Evaluation of cyclic resistance of providence silts using mini-cone penetration and standard penetration tests.

DOT National Transportation Integrated Search

2010-12-01

Most areas of coastal Rhode Island are underlain by thick layers of non-plastic silt and it is important to : know if the existing standard-of-practice liquefaction potential evaluations (e.g. Robertson and Wride (1998) or : Seed et al. (1985)) are a...

Nutrient leaching when compost is part of plant growth media

USDA-ARS?s Scientific Manuscript database

Bioretention cells collect urban runoff and are used to slow storm water surge, reduce or remove nutrients or other pollutants, and provide aesthetics to the landscape. A cell is filled with soil mixed with sand, compost, and other materials, and underlain by an aggregate layer and drainage pipe. Th...

Deep electromagnetic sounding of the moon with Lunokhod 2 data

NASA Technical Reports Server (NTRS)

Vanyan, L. L.; Yegorov, I. V.; Faynberg, E. B.

1977-01-01

Results of electromagnetic sounding distinguished an outer high resistance shell about 200 km thick in the moon's structure. A preliminary petrological interpretation of the moon's layers indicated their origin as a consequence of differentiation of the initial peridotite material. Upon melting, 20% to 40% of the material melts and is removed to form a high resistance basaltic shell underlain by a layer of spinal peridotites enriched in divalent iron oxides and having a reduced resistance.

An appraisal of subsurface geology and groundwater resources of Owerri and environs based on electrical resistivity survey and borehole data evaluation.

PubMed

Ibe, K M; Uzoukwu, S C

2001-09-01

The research was aimed at determining the depth to the water table, aquifer thickness and subsurface geology of the study area thus revealing its groundwater distribution as well as its potential as a substitute to the surface water resources. Vertical electrical soundings were carried out in the study area with maximum electrode spread. The Schlumberger electrode configuration technique was adopted. VES data were processed using Schlumberger analysis package. Lithologic logs of already existing boreholes in the study area were collected, evaluated and comparison were carried out. The results reveal alternating layers of sands, sandstones, gravel and clay. The lithologic logs revealed that the study area is underlain by coastal sands (Benin formation). The water table varies from 10-64 m and thickness of the aquifer ranges from 20-80 m. Results show that the study area is underlain by a thick extensive aquifer that has a transmissivity of 2.8 x 10(-2) m2 s(-1) to 3.3 x 10(-1) m2 s(-1) and storativity 1.44 x 10(-4) to 1.68 x 10(-3) m s(-1) values. The specific yield is about 0.31. The sandy component of the study area forms more than 90% of the sequence, therefore the permeability, the transmissivity and the storage coefficient are high with an excellent source of groundwater resources.

Conceptualizing Peatlands in a Physically-Based Spatially Distributed Hydrologic Model

NASA Astrophysics Data System (ADS)

Downer, Charles; Wahl, Mark

2017-04-01

In as part of a research effort focused on climate change effects on permafrost near Fairbanks, Alaska, it became apparent that peat soils, overlain by thick sphagnum moss, had a considerable effect on the overall hydrology. Peatlands represent a confounding mixture of vegetation, soils, and water that present challenges for conceptualizing and parametrizing hydrologic models. We employed the Gridded Surface Subsurface Hydrologic Analysis Model (GSSHA) in our analysis of the Caribou Poker Creek Experimental Watershed (CPCRW). GSSHA is a physically-based, spatially distributed, watershed model developed by the U.S. Army to simulate important streamflow-generating processes (Downer and Ogden, 2004). The model enables simulation of surface water and groundwater interactions, as well as soil temperature and frozen ground effects on subsurface water movement. The test site is a 104 km2 basin located in the Yukon-Tanana Uplands of the Northern Plateaus Physiographic Province centered on 65˚10' N latitude and 147˚30' W longitude. The area lies above the Chattanika River floodplain and is characterized by rounded hilltops with gentle slopes and alluvium-floored valleys having minimal relief (Wahrhaftig, 1965) underlain by a mica shist of the Birch Creek formation (Rieger et al., 1972). The region has a cold continental climate characterized by short warm summers and long cold winters. Observed stream flows indicated significant groundwater contribution with sustained base flows even during dry periods. A site visit exposed the presence of surface water flows indicating a mixed basin that would require both surface and subsurface simulation capability to properly capture the response. Soils in the watershed are predominately silt loam underlain by shallow fractured bedrock. Throughout much of the basin, a thick layer of live sphagnum moss and fine peat covers the ground surface. A restrictive layer of permafrost is found on north facing slopes. The combination of thick moss and peat soils presented a conundrum in terms of conceptualizing the hydrology and identifying reasonable parameter ranges for physical properties. Various combinations of overland roughness, surface retention, and subsurface flow were used to represent the peatlands. The process resulted in some interesting results that may shed light on the dominant hydrologic processes associated with peatland, as well as what hydrologic conceptualizations, simulation tools, and approaches are applicable in modeling peatland hydrology. Downer, C.W., Ogden, F.L., 2004. GSSHA: Model to simulate diverse stream flow producing processes. J. Hydrol. Eng. 161-174. Rieger, S., Furbush, C.E., Schoephorster, D.B., Summerfield Jr., H., Geiger, L.C., 1972. Soils of the Caribou-Poker Creeks Research Watershed, Interior Alaska. Hanover, New Hampshire. Wahrhaftig, C., 1965. Physiographic Divisions of Alaska. Washington, DC.

Passive microwave studies of frozen lakes

NASA Technical Reports Server (NTRS)

Hall, D. K.; Foster, J. L.; Rango, A.; Chang, A. T. C.

1978-01-01

Lakes of various sizes, depths and ice thicknesses in Alaska, Utah and Colorado were overflown with passive microwave sensors providing observations at several wavelengths. A layer model is used to calculate the microwave brightness temperature, T sub B (a function of the emissivity and physical temperatures of the object), of snowcovered ice underlain with water. Calculated T sub B's are comparable to measured T sub B's. At short wavelengths, e.g., 0.8 cm, T sub B data provide information on the near surface properties of ice covered lakes where the long wavelength, 21.0 cm, observations sense the entire thickness of ice including underlying water. Additionally, T sub B is found to increase with ice thickness. 1.55 cm observations on Chandalar Lake in Alaska show a T sub B increase of 38 K with an approximate 124 cm increase in ice thickness.

Rainfall-soil moisture relations in landslide-prone areas of a tropical rain forest, Puerto Rico

USGS Publications Warehouse

Larsen, Matthew C.; Torres-Sanchez, Angel J.; Krishna, J.H.; Quinones-Aponte, Vicente; Gomez-Gomez, Fernando; Morris, G.L.

1990-01-01

Detailed studies of the relation between rainfall and soil moisture are underway at two forested sites on slopes in the CNF. Soil at the sites is characterized by a layer of silty-clay colluvial soil about 1 m thick, which is underlain by up to 10 m of saprolite, and overlies weathered volcaniclastic or quartz-diorite bedrock. Although considerable surface runoff has been observed at the study sites, data show moderate to rapid increases in pore pressure in repsonse to short duration storm events. Pore-pressure increases are greatest in the lower sections of concave slopes apparently due to convergent flow. It is anticipated that these pore-pressure data will provide a means of assessing rainfall characteristics leading to landslide initiation as well as insight to the mechanics of shallow landslides

Multi-omics of permafrost, active layer and thermokarst bog soil microbiomes

NASA Astrophysics Data System (ADS)

Hultman, Jenni; Waldrop, Mark P.; Mackelprang, Rachel; David, Maude M.; McFarland, Jack; Blazewicz, Steven J.; Harden, Jennifer; Turetsky, Merritt R.; McGuire, A. David; Shah, Manesh B.; Verberkmoes, Nathan C.; Lee, Lang Ho; Mavrommatis, Kostas; Jansson, Janet K.

2015-05-01

Over 20% of Earth's terrestrial surface is underlain by permafrost with vast stores of carbon that, once thawed, may represent the largest future transfer of carbon from the biosphere to the atmosphere. This process is largely dependent on microbial responses, but we know little about microbial activity in intact, let alone in thawing, permafrost. Molecular approaches have recently revealed the identities and functional gene composition of microorganisms in some permafrost soils and a rapid shift in functional gene composition during short-term thaw experiments. However, the fate of permafrost carbon depends on climatic, hydrological and microbial responses to thaw at decadal scales. Here we use the combination of several molecular `omics' approaches to determine the phylogenetic composition of the microbial communities, including several draft genomes of novel species, their functional potential and activity in soils representing different states of thaw: intact permafrost, seasonally thawed active layer and thermokarst bog. The multi-omics strategy reveals a good correlation of process rates to omics data for dominant processes, such as methanogenesis in the bog, as well as novel survival strategies for potentially active microbes in permafrost.

Multi-omics of permafrost, active layer and thermokarst bog soil microbiomes.

PubMed

Hultman, Jenni; Waldrop, Mark P; Mackelprang, Rachel; David, Maude M; McFarland, Jack; Blazewicz, Steven J; Harden, Jennifer; Turetsky, Merritt R; McGuire, A David; Shah, Manesh B; VerBerkmoes, Nathan C; Lee, Lang Ho; Mavrommatis, Kostas; Jansson, Janet K

2015-05-14

Over 20% of Earth's terrestrial surface is underlain by permafrost with vast stores of carbon that, once thawed, may represent the largest future transfer of carbon from the biosphere to the atmosphere. This process is largely dependent on microbial responses, but we know little about microbial activity in intact, let alone in thawing, permafrost. Molecular approaches have recently revealed the identities and functional gene composition of microorganisms in some permafrost soils and a rapid shift in functional gene composition during short-term thaw experiments. However, the fate of permafrost carbon depends on climatic, hydrological and microbial responses to thaw at decadal scales. Here we use the combination of several molecular 'omics' approaches to determine the phylogenetic composition of the microbial communities, including several draft genomes of novel species, their functional potential and activity in soils representing different states of thaw: intact permafrost, seasonally thawed active layer and thermokarst bog. The multi-omics strategy reveals a good correlation of process rates to omics data for dominant processes, such as methanogenesis in the bog, as well as novel survival strategies for potentially active microbes in permafrost.

Microtopographic Evidence of Hillslope Susceptibility to Active Layer Detachments and Rapid Soil Erosion in Permafrost-dominated Watersheds

NASA Astrophysics Data System (ADS)

Rowland, J. C.; Shelef, E.; Sutfin, N. A.; Piliouras, A.; Andresen, C. G.; Wilson, C. J.

2017-12-01

Movement and storage rates of soil and carbon along permafrost-dominated hillslopes may vary dramatically from long-term steady creeping, at centimeters per year, to rapid gullying, land sliding, and active layer detachments of meter to decimeter sized portions of hillslopes. The rate and drivers of hillslope soil processes may have strong feedbacks on microtopography and hydrology that in turn strongly influence vegetation dynamics and biogeochemistry within watersheds. We observed evidence of both steady soil creep and more catastrophic soil erosion processes occurring across three small watersheds in the southern Seward Peninsula, AK. In these watersheds, we inferred active soil creep processes from the occurrence of solifluction lobes with partially buried shrubs and tilted survey benchmarks on slopes lacking lobes. More dramatic and rapid erosion of soils was evidenced by active layer detachments, extensional cracks in the tundra vegetation, gullying, and both small- and large-scale soil failure scarps. The margins and heads of valley hollows exhibited failure scars up to 4m in height. The spatial distribution of actively eroding areas suggests that some portions of hilllslopes may be more susceptible to rapid erosion. Coring of hillslope soils suggests a possible association between more actively eroding areas and the presence of an ice-rich layer (> 50%) at depths of approximately 90 cm down to the inferred top of bedrock at depths at 170 to 200 cm. We observed that the surface of these hillslope regions appears to have greater microtopographic roughness with a more chaotic and "lumpy" surface than portions of the hillslope were no massive ice layers were encountered. We hypothesize that the extensional cracking and chaotic surface roughness may arise from small-scale soil failures triggered when the seasonal thaw depth intersects the ice-rich layer. It may be possible to identify hillslope regions underlain by ice-rich layers with greater susceptibility for localized erosion and deformation based on a quantitative characterization of the hillslope microtopography. Using drone-based LiDAR topographic data to be acquired in late summer of 2017, we will quantitatively explore the relationship between microtopography and hillslope ice-content.

National Uranium Resource Evaluation: Newcastle Quadrangle, Wyoming and South Dakota

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

Santos, E S; Robinson, K; Geer, K A

1982-09-01

Uranium resources of the Newcastle 1/sup 0/x2/sup 0/ Quadrangle, Wyoming and South Dakota were evaluated to a depth of 1500 m (5000 ft) using available surface and subsurface geologic information. Many of the uranium occurrences reported in the literature and in reports of the US Atomic Energy Commission were located, sampled and described. Areas of anomalous radioactivity, interpreted from an aerial radiometric survey, were outlined. Areas favorable for uranium deposits in the subsurface were evaluated using gamma-ray logs. Based on surface and subsurface data, two areas have been delineated which are underlain by rocks deemed favorable as hosts for uraniummore » deposits. One of these is underlain by rocks that contain fluvial arkosic facies in the Wasatch and Fort Union Formations of Tertiary age; the other is underlain by rocks containing fluvial quartzose sandstone facies of the Inyan Kara Group of Early Cretaceous age. Unfavorable environments characterize all rock units of Tertiary age above the Wasatch Formation, all rock units of Cretaceous age above the Inyan Kara Group, and most rock units of Mesozoic and Paleozoic age below the Inyan Kara Group. Unfavorable environments characterize all rock units of Cretaceous age above the Inyan Kara Group, and all rock units of Mesozoic and Paleozoic age below the Inyan Kara Group.« less

Contribution of Uranium-Bearing Evaporites to Plume Persistence Issues at a Former Uranium Mill Site Riverton, Wyoming, USA

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

Johnson, Raymond; Dam, William; Campbell, Sam

2016-08-01

• Evaporites occur in an unsaturated silt layer, which is underlain by a sand and gravel aquifer. • These evaporites are rich in chloride across the site. • Uranium concentrations are higher in the evaporites that overlie the uranium contaminant plume. • Flooding can solubilize the evaporites in the silt layer and release chloride, sulfate (not shown), and uranium into the underlyingsand and gravel aquifer. • The uranium-rich evaporites can delay natural flushing, creating plume persistence near the Little Wind River.

Seismic structure of the Mid-Atlantic Ridge, 8-9°S

NASA Astrophysics Data System (ADS)

Minshull, T. A.; Bruguier, N. J.; Brozena, J. M.

2003-11-01

The Mid-Atlantic Ridge at 8-9°S is characterized by a transition from axial valley to axial high and recent episodes of ridge jumping and ridge propagation. We present constraints on the structure of 0-4 Ma crust in this region on the basis of the analysis of wide-angle seismic data from a grid of profiles across and parallel to the current and abandoned spreading centers. A 350-800 m thick oceanic layer 2A, interpreted as high-porosity extrusive basalts, is underlain by a ˜2.0-2.5 km layer 2B with velocities which increase with age and decrease in the vicinity of the pseudofaults. Layer 3 velocities are uniform across the area except for a possible localized anomaly at the ridge axis. The crustal thickness varies from 6-7 km near the pseudofaults formed by ridge propagation to 9-10 km at the segment center of the recently (˜0.3 Ma) abandoned spreading center. Seismically determined crustal thickness and density variations and age-related lithospheric cooling can plausibly account for all observed variations in gravity across the area, and there is no requirement for the thicker crust at the segment center to be underlain by hot mantle. The transition from axial valley to axial high occurs at a crustal thickness of ˜8 km.

Field Verification of Stable Perched Groundwater in Layered Bedrock Uplands

USGS Publications Warehouse

Carter, J.T.; Gotkowitz, M.B.; Anderson, M.P.

2011-01-01

Data substantiating perched conditions in layered bedrock uplands are rare and have not been widely reported. Field observations in layered sedimentary bedrock in southwestern Wisconsin, USA, provide evidence of a stable, laterally extensive perched aquifer. Data from a densely instrumented field site show a perched aquifer in shallow dolomite, underlain by a shale-and-dolomite aquitard approximately 25 m thick, which is in turn underlain by sandstone containing a 30-m-thick unsaturated zone above a regional aquifer. Heads in water supply wells indicate that perched conditions extend at least several kilometers into hillsides, which is consistent with published modeling studies. Observations of unsaturated conditions in the sandstone over a 4-year period, historical development of the perched aquifer, and perennial flow from upland springs emanating from the shallow dolomite suggest that perched groundwater is a stable hydrogeologic feature under current climate conditions. Water-table hydrographs exhibit apparent differences in the amount and timing of recharge to the perched and regional flow systems; steep hydraulic gradients and tritium and chloride concentrations suggest there is limited hydraulic connection between the two. Recognition and characterization of perched flow systems have practical importance because their groundwater flow and transport pathways may differ significantly from those in underlying flow systems. Construction of multi-aquifer wells and groundwater withdrawal in perched systems can further alter such pathways. ?? 2010 The Author(s). Journal compilation ?? 2010 National Ground Water Association.

Analysis of Terrestrial Carbon Stocks in a Small Catchment of Northeastern Siberia

NASA Astrophysics Data System (ADS)

Heard, K.; Natali, S.; Bunn, A. G.; Loranty, M. M.; Kholodov, A. L.; Schade, J. D.; Berner, L. T.; Spektor, V.; Zimov, N.; Alexander, H. D.

2015-12-01

As arctic terrestrial ecosystems comprise about one-third of the global terrestrial ecosystem carbon total, understanding arctic carbon cycling and the feedback of terrestrial carbon pools to accelerated warming is an issue of global concern. For this research, we examined above- and belowground carbon stocks in a larch-dominated catchment underlain by yedoma and located within the Kolyma River watershed in northeastern Siberia. We quantified carbon stocks in vegetation, active layer, and permafrost, and we assessed the correlation between plant and active layer carbon pools and four environmental correlates — slope, solar insolation, canopy density, and leaf area index ­— at 20 sites. Carbon in the active layer was approximately four times greater than aboveground carbon pools (972 g C m-2), and belowground carbon to 1 m depth was approximately 18 times greater than aboveground carbon pools. Canopy density and slope had a robust positive association with aboveground carbon pools, and soil moisture was positively related to %C in organic, thawed mineral and permafrost soil. Thaw depth was negatively correlated with moss cover and larch biomass, highlighting the importance of vegetation and surface characteristics on permafrost carbon vulnerability. These data suggest that landscape and ecosystem characteristics affect carbon accumulation and storage, but they also play an important role in stabilizing permafrost carbon pools.

Layered/Pancake-like Ejecta on Ceres: Inferring the Composition and Mechanical Properties of the Cerean Surface through Modeling of Ejecta Emplacement

NASA Astrophysics Data System (ADS)

Hughson, K.; Russell, C. T.; Schmidt, B. E.; Chilton, H.; Scully, J. E. C.; Sizemore, H. G.; Byrne, S.; Platz, T.; Raymond, C. A.

2017-12-01

During the Survey, High Altitude Mapping Orbit, and Low Altitude Mapping Orbit phases of the primary mission Dawn's Framing Camera observed a multitude of globally distributed lobate deposits. These flows were broadly interpreted as either similar to ice-cored/ice-cemented flows (Type 1 flows) on Earth and Mars, long run-out terrestrial or martian landslides (Type 2 flows), or highly mobile fluidized ejecta-like deposits (Type 3 flows) (Buczckowski et al., 2016; Schmidt et al., 2017). The Type 3 flows are morphologically similar to layered/pancake ejecta found on Mars and Ganymede where they are thought to be caused by impacts into ground ice rich substrates (Mouginis-Mark, 1979; Boyce et al., 2010). We assess the effects of target material strength, sliding friction, and vapor entrainment on the production of these features by comparing the ejecta mobility (EM: the ratio of the radius of the ejecta blanket to the radius of the parent crater) values for all Type 3 cerean flows to a ballistic/kinematic sliding model similar to the one developed by Weiss et al. (2014) to model EM for impacts into a variety of ground ice rich substrates of differing volatile content on Mars. Initial results suggest that, in order for these features to form, the cerean surface requires a large coefficient of sliding friction (>0.1), and that significant amounts of water be vaporized during impact. However, the model does not tightly constrain the strength of the target material (best-fit values range from granite-like to unconsolidated-sand-like). These results are consistent with a largely dry, rough, and thin surface layer underlain by material rich in pore-filling ground ice, even at low latitudes. Additionally, before the Fall Meeting we will attempt to constrain the thickness of the ice-poor surface layer. This will be done through a combined analysis of model results and morphometric parameters of individual Type 3 flows. Future implementation of this model will further incorporate compositional and geophysical knowledge attained from Dawn in order to better constrain the strength of the cerean surface.

Lime-mud layers in high-energy tidal channels: A record of hurricane deposition

NASA Astrophysics Data System (ADS)

Shinn, Eugene A.; Steinen, Randolph P.; Dill, Robert F.; Major, Richard

1993-07-01

During or immediately following the transit of Hurricane Andrew (August 23-24, 1992) across the northern part of the Great Bahama Bank, thin laminated beds of carbonate mud were deposited in high-energy subtidal channels (4 m depth) through the ooid shoals of south Cat Cay and Joulters Cays. During our reconnaissance seven weeks later, we observed lime-mud beds exposed in the troughs of submarine oolite dunes and ripples. The mud layers were underlain and locally covered by ooid sand. The mud beds were lenticular and up to 5 cm thick. Their bases cast the underlying rippled surface. The layers were composed of soft silt- and sand-sized pellets and peloids and in some areas contained freshly preserved Thalassia blades and other organic debris along planes of lamination. The beds had a gelatinous consistency and locally had been penetrated by burrowers and plants. Layers of lime mud had also settled on bioturbated, plant-stabilized flats and in lagoonal settings but were quickly reworked and made unrecognizable by the burrowing of organisms. Thicker, more cohesive (and therefore older) mud beds and angular mud fragments associated with ooids from Joulters Cays have similar characteristics but lack fresh plant fragments. We infer that these older beds were similarly deposited and thus record the passage of previous hurricanes or tropical storms. Storm layers are preserved within channel sediments because migrating ooids prevent attack by the burrowing activity off organisms.

Interpretation of shallow electrical features from electromagnetic and magnetotelluric surveys at Mount Hood, Oregon

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

Goldstein, N.E.; Mozley, E.; Wilt, M.

1982-04-10

A magnetotelluric survey was conducted at accessible locations around Mount Hood, Oregon. Thirty-eight tensor magnetotelluric (MT) and remote telluric stations were set up in clusters around the volcano except for the northwest quadrant, a wilderness area. Because of limited access, station locations were restricted to elevations below 1829 m. On the basis of the MT results, three areas were later investigated in more detail using a large-moment, controlled-source electromagnetic (EM) system. One-dimensional interpretations of EM and MT data on the northeast flank of the mountain near the Cloud Cap eruptive center and on the south flank near Timberline Lodge showmore » a similar subsurface resistivity pattern: a resistive surface layer 400--700 m thick, underlain by a conductive layer with variable thickness and resistivity of <20 ohm m. It is speculated that the surface layer consists of volcanics partially saturated with cold meteoric water. The underlying conductive zone is presumed to be volcanics saturated with water heated within the region of the central conduit and, possibly, at the Cloud Cap side vent. This hypothesis is supported by the existence of warm springs at the base of the mountain, most notably Swim Warm Springs on the south flank, and by several geothermal test wells, one of which penetrates the conductor south of Timberline Lodge. The mT data typically gave a shallower depth to the conductive zone than did the Em data. On the other hand, MT was better for resolving the thickness of the conductive layer and deeper structure. The MT data show evidence for a moderately conductive north-south structure on the south flank below the Timberline Lodge and for a broad zone of late Tertiary intrusives concealed on the southeast flank.« less

Assimilation of old carbon by stream food webs in arctic Alaska

NASA Astrophysics Data System (ADS)

O'Donnell, J. A.; Carey, M.; Xu, X.; Koch, J. C.; Walker, J. C.; Zimmerman, C. E.

2017-12-01

Permafrost thaw in arctic and sub-arctic region is mobilizing old carbon (C) from perennially frozen soils, driving the release of old C to the atmosphere and to aquatic ecosystems. Much research has focused on the transport and lability of old dissolved organic C (DOC) as a possible feedback to the climate system following thaw. However, little is known about the role of old C as a source to aquatic food webs in watersheds underlain by thawing permafrost. To quantify the contributions of old C to Arctic stream food-webs, we measured the radiocarbon (Δ14C) and stable isotope (δ13C, δ15N) contents of periphyton, macroinvertebrates, and resident fish species (Arctic Grayling (Thymallus arcticus) and Dolly Varden (Salvelinus malma)). We also characterized the isotopic composition of possible C sources, including DOC, dissolved inorganic carbon (DIC), and soil organic matter. Samples were collected across 10 streams in Arctic Alaska, draining watersheds underlain by varying parent material and ground-ice content, from ice-poor bedrock to ice-rich loess (i.e. Yedoma). Fraction modern (FM) values for Arctic Grayling and Dolly Varden ranged from 0.6720 to 1.0101 (3195 years BP to modern) across all streams, and closely tracked spatial variation in Δ14C content of periphyton. Parent material and ground-ice content appear to govern the age and form of dissolved C sources to stream biota. For instance, in watersheds underlain by ice-poor bedrock, old DIC (< 5000 years BP) was the dominant C source to stream biota, reflecting contributions from carbonate weathering and soil respiration. In streams draining ice-rich Yedoma, high concentrations of younger DOC were the primary C source to stream biota, reflecting leaching of DOC from saturated, peaty soils of the active layer. These findings highlight the importance of permafrost characteristics as a control on subsurface hydrology and the delivery of aged C to surface waters. Given the large stores Pleistocene-aged organic C in Yedoma deposits, we hypothesize that older C may become a more important contribution to stream biota under warmer conditions that promote thaw.

A Simplified Analytic Investigation of the Riverside Effects of Sediment Diversions

DTIC Science & Technology

2013-09-01

demonstrated that the river bed consists of a sand layer of variable thickness, underlain by erosion resistant strata (either relict glacial deposits...following analysis. Simplifications and Initial Conditions. Consider a river modeled as a wide rectangular channel of constant width (Figure 1). The...CHETN-VII-13 September 2013 14  Short term effects include the redistribution of sediment by erosion upstream of the diversion to deposition

The formation of Laurentia: Evidence from shear wave splitting

NASA Astrophysics Data System (ADS)

Liddell, Mitch V.; Bastow, Ian; Darbyshire, Fiona; Gilligan, Amy; Pugh, Stephen

2017-12-01

The northern Hudson Bay region in Canada comprises several Archean cratonic nuclei, assembled by a number of Paleoproterozoic orogenies including the Trans-Hudson Orogen (THO) and the Rinkian-Nagssugtoqidian Orogen. Recent debate has focused on the extent to which these orogens have modern analogues such as the Himalayan-Karakoram-Tibet Orogen. Further, the structure of the lithospheric mantle beneath the Hudson Strait and southern Baffin Island is potentially indicative of Paleoproterozoic underthrusting of the Superior plate beneath the Churchill collage. Also in question is whether the Laurentian cratonic root is stratified, with a fast, depleted, Archean core underlain by a slower, younger, thermally-accreted layer. Plate-scale process that create structures such as these are expected to manifest as measurable fossil seismic anisotropic fabrics. We investigate these problems via shear wave splitting, and present the most comprehensive study to date of mantle seismic anisotropy in northern Laurentia. Strong evidence is presented for multiple layers of anisotropy beneath Archean zones, consistent with the episodic development model of stratified cratonic keels. We also show that southern Baffin Island is underlain by dipping anisotropic fabric, where underthrusting of the Superior plate beneath the Churchill has previously been interpreted. This provides direct evidence of subduction-related deformation at 1.8 Ga, implying that the THO developed with modern plate-tectonic style interactions.

Characteristics of Viscoelastic Crustal Deformation Following a Megathrust Earthquake: Discrepancy Between the Apparent and Intrinsic Relaxation Time Constants

NASA Astrophysics Data System (ADS)

Fukahata, Yukitoshi; Matsu'ura, Mitsuhiro

2018-02-01

The viscoelastic deformation of an elastic-viscoelastic composite system is significantly different from that of a simple viscoelastic medium. Here, we show that complicated transient deformation due to viscoelastic stress relaxation after a megathrust earthquake can occur even in a very simple situation, in which an elastic surface layer (lithosphere) is underlain by a viscoelastic substratum (asthenosphere) under gravity. Although the overall decay rate of the system is controlled by the intrinsic relaxation time constant of the asthenosphere, the apparent decay time constant at each observation point is significantly different from place to place and generally much longer than the intrinsic relaxation time constant of the asthenosphere. It is also not rare that the sense of displacement rate is reversed during the viscoelastic relaxation. If we do not bear these points in mind, we may draw false conclusions from observed deformation data. Such complicated transient behavior can be explained mathematically from the characteristics of viscoelastic solution: for an elastic-viscoelastic layered half-space, the viscoelastic solution is expressed as superposition of three decaying components with different relaxation time constants that depend on wavelength.

Shallow groundwater systems in a polar desert, McMurdo Dry Valleys, Antarctica

NASA Astrophysics Data System (ADS)

Gooseff, Michael N.; Barrett, John E.; Levy, Joseph S.

2013-02-01

The McMurdo Dry Valleys (MDVs), Antarctica, exist in a hyperarid polar desert, underlain by deep permafrost. With an annual mean air temperature of -18 °C, the MDVs receive <10 cm snow-water equivalent each year, collecting in leeward patches across the landscape. The landscape is dominated by expansive ice-free areas of exposed soils, mountain glaciers, permanently ice-covered lakes, and stream channels. An active layer of seasonally thawed soil and sediment extends to less than 1 m from the surface. Despite the cold and low precipitation, liquid water is generated on glaciers and in snow patches during the austral summer, infiltrating the active layer. Across the MDVs, groundwater is generally confined to shallow depths and often in unsaturated conditions. The current understanding and the biogeochemical/ecological significance of four types of shallow groundwater features in the MDVs are reviewed: local soil-moisture patches that result from snow-patch melt, water tracks, wetted margins of streams and lakes, and hyporheic zones of streams. In general, each of these features enhances the movement of solutes across the landscape and generates soil conditions suitable for microbial and invertebrate communities.

Heavy metal distributions in Peru Basin surface sediments in relation to historic, present and disturbed redox environments

NASA Astrophysics Data System (ADS)

Koschinsky, Andrea

Heavy metal distributions in deep-sea surface sediments and pore water profiles from five areas in the Peru Basin were investigated with respect to the redox environment and diagenetic processes in these areas. The 10-20-cm-thick Mn oxide-rich and minor metal-rich top layer is underlain by an increase in dissolved Mn and Ni concentrations resulting from the reduction of the MnO 2 phase below the oxic zone. The mobilised associated metals like Co, Zn and Cu are partly immobilised by sorption on clay, organic or Fe compounds in the post-oxic environment. Enrichment of dissolved Cu, Zn, Ni, Co, Pb, Cd, Fe and V within the upper 1-5 cm of the oxic zone can be attributed to the degradation of organic matter. In a core from one area at around 22-25 cm depth, striking enrichments of these metals in dissolved and solid forms were observed. Offset distributions between oxygen penetration and Mn reduction and the thickness of the Mn oxide-rich layer indicate fluctuations of the Mn redox boundary on a short-term time scale. Within the objectives of the German ATESEPP research programme, the effect of an industrial impact such as manganese nodule mining on the heavy metal cycle in the surface sediment was considered. If the oxic surface were to be removed or disturbed, oxygen would penetrate deep into the formerly suboxic sediment and precipitate Mn 2+ and metals like Ni and Co which are preferably scavenged by MnO 2. The solid enrichments of Cd, V, and other metals formed in post-oxic environments would move downward with the new redox boundary until a new equilibrium between oxygen diffusion and consumption is reached.

Holocene paleoenviroments of northwest Iowa

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

Baker, R.G.; Bettis, E.A. III; Schwert, D.P.

1996-05-01

This paper presents the biotic, sedimentary, geomorphic, and climatic history of the upper part of the Roberts Creek Basin, northeastern Iowa for the late-glacial and Holocene, and compares these records with a C-O isotopic sequence from Coldwater Cave, 60 km northwest of Roberts Creek. the biotic record (pollen, vascular plant and bryophyte macrofossils, and insects) is preserved in floodplain alluvium that underlies three constructional surfaces separated by low scarps. Each surface is underlain by a lithologically and temporally distinct alluvial fill. The highest surface is underlain by the Gunder Member of the Deforest Formation, dating from 11,000 to 4000 yrmore » BP; beneath the intermediate level is the Roberts Creek Member, dating from 4000 to 400 yr BP; and the lowest level is underlain by the Camp Creek Member, deposited during the last 380 yr. Pollen and plant macrofossils in the alluvial fill show that a typical late-glacial spruce forest was replaced by Quercus and Ulmus in the early Holocene. This early-to-middle Holocene forest became dominated by medic elements such as Acer saccharum, Tila americana, Ostyra virginiana, and Carpinus caroliniana as late as 5500 yr BP; in contrast, the closest sites to the west and north were at their warmest and driest were covered by prairie vegetation between 6500 and 5500 yr BP. After 5500 yr BP, the forest in the roberts Creek area was replaced by prairie, as indicated by a rich assemblage of plant macrofossils, although only Ambrosia and Poaceae became abundant in the pollen record. The return of Quercus {approx} 3000 BP (while nonarboreal pollen percentages remained relatively high) indicates the oak savanna prevailed with little change until settlement time. 83 refs., 17 figs., 5 tabs.« less

Geology and Geophysical Surveys to Infer the Structure of the Upper San Pedro River Basin, Sonora, Mexico for Use in a Ground-Water-Flow Model

NASA Astrophysics Data System (ADS)

Pool, D.; Gray, F.; Callegary, J. B.

2005-05-01

Data on geology and geophysics in the San Pedro River Basin in Sonora, Mexico were combined to develop a three-dimensional conceptual model of the alluvial-fill aquifer in the basin that is being used to construct a regional ground-water-flow model. In Mexico, the headwater region of the river encompasses approximately 1,800 square kilometers of an ungaged catchment system. This feeds a 58 kilometer-long series of intermittent and perennial stream reaches in the United States that extend from just north of the international border to the town of St. David, Arizona. The river forms part of a north-south riparian corridor that provides habitat for more than 100 resident and 250 migratory bird species. Ground water in the basin is used extensively on both sides of the border and information on basin structure and composition will help to address questions regarding ground- and surface-water sustainability and planning. Interpretations of bedrock and alluvial-fill geometry indicate that a significant portion of the catchment area in Mexico is underlain by bedrock composed of highly indurated (compacted) Cretaceous sedimentary, volcanic, volcano-sedimentary, and granitic intrusive rocks. Aeromagnetic surveys were used to estimate depth to bedrock underlying alluvial sediments. Satellite photographs, older geologic maps, and recent field observations were used to delineate the boundaries between bedrock and alluvium. About 655 square kilometers, or 36 percent, of the Mexican portion of the river basin is underlain by alluvial fill. In the southern part of the study area, detailed information on thickness and composition of subsurface layers to depths of 500 meters was derived from drill logs. An extensive network of vertical electrical soundings covering much of the central part of the basin allowed for estimates of the location and thickness of clay layers that are confining units within the aquifer system. Across much of the area, the thickness of the silt and confining units was difficult to determine because of problems in distinguishing between these layers and underlying, electrically-conductive Cretaceous siltstone and mudstone. In general, two hydraulically connected sub-basins were identified: one in the southern part of the study area and one in the northern part.

Comments on Interior’s Surface Mining Regulations.

DTIC Science & Technology

1981-08-05

regulations and responses to pro- posed regulati n, (2) identified studies on cost/benefit analy- sis of environme ital regulations and selected ...agricultural production at the national level, in some rural counties essentially the entire area is underlain with strippable coal. obviously, surface mining...1980).) Illinois, which has the most strippable coal reserves underlying prime farmland, has two heavily worked coal seams which are continuous. One

Liquefaction and soil failure during 1994 northridge earthquake

USGS Publications Warehouse

Holzer, T.L.

1999-01-01

The 1994 Northridge, Calif., earthquake caused widespread permanent ground deformation on the gently sloping alluvial fan surface of the San Fernando Valley. The ground cracks and distributed deformation damaged both pipelines and surface structures. To evaluate the mechanism of soil failure, detailed subsurface investigations were conducted at four sites. Three sites are underlain by saturated sandy silts with low standard penetration test and cone penetration test values. These soils are similar to those that liquefied during the 1971 San Fernando earthquake, and are shown by widely used empirical relationships to be susceptible to liquefaction. The remaining site is underlain by saturated clay whose undrained shear strength is approximately half the value of the earthquake-induced shear stress at this location. This study demonstrates that the heterogeneous nature of alluvial fan sediments in combination with variations in the ground-water table can be responsible for complex patterns of permanent ground deformation. It may also help to explain some of the spatial variability of strong ground motion observed during the 1994 earthquake. ?? ASCE,.

Resistivity imaging of Aluto-Langano geothermal field using 3-D magnetotelluric inversion

NASA Astrophysics Data System (ADS)

Cherkose, Biruk Abera; Mizunaga, Hideki

2018-03-01

Magnetotelluric (MT) method is a widely used geophysical method in geothermal exploration. It is used to image subsurface resistivity structures from shallow depths up to several kilometers of depth. Resistivity imaging using MT method in high-enthalpy geothermal systems is an effective tool to identify conductive clay layers that cover the geothermal systems and to detect a potential reservoir. A resistivity model is vital for deciding the location of pilot and production sites at the early stages of a geothermal project. In this study, a 3-D resistivity model of Aluto-Langano geothermal field was constructed to map structures related to a geothermal resource. The inversion program, ModEM was used to recover the 3-D resistivity model of the study area. The 3-D inversion result revealed the three main resistivity structures: a high-resistivity surface layer related to unaltered volcanic rocks at shallow depth, underlain by a conductive zone associated with the presence of conductive clay minerals, predominantly smectite. Beneath the conductive layer, the resistivity increases gradually to higher values related to the formation of high-temperature alteration minerals such as chlorite and epidote. The resistivity model recovered from 3-D inversion in Aluto-Langano corresponds very well to the conceptual model for high-enthalpy volcanic geothermal systems. The conductive clay cap is overlying the resistive propylitic upflow zone as confirmed by the geothermal wells in the area.

Wetland and water supply

USGS Publications Warehouse

Baker, John Augustus

1960-01-01

The Geological Survey has received numerous inquiries about the effects of proposed changes in the wetland environment. The nature of the inquiries suggests a general confusion in the public mind as to wetland values and an increasing concern by the public with the need for facts as a basis for sound decisions when public action is required. Perhaps the largest gap in our knowledge is in regard to the role played by the wetland in the natural water scheme. Specialists in such fields as agriculture and conservation have studied the wetland in relation to its special uses and values for farming and as a habitat for fish and wildlife. However, except as studied incidentally by these specialists, the role of the wetland with respect to water has been largely neglected. This facet of the wetland problem is of direct concern to the Geological Survey. We commonly speak of water in terms of its place in the hydrologic environment---as, for example, surface water or ground water. These terms imply that water can be neatly pigeonholed. With respect to the wetland environment nothing can be further from the truth. In fact, one objective of this discussion is to demonstrate that for the wetland environment surface water, ground water, and soil water cannot be separated realistically, but are closely interrelated and must be studied together. It should be noted that this statement holds true for the hydrologic environment in general, and that the wetland environment is by no means unique in this respect. Our second and principal objective is to identify some of the problems that must be studied in order to clarify the role of the wetland in relation to water supply. We have chosen to approach these objectives by briefly describing one area for which we have some information, and by using this example to point out some of the problems that need study. First, however, let us define what we, as geohydrologists, mean by wetland and briefly consider wetland classifications. For our purpose wetlands are land areas that are covered with shallow water or subjected to intermittent flooding and subsequent slow drainage, and which generally are characterized by an accumulation of organic matter hereafter termed swamp deposits.' These wetlands may be classified in a number of different ways depending on the purpose of the classifier. For example, the Fish and Wildlife Service classifies wetlands into 20 different types based on water quality (fresh or salty), drainage, and vegetation. At the risk of some oversimplification we might consider 4 types of wetland from the standpoint of hydrology: (1) fresh-water swamps in which the swamp deposits are underlain by glacial till or bedrock; (2)fresh-water swamps in which the swamp deposits are underlain by marine or lacustrine clay and silt; (3) fresh-water swamps in which the swamp deposits are underlain by glacial outwash or alluvium consisting mostly of sand or sand and gravel; and (4) salt .marshes and salt meadows. The three fresh-water types of wetland are of interest with respect to water supply, and of these, the type in which swamp deposits are underlain by glacial outwash is of particular interest in New England. In the Ipswich River basin above the Geological Survey gaging station at South Middleton, Mass., is an area of 44 square miles which forms the headwaters section of the basin. The relief of the area is low. About half the area consists of hills mostly underlain by bedrock but mantled by a thin layer of glacial till. The other half consists Of lowlands---including swamps, low terraces and plains---underlain by glacial outwash, Swampland, used hereafter as a synonym for wetland, forms about a fourth of the area. Some of the swamps occupy depressions in the till blanket and are situated at somewhat higher levels than the lowlands. The largest swamps, however, border the Ipswich River and its tributaries. Here the swamp deposits, which consist of muck and peat mixed with s

Magma differentiation in shallow sills controlled by compaction and surface tension: San Rafael desert, Utah

NASA Astrophysics Data System (ADS)

Diez, M.; Savov, I. P.; Connor, C.

2010-12-01

Veinlets, veins, sheet or layers of syenite are common structures found in alkaline basalt sills. The mechanism usually invoked to explain their formation are liquid immiscibility, multiple intrusion or crystal fractionation from primitive mafic melt. Syenite veins of few centimeters to sheets of up to 1-2 m thick are ubiquitous in remarkably well-exposed sills of the San Rafael subvolcanic field in the Colorado Plateau, Utah. In some of these exposures we have found an intriguing configuration in which the main body of the alkaline sill is underlain by a lower density sheet of syenite of ~ 1 m thick. The contact is flat and is not a chilled margin, therefore a multiple intrusion scenario with long intervals between injections can be disregarded. This implies that both layers were fluid at the time of magma emplacement. As the more felsic less dense syenite is at the bottom of the sill any mechanism governed exclusively by bouyancy would be problematic. In an attempt to shed light on this apparent riddle we propose the following geological scenario: The sill is built by continuous injections. Magma starts to cool and fractional crystallization operates at this stage to differentiate the alkaline magma into syenite. By the time ~60% of crystallization is attained the system can be described as two-phase flow consisting of pore-syenite melt in hot-creeping matrix. The forces acting to segregate melt into veins or sheets are the gravitational force and surface tension. When surface tension is stronger than the gravitational force, differences in average curvature or surface tension translates into pressure differences that drive melt flow from low to high porosity regions. If the last injections occur at the bottom of the sill a syenite layer may be formed. With the aid of dimensional analysis and two-phase numerical models that account for gravitational compaction and surface tension effects, we explore the conditions that allow for centimeter-scale veins to meter-scale sheets formation in shallow sills. After combining field observations, petrological studies and numerical models of shallow sills in the San Rafael subvolcanic field, we will report the conditions that control magma differentiation in shallow intraplate settings.

Viscoelastic crustal deformation by magmatic intrusion: A case study in the Kutcharo caldera, eastern Hokkaido, Japan

NASA Astrophysics Data System (ADS)

Yamasaki, Tadashi; Kobayashi, Tomokazu; Wright, Tim J.; Fukahata, Yukitoshi

2018-01-01

Geodetic signals observed at volcanoes, particularly their temporal patterns, have required us to make the correlation between the surface displacement and magmatic process at depth in terms of viscoelastic crustal rheology. Here we use a parallelized 3-D finite element model to examine the response of the linear Maxwell viscoelastic crust and mantle to the inflation of a sill in order to show the characteristics of a long-term volcano deformation. In the model, an oblate-spheroidal sill is instantaneously or gradually inflated in a two-layered medium that consists of an elastic layer underlain by a viscoelastic layer. Our numerical experiments show that syn-inflation surface uplift is followed by post-inflation surface subsidence as the viscoelastic substrate relaxes. For gradual inflation events, the magnitude of inflation-induced uplift is reduced by the relaxation, through which the volume of a magma inferred by matching the prediction of an elastic model with observed surface uplift could be underestimated. For a given crustal viscosity, sill depth is the principal factor controlling subsidence caused by viscoelastic relaxation. The subsidence rate is highest when the inflation occurs at the boundary between the elastic and the viscoelastic layers. The mantle viscosity has an insignificant impact unless the depth of the inflation is greater than a half the crustal thickness. We apply the viscoelastic model to the interferometric synthetic aperture radar (InSAR) data in the Kutcharo caldera, eastern Hokkaido, Japan, where the surface has slowly subsided over a period of approximately three years following about a two-year period of inflation. The emplacement of a magmatic sill is constrained to occur at a depth of 4.5 km, which is significantly shallower than the geophysically imaged large-scale magma chamber. The geodetically detected deformation in the caldera reflects the small-scale emplacement of a magma that ascended from the deeper chamber, but not the inflation of the chamber itself. The observed ground displacement is controlled by a lower-crustal viscosity of 4 × 1017 Pa s, which is lower than that inferred from some studies of post-seismic deformation, perhaps due to higher temperatures beneath the active caldera. Our results suggest that geodetic signals observed during and following magmatic intrusions need to be revisited. Uzs‧ is the uplift at t‧ = Δt‧ for models with Δt‧ > 0.

Base of moderately saline ground water in the Uinta Basin, Utah, with an introductory section describing the methods used in determining its position

USGS Publications Warehouse

Howells, Lewis; Longson, M.S.; Hunt, Gilbert L.

1987-01-01

The base of the moderately saline water (water that contains from 3,000 to 10,000 milligrams per liter of dissolved solids) was mapped by using available water-quality data and by determining formation-water resistivities from geophysical well logs based on the resistivity-porosity, spontaneous potential, and resistivity-ratio methods. The contour map developed from these data showed a mound of very saline and briny water, mostly of sodium chloride and sodium bicarbonate type, in most of that part of the Uinta Basin that is underlain by either the Green River or Wasatch Formations. Along its northern edge, the mound rises steeply from below sea level to within 2,000 feet of the land surface and, locally, to land surface. Along its southern edge, the mound rises less steeply and is more complex in outline. This body of very saline to briny water may be a lens; many wells or test holes drilled within the area underlain by the mound re-entered fresh to moderately saline water at depths of 8,000 to 15,000 feet below lam surface.

Regional Supplement to the Corps of Engineers Wetland Delineation Manual: Arid West Region (Version 2.0)

DTIC Science & Technology

2008-09-01

23 Table 5. Example of the Prevalence Index using the same data as in Table 4. .................................25 Table 6. Proportion of fibers ...Mountains in Washington, Oregon, and southern Idaho. Much of the subregion is covered by deposits of loess, volcanic ash, and basalt . The climate is semi...usually underlain by an impermeable layer such as a hardpan, claypan, or basalt . Vernal pools often fill and empty several times during the rainy

Permafrost thaw in a nested groundwater-flow system

USGS Publications Warehouse

McKenzie, Jeffery M.; Voss, Clifford I.

