Au; Ni, Pd, Pt; Co, Rh, Ir; Fe, Ru, Os; Mn, Re; and Cr, Mo, W) interact with terrace sites of MgO. We found bonding with F(s) and F(s+) defects to be in general stronger than that with O2- sites, except for Mn-, Re-, and Fe/F(s) complexes. In M/F(s) systems, electron density is accumulated on the metal center in a notable fashion. The binding energy on both kinds of O defects increases from 3d- to 4d- to 5d-atoms of a given group, at variance with the binding energy trend established earlier for the M/O2- complexes, 4d < 3d < 5d. Regarding the evolution of the binding energy along a period, group 7 atoms are slightly destabilized compared to their group 6 congeners in both the F(s) and F(s+) complexes; for later transition elements, the binding energy increases gradually up to group 10 and finally decreases again in group 11, most strongly on the F(s) site. This trend is governed by the negative charge on the adsorbed atoms. We discuss implications for an experimental detection of metal atoms on oxide supports based on computed core-level energies.

Observation of Landau levels on nitrogen-doped flat graphite surfaces without external magnetic fields

PubMed Central

Kondo, Takahiro; Guo, Donghui; Shikano, Taishi; Suzuki, Tetsuya; Sakurai, Masataka; Okada, Susumu; Nakamura, Junji

2015-01-01

Under perpendicular external magnetic fields, two-dimensional carriers exhibit Landau levels (LLs). However, it has recently been reported that LLs have been observed on graphene and graphite surfaces without external magnetic fields being applied. These anomalous LLs have been ascribed primarily to a strain of graphene sheets, leading to in-plane hopping modulation of electrons. Here, we report the observation of the LLs of massive Dirac fermions on atomically flat areas of a nitrogen-doped graphite surface in the absence of external magnetic fields. The corresponding magnetic fields were estimated to be as much as approximately 100 T. The generation of the LLs at the area with negligible strain can be explained by inequivalent hopping of π electrons that takes place at the perimeter of high-potential domains surrounded by positively charged substituted graphitic-nitrogen atoms. PMID:26549618

Evaluation of preparation methods for suspended nano-objects on substrates for dimensional measurements by atomic force microscopy

PubMed Central

Göhler, Daniel; Wessely, Benno; Stintz, Michael; Lazzerini, Giovanni Mattia; Yacoot, Andrew

2017-01-01

Dimensional measurements on nano-objects by atomic force microscopy (AFM) require samples of safely fixed and well individualized particles with a suitable surface-specific particle number on flat and clean substrates. Several known and proven particle preparation methods, i.e., membrane filtration, drying, rinsing, dip coating as well as electrostatic and thermal precipitation, were performed by means of scanning electron microscopy to examine their suitability for preparing samples for dimensional AFM measurements. Different suspensions of nano-objects (with varying material, size and shape) stabilized in aqueous solutions were prepared therefore on different flat substrates. The drop-drying method was found to be the most suitable one for the analysed suspensions, because it does not require expensive dedicated equipment and led to a uniform local distribution of individualized nano-objects. Traceable AFM measurements based on Si and SiO2 coated substrates confirmed the suitability of this technique. PMID:28904839

Evaluation of preparation methods for suspended nano-objects on substrates for dimensional measurements by atomic force microscopy.

PubMed

Fiala, Petra; Göhler, Daniel; Wessely, Benno; Stintz, Michael; Lazzerini, Giovanni Mattia; Yacoot, Andrew

2017-01-01

Dimensional measurements on nano-objects by atomic force microscopy (AFM) require samples of safely fixed and well individualized particles with a suitable surface-specific particle number on flat and clean substrates. Several known and proven particle preparation methods, i.e., membrane filtration, drying, rinsing, dip coating as well as electrostatic and thermal precipitation, were performed by means of scanning electron microscopy to examine their suitability for preparing samples for dimensional AFM measurements. Different suspensions of nano-objects (with varying material, size and shape) stabilized in aqueous solutions were prepared therefore on different flat substrates. The drop-drying method was found to be the most suitable one for the analysed suspensions, because it does not require expensive dedicated equipment and led to a uniform local distribution of individualized nano-objects. Traceable AFM measurements based on Si and SiO 2 coated substrates confirmed the suitability of this technique.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kautsky, Mark; Ranalli, Tony; Dander, David

The objective of this investigation was to identify and differentiate potential non- mill-related water inputs to a shallow terrace groundwater system through the use of aqueous chemical and isotopic tracers at a former uranium- and vanadium-ore processing facility. Terrace groundwater in the vicinity of the Shiprock, New Mexico, site is hypothesized to be largely anthropogenic because natural rates of recharge in the terrace are likely insufficient to sustain a continuous water table in the terrace alluvial system, as observed in several analogue terrace locations east of the site and in response to post-mill dewatering efforts across the site. The terracemore » is composed of alluvial sand and gravel and weathered and unweathered Mancos Shale. Terrace groundwater exists and flows in the alluvium and to a much less extent in the Mancos Shale. Historical data established that in both the terrace and floodplain below the terrace, mill-derived uranium and sulfate is found primarily in the alluvium and the upper portion of the weathered Mancos Shale. Groundwater extraction is being conducted in the vicinity of former mill operations and in washes and seeps to dewater the formation and remove contamination, thus eliminating these exposure pathways and minimizing movement to the floodplain. However, past and present contribution of non-mill anthropogenic water sources may be hindering the dewatering effort, resulting in reduced remedy effectiveness. Groundwater source signatures can be determined based on chemical and isotopic ratios and are used to help identify and delineate both mill and non-mill water contributions. Aqueous chemical and isotopic tracers, such as 234U/238U activity ratios and uranium concentrations, δ34S sulfate and sulfate concentrations, tritium concentrations, and δ2Hwater and δ18O water are being used in this Phase I study. The aqueous chemical and isotopic analysis has identified areas on the terrace where groundwater is derived from mill-related activities and areas where the groundwater is associated with non-mill activities. A separate field effort of Phase II work will follow, including investigating additional locations for these isotopes and examination of δ18Osulfate , δ34Ssulfate , and chlorofluorocarbon signatures.« less

[Impacts of dominated landscape types on hydrogen and oxygen isotope effects of spring water in the Hani Rice Terraces].

PubMed

Jiao, Yuan Mei; Liu, Cheng Jing; Liu, Xin; Liu, Zhi Lin; Ding, Yin Ping

2017-07-18

Analysis of hydrogen and oxygen stable isotopes is an effective method to track the water cycle in watershed. Impact of landscape pattern on the isotope effects of spring water is a new interdisciplinary topic between landscape ecology and isotope hydrology. Taking the Quanfuzhuang River basin located in the core area of UNESCO World Cultural Heritage of Honghe Hani Rice Terrace as the object, collecting the monthly samples of 78 points of spring water and 39 precipitation at altitude of 1500 m (terraces), 1700 m (terraces) and 1900 m (forest) from March 2015 to March 2016, we analyzed the hydrogen and oxygen stable isotopes of water samples under the different landscape types. The results indicated that the dominated landscape types were forests and rice terraces, being 66.6% and 22.1% of the whole landscape area respectively, and they had a spatial vertical pattern of forest located at the mountain top and rice terraces at the down-slope. The correlation analysis showed that the spring water not only came from the precipitation, but also from other water sources which had a more positive δ 18 O and δD values, the spring water in up-slope forests mainly came from precipitation, while that in down-slope rice terraces came from precipitation, ri-ver water, rice terrace water and under ground water. Therefore, the mixing effects of spring water δ 18 O and δD were more significant in rice terraces. The overall altitude effect of the hydrogen and oxygen stable isotopes in spring water was obvious. The linear decreasing rates of δ 18 O and δD values were -0.125‰·(100 m) -1 and -0.688‰·(100 m) -1 , respectively. The deuterium surplus value increased with the altitude because of the impacts of landscape pattern and the local cycle of water isotopes. In summary, the dominant landscape types had a significant impact on the hydrogen and oxygen isotopes of spring water, which could be used as response indicator to reveal the impacts of landscape pattern on hydrological process.

Refining fault slip rates using multiple displaced terrace risers-An example from the Honey Lake fault, NE California, USA

NASA Astrophysics Data System (ADS)

Gold, Ryan D.; Briggs, Richard W.; Crone, Anthony J.; DuRoss, Christopher B.

2017-11-01

Faulted terrace risers are semi-planar features commonly used to constrain Quaternary slip rates along strike-slip faults. These landforms are difficult to date directly and therefore their ages are commonly bracketed by age estimates of the adjacent upper and lower terrace surfaces. However, substantial differences in the ages of the upper and lower terrace surfaces (a factor of 2.4 difference observed globally) produce large uncertainties in the slip-rate estimate. In this investigation, we explore how the full range of displacements and bounding ages from multiple faulted terrace risers can be combined to yield a more accurate fault slip rate. We use 0.25-m cell size digital terrain models derived from airborne lidar data to analyze three sites where terrace risers are offset right-laterally by the Honey Lake fault in NE California, USA. We use ages for locally extensive subhorizontal surfaces to bracket the time of riser formation: an upper surface is the bed of abandoned Lake Lahontan having an age of 15.8 ± 0.6 ka and a lower surface is a fluvial terrace abandoned at 4.7 ± 0.1 ka. We estimate lateral offsets of the risers ranging between 6.6 and 28.3 m (median values), a greater than fourfold difference in values. The amount of offset corresponds to the riser's position relative to modern stream meanders: the smallest offset is in a meander cutbank position, whereas the larger offsets are in straight channel or meander point-bar positions. Taken in isolation, the individual terrace-riser offsets yield slip rates ranging from 0.3 to 7.1 mm/a. However, when the offset values are collectively assessed in a probabilistic framework, we find that a uniform (linear) slip rate of 1.6 mm/a (1.4-1.9 mm/a at 95% confidence) can satisfy the data, within their respective uncertainties. This investigation demonstrates that integrating observations of multiple offset elements (crest, midpoint, and base) from numerous faulted and dated terrace risers at closely spaced sites can refine slip-rate estimates on strike-slip faults.

Refining fault slip rates using multiple displaced terrace risers—An example from the Honey Lake fault, NE California, USA

USGS Publications Warehouse

Gold, Ryan D.; Briggs, Richard; Crone, Anthony J.; Duross, Christopher

2017-01-01

Faulted terrace risers are semi-planar features commonly used to constrain Quaternary slip rates along strike-slip faults. These landforms are difficult to date directly and therefore their ages are commonly bracketed by age estimates of the adjacent upper and lower terrace surfaces. However, substantial differences in the ages of the upper and lower terrace surfaces (a factor of 2.4 difference observed globally) produce large uncertainties in the slip-rate estimate. In this investigation, we explore how the full range of displacements and bounding ages from multiple faulted terrace risers can be combined to yield a more accurate fault slip rate. We use 0.25-m cell size digital terrain models derived from airborne lidar data to analyze three sites where terrace risers are offset right-laterally by the Honey Lake fault in NE California, USA. We use ages for locally extensive subhorizontal surfaces to bracket the time of riser formation: an upper surface is the bed of abandoned Lake Lahontan having an age of 15.8 ± 0.6 ka and a lower surface is a fluvial terrace abandoned at 4.7 ± 0.1 ka. We estimate lateral offsets of the risers ranging between 6.6 and 28.3 m (median values), a greater than fourfold difference in values. The amount of offset corresponds to the riser's position relative to modern stream meanders: the smallest offset is in a meander cutbank position, whereas the larger offsets are in straight channel or meander point-bar positions. Taken in isolation, the individual terrace-riser offsets yield slip rates ranging from 0.3 to 7.1 mm/a. However, when the offset values are collectively assessed in a probabilistic framework, we find that a uniform (linear) slip rate of 1.6 mm/a (1.4–1.9 mm/a at 95% confidence) can satisfy the data, within their respective uncertainties. This investigation demonstrates that integrating observations of multiple offset elements (crest, midpoint, and base) from numerous faulted and dated terrace risers at closely spaced sites can refine slip-rate estimates on strike-slip faults.

Characterization of the surface charge distribution on kaolinite particles using high resolution atomic force microscopy

NASA Astrophysics Data System (ADS)

Kumar, Naveen; Zhao, Cunlu; Klaassen, Aram; van den Ende, Dirk; Mugele, Frieder; Siretanu, Igor

2016-02-01

Most solid surfaces, in particular clay minerals and rock surfaces, acquire a surface charge upon exposure to an aqueous environment due to adsorption and/or desorption of ionic species. Macroscopic techniques such as titration and electrokinetic measurements are commonly used to determine the surface charge and ζ -potential of these surfaces. However, because of the macroscopic averaging character these techniques cannot do justice to the role of local heterogeneities on the surfaces. In this work, we use dynamic atomic force microscopy (AFM) to determine the distribution of surface charge on the two (gibbsite-like and silica-like) basal planes of kaolinite nanoparticles immersed in aqueous electrolyte with a lateral resolution of approximately 30 nm. The surface charge density is extracted from force-distance curves using DLVO theory in combination with surface complexation modeling. While the gibbsite-like and the silica-like facet display on average positive and negative surface charge values as expected, our measurements reveal lateral variations of more than a factor of two on seemingly atomically smooth terraces, even if high resolution AFM images clearly reveal the atomic lattice on the surface. These results suggest that simple surface complexation models of clays that attribute a unique surface chemistry and hence homogeneous surface charge densities to basal planes may miss important aspects of real clay surfaces.

Matrix Synthesis of Graphene on a Diamond Surface and Its Simulation

NASA Astrophysics Data System (ADS)

Alekseev, N. I.

2018-07-01

A quantum-chemical simulation is performed for the transformation of the upper sublayer of carbon atoms in the lattice of single-crystal diamond into a flat graphene lattice under the influence of the atoms of a molten copper film on the diamond surface. It is established that the stable system configuration corresponds to the thermally activated motion of carbon atoms in the lower sublayer of the interface diamond layer to the position of graphene, i.e., at the same level as the atoms of the upper sublayer. The energy gain in comparison to the noninteracting subsystems of the copper and diamond atoms is approximately 0.7 eV per atom of the lower sublayer. The maximum size of the resulting graphene film is estimated and a possible mechanism for its rupture is considered.

Understanding and controlling the step bunching instability in aqueous silicon etching

NASA Astrophysics Data System (ADS)

Bao, Hailing

Chemical etching of silicon has been widely used for more than half a century in the semiconductor industry. It not only forms the basis for current wafer cleaning processes, it also serves as a powerful tool to create a variety of surface morphologies for different applications. Its potential for controlling surface morphology at the atomic scale over micron-size regions is especially appealing. In spite of its wide usage, the chemistry of silicon etching is poorly understood. Many seemingly simple but fundamental questions have not been answered. As a result, the development of new etchants and new etching protocols are based on expensive and tedious trial-and-error experiments. A better understanding of the etching mechanism would direct the rational formulation of new etchants that produce controlled etch morphologies. Particularly, micron-scale step bunches spontaneously develop on the vicinal Si(111) surface etched in KOH or other anisotropic aqueous etchants. The ability to control the size, orientation, density and regularity of these surface features would greatly improve the performance of microelectromechanical devices. This study is directed towards understanding the chemistry and step bunching instability in aqueous anisotropic etching of silicon through a combination of experimental techniques and theoretical simulations. To reveal the cause of step-bunching instability, kinetic Monte Carlo simulations were constructed based on an atomistic model of the silicon lattice and a modified kinematic wave theory. The simulations showed that inhomogeneity was the origin of step-bunching, which was confirmed through STM studies of etch morphologies created under controlled flow conditions. To quantify the size of the inhomogeneities in different etchants and to clarify their effects, a five-parallel-trench pattern was fabricated. This pattern used a nitride mask to protect most regions of the wafer; five evenly spaced etch windows were opened to the Si(110) substrate. Combining data from these etched patterns and surface IR spectra, a modified mechanism, which explained most experimental observations, was proposed. Control of the step-bunching instability was accomplished with a second micromachined etch barrier pattern which consisted of a circular array of seventy-two long, narrow trenches in an etch mask. Using this pattern, well aligned, regularly shaped, evenly-distributed, near-atomically flat terraces in micron size were produced controllably.

Isochron burial dating of Danube terraces in the course of an interlaboratory comparison on sample preparation in Vienna and Budapest

NASA Astrophysics Data System (ADS)

Neuhuber, Stephanie; Ruszkiczay-Rüdiger, Zsófia; Decker, Kurt; Braucher, Regis; Fiebig, Markus; Braun, Mihály; Häuselmann, Philipp; Aster Team

2016-04-01

The Neogene development of the Vienna Basin's tectonic history is well-documented in seismic sections and hydrocarbon wells. The late Neogene to Quaternary history is less well preserved due to a gap in the sediment record starting from the Late Pannonian due to a large-scale uplift during a phase of basin inversion [1]. Quaternary sediments in the Vienna Basin form prominent Pleistocene terraces north and south of the Danube's recent floodplain. The Danube's course currently shifts to the south where it erodes into its own gravel terraces that were presumably accumulated during the Pliocene and Early to Middle Pleistocene. North of the Danube, a wide alluvial plain has developed with one prominent Middle Quaternary terrace level 17-25 m above the river (Gänserndorf and Schlosshof Terraces). The most recent tectonic events related to the sinistral movement of the Vienna Basin transform fault system are recorded north of the Danube by faulted terrace segments that were identified by paleoseismological trenching in combination with OSL [2]. In contrast, terraces south of the Danube form a staircase with altitudes ranging between 25 and 130 m above todays water level. The terraces in the south have also been strongly dissected by faults [3], each fault block preserved a slightly different succession of terraces. The fault-related vertical displacements south of the Danube have not yet been quantified. To better understand the Quaternary terrace sequence and its displacement in the southern zone, we use the cosmogenic nuclide pair of 26Al and 10Be for isochron burial dating of a Danube terrace at Haslau an der Donau (~40 m above river level). This terrace is locally the lowest of a staircase of a total of 6 different levels. Based on published geomorphological works, the expected age is Middle Pleistocene. The isochron burial dating method is therefore well-suited to date this sedimentary setting due to the presence of large individual clasts that share the same post-depositional history, but have different pre-exposure and transport histories [4]. The sandy gravel of the Haslau terrace was sampled in an active gravel pit. At this location, two major sedimentary units are separated by an erosional hiatus of unknown duration. The upper sequence was sampled at 5.5 m depth and the lower one was sampled at 11.8 m depth. From both depths six quartzite or quartz-bearing cobbles were taken together with a bulk sample from the matrix for isochron burial duration determination. Five samples were split after crushing and sieving and were processed at both the Cosmogenic Nuclide Sample Preparation Laboratory at Vienna and at Budapest (http://www.geochem.hu/kozmogen/Lab_en.html), in order to assess and compare the sample processing preocedures of these recently operating sample preparation laboratories. AMS measurements were performed at the French national facility ASTER (CEREGE (Aix-en-Provence, France). Thanks to OTKA PD83610, NKM-96/2014, NKM-31/2015; OMAA 90öu17; LP2012-27/2012. INSU/CNRS, the ANR through the program "EQUIPEX Investissement d'Avenir", IRD and CEA. [1] Decker et al., 2005. QSR 24, 307-322 [2] Hintersberger et al, 2013, EGU2013-12755 [3] Salcher et al. 2012. Tectonics, 31, TC3004, doi:10.1029/2011TC002979 [4] Balco and Rovey, 2008. AJS 908, 1083-1114 [5] Fuchs and Grill, 1984, Geologische Gebietskarte der Republik Österreich 1:200 000 Wien und Umgebung

Monitoring and modelling for dry-stone walls terracement maintenance

NASA Astrophysics Data System (ADS)

Preti, Federico; Errico, Alessandro; Giambastiani, Yamuna; Guastini, Enrico; Penna, Daniele

2017-04-01

An analysis of dry-stone walls stability in agricultural areas based on innovative monitoring and modeling is here presented The field test took place in Lamole, a terraced rural area located in the province of Florence, Tuscany, central Italy, where wine production is the most important agricultural activity business. Results show a good capability of the model to predict the time-space distribution and the intensity of stresses on the instrumented dry-stone wall and to describe the bulging of the ancient ones. We obtained significant information on how the terrace failure in Lamole resulted mainly related to the water concentration pathways at specific portions of the walls. An accurate drainage of the terraced slopes, even by means of simple ditches, could reduce the concentration factor at the critical parts of terraces strongly reducing the water pressures on the walls. The analysis of the effects caused by high return time events has been carried out by means of artificially reproduced severe rainfalls on the presented experimental area.

Marine Terrace Deposits along the Mediterranean Coast on the Southeastern Turkey and Their Implications for Tectonic Uplift and Sea Level Change

NASA Astrophysics Data System (ADS)

Tari, U.; Tüysüz, O.; Blackwell, B. A. B.; Genç, Ş. C.; Florentin, J. A.; Mahmud, Z.; Li, G. L.; Blickstein, J. I. B.; Skinner, A. R.

2016-12-01

Tectonic movements among the African, Arabian and Anatolian Plates have deformed the eastern Mediterranean. These movements caused transtensional opening of the NE-trending Antakya Graben since the late Pliocene. Tectonic uplift coupled with Quaternary sealevel fluctuations has produced several stacked marine terraces along the Mediterranean coasts on the graben. Here, marine terrace deposits that sit on both flanks of the graben at elevations between 3 and 175 m were dated using electron spin resonance (ESR) method in order to calculate uplift rates. The ESR ages range from 12 ka in late MIS 2 to 457 ka in MIS 9-11, but most of the terraces contain molluscs reworked from several earlier deposits due to successive tectonic movements and sealevel fluctuations. By dating in situ fossils, along the basal contacts of the marine terraces, uplift rates were calculated on both sides of the Antakya Graben. Results indicate that these deposits were mainly uplifted by local active faults rather than regional movements.

Ground-water conditions in the Dutch Flats area, Scotts Bluff and Sioux Counties, Nebraska, with a section on chemical quality of the ground water

USGS Publications Warehouse

Babcock, H.M.; Visher, F.N.; Durum, W.H.

1951-01-01

The U.S. Department of the Interior (DOI) studied contamination induced by irrigation drainage in 26 areas of the Western United States during 1986-95. Comprehensive compilation, synthesis, and evaluation of the data resulting from these studies were initiated by DOI in 1992. Soils and ground water in irrigated areas of the West can contain high concentrations of selenium because of (1) residual selenium from the soil's parent rock beneath irrigated land; (2) selenium derived from rocks in mountains upland from irrigated land by erosion and transport along local drainages, and (3) selenium brought into the area in surface water imported for irrigation. Application of irrigation water to seleniferous soils can dissolve and mobilize selenium and create hydraulic gradients that cause the discharge of seleniferous ground water into irrigation drains. Given a source of selenium, the magnitude of selenium contamination in drainage-affected aquatic ecosystems is strongly related to the aridity of the area and the presence of terminal lakes and ponds. Marine sedimentary rocks and deposits of Late Cretaceous or Tertiary age are generally seleniferous in the Western United States. Depending on their origin and history, some Tertiary continental sedimentary deposits also are seleniferous. Irrigation of areas associated with these rocks and deposits can result in concentrations of selenium in water that exceed criteria for the protection of freshwater aquatic life. Geologic and climatic data for the Western United States were evaluated and incorporated into a geographic information system (GIS) to produce a map identifying areas susceptible to irrigation-induced selenium contamination. Land is considered susceptible where a geologic source of selenium is in or near the area and where the evaporation rate is more than 2.5 times the precipitation rate. In the Western United States, about 160,000 square miles of land, which includes about 4,100 square miles (2.6 million acres) of land irrigated for agriculture, has been identified as being susceptible. Biological data were used to evaluate the reliability of the map. In 12 of DOI's 26 study areas, concentrations of selenium measured in bird eggs were elevated sufficiently to significantly reduce hatchability of the eggs. The GIS map identifies 9 of those 12 areas. Deformed bird embryos having classic symptoms of selenium toxicosis were found in four of the study areas, and the map identifies all four as susceptible to irrigation-induced selenium contamination. The report describes the geography, geology, and ground-water resources of the Dutch Flats area in Scotts Bluff and Sioux Counties, Nebr. The area comprises about 60 square miles and consists predominantly of relatively flat-lying terraces. Farming is the principal occupation in the area. The farm lands are irrigated largely from surface water; ground water is used only as a supplementary supply during drought periods. The climate in the area is semiarid, and the mean annual precipitation is about 16 inches. The rocks exposed in the Dutch Flats area are of Tertiary sad Quaternary age. A map showing the areas of outcrop of the rock formations is included in the report. Sufficient unconfined ground water for irrigation supplies is contained in the deposits of the .third terrace, and wells that yield 1,000 to 2,000 gallons a minute probably could be developed. The depth to water in the area ranges from a few feet to about 80 feet sad averages about 30 feet. The depth to water varies throughout the year; it is least in the late summer when the recharge from irrigation is greatest, sad it is greatest in the early spring before irrigation is begun. A map showing the depth to water in September 1949 is included in the report. The ground-water reservoir is recharged by seepage from irrigation canals and laterals, by seepage from irrigation water applied to the farms, and, to a much lesser extent, by precipitation. In the area b

Topographic growth around the Orange River valley, southern Africa: A Cenozoic record of crustal deformation and climatic change

NASA Astrophysics Data System (ADS)

Dauteuil, Olivier; Bessin, Paul; Guillocheau, François

2015-03-01

We reconstruct the history of topographic growth in southern Africa on both sides of the Orange River valley from an integrated analysis of erosion surfaces, crustal deformation and climate change. First, we propose an inventory of erosion surfaces observed in the study area and classify them according to their most likely formative process, i.e. chemical weathering or mechanical erosion. Among the various land units observed we define a new class of landform: the pedivalley, which corresponds to a wide valley with a flat erosional floor. In the Orange River valley, we mapped three low-relief erosion surfaces, each bevelling a variety of lithologies. The oldest and most elevated is (1) a stripped etchplain evolving laterally into (2) a stepped pediplain bearing residual inselbergs; (3) a younger pediplain later formed in response to a more recent event of crustal deformation. These are all Cenozoic landforms: the etchplain is associated with a late Palaeocene to middle Eocene weathering event, and the two pediplains are older than the middle Miocene alluvial terraces of the Orange River. Landscape evolution was first driven by slow uplift (10 m/Ma), followed by a second interval of uplift involving a cumulative magnitude of at least 200 m. This event shaped the transition between the two pediplains and modified the drainage pattern. A final phase of uplift (magnitude: 60 m) occurred after the Middle Miocene and drove the incision of the lower terraces of the Orange River. Climate exerted a major control over the denudation process, and involved very humid conditions responsible for lateritic weathering, followed by more arid conditions, which promoted the formation of pedivalleys. Collectively, these produce pediplains.

Architecture and morphology of coral reef sequences. Modeling and observations from uplifting islands of SE Sulawesi, Indonesia

NASA Astrophysics Data System (ADS)

Pastier, Anne-Morwenn; Husson, Laurent; Bezos, Antoine; Pedoja, Kevin; Elliot, Mary; Hafidz, Abdul; Imran, Muhammad; Lacroix, Pascal; Robert, Xavier

2016-04-01

During the Late Neogene, sea level oscillations have profoundly shaped the morphology of the coastlines of intertropical zones, wherein relative sea level simultaneously controlled reef expansion and erosion of earlier reef bodies. In uplifted domains like SE Sulawesi, the sequences of fossil reefs display a variety of fossil morphologies. Similarly, the morphologies of the modern reefs are highly variable, including cliff notches, narrow fringing reefs, wide flat terraces, and barriers reefs. In this region, where uplift rates vary rapidly laterally, the entire set of morphologies is displayed within short distances. We developed a numerical model that predicts the architecture of fossil reefs sequences and apply it to observations from SE Sulawesi, accounting -amongst other parameters- for reef growth, coastal erosion, and uplift rates. The observations that we use to calibrate our models are mostly the morphology of both the onshore (dGPS and high-resolution Pleiades DEM) and offshore (sonar) coast, as well as U-Th radiometrically dated coral samples. Our method allows unravelling the spatial and temporal evolution of large domains on map view. Our analysis indicates that the architecture and morphology of uplifting coastlines is almost systematically polyphased (as attested by samples of different ages within a unique terrace), which assigns a primordial role to erosion, comparable to reef growth. Our models also reproduce the variety of modern morphologies, which are chiefly dictated by the uplift rates of the pre-existing morphology of the substratum, itself responding to the joint effects of reef building and subsequent erosion. In turn, we find that fossil and modern morphologies can be returned to uplift rates rather precisely, as the parametric window of each specific morphology is often narrow.

Oxygen and sulfur adsorption on vicinal surfaces of copper and silver: Preferred adsorption sites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Da-Jiang; Thiel, Patricia A.

We present an extensive density functional theory (DFT) study of adsorption site energetics for oxygen and sulfur adsorbed on two vicinal surfaces of Cu and Ag, with the goal of identifying the most stable adsorption site(s), identifying trends and common themes, and comparing with experimental work in the literature where possible. We also present benchmark calculations for adsorption on the flat (111) and (100) surfaces. The first vicinal surface is the (211), and results are similar for both metals. Here, we find that the step-doubling reconstruction is favored with both adsorbates and is driven by the creation of a specialmore » stable fourfold hollow (4fh) site at the reconstructed step. Zig-zag chain structures consisting of X–M–X units (X = chalcogen, M = metal) at the step edge are considered, in which the special 4fh site is partially occupied. The zig-zag configuration is energetically competitive for oxygen but not sulfur. DFT results for oxygen agree with experiment in terms of the stability of the reconstruction, but contradict the original site assignment. The second vicinal surface is the (410), where again results are similar for both metals. For oxygen, DFT predicts that step sites are filled preferentially even at lowest coverage, followed by terrace sites, consistent with the experiment. For sulfur, in contrast, DFT predicts that terrace sites fill first. Oxygen forms O–M–O rows on the top edge of the step, where it occupies incomplete 4fh sites. This resolves an experimental ambiguity in the site assignment. Finally, for both the (211) and (410) surfaces, the interaction energy that stabilizes the X–M–X chain or row correlates with the linearity of the X–M–X unit, which may explain key differences between oxygen and sulfur.« less

Oxygen and sulfur adsorption on vicinal surfaces of copper and silver: Preferred adsorption sites

DOE PAGES

Liu, Da-Jiang; Thiel, Patricia A.

2018-03-28

We present an extensive density functional theory (DFT) study of adsorption site energetics for oxygen and sulfur adsorbed on two vicinal surfaces of Cu and Ag, with the goal of identifying the most stable adsorption site(s), identifying trends and common themes, and comparing with experimental work in the literature where possible. We also present benchmark calculations for adsorption on the flat (111) and (100) surfaces. The first vicinal surface is the (211), and results are similar for both metals. Here, we find that the step-doubling reconstruction is favored with both adsorbates and is driven by the creation of a specialmore » stable fourfold hollow (4fh) site at the reconstructed step. Zig-zag chain structures consisting of X–M–X units (X = chalcogen, M = metal) at the step edge are considered, in which the special 4fh site is partially occupied. The zig-zag configuration is energetically competitive for oxygen but not sulfur. DFT results for oxygen agree with experiment in terms of the stability of the reconstruction, but contradict the original site assignment. The second vicinal surface is the (410), where again results are similar for both metals. For oxygen, DFT predicts that step sites are filled preferentially even at lowest coverage, followed by terrace sites, consistent with the experiment. For sulfur, in contrast, DFT predicts that terrace sites fill first. Oxygen forms O–M–O rows on the top edge of the step, where it occupies incomplete 4fh sites. This resolves an experimental ambiguity in the site assignment. Finally, for both the (211) and (410) surfaces, the interaction energy that stabilizes the X–M–X chain or row correlates with the linearity of the X–M–X unit, which may explain key differences between oxygen and sulfur.« less

Biologic origin of iron nodules in a marine terrace chronosequence, Santa Cruz, California

USGS Publications Warehouse

Schulz, M.S.; Vivit, D.; Schulz, C.; Fitzpatrick, J.; White, A.