2013-01-01

Groundwater flow in cold regions containing permafrost accelerates climate-warming-driven thaw and changes thaw patterns. Simulation analyses of groundwater flow and heat transport with freeze/thaw in typical cold-regions terrain with nested flow indicate that early thaw rate is particularly enhanced by flow, the time when adverse environmental impacts of climate-warming-induced permafrost loss may be severest. For the slowest climate-warming rate predicted by the Intergovernmental Panel on Climate Change (IPCC), once significant groundwater flow begins, thick permafrost layers can vanish in several hundred years, but survive over 1,000 years where flow is minimal. Large-scale thaw depends mostly on the balance of heat advection and conduction in the supra-permafrost zone. Surface-water bodies underlain by open taliks allow slow sub-permafrost flow, with lesser influence on regional thaw. Advection dominance over conduction depends on permeability and topography. Groundwater flow around permafrost and flow through permafrost impact thaw differently; the latter enhances early thaw rate. Air-temperature seasonality also increases early thaw. Hydrogeologic heterogeneity and topography strongly affect thaw rates/patterns. Permafrost controls the groundwater/surface-water-geomorphology system; hence, prediction and mitigation of impacts of thaw on ecology, chemical exports and infrastructure require improved hydrogeology/permafrost characterization and understanding

Ancient Lavas in Shenandoah National Park near Luray, Virginia

USGS Publications Warehouse

Reed, John Calvin

1969-01-01

In the Blue Ridge Province of northern Virginia, Maryland, and southern Pennsylvania, Lower Cambrian beds are underlain by a thick sequence of greenstone and interbedded sedimentary rocks known as the Catoctin Formation. An area near Luray, Va., was studied to determine the thickness of the formation, its relationship to overlying and underlying rocks, and the original nature of the lavas from which the Catoctin greenstone was derived. There the Catoctin Formation lies unconformably on granitic rocks. Its basal sedimentary layer ranges from a few inches to 150 feet in thickness and contains pebbles of underlying basement rocks. The erosion surface beneath the Catoctin is irregular, and in several places, hills as much as 1,000 feet high were buried beneath the Catoctin lavas. No important time break is indicated between the deposition of the Catoctin Formation and the overlying Cambrian sediments. The original Catoctin lavas were basaltic and were probably normal plateau basalts. Columnar joints, amygdules, sedimentary dikes, flow breccias low-dipping primary joints, and other primary structures are well preserved.

Lateral variation in crustal and mantle structure in Bay of Bengal based on surface wave data

NASA Astrophysics Data System (ADS)

Kumar, Amit; Mukhopadhyay, Sagarika; Kumar, Naresh; Baidya, P. R.

2018-01-01

Surface waves generated by earthquakes that occurred near Sumatra, Andaman-Nicobar Island chain and Sunda arc are used to estimate crustal and upper mantle S wave velocity structure of Bay of Bengal. Records of these seismic events at various stations located along the eastern coast of India and a few stations in the north eastern part of India are selected for such analysis. These stations lie within regional distance of the selected earthquakes. The selected events are shallow focused with magnitude greater than 5.5. Data of 65, 37, 36, 53 and 36 events recorded at Shillong, Bokaro, Visakhapatnam, Chennai and Trivandrum stations respectively are used for this purpose. The ray paths from the earthquake source to the recording stations cover different parts of the Bay of Bengal. Multiple Filtering Technique (MFT) is applied to compute the group velocities of surface waves from the available data. The dispersion curves thus obtained for this data set are within the period range of 15-120 s. Joint inversion of Rayleigh and Love wave group velocity is carried out to obtain the subsurface information in terms of variation of S wave velocity with depth. The estimated S wave velocity at a given depth and layer thickness can be considered to be an average value for the entire path covered by the corresponding ray paths. However, we observe variation in the value of S wave velocity and layer thickness from data recorded at different stations, indicating lateral variation in these two parameters. Thick deposition of sediments is observed along the paths followed by surface waves to Shillong and Bokaro stations. Sediment thickness keeps on decreasing as the surface wave paths move further south. Based on velocity variation the sedimentary layer is further divided in to three parts; on top lay unconsolidated sediment, underlain by consolidated sediment. Below this lies a layer which we consider as meta-sediments. The thickness and velocity of these layers decrease from north to south. The crustal material has higher velocity at the southern part compared to that at the northern part of Bay of Bengal indicating that it changes from more oceanic type in the southern part of the Bay to more continental type to its north. Both Moho and lithosphere - asthenosphere boundary (LAB) dips gently towards north. Thicknesses of both lithosphere and asthenosphere also increase in the same direction. The mantle structure shows complex variation from south to north indicating possible effect of repeated changes in type of tectonic activity in the Bay of Bengal.

Dissolved organic matter composition of Arctic rivers: Linking permafrost and parent material to riverine carbon

USGS Publications Warehouse

O’Donnell, Jonathan A.; Aiken, George R.; Swanson, David K.; Santosh, Panda; Butler, Kenna D.; Baltensperger, Andrew P.

2016-01-01

Recent climate change in the Arctic is driving permafrost thaw, which has important implications for regional hydrology and global carbon dynamics. Permafrost is an important control on groundwater dynamics and the amount and chemical composition of dissolved organic matter (DOM) transported by high-latitude rivers. The consequences of permafrost thaw for riverine DOM dynamics will likely vary across space and time, due in part to spatial variation in ecosystem properties in Arctic watersheds. Here we examined watershed controls on DOM composition in 69 streams and rivers draining heterogeneous landscapes across a broad region of Arctic Alaska. We characterized DOM using bulk dissolved organic carbon (DOC) concentration, optical properties, and chemical fractionation and classified watersheds based on permafrost characteristics (mapping of parent material and ground ice content, modeling of thermal state) and ecotypes. Parent material and ground ice content significantly affected the amount and composition of DOM. DOC concentrations were higher in watersheds underlain by fine-grained loess compared to watersheds underlain by coarse-grained sand or shallow bedrock. DOC concentration was also higher in rivers draining ice-rich landscapes compared to rivers draining ice-poor landscapes. Similarly, specific ultraviolet absorbance (SUVA254, an index of DOM aromaticity) values were highest in watersheds underlain by fine-grained deposits or ice-rich permafrost. We also observed differences in hydrophobic organic acids, hydrophilic compounds, and DOM fluorescence across watersheds. Both DOC concentration and SUVA254 were negatively correlated with watershed active layer thickness, as determined by high-resolution permafrost modeling. Together, these findings highlight how spatial variations in permafrost physical and thermal properties can influence riverine DOM.

Hydrogeological characterisation and prospect of basement Aquifers of Ibarapa region, southwestern Nigeria

NASA Astrophysics Data System (ADS)

Akanbi, Olanrewaju Akinfemiwa

2018-06-01

The present study involved the use of 82 geo-electric soundings, and the measurement of well inventory and conduct of yield tests in 19 wells across the various bedrock terrains of Ibarapa region of southwestern Nigeria. The aim is to proffer solution to the unsustainable yield of the available boreholes in order to effectively exploit the existing groundwater resource in the area. From the geological reports, the area is underlain by four principal crystalline rocks that include porphyritic granite, gneisses, amphibolite and migmatite. The geo-electric studies revealed that the degree and extent of development of the weathered-fractured component varied, leading to diversity in groundwater yield and in aquifer vulnerability to contamination. The thickness of the weathered layer is greater than 18 m in areas underlain by amphibolite and gneisses and less than 13 m within migmatite and porphyritic granite terrains. High groundwater yield greater than 70 m3/day was recorded in wells within the zones of rock contacts and in areas with large concentration of bedrock fractures and elevated locations across the various bedrock terrains. Aquifer vulnerability is low in amphibolite, high in granitic terrains, low to moderate in gneisses and high to moderate in migmatite. Also, wells' depths and terrain elevation have a moderate to strong indirect relationship with groundwater yield in most bedrock terrains, except in high topographic areas underlain by porphyritic granite. Therefore, there is need for modification of well depth in accordance with the terrain elevation and hydrogeological complexity of the weathered-fractured components of the variuos bedrock terrains, so as to ensure a sustainable groundwater yield.

Constraints on the anisotropic contributions to velocity discontinuities at ∼60 km depth beneath the Pacific

PubMed Central

Harmon, Nicholas

2017-01-01

Abstract Strong, sharp, negative seismic discontinuities, velocity decreases with depth, are observed beneath the Pacific seafloor at ∼60 km depth. It has been suggested that these are caused by an increase in radial anisotropy with depth, which occurs in global surface wave models. Here we test this hypothesis in two ways. We evaluate whether an increase in surface wave radial anisotropy with depth is robust with synthetic resolution tests. We do this by fitting an example surface wave data set near the East Pacific Rise. We also estimate the apparent isotropic seismic velocity discontinuities that could be caused by changes in radial anisotropy in S‐to‐P and P‐to‐S receiver functions and SS precursors using synthetic seismograms. We test one model where radial anisotropy is caused by olivine alignment and one model where it is caused by compositional layering. The result of our surface wave inversion suggests strong shallow azimuthal anisotropy beneath 0–10 Ma seafloor, which would also have a radial anisotropy signature. An increase in radial anisotropy with depth at 60 km depth is not well‐resolved in surface wave models, and could be artificially observed. Shallow isotropy underlain by strong radial anisotropy could explain moderate apparent velocity drops (<6%) in SS precursor imaging, but not receiver functions. The effect is diminished if strong anisotropy also exists at 0–60 km depth as suggested by surface waves. Overall, an increase in radial anisotropy with depth may not exist at 60 km beneath the oceans and does not explain the scattered wave observations. PMID:29097907

Constraints on the anisotropic contributions to velocity discontinuities at ∼60 km depth beneath the Pacific.

PubMed

Rychert, Catherine A; Harmon, Nicholas

2017-08-01

Strong, sharp, negative seismic discontinuities, velocity decreases with depth, are observed beneath the Pacific seafloor at ∼60 km depth. It has been suggested that these are caused by an increase in radial anisotropy with depth, which occurs in global surface wave models. Here we test this hypothesis in two ways. We evaluate whether an increase in surface wave radial anisotropy with depth is robust with synthetic resolution tests. We do this by fitting an example surface wave data set near the East Pacific Rise. We also estimate the apparent isotropic seismic velocity discontinuities that could be caused by changes in radial anisotropy in S-to-P and P-to-S receiver functions and SS precursors using synthetic seismograms. We test one model where radial anisotropy is caused by olivine alignment and one model where it is caused by compositional layering. The result of our surface wave inversion suggests strong shallow azimuthal anisotropy beneath 0-10 Ma seafloor, which would also have a radial anisotropy signature. An increase in radial anisotropy with depth at 60 km depth is not well-resolved in surface wave models, and could be artificially observed. Shallow isotropy underlain by strong radial anisotropy could explain moderate apparent velocity drops (<6%) in SS precursor imaging, but not receiver functions. The effect is diminished if strong anisotropy also exists at 0-60 km depth as suggested by surface waves. Overall, an increase in radial anisotropy with depth may not exist at 60 km beneath the oceans and does not explain the scattered wave observations.

High-resolution electrical resistivity and aeromagnetic imaging reveal the causative fault of the 2009 Mw 6.0 Karonga, Malawi earthquake

NASA Astrophysics Data System (ADS)

Kolawole, F.; Atekwana, E. A.; Laó-Dávila, D. A.; Abdelsalam, M. G.; Chindandali, P. R.; Salima, J.; Kalindekafe, L.

2018-05-01

Seismic events of varying magnitudes have been associated with ruptures along unknown or incompletely mapped buried faults. The 2009 Mw 6.0 Karonga, Malawi earthquake caused a surface rupture length of 14-18 km along a single W-dipping fault [St. Mary Fault (SMF)] on the hanging wall of the North Basin of the Malawi Rift. Prior to this earthquake, there was no known surface expression or knowledge of the presence of this fault. Although the earthquake damage zone is characterized by surface ruptures and coseismic liquefaction-induced sand blows, the origin of the causative fault and the near-surface structure of the rupture zone are not known. We used high-resolution aeromagnetic and electrical resistivity data to elucidate the relationship between surface rupture locations and buried basement structures. We also acquired electrical resistivity tomography (ERT) profiles along and across the surface rupture zone to image the near-surface structure of the damaged zone. We applied mathematical derivative filters to the aeromagnetic data to enhance basement structures underlying the rupture zone and surrounding areas. Although several magnetic lineaments are visible in the basement, mapped surface ruptures align with a single 37 km long, 148°-162°—striking magnetic lineament, and is interpreted as the ruptured normal fault. Inverted ERT profiles reveal three regional geoelectric layers which consist of 15 m thick layer of discontinuous zones of high and low resistivity values, underlain by a 27 m thick zone of high electrical resistivity (up to 100 Ω m) and a basal layer of lower resistivity (1.0-6.0 Ω m) extending from 42 m depth downwards (the maximum achieved depth of investigation). The geoelectric layers are truncated by a zone of electrical disturbance (electrical mélange) coinciding with areas of coseismic surface rupturing and sediment liquefaction along the ruptured. Our study shows that the 2009 Karonga earthquake was associated with the partial rupture of the buried SMF, and illuminates other potential seismogenic buried faults within the Karonga area of the North Basin. Although our electrical surveys were conducted 6 yr after the 2009 Karonga earthquake, we observe that near-surface lenses of electrically conductive sediments imaged by our ERT profiles, coincide with zones of coseismic surface rupture and liquefaction sand blows. We suggest that the presence of these preserved near-surface lenses of potentially water-saturated sand pose potential hazard in the event of a future earthquake in the area. In addition, our ERT profiles reveal structures that could represent relics of previous earthquake events along the SMF. In addition, our study demonstrates that the integration of ERT and aeromagnetic data can be very useful in illuminating seismogenic buried faults, thereby significantly improving seismic hazard analysis in tectonically active areas.

Lithospheric Velocity Structure of the Anatolain plateau-Caucasus-Caspian Regions

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

Gok, R; Mellors, R J; Sandvol, E

Anatolian Plateau-Caucasus-Caspian region is an area of complex structure accompanied by large variations in seismic wave velocities. Despite the complexity of the region little is known about the detailed lithospheric structure. Using data from 29 new broadband seismic stations in the region, a unified velocity structure is developed using teleseismic receiver functions and surface waves. Love and Rayleigh surface waves dispersion curves have been derived from event-based analysis and ambient-noise correlation. We jointly inverted the receiver functions with the surface wave dispersion curves to determine absolute shear wave velocity and important discontinuities such as sedimentary layer, Moho, lithospheric-asthenospheric boundary. Wemore » combined these new station results with Eastern Turkey Seismic Experiment results (29 stations). Caspian Sea and Kura basin underlained by one of the thickest sediments in the world. Therefore, short-period surface waves are observed to be very slow. The strong crustal multiples in receiver functions and the slow velocities in upper crust indicate the presence of thick sedimentary unit (up to 20 km). Crustal thickness varies from 34 to 52 km in the region. The thickest crust is in Lesser Caucasus and the thinnest is in the Arabian Plate. The lithospheric mantle in the Greater Caucasus and the Kura depression is faster than the Anatolian Plateau and Lesser Caucasus. This possibly indicates the presence of cold lithosphere. The lower crust is slowest in the northeastern part of the Anatolian Plateau where Holocene volcanoes are located.« less

Application of 2D electrical resistivity imaging and cone penetration test (CPT) to assess the harzadous effect of near surface water on foundations in Lagos Nigeria

NASA Astrophysics Data System (ADS)

Adewoyin, O. O.; Joshua, E. O.; Akinyemi, M. L.; Omeje, M.; Joel, E. S.

2017-05-01

Adequate information on the condition of the subsurface is very important for site evaluation for engineering purposes. In this study two dimensional (2D) geoelectrical resistivity survey and cone penetration tests were conducted to study the hazardous effect of excess near surface water on the foundation of building in a reclaimed land located at Victoria Island area of Lagos State. The results of the inverted 2D geoelectrical resistivity data revealed three distinct geoelectrical layers characterized by low to moderate electrical resistivity of 2.23 and 129Ωm and 9.46 to 636Ωm respectively. The topsoil is characterized by wet sandy soil, which is underlain by sandy clay and banded at the below by a geologic formation of low resistivity which is suspected to be clay. The clay material may be responsible for the excess water retention observed in the area. The CPT method on the other hand revealed a geological formation of low resistance to penetration between 2-3 kg/cm2 from the topsoil to a depth of 7 m, which may be the effect of excess water in the near surface. This study revealed that the foundation of building may not be founded directly on the soil in any reclaimed land as this may result in collapse as a result of upward migration of water to the near surface.

Pore Pressure Distribution and Flank Instability in Hydrothermally Altered Stratovolcanoes

NASA Astrophysics Data System (ADS)

Ball, J. L.; Taron, J.; Hurwitz, S.; Reid, M. E.

2015-12-01

Field and geophysical investigations of stratovolcanoes with long-lived hydrothermal systems commonly reveal that initially permeable regions (such as brecciated layers of pyroclastic material) can become both altered and water-bearing. Hydrothermal alteration in these regions, including clay formation, can turn them into low-permeability barriers to fluid flow, which could increase pore fluid pressures resulting in flank slope instability. We examined elevated pore pressure conditions using numerical models of hydrothermal flow in stratovolcanoes, informed by geophysical data about internal structures and deposits. Idealized radially symmetric meshes were developed based on cross-sectional profiles and alteration/permeability structures of Cascade Range stratovolcanoes. We used the OpenGeoSys model to simulate variably saturated conditions in volcanoes heated only by regional heat fluxes, as well as 650°C intrusions at two km depth below the surface. Meteoric recharge was estimated from precipitation rates in the Cascade Range. Preliminary results indicate zones of elevated pore pressures form: 1) where slopes are underlain by continuous low-permeability altered layers, or 2) when the edifice has an altered core with saturated, less permeable limbs. The first scenario might control shallow collapses on the slopes above the altered layers. The second could promote deeper flank collapses that are initially limited to the summit and upper slopes, but could progress to the core of an edifice. In both scenarios, pore pressures can be further elevated by shallow intrusions, or evolve over longer time scales under forcing from regional heat flux. Geometries without confining low-permeability layers do not show these pressure effects. Our initial scenarios use radially symmetric models, but we are also simulating hydrothermal flow under real 3D geometries with asymmetric subsurface structures (Mount Adams). Simulation results will be used to inform 3D slope-stability models.

Distribution and Characteristics of Boulder Halos at High Latitudes on Mars: Ground Ice and Surface Processes Drive Surface Reworking

NASA Astrophysics Data System (ADS)

Levy, J. S.; Fassett, C. I.; Rader, L. X.; King, I. R.; Chaffey, P. M.; Wagoner, C. M.; Hanlon, A. E.; Watters, J. L.; Kreslavsky, M. A.; Holt, J. W.; Russell, A. T.; Dyar, M. D.

2018-02-01

Boulder halos are circular arrangements of clasts present at Martian middle to high latitudes. Boulder halos are thought to result from impacts into a boulder-poor surficial unit that is rich in ground ice and/or sediments and that is underlain by a competent substrate. In this model, boulders are excavated by impacts and remain at the surface as the crater degrades. To determine the distribution of boulder halos and to evaluate mechanisms for their formation, we searched for boulder halos over 4,188 High Resolution Imaging Science Experiment images located between 50-80° north and 50-80° south latitude. We evaluate geological and climatological parameters at halo sites. Boulder halos are about three times more common in the northern hemisphere than in the southern hemisphere (19% versus 6% of images) and have size-frequency distributions suggesting recent Amazonian formation (tens to hundreds of millions of years). In the north, boulder halo sites are characterized by abundant shallow subsurface ice and high thermal inertia. Spatial patterns of halo distribution indicate that excavation of boulders from beneath nonboulder-bearing substrates is necessary for the formation of boulder halos, but that alone is not sufficient. Rather, surface processes either promote boulder halo preservation in the north or destroy boulder halos in the south. Notably, boulder halos predate the most recent period of near-surface ice emplacement on Mars and persist at the surface atop mobile regolith. The lifetime of observed boulders at the Martian surface is greater than the lifetime of the craters that excavated them. Finally, larger minimum boulder halo sizes in the north indicate thicker icy soil layers on average throughout climate variations driven by spin/orbit changes during the last tens to hundreds of millions of years.

Environmental Assessment: Implementation of the Tyndall Air Force Base Integrated Natural Resources Management Plan

DTIC Science & Technology

2006-04-01

3-21 TPA060050033/TYNDALLINRMPEAFINAL.DOC VI Acronyms and Abbreviations ACM asbestos-containing materials ...Inventory FONPA Finding of No Practicable Alternative FONSI Finding of No Significant Impact HAZMO Hazardous Materials Management Office ICRMP...land surface (bls) by unconsolidated sands and clayey sands deposited since the Pliocene age. This material is relatively permeable and is underlain

Eogenetic siderite as an indicator for fluctuations in sedimentation rate in the Oligocene Boom Clay Formation (Belgium)

NASA Astrophysics Data System (ADS)

Laenen, B.; De Craen, M.

2004-01-01

Horizons with septarian concretions are a salient feature of the marine Boom Clay Formation. At most horizons, the concretions consist of ferroan calcite with variable amounts of pyrite, but at stratigraphic level S60 they also contain siderite. S60 is situated at the centre of an intensely bioturbated zone that is underlain by a pyrite-rich layer. Furthermore, the enclosing clay is strongly enriched in iron, manganese and phosphorous. The sedimentological and chemical zoning is indicative for low sedimentation rates, which allowed the concentration of iron in the aerobic zone of the sediment. Concentration of iron was the prerequisite for the formation of the siderite-containing concretions. The co-precipitation with pyrite is an argument for a formation in the sulphate reduction zone, and is indicative for a high rate of iron-reduction. The latter was due to the rapid burial of the iron-enriched layer below the redox boundary. The abrupt fluctuations in sedimentation rate were a response to the maximum flooding event of the second Rupelian third-order relative sea-level cycle, which caused a brief pushback of the detrital sediment wedge to its source areas. As this response is logically explained by the general sequence stratigraphic model [Spec. Publ.-Soc. Econ. Paleontol. Mineral. 42 (1988) 109], early diagenetic siderite may be widespread at maximum flooding surfaces in rapidly prograding marine mudstones.

Effects of local factors and climate on permafrost conditions and distribution in Beiluhe basin, Qinghai-Tibet Plateau, China.

PubMed

Yin, Guoan; Niu, Fujun; Lin, Zhanju; Luo, Jing; Liu, Minghao

2017-03-01

Beiluhe basin is underlain by warm and ice-rich permafrost, and covered by vegetation and soils characteristic of the Qinghai-Tibet Plateau. A field monitoring network was established to investigate permafrost conditions and to assess potential impacts of local factors and climate change. This paper describes the spatial variations in permafrost conditions from instrumented boreholes, controlling environmental factors, and recent thermal evolution of permafrost in the basin. The study area was divided into 10 ecotypes using satellite imagery based classification. The field investigations and cluster analysis of ground temperatures indicated that permafrost underlies most of the ground in swamp meadow, undisturbed alpine meadow, degrading alpine meadow, and desert alpine grassland, but is absent in other cover types. Permafrost-ecotope relations examined over a 2-year (2014-2016) period indicated that: (i) ground surface temperatures varied largely among ecotopes; (ii) annual mean ground temperatures ranged from -1.5 to 0°C in permafrost, indicating sensitive permafrost conditions; (iii) active-layer thicknesses ranged from 1.4m to 3.4m; (iv) ground ice content at the top of permafrost is high, but the active-layer soil is relatively dry. Long-term climate warming has driven thermal changes to permafrost, but ground surface characteristics and soil moisture content strongly influence the ground thermal state. These factors control local-scale spatial variations in permafrost conditions. The warm permafrost in the basin is commonly in thermal disequilibrium, and is sensitive to future climate change. Active-layer thicknesses have increased by at least 42cm and the mean annual ground temperatures have increased by up to 0.2°C in the past 10years over the basin. A permafrost distribution map was produced based on ecotypes, suggesting that permafrost underlies 64% of the study region. Copyright © 2017 Elsevier B.V. All rights reserved.

A preliminary summary of a seismic-refraction survey in the vicinity of the Tonto Forest Observatory, Arizona

USGS Publications Warehouse

Roller, J.C.; Jackson, W.H.; Warren, D.H.; Healy, J.H.

1964-01-01

The U.S. Geological Survey complete d a seismic-refraction survey in the vicinity of the Tonto Forest Seismological Observatory (T.F.S.O.) in April and May 1964. More than 1200 km of reversed profiles were surveyed to determine the crustal structure and crustal and upper mantle velocities in this area. The purpose of this work was to provide information on wave-propagation paths of seismic events recorded at T.F.S.O. and to improve the performance of the Observatory in locating and identifying these events. First arrivals indicate that the Mohorovicic discontinuity dips to the northeast by as much as 6 degrees under T.F.S.O., and may even be displaced vertically by as much as 5 km immediately north of the Observatory near the boundary of the Basin and Range a n d t he Colorado Plateau Provinces. A preliminary examination of the first arrivals indicates that the crust at T.F.S.O. is at least 30 km thick and is made up of at least two seismic layers. A thin veneer at the surface with a velocity of approximately 4 km/sec is underlain by a layer with a velocity of approximately 5.9 km/sec to 6.1 km/sec. An intermediate layer with velocity of 6.6 to 7.0 km/sec is probably present in the lower crust, but is not revealed by first arrivals. The velocity of seismic waves in the upper mantle is about 7.9 km/sec.

High-frequency observations and source parameters of microearthquakes recorded at hard-rock sites

USGS Publications Warehouse

Cranswick, Edward; Wetmiller, Robert; Boatwright, John

1985-01-01

We have estimated the source parameters of 53 microearthquakes recorded in July 1983 which were aftershocks of the Miramichi, New Brunswick, earthquake that occurred on 9 January 1982. These events were recorded by local three-component digital seismographs at 400 sps/component from 2-Hz velocity transducers sited directly on glacially scoured crystalline basement outcrop. Hypocentral distances are typically less than 5 km, and the hypocenters and the seven digital seismograph stations established all lie essentially within the boundaries of a granitic pluton that encompasses the faults that ruptured during the main shock and major aftershocks. The P-wave velocity is typically 5 km/sec at the surface and at least 6 km/sec at depths greater than about 1 km.The events have S-wave corner frequencies in the band 10 to 40 Hz, and the calculated Brune model seismic moments range from 1015 to 1018 dyne-cm. The corresponding stress drops are generally less than 1.0 bars, but there is considerable evidence that the seismic-source signals have been modified by propagation and/or site-effects. The data indicate: (a) there is a velocity discontinuity at 0.5 km depth; (b) the top layer has strong scattering/attenuating properties; (c) some source-receiver paths differentiate the propagated signal; (d) there is a hard-rock-site P-wave “fmax” between 50 and 100 Hz; and (e) some hard-rock sites are characterized by P-wave resonance frequencies in the range 50 to 100 Hz. Comparison of this dataset with the January 1982 New Brunswick digital seismograms which were recorded at sites underlain by several meters of low-velocity surface sediments suggests that some of the hard-rock-site phenomena listed above can be explained in terms of a layer-over-a-half-space model. For microearthquakes, this result implies that spectrally determined source dimension scales with site dimension (thickness of the layer). More generally, it emphasizes that it is very difficult to accurately observe the details of seismogenic processes from the earth's surface.

The impact of periglacial cover beds on runoff generation in a small spring catchment, Ore Mountains

NASA Astrophysics Data System (ADS)

Heller, Katja; Hübner, Rico; Kleber, Arno

2010-05-01

The knowledge of hillslope processes is essential to improve pollutant research and flood prediction. Relic periglacial covers are widespread on slopes of the central European low mountain ranges. Cover beds are assumed to be an important control factor for subcutaneous water flow paths. Periglacial cover beds originated by solifluction, kryoturbation and accumulation of loess during Pleistocene times. Differences in bulk density, sediment type, as well as structure and rate of coarse clasts in the layers result in vertical disparity in hydraulic conductivity (anisotropy), leading to interflow. This hypothesis has been testing in an ongoing study in a small spring catchment (6 ha) in the eastern Ore Mountains, south-eastern Germany, since November 2007. The study area is underlain by gneiss and is formed as a slope hollow. The cover beds consist of a 3-layer complex with upper layer, intermediate layer and basal layer. Soil water tension within the layers is measured with 76 recording tensiometers. Electrical resistivity tomography was used to monitor the spatial dispersal of soil moisture. Results of hydrometrical measurements and of electrical resistivity surveys will be described and new findings on slope water dynamics will be presented.

Interpretation of shallow electrical features from electromagnetic and magnetotelluric surveys at Mount Hood, Oregon

NASA Astrophysics Data System (ADS)

Goldstein, N. E.; Mozley, E.; Wilt, M.

1982-04-01

A magnetotelluric survey, with a reference magnetometer for noise cancellation, was conducted at accessible locations around Mount Hood, Oregon. Thirty-eight tensor magnetotelluric (MT) and remote telluric stations were set up in clusters around the volcano except for the northwest quadrant, a wilderness area. Because of limited access, station locations were restricted to elevations below 1829 m, or no closer than 5 km from the 3424-m summit. On the basis of the MT results, three areas were later investigated in more detail using a large-moment, controlled-source electromagnetic (EM) system developed at Lawrence Berkeley Laboratory and the University of California at Berkeley. One-dimensional interpretations of EM and MT data on the northeast flank of the mountain near the Cloud Cap eruptive center and on the south flank near Timberline Lodge show a similar subsurface resistivity pattern: a resistive surface layer 400-700 m thick, underlain by a conductive layer with variable thickness and resistivity of <20 ohm m. It is speculated that the surface layer consists of volcanics partially saturated with cold meteoric water. The underlying conductive zone is presumed to be volcanics saturated with water heated within the region of the central conduit and, possibly, at the Cloud Cap side vent. This hypothesis is supported by the existence of warm springs at the base of the mountain, most notably Swim Warm Springs on the south flank, and by several geothermal test wells, one of which penetrates the conductor south of Timberline Lodge. The MT data typically gave a shallower depth to the conductive zone than did the EM data. This is attributed, in part, to the error inherent in one-dimensional MT interpretations of geologically or topographically complex areas. On the other hand, MT was better for resolving the thickness of the conductive layer and deeper structure. The MT data show evidence for a moderately conductive north-south structure on the south flank below the Timberline Lodge and for a broad zone of late Tertiary intrusives concealed on the southeast flank.

INTERPRETATION OF SHALLOW ELECTRICAL FEATURES FROM ELECTROMAGNETIC AND MAGNETOTELLURIC SURVEYS AT MOUNT HOOD, OREGON

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

Wilt, M.; Goldstein, N.E.; Mozley, E.

1981-04-01

A magnetotelluric survey, with a reference magnetometer for noise cancellation, was conducted at accessible locations around Mount Hood, Oregon. Thirty-eight tensor magnetotelluric (MT) and remote telluric stations were set up in clusters around the volcano except for the northwest quadrant, a wilderness area. Because of limited access, station locations were restricted to elevations below 1829 m, or no closer than 5 km from the 3424-m summit. On the basis of the MT results, three areas were later investigated in more detail using a large-moment, controlled-source electromagnetic (EM) system developed at Lawrence Berkeley Laboratory and the University of California at Berkeley.more » One-dimensional interpretations of EM and MT data on the northeast flank of the mountain near the Cloud Cap eruptive center and on the south flank near Timberline Lodge show a similar subsurface resistivity pattern: a resistive surface layer 400-700 m thick, underlain by a conductive layer with variable thickness and resistivity of <20 ohm m. It is speculated that the surface layer consists of volcanics partially saturated with cold meteoric water. The underlying conductive zone is presumed to be volcanics saturated with water heated within the region of the central conduit and, possibly, at the Cloud Cap side vent. This hypothesis is supported by the existence of warm springs at the base of the mountain, most notably Swim Warm Springs on the south flank, and by several geothermal test wells, one of which penetrates the conductor south of Timberline Lodge. The MT data typically gave a shallower depth to the conductive zone than did the EM data. This is attributed, in part, to the error inherent in one-dimensional MT interpretations of geologically or topographically complex areas. On the other hand, MT was better for resolving the thickness of the conductive layer and deeper structure. The MT data show evidence for a moderately conductive north-south structure on the south flank below the Timberline Lodge and for a broad zone of late Tertiary intrusives concealed on the southeast flank.« less

Characterization of major lithologic units underlying the lower American River using water-borne continuous resistivity profiling, Sacramento, California, June 2008

USGS Publications Warehouse

Ball, Lyndsay B.; Teeple, Andrew

2013-01-01

The levee system of the lower American River in Sacramento, California, is situated above a mixed lithology of alluvial deposits that range from clay to gravel. In addition, sand deposits related to hydraulic mining activities underlie the floodplain and are preferentially prone to scour during high-flow events. In contrast, sections of the American River channel have been observed to be scour resistant. In this study, the U.S. Geological Survey, in cooperation with the U.S. Army Corps of Engineers, explores the resistivity structure of the American River channel to characterize the extent and thickness of lithologic units that may impact the scour potential of the area. Likely lithologic structures are interpreted, but these interpretations are non-unique and cannot be directly related to scour potential. Additional geotechnical data would provide insightful data on the scour potential of certain lithologic units. Additional interpretation of the resistivity data with respect to these results may improve interpretations of lithology and scour potential throughout the American River channel and floodplain. Resistivity data were collected in three profiles along the American River using a water-borne continuous resistivity profiling technique. After processing and modeling these data, inverted resistivity profiles were used to make interpretations about the extent and thickness of possible lithologic units. In general, an intermittent high-resistivity layer likely indicative of sand or gravel deposits extends to a depth of around 30 feet (9 meters) and is underlain by a consistent low-resistivity layer that likely indicates a high-clay content unit that extends below the depth of investigation (60 feet or 18 meters). Immediately upstream of the Watt Avenue Bridge, the high-resistivity layer is absent, and the low-resistivity layer extends to the surface where a scour-resistant layer has been previously observed in the river bed.

Controls on selenium distribution and mobilization in an irrigated shallow groundwater system underlain by Mancos Shale, Uncompahgre River Basin, Colorado, USA

USGS Publications Warehouse

Mills, Taylor J.; Mast, M. Alisa; Thomas, Judith C.; Keith, Gabrielle L.

2016-01-01

Elevated selenium (Se) concentrations in surface water and groundwater have become a concern in areas of the Western United States due to the deleterious effects of Se on aquatic ecosystems. Elevated Se concentrations are most prevalent in irrigated alluvial valleys underlain by Se-bearing marine shales where Se can be leached from geologic materials into the shallow groundwater and surface water systems. This study presents groundwater chemistry and solid-phase geochemical data from the Uncompahgre River Basin in Western Colorado, an irrigated alluvial landscape underlain by Se-rich Cretaceous marine shale. We analyzed Se species, major and trace elements, and stable nitrogen and oxygen isotopes of nitrate in groundwater and aquifer sediments to examine processes governing selenium release and transport in the shallow groundwater system. Groundwater Se concentrations ranged from below detection limit (< 0.5 μg L− 1) to 4070 μg L− 1, and primarily are controlled by high groundwater nitrate concentrations that maintain oxidizing conditions in the aquifer despite low dissolved oxygen concentrations. High nitrate concentrations in non-irrigated soils and nitrate isotopes indicate nitrate is largely derived from natural sources in the Mancos Shale and alluvial material. Thus, in contrast to areas that receive substantial NO3 inputs through inorganic fertilizer application, Se mitigation efforts that involve limiting NO3 application might have little impact on groundwater Se concentrations in the study area. Soluble salts are the primary source of Se to the groundwater system in the study area at-present, but they constitute a small percentage of the total Se content of core material. Sequential extraction results indicate insoluble Se is likely composed of reduced Se in recalcitrant organic matter or discrete selenide phases. Oxidation of reduced Se species that constitute the majority of the Se pool in the study area could be a potential source of Se in the future as soluble salts are progressively depleted.

Controls on selenium distribution and mobilization in an irrigated shallow groundwater system underlain by Mancos Shale, Uncompahgre River Basin, Colorado, USA.

PubMed

Mills, Taylor J; Mast, M Alisa; Thomas, Judith; Keith, Gabrielle

2016-10-01

Elevated selenium (Se) concentrations in surface water and groundwater have become a concern in areas of the Western United States due to the deleterious effects of Se on aquatic ecosystems. Elevated Se concentrations are most prevalent in irrigated alluvial valleys underlain by Se-bearing marine shales where Se can be leached from geologic materials into the shallow groundwater and surface water systems. This study presents groundwater chemistry and solid-phase geochemical data from the Uncompahgre River Basin in Western Colorado, an irrigated alluvial landscape underlain by Se-rich Cretaceous marine shale. We analyzed Se species, major and trace elements, and stable nitrogen and oxygen isotopes of nitrate in groundwater and aquifer sediments to examine processes governing selenium release and transport in the shallow groundwater system. Groundwater Se concentrations ranged from below detection limit (<0.5μgL(-1)) to 4070μgL(-1), and primarily are controlled by high groundwater nitrate concentrations that maintain oxidizing conditions in the aquifer despite low dissolved oxygen concentrations. High nitrate concentrations in non-irrigated soils and nitrate isotopes indicate nitrate is largely derived from natural sources in the Mancos Shale and alluvial material. Thus, in contrast to areas that receive substantial NO3 inputs through inorganic fertilizer application, Se mitigation efforts that involve limiting NO3 application might have little impact on groundwater Se concentrations in the study area. Soluble salts are the primary source of Se to the groundwater system in the study area at-present, but they constitute a small percentage of the total Se content of core material. Sequential extraction results indicate insoluble Se is likely composed of reduced Se in recalcitrant organic matter or discrete selenide phases. Oxidation of reduced Se species that constitute the majority of the Se pool in the study area could be a potential source of Se in the future as soluble salts are progressively depleted. Published by Elsevier B.V.

Determination of geohydrologic framework and extent of d- water contamination using surface geophysical techniques at Picatinny Arsenal, New Jersey

USGS Publications Warehouse

Lacombe, Pierre

1986-01-01

Seismic-refraction, electric-resistivity sounding, and electromagnetic conductivity techniques were used to determine the geohydrologic framework and extent of groundwater contamination at Picatinny Arsenal in northern New Jersey. The area studied encompasses about 4 sq mi at the southern end of the Arsenal. The bedrock surface beneath the glacial sediments was delineated by seismic-refraction techniques. Data for 12 seismic lines were collected using a 12-channel engineering seismograph. Competent bedrock crops out on both sides of the valley, but is about 290 ft below land surface in the deepest part of the topographic valley. Where the exposed bedrock surface forms steep slopes on the valley side, it remains steep below the valley fill. Likewise, gentle bedrock valley slopes have gentle subsurface slopes. The deepest part of the bedrock valley is along the southern extension of the Green Pond fault. The electric-resistivity sounding technique was used to determine the sediment types. Data were collected from four sites using the offset Wenner electrode configuration. Below the surface layer, the sediments have apparent and computed resistivity values of 120 to 170 ohm-meters. These values correspond to a saturated fine-grained sediment such as silt or interbedded sand and clay. Groundwater contamination was by electromagnetic conductivity techniques using transmitting and receiving coils separated by 32.8 ft and 12 ft. Thirteen sites have apparent conductivity values exceeding 15 millimhos/m. Of these, seven sites indicate groundwater contamination from a variety of sources including a sanitary landfill, pyrotechnic testing ground, burning area, former domestic sewage field, salt storage facility, hazardous waste disposal lagoon, sewage treatment plant, and fertilizer storage shed. Three areas underlain by clay or muck are interpreted to be free of contamination. (Author 's abstract)

Dark gray soils on two-layered deposits in the north of Tambov Plain: Agroecology, properties, and diagnostics

NASA Astrophysics Data System (ADS)

Zaidelman, F. R.; Nikiforova, A. S.; Stepantsova, L. V.; Volokhina, V. P.

2012-05-01

Dark gray soils in the Tambov Plain are developed from the light-textured glaciofluvial deposits underlain by the calcareous loam. Their morphology, water regime, and productivity are determined by the depth of the slightly permeable calcareous loamy layer, relief, and the degree of gleyzation. The light texture of the upper layer is responsible for its weak structure, high density, the low content of productive moisture, and the low water-holding capacity. If the calcareous loam is at a depth of 100-130 cm, dark gray soils are formed; if it lies at a depth of 40-70 cm, temporary perched water appears in the profile, and dark gray contact-gleyed soils are formed. Their characteristic pedofeatures are skeletans in the upper layers, calcareous nodules in the loamy clay layer, and iron nodules in the podzolized humus and podzolic horizons. The appearance of Fe-Mn concretions is related to gleyzation. The high yield of winter cereals is shown to be produced on the dark gray soils; the yields of spring crops are less stable. Spring cereals should not be grown on the contact-gleyed dark gray soils.

Localized geohazards in West Texas, captured by multi-temporal Sentinel-1A/B interferometry

NASA Astrophysics Data System (ADS)

Kim, J. W.; Lu, Z.

2017-12-01

West Texas contains the Permian Basin and is particularly composed of three major geologic sedimentary basins: Delaware Basin, Central Basin Platform, and Midland Basin. Because the vast region was once covered by a shallow sea and had experienced long-lasting evaporation million years ago, the West Texas is underlain by a thick layer of water soluble rocks including the carbonate and evaporite rocks. In addition, the geologic composition provided abundant hydrocarbons in the depth of several kilometers, but the human activities exploiting the massive oil and gas from the subsurface made negative impacts on the stability of underground and ground surface. Most deformation and localized geohazards have been unnoticed by means of field measurements or remote sensing methods, because the West Texas is located in the low populated, remote region. The Sentinel-1A/B has continuously acquired the SAR imagery with a large swath of 250 km over the region, and its multi-temporal measurements can provide clues on what are really taking place on the ground surface, what are the causes to trigger the localized subsidence/uplift, and what should be done to prevent more severe disasters in the future. We have established an automated Sentinel-1A/B InSAR processing system on SMU supercomputer (Maneframe), its continuous monitoring will help us unveil the current status of deformation occurring in West Texas.

Quaternary bedrock erosion and landscape evolution in the Sør Rondane Mountains, East Antarctica: Reevaluating rates and processes

NASA Astrophysics Data System (ADS)

Matsuoka, Norikazu; Thomachot, Céline E.; Oguchi, Chiaki T.; Hatta, Tamao; Abe, Masahiro; Matsuzaki, Hiroyuki

2006-11-01

Rates and processes of rock weathering, soil formation, and mountain erosion during the Quaternary were evaluated in an inland Antarctic cold desert. The fieldwork involved investigations of weathering features and soil profiles for different stages after deglaciation. Laboratory analyses addressed chemistry of rock coatings and soils, as well as 10Be and 26Al exposure ages of the bedrock. Less resistant gneiss bedrock exposed over 1 Ma shows stone pavements underlain by in situ produced silty soils thinner than 40 cm and rich in sulfates, which reflect the active layer thickness, the absence of cryoturbation, and the predominance of salt weathering. During the same exposure period, more resistant granite bedrock has undergone long-lasting cavernous weathering that produces rootless mushroom-like boulders with a strongly Fe-oxidized coating. The red coating protects the upper surface from weathering while very slow microcracking progresses by the growth of sulfates. Geomorphological evidence and cosmogenic exposure ages combine to provide contrasting average erosion rates. No erosion during the Quaternary is suggested by a striated roche moutonnée exposed more than 2 Ma ago. Differential erosion between granite and gneiss suggests a significant lowering rate of desert pavements in excess of 10 m Ma - 1 . The landscape has been (on the whole) stable, but the erosion rate varies spatially according to microclimate, geology, and surface composition.

Use of the Biotic Ligand Model to predict metal toxicity to aquatic biota in areas of differing geology

USGS Publications Warehouse

Smith, Kathleen S.

2005-01-01

This work evaluates the use of the biotic ligand model (BLM), an aquatic toxicity model, to predict toxic effects of metals on aquatic biota in areas underlain by different rock types. The chemical composition of water, soil, and sediment is largely derived from the composition of the underlying rock. Geologic source materials control key attributes of water chemistry that affect metal toxicity to aquatic biota, including: 1) potentially toxic elements, 2) alkalinity, 3) total dissolved solids, and 4) soluble major elements, such as Ca and Mg, which contribute to water hardness. Miller (2002) compiled chemical data for water samples collected in watersheds underlain by ten different rock types, and in a mineralized area in western Colorado. He found that each rock type has a unique range of water chemistry. In this study, the ten rock types were grouped into two general categories, igneous and sedimentary. Water collected in watersheds underlain by sedimentary rock has higher mean pH, alkalinity, and calcium concentrations than water collected in watersheds underlain by igneous rock. Water collected in the mineralized area had elevated concentrations of calcium and sulfate in addition to other chemical constituents. Miller's water-chemistry data were used in the BLM (computer program) to determine copper and zinc toxicity to Daphnia magna. Modeling results show that waters from watersheds underlain by different rock types have characteristic ranges of predicted LC 50 values (a measurement of aquatic toxicity) for copper and zinc, with watersheds underlain by igneous rock having lower predicted LC 50 values than watersheds underlain by sedimentary rock. Lower predicted LC 50 values suggest that aquatic biota in watersheds underlain by igneous rock may be more vulnerable to copper and zinc inputs than aquatic biota in watersheds underlain by sedimentary rock. For both copper and zinc, there is a trend of increasing predicted LC 50 values with increasing dissolved organic carbon (DOC) concentrations. Predicted copper LC 50 values are extremely sensitive to DOC concentrations, whereas alkalinity appears to have an influence on zinc toxicity at alkalinities in excess of about 100 mg/L CaCO 3 . These findings show promise for coupling the BLM (computer program) with measured water-chemistry data to predict metal toxicity to aquatic biota in different geologic settings and under different scenarios. This approach may ultimately be a useful tool for mine-site planning, mitigation and remediation strategies, and ecological risk assessment.

Predicting Phosphorus Dynamics Across Physiographic Regions Using a Mixed Hortonian Non-Hortonian Hydrology Model

NASA Astrophysics Data System (ADS)

Collick, A.; Easton, Z. M.; Auerbach, D.; Buchanan, B.; Kleinman, P. J. A.; Fuka, D.

2017-12-01

Predicting phosphorus (P) loss from agricultural watersheds depends on accurate representation of the hydrological and chemical processes governing P mobility and transport. In complex landscapes, P predictions are complicated by a broad range of soils with and without restrictive layers, a wide variety of agricultural management, and variable hydrological drivers. The Soil and Water Assessment Tool (SWAT) is a watershed model commonly used to predict runoff and non-point source pollution transport, but is commonly only used with Hortonian (traditional SWAT) or non-Hortonian (SWAT-VSA) initializations. Many shallow soils underlain by a restricting layer commonly generate saturation excess runoff from variable source areas (VSA), which is well represented in a re-conceptualized version, SWAT-VSA. However, many watersheds exhibit traits of both infiltration excess and saturation excess hydrology internally, based on the hydrologic distance from the stream, distribution of soils across the landscape, and characteristics of restricting layers. The objective of this research is to provide an initial look at integrating distributed predictive capabilities that consider both Hortonian and Non-Hortonian solutions simultaneously within a single SWAT-VSA initialization. We compare results from all three conceptual watershed initializations against measured surface runoff and stream P loads and to highlight the model's ability to drive sub-field management of P. All three initializations predict discharge similarly well (daily Nash-Sutcliffe Efficiencies above 0.5), but the new conceptual SWAT-VSA initialization performed best in predicting P export from the watershed, while also identifying critical source areas - those areas generating large runoff and P losses at the sub field level. These results support the use of mixed Hortonian non-Hortonian SWAT-VSA initializations in predicting watershed-scale P losses and identifying critical source areas of P loss in landscapes with VSA hydrology.

Crustal structure along the geosciences transect from Altay to Altun Tagh

USGS Publications Warehouse

Wang, Y.-X.; Han, G.-H.; Jiang, M.; Yuan, X.-C.; Mooney, W.D.; Coleman, R.G.

2004-01-01

Based upon the P- and S-wave data acquired along the geoscience transect from Altay to Altun Tagh in Northwest China, the crustal structures of velocities and Poisson's ratio are determined. The crustal velocity structure features an obvious three-layer structure with velocities of 6. 0 ??? 6. 3km/s, 6. 3 ??? 6. 6km/s and 6.9 ??? 7. Okm/s from surface to depth, respectively. The crustal thickness along the. entire profile is mostly 50km with the thickest crust (56km) beneath the Altay and the thinnest (46km) beneath the Junggar basin. The velocities underlying Moho are 7.7 to 7.8km/s between the Tianshan and the Junggar basin, and 7.9 to 8.0km/s below the Altay Mountains and eastern margin of the Tarim basin. The southern half of the profile, including the eastern Tianshan Mountains and eastern margin of the Tarim basin, shows low P-wave velocities and ?? = 0. 25 to a depth, of 30km, which suggests a quartz-rich, granitic upper crustal composition. The northern half of the profile below the Altay Mountains and Junggar Accretional Belt has a higher Poisson's ratio of ?? = 0.26 ??? 0.27 to a depth of 30km, indicative of an intermediate crustal composition, The entire profile is underlain by a 15 to 30km thick high-velocity (6.9 ??? 7.0km/s; ?? = 0. 26 - 0.28) lower crustal layer that we interpret to have a bulk composition of mafic granulite. At the southern end of the profile a 5km-thick midcrustal low-velocity layer ( Vp, = 5.9km/s, ?? = 0.25) underlies the Tianshan and the region to the south, and may be indicative of granitic intrusive in Late Paleozoic.

Rapid runoff via shallow throughflow and deeper preferential flow in a boreal catchment underlain by frozen silt (Alaska, USA)

USGS Publications Warehouse

Koch, Joshua C.; Ewing, Stephanie A.; Striegl, Robert G.; McKnight, Diane M.

2013-01-01

In high-latitude catchments where permafrost is present, runoff dynamics are complicated by seasonal active-layer thaw, which may cause a change in the dominant flowpaths as water increasingly contacts mineral soils of low hydraulic conductivity. A 2-year study, conducted in an upland catchment in Alaska (USA) underlain by frozen, well-sorted eolian silt, examined changes in infiltration and runoff with thaw. It was hypothesized that rapid runoff would be maintained by flow through shallow soils during the early summer and deeper preferential flow later in the summer. Seasonal changes in soil moisture, infiltration, and runoff magnitude, location, and chemistry suggest that transport is rapid, even when soils are thawed to their maximum extent. Between June and September, a shift occurred in the location of runoff, consistent with subsurface preferential flow in steep and wet areas. Uranium isotopes suggest that late summer runoff erodes permafrost, indicating that substantial rapid flow may occur along the frozen boundary. Together, throughflow and deep preferential flow may limit upland boreal catchment water and solute storage, and subsequently biogeochemical cycling on seasonal to annual timescales. Deep preferential flow may be important for stream incision, network drainage development, and the release of ancient carbon to ecosystems

Ice sheets on plastically-yielding beds

NASA Astrophysics Data System (ADS)

Hewitt, Ian

2016-11-01

Many fast flowing regions of ice sheets are underlain by a layer of water-saturated sediments, or till. The rheology of the till has been the subject of some controversy, with laboratory tests suggesting almost perfectly plastic behaviour (stress independent of strain rate), but many models adopting a pseudo-viscous description. In this work, we consider the behaviour of glaciers underlain by a plastic bed. The ice is treated as a viscous gravity current, on a bed that allows unconstrained slip above a critical yield stress. This simplified description allows rapid sliding, and aims to investigate 'worst-case' scenarios of possible ice-sheet disintegration. The plastic bed results in an approximate ice-sheet geometry that is primarily controlled by force balance, whilst ice velocity is determined from mass conservation (rather than the other way around, as standard models would hold). The stability of various states is considered, and particular attention is given to the pace at which transitions between unstable states can occur. Finally, we observe that the strength of basal tills depends strongly on pore pressure, and combine the model with a description of subglacial hydrology. Implications for the present-day ice sheets in Greenland and Antarctica will be discussed. Funding: ERC Marie Curie FP7 Career Integration Grant.

Pits and Channels of Hebrus Valles

NASA Image and Video Library

2017-01-26

The drainages in this image are part of Hebrus Valles, an outflow channel system likely formed by catastrophic floods. Hebrus Valles is located in the plains of the Northern lowlands, just west of the Elysium volcanic region. Individual channels range from several hundred meters to several kilometers wide and form multi-threaded (anastamosing) patterns. Separating the channels are streamlined forms, whose tails point downstream and indicate that channel flow is to the north. The channels seemingly terminate in an elongated pit that is approximately 1875 meters long and 1125 meters wide. Using the shadow that the wall has cast on the floor of the pit, we can estimate that the pit is nearly 500 meters deep. The pit, which formed after the channels, exposes a bouldery layer below the dusty surface mantle and is underlain by sediments. Boulders several meters in diameter litter the slopes down into the pit. Pits such as these are of interest as possible candidate landing sites for human exploration because they might retain subsurface water ice (Schulze-Makuch et al. 2016, 6th Mars Polar Conf.) that could be utilized by future long-term human settlements. http://photojournal.jpl.nasa.gov/catalog/PIA11704

Potentiometric surfaces of the intermediate aquifer system, west-central Florida, September 2000

USGS Publications Warehouse

Duerr, A.D.

2001-01-01

The intermediate aquifer system underlies a 5,000-square-mile area within the Southwest Florida Water Management District including De Soto, Sarasota, Hardee, Manatee, and parts of Charlotte, Hillsborough, Highlands, Polk, and Lee Counties.  The intermediate aquifer system is overlain by the surficial aquifer system and is underlain by the Floridan aquifer system.  The intermediate aquifer system consists of layers of sand, shell, clay, calcareous clay, limestone, and dolomite of the Tamiami Formation and Hawthorn Group of Oligocene to Pleistocene age (Wingard and others, 1995).  The intermediate aquifer system contains one or more water-bearing units separated by discontinuous confining units.  The intermediate aquifer system is the principal source of potable water in the southwestern part of the study area and is widely used as a source of water where wells are open to the intermediate aquifer system or to both the intermediate and Floridan aquifer systems.  Yields of individual wells open to the intermediate aquifer system vary from a few gallons to several hundred gallons per minute.  The volume of water withdrawn from the intermediate aquifer system is considerably less than that withdrawn from the Floridan aquifer system in the study area (Duerr and others, 1988).

Evaluation on expansive performance of the expansive soil using electrical responses

NASA Astrophysics Data System (ADS)

Chu, Ya; Liu, Songyu; Bate, Bate; Xu, Lei

2018-01-01

Light structures, such as highways and railroads, built on expansive soils are prone to damages from the swelling of their underlain soil layers. Considerable amount of research has been conducted to characterize the swelling properties of expansive soils. Current swell characterization models, however, are limited by lack of standardized tests. Electrical methods are non-destructive, and are faster and less expensive than the traditional geotechnical methods. Therefore, geo-electrical methods are attractive for defining soil characteristics, including the swelling behavior. In this study, comprehensive laboratory experiments were undertaken to measure the free swelling and electrical resistivity of the mixtures of commercial kaolinite and bentonite. The electrical conductivity of kaolinite-bentonite mixtures was measured by a self-developed four-electrode soil resistivity box. Increasing the free swelling rate of the kaolinite-bentonite mixtures (0.72 to 1 of porosity of soils samples) led to a reduction in the electrical resistivity and an increase in conductivity. A unique relationship between free swelling rate and normalized surface conductivity was constructed for expensive soils by eliminating influences of porosity and m exponent. Therefore, electrical response measurement can be used to characterize the free swelling rate of expensive soils.

Marine magnetotelluric inversion with an unstructured tetrahedral mesh

NASA Astrophysics Data System (ADS)

Usui, Yoshiya; Kasaya, Takafumi; Ogawa, Yasuo; Iwamoto, Hisanori

2018-05-01

The finite element method using an unstructured tetrahedral mesh is one of the most effective methods for the three-dimensional modelling of marine magnetotelluric data which are strongly affected by bathymetry, because it enables us to incorporate both small-scale and regional-scale bathymetry into a computational mesh with a practical number of elements. The authors applied a three-dimensional inversion scheme using mesh of this type to marine magnetotelluric problems for the first time and verified its applicability. Forward calculations for two bathymetry models demonstrated that the results obtained with an unstructured tetrahedral mesh are close to the reference solutions. To evaluate the forward calculation results, we developed a general TM-mode analytical formulation for a two-dimensional sinusoidal topography. Moreover, synthetic inversion test results confirmed that a three-dimensional inversion scheme with an unstructured tetrahedral mesh enables us to recover subseafloor resistivity structure properly even for a model including a land-sea boundary as well as seafloor undulations. The verified inversion scheme was subsequently applied to a set of marine magnetotelluric data observed around the Iheya North Knoll, the middle Okinawa Trough. Three-dimensional modelling using a mesh with precise bathymetry demonstrated that the data observed around the Iheya North Knoll are strongly affected by bathymetry, especially by the sea-depth differences between the depression of the trough and the shallow East China Sea. The estimated resistivity structure under the knoll is characterized by a conductive surface layer underlain by a resistive layer. The conductive layer implies permeable pelagic/hemi-pelagic sediments, which are consistent with a previous seismological study. Furthermore, the conductive layer has a resistive part immediately below the knoll, which is regarded as the consolidated magma intrusion that formed the knoll. Furthermore, at depth of 10 km, we found that the resistor underneath the knoll extends to the southeast, implying that subseafloor resistivity under the Volcanic Arc Migration Phenomenon (VAMP) area is more resistive than the surroundings due to the presence of consolidated magma.

From Hills to Holes: How Climate Change and Mining are Altering Runoff Processes in Canada

NASA Astrophysics Data System (ADS)

Carey, S. K.

2015-12-01

Canadian environments are under considerable pressure from both climate and land-use change. While warming temperatures are widespread and amplified in the north, surface mining has resulted in large-scale landscape disturbance. How these changes affect catchment response is profound, fundamentally altering the cycling and delivery of water and geochemicals to the drainage network. In permafrost-underlain environments, coupled mass and energy processes control runoff response, and as ground thaw increases, new subsurface pathways become accessible while changing overall catchment storage. With surface mining, watersheds are altered such that they bare little resemblance to what existed prior to mining. In this presentation, data will be presented from long-term experiments exploring the impact of climate and mining on runoff processes in cold catchments using stable isotopes of water and associated hydrometric measurements. In southern Yukon, results from the Wolf Creek Research Basin highlights the influence of surface energy balances on controlling the timing and magnitude of flow response, with inter-annual variability largely driven by how atmospheric forcing interacts with permafrost-underlain areas of the catchment. In mountainous areas of southern British Columbia, surface mining reconfigures landscapes as valleys are filled with waste-rock. Mine-influenced catchments exhibit attenuated flows with delays in spring freshet and a more muted to precipitation. Stable isotopes in stream water suggests that both waste-rock and reference catchments are well mixed, however reference catchments are more responsive to enrichment and depletion events and that mine-influenced catchments had a heavier isotope signature than reference watersheds, suggesting enhanced influence of rainfall on recharge. In both cases, snow storage and release exerts considerable control on streamflow responses, and future changes in streamflow regimes will reflect both a changes in the snow regime and inherent catchment storage properties that are dynamic with time.

Large scale reactive transport of nitrate across the surface water divide

NASA Astrophysics Data System (ADS)

Kortunov, E.; Lu, C.; Amos, R.; Grathwohl, P.

2016-12-01

Groundwater pollution caused by agricultural and atmospheric inputs is a pressing issue in environmental management worldwide. Various researchers have studied different aspects of nitrate contamination since the substantial increase of the agriculture pollution in the second half of the 20th century. This study addresses large scale reactive solute transport in a typical Germany hilly landscapes in a transect crossing 2 valleys: River Neckar and Ammer. The numerical model was constructed compromising a 2-D cross-section accounting for typical fractured mudstones and unconsolidated sediments. Flow modelling showed that the groundwater divide significantly deviates from the surface water divide providing conditions for inter-valley flow and transport. Reactive transport modelling of redox-sensitive solutes (e.g. agriculture nitrate and natural sulfate, DOC, ammonium) with MIN3P was used to elucidate source of nitrate in aquifers and rivers. Since both floodplains, in the Ammer and Neckar valley contain Holocene sediments relatively high in organic carbon, agricultural nitrate is reduced therein and does not reach the groundwater. However, nitrate applied in the hillslopes underlain by fractured oxidized mudrock is transported to the high yield sand and gravel aquifer in the Neckar valley. Therefore, the model predicts that nitrate in the Neckar valley comes, to a large extent, from the neighboring Ammer valley. Moreover, nitrate observed in the rivers and drains in the Ammer valley is very likely geogenic since frequent peat layers there release ammonium which is oxidized as it enters the surface water. Such findings are relevant for land and water quality management.

Crustal velocity structure across the Main Ethiopian Rift: results from two-dimensional wide-angle seismic modelling

NASA Astrophysics Data System (ADS)

Mackenzie, G. D.; Thybo, H.; Maguire, P. K. H.

2005-09-01

We present the results of velocity modelling of a recently acquired wide-angle seismic reflection/refraction profile across the Main Ethiopian Rift. The models show a continental type of crust with significant asymmetry between the two sides of the rift. A 2- to 5-km-thick layer of sedimentary and volcanic sequences is modelled across the entire region. This is underlain by a 40- to 45-km-thick crust with a c. 15-km-thick high-velocity lowest crustal layer beneath the western plateau. This layer is absent from the eastern side, where the crust is 35 km thick beneath the sediments. We interpret this layer as underplated material associated with the Oligocene flood basalts of the region with possible subsequent addition by recent magmatic events. Slight crustal thinning is observed beneath the rift, where Pn velocities indicate the presence of hot mantle rocks containing partial melt. Beneath the rift axis, the velocities of the upper crustal layers are 5-10 per cent higher than outside the rift, which we interpret as resulting from mafic intrusions that can be associated with magmatic centres observed in the rift valley. Variations in seismic reflectivity suggest the presence of layering in the lower crust beneath the rift, possibly indicating the presence of sills, as well as some layering in the proposed underplated body.

Effects of coal mine subsidence in the Sheridan, Wyoming, area

USGS Publications Warehouse

Dunrud, C. Richard; Osterwald, Frank W.

1980-01-01

Analyses of the surface effects of past underground coal mining in the Sheridan, Wyoming, area suggest that underground mining of strippable coal deposits may damage the environment more over long periods of time than would modern surface mining, provided proper restoration procedures are followed after surface mining. Subsidence depressions and pits are a continuing hazard to the environment and to man's activities in the Sheridan, Wyo., area above abandoned underground mines in weak overburden less than about 60 m thick and where the overburden is less than about 10-15 times the thickness of coal mined. In addition, fires commonly start by spontaneous ignition when water and air enter the abandoned mine workings via subsidence cracks and pits. The fires can then spread to unmined coal as they create more cavities, more subsidence, and more cracks and pits through which air can circulate. In modern surface mining operations the total land surface underlain by minable coal is removed to expose the coal. The coal is removed, the overburden and topsoil are replaced, and the land is regraded and revegetated. The land, although disturbed, can be more easily restored and put back into use than can land underlain by abandoned underground mine workings in areas where the overburden is less than about 60 m thick or less than about 10-15 times the thickness of coal mined. The resource recovery of modern surface mining commonly is much greater than that of underground mining procedures. Although present-day underground mining technology is advanced as compared to that of 25-80 years ago, subsidence resulting from underground mining of thick coal beds beneath overburden less than about 60 m thick can still cause greater damage to surface drainage, ground water, and vegetation than can properly designed surface mining operations. This report discusses (11 the geology and surface and underground effects of former large-scale underground coal mining in a 50-km 2 area 5-20 km north of Sheridan, Wyo., (2) a ground and aerial reconnaissance study of a 5-km^2 coal mining area 8-10 km west of Sheridan, and (31 some environmental consequences and problems caused by coal mining.

Predicting alpine headwater stream intermittency: a case study in the northern Rocky Mountains

USGS Publications Warehouse

Sando, Thomas R.; Blasch, Kyle W.

2015-01-01

This investigation used climatic, geological, and environmental data coupled with observational stream intermittency data to predict alpine headwater stream intermittency. Prediction was made using a random forest classification model. Results showed that the most important variables in the prediction model were snowpack persistence, represented by average snow extent from March through July, mean annual mean monthly minimum temperature, and surface geology types. For stream catchments with intermittent headwater streams, snowpack, on average, persisted until early June, whereas for stream catchments with perennial headwater streams, snowpack, on average, persisted until early July. Additionally, on average, stream catchments with intermittent headwater streams were about 0.7 °C warmer than stream catchments with perennial headwater streams. Finally, headwater stream catchments primarily underlain by coarse, permeable sediment are significantly more likely to have intermittent headwater streams than those primarily underlain by impermeable bedrock. Comparison of the predicted streamflow classification with observed stream status indicated a four percent classification error for first-order streams and a 21 percent classification error for all stream orders in the study area.

Selenium in irrigated agricultural areas of the western United States

USGS Publications Warehouse

Nolan, B.T.; Clark, M.L.

1997-01-01

A logistic regression model was developed to predict the likelihood that Se exceeds the USEPA chronic criterion for aquatic life (5 ??g/L) in irrigated agricultural areas of the western USA. Preliminary analysis of explanatory variables used in the model indicated that surface-water Se concentration increased with increasing dissolved solids (DS) concentration and with the presence of Upper Cretaceous, mainly marine sediment. The presence or absence of Cretaceous sediment was the major variable affecting Se concentration in surface-water samples from the National Irrigation Water Quality Program. Median Se concentration was 14 ??g/L in samples from areas underlain by Cretaceous sediments and < 1 ??g/L in samples from areas underlain by non-Cretaceous sediments. Wilcoxon rank sum tests indicated that elevated Se concentrations in samples from areas with Cretaceous sediments, irrigated areas, and from closed lakes and ponds were statistically significant. Spearman correlations indicated that Se was positively correlated with a binary geology variable (0.64) and DS (0.45). Logistic regression models indicated that the concentration of Se in surface water was almost certain to exceed the Environmental Protection Agency aquatic-life chronic criterion of 5 ??g/L when DS was greater than 3000 mg/L in areas with Cretaceous sediments. The 'best' logistic regression model correctly predicted Se exceedances and nonexceedances 84.4% of the time, and model sensitivity was 80.7%. A regional map of Cretaceous sediment showed the location of potential problem areas. The map and logistic regression model are tools that can be used to determine the potential for Se contamination of irrigated agricultural areas in the western USA.

Influence of rock composition on the geochemistry of stream and spring waters from mountainous watersheds in the Gunnison, Uncompahgre, and Grand Mesa National Forests, Colorado

USGS Publications Warehouse

Miller, William Roger

2002-01-01

The ranges of geochemical baselines for stream and spring waters were determined and maps were constructed showing acid-neutralizing capacity and potential release of total dissolved solids for streams and spring waters for watersheds underlain by each of ten different rock composition types in the Gunnison, Uncompahgre, and Grand Mesa National Forests, Colorado (GMUG). Water samples were collected in mountainous headwater watersheds that have comparatively high precipitation and low evapotranspiration rates and that generally lack extensive ground-water reservoirs. Mountainous headwaters react quickly to changes in input of water from rain and melting snow and they are vulnerable to anthropogenic impact. Processes responsible for the control and mobility of elements in the watersheds were investigated. The geochemistry of water from the sampled watersheds in the GMUG, which are underlain by rocks that are relatively unmineralized, is compared to the geochemistry of water from the mineralized Redcloud Peak area. The water with the highest potential for release of total dissolved solids is from watersheds that are underlain by Paleozoic sedimentary rocks; that high potential is caused primarily by gypsum in those rocks. Water that has the highest acid-neutralizing capacity is from watersheds that are underlain by Paleozoic sedimentary rocks. The water from watersheds underlain by the Mancos Shale has the next highest acid-neutralizing capacity. Water that has the lowest acid-neutralizing capacity is from watersheds that are underlain by Tertiary ash-flow tuff. Tertiary sedimentary rocks containing oil shale, the Mesavede Formation containing coal, and the Mancos Shale all contain pyrite with elevated metal contents. In these mountainous head-water areas, water from watersheds underlain by these rock types is only slightly impacted by oxidation of pyrite, and over-all it is of good chemical quality. These geochemical baselines demonstrate the importance of rock composition in determining the types of waters that are in the headwater areas. The comparison of these geochemical baselines to later geochemical base-lines will allow recognition of any significant changes in water quality that may occur in the future.

Arsenic, metals, and nutrients in runoff from two detention basins to Raccoon Creek, New Jersey Coastal Plain, 2008

USGS Publications Warehouse

Barringer, Julia L.; Szabo, Zoltan; Bonin, Jennifer L.; McGee, Craig K.

2011-01-01

Arsenic (As) concentrations in the waters of Raccoon Creek in southern New Jersey commonly exceed the State\\'s Surface Water Quality Standard (SWQS) for freshwater of 0.017 microgram per liter (mu or ug/L). In order to assess contributions of As from residential runoff to the creek, samples of runoff water were collected from a detention basin in each of two residential developments underlain by different geologic formations and at the outlets of those basins. Samples of streamwater also were collected from Raccoon Creek adjacent to the developments. The samples were analyzed to determine concentrations of As, selected metals, organic carbon, and nutrients. Soil samples in and downgradient from the basins also were collected and analyzed. Concentrations of As in unfiltered water samples of runoff from the basin underlain by glauconitic clays generally were higher (up to 4.35 mu or ug/L) than in runoff from the basin underlain by predominantly quartz sands and silts (up to 2.68 mu or ug/L). Chromium (Cr) concentrations also were higher in runoff from the basin underlain by glauconitic clays than in runoff from the basin underlain by quartz sand and silt. In addition, Cr concentrations were higher in the glauconitic soils than in the quartz-rich soils. Metals such as aluminum (Al), iron (Fe), lead (Pb), and manganese (Mn) in the runoff and in the streamwater were mostly in particulate form. Arsenic, most metals, and phosphorus (P) however, were mostly in dissolved form in runoff but in particulate form in the streamwater. Total organic carbon concentrations in the runoff ranged from about 10 to nearly 16 milligrams per liter (mg/L). Given such levels of organic carbon and strong correlations between concentrations of some metals and organic carbon, it may be that many of the metals were complexed with dissolved organic carbon and transported in that form in the runoff. Although underlying geologic materials and soils appear to be major contributors of As to the streamwater, As also could have been contributed from lead arsenate pesticide residues. The residential development underlain by quartz-rich sediments formerly had been an orchard where such pesticides may have been used. The substantial inputs of As to runoff at this site may be attributable to this former land use, although Pb concentrations were about the same in runoff from both sites. The streamwater at both sites, however, contained Pb concentrations well above those in runoff, indicating that there are additional inputs of Pb, perhaps from roadside soils, upstream from the two sampling sites in this study. Positive relations between concentrations of As and some metals with dissolved organic carbon in runoff and streamwater indicate that complexation with organic carbon may provide a mechanism by which these constituents can be transported. Sorption of As, Pb, and P to Fe hydroxides may be indicated by the observed positive relation of particulate As, Pb, and P to particulate Fe, however, representing an additional mechanism for transport of these constituents.

The Effects of Different Scales of Topographic Variation on Shallow Groundwater Flow in an Arctic Watershed

NASA Astrophysics Data System (ADS)

Nicholaides, K. D.; O'Connor, M.; Cardenas, M. B.; Neilson, B. T.; Kling, G. W.

2017-12-01

Arctic permafrost degradation is occurring as global temperatures increase. In addition, recent evidence shows the Arctic is shifting from a sink to a source of carbon to the atmosphere. However, the cause of this shift is unclear, as is the role of newly exposed organic soil carbon leaching into groundwater and transported to surface water. This soil carbon may be photo-oxidized to CO2 or microbially respired to CO2 and methane, adding greenhouse gases to the atmosphere. The fate of carbon in permafrost is largely governed by the length of time spent in transport and the surface or subsurface route it follows. However, groundwater flow regimes within shallow active layer aquifers overlying permafrost is poorly understood. We determined to what extent smaller scale topography influences groundwater flow and residence times in arctic tundra. The study focused on Imnavait Creek watershed, a 1st-order drainage on the Alaskan North Slope underlain by continuous permafrost. We used direct measurements of hydraulic conductivities and porosities over a range of depths as well as basin-scale topography to develop vertically-integrated groundwater flow models. By systematically decreasing the amount of topographic detail, we were able to compare the influence of more detailed topography on groundwater flow estimates. Scaling up this model will be a useful tool in understanding how larger basins in permafrost will respond to future climate change and their contributions to greenhouse gases in the atmosphere.

Ratite eggshells from lanzarote, canary islands.

PubMed

Franz Sauer, E G; Rothe, P

1972-04-07

Struthious and aepyornithoid eggshells from Tertiary calcareous sediments on Lanzarote prove the presence, until about 12 million years ago, of large flightless birds. The calcarenite horizon is recognized as an old land surface. Mesozoic sedimentary rocks in the basement of the volcanic islands of Lanzarote and neighboring Fuerteventura indicate that at least part of the Canary Archipelago is underlain by continental crust. Separation of the eastern Canaries from Africa raight have been by rifting, and a land connection might still have existed in the lower Pliocene.

Hydrological controls on DOC  :  nitrate resource stoichiometry in a lowland, agricultural catchment, southern UK

NASA Astrophysics Data System (ADS)

Heppell, Catherine M.; Binley, Andrew; Trimmer, Mark; Darch, Tegan; Jones, Ashley; Malone, Ed; Collins, Adrian L.; Johnes, Penny J.; Freer, Jim E.; Lloyd, Charlotte E. M.

2017-09-01

The role that hydrology plays in governing the interactions between dissolved organic carbon (DOC) and nitrogen in rivers draining lowland, agricultural landscapes is currently poorly understood. In light of the potential changes to the production and delivery of DOC and nitrate to rivers arising from climate change and land use management, there is a pressing need to improve our understanding of hydrological controls on DOC and nitrate dynamics in such catchments. We measured DOC and nitrate concentrations in river water of six reaches of the lowland river Hampshire Avon (Wiltshire, southern UK) in order to quantify the relationship between BFI (BFI) and DOC : nitrate molar ratios across contrasting geologies (Chalk, Greensand, and clay). We found a significant positive relationship between nitrate and BFI (p < 0. 0001), and a significant negative relationship between DOC and BFI (p < 0. 0001), resulting in a non-linear negative correlation between DOC : nitrate molar ratio and BFI. In the Hampshire Avon, headwater reaches which are underlain by clay and characterized by a more flashy hydrological regime are associated with DOC : nitrate ratios > 5 throughout the year, whilst groundwater-dominated reaches underlain by Chalk, with a high BFI have DOC : nitrate ratios in surface waters that are an order of magnitude lower (< 0.5). Our analysis also reveals significant seasonal variations in DOC : nitrate transport and highlights critical periods of nitrate export (e.g. winter in sub-catchments underlain by Chalk and Greensand, and autumn in drained, clay sub-catchments) when DOC : nitrate molar ratios are low, suggesting low potential for in-stream uptake of inorganic forms of nitrogen. Consequently, our study emphasizes the tight relationship between DOC and nitrate availability in agricultural catchments, and further reveals that this relationship is controlled to a great extent by the hydrological setting.

Application of the precipitation-runoff model in the Warrior coal field, Alabama

USGS Publications Warehouse

Kidd, Robert E.; Bossong, C.R.

1987-01-01

A deterministic precipitation-runoff model, the Precipitation-Runoff Modeling System, was applied in two small basins located in the Warrior coal field, Alabama. Each basin has distinct geologic, hydrologic, and land-use characteristics. Bear Creek basin (15.03 square miles) is undisturbed, is underlain almost entirely by consolidated coal-bearing rocks of Pennsylvanian age (Pottsville Formation), and is drained by an intermittent stream. Turkey Creek basin (6.08 square miles) contains a surface coal mine and is underlain by both the Pottsville Formation and unconsolidated clay, sand, and gravel deposits of Cretaceous age (Coker Formation). Aquifers in the Coker Formation sustain flow through extended rainless periods. Preliminary daily and storm calibrations were developed for each basin. Initial parameter and variable values were determined according to techniques recommended in the user's manual for the modeling system and through field reconnaissance. Parameters with meaningful sensitivity were identified and adjusted to match hydrograph shapes and to compute realistic water year budgets. When the developed calibrations were applied to data exclusive of the calibration period as a verification exercise, results were comparable to those for the calibration period. The model calibrations included preliminary parameter values for the various categories of geology and land use in each basin. The parameter values for areas underlain by the Pottsville Formation in the Bear Creek basin were transferred directly to similar areas in the Turkey Creek basin, and these parameter values were held constant throughout the model calibration. Parameter values for all geologic and land-use categories addressed in the two calibrations can probably be used in ungaged basins where similar conditions exist. The parameter transfer worked well, as a good calibration was obtained for Turkey Creek basin.

Magnetotelluric investigations of the lithosphere beneath the central Rae craton, mainland Nunavut, Canada

NASA Astrophysics Data System (ADS)

Spratt, Jessica E.; Skulski, Thomas; Craven, James A.; Jones, Alan G.; Snyder, David B.; Kiyan, Duygu

2014-03-01

New magnetotelluric soundings at 64 locations throughout the central Rae craton on mainland Nunavut constrain 2-D resistivity models of the crust and lithospheric mantle beneath three regional transects. Responses determined from colocated broadband and long-period magnetotelluric recording instruments enabled resistivity imaging to depths of > 300 km. Strike analysis and distortion decomposition on all data reveal a regional trend of 45-53°, but locally the geoelectric strike angle varies laterally and with depth. The 2-D models reveal a resistive upper crust to depths of 15-35 km that is underlain by a conductive layer that appears to be discontinuous at or near major mapped geological boundaries. Surface projections of the conductive layer coincide with areas of high grade, Archean metasedimentary rocks. Tectonic burial of these rocks and thickening of the crust occurred during the Paleoproterozoic Arrowsmith (2.3 Ga) and Trans-Hudson orogenies (1.85 Ga). Overall, the uppermost mantle of the Rae craton shows resistivity values that range from 3000 Ω m in the northeast (beneath Baffin Island and the Melville Peninsula) to 10,000 Ω m beneath the central Rae craton, to >50,000 Ω m in the south near the Hearne Domain. Near-vertical zones of reduced resistivity are identified within the uppermost mantle lithosphere that may be related to areas affected by mantle melt or metasomatism associated with emplacement of Hudsonian granites. A regional decrease in resistivities to values of 500 Ω m at depths of 180-220 km, increasing to 300 km near the southern margin of the Rae craton, is interpreted as the lithosphere-asthenosphere boundary.

Environmental and physical controls on northern terrestrial methane emissions across permafrost zones

USGS Publications Warehouse

Olefeldt, David; Turetsky, Merritt R.; Crill, Patrick M.; McGuire, A. David

2013-01-01

Methane (CH4) emissions from the northern high-latitude region represent potentially significant biogeochemical feedbacks to the climate system. We compiled a database of growing-season CH4 emissions from terrestrial ecosystems located across permafrost zones, including 303 sites described in 65 studies. Data on environmental and physical variables, including permafrost conditions, were used to assess controls on CH4 emissions. Water table position, soil temperature, and vegetation composition strongly influenced emissions and had interacting effects. Sites with a dense sedge cover had higher emissions than other sites at comparable water table positions, and this was an effect that was more pronounced at low soil temperatures. Sensitivity analysis suggested that CH4 emissions from ecosystems where the water table on average is at or above the soil surface (wet tundra, fen underlain by permafrost, and littoral ecosystems) are more sensitive to variability in soil temperature than drier ecosystems (palsa dry tundra, bog, and fen), whereas the latter ecosystems conversely are relatively more sensitive to changes of the water table position. Sites with near-surface permafrost had lower CH4 fluxes than sites without permafrost at comparable water table positions, a difference that was explained by lower soil temperatures. Neither the active layer depth nor the organic soil layer depth was related to CH4 emissions. Permafrost thaw in lowland regions is often associated with increased soil moisture, higher soil temperatures, and increased sedge cover. In our database, lowland thermokarst sites generally had higher emissions than adjacent sites with intact permafrost, but emissions from thermokarst sites were not statistically higher than emissions from permafrost-free sites with comparable environmental conditions. Overall, these results suggest that future changes to terrestrial high-latitude CH4 emissions will be more proximately related to changes in moisture, soil temperature, and vegetation composition than to increased availability of organic matter following permafrost thaw.

Stratigraphic response of salt marshes to slow rates of sea-level change

NASA Astrophysics Data System (ADS)

Daly, J.; Bell, T.

2006-12-01

Conventional models of salt-marsh development show an idealized spatial relationship between salt-marsh floral and foraminiferal zones, where the landward margin of the marsh gradually migrates inland in response to sea-level rise. This model predicts that transgression will result in persistent and possibly expanded salt marshes at the surface, depending on a variety of factors including sediment supply, hydrologic conditions, tidal range, and rate of sea-level rise. However, in areas with abundant sediment supply and slow rates of sea- level rise, the extent of back-barrier salt marshes may decline over time as the barrier-spits mature. Sea level around the northeast coast of Newfoundland is rising at a very slow rate during the late Holocene (<0.5 mm/yr). Sandy barrier-spits and tombolos are common coastal features, but salt marshes are rare. The generalized stratigraphy of dutch cores collected in back-barrier settings in this region is a surface layer of sphagnum peat with abundant woody roots, underlain by sedge-dominated peat that transitions gradually to a thin layer of Juncus sp. peat with agglutinated foraminifera, dominantly Jadammina macrescens and Balticammina pseudomacrescens. These basal peats are interpreted as salt-marsh peats, characterized by the presence of foraminifera that are absent in overlying peat units. This sequence indicates that salt marshes developed in back-barrier environments during the initial stages of barrier progradation, then gradually transitioned to environments increasingly dominated by freshwater flora. These transitions are interpreted to reflect the progradation of the spit, decreased tidal exchange in the back-barrier, and increased influence of freshwater streams discharging into the back-barrier setting. Decreased marine influence on the back-barrier environment leads to a floral and faunal shift associated with a regressive stratigraphy in an area experiencing sea-level rise. For studies of Holocene sea-level change requiring salt-marsh stratigraphic records, it is necessary to account for changing micro-environments to locate sites appropriate for study; salt marshes may play an important role in defining the record, but may not exist at the surface to guide investigation.

Compositional and Microstructural Evolution of Olivine During Pulsed Laser Irradiation: Insights Based on a FIB/Field-Emission TEM Study

NASA Technical Reports Server (NTRS)

Christoffersen, R.; Loeffler, M. J.; Dukes, C. A.; Baragiola, R. A.

2015-01-01

Introduction: The use of pulsed laser irradiation to simulate the short duration, high-energy conditions characteristic of micrometeorite impacts is now an established approach in experimental space weathering studies. The laser generates both melt and vapor deposits that contain nanophase metallic Fe (npFe(sup 0)) grains with size distributions and optical properties similar to those in natural impact-generated melt and vapor deposits. There remains uncertainty, however, about how well lasers simulate the mechanical work and internal (thermal) energy partitioning that occurs in actual impacts. We are currently engaged in making a direct comparison between the products of laser irradiation and experimental/natural hypervelocity impacts. An initial step reported here is to use analytical TEM is to attain a better understanding of how the microstructure and composition of laser deposits evolve over multiple cycles of pulsed laser irradiation. Experimental Methods: We irradiated pressed-powder pellets of San Carlos olivine (Fo(sub 90)) with up to 99 rastered pulses of a GAM ArF excimer laser. The irradiated surface of the sample were characterized by SEM imaging and areas were selected for FIB cross sectioning for TEM study using an FEI Quanta dual-beam electron/focused ion beam instrument. FIB sections were characterized using a JEOL2500SE analytical field-emission scanning transmission electron microscope (FE-STEM) optimized for quantitative element mapping at less than 10 nm spatial resolutions. Results: In the SEM the 99 pulse pressed pellet sample shows a complex, inhomogeneous, distribution of laser-generated material, largely concentrated in narrow gaps and larger depressions between grains. Local concentrations of npFe0 spherules 0.1 to 1 micrometers in size are visible within these deposits in SEM back-scatter images. Fig. 1 shows bright-field STEM images of a FIB cross-section of a one of these deposits that continuously covers the top and sloping side of an olivine grain. The deposit has 3 microstructurally distinct sub-layers composed of silicate glass with varying modal fractions and size distributions of npFe( sup 0) spherules, along with nanocrystalline silicate material. A relatively thin (50-300 nm) topmost surface layer has a high-concentration of npFe0 spherules 5-20 nm in size. Element mapping shows the layer to be enriched in Fe by a factor of 2.5 relative to the olivine substrate, with Mg and Si depleted by 20% and 10% respectively. This is compositionally complementary to the underlying, middle layer of the deposit that is depleted in Fe, enriched in Mg and has a much lower npFe0 concentration. A third layer of nanocrystalline olivine occurs at the substrate interface. Discussion: The FE-STEM results suggest the topmost layer is a vapor deposit, underlain by a thicker microstructurally complex melt-generated layer. The compositional relations suggest the melt layer was partially vaporized, preferentially losing more volatile elements (e.g., Fe). The vaporized material re-condensed to form the thin, npFe(sup 0)-rich surface deposit during or immediately after the scan cycle. Nanocrystalline olivine that grew within the melt layer as it formed and cooled is similar in volume and microstructure to what we have observed in the impact melt lining of a micrometeorite impact crater in olivine. This suggest the time-temperature relations attained in the laser sample may not be too different from a micrometeorite impact. Our TEM observations, however, do not show evidence for the same level of mechanical dam-age (e.g., fracturing) seen around the natural micrometeorite crater.

Precambrian crust and lithosphere beneath the Northern Canadian Cordillera discovered by LITHOPROBE seismic reflection profiling

NASA Astrophysics Data System (ADS)

Clowes, R. M.; Cook, F. A.; Snyder, D. B.; van der Velden, A. J.; Hall, K. W.; Erdmer, P.; Evenchick, C. A.

2003-04-01

The Cordillera in northern Canada is underlain by westward tapering layers that can be followed from outcrops of Proterozoic strata in the Foreland Belt to the lowermost crust of the orogenic interior, a distance of as much as 500 km across strike. The layering was discovered on two new deep seismic reflection profiles in the Yukon (Line 3; ~650 km) and northern British Columbia (Line 2; ~1245 km in two segments) that were acquired as part of the LITHOPROBE Slave - Northern Cordillera Lithospheric Evolution (SNORCLE) transect. Along Line 3, the layering is visible between 5.0 and 12.0 s (~15 to 36 km depth). It is followed southwestward for nearly 650 km (~500 km across strike) and thins to less than 1.0 s (~3.0-3.5 km thickness) near the Moho at the Yukon-Alaska international boundary. Farther south, along Line 2, the upper part of the layering correlates with outcrops of Proterozoic (1.76-1.0 Ga) strata on the east. Near the outcrop, the layering is >15 km thick. It projects westward into the middle and lower crust for ~700 km (~300 km across strike) where it disappears as a thin taper at the base of the crust. The layering is disrupted at the Tintina fault zone, a late to post-orogenic strike-slip fault with up to 800 km of displacement, which appears as a vertical zone of little reflectivity on both profiles (~300 km apart). The base of the layered reflection zone coincides with the Moho, which exhibits variable character and undulates in a series of broad (~150 km) arches. Although the mantle is generally non-reflective, an event dips eastward from ~14.0 s (~45 km) at the western end of Line 3 near the coast to ~21.0 s (73 km depth) beneath exposed Eocene magmatic rocks. It is interpreted as a relict subduction surface of the Kula plate. Some implications of the interpretation of Proterozoic layered rocks beneath most of the northern Cordillera are: (1) ancient North American crust and lithosphere project westward beneath most of the Northern Cordillera, (2) the detachments that carry deformed rocks the northern Canadian Cordillera are largely confined to the crust above the layering, and (3) rocks of most of the accreted terranes overlie the layering. Most of the accreted rocks thus appear to be thin (<10 km thick), far-traveled flakes. However, one major terrane, Stikinia, may thicken westward as the underlying layered zone thins such that the lower crustal layering disappears beneath the northeastern portion of Stikinia; the boundary between Stikinia and adjacent rocks to the east may be a crustal-scale tectonic wedge above the deep layering.

Stream dissolved organic matter bioavailability and composition in watersheds underlain with discontinuous permafrost

Treesearch

Kelly L. Balcarczyk; Jeremy B. Jones; Rudolf Jaffe; Nagamitsu Maie

2009-01-01

We examined the impact of permafrost on dissolved organic matter (DOM) composition in Caribou-Poker Creeks Research Watershed (CPCRW), a watershed underlain with discontinuous permafrost, in interior Alaska. The stream draining the high permafrost watershed had higher DOC and dissolved organic nitrogen (DON) concentrations, higher DOCDON and greater specific...

Preliminary geologic map of the Murrieta 7.5' quadrangle, Riverside County, California

USGS Publications Warehouse

Kennedy, Michael P.; Morton, Douglas M.

2003-01-01

The Murrieta quadrangle is located in the northern part of the Peninsular Ranges Province and includes parts of two structural blocks, or structural subdivisions of the province. The quadrangle is diagonally crossed by the active Elsinore fault zone, a major fault zone of the San Andreas fault system, and separates the Santa Ana Mountains block to the west from the Perris block to the east. Both blocks are relatively stable internally and within the quadrangle are characterized by the presence of widespread erosional surfaces of low relief. The Santa Ana Mountains block, in the Murrieta quadrangle, is underlain by undifferentiated, thick-layered, granular, impure quartzite and well-layered, fissile, phyllitic metamorphic rock of low metamorphic grade. Both quartzite and phyllitic rocks are Mesozoic. Unconformably overlying the metamorphic rocks are remnants of basalt flows having relatively unmodified flow surfaces. The age of the basalt is about 7-8Ma. Large shallow depressions on the surface of the larger basalt remnants form vernal ponds that contain an endemic flora. Beneath the basalt the upper part of the metamorphic rocks is deeply weathered. The weathering appears to be the same as the regional Paleocene saprolitic weathering in southern California. West of the quadrangle a variable thickness sedimentary rock, physically resembling Paleogene rocks, occurs between the basalt and metamorphic rock. Where not protected by the basalt, the weathered rock has been removed by erosion. The dominant feature on the Perris block in the Murrieta quadrangle is the south half of the Paloma Valley ring complex, part of the composite Peninsular Ranges batholith. The complex is elliptical in plan view and consists of an older ring-dike with two subsidiary short-arced dikes that were emplaced into gabbro by magmatic stoping. Small to large stoped blocks of gabbro are common within the ring-dikes. A younger ring-set of hundreds of thin pegmatite dikes occur largely within the central part of the complex. These pegmatite dikes were emplaced into a domal fracture system, apparently produced by cauldron subsidence, and include in the center of the complex, a number of flat-floored granophyre bodies. The granophyre is interpreted to be the result of pressure quenching of pegmatite magma. Along the eastern edge of the quadrangle is the western part of a large septum of medium metamorphic grade Mesozoic schist. A dissected basalt flow caps the Hogbacks northeast of Temecula, and represents remnants of a channel filling flow. Beneath the basalt is a thin deposit of stream gravel. Having an age of about 10Ma, this basalt is about 2-3Ma older than the basalt flows in the Santa Ana Mountains. The Elsinore fault zone forms a complex of pull-apart basins. The west edge of the fault zone, the Willard Fault, is marked by the high, steep eastern face of the Santa Ana Mountains. The east side of the zone, the Wildomar Fault, forms a less pronounced physiographic step. In the center of the quadrangle a major splay of the fault zone, the Murrieta Hot Springs Fault, strikes east. Branching of the fault zone causes the development of a broad alluvial valley between the Willard Fault and the Murrieta Hot Springs Fault. All but the axial part of the zone between the Willard and Wildomar Faults consist of dissected Pleistocene sedimentary units. The axial part of the zone is underlain by Holocene and latest Pleistocene sedimentary units.

Thermal contraints on high-pressure granulite metamorphism of supracrustal rocks

NASA Technical Reports Server (NTRS)

Ashwal, L. D.; Morgan, P.; Leslie, W. W.

1983-01-01

The circumstances leading to the formation and exposure at the Earth's surface of supracrustal granulites are examined. These are defined as sediments, volcanics, and other rock units which originally formed at the surface of the Earth, were metamorphosed to high-pressure granulite facies (T = 700-900 C, P = 5-10 kbar), and reexposed at the Earth's surface, in many cases underlain by normal thicknesses of continental crust (30-40 km). Five possible heating mechanisms to account for granulite metamorphism of supracrustal rocks are discussed: magnetic heating, thermal relaxation of perturbed temperature profiles following underthrusting of the continental crust, thermal relaxation after underthrusting of thin slivers of supracrustal rocks below continental crust of normal thickness, major preheating of the upper plate, and shear heating caused by frictional stress along the thrust plane.

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

Lowenstien, T.K.; Casas, E.; Schubel, K.A.

Dabusun Lake (200 km{sup 2}) is a shallow ({lt}1 m) perennial saline lake in the high altitude Qaidam basin (120,000 km{sup 2}) of western China. It is underlain by {gt}40 m of salt and siliciclastic sediments ({approximately}54,000 years old). Petrographic features in two 50 m cores (chevron halite, halite cumulates, rafts, and siliciclastic mud, minor solution and no subaerial exposure features except in the top meter) indicate continuous shallow perennial lake conditions. The chemical composition of fluid inclusions trapped in halite crystals show lakewaters have generally undergone progressive concentration to the present. Modern Dabusun Lake is chemically uniform (Na-Mg-Cl-rich), nonstratified,more » and at or near halite saturation. Evaporites accumulate in zones on the restricted lake margins as halite (cumulate and raft layers with rippled surfaces and chevron mounds), halite + carnallite (KCl{center dot}MgCl{sub 2}{center dot}6H{sub 2}O), and finally carnallite (ephemeral fine-grained crystal mush). The carnallite zone merges with a 25 m wide shoreline facies, highlighted by a 1 m wide zone of halite ooids/pisoids that border a 20-30 cm tall overhanging salt crust (1967 shoreline). Lower lake levels since that time have produced vadose diagenetic features in the shoreline halites including: pendant cements, meniscus cements, halite 'popcorn,' and solution voids with muddy geopetal fills. A large flood (July-September 1989) expanded Dabusun Lake to 800 km{sup 2}, and dissolved all surface carnallite deposits. Diagenetic carnallite cements, formed by downward migration and cooking of carnallite saturated surface brines, however, remain in the subsurface to depths of 13 m. These potash mineral cements are similar in texture to many ancient potash evaporites.« less

Vs30 mapping at selected sites within the Greater Accra Metropolitan Area

NASA Astrophysics Data System (ADS)

Nortey, Grace; Armah, Thomas K.; Amponsah, Paulina

2018-06-01

A large part of Accra is underlain by a complex distribution of shallow soft soils. Within seismically active zones, these soils hold the most potential to significantly amplify seismic waves and cause severe damage, especially to structures sited on soils lacking sufficient stiffness. This paper presents preliminary site classification for the Greater Accra Metropolitan Area of Ghana (GAMA), using experimental data from two-dimensional (2-D) Multichannel Analysis of Surface Wave (MASW) technique. The dispersive characteristics of fundamental mode Rayleigh type surface waves were utilized for imaging the shallow subsurface layers (approx. up to 30 m depth) by estimating the 1D (depth) and 2D (depth and surface location) shear wave velocities at 5 selected sites. The average shear wave velocity for 30 m depth (Vs30), which is critical in evaluating the site response of the upper 30 m, was estimated and used for the preliminary site classification of the GAM area, as per NEHRP (National Earthquake Hazards Reduction Program). Based on the Vs30 values obtained in the study, two common site types C, and D corresponding to shallow (>6 m < 30 m) weathered rock and deep (up 30 m thick) stiff soils respectively, have been identified within the study area. Lower velocity profiles are inferred for the residual soils (sandy to silty clays), derived from the Accraian Formation that lies mainly within Accra central. Stiffer soil sites lie to the north of Accra, and to the west near Nyanyano. The seismic response characteristics over the residual soils in the GAMA have become apparent using the MASW technique. An extensive site effect map and a more robust probabilistic seismic hazard analysis can now be efficiently built for the metropolis, by considering the site classes and design parameters obtained from this study.