2010-01-01

The distribution, chemistry, and morphology of Fe nodules were studied in a marine terrace soil chronosequence northwest of Santa Cruz, California. The Fe nodules are found at depths <1 m on all terraces. The nodules consisted of soil mineral grains cemented by Fe oxides. The nodules varied in size from 0.5 to 25 mm in diameter. Nodules did not occur in the underlying regolith. The Fe-oxide mineralogy of the nodules was typically goethite; however, a subset of nodules consisted of maghemite. There was a slight transformation to hematite with time. The abundance of soil Fe nodules increased with terrace age on the five terraces studied (aged 65,000-226,000 yr). Scanning electron microscopy (SEM) revealed Fe-oxide-containing fungal hyphae throughout the nodules, including organic structures incorporating fine-grained Fe oxides. The fine-grained nature of the Fe oxides was substantiated by M??ssbauer spectroscopy. Our microscopic observations led to the hypothesis that the nodules in the Santa Cruz terrace soils are precipitated by fungi, perhaps as a strategy to sequester primary mineral grains for nutrient extraction. The fungal structures are fixed by the seasonal wetting and dry cycles and rounded through bioturbation. The organic structures are compacted by the degradation of fungal C with time. ?? Soil Science Society of America. All rights reserved.

Sustainability of terraced paddy fields in traditional satoyama landscapes of Japan.

PubMed

Fukamachi, Katsue

2017-11-01

Terraced paddy fields are essential components of the traditional cultural landscape of Japan, the satoyama landscape. They have been sustainably cultivated in a variety of ecological and social environments through time, and are highly valued as local resources with multiple functions. This paper reviews the recent nationwide movement for conservation of satoyama landscapes and shows that over the last decades, the government has increasingly created policies based on national regulation or international frameworks that concern the culture and environment in rural areas. Recent measures for the sustainability of terraced paddy fields do not only focus on rice terraces, but are directed at each satoyama landscape as a whole under careful consideration of how landscape elements are connected while taking into account the unique features of each area. Nevertheless, it has become difficult to ensure the continued use and maintenance of terraced rice paddies both in depopulated and suburban satoyama landscapes. The motivation for conserving satoyama landscapes, including those with terraced rice paddies, can be found in the awareness and appreciation of the unique characteristics of each locality that offer opportunities that can only be experienced in that particular area. A satoyama landscape that offers such opportunities allows continuity of traditional practices while integrating necessary changes. Copyright © 2016 Elsevier Ltd. All rights reserved.

U-series ages of solitary corals from the California coast by mass spectrometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stein, M.; Wasserburg, G.J.; Chen, J.H.

1991-12-01

The purpose of this study is to evaluate the feasibility of dating fossil solitary corals from Pleistocene marine strandlines outside tropical latitudes using the recently developed high sensitivity, high-precision U-series technique based on thermal-ionization mass-spectrometry (TIMS). The TIMS technique is much more efficient than conventional {alpha} spectrometry and, as a result, multiple samples of an individual coral skeleton, or different specimens from the same bed can be analyzed. Detached and well-rounded fossil specimens of the solitary coral Balanophyllia elegans were collected from relict littoral deposits on emergent marine terraces along the California coast at Cayucos terrace, Shell Beach terrace, Nestormore » terrace, San Diego, Bird Rock terrace, San Diego. Attached living specimens were collected from the intertidal zone on the modern terrace at Moss Beach. The calculated initial {sup 234}U activities in the fossil specimens of Balanophyllia elegans are higher than the {sup 234}U activity in modern seawater or in the modern specimen. The higher initial activities could possibly reflect the influx of {sup 234}U-enriched continental water into Pleistocene coastal waters, or it could reflect the influx of {sup 234}U-enriched continental water into Pleistocene coastal waters, or it could reflect minor diagenetic alteration, a persistent and fundamental problem in dating all corals.« less

River terrace development in the NE Mediterranean region (Syria and Turkey): Patterns in relation to crustal type

NASA Astrophysics Data System (ADS)

Bridgland, David R.; Demir, Tuncer; Seyrek, Ali; Daoud, Mohamad; Abou Romieh, Mohammad; Westaway, Rob

2017-06-01

It is widely recognized that the optimal development of river terraces globally has been in the temperate latitudes, with NW and Central Europe being areas of particular importance for the preservation of such archives of Quaternary environmental change. There is also a growing consensus that the principal drivers of terrace formation have been climatic fluctuation against a background of progressive (but variable) uplift. Nonetheless river terraces are widely preserved in the Mediterranean region, where they have often been attributed to the effects of neotectonic activity, with a continuing debate about the relative significance of fluctuating temperature (glacials-interglacials) and precipitation (pluvials-interpluvials). Research in Syria and southern-central Turkey (specifically in the valleys of the Tigris and Ceyhan in Turkey, the Kebir in Syria and the trans-border rivers Orontes and Euphrates) has underlined the importance of uplift rates in dictating the preservation pattern of fluvial archives and has revealed different patterns that can be related to crustal type. The NE Mediterranean coastal region has experienced unusually rapid uplift in the Late Quaternary. The relation between the Kebir terraces and the staircase of interglacial raised beaches preserved along the Mediterranean coastline of NW Syria reinforces previous conclusions that the emplacement of the fluvial terrace deposits in the Mediterranean has occurred during colder climatic episodes.

Phenotype diversity analysis of red-grained rice landraces from Yuanyang Hani's terraced fields, China

NASA Astrophysics Data System (ADS)

Li, Lianjie; Cheng, Long

2017-10-01

There are many areas in the world have terraced fields, Yuanyang Rani's terraced fields are examples in the world, and their unique ecological diversity is beyond other terraced fields, rice landraces are very rich. In order to provide useful information for protection and utilization of red-grained rice landraces from Rani's terraced fields, 61 red-grained rice landraces were assessed based 20 quantitative traits. Principal component analysis (PCA) suggested that 20 quantitative characters could be simplified to seven principal components, and their accumulative contribution ration amounted to 78.699%. The first principal component (PC1) explained 18.375% of the total variance, which was contributed by filled grain number, 1000-grain weight, spikelets per panicle, secondary branch number, grain length, and grain thickness. PC2 accounted for 16.548% of the variance and featured flag leaf width, flag leaf area, panicle neck length and primary branch number. These traits were the most effective parameters to discriminate individuals. At the request of the proceedings editor and with the approval of all authors, article 040111 titled, "Phenotype diversity analysis of red-grained rice landraces from Yuanyang Hani's terraced fields, China," is being retracted from the public record due to the fact that it is a duplication of article 040110 published in the same volume.

An Introduction to Atomic Layer Deposition

NASA Technical Reports Server (NTRS)

Dwivedi, Vivek H.

2017-01-01

Atomic Layer Deposition has been instrumental in providing a deposition method for multiple space flight applications. It is well known that ALD is a cost effective nanoadditive-manufacturing technique that allows for the conformal coating of substrates with atomic control in a benign temperature and pressure environment. Through the introduction of paired precursor gases, thin films can be deposited on a myriad of substrates from flat surfaces to those with significant topography. By providing atomic layer control, where single layers of atoms can be deposited, the fabrication of metal transparent films, precise nano-laminates, and coatings of nano-channels, pores and particles is achievable. The feasibility of this technology for NASA line of business applications range from thermal systems, optics, sensors, to environmental protection. An overview of this technology will be presented.

Ground-water resources of the Paintrock irrigation project, Wyoming, with a section on the quality of the water

USGS Publications Warehouse

Swenson, Frank Albert; Bach, W. Kenneth; Swenson, Herbert A.

1951-01-01

The ground-water conditions of the area covered by the Paintrock irrigation project, in north-central Wyoming, were investigated during the summer of 1947. The purpose of the study was to obtain a general evaluation of ground-water recharge, discharge, and storage in the area now irrigated and in the adjacent areas where additional lands are to be irrigated.Much of the area covered by this report consists of flat to gently sloping stream terraces and alluvial-bottoms along Nowood, Paintrock, and Medicine Lodge Creeks. The stream-terrace materials consist of fluviatile sand, clay, and gravel. The alluvium is very fine grained and in general has low permeability. The materials underlying the stream terraces and the bottomlands became progressively finer grained and less permeable downstream.The bedrock formations underlying the area studied range from the Madison limestone of Mississippian age to the Fort Union formation of Paleocene age. Beds have been folded into several prominent structures which trend northwest-southeast across the area. Several of the formations exposed in the area serve as aquifers and yield water to domestic and stock wells. The most important bedrock aquifers are the Fort Union, Lance, Meeteetee, Mesaverde, Frontier, Cloverly and Morrison formations , the Tensleep sandstone, the Amsden formation, and the Madison limestone. More than 7,000 feet of strata are exposed in the area, the older beds being exposed on the western flank of the Big Horn Range near the eastern end of the area.The quality of the water in the project ranges within wide limits. The concentration of dissolved solids in seven samples of ground water ranges from 279 parts per million for a water in the Tensleep sandstone to 4,590 parts per million for a water in the Morrison formation. The hardness as calcium carbonate (CaCO3) ranges from 13 to 1,680 parts per million. Limited data on the quality of water in Nowood and Paintrock Creeks indicate that these waters are suitable for irrigation. The water in Paintrock Creek near Tensleep is higher in mineral content and hardness than the water upstream at Hyattville as a result of return flow of the irrigation water that is applied to farm lands above Tensleep.

Automatic identification of agricultural terraces through object-oriented analysis of very high resolution DSMs and multispectral imagery obtained from an unmanned aerial vehicle.

PubMed

Diaz-Varela, R A; Zarco-Tejada, P J; Angileri, V; Loudjani, P

2014-02-15

Agricultural terraces are features that provide a number of ecosystem services. As a result, their maintenance is supported by measures established by the European Common Agricultural Policy (CAP). In the framework of CAP implementation and monitoring, there is a current and future need for the development of robust, repeatable and cost-effective methodologies for the automatic identification and monitoring of these features at farm scale. This is a complex task, particularly when terraces are associated to complex vegetation cover patterns, as happens with permanent crops (e.g. olive trees). In this study we present a novel methodology for automatic and cost-efficient identification of terraces using only imagery from commercial off-the-shelf (COTS) cameras on board unmanned aerial vehicles (UAVs). Using state-of-the-art computer vision techniques, we generated orthoimagery and digital surface models (DSMs) at 11 cm spatial resolution with low user intervention. In a second stage, these data were used to identify terraces using a multi-scale object-oriented classification method. Results show the potential of this method even in highly complex agricultural areas, both regarding DSM reconstruction and image classification. The UAV-derived DSM had a root mean square error (RMSE) lower than 0.5 m when the height of the terraces was assessed against field GPS data. The subsequent automated terrace classification yielded an overall accuracy of 90% based exclusively on spectral and elevation data derived from the UAV imagery. Copyright © 2014 Elsevier Ltd. All rights reserved.

Eccentricity-driven fluvial fill terrace formation in the southern-central Andes, NW Argentina

NASA Astrophysics Data System (ADS)

Tofelde, Stefanie; Savi, Sara; Wickert, Andrew D.; Wittmann, Hella; Alonso, Ricardo; Strecker, Manfred R.; Schildgen, Taylor F.

2016-04-01

Across the world, fill-terrace formation in glaciated catchments has been linked to variable sediment production and river discharge over glacial-interglacial cycles. Little is known, however, how variability in global climate may have affected rainfall patterns and associated surface-processes on multi-millennial timescales in regions far from major glaciers and ice sheets, and how those changes might be reflected in the landscape. Here, we investigate the timing of fluvial fill terrace planation and abandonment in the Quebrada del Toro, an intermontane basin located in the Eastern Cordillera of the southern-central Andes of NW Argentina. Fluvial fills in the valley reach more than 150 m above the current river level. Sculpted into the fills, we observe at least 5 terrace levels with pronounced differences in their extent and preservation. We sampled four TCN (in situ 10Be) depth profiles to date the abandonment of the most extensive terrace surfaces in locations, where subsequent overprint by erosion and deposition was not pronounced. We interpret unexpectedly low 10Be concentrations at shallow depths and surface samples to be related to aeolian input, causing surface inflation. Correcting the depth profiles for inflation results in a reduction of the terrace surface ages by up to 70 ka. The inflation-corrected ages fall within the late Pleistocene (~140 - 370 ka) and suggest a potential link to orbital eccentricity (~100 ka) cycles. The studied fills in the Toro Basin document successive episodes of incision, punctuated by periods of lateral planation and possible partial re-filling. We propose climate cycles as a potentially-dominant factor in forming these terraces. To our knowledge, none of the previously studied fluvial terraces in the Andes date back more than 2 glacial cycles, thus making the Quebrada del Toro an important archive of paleoenvironmental conditions over longer timescales.

Long river profiles, tectonism, and eustasy: A guide to interpreting fluvial terraces

NASA Technical Reports Server (NTRS)

Merritts, Dorothy J.; Vincent, Kirk R.; Wohl, Ellen E.

1994-01-01

Along three rivers at the Mendocino triple junction, northern California, strath, cut, and fill terraces have formed in response to tectonic and eustatic processes. Detailed surveying and radiometric dating at multiple sites indicate that lower reaches of the rivers are dominated by the effects of oscillating sea level, primarily aggradation and formation of fill terraces during sea level high stands, alternating with deep incision during low stands. A eustasy-driven depositional wedge extends tens of kilometers upstream on all rivers (tapering to zero thickness). This distance is greater than expected from studies of the effects of check dams on much smaller streams elsewhere, due in part to the large size of these rivers. However, the change in gradient is nearly identical to other base level rise studies: the depositional gradient is about half that of the original channel. Middle to upper reaches of each river are dominated by the effects of long-term uplift, primarily lateral and vertical erosion and formation of steep, unpaired strath terraces exposed only upstream of the depositional wedge. Vertical incision at a rate similar to that of uplift has occurred even during the present sea level high stand along rivers with highest uplift rates. Strath terraces have steeper gradients than the modern channel bed and do not merge with marine terraces at the river mouth; consequently, they cannot be used to determine altitudes of sea level high stands. Strath formation is a continuous process of response to long-term uplift, and its occurrence varies spatially along a river depending on stream power, and hence position, upstream. Strath terraces are found only along certain parts of a coastal stream: upstream of the aggradational effects of oscillating sea level, and far enough downstream that stream power is in excess of that needed to transport the prevailing sediment load. For a given size river, the greater the uplift rate, the greater the rate of vertical incision and, consequently, the less the likelihood of strath terrace formation and preservation.

Agronomic Challenges and Opportunities for Smallholder Terrace Agriculture in Developing Countries

PubMed Central

Chapagain, Tejendra; Raizada, Manish N.

2017-01-01

Improving land productivity is essential to meet increasing food and forage demands in hillside and mountain communities. Tens of millions of smallholder terrace farmers in Asia, Africa, and Latin America who earn $1–2 per day do not have access to peer-reviewed knowledge of best agronomic practices, though they have considerable traditional ecological knowledge. Terrace farmers also lack access to affordable farm tools and inputs required to increase crop yields. The objectives of this review are to highlight the agronomic challenges of terrace farming, and offer innovative, low-cost solutions to intensify terrace agriculture while improving local livelihoods. The article focuses on smallholder farmers in developing nations, with particular reference to Nepal. The challenges of terrace agriculture in these regions include lack of quality land area for agriculture, erosion and loss of soil fertility, low yield, poor access to agricultural inputs and services, lack of mechanization, labor shortages, poverty, and illiteracy. Agronomic strategies that could help address these concerns include intensification of terraces using agro-ecological approaches along with introduction of light-weight, low-cost, and purchasable tools and affordable inputs that enhance productivity and reduce female drudgery. To package, deliver, and share these technologies with remote hillside communities, effective scaling up models are required. One opportunity to enable distribution of these products could be to “piggy-back” onto pre-existing snackfood/cigarette/alcohol distribution networks that are prevalent even in the most remote mountainous regions of the world. Such strategies, practices, and tools could be supported by formalized government policies dedicated to the well-being of terrace farmers and ecosystems, to maintain resiliency at a time of alarming climate change. We hope this review will inform governments, non-governmental organizations, and the private sector to draw attention to this neglected and vulnerable agro-ecosystem in developing countries. PMID:28367150

On the hydrological-hydraulic modelling of hillslope dry-stone walls

NASA Astrophysics Data System (ADS)

Perlotto, Chiara; Michelini, Tamara; D'Agostino, Vincenzo

2015-04-01

Terraces are among the most evident human signatures on the landscape as they cover large cultivated territories of the Earth. The importance of dry-stone walls to realize bench terraces has always played a key role in the management of the agricultural hilly/mountain areas. These works are generally built to allow tractors and ploughs to operate under acceptable conditions, to make human work in the slopes easy and comfortable, and to promote irrigation. Few studies in literature are available on rainfall-runoff transformation and flood risk mitigation in terrace areas. Then, research results in this field are still scarce. Bench terraces reduce the terrain slope and the length of the overland flow, quantitatively controlling the runoff flow velocity, facilitating the drainage and thus leading to a reduction of soil erosion. As to the hydrological response, a terraced slope should result in a reduction in the peak runoff at the toe of hillslope and in a delay in the passage of the peak flows. This fact occurs mainly due to the change of the original land topography. The goal of this study is highlighting the benefit in terms of runoff reduction, which is provided by sequence of dry-stone walls under different space arrangements along the hillslope. In particular, the FLO-2D model was recursively applied to a schematic hillslope simulating both the local variations of the hydrological soil characteristics and the morphological stepped profile of the bench terraces. The simulations have been carried out by varying the main parameters underlying the design of the terrace system (spacing, height and number of terraces). The results have shown an interesting clear linkage between the peak-discharge reduction of the overland flows and the area extent, which is consolidated by means of the dry-stone walls. The modelling outcomes well support and inform design criteria, cost-benefit analysis and the assessment of the functionality level of this historical consolidation system.

New 40Ar/39Ar eruption ages for the western Aeolian Arc, Southern Italy

NASA Astrophysics Data System (ADS)

Creamer, J. B.; Calvert, A. T.; Spera, F. J.

2011-12-01

New 40Ar/39Ar ages are presented for the western Aeolian Arc, southern Italy which help constrain eruption frequency and revise the local uplift history through bracketing the timing of marine terrace formation. The islands of Alicudi, Filicudi, and Salina are late-Quaternary composite stratovolcanoes which feature basaltic to dacitic calc-alkaline and high-K series lavas and pyroclastics. These islands have been the focus of several geochronologic studies in the past but many open questions remain due to recently revised mapping, conflicting ages, and incomplete coverage of eruptive sequences. On Salina, a single new age constrains the previously undated Corvo volcano to 128.8 +/- 5.3 ka. On Filicudi, three new dates constrain the oldest exposed episodes of volcanism to ~200-205 ka, in good agreement with previous K/Ar ages. The age of an intervening marine terrace is constrained by these oldest units to c. 200 ka. Additionally there is one new date of 80.4 ± 9.4 ka on the youngest effusive eruption on Filicudi, a dacite dome that overlies the youngest marine terrace on the island. On Alicudi, five new dates constrain the oldest exposed units (Paleo Alicudi Synthem) to 167.4 ± 26.1 ka, the Scoglio Galera to Spano synthems between 64.1 ± 4.1 ka and 59.3 ± 1.3 ka, and confirm the youngest eruptions (Fillo dell'Arpa Fm) at 30.0 ± 0.7 ka. Importantly, an undated formation that overlies the 59.3 ka unit is cut by a marine terrace that was previously interpreted to be ~80 ka (MIS 5a highstand). This result calls into question the archipelago-wide age correlation of marine terraces attempted by Lucchi et al. 2008 since the youngest terrace on Alicudi is younger than eruptive units that overly all terraces on Filicudi. Previous work suggesting that marine terraces on Filicudi were formed during Marine Isotope Stages (MIS) 5a,c, and e is permitted by our new ages, but the oldest terrace ('Paleoshoreline B') on Filicudi was possibly formed during MIS 7 rather than MIS 9, and terraces on Alicudi were likely formed during MIS 3 rather than MIS 5. This would require that the volcanoes have uplift histories that are much more independent of each other than previously thought, suggesting in turn that uplift may be controlled by individual magmatic systems rather than a regional phenomenon.

Lattice Gas Model Based Optimization of Plasma-Surface Processes for GaN-Based Compound Growth

NASA Astrophysics Data System (ADS)

Nonokawa, Kiyohide; Suzuki, Takuma; Kitamori, Kazutaka; Sawada, Takayuki

2001-10-01

Progress of the epitaxial growth technique for GaN-based compounds makes these materials attractive for applications in high temperature/high-power electronic devices as well as in short-wavelength optoelectronic devices. For MBE growth of GaN epilayer, atomic nitrogen is usually supplied from ECR-plasma while atomic Ga is supplied from conventional K-cell. To grow high-quality epilayer, fundamental knowledge of the detailed atomic process, such as adsorption, surface migration, incorporation, desorption and so forth, is required. We have studied the influence of growth conditions on the flatness of the growth front surface and the growth rate using Monte Carlo simulation based on the lattice gas model. Under the fixed Ga flux condition, the lower the nitrogen flux and/or the higher the growth temperature, the better the flatness of the front surface at the sacrifice of the growth rate of the epilayer. When the nitrogen flux is increased, the growth rate reaches saturation value determined from the Ga flux. At a fixed growth temperature, increasing of nitrogen to Ga flux ratio results in rough surface owing to 3-dimensional island formation. Other characteristics of MBE-GaN growth using ECR-plasma can be well reproduced.

66. FONTHILL GARAGE (1913) AND TERRACE PAVILION (192628), FROM SOUTH. ...

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

66. FONTHILL GARAGE (1913) AND TERRACE PAVILION (1926-28), FROM SOUTH. POURED ATOP AN EARLIER STONE BARN. THE FIRST FLOOR OF THIS STRUCTURE SERVERD AS A GARAGE FOR FONTHILL. IN 1926, MERCER BEGAN CONVERTING THE SECOND FLOOR INTO AND ELABORATELY DECORATED MEETING HOUSE FOR THE DOYLESTOWN NATURE CLUB, CALLED THE TERRACE PAVILION. - Moravian Pottery & Tile Works, Southwest side of State Route 313 (Swamp Road), Northwest of East Court Street, Doylestown, Bucks County, PA

Sixth-Year Results Following Partial Cutting For Timber and Wildlife Habitat in a Mixed Oak-Sweetgum-Pine Stand on a Minor Creek Terrace in Southeast Louisiana

Treesearch

Brian Roy Lockhart; Norwin E. Linnartz

2002-01-01

Hardwood management has primarily focused on highly productive river bottom and upland sites. Less is known about hardwood growth and development on terrace sites. Such sites are usually converted to other uses, especially pine plantations. The objectives of this study, implemented in a minor creek terrace in southeast Louisiana, were to describe changes in stand...

Securing a Suicide Hot Spot: Effects of a Safety Net at the Bern Muenster Terrace

ERIC Educational Resources Information Center

Reisch, Thomas; Michel, Konrad

2005-01-01

The city of Bern has a high percentage of suicides by jumping (28.6%). Related to other local hotspots, the highest number of deaths (mean 2.5 per year) is found at the Muenster Terrace in the old city. In 1998, after a series of suicides, a safety net was built to prevent people from leaping from the terrace and to avoid further traumatization of…

Terraces on the Florida escarpment: Implications for erosional processes

USGS Publications Warehouse

Twichell, D.C.; Paull, C.K.; Parson, L.M.

1991-01-01

SeaBeam bathymetric data and GLORIA (Geologic LOng-Range Inclined Asdic) sidescan sonar images of a 175-km-long section of the Florida escarpment in the eastern Guff of Mexico show that this carbonate escarpment has been eroded since its initial formation, but its morphology suggests that erosional processes have not acted uniformly on the escarpment. Parts of the escarpment are notched by box canyons that have extremely steep headwalls and may be sites off active ground-water sapping. The intercanyon areas commonly have previously unrecognized terraces below 2600 m. Above 2600 m, the escarpment is steeper and has no terraces. The terraces may reflect differences in platform strata exposed at the escarpment that are responding differently to erosional processes.

Three-dimensional spin mapping of antiferromagnetic nanopyramids having spatially alternating surface anisotropy at room temperature.

PubMed

Wang, Kangkang; Smith, Arthur R

2012-11-14

Antiferromagnets play a key role in modern spintronic devices owing to their ability to modify the switching behavior of adjacent ferromagnets via the exchange bias effect. Consequently, detailed measurements of the spin structure at antiferromagnetic interfaces and surfaces are highly desirable, not only for advancing technologies but also for enabling new insights into the underlying physics. Here using spin-polarized scanning tunneling microscopy at room-temperature, we reveal in three-dimensions an orthogonal spin structure on antiferromagnetic compound nanopyramids. Contrary to expected uniaxial anisotropy based on bulk properties, the atomic terraces are found to have alternating in-plane and out-of-plane magnetic anisotropies. The observed layer-wise alternation in anisotropy could have strong influences on future nanoscale spintronic applications.

Active Faults in Eastern Hispaniola: The Hispaniola-Puerto Rico Microplate Boundary?

NASA Astrophysics Data System (ADS)

McCann, W. R.

2007-12-01

An extensive tract of limestone of mostly Pleistocene-Recent age covers the Eastern part of the Dominican Republic. Numerous distinctive marine terraces outcrop along the southern and eastern coast, the lowest of which has been dated at about 125Ka. In the eastern area, the highest terrace is about 50m asl, is very variable in elevation, and correlates with a terrace of about 50 m asl along the southern coast. This feature might correlate with a feature of similar height on the Island of Marie Galante in the Lesser Antilles, dated at 250Ka. Manipulation of 3 arc-sec grid of SRTM land data and a 12 arc-sec grid of marine data reveals the location of the upper marine terrace as well as numerous scarps with 10's of meters of relief tending WNW across the region. The 2nd derivative of the relief grid is used to objectively identify the location of the upper terrace, which is compared to the elevation grid to develop an along escarpment profile of terrace elevation. If undisturbed, this feature should be contour parallel, that is all at the same elevation. Systematic elevation changes along profile suggest titling and numerous abrupt vertical (~30-50m) and at least one horizontal offset (375m) of this feature. Terrace displacing scarps can be traced many kilometers from offshore, across the coast paralleling marine terraces, and continuing inland as linear features that I interpret as active normal faults cutting the limestone platform. Five systems of normal faults have been identified in this manner, the longest of which may be capable of generating earthquakes of about magnitude 7-7 1/4. If the age of the upper terrace is roughly about 250Ka, then the observed horizontal displacements of about 375 meters suggest a rate of fault motion on the order of mm"s/yr for each of the5 faults. This total rate of deformation of several mm/yr is similar to the rate of deformation calculated from GPS studies for the rate of motion between the Hispaniola and Puerto Rico microplates, suggesting that much of the inter-microplate motion is not contained to the offshore regions of the Mona Passage, but rather passes on shore in the eastern part of the Dominican Republic.

Contrasted terrace systems of the lower Moulouya valley as indicator of crustal deformation in NE Morocco

NASA Astrophysics Data System (ADS)

Rixhon, Gilles; Bartz, Melanie; El Ouahabi, Meriam; Szemkus, Nina; Brueckner, Helmut

2016-04-01

The Moulouya river has the largest catchment in Morocco and drains an area which is characterized by active crustal deformation during the Late Cenozoic due to the convergence between the African and Eurasian plates. As yet, its Pleistocene terrace sequence remains poorly documented. Our study focuses on the lowermost reach of the river in NE Morocco, which drains the Triffa sedimentary basin directly upstream of the estuary. New field observations, measurements and sedimentological data reveal contrasted fluvial environments on either side of a newly identified thrust zone, which disrupts the whole sedimentary basin and is associated with N-S compressive shortening in this region (Barcos et al., 2014). Long-lasting fluvial aggradation, materialized by ≥37 m-thick stacked fill terraces, and the development of a well-preserved terrace staircase, with (at least) three Pleistocene terrace levels, occur in the footwall and the hanging wall of the thrust, respectively. Same as for the Pleistocene terrace sediments of the middle Moulouya, a recurrent sedimentary pattern, characterized by fining-upward sequences was observed in the studied terrace profiles. Assessing the rates of crustal deformation along this main thrust zone requires age estimations for these Pleistocene terrace deposits of the lower Moulouya on each side of the thrust. Samples for luminescence (OSL/IRSL), electron spin resonance (ESR, on quartz) and cosmogenic nuclide dating (26Al/10Be, burial dating) were collected in terrace deposits located both in the foot- and hanging walls. Sample preparation and analysis as well as age determination are in progress. The preliminary data mentioned above, soon to be completed by chronological data, agree well with morphometric indicators stating that the whole Moulouya catchment is at disequilibrium state (Barcos et al., 2014). This is confirmed by several knickpoints in its longitudinal profile. Late Cenozoic uplift associated with crustal shortening, which occurred in the lowermost reach of the river, may have both hindered profile rectification of the Moulouya and, at the same time, buffered the effects of long-term base-level changes due to eustatic sea-level variations. Reference: Barcos, L., Jabaloy, A., Azdimousa, A., Asebriy, L., Gómez-Ortiz, D., Rodríguez-Peces, M.J., Tejero, R., Pérez-Peña, J.V., 2014. Study of relief changes related to active doming in the eastern Moroccan Rif (Morocco) using geomorphological indices. J. African Earth Sci. 100, 493-509.

Capturing sediment and nutrients in irrigated terraced landscapes

NASA Astrophysics Data System (ADS)

Slaets, Johanna; Schmitter, Petra; Hilger, Thomas; Piepho, Hans-Peter; Dercon, Gerd; Cadisch, Georg

2016-04-01

Terraces are often promoted as green filters in landscapes, buffering discharge and constituent peaks. For irrigated rice terraces, however, this mitigating potential has not been assessed at the landscape level. Additionally, sediment and nutrient inputs potentially affect soil fertility in agricultural terraces and therefore yield - the extent of the impact depending on the quality and quantity of the captured material. Quantifying such upland-lowland linkages is particularly important in intensely cultivated landscapes, as declining upland soil fertility could alter beneficial hydrological connectivity between terraces and surrounding landscapes. In this study, we therefore quantified the sediment, sediment-associated organic carbon and nitrogen inputs and losses for a 13 ha paddy rice area, surrounded by upland maize cultivation in Northwest Vietnam in 2010 and 2011. Turbidity sensors were used in combination with a linear mixed model in order to obtain continuous predictions of the constituent concentrations. Sediment texture was determined using mid-infrared spectroscopy. Uncertainty on annual load estimates was quantified by calculating 95% confidence intervals with a bootstrap approach. Sediment inputs from irrigation water to the rice area amounted to 48 Mg ha-1 a-1 and runoff during rainfall events contributed an additional 16 Mg ha-1 a-1. Export from the rice terraces equalled 63 Mg ha-1 a-1 of sediments, resulting in a net balance of 28 Mg ha-1 a-1 or a trapping of almost half of the annual sediment inputs. Runoff contributed one third of the sand inputs, while irrigated sediments were predominantly silty. As paddy outflow contained almost exclusively silt- and clay-sized material, 24 Mg ha-1 a-1 of captured sediments consisted of sand. The sediment-associated organic carbon resulted in a deposit of 1.09 Mg ha-1 a-1. For sediment-associated nitrogen, 0.68 Mg ha-1 a-1 was trapped in the terraces. Combining both sediment-associated and dissolved nitrogen, irrigation water provided a total input of 1.11 Mg ha-1 a-1, of which 54% was in the plant-available forms of ammonium and nitrate - an input larger than the recommended application of chemical fertilizer. Rice terraces were net traps for sediment and protected downstream areas by filtering coarse sediments. Combined with the importance of irrigation water as a source of organic carbon and nitrogen for the rice, this connectivity underscores the vulnerability of agricultural terraces to changes in surrounding land use.