Himalayan tectonics explained by extrusion of a low-viscosity crustal channel coupled to focused surface denudation.

PubMed

Beaumont, C; Jamieson, R A; Nguyen, M H; Lee, B

2001-12-13

Recent interpretations of Himalayan-Tibetan tectonics have proposed that channel flow in the middle to lower crust can explain outward growth of the Tibetan plateau, and that ductile extrusion of high-grade metamorphic rocks between coeval normal- and thrust-sense shear zones can explain exhumation of the Greater Himalayan sequence. Here we use coupled thermal-mechanical numerical models to show that these two processes-channel flow and ductile extrusion-may be dynamically linked through the effects of surface denudation focused at the edge of a plateau that is underlain by low-viscosity material. Our models provide an internally self-consistent explanation for many observed features of the Himalayan-Tibetan system.

Geohydrology of the central Mesilla Valley, Dona Ana County, New Mexico

USGS Publications Warehouse

Wilson, Clyde A.; White, Robert R.

1984-01-01

Five large-capacity irrigation wells, with depths ranging from 370 to 686 feet, were drilled by the Elephant Butte Irrigation District between 1973 and 1975, in the Mesilla Valley about 7 miles south of Las Cruces, New Mexico. These were the first deep wells in the area, and their installation provided an opportunity to conduct extensive aquifer tests under relatively undisturbed conditions. The deep irrigation wells are perforated in the Santa Fe Group of Miocene to Pleistocene Age. The Santa Fe Group is composed of interfingering and alternating beds of clay, silt, sand, and small gravel. In the area of these wells, the upper part of the saturated zone contains slightly saline water to a depth of about 100 to 175 feet below the water table, underlain by a freshwater zone extending to depths greater than 1,200 feet. As water is pumped from the freshwater zone, leakage occurs from above and below the perforated interval. At one of the irrigation district wells, slightly saline water moved downward because of a lack of confining layers in the aquifer. At three other wells, the surface casing was not set deep enough and slightly saline water moved into the top of the perforations , downward in the casing, and into the freshwater part of the aquifer. (USGS)

The 20 April 2013 Lushan, Sichuan, mainshock, and its aftershock sequence: tectonic implications

NASA Astrophysics Data System (ADS)

Lei, Jianshe; Zhang, Guangwei; Xie, Furen

2014-02-01

Using the double-difference relocation algorithm, we relocated the 20 April 2013 Lushan, Sichuan, earthquake ( M S 7.0), and its 4,567 aftershocks recorded during the period between 20 April and May 3, 2013. Our results showed that most aftershocks are relocated between 10 and 20 km depths, but some large aftershocks were relocated around 30 km depth and small events extended upward near the surface. Vertical cross sections illustrate a shovel-shaped fault plane with a variable dip angle from the southwest to northeast along the fault. Furthermore, the dip angle of the fault plane is smaller around the mainshock than that in the surrounding areas along the fault. These results suggest that it may be easy to generate the strong earthquake in the place having a small dip angle of the fault, which is somewhat similar to the genesis of the 2008 Wenchuan earthquake. The Lushan mainshock is underlain by the seismically anomalous layers with low-VP, low-VS, and high-Poisson's ratio anomalies, possibly suggesting that the fluid-filled fractured rock matrices might significantly reduce the effective normal stress on the fault plane to bring the brittle failure. The seismic gap between Lushan and Wenchuan aftershocks is suspected to be vulnerable to future seismic risks at greater depths, if any.

The thin brown line: The crucial role of peat in protecting permafrost in Arctic Alaska

NASA Astrophysics Data System (ADS)

Gaglioti, B.; Mann, D. H.; Farquharson, L. M.; Baughman, C. A.; Jones, B. M.; Romanovsky, V. E.; Williams, A. P.; Andreu-Hayles, L.

2017-12-01

Ongoing warming threatens to thaw Arctic permafrost and release its stored carbon, which could trigger a permafrost-carbon feedback capable of augmenting global warming. The effects of warming air temperatures on permafrost are complicated by the fact that across much of the Arctic and Subarctic a mat of living plants and decaying litter cover the ground and buffer underlying permafrost from air temperatures. For simplicity here, we refer to this organic mat as "peat". Because this peat modifies heat flow between ground and air, the rate and magnitude of permafrost responses to changing climate - and hence the permafrost-carbon feedback - are partly slaved to the peat layer's slower dynamics. To explore this relationship, we used 14C-age offsets within lake sediments in Alaskan watersheds underlain by yedoma deposits to track the changing responses of permafrost thaw to fluctuating climate as peat accumulated over the last 14,000 years. As the peat layer built up, warming events became less effective at thawing permafrost and releasing ancient carbon. Consistent with this age-offset record, the geological record shows that early in post-glacial times when the peat cover was still thin and limited in extent, warm intervals triggered extensive thermokarst that resulted in rapid aggradation of floodplains. Today in contrast, hillslopes and floodplains remain stable despite rapid warming, probably because of the buffering effects of the extensive peat cover. Another natural experiment is provided by tundra fires like the 2007 Anaktuvuk River fire that removed the peat cover from tundra underlain by continuous permafrost and resulted in widespread thermkarsting. Further support for peat's critical role in protecting permafrost comes from the results of modeling how permafrost temperatures under different peat thicknesses respond to warming air temperature. Although post-industrial warming has not yet surpassed the buffering capacity of 14,000 years of peat buildup in Arctic Alaska, modeling suggests that a threshold is imminent.

Chemical stratification of cratonic lithosphere: constraints from the Northern Slave craton, Canada

NASA Astrophysics Data System (ADS)

Kopylova, Maya G.; Russell, James K.

2000-08-01

We describe the mineralogical and chemical composition of the Northern Slave mantle as deduced from xenoliths of peridotite within the Jericho kimberlite, Northwest Territories. Our data set includes modal, major, trace and rare earth element compositions of bulk samples of spinel peridotite, low-T and high-T garnet peridotite and minor pyroxenite. Compared to primitive upper mantle, Jericho peridotite shows depletion in the major elements and enrichment in incompatible elements (except for HREE). The Slave mantle is also uniquely stratified. Older, depleted spinel peridotite extends to a depth of 80-100 km and is underlain by garnet peridotite which shows a gradual decrease in Mg# with depth to 200 km. The youngest layer of fertile garnet peridotite, enriched in clinopyroxene and garnet, is underlain by a pyroxenite-rich horizon at the base of the petrological lithosphere. The Northern Slave is further distinguished from the Kaapvaal and Siberian upper mantle by a marked vertical stratification in Mg#, lower abundances of orthopyroxene and higher abundances of clinopyroxene. In addition, a deeper layer of garnet peridotite below Jericho shows less depletion than low-T peridotite from other cratons. The Northern Slave peridotite results from a series of chemical events that include: (i) high-degree melting of pyrolite at P>3 Gpa for low-T peridotite and lower pressure melting for high-T peridotite, (ii) enrichment of low-T spinel peridotite in orthopyroxene, and (iii) pervasive metasomatic enrichment in alkali and LREE's by kimberlite-related fluids. The chemical stratification described for two of the three lithospheric domains of the Slave craton makes this craton an exception among cratons with commonly unstratified lithospheres. The gradual increase in fertility with depth below the Slave craton is related to age stratification and may have formed by incremental downward growth of mantle lithosphere with time, and/or later re-fertilization of deeper mantle horizons.

Calculation of dispersion curves and amplitude-depth distributions of Love channel waves in horizontally-layered media. [In seam; various boundary conditions

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

Rader, D.; Dresen, L.; Ruter, H.

We present dispersion curves, and amplitude-depth distributions of the fundamental and first higher mode of Love seam waves for two characteristic seam models. The first model consists of four layers, representing a coal seam underlain by a root clay of variable thickness. The second model consists of five layers, representing coal seams containing a dirt band with variable position and thickness. The simple three-layer model is used for reference. It is shown that at higher frequencies, depending on the thickness of the root clay and the dirt band, the coal layers alone act as a wave guide, whereas at lowmore » frequencies all layers act together as a channel. Depending on the thickness, and position of the dirt band and the root clay, in the dispersion curves of the group velocity, secondary minima grow in addition to the absolute minima. Furthermore, the dispersion curves of the group velocity of the two modes can overlap. In all these cases, wave groups in addition to the Airy phase of the fundamental mode (propagating with minimum group velocity) occur on the seismograms recorded in in-seam seismic surveys, thus impeding their interpretation. Hence, we suggest the estimation of the dispersion characteristics of Love seam waves in coal seams under investigation preceding actual field surveys. All numerical calculations were performed using a fast and stable phase recursion algorithm.« less

Microchemical and Structural Evidence for Space Weathering in Soils from Asteroid Itokawa

NASA Technical Reports Server (NTRS)

Thompson, M. S.; Christoffersen, R.; Zega, T. J.

2013-01-01

The chemistry, microstructure and optical properties of grains on the surfaces of airless bodies are continu-ously modified due to their interactions predominantly with solar energetic ions and micrometeorite impacts. Collectively known as space weathering, this phenomenon results in a discrepancy between remotely sensed spectra from asteroids and those ac-quired directly from meteorites. The return of pristine samples from the asteroid Itokawa provides insight into surface processes on airless bodies and will help in correlating remote sensing data with laboratory analysis of meteorites. Samples and Methods: We examined Itokawa samples RA-QD02-0042-01 and RA-QD-02-0042-02, ultramicrotomed sec-tions of a singular grain prepared by the Hayabusa sample cura-tion team. We analyzed these slices using a 200 keV JEOL 2010F transmission electron microscope (TEM) at Arizona State Uni-versity and a 200 keV JEOL 2500SE TEM at NASA JSC. Both field emission TEMs are equipped with energy-dispersive X-ray spectrometers (EDS) and scanning TEM (STEM) detectors. Results and Discussion: TEM observations reveal that the sectioned grain predominantly consists of a single crystal of low-Ca orthopyroxene, with subsidiary smaller regions of olivine, Fe-Ni sulfide, and Fe-Ni metal. EDS-spectrum imaging and high-resolution TEM (HRTEM) show local, nanocrystalline regions of the outermost 2 to 5 nm of the pyroxene are composed of an Fe-Mg-S-rich and Si- and O-depleted layer that is underlain by a 2- to 5-nm thick amorphous zone enriched in Si. These layers occur in multiple microtome slices and have uniform thicknesses. We also observe localized 'islands' of material on the surface of the pyroxene which HRTEM imaging indicates are amorphous and EDS measurements show are compositionally heterogeneous. A 10- to 60-nm thick partially amorphous zone occurs below the compositionally distinct rim. While this this zone is associated with the compositionally heterogeneous outer layer, it also occurs as a local stand-alone feature on the exterior rim of the grain. Ar-eas of the pyroxene grain rim also exhibit a vesicular texture. The TEM data indicate a complex history of space weather-ing for samples RA-QD02-0042-01 and -02. The outermost layer of nanocrystalline material with varied composition is consistent with previously suggested [3-4] chemical and structural pro-cessing by solar wind ions, with a possible additional role for im-pact vapor deposition [3-4]. The amorphous and compositionally distinct islands on the surface of this grain, similar to lunar glasses, suggest formation through vapor deposition via micrometeor-ite impact events. In comparison, the amorphization and vesicula-tion textures are likely a product of radiation damage from the solar wind. The depth and degree of amorphization, in conjunction with model calculations, will help provide an upper limit on exposure time for these particles.

Under-ice melt ponds in the Arctic

NASA Astrophysics Data System (ADS)

Smith, Naomi; Flocco, Daniela; Feltham, Daniel

2017-04-01

In the summer months, melt water from the surface of the Arctic sea ice can percolate down through the ice and flow out of its base. This water is relatively warm and fresh compared to the ocean water beneath it, and so it floats between the ice and the oceanic mixed layer, forming pools of melt water called under-ice melt ponds. Double diffusion can lead to the formation of a sheet of ice, which is called a false bottom, at the interface between the fresh water and the ocean. These false bottoms isolate under-ice melt ponds from the ocean below, trapping the fresh water against the sea ice. These ponds and false bottoms have been estimated to cover between 5 and 40% of the base of the sea ice. [Notz et al. Journal of Geophysical Research 2003] We have developed a one-dimensional thermodynamic model of sea ice underlain by an under-ice melt pond and false bottom. Not only has this allowed us to simulate the evolution of under-ice melt ponds over time, identifying an alternative outcome than previously observed in the field, but sensitivity studies have helped us to estimate the impact that these pools of fresh water have on the mass-balance sea ice. We have also found evidence of a possible positive feedback cycle whereby increasingly less ice growth is seen due to the presence of under-ice melt ponds as the Arctic warms. Since the rate of basal ablation is affected by these phenomena, their presence alters the salt and freshwater fluxes from the sea ice into the ocean. We have coupled our under-ice melt pond model to a simple model of the oceanic mixed layer to determine how this affects mixed layer properties such as temperature, salinity, and depth. In turn, this changes the oceanic forcing reaching the sea ice.

Ottawa, Quebec Province, Canada and Glaciated Landscape

NASA Image and Video Library

1973-06-22

SL2-05-380 (22 June 1973) --- Ottawa, in the province of Ontario, (46.5N, 75.5W) is the capital of Canada and can be seen near the bottom of this scene on the Ottawa River. The region shown lies within the Canadian Shield. The glaciated surface of the land is underlain by lower Precambrian granite and sedimentary rock. Long fractures within these crystalline rocks have, in places, been carved out by glacial action. The resultant depressions are often water filled bogs and lakes. Photo credit: NASA

Turtle Mtns., ND

NASA Image and Video Library

2015-04-24

This image from NASA Terra spacecraft shows the Turtle Mountains, which straddle the US-Canada border in central North Dakota. Underlain by 55 million year old sandstones and shales of the Cannonball Formation, the upland surface was sculpted by glaciations. Due to the mountain's 150m elevation above the surrounding lowlands, glacial ice tended to stagnate, forming thousands of lakes and sloughs. The image was acquired May 19, 2006, covers an area of 43.5 x 53.1 km, and is located at 49 degrees north, 100.1 degrees west. http://photojournal.jpl.nasa.gov/catalog/PIA19435

The "LARSE" Project - Working Toward a Safer Future for Los Angeles

USGS Publications Warehouse

Henyey, Thomas L.; Fuis, Gary S.; Benthien, Mark L.; Burdette, Thomas R.; Christofferson, Shari A.; Clayton, Robert W.; Davis, Paul M.; Hendley, James W.; Kohler, Monica D.; Lutter, William J.; McRaney, John K.; Murphy, Janice M.; Okaya, David A.; Ryberg, Trond; Similia, Gerald W.; Stauffer, Peter H.

1999-01-01

The Los Angeles region is underlain by a network of active faults, including many that are deep and do not break the Earth's surface. These hidden faults include the previously unknown one responsible for the devastating January 1994 Northridge earthquake, the costliest quake in U.S. history. So that structures can be built or strengthened to withstand the quakes that are certain in the future, the Los Angeles Region Seismic Experiment (LARSE) is locating hidden earthquake hazards beneath the region to help scientists determine where the strongest shaking will occur.

Ecohydrology of permafrost-affected boreal forest ecosystems: sources of water utilized by plants and fluxed by ecosystems

NASA Astrophysics Data System (ADS)

Cable, J. M.; Ogle, K.; Cable, B.; Welker, J. M.

2010-12-01

The interior Alaskan boreal forest ecosystem is underlain by permafrost and thus has complex soil moisture and soil thermal properties, and this complexity is further amplified by its dry climate with low snow in winter and minimal summer rain. This combination of climate, cryosphere, and hydrology characteristics impact vegetation ecophysiological and ecohydrological processes, such as the distribution of plant-available water sources and the temporal dynamics of evapotranspiration (ET). As a major component of ET, plant transpiration is typically sustained throughout a variety of climatic conditions. The water sources (rain, thawing ground ice, etc) supporting plant transpiration are relatively unquantified, particularly on a seasonal time scale. In this study, we ask: what are the seasonal dynamics of plant water use in the boreal forest, and how are the trends at the plant scale translated into ecosystem-level water fluxes? Thus, the objective of this study was to characterize the spatial and temporal dynamics of boreal plant water use and water flux throughout the growing season. To do this, we measured the stable isotope (δ18O and δD) composition of water from precipitation, ground ice, soils, plants, and vapor from 5 heights in the ecosystem during the growing season in a boreal system near Fairbanks, Alaska underlain by permafrost. We analyzed the plant water, soil water, and vapor isotope data in a Bayesian framework to quantify the plant water uptake profiles and to explore the implications of shifting water sources for ecosystem ET. The vapor isotope data (across all heights) ranged from -216 to -190 ‰ (δD) and -27 to -21 ‰ (δ18O) in late July to slightly more depleted in late August, with values ranging from -232 to -203 ‰ (δD) and -29 to -20 ‰ (δ18O). Diurnal trends are such that the isotope composition of vapor became more enriched over the day as ET rates increased, and vapor at the 0.25 m height was generally more enriched relative to the 6 m height. Plant and soil isotope sampling from prior years shows that dwarf birch (B. nana, the dominant shrub in the ecosystem sampled by the vapor analyzer) gets about 50% of its water from surface, rain-fed soil layers and 50% of its water from deeper soil layers (fed by thawing ground ice). This is one of the first studies to show the patterns of boreal ecosystem water isotopes at diurnal (vapor) and seasonal (plant) scales. Understanding the isotopic composition of water vapor from northern ecosystems is paramount to advancing estimates of biosphere-atmosphere interactions and the nature of ecohydrologic feedbacks to the changing state of the North.

Geology and mineral deposits of Churchill County, Nevada

USGS Publications Warehouse

Willden, Ronald; Speed, Robert C.

1974-01-01

Churchill County, in west-central Nevada, is an area of varied topography and geology that has had a rather small total mineral production. The western part of the county is dominated by the broad low valley of the Carson Sink, which is underlain by deposits of Lake Lahontan. The bordering mountain ranges to the west and south are of low relief and underlain largely by Tertiary volcanic and sedimentary units. Pre-Tertiary rocks are extensively exposed east of the Carson Sink in the Stillwater Range, Clan Alpine Mountains, Augusta Mountains, and New Pass Mountains. The eastern valleys are underlain by Quaternary alluvial and lacustrine deposits contemporaneous with the western deposits of Lake Lahontan. The eastern mountain ranges are more rugged than the western ranges and have higher relief; the eastern valleys are generally narrower.

Comparing horizontal-to-vertical spectral ratios with sediment-to-bedrock spectral ratios in a region with a thin layer of unconsolidated sediments

NASA Astrophysics Data System (ADS)

Schleicher, L.; Pratt, T. L.

2017-12-01

Underlying sediment can amplify ground motions during earthquakes, making site response estimates key components in seismic evaluations for building infrastructure. The horizontal-to-vertical spectral ratio (HVSR) method, using either earthquake signals or ambient noise as input, is an appealing method for estimating site response because it uses only a single seismic station rather than requiring two or more seismometers traditionally used to compute a horizontal sediment-to-bedrock spectral ratio (SBSR). A number of studies have had mixed results when comparing the accuracy of the HVSR versus SBSR methods for identifying the frequencies and amplitudes of the primary resonance peaks. Many of these studies have been carried out in areas of complex geology, such as basins with structures that can introduce 3D effects. Here we assess the effectiveness of the HVSR method by a comparison with the SBSR method and models of transfer functions in an area dominated by a flat and thin, unconsolidated sediment layer over bedrock, which should be an ideal setting for using the HVSR method. In this preliminary study, we analyze teleseismic and regional earthquake recordings from a temporary seismometer array deployed throughout Washington, DC, which is underlain by a wedge of 0 to 270 m thick layer of unconsolidated Atlantic Coastal Plain sedimentary strata. At most sites, we find a close match in the amplitudes and frequencies of large resonance peaks in horizontal ground motions at frequencies of 0.7 to 5 Hz in site response estimates using the HVSR and SBSR methods. Amplitudes of the HVSRs tend to be slightly lower than SBSRs at 3 Hz and less, but the amplitudes of the fundamental resonance peaks often match closely. The results suggest that the HVSR method could be a successful approach to consider for computing site response estimates in areas of simple shallow geology consisting of thin sedimentary layers with a strong reflector at the underlying bedrock surface. [This publication represents the views of the authors and does not necessarily represent the views of the Defense Nuclear Facilities Safety Board.

Three-dimensional model of an ultramafic feeder system to the Nikolai Greenstone mafic large igneous province, central Alaska Range

USGS Publications Warehouse

Glen, J.M.G.; Schmidt, J.M.; Connard, G.G.

2011-01-01

The Amphitheater Mountains and southern central Alaska Range expose a thick sequence of Triassic Nikolai basalts that is underlain by several mafic-ultramafic complexes, the largest and best exposed being the Fish Lake and Tangle (FL-T) mafic-ultramafic sills that flank the Amphitheater Mountains synform. Three-dimensional (3-D) modeling of gravity and magnetic data reveals details of the structure of the Amphitheater Mountains, such as the orientation and thickness of Nikolai basalts, and the geometry of the FL-T intrusions. The 3-D model (50 ?? 70 km) includes the full geographic extent of the FL-T complexes and consists of 11 layers. Layer surfaces and properties (density and magnetic susceptibility) were modified by forward and inverse methods to reduce differences between the observed and calculated gravity and magnetic grids. The model suggests that the outcropping FL-T sills are apparently connected and traceable at depth and reveals variations in thickness, shape, and orientation of the ultramafic bodies that may identify paths of magma flow. The model shows that a significant volume (2000 km3) of ultramafic material occurs in the subsurface, gradually thickening and plunging westward to depths exceeding 4 km. This deep ultramafic material is interpreted as the top of a keel or root system that supplied magma to the Nikolai lavas and controlled emplacement of related magmatic intrusions. The presence of this deep, keel-like structure, and asymmetry of the synform, supports a sag basin model for development of the Amphitheater Mountains structure and reveals that the feeders to the Nikolai are much more extensive than previously known. Copyright 2011 by the American Geophysical Union.

High-resolution Mapping of Permafrost and Soil Freeze/thaw Dynamics in the Tibetan Plateau Based on Multi-sensor Satellite Observations

NASA Astrophysics Data System (ADS)

Zhang, W.; Yi, Y.; Yang, K.; Kimball, J. S.

2016-12-01

The Tibetan Plateau (TP) is underlain by the world's largest extent of alpine permafrost ( 2.5×106 km2), dominated by sporadic and discontinuous permafrost with strong sensitivity to climate warming. Detailed permafrost distributions and patterns in most of the TP region are still unknown due to extremely sparse in-situ observations in this region characterized by heterogeneous land cover and large temporal dynamics in surface soil moisture conditions. Therefore, satellite-based temperature and moisture observations are essential for high-resolution mapping of permafrost distribution and soil active layer changes in the TP region. In this study, we quantify the TP regional permafrost distribution at 1-km resolution using a detailed satellite data-driven soil thermal process model (GIPL2). The soil thermal model is calibrated and validated using in-situ soil temperature/moisture observations from the CAMP/Tibet field campaign (9 sites: 0-300 cm soil depth sampling from 1997-2007), a multi-scale soil moisture and temperature monitoring network in the central TP (CTP-SMTMN, 57 sites: 5-40 cm, 2010-2014) and across the whole plateau (China Meteorology Administration, 98 sites: 0-320 cm, 2000-2015). Our preliminary results using the CAMP/Tibet and CTP-SMTMN network observations indicate strong controls of surface thermal and soil moisture conditions on soil freeze/thaw dynamics, which vary greatly with underlying topography, soil texture and vegetation cover. For regional mapping of soil freeze/thaw and permafrost dynamics, we use the most recent soil moisture retrievals from the NASA SMAP (Soil Moisture Active Passive) sensor to account for the effects of temporal soil moisture dynamics on soil thermal heat transfer, with surface thermal conditions defined by MODIS (Moderate Resolution Imaging Spectroradiometer) land surface temperature records. Our study provides the first 1-km map of spatial patterns and recent changes of permafrost conditions in the TP.

Critical Zone Co-dynamics: Quantifying Interactions between Subsurface, Land Surface, and Vegetation Properties Using UAV and Geophysical Approaches

NASA Astrophysics Data System (ADS)

Dafflon, B.; Leger, E.; Peterson, J.; Falco, N.; Wainwright, H. M.; Wu, Y.; Tran, A. P.; Brodie, E.; Williams, K. H.; Versteeg, R.; Hubbard, S. S.

2017-12-01

Improving understanding and modelling of terrestrial systems requires advances in measuring and quantifying interactions among subsurface, land surface and vegetation processes over relevant spatiotemporal scales. Such advances are important to quantify natural and managed ecosystem behaviors, as well as to predict how watershed systems respond to increasingly frequent hydrological perturbations, such as droughts, floods and early snowmelt. Our study focuses on the joint use of UAV-based multi-spectral aerial imaging, ground-based geophysical tomographic monitoring (incl., electrical and electromagnetic imaging) and point-scale sensing (soil moisture sensors and soil sampling) to quantify interactions between above and below ground compartments of the East River Watershed in the Upper Colorado River Basin. We evaluate linkages between physical properties (incl. soil composition, soil electrical conductivity, soil water content), metrics extracted from digital surface and terrain elevation models (incl., slope, wetness index) and vegetation properties (incl., greenness, plant type) in a 500 x 500 m hillslope-floodplain subsystem of the watershed. Data integration and analysis is supported by numerical approaches that simulate the control of soil and geomorphic characteristic on hydrological processes. Results provide an unprecedented window into critical zone interactions, revealing significant below- and above-ground co-dynamics. Baseline geophysical datasets provide lithological structure along the hillslope, which includes a surface soil horizon, underlain by a saprolite layer and the fractured Mancos shale. Time-lapse geophysical data show very different moisture dynamics in various compartments and locations during the winter and growing season. Integration with aerial imaging reveals a significant linkage between plant growth and the subsurface wetness, soil characteristics and the topographic gradient. The obtained information about the organization and connectivity of the landscape is being transferred to larger regions using aerial imaging and will be used to constrain multi-scale, multi-physics hydro-biogeochemical simulations of the East River watershed response to hydrological perturbations.

Hydrology of area 18, Eastern Coal Province, Tennessee

USGS Publications Warehouse

May, V.J.

1981-01-01

The Eastern Coal Province is divided into 24 hydrologic reporting areas. This report describes the hydrology of area 18 which is located in the Cumberland River basin in central Tennessee near the southern end of the Province. Hydrologic information and sources are presented as text, tables, maps, and other illustrations designed to be useful to mine owners, operators, and consulting engineers in implementing permit applications that comply with the environmental requirements of the ' Surface Mining Control and Reclamation Act of 1977. ' Area 18 encompasses parts of three physiographic regions; from east to west the Cumberland Plateau, Highland Rim, and Central Basin. The Plateau is underlain by sandstones and shales, with thin interbedded coal beds, of Pennsylvanian age. The Highland Rim and Central Basin are underlain by limestone and dolomite of Mississippian age. Field and laboratory analyses of chemical and physical water-quality parameters of streamflow samples show no widespread water quality problems. Some streams, however, in the heavily mined areas have concentrations of sulfate, iron, manganese, and sediment above natural levels, and pH values below natural levels. Mine seepage and direct mine drainage were not sampled. Ground water occurs in and moves through fractures in the sandstones and shales and solution openings in the limestones and dolomites. Depth to water is variable, ranging from about 5 to 70 feet below land-surface in the limestones and dolomites, and 15 to 40 feet in the coal-bearing rocks. The quality of ground water is generally good. Locally, in coal-bearing rocks, acidic water and high concentrations of manganese, chloride, and iron have been detected. (USGS)

The African Lithosphere

NASA Astrophysics Data System (ADS)

Priestley, K.; Debayle, E.; McKenzie, D.; Pilidou, S.

2007-12-01

There have been a number of prior, large scale surface wave studies of Africa, the majority of which rely on fundamental mode observations. In this study we use a large data set of multi-mode surface waves recorded over epicentral distances most of which are shorter than 6000 km, to investigate the Sv wave speed heterogeneity of the upper mantle beneath Africa. The inclusion of the higher mode data allow us to build an upper mantle model for the African plate with a horizontal resolution of a few hundred kilometers and a vertical resolution of a few tens of kilometers extending to about 400 km depth. Our tomographic images of the upper mantle beneath Africa displays significant shear velocity features, much of which correlate with surface geology. High velocity mantle persists beneath the West African and Congo cratons to 225-250 km depth, but the high velocity root beneath Kalahari Craton extends to only about 175 km depth. Low velocity upper mantle underlies the Pan- African terranes of Africa with the exception of the Damara mobile belt separating the Congo and Kalahari Cratons. The Damara mobile belt is underlain by a thick high velocity upper mantle lid which is indistinguishable from that beneath the Congo Craton to the north and the Kalahari Craton to the south. Low velocity upper mantle underlie the Hoggar, Tebesti and Darfur volcanic areas of northern Africa, and very low velocities underlie the Afar region to at least 400 km depth. We use the relationship between shear velocity and temperature of Priestley & McKenzie (2006) to derive a model for the African thermal lithosphere. Two types of lithosphere underlie Africa. Thick lithosphere underlies most of western Africa and all of southern Africa; in the latter the extent of the thick lithosphere is significantly different from the distribution of Archean crust mapped at the surface. Thick lithosphere forms one continuous structure beneath the Congo and Kalahari Cratons. Other than the Pan-African Damara mobile belt, the only Pan-African terrane of Africa free of recent (<30 Ma) volcanism, all of the Pan- African is underlain by lithosphere whose thickness is too thin to be resolved by our current surface wave analysis.

Karst in the United States: a digital map compilation and database

USGS Publications Warehouse

Weary, David J.; Doctor, Daniel H.

2014-01-01

This report describes new digital maps delineating areas of the United States, including Puerto Rico and the U.S. Virgin Islands, having karst or the potential for development of karst and pseudokarst. These maps show areas underlain by soluble rocks and also by volcanic rocks, sedimentary deposits, and permafrost that have potential for karst or pseudokarst development. All 50 States contain rocks with potential for karst development, and about 18 percent of their area is underlain by soluble rocks having karst or the potential for development of karst features. The areas of soluble rocks shown are based primarily on selection from State geologic maps of rock units containing significant amounts of carbonate or evaporite minerals. Areas underlain by soluble rocks are further classified by general climate setting, degree of induration, and degree of exposure. Areas having potential for volcanic pseudokarst are those underlain chiefly by basaltic-flow rocks no older than Miocene in age. Areas with potential for pseudokarst features in sedimentary rocks are in relatively unconsolidated rocks from which pseudokarst features, such as piping caves, have been reported. Areas having potential for development of thermokarst features, mapped exclusively in Alaska, contain permafrost in relatively thick surficial deposits containing ground ice. This report includes a GIS database with links from the map unit polygons to online geologic unit descriptions.

Wrinkle ridges, reverse faulting, and the depth penetration of lithospheric stress in lunae planum, Mars

NASA Technical Reports Server (NTRS)

Zuber, M. T.

1993-01-01

Tectonic features on a planetary surface are commonly used as constraints on models to determine the state of stress at the time the features formed. Quantitative global stress models applied to understand the formation of the Tharsis province on Mars constrained by observed tectonics have calculated stresses at the surface of a thin elastic shell and have neglected the role of vertical structure in influencing the predicted pattern of surface deformation. Wrinkle ridges in the Lunae Planum region of Mars form a conentric pattern of regularly spaced features in the eastern and southeastern part of Tharsis; they are formed due to compressional stresses related to the response of the Martian lithosphere to the Tharsis bulge. As observed in the exposures of valley walls in areas such as the Kasei Valles, the surface plains unit is underlain by an unconsolidated impact-generated megaregolith that grades with depth into structurally competent lithospheric basement. The ridges have alternatively been hypothesized to reflect deformation restricted to the surface plains unit ('thin skinned deformation') and deformation that includes the surface unit, megaregolith and basement lithosphere ('thick skinned deformation'). We have adopted a finite element approach to quantify the nature of deformation associated with the development of wrinkle ridges in a vertically stratified elastic lithosphere. We used the program TECTON, which contains a slippery node capability that allowed us to explicitly take into account the presence of reverse faults believed to be associated with the ridges. In this study we focused on the strain field in the vicinity of a single ridge when slip occurs along the fault. We considered two initial model geometries. In the first, the reverse fault was assumed to be in the surface plains unit, and in the second the initial fault was located in lithospheric basement, immediately beneath the weak megaregolith. We are interested in the conditions underwhich strain in the surface layer and basement either penetrates or fails to penetrate through the megaregolith. We thus address the conditions required for an initial basement fault to propagate through the megaregolith to the surface, as well as the effect of the megareolith on the strain tensor in the vicinity of a fault that nucleates in the surface plains unit.

Wrinkle ridges, reverse faulting, and the depth penetration of lithospheric stress in lunae planum, Mars

NASA Astrophysics Data System (ADS)

Zuber, M. T.

1993-03-01

Tectonic features on a planetary surface are commonly used as constraints on models to determine the state of stress at the time the features formed. Quantitative global stress models applied to understand the formation of the Tharsis province on Mars constrained by observed tectonics have calculated stresses at the surface of a thin elastic shell and have neglected the role of vertical structure in influencing the predicted pattern of surface deformation. Wrinkle ridges in the Lunae Planum region of Mars form a conentric pattern of regularly spaced features in the eastern and southeastern part of Tharsis; they are formed due to compressional stresses related to the response of the Martian lithosphere to the Tharsis bulge. As observed in the exposures of valley walls in areas such as the Kasei Valles, the surface plains unit is underlain by an unconsolidated impact-generated megaregolith that grades with depth into structurally competent lithospheric basement. The ridges have alternatively been hypothesized to reflect deformation restricted to the surface plains unit ('thin skinned deformation') and deformation that includes the surface unit, megaregolith and basement lithosphere ('thick skinned deformation'). We have adopted a finite element approach to quantify the nature of deformation associated with the development of wrinkle ridges in a vertically stratified elastic lithosphere. We used the program TECTON, which contains a slippery node capability that allowed us to explicitly take into account the presence of reverse faults believed to be associated with the ridges. In this study we focused on the strain field in the vicinity of a single ridge when slip occurs along the fault. We considered two initial model geometries. In the first, the reverse fault was assumed to be in the surface plains unit, and in the second the initial fault was located in lithospheric basement, immediately beneath the weak megaregolith. We are interested in the conditions under which strain in the surface layer and basement either penetrates or fails to penetrate through the megaregolith. We thus address the conditions required for an initial basement fault to propagate through the megaregolith to the surface, as well as the effect of the megareolith on the strain tensor in the vicinity of a fault that nucleates in the surface plains unit.

Preliminary evaluation of ground-water flow in Bear Creek Valley, the Oak Ridge Reservation, Tennessee

USGS Publications Warehouse

Bailey, Z.C.

1988-01-01

Bear Creek Valley, Tennessee contains hazardous waste disposal sites where contaminants leach into ground and surface water. Groundwater flow and the potential migration of contaminants is poorly understood. The Valley is underlain by calcareous shale that contains limestone units. Ridges to the north and south are underlain by interbedded sandstones, siltstone and shale, and by massive, siliceous dolomite, respectively. The bedrock, which dips about 45 degrees southeast, is overlain by regolith to a maximum thickness of 80 ft. Observed hydraulic conductivities for the regolith range from 0.01 to 13 ft/day, and for the bedrock, from 0.001 to 11 ft/day. Groundwater flow is probably toward streams and is preferential along strike because of an areal anisotropy in hydraulic conductivity. A cross sectional groundwater flow model was used to test the conceptualized flow system and to help identify areas where additional data are needed. The preliminary model shows a pattern of recharge at both ridges, flow toward the valley, and upward flow that discharges into Bear Creek. Final model values of hydraulic conductivity in the bedrock range from 0.01 to 0.1 ft/day and reflect an areal anisotropy ratio of 1:5. Simulated recharge was 10 inches/year. (USGS)

Estimating Age Distributions of Base Flow in Watersheds Underlain by Single and Dual Porosity Formations Using Groundwater Transport Simulation and Weighted Weibull Functions

NASA Astrophysics Data System (ADS)

Sanford, W. E.

2015-12-01

Age distributions of base flow to streams are important to estimate for predicting the timing of water-quality responses to changes in distributed inputs of nutrients or pollutants at the land surface. Simple models of shallow aquifers will predict exponential age distributions, but more realistic 3-D stream-aquifer geometries will cause deviations from an exponential curve. In addition, in fractured rock terrains the dual nature of the effective and total porosity of the system complicates the age distribution further. In this study shallow groundwater flow and advective transport were simulated in two regions in the Eastern United States—the Delmarva Peninsula and the upper Potomac River basin. The former is underlain by layers of unconsolidated sediment, while the latter consists of folded and fractured sedimentary rocks. Transport of groundwater to streams was simulated using the USGS code MODPATH within 175 and 275 watersheds, respectively. For the fractured rock terrain, calculations were also performed along flow pathlines to account for exchange between mobile and immobile flow zones. Porosities at both sites were calibrated using environmental tracer data (3H, 3He, CFCs and SF6) in wells and springs, and with a 30-year tritium record from the Potomac River. Carbonate and siliciclastic rocks were calibrated to have mobile porosity values of one and six percent, and immobile porosity values of 18 and 12 percent, respectively. The age distributions were fitted to Weibull functions. Whereas an exponential function has one parameter that controls the median age of the distribution, a Weibull function has an extra parameter that controls the slope of the curve. A weighted Weibull function was also developed that potentially allows for four parameters, two that control the median age and two that control the slope, one of each weighted toward early or late arrival times. For both systems the two-parameter Weibull function nearly always produced a substantially better fit to the data than the one-parameter exponential function. For the single porosity system it was found that the use of three parameters was often optimal for accurately describing the base-flow age distribution, whereas for the dual porosity system the fourth parameter was often required to fit the more complicated response curves.

Hydrogeology of, and Simulation of Ground-Water Flow In, the Pohatcong Valley, Warren County, New Jersey

USGS Publications Warehouse

Carleton, Glen B.; Gordon, Alison D.

2007-01-01

A numerical ground-water-flow model was constructed to simulate ground-water flow in the Pohatcong Valley, including the area within the U.S. Environmental Protection Agency Pohatcong Valley Ground Water Contamination Site. The area is underlain by glacial till, alluvial sediments, and weathered and competent carbonate bedrock. The northwestern and southeastern valley boundaries are regional-scale thrust faults and ridges underlain by crystalline rocks. The unconsolidated sediments and weathered bedrock form a minor surficial aquifer and the carbonate rocks form a highly transmissive fractured-rock aquifer. Ground-water flow in the carbonate rocks is primarily downvalley towards the Delaware River, but the water discharges through the surficial aquifer to Pohatcong Creek under typical conditions. The hydraulic characteristics of the carbonate-rock aquifer are highly heterogeneous. Horizontal hydraulic conductivities span nearly five orders of magnitude, from 0.5 feet per day (ft/d) to 1,800 ft/d. The maximum transmissivity calculated is 37,000 feet squared per day. The horizontal hydraulic conductivities calculated from aquifer tests using public supply wells open to the Leithsville Formation and Allentown Dolomite are 34 ft/d (effective hydraulic conductivity) and 85 to 190 ft/d (minimum and maximum hydraulic conductivity, respectively, yielding a horizontal anisotropy ratio of 0.46). Stream base-flow data were used to estimate the net gain (or loss) for selected reaches on Brass Castle Creek, Shabbecong Creek, three smaller tributaries to Pohatcong Creek, and for five reaches on Pohatcong Creek. Estimated mean annual base flows for Brass Castle Creek, Pohatcong Creek at New Village, and Pohatcong Creek at Carpentersville (from correlations of partial- and continuous-record stations) are 2.4, 25, and 45 cubic feet per second (ft3/s) (10, 10, and 11 inches per year (in/yr)), respectively. Ground-water ages estimated using sulfur hexafluoride (SF6), chlorofluorocarbon (CFC), and tritium-helium age-dating techniques range from 0 to 27 years, with a median age of 6 years. Land-surface and ground-water water budgets were calculated, yielding an estimated rate of direct recharge tothe surficial aquifer of about 23 in/yr, and an estimated net recharge to the ground-water system within the area underlain by carbonate rock (11.4 mi2) of 29 in/yr (10 in/yr over the entire 33.3 mi2 basin). A finite-difference, numerical model was developed to simulate ground-water flow in the Pohatcong Valley. The four-layer model encompasses the entire carbonate-rock part of the valley. The carbonate-rock aquifer was modeled as horizontally anisotropic, with the direction of maximum transmissivity aligned with the longitudinal axis of the valley. All lateral boundaries are no-flow boundaries. Recharge was applied uniformly to the topmost active layer with additional recharge added near the lateral boundaries to represent infiltration of runoff from adjacent crystalline-rock areas. The model was calibrated to June 2001 water levels in wells completed in the carbonate-rock aquifer, August 2000 stream base-flow measurements, and the approximate ground-water age. The ground-water-flow model was constructed in part to test possible site contamination remediation alternatives. Four previously determined ground-water remediation alternatives (GW1, GW2, GW3, and GW4) were simulated. For GW1, the no-action alternative, simulated pathlines originating in the tetrachloroethene (PCE) and trichloroethene (TCE) source areas within the Ground-Water Contamination Site end at Pohatcong Creek near the confluence with Shabbecong Creek, although some particles went deeper in the aquifer system and ultimately discharge to Pohatcong Creek about 10 miles downvalley in Pohatcong Township. Remediation alternatives GW2, GW3, and GW4 include ground-water withdrawal, treatment, and reinjection. The design for GW2 includes wells in the TCE and PCE source areas that wit

Use of electrical resistivity to detect underground mine voids in Ohio

USGS Publications Warehouse

Sheets, Rodney A.

2002-01-01

Electrical resistivity surveys were completed at two sites along State Route 32 in Jackson and Vinton Counties, Ohio. The surveys were done to determine whether the electrical resistivity method could identify areas where coal was mined, leaving air- or water-filled voids. These voids can be local sources of potable water or acid mine drainage. They could also result in potentially dangerous collapse of roads or buildings that overlie the voids. The resistivity response of air- or water-filled voids compared to the surrounding bedrock may allow electrical resistivity surveys to delineate areas underlain by such voids. Surface deformation along State Route 32 in Jackson County led to a site investigation, which included electrical resistivity surveys. Several highly resistive areas were identified using axial dipole-dipole and Wenner resistivity surveys. Subsequent drilling and excavation led to the discovery of several air-filled abandoned underground mine tunnels. A site along State Route 32 in Vinton County, Ohio, was drilled as part of a mining permit application process. A mine void under the highway was instrumented with a pressure transducer to monitor water levels. During a period of high water level, electrical resistivity surveys were completed. The electrical response was dominated by a thin, low-resistivity layer of iron ore above where the coal was mined out. Nearby overhead powerlines also affected the results.

Climate Change and Thawing Permafrost in Two Iñupiaq Communities of Alaska's Arctic: Observations, Implications, and Resilience

NASA Astrophysics Data System (ADS)

Woodward, A.; Kofinas, G.

2013-12-01

For thousands of years the Iñupiat of northern Alaska have relied on ecosystems underlain by permafrost for material and cultural resources. As permafrost thaws across the Arctic, these social-ecological systems are changing rapidly. Community-based research and extensive local knowledge of Iñupiaq villagers offer unique and valuable contributions to understanding permafrost change and its implications for humans. We partnered with two Iñupiaq communities in Alaska's Arctic to investigate current and potential effects of thawing permafrost on social-ecological systems. Anaktuvuk Pass is situated on thaw-stable consolidated gravel in the Brooks Range, while Selawik rests on ice-rich permafrost in Beringia lowland tundra. Using the transdisciplinary approach of resilience theory and mixed geophysical and ethnographic methods, we measured active layer thaw depths and documented local knowledge about climate and permafrost change. Thaw depths were greater overall in Selawik. Residents of both communities reported a variety of changes in surface features, hydrology, weather, flora, and fauna that they attribute to thawing permafrost and / or climate change. Overall, Selawik residents described more numerous and extreme examples of such changes, expressed higher degrees of certainty that change is occurring, and anticipated more significant and negative implications for their way of life than did residents of Anaktuvuk Pass. Of the two villages, Selawik faces greater and more immediate challenges to the resilience of its social-ecological system as permafrost thaws.

ARC-1989-A89-7030

NASA Image and Video Library

1989-08-25

P-34692 Range : 500 km. ( 300 miles ) Smallest Resolvable Feature : 900 m. or 2,700 ft. Part of Triton's complex geological history canbe seen in this image, shot by Voyager 2. Part of a sequence, it shows a surface dominated by many roughly circular, polygonal, and arcuate features between 30 and 50 km (18 and 30 miles ) across. Some resemble degraded impact craters of Mars, while others resemble the 'palimpsest' features of Jupiter's satellite Ganymede. Peculiar intersecting, double ridged lines are 15 to 20 km. or 9 to 12 miles wide and hundreds of kilometers long. Theyresemble some deformational belts of Ganymede. Patches of plainsforming material tend to occur in local depressions. The geologic features of Triton and spectroscopic information indicates that the surface of Triton is underlain by a mixture of ices.

Hydrologic controls on the transport and cycling of carbon and nitrogen in a boreal catchment underlain by continuous permafrost

NASA Astrophysics Data System (ADS)

Koch, J. C.; Runkel, R. L.; Striegl, R.; McKnight, D. M.

2013-06-01

ecosystems represent a large carbon (C) reservoir and a substantial source of greenhouse gases. Hydrologic conditions dictate whether C leached from boreal soils is processed in catchments or flushed to less productive environments via the stream. This study quantified hydrologic and biogeochemical C loss from a boreal catchment underlain by frozen silt, where flowpaths may deepen as the active layer thaws over the summer. We hypothesized a decrease in the magnitude of C mineralization over the summer associated with changing flowpaths and decreasing hydrologic connectivity, organic matter lability, and nitrogen (N) availability. Conservative tracers were used to partition C and N loss between catchment export and biogeochemical processing. Coupling tracers with tributary and porewater chemistry indicated C and N cycling in soil flowpaths, with an exponential decrease over the summer. Nitrate was primarily reduced in hillslope flowpaths and the lack of N reaching the stream appeared to limit C mineralization. Stream export accounted for the greatest loss of C, removing 247 and 113 mol hr-1 in the early and late summer, respectively. Reactivity was related to hydrologic connectivity between the soils and stream, which was greatest early in the summer and following a large flood. While a warming climate may increase storage potential in thawed soils, the early-season flush of labile material and late-season runoff through mineral flowpaths may maintain high C export rates. Therefore, we highlight physical export as a dominant cause of aqueous C loss from silty catchments as the Arctic continues to thaw.

Spatial distribution of thermokarst terrain in Arctic Alaska

USGS Publications Warehouse

Farquharson, Louise; Mann, Dan H; Grosse, Guido; Jones, Benjamin M.; Romanovsky, Vladimir

2016-01-01

In landscapes underlain by ice-rich permafrost, the development of thermokarst landforms can have drastic impacts on ecosystem processes and human infrastructure. Here we describe the distribution of thermokarst landforms in the continuous permafrost zone of Arctic Alaska, analyze linkages to the underlying surficial geology, and discuss the vulnerability of different types of landscapes to future thaw. We identified nine major thermokarst landforms and then mapped their distributions in twelve representative study areas totaling 300-km2. These study areas differ in their geologic history, permafrost-ice content, and ground thermal regime. Results show that 63% of the entire study area is occupied by thermokarst landforms and that the distribution of thermokarst landforms and overall landscape complexity varies markedly with surficial geology. Areas underlain by ice-rich marine silt are the most affected by thermokarst (97% of total area), whereas areas underlain by glacial drift are least affected (14%). Drained thermokarst-lake basins are the most widespread thermokarst landforms, covering 33% of the entire study region, with greater prevalence in areas of marine silt (48% coverage), marine sand (47%), and aeolian silt (34%). Thermokarst-lakes are the second most common thermokarst landform, covering 16% of the study region, with highest coverage in areas underlain by marine silt (39% coverage). Thermokarst troughs and pits cover 7% of the study region and are the third most prevalent thermokarst landform. They are most common in areas underlain by deltaic sands and gravels (18% coverage) and marine sand (12%). Alas valleys are widespread in areas of aeolian silt (14%) located in gradually sloping uplands. Areas of marine silt have been particularly vulnerable to thaw in the past because they are ice-rich and have low-gradient topography facilitating the repeated development of thermokarst-lakes. In the future, ice-rich aeolian, upland terrain (yedoma) will be particularly susceptible to thaw because it still contains massive concentrations of ground ice in the form of syngenetic ice-wedges that have remained largely intact since the Pleistocene.