Linking the runoff response at micro-plot and catchment scale following wildfire and terracing, north-central Portugal

NASA Astrophysics Data System (ADS)

Martins, Martinho A. S.; Rial-Rivas, María E.; Machado, Ana I.; Serpa, Dalila; Prats, Sergio A.; Faria, Sílvia R.; Varela, María E. T.; González-Pelayo, Óscar; Keizer, J. Jacob

2015-04-01

Wildfires are known as one of the principal natural hazards affecting the Mediterranean region. This includes Portugal, where wildfires have affected some 100.000 ha of rural lands each year. The effects of wildfires on runoff generation and/or the associated soil (fertility) losses have been studied in Portugal for more than two decades. Some of these studies have reported strong and sometimes extreme hydrological responses in recently burnt areas. Forestry operations in such areas have increasingly come to include bench terracing in preparation of new eucalypt plantations. The hydrological impacts of bench terracing, however, have received little research attention so far and the few existing publications are limited to small spatial scales. The construction of terraces is commonly considered an effective practice for soil conservation on steep slopes, having been applied by mankind since early history. Nonetheless, the present authors have measured high rates of splash as well as inter-rill erosion on recently constructed terraces, and have regularly observed rill formation, including on forest tracks which typically constitute an extensive network in such bench terraced plantations. The present study was carried out in a 29-ha forest catchment in north-central Portugal that was burnt by a wildfire during the summer of 2010, logged during early winter 2010/11, and then bench terraced with bulldozers during late winter 2011, some 6 months after the wildfire. The catchment outlet was instrumented immediately after the fire with an automatic hydrometric station comprising two subsequent flumes with maximum discharge capacities of 120 and 1700 l sec-1. Within the catchment, rainfall was measured using several automatic and storage gauges and overland flow was monitored on two contrasting slopes using 3 micro-plots of approximately 0.25m2 on each slope.Overland flow was measured at 1- to 2-weekly intervals during the hydrological years of 2010/11 and 2011/12, i.e. during the first six months after the wildfire but before the bench terracing and during the subsequent 18 months. While data analysis is still ongoing, preliminary results suggested that bench terracing had a greater impact on runoff generation than the wildfire itself, especially at the micro-plot scale

Geochemistry of soils from the San Rafael Valley, Santa Cruz County, Arizona

USGS Publications Warehouse

Folger, Helen W.; Gray, Floyd

2013-01-01

This study was conducted to determine whether surficial geochemical methods can be used to identify subsurface mineraldeposits covered by alluvium derived from surrounding areas. The geochemical investigation focused on an anomalous geo-physical magnetic high located in the San Rafael Valley in Santa Cruz County, Arizona. The magnetic high, inferred to be asso-ciated with a buried granite intrusion, occurs beneath Quaternary alluvial and terrace deposits. Soil samples were collected at a depth of 10 to 30 centimeters below land surface along transects that traverse the inferred granite. The samples were analyzed by inductively coupled plasma-mass spectrometry and by the partial-leach Mobile Metal Ion™ method. Principal component and factor analyses showed a strong correlation between the soils and source rocks hosting base-metal replacement deposits in the Harshaw and Patagonia Mining Districts. Factor analysis also indicated areas of high metal concentrations associated with the Meadow Valley Flat. Although no definitive geochemical signature was identified for the inferred granite, concentrations otungsten and iron in the surrounding area were slightly elevated.

Holocene changes in sea level: Evidence in Micronesia

USGS Publications Warehouse

Shepard, F.P.; Curray, Joseph R.; Newman, W.A.; Bloom, A.L.; Newell, N.D.; Tracey, J.I.; Veeh, H.H.

1967-01-01

Investigation of 33 islands, scattered widely across the Caroline and Marshall Island groups in the Central Pacific revealed no emerged reefs in which corals had unquestionably formed in situ, or other direct evidence of postglacial high stands of sea level. Low unconsolidated rock terraces and ridges of reef-flat islands, mostly lying between tide levels, were composed of rubble conglomerates; carbon-14 dating of 11 samples from the conglomerates so far may suggest a former slightly higher sea level (nine samples range between 1890 and 3450 and one approaches 4500 years ago). However, recent hurricanes have produced ridges of comparable height and material, and in the same areas relics from World War II have been found cemented in place. Thus these datings do not in themselves necessarily indicate formerly higher sea levels. Rubble tracts are produced by storms under present conditions without any change in datum, and there seems to be no compelling evidence that they were not so developed during various periods in the past.

Quaternary landscape evolution of the Helmand Basin, Afghanistan: Insights from staircase terraces, deltas, and paleoshorelines using high-resolution remote sensing analysis

NASA Astrophysics Data System (ADS)

Evenstar, L. A.; Sparks, R. S. J.; Cooper, F. J.; Lawton, M. N.

2018-06-01

The Helmand Basin in southern Afghanistan is a large (310,000 km2), structurally controlled, endorheically drained basin with a hyperarid climate. The basin hosts a high elevation ( 200 m) plateau (the Dasht-i Margo), 11 fluvial staircase terraces (T11 to T1), 7 delta systems (D1 to D7), and 6 paleolake shorelines (SL1 to SL6) within the Sistan Depression on the western side of the basin. Mapping and surveying of these features by remote sensing is integrated with geological observations to reconstruct Quaternary landscape evolution of the basin. The fluvial systems, deltas, and paleolake shorelines are correlated with one another and with the younger terraces (T7 to T1). The shape of fluvial longitudinal profiles changes depending on whether they formed pre-, syn-, or post-growth of the Koh-i Khannesin volcano on the southern margin of the Helmand River. The age of the volcano ( 0.6 Ma) and correlation of the terraces with the global history of glacial-interglacial cycles constrain the age of the younger terraces to the late Pleistocene and indicates that the older terraces are middle Pleistocene (dating back to 800 ka). The Helmand Basin once hosted a large lake, called here the Sistan paleolake, which at SL6 times and before had a surface area >50,000 km2. Since that time the lake elevation and area have decreased, evolving to the present-day dried out Sistan Depression with small ephemeral playa lakes. Episodic formation of terraces, deltas, and paleolake shorelines is attributed to changes in base level modulated by climate change related to Milankovitch cycles.

Evidence for the recurrence of large-magnitude earthquakes along the Makran coast of Iran and Pakistan

USGS Publications Warehouse

Page, W.D.; Alt, J.N.; Cluff, L.S.; Plafker, G.

1979-01-01

The presence of raised beaches and marine terraces along the Makran coast indicates episodic uplift of the continental margin resulting from large-magnitude earthquakes. The uplift occurs as incremental steps similar in height to the 1-3 m of measured uplift resulting from the November 28, 1945 (M 8.3) earthquake at Pasni and Ormara, Pakistan. The data support an E-W-trending, active subduction zone off the Makran coast. The raised beaches and wave-cut terraces along the Makran coast are extensive with some terraces 1-2 km wide, 10-15 m long and up to 500 m in elevation. The terraces are generally capped with shelly sandstones 0.5-5 m thick. Wave-cut cliffs, notches, and associated boulder breccia and swash troughs are locally preserved. Raised Holocene accretion beaches, lagoonal deposits, and tombolos are found up to 10 m in elevation. The number and elevation of raised wave-cut terraces along the Makran coast increase eastward from one at Jask, the entrance to the Persian Gulf, at a few meters elevation, to nine at Konarak, 250 km to the east. Multiple terraces are found on the prominent headlands as far east as Karachi. The wave-cut terraces are locally tilted and cut by faults with a few meters of displacement. Long-term, average rates of uplift were calculated from present elevation, estimated elevation at time of deposition, and 14C and U-Th dates obtained on shells. Uplift rates in centimeters per year at various locations from west to east are as follows: Jask, 0 (post-Sangamon); Konarak, 0.031-0.2 (Holocene), 0.01 (post-Sangamon); Ormara 0.2 (Holocene). ?? 1979.

Late Quaternary Deformation and Relative Sea Level Changes in Southwest Luzon, Philippines Constrained from Emergent Coral Reef Terraces

NASA Astrophysics Data System (ADS)

Maxwell, K. V.; Ramos, N. T.; Tsutsumi, H.; Shen, C. C.

2017-12-01

Emergent coral reef terraces fringing the islands of Lubang and Cabra located offshore southwest Luzon Island, Philippines are studied to understand Late Quaternary deformation and relative sea level changes along the southern terminus of the Manila subduction zone. In both islands, the emergent coral reef platforms have two to three terrace steps with meter-scale terrace risers and often well preserved. We also observed varied elevations of emergent coral reef platforms in both localities. In the northwest portion of Lubang Island, we identified three terrace steps, which rise to about 5 m above mean sea level (amsl). Cabra Island is a coral island that is fringed by two to possibly three steps of emergent coral reef terraces rising up to 11.9 m amsl with TI measured at 3-6 m, TII: 7-8 m, and TIII: 11.9 m amsl. Age constraints are provided by Thorium-230 of fossil corals taken on terrace surfaces. Thorium-230 ages obtained from attached fossil coral samples yielded mid-Holocene ages of 5,121 ± 16 and 3,221 ± 10 years BP. Late Holocene ages of 76 ± 2, 153 ± 2, and 330 ± 3 years BP are meanwhile provided by coral boulders found on the surface of TI in Cabra Island. The two sets of Holocene ages provide interesting insights on relative sea level changes and uplift along the southern end of the Manila Trench. The mid-Holocene ages possibly account for accumulated uplift in southwest Luzon while the late Holocene ages could provide evidence for extreme wave events that occurred in the region since the 1600s.

Uplift rates of marine terraces as a constraint on fault-propagation fold kinematics: Examples from the Hawkswood and Kate anticlines, North Canterbury, New Zealand

NASA Astrophysics Data System (ADS)

Oakley, David O. S.; Fisher, Donald M.; Gardner, Thomas W.; Stewart, Mary Kate

2018-01-01

Marine terraces on growing fault-propagation folds provide valuable insight into the relationship between fold kinematics and uplift rates, providing a means to distinguish among otherwise non-unique kinematic model solutions. Here, we investigate this relationship at two locations in North Canterbury, New Zealand: the Kate anticline and Haumuri Bluff, at the northern end of the Hawkswood anticline. At both locations, we calculate uplift rates of previously dated marine terraces, using DGPS surveys to estimate terrace inner edge elevations. We then use Markov chain Monte Carlo methods to fit fault-propagation fold kinematic models to structural geologic data, and we incorporate marine terrace uplift into the models as an additional constraint. At Haumuri Bluff, we find that marine terraces, when restored to originally horizontal surfaces, can help to eliminate certain trishear models that would fit the geologic data alone. At Kate anticline, we compare uplift rates at different structural positions and find that the spatial pattern of uplift rates is more consistent with trishear than with a parallel-fault propagation fold kink-band model. Finally, we use our model results to compute new estimates for fault slip rates ( 1-2 m/ka at Kate anticline and 1-4 m/ka at Haumuri Bluff) and ages of the folds ( 1 Ma), which are consistent with previous estimates for the onset of folding in this region. These results are consistent with previous work on the age of onset of folding in this region, provide revised estimates of fault slip rates necessary to understand the seismic hazard posed by these faults, and demonstrate the value of incorporating marine terraces in inverse fold kinematic models as a means to distinguish among non-unique solutions.

River Incision and Knickpoints on the Flank of the Yellowstone Hotspot — Alpine Canyon of the Snake River, Wyoming

NASA Astrophysics Data System (ADS)

Tuzlak, D.; Pederson, J. L.

2015-12-01

Understanding patterns of deformation and testing geophysical models in the dynamic region of the Yellowstone Hotspot requires Quaternary-scale records of incision and uplift, which are currently absent. This study examines fluvial terraces and longitudinal-profile metrics along Alpine Canyon of the Snake River, WY. Because the Snake is the only regional river crossing from the uplifting Yellowstone Plateau and flowing into the subsiding Eastern Snake River Plain, it provides an opportunity to investigate both ends of the phenomenon. Field observations through Alpine Canyon indicate that Pleistocene incision rates in this region are relatively high for the interior western U.S., that the river switches between bedrock and alluvial forms, and that incision/uplift is not uniform. Two endmembers of regional deformation may be tested: 1) the arch of high topography surrounding Yellowstone is uplifting and terraces converge downstream as incision rates decrease towards the Snake River Plain, or 2) baselevel fall originates at the subsiding Snake River Plain and terraces diverge as incision rates increase downstream. Datasets include surficial mapping, rock strength measurements, surveying of the longitudinal profile and terraces using RTK-GPS, optically stimulated luminescence dating of fluvial-terrace deposits, and investigation of drainages through ksn and χ analyses. Initial results indicate that there are four primary terrace deposits along the canyon, three of which are timed with glacial epochs. Considering the relative heights of terrace straths and preliminary ages, incision rates are indeed relatively high. There is a major knickzone covering the last 15 km of the canyon that is also reflected in tributary profiles and is consistent with a wave of incision propagating upstream, favoring the second endmember of active baselevel fall downstream.

Surface-state depopulation on small Ag(111) terraces.

PubMed

Morgenstern, Karina; Braun, Kai-Felix; Rieder, Karl-Heinz

2002-11-25

The dependence of the local density of states near the Fermi energy E(F) on the width of terraces T is investigated by tunneling scanning spectroscopy on Ag(111) at 7 K. With decreasing T, the electronic density in the occupied surface state shifts monotonically towards E(F), leading to a depopulation at T=3.2 nm in quantitative agreement with a Fabry-Pérot model. Depopulation coincides with a switch from confinement by terrace modulation to step modulation.

Interface and Electronic Characterization of Thin Epitaxial Co3O4 Films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vaz, C.A.; Zhu, Y.; Wang, H.-Q.

2009-01-15

The interface and electronic structure of thin ({approx} 20-74 nm) Co{sub 3}O{sub 4}(1 1 0) epitaxial films grown by oxygen-assisted molecular beam epitaxy on MgAl{sub 2}O{sub 4}(1 1 0) single crystal substrates have been investigated by means of real and reciprocal space techniques. As-grown film surfaces are found to be relatively disordered and exhibit an oblique low energy electron diffraction (LEED) pattern associated with the O-rich CoO{sub 2} bulk termination of the (1 1 0) surface. Interface and bulk film structure are found to improve significantly with post-growth annealing at 820 K in air and display sharp rectangular LEED patterns,more » suggesting a surface stoichiometry of the alternative Co{sub 2}O{sub 2} bulk termination of the (1 1 0) surface. Non-contact atomic force microscopy demonstrates the presence of wide terraces separated by atomic steps in the annealed films that are not present in the as-grown structures; the step height of {approx}2.7 {angstrom} corresponds to two atomic layers and confirms a single termination for the annealed films, consistent with the LEED results. A model of the (1 x 1) surfaces that allows for compensation of the polar surfaces is presented.« less

On the tungsten single crystal coatings achieved by chemical vapor transportation deposition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shi, J.Q.; Shen, Y.B.; Yao, S.Y.

2016-12-15

The tungsten single crystal has many excellent properties, namely a high melting point, high anti-creeping strength. Chemical vapor transportation deposition (CVTD) is a possible approach to achieve large-sized W single crystals for high-temperature application such as the cathode of a thermionic energy converter. In this work, CVTD W coatings were deposited on the monocrystalline molybdenum substrate (a tube with < 111 > axial crystalline orientation) using WCl{sub 6} as a transport medium. The microstructures of the coatings were investigated by a scanning electron microscope (SEM) and electron backscatter diffraction (EBSD). The as-deposited coatings are hexagonal prisms—rough surfaces perpendicular to with alternating hill-like bulges and pits at the side edges of the prisms, and flat surfaces perpendicular to < 112 > with arc-shaped terraces at the side faces. This can be explained by two-dimensional nucleation -mediated lateral growth model. Some parts of the coatings contain hillocks of an exotic morphology (noted as “abnormal growth”). The authors hypothesize that the abnormal growth is likely caused by the defects of the Mo substrate, which facilitate W nucleation sites, cause orientation difference, and may even form boundaries in the coatings. A dislocation density of 10{sup 6} to 10{sup 7} (counts/cm{sup 2}) was revealed by an etch-pit method and synchrotron X-ray diffraction. As the depositing temperature rises, the dislocation density decreases, and no sub-boundaries are found on samples deposited over 1300 °C, as a result of atom diffusion and dislocation climbing. - Highlights: •The varied growth rate causes the different morphologies of different planes. •The W coating is a single crystal when only single hillocks appear. •The (110) plane tends to have the lowest dislocation density. •The dislocation density tends to decrease as the temperature increases.« less

Quaternary marine terraces as indicators of neotectonic activity of the Ierapetra normal fault SE Crete (Greece)

NASA Astrophysics Data System (ADS)

Gaki-Papanastassiou, K.; Karymbalis, E.; Papanastassiou, D.; Maroukian, H.

2009-03-01

Along the southern coast of the island of Crete, a series of east-west oriented Late Pleistocene marine terraces exist, demonstrating the significant coastal uplift of this area. Five uplifted terraces were mapped in detail and correlated with Middle-Late Pleistocene sea-level stands following the global sea-level fluctuations. These terraces are deformed by the vertical movements of the NNE-SSW trending and dipping west Ierapetra normal fault. The elevation of the inner edges of the terraces was estimated at several sites by using aerial photographs and detailed topographic maps and diagrams, supported by extensive field observations. In this way detailed geomorphological maps were constructed utilizing GIS technology. All these allowed us to obtain rates of 0.3 mm/yr for the regional component of uplift and 0.1 mm/yr for the vertical slip movements of the Ierapetra fault. Based on the obtained rates and the existence of coastal archaeological Roman ruins it is concluded that Ierapetra fault should have been reactivated sometime after the Roman period.

Interfacial Structure and Chemistry of GaN on Ge(111)

NASA Astrophysics Data System (ADS)

Zhang, Siyuan; Zhang, Yucheng; Cui, Ying; Freysoldt, Christoph; Neugebauer, Jörg; Lieten, Ruben R.; Barnard, Jonathan S.; Humphreys, Colin J.

2013-12-01

The interface of GaN grown on Ge(111) by plasma-assisted molecular beam epitaxy is resolved by aberration corrected scanning transmission electron microscopy. A novel interfacial structure with a 5∶4 closely spaced atomic bilayer is observed that explains why the interface is flat, crystalline, and free of GeNx. Density functional theory based total energy calculations show that the interface bilayer contains Ge and Ga atoms, with no N atoms. The 5∶4 bilayer at the interface has a lower energy than a direct stacking of GaN on Ge(111) and enables the 5∶4 lattice-matching growth of GaN.

Length-extension resonator as a force sensor for high-resolution frequency-modulation atomic force microscopy in air.

PubMed

Beyer, Hannes; Wagner, Tino; Stemmer, Andreas

2016-01-01

Frequency-modulation atomic force microscopy has turned into a well-established method to obtain atomic resolution on flat surfaces, but is often limited to ultra-high vacuum conditions and cryogenic temperatures. Measurements under ambient conditions are influenced by variations of the dew point and thin water layers present on practically every surface, complicating stable imaging with high resolution. We demonstrate high-resolution imaging in air using a length-extension resonator operating at small amplitudes. An additional slow feedback compensates for changes in the free resonance frequency, allowing stable imaging over a long period of time with changing environmental conditions.

Graphene nanoribbons production from flat carbon nanotubes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Melo, W. S.; Guerini, S.; Diniz, E. M., E-mail: eduardo.diniz@ufma.br

2015-11-14

Graphene nanoribbons are of great interest for pure and applied sciences due to their unique properties which depend on the nanoribbon edges, as, for example, energy gap and antiferromagnetic coupling. Nevertheless, the synthesis of nanoribbons with well-defined edges remains a challenge. To collaborate with this subject, here we propose a new route for the production of graphene nanoribbons from flat carbon nanotubes filled with a one-dimensional chain of Fe atoms by first principles calculations based on density functional theory. Our results show that Fe-filled flat carbon nanotubes are energetically more stable than non flattened geometries. Also we find that bymore » hydrogenation or oxygenation of the most curved region of the Fe-filled flat armchair carbon nanotube, it occurred a spontaneous production of zigzag graphene nanoribbons which have metallic or semiconducting behavior depending on the edge and size of the graphene nanoribbon. Such findings can be used to create a new method of synthesis of regular-edge carbon nanoribbons.« less

The last interglacial period on the Pacific Coast of North America: Timing and paleoclimate

USGS Publications Warehouse

Muhs, D.R.; Simmons, K.R.; Kennedy, G.L.; Rockwell, T.K.

2002-01-01

New, high-precision U-series ages of solitary corals (Balanophyllia elegans) coupled with molluscan faunal data from marine terraces on the Pacific Coast of North America yield information about the timing and warmth of the last interglacial sea-level highstand. Balanophyllia elegans takes up U in isotopic equilibrium with seawater during growth and shortly after death. Corals from the second terrace on San Clemente Island (offshore southern California), the third terrace on Punta Banda (on the Pacific Coast of northern Baja California), and the Discovery Point Formation on Isla de Guadalupe (in the Pacific Ocean offshore Baja California) date to the peak of the last interglacial period and have U-series ages ranging from ca. 123 to 114 ka. The first terrace on Punta Banda has corals with ages ranging from ca. 83 to 80 ka, which corresponds to a sea-level highstand formed in the late last interglacial period. U-series analyses of corals from the Cayucos terrace (central California) and the Nestor terrace at Point Loma (southern California) show that these fossils have evidence of open-system history, similar to what has been reported by other workers for the same localities. Nevertheless, a model of continuous, secondary U and Th uptake shows that two ages of corals are likely present at these localities, representing the ca. 105 and ca. 120 ka sea-level highstands reported elsewhere. U-series ages of last interglacial corals from the Pacific Coast overlap with, but are on average younger than the ages of corals from Barbados, the Bahamas, and Hawaii. This age difference is explained by the nature of the geomorphic response to sea-level change: fringing or barrier reefs on low-latitude coastlines have an accretionary growth style that keeps pace with rising sea level, whether on a tectonically rising or stable coastline. In contrast, midlatitude, high-energy coastlines are sites of platform cutting during the early part of a sea-level high stand and terrace scouring and concomitant sediment and fossil deposition as sea level starts to recede. The youngest ages of corals from the Pacific Coast suggest that sea level was still relatively high at ca. 116 ka, which is not in agreement with other estimates of relatively large global ice volume at that time. Reliably dated, ca. 120 ka marine-terrace deposits on the Pacific Coast have fossil mollusks that indicate water temperatures as warm or warmer than at present. In contrast, ca. 80 ka marine deposits reported here and elsewhere have fossil mollusks indicating cooler-than-modern water temperatures. The presence of both ca. 105 ka and ca. 120 ka corals on the Nestor and Cayucos terraces explains a previously enigmatic mixture of warm-water and cool-water mollusks. At ca. 105 ka, a relatively high sea level with cool waters may have "captured" the terrace formed during the 120 ka sea-level highstand, in areas of low uplift rate. The inference of cooler-than-modern waters off the Pacific Coast of North America at ca. 80 ka and ca. 105 ka, based on marine-terrace faunas, does not agree with estimates of sea-surface temperatures derived from alkenone studies in the Santa Barbara Basin. However, cooler water temperatures at these times are in agreement with paleo-temperature estimates from planktonic foraminiferal data for the Santa Barbara Basin. All records, from central California to Baja California, whether from marine terraces or offshore cores, indicate at least seasonably warmer-than-modern waters during the peak of the last interglacial period at ca. 120 ka.

Covalent immobilization of native biomolecules onto Au(111) via N-hydroxysuccinimide ester functionalized self-assembled monolayers for scanning probe microscopy.

PubMed Central

Wagner, P; Hegner, M; Kernen, P; Zaugg, F; Semenza, G

1996-01-01

We have worked out a procedure for covalent binding of native biomacromolecules on flat gold surfaces for scanning probe microscopy in aqueous buffer solutions and for other nanotechnological applications, such as the direct measurement of interaction forces between immobilized macromolecules, of their elastomechanical properties, etc. It is based on the covalent immobilization of amino group-containing biomolecules (e.g., proteins, phospholipids) onto atomically flat gold surfaces via omega-functionalized self-assembled monolayers. We present the synthesis of the parent compound, dithio-bis(succinimidylundecanoate) (DSU), and a detailed study of the chemical and physical properties of the monolayer it forms spontaneously on Au(111). Scanning tunneling microscopy and atomic force microscopy (AFM) revealed a monolayer arrangement with the well-known depressions that are known to stem from an etch process during the self-assembly. The total density of the omega-N-hydroxysuccinimidyl groups on atomically flat gold was 585 pmol/cm(2), as determined by chemisorption of (14)C-labeled DSU. This corresponded to approximately 75% of the maximum density of the omega-unsubstituted alkanethiol. Measurements of the kinetics of monolayer formation showed a very fast initial phase, with total coverage within 30 S. A subsequent slower rearrangement of the chemisorbed molecules, as indicated by AFM, led to a decrease in the number of monolayer depressions in approximately 60 min. The rate of hydrolysis of the omega-N-hydroxysuccinimide groups at the monolayer/water interface was found to be very slow, even at moderately alkaline pH values. Furthermore, the binding of low-molecular-weight amines and of a model protein was investigated in detail. Images FIGURE 1 FIGURE 2 FIGURE 9 PMID:9172730

High sensitivity flat SiO2 fibres for medical dosimetry

NASA Astrophysics Data System (ADS)

Abdul Sani, Siti. F.; Alalawi, Amani I.; Azhar, Hairul A. R.; Amouzad Mahdiraji, Ghafour; Tamchek, Nizam; Nisbet, A.; Maah, M. J.; Bradley, D. A.

2014-11-01

We describe investigation of a novel undoped flat fibre fabricated for medical radiation dosimetry. Using high energy X-ray beams generated at a potential of 6 MV, comparison has been made of the TL yield of silica flat fibres, TLD-100 chips and Ge-doped silica fibres. The flat fibres provide competitive TL yield to that of TLD-100 chips, being some 100 times that of the Ge-doped fibres. Pt-coated flat fibres have then been used to increase photoelectron production and hence local dose deposition, obtaining significant increase in dose sensitivity over that of undoped flat fibres. Using 250 kVp X-ray beams, the TL yield reveals a progressive linear increase in dose for Pt thicknesses from 20 nm up to 80 nm. The dose enhancement factor (DEF) of (0.0150±0.0003) nm-1 Pt is comparable to that obtained using gold, agreeing at the 1% level with the value expected on the basis of photoelectron generation. Finally, X-ray photoelectron spectroscopy (XPS) has been employed to characterize the surface oxidation state of the fibre medium. The charge state of Si2p was found to lie on 103.86 eV of binding energy and the atomic percentage obtained from the XPS analysis is 22.41%.

Stereo Topography of the South Polar of Mar: Volatile Inventory and Mars Polar Landing Landing Site

NASA Technical Reports Server (NTRS)

Schenk, Paul M.; Moore, Jeffrey M.

2000-01-01

Viking stereo images and topographic maps reveal that the south polar layered deposits of Mars are topographically complex and morphologically distinct from the north polar layered deposits. The dominant feature is a 500-km-wide topographic dome that rises 3 km above the surrounding plains. This dome underlies the residual ice cap but is at least 50% larger in area. Erosional scarps and terraces indicate that this dome was once more extensive and has undergone erosional retreat. Adjacent to the dome, layered deposits form a vast plateau 1-1.5 km high extending approximately 1000 km beyond and to one side of the residual south polar cap. This plateau is relatively flat at kilometer scales, although it is cut in places by troughs and depressions, which have locally steep scarps up to 2 km high and sloping up to roughly 10 deg. Contiguously flat kilometer-scale regions the size of the Mars Polar Lander (MPL) landing ellipse are present. These are in the form of plateaus 100-300 km wide and 1-2 km high. One of the largest of these plateaus has been proposed as a landing site for the Mars Polar Lander (MPL). The volume associated with the south polar layered deposits may be comparable to those of the layered deposits at the north pole. Although this doubles the current probable inventory of surface ice on Mars, it still falls far short of accounting for the inferred volume of water on Mars in the past.

Geologic map of the Jam Up Cave and Pine Crest quadrangles, Shannon, Texas, and Howell Counties, Missouri

USGS Publications Warehouse

Weary, David J.; Orndorff, Randall C.; Repetski, John E.

2013-01-01

The Jam Up Cave and Pine Crest 7.5-minute quadrangles are located in south-central Missouri within the Salem Plateau region of the Ozark Plateaus physiographic province. About 2,400 to 3,100 feet (ft) of flat-lying to gently dipping Lower Paleozoic sedimentary rocks, mostly dolomite, chert, sandstone, and orthoquartzite, overlie Mesoproterozoic igneous basement rocks. Unconsolidated residuum, colluvium, terrace deposits, and alluvium overlie the sedimentary rocks. Numerous karst features, such as sinkholes, caves, and springs, have formed in the carbonate rocks. Many streams are spring fed. The topography is a dissected karst plain with elevations ranging from about 690 ft where the Jacks Fork River exits the northeastern corner of the Jam Up Cave quadrangle to about 1,350 ft in upland areas along the north-central edge and southwestern corner of the Pine Crest quadrangle. The most prominent physiographic feature is the valley of the Jacks Fork River. This reach of the upper Jacks Fork, with its clean, swiftly-flowing water confined by low cliffs and bluffs, provides one of the most beautiful canoe float trips in the nation. Most of the land in the quadrangles is privately owned and used primarily for grazing cattle and horses and growing timber. A large minority of the land within the quadrangles is publicly owned by the Ozark National Scenic Riverways of the National Park Service. Geologic mapping for this investigation was conducted in 2005 and 2006.

Sharp transition from ripple patterns to a flat surface for ion beam erosion of Si with simultaneous co-deposition of iron

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, K.; Broetzmann, M.; Hofsaess, H.

We investigate pattern formation on Si by sputter erosion under simultaneous co-deposition of Fe atoms, both at off-normal incidence, as function of the Fe surface coverage. The patterns obtained for 5 keV Xe ion irradiation at 30 Degree-Sign incidence angle are analyzed with atomic force microscopy. Rutherford backscattering spectroscopy of the local steady state Fe content of the Fe-Si surface layer allows a quantitative correlation between pattern type and Fe coverage. With increasing Fe coverage the patterns change, starting from a flat surface at low coverage (< 2 Multiplication-Sign 10{sup 15} Fe/cm{sup 2}) over dot patterns (2-8 Multiplication-Sign 10{sup 15}more » Fe/cm{sup 2}), ripples patterns (8-17 Multiplication-Sign 10{sup 15} Fe/cm{sup 2}), pill bug structures (1.8 Multiplication-Sign 10{sup 16} Fe/cm{sup 2}) and a rather flat surface with randomly distributed weak pits at high Fe coverage (>1.8 Multiplication-Sign 10{sup 16} Fe/cm{sup 2}). Our results confirm the observations by Macko et al. for 2 keV Kr ion irradiation of Si with Fe co-deposition. In particular, we also find a sharp transition from pronounced ripple patterns with large amplitude (rms roughness {approx} 18 nm) to a rather flat surface (rms roughness {approx} 0.5 nm). Within this transition regime, we also observe the formation of pill bug structures, i.e. individual small hillocks with a rippled structure on an otherwise rather flat surface. The transition occurs within a very narrow regime of the steady state Fe surface coverage between 1.7 and 1.8 Multiplication-Sign 10{sup 16} Fe/cm{sup 2}, where the composition of the mixed Fe-Si surface layer of about 10 nm thickness reaches the stoichiometry of FeSi{sub 2}. Phase separation towards amorphous iron silicide is assumed as the major contribution for the pattern formation at lower Fe coverage and the sharp transition from ripple patterns to a flat surface.« less

Atomic Force Microscope Observation of Growth and Defects on As-Grown (111) 3C-SiC Mesa Surfaces

NASA Technical Reports Server (NTRS)

Neudeck, Philip G.; Trunek, Andrew J.; Powell, J. Anthony

2004-01-01

This paper presents experimental atomic force microscope (AFM) observations of the surface morphology of as-grown (111) silicon-face 3C-SiC mesa heterofilms. Wide variations in 3C surface step structure are observed as a function of film growth conditions and film defect content. The vast majority of as-grown 3C-SiC surfaces consisted of trains of single bilayer height (0.25 nm) steps. Macrostep formation (i.e., step-bunching) was rarely observed, and then only on mesa heterofilms with extended crystal defects. As supersaturation is lowered by decreasing precursor concentration, terrace nucleation on the top (111) surface becomes suppressed, sometimes enabling the formation of thin 3C-SiC film surfaces completely free of steps. For thicker films, propagation of steps inward from mesa edges is sometimes observed, suggesting that enlarging 3C mesa sidewall facets begin to play an increasingly important role in film growth. The AFM observation of stacking faults (SF's) and 0.25 nm Burgers vector screw component growth spirals on the as-grown surface of defective 3C films is reported.

In situ REM and ex situ SPM studies of silicon (111) surface

NASA Astrophysics Data System (ADS)

Aseev, A. L.; Kosolobov, S. S.; Latyshev, A. V.; Song, Se Ahn; Saranin, A. A.; Zotov, A. V.; Lifshits, V. G.

2005-09-01

Combination of experimental methods, including ultrahigh vacuum in situ reflection electron microscopy, scanning tunnelling microscopy and atomic force microscopy, has been applied for analysis of surface structure and dynamic processes on silicon (111) surfaces during sublimation, rapid temperature cooling, oxygen reactions and metal-silicon surface phase formation. From analysis of triangular negative islands, 0.08 nm in depth, which were forming during quenching, it was deduced the effective activation energy of the island generation is equalled to 0.35 eV and made conclusion that the (1 × 1) (7 × 7) phase transition on Si(111) assumes to be responsible for the negative island nucleation. On the base of the in situ REM study, the dependence of step motion, initiated by surface vacancies generation during oxygen-silicon interaction, on the terrace width was measured. Peculiarities of the initial stages of silicon surface oxidation at low pressures were considered. From precision measurements, the top silicon atom density was determined for the metal-silicon surface phase formed during Na, Ca, Mg and Ag deposition on clean silicon (111) surface.

Enhancement of surface migration by Mg doping in the metalorganic vapor phase epitaxy of N-polar (000\\bar{1}) GaN/sapphire

NASA Astrophysics Data System (ADS)

Tanikawa, Tomoyuki; Shojiki, Kanako; Aisaka, Takashi; Kimura, Takeshi; Kuboya, Shigeyuki; Hanada, Takashi; Katayama, Ryuji; Matsuoka, Takashi

2014-01-01

With respect to N-polar (000\\bar{1}) GaN grown on a sapphire substrate, the effects of Mg doping on the surface morphology, and the optical, and electrical properties are precisely investigated. By doping Mg, hillocks observed on the surface of (000\\bar{1}) GaN can be suppressed, while step bunching becomes severe. The atomic terrace width is extended with increasing Mg/Ga precursor ratio. Mg doping can promote the surface migration of Ga adatoms on a GaN surface during growth. In the case of heavily Mg-doped GaN, atomic steps become wavy. From photoluminescence spectra, the dominant transition was found to change from near-band-edge transition to donor-acceptor-pair transition. Hall-effect measurement shows p-type conduction at room temperature for a sample grown with the Mg/Ga precursor ratio of 4.5 × 10-3. The activation energy is 143 meV, which is comparable to that of Mg in the conventional Ga-polar (0001) GaN.

The Connection Between Sediment Supply and Paired Strath Terrace Formation at Arroyo Seco, CA, USA.

NASA Astrophysics Data System (ADS)

Finnegan, N. J.

2015-12-01

Although wide, longitudinally traceable, paired strath terraces in river canyons are frequently argued to reflect periods of higher sediment supply, there is no consensus on how changes in sediment supply translate into dramatic changes in valley morphology. Here, quantitative analysis of LiDAR data is combined with field observations in Arroyo Seco, in the Santa Lucia Range of Central California, to develop a conceptual model for paired bedrock terrace formation and its connection to sediment supply. The most recently formed bedrock terrace in Arroyo Seco grades onto a prominent alluvial fan surface, suggesting that planation of straths in Arroyo Seco occurs as downstream alluvial fans aggrade. This aggradation apparently buffers Arroyo Seco's bedrock channel from base level fall on the Reliz Canyon Fault, which separates the bedrock and alluvial sections of the river. Notably, despite the fact that bedrock terraces grade smoothly onto alluvial fan surfaces, the deep aggradation of sediment downstream is not seen upstream in bedrock channel sections. Gravel on straths is typically only 0.5-1 m thick. Instead, excess gravel appears to be accommodated by the lateral planation of the wide strath itself. LiDAR evidence suggests that strath planation is associated with braiding, which is often triggered by increases in sediment supply. Given the high lateral mobility of braided streams and the extremely fractured (and hence easily detached) mudstone valley walls along Arroyo Seco, braiding provides a simple connection between sediment supply and lateral planation in Arroyo Seco. In Arroyo Seco, fan incision (under decreased sediment supply) should exhume a bedrock step whose height represents the accumulated fault slip during fan aggradation. The upstream propagation of this exhumed step as a knickpoint provides a simple mechanism to connect drops in sediment supply to rapid vertical incision, valley narrowing and strath terrace formation. Long profile data for Arroyo Seco shows clear evidence that the last two generations of strath terraces terminate upstream at knickpoints. OSL dating (Taylor and Sweetkind, 2014) constrains the formation of the two most recent strath terraces to the last ~ 35 kyr, implying at least two reductions in sediment supply relative to capacity during this interval.

Holocene aggradation of the Dry Tortugas coral reef ecosystem

USGS Publications Warehouse

Brock, J.C.; Palaseanu-Lovejoy, M.; Poore, R.Z.; Nayegandhi, A.; Wright, C.W.

2010-01-01

Radiometric age dating of reef cores acquired at the Dry Tortugas coral reef ecosystem (DTCRE) was merged with lidar topographic mapping to examine Holocene reef development linked to spatial variation in growth and erosion under the control of sea level. Analysis of variance of lidar topography confirmed the presence of three distinct terraces on all three major DTCRE banks (Loggerhead Bank, Garden Bank, and Pulaski Bank). Reef building on the middle terrace (T2) began atop Pleistocene edifices on Loggerhead Bank by 8.0 ka (thousands of years ago) and on Garden Bank by 7.2 ka at elevations of about −16.0 m and −11.9 m, respectively, relative to present mean sea level. Following this initiation at different elevations, T2 aggraded vertically on both banks at different rates during the early Holocene under foundering conditions until a highstand at 5.2 ka, resulting in a 2.21 m offset in present mean T2 elevation between these banks. Initiation of an upper terrace (T1) occurred on both Loggerhead Bank and Garden Bank in association with sea-level fall to a lowstand at near 4.8 ka. This upper terrace initiated on Garden Bank at about 5.0 ka and then grew upward at rate of 2.5 mm year−1 until approximately 3.8 ka. On Loggerhead Bank, the upper T1 terrace formed after 4.5 ka at a higher vertical aggradation rate of 4.1 mm year−1, but at a lower elevation than on Garden Bank. Terrace T1 aggraded on Loggerhead Bank below the elevation of lowstands during late Holocene sea-level oscillation, and consequently erosion on Loggerhead Bank was minimal and likely limited to the crest of the upper terrace. In contrast, after 3.8 ka terrace T1 on Garden Bank likely tracked sea level and consequently underwent erosion when sea level fell to second, third and fourth lowstands at 3.3, 1.1, and 0.3 ka.

Erosion in vineyards and LiDAR: new opportunities for anthropogenic terraced landscapes

NASA Astrophysics Data System (ADS)

Tarolli, Paolo; Sofia, Giulia; Calligaro, Simone; Prosdocimi, Massimo; Preti, Federico; Dalla Fontana, Giancarlo

2014-05-01

Vineyard landscapes are a relevant part of the European cultivated land, and several authors concluded that they are the agricultural practice that causes the highest soil loss. Since grape quality depends on the availability of water for the vineyards, and since soil erosion is an important parameter dictating the sustainability of vineyards, soil and water conservation are often implemented. The most widely used measure for soil conservation for vineyards in hilly/mountainous landscapes is terracing. However, while improving vineyards stability, the same changes in hillslope hydrology caused by these anthropogenic structures to favor agricultural activities, often result in situations that may lead to local instabilities. Terraces, in fact, when not properly maintained can create hazards for people and settlements, but also for cultivations and for the related economy. Agricultural roads also serve terraced lands, and the construction of these types of anthropogenic features can have deep effects on water flows, in a way similar to the one already registered for forest roads. The goal of this research is to use LiDAR data for the high-resolution hydro-geomorphological analysis of vineyards, underlining the capability of high-resolution topography to provide new tools for a correct management of vineyards terraced landscapes. The work focus on terraced- and road-induced erosion, and it considers a methodology successfully applied to a different environmental context (the RPII index, Tarolli et al. 2013). The index is applied to two study areas, located in the center of Italy, where soil erosion and terrace failures represent a critical issue. The results highlight the effectiveness of high-resolution topography in the analysis of surface erosion, thus providing useful tool to schedule a suitable environmental planning for a sustainable development, and so, to mitigate the consequences of the anthropogenic alterations induced by the terraces structures and agricultural roads. References Tarolli, P., Calligaro, S., Cazorzi, F., Dalla Fontana, G. (2013). Recognition of surface flow processes influeced by roads and trails in mountain areas using high-resolution topography. European Journal of Remote Sensing, 46, 176-197, doi:10.5721/EuJRS20134610.

Episodic Aggradation and Asynchronous Incision of River Terraces in the Kyrgyz Tien Shan

NASA Astrophysics Data System (ADS)

Burgette, R. J.; Weldon, R. J.; Abdkrakhmatov, K. Y.; Ormukov, C.

2006-12-01

Sequences of terraces and alluvial fans with characteristic geomorphic expression lie above or at the mouth of rivers in all of the major basins in the Tien Shan mountains of Kyrgyzstan. The similarity of terraces and fans in different drainage basins, despite being bounded by faults of varying activity and style, has been used to argue for synchronous regional climatic variations controlling the timing of aggradation and incision. Our emerging set of radiocarbon dates (currently 24) from terrace deposits and overlying sediments suggest that despite the general regional synchroneity of a late Pleistocene terrace-forming event, deep incision below broad aggradational surfaces may be locally controlled and occurred over time spans up to 30 k.y. The most prominent intra-canyon terrace is known as QIII(2) in the characteristic sequence of Tien Shan terraces. QIII(2) is a fill terrace everywhere except for the hanging walls of the most active thrust faults in the Tien Shan, where it has a strath terrace morphology. In many places the base of the QIII(2) fill is not visible even at the level of the modern river. Five dates in the fill from the Ak-Terek and Tong Rivers in the Issyk-Kul basin and Kajerty River in the Naryn basin are all >40 Ka, and may be beyond the limit of radiocarbon. The Issyk-Kul basin is occupied by a large lake, which provides additional dating possibilities, while potentially complicating the geomorphic system. In Issyk-Kul dates from sediment overlying the QIII(2) gravel in thick colluvial wedges far from the edge of the riser to lower terraces along the Ak-Terek and Tamga rivers show that at least the highest level of the fill was abandoned by 33-30 Ka. However, the downstream reaches of Issyk- Kul rivers' QIII(2) surfaces clearly remained active through a high stand of the lake that persisted from 38 to 20 Ka. Remnants of terraces with steeper gradients that merge upstream with surfaces inset only a few m into the main QIII(2) post-date the high stand and are locally preserved at the mouths of some rivers. To the west of Issyk-Kul, abandonment of the QIII(2) surface appears to have occurred at approximately 13 Ka in three basins of central Kyrgyzstan (Thompson et al., 2002). Taken together, these data show that QIII(2) aggradation was complete before 33 Ka and possibly as early as 40 Ka. Most rivers stayed at the level of the top of the fill with minor aggradation or incision for the next 13 to 25 k.y. Such long-lived stability results in a landscape where late Pleistocene surfaces that are at almost indistinguishable levels may vary in age by a factor >2. Similarly, ages of deposits in such fill terraces may be much older than the surfaces cut into them. While it is not yet clear over what region our results may apply, our observations suggest that the "same" geomorphic surface may be abandoned over a wide range of time and the upper few meters of gravel may be quite different in age than the bulk of the fill that forms the geomorphic feature. How this will affect slip rate estimates in central Asia is yet to be determined, but our observations motivate caution in assuming synchroneity of fills and their incision or synchroneity of similar- looking geomorphic features. Calculating accurate slip rates requires that one understands well the relationship between the feature where it is offset and where it is dated, particularly for relatively young terraces that do not average across many aggradation/incision cycles.

A new method for mapping the three-dimensional atomic distribution within nanoparticles by atom probe tomography (APT).

PubMed

Kim, Se-Ho; Kang, Phil Woong; Park, O Ok; Seol, Jae-Bok; Ahn, Jae-Pyoung; Lee, Ji Yeong; Choi, Pyuck-Pa

2018-07-01

We present a new method of preparing needle-shaped specimens for atom probe tomography from freestanding Pd and C-supported Pt nanoparticles. The method consists of two steps, namely electrophoresis of nanoparticles on a flat Cu substrate followed by electrodeposition of a Ni film acting as an embedding matrix for the nanoparticles. Atom probe specimen preparation can be subsequently carried out by means of focused-ion-beam milling. Using this approach, we have been able to perform correlative atom probe tomography and transmission electron microscopy analyses on both nanoparticle systems. Reliable mass spectra and three-dimensional atom maps could be obtained for Pd nanoparticle specimens. In contrast, atom probe samples prepared from C-supported Pt nanoparticles showed uneven field evaporation and hence artifacts in the reconstructed atom maps. Our developed method is a viable means of mapping the three-dimensional atomic distribution within nanoparticles and is expected to contribute to an improved understanding of the structure-composition-property relationships of various nanoparticle systems. Copyright © 2018 Elsevier B.V. All rights reserved.

Flat-band superconductivity in strained Dirac materials

NASA Astrophysics Data System (ADS)

Kauppila, V. J.; Aikebaier, F.; Heikkilä, T. T.

2016-06-01

We consider superconducting properties of a two-dimensional Dirac material such as graphene under strain that produces a flat-band spectrum in the normal state. We show that in the superconducting state, such a model results in a highly increased critical temperature compared to the case without the strain, inhomogeneous order parameter with two-peak shaped local density of states and yet a large and almost uniform and isotropic supercurrent. This model could be realized in strained graphene or ultracold atom systems and could be responsible for unusually strong superconductivity observed in some graphite interfaces and certain IV-VI semiconductor heterostructures.

Athermally photoreduced graphene oxides for three-dimensional holographic images

PubMed Central

Li, Xiangping; Ren, Haoran; Chen, Xi; Liu, Juan; Li, Qin; Li, Chengmingyue; Xue, Gaolei; Jia, Jia; Cao, Liangcai; Sahu, Amit; Hu, Bin; Wang, Yongtian; Jin, Guofan; Gu, Min

2015-01-01

The emerging graphene-based material, an atomic layer of aromatic carbon atoms with exceptional electronic and optical properties, has offered unprecedented prospects for developing flat two-dimensional displaying systems. Here, we show that reduced graphene oxide enabled write-once holograms for wide-angle and full-colour three-dimensional images. This is achieved through the discovery of subwavelength-scale multilevel optical index modulation of athermally reduced graphene oxides by a single femtosecond pulsed beam. This new feature allows for static three-dimensional holographic images with a wide viewing angle up to 52 degrees. In addition, the spectrally flat optical index modulation in reduced graphene oxides enables wavelength-multiplexed holograms for full-colour images. The large and polarization-insensitive phase modulation over π in reduced graphene oxide composites enables to restore vectorial wavefronts of polarization discernible images through the vectorial diffraction of a reconstruction beam. Therefore, our technique can be leveraged to achieve compact and versatile holographic components for controlling light. PMID:25901676

Formation of self-assembled monolayer of curcuminoid molecules on gold surfaces

NASA Astrophysics Data System (ADS)

Berlanga, Isadora; Etcheverry-Berríos, Álvaro; Mella, Andy; Jullian, Domingo; Gómez, Victoria Alejandra; Aliaga-Alcalde, Núria; Fuenzalida, Victor; Flores, Marcos; Soler, Monica

2017-01-01

We investigated the formation of self-assembled monolayers of two thiophene curcuminoid molecules, 2-thphCCM (1) and 3-thphCCM (2), on polycrystalline gold substrates prepared by immersion of the surfaces in a solution of the molecules during 24 h. The functionalized surfaces were studied by scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS). Despite the fact that both molecules have the same composition and almost the same structure, these molecules exhibit different behavior on the gold surface, which can be explained by the different positions of the sulfur atoms in the terminal aromatic rings. In the case of molecule 1, the complete formation of a SAM can be observed after 24 h of immersion. In the case of molecule 2, the transition from flat-lying to upright configuration on the surface is still in process after 24 h of immersion. This is attributed to the fact that molecule 2 have the sulfur atoms more exposed than molecule 1.

Seafloor morphology in the different domains of the Calabrian Arc subduction complex - Ionian Sea

NASA Astrophysics Data System (ADS)

Riminucci, F.; Polonia, A.; Torelli, L.; Mussoni, P.

2010-05-01

The Calabrian Arc (CA) is a subduction system that develops along the African-Eurasian plate boundary in the Ionian Sea and connects the E-W trending Sicilian Maghrebian belt with the NW-SE trending Southern Apennines. The first systematic geophysical investigation in the offshore region of the CA was conducted during the 70's by the Institute of Marine Geology (now ISMAR) with the R/V 'Bannock' [1]. In the last 30 years, further geophysical data (high penetration multichannel seismics, CHIRP and multibeam data) has been acquired in the offshore of the CA, down to the Ionian Abyssal Plain. The integrated interpretation of the existing geophysical data [2] has outlined the regional architecture of the subduction complex, the main tectonic features absorbing plate motion and variation of seafloor morphology in the different structural domains. Pre-stack depth migrated seismic profiles has revealed that the accretionary complex is constituted by two distinct wedges whose geometry, structural style and seafloor morphology widely vary. The outermost accretionary wedge has been emplaced in post-messinian times. It is a salt-bearing complex as pointed out by the internal structure of the wedge (acoustically transparent assemblage), very low taper angle and high seismic velocities. The seafloor shows a rough morphology, short wavelength folds and depressions superimposed on a rather constant gentle regional slope. Landward of the outer wedge, the evaporites are no longer present and the transition to the clastic rock assemblage is reflected in a different structural architecture, which shows steeper slopes and a succession of topographic scarps separated by sedimentary basins and mid slope terraces. The topographic scarps are controlled in depth by a series of high angle landward dipping reflectors, that we interpreted as out of sequence thrust faults absorbing shortening at the rear of the wedge. Landward of the inner wedge a mid slope terrace develops (inner plateau) between 1300 and 1600 m water depth. It is a relatively flat area of variable width ranging from 10 to 50 Km, represented by the forearc basin and the innermost accretionary wedge. Seafloor morphology is related to small undulation of the seafloor. A thick section of Plio-Quaternary and Messinian sediments is present below the flat terrace. Sediments appear to be folded and, in some regions highly disrupted along local sub-circular structures that affect the seafloor morphology as well. Geometry and seismic facies of these sub-circular swells rising from the surrounding suggest they are diapiric structures. Variation of seafloor morphology is strictly related to the progression of structural domains within the Calabrian Arc subduction complex. The integrated analysis of seafloor morphology and structural style through an integrated approach involving the interpretation of seismic data at different scales has been carried out in order to outline relationships between shallow tectonic processes and deep structures. Moreover, the analysis of morphobathymetric and seismic data, combined with well targeted sediment samples has the potential to reveal relationships between tectonics, sedimentation and fluid flow in the different portions of the accretionary wedge. References: 1 - Rossi S., Sartori R. 1981. A seismic reflection study of the External Calabrian Arc in the Northern Ionian Sea (Eastern Mediterranean). Marine Geoph. Res., 4, 403-426. 2 - Polonia A. et al., The Calabrian Arc subduction complex: plate convergence, active faults, and mud diapirism. New results from the CALAMARE-2008 cruise (N/R CNR Urania). Submitted to G3.

Temperature dependence of the crystalline quality of AlN layer grown on sapphire substrates by metalorganic chemical vapor deposition

NASA Astrophysics Data System (ADS)

Li, Xiao-Hang; Wei, Yong O.; Wang, Shuo; Xie, Hongen; Kao, Tsung-Ting; Satter, Md. Mahbub; Shen, Shyh-Chiang; Douglas Yoder, P.; Detchprohm, Theeradetch; Dupuis, Russell D.; Fischer, Alec M.; Ponce, Fernando A.

2015-03-01

We studied temperature dependence of crystalline quality of AlN layers at 1050-1250 °C with a fine increment step of around 18 °C. The AlN layers were grown on c-plane sapphire substrates by metalorganic chemical vapor deposition (MOCVD) and characterized by X-ray diffraction (XRD) ω-scans and atomic force microscopy (AFM). At 1050-1068 °C, the templates exhibited poor quality with surface pits and higher XRD (002) and (102) full-width at half-maximum (FWHM) because of insufficient Al atom mobility. At 1086 °C, the surface became smooth suggesting sufficient Al atom mobility. Above 1086 °C, the (102) FWHM and thus edge dislocation density increased with temperatures which may be attributed to the shorter growth mode transition from three-dimension (3D) to two-dimension (2D). Above 1212 °C, surface macro-steps were formed due to the longer diffusion length of Al atoms than the expected step terrace width. The edge dislocation density increased rapidly above 1212 °C, indicating this temperature may be a threshold above which the impact of the transition from 3D to 2D is more significant. The (002) FWHM and thus screw dislocation density were insensitive to the temperature change. This study suggests that high-quality AlN/sapphire templates may be potentially achieved at temperatures as low as 1086 °C which is accessible by most of the III-nitride MOCVD systems.

4. LOWER TERRACE LOOKING EAST, SHOWING POOL AND PRESIDENT BUCHANAN ...

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

4. LOWER TERRACE LOOKING EAST, SHOWING POOL AND PRESIDENT BUCHANAN MEMORIAL, February 1976 - Meridian Hill Park, Bounded by Fifteenth, Sixteenth, Euclid & W Streets, Northwest, Washington, District of Columbia, DC

6. LOWER TERRACE, LOOKING WEST FROM BUCHANAN MEMORIAL, NOTE HUMANSCALE ...

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

6. LOWER TERRACE, LOOKING WEST FROM BUCHANAN MEMORIAL, NOTE HUMAN-SCALE CHESS BOARD, August 1976 - Meridian Hill Park, Bounded by Fifteenth, Sixteenth, Euclid & W Streets, Northwest, Washington, District of Columbia, DC

View of main terrace with mature tree, camera facing southeast ...

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

View of main terrace with mature tree, camera facing southeast - Naval Training Station, Senior Officers' Quarters District, Naval Station Treasure Island, Yerba Buena Island, San Francisco, San Francisco County, CA

33. SOLARIUM AND TERRACE IN EXECUTIVE SUITE LOOKING NORTH PAST ...

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

33. SOLARIUM AND TERRACE IN EXECUTIVE SUITE LOOKING NORTH PAST SLIDING GLASS WALL THAT DIVIDES SOLARIUM FROM EXECUTIVE DINING ROOM - Philadelphia Saving Fund Society, Twelfth & Market Streets, Philadelphia, Philadelphia County, PA

Physical parameters of Fluvisols on flooded and non-flooded terraces

NASA Astrophysics Data System (ADS)

Kercheva, Milena; Sokołowska, Zofia; Hajnos, Mieczysław; Skic, Kamil; Shishkov, Toma

2017-01-01

The heterogeneity of soil physical properties of Fluvisols, lack of large pristine areas, and different moisture regimes on non-flooded and flooded terraces impede the possibility to find a soil profile which can serve as a baseline for estimating the impact of natural or anthropogenic factors on soil evolution. The aim of this study is to compare the pore size distribution of pristine Fluvisols on flooded and non-flooded terraces using the method of the soil water retention curve, mercury intrusion porosimetry, nitrogen adsorption isotherms, and water vapour sorption. The pore size distribution of humic horizons of pristine Fluvisols on the non-flooded terrace differs from pore size distribution of Fluvisols on the flooded terrace. The peaks of textural and structural pores are higher in the humic horizons under more humid conditions. The structural characteristics of subsoil horizons depend on soil texture and evolution stage. The peaks of textural pores at about 1 mm diminish with lowering of the soil organic content. Structureless horizons are characterized by uni-modal pore size distribution. Although the content of structural pores of the subsoil horizons of Fluvisols on the non-flooded terrace is low, these pores are represented by biopores, as the coefficient of filtration is moderately high. The difference between non-flooded and flooded profiles is well expressed by the available water storage, volume and mean radius of pores, obtained by mercury intrusion porosimetry and water desorption, which are higher in the surface horizons of frequently flooded Fluvisols.

Middle-Late Pleistocene marine terraces and fault activity in the Sant'Agata di Militello coastal area (north-eastern Sicily)

NASA Astrophysics Data System (ADS)

Giunta, Giuseppe; Gueli, Anna M.; Monaco, Carmelo; Orioli, Silvia; Ristuccia, Gloria M.; Stella, Giuseppe; Troja, Sebastiano O.

2012-04-01

The coastal sector of Sant'Agata di Militello (north-eastern Sicily) is characterized by a flight of raised Middle-Upper Pleistocene marine terraces occurring at different heights with respect to present sea level. In particular, the geomorphological survey and the analysis of stereo-pairs of aerial photographs allowed to recognize at least five main orders of well preserved Quaternary surfaces and relative deposits mostly located at the hanging wall and at the footwall of the Pleistocene northwest-dipping Capo d'Orlando normal fault, which controlled the geomorphological evolution of the coastal area. The marine terraces show an overall good morphological continuity and are formed by marine platforms overlain by littoral deposits made up of yellow littoral sand and gravels in a sandy matrix. The continental sedimentary cover of the 3rd order terrace contains mammal-bearing deposits that were previously dated 200 ± 40 ka BP by isoleucine epimerization method, allowing to relate them to MIS 7.1 high-stand. In order to better define the whole terrace chronology, deposit samples were analyzed by Optically Stimulated Luminescence (OSL) methodology, a conventional SAR protocol used with sand-sized quartz. New datings, together with the detailed morphostructural analysis, allow to relate the 2nd and 4th order terraces to MIS 5.5 and 8.5, respectively, and to reconstruct the tectonic evolution of this coastal area, constraining the activity of the Capo d'Orlando fault.

Assessing the Reliability of Land-Use Data in Slovenia: A Case Study of Terraced Landscapes

NASA Astrophysics Data System (ADS)

Ažman Momirski, Lucija

2017-10-01

Land use relates to the exploitation of land through human activity in the landscape. Land use is also one of the best indicators of a landscape’s structure and processes. Land cover comprises manmade surfaces, agricultural areas, forest and semi-natural areas, wetlands, and bodies of water. In Slovenia more than half of the land (63%) is forested. Manmade surfaces represent less than 5%. A large proportion of relatively inaccessible forest is the main reason why society had a less critical impact on forests in the past in Slovenia in comparison to the majority of central European countries. Regarding the high-quality landscape in the country, Slovenia’s natural features are characterized by a mix of forest and farmland. These land categories (i.e., complex cultivation patterns and land principally used for agriculture with significant areas of natural vegetation) cover 23% of Slovenia. Land-use data for farmland are gathered and provided to the relevant institutions by landowners, who are not specialists in land-use data. In addition, land use is only a two-dimensional tool, which does not recognize elevation differences and terraced slopes. Terraced areas are either omitted from the inventory of land-use data because landowners do not report them, or they are included in the inventory because landowners do not realize that their land is not terraced. Consequently, the differences between the official data on vineyards, orchards, and olive groves on terraces and actual terraced slopes with such land use may differ significantly.

Unsteady heat-flux measurements of second-mode instability waves in a hypersonic flat-plate boundary layer

NASA Astrophysics Data System (ADS)

Kegerise, Michael A.; Rufer, Shann J.

2016-08-01

In this paper, we report on the application of the atomic layer thermopile (ALTP) heat-flux sensor to the measurement of laminar-to-turbulent transition in a hypersonic flat-plate boundary layer. The centerline of the flat-plate model was instrumented with a streamwise array of ALTP sensors, and the flat-plate model was exposed to a Mach 6 freestream over a range of unit Reynolds numbers. Here, we observed an unstable band of frequencies that are associated with second-mode instability waves in the laminar boundary layer that forms on the flat-plate surface. The measured frequencies, group velocities, phase speeds, and wavelengths of these instability waves are consistent with data previously reported in the literature. Heat flux time series, and the Morlet wavelet transforms of them, revealed the wave-packet nature of the second-mode instability waves. In addition, a laser-based radiative heating system was used to measure the frequency response functions (FRF) of the ALTP sensors used in the wind tunnel test. These measurements were used to assess the stability of the sensor FRFs over time and to correct spectral estimates for any attenuation caused by the finite sensor bandwidth.

Sub-monolayer growth of Ag on flat and nanorippled SiO{sub 2} surfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bhatnagar, Mukul; Ranjan, Mukesh; Mukherjee, Subroto

2016-05-30

In-situ Rutherford Backscattering Spectrometry (RBS) and Molecular Dynamics (MD) simulations have been used to investigate the growth dynamics of silver on a flat and the rippled silica surface. The calculated sticking coefficient of silver over a range of incidence angles shows a similar behaviour to the experimental results for an average surface binding energy of a silver adatom of 0.2 eV. This value was used to parameterise the MD model of the cumulative deposition of silver in order to understand the growth mechanisms. Both the model and the RBS results show marginal difference between the atomic concentration of silver on themore » flat and the rippled silica surface, for the same growth conditions. For oblique incidence, cluster growth occurs mainly on the leading edge of the rippled structure.« less

Ultrathin and Atomically Flat Transition-Metal Oxide: Promising Building Blocks for Metal-Insulator Electronics.

PubMed

Cui, Qingsong; Sakhdari, Maryam; Chamlagain, Bhim; Chuang, Hsun-Jen; Liu, Yi; Cheng, Mark Ming-Cheng; Zhou, Zhixian; Chen, Pai-Yen

2016-12-21

We present a new and viable template-assisted thermal synthesis method for preparing amorphous ultrathin transition-metal oxides (TMOs) such as TiO 2 and Ta 2 O 5 , which are converted from crystalline two-dimensional (2D) transition-metal dichalcogenides (TMDs) down to a few atomic layers. X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and scanning transmission electron microscopy (STEM) were used to characterize the chemical composition and bonding, surface morphology, and atomic structure of these ultrathin amorphous materials to validate the effectiveness of our synthesis approach. Furthermore, we have fabricated metal-insulator-metal (MIM) diodes using the TiO 2 and Ta 2 O 5 as ultrathin insulating layers with low potential barrier heights. Our MIM diodes show a clear transition from direct tunneling to Fowler-Nordheim tunneling, which was not observed in previously reported MIM diodes with TiO 2 or Ta 2 O 5 as the insulating layer. We attribute the improved performance of our MIM diodes to the excellent flatness and low pinhole/defect densities in our TMO insulting layers converted from 2D TMDs, which enable the low-threshold and controllable electron tunneling transport. We envision that it is possible to use the ultrathin TMOs converted from 2D TMDs as the insulating layer of a wide variety of metal-insulator and field-effect electronic devices for various applications ranging from microwave mixing, parametric conversion, infrared photodetection, emissive energy harvesting, to ultrafast electronic switching.