Coral ages and island subsidence, Hilo drill hole

USGS Publications Warehouse

Moore, J.G.; Ingram, B.L.; Ludwig, K. R.; Clague, D.A.

1996-01-01

A 25.8-m-thick sedimentary section containing coral fragments occurs directly below a surface lava flow (the ???1340 year old Panaewa lava flow) at the Hilo drill hole. Ten coral samples from this section dated by accelerator mass spectrometry (AMS) radiocarbon and five by thermal infrared multispectral scanner (TIMS) 230Th/U methods show good agreement. The calcareous unit is 9790 years old at the bottom and 1690 years old at the top and was deposited in a shallow lagoon behind an actively growing reef. This sedimentary unit is underlain by a 34-m-thick lava flow which in turn overlies a thin volcaniclastic silt with coral fragments that yield a single 14C date of 10,340 years. The age-depth relations of the dated samples can be compared with proposed eustatic sea level curves after allowance for island subsidence is taken. Island subsidence averages 2.2 mm/yr for the last 47 years based on measurements from a tide gage near the drill hole or 2.5-2.6 mm/yr for the last 500,000 years based on the ages and depths of a series of drowned coral reefs offshore from west Hawaii. The age-depth measurements of coral fragments are more consistent with eustatic sea levels as determined by coral dating at Barbados and Albrolhos Islands than those based on oxygen isotopic data from deep sea cores. The Panaewa lava flow entered a lagoon underlain by coral debris and covered the drill site with 30.9 m of lava of which 11 m was above sea level. This surface has now subsided to 4.2 m above sea level, but it demonstrates how a modern lava flow entering Hilo Bay would not only change the coastline but could extensively modify the offshore shelf.

Texture and depositional history of near-surface alluvial deposits in the central part of the western San Joaquin Valley, California

USGS Publications Warehouse

Laudon, Julie; Belitz, Kenneth

1989-01-01

Saline conditions and associated high levels of selenium and other soluble trace elements in soil, shallow ground water, and agricultural drain water of the western San Joaquin Valley, California, have prompted a study of the texture of near-surface alluvial deposits in the central part of the western valley. Texture is characterized by the percentage of coarse-grained sediment present within a specified subsurface depth interval and is used as a basis for mapping the upper 50 feet of deposits. Resulting quantitative descriptions of the deposits are used to interpret the late Quaternary history of the area. Three hydrogeologic units--Coast Range alluvium, flood-basin deposits, and Sierran sand--can be recognized in the upper 50 feet of deposits in the central part of the western San Joaquin Valley. The upper 30 feet of Coast Range alluvium and the adjacent 5 to 35 feet of flood-basin deposits are predominantly fine grained. These fine-grained Coast Range deposits are underlain by coarse-grained channel deposits. The fine-grained flood basin deposits are underlain by coarse-grained Sierran sand. The extent and orientation of channel deposits below 20 feet in the Coast Range alluvium indicate that streams draining the Coast Range may have been tributary to the axial stream that deposited the Sierran sand and that streamflow may have been to the southeast. The fining-upward stratigraphic sequence in the upper 50 feet of deposits and the headward retreat of tributary stream channels from the valley trough with time support a recent hypothesis of climatic control of alluviation in the western San Joaquin Valley.

Magnetotelluric Imaging of the Lithosphere Across the Variscan Orogen (Iberian Autochthonous Domain, NW Iberia)

NASA Astrophysics Data System (ADS)

Alves Ribeiro, J.; Monteiro-Santos, F. A.; Pereira, M. F.; Díez Fernández, R.; Dias da Silva, Í.; Nascimento, C.; Silva, J. B.

2017-12-01

A new magnetotelluric (MT) survey comprising 17 MT soundings throughout a 30 km long N30°W transect in the Iberian autochthons domain of NW Iberia (Central Iberian Zone) is presented. The 2-D inversion model shows the resistivity structure of the continental crust up to 10 km depth, heretofore unavailable for this region of the Variscan Orogen. The MT model reveals a wavy structure separating a conductive upper layer underlain by a resistive layer, thus picturing the two main tectonic blocks of a large-scale D2 extensional shear zone (i.e., Pinhel shear zone). The upper layer represents a lower grade metamorphic domain that includes graphite-rich rocks. The lower layer consists of high-grade metamorphic rocks that experienced partial melting and are associated with granites (more resistive) emplaced during crustal thinning. The wavy structure is the result of superimposed crustal shortening responsible for the development of large-scale D3 folds (e.g., Marofa synform), later deflected and refolded by a D4 strike-slip shear zone (i.e., Juzbado-Penalva do Castelo shear zone). The later contribution to the final structure of the crust is marked by the intrusion of postkinematic granitic rocks and the propagation of steeply dipping brittle fault zones. Our study demonstrates that MT imaging is a powerful tool to understand complex crustal structures of ancient orogens in order to design future prospecting surveys for mineral deposits of economic interest.

A FORTRAN program for calculating nonlinear seismic ground response

USGS Publications Warehouse

Joyner, William B.

1977-01-01

The program described here was designed for calculating the nonlinear seismic response of a system of horizontal soil layers underlain by a semi-infinite elastic medium representing bedrock. Excitation is a vertically incident shear wave in the underlying medium. The nonlinear hysteretic behavior of the soil is represented by a model consisting of simple linear springs and Coulomb friction elements arranged as shown. A boundary condition is used which takes account of finite rigidity in the elastic substratum. The computations are performed by an explicit finite-difference scheme that proceeds step by step in space and time. A brief program description is provided here with instructions for preparing the input and a source listing. A more detailed discussion of the method is presented elsewhere as is the description of a different program employing implicit integration.

The use of LANDSAT imagery in relation to air survey imagery for terrain analysis in northwest Queensland, Australia, volume 1

NASA Technical Reports Server (NTRS)

Cole, M. M.; Owen-Jones, E. S. (Principal Investigator)

1977-01-01

The author has identified the following significant results. Distinctive spectral signatures discriminated areas underlain by distinctive lithological/stratigraphical units where bedrock either outcrops or is relatively near to surface in the Lady Annie-Mt. Gordon fault zone, the Mary Kathleen, and Dugald River-Naraku areas. Spectral signatures associated with discrete plant communities distinguished different types of superficial deposits over the Cloncurry Plains. Distinctive spectral signatures also revealed the presence and nature of concealed bedrock beneath cover of residuum and superficial deposits where this is relatively thin in the Cloncurry Plains. Major faults were clearly displayed in areas of outcropping and near surface bedrock. Sets of lineaments with preferred orientations were identified in the Lady Annie and Dugald River areas. Known base metal deposits occur along these features.

Rainfall and Erosion Response Following a Southern California Wildfire

NASA Astrophysics Data System (ADS)

Wohlgemuth, P. M.; Robichaud, P. R.; Brown, R. E.

2011-12-01

Wildfire renders landscapes susceptible to flooding and accelerated surface erosion. Consumption of the vegetation canopy and the litter or duff layer removes resistances to the agents of erosion. Moreover, changes in soil properties can restrict infiltration, increasing the effectiveness of the driving forces of rainsplash and surface runoff. However, it is unclear whether surface erosion varies linearly with rainfall amounts and intensities or if thresholds exist beyond which erosion increases in a different trajectory. The Santiago Fire burned over 11000 ha in northeastern Orange County, California in October 2007. The burn area consists of a deeply dissected mountain block underlain by sedimentary and metamorphic rocks that produce erosive soils. Regional erosion and sediment transport is triggered by winter cyclonic storms. Recording raingages were deployed across a vertical gradient within the burned area and silt fences were constructed to monitor hillslope erosion. During the study period initial storms were characterized by moderate rainfall (amounts less than 25 mm with peak 10-minute intensities of less than 10 mm per hr). Surface erosion was concomitantly minor, less than 0.4 Mg per ha. However, an unusual thunderstorm in late May 2008 produced spatially variable rainfall and consequent surface erosion across the study area. The raingage at a lower elevation site measured 41.4 mm of rain for this storm with a peak 10-minute intensity of 81 mm per hr. The silt fences were overtopped, yielding a minimum value of 18.5 Mg per ha. In contrast, the raingage at an upper elevation site recorded 19.6 mm of rain with a peak 10-minute intensity of 50 mm per hr. Surface erosion in the higher elevation sites was negligible (0.1 Mg per ha). Subsequently, individual storms exceeded 100 mm of rainfall but peak 10-minute intensities never approached those of the May thunderstorm. Erosion was moderate (mostly less than 5 Mg per ha), albeit influenced by the presence of regrowing vegetation. We therefore believe that surface erosion in the immediate postfire environment is more related to storm intensity than rainfall amount. Even allowing for site-to-site differences and site changes over the first postfire winter season, it is clear that some threshold in erosion response was crossed at the lower elevation sites during the May 2008 thunderstorm. We suggest that this represents a threshold of peak 10-minute intensity of between 50 and 80 mm per hr.

Relation between selected well-construction characteristics and occurrence of bacteria in private household-supply wells, south-central and southeastern Pennsylvania

USGS Publications Warehouse

Zimmerman, Tammy M.; Zimmerman, Michele L.; Lindsey, Bruce D.

2001-01-01

Total coliform and Escherichia coli (E. coli) bacteria were analyzed in ground water sampled from 78 private household-supply wells as part of a study by the U.S. Geological Survey in cooperation with the Pennsylvania Department of Environmental Protection to evaluate the relation between well construction characteristics and the occurrence of bacteria in ground water. Sampling was done in eight counties in south-central and southeastern Pennsylvania from September 2000 to March 2001. All samples were collected from wells in close proximity to agricultural land-use areas.Total coliform bacteria were found in water from 62 percent (48 of 78) of the wells, and bacteria were just as likely to be found in sanitary wells (grouted/loose-fitting well cap or grouted/sanitary sealed well cap) as in nonsanitary wells (nongrouted/ loose-fitting well cap). The areas underlain by carbonate bedrock had the highest percentages of total coliform detected (about 75 percent). Nearly half of the samples collected in the areas underlain by noncarbonate bedrock also were found to have total coliform present. E. coli bacteria were found in water from 10 percent of the wells. Seventeen percent of the samples that were positive for total coliform also were positive for E. coli. The presence of E. coli bacteria was more likely in water from nonsanitary wells. Additionally, the presence of E. coli bacteria was more likely in ground water from wells underlain by carbonate bedrock. A further breakdown of the data into four groups on the basis of sanitary construction and bedrock type indicated the presence of E. coli was more likely in water from nonsanitary wells in areas underlain by carbonate bedrock.Statistical analysis of other well-construction characteristics that might relate to occurrence of bacteria showed that the presence of total coliform bacteria was related to the depth to water-bearing zone in both sanitary and nonsanitary wells in areas underlain by carbonate bedrock. Relations also are present between the presence of total coliform bacteria and casing length in nonsanitary wells in areas underlain by noncarbonate bedrock. Bacteria were found in wells both with and without insects observed on the underside of the well cap. Because of the small number of wells sampled that had sanitary sealed caps, it is uncertain whether installation of sanitary sealed well caps would reduce the incidence of bacteria in ground water from wells or if the presence of bacteria is because of a combination of well-construction characteristics or aquifer-wide contamination of limited or broad areal extent.

Hydrogeology and groundwater quality of Highlands County, Florida

USGS Publications Warehouse

Spechler, Rick M.

2010-01-01

Groundwater is the main source of water supply in Highlands County, Florida. As the demand for water in the county increases, additional information about local groundwater resources is needed to manage and develop the water supply effectively. To address the need for additional data, a study was conducted to evaluate the hydrogeology and groundwater quality of Highlands County. Total groundwater use in Highlands County has increased steadily since 1965. Total groundwater withdrawals increased from about 37 million gallons per day in 1965 to about 107 million gallons per day in 2005. Much of this increase in water use is related to agricultural activities, especially citrus cultivation, which increased more than 300 percent from 1965 to 2005. Highlands County is underlain by three principal hydrogeologic units. The uppermost water-bearing unit is the surficial aquifer, which is underlain by the intermediate aquifer system/intermediate confining unit. The lowermost hydrogeologic unit is the Floridan aquifer system, which consists of the Upper Floridan aquifer, as many as three middle confining units, and the Lower Floridan aquifer. The surficial aquifer consists primarily of fine-to-medium grained quartz sand with varying amounts of clay and silt. The aquifer system is unconfined and underlies the entire county. The thickness of the surficial aquifer is highly variable, ranging from less than 50 to more than 300 feet. Groundwater in the surficial aquifer is recharged primarily by precipitation, but also by septic tanks, irrigation from wells, seepage from lakes and streams, and the lateral groundwater inflow from adjacent areas. The intermediate aquifer system/intermediate confining unit acts as a confining layer (except where breached by sinkholes) that restricts the vertical movement of water between the surficial aquifer and the underlying Upper Floridan aquifer. The sediments have varying degrees of permeability and consist of permeable limestone, dolostone, or sand, or relatively impermeable layers of clay, clayey sand, or clayey carbonates. The thickness of the intermediate aquifer system/ intermediate confining unit ranges from about 200 feet in northwestern Highlands County to more than 600 feet in the southwestern part. Although the intermediate aquifer system is present in the county, it is unclear where the aquifer system grades into a confining unit in the eastern part of the county. Up to two water-bearing units are present in the intermediate aquifer system within the county. The lateral continuity and water-bearing potential of the various aquifers within the intermediate aquifer system are highly variable. The Floridan aquifer system is composed of a thick sequence of limestone and dolostone of Upper Paleocene to Oligocene age. The top of the aquifer system ranges from less than 200 feet below NGVD 29 in extreme northwestern Highlands County to more than 600 feet below NGVD 29 in the southwestern part. The principal source of groundwater supply in the county is the Upper Floridan aquifer. As of 2005, about 89 percent of the groundwater withdrawn from the county was obtained from this aquifer, mostly for agricultural irrigation and public supply. Over most of Highlands County, the Upper Floridan aquifer generally contains freshwater, and the Lower Floridan aquifer contains more mineralized water. The potentiometric surface of the Upper Floridan aquifer is constantly fluctuating, mainly in response to seasonal variations in rainfall and groundwater withdrawals. The potentiometric surface of the Upper Floridan aquifer in May 2007, which represents the hydrologic conditions near the end of the dry season when water levels generally are near their lowest, ranged from about 79 feet above NGVD 29 in northwestern Highlands County to about 40 feet above NGVD 29 in the southeastern part of the county. The potentiometric surface of the Upper Floridan aquifer in September 2007 was about 3 to 10 feet high

Multimode seismoelectric phenomena generated using explosive and vibroseis sources

NASA Astrophysics Data System (ADS)

Butler, Karl E.; Kulessa, Bernd; Pugin, André J.-M.

2018-05-01

A field trial of seismoelectric surveying was carried out at a site underlain by 20 m of water-saturated clayey Champlain Sea sediments, renowned for their amenability to high resolution imaging by seismic reflection surveys. Seismically induced electrokinetic effects were recorded using an array of 26 grounded dipole electric field antennas, and two different seismic sources including an eight-gauge shotgun, and a moderate power (10 000 lb Minivib) vibrator. Despite the high electrical conductivity of the sediments, shot records show evidence of possible interfacial seismoelectric conversions caused by the arrival of P-waves at the base of the clay/top of bedrock and at the top of a layer of elevated porosity and conductivity within the clay at 7 m depth. However, the data are more remarkable for the fact that P-wave, S-wave, and PS/SP converted wave reflections evident in the seismic records all give rise to electrical arrivals exhibiting very similar moveout patterns in the seismoelectric records. Superficially, these electrical responses could be misinterpreted as simple coseismic seismoelectric effects associated with the arrival of reflected seismic waves at each dipole antenna on surface. However, their broader bandwidth, superior coherency and earlier arrival times compared to their corresponding seismic arrivals indicate that the electrical effects are generated by the arrival of seismic reflections below each dipole at the shallow intraclay interface 7 m below surface. Such quasi-coseismic arrivals have recently been predicted by full-waveform seismoelectric modelling and characterized as evanescent electromagnetic (EM) waves. In retrospect, they were also observed in earlier seismoelectric field trials, but not measured as clearly nor recognized as a distinct seismoelectric mode intermediate between interfacial and coseismic effects. We propose that the observed quasi-coseismic effect can be understood physically as a fringing field emanating from the travelling charge separation associated with a P-wave (direct or mode-converted) crossing a subsurface interface at an oblique angle. Such effects may be nearly indistinguishable from coseismic effects if the interface depth is small compared to the seismic wavelength, but recognition of the phenomenon contributes to an improved understanding of the seismoelectric wavefield, and will lead to improved interpretations. From a practical standpoint, the results of this field trial suggest that using electric field receivers to supplement geophones on surface could yield significantly higher resolution seismic reflection images in those areas where suitable near-surface layers exist for the generation of quasi-coseismic effects. The results also reinforce the importance of using multichannel recording to allow interfacial seismoelectric conversions originating at depth to be distinguished from stronger coseismic and quasi-coseismic arrivals originating in the near-surface by measurement of their arrival time versus offset (moveout) and amplitude versus offset behaviours.

Precambrian crust beneath the Mesozoic northern Canadian Cordillera discovered by Lithoprobe seismic reflection profiling

NASA Astrophysics Data System (ADS)

Cook, Frederick A.; Clowes, Ronald M.; Snyder, David B.; van der Velden, Arie J.; Hall, Kevin W.; Erdmer, Philippe; Evenchick, Carol A.

2004-04-01

The Cordillera in northern Canada is underlain by westward tapering layers that can be followed from outcrops of Proterozoic strata in the Foreland belt to the lowermost crust of the orogenic interior, a distance of as much as 500 km across strike. They are interpreted as stratified Proterozoic rocks, including ˜1.8-0.7 Ga supracrustal rocks and their basement. The layering was discovered on two new deep seismic reflection profiles in the Yukon (Line 3; ˜650 km) and northern British Columbia (Line 2; ˜1245 km in two segments) that were acquired as part of the Lithoprobe Slave-Northern Cordillera Lithospheric Evolution (SNORCLE) transect. In the Mackenzie Mountains of the eastern Yukon, the layering in Line 3 is visible between 5.0 and 12.0 s (˜15 to 36 km depth). It is followed southwestward for nearly 650 km (˜500 km across strike) and thins to less than 1.0 s (˜3.0-3.5 km thickness) near the Moho at the Yukon-Alaska international boundary. In the northern Rocky Mountains of British Columbia, the upper part of the layering on Line 2 correlates with outcrops of Proterozoic (1.76-1.0 Ga) strata in the Muskwa anticlinorium. At this location, the layering is at least 15 km thick and is followed westward then southward into the middle and lower crust for ˜700 km (˜300 km across strike). It disappears as a thin taper at the base of the crust ˜150 km east of the coast of the Alaskan panhandle. The only significant disruption in the layering occurs at the Tintina fault zone, a late to postorogenic strike-slip fault with up to 800 km of displacement, which appears as a vertical zone of little reflectivity that disrupts the continuity of the deep layering on both profiles (˜300 km apart). The base of the layered reflection zone coincides with the Moho, which exhibits variable character and undulates in a series of broad arches with widths of ˜150 km. In general, the mantle appears to have few reflections. However, at the southwest end of Line 3 near the Alaska-British Columbia border, a reflection dips eastward from ˜14.0 s to ˜21.0 s (˜45 to 73 km depth) beneath exposed Eocene magmatic rocks. It is interpreted as a relict subduction surface of the Kula plate. Our interpretation of Proterozoic layered rocks beneath most of the northern Cordillera suggests a much different crustal structure than previously considered: (1) Ancient North American crust comprising up to 25 km of metamorphosed Proterozoic to Paleozoic sediments plus 5-10 km of pre-1.8 Ga crystalline basement projects westward beneath most of the northern Canadian Cordillera. (2) The lateral (500 km by at least 1000 km) and vertical (up to 25 km) extent of the Proterozoic layers and their internal deformation are consistent with a long-lived margin for northwestern North America with alternating episodes of extension and contraction. (3) The detachments that carry deformed rocks of the Mackenzie Mountains and northern Rocky Mountains are largely confined to the upper crustal region above the layering. (4) Accreted terranes include thin klippen that were thrust over North American pericratonic strata (e.g., Yukon-Tanana), and terranes such as Nisling and Stikinia that thicken westward as the underlying Proterozoic layers taper and disappear. (5) The ages of exposed rocks are not necessarily indicative of the ages of underlying crust, a frequent observation in Lithoprobe interpretations, so that estimates of crustal growth based on surface geology may not be representative.

Quaternary geology of the Kenai Lowland and glacial history of the Cook Inlet region, Alaska

USGS Publications Warehouse

Karlstrom, Thor N.V.

1964-01-01

The Kenai Lowland is part of the Cook Inlet Lowland physiographic subprovince that borders Cook Inlet, a major marine reentrant along the Pacific Ocean coastline of south-central Alaska. The Cook Inlet Lowland occupies a structural trough underlain by rocks of Tertiary age and mantled by Quaternary deposits of varying thicknesses. The bordering high alpine mountains—the Aleutian and Alaska Ranges to the northwest and north and the Talkeetna, Chugach, and Kenai Mountains to the northeast and southeast—are underlain by rocks of Mesozoic and older ages.

Spatial distribution of residence time, microbe and storage volume of groundwater in headwater catchments

NASA Astrophysics Data System (ADS)

Tsujimura, Maki; Ogawa, Mahiro; Yamamoto, Chisato; Sakakibara, Koichi; Sugiyama, Ayumi; Kato, Kenji; Nagaosa, Kazuyo; Yano, Shinjiro

2017-04-01

Headwater catchments in mountainous region are the most important recharge area for surface and subsurface waters, and time and stock information of the water is principal to understand hydrological processes in the catchments. Also, a variety of microbes are included in the groundwater and spring water, and those varies in time and space, suggesting that information of microbe could be used as tracer for groundwater flow system. However, there have been few researches to evaluate the relationship among the residence time, microbe and storage volume of the groundwater in headwater catchments. We performed an investigation on age dating using SF6 and CFCs, microbe counting in the spring water, and evaluation of groundwater storage volume based on water budget analysis in 8 regions underlain by different lithology, those are granite, dacite, sedimentary rocks, serpentinite, basalt and volcanic lava all over Japan. We conducted hydrometric measurements and sampling of spring water in base flow conditions during the rainless periods 2015 and 2016 in those regions, and SF6, CFCs, stable isotopic ratios of oxygen-18 and deuterium, inorganic solute concentrations and total number of prokaryotes were determined on all water samples. Residence time of spring water ranged from 0 to 16 years in all regions, and storage volume of the groundwater within topographical watershed was estimated to be 0.1 m to 222 m in water height. The spring with the longer residence time tends to have larger storage volume in the watershed, and the spring underlain by dacite tends to have larger storage volume as compared with that underlain by sand stone and chert. Also, total number of prokaryotes in the spring water ranged from 103 to 105 cells/mL, and the spring tends to show clear increasing of total number of prokaryotes with decreasing of residence time. Thus, we observed a certain relationship among residence time, storage volume and total number of prokaryotes in the spring water, and these parameters are effective to evaluate hydrological characteristics in the headwaters, and the microbe information could be an excellent tracer for groundwater flow research.

Structural characteristics of cohesive flow deposits, and a sedimentological approach on their flow mechanisms.

NASA Astrophysics Data System (ADS)

Tripsanas, E. K.; Bryant, W. R.; Prior, D. B.

2003-04-01

A large number of Jumbo Piston cores (up to 20 m long), acquired from the continental slope and rise of the Northwest Gulf of Mexico (Bryant Canyon area and eastern Sigsbee Escarpment), have recovered various mass-transport deposits. The main cause of slope instabilities over these areas is oversteepening of the slopes due to the seaward mobilization of the underlying allochthonous salt masses. Cohesive flow deposits were the most common recoveries in the sediment cores. Four types of cohesive flow deposits have been recognized: a) fluid debris flow, b) mud flow, c) mud-matrix dominated debris flow, and d) clast-dominated debris flow deposits. The first type is characterized by its relatively small thickness (less than 1 m), a mud matrix with small (less than 0.5 cm) and soft mud-clasts, and a faint layering. The mud-clasts reveal a normal grading and become more abundant towards the base of each layer. That reveals that their deposition resulted by several successive surges/pulses, developed in the main flow, than the sudden “freezing” of the whole flow. The main difference between mud flow and mud-matrix dominated debris flow deposits is the presence of small to large mud-clasts in the later. Both deposits consist of a chaotic mud-matrix, and a basal shear laminated zone, where the strongest shearing of the flow was exhibited. Convolute laminations, fault-like surfaces, thrust faults, and microfaults are interpreted as occurring during the “freezing” of the flows and/or by adjustments of the rested deposits. Clast-dominated debris flow deposits consist of three zones: a) an upper plug-zone, characterized by large interlocked clasts, b) a mid-zone, of higher reworked, inversely graded clasts, floating in a mud-matrix, and c) a lower shear laminated zone. The structure of the last three cohesive flow deposits indicate that they represent deposition of typical Bingham flows, consisting of an upper plug-zone in which the yield stress is not exceeded and an underlain shearing zone, where the shear stress exceeded the yield strength of the sediments. Mud-matrix, and clast-dominated debris flow deposits are the pervasive ones. Intensely sheared thin layers (5- to 20 cm) with sharp bases, displayed as successive layers at the base of mud/debris flow deposits, or as isolated depositional units interbedded in hemipelagic sediments, are as interesting, as enigmatic. They are interpreted as basal self-lubricating layers, of having high shear stress and pore pressures, over which the mud/debris flows were able to travel for very long distances.

Comparison of mineral weathering and biomass nutrient uptake in two small forested watersheds underlain by quartzite bedrock, Catoctin Mountain, Maryland, USA

USGS Publications Warehouse

Rice, Karen; Price, Jason R.

2014-01-01

To quantify chemical weathering and biological uptake, mass-balance calculations were performed on two small forested watersheds located in the Blue Ridge Physiographic Province in north-central Maryland, USA. Both watersheds, Bear Branch (BB) and Fishing Creek Tributary (FCT), are underlain by relatively unreactive quartzite bedrock. Such unreactive bedrock and associated low chemical-weathering rates offer the opportunity to quantify biological processes operating within the watershed. Hydrologic and stream-water chemistry data were collected from the two watersheds for the 9-year period from June 1, 1990 to May 31, 1999. Of the two watersheds, FCT exhibited both higher chemical-weathering rates and biomass nutrient uptake rates, suggesting that forest biomass aggradation was limited by the rate of chemical weathering of the bedrock. Although the chemical-weathering rate in the FCT watershed was low relative to the global average, it masked the influence of biomass base-cation uptake on stream-water chemistry. Any differences in bedrock mineralogy between the two watersheds did not exert a significant influence on the overall weathering stoichiometry. The difference in chemical-weathering rates between the two watersheds is best explained by a larger proportion of reactive phyllitic layers within the bedrock of the FCT watershed. Although the stream gradient of BB is about two-times greater than that of FCT, its influence on chemical weathering appears to be negligible. The findings of this study support the biomass nutrient uptake stoichiometry of K1.0Mg1.1Ca0.97 previously determined for the study site. Investigations of the chemical weathering of relatively unreactive quartzite bedrock may provide insight into critical zone processes.

Formation of cratonic lithosphere during the initiation of plate tectonics

NASA Astrophysics Data System (ADS)

Moresi, L. N.; Beall, A.; Cooper, C. M.

2017-12-01

The Earth's oldest near-surface material, the cratonic crust, is typically underlain by unusually thick Archean lithosphere (<300 km). This cratonic lithosphere likely thickened in a high compressional stress environment. Mantle convection in the hotter Archean Earth would have imparted relatively low stresses on the lithosphere, whether or not tectonics was operating, so a high stress signal from the early Earth is paradoxical. We propose that a rapid transition, from a stagnant lid Earth to the onset of plate tectonics, generated the high stresses required to thicken the cratonic lithosphere. Numerical calculations are used to demonstrate that an existing buoyant and strong layer, representing harzburgite and felsic crust, can thicken and stabilize during the lid-breaking event. The peak compressional stress experienced by lithosphere is 3-4 higher than for the stagnant lid or mobile lid regimes immediately before and after. It is plausible that the cratonic lithosphere has still not returned to this high stress-state, explaining its stability. The lid-breaking thickening event reproduces craton features previously attributed to subduction: thrust structures, assembled crustal fragments and transport of basaltic upper crust to depths required to generate felsic melt. Palaeoarchean `pre-tectonic' structures can also survive the lid-breaking event, acting as strong crustal rafts. Together, the results indicate that the signature of a catastrophic switch, from a stagnant lid Earth to the initiation of plate tectonics, has been captured and preserved in the unusual characteristics of cratonic crust and lithosphere.

Geologic controls of subdivision damage near Denver, Colorado

USGS Publications Warehouse

Noe, D.C.

2005-01-01

This case study investigates the geologic controls on damaging ground deformations in a residential subdivision near Denver, Colo. Moderate to severe damage has occurred in certain areas where linear, parallel heave features with up to 0.3 in (1 ft) of differential displacement have formed across roads and under houses. Other areas have small, localized depressions that have formed in the roadsides with no discernable damage to nearby houses. Still other areas show no evidence of ground movements. The bedrock beneath the subdivision consists of steeply dipping Cretaceous strata of the Benton Shale, Niobrara Formation, and Pierre Shale. Quaternary soil deposits and fill, 0-16 m (0-53 ft) thick, overlie the bedrock. The most pronounced and damaging linear-heave features are coincident with steeply dipping, silty claystone with thin layers of very highly plastic bentonite. These heave features diminish as the depth to bedrock increases, and become small to negligible where the bedrock is overlain by 3 m (10 ft) or more of overburden soil deposits or fill. In contrast, areas having no visible damage and those having localized surface depressions are typically underlain by 1-12 m (3-39 ft) of alluvial-terrace deposits or fill. The depressions appear to have been caused by settlement over improperly filled water-and-sewer line trenches. The overall relationship between geology and ground deformations as seen in this subdivision may be useful for predicting, and thereby reducing, damage for future subdivision projects. Journal of Geotechnical and Geoenvironmental Engineering ?? ASCE.

Monitoring thermokarst activity and landscape change in the Eureka Sound Lowlands, Ellesmere Island, Nunavut

NASA Astrophysics Data System (ADS)

Ward, M. K.; Pollard, W. H.

2016-12-01

The Eureka Sound Lowlands is an area underlain with over 500 m of ice-rich permafrost largely composed of massive ground ice and ice wedge polygons with a thin active layer of a mean thickness of 57cm. The region has a polar desert climate, with a mean annual air temperature of -19°C, and approximately 67mm of annual precipitation (falling mostly as snow). The area has an Environment Canada Weather Station (located at Eureka at 79°59'N, 85°56'W) that has been conducting daily meteorological measurements since it was founded in 1947. The area is sensitive to increasing summer temperatures as observed during the summer of 2012: as one of the warmest summer on record, there was a three-fold increase in thermokarst (collapse of the land surface from melting ground ice) with the accelerated collapse of ice wedge polygon troughs and widespread development of retrogressive thaw slumps. This study monitors thermokarst activity within the area using air photos from 1959, 1974 and 1982, satellite imagery (WorldView2) from 2009 and 2012, and annual air surveys (since 1989). Thermokarst activity between 2013 and 2016 has been monitored in the field using a differential GPS (Global Positioning System) to survey headwall locations of retrogressive thaw slumps. The purpose of this study is to provide a detailed baseline of landscape processes to compare future landscape changes resulting from thermokarst in the area.

Spatial variations in drainage efficiency in a boreal wetland environment as a function of lidar and radar-derived deviations from the regional hydraulic gradient

NASA Astrophysics Data System (ADS)

Hopkinson, C.; Brisco, B.; Chasmer, L.; Devito, K.; Montgomery, J. S.; Patterson, S.; Petrone, R. M.

2017-12-01

The dense forest cover of the Western Boreal Plains of northern Alberta is underlain by a mix of glacial moraines, sandy outwash sediments and clay plains possessing spatially variable hydraulic conductivities. The region is also characterised by a large number of post-glacial surface depression wetlands that have seasonally and topographically limited surface connectivity. Consequently, drainage along shallow regional hydraulic gradients may be dominated either by variations in surface geology or local variations in Et. Long-term government lake level monitoring is sparse in this region, but over a decade of hydrometeorological monitoring has taken place around the Utikuma Regional Study Area (URSA), a research site led by the University of Alberta. In situ lake and ground water level data are here combined with time series of airborne lidar and RadarSat II synthetic aperture radar (SAR) data to assess the spatial variability of water levels during late summer period characterised by flow recession. Long term Lidar data were collected or obtained by the authors in August of 2002, 2008, 2011 and 2016, while seasonal SAR data were captured approximately every 24 days during the summers of 2015, 2016 and 2017. Water levels for wetlands exceeding 100m2 in area across a north-trending 20km x 5km topographic gradient north of Utikuma Lake were extracted directly from the lidar and indirectly from the SAR. The recent seasonal variability in spatial water levels was extracted from SAR, while the lidar data illustrated more long term trends associated with land use and riparian vegetation succession. All water level data collected in August were combined and averaged at multiple scales using a raster focal statistics function to generate a long term spatial map of the regional hydraulic gradient and scale-dependent variations. Areas of indicated high and low drainage efficiency were overlain onto layers of landcover and surface geology to ascertain causal relationships. Areas associated with high spatial variability in water level illustrate reduced drainage connectivity, while areas of reduced variability indicate high surface connectivity and/or hydraulic conductivity. The hypothesis of surface geology controls on local wetland connectivity and landscape drainage efficiency is supported through this analysis.

Soil organic matter decomposition and temperature sensitivity after forest fire in permafrost regions in Canada

NASA Astrophysics Data System (ADS)

Aaltonen, Heidi; Palviainen, Marjo; Köster, Kajar; Berninger, Frank; Pumpanen, Jukka

2017-04-01

On the Northern Hemisphere, 24% of soils are underlain by permafrost. These soils contain 50% of the global soil carbon pool. The Northern Hemisphere is also the region which is predicted to be most affected by climate warming and this causes uncertainties over the future of the permafrost. It has been estimated that 25% of permafrost might thaw by 2100, exposing previously frozen carbon pools to decomposition. In addition, global warming is expected to cause increase in the frequency of wild fires, which further increase permafrost melting by removing the insulating organic surface layer. The amount of released soil carbon from permafrost soils after forest fire is affected by degradability and temperature sensitivity of the soil organic matter, as well as soil depth and the stage of succession. Yet the common effect of these factors remains unclear. We studied how soil respiration and its temperature sensitivity (Q10) vary in different depths and within time by taking soil samples from different fire chronosequence areas (burned 3, 25, 46 and 100 years ago) from permafrost region in Northern Canada (Yukon and Northwest Territories, along Dempster Highway). The samples from three different depths (5, 10 and 30 cm) were incubated in four different temperatures (1, 7, 13 and 19°C) over 24h. Our results showed that the CO2 fluxes followed the stages of succession, with recently burned sites having lowest rates. The organic matter at 5 cm depth proved to be more labile and temperature sensitive than in deeper depths. The Q10 values, however, did not differ between sites, excluding 30 cm at the most recently burned site that had a significantly higher Q10 value than the other sites. The results implicate that heterotrophic soil respiration decreases on permafrost regions during the first stages after forest fire. At the same time the temperature sensitivity in deeper soil layers may increase.

Lithospheric-Mantle Structure of the Kaapvaal Craton, South Africa, Derived From Thermodynamically Self-Consistent Modelling of Seismic Surface-Wave and S-wave Receiver Function, Heat-flow, Elevation, Xenolith and Magnetotelluric Observations

NASA Astrophysics Data System (ADS)

Muller, M. R.; Fullea, J.; Jones, A. G.; Adam, J.; Lebedev, S.; Piana Agostinetti, N.

2012-12-01

Results from recent geophysical and mantle-xenolith geochemistry studies of the Kaapvaal Craton appear, at times, to provide disparate views of the physical, chemical and thermal structure of the lithosphere. Models from our recent SAMTEX magnetotelluric (MT) surveys across the Kaapvaal Craton indicate a resistive, 220-240 km thick lithosphere for the central core of the craton. One published S-wave receiver function (SRF) study and other surface-wave studies suggest a thinner lithosphere characterised by a ~160 km thick high-velocity "lid" underlain by a low-velocity zone (LVZ) of between 65-150 km in thickness. Other seismic studies suggest that the (high-velocity) lithosphere is thicker, in excess of 220 km. Mantle xenolith pressure-temperature arrays from Mesozoic kimberlites require that the base of the "thermal" lithosphere (i.e., the depth above which a conductive geotherm is maintained) is at least 220 km deep, to account for mantle geotherms in the range 35-38 mWm-2. Richly diamondiferous kimberlites across the Kaapvaal Craton require a lithospheric thickness substantially greater than 160 km - the depth of the top of the diamond stability field. In this paper we use the recently developed LitMod software code to derive, thermodynamically consistently, a range of 1-D seismic velocity, density, electrical resistivity and temperature models from layered geochemical models of the lithosphere based on mantle xenolith compositions. In our work, the "petrological" lithosphere-asthenosphere boundary (pLAB) (i.e., the top of the fertile asthenospheric-mantle) and the "thermal" LAB (tLAB as defined above) are coincident. Lithospheric-mantle models are found simultaneously satisfying all geophysical observables: new surface-wave dispersion data, published SRFs, MT responses, surface elevation and heat-flow. Our results show: 1. All lithospheric-mantle models are characterised by a seismic LVZ with a minimum velocity at the depth of the petrological/thermal LAB. The top of the LVZ does not correspond with the LAB. 2. Thin (~160 km-thick) lithospheric-mantle models are consistent with surface elevation and heat-flow observations only for unreasonably low average crustal heat production values (~0.4 μWm-3). However, such models are inconsistent both with the surface-wave dispersion data and youngest (Group I) palaeo-geotherms defined by xenolith P-T arrays. 3. A three-layered geochemical model (consistent with mantle xenoliths), with lithospheric thickness in excess of 220 km, is required to match all geophysical constraints. 4. The chemical transition from a depleted harzburgitic composition (above) to a refertilised high-T lherzolitic composition (below) at 160 km depth produces a sharp onset of the seismic LVZ and a sharp increase in density. Synthetic SRFs will assess whether this chemical transition may account for the reported S-to-P conversion event at 160 km depth. However, in this this instance the SRF conversion event would not represent the petrological/thermal LAB.

Lithospheric-Mantle Structure of the Kaapvaal Craton, South Africa, Derived from Thermodynamically Self-Consistent Modelling of Magnetotelluric, Surface-Wave Dispersion, S-wave Receiver Function, Heat-flow, Elevation and Xenolith Observations

NASA Astrophysics Data System (ADS)

Muller, Mark; Fullea, Javier; Jones, Alan G.; Adam, Joanne; Lebedev, Sergei; Piana Agostinetti, Nicola

2013-04-01

Results from recent geophysical and mantle-xenolith geochemistry studies of the Kaapvaal Craton appear, at times, to provide disparate views of the physical, chemical and thermal structure of the lithosphere. Models from our recent SAMTEX magnetotelluric (MT) surveys across the Kaapvaal Craton indicate a resistive, 220-240 km thick lithosphere for the central core of the craton. One published S-wave receiver function (SRF) study and other surface-wave studies suggest a thinner lithosphere characterised by a ~160 km thick high-velocity "lid" underlain by a low-velocity zone (LVZ) of between 65-150 km in thickness. Other seismic studies suggest that the (high-velocity) lithosphere is thicker, in excess of 220 km. Mantle xenolith pressure-temperature arrays from Mesozoic kimberlites require that the base of the "thermal" lithosphere (i.e., the depth above which a conductive geotherm is maintained - the tLAB) is at least 220 km deep, to account for mantle geotherms in the range 35-38 mWm-2. Richly diamondiferous kimberlites across the Kaapvaal Craton require a lithospheric thickness substantially greater than 160 km - the depth of the top of the diamond stability field. In this paper we use the recently developed LitMod software code to derive, thermodynamically consistently, a range of 1-D electrical resistivity, seismic velocity, density and temperature models from layered geochemical models of the lithosphere based on mantle xenolith compositions. In our work, the "petrological" lithosphere-asthenosphere boundary (pLAB) (i.e., the top of the fertile asthenospheric-mantle) and the "thermal" LAB (tLAB) are coincident. Lithospheric-mantle models are found simultaneously satisfying all geophysical observables: MT responses, new surface-wave dispersion data, published SRFs, surface elevation and heat-flow. Our results show: 1. All lithospheric-mantle models are characterised by a seismic LVZ with a minimum velocity at the depth of the petrological/thermal LAB. The top of the LVZ does not correspond with the LAB. 2. Thin (~160 km-thick) lithospheric-mantle models are consistent with surface elevation and heat-flow observations only for unreasonably low average crustal heat production values (~0.4 µWm-3). However, such models are inconsistent both with the surface-wave dispersion data and youngest (Group I) palaeo-geotherms defined by xenolith P-T arrays. 3. A three-layered geochemical model, with lithospheric thickness in excess of 230 km, is required to match all geophysical and xenolith constraints. 4. The chemical transition from a depleted harzburgitic composition (above) to a refertilised high-T lherzolitic composition (below) at 160 km depth produces a sharp onset of the seismic LVZ and a sharp increase in density. Synthetic SRFs indicate that this chemical transition is able to account for the reported S-to-P conversion event at 160 km depth. In this this instance the 160 km deep SRF event does not represent the petrological/thermal LAB.

Summary groundwater resources of Centre County, Pennsylvania

USGS Publications Warehouse

Wood, Charles R.

1980-01-01

The northwest third of Centre County lies in the Appalachian Plateaus physiographic province. The higher altitudes are underlain by the Conemaugh, Allegheny, and Pottsville Groups, which consist of sandstone, shale, and thin limestone and coal beds. The average yield of nondomestic wells in the Allegheny Group is 20 gpm (gallons per minute) and that in the Pottsville Group 100 gpm. Water from wells in these groups commonly has a high concentration of iron. Most of the rest of the Appalachian Plateaus province is underlain by the Burgoon Sandstone. The Burgoon yields soft water, and the average yield of nondomestic wells is 70 gpm.

Investigation of the groundwater system at Masaya Caldera, Nicaragua, using transient electromagnetics and numerical simulation

USGS Publications Warehouse

MacNeil, R.E.; Sanford, W.E.; Connor, C.B.; Sandberg, S.K.; Diez, M.

2007-01-01

The distribution of groundwater beneath Masaya Volcano, in Nicaragua, and its surrounding caldera was characterized using the transient electromagnetic method (TEM). Multiple soundings were conducted at 30 sites. Models of the TEM data consistently indicate a resistive layer that is underlain by one or more conductive layers. These two layers represent the unsaturated and saturated zones, respectively, with the boundary between them indicating the water-table elevation. A map of the TEM data shows that the water table in the caldera is a subdued replica of the topography, with higher elevations beneath the edifice in the south-central caldera and lower elevations in the eastern caldera, coinciding with the elevation of Laguna de Masaya. These TEM data, combined with regional hydrologic data, indicate that the caldera in hydrologically isolated from the surrounding region, with as much as 60??m of difference in elevation of the groundwater table across caldera-bounding faults. The water-table information and estimates of fluxes of water through the system were used to constrain a numerical simulation of groundwater flow. The simulation results indicate that basalt flows in the outer parts of the caldera have a relatively high transmissivity, whereas the central edifice has a substantially lower transmissivity. A layer of relatively high transmissivity must be present at depth within the edifice in order to deliver the observed flux of water and steam to the active vent. This hydrologic information about the caldera provides a baseline for assessing the response of this isolated groundwater system to future changes in magmatic activity. ?? 2007.

Application of cluster and discriminant analyses to diagnose lithological heterogeneity of the parent material according to its particle-size distribution

NASA Astrophysics Data System (ADS)

Giniyatullin, K. G.; Valeeva, A. A.; Smirnova, E. V.

2017-08-01

Particle-size distribution in soddy-podzolic and light gray forest soils of the Botanical Garden of Kazan Federal University has been studied. The cluster analysis of data on the samples from genetic soil horizons attests to the lithological heterogeneity of the profiles of all the studied soils. It is probable that they are developed from the two-layered sediments with the upper colluvial layer underlain by the alluvial layer. According to the discriminant analysis, the major contribution to the discrimination of colluvial and alluvial layers is that of the fraction >0.25 mm. The results of canonical analysis show that there is only one significant discriminant function that separates alluvial and colluvial sediments on the investigated territory. The discriminant function correlates with the contents of fractions 0.05-0.01, 0.25-0.05, and >0.25 mm. Classification functions making it possible to distinguish between alluvial and colluvial sediments have been calculated. Statistical assessment of particle-size distribution data obtained for the plow horizons on ten plowed fields within the garden indicates that this horizon is formed from colluvial sediments. We conclude that the contents of separate fractions and their ratios cannot be used as a universal criterion of the lithological heterogeneity. However, adequate combination of the cluster and discriminant analyses makes it possible to give a comprehensive assessment of the lithology of soil samples from data on the contents of sand and silt fractions, which considerably increases the information value and reliability of the results.

Oceanographic controls over sediment water content: northern Bermuda rise

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

Baker, M.; Laine, E.P.

1985-01-01

Cores taken from the plateaus of Northern Bermuda Rise show that the region is underlain at depths of 1-5 m by a 1-3 m thick layer of hemipelagic lutites with anomalously high water contents. The lack of visually apparent textural and lithological changes in this extremely fine grained sediment rule out these common causes for variation in water content. The water content averages 175% within this layer and 100% immediately above and below it. This is an increase of 9.5% in porosity. The high water content sediment is confined to a period between 12 and 16 ka. Current work onmore » the mineralogy of the sediments which comprise this layer suggest two oceanographic factors that may have influenced its formation. A meltwater spike associated with deglaciation may have altered the ecological conditions above the thermocline sufficiently to promote the increased production of radiolaria, resulting in the deposition of silica enriched sediment on the sea floor. A combination of textural and perhaps chemical factors caused by the silica enrichment may have influenced the increase in water content. Intensified bottom currents at this time also may have eroded smectite rich sediments from exposures of Neogene age and deposited them on the plateaus. An increase in smectite would increase the water content due to the extremely fine grain size and the chemistry of the clay. Thus, the lateral continuity and isochroniety of this layer, combined with its mineralogical characteristics suggests that oceanographic changes can influence water content and perhaps other geotechnical properties on a regional scale.« less

Solar cell modules with improved backskin and methods for forming same

DOEpatents

Hanoka, Jack I.