Regioselective atomic layer deposition in metal–organic frameworks directed by dispersion interactions

DOE PAGES

Gallington, Leighanne C.; Kim, In Soo; Liu, Wei-Guang; ...

2016-10-03

The application of atomic layer deposition (ALD) to metal–organic frameworks (MOFs) offers a promising new approach to synthesize designer functional materials with atomic precision. While ALD on flat substrates is well established, the complexity of the pore architecture and surface chemistry in MOFs present new challenges. Through in situ synchrotron X-ray powder diffraction, we visualize how the deposited atoms are localized and redistribute within the MOF during ALD. We demonstrate that the ALD is regioselective, with preferential deposition of oxy-Zn(II) species within the small pores of NU-1000. As a result, complementary density functional calculations indicate that this startling regioselectivity ismore » driven by dispersion interactions associated with the preferential adsorption sites for the organometallic precursors prior to reaction.« less

Effect of rattling motion without cage structure on lattice thermal conductivity in LaOBiS2-xSex

NASA Astrophysics Data System (ADS)

Lee, C. H.; Nishida, A.; Hasegawa, T.; Nishiate, H.; Kunioka, H.; Ohira-Kawamura, S.; Nakamura, M.; Nakajima, K.; Mizuguchi, Y.

2018-01-01

Low energy phonons in LaOBiS2-xSex are studied using inelastic neutron scattering. Dispersionless flat phonon branches that are mainly associated with a large vibration of Bi atoms are observed at a relatively low energy of E = 6-6.7 meV. The phonon energy softens upon Se doping presumably owing to its heavier atomic mass than the S atom and the expansion of the lattice constant. Simultaneously, the lattice thermal conductivity lowered upon Se doping as the same manner of the phonon softening. These suggest that despite the lack of an oversized cage in LaOBiS2-xSex, rattling motions of Bi atoms can scatter phonon like rattling in cage compounds, contributing to enhance the thermoelectric property.

Regioselective atomic layer deposition in metal–organic frameworks directed by dispersion interactions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gallington, Leighanne C.; Kim, In Soo; Liu, Wei-Guang

The application of atomic layer deposition (ALD) to metal–organic frameworks (MOFs) offers a promising new approach to synthesize designer functional materials with atomic precision. While ALD on flat substrates is well established, the complexity of the pore architecture and surface chemistry in MOFs present new challenges. Through in situ synchrotron X-ray powder diffraction, we visualize how the deposited atoms are localized and redistribute within the MOF during ALD. We demonstrate that the ALD is regioselective, with preferential deposition of oxy-Zn(II) species within the small pores of NU-1000. As a result, complementary density functional calculations indicate that this startling regioselectivity ismore » driven by dispersion interactions associated with the preferential adsorption sites for the organometallic precursors prior to reaction.« less

Formation of atomically smooth epitaxial metal films on a chemically reactive interface: Mg on Si(111)

NASA Astrophysics Data System (ADS)

Özer, Mustafa M.; Weitering, Hanno H.

2013-07-01

Deposition of Mg on Si(111)7 × 7 produces an epitaxial magnesium silicide layer. Under identical annealing conditions, the thickness of this Mg2Si(111) layer increases with deposition amount, reaching a maximum of 4 monolayer (ML) and decreasing to ˜3 ML at higher Mg coverage. Excess Mg coalesces into atomically flat, crystalline Mg(0001) films. This surprising growth mode can be attributed to the accidental commensurability of the Mg(0001), Si(111), and Mg2Si(111) interlayer spacing and the concurrent minimization of in-plane Si mass transfer and domain-wall energies. The commensurability of the interlayer spacing defines a highly unique solid-phase epitaxial growth process capable of producing trilayer structures with atomically abrupt interfaces and atomically smooth surface morphologies.

Changes in hydrological connectivity due to vegetation recovery and wall collapse in abandoned terraced fields

NASA Astrophysics Data System (ADS)

Lana-Renault, Noemí; López-Vicente, Manuel; Oranjuren, Rafael; Ángel Llorente, José; Ruiz-Flaño, Purificación; Arnáez, José

2017-04-01

Agricultural terraces have been built in mountain regions worldwide in order to provide a larger surface for cultivation, improve water availability and reduce soil erosion, as they favour infiltration and reduce runoff and sediment connectivity from hillslopes to streams. In many Mediterranean countries, farmland abandonment has led to progressive natural revegetation and, in terraced slopes, due to a lack of maintenance, to a collapse of the water conservation structures, often followed by small mass movements and gullying. Little is known about the effect of such failures on the hydrological system, especially at catchment scale. The aim of this study is to contributing to fill in this gap by exploring the effect of vegetation recovery and terrace failure on hydrological connectivity in a small catchment (192 ha) in northern Spain mostly occupied by abandoned terraced fields. For this purpose, we applied a modified version of the Borselli's index of runoff and sediment connectivity (IC). Besides using the C-RUSLE factor, as used by many authors, we tested the inclusion of an infiltration component (Kf) to assess the landscape-weighting factor. The Kf factor accounted for the high infiltration rates observed in the terraced soils and was estimated using the permeability classes of the K-RUSLE factor. A 2x2 m resolution DEM was used to capture the terraced fields and run the IC model. Following the recommendation of Cavalli et al. (2015), we used the D-infinity flow accumulation algorithm (Tarboton, 1997) to represent the real flow paths, especially on hillslopes, where divergent flow predominates, and on stream channels. To ensure the continuity of the flow path lines, local sinks were filled in with the algorithm of Planchon & Darboux (2001) that preserved a minimum slope gradient of 0.01 degrees. Finally, linear landscape elements such as stonewalls, rock outcrops, and trails and forest roads were also considered. The IC was calculated for the current scenario and the results were validated in the field by identifying stable, erosion, delivery and sedimentation forms in a representative sub-catchment. We then applied the IC for the past scenario, when all terraced fields were cultivated, and we analysed the changes in connectivity due to farmland abandonment, including the separate effect of changes in vegetation, linear landscape elements and water conservation structures. Results of this study have implications for other agro-ecosystems sensitive to farmland abandonment as well as where terrace failure may happen.

Quaternary geologic map of the north-central part of the Salinas River Valley and Arroyo Seco, Monterey County, California

USGS Publications Warehouse

Taylor, Emily M.; Sweetkind, Donald S.

2014-01-01

Arroyo Seco, a perennial drainage in the central Coast Range of California, records a sequence of strath terraces. These terraces preserve an erosional and depositional history, controlled by both climate change and regional tectonics. These deposits have been mapped and correlated on the basis of field investigations, digital terrain analysis, stream gradient profiles, evaluation of published regional soil maps, and satellite imagery. Seven of the strath terraces and associated alluvial fans have been dated by optically stimulated luminescence (OSL) or infrared stimulated luminescence (IRSL). The OSL and IRSL dates on seven of the strath terraces and associated alluvial fans in Arroyo Seco are approximately >120 ka, >65 ka, 51–46 ka, 36–35 ka, 9 ka, and 2–1 ka. These dates generally fall within the range of ages reported from many well-dated marine terraces on the California coast that are formed during sea-level high stands. Tectonic movements, consistently upward, result in a constantly and slowly emerging coastline, however, the regional effects of climate change and resulting eustatic sea-level rises are interpreted as the driving mechanism for erosion and aggradation in Arroyo Seco.

Active tectonics in southern Xinjiang, China: Analysis of terrace riser and normal fault scarp degradation along the Hotan-Qira fault system

NASA Technical Reports Server (NTRS)

Avouac, Jean-Philippe; Peltzer, Gilles

1993-01-01

The northern piedmont of the western Kunlun mountains (Xinjiang, China) is marked at its easternmost extremity, south of the Hotan-Qira oases, by a set of normal faults trending N50E for nearly 70 km. Conspicuous on Landsat and SPOT images, these faults follow the southeastern border of a deep flexural basin and may be related to the subsidence of the Tarim platform loaded by the western Kunlun northward overthrust. The Hotan-Qira normal fault system vertically offsets the piedmont slope by 70 m. Highest fault scarps reach 20 m and often display evidence for recent reactivations about 2 m high. Successive stream entrenchments in uplifted footwallls have formed inset terraces. We have leveled topographic profiles across fault scarps and transverse abandoned terrace risers. The state of degradation of each terrace edge has been characterized by a degradation coefficient tau, derived by comparison with analytical erosion models. Edges of highest abandoned terraces yield a degradation coefficient of 33 +/- 4 sq.m. Profiles of cumulative fault scarps have been analyzed in a similar way using synthetic profiles generated with a simple incremental fault scarp model.

Towards the preparation of realistic model Ziegler-Natta catalysts: XPS study of the MgCl 2/TiCl 4 interaction with flat SiO 2/Si(1 0 0)

NASA Astrophysics Data System (ADS)

Siokou, Angeliki; Ntais, Spyridon

2003-08-01

Despite of the wide use of supported Ti based Ziegler-Natta catalysts in the olefin polymerization industry, questions concerning the role of each one of the catalyst components in the polymerization process, have not found a satisfactory answer yet. This is mainly because of the high sensitivity of these systems to oxygen and atmospheric moisture that makes their study in an atomic level rather complicated. Realistic surface science models of the pre-activated SiO 2 supported MgCl 2/TiCl 4 and TiCl 4 Ziegler-Natta catalysts were prepared by spin coating on flat conductive SiO 2/Si(1 0 0) supports under inert atmosphere. This preparation technique resembles the wet chemical impregnation which is the industrial method of the catalyst preparation. XPS analysis showed that the catalyst precursor anchors on the silica surface through bonding of the Ti atoms with surface silanes or siloxanes, while Mg is attached to the Ti through chlorine bridges. Thermal treatment of the catalysts at 723 K leads to total Cl desorption when MgCl 2 is not present while a significant amount of the Ti atoms is reduced to the Ti 3+ state.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tyson, T. A.; Gao, W.; Chen, Y. -S.

Solar cells based on hybrid perovskites have shown high efficiency while possessing simple processing methods. To gain a fundamental understanding of their properties on an atomic level, we investigate single crystals of CH 3NH 3PbI 3 with a narrow transition (~5 K) near 327 K. Temperature dependent structural measurements reveal a persistent tetragonal structure with smooth changes in the atomic displacement parameters (ADPs) on crossing T*. We show that the ADPs for I ions yield extended flat regions in the potential wells consistent with the measured large thermal expansion parameter. Molecular dynamics simulations reveal that this material exhibits significant asymmetriesmore » in the Pb-I pair distribution functions. We also show that the intrinsically enhanced freedom of motion of the iodine atoms enables large deformations. This flexibility (softness) of the atomic structure results in highly localized atomic relaxation about defects and hence accounts for both the high carrier mobility as well as the structural instability.« less

5. GUN MOUNT ON TERRACE, EAST VIEW (1992). WrightPatterson ...

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

5. GUN MOUNT ON TERRACE, EAST VIEW (1992). - Wright-Patterson Air Force Base, Area B, Building 71, Power Plant Engine Test Torque Stands, Seventh Street between D & G Streets, Dayton, Montgomery County, OH

CH4 dehydrogenation on Cu(1 1 1), Cu@Cu(1 1 1), Rh@Cu(1 1 1) and RhCu(1 1 1) surfaces: A comparison studies of catalytic activity

NASA Astrophysics Data System (ADS)

Zhang, Riguang; Duan, Tian; Ling, Lixia; Wang, Baojun

2015-06-01

In the CVD growth of graphene, the reaction barriers of the dehydrogenation for hydrocarbon molecules directly decide the graphene CVD growth temperature. In this study, density functional theory method has been employed to comparatively probe into CH4 dehydrogenation on four types of Cu(1 1 1) surface, including the flat Cu(1 1 1) surface (labeled as Cu(1 1 1)) and the Cu(1 1 1) surface with one surface Cu atom substituted by one Rh atom (labeled as RhCu(1 1 1)), as well as the Cu(1 1 1) surface with one Cu or Rh adatom (labeled as Cu@Cu(1 1 1) and Rh@Cu(1 1 1), respectively). Our results show that the highest barrier of the whole CH4 dehydrogenation process is remarkably reduced from 448.7 and 418.4 kJ mol-1 on the flat Cu(1 1 1) and Cu@Cu(1 1 1) surfaces to 258.9 kJ mol-1 on RhCu(1 1 1) surface, and to 180.0 kJ mol-1 on Rh@Cu(1 1 1) surface, indicating that the adsorbed or substituted Rh atom on Cu catalyst can exhibit better catalytic activity for CH4 complete dehydrogenation; meanwhile, since the differences for the highest barrier between Cu@Cu(1 1 1) and Cu(1 1 1) surfaces are smaller, the catalytic behaviors of Cu@Cu(1 1 1) surface are very close to the flat Cu(1 1 1) surface, suggesting that the morphology of Cu substrate does not obviously affect the dehydrogenation of CH4, which accords with the reported experimental observations. As a result, the adsorbed or substituted Rh atom on Cu catalyst exhibit a better catalytic activity for CH4 dehydrogenation compared to the pure Cu catalyst, especially on Rh-adsorbed Cu catalyst, we can conclude that the potential of synthesizing high-quality graphene with the help of Rh on Cu foils may be carried out at relatively low temperatures. Meanwhile, the adsorbed Rh atom is the reaction active center, namely, the CVD growth can be controlled by manipulating the graphene nucleation position.

The effect of pre-Hispanic agriculture practices on soils in the Western Cordillera of the Peruvian Andes (region Laramate, 14.5°S)

NASA Astrophysics Data System (ADS)

Leceta, Fernando; Mächtle, Bertil; Schukraft, Gerd; Eitel, Bernhard

2013-04-01

An integrated geoarchaeological study focuses on a group of three archaeological sites. This study comprises soils on pre-Columbian artificial terraces against their nondisturbed pedological context. Six terraces and three soils lacking of archaeological evidence and actual use, are examined to identify morphological and geochemical features generated by the sustained agrarian use. Aim is to understand the land-use and pedological history of the Laramate region, as an agricultural center in pre-Columbian times. Preliminary results show recurrent sequences within the terraces, characterized by two edaphic cycles; a poorly developed Ap modern topsoil is underlaid by one well-preserved 2Ah paleosol. Analytical data shows prehispanic terraces as a sustained agricultural system. Marked by its use and position, higher availability of nutrients and deeper soils, are found at agricultural terraces, located over a debris cone. Significant charcoal fragments for radiocarbon dating at Ayllapampa and Sihulca archeological sites, with a minimum age for terrace construction of Cal 1 sigma AD 675-766 and 782-893 respectively; it remains unclear if another stage of construction. There is no evidence that the terraces have alternated between periods of cultural decline and boom. Rather, reconstructions or modifications to the original structure and the absence of paleosols, address to a continuous use until its abandonment. Today, they produce only under fallow-system. There are no archeological signs of massive irrigation systems (Reindel 2011, pers. comm.). Its installation could only be linked to more favorable climatic conditions, like those described for The Early Horizon (800-200 BC), The Early Intermediate Period (200 BC-600 AD), and The Late Intermediate (Period 1000-1438 AD) (Eitel et al. 2005, Mächtle 2007). As reported on other archeological sites in southern Peru (Branch et al. 2007), an extensive terrace agricultural system during the Middle Horizon (500-1000 AD) could be also attested in the Laramate area. Retention of eroded loessic material transported against the terrace walls could be associated to periods of increased geomorphodynamics founded in the surroundings by 600 AD (Forbriger & Schittek 2011, unpublished raw data). References Branch, N., Kemp, R., Silva, B., Meddens F., Williams, A., Kendall, A., Vivanco Pomacanchari, C. (2007): Testing the sustainability and sensitivity to climatic change of terrace agricultural systems in the Peruvian Andes: a pilot study. Journal of Archaeological Science 34 (2007) 1-9. Eitel, B., Hecht, S., Mächtle, B., Schukraft, G., Kadereit, A., Wagner, G. A., Kromer, B., Unkel, I., Reindel, M. (2005): Geoarchaeological evidence from desert loess in the Nasca-Palpa region, southern Peru: Palaeoenvironmental changes and their impact on Pre-Columbian cultures. Archaeometry 47, 137-185. Mächtle, B. (2007): Geomorphologisch-bodenkundliche Untersuchungen zur Rekonstruktion der holozänen Umweltgeschichte in der nördlichen Atacama im Raum Palpa/Südperu. Dissertation, Heidelberger Geographische Arbeiten 123.- 227 S.

Atomic Force Microscopy of Biological Membranes

PubMed Central

Frederix, Patrick L.T.M.; Bosshart, Patrick D.; Engel, Andreas

2009-01-01

Abstract Atomic force microscopy (AFM) is an ideal method to study the surface topography of biological membranes. It allows membranes that are adsorbed to flat solid supports to be raster-scanned in physiological solutions with an atomically sharp tip. Therefore, AFM is capable of observing biological molecular machines at work. In addition, the tip can be tethered to the end of a single membrane protein, and forces acting on the tip upon its retraction indicate barriers that occur during the process of protein unfolding. Here we discuss the fundamental limitations of AFM determined by the properties of cantilevers, present aspects of sample preparation, and review results achieved on reconstituted and native biological membranes. PMID:19167286

The notion of climate-driven strath-terrace production assessed via dissimilar stream-process response to late Quaternary climate

USGS Publications Warehouse

García, Antonio F.; Mahan, Shannon

2014-01-01

Previous research results from the Gabilan Mesa are combined with new optically stimulated luminescence (OSL) age estimates and sedimentological analyses with the aim of identifying factors that inhibit climate-driven strath-terrace production, and factors that make possible strath-terrace production independent of climate forcing. The factors are revealed by comparing the morphostratigraphy and OSL age estimates of terraces in the adjacent San Lorenzo Creek and Pancho Rico Creek drainage basins of the central California Coast Ranges. OSL age estimates on San Lorenzo Creek fill-terrace alluvium overlying bedrock at two paleofluvial levels range between 50.5 and 41.3 ka and between 33.4 and 18.2 ka. These OSL age estimates indicate that although the channel of Pancho Rico Creek was degrading at these times, San Lorenzo Creek aggradation was synchronous with previously documented regional, climatically driven aggradation that elsewhere in southern California led to strath production and alluvial deposition. The regional-scale climate forcing events had different effects on San Lorenzo and Pancho Rico Creeks because of the influences of drainage-basin lithology on bedload size and tectonic tilting direction on base-level fall. The Holocene history of channel denudation and strath production of Pancho Rico Creek is also different from that of San Lorenzo Creek, and different from that of many other streams in southern California. After Pancho Rico Creek captured the upper part of the drainage basin of San Lorenzo Creek sometime after 15.5 to 11.7 ka, Pancho Rico Creek has been producing unpaired, erosional strath terraces. The weak, clay rich, fine-grained sedimentary rock underlying Pancho Rico Valley is an ideal substrate in which to form straths. The meandering channel of Pancho Rico Creek produces straths, and weathering resistant, relatively hard bedload introduced by stream capture ensures their preservation as strath terraces.

Late Quaternary stream piracy and strath terrace formation along the Belle Fourche and lower Cheyenne Rivers, South Dakota and Wyoming

USGS Publications Warehouse

Stamm, John F.; Hendricks, Robert R.; Sawyer, J. Foster; Mahan, Shannon; Zaprowski, Brent J.; Geibel, Nicholas M.; Azzolini, David C.

2013-01-01

Stream piracy substantially affected the geomorphic evolution of the Missouri River watershed and drainages within, including the Little Missouri, Cheyenne, Belle Fourche, Bad, and White Rivers. The ancestral Cheyenne River eroded headward in an annular pattern around the eastern and southern Black Hills and pirated the headwaters of the ancestral Bad and White Rivers after ~ 660 ka. The headwaters of the ancestral Little Missouri River were pirated by the ancestral Belle Fourche River, a tributary to the Cheyenne River that currently drains much of the northern Black Hills. Optically stimulated luminescence (OSL) dating techniques were used to estimate the timing of this piracy event at ~ 22–21 ka. The geomorphic evolution of the Cheyenne and Belle Fourche Rivers is also expressed by regionally recognized strath terraces that include (from oldest to youngest) the Sturgis, Bear Butte, and Farmingdale terraces. Radiocarbon and OSL dates from fluvial deposits on these terraces indicate incision to the level of the Bear Butte terrace by ~ 63 ka, incision to the level of the Farmingdale terrace at ~ 40 ka, and incision to the level of the modern channel after ~ 12–9 ka. Similar dates of terrace incision have been reported for the Laramie and Wind River Ranges. Hypothesized causes of incision are the onset of colder climate during the middle Wisconsinan and the transition to the full-glacial climate of the late-Wisconsinan/Pinedale glaciation. Incision during the Holocene of the lower Cheyenne River is as much as ~ 80 m and is 3 to 4 times the magnitude of incision at ~ 63 ka and ~ 40 ka. The magnitude of incision during the Holocene might be due to a combined effect of three geomorphic processes acting in concert: glacial isostatic rebound in lower reaches (~ 40 m), a change from glacial to interglacial climate, and adjustments to increased watershed area resulting from piracy of the ancestral headwaters of the Little Missouri River.

Late Holocene evolution of playa lakes in the central Ebro depression based on geophysical surveys and morpho-stratigraphic analysis of lacustrine terraces

NASA Astrophysics Data System (ADS)

Gutiérrez, F.; Valero-Garcés, B.; Desir, G.; González-Sampériz, P.; Gutiérrez, M.; Linares, R.; Zarroca, M.; Moreno, A.; Guerrero, J.; Roqué, C.; Arnold, L. J.; Demuro, M.

2013-08-01

The origin and morpho-stratigraphic evolution of the largest playa-lake system (La Playa-El Pueyo) in the Bujaraloz-Sástago endorheic area, located in the semiarid central sector of the Ebro Depression, are analysed. The enclosed depressions are developed on gypsiferous Tertiary bedrock and show a prevalent WNW-ESE orientation parallel to the direction of the prevalent strong local wind (Cierzo). Yardangs have been carved in bedrock and unconsolidated terrace deposits in the leeward sector of the largest lake basins. A sequence of three lacustrine terrace levels has been identified by detailed geomorphological mapping. The treads of the upper, middle and lower terrace levels are situated at + 9 m, + 6 m and + 0.5 m above the playa-lake floors, respectively. Seismic refraction and electrical resistivity profiles acquired in La Playa reveal a thin basin fill (~ 2 m) with a planar base. These data allow ruling out the genetic hypothesis for the depressions involving the collapse of large bedrock cavities and support a mixed genesis of combined widespread dissolution and subsidence by groundwater discharge and eolian deflation during dry periods. The 5 m thick deposit of the middle terrace was investigated in hand-dug and backhoe trenches. Six AMS radiocarbon ages from this terrace indicate an aggradation phase between 3.9 ka and ca. 2 ka. These numerical ages yield a maximum average aggradation rate of 2.6 mm/yr and a minimum excavation rate by wind deflation of 3 mm/yr subsequent to the accumulation of the middle terrace. The latter figure compares well with those calculated in several arid regions of the world using yardangs carved in palaeolake deposits. The aggradation phase between 4 and 2 ka is coherent with other Iberian and Mediterranean records showing relatively more humid conditions after 4 ka, including the Iron Ages and the Iberian-Roman Period.

Late Quaternary stream piracy and strath terrace formation along the Belle Fourche and lower Cheyenne Rivers, South Dakota and Wyoming

NASA Astrophysics Data System (ADS)

Stamm, John F.; Hendricks, Robert R.; Sawyer, J. Foster; Mahan, Shannon A.; Zaprowski, Brent J.; Geibel, Nicholas M.; Azzolini, David C.

2013-09-01

Stream piracy substantially affected the geomorphic evolution of the Missouri River watershed and drainages within, including the Little Missouri, Cheyenne, Belle Fourche, Bad, and White Rivers. The ancestral Cheyenne River eroded headward in an annular pattern around the eastern and southern Black Hills and pirated the headwaters of the ancestral Bad and White Rivers after ~ 660 ka. The headwaters of the ancestral Little Missouri River were pirated by the ancestral Belle Fourche River, a tributary to the Cheyenne River that currently drains much of the northern Black Hills. Optically stimulated luminescence (OSL) dating techniques were used to estimate the timing of this piracy event at ~ 22-21 ka. The geomorphic evolution of the Cheyenne and Belle Fourche Rivers is also expressed by regionally recognized strath terraces that include (from oldest to youngest) the Sturgis, Bear Butte, and Farmingdale terraces. Radiocarbon and OSL dates from fluvial deposits on these terraces indicate incision to the level of the Bear Butte terrace by ~ 63 ka, incision to the level of the Farmingdale terrace at ~ 40 ka, and incision to the level of the modern channel after ~ 12-9 ka. Similar dates of terrace incision have been reported for the Laramie and Wind River Ranges. Hypothesized causes of incision are the onset of colder climate during the middle Wisconsinan and the transition to the full-glacial climate of the late-Wisconsinan/Pinedale glaciation. Incision during the Holocene of the lower Cheyenne River is as much as ~ 80 m and is 3 to 4 times the magnitude of incision at ~ 63 ka and ~ 40 ka. The magnitude of incision during the Holocene might be due to a combined effect of three geomorphic processes acting in concert: glacial isostatic rebound in lower reaches (~ 40 m), a change from glacial to interglacial climate, and adjustments to increased watershed area resulting from piracy of the ancestral headwaters of the Little Missouri River.

Pleistocene glaciation of the Jackson Hole area, Wyoming

USGS Publications Warehouse

Pierce, Kenneth L.; Licciardi, Joseph M.; Good, John M.; Jaworowski, Cheryl

2018-01-24

Pleistocene glaciations and late Cenozoic offset on the Teton fault have played central roles in shaping the scenic landscapes of the Teton Range and Jackson Hole area in Wyoming. The Teton Range harbored a system of mountain-valley glaciers that produced the striking geomorphic features in these mountains. However, the comparatively much larger southern sector of the Greater Yellowstone glacial system (GYGS) is responsible for creating the more expansive glacial landforms and deposits that dominate Jackson Hole. The glacial history is also inextricably associated with the Yellowstone hotspot, which caused two conditions that have fostered extensive glaciation: (1) uplift and consequent cold temperatures in greater Yellowstone; and (2) the lowland track of the hotspot (eastern Snake River Plain) that funneled moisture to the Yellowstone Plateau and the Yellowstone Crescent of High Terrain (YCHT).The penultimate (Bull Lake) glaciation filled all of Jackson Hole with glacial ice. Granitic boulders on moraines beyond the south end of Jackson Hole have cosmogenic 10Be exposure ages of ~150 thousand years ago (ka) and correlate with Marine Isotope Stage 6. A thick loess mantle subdues the topography of Bull Lake moraines and caps Bull Lake outwash terraces with a reddish buried soil near the base of the loess having a Bk horizon that extends down into the outwash gravel. The Bull Lake glaciation of Jackson Hole extended 48 kilometers (km) farther south than the Pinedale, representing the largest separation of these two glacial positions in the Western United States. The Bull Lake is also more extensive than the Pinedale on the west (22 km) and southwest (23 km) margins of the GYGS but not on the north and east. This pattern is explained by uplift and subsidence on the leading and trailing “bow-wave” of the YCHT, respectively.During the last (Pinedale) glaciation, mountain-valley glaciers of the Teton Range extended to the western edge of Jackson Hole and built bouldery moraines that commonly enclose lakes. On the southern margin of the GYGS, prominent glacial outwash terraces define three phases of the Pinedale glaciation in Jackson Hole: Pinedale-1 (Pd-1) by Antelope Flats with subdued channel patterns on the east side of Jackson Hole; Pinedale-2 (Pd-2) by a large outwash fan that includes Baseline Flat on the west side of Jackson Hole with well-defined channel patterns; and Pinedale-3 (Pd-3) by The Potholes and other outwash fans farther up the Snake River in central Jackson Hole. During Pinedale glaciation, three glacial lobes of the GYGS fed into Jackson Hole, and the relative importance of these lobes changed dramatically through time. During the Pd-1 glaciation, the eastern Buffalo Fork lobe dominated whereas in Pd-2 and Pd-3 time the northern Snake River lobe dominated. This is consistent with migration of the GYGS center of ice mass westward and southward as glaciers built up towards the moisture source provided by storms moving northeastward up the eastern Snake River Plain. The recession of the eastern Buffalo Fork lobe in Pd-2 and Pd-3 times is consistent with an enlarged ice mass on the Yellowstone Plateau that placed the eastern part of the GYGS in a precipitation or snow shadow.In Pd-1 time, the Buffalo Fork lobe reached its maximum extent and was joined by the Pacific Creek lobe. This culmination may correlate with the ~21–18 ka ages of moraines in the Teton Range and nearby ranges. Three subdivisions of Pd-1 glaciation built moraines that are nearly or entirely covered by outwash almost 100 meters thick. In Pd-2 time, the Snake River lobe joined with the Pacific Creek lobe and built a large outwash fan south of the present-day Jackson Lake. Boulders on a moraine at the head of this fan are dated to 15.5 ± 0.5 ka. The relation between Teton glaciers and those of the GYGS is indicated by outwash from these Pd-2 moraines that partly buries outer Jenny Lake moraines dated to 15.2 ± 0.7 ka. East of the large outwash fan, Pd-2 ice advanced across the glacial-age Triangle X-2 lake sediments, perhaps in a surge. The Buffalo Fork lobe retreated more than 20 km up valley from its Pd-1 position and Pd-2 ice of the Snake River and Pacific Creek lobes advanced into the area previously occupied by the Buffalo Fork lobe. The Pd-3 position flanks the margin of Jackson Lake and represents a retreat to a stable position after the Pd-2 7-km advance that may have been a surge across the Triangle X-2 lake sediments. The Potholes and South Landing outwash fans were built in the area deglaciated by the retreat from Pd-2 to Pd-3 time. The Spalding Bay outwash fan continued to incise and a meltwater stream flowed just outside the Teton glacier that filled the present Jenny Lake and deposited the 14.4 ± 0.8 ka inner Jenny Lake moraines.Glacial outwash terraces increase in slope toward their respective moraines of the GYGS and are complex in both north-south and east-west directions. The Pd-1 terrace slopes to the west where it is buried by the Pd-2 outwash. The post-depositional tilting of the Pd-1 outwash terrace is an order of magnitude smaller than the original westward depositional slope. The Pd-1, 2, and 3 terraces have a shingle-like geometry such that the highest terrace decreases in age down valley, and in southern Jackson Hole, the Pd-3 terrace is only 3–5 m above the Snake River.In Pd-1 time the combined Buffalo Fork and Pacific Creek lobes scoured out four basins: (1) Emma Matilda Lake; (2) Two Ocean Lake; (3) a deep basin from lower Pacific Creek to beneath the Oxbows and Jackson Lake Dam; and (4) the largest basin from the lower Buffalo Fork to Deadmans Bar of the Snake River. These basins are largely filled with fine-grained sediment and are now marked by moist lowlands or lakes. In Pd-2 and Pd-3 time the Snake River lobe scoured the present 120-m deep Jackson Lake and possibly the 120-m deeper sediment-filled basin. Subglacial erosion of the Jackson Lake basin by confined water jets is supported by eskers that climb up to the head of the South Landing outwash fan. 

6. INTERIOR DETAIL OF GUN MOUNT ON TERRACE, LOOKING EAST ...

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

6. INTERIOR DETAIL OF GUN MOUNT ON TERRACE, LOOKING EAST (1992). - Wright-Patterson Air Force Base, Area B, Building 22, Armament Laboratory & Gun Range, On flightline between Tenth & Eleventh Streets, Dayton, Montgomery County, OH

Tectonic Geomorphology.

ERIC Educational Resources Information Center

Bull, William B.

1984-01-01

Summarizes representative quantitative tectonic-geomorphology studies made during the last century, focusing on fault-bounded mountain-front escarpments, marine terraces, and alluvial geomorphic surfaces (considering stream terraces, piedmont fault scarps, and soils chronosequences). Also suggests where tectonic-geomorphology courses may best fit…

View of main terrace retaining wall with mature tree on ...

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

View of main terrace retaining wall with mature tree on left center, camera facing southeast - Naval Training Station, Senior Officers' Quarters District, Naval Station Treasure Island, Yerba Buena Island, San Francisco, San Francisco County, CA

Basal Terraces on Melting Ice Shelves

NASA Astrophysics Data System (ADS)

Dutrieux, P.; Stewart, C.; Jenkins, A.; Nicholls, K. W.; Corr, H. F. J.; Rignot, E. J.; Steffen, K.

2014-12-01

Ocean waters melt the margins of Antarctic and Greenland glaciers and individualglaciers' responses and the integrity of their ice shelves are expected to depend on thespatial distribution of melt. The bases of the ice shelves associated with Pine IslandGlacier (West Antarctica) and Petermann Glacier (Greenland) have similar geometries,including kilometers-wide, hundreds-of-meter-high channels oriented along and acrossthe direction of ice flow. The channels are enhanced by, and constrain, oceanic melt.New, meter-scale observations of basal topography reveal peculiar glaciated landscapes.Channel flanks are not smooth, but are instead stepped, with hundreds-of-meters-wideflat terraces separated by 5-50 m-high walls. Melting is shown to be modulated by thegeometry: constant across each terrace, changing from one terrace to the next, and greatlyenhanced on the ~45°-inclined walls. Melting is therefore fundamentally heterogeneousand likely associated with stratification in the ice-ocean boundary layer, challengingcurrent models of ice shelf-ocean interactions.

Surface Chemistry of Trimethylaluminum on Pd(111) and Pt(111)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gharachorlou, Amir; Detwiler, Michael D.; Mayr, Lukas

The behavior of trimethylaluminum (TMA) was investigated on the surfaces of Pt(111) and Pd(111) single crystals. TMA was found to dissociatively adsorb on both surfaces between 300–473 K. Surfaces species observed by high-resolution electron energy loss spectroscopy (HREELS) and X-ray photoelectron spectroscopy (XPS) after TMA adsorption at 300 K included Al-CH3 and CHx,ads (x = 1, 2, or 3) on Pt(111), and ethylidyne (CCH3), CHx,ads (x = 1, 2, or 3), and metallic Al on Pd(111). Density functional theory (DFT) calculations predicted methylaluminum (MA, Al-CH3) to be the most kinetically favorable TMA decomposition product on (111) terraces of both surfaces,more » however, HREELS signatures for Al-CH3 were detected only on Pt(111), whereas ethylidyne was observed on Pd(111). XPS demonstrated higher amounts of carbonaceous species on Pt(111) than on Pd(111). DFT calculations showed that further dissociation of MA to metallic aluminum and methyl groups to be more kinetically favorable on step sites of both metals. In our proposed reaction mechanism, MA migrates to and dissociates at Pd(111) steps at 300 K forming adsorbed methyl groups and metallic Al. Some methyl groups dehydrogenate and recombine forming ethylidyne. Metallic Al or ejected Pd atoms from steps diffuse across Pd(111) terraces until coalescing into irregularly shaped islands on terraces or steps, as observed by scanning tunneling microscopy (STM). Upon heating above 300 K, the Pd–Al alloy diffuses into the Pd bulk. On Pt(111), a high coverage of carbon-containing species following TMA adsorption at 300 K prevented MA diffusion and dissociation at steps, as evidenced by isolated clusters of MA in STM images. Heating above 300 K resulted in MA dissociation, but no Pt–Al alloy formation was observed. We conclude that the differing abilities of Pd and Pt to hydrogenate carbonaceous species plays a key role in MA dissociation and alloy formation, and therefore, the adsorption and dissociation chemistry of TMA depends on properties of the metal substrate surface and determines thin film morphology and composition.« less

Homoepitaxial and Heteroepitaxial Growth on Step-Free SiC Mesas

NASA Technical Reports Server (NTRS)

Neudeck, Philip G.; Powell, J. Anthony

2004-01-01

This article describes the initial discovery and development of new approaches to SiC homoepitaxial and heteroepitaxial growth. These approaches are based upon the previously unanticipated ability to effectively supress two-dimensional nucleation of 3C-SiC on large basal plane terraces that form between growth steps when epitaxy is carried out on 4H- and 6H-SiC nearly on-axis substrates. After subdividing the growth surface into mesa regions, pure stepflow homoeptixay with no terrace nucleation was then used to grow all existing surface steps off the edges of screw-dislocation-free mesas, leaving behind perfectly on-axis (0001) basal plane mesa surfaces completely free of atomic-scale steps. Step-free mesa surfaces as large as 0.4 mm x 0.4 mm were experimentally realized, with the yield and size of step-free mesas being initally limited by substrate screw dislocations. Continued epitaxial growth following step-free surface formation leads to the formation of thin lateral cantilevers that extend the step-free surface area from the top edge of the mesa sidewalls. By selecting a proper pre-growth mesa shape and crystallographic orientation, the rate of cantilever growth can be greatly enhanced in a web growth process that has been used to (1) enlarge step-free surface areas and (2) overgrow and laterally relocate micropipes and screw dislocations. A new growth process, named step-free surface heteroepitaxy, has been developed to achieve 3C-SiC films on 4H- and 6H-SiC substrate mesas completely free of double positioning boundary and stacking fault defects. The process is based upon the controlled terrace nucleation and lateral expansion of a single island of 3C-SiC across a step-free mesa surface. Experimental results indicate that substrateepilayer lattice mismatch is at least partially relieved parallel to the interface without dislocations that undesirably thread through the thickness of the epilayer. These results should enable realization of improved SiC homojunction and heterojunction devices. In addition, these experiments offer important insights into the nature of polytypism during SiC crystal growth.

Can we follow the neotectonic activity of the Hluboká-fault by reconstructing the evolution of the Vltava river course? - Mapping of fluvial terraces around the Budejovice-basin using historic maps

NASA Astrophysics Data System (ADS)

Homolova, Dana; Lomax, Johanna; Prachar, Ivan; Spacek, Petr; Zamolyi, Andras; Decker, Kurt

2010-05-01

The Budějovice Basin in the Bohemian Massif (Czech Republic) is a fault-bounded sedimentary basin with a multiple subsidence history overlying Variscan crystalline basement. Permian, Cretaceous and Miocene sediments record repeated reactivations of faults at or close to the basin margin, which may have continued into the Quaternary. The latter is indicated by geomorphological features such as linear topographic scarps, which characterize part of the faults within and at the border of the Budějovice Basin. In a current study we assess possible Quaternary displacements along the faults delimiting the basin using geomorphological data, analyses of river planform patterns and correlations of Quaternary terraces of the Vltava River, which crosses the basin and its boundary faults. The regionally most important tectonic feature - the Hluboká fault -forms the northeastern margin of the Budějovice basin. The fault crosses the course of the river Vltava, a fact that guided our research to take a more precise look at the character and distribution of fluvial sediments in this area. Our main focus is on dating of terrace bodies around the Hluboká fault. According to the scheme used in most European regions, influences by the Pleistocene glacial cycles, the Vltava river terraces were assigned by most scientists to the 4(5) main alpine glacial periods. This dating is not straightforward as terraces are not connected to moraine bodies like in the Alps. The terraces were basically correlated by their altitude above the river and by their lithology (clastic content and grain size composition), but mostly without any numerical age determination. Our studies include several field and laboratory methods, supported by computer analyses of various types of spatial data. Data sources include: (i) modern topographic maps, (ii) geological maps, (iii) georeferenced historic map sheets of the Austrian Second Military Survey (provided by the Geoinformatics Laboratory of the University J. E. Purkyně, 2005). The georeferenced map sheets of the Second Military Survey provide a very exact base map (Timár et al., 2006) for investigating the location of possible terrace bases. Since the georeferencing accuracy is < 10 m, data from these map sheets can be integrated into the geomorphologic studies providing information about the geomorphologic situation in the study area of the years 1836-1842, i.e., with less anthropogenic impact on geomorphological features than today. These data sources are combined with data from boreholes and thus help us identifying potential terrace bodies and choosing appropriate investigation sites. In the field, morphological, sedimentological and pedological methods are used to obtain relevant data about the sediment stratigraphy. Several laboratory analyses were carried out to gain information on the age of the terraces. We use OSL-dating in combination with the analysis of heavy minerals and clay minerals, as well as grain size analysis. After gathering information about the absolute ages of the terrace bodies upstream and downstream the Hluboká fault, we may be able to declare if the building of terrace staircases was influenced by tectonic activity of the fault or not. Timár, G., Molnár, G., Székely, B., Biszak, S., Varga, J., Jankó, A. (2006): Digitized maps of the Habsburg Empire - The map sheets of the second military survey and their georeferenced version. Arcanum, Budapest, 59 p. ISBN 963-7374-33-7

Evolution of the Kιzιlιrmak river and its interaction with the North Anatolian Fault, Turkey

NASA Astrophysics Data System (ADS)

Drab, L.; Hubert Ferrari, A.; Benedetti, L.; van der Woerd, J.

2010-12-01

The North Anatolian Fault (NAF) is a 1500km long dextral strike-slip fault, which accommodates the extrusion of the Anatolian Plate away from the Arabia/Eurasia collision zone at a rate of 20-25mm/yr. The fault strongly affects the whole drainage network and, especially, the Kιzιlιrmak River. The Kιzιlιrmak River is the longest river in Turkey (1350km); it formed during the Pliocene and rose in eastern Anatolia. The river drains a part of the Anatolian Plateau, crosses the North Anatolian Fault and the Pontides mountains before reaching the Black Sea. Whereas wide terraces are preserved along the Kιzιlιrmak River in the Anatolian Plateau, where a recent study (Dogan 2009) determines an incision rate of 0.08 mm/yr according to 40Ar/39Ar datations on basalts, no clear terraces can be mapped further North where the river incises through the Pontides Mountains. Our study focuses on the central part of the fault affected by the 280 km long 1943 Tosya earthquake rupture. In this area the NAF makes a wide convex arc about 100km south to the Black Sea coast, and offset by 30 km the Kιzιlιrmak River. Indeed, south of the NAF the Kιzιlιrmak River flows to North/East. Then it is deviated along the NAF in the Kargι pull-apart and flows to the East parallel to the fault for 30km before bending again to the North/East in the Kamil pull-apart. Around the two bends of the River three alluvial terraces can be mapped. The lowest one (10m high above the present river level) is preserved in the Kargι pull-apart. The two other ones (60 and 100m above the Kιzιlιrmak River) are situated further east in the Kamil pull-apart. The highest terrace is offset by at least 300m offset along the NAF. The ages of sampled terraces are constrained using 10Be and 36Cl cosmogenic dating methods. The in situ cosmogenic 36Cl exposure ages calculated apply from 22ka for the lowest terrace, to 100 ka for the highest terrace in the erosion preserved area. The highest terrace shows a contribution of younger ages (the same time interval of 50ka of the intermediate terrace) certainly coming from the catchement just above. The proximity of ages may be due to the short time-interval between the both highest terraces incision by the Kιzιlιrmak river. 10Be measurements on sand coming from river beds will provide past to actual erosion rates along the Kιzιlιrmak River as well as present erosion rate from small rivers flowing to the river. The goals of this study are to constrain, 1/ the origin of the terraces (climatic or tectonic), 2/ the slip rate of the NAF integrated over more than 20 000 years, 3/ the evolution of the Kιzιlιrmak River incision rate, 4/ the influence of the vertical motion in the NAF convex arc region on the present incision rate of small rivers flowing toward the Kιzιlιrmak.

Planar regions of GaAs (001) prepared by Ga droplet motion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zheng, Changxi, E-mail: changxi.zheng@monash.edu; Tang, Wen-Xin; Jesson, David E., E-mail: jessonDE@cardiff.ac.uk

2016-07-15

The authors describe a simple method for obtaining planar regions of GaAs (001) suitable for surface science studies. The technique, which requires no buffer layer growth, atomic hydrogen source, or the introduction of As flux, employs controllable Ga droplet motion to create planar trail regions during Langmuir evaporation. Low-energy electron microscopy/diffraction techniques are applied to monitor the droplet motion and characterize the morphology and the surface reconstruction. It is found that the planar regions exhibit atomic flatness at the level of a high-quality buffer layer.

Carbon-containing cathodes for enhanced electron emission

DOEpatents

Cao, Renyu; Pan, Lawrence; Vergara, German; Fox, Ciaran

2000-01-01

A cathode has electropositive atoms directly bonded to a carbon-containing substrate. Preferably, the substrate comprises diamond or diamond-like (sp.sup.3) carbon, and the electropositive atoms are Cs. The cathode displays superior efficiency and durability. In one embodiment, the cathode has a negative electron affinity (NEA). The cathode can be used for field emission, thermionic emission, or photoemission. Upon exposure to air or oxygen, the cathode performance can be restored by annealing or other methods. Applications include detectors, electron multipliers, sensors, imaging systems, and displays, particularly flat panel displays.

A landscape character assessment of three terraced areas in Campania region, Italy

NASA Astrophysics Data System (ADS)

Gravagnuolo, Antonia; Ronza, Maria; Di Martino, Ferdinando; De Rosa, Fortuna

2017-04-01

Agricultural terraces represent the territorial structure of many cultural landscapes in the Campania region, Italy. Historic urban/rural settlements and hydraulic-agrarian systems have been developed on mountains and hills, producing diverse cultural landscapes depending on the specific geological, pedological and geomorphological characteristics, which influenced the character and functions of terraces. These unique landscapes are multi-functional and provide many ecosystem services: provisioning (food, water retention, building materials); regulating and maintenance (hydrogeological stability, soil fertility, protection from soil erosion, maintenance of genetic diversity, habitat); cultural services (heritage and traditional knowledge conservation, tourism and recreation, spiritual experience, education, aesthetic quality). Three terraced landscapes in Campania are analysed, which present a rich diversity in the geological structure and formal/functional characteristics: the Roccamonfina vulcanic area, a highly fertile and lapillous soil; the Monte di Bulgheria, a clay-rich area; and finally the well-known UNESCO World Heritage site of the Amalfi Coast, a calcareous, steep rock faced area. A landscape character assessment of the three sites is processed, identifying the biophysical structure of the sites, natural systems and land use, and cultural and anthropic elements. Terraced landscapes in Campania can be regenerated, taking again an active social and economic role for the society, enhancing their multifunctionality as a key source of wellbeing. Ecosystem services are mapped and evaluated to assess benefits and costs in a multidimensional framework. Spatial analysis in GIS environment supports this process, providing a decision-support tool for mapping and assessment of terraced landscapes, to convert their actual and potential value into a resource of economic sustainable development.

Agricultural terraces and slope instability at Cinque Terre (NW Italy)

NASA Astrophysics Data System (ADS)

Brandolini, Pierluigi; Cevasco, Andrea

2015-04-01

Cinque Terre, located in the eastern Liguria, are one of the most representative examples of terraced coastal landscape within the Mediterranean region. They are the result of a century-old agricultural practice and constitute an outstanding example of human integration with the natural landscape. For this highly unusual man-made coastal landscape, the Cinque Terre have been recognized as a World Heritage Site by UNESCO since 1997 and became National Park in 1999. The complex network of retaining dry stone walls and drainage networks ensured through times the control of shallow water erosion and therefore, indirectly, favoured debris cover stability. The lack of maintenance of terracing due to farmer abandonment since the 1950s led to widespread slope erosion phenomena. The effects of such phenomena culminated during the 25 October 2011 storm rainfall event, when slope debris materials charged by streams gave rise to debris floods affecting both Monterosso and Vernazza villages. As the analysis of the relationships between geo-hydrological processes and land use in the Vernazza catchment highlighted, abandoned and not well maintained terraces were the most susceptible areas to shallow landsliding and erosion triggered by intense rainfall. As a consequence, the thousands of kilometres of dry stone walls retaining millions of cubic metres of debris cover at Cinque Terre currently constitute a potential menace for both villages, that are mainly located at the floor of deep cut valleys, and tourists. Given the increasing human pressure due to tourist activities, geo-hydrological risk mitigation measures are urgently needed. At the same time, restoration policies are necessary to preserve this extraordinary example of terraced coastal landscape. In this framework, the detailed knowledge of the response of terraced areas to intense rainfall in terms of slope instability is a topic issue in order to identify adequate land planning strategies as well as the areas where interventions should be focused primarily. In this study, with the aim to contribute to a better understanding of geo-hydrological hazards at basin scale, the main types of slope instability phenomena that occurred on agricultural terraces at Cinque Terre following the 25 October 2011 rainfall event are presented in relation to different geological and geomorphological conditions. In particular, selected examples of shallow landslides and erosive slope processes due to running water affecting abandoned or cultivated terraces for vineyards and olive grooves will be shown.

Terraced landscape: from an old best practice to a rising land abandoned-related soil erosion risk

NASA Astrophysics Data System (ADS)

Tarolli, Paolo; Preti, Federico; Romano, Nunzio

2013-04-01

Among the most evident landscape signatures of human fingerprint during the Holocene, the terraces related to agricultural activities deserve a great importance. Landscape terracing probably represents one of the oldest best practice primarily for crop production, but also for mitigating soil erosion and stabilizing hillslopes in landforms dominated by steep slopes. This technique is widely used in various parts of the world even under different environmental conditions. In some zones, terraced landscapes, because of their history and locations, can also be considered a historical heritage and a sort of "cultural landscape" to preserve, an absolutely value for tourism. To preserve their original role of soil erosion prevention, terraces should be properly designed built according to specific and sustainable engineering rules. Then, their maintenance is the most critical issue to deal with. It is well known from literature that terraced landscapes subject to abandonment would result in an increasing of terrace failure and related land degradation. If not maintained, a progressively increasing of gully erosion affects the structure of the walls. The results of this process is the increasing of connectivity and runoff. During the last few years and partly because of changing in the society perspective and migration toward metropolitan areas, some Countries have been affected by a serious and wider land abandonment with an increasing of soil erosion and derived landslide risk. Italy is one example. In this work, we consider three typical case studies of a terraced landscape where the lack of maintenance characterizing the last few years, increased the landslide risk with several problems to the population. The first case study is located along the renowed "Amalfi Coast" (a portion of land located near Salerno, southern Italy), the second is placed in the north of Toscana (a region located in Central Italy), and the third one along the so-called "Cinque Terre" (a region located near La Spezia, in Central Italy). The goals are to present the state of the art of such issue by integrating historical and cultural point of views, to land use and hydrogeomorphological analysis, also through remotely sensed technologies such LiDAR. Only with a fully integrated approach it is possible to mitigate such problem, planning new sustainable soil conservation practices, and at the same way maintaining agricultural activities.

MULTI-FOLD, SEISMIC-STYLE TDEM INDUCTION OFFSET PROFILING AT KENTLAND FARMS, VA

NASA Astrophysics Data System (ADS)

Kazlauskas, E. M.; Weiss, C. J.

2009-12-01

An outstanding question in Valley and Ridge geology is the geomorphological history and hydrologic framework of the New River terraces. And while depth to bedrock on the upper terraces remains unknown, knowledge of the bedrock interface is key to addressing two specific issues: What is the geometry and connectivity of karst features such as sinkholes and what is the structure and depositional history of these terraces? To answer these questions, Kentland Farms (located in the Valley and Ridge of Southwest Virginia) has been chosen as the study site for its exceptional development of terrace deposits, nearly unrestricted access to its grounds, sparse vegetation coverage, and numerous sinkholes with a clear topographic expression. The Kentland Farms study area is characterized by heavily weathered, fluvial terrace deposits ranging from a few meters thickness to an estimated 70 m, overlying a karstic, Cambrian aged Elbrook Formation limestone. The terrace deposits consist of weathered clay units of varying composition with interbedded cobble and gravel horizons. The nature of the underlying bedrock coupled with the complex structure of the terrace deposits present difficulties in location of the bedrock interface. Due to complicated geology, a novel, multi-fold, seismic-style, Time Domain Electromagnetic (TDEM) induction survey was conducted in order to provide a more robust data set than a traditional common offset survey as well as to increase lateral resolution. This approach consists of taking multiple transmitter “shots” at a fixed position with a spread of receiver locations at fixed offset intervals (10m in this survey). The procedure is then repeated by moving the transmitter one interval at a time until the line is complete. 1-D inversions generated by using different transmitter-receiver offsets were analyzed to create a set of laterally constrained vertical profiles. In addition, multi-fold, seismic-style TDEM induction offset profiling allowed for split-spread moveout analysis, which shows possible evidence of super diffusion of eddy currents. While the ultimate goals of the research are twofold - to resolve sinkhole geometry to further our understanding of hydrologic framework in the area, and to provide additional constraints on the uncertainty in ages of the terraces - this presentation will focus on a discussion of the novel experiment design and the associated preliminary results.

Impacts of terracing on soil erosion control and crop yield in two agro-ecological zones of Rwanda

NASA Astrophysics Data System (ADS)

Rutebuka, Jules; Ryken, Nick; Uwimanzi, Aline; Nkundwakazi, Olive; Verdoodt, Ann

2017-04-01

Soil erosion remains a serious limiting factor to the agricultural production in Rwanda. Terracing has been widely adopted in many parts of the country in the past years, but its effectiveness is not yet known. Besides the standard radical (bench) terraces promoted by the government, also progressive terraces (with living hedges) become adopted mainly by the farmers. The aim of this study was to measure short-term (two consecutive rainy seasons 2016A and 2016B) run-off and soil losses for existing radical (RT) and progressive (PT) terraces versus non-protected (NP) fields using erosion plots installed in two agro-ecological zones, i.e. Buberuka highlands (site Tangata) and Eastern plateau (site Murehe) and determine their impacts on soil fertility and crop production. The erosion plot experiment started with a topsoil fertility assessment and during the experiment, maize was grown as farmer's cropping preference in the area. Runoff data were captured after each rainfall event and the collected water samples were dried to determine soil loss. Both erosion control measures reduced soil losses in Tangata, with effectiveness indices ranging from 43 to 100% when compared to the NP plots. RT showed the highest effectiveness, especially in season A. In Murehe, RT minimized runoff and soil losses in both seasons. Yet, the PT were largely inefficient, leading to soil losses exceeding those on the NP plots (ineffectiveness index of -78% and -65% in season A and B, respectively). Though topsoil fertility assessment in the erosion plots showed that the soil quality parameters were significantly higher in RT and NP plots compared to the PT plots on both sites, maize grain yield was not correlated with the physical effectiveness of the erosion control measures. Finally, the effectiveness of soil erosion control measures as well as their positive impacts on soil fertility and production differ not only by terracing type but also by agro-ecological zone and the management or maintenance adopted by farmers. Terracing should be complemented by continuous fertility amendments (organic material inputs), use of improved agronomic and management practices considering agro-ecological zone conditions. In general, radical terracing was found to be the most effective soil erosion control measure on both sites.

Possible connection between large volcanic eruptions and level rise episodes in the Dead Sea Basin

NASA Astrophysics Data System (ADS)

Bookman, R.; Filin, S.; Avni, Y.; Rosenfeld, D.; Marco, S.

2014-12-01

The June 1991 Pinatubo volcanic eruption perturbed the atmosphere, triggering short-term worldwide changes in climate. The following winter was anomalously wet in the Levant, with a ~2-meter increase in the Dead Sea level that created a morphological terrace along the lake's shore. Given the global effects of volcanogenic aerosols, we tested the hypothesis that the 1991-92 shore terrace is a modern analogue to the linkage between past volcanic eruptions and a sequence of shore terraces in the Dead Sea Basin. Analysis of precipitation series from Jerusalem showed a significant positive correlation between the Dust Veil Index (DVI) of the modern eruptions and annual rainfall. The DVI was found to explain nearly 50% of the variability in the annual rainfall, such that greater DVI means more rainfall. Other factors that may affect the annual rainfall in the region as the Southern Oscillation Index (SOI) and the North Atlantic oscillations (NAO) were incorporated along with the DVI in a linear multiple regression model. It was found that the NAO did not contribute anything except for increased noise, but the added SOI increased the explained variability of rainfall to more than 60%. Volcanic eruptions with a VEI of 6, as in the Pinatubo, occurred about once a century during the Holocene and the last glacial-interglacial cycle. This occurrence is similar to the frequency of shore terrace build-up during the Lake Lisan desiccation. Sixteen shore terraces, detected using airborne laser scanning data, were interpreted as indicating short-term level rises due to episodes of enhanced precipitation and runoff during the dramatic drop in Lake Lisan's (palaeo-Dead Sea) level at the end of the LGM. The terraces were compared with a time series of volcanogenic sulfate from the GISP2 record, and similar numbers of sulfate concentration peaks and terraces were found. Furthermore, a significant correlation was found between SO4 concentration peaks and the terraces heights. This correlation may indicate a link between the explosivity, magnitude of stratospheric injection, and the impact on the northern hemisphere water balance. The record of such short-term climato-hydrological effects is made possible by the dramatic desiccation of Lake Lisan. Detailed records of such events provide a demonstration of global climatic teleconnections.

Quaternary crustal deformation along a major branch of the San Andreas fault in central California

USGS Publications Warehouse

Weber, G.E.; Lajoie, K.R.; Wehmiller, J.F.

1979-01-01

Deformed marine terraces and alluvial deposits record Quaternary crustal deformation along segments of a major, seismically active branch of the San Andreas fault which extends 190 km SSE roughly parallel to the California coastline from Bolinas Lagoon to the Point Sur area. Most of this complex fault zone lies offshore (mapped by others using acoustical techniques), but a 4-km segment (Seal Cove fault) near Half Moon Bay and a 26-km segment (San Gregorio fault) between San Gregorio and Point Ano Nuevo lie onshore. At Half Moon Bay, right-lateral slip and N-S horizontal compression are expressed by a broad, synclinal warp in the first (lowest: 125 ka?) and second marine terraces on the NE side of the Seal Cove fault. This structure plunges to the west at an oblique angle into the fault plane. Linear, joint0controlled stream courses draining the coastal uplands are deflected toward the topographic depression along the synclinal axis where they emerge from the hills to cross the lowest terrace. Streams crossing the downwarped part of this terrace adjacent to Half Moon Bay are depositing alluvial fans, whereas streams crossing the uplifted southern limb of the syncline southwest of the bay are deeply incised. Minimum crustal shortening across this syncline parallel to the fault is 0.7% over the past 125 ka, based on deformation of the shoreline angle of the first terrace. Between San Gregorio and Point Ano Nuevo the entire fault zone is 2.5-3.0 km wide and has three primary traces or zones of faulting consisting of numerous en-echelon and anastomozing secondary fault traces. Lateral discontinuities and variable deformation of well-preserved marine terrace sequences help define major structural blocks and document differential motions in this area and south to Santa Cruz. Vertical displacement occurs on all of the fault traces, but is small compared to horizontal displacement. Some blocks within the fault zone are intensely faulted and steeply tilted. One major block 0.8 km wide east of Point Ano Nuevo is downdropped as much as 20 m between two primary traces to form a graben presently filling with Holocene deposits. Where exposed in the sea cliff, these deposits are folded into a vertical attitude adjacent to the fault plane forming the south-west margin of the graben. Near Point Ano Nuevo sedimentary deposits and fault rubble beneath a secondary high-angle reverse fault record three and possibly six distinct offset events in the past 125 ka. The three primary fault traces offset in a right-lateral sense the shoreline angles of the two lowest terraces east of Point Ano Nuevo. The rates of displacement on the three traces are similar. The average rate of horizontal offset across the entire zone is between 0.63 and 1.30 cm/yr, based on an amino-acid age estimate of 125 ka for the first terrace, and a reasonable guess of 200-400 ka for the second terrace. Rates of this magnitude make up a significant part of the deficit between long-term relative plate motions (estimated by others to be about 6 cm/yr) and present displacement rates along other parts of the San Andreas fault system (about 3.2 cm/yr). Northwestward tilt and convergence of six marine terraces northeast of Ano Nuevo (southwest side of the fault zone) indicate continuous gentle warping associated with right-lateral displacement since early or middle Pleistocene time. Minimum local crustal shortening of this block parallel to the fault is 0.2% based on tilt of the highest terrace. Five major, evenly spaced terraces southeast of Ano Nuevo on the southwest flank of Mt. Ben Lomond (northeast side of the fault zone) rise to an elevation of 240 m, indicating relatively constant uplift (about 0.19 m/ka and southwestward tilt since Early or Middle Pleistocene time (Bradley and Griggs, 1976). ?? 1979.

Prediction of large gap flat Chern band in a two-dimensional metal-organic framework

NASA Astrophysics Data System (ADS)

Su, Ninghai; Jiang, Wei; Wang, Zhengfei; Liu, Feng

2018-01-01

Systems with a flat Chern band have been extensively studied for their potential to realize high-temperature fractional quantum Hall states. To experimentally observe the quantum transport properties, a sizable topological gap is highly necessary. Here, taking advantage of the high tunability of two-dimensional (2D) metal-organic frameworks (MOFs), whose crystal structures can be easily tuned using different metal atoms and molecular ligands, we propose a design of a 2D MOF [Tl2(C6H4)3, Tl2Ph3] showing nontrivial topological states with an extremely large gap in both the nearly flat Chern band and the Dirac bands. By coordinating π-conjugated thallium ions and benzene rings, crystalline Tl2Ph3 can be formed with Tl and Ph constructing honeycomb and kagome lattices, respectively. The px,y orbitals of Tl on the honeycomb lattice form ideal pxy four-bands, through which a flat Chern band with a spin-orbit coupling (SOC) gap around 140 meV evolves below the Fermi level. This is the largest SOC gap among all the theoretically proposed organic topological insulators so far.

Efficient Nonlinear Atomization Model for Thin 3D Free Liquid Films

NASA Astrophysics Data System (ADS)

Mehring, Carsten

2007-03-01

Reviewed is a nonlinear reduced-dimension thin-film model developed by the author and aimed at the prediction of spray formation from thin films such as those found in gas-turbine engines (e.g., prefilming air-blast atomizers), heavy-fuel-oil burners (e.g., rotary-cup atomizers) and in the paint industry (e.g., flat-fan atomizers). Various implementations of the model focusing on different model-aspects, i.e., effect of film geometry, surface tension, liquid viscosity, coupling with surrounding gas-phase flow, influence of long-range intermolecular forces during film rupture are reviewed together with a validation of the nonlinear wave propagation characteristics predicted by the model for inviscid planar films using a two-dimensional vortex- method. An extension and generalization of the current nonlinear film model for implementation into a commercial flow- solver is outlined.

Quantitative Raman spectrum and reliable thickness identification for atomic layers on insulating substrates.