1998-04-21

A laminated solar cell module with a backskin layer that reduces the materials and labor required during the manufacturing process. The solar cell module includes a rigid front support layer formed of light transmitting material having first and second surfaces. A transparent encapsulant layer has a first surface disposed adjacent the second surface of the front support layer. A plurality of interconnected solar cells have a first surface disposed adjacent a second surface of the transparent encapsulant layer. The backskin layer is formed of a thermoplastic olefin, which includes first ionomer, a second ionomer, glass fiber, and carbon black. A first surface of the backskin layer is disposed adjacent a second surface of the interconnected solar cells. The transparent encapsulant layer and the backskin layer, in combination, encapsulate the interconnected solar cells. An end portion of the backskin layer can be wrapped around the edge of the module for contacting the first surface of the front support layer to form an edge seal. A laminated solar cell module with a backskin layer that reduces the materials and labor required during the manufacturing process. The solar cell module includes a rigid front support layer formed of light transmitting material having first and second surfaces. A transparent encapsulant layer has a first surface disposed adjacent the second surface of the front support layer. A plurality of interconnected solar cells have a first surface disposed adjacent a second surface of the transparent encapsulant layer. The backskin layer is formed of a thermoplastic olefin, which includes first ionomer, a second ionomer, glass fiber, and carbon black. A first surface of the backskin layer is disposed adjacent a second surface of the interconnected solar cells. The transparent encapsulant layer and the backskin layer, in combination, encapsulate the interconnected solar cells. An end portion of the backskin layer can be wrapped around the edge of the module for contacting the first surface of the front support layer to form an edge seal.

Tunnel barrier schottky

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

Chu, Rongming; Cao, Yu; Li, Zijian

2018-02-20

A diode includes: a semiconductor substrate; a cathode metal layer contacting a bottom of the substrate; a semiconductor drift layer on the substrate; a graded aluminum gallium nitride (AlGaN) semiconductor barrier layer on the drift layer and having a larger bandgap than the drift layer, the barrier layer having a top surface and a bottom surface between the drift layer and the top surface, the barrier layer having an increasing aluminum composition from the bottom surface to the top surface; and an anode metal layer directly contacting the top surface of the barrier layer.

Preliminary map of peak horizontal ground acceleration for the Hanshin-Awaji earthquake of January 17, 1995, Japan - Description of Mapped Data Sets

USGS Publications Warehouse

Borcherdt, R.D.; Mark, R.K.

1995-01-01

The Hanshin-Awaji earthquake (also known as the Hyogo-ken Nanbu and the Great Hanshin earthquake) provided an unprecedented set of measurements of strong ground shaking. The measurements constitute the most comprehensive set of strong- motion recordings yet obtained for sites underlain by soft soil deposits of Holocene age within a few kilometers of the crustal rupture zone. The recordings, obtained on or near many important structures, provide an important new empirical data set for evaluating input ground motion levels and site amplification factors for codes and site-specific design procedures world wide. This report describes the data used to prepare a preliminary map summarizing the strong motion data in relation to seismicity and underlying geology (Wentworth, Borcherdt, and Mark., 1995; Figure 1, hereafter referred to as Figure 1/I). The map shows station locations, peak acceleration values, and generalized acceleration contours superimposed on pertinent seismicity and the geologic map of Japan. The map (Figure 1/I) indicates a zone of high acceleration with ground motions throughout the zone greater than 400 gal and locally greater than 800 gal. This zone encompasses the area of most intense damage mapped as JMA intensity level 7, which extends through Kobe City. The zone of most intense damage is parallel, but displaced slightly from the surface projection of the crustal rupture zone implied by aftershock locations. The zone is underlain by soft-soil deposits of Holocene age.

The Layer Cake Walls of Valles Marineris

NASA Technical Reports Server (NTRS)

2007-01-01

This image of the northern wall of Coprates Chasma, in Valles Marineris, was taken by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) at 1227 UTC (8:27 a.m. EDT) on June 16, 2007, near 13.99 degrees south latitude, 303.09 degrees east longitude. CRISM's image was taken in 544 colors covering 0.36-3.92 micrometers, and shows features as small as 20 meters (66 feet) across. The region covered is just over 10 kilometers (6.2 miles) wide at its narrowest point.

Valles Marineris is a large canyon system straddling Mars' equator, with a total size approximating the Mediterranean Sea emptied of water. It is subdivided into several interconnected 'chasmata' each hundreds of kilometers wide and, in some cases, thousands of kilometers long. The walls of several of the chasmata, including Coprates Chasma, expose a section of Mars' upper crust about 5 kilometers (3 miles) in depth. Exposures like these show the layers of rock that record the formation of Mars' crust over geologic time, much as the walls of the Grand Canyon on Earth show part of our planet's history.

The upper panel of this montage shows the location of the CRISM image on a mosaic from the Mars Odyssey spacecraft's Thermal Emission Imaging System (THEMIS), taken in longer infrared wavelengths than measured by CRISM. The CRISM image samples the base of Coprates Chasma's wall, including a conspicuous horizontal band that continues along the wall for tens of kilometers to the east and west, and a topographic shelf just above that.

The middle two panels show the CRISM image in visible and infrared light. In the middle left panel, the red, green, and blue image planes show brightness at 0.59, 0.53, and 0.48 microns, similar to what the human eye would see. Color variations are subdued by the presence of dust on all exposed surfaces. In the middle right panel, the red, green, and blue image planes show brightness at 2.53, 1.51, and 1.08 microns. These three infrared wavelengths are the 'usual' set that the CRISM team uses to provide an overview of infrared data, because dust has a less obscuring effect, and because they are sensitive to a wide variety of minerals. Layering is clearly evident in the wall rocks. The conspicuous band running along the base of the chasma wall appears slightly yellowish, and the scarp at the edge of the topographic bench appears slightly green.

The bottom two panels use combinations of wavelengths to show the strengths of absorptions that provide 'fingerprints' of different minerals. In the lower left panel, red shows strength of a 0.53-micron absorption due to oxidized iron in dust, green shows strength of an inflection in the spectrum at 0.6 microns that may be related to rock coatings, and blue shows strength of a 1-micron absorption due to the igneous minerals olivine and pyroxene. The conspicuous horizontal band appears slightly blue, indicating a stronger signature of olivine and/or pyroxene. In the lower right panel, red is a measure of an absorption particular to olivine, green is a measure of a 2.3-micron absorption due to phyllosilicates (clay-like minerals formed when rock was subjected to liquid water), and blue is a measure of absorptions particular to pyroxene. The conspicuous horizontal band is now resolved into an upper portion richer in pyroxene, underlain by material richer in olivine than the rest of the wall rock. Also, erosion-resistant material forming the topographic bench is underlain by phyllosilicate-containing material exposed on the scarp.

Taken together, these data reveal a layer cake-like composition of the crustal material exposed in Coprates Chasma's wall. Most of the rock is rich in pyroxene, which is expected because much of Mars' crust consists of volcanic basaltic rock. However discrete layers are richer in olivine, and in some layers the presence of phyllosilicates indicates interaction of rock with liquid water. Because the phyllosilicate-containing layer is low on the walls and deeply buried, it likely represents an early period of Mars' history that was exposed when the canyon system formed.

The Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) is one of six science instruments on NASA's Mars Reconnaissance Orbiter. Led by The Johns Hopkins University Applied Physics Laboratory, the CRISM team includes expertise from universities, government agencies and small businesses in the United States and abroad.

Thickness and quality of Springfield Coal Member, Gibson County, Indiana, as a function of differential compaction of precursor sediments

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

Eggert, D.L.

1983-09-01

The Springfield Coal Member is a time transgressive coal that formed during the Pennsylvanian on a delta platform within the slowly subsiding Illinois basin. In Gibson County, Indiana, the locations of the major Galatia channel and the minor Leslie Cemetery channel were determined by differential compaction of precursor sediments beneath this platform. The springfield coal is thick proximal to both channels, but proximal to the Galatia channel it is either a low-sulfur or a high-sulfur coal. It is a low-sulfur coal where it is underlain by a thick platform of shale with some sandstone and overlain by nonmarine shale. Itmore » is a high-sulfur coal where it is underlain by a thick platform of fluvial sandstone and overlain by brackish to marine rocks. Distal to both channels the coal is thin and high in sulfur. At distal locations the Springfield is underlain by a platform of either thick bay-fill sandstone or fluvial sandstone and overlain by brackish to marine shale and limestone. Compaction of pre-Springfield delta sediments allowed for accumulation of thicker peat along the axis of more rapid local subsidence. Compaction of muddy parts of the delta platform proximal to the Galatia channel resulted in rapid subsidence and the deposition of nonmarine shale over the peat. In the areas underlain by bay-fill and fluvial sandstone where compaction was less, the peat became a relatively thin and high-sulfur coal. Differences in coal thickness and quality in this 500 mi/sup 2/ (1,300 km/sup 2/) area of Gibson County can be explained largely by differential compaction and deltaic sedimentation.« less

Geophysical characteristics of the hydrothermal systems of Kilauea volcano, Hawaii

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

Kauahikaua, J.

1993-08-01

Clues to the structure of Kilauea volcano can be obtained from spatial studies of gravity, magnetic, and seismic velocity variations. The rift zones and summit are underlain by dense, magnetic, and seismic velocity variations. The rift zones and summit are underlain by dense, magnetic, high P-wave-velocity rocks at depths of about 2 km less. The gravity and seismic velocity studies indicate that the rift structures are broad, extending farther to the north than to the south of the surface features. The magnetic data allow separation into a narrow, highly-magnetized, shallow zone and broad, flanking, magnetic lows. The patterns of gravity,more » magnetic variations, and seismicity document the southward migration of the upper east rift zone. Regional, hydrologic features of Kilauea can be determined from resistivity and self-potential studies. High-level groundwater exists beneath Kilauea summit to elevations of +800 m within a triangular area bounded by the west edge of the upper southwest rift zone, the east edge of the upper east rift zone, and the Koa'e fault system. High-level groundwater is present within the east rift zone beyond the triangular summit area. Self-potential mapping shows that areas of local heat produce local fluid circulation in the unconfined aquifer (water table). Shallow seismicity and surface deformation indicate that magma is intruding and that fractures are forming beneath the rift zones and summit area. Heat flows of 370--820 mW/m[sup 2] are calculated from deep wells within the lower east rift zone. The estimated heat input rate for Kilauea of 9 gigawatts (GW) is at least 25 times higher than the conductive heat loss as estimated from the heat flow in wells extrapolated over the area of the summit caldera and rift zones. 115 refs., 13 figs., 1 tab.« less

Hydrogeology and ground-water flow of the drift and Platteville aquifer system, St Louis Park, Minnesota

USGS Publications Warehouse

Lindgren, R.J.

1995-01-01

Model simulations indicate that vertical ground-water flow from the drift aquifers and from the Platteville aquifer to underlying bedrock aquifers is greatest through bedrock valleys. The convergence of flow paths near bedrock valleys and the greater volume of water moving through the valleys would likely result in both increased concentrations and greater vertical movement of contaminants in areas underlain by bedrock valleys as compared to areas not underlain by bedrock valleys. Model results also indicate that field measurements of hydraulic head might not help locate discontinuities in confining units and additional test drilling to locate discontinuities might be necessary.

Geologic map of the Santa Ana Pueblo quadrangle, Sandoval County, New Mexico

USGS Publications Warehouse

Personius, Stephen F.

2002-01-01

The Santa Ana Pueblo quadrangle is located in the northern part of the Albuquerque basin, which is the largest basin or graben within the Rio Grande rift. The quadrangle is underlain by poorly consolidated sedimentary rocks of the Santa Fe Group and is dominated by Santa Ana Mesa, a volcanic tableland underlain by basalt flows of the San Felipe volcanic field. The San Felipe volcanic field is the largest area of basaltic lavas exposed in the Albuquerque basin. The structural fabric of the quadrangle is dominated by dozens of generally north striking, east- and west-dipping normal faults associated with the Neogene Rio Grande rift.

Systems and methods for advanced ultra-high-performance InP solar cells

DOEpatents

Wanlass, Mark

2017-03-07

Systems and Methods for Advanced Ultra-High-Performance InP Solar Cells are provided. In one embodiment, an InP photovoltaic device comprises: a p-n junction absorber layer comprising at least one InP layer; a front surface confinement layer; and a back surface confinement layer; wherein either the front surface confinement layer or the back surface confinement layer forms part of a High-Low (HL) doping architecture; and wherein either the front surface confinement layer or the back surface confinement layer forms part of a heterointerface system architecture.

Bimetallic alloy electrocatalysts with multilayered platinum-skin surfaces

DOEpatents

Stamenkovic, Vojislav R.; Wang, Chao; Markovic, Nenad M.

2016-01-26

Compositions and methods of preparing a bimetallic alloy having enhanced electrocatalytic properties are provided. The composition comprises a PtNi substrate having a surface layer, a near-surface layer, and an inner layer, where the surface layer comprises a nickel-depleted composition, such that the surface layer comprises a platinum skin having at least one atomic layer of platinum.

Electromagnetic, seismic and petro-physical investigations of the lithosphere-asthenosphere boundary in central Tibet

NASA Astrophysics Data System (ADS)

Vozar, J.; Fullea, J.; Jones, A. G.; Agius, M. R.; Lebedev, S.

2011-12-01

Combined seismological and electromagnetic investigations of the lithosphere and underlying asthenosphere have the potential to yield superior inferences than using either one on its own. Central Tibet offers an excellent natural laboratory for testing such approaches, given the high quality seismological and magnetotelluric (MT) data available as a consequence of INDEPTH studies. In particular, the presence and lateral and vertical extent of the Indian lithosphere beneath Tibet is highly debated. Integrated petrological-geophysical modeling of MT and surface-wave data, which are differently sensitive to temperature and composition, allows us to reduce the uncertainties associated with modeling these two data sets independently, as commonly undertaken. For the MT data, we use selected distortion-corrected MT transfer functions, from INDEPTH Phase III line 500 across central Tibet for 1D modeling. The selected data fit well the 1D assumption and exhibit large penetration depth. Our deep resistivity models can be classified into two different groups: i) the Lhasa Terrane and ii) the Qiangtang Terrane. For the Lhasa Terrane group, the models show the existence of two high conductive layers localized at depths of 60-80 km and more than 200 km, whereas for the Qiangtang Terrane these conductive layers appears to be occur at shallower depths, namely 30-50 km and 120 km depth respectively. Our dispersion curves for Rayleigh and Love surface waves were measured using seismograms recorded by stations of INDEPTH and PASSCAL experiments. Dispersion curves for central Lhasa and Qiangtang terranes show similarly low phase velocities at periods sampling the thick crust beneath the regions, but differ at periods sampling the mantle. Inverting the dispersion data for 1D, radially-anisotropic Vs profiles, we find that beneath central Qiangtang terrane shear velocity is lower than the global average down to 75 km below the Moho, indicating relatively high temperatures, whereas beneath Central Lhasa terrane S-velocities are close to global-average values. We perform the integrated petro-physical modeling of MT and surface-wave data using the software package LitMod. The program facilitates definition of realistic temperature and pressure distributions within the upper mantle, and characterizes the mineral assemblages given bulk chemical compositions as well as water content. This allows us to firstly define a bulk geoelectric and seismic model of the upper mantle based on laboratory and xenolith data for the most relevant mantle minerals, and secondly to compute synthetic geophysical observables that are compared with measured data (i.e., MT responses, surface-wave dispersion curves, topography, and surface heat flow). Our preliminary results suggest an 80-120 km-thick, dry lithosphere in the central part of the Qiangtang Terrane. In the central Lhasa Terrane the data can be explained by a relatively warm 100-120 km-thick Tibetian lithosphere underlain by an 80-120-km-thick Indian lithosphere. The mid-lower crust in Lhasa shows strong seismic and electric anisotropy, with a predominant E-W oriented high velocity/conductivity axis.

Multitracer Study of Flow to Tile Drains in Irrigated Macroporous Soil

NASA Astrophysics Data System (ADS)

Bishop, J. M.; Callaghan, M. V.; Cey, E.; Bentley, L. R.

2010-12-01

Multiple tracer experiments have been conducted to test the effectiveness of using irrigation along with a tile drain system for salt remediation in west central Alberta, Canada. The experiments were designed to characterize the shallow flow system as part of a salt flushing pilot study and to determine the role of macroporosity in groundwater flow and transport. Soils at the site are primarily silty glaciolacustrine material underlain by a relatively impermeable till layer at approximately 2.5 m below ground surface. A 20 m by 20 m infiltration test plot is underlain by two tile drains at 2 m depth that are separated by 10 m. The test plot contains a drip irrigation system and has been irrigated regularly in the summer months over the past three seasons (2008-2010). Two reportedly conservative tracers, 2,6-difluorobenzoic acid [2,6-DFBA] and pentafluorobenzoic acid [PFBA], have been used on the plot and the pre-existing soil salinity was also used as a tracer. In August of 2009 a 2,6-DFBA solution (865g/L) was applied to the surface of the plot. Irrigation of the study plot continued after tracer application on a schedule that averaged roughly 12mm/day, applied 3 days a week. During the 2010 field season, a PFBA solution (at 4.2 g/L) was injected into two separate monitoring wells. One monitoring well is situated 0.5 m directly above the north tile drain (in which samples were collected regularly). The other well is situated at 2 m depth in the center of the study plot and samples were collected from a down gradient well. Tracer concentrations in the subsurface were monitored through sampling of tile drain effluent and monitoring wells in and around the plot, in addition to soil core extractions taken at several locations within the test plot at the end of the 2009 field season. Initial breakthrough of the DFBA in the tile drains occurred 24 hours after application and remained in all subsequent water samples at concentrations of 2 to 6 mg/L. Results from the DFBA analysis showed that the tiles are highly affected by the lateral and vertical contributions to the drains. Distribution of the DFBA in the soil showed that 82% of the tracer remained in the top 75 cm of the soil profile at the end of the 2009 season. This indicates that macropore flow is occurring, but has a minor influence on the movement of the salt mass. This result is important because it illustrates that although the salt mass has migrated slowly, macroporosity can transport contaminants quickly enough to exceeded drinking water quality guidelines. Breakthrough of the PFBA occurred in the north tile drain 13 hrs after application and peaked at a concentration of 10 mg/L, followed by a sharp decrease and stabilization to concentrations of 1.0 mg/L. This shows that macropore flow is occurring at depth in addition to the surface and that contaminant transport can occur rapidly in soils with lower hydraulic conductivity. Salt concentrations in the effluent were measured at high concentrations, showing that effective salt flushing of the matrix is still occurring.

Modelling hazardous surface hoar layers in the mountain snowpack over space and time

NASA Astrophysics Data System (ADS)

Horton, Simon Earl

Surface hoar layers are a common failure layer in hazardous snow slab avalanches. Surface hoar crystals (frost) initially form on the surface of the snow, and once buried can remain a persistent weak layer for weeks or months. Avalanche forecasters have difficulty tracking the spatial distribution and mechanical properties of these layers in mountainous terrain. This thesis presents numerical models and remote sensing methods to track the distribution and properties of surface hoar layers over space and time. The formation of surface hoar was modelled with meteorological data by calculating the downward flux of water vapour from the atmospheric boundary layer. The timing of surface hoar formation and the modelled crystal size was verified at snow study sites throughout western Canada. The major surface hoar layers over several winters were predicted with fair success. Surface hoar formation was modelled over various spatial scales using meteorological data from weather forecast models. The largest surface hoar crystals formed in regions and elevation bands with clear skies, warm and humid air, cold snow surfaces, and light winds. Field surveys measured similar regional-scale patterns in surface hoar distribution. Surface hoar formation patterns on different slope aspects were observed, but were not modelled reliably. Mechanical field tests on buried surface hoar layers found layers increased in shear strength over time, but had persistent high propensity for fracture propagation. Layers with large crystals and layers overlying hard melt-freeze crusts showed greater signs of instability. Buried surface hoar layers were simulated with the snow cover model SNOWPACK and verified with avalanche observations, finding most hazardous surface hoar layers were identified with a structural stability index. Finally, the optical properties of surface hoar crystals were measured in the field with spectral instruments. Large plate-shaped crystals were less reflective at shortwave infrared wavelengths than other common surface snow grains. The methods presented in this thesis were developed into operational products that model hazardous surface hoar layers in western Canada. Further research and refinements could improve avalanche forecasts in regions prone to hazardous surface hoar layers.

ARC-1989-A89-7048

NASA Image and Video Library

1989-08-27

P-34713 This Voyager image of Triton reveals two kinds of mid-latitude terrain. Near the center and the lower half of the frame is a gently rolling terrain pock-marked with a modest number of impact craters. The density of impact craters is somewhat similiar to that found on the mare surface of Earth's moon. Crossing this rolling surface are narrow rifts, one of which grades into a chain of craters that probably are of collapse origin. In the upper right part of the frame is a smooth terrain with very sparse impact craters. This terrain evidently has been formed by flooding of the surface by low-viscosity fluids rather late in geologic time. One of the vents from which these fluids erupted probably is represented by a deep, elongate crater near the middle of the right side of the image. Two slightly dark regions underlain by late eruptive material also occur in the left half of the image. Apparent vents for these eruptions are marked by shallow depressiions, which may have been formed by drain back of material at the end of the eruptive episode.

Seismic imaging beneath an InSAR anomaly in eastern Washington State: Shallow faulting associated with an earthquake swarm in a low-hazard area

USGS Publications Warehouse

Stephenson, William J.; Odum, Jackson K.; Wicks, Chuck; Pratt, Thomas L.; Blakely, Richard J.

2016-01-01

In 2001, a rare swarm of small, shallow earthquakes beneath the city of Spokane, Washington, caused ground shaking as well as audible booms over a five‐month period. Subsequent Interferometric Synthetic Aperture Radar (InSAR) data analysis revealed an area of surface uplift in the vicinity of the earthquake swarm. To investigate the potential faults that may have caused both the earthquakes and the topographic uplift, we collected ∼3  km of high‐resolution seismic‐reflection profiles to image the upper‐source region of the swarm. The two profiles reveal a complex deformational pattern within Quaternary alluvial, fluvial, and flood deposits, underlain by Tertiary basalts and basin sediments. At least 100 m of arching on a basalt surface in the upper 500 m is interpreted from both the seismic profiles and magnetic modeling. Two west‐dipping faults deform Quaternary sediments and project to the surface near the location of the Spokane fault defined from modeling of the InSAR data.

Water resources of Clallam County, Washington; Phase I report

USGS Publications Warehouse

Drost, B.W.

1983-01-01

An inventory of the water resources of Clallam County, Washington, showed that sufficient water is available to supply all present demands. Domestic water supplies can be obtained from wells drilled 100 ft or less into glacial and alluvial deposits; in areas underlain by bedrock, wells more than 100 ft deep can generally supply one home per well. Surface water is abundant, and is the source for most public water systems. Extreme low flows were observed only in small drainage basins in bedrock in the mountainous interior and along parts of the coastline in the Strait of Juan de Fuca. The quality of ground and surface waters is generally excellent. In coastal areas, some wells may yield water with large concentrations of chloride and dissolved solids. A quarter of the wells tested had excessive concentrations of iron and (or) manganese. High values of turbidity, color, and coliform bacteria are widespread surface water problems, but standard filtering and chlorination treatment make the water suitable for public supplies. High concentrations of coliform bacteria apparently originate naturally in soils. High ammonia concentration observed at one site is probably caused by sewage disposal practices. (USGS)

Geology and ground water in Door County, Wisconsin, with emphasis on contamination potential in the Silurian dolomite

USGS Publications Warehouse

Sherrill, Marvin G.

1977-01-01

Door County, a recreational and fruit-growing area bordering Lake Michigan in northeastern Wisconsin, has had a long history of ground-water contamination from surface and near-surface sources. Contamination is most severe in late summer when fruit-canning operations and the influx of tourists create additional wastes. Silurian dolomite is the upper bedrock unit in the county and yields generally adequate supplies of very hard water with locally objectionable concentrations of iron and nitrate. Thin soil cover and well-fractured dolomitic bedrock give easy entry to ground-water contaminants throughout large parts of Door County. Many contaminants enter the dolomite by surface or near-surface seepage. There is little attenuation of contamination concentrations in the well-jointed dolomite, and contaminants may travel long distances underground in a relatively short time. The major source of ground-water contamination is bacteria, from individual waste-disposal systems, agricultural, industrial, and municipal wastes. Areas of the county underlain by contaminated zones include only a small percentage of the total ground-water system and are separated by large volumes of ground water free of contamination. (Woodard-USGS)

Protecting the surface of a light absorber in a photoanode

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

Hu, Shu; Lewis, Nathan S.

A photoanode includes a passivation layer on a light absorber. The passivation layer is more resistant to corrosion than the light absorber. The photoanode includes a surface modifying layer that is location on the passivation layer such that the passivation layer is between the light absorber and the surface modifying layer. The surface modifying layer reduces a resistance of the passivation layer to conduction of holes out of the passivation layer.

Internal structures of the nieuwpoort bank (southern north sea)

NASA Astrophysics Data System (ADS)

de Maeyer, P.; Wartel, S.; de Moor, G.

The subbottom survey of the Nieuwpoort Banks allows recognition of 4 successive stages underlain by leper Clay: (1) The bank rests upon a sedimentary unit, at least 2 to 5 m thick, having a subhorizontal or wedge-like interior stratification. (2) This unit is cut by a subhorizontal erosive surface. (3) On top of this a first ridge, still recognizable on its interior structure and with shoreward-dipping foreset beds, developed. (4) On top of this former ridge the present-day bank was formed with shoreward-dipping foreset beds. Since the same structures are observed in the Stroom Bank, it seems likely that the above mentioned scheme can be generalized for all near-shore ridges close to the Belgian coast.

Integrating GIS-based geologic mapping, LiDAR-based lineament analysis and site specific rock slope data to delineate a zone of existing and potential rock slope instability located along the grandfather mountain window-Linville Falls shear zone contact, Southern Appalachian Mountains, Watauga County, North Carolina

USGS Publications Warehouse

Gillon, K.A.; Wooten, R.M.; Latham, R.L.; Witt, A.W.; Douglas, T.J.; Bauer, J.B.; Fuemmeler, S.J.

2009-01-01

Landslide hazard maps of Watauga County identify >2200 landslides, model debris flow susceptibility, and evaluate a 14km x 0.5km zone of existing and potential rock slope instability (ZEPRSI) near the Town of Boone. The ZEPRSI encompasses west-northwest trending (WNWT) topographic ridges where 14 active/past-active rock/weathered rock slides occur mainly in rocks of the Grandfather Mountain Window (GMW). The north side of this ridgeline is the GMW / Linville Falls Fault (LFF) contact. Sheared rocks of the Linville Falls Shear Zone (LFSZ) occur along the ridge and locally in the valley north of the contact. The valley is underlain principally by layered granitic gneiss comprising the Linville Falls/Beech Mountain/Stone Mountain Thrust Sheet. The integration of ArcGIS??? - format digital geologic and lineament mapping on a 6m LiDAR (Light Detecting and Ranging) digital elevation model (DEM) base, and kinematic analyses of site specific rock slope data (e.g., presence and degree of ductile and brittle deformation fabrics, rock type, rock weathering state) indicate: WNWT lineaments are expressions of a regionally extensive zone of fractures and faults; and ZEPRSI rock slope failures concentrate along excavated, north-facing LFF/LFSZ slopes where brittle fabrics overprint older metamorphic foliations, and other fractures create side and back release surfaces. Copyright 2009 ARMA, American Rock Mechanics Association.

Alteration mineral mapping for iron prospecting using ETM+ data, Tonkolili iron field, northern Sierra Leone

NASA Astrophysics Data System (ADS)

Mansaray, Lamin R.; Liu, Lei; Zhou, Jun; Ma, Zhimin

2013-10-01

The Tonkolili iron field in northern Sierra Leone has the largest known iron ore deposit in Africa. It occurs in a greenstone belt in an Achaean granitic basement. This study focused mainly on mapping areas with iron-oxide and hydroxyl bearing minerals, and identifying potential areas for haematite mineralization and banded iron formations (BIFs) in Tonkolili. The predominant mineral assemblage at the surface (laterite duricrust) of this iron field is haematitegoethite- limonite ±magnetite. The mineralization occurs in quartzitic banded ironstones, layered amphibolites, granites, schists and hornblendites. In this study, Crosta techniques were applied on Enhanced Thematic Mapper (ETM+) data to enhance areas with alteration minerals and target potential areas of haematite and BIF units in the Tonkolili iron field. Synthetic analysis shows that alteration zones mapped herein are consistent with the already discovered magnetite BIFs in Tonkolili. Based on the overlaps of the simplified geological map and the remote sensing-based alteration mineral maps obtained in this study, three new haematite prospects were inferred within, and one new haematite prospect was inferred outside the tenement boundary of the Tonkolili exploration license. As the primary iron mineral in Tonkolili is magnetite, the study concludes that, these haematite prospects could also be underlain by magnetite BIFs. This study also concludes that, the application of Crosta techniques on ETM+ data is effective not only in mapping iron-oxide and hydroxyl alterations but can also provide a basis for inferring areas of potential iron resources in Algoma-type banded iron formations (BIFs), such as those in the Tonkolili field.

Using hydrochemical tracers to conceptualise hydrological function in a larger scale catchment draining contrasting geologic provinces

NASA Astrophysics Data System (ADS)

Capell, R.; Tetzlaff, D.; Malcolm, I. A.; Hartley, A. J.; Soulsby, C.

2011-09-01

SummaryA year-long multivariate tracer study in the 749 km 2 catchment of the North-Esk in north east Scotland was carried out to infer the dominant runoff generation processes in two markedly different geologic provinces. The upper 60% of the catchment has montane headwaters dominated by impermeable metamorphic rocks, steep topography, peaty soils and a sub-arctic climate with over 1400 mm of precipitation. The lowlands of the catchment are underlain by a major sandstone aquifer, and mainly have freely draining, fertile soils that support intensive arable farming under a drier climate with around 800 mm of precipitation. Storm runoff in the uplands is dominated by near-surface processes in soils and sedimentary layers which generate around 60% of annual stream flows with water of low alkalinity and ionic strength. In contrast, tributaries in the lower parts of the catchment are dominated by groundwater-fed base flows which account for 75% of annual runoff and are characterised by alkaline waters with high concentrations of base cations and high levels of nitrate. Multivariate statistical methods were used to derive a generic typology of catchment source waters, their spatial and temporal dynamics and particularly, how they integrate together at the larger catchment scale. The uplands dominate the winter high flow response of the whole catchment. The influence of lowland groundwater from major aquifers becomes more apparent under low flows. However, groundwater from small upland aquifers plays a critical role for ecosystem service in dry periods providing baseflows which dilute pollutant inputs from lowland areas at the large catchment scale.

Seismic motion in urban sites consisting of blocks in welded contact with a soft layer overlying a hard half-space

NASA Astrophysics Data System (ADS)

Groby, Jean-Philippe; Wirgin, Armand

2008-02-01

We address the problem of the response to a seismic wave of an urban site consisting of Nb blocks overlying a soft layer underlain by a hard substratum. The results of a theoretical analysis, appealing to a space-frequency mode-matching (MM) technique, are compared to those obtained by a space-time finite-element (FE) technique. The two methods are shown to give rise to the same prediction of the seismic response for Nb = 1, 2 and 40 blocks. The mechanism of the interaction between blocks and the ground, as well as that of the mutual interaction between blocks, are studied. It is shown, in the first part of this paper, that the presence of a small number of blocks modifies the seismic disturbance in a manner which evokes qualitatively, but not quantitatively, what was observed during the 1985 Michoacan earthquake in Mexico City. Anomalous earthquake response at a much greater level, in terms of duration, peak and cumulative amplitude of motion, is shown, by a theoretical and numerical analysis in the second part of this paper, to be induced by the presence of a large (>=10) number of identical equi-spaced blocks that are present in certain districts of many cities.

Thickness and character of regolith on mountain slopes in the vicinity of Mountain Lake, Virginia, as indicated by seismic refraction, and implications for hillslope evolution

NASA Astrophysics Data System (ADS)

Mills, Hugh H.

1990-06-01

Seismic refraction was used to determine the variation in thickness and seismic velocities of regolith on boulder-mantled mountain flanks underlain by shale in the Valley and Ridge province near Mountain Lake, southwestern Virginia. Emphasis was on cross-slope variations, particularly the difference between dells (hollows) and noses. Four types of material were distinguished on the basis of seismic velocity. Soil material within 1-2 m of the ground surface affected by pedogenesis had a velocity generally less than 400 m/s. Unconsolidated bouldery colluvium, up to 6 m thick, had a velocity of about 400-800 m/s. Old, weathered and consolidated colluvium had a velocity of 800-2000 m/s. Bedrock residuum and highly weathered bedrock showed similar velocities, however, so that all material in this range was collectively termed "weathered regolith." Its thickness exceeded 30 m in places. Relatively unweathered bedrock showed velocities of at least 2000 m/s. On average, seismic profiles showed regolith thicknesses in excess of 10 m, the greater part being residuum or weathered bedrock. This finding contrasts with one study near the glacial border in Pennsylvania, which showed that colluvium generally directly overlies bedrock. This difference may reflect less-intense Pleistocene periglacial erosion in Virginia than in Pennsylvania. Topography generally was not a good predictor of regolith thickness. Hollows showed greater thicknesses of ypung colluvium than did noses, but dells and noses showed little difference in total regolith thickness. Both dells and noses showed great variation in regolith thickness. The largest systematic difference was found between dell floors (or parts thereof) that seemed to be undergoing long-term downcutting and those that appeared to be relict features no longer associated with active drainageways. The former were underlain by a mean of 5.5 m of weathered regolith, whereas the latter were underlain by a mean of 14.0 m, indicative of a greater depth of weathering and therefore a greater antiquity. On three noses, closely spaced seismic profiles were used to demonstrate asymmetric distribution of regolith thickness in a direction transverse to nose axes. Findings are compatible with the concept that noses and dells on the boulder-mantled mountain slopes undergo topographic inversion during long-term retreat of the mountain front.

Resistivity Surveys on the Mauna Kea Saddle: Implications for groundwater resources on the Island of Hawaii

NASA Astrophysics Data System (ADS)

Thomas, D. M.; Pierce, H. A.

2009-12-01

A sequence of Audiomagnetotelluric (AMT) and Magnetotelluric (MT) surveys was recently completed on the Island of Hawaii along a transect spanning the 2000 m high Humu'ula Saddle region bounded by Mauna Kea, Mauna Loa and Hualalai volcanoes. The surveys extended down to an elevation of ~600 m on the eastern flank of the island and to 1,100 m on the drier, western slope of Mauna Kea and were intended to define the depth to the local groundwater table across the interior of the island. The results of the surveys present a much more complicated picture of the interior structure, and associated hydrology, of the island than has generally been assumed. At the eastern end of the transect, where existing wells unequivocally define the depth to the water table, young Mauna Kea basalts saturated with freshwater yielded a resistivity of ~600 ohm-meters. At increasing elevations toward the west, where rainfall rates decline markedly, the resistivity/depth profiles are consistent with progressively drier, resistive rocks to depths approaching 1000 m below the surface. These are underlain by well-defined, moderately resistive zones consistent with freshwater saturated basalts. As the transect approaches an inferred southeasterly-trending rift zone near the crest of the Saddle, the moderately resistive intervals are underlain by less resistive rocks near sea level that fall into the range expected for either (cold) saltwater or heated freshwater. Near the center of the transect, freshwater resistivity values extend to elevations of ~1000 m above sea level and are, again, underlain by significantly less resistive intervals near sea level. We believe that the moderately resistive intervals reflect substantial quantities of freshwater that are bounded by rift systems of Mauna Kea and Hualalai and the northern flank of Mauna Loa. The unexpectedly low resistivity values near sea level are considered to more probably reflect leakage of thermal fluids from the interior of Mauna Kea rather than saltwater intrusion from below the freshwater system. Alternatively, the less resistive formations may be the result of hydrothermal alteration from now-extinct geothermal leakage from Mauna Kea. The presence of freshwater to 1000 m above sea level within the Mauna Kea flanks, if confirmed by planned drilling, will increase estimates of groundwater storage within the island by as much as a factor of ten above those projected by traditional ocean island groundwater models.

Environmental Impact Assessment of Dumpsite: Case Study from southwestern Saudi Arabia

NASA Astrophysics Data System (ADS)

Alfaifi, H. J.; Alhumidan, S. M.; Kahal, A. Y.; Abdel Rahman, K.; Al-Qadasi, B.

2017-12-01

The dumpsite is underlain by highly fractured Precambrian basement complex of metamorphosed igneous and sedimentary rocks. Minor Tertiary, Quaternary basalts and Quaternary alluvial deposits overlie the basement rocks. Structurally, the area is affected by intersected series of north-to northwest trending faults. Hydrogeological setting of the study area is characterized by shallow groundwater aquifers in the fractured and weathered basement rocks. Moreover, the area exposes heavy rains especially during summer seasons, which may accelerate the transferring of contaminated water to the neighbouring valleys and low land. At present, the residential and Khamis Mushait new industrial zone are situated close to the dumpsite. The main objective of this study is to assess the leachate intrusion and groundwater contamination in the urban area of Khamis Mushait. Geophysical and geochemical techniques have been successfully applied in the assessment of environmental impact of dumpsites globally. Near-surface geophysical investigations such as Seismic refraction tomography, Schlumberger vertical electrical soundings (VES) and ground magnetic survey have been conducted to detect the controlling structures and lithological variation of the dumpsite. In addition, four water samples from hand dug wells and two surface water samples were collected from and around dumpsite. These water samples were analysed geochemically to inspect the presence of heavy metals, salts (sulphates, nitrates and chlorides), radioactive elements and physically to assess pH, TDS, DO, salinity, total hardness, turbidity, electrical conductivity and temperature. Results of VES illustrate low resistivity zones (≤ 30 Ohm-m) due to conductive leachate from dumpsite while seismic models and ground magnetic intensity map delineated fractures beneath the weathered basement layer which may provide pathways for the contaminants. The physico-chemical analysis of the collected groundwater samples revealed that there are considerable impacts of dumpsite leachate in the shallow groundwater. pH values of the representative samples indicate its unsuitability for human consumption. Leachate flow direction is oriented NNW-SSE and follows the similar flow pattern as deduced from hydrogeological investigation.

Recharge of an Unconfined Pumice Aquifer: Winter Rainfall Versus Snow Pack, South-central Oregon

NASA Astrophysics Data System (ADS)

Cummings, M. L.; Weatherford, J. M.; Eibert, D.

2015-12-01

Walker Rim study area, an uplifted fault block east of the Cascade Range, south-central Oregon, exceeds 1580 m elevation and includes Round Meadow-Sellers Marsh closed basin, and headwaters of Upper Klamath Basin, Deschutes Basin, and Christmas Lake Valley in the Great Basin. The water-bearing unit is 2.8 to 3.0 m thick Plinian pumice fall from the Holocene eruption of Mount Mazama, Cascade Range. The perched pumice aquifer is underlain by low permeability regolith and bedrock. Disruption of the internal continuity of the Plinian pumice fall by fluvial and lacustrine processes resulted in hydrogeologic environments that include fens, wet meadows, and areas of shallow water table. Slopes are low and surface and groundwater pathways follow patterns inherited from the pre-eruption landscape. Discharge for streams and springs and depth to water table measured in open-ended piezometers slotted in the pumice aquifer have been measured between March and October, WY 2011 through WY2015. Yearly occupation on same date has been conducted for middle April, June 1st, and end of October. WY2011 and WY2012 received more precipitation than the 30 year average while WY2014 was the third driest year in 30 years of record. WY2014 and WY2015 provide an interesting contrast. Drought conditions dominated WY2014 while WY2015 was distinct in that the normal cold-season snow pack was replaced by rainfall. Cumulative precipitation exceeded the 30-year average between October and March. The pumice aquifer of wet meadows and areas of shallow water table experienced little recharge in WY2015. Persistence of widespread diffuse discharge from fens declined by middle summer as potentiometric surfaces lowered into confining peat layers or in some settings into the pumice aquifer. Recharge of the perched pumice aquifer in rain-dominated WY2015 was similar to or less than in the snow-dominated drought of WY2014. Rain falling on frozen ground drove runoff rather than aquifer recharge.

Volcanic geothermal system in the Main Ethiopian Rift: insights from 3D MT finite-element inversion and other exploration methods

NASA Astrophysics Data System (ADS)

Samrock, F.; Grayver, A.; Eysteinsson, H.; Saar, M. O.

2017-12-01

In search for geothermal resources, especially in exploration for high-enthalpy systems found in regions with active volcanism, the magnetotelluric (MT) method has proven to be an efficient tool. Electrical conductivity of the subsurface, imaged by MT, is used for detecting layers of electrically highly conductive clays which form around the surrounding strata of hot circulating fluids and for delineating magmatic heat sources such as zones with partial melting. We present a case study using a novel 3-D inverse solver, based on adaptive local mesh refinement techniques, applied to decoupled forward and inverse mesh parameterizations. The flexible meshing allows accurate representation of surface topography, while keeping computational costs at a reasonable level. The MT data set we analyze was measured at 112 sites, covering an area of 18 by 11 km at a geothermal prospect in the Main Ethiopian Rift. For inverse modelling, we tested a series of different settings to ensure that the recovered structures are supported by the data. Specifically, we tested different starting models, regularization functionals, sets of transfer functions, with and without inclusion of topography. Several robust subsurface structures were revealed. These are prominent features of a high-enthalpy geothermal system: A highly conductive shallow clay cap occurs in an area with high fumarolic activity, and is underlain by a more resistive zone, which is commonly interpreted as a propylitic reservoir and is the main geothermal target for drilling. An interesting discovery is the existence of a channel-like conductor connecting the geothermal field at the surface with an off-rift conductive zone, whose existence was proposed earlier as being related to an off-rift volcanic belt along the western shoulder of the Main Ethiopian Rift. The electrical conductivity model is interpreted together with results from other geoscientific studies and outcomes from satellite remote sensing techniques.

Shallow Sub-Permafrost Groundwater Systems In A Buried Fjord: Taylor Valley, Antarctica

NASA Astrophysics Data System (ADS)

Foley, N.; Tulaczyk, S. M.; Auken, E.; Mikucki, J.

2014-12-01

The McMurdo Dry Valleys (MDV), Antarctica, represent a unique geologic setting where permanent lakes, ephemeral streams, and subglacial waters influence surface hydrology in a cold polar desert. Past research suggested that the MDV are underlain by several hundreds of meters of permafrost. Here, we present data collected from an Airborne EM (AEM) resistivity sensor flown over the MDV during the 2011-12 austral summer. A focus of our survey was over the Taylor Glacier where saline, iron-rich subglacial fluid releases at the glacier snout at a feature known as Blood Falls, and over Taylor Valley, where a series of isolated lakes lie between Taylor Glacier and the Ross Sea. Our data show that in Taylor Valley there are extensive areas of low resistivity, interpreted as hypersaline brines, beneath a relatively thin layer of high resistivity material, interpreted as dry- or ice-cemented permafrost. These hypersaline brines remain liquid at temperatures well below 0°C due to their salinity. They appear to be contained within the sedimentary fill deposited in Taylor Valley when it was still a fjord. This brine system continues up valley and has a subglacial extension beneath Taylor Glacier, where it may provide the source that feeds Blood Falls. By categorizing the resistivity measurements according to surficial land cover, we are able to distinguish between ice, permafrost, lake water, and seawater based on characteristic resistivity distributions. Furthermore, this technique shows that areas of surface permafrost become increasingly conductive (brine-filled) with depth, whereas the large lakes exhibit taliks that extend through the entire thickness of the permafrost. The subsurface brines represent a large, unstudied and potentially connected hydrogeologic system, in which subsurface flows may help transfer water and nutrients between lakes in the MDV and into the Ross Sea. Such a system is a potential habitat for extremophile life, similar to that already detected in the Blood Falls outflow, and may serve as a terrestrial analogue to potential extraterrestrial habits, where liquid surface waters are not expected to exist.

Analysis of Earthquake Recordings Obtained from the Seafloor Earthquake Measurement System (SEMS) Instruments Deployed off the Coast of Southern California

USGS Publications Warehouse

Boore, D.M.; Smith, C.E.

1999-01-01

For more than 20 years, a program has been underway to obtain records of earthquake shaking on the seafloor at sites offshore of southern California, near oil platforms. The primary goal of the program is to obtain data that can help determine if ground motions at offshore sites are significantly different than those at onshore sites; if so, caution may be necessary in using onshore motions as the basis for the seismic design of oil platforms. We analyze data from eight earthquakes recorded at six offshore sites; these are the most important data recorded on these stations to date. Seven of the earthquakes were recorded at only one offshore station; the eighth event was recorded at two sites. The earthquakes range in magnitude from 4.7 to 6.1. Because of the scarcity of multiple recordings from any one event, most of the analysis is based on the ratio of spectra from vertical and horizontal components of motion. The results clearly show that the offshore motions have very low vertical motions compared to those from an average onshore site, particularly at short periods. Theoretical calculations find that the water layer has little effect on the horizontal components of motion but that it produces a strong spectral null on the vertical component at the resonant frequency of P waves in the water layer. The vertical-to-horizontal ratios for a few selected onshore sites underlain by relatively low shear-wave velocities are similar to the ratios from offshore sites for frequencies less than about one-half the water layer P-wave resonant frequency, suggesting that the shear-wave velocities beneath a site are more important than the water layer in determining the character of the ground motions at lower frequencies.

Reconciling Electromagnetic and Seismic Constraints on Lithospheric Thickness and Composition of the Kaapvaal Craton, South Africa

NASA Astrophysics Data System (ADS)

Muller, M. R.; Fullea, J.; Jones, A. G.

2010-12-01

Much of the long-running debate regarding the depth extent of the continental lithosphere beneath Archean shield areas has focussed on the Kaapvaal Craton of South Africa. Our recent magnetotelluric surveys across the Kaapvaal Craton, as part of the Southern African Magnetotelluric Experiment (SAMTEX), indicate a lithospheric thickness of the order of 220 km or greater for the central core of the craton. In contrast, a recently published S-wave receiver function study and several surface wave studies suggest that the Kaapvaal lithosphere is characterized by an approximately 160 km thick high-velocity “lid” underlain by a low-velocity layer that is between 65 - 150 km thick, with the base of the high-velocity lid inferred to represent the “lithosphere-asthenosphere boundary”. Other body-wave, surface wave and S-wave receiver function studies in the area suggest that the (high-velocity) lithosphere is substantially thicker, in excess of 250 km for the most part. Evidence from mantle xenolith pressure-temperature arrays derived from Mesozoic kimberlites found across the Kaapvaal Craton requires that the base of the lithosphere (i.e., the base of the thermal boundary layer above which a conductive geotherm is maintained) be at least 220 km deep, if observed mantle geotherms in the range 35 - 38 mWm-2 are to be accounted for. The presence of richly diamondiferous kimberlites across the Kaapvaal Craton is also impossible to reconcile with a 160 km lithospheric thickness: the top of the diamond (pressure-temperature) stability field is deeper than 160 km for the mantle geotherm associated with a 160 km lithospheric thickness. In the work presented here, we use the recently developed LitMOD software package to derive both seismic velocity and electrical resistivity models for the lithosphere that are fully chemically, petrologically and thermodynamically consistent, and assess whether these apparently disparate views of the Kaapvaal lithosphere - provided by seismic, magnetotelluric and xenolith studies - can be reconciled. We address directly several key issues: (i) whether a 160 km lithospheric thickness (and its associated temperature and pressure variation with depth) is “internally” consistent with the high (> 4.7 km/s) S-wave velocities predicted for the seismic high-velocity lid, given typical Kaapvaal geochemical compositions from xenolith analyses, (ii) whether a 160 km lithospheric thickness and its associated electrical resistivity variation with depth is consistent with observed magnetotelluric responses, and (iii) whether the observed (negative) mantle conversion event at 160 km depth in one S-wave receiver function study can be explained by compositional layering within the Kaapvaal Craton, given that the geochemistry of xenoliths from younger Group I kimberlites provides evidence for chemical refertilization of the lithosphere in the depth range 160 - 200 km.

MEMS based pyroelectric thermal energy harvester

DOEpatents

Hunter, Scott R; Datskos, Panagiotis G

2013-08-27

A pyroelectric thermal energy harvesting apparatus for generating an electric current includes a cantilevered layered pyroelectric capacitor extending between a first surface and a second surface, where the first surface includes a temperature difference from the second surface. The layered pyroelectric capacitor includes a conductive, bimetal top electrode layer, an intermediate pyroelectric dielectric layer and a conductive bottom electrode layer. In addition, a pair of proof masses is affixed at a distal end of the layered pyroelectric capacitor to face the first surface and the second surface, wherein the proof masses oscillate between the first surface and the second surface such that a pyroelectric current is generated in the pyroelectric capacitor due to temperature cycling when the proof masses alternately contact the first surface and the second surface.

Landscape Evolution and the Reincarnation of the Residual CO2 Ice Cap of Mars

NASA Astrophysics Data System (ADS)

Byrne, S.; Zuber, M.

2006-12-01

Observations of the southern residual CO2 cap of Mars reveal a wide range of landforms including flat-floored quasi-circular pits with steep walls (dubbed Swiss-cheese features). Interannual comparisons show that these depressions are expanding laterally at rates of ~2m/yr to ~4m/yr, prompting suggestions of climate change. The residual CO2 ice cap is up to 10m thick and underlain by an involatile basement, it also contains layers roughly 2m thick representing different accumulation episodes in the recent past. Changes in the appearance of the residual ice between the Mariner 9 and Viking missions indicate that the top-most layer was deposited in that time-frame, soon after the global dust storm of 1971. The spatial density of the Swiss-cheese features, and the rate at which they expand, mean that it is unlikely that any part of the residual ice cap is older than a few centuries. Given this, we may ask: how can there be a residual cap present today for us to observe? To answer this and other questions we have developed a model to examine the evolution of a CO2 ice landscape. This model reproduces the morphologies and expansion rates seen in the actual residual CO2 ice cap. Our model results indicate that the fate of CO2 ice surfaces is controlled by their surface roughness. Surface roughness always increases with time, which results in an unstable situation. When the surface roughness exceeds a critical point small pits can begin to develop. The walls of these pits rapidly steepen and begin retreating which enlarges and deepens the pit. This situation always occurs even if the surface of the CO2 slab has a high enough albedo to have a net mass gain each year. Once these pits begin expanding they quickly erode the entire ice slab. When the underlying non-CO2 material is exposed, it will not frost over again if Mars were to repeat like clockwork every year. We conclude that interannual climatic variability is actually a requirement for the continued existence of a residual CO2 ice cap. We invoke unusual depositional episodes (which have a surface smoothing effect) after which the cap can begin accumulating mass and growing in thickness again. This continues until the surface roughness again exceeds a stable state and the process repeats itself. The thickness of the residual cap therefore oscillates on timescales of centuries. The total cap volume may also be affected by variations in residual cap extent. The cap is not 'stable' in the usual sense of the word, but instead is constantly being destroyed and recreated. Evidence suggests that these rejuvenating depositional events are linked to global dust storms. The 10m thick stratigraphic record thus provides a unique measure of interannual variability of the current climate, the expanding Swiss-cheese features do not indicate secular climate change, but instead are just part of the larger life-cycle of this ice deposit. We will report on this surface modeling which reproduces other morphologies within the residual cap and present a historical model based on combining our modeling with the feature sizes and ablation rates found within the present residual ice cap.

A baseline for upper crustal velocity variations along the East Pacific Rise at 13 deg N

NASA Astrophysics Data System (ADS)

Kappus, Mary E.; Harding, Alistair J.; Orcutt, John A.

1995-04-01

A wide aperture profile of the East Pacific Rise at 13 deg N provides data necessary to make a high-resolution seismic velocity profile of the uppermost crust along a 52-km segment of ridge crest. Automated and objective processing steps, including r-p analysis and waveform inversion, allow the construction of models in a consistent way so that comparisons are meaningful. A continuous profile is synthesized from 70 independent one-dimensional models spaced at 750-km intervals along the ridge. The resulting seismic velocity structure of the top 500 m of crust is remarkable in its lack of variability. The main features are a thin low-velocity layer 2A at the top with a steep gradient to layer 2B. The seafloor velocity is nearly constant at 2.45 km/s +/- 3% along the entire ridge. The velocity at the top of layer 2B is 5.0 km/s +/- 10%. The depth to the 4 km/s isovelocity contour within layer 2A is 130 +/- 20 m from 13 deg to 13 deg 20 min N, north of which it increases to 180 m. The increase in thickness is coincident with a deviation from axial linearity (DEVAL) noted by both a slight change in axis depth and orientation and in geochemistry. The waveform inversion, providing more details plus velocity gradient information, shows a layer 2A with about 80 m of constant-velocity material underlain by 150 m of high velocity gradient material, putting the base of layer 2A at approximately 230 m depth south of 13 deg 20 min N and about 50 m thicker north of the DEVAL. The overall lack of variability, combined with other recent measurements of layer 2A thickness along and near the axis, indicates that the thickness of volcanic extrusives is controlled not by levels of volcanic productivity, but the dynamics of emplacement. The homogeneity along axis also provides a baseline of inherent variability in crustal structure of about 10% against which other observed variations in similar regimes can be compared.

Response of permafrost to projected climate change: Results from global offline model simulations with JSBACH

NASA Astrophysics Data System (ADS)

Blome, Tanja; Ekici, Altug; Beer, Christian; Hagemann, Stefan

2014-05-01

Permafrost or perennially frozen ground is an important part of the terrestrial cryosphere; roughly one quarter of Earth's land surface is underlain by permafrost. As it is a thermal phenomenon, its characteristics are highly dependent on climatic factors. The impact of the currently observed warming, which is projected to persist during the coming decades due to anthropogenic CO2 input, certainly has effects for the vast permafrost areas of the high northern latitudes. The quantification of these effects, however, is scientifically still an open question. This is partly due to the complexity of the system, where several feedbacks are interacting between land and atmosphere, sometimes counterbalancing each other. Moreover, until recently, many global circulation models (GCMs) lacked the sufficient representation of permafrost physics in their land surface schemes. In order to assess the response of permafrost to projected climate change for the 21st century, the land surface scheme of the Max-Planck-Institute for Meteorology, JSBACH, has recently been equipped with the important physical processes for permafrost studies, and was driven globally with bias corrected climate data, thereby spanning a period from 1850 until 2100. The applied land surface scheme JSBACH now considers the effects of freezing and thawing of soil water for both energy and water cycles, thermal properties depending on soil water and ice contents, and soil moisture movement being influenced by the presence of soil ice. To address the uncertainty range arising through different greenhouse gas concentrations as well as through different climate realisations when using various climate models, combinations of two Representative Concentration Pathways (RCPs) and two GCMs were used as driving data. In order to focus only on the climatic impact on permafrost, effects due to feedbacks between climate and permafrost (namely via carbon fluxes between land and atmosphere) are excluded in the experiments. Differences between future time slices and today's climate are analysed. The effect in relevant variables, such as permafrost extent, depth of the Active Layer, ground temperature, and amount of soil carbon, is investigated. The experiments (as well as the development of JSBACH with respect to permafrost soil physics) are part of the European project PAGE21, where a focus is set on interactions between the changing climate and its impact on permafrost, especially for the 21st century.

Solare Cell Roof Tile And Method Of Forming Same

DOEpatents

Hanoka, Jack I.; Real, Markus

1999-11-16

A solar cell roof tile includes a front support layer, a transparent encapsulant layer, a plurality of interconnected solar cells and a backskin layer. The front support layer is formed of light transmitting material and has first and second surfaces. The transparent encapsulant layer is disposed adjacent the second surface of the front support layer. The interconnected solar cells has a first surface disposed adjacent the transparent encapsulant layer. The backskin layer has a first surface disposed adjacent a second surface of the interconnected solar cells, wherein a portion of the backskin layer wraps around and contacts the first surface of the front support layer to form the border region. A portion of the border region has an extended width. The solar cell roof tile may have stand-offs disposed on the extended width border region for providing vertical spacing with respect to an adjacent solar cell roof tile.

Multidecadal increases in the Yukon River Basin of chemical fluxes as indicators of changing flowpaths, groundwater, and permafrost

USGS Publications Warehouse

Toohey, Ryan C; Herman-Mercer, Nicole M.; Schuster, Paul F.; Mutter, Edda A.; Koch, Joshua C.

2016-01-01

The Yukon River Basin, underlain by discontinuous permafrost, has experienced a warming climate over the last century that has altered air temperature, precipitation, and permafrost. We investigated a water chemistry database from 1982 to 2014 for the Yukon River and its major tributary, the Tanana River. Significant increases of Ca, Mg, and Na annual flux were found in both rivers. Additionally, SO4 and P annual flux increased in the Yukon River. No annual trends were observed for dissolved organic carbon (DOC) from 2001 to 2014. In the Yukon River, Mg and SO4 flux increased throughout the year, while some of the most positive trends for Ca, Mg, Na, SO4, and P flux occurred during the fall and winter months. Both rivers exhibited positive monthly DOC flux trends for summer (Yukon River) and winter (Tanana River). These trends suggest increased active layer expansion, weathering, and sulfide oxidation due to permafrost degradation throughout the Yukon River Basin.

Hydrogeologic controls on water quality at a university dairy farm

NASA Astrophysics Data System (ADS)

McKay, L. D.; Hunter, R. W.; Lee, J.

2010-12-01

Dairy farms typically produce large quantities of manure and other waste products which are often stored or treated in lagoons and then applied to local fields as fertilizer. Contamination of nearby streams by dairy farm wastes through surface runnoff, drainage tile discharge, direct release of wastes or inundation of waste storage facilities during seasonal flooding have long been recognized as major environmental concerns. However, much less attention has been paid to fate and transport of dairy wastes in the subsurface and their potential impact on water quality in aquifers or in groundwater discharge to streams. One of the challenges in evaluating the environmental impact of dairy operations is that there are relatively few field research sites where all of the potential pathways for waterborne transport of dairy wastes are monitored and quantititatively evaluated. There are even fewer sites where extensive baseline water quality monitoring programs were established prior to operation of the dairy. This is essential to distinguish between environmental impacts from dairy operations and other nearby sources, such as beef production and human sewage from septic fields. This talk describes the development of a an integrated hydrogeologic/hydrologic site assessment and groundwater/surface water quality monitoring program at the University of Tennessee - Little River Dairy Farm, located near Townsend, TN. The dairy is currently under construction and the first cows are expected to arrive in late 2010. Hydrologic/hydrogeologic investigations of streams and groundwater at the site have been underway for more than 3 years, and these are expected to provide background data for assessing impacts of dairy wastes and for testing the effectiveness of different management practises. The lower half of the ~180 ha site consists of low-relief fields used for row crops, which are underlain by 4 - 8 m of alluvial deposits (mainly interbedded silt and fine-grained sands) on top of by black shale or limestone. Several active sinkholes are present in the portion of the fields underlain by limestone. The fields are bounded on two sides by the Little River, a popular recreational river, and on the third side by Ellejoy Creek, which is on the state’s 303(d) list for impairment by nutrients, sediment and fecal microorganisms, which are derived from upstream agricultural and rural residential development. These fields will be fertilized with treated dairy wastes and are the main area of concern for offsite migration of contaminants through groundwater, drainage ditches and (eventually) a tile drain system. A secondary area of concern is the dairy waste treatment pond which is located, along with the dairy barns, on the upland portion of the site, which is underlain by 1-2 m of clay-rich residual soils developed on fractured shale bedrock. Long term water quality monitoring of runnoff, streams, drainage ditches and groundwater is planned, with the intent of measuring environmental impact of dairy operations and testing the effectiveness of different management practises.

Apulian crust: Top to bottom

NASA Astrophysics Data System (ADS)

Amato, Alessandro; Bianchi, Irene; Agostinetti, Nicola Piana

2014-12-01

We investigate the crustal seismic structure of the Adria plate using teleseismic receiver functions (RF) recorded at 12 broadband seismic stations in the Apulia region. Detailed models of the Apulian crust, e.g. the structure of the Apulian Multi-layer Platform (AMP), are crucial for assessing the presence of potential décollements at different depth levels that may play a role in the evolution of the Apenninic orogen. We reconstruct S-wave velocity profiles applying a trans-dimensional Monte Carlo method for the inversion of RF data. Using this method, the resolution at the different depth level is completely dictated by the data and we avoid introducing artifacts in the crustal structure. We focus our study on three different key-elements: the Moho depth, the lower crust S-velocity, and the fine-structure of the AMP. We find a well defined and relatively flat Moho discontinuity below the region at 28-32 km depth, possibly indicating that the original Moho is still preserved in the area. The lower crust appears as a generally low velocity layer (average Vs = 3.7 km/s in the 15-26 km depth interval), likely suggestive of a felsic composition, with no significant velocity discontinuities except for its upper and lower boundaries where we find layering. Finally, for the shallow structure, the comparison of RF results with deep well stratigraphic and sonic log data allowed us to constrain the structure of the AMP and the presence of underlying Permo-Triassic (P-T) sediments. We find that the AMP structure displays small-scale heterogeneities in the region, with a thickness of the carbonates layers varying between 4 and 12 km, and is underlain by a thin, discontinuous layer of P-T terrigenous sediments, that are lacking in some areas. This fact may be due to the roughness in the original topography of the continental margins or to heterogeneities in its shallow structure due to the rifting process.

Multi-modality nanoparticles having optically responsive shape

DOEpatents

Chen, Fanqing; Bouchard, Louis-Serge

2015-05-19

In certain embodiments novel nanoparticles (nanowontons) are provided that are suitable for multimodal imaging and/or therapy. In one embodiment, the nanoparticles include a first biocompatible (e.g., gold) layer, an inner core layer (e.g., a non-biocompatible material), and a biocompatible (e.g., gold) layer. The first gold layer includes a concave surface that forms a first outer surface of the layered nanoparticle. The second gold layer includes a convex surface that forms a second outer surface of the layered nanoparticle. The first and second gold layers encapsulate the inner core material layer. Methods of fabricating such nanoparticles are also provided.

Electrical conductivity sensors as a means to quantify hydrologic connectivity of desert riverscapes

NASA Astrophysics Data System (ADS)

Jaeger, K. L.; Olden, J. D.

2010-12-01

Fundamental to addressing issues in the emerging fields of landscape conservation biogeography and genetics is an understanding of the physical processes, in particular hydrologic processes, under which that landscape is operating. In arid and semi-arid landscapes, however, quantifying the considerable spatial and temporal variability of streamflow patterns historically has been limited by the substantial physical effort and monetary cost required to install monitoring equipment. Recently, internally-recording temperature sensors have been modified to measure relative conductivity as an indicator for the onset and cessation of streamflow, providing an inexpensive method of quantifying the timing, duration, and frequency of surface flow that can be implemented at a broad spatial scale. In this study, we characterize surface water connectivity across several mountain watersheds as a means to understanding landscape-scale hydrologic connectivity important to aquatic biota, in particular, amphibians. In the semi-arid Huachuca mountain range of southeastern Arizona, USA, a total of 44 conductivity sensors were installed at approximately 2-km intervals throughout 8 canyons underlain by granite, limestone, and other sedimentary geologic units. Sensor locations represent a range of hydrologic and geomorphic settings including perennial, intermittent, and ephemeral reaches within bedrock, travertine, sand-bedded and coarser-grained channel morphologies. Sensors were deployed in early April 2010 at a 15-minute logging interval and data from 31 sensors were retrieved in mid-August 2010; a time period representing the cessation of the spring snow runoff period and approximately the middle of the North American monsoon period. Cessation and onset of surface flow were identified by a large negative or positive increase in the slope (first derivative) of the data record, respectively. The sensors indicate a distinct springtime stream drying (mid-April to early May 2010) demarcating the cessation of snowmelt runoff, and clear catchment-wide connectivity of streamflow in response to monsoon precipitation beginning in July 2010. As expected, streamflow is closely coupled to local precipitation, although the occurrence of perennial reaches in locations underlain by limestone in several of the canyons indicate potentially strong bedrock controls on the hydrology. These data will be applied to a collaborative study of landscape genetics of amphibian metapopulations in the Huachuca Mountains that will assess their vulnerability to climate change.

Method of depositing an electrically conductive oxide buffer layer on a textured substrate and articles formed therefrom

DOEpatents

Paranthaman, M. Parans; Aytug, Tolga; Christen, David K.

2005-10-18

An article with an improved buffer layer architecture includes a substrate having a textured metal surface, and an electrically conductive lanthanum metal oxide epitaxial buffer layer on the surface of the substrate. The article can also include an epitaxial superconducting layer deposited on the epitaxial buffer layer. An epitaxial capping layer can be placed between the epitaxial buffer layer and the superconducting layer. A method for preparing an epitaxial article includes providing a substrate with a metal surface and depositing on the metal surface a lanthanum metal oxide epitaxial buffer layer. The method can further include depositing a superconducting layer on the epitaxial buffer layer, and depositing an epitaxial capping layer between the epitaxial buffer layer and the superconducting layer.

Method of depositing an electrically conductive oxide buffer layer on a textured substrate and articles formed therefrom

DOEpatents

Paranthaman, M. Parans; Aytug, Tolga; Christen, David K.

2003-09-09

An article with an improved buffer layer architecture includes a substrate having a textured metal surface, and an electrically conductive lanthanum metal oxide epitaxial buffer layer on the surface of the substrate. The article can also include an epitaxial superconducting layer deposited on the epitaxial buffer layer. An epitaxial capping layer can be placed between the epitaxial buffer layer and the superconducting layer. A method for preparing an epitaxial article includes providing a substrate with a metal surface and depositing on the metal surface a lanthanum metal oxide epitaxial buffer layer. The method can further include depositing a superconducting layer on the epitaxial buffer layer, and depositing an epitaxial capping layer between the epitaxial buffer layer and the superconducting layer.

Enrichment and association of lead and bacteria at particulate surfaces in a salt-marsh surface layer

USGS Publications Warehouse

Harvey, R.W.; Lion, Leonard W.; Young, L.Y.; Leckie, J.O.

1982-01-01

The particle-laden surface layer (approx 150-370 mu m) and subsurface waters of a South San Francisco Bay salt marsh were sampled over 2 tidal cycles and analyzed for particle numbers and particulate-associated and total concentrations of Pb and bacteria. Laboratory studies examined the ability of a bacterial isolate from the surface layer and a bacterial 'film-former' to sorb Pb at environmentally significant concentrations in seawater. Degrees by which Pb concentrated in the surface layer relative to the subsurface strongly correlated with enrichments of surface layer bacteria (bacterioneuston). A significant fraction of the bacterioneuston and surface layer Pb were associated with particles. Particle-bound bacterioneuston may interact with Pb at particulate surfaces in this microenvironment.

Receiver function and gravity constraints on crustal structure and vertical movements of the Upper Mississippi Embayment and Ozark Uplift

NASA Astrophysics Data System (ADS)

Liu, Lin; Gao, Stephen S.; Liu, Kelly H.; Mickus, Kevin

2017-06-01

The Upper Mississippi Embayment (UME), where the seismically active New Madrid Seismic Zone resides, experienced two phases of subsidence commencing in the Late Precambrian and Cretaceous, respectively. To provide new constraints on models proposed for the mechanisms responsible for the subsidence, we computed and stacked P-to-S receiver functions recorded by 49 USArray and other seismic stations located in the UME and the adjacent Ozark Uplift and modeled Bouguer gravity anomaly data. The inferred thickness, density, and Vp/Vs of the upper and lower crustal layers suggest that the UME is characterized by a mafic and high-density upper crustal layer of ˜30 km thickness, which is underlain by a higher-density lower crustal layer of up to ˜15 km. Those measurements, in the background of previously published geological observations on the subsidence and uplift history of the UME, are in agreement with the model that the Cretaceous subsidence, which was suggested to be preceded by an approximately 2 km uplift, was the consequence of the passage of a previously proposed thermal plume. The thermoelastic effects of the plume would have induced wide-spread intrusion of mafic mantle material into the weak UME crust fractured by Precambrian rifting and increased its density, resulting in renewed subsidence after the thermal source was removed. In contrast, the Ozark Uplift has crustal density, thickness, and Vp/Vs measurements that are comparable to those observed on cratonic areas, suggesting an overall normal crust without significant modification by the proposed plume, probably owing to the relatively strong and thick lithosphere.

Geohydrology of the near-surface unsaturated zone adjacent to the disposal site for low-level radioactive waste near Beatty, Nevada: A section in Safe disposal of radionuclides in low-level radioactive-waste repository sites; Low-level radioactive-waste disposal workshop, U.S. Geological Survey, July 11-16, 1987, Big Bear Lake, Calif., Proceedings (Circular 1036)

USGS Publications Warehouse

Fisher, Jeffrey M.; Bedinger, Marion S.; Stevens, Peter R.

1990-01-01

Shallow-land burial in arid areas is considered the best method for isolating low-level radioactive waste from the environment (Nichols and Goode, this report; Mercer and others, 1983). A major threat to waste isolation in shallow trenches is ground-water percolation. Repository sites in arid areas are believed to minimize the risk of ground-water contamination because such sites receive minimal precipitation and are underlain by thick unsaturated zones. Unfortunately, few data are available on rates of water percolation in an arid environment.

Modern stromatolites in a saline maar in the Western District of Victoria, Australia: a possible analogue for Precambrian marine carbonates

NASA Astrophysics Data System (ADS)

Lynch, J. E.; Wallace, M. W.

2011-12-01

Stromatolites and thrombolites are microbially-mediated, sedimentary structures of various size and morphology, found throughout the rock record. Although they do not always contain fossils of microbial cells, ancient stromatolitic structures are considered biogenic in origin and, therefore, evidence of early life. Modern, living stromatolites are found in lacustrine and marine environments and can provide a window in which to observe some of Earth's earliest biological processes. However, secular variation in marine chemistry over geological time means that modern marine settings are not always the best analogues for ancient carbonates. This study describes the occurrence of modern stromatolites in a saline, alkaline maar in Victoria, Australia. Dolomite is a principle carbonate mineral precipitating from this lake, an unusual and poorly understood occurrence in modern environments, but one that was common in the Precambrian. The peculiar lacustrine chemistry in this volcanic region may, therefore, provide a better analogue for Precambrian marine carbonates than modern marine environments. Several types of stromatolites/thrombolites are observed occurring around this maar. Living thrombolites grow just below the shoreline to ~60 cm below the surface of the water. They are nucleating on the cemented surfaces of older lake carbonates, as well as cattle skulls and fence wires that have become submerged. Distinct microbial mats are observed, the uppermost being cyanobacteria, followed by purple sulfur bacteria, and underlain by sulfate reducing bacteria. Older exposed stromatolites are more consolidated and have a more clearly defined laminated and columnar morphology. The thickness ranges from a few to 15 cm and each column is up to a centimeter in diameter. Together these give the surface of the rock a "bubbly" appearance. Along the shore, a sandy-gravel composed of stromatolite remnants has formed, indicating that wind-generated surface waves of substantial strength to break apart stomatolites can form in the lake. The next bench contains mudstone layers with clasts of basalt and olivine from the surrounding volcanic tuff, but lacks stromatolitic features. Visible ostrocod shells are abundant in these layers, perhaps suggesting that microorganisms could not compete with grazers at this time to form mats of sufficient size to form stromatolites. Finally, a bench lying about 1.8 m above the current water level is a carbonate rock containing small cavities (mm to a few cm in size) in which cements have formed. Also present are ooids of ~1-2 cm diameter. The mineralogy of these cements, ooids, and stromatolites will be determined by XRD and SEM. These data will be combined with an assessment of microbial 16S rRNA gene phylogeny in order to interpret the stromatolite morphogenesis of this unique lake. By studying stromatolite morphogenesis and microbial ecology in a modern dolomite-precipitating saline maar, we hope to gain a better understanding of the factors that controlled ancient stromatolite morphogenesis; and to examine the extent to which microorganisms versus the environment drive these processes.

Relating sub-surface ice features to physiological stress in a climate sensitive mammal, the American pika (Ochotona princeps).

PubMed

Wilkening, Jennifer L; Ray, Chris; Varner, Johanna

2015-01-01

The American pika (Ochotona princeps) is considered a sentinel species for detecting ecological effects of climate change. Pikas are declining within a large portion of their range, and ongoing research suggests loss of sub-surface ice as a mechanism. However, no studies have demonstrated physiological responses of pikas to sub-surface ice features. Here we present the first analysis of physiological stress in pikas living in and adjacent to habitats underlain by ice. Fresh fecal samples were collected non-invasively from two adjacent sites in the Rocky Mountains (one with sub-surface ice and one without) and analyzed for glucocorticoid metabolites (GCM). We also measured sub-surface microclimates in each habitat. Results indicate lower GCM concentration in sites with sub-surface ice, suggesting that pikas are less stressed in favorable microclimates resulting from sub-surface ice features. GCM response was well predicted by habitat characteristics associated with sub-surface ice features, such as lower mean summer temperatures. These results suggest that pikas inhabiting areas without sub-surface ice features are experiencing higher levels of physiological stress and may be more susceptible to changing climates. Although post-deposition environmental effects can confound analyses based on fecal GCM, we found no evidence for such effects in this study. Sub-surface ice features are key to water cycling and storage and will likely represent an increasingly important component of water resources in a warming climate. Fecal samples collected from additional watersheds as part of current pika monitoring programs could be used to further characterize relationships between pika stress and sub-surface ice features.

Mechanical Properties of Degraded PMR-15 Resin

NASA Technical Reports Server (NTRS)

Tsuji, Luis C.; McManus, Hugh L.; Bowles, Kenneth J.

1998-01-01

Thermo-oxidative aging produces a non-uniform degradation state in PMR-15 resin. A surface layer, usually attributed to oxidative degradation, forms. This surface layer has different properties from the inner material. A set of material tests was designed to separate the properties of the oxidized surface layer from the properties of interior material. Test specimens were aged at 316 C in either air or nitrogen, for durations of up to 800 hours. The thickness of the oxidized surface layer in air aged specimens, and the shrinkage and Coefficient of Thermal Expansion (CTE) of nitrogen aged specimens were measured directly. Four-point-bend tests were performed to determine modulus of both the oxidized surface layer and the interior material. Bimaterial strip specimens consisting of oxidized surface material and unoxidized interior material were constructed and used to determine surface layer shrinkage and CTE. Results confirm that the surface layer and core materials have substantially different properties.

A Novel Surface Structure Consisting of Contact-active Antibacterial Upper-layer and Antifouling Sub-layer Derived from Gemini Quaternary Ammonium Salt Polyurethanes.

PubMed

He, Wei; Zhang, Yi; Li, Jiehua; Gao, Yunlong; Luo, Feng; Tan, Hong; Wang, Kunjie; Fu, Qiang

2016-08-26

Contact-active antibacterial surfaces play a vital role in preventing bacterial contamination of artificial surfaces. In the past, numerous researches have been focused on antibacterial surfaces comprising of antifouling upper-layer and antibacterial sub-layer. In this work, we demonstrate a reversed surface structure which integrate antibacterial upper-layer and antifouling sub-layer. These surfaces are prepared by simply casting gemini quaternary ammonium salt waterborne polyurethanes (GWPU) and their blends. Due to the high interfacial energy of gemini quaternary ammonium salt (GQAS), chain segments containing GQAS can accumulate at polymer/air interface to form an antibacterial upper-layer spontaneously during the film formation. Meanwhile, the soft segments composed of polyethylene glycol (PEG) formed the antifouling sub-layer. Our findings indicate that the combination of antibacterial upper-layer and antifouling sub-layer endow these surfaces strong, long-lasting antifouling and contact-active antibacterial properties, with a more than 99.99% killing efficiency against both gram-positive and gram-negative bacteria attached to them.

A Novel Surface Structure Consisting of Contact-active Antibacterial Upper-layer and Antifouling Sub-layer Derived from Gemini Quaternary Ammonium Salt Polyurethanes

PubMed Central

He, Wei; Zhang, Yi; Li, Jiehua; Gao, Yunlong; Luo, Feng; Tan, Hong; Wang, Kunjie; Fu, Qiang

2016-01-01

Contact-active antibacterial surfaces play a vital role in preventing bacterial contamination of artificial surfaces. In the past, numerous researches have been focused on antibacterial surfaces comprising of antifouling upper-layer and antibacterial sub-layer. In this work, we demonstrate a reversed surface structure which integrate antibacterial upper-layer and antifouling sub-layer. These surfaces are prepared by simply casting gemini quaternary ammonium salt waterborne polyurethanes (GWPU) and their blends. Due to the high interfacial energy of gemini quaternary ammonium salt (GQAS), chain segments containing GQAS can accumulate at polymer/air interface to form an antibacterial upper-layer spontaneously during the film formation. Meanwhile, the soft segments composed of polyethylene glycol (PEG) formed the antifouling sub-layer. Our findings indicate that the combination of antibacterial upper-layer and antifouling sub-layer endow these surfaces strong, long-lasting antifouling and contact-active antibacterial properties, with a more than 99.99% killing efficiency against both gram-positive and gram-negative bacteria attached to them. PMID:27561546

How to make a craton

NASA Astrophysics Data System (ADS)

Lee, C.; Chin, E. J.; Erdman, M.; Gaschnig, R. M.; Lederer, G. W.; Savage, P. S.; Zhong, S.; Zincone, S.

2013-12-01

Most Archean cratons are underlain by long-lived 200-300 km thick thermal boundary layers, significantly thicker than oceanic boundary layers, which eventually subduct. The longevity of cratons is perplexing because cold thermal boundary layers should be gravitationally unstable or should thermally erode with time. However, it is agreed that thermal contraction of the cratonic root is compensated by intrinsic compositional buoyancy due to extreme melt depletion. This melt depletion is also thought to have dehydrated the peridotitic residue, strengthening the cratonic mantle, making it resistant to thermo-mechanical erosion. Exactly how cratonic mantle arrives at this chemically buoyant and dehydrated state is unknown. Possible scenarios include formation by melting within a large plume head, accretion of oceanic lithosphere, and accretion of sub-arc mantle. The high degrees of melting would seem to imply formation in hot plume heads, but low Al and heavy rare earth element contents suggest formation in the spinel stability field, implying formation at shallower depths than their current equilibration pressures. We present a new thermobarometer designed to estimate the average melting pressures and temperatures of residual peridotites using whole rock major element compositions. We find that the average melting pressures and temperatures of cratonic peridotites range between 3-4 GPa and 1600 °C. If cratonic peridotites melted via adiabatic decompression, these average pressures represent maximum bounds on the final pressures of melt extraction. Currently, cratonic peridotites derive from 4-7 GPa, implying that the building blocks of peridotites experienced an increase of 1-3 GPa, equivalent to 30-90 km of overburden. Our results thus imply that cratonic mantle most likely formed by tectonic thickening of oceanic or arc lithospheres. But because both arc and oceanic lithospheres might be expected to be wet due to hydrous flux melting and serpentinization, respectively, cratons should be weak. This dilemma can be reconciled by considering the thermal and magmatic evolution of juvenile crust formed in the Archean. Thickening of juvenile crust increases total heat production within the upper part of the nascent lithosphere. With higher heat production in the past, such thickening causes the crust to heat up on timescales of 100 Myr, resulting in a post-orogenic thermal pulse that generates a wave of crustal anatexis and downward heating of the lithospheric mantle, driving off residual water and increasing the kinetics of grain growth, both of which strengthen the lithosphere. Crustal melting will also advectively concentrate radiogenics towards the surface with no observable change in surface heat flow. This upward migration of radiogenics will be followed by cooling of the lower crust and lithospheric mantle, causing further strengthening. With secular cooling of the ambient convecting mantle over much longer timescales, cratons emerge in elevation, leading to erosion of the radiogenically enriched upper crust and leaving behind a continental block with the low surface heat flow characteristic of cratons today. In summary, cratons form by tectonic thickening of cold building blocks, followed by a thermal pulse that further dehydrates and anneals the cratonic mantle. The last step requires sufficient radiogenics to operate, which may explain why cratons formed early in Earth's history.

Hot gas path component cooling system

DOEpatents

Lacy, Benjamin Paul; Bunker, Ronald Scott; Itzel, Gary Michael

2014-02-18

A cooling system for a hot gas path component is disclosed. The cooling system may include a component layer and a cover layer. The component layer may include a first inner surface and a second outer surface. The second outer surface may define a plurality of channels. The component layer may further define a plurality of passages extending generally between the first inner surface and the second outer surface. Each of the plurality of channels may be fluidly connected to at least one of the plurality of passages. The cover layer may be situated adjacent the second outer surface of the component layer. The plurality of passages may be configured to flow a cooling medium to the plurality of channels and provide impingement cooling to the cover layer. The plurality of channels may be configured to flow cooling medium therethrough, cooling the cover layer.

Antisoiling technology: Theories of surface soiling and performance of antisoiling surface coatings

NASA Technical Reports Server (NTRS)

Cuddihy, E. F.; Willis, P. B.

1984-01-01

Physical examination of surfaces undergoing natural outdoor soiling suggests that soil matter accumulates in up to three distinct layers. The first layer involves strong chemical attachment or strong chemisorption of soil matter on the primary surface. The second layer is physical, consisting of a highly organized arrangement of soil creating a gradation in surface energy from a high associated with the energetic first layer to the lowest possible state on the outer surfce of the second layer. The lowest possible energy state is dictated by the physical nature of the regional atmospheric soiling materials. These first two layers are resistant to removal by rain. The third layer constitutes a settling of loose soil matter, accumulating in dry periods and being removed during rainy periods. Theories and evidence suggest that surfaces that should be naturally resistant to the formation of the first two-resistant layers should be hard, smooth, hydrophobic, free of first-period elements, and have the lowest possible surface energy. These characteristics, evolving as requirements for low-soiling surfaces, suggest that surfaces or surface coatings should be of fluorocarbon chemistry. Evidence for the three-soil-layer concept, and data on the positive performance of candidate fluorocarbon coatings on glass and transparent plastic films after 28 months of outdoor exposure, are presented.

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

Vargas, Edmundo; Reyes, Rolando; Palattao, Maria Visitacion

The Philippine Nuclear Research Institute (PNRI) in collaboration with the interagency technical committee on radioactive waste has been undertaking a national project to find a final solution to the country's low to intermediate level radioactive waste. The strategy adopted was to co-locate 2 disposal concepts that will address the types of radioactive waste generated from the use of radioactive materials. This strategy is expected to compensate for the small volumes of waste generated in the Philippines as compared to countries with big nuclear energy programs. It will also take advantage of the benefits of a shared infrastructure and R andmore » D work that accompany such project. The preferred site selected from previous site selection and investigations is underlain by highly fractured 'andesitic volcaniclastics' mantled by residual clayey soil which act as the aquifer or water bearing layer. Results of investigation show that the groundwater in the area is relatively dilute and acidic. Springs at the lower elevations of the footprint also indicate acidic waters. The relatively acidic water is attributed to the formation of sulfuric acid by the oxidation of the pyrite in the andesite. A preliminary post closure safety assessment was carried out using the GMS MODFLOW and HYDRUS softwares purchased through the International Atomic Energy Agency (IAEA) technical assistance. Results from MODFLOW modeling show that the radionuclide transport follows the natural gradient from the top of the hill down to the natural discharge zones. The vault dispersion model shows a circular direction from the vaults towards the faults and eventually to the creeks. The contaminant transport from borehole shows at least one confined plume from the borehole towards the creek designated as Repo1 and eventually follows downstream. The influx of surface water and rainfall to the disposal vault was modeled using the HYDRUS software. The pressure head and water content at the base of the foundation layer and the bottom of the concrete is where a significant reduction in water content can be observed. It is also noted that water content and pressure remain constant after one year. (authors)« less

Water exchange in raised bogs: revised views especially in relation to biogeochemistry

NASA Astrophysics Data System (ADS)

Sirin, Andrey; Kravchenko, Irina; Yurova, Alla; Markina, Anastasiya

2017-04-01

Raised bogs are one of the most common and exciting mire type within the boreal zone and appear in the other zones including mountain regions in the tropics. They receive water and nutrients from the atmosphere and pore water stored in their domes is spaced above the surrounding area (up to 10 m in height). Traditionally it is assumed that water flow occurs mainly in a peat layer near to the surface and water transport is negligible in deeper layers (lvanov, 1981; Ingram, 1982; etc.). The «acrotelm/catotelm» paradigm on active and inert horizons for the peat above and below the lowest water level is still widely spread in peatland hydrology. However, recent studies have shown that deep water movement is much more dynamic in raised bogs than was previously thought (Sirin et al., 1997, Reeve et al., 2000; etc.). Relying on isotope studies we conclude that all the mounded strata of the raised bogs have relatively active water exchange although water residence time changes with depth. The study included two raised bogs, representing different typical hydrological conditions (underlain by outwash sands and moraine clay) at the Zapadnaya Dvina Peatland Field Station of the Institute of Forest Science RAS located 400 km west of Moscow (56 N, 32 E). Peatlands, among which raised bogs dominate, constitute > 30% of the area, and maximum peat thickness exceeds 7 m. To evaluate water residence time in peat strata specially determined mathematical model which include the equations of water mass and tritium balance, imbedded in a conceptual framework of water dynamics within a raised bog peat body, have been developed and tested. The results from isotope studies (3H, 18O, 2H) were additionally supported by geochemical (pH, Eh, electrical conductivity) and temperature long term monitoring, as well as dissolved CO2 and CH4 monitoring within vertical profiles of the studied raised bogs (Sirin et al., 1998). Later it was also supported by microbiology data of methane cycle in the profile of peat bogs (Kravchenko, Sirin, 2007). The obtained results confirm that the hydrological stratification of peat bogs is a more complicated picture than previously thought and need to be considered.

Organic light emitting diode with surface modification layer

DOEpatents

Basil, John D.; Bhandari, Abhinav; Buhay, Harry; Arbab, Mehran; Marietti, Gary J.

2017-09-12

An organic light emitting diode (10) includes a substrate (12) having a first surface (14) and a second surface (16), a first electrode (32), and a second electrode (38). An emissive layer (36) is located between the first electrode (32) and the second electrode (38). The organic light emitting diode (10) further includes a surface modification layer (18). The surface modification layer (18) includes a non-planar surface (30, 52).

Generation and characterization of surface layers on acoustically levitated drops.

PubMed

Tuckermann, Rudolf; Bauerecker, Sigurd; Cammenga, Heiko K

2007-06-15

Surface layers of natural and technical amphiphiles, e.g., octadecanol, stearic acid and related compounds as well as perfluorinated fatty alcohols (PFA), have been investigated on the surface of acoustically levitated drops. In contrast to Langmuir troughs, traditionally used in the research of surface layers at the air-water interface, acoustic levitation offers the advantages of a minimized and contact-less technique. Although the film pressure cannot be directly adjusted on acoustically levitated drops, it runs through a wide pressure range due to the shrinking surface of an evaporating drop. During this process, different states of the generated surface layer have been identified, in particular the phase transition from the gaseous or liquid-expanded to the liquid-condensed state of surface layers of octadecanol and other related amphiphiles. Characteristic parameters, such as the relative permeation resistance and the area per molecule in a condensed surface layer, have been quantified and were found comparable to results obtained from surface layers generated on Langmuir troughs.

Forming aspheric optics by controlled deposition

DOEpatents

Hawryluk, A.M.

1998-04-28

An aspheric optical element is disclosed formed by depositing material onto a spherical surface of an optical element by controlled deposition to form an aspheric surface of desired shape. A reflecting surface, single or multi-layer, can then be formed on the aspheric surface by evaporative or sputtering techniques. Aspheric optical elements are suitable for deep ultra-violet (UV) and x-ray wavelengths. The reflecting surface may, for example, be a thin ({approx}100 nm) layer of aluminum, or in some cases the deposited modifying layer may function as the reflecting surface. For certain applications, multi-layer reflective surfaces may be utilized, such as chromium-carbon or tungsten-carbon multi-layer, with the number of layers and thickness being determined by the intended application. 4 figs.

Forming aspheric optics by controlled deposition

DOEpatents

Hawryluk, Andrew M.

1998-01-01

An aspheric optical element formed by depositing material onto a spherical surface of an optical element by controlled deposition to form an aspheric surface of desired shape. A reflecting surface, single or multi-layer, can then be formed on the aspheric surface by evaporative or sputtering techniques. Aspheric optical elements are suitable for deep ultra-violet (UV) and x-ray wavelengths. The reflecting surface may, for example, be a thin (.about.100 nm) layer of aluminum, or in some cases the deposited modifying layer may function as the reflecting surface. For certain applications, multi-layer reflective surfaces may be utilized, such as chromium-carbon or tungsten-carbon multi-layer, with the number of layers and thickness being determined by the intended application.

Modeling the development of martian sublimation thermokarst landforms

USGS Publications Warehouse

Dundas, Colin M.; Byrne, Shane; McEwen, Alfred S.

2015-01-01

Sublimation-thermokarst landforms result from collapse of the surface when ice is lost from the subsurface. On Mars, scalloped landforms with scales of decameters to kilometers are observed in the mid-latitudes and considered likely thermokarst features. We describe a landscape evolution model that couples diffusive mass movement and subsurface ice loss due to sublimation. Over periods of tens of thousands of Mars years under conditions similar to the present, the model produces scallop-like features similar to those on the Martian surface, starting from much smaller initial disturbances. The model also indicates crater expansion when impacts occur in surfaces underlain by excess ice to some depth, with morphologies similar to observed landforms on the Martian northern plains. In order to produce these landforms by sublimation, substantial quantities of excess ice are required, at least comparable to the vertical extent of the landform, and such ice must remain in adjacent terrain to support the non-deflated surface. We suggest that Martian thermokarst features are consistent with formation by sublimation, without melting, and that significant thicknesses of very clean excess ice (up to many tens of meters, the depth of some scalloped depressions) are locally present in the Martian mid-latitudes. Climate conditions leading to melting at significant depth are not required.

Lead isotopic compositions of soil and near-surface till profiles from a watershed containing arsenic-enriched groundwater in coastal Maine

USGS Publications Warehouse

Ayuso, Robert; Foley, Nora; Wandless, Gregory; Dillingham, Jeremy; Colvin, Anna

2005-01-01

Lead isotope compositions of soils and near-surface tills from an area of coastal Maine known to have groundwater with anomalously high arsenic contents were measured in order to determine the source of the lead and, by inference, possible sources of arsenic. Five soil and till sites were selected for detailed chemical and isotopic analysis. To construct profiles of the soil and till horizons, five samples were collected at 10-cm intervals from the surface to the base of each horizon. Total lead and arsenic concentrations and lead isotopic compositions were measured for 48 leaches and bulk residues. The soils and tills are underlain by sulfidic schists of the Penobscot Formation. Several generations of minerals containing arsenic and lead exist in the regional bedrock, including rock-forming silicates (feldspar and micas), sulfide minerals formed during diagenesis (for example, arsenic-rich pyrite), and sulfide and oxide minerals that formed as a result of Silurian metamorphic and igneous events (for example, arsenopyrite, galena, iron-oxides, and arsenic-sulfides). A young group of secondary minerals (for example, iron-hydroxides, arsenic-hydroxides, lead-sulfate, and arsenic-jarosite) formed from recent weathering and pedogenic processes.

Different Conformations of Surface Cellulose Molecules in Native Cellulose Microfibrils Revealed by Layer-by-Layer Peeling.

PubMed

Funahashi, Ryunosuke; Okita, Yusuke; Hondo, Hiromasa; Zhao, Mengchen; Saito, Tsuguyuki; Isogai, Akira

2017-11-13

Layer-by-layer peeling of surface molecules of native cellulose microfibrils was performed using a repeated sequential process of 2,2,6,6-tetramethylpiperidine-1-oxyl radical-mediated oxidation followed by hot alkali extraction. Both highly crystalline algal and tunicate celluloses and low-crystalline cotton and wood celluloses were investigated. Initially, the C6-hydroxy groups of the outermost surface molecules of each algal cellulose microfibril facing the exterior had the gauche-gauche (gg) conformation, whereas those facing the interior had the gauche-trans (gt) conformation. All the other C6-hydroxy groups of the cellulose molecules inside the microfibrils contributing to crystalline cellulose I had the trans-gauche (tg) conformation. After surface peeling, the originally second-layer molecules from the microfibril surface became the outermost surface molecules, and the original tg conformation changed to gg and gt conformations. The plant cellulose microfibrils likely had disordered structures for both the outermost surface and second-layer molecules, as demonstrated using the same layer-by-layer peeling technique.

Durable superhydrophobic surfaces made by intensely connecting a bipolar top layer to the substrate with a middle connecting layer.

PubMed

Zhi, Jinghui; Zhang, Li-Zhi

2017-08-30

This study reported a simple fabrication method for a durable superhydrophobic surface. The superhydrophobic top layer of the durable superhydrophobic surface was connected intensely to the substrate through a middle connecting layer. Glycidoxypropyltrimethoxysilane (KH-560) after hydrolysis was used to obtain a hydrophilic middle connecting layer. It could be adhered to the hydrophilic substrate by covalent bonds. Ring-open reaction with octadecylamine let the KH-560 middle layer form a net-like structure. The net-like sturcture would then encompass and station the silica particles that were used to form the coarse micro structures, intensely to increase the durability. The top hydrophobic layer with nano-structures was formed on the KH-560 middle layer. It was obtained by a bipolar nano-silica solution modified by hexamethyldisilazane (HMDS). This layer was connected to the middle layer intensely by the polar Si hydroxy groups, while the non-polar methyl groups on the surface, accompanied by the micro and nano structures, made the surface rather hydrophobic. The covalently interfacial interactions between the substrate and the middle layer, and between the middle layer and the top layer, strengthened the durability of the superhydrophobic surface. The abrasion test results showed that the superhydrophobic surface could bear 180 abrasion cycles on 1200 CW sandpaper under 2 kPa applied pressure.

Increased forest ecosystem carbon and nitrogen storage from nitrogen rich bedrock.

PubMed

Morford, Scott L; Houlton, Benjamin Z; Dahlgren, Randy A

2011-08-31

Nitrogen (N) limits the productivity of many ecosystems worldwide, thereby restricting the ability of terrestrial ecosystems to offset the effects of rising atmospheric CO(2) emissions naturally. Understanding input pathways of bioavailable N is therefore paramount for predicting carbon (C) storage on land, particularly in temperate and boreal forests. Paradigms of nutrient cycling and limitation posit that new N enters terrestrial ecosystems solely from the atmosphere. Here we show that bedrock comprises a hitherto overlooked source of ecologically available N to forests. We report that the N content of soils and forest foliage on N-rich metasedimentary rocks (350-950 mg N kg(-1)) is elevated by more than 50% compared with similar temperate forest sites underlain by N-poor igneous parent material (30-70 mg N kg(-1)). Natural abundance N isotopes attribute this difference to rock-derived N: (15)N/(14)N values for rock, soils and plants are indistinguishable in sites underlain by N-rich lithology, in marked contrast to sites on N-poor substrates. Furthermore, forests associated with N-rich parent material contain on average 42% more carbon in above-ground tree biomass and 60% more carbon in the upper 30 cm of the soil than similar sites underlain by N-poor rocks. Our results raise the possibility that bedrock N input may represent an important and overlooked component of ecosystem N and C cycling elsewhere.

Platinum mineralization in the Kapalagulu Intrusion, western Tanzania

NASA Astrophysics Data System (ADS)

Wilhelmij, Harry R.; Cabri, Louis J.

2016-03-01

Low-grade copper and nickel mineralization was found near the eastern shore of Lake Tanganyika at Kungwe Bay in the early part of the twentieth century. The mineralization occurs in harzburgite at the base of a layered gabbro complex known as the Kapalagulu Intrusion, emplaced between the Paleoproterozoic Ubendian basement and overlying Neoproterozoic Itiaso Group metasediments. Several mining and exploration companies continued the geophysical and drilling exploration for base metals throughout the last century culminating in the discovery of high-grade platinum-group element (PGE) mineralization associated with chromitite and sulfide-bearing harzburgite within the southeastern extension of the Kapalagulu Intrusion (known as the Lubalisi Zone) that is covered by a layer of nickel-rich laterite regolith. The poorly layered southeastern harzburgite forms part of the >1500 m-thick Lower Ultramafic Sequence and resembles a dike-like body that flares upwards into a succession of well-layered gabbroic rocks of the Upper Mafic Sequence. No PGE mineralization has been found in the layered gabbro; all the mineralization is associated with the chromite- and sulfide-rich harzburgite of the Lower Ultramafic Sequence and the laterite regolith overlying the mineralized harzburgite. The Lubalisi Zone harzburgite is underlain by basal dunite and overlain by an interval of layered harzburgite and troctolite and this ultramafic sequence is folded into a syncline that plunges towards the northwest that has been modified by major dolerite-filled faults orientated subparallel to the fold axial surface. Extensive deep drilling in the Lubalisi Zone of the Kapalagulu Intrusion shows that the folded harzburgite can be subdivided into a lower feldspathic harzburgite, a harzburgite containing chromitite seams and intervals of sulfide and chromite mineralization known as the Main Chromite Sulfide Succession (MCSS), an overlying sulfide-rich harzburgite, and an upper feldspathic harzburgite. Impersistent, stratiform PGE mineralized horizons occur within the MCSS harzburgite from which drill core samples were taken for platinum-group mineral (PGM) characterization from two drill holes. Where the PGE reefs reach the surface there is residual PGE mineralization within the laterite regolith from which drill core samples were taken from various laterite lithological units for PGM characterization. As the harzburgite PGE reefs contain significant concentrations of both sulfide and chromite (including chromitite seams) they resemble the PGE-rich chromitite seams of the Bushveld Complex rather than the PGE-bearing Main Sulfide Zone of the Great Dyke and Main Sulfide Layer of the Munni Munni Complex. The dominant Pd PGM in three PGE reef samples varies, ranging ( n = 164, relative wt%) from bismuthides (63 %), bismuthtellurides (19 %), and tellurides (6 %), to tellurides (39 %), bismuthtellurides (24 %), stannides (14 %), and alloys (13 %), and to antimon-arsenides (33 %), stannides (21 %), bismuthides (17 %), tellurides (13 %), and alloys (10 %). From 13.5 % to 21.0 % of the total Pd occurs as a solid solution in pentlandite. The three samples have similar Pt PGM modal distributions ( n = 172, relative wt%); the dominant Pt mineral is sperrylite (79, 58, and 47 %) followed by tellurides (15, 17, 21 %), alloys (2, 1, 1 %), and sulfides (2, 1, 0 %). Comparison of Pd/Pt ratios from assays to those calculated from minerals show that the data for the Pt and Pd PGM are very robust, confirming the concentration methodology and characterization. Study of samples from a shallow drill hole penetrating the laterite regolith shows that the primary Pd mineralization has not survived oxidation, is mainly dispersed, but some was reconstituted to form secondary minerals: cabriite, unnamed tellurides, a selenide, a Pd-Te-Hg mineral, alloys and Pd-bearing secondary sulfides (millerite and heazlewoodite). The primary Pt minerals are more resistant to oxidation and dissolution, especially sperrylite and isoferroplatinum, but it is likely that other Pt alloys (tetraferroplatinum and tulameenite) are of secondary origin after dissolution of Pt tellurides.

Improve oxidation resistance at high temperature by nanocrystalline surface layer

NASA Astrophysics Data System (ADS)

Xia, Z. X.; Zhang, C.; Huang, X. F.; Liu, W. B.; Yang, Z. G.

2015-08-01

An interesting change of scale sequence occurred during oxidation of nanocrystalline surface layer by means of a surface mechanical attrition treatment. The three-layer oxide structure from the surface towards the matrix is Fe3O4, spinel FeCr2O4 and corundum (Fe,Cr)2O3, which is different from the typical two-layer scale consisted of an Fe3O4 outer layer and an FeCr2O4 inner layer in conventional P91 steel. The diffusivity of Cr, Fe and O is enhanced concurrently in the nanocrystalline surface layer, which causes the fast oxidation in the initial oxidation stage. The formation of (Fe,Cr)2O3 inner layer would inhabit fast diffusion of alloy elements in the nanocrystalline surface layer of P91 steel in the later oxidation stage, and it causes a decrease in the parabolic oxidation rate compared with conventional specimens. This study provides a novel approach to improve the oxidation resistance of heat resistant steel without changing its Cr content.

Hydrology of the dunes area north of Coos Bay, Oregon

USGS Publications Warehouse

Robison, J.H.

1973-01-01

Hydrology of a 20-square-mile area of dunes along the central Oregon coast was studied. The area is underlain by 80 to 150 feet of Quaternary dune and marine sand which overlies Tertiary marine clay and shale. Ground water for industrial and municipal use is being withdrawn at a rate of 4 million gallons per day. Original plans to withdraw as much as 30 million gallons per day are evidently limited by the prospect of excessive lowering of levels in shallow lakes near the wells, and possibly sea-water intrusion, if water-level gradients are reversed. At the present stage of development there are 18 production wells, each capable of producing 200-300 gallons per minute from the lower part of the sand deposits. Except for thin layers of silt, clay, and organic matter, the deposits of sand are clean and uniform; horizontal permeability is two orders of magnitude times the vertical permeability. Because of the low vertical permeability, drawdown cones are not evident in the upper part of the aquifer adjacent to the wells. However, present pumping lowers general water levels in the lakes and the shallow ground-water zone as much as several feet. A two-layer electric analog model was built to analyze effects of present and projected development as well as any alternate plans. Model results were used to develop curves for short-term prediction of water levels.

Mechanical Properties of Degraded PMR-15 Resin

NASA Technical Reports Server (NTRS)

Tsuji, Luis C.

2000-01-01

Thermo-oxidative aging produces a nonuniform degradation state in PMR-15 resin. A surface layer, usually attributed to oxidative degradation, forms. This surface layer has different properties from the inner material. A set of material tests was designed to separate the properties of the oxidized surface layer from the properties of interior material. Test specimens were aged at 316 C in either air or nitrogen, for durations of up to 800 hr. The thickness of the oxidized surface layer in air aged specimens, and the shrinkage and coefficient of thermal expansion (CTE) of nitrogen aged specimens were measured directly. The nitrogen-aged specimens were assumed to have the same properties as the interior material in the air-aged specimens. Four-point-bend tests were performed to determine modulus of both the oxidized surface layer and the interior material. Bimaterial strip specimens consisting of oxidized surface material and unoxidized interior material were constructed and used to determine surface layer shrinkage and CTE. Results confirm that the surface layer and core materials have substantially different properties.

Geochemistry of carbonate cements in surficial alluvial conglomerates and their paleoclimatic implications, Sultanate of Oman

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

Burns, S.J.; Matter, A.

1995-01-02

Early diagenetic carbonate cements are a common feature of Quaternary alluvial conglomerates in Oman. Cements are formed in the vadose and, more commonly, phreatic zones from near-surface groundwaters. In drainage areas underlain by the Semail Ophiolite, groundwaters have Mg{sup 2+}/Ca{sup 2+} ratios greater than two, and cements are often dolomite or high-magnesium calcite in addition to low-magnesium calcite. In drainage areas underlain by limestone, groundwaters have Mg{sup 2+}/Ca{sup 2+} ratios of around one or less and cement mineralogy is nearly always low-magnesium calcite. The oxygen and carbon stable isotopic ratios of the cements vary widely, from {minus}10.6{per_thousand} to +3.0{per_thousand} PDBmore » and from {minus}10.0{per_thousand} to +0.7{per_thousand} PDB, respectively. Cement {delta}{sup 18}O values principally reflect variation in rainfall {delta}{sup 18}O over a time scale of several thousand years. Rainfall and cement {delta}{sup 18}O values probably are inversely correlated with the amount of rainfall, which is related to the frequency and intensity of the Indian Ocean monsoon. Thus, cement {delta}{sup 18}O is potentially a proxy indicator of relative rainfall and monsoon activity. For each of three sampling areas, {delta}{sup 13}C is positively correlated to {delta}{sup 18}O. Cement {delta}{sup 13}C values are also related to rainfall amount because rainfall controls the plant population. Greater plant respiration of isotopically depleted CO{sub 2} to shallow groundwaters and burial of organic material in conglomerate deposits results in lower cement {delta}{sup 13}C values compared to periods of lesser plant activity.« less

Environmental setting of fixed sites in the western Lake Michigan drainages, Michigan and Wisconsin

USGS Publications Warehouse

Sullivan, D.J.; Peterson, E.M.; Richards, K.D.

1995-01-01

This report describes selected environmental- setting features for 11 fixed surface-water sites in the Western Lake Michigan Drainages study unit of the National Water-Quality Assessment Pro- gram. The study unit, which includes 10 major river systems draining to Lake Michigan, is bounded on the south by the Illinois State line and extends north to about 31 miles north of Escanaba, Mich. The fixed sites are on the following streams: Peshekee River, Popple River, Menominee River, Pensaukee River, Duck Creek, Tomorrow River, East River, Fox River, North Branch Milwaukee River, Lincoln Creek, and Milwaukee River. Drainage basins above these sites receive runoff from land uses and land covers, bedrock types, and surficial deposits representative of the main types of each of these characteristics in the study unit. Data types collected at the fixed sites include water chemistry; organic compounds and trace elements in streambed sediment and biological tissues; algal, benthic-invertebrate, and fish communities; and aquatic habitat. Field measurements include water temperature, pH, specific conductance, alkalinity, and dissolved oxygen. Results of water- quality field measurements indicate little variation in temperature among the fixed sites. Specific conductance and alkalinity were generally higher at sites underlain by carbonate bedrock than at sites underlain by igneous/metamorphic bedrock. Differences in pH among the fixed sites were less than those for specific conductance and alkalinity, but pH seemed to increase slightly from north to south. Dissolved-oxygen concentration varied more at agricultural sites than at forested and urban sites, perhaps because of higher nutrient inputs at agricultural sites. The information included in this report has been assembled as reference material for ongoing studies at the fixed sites.

Seismic Velocity Structure of the Pacific Upper Mantle in the NoMelt Region from Finite-Frequency Traveltime Tomography

NASA Astrophysics Data System (ADS)

Hung, S. H.; Lin, P. Y.; Gaherty, J. B.; Russell, J. B.; Jin, G.; Collins, J. A.; Lizarralde, D.; Evans, R. L.; Hirth, G.

2017-12-01

Surface wave dispersion and magnetotelluric survey from the NoMelt Experiment conducted on 70 Ma central Pacific seafloor revealed an electrically resistive, high shear wave velocity lid of 80 km thick underlain by a non-highly conductive, low-velocity layer [Sarafian et al., 2015; Lin et al., 2016]. The vertical structure of the upper mantle consistent with these observational constraints suggests a plausible convection scenario, where the seismically fast, dehydrated lithosphere preserving very strong fossil spreading fabric moves at a constant plate speed over the hydrated, melt-free athenospheric mantle with the presence of either pressure-driven return flow or thermally-driven small scale circulation. To explore 3-D variations in compressional shear wave velocities related to the lithospheric and asthenospheric mantle dynamics, we employ a multichannel cross correlation method to measure relative traveltime residuals based on the vertical P and traverse S waveforms filtered at 10-33 s from telseismic earthquakes at epicentral distance between 30 and 98 degrees. The obtained P and S residuals show on average peak-to-peak variations of ±0.5 s and ±1 s, respectively, across the NoMelt OBS array. Particularly, the P residuals for most of the events display an asymmetrical pattern with respect to an axis oriented nearly N-S to NE-SW through the array. Preliminary ray-based P tomography results reveal similar asymmetric variations in the uppermost 100 km mantle. To verify the resulting structural features, we will further perform both the P and S traveltime tomography and resolution tests based on a multiscale finite-frequency approach which properly takes into account both the 3D off-path sensitivities of the measured residuals and data-adaptive resolution of the model.

Coal Fields and Federal Lands of the Conterminous United States

USGS Publications Warehouse

Biewick, Laura

1997-01-01

The map depicts the relationship of coal and public lands in the conterminous U. S. Multiple GIS layers are being created for the purpose of deriving estimates of how much coal is owned and administered by the Federal government. Federal coal areas have a profound effect on land-management decisions. Regulatory agencies attempt to balance energy development with alternative land-use and environmental concerns. A GIS database of Federal lands used in energy resource assessments is being developed by the U. S. Geological Survey (USGS) in cooperation with the U.S. Bureau of Land Management (BLM) to integrate information on status of public land, and minerals owned by the Federal government with geologic information on coal resources, other spatial data, coal quality characteristics, and coal availability for development. Using national-scale data we estimate that approximately 60 percent of the area underlain by coal-bearing rocks in the conterminous United States are under Federal surface. Coal produced from Federal leases has tripled from about 12 percent of the total U.S. production in 1976 to almost 34 percent in 1995 (Energy Information Administration website ftp://ftp.eia.doe.gov/pub/coal/cia_95_tables/t13p01.txt). The reason for this increase is demand for low-sulfur coal for use in power plants and the fact that large reserves of this low-sulfur coal are in the western interior U.S., where the Federal government owns the rights to most of the coal reserves. The map was created using Arc/Info 7.0.3 on a UNIX system. The HPGL2 plot file for this map is available from the USGS Energy Resource Surveys Team from http://energy.cr.usgs.gov:8080/energy/coal.html.

Ecosystem CO2 and CH4 exchange in a mixed tundra and a fen within a hydrologically diverse Arctic landscape: 1. Modeling versus measurements

NASA Astrophysics Data System (ADS)

Grant, R. F.; Humphreys, E. R.; Lafleur, P. M.

2015-07-01

CO2 and CH4 exchange are strongly affected by hydrology in landscapes underlain by permafrost. Hypotheses for these effects in the model ecosys were tested by comparing modeled CO2 and CH4 exchange with CO2 fluxes measured by eddy covariance from 2006 to 2009, and with CH4 fluxes measured with surface chambers in 2008, along a topographic gradient at Daring Lake, NWT. In an upland tundra, rises in net CO2 uptake in warmer years were constrained by declines in CO2 influxes when vapor pressure deficits (D) exceeded 1.5 kPa and by rises in CO2 effluxes with greater active layer depth. Consequently, net CO2 uptake rose little with warming. In a lowland fen, CO2 influxes declined less with D and CO2 effluxes rose less with warming, so that rises in net CO2 uptake were greater than those in the tundra. Greater declines in CO2 influxes with warming in the tundra were modeled from greater soil-plant-atmosphere water potential gradients that developed under higher D in drained upland soil, and smaller rises in CO2 effluxes with warming in the fen were modeled from O2 constraints to heterotrophic and belowground autotrophic respiration from a shallow water table in poorly drained lowland soil. CH4 exchange modeled during July and August indicated very small influxes in the tundra and larger effluxes characterized by afternoon emission events caused by degassing of warming soil in the fen. Emissions of CH4 modeled from degassing during soil freezing in October-November contributed about one third of the annual total.

Joint inversions of three types of electromagnetic data explicitly constrained by seismic observations: results from the central Okavango Delta, Botswana

NASA Astrophysics Data System (ADS)

Kalscheuer, Thomas; Blake, Sarah; Podgorski, Joel E.; Wagner, Frederic; Green, Alan G.; Maurer, Hansruedi; Jones, Alan G.; Muller, Mark; Ntibinyane, Ongkopotse; Tshoso, Gomotsang

2015-09-01

The Okavango Delta of northern Botswana is one of the world's largest inland deltas or megafans. To obtain information on the character of sediments and basement depths, audiomagnetotelluric (AMT), controlled-source audiomagnetotelluric (CSAMT) and central-loop transient electromagnetic (TEM) data were collected on the largest island within the delta. The data were inverted individually and jointly for 1-D models of electric resistivity. Distortion effects in the AMT and CSAMT data were accounted for by including galvanic distortion tensors as free parameters in the inversions. By employing Marquardt-Levenberg inversion, we found that a 3-layer model comprising a resistive layer overlying sequentially a conductive layer and a deeper resistive layer was sufficient to explain all of the electromagnetic data. However, the top of the basal resistive layer from electromagnetic-only inversions was much shallower than the well-determined basement depth observed in high-quality seismic reflection images and seismic refraction velocity tomograms. To resolve this discrepancy, we jointly inverted the electromagnetic data for 4-layer models by including seismic depths to an interface between sedimentary units and to basement as explicit a priori constraints. We have also estimated the interconnected porosities, clay contents and pore-fluid resistivities of the sedimentary units from their electrical resistivities and seismic P-wave velocities using appropriate petrophysical models. In the interpretation of our preferred model, a shallow ˜40 m thick freshwater sandy aquifer with 85-100 Ωm resistivity, 10-32 per cent interconnected porosity and <13 per cent clay content overlies a 105-115 m thick conductive sequence of clay and intercalated salt-water-saturated sands with 15-20 Ωm total resistivity, 1-27 per cent interconnected porosity and 15-60 per cent clay content. A third ˜60 m thick sandy layer with 40-50 Ωm resistivity, 10-33 per cent interconnected porosity and <15 per cent clay content is underlain by the basement with 3200-4000 Ωm total resistivity. According to an interpretation of helicopter TEM data that cover the entire Okavango Delta and borehole logs, the second and third layers may represent lacustrine sediments from Paleo Lake Makgadikgadi and a moderately resistive freshwater aquifer comprising sediments of the recently proposed Paleo Okavango Megafan, respectively.

The influence of lithology on surface water sources | Science ...

EPA Pesticide Factsheets

Understanding the temporal and spatial variability of surface water sources within a basin is vital to our ability to manage the impacts of climate variability and land cover change. Water stable isotopes can be used as a tool to determine geographic and seasonal sources of water at the basin scale. Previous studies in the Coastal Range of Oregon reported that the variation in the isotopic signatures of surface water does not conform to the commonly observed “rainout effect”, which exhibits a trend of increasing isotopic depletion with rising elevation. The primary purpose of this research is to investigate the mechanisms governing seasonal and spatial variations in the isotopic signature of surface waters within the Marys River Basin, located in the leeward side of the Oregon Coastal Range. Surface water and precipitation samples were collected every 2-3 weeks for isotopic analysis of δ18O and δ2H for one year. Results indicate a significant difference in isotopic signature between watersheds underlain by basalt and sandstone. The degree of separation was the most distinct during the summer when low flows reflect deeper groundwater sources, whereas isotopic signatures during the rainy season (fall and winter) showed a greater degree of similarity between the two lithologies. This indicates that baseflow within streams drained by sandstone versus basalt is being supplied from two distinctly separate water sources. In addition, Marys River flow at the outle

Laser modification of macroscopic properties of metal surface layer

NASA Astrophysics Data System (ADS)

Kostrubiec, Franciszek

1995-03-01

Surface laser treatment of metals comprises a number of diversified technological operations out of which the following can be considered the most common: oxidation and rendering surfaces amorphous, surface hardening of steel, modification of selected physical properties of metal surface layers. In the paper basic results of laser treatment of a group of metals used as base materials for electric contacts have been presented. The aim of the study was to test the usability of laser treatment from the viewpoint of requirements imposed on materials for electric contacts. The results presented in the paper refer to two different surface treatment technologies: (1) modification of infusible metal surface layer: tungsten and molybdenum through laser fusing of their surface layer and its crystallization, and (2) modification of surface layer properties of other metals through laser doping of their surface layer with foreign elements. In the paper a number of results of experimental investigations obtained by the team under the author's supervision are presented.

Self-cleaning skin-like prosthetic polymer surfaces

DOEpatents

Simpson, John T [Clinton, TN; Ivanov, Ilia N [Knoxville, TN; Shibata, Jason [Manhattan Beach, CA

2012-03-27

An external covering and method of making an external covering for hiding the internal endoskeleton of a mechanical (e.g., prosthetic) device that exhibits skin-like qualities is provided. The external covering generally comprises an internal bulk layer in contact with the endoskeleton of the prosthetic device and an external skin layer disposed about the internal bulk layer. The external skin layer is comprised of a polymer composite with carbon nanotubes embedded therein. The outer surface of the skin layer has multiple cone-shaped projections that provide the external skin layer with superhydrophobicity. The carbon nanotubes are preferably vertically aligned between the inner surface and outer surface of the external skin layer in order to provide the skin layer with the ability to transmit heat. Superhydrophobic powders may optionally be used as part of the polymer composite or applied as a coating to the surface of the skin layer to enhance superhydrophobicity.

Method of making self-cleaning skin-like prosthetic polymer surfaces

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

Simpson, John T.; Ivanov, Ilia N.; Shibata, Jason

An external covering and method of making an external covering for hiding the internal endoskeleton of a mechanical (e.g., prosthetic) device that exhibits skin-like qualities is provided. The external covering generally comprises an internal bulk layer in contact with the endoskeleton of the prosthetic device and an external skin layer disposed about the internal bulk layer. The external skin layer is comprised of a polymer composite with carbon nanotubes embedded therein. The outer surface of the skin layer has multiple cone-shaped projections that provide the external skin layer with superhydrophobicity. The carbon nanotubes are preferably vertically aligned between the innermore » surface and outer surface of the external skin layer in order to provide the skin layer with the ability to transmit heat. Superhydrophobic powders may optionally be used as part of the polymer composite or applied as a coating to the surface of the skin layer to enhance superhydrophobicity.« less

Chemical solution deposition method of fabricating highly aligned MgO templates

DOEpatents

Paranthaman, Mariappan Parans [Knoxville, TN; Sathyamurthy, Srivatsan [Knoxville, TN; Aytug, Tolga [Knoxville, TN; Arendt, Paul N [Los Alamos, NM; Stan, Liliana [Los Alamos, NM; Foltyn, Stephen R [Los Alamos, NM

2012-01-03

A superconducting article includes a substrate having an untextured metal surface; an untextured barrier layer of La.sub.2Zr.sub.2O.sub.7 or Gd.sub.2Zr.sub.2O.sub.7 supported by and in contact with the surface of the substrate; a biaxially textured buffer layer supported by the untextured barrier layer; and a biaxially textured superconducting layer supported by the biaxially textured buffer layer. Moreover, a method of forming a buffer layer on a metal substrate includes the steps of: providing a substrate having an untextured metal surface; coating the surface of the substrate with a barrier layer precursor; converting the precursor to an untextured barrier layer; and depositing a biaxially textured buffer layer above and supported by the untextured barrier layer.

Photovoltaic module with adhesion promoter

DOEpatents

Xavier, Grace

2013-10-08

Photovoltaic modules with adhesion promoters and methods for fabricating photovoltaic modules with adhesion promoters are described. A photovoltaic module includes a solar cell including a first surface and a second surface, the second surface including a plurality of interspaced back-side contacts. A first glass layer is coupled to the first surface by a first encapsulating layer. A second glass layer is coupled to the second surface by a second encapsulating layer. At least a portion of the second encapsulating layer is bonded directly to the plurality of interspaced back-side contacts by an adhesion promoter.

Surface modified stainless steels for PEM fuel cell bipolar plates

DOEpatents

Brady, Michael P [Oak Ridge, TN; Wang, Heli [Littleton, CO; Turner, John A [Littleton, CO

2007-07-24

A nitridation treated stainless steel article (such as a bipolar plate for a proton exchange membrane fuel cell) having lower interfacial contact electrical resistance and better corrosion resistance than an untreated stainless steel article is disclosed. The treated stainless steel article has a surface layer including nitrogen-modified chromium-base oxide and precipitates of chromium nitride formed during nitridation wherein oxygen is present in the surface layer at a greater concentration than nitrogen. The surface layer may further include precipitates of titanium nitride and/or aluminum oxide. The surface layer in the treated article is chemically heterogeneous surface rather than a uniform or semi-uniform surface layer exclusively rich in chromium, titanium or aluminum. The precipitates of titanium nitride and/or aluminum oxide are formed by the nitriding treatment wherein titanium and/or aluminum in the stainless steel are segregated to the surface layer in forms that exhibit a low contact resistance and good corrosion resistance.

System for rapid biohydrogen phenotypic screening of microorganisms using a chemochromic sensor

DOEpatents

Seibert, Michael; Benson, David K.; Flynn, Timothy Michael

2002-01-01

Provided is a system for identifying a hydrogen gas producing organism. The system includes a sensor film having a first layer comprising a transition metal oxide or oxysalt and a second layer comprising a hydrogen-dissociative catalyst metal, the first and second layers having an inner and an outer surface wherein the inner surface of the second layer is deposited on the outer surface of the first layer, and a substrate adjacent to the outer surface of the second layer, the organism isolated on the substrate.

Method and apparatus for rapid biohydrogen phenotypic screening of microorganisms using a chemochromic sensor

DOEpatents

Seibert, Michael; Benson, David K.; Flynn, Timothy Michael

2001-01-01

The invention provides an assay system for identifying a hydrogen-gas-producing organism, including a sensor film having a first layer comprising a transition metal oxide or oxysalt and a second layer comprising hydrogen-dissociative catalyst metal, the first and second layers having an inner and an outer surface wherein the inner surface of the second layer is deposited on the outer surface of the first layer, and a substrate disposed proximally to the outer surface of the second layer, the organism being isolated on the substrate.

Surface-stabilized gold nanocatalysts

DOEpatents

Dai, Sheng [Knoxville, TN; Yan, Wenfu [Oak Ridge, TN

2009-12-08

A surface-stabilized gold nanocatalyst includes a solid support having stabilizing surfaces for supporting gold nanoparticles, and a plurality of gold nanoparticles having an average particle size of less than 8 nm disposed on the stabilizing surfaces. The surface-stabilized gold nanocatalyst provides enhanced stability, such as at high temperature under oxygen containing environments. In one embodiment, the solid support is a multi-layer support comprising at least a first layer having a second layer providing the stabilizing surfaces disposed thereon, the first and second layer being chemically distinct.

Hydrogeologic Framework in Three Drainage Basins in the New Jersey Pinelands, 2004-06

USGS Publications Warehouse

Walker, Richard L.; Reilly, Pamela A.; Watson, Kara M.

2008-01-01

The U.S. Geological Survey, in cooperation with the New Jersey Pinelands Commission, began a multi-phase hydrologic investigation in 2004 to characterize the hydrologic system supporting the aquatic and wetland communities of the New Jersey Pinelands area (Pinelands). The Pinelands is an ecologically diverse area in the southern New Jersey Coastal Plain underlain by the Kirkwood-Cohansey aquifer system. The demand for ground water from this aquifer system is increasing as local development increases. To assess the effects of ground-water withdrawals on Pinelands stream and wetland water levels, three drainage basins were selected for detailed hydrologic assessments, including the Albertson Brook, McDonalds Branch and the Morses Mill Stream basins. Study areas were defined surrounding the three drainage basins to provide sub-regional hydrogeologic data for the ground-water flow modeling phase of this study. In the first phase of the hydrologic assessments, a database of hydrogeologic information and a hydrogeologic framework model for each of the three study areas were produced. These framework models, which illustrate typical hydrogeologic variations among different geographic subregions of the Pinelands, are the structural foundation for predictive ground-water flow models to be used in assessing the hydrologic effects of increased ground-water withdrawals. During 2004-05, a hydrogeologic database was compiled using existing and new geophysical and lithologic data including suites of geophysical logs collected at 7 locations during the drilling of 21 wells and one deep boring within the three study areas. In addition, 27 miles of ground-penetrating radar (GPR) surface geophysical data were collected and analyzed to determine the depth and extent of shallow clays in the general vicinity of the streams. On the basis of these data, the Kirkwood-Cohansey aquifer system was divided into 7 layers to construct a hydrogeologic framework model for each study area. These layers are defined by their predominant sediment textures as aquifers and leaky confining layers. The confining layer at the base of the Kirkwood-Cohansey aquifer system, depending on location, is defined as one of two distinct clays of the Kirkwood Formation. The framework models are described using hydrogeologic sections, maps of structure tops of layers, and thickness maps showing variations of sediment textures of the various model layers. The three framework models are similar in structure but unique to their respective study areas. The hydraulic conductivity of the Kirkwood-Cohansey aquifer system in the vicinity of the three study areas was determined from analysis of 16 slug tests and 136 well-performance tests. The mean values for hydraulic conductivity in the three study areas ranged from about 84 feet per day to 130 feet per day. With the exception of the basal confining layers, the variable and discontinuous nature of clay layers within the Kirkwood-Cohansey aquifer system was confirmed by the geophysical and lithologic records. Leaky confining layers and discontinuous clays are generally more common in the upper part of the aquifer system. Although the Kirkwood-Cohansey aquifer system generally has been considered a water-table aquifer in most areas, localized clays in the aquifer layers and the effectiveness of the leaky confining layers may act to impede the flow of ground water in varying amounts depending on the degree of confinement and the location, duration, and magnitude of the hydraulic stresses applied. Considerable variability exists in the different sediment textures. The extent to which this hydrogeologic variability can be characterized is constrained by the extent of the available data. Thus, the hydraulic properties of the modeled layers were estimated on the basis of available horizontal hydraulic conductivity data and the range of sediment textures estimated from geophysical and lithologic data.

Thermal barriers for compartments

DOEpatents

Kreutzer, Cory J.; Lustbader, Jason A.

2017-10-17

An aspect of the present disclosure is a thermal barrier that includes a core layer having a first surface, a second surface, and a first edge, and a first outer layer that includes a third surface and a second edge, where the third surface substantially contacts the first surface, the core layer is configured to minimize conductive heat transfer through the barrier, and the first outer layer is configured to maximize reflection of light away from the barrier.

Nanoscale surface modification of Li-rich layered oxides for high-capacity cathodes in Li-ion batteries

NASA Astrophysics Data System (ADS)

Lan, Xiwei; Xin, Yue; Wang, Libin; Hu, Xianluo

2018-03-01

Li-rich layered oxides (LLOs) have been developed as a high-capacity cathode material for Li-ion batteries, but the structural complexity and unique initial charging behavior lead to several problems including large initial capacity loss, capacity and voltage fading, poor cyclability, and inferior rate capability. Since the surface conditions are critical to electrochemical performance and the drawbacks, nanoscale surface modification for improving LLO's properties is a general strategy. This review mainly summarizes the surface modification of LLOs and classifies them into three types of surface pre-treatment, surface gradient doping, and surface coating. Surface pre-treatment usually introduces removal of Li2O for lower irreversible capacity while surface doping is aimed to stabilize the structure during electrochemical cycling. Surface coating layers with different properties, protective layers to suppress the interface side reaction, coating layers related to structural transformation, and electronic/ionic conductive layers for better rate capability, can avoid the shortcomings of LLOs. In addition to surface modification for performance enhancement, other strategies can also be investigated to achieve high-performance LLO-based cathode materials.

Articles including thin film monolayers and multilayers

DOEpatents

Li, DeQuan; Swanson, Basil I.

1995-01-01

Articles of manufacture including: (a) a base substrate having an oxide surface layer, and a multidentate ligand, capable of binding a metal ion, attached to the oxide surface layer of the base substrate, (b) a base substrate having an oxide surface layer, a multidentate ligand, capable of binding a metal ion, attached to the oxide surface layer of the base substrate, and a metal species attached to the multidentate ligand, (c) a base substrate having an oxide surface layer, a multidentate ligand, capable of binding a metal ion, attached to the oxide surface layer of the base substrate, a metal species attached to the multidentate ligand, and a multifunctional organic ligand attached to the metal species, and (d) a base substrate having an oxide surface layer, a multidentate ligand, capable of binding a metal ion, attached to the oxide surface layer of the base substrate, a metal species attached to the multidentate ligand, a multifunctional organic ligand attached to the metal species, and a second metal species attached to the multifunctional organic ligand, are provided, such articles useful in detecting the presence of a selected target species, as nonliear optical materials, or as scavengers for selected target species.

Electrode materials

DOEpatents

Amine, Khalil; Abouimrane, Ali; Belharouak, Ilias

2017-01-31

A process for forming a surface-treatment layer on an electroactive material includes heating the electroactive material and exposing the electroactive material to a reducing gas to form a surface-treatment layer on the electroactive material, where the surface-treatment layer is a layer of partial reduction of the electroactive material.

Inversion layer solar cell fabrication and evaluation

NASA Technical Reports Server (NTRS)

Call, R. L.

1972-01-01

Silicon solar cells with induced junctions were created by forming an inversion layer near the surface of the silicon by supplying a sheet of positive charge above the surface. This charged layer was supplied through three mechanisms: (1) supplying a positive potential to a transparent electrode separated from the silicon surface by a dielectric, (2) contaminating the oxide layer with positive ions, and (3) forming donor surface states that leave a positive charge on the surface. A movable semi-infinite shadow delineated the extent of sensitivity of the cell due to the inversion region. Measurements of the inversion layer cell response to light of different wavelengths indicated it to be more sensitive to the shorter wavelengths of the sun's spectrum than conventional cells. Theory of the conductance of the inversion layer vs. strength of the inversion layer was compared with experiment and found to match. Theoretical determinations of junction depth and inversion layer strength were made as a function of the surface potential for the transparent electrode cell.

Electroluminescent device having improved light output

DOEpatents

Tyan,; Yuan-Sheng, [Webster, NY; Preuss, Donald R [Rochester, NY; Farruggia, Giuseppe [Webster, NY; Kesel, Raymond A [Avon, NY; Cushman, Thomas R [Rochester, NY

2011-03-22

An OLED device including a transparent substrate having a first surface and a second surface, a transparent electrode layer disposed over the first surface of the substrate, a short reduction layer disposed over the transparent electrode layer, an organic light-emitting element disposed over the short reduction layer and including at least one light-emitting layer and a charge injection layer disposed over the light emitting layer, a reflective electrode layer disposed over the charge injection layer and a light extraction enhancement structure disposed over the first or second surface of the substrate; wherein the short reduction layer is a transparent film having a through-thickness resistivity of 10.sup.-9 to 10.sup.2 ohm-cm.sup.2; wherein the reflective electrode layer includes Ag or Ag alloy containing more than 80% of Ag; and the total device size is larger than 10 times the substrate thickness.

Expansible apparatus for removing the surface layer from a concrete object

DOEpatents

Allen, Charles H.

1979-01-01

A method and apparatus for removing the surface layer from a concrete object. The method consists of providing a hole having a circular wall in the surface layer of the object, the hole being at least as deep as the thickness of the surface layer to be removed, and applying an outward wedging pressure on the wall of the hole sufficient to spall the surface layer around the hole. By the proper spacing of an appropriate number of holes, it is possible to remove the entire surface layer from an object. The apparatus consists of an elongated tubular-shaped body having a relatively short handle with a solid wall at one end, the wall of the remainder of the body containing a plurality of evenly spaced longitudinal cuts to form a relatively long expandable section, the outer end of the expandable section having an expandable, wedge-shaped spalling edge extending from the outer surface of the wall, perpendicular to the longitudinal axis of the body, and expanding means in the body for outwardly expanding the expandable section and forcing the spalling edge into the wall of a hole with sufficient outward pressure to spall away the surface layer of concrete. The method and apparatus are particularly suitable for removing surface layers of concrete which are radioactively contaminated.

Quasi-Geostrophic Diagnosis of Mixed-Layer Dynamics Embedded in a Mesoscale Turbulent Field

NASA Astrophysics Data System (ADS)

Chavanne, C. P.; Klein, P.

2016-02-01

A new quasi-geostrophic model has been developed to diagnose the three-dimensional circulation, including the vertical velocity, in the upper ocean from high-resolution observations of sea surface height and buoyancy. The formulation for the adiabatic component departs from the classical surface quasi-geostrophic framework considered before since it takes into account the stratification within the surface mixed-layer that is usually much weaker than that in the ocean interior. To achieve this, the model approximates the ocean with two constant-stratification layers : a finite-thickness surface layer (or the mixed-layer) and an infinitely-deep interior layer. It is shown that the leading-order adiabatic circulation is entirely determined if both the surface streamfunction and buoyancy anomalies are considered. The surface layer further includes a diabatic dynamical contribution. Parameterization of diabatic vertical velocities is based on their restoring impacts of the thermal-wind balance that is perturbed by turbulent vertical mixing of momentum and buoyancy. The model skill in reproducing the three-dimensional circulation in the upper ocean from surface data is checked against the output of a high-resolution primitive-equation numerical simulation. Correlation between simulated and diagnosed vertical velocities are significantly improved in the mixed-layer for the new model compared to the classical surface quasi-geostrophic model, reaching 0.9 near the surface.

Method of adhesion between an oxide layer and a metal layer

DOEpatents

Jennison, Dwight R.; Bogicevic, Alexander; Kelber, Jeffry A.; Chambers, Scott A.

2004-09-14

A method of controlling the wetting characteristics and increasing the adhesion between a metal and an oxide layer. By introducing a negatively-charged species to the surface of an oxide layer, layer-by-layer growth of metal deposited onto the oxide surface is promoted, increasing the adhesion strength of the metal-oxide interface. The negatively-charged species can either be deposited onto the oxide surface or a compound can be deposited that dissociates on, or reacts with, the surface to form the negatively-charged species. The deposited metal adatoms can thereby bond laterally to the negatively-charged species as well as vertically to the oxide surface as well as react with the negatively charged species, be oxidized, and incorporated on or into the surface of the oxide.

Using hydrogeologic data to evaluate geothermal potential in the eastern Great Basin

USGS Publications Warehouse

Masbruch, Melissa D.; Heilweil, Victor M.; Brooks, Lynette E.

2012-01-01

In support of a larger study to evaluate geothermal resource development of high-permeability stratigraphic units in sedimentary basins, this paper integrates groundwater and thermal data to evaluate heat and fluid flow within the eastern Great Basin. Previously published information from a hydrogeologic framework, a potentiometric-surface map, and groundwater budgets was compared to a surficial heat-flow map. Comparisons between regional groundwater flow patterns and surficial heat flow indicate a strong spatial relation between regional groundwater movement and surficial heat distribution. Combining aquifer geometry and heat-flow maps, a selected group of subareas within the eastern Great Basin are identified that have high surficial heat flow and are underlain by a sequence of thick basin-fill deposits and permeable carbonate aquifers. These regions may have potential for future geothermal resources development.

Permafrost Meta-Omics and Climate Change

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

Mackelprang, Rachel; Saleska, Scott R.; Jacobsen, Carsten Suhr

2016-06-29

Permafrost (i.e., soil that has been frozen for at least 2 consecutive years) represents a habitat for microbial life at subzero temperatures (Gilichinsky et al. 2008). Approximately one quarter of the Earth’s surface is underlain by permafrost, which contains 25-50% of the total global soil carbon pool (Schuur et al. 2008, Tarnocai et al. 2009). This carbon is largely protected from microbial decomposition by reduced microbial activity in frozen conditions, but climate change is threatening to induce large-scale permafrost thaw thus exposing it to degradation. The resulting emissions of greenhouse gasses (GHGs) can produce a positive feedback loop and significantlymore » amplify the effects of global warming. Increasing temperatures at high latitudes, changes in precipitation patterns, and frequent fire events have already initiated a widespread degradation of permafrost (Schuur et al. 2015).« less

Strain-tolerant ceramic coated seal

DOEpatents

Schienle, James L.; Strangman, Thomas E.

1994-01-01

A metallic regenerator seal is provided having multi-layer coating comprising a NiCrAlY bond layer, a yttria stabilized zirconia (YSZ) intermediate layer, and a ceramic high temperature solid lubricant surface layer comprising zinc oxide, calcium fluoride, and tin oxide. An array of discontinuous grooves is laser machined into the outer surface of the solid lubricant surface layer making the coating strain tolerant.

Influence of Cooling Condition on the Performance of Grinding Hardened Layer in Grind-hardening

NASA Astrophysics Data System (ADS)

Wang, G. C.; Chen, J.; Xu, G. Y.; Li, X.

2018-02-01

45# steel was grinded and hardened on a surface grinding machine to study the effect of three different cooling media, including emulsion, dry air and liquid nitrogen, on the microstructure and properties of the hardened layer. The results show that the microstructure of material surface hardened with emulsion is pearlite and no hardened layer. The surface roughness is small and the residual stress is compressive stress. With cooling condition of liquid nitrogen and dry air, the specimen surface are hardened, the organization is martensite, the surface roughness is also not changed, but high hardness of hardened layer and surface compressive stress were obtained when grinding using liquid nitrogen. The deeper hardened layer grinded with dry air was obtained and surface residual stress is tensile stress. This study provides an experimental basis for choosing the appropriate cooling mode to effectively control the performance of grinding hardened layer.

Influence of substrate preparation on the shaping of the topography of the surface of nanoceramic oxide layers

NASA Astrophysics Data System (ADS)

Bara, Marek; Kubica, Marek

2014-02-01

The paper discusses the shaping mechanism and changes occurring in the structure and topography of the surface of nanoceramic oxide layers during their formation. The paper presents the influence of substrate preparation on the surface topography of oxide layers. The layers were produced via hard anodizing on the EN AW-5251 aluminum alloy. The layers obtained were subjected to microscope examinations, image and chemical composition analyses, and stereometric examinations. Heredity of substrate properties in the topography of the surface of nanoceramic oxide layers formed as a result of electrochemical oxidation has been shown.

Relating Sub-Surface Ice Features to Physiological Stress in a Climate Sensitive Mammal, the American Pika (Ochotona princeps)

PubMed Central

Wilkening, Jennifer L.; Ray, Chris; Varner, Johanna

2015-01-01

The American pika (Ochotona princeps) is considered a sentinel species for detecting ecological effects of climate change. Pikas are declining within a large portion of their range, and ongoing research suggests loss of sub-surface ice as a mechanism. However, no studies have demonstrated physiological responses of pikas to sub-surface ice features. Here we present the first analysis of physiological stress in pikas living in and adjacent to habitats underlain by ice. Fresh fecal samples were collected non-invasively from two adjacent sites in the Rocky Mountains (one with sub-surface ice and one without) and analyzed for glucocorticoid metabolites (GCM). We also measured sub-surface microclimates in each habitat. Results indicate lower GCM concentration in sites with sub-surface ice, suggesting that pikas are less stressed in favorable microclimates resulting from sub-surface ice features. GCM response was well predicted by habitat characteristics associated with sub-surface ice features, such as lower mean summer temperatures. These results suggest that pikas inhabiting areas without sub-surface ice features are experiencing higher levels of physiological stress and may be more susceptible to changing climates. Although post-deposition environmental effects can confound analyses based on fecal GCM, we found no evidence for such effects in this study. Sub-surface ice features are key to water cycling and storage and will likely represent an increasingly important component of water resources in a warming climate. Fecal samples collected from additional watersheds as part of current pika monitoring programs could be used to further characterize relationships between pika stress and sub-surface ice features. PMID:25803587

Acoustic Tomography of the Atmospheric Surface Layer

DTIC Science & Technology

2014-11-28

Report Title Acoustic tomography of the atmospheric surface layer (ASL) is based on the measurements of the travel times of sound propagation between...SECURITY CLASSIFICATION OF: Acoustic tomography of the atmospheric surface layer (ASL) is based on the measurements of the travel times of sound ...organ. In the case of acoustic tomography of the atmospheric surface layer (ASL), the travel times of sound propagation between speakers and

Structure of the southern Rio Grande rift from gravity interpretation

NASA Technical Reports Server (NTRS)

Daggett, P. H.; Keller, G. R.; Wen, C.-L.; Morgan, P.

1986-01-01

Regional Bouguer gravity anomalies in southern New Mexico have been analyzed by two-dimensional wave number filtering and poly-nomial trend surface analysis of the observed gravity field. A prominent, regional oval-shaped positive gravity anomaly was found to be associated with the southern Rio Grande rift. Computer modeling of three regional gravity profiles suggests that this anomaly is due to crustal thinning beneath the southern Rio Grande rift. These models indicate a 25 to 26-km minimum crustal thickness within the rift and suggest that the rift is underlain by a broad zone of anomalously low-density upper mantle. The southern terminus of the anomalous zone is approximately 50 km southwest of El Paso, Texas. A thinning of the rifted crust of 2-3 km relative to the adjacent Basin and Range province indicates an extension of about 9 percent during the formation of the modern southern Rio Grande rift. This extension estimate is consistent with estimates from other data sources. The crustal thinning and anomalous mantle is thought to result from magmatic activity related to surface volcanism and high heat flow in this area.

Characteristics of the nocturnal boundary layer inferred from ozone measurements onboard a Zeppelin airship

NASA Astrophysics Data System (ADS)

Rohrer, Franz; Li, Xin; Hofzumahaus, Andreas; Ehlers, Christian; Holland, Frank; Klemp, Dieter; Lu, Keding; Mentel, Thomas F.; Kiendler-Scharr, Astrid; Wahner, Andreas

2014-05-01

The nocturnal boundary layer (NBL) is a sublayer within the planetary boundary layer (PBL) which evolves above solid land each day in the late afternoon due to radiation cooling of the surface. It is a region of several hundred meters thickness which inhibits vertical mixing. A residual and a surface layer remain above and below the NBL. Inside the surface layer, almost all direct emissions of atmospheric constituents take place during this time. This stratification lasts until the next morning after sunrise. Then, the heating of the surface generates a new convectionally mixed layer which successively eats up the NBL from below. This process lasts until shortly before noon when the NBL disappears completely and the PBL is mixed convectionally. Ozone measurements onboard a Zeppelin airship in The Netherlands, in Italy, and in Finland are used to analyse this behaviour with respect to atmospheric constituents and consequences for the diurnal cycles observed in the surface layer, the nocturnal boundary layer, and the residual layer are discussed.

Thickness-dependent surface energies of few-layered arsenene and antimonene films in α and β phases

NASA Astrophysics Data System (ADS)

Zhao, N.; Zhu, Y. F.; Jiang, Q.

2018-07-01

Group V elemental few-layered materials with semiconducting electronic properties are emerging as promising 2D layered materials. Since the layered configurations need substrate for device fabrications, their surface energy values could decide their properties. Here, we have performed a systematic density functional theory (DFT) investigation on the surface energies of arsenene and antimonene films as the function of thickness. The results show that the surface energy of β phase increases with increased layered numbers and converges to a constant value at about five layers, while the surface energy of α phase is size-independent. Since the surface energies of both α and β phase are similar, there is the existence possibility of α phase. Those could give references for future manufacture of arsenene and antimonene nano-devices.

Determination of Surface Potential and Electrical Double-Layer Structure at the Aqueous Electrolyte-Nanoparticle Interface

NASA Astrophysics Data System (ADS)

Brown, Matthew A.; Abbas, Zareen; Kleibert, Armin; Green, Richard G.; Goel, Alok; May, Sylvio; Squires, Todd M.

2016-01-01

The structure of the electrical double layer has been debated for well over a century, since it mediates colloidal interactions, regulates surface structure, controls reactivity, sets capacitance, and represents the central element of electrochemical supercapacitors. The surface potential of such surfaces generally exceeds the electrokinetic potential, often substantially. Traditionally, a Stern layer of nonspecifically adsorbed ions has been invoked to rationalize the difference between these two potentials; however, the inability to directly measure the surface potential of dispersed systems has rendered quantitative measurements of the Stern layer potential, and other quantities associated with the outer Helmholtz plane, impossible. Here, we use x-ray photoelectron spectroscopy from a liquid microjet to measure the absolute surface potentials of silica nanoparticles dispersed in aqueous electrolytes. We quantitatively determine the impact of specific cations (Li+ , Na+ , K+ , and Cs+ ) in chloride electrolytes on the surface potential, the location of the shear plane, and the capacitance of the Stern layer. We find that the magnitude of the surface potential increases linearly with the hydrated-cation radius. Interpreting our data using the simplest assumptions and most straightforward understanding of Gouy-Chapman-Stern theory reveals a Stern layer whose thickness corresponds to a single layer of water molecules hydrating the silica surface, plus the radius of the hydrated cation. These results subject electrical double-layer theories to direct and falsifiable tests to reveal a physically intuitive and quantitatively verified picture of the Stern layer that is consistent across multiple electrolytes and solution conditions.

Effects of Surface Roughness and Mechanical Properties of Cover-Layer on Near-Field Optical Recording

NASA Astrophysics Data System (ADS