PubMed

Li, Song-Lin; Miyazaki, Hisao; Song, Haisheng; Kuramochi, Hiromi; Nakaharai, Shu; Tsukagoshi, Kazuhito

2012-08-28

We demonstrate the possibility in quantifying the Raman intensities for both specimen and substrate layers in a common stacked experimental configuration and, consequently, propose a general and rapid thickness identification technique for atomic-scale layers on dielectric substrates. Unprecedentedly wide-range Raman data for atomically flat MoS(2) flakes are collected to compare with theoretical models. We reveal that all intensity features can be accurately captured when including optical interference effect. Surprisingly, we find that even freely suspended chalcogenide few-layer flakes have a stronger Raman response than that from the bulk phase. Importantly, despite the oscillating intensity of specimen spectrum versus thickness, the substrate weighted spectral intensity becomes monotonic. Combined with its sensitivity to specimen thickness, we suggest this quantity can be used to rapidly determine the accurate thickness for atomic layers.

75 FR 67389 - Notice of Availability of the Draft Environmental Impact Statement for the Yesler Terrace...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-11-02

... Terrace, street vacation, preliminary and final plat approval, adoption of a Planned Action Ordinance... the time a permit application is made to an earlier phase in the process, such as at the Comprehensive...

Terrace Town

ERIC Educational Resources Information Center

Sabin, Heather

2010-01-01

The "Terrace Town" program brings architecture and city planning curriculum to elementary schools in Madison, Wisconsin, and surrounding areas. Over eight weeks, classrooms discuss what makes a community livable, sustainable, and kid-friendly. Throughout the process, students gain a better understanding of their own city environments and…

Taphonomic problems in reconstructing sea-level history from the late Quaternary marine terraces of Barbados

USGS Publications Warehouse

Muhs, Daniel; Simmons, Kathleen R.

2017-01-01

Although uranium series (U-series) ages of growth-position fossil corals are important to Quaternary sea-level history, coral clast reworking from storms can yield ages on a terrace dating to more than one high-sea stand, confounding interpretations of sea-level history. On northern Barbados, U-series ages corals from a thick storm deposit are not always younger with successively higher stratigraphic positions, but all date to the last interglacial period (~127 ka to ~112 ka), Marine Isotope Substage (MIS) 5.5. The storm deposit ages are consistent with the ages of growth-position corals found at the base of the section and at landward localities on this terrace. Thus, in this case, analysis of only a few corals would not have led to an error in interpreting sea-level history. In contrast, a notch cut into older Pleistocene limestone below the MIS 5.5 terrace contains corals that date to both MIS 5.5 (~125 ka) and MIS 5.3 (~108 ka). We infer that the notch formed during MIS 5.3 and the MIS 5.5 corals are reworked. Similar multiple ages of corals on terraces have been reported elsewhere on Barbados. Thus, care must be taken in interpreting U-series ages of corals that are reported without consideration of taphonomy.

Soil slips and debris flows on terraced slopes

NASA Astrophysics Data System (ADS)

Crosta, G. B.; Dal Negro, P.; Frattini, P.

Terraces cover large areas along the flanks of many alpine and prealpine valleys. Soil slips and soil slips-debris flows are recurrent phenomena along terraced slopes. These landslides cause damages to people, settlements and cultivations. This study investigates the processes related to the triggering of soil slip-debris flows in these settings, analysing those occurred in Valtellina (Central Alps, Italy) on November 2000 after heavy prolonged rainfalls. 260 landslides have been recognised, mostly along the northern valley flank. About 200 soil slips and slumps occurred in terraced areas and a third of them evolved into debris flows. Field work allowed to recognise the settings at soil slip-debris flow source areas. Landslides affected up to 2.5 m of glacial, fluvioglacial and anthropically reworked deposits overlying metamorphic basement. Laboratory and in situ tests allowed to characterise the geotechnical and hydraulic properties of the terrains involved in the initial failure. Several stratigraphic and hydrogeologic factors have been individuated as significant in determining instabilities on terraced slopes. They are the vertical changes of physical soil properties, the presence of buried hollows where groundwater convergence occurs, the rising up of perched groundwater tables, the overflow and lateral infiltration from superficial drainage network, the runoff concentration by means of pathways and the insufficient drainage of retaining walls.

The physical model of a terraced plot: first results

NASA Astrophysics Data System (ADS)

Perlotto, Chiara; D'Agostino, Vincenzo; Buzzanca, Giacomo

2017-04-01

Terrace building have been expanded in the 19th century because of the increased demographic pressure and the need to crop additional areas at steeper slopes. Terraces are also important to regulate the hydrological behavior of the hillslope. Few studies are available in literature on rainfall-runoff processes and flood risk mitigation in terraced areas. Bench terraces, reducing the terrain slope and the length of the overland flow, quantitatively control the runoff flow velocity, facilitating the drainage and thus leading to a reduction of soil erosion. The study of the hydrologic-hydraulic function of terraced slopes is essential in order to evaluate their possible use to cooperate for flood-risk mitigation also preserving the landscape value. This research aims to better focus the times of the hydrological response, which are determined by a hillslope plot bounded by a dry-stone wall, considering both the overland flow and the groundwater. A physical model, characterized by a quasi-real scale, has been built to reproduce the behavior of a 3% outward sloped terrace at bare soil condition. The model consists of a steel metal box (1 m large, 3.3 m long, 2 m high) containing the hillslope terrain. The terrain is equipped with two piezometers, 9 TDR sensors measuring the volumetric water content, a surface spillway at the head releasing the steady discharge under test, a scale at the wall base to measure the outflowing discharge. The experiments deal with different initial moisture condition (non-saturated and saturated), and discharges of 19.5, 12.0 and 5.0 l/min. Each experiment has been replicated, conducting a total number of 12 tests. The volumetric water content analysis produced by the 9 TDR sensors was able to provide a quite satisfactory representation of the soil moisture during the runs. Then, different lag times at the outlet since the inflow initiation were measured both for runoff and groundwater. Moreover, the time of depletion and the piezometer response have been monitored and analyzed, well corroborating the findings on the kinematics of the terrace plot. Finally, the computation of the specific Curve Number (Soil Conservation Service) of the physical model has revealed values rather large if compared with those reported in the literature. This phenomena was likely caused by the high values of the inflow discharge, the limited cross-width of the model (1 m) and the increasing compactness of the soil owing to the experiment repetition. These pioneering experiments have produced some remarkable outcomes on the important role of lag-times (runoff and groundwater) of a terraced system as well as many ideas on improving the physical model and its setting in a next investigation.

Luminescence dating of river terrace formation - methodological challenges and complexity of result interpretation: a case study from the headwaters of the River Main, Germany

NASA Astrophysics Data System (ADS)

Kolb, Thomas; Fuchs, Markus; Zöller, Ludwig

2015-04-01

River terraces are widespread geomorphic features of Quaternary landscapes. Besides tectonics, their formation is predominantly controlled by climatic conditions. Changes in either conditions cause changes in fluvial discharge and sediment load. Therefore, fluvial terraces are widely used as important non-continuous sedimentary archives for paleotectonic and paleoenvironmental reconstruction. The informative value of fluvial archives and their significance for paleoenvironmental research, however, strongly depend on a precise dating of the terrace formation. Over the last decades, various luminescence dating techniques have successfully been applied on fluvial deposits and were able to provide reliable age information. In contrast to radiocarbon dating, modern luminescence dating techniques provide an extended dating range, which enables the determination of age information for fluvial and other terrestrial archives far beyond the last glacial-interglacial cycle. Due to the general abundance of quartz and feldspar minerals, there is almost no limitation of dateable material, so that luminescence dating methods can be applied on a wide variety of deposits. When using luminescence dating techniques, however, some methodological difficulties have to be considered. Due to the mechanism of fluvial transport, this is especially true for fluvial sediments, for which two major problems have been identified to be the main reasons of incorrect age estimations: (1) incomplete resetting of the luminescence signal during transport and (2) dosimetric inaccuracies as a result of the heterogeneity of terrace gravels. Thus, luminescence dating techniques are still far from being standard methods for dating fluvial archives and the calculated sedimentation ages always demand a careful interpretation. This contribution reveals some of the difficulties that may occur when luminescence dating techniques are applied on river terraces and illustrates several strategies used for overcoming these problems and for determining correct sedimentation ages. The presented results are based on a case study, located in the headwaters of the River Main, the longest right bank tributary of the Rhine drainage system. Here, within an oversized dry valley in Northern Bavaria (Germany), five Pleistocene terraces are distinguished. The terraces are interpreted as the result of a complex landscape evolution, which is characterized by multiple river deflections. The need for a careful interpretation of luminescence results is illustrated by some optically stimulated luminescence (OSL) ages calculated for the youngest of these five Pleistocene terraces. These results show different sedimentation ages of samples originating from the same morphological unit. Thus, these ages may be interpreted as evidence for a diachronic character of river incision and, hence, point to the complexity of fluvial systems' response to climatically and/or tectonically forced changes in local and regional paleoenvironmental conditions.

Determination of tectonic shortening rates from progressively deformed flights of terraces above the Chelungpu and Changhua thrust ramps, Taiwan

NASA Astrophysics Data System (ADS)

Yue, L.; Suppe, J.

2007-12-01

The Chelungpu and Changhua thrust ramps in central Taiwan show contrasting hanging-wall structural geometries that suggest different kinematics, even though they involve the same stratigraphic section and basal detachment. The Chelungpu thrust shows a classic fault-bend folding geometry, which predicts folding solely by kink-band migration, whereas the hanging wall of the Changhua thrust demonstrates the characteristic geometry of a shear fault-bend folding, which predicts a progressive limb rotation with minor kink-band migration. We test the kinematic predictions of classic and shear fault-bend folding theories by analyzing deformed flights of terraces and coseismic displacements in the Mw=7.6 Chi-Chi earthquake. The Chelungpu terraces shows differences in uplift magnitudes across active axial surfaces that closely approximate the assumptions of classical fault-bend folding, including constant fault-parallel displacement, implying conservation of bed length, and hanging-wall uplift rates that are proportional to the sine of the fault dip. This provides a basis for precise determination of total fault slip since the formation of each terrace and combined with terrace dating gives long- term fault-slip rates for the Chelungpu thrust system. An estimation of the long term fault-slip rate of the Chelungpu thrust in the north Hsinshe terrace yields 15 mm/yr over the last 55 ka, which is similar to the combined shortening rate of 16 mm/y on the Chelungpu and Chushiang thrusts in the south estimated by Simoes et al. in 2006. Evan the coseismic displacements of 3 to 9m in the Chi-Chi earthquake are approximately fault-parallel but have additional transient components that are averaged out over the timescale of terrace deformation, which represents 10-100 large earthquakes. In contrast, terrace deformation in the hanging wall of the Changhua thrust ramp shows progressive limb rotation, as predicted from its shear fault-bend folding geometry, which combined with terrace dating allows an estimation of the long term fault-slip rate of 21 mm/yr over the last 31 ka. A combined shortening rate of 37 mm/yr is obtained for this part of the western Taiwan thrust belt, which is about 45 percent of the total plate-tectonic shortening rate across Taiwan. The Changhua shear fault-bend fold ramp is in the early stages of its development with only 1.7km total displacement whereas the Chelungpu classical fault-bend folding ramp in the same stratigraphy has nearly an order of magnitude more displacement (~14 km). We suggest that shear fault-bend folding may be favored mechanically at low displacement, whereas classical fault-bend folding would be favored at large displacement.

Determination of tectonic shortening rates from progressively deformed flights of terraces above the Chelungpu and Changhua thrust ramps, Taiwan

NASA Astrophysics Data System (ADS)

Yue, L.; Suppe, J.

2004-12-01

The Chelungpu and Changhua thrust ramps in central Taiwan show contrasting hanging-wall structural geometries that suggest different kinematics, even though they involve the same stratigraphic section and basal detachment. The Chelungpu thrust shows a classic fault-bend folding geometry, which predicts folding solely by kink-band migration, whereas the hanging wall of the Changhua thrust demonstrates the characteristic geometry of a shear fault-bend folding, which predicts a progressive limb rotation with minor kink-band migration. We test the kinematic predictions of classic and shear fault-bend folding theories by analyzing deformed flights of terraces and coseismic displacements in the Mw=7.6 Chi-Chi earthquake. The Chelungpu terraces shows differences in uplift magnitudes across active axial surfaces that closely approximate the assumptions of classical fault-bend folding, including constant fault-parallel displacement, implying conservation of bed length, and hanging-wall uplift rates that are proportional to the sine of the fault dip. This provides a basis for precise determination of total fault slip since the formation of each terrace and combined with terrace dating gives long- term fault-slip rates for the Chelungpu thrust system. An estimation of the long term fault-slip rate of the Chelungpu thrust in the north Hsinshe terrace yields 15 mm/yr over the last 55 ka, which is similar to the combined shortening rate of 16 mm/y on the Chelungpu and Chushiang thrusts in the south estimated by Simoes et al. in 2006. Evan the coseismic displacements of 3 to 9m in the Chi-Chi earthquake are approximately fault-parallel but have additional transient components that are averaged out over the timescale of terrace deformation, which represents 10-100 large earthquakes. In contrast, terrace deformation in the hanging wall of the Changhua thrust ramp shows progressive limb rotation, as predicted from its shear fault-bend folding geometry, which combined with terrace dating allows an estimation of the long term fault-slip rate of 21 mm/yr over the last 31 ka. A combined shortening rate of 37 mm/yr is obtained for this part of the western Taiwan thrust belt, which is about 45 percent of the total plate-tectonic shortening rate across Taiwan. The Changhua shear fault-bend fold ramp is in the early stages of its development with only 1.7km total displacement whereas the Chelungpu classical fault-bend folding ramp in the same stratigraphy has nearly an order of magnitude more displacement (~14 km). We suggest that shear fault-bend folding may be favored mechanically at low displacement, whereas classical fault-bend folding would be favored at large displacement.

Dopant Distribution in Atomic Layer Deposited ZnO:Al Films Visualized by Transmission Electron Microscopy and Atom Probe Tomography.

PubMed

Wu, Yizhi; Giddings, A Devin; Verheijen, Marcel A; Macco, Bart; Prosa, Ty J; Larson, David J; Roozeboom, Fred; Kessels, Wilhelmus M M

2018-02-27

The maximum conductivity achievable in Al-doped ZnO thin films prepared by atomic layer deposition (ALD) is limited by the low doping efficiency of Al. To better understand the limiting factors for the doping efficiency, the three-dimensional distribution of Al atoms in the ZnO host material matrix has been examined on the atomic scale using a combination of high-resolution transmission electron microscopy (TEM) and atom probe tomography (APT). Although the Al distribution in ZnO films prepared by so-called "ALD supercycles" is often presented as atomically flat δ-doped layers, in reality a broadening of the Al-dopant layers is observed with a full-width-half-maximum of ∼2 nm. In addition, an enrichment of the Al at grain boundaries is observed. The low doping efficiency for local Al densities > ∼1 nm -3 can be ascribed to the Al solubility limit in ZnO and to the suppression of the ionization of Al dopants from adjacent Al donors.

Dopant Distribution in Atomic Layer Deposited ZnO:Al Films Visualized by Transmission Electron Microscopy and Atom Probe Tomography

PubMed Central

2018-01-01

The maximum conductivity achievable in Al-doped ZnO thin films prepared by atomic layer deposition (ALD) is limited by the low doping efficiency of Al. To better understand the limiting factors for the doping efficiency, the three-dimensional distribution of Al atoms in the ZnO host material matrix has been examined on the atomic scale using a combination of high-resolution transmission electron microscopy (TEM) and atom probe tomography (APT). Although the Al distribution in ZnO films prepared by so-called “ALD supercycles” is often presented as atomically flat δ-doped layers, in reality a broadening of the Al-dopant layers is observed with a full-width–half-maximum of ∼2 nm. In addition, an enrichment of the Al at grain boundaries is observed. The low doping efficiency for local Al densities > ∼1 nm–3 can be ascribed to the Al solubility limit in ZnO and to the suppression of the ionization of Al dopants from adjacent Al donors. PMID:29515290

Water supply for the Nuclear Rocket Development Station at the U.S. Atomic Energy Commission's Nevada Test Site

USGS Publications Warehouse

Young, Richard Arden

1972-01-01

The Nuclear Rocket Development Station, in Jackass Flats, occupies about 123 square miles in the southwestern part of the U.S. Atomic Energy Commission's Nevada Test Site. Jackass Flats, an intermontane valley bordered by highlands on all sides except for a drainage outlet in the southwestern corner, has an average annual rainfall of 4 inches. Jackass Flats is underlain by alluvium, colluvium, and volcanic rocks of Cenozoic age and, at greater depth, by sedimentary rocks of Paleozoic age. The alluvium and the colluvium lie above the saturated zone throughout nearly all of Jackass Flats. The Paleozoic sedimentary rocks contain limestone and dolomite units that are excellent water producers elsewhere ; however, these units are too deep in Jackass Flats to be economic sources of water. The only important water-producing unit known in the vicinity of the Nuclear Rocket Development Station is a welded-tuff aquifer, the Topopah Spring Member of the Paintbrush Tuff, which receives no significant recharge. This member contains about 500 feet of highly fractured rock underlying an area 11 miles long and 3 miles wide in western Jackass Flats. Permeability of the aquifer is derived mostly from joints and fractures; however, some permeability may be derived from gas bubbles in the upper part of the unit. Transmissivity, obtained from pumping tests, ranges from 68,000 to 488,000 gallons per day per foot. Volume of the saturated part of the aquifer is about 3.5 cubic miles, and the average specific yield probably ranges from 1 to 5 percent. The volume of ground water in storage is probably within the range of 37-187 billion gallons. This large amount of water should be sufficient to supply the needs of the Nuclear Rocket Development Station for many years. Water at the Nuclear Rocket Development Station is used for public supply, construction, test-cell coolant, exhaust cooling, and thermal shielding during nuclear reactor and engine testing, and washdown. Present (1967) average consumption of water is 520,000 gallons per day--all supplied by one well. This supply well and a standby well have a production capability of 1.6 million gallons per day--adequate for present needs. Water in the welded-tuff aquifer is of the sodium bicarbonate type. Dissolved-solids content of the water in Jackass Flats is in the general range 230 milligrams per liter in the western part to 890 milligrams per liter in the eastern part.

Monitoring tectonic uplift and paleoenvironmental reconstruction for marine terraces near Maǧaracik and Samandaǧ, Hatay Province, Turkey.

PubMed

Florentin, Jonathan A; Blackwell, Bonnie A B; Tüysüz, Okan; Tarı, Ufuk; Can Genç, Ş; İmren, Caner; Mo, Shirley; Huang, Yiwen E W; Blickstein, Joel I B; Skinner, Anne R; Kim, Maria

2014-06-01

Near Hatay, the Antakya-Samandağ-Cyprus Fault (ASCF), East Anatolian and Dead Sea Fault Zones, the large faults that form the edges of the African, Anatolian, Cyprus and Arabian Plates, all produce large earthquakes, which have decimated Hatay repeatedly. Near Samandağ, Hatay, differential vertical displacement on the ASCF has uplifted the southeastern side relative to northwestern side, producing large fault scarps that parallel the Asi (Orontes) River. Tectonic uplift coupled with Quaternary sealevel fluctuations has produced several stacked marine terraces stranded above current sealevel. This study dated 24 mollusc samples from 10 outcrops on six marine terraces near Samandağ electron spin resonance (ESR). Ages were calculated using time-averaged and volumetrically averaged external dose rates, modelled by assuming typical water depths for the individual species and sediment thicknesses estimated from geological criteria. Uplift rates were then calculated for each fault block. At all the Mağaracık terraces, the dates suggest that many shells were likely reworked. On the 30 m terrace at Mağaracık IV (UTM 766588-3999880), Lithophagus burrows with in situ shells cross the unconformity. One such shell dated to 62 ± 6 ka, setting the minimum possible age for the terrace. For all the Mağaracık terraces at ∼30 m above mean sealevel (amsl), the youngest ages for the reworked shells, which averaged 60 ± 3 ka for six separate analyses, sets the maximum possible age for this unit. Thus, the terrace must date to 60-62 ± 3 ka, at the MIS 3/4 boundary when temperatures and sealevels were fluctuating rapidly. Older units dating to MIS 7, 6, and 5 likely were being eroded to supply some fossils found in this terrace. At Mağaracık Dump (UTM 765391-4001048), ∼103 m amsl, Ostrea and other shells were found cemented in growth position to the limestone boulders outcropping there <2.0 m above a wave-eroded notch. If the oysters grew at the same time as the wave-cut notch and the related terrace, the date, 91 ± 13 ka, for the oysters, this fault block has been uplifted at 1.19 ± 0.15 m ky(-1), since MIS 5c. At Samandağ Kurt Stream at 38 m amsl, molluscs were deposited fine sandy gravel, which was likely formed in a large tidal channel. Four molluscs averaged 116 ± 5 ka. If these molluscs have not been reworked, this fault block has uplifted at 0.34 ± 0.05 m ky(-1) since the MIS 5d/5e boundary. The differences in these uplift rates suggests that at least one, and possibly two, hitherto undiscovered faults may separate the Mağaracık Dump site from the other Mağaracık sites and from the Samandağ Kurt Stream site. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Quantification of fluvial response to tectonic deformation in the Central Pontides, Turkey; inferences from OSL dating of fluvial terraces

NASA Astrophysics Data System (ADS)

McClain, Kevin; Yıldırım, Cengiz; Çiner, Attila; Akif Sarıkaya, M.; Şahin, Sefa; Özcan, Orkan; Güneç Kıyak, Nafiye; Öztürk, Tuǧba

2017-04-01

From Late Miocene to present, Anatolia's rapid counterclockwise movement, which increases in velocity towards the Hellenic Arc, has formed the North Anatolian Fault (NAF), a dextral transform fault along the Anatolia-Eurasia plate boundary and the northern margin of the Central Anatolian Plateau (CAP). A zone of transpression referred to as the Central Pontides exists between the broad restraining bend of the NAF and the Black Sea Basin, uplifting what is interpreted as a detached flower structure. Dating of Quaternary landforms in the eastern flank of the Central Pontides has helped to understand its recent deformation. However, in the western flank of the Central Pontides there is an absence of Quaternary studies, relatively quiet modern seismicity, and difficulties locating or observing fault scarps. This led us to use optically stimulated luminescence dating (OSL-dating) of fluvial terrace sediments and the study of geomorphic features to gain insight into the influence of climate and tectonics on landscape evolution of this area. In this area, the Filyos River crosses the Karabük Fault (reverse fault) and deeply incises a gorge through the Karabük Range before flowing towards the Black Sea. In the gorge an abundance of indicators of tectonic deformation were mapped, such as hanging valleys, wind gaps, bedrock gorges, landslides, steep V-shaped channels, tilted basins, as well as fluvial strath terraces. In particular, strath terraces of at least 8 levels within just 1.5 km of horizontal distance were examined. We used OSL-dating to estimate five deposition ages of fluvial strath terrace sediments, leading to an estimation of incision and uplift rates over time. Using three samples per terrace with strath elevations of 246 ± 0.2 m, 105.49 ± 0.2 m, 43.6 ± 0.2 m, 15.3 ± 0.2 m and 3.6 ± 0.2 m above the Filyos River, we determined corresponding ages of 841 ± 76 ka, 681 ± 49 ka, 386 ± 18 ka, 88 ± 5.1 ka and 50.9 ± 2.8 ka. Incision rates over time (oldest terrace to youngest) suggest uplift of 0.29 ± 0.03 mm/y, 0.16 ± 0.01 mm/y, 0.10 ± 0.01 mm/y, 0.17 ± 0.01 mm/y and 0.07 ± 0.004 mm/y. Collectively, our ages infer decelerating fluvial incision and rock uplift rates in the Karabük Range of the Central Pontides. The highest rate that belongs to oldest terrace level (841 ± 76 ka) also implies long-term mean uplift, which is well correlated with long term ( 350 ka) mean uplift rate obtained from fluvial terraces in the eastern flank of the (Gökırmak Basin) Central Pontides. These results indicate Quaternary activity of the Karabük Fault despite the fact that very low modern seismicity and partition of strain in the north of the North Anatolian Fault. Keywords: Tectonics, Geomorphology, Fluvial Terrace, OSL Dating, Central Pontides, North Anatolian Fault, Filyos River, Turkey, Central Anatolian Plateau

Terraces and contour farming

USDA-ARS?s Scientific Manuscript database

Terraces are earthen embankments constructed across the prevailing field land slope. They have been used in differing forms for thousands of years in an attempt to protect steep land slopes from runoff induced erosion. Contour farming, where tillage and planting create ridges and furrows at nearly...

77 FR 64816 - National Human Genome Research Institute; Notice of Meeting

Federal Register 2010, 2011, 2012, 2013, 2014

2012-10-23

... sign language interpretation or other reasonable accommodations, should notify the Contact Person... relevance. Place: National Human Genome Research Institute, 5635 Fishers Lane, Terrace Level Conference Room... Genome Research Institute, 5635 Fishers Lane, Terrace Level Conference Room, Rockville, MD 20892. Contact...

Complex carbonate and clastic stratigraphy of the inner shelf off west-central Florida

DOE Office of Scientific and Technical Information (OSTI.GOV)

Locker, S.D.; Doyle, L.J.; Hine, A.C.

1990-05-01

The near surface stratigraphy (< 30 m) of the inner shelf off the west coast of Florida was investigated using high-resolution seismic, side-scan sonar, and continuous underwater video camera coverage. The simultaneous operation of all three systems provided a unique opportunity to calibrate acoustic data with actual video images of the sea floor in a geologically complex area characterized by limestone dissolution structures, hard-bottom exposures, and overlain by a limited supply of terrigenous clastics. Three principle bottom types, grass, sand, and hard-bottom mapped using video and side-scan sonographs, show a correlation with two subsurface stratigraphic zones. The nearshore subsurface zonemore » extending to 6-7 m water depth is characterized by flat or rolling strata and sinkholes that increase in size (200-1,200 m in diameter) and become more numerous further offshore. This zone is truncated by a major erosional unconformity overlain by a thin (<3 m) sequence of Holocene sediment, which together form a terrace upon which the Anclote Key barrier island formed. The offshore subsurface zone (7-11 m water depth) exhibits irregular and discontinuous high-amplitude flat or inclined reflections and few sinkholes. Offshore, extensive hard-bottom exposures are common with discontinuous sediment that occur as lenses or sand waves. The complex stratigraphy of the west Florida shelf includes outcropping Neogene limestones that have undergone dissolution during sea level lowstands. Carbonates and clastics dispersed during multiple sea level changes overlie the Neogene limestones. Dissolution styles and erosional unconformities produced bedrock topography and now control modern geological and biological processes.« less

Latest Pleistocene to Holocene Thrusting Recorded by a Flight of Strath Terraces in the Eastern Qilian Shan, NE Tibetan Plateau

NASA Astrophysics Data System (ADS)

Xiong, Jianguo; Li, Youli; Zhong, Yuezhi; Lu, Honghua; Lei, Jinghao; Xin, Weilin; Wang, Libo; Hu, Xiu; Zhang, Peizhen

2017-12-01

At the eastern Qilian Shan mountain front in the NE Tibetan Plateau, the Minle-Damaying Fault (MDF), the southernmost fault of the North Frontal Thrust (NFT) system, has previously been proposed as an inactive structure during the Holocene. Here we present a detailed record of six strath terraces of the Xie River that document the history of active deformation of the MDF. One optically stimulated luminescence dating sample constrains abandonment of the highest terrace T6 at 12.7 ± 1.4 ka. The formation ages of the lower terraces (T4-T1) are dated by AMS 14C dating. The cumulative vertical offsets of the MDF recorded by these terraces are determined as 12.2 ± 0.4 m (T6), 8.0 ± 0.4 m (T5), 6.4 ± 0.4 m (T4), 4.6 ± 0.1 m (T3), and 3.2 ± 0.2 m (T1c) by an unmanned aerial vehicle system, respectively. A long-term vertical slip rate of the MDF of 0.9 ± 0.2 mm/yr is then estimated from the above data of terrace age and vertical offset by a linear regression. Assuming that the fault dip of 35 ± 5° measured at the surface is representative for the depth-averaged fault dip, horizontal shortening rates of 0.83-1.91 mm/yr are inferred for the MDF. Our new data show that the proximal fault (the MDF) of the NFT system at the eastern Qilian Shan mountain front has remained active when the deformation propagated basinward, a different scenario from that observed at both the western and central Qilian Shan mountain front.

Subsidence and volcanism of the Haleakala Ridge, Hawaii

USGS Publications Warehouse

Moore, J.G.; Clague, D.A.; Ludwig, K. R.; Mark, R.K.

1990-01-01

Side-looking sonar (GLORIA) mapping has revealed a series of four arcuate bands of high sonic backscatter on the crest of the Haleakala Ridge, a major rift-zone ridge extending 135 km east of the island of Maui. Dredge recovery indicates that the shallowest of these bands is a drowned coral reef, and the deeper bands are also inferred to be coral reefs. The reefs occur above a prominent submarine bench 1500-2500 m deep on the ridge (H-terrace) that marks the shoreline at the end of vigorous shield building of Haleakala volcano when lava flows ceased crossing and reworking the shoreline. Since their growth these reefs have subsided as much as 2200 m and have tilted systematically about 20 m/km southward as a result of post-reef volcanic loading on the island of Hawaii, whose center of mass is about directly south of the Haleakala Ridge. The 234U/238U age of the dredged coral is 750 ?? 13 ka, in reasonable agreement with an age of 850 ka for the underlying H terrace previously estimated from its relationship to other dated reefs to the southwest. Basalt glass fragments dredged from the Haleakala Ridge below the H terrace are tholeiitic and contain high sulfur indicative of eruption in water deeper than 200 m. Basalt glass fragments associated with the reefs above the H terrace are dominantly tholeiitic and contain intermediate sulfur contents, indicative of subaqueous eruption in shallow, near-shore conditions. One alkalic glass fragment was recovered above the H terrace. These relations indicate that the morphologic end of shield building as recorded by construction of the H terrace was not accompanyed by a change from tholeiitic to alkalic basalt; instead tholeiite eruptions continued for some time before the erupted lava became alkalic. ?? 1990.

Tectonic Reversal of the New Hebrides Forearc Recorded by Fossil Coral Terraces on Araki, Solomon Islands

NASA Astrophysics Data System (ADS)

Gallup, C. D.; Taylor, F. W.; Edwards, R. L.

2016-12-01

Araki is a small island in the New Hebrides forearc that exhibits a series of coral terraces. High precision 230Th ages of the corals and their elevations reveal a complicated tectonic history. Prior to the collision of the Bouganville Guyot on the subducting Australian plate with the forearc, the forearc was subsiding (Taylor et al., 2005). The highest elevation terrace on Araki has both last interglacial age (128 ka) corals and corals that grew between 103 and 107 ka present, when sea level was certainly lower than during the last interglacial period. However, the last interglacial corals occur in a cliff somewhat below the summit of Araki. We suggest this juxtaposition was produced by subsidence of the island during and after the last interglacial corals, potentially through the deposition of the 103 and 107 ka corals. At some point before or after their deposition, the island started to uplift, producing a series of terraces. Many of the corals on the lower terraces were deposited during periods of low sea level, between 33 and 62 ka. The lowest terrace is composed of Holocene corals. The mean uplift rate of Araki produced by using published sea level records for the corals deposited between 33 and 62 ka is approximately 2.4 mm/y. The uplift rate calculated based on the Holocene corals is much faster at approximately 4.7 mm/yr. A similar pattern of subsidence, to uplift, to faster uplift is found on Espiritu Santo and Malekula, encompassing 250 km of the forearc. The fossil corals thus record the changing tectonic conditions on the forearc associated with the subduction of the Bougainville Guyot. F.W. Taylor et al. (2005) TECTONICS, VOL. 24, TC6005, doi:10.1029/2004TC001650.

Pacing the post-Last Glacial Maximum demise of the Animas Valley glacier and the San Juan Mountain ice cap, Colorado

NASA Astrophysics Data System (ADS)

Guido, Zackry S.; Ward, Dylan J.; Anderson, Robert S.

2007-08-01

During the Last Glacial Maximum (LGM), a 5000 km2 ice cap covered the San Juan Mountains of southwest Colorado. The largest valley glacier draining this ice cap occupied the Animas Valley and flowed 91 km to the south. To characterize the post-LGM demise of the Animas Valley glacier, we employ cosmogenic 10Be to date the LGM terrace outside the terminal moraines and a suite of seven glacially polished bedrock samples. The 10Be depth profile within the terrace sediments suggests abandonment at 19.4 ± 1.5 ka. As deglaciation began, the ponding of Glacial Lake Durango behind the terminal moraines shut off fluvial sediment supply and caused terrace abandonment. The age of the terrace therefore records the initiation of LGM retreat. Negligible 10Be inheritance in the terrace profile suggests that glacial erosion of the bedrock valley floor from which sediments were derived erased all cosmogenic inventory. Glacial polish exposure ages monotonically decrease up-valley from 17.1 to 12.3 ka, with the single exception of a sample collected from a quartzite rib, yielding an average retreat rate of 15.4 m/yr. This trend and the lack of inherited cosmogenic nuclides in the terrace sediments imply that polish ages accurately record the glacial retreat history. Retreat of the Animas lobe began at a time of regional drying recorded in sediments and shoreline elevations of large lakes. Deglaciation lasted for ˜7.2 k.y., and was complete by 12.3 ± 1.0 ka. The retreat history followed the pattern of increasing insolation and was perhaps fastest during a time of regional drying.

Digital data sets that describe aquifer characteristics of the alluvial and terrace deposits along the Cimarron River from Freedom to Guthrie in northwestern Oklahoma

USGS Publications Warehouse

Adams, G.P.; Runkle, Donna; Rea, Alan; Cederstrand, J.R.

1997-01-01

ARC/INFO export and nonproprietary format files This diskette contains digitized aquifer boundaries, maps of hydraulic conductivity, recharge, and ground-water level elevation contours for the alluvial and terrace deposits along the Cimarron River from Freedom to Guthrie in northwestern Oklahoma. Ground water in 1,305 square miles of Quaternary-age alluvial and terrace deposits along the the Cimarron River from Freedom to Guthrie is an important source of water for irrigation, industrial, municipal, stock, and domestic supplies. Alluvial and terrace deposits are composed of interfingering lenses of clay, sandy clay, and cross-bedded poorly sorted sand and gravel. The aquifer is composed of hydraulically connected alluvial and terrace deposits that unconformably overlie the Permian-age Formations. The aquifer boundaries are from a ground-water modeling report on the alluvial and terrace aquifer along the Cimarron River from Freedom to Guthrie in northwestern Oklahoma and published digital surficial geology data sets. The aquifer boundary data set was created from digital geologic data sets from maps published at a scale of 1:250,000. The hydraulic conductivity values, recharge rates, and ground-water level elevation contours are from the ground-water modeling report. Water-level elevation contours were digitized from a map at a scale of 1:250,000. The maps were published at a scale of 1:900,000. Ground-water flow models are numerical representations that simplify and aggregate natural systems. Models are not unique; different combinations of aquifer characteristics may produce similar results. Therefore, values of hydraulic conductivity and recharge used in the model and presented in this data set are not precise, but are within a reasonable range when compared to independently collected data.

Socioeconomic Dimensions of Changes in the Agricultural Landscape of the Mediterranean Basin: A Case Study of the Abandonment of Cultivation Terraces on Nisyros Island, Greece

NASA Astrophysics Data System (ADS)

Petanidou, Theodora; Kizos, Thanasis; Soulakellis, Nikolaos

2008-02-01

Agricultural landscapes illustrate the impact of human actions on physical settings, and differential human pressures cause these landscapes to change with time. Our study explored changes in the terraced landscapes of Nisyros Island, Greece, focusing on the socioeconomic aspects during two time periods using field data, cadastral research, local documents, and published literature, as well as surveys of the islanders. Population increases during the late 19th to early 20th centuries marked a significant escalation of terrace and dry stone wall construction, which facilitated cultivation on 58.4% of the island. By the mid-20th century, the economic collapse of agricultural activities and consequent emigration caused the abandonment of cultivated land and traditional management practices, dramatically reducing farm and field numbers. Terrace abandonment continued in recent decades, with increased livestock grazing becoming the main land management tool; as a result, both farm and pasture sizes increased. Neglect and changing land use has led to deterioration and destruction of many terraces on the island. We discuss the socioeconomic and political backgrounds responsible for the land-use change before World War II (annexation of Nisyros Island by the Ottoman Empire, Italy, and Greece; overseas migration opportunities; and world transportation changes) and after the war (social changes in peasant societies; worldwide changes in agricultural production practices). The adverse landscape changes documented for Nisyros Island appear to be inevitable for modern Mediterranean rural societies, including those on other islands in this region. The island’s unique terraced landscapes may qualify Nisyros to become an archive or repository of old agricultural management techniques to be used by future generations and a living resource for sustainable management.

Socioeconomic dimensions of changes in the agricultural landscape of the Mediterranean basin: a case study of the abandonment of cultivation terraces on Nisyros Island, Greece.

PubMed

Petanidou, Theodora; Kizos, Thanasis; Soulakellis, Nikolaos

2008-02-01

Agricultural landscapes illustrate the impact of human actions on physical settings, and differential human pressures cause these landscapes to change with time. Our study explored changes in the terraced landscapes of Nisyros Island, Greece, focusing on the socioeconomic aspects during two time periods using field data, cadastral research, local documents, and published literature, as well as surveys of the islanders. Population increases during the late 19th to early 20th centuries marked a significant escalation of terrace and dry stone wall construction, which facilitated cultivation on 58.4% of the island. By the mid-20th century, the economic collapse of agricultural activities and consequent emigration caused the abandonment of cultivated land and traditional management practices, dramatically reducing farm and field numbers. Terrace abandonment continued in recent decades, with increased livestock grazing becoming the main land management tool; as a result, both farm and pasture sizes increased. Neglect and changing land use has led to deterioration and destruction of many terraces on the island. We discuss the socioeconomic and political backgrounds responsible for the land-use change before World War II (annexation of Nisyros Island by the Ottoman Empire, Italy, and Greece; overseas migration opportunities; and world transportation changes) and after the war (social changes in peasant societies; worldwide changes in agricultural production practices). The adverse landscape changes documented for Nisyros Island appear to be inevitable for modern Mediterranean rural societies, including those on other islands in this region. The island's unique terraced landscapes may qualify Nisyros to become an archive or repository of old agricultural management techniques to be used by future generations and a living resource for sustainable management.

Sea-level history and tectonic uplift during the last-interglacial period (LIG): Inferred from the Bab al-Mandab coral reef terraces, southern Red Sea

NASA Astrophysics Data System (ADS)

Al-Mikhlafi, Ahmed Saif; Edwards, Lawrence R.; Cheng, Hai

2018-02-01

Results of U-series dating of late Pleistocene raised coral reef terraces from the Bab al-Mandab area, define two distinct groups: (1) well-preserved aragonitic fossil corals recorded from the Al-Hajaja terrace (Tr3) yield ages for last-interglacial period (LIG); and (2) calcitic fossil corals recovered from Perim Island terrace (Tr1) show varying degrees of U-series open system behavior and yield coral assemblage ages of LIG and older ages. Fossil corals from Tr1 are recrystallized corals, have anomalously high initial δ234U ranged from (152 ± 2‰ to 287 ± 7‰), corresponding to ages of ∼120 ka and ∼406 ka, respectively. Applying age reliability criteria on the current data suggest majority of the ages cannot be considered reliable and all are suspected for open system behavior associated with U loss/addition that significantly affects the 230Th/U ages. The diagenesis shown by these corals occurred probably due to extensive interaction of fossil corals with freshwater during the wet periods prevailed in southern Arabia coeval with the African monsoon, which led to U loss. Post-depositional U loss suggest (230Th/238U) increase, which shift the U-Th ages to unexpectedly higher levels as it is shown here. Measured elevation at the Al-Hajaja terrace (Tr3) is ∼4 ± 2 m above present sea level (apsl) consistent with eustatic sea level changes and indicates that the Bab al-Mandab area is stable at least since the LIG period. The Perim Island terrace (Tr1) is at elevation of 7 ± 2 m apsl; its reef yields diageneticaly-altered corals of multiple ages and cannot be used for sea level reconstructions.

A convenient method for large-scale STM mapping of freestanding atomically thin conductive membranes

NASA Astrophysics Data System (ADS)

Uder, B.; Hartmann, U.

2017-06-01

Two-dimensional atomically flat sheets with a high flexibility are very attractive as ultrathin membranes but are also inherently challenging for microscopic investigations. We report on a method using Scanning Tunneling Microscopy (STM) under ultra-high vacuum conditions for large-scale mapping of several-micrometer-sized freestanding single and multilayer graphene membranes. This is achieved by operating the STM at unusual parameters. We found that large-scale scanning on atomically thin membranes delivers valuable results using very high tip-scan speeds combined with high feedback-loop gain and low tunneling currents. The method ultimately relies on the particular behavior of the freestanding membrane in the STM which is much different from that of a solid substrate.

75 FR 16162 - Notice of Intent To Prepare an Environmental Impact Statement for the Yesler Terrace...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-03-31

... the Land Use Code to allow a new zone for Yesler Terrace, street vacation, preliminary and final plat... project that shifts environmental review from the time a permit application is made to an earlier phase in...

Erosion and runoff evaluation using the SWAT-T model

USDA-ARS?s Scientific Manuscript database

Agricultural terraces are an effective conservation practice to reduce concentrated flow erosion. Researchers have simulated terrace effects using the Soil and Water Assessment Tool (SWAT) by adjusting the slope length and the USLE Practice P-factor. An algorithm was incorporated into SWAT (SWAT-Ter...

75 FR 51828 - National Human Genome Research Institute; Notice of Meetings

Federal Register 2010, 2011, 2012, 2013, 2014

2010-08-23

... space available. Individuals who plan to attend and need special assistance, such as sign language.... Place: National Institutes of Health, 5635 Fishers Lane, Terrace Level Conference Center, Bethesda, MD.../or proposals. Place: National Institutes of Health, 5635 Fishers Lane, Terrace Level Conference...

78 FR 20932 - National Institute on Alcohol Abuse and Alcoholism; Notice of Meeting

Federal Register 2010, 2011, 2012, 2013, 2014

2013-04-08

... sign language interpretation or other reasonable accommodations, should notify the Contact Person... applications. Place: National Institutes of Health, 5635 Fishers Lane, Terrace Level Conference Rooms, Bethesda... council. Place: National Institutes of Health, 5635 Fishers Lane, Terrace Level Conference Rooms...

A terracing operator for physical property mapping with potential field data

USGS Publications Warehouse

Cordell, L.; McCafferty, A.E.

1989-01-01

The terracing operator works iteratively on gravity or magnetic data, using the sense of the measured field's local curvature, to produce a field comprised of uniform domains separated by abrupt domain boundaries. The result is crudely proportional to a physical-property function defined in one (profile case) or two (map case) horizontal dimensions. This result can be extended to a physical-property model if its behavior in the third (vertical) dimension is defined, either arbitrarily or on the basis of the local geologic situation. The terracing algorithm is computationally fast and appropriate to use with very large digital data sets. The terracing operator was applied separately to aeromagnetic and gravity data from a 136km x 123km area in eastern Kansas. Results provide a reasonable good physical representation of both the gravity and the aeromagnetic data. Superposition of the results from the two data sets shows many areas of agreement that can be referenced to geologic features within the buried Precambrian crystalline basement. -from Authors

Molecular insight into the nanoconfined calcite–solution interface

PubMed Central

Diao, Yijue; Espinosa-Marzal, Rosa M.

2016-01-01

Little is known about the influence of nanoconfinement on calcium carbonate mineralization. Here, colloidal probe atomic force microscopy is used to confine the calcite–solution interface with a silica microsphere and to measure Derjaguin–Landau–Verwey–Overbeek (DLVO) and non-DLVO forces as a function of the calcium concentration, also after charge reversal of both surfaces occurs. Through the statistical analysis of the oscillatory component of a strong hydration force, the subnanometer interfacial structure of the confined atomically flat calcite is resolved in aqueous solution. By applying a mechanical work, both water and hydrated counterions are squeezed out from the nanoconfined solution, leaving the calcite surface more negatively charged than the analogous unconfined surfaces. Layer size and applied work allow a distinction between the hydration states of the counterions in the Stern layer; we propose counterions to be inner- and outer-sphere calcium ions, with a population of inner-sphere calcium ions larger than on unconfined calcite surfaces. It is also shown that the composition of the nanoconfined solution can be tuned by varying calcium concentration. This is a fundamental study of DLVO and hydration forces, and of their connection, on atomically flat calcite. More broadly, our work scrutinizes the greatly unexplored relation between surface science and confined mineralization, with implications for diverse areas of inquiry, such as nanoconfined biomineralization, CO2 sequestration in porous aquifers, and pressure solution and crystallization in confined hydrosystems. PMID:27790988

U-Th dating of calcite corals from the Gulf of Aqaba

NASA Astrophysics Data System (ADS)

Yehudai, Maayan; Lazar, Boaz; Bar, Neta; Kiro, Yael; Agnon, Amotz; Shaked, Yonathan; Stein, Mordechai

2017-02-01

Most of the fossil corals in the elevated reef terraces along the Gulf of Aqaba (GOA) were extensively altered to calcite. This observation indicates extensive interaction with freshwater, possibly when the terraces passed through a coastal aquifer that existed along the shores of the GOA, implying a wetter climate during the time of recrystallization from aragonite to calcite. Thus, dating of the recrystallization events should yield the timing of past wetter conditions in the current hyper-arid area of the GOA. In the present study, 18 aragonite and calcite corals were collected from several elevated coral reef terraces off the coast, south of the city of Aqaba. While aragonite corals were dated with the conventional closed system age equation (assuming zero initial Th), the dating of the calcite corals required the development of adequate equations to allow the calculation of both the initial formation age of the aragonite corals and the time of recrystallization to calcite. The two age calculations were based on the assumptions that each reef terrace went through a single and rapid recrystallization event and that the pristine aragonite corals were characterized by a rather uniform initial U concentration, typical for pristine modern corals. Two recrystallization events were identified at 104 ± 6 ka and 124 ± 8 ka. The ages coincide with the timing of sapropel events S4 and S5, respectively, when the African monsoon induced enhanced wetness in the desert area. Considering the age uncertainties, the times of formation of the two major reef terraces are estimated to be ∼124 ka (reef terrace R2) and ∼130 ka (reef terrace R3), matching the peaks in the global sea level during the last interglacial MIS 5e stage. Apparently, sea level of the GOA did not fluctuate a lot during the period between ∼130 ka and ∼104 ka and remained close to the Marine Isotopic stage (MIS) 5e highstand. The availability of freshwater (during the sapropel periods) and limited sea level fluctuations facilitated the recrystallization of the GOA reef corals to calcite.

HAADF-STEM atom counting in atom probe tomography specimens: Towards quantitative correlative microscopy.

PubMed

Lefebvre, W; Hernandez-Maldonado, D; Moyon, F; Cuvilly, F; Vaudolon, C; Shinde, D; Vurpillot, F

2015-12-01

The geometry of atom probe tomography tips strongly differs from standard scanning transmission electron microscopy foils. Whereas the later are rather flat and thin (<20 nm), tips display a curved surface and a significantly larger thickness. As far as a correlative approach aims at analysing the same specimen by both techniques, it is mandatory to explore the limits and advantages imposed by the particular geometry of atom probe tomography specimens. Based on simulations (electron probe propagation and image simulations), the possibility to apply quantitative high angle annular dark field scanning transmission electron microscopy to of atom probe tomography specimens has been tested. The influence of electron probe convergence and the benefice of deconvolution of electron probe point spread function electron have been established. Atom counting in atom probe tomography specimens is for the first time reported in this present work. It is demonstrated that, based on single projections of high angle annular dark field imaging, significant quantitative information can be used as additional input for refining the data obtained by correlative analysis of the specimen in APT, therefore opening new perspectives in the field of atomic scale tomography. Copyright © 2015 Elsevier B.V. All rights reserved.

Interfacial preparation and optical transmission surface plasmon resonance of Janus metamaterials membrane

NASA Astrophysics Data System (ADS)

Du, Yixuan; Zhang, Xiaowei; Li, Yunbo

2018-01-01

Janus metamaterials membrane had been fabricated using self-assembly strategy at the oil/water interface with thiol-terminated polymers. Janus metamaterials membrane exhibits a characteristic surface plasmon absorption band, in which the peak position is sensitive to the addition of polymer. The optical transmission surface plasmon resonance (T-SPR) peak has a blue shift at the visible region with addition of thiol-terminated polystyrene (PS-SH). With thiol-terminated poly (ethylene glycol) (PEG-SH) attachment onto the surface side of gold nanoparticles (AuNPs), the T-SPR band has a successive blue shift. One surprising thing is that it has a flat terrace on T-SPR band from 580 to 740 nm. In addition, The T-SPR of Janus metamaterials membrane dramatically changed with the addition PS-SH when the PEG-SH was capped on the opposite side. The morphologies of AuNPs membrane and Janus metamaterials membrane support the above mentioned result of SPR. In virtue of tunable SPR band, the Janus metamaterials membrane has great potential application in science-based design of optical sensing sensors and surface-enhanced optic sensitive detection.

Resonance interatomic energy in a Schwarzschild spacetime

NASA Astrophysics Data System (ADS)

Zhou, Wenting; Yu, Hongwei

2017-08-01

We study, in the Schwarzschild spacetime, the resonance interatomic energy (RIE) of two static identical atoms with an interatomic separation L along the radial direction and correlated by a symmetric/antisymmetric entangled state. The atoms are assumed to be coupled to massless scalar fields in the Boulware, Unruh, and Hartle-Hawking vacua, and approximate analytical results are obtained both at infinity and near the horizon. Our results show that at infinity, the RIE approaches that in a flat spacetime, while, near the horizon, they can deviate dramatically from each other. Besides, different from other atomic radiative properties such as the Lamb shift of a single atom or the interatomic energy between two uncorrelated atoms, which can be obviously affected by the thermal character of quantum fields, the RIE of two atoms in a symmetric/antisymmetric entangled state in the Boulware, Unruh, and Hartle-Hawking vacua are exactly the same as a result of the fact that the RIE of two such atoms depends only on the atomic self-reaction, i.e., it does not feel the vacuum fluctuations. This suggests that the RIE of two static atoms in a symmetric/antisymmetric entangled state outside a black hole is oblivious to the Hawking radiation, in contrast to those uncorrelated atoms.

Listings of model values for the simulation of ground-water flow in the Cimarron River alluvium and terrace deposits from Freedom to Guthrie, Oklahoma

USGS Publications Warehouse

Adams, G.P.

1995-01-01

This report contains MODFLOW input and output listings for the simulation of ground-water flow in alluvium and terrace deposits associated with the Cimarron River from Freedom to Guthrie, Oklahoma. These values are to be used in conjuction with the report, 'Geohydrology of alluvium and terrace deposits of the Cimarron River from Freedom to Guthrie, Oklahoma,' by G.P. Adams and D.L. Bergman, published as U.S. Geological Survey Water-Resources Investigatons Report 95-4066. The simulation used a digital ground-water flow model and was evaluated by a management and statistical program.

Structural interpretation and physical property estimates based on COAST 2012 seismic reflection profiles offshore central Washington, Cascadia subduction zone

NASA Astrophysics Data System (ADS)

Webb, S. I.; Tobin, H. J.; Everson, E. D.; Fortin, W.; Holbrook, W. S.; Kent, G.; Keranen, K. M.

2014-12-01

The Cascadia subduction zone has a history of large magnitude earthquakes, but a near-total lack of plate interface seismicity, making the updip limit of the seismogenic zone difficult to locate. In addition, the central Cascadia accretionary prism is characterized by an extremely low wedge taper angle, landward vergent initial thrusting, and a flat midslope terrace between the inner and outer wedges, unlike most other accretionary prisms (e.g. the Nankai Trough, Japan). The Cascadia Open Access Seismic Transect (COAST) lines were shot by R/V Marcus Langseth in July of 2012 off central Washington to image this subduction zone. Two trench-parallel and nine trench-perpendicular lines were collected. In this study, we present detailed seismic interpretation of both time- and depth-migrated stacked profiles, focused on elucidating the deposition and deformation of both pre- and syn-tectonic sediment in the trench and slope. Distribution and timing of sediments and their deformation is used to unravel the evolution of the wedge through time. Initially, interpretation of the time-sections is carried out to support the building of tomographic velocity models to aid in the pre-stack depth migration (PSDM) of selected lines. In turn, we use PSDM velocity models to estimate porosity and pore pressure conditions at the base of the wedge and across the basal plate interface décollement where possible, using established velocity-porosity transforms. Interpretation in this way incorporates both accurate structural relationships and robust porosity models to document wedge development and present-day stress state, in particular regions of potential overpressure. Results shed light on the origin and evolution of the mid-slope terrace and the low taper angle for the forearc wedge. This work may shed light ultimately on the position of the potential updip limit of the seismogenic zone beneath the wedge.

Relationships between molecular structure and kinetic and thermodynamic controls in lipid systems. Part II: Phase behavior and transformation paths of SSS, PSS and PPS saturated triacylglycerols--effect of chain length mismatch.

PubMed

Bouzidi, Laziz; Narine, Suresh S

2012-01-01

The kinetic phase behavior and phase transformation paths of purified tristearoylglycerol (SSS), 3-palmitoyl-1,2-distearoyl-sn-glycerol (PSS) and 1,2-dipalmitoyl-3-stearoyl-sn-glycerol (PPS) were investigated in terms of polymorphism, crystallization and melting. The details of the phase transformation paths were obtained using the heating cycles of two sets of experiments: (a) cooling rate was varied and heating rate fixed and (b) cooling rate was fixed and heating rate varied. Kinetic effects were manifest in all measured properties, underscoring the complexity of the phase transformation paths for each TAG, and the intricate thermodynamics-molecular relationships. For the first time, XRD data obtained for SSS, PSS and PPS TAGs, cooled at rates higher than 0.5°C/min, suggested the formation of a transient structure similar to the so-called α(2)-phase which has been observed in mixed saturated-unsaturated TAGs quenched from the melt. The more stable phases (β' in PSS and PPS, and β in SSS) were only observed for cooling rates lower than 1.0°C/min. The kinetic and thermodynamic differences observed in the crystallization, structure and melting of SSS, PSS and PPS are proposed to be mainly due to the disturbances introduced at the "terrace" level via methyl-end group interactions, i.e., the missing of two or four CH(2) groups compared to SSS. The symmetrical SSS with a relatively flat "terrace" crystallizes preferably in the most stable β-form. Two missing CH(2) groups at the sn-1 position (PSS) introduces enough structural disturbances to promote the relative prevalence and persistence of the β'-phase, and four missing CH(2) groups at the sn-1 and sn-2 positions (PPS) is relatively too large of a disturbance and therefore favors the α-form. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

Zimbabwe Culture before Mapungubwe: New Evidence from Mapela Hill, South-Western Zimbabwe

PubMed Central

Chirikure, Shadreck; Manyanga, Munyaradzi; Pollard, A. Mark; Bandama, Foreman; Mahachi, Godfrey; Pikirayi, Innocent

2014-01-01

Across the globe, the emergence of complex societies excites intense academic debate in archaeology and allied disciplines. Not surprisingly, in southern Africa the traditional assumption that the evolution of socio-political complexity began with ideological transformations from K2 to Mapungubwe between CE1200 and 1220 is clouded in controversy. It is believed that the K2−Mapungubwe transitions crystallised class distinction and sacred leadership, thought to be the key elements of the Zimbabwe culture on Mapungubwe Hill long before they emerged anywhere else. From Mapungubwe (CE1220–1290), the Zimbabwe culture was expressed at Great Zimbabwe (CE1300–1450) and eventually Khami (CE1450–1820). However, new fieldwork at Mapela Hill, when coupled with a Bayesian chronology, offers tremendous fresh insights which refute this orthodoxy. Firstly, Mapela possesses enormous prestige stone-walled terraces whose initial construction date from the 11th century CE, almost two hundred years earlier than Mapungubwe. Secondly, the basal levels of the Mapela terraces and hilltop contain élite solid dhaka (adobe) floors associated with K2 pottery and glass beads. Thirdly, with a hilltop and flat area occupation since the 11th century CE, Mapela exhibits evidence of class distinction and sacred leadership earlier than K2 and Mapungubwe, the supposed propagators of the Zimbabwe culture. Fourthly, Mapungubwe material culture only appeared later in the Mapela sequence and therefore post-dates the earliest appearance of stone walling and dhaka floors at the site. Since stone walls, dhaka floors and class distinction are the essence of the Zimbabwe culture, their earlier appearance at Mapela suggests that Mapungubwe can no longer be regarded as the sole cradle of the Zimbabwe culture. This demands not just fresh ways of accounting for the rise of socio-political complexity in southern Africa, but also significant adjustments to existing models. PMID:25360782

Zimbabwe culture before Mapungubwe: new evidence from Mapela Hill, South-Western Zimbabwe.

PubMed

Chirikure, Shadreck; Manyanga, Munyaradzi; Pollard, A Mark; Bandama, Foreman; Mahachi, Godfrey; Pikirayi, Innocent

2014-01-01

Across the globe, the emergence of complex societies excites intense academic debate in archaeology and allied disciplines. Not surprisingly, in southern Africa the traditional assumption that the evolution of socio-political complexity began with ideological transformations from K2 to Mapungubwe between CE1200 and 1220 is clouded in controversy. It is believed that the K2-Mapungubwe transitions crystallised class distinction and sacred leadership, thought to be the key elements of the Zimbabwe culture on Mapungubwe Hill long before they emerged anywhere else. From Mapungubwe (CE1220-1290), the Zimbabwe culture was expressed at Great Zimbabwe (CE1300-1450) and eventually Khami (CE1450-1820). However, new fieldwork at Mapela Hill, when coupled with a Bayesian chronology, offers tremendous fresh insights which refute this orthodoxy. Firstly, Mapela possesses enormous prestige stone-walled terraces whose initial construction date from the 11th century CE, almost two hundred years earlier than Mapungubwe. Secondly, the basal levels of the Mapela terraces and hilltop contain élite solid dhaka (adobe) floors associated with K2 pottery and glass beads. Thirdly, with a hilltop and flat area occupation since the 11th century CE, Mapela exhibits evidence of class distinction and sacred leadership earlier than K2 and Mapungubwe, the supposed propagators of the Zimbabwe culture. Fourthly, Mapungubwe material culture only appeared later in the Mapela sequence and therefore post-dates the earliest appearance of stone walling and dhaka floors at the site. Since stone walls, dhaka floors and class distinction are the essence of the Zimbabwe culture, their earlier appearance at Mapela suggests that Mapungubwe can no longer be regarded as the sole cradle of the Zimbabwe culture. This demands not just fresh ways of accounting for the rise of socio-political complexity in southern Africa, but also significant adjustments to existing models.

Synthesis of octahedral gold tip-blobbed nanoparticles and their dielectric sensing properties.

PubMed

Zhang, Liqiu; Jang, Hee-Jeong; Yoo, Sung Jae; Cho, Sanghyun; Won, Ji Hye; Liu, Lichun; Park, Sungho

2018-06-22

Site-selective synthesis of nanostructures is an important topic in the nanoscience community. Normally, the difference between seeds and deposition atoms in terms of crystallinity triggers the deposition atoms to grow initially at the specific site of nucleation. It is more challenging to control the deposition site of atoms that have the same composition as the seeds because the atoms tend to grow epitaxially, covering the whole surface of the seed nanoparticles. Gold (Au) nano-octahedrons used as seeds in this study possess obvious hierarchical surface energies depending on whether they are at vertices, edges, or terraces. Although vertices of Au nano-octahedrons have the highest surface energy, it remains a challenge to selectively deposit Au atoms at the vertices but not at the edges and faces; this selectivity is required to meet the ever-increasing demands of engineered nanomaterial properties. This work demonstrates an easy and robust method to precisely deposit Au nanoparticles at the vertices of Au nano-octahedrons via wet-chemical seed-mediated growth. The successful synthesis of octahedral Au tip-blobbed nanoparticles (Oh Au TBPs) benefited from the cooperative use of thin silver (Ag) layers at the surface of Au nano-octahedron seeds and iodide ions in the Au growth solution. As-synthesized Au nanostructures gave rise to hybrid optical properties, as evidenced from the UV-VIS-NIR extinction spectra, in which a new extinction peak appeared after Au nanoparticles were formed at the vertices of Au nano-octahedrons. A sensitivity evaluation toward dielectric media of a mixture of dimethyl sulfoxide and water suggested that Au TBPs were more optically sensitive compared to the original Au nano-octahedrons. The method demonstrated in this work is promising in the synthesis of advanced Au nanostructures with hybrid optical properties for versatile applications by engineering the surface energy of vertex-bearing Au nanostructures to trigger site-selective overgrowth of congener Au atoms. © 2018 IOP Publishing Ltd.

Atomic force microscopy investigation of the kinetic growth mechanisms of sputtered nanostructured Au film on mica: towards a nanoscale morphology control

PubMed Central

2011-01-01

The study of surface morphology of Au deposited on mica is crucial for the fabrication of flat Au films for applications in biological, electronic, and optical devices. The understanding of the growth mechanisms of Au on mica allows to tune the process parameters to obtain ultra-flat film as suitable platform for anchoring self-assembling monolayers, molecules, nanotubes, and nanoparticles. Furthermore, atomically flat Au substrates are ideal for imaging adsorbate layers using scanning probe microscopy techniques. The control of these mechanisms is a prerequisite for control of the film nano- and micro-structure to obtain materials with desired morphological properties. We report on an atomic force microscopy (AFM) study of the morphology evolution of Au film deposited on mica by room-temperature sputtering as a function of subsequent annealing processes. Starting from an Au continuous film on the mica substrate, the AFM technique allowed us to observe nucleation and growth of Au clusters when annealing process is performed in the 573-773 K temperature range and 900-3600 s time range. The evolution of the clusters size was quantified allowing us to evaluate the growth exponent 〈z〉 = 1.88 ± 0.06. Furthermore, we observed that the late stage of cluster growth is accompanied by the formation of circular depletion zones around the largest clusters. From the quantification of the evolution of the size of these zones, the Au surface diffusion coefficient was evaluated in D(T) = [(7.42 × 10−13) ± (5.94 × 10−14) m2/s]exp(−(0.33±0.04) eVkT). These quantitative data and their correlation with existing theoretical models elucidate the kinetic growth mechanisms of the sputtered Au on mica. As a consequence we acquired a methodology to control the morphological characteristics of the Au film simply controlling the annealing temperature and time. PMID:24576328

78 FR 47715 - National Human Genome Research Institute; Notice of Meeting

Federal Register 2010, 2011, 2012, 2013, 2014

2013-08-06

... space available. Individuals who plan to attend and need special assistance, such as sign language...: National Institutes of Health, Terrace Level Conference Room, 5635 Fishers Lane, Rockville, MD 20892. Open... Institutes of Health, Terrace Level Conference Room, 5635 Fishers Lane, Rockville, MD 20892. Closed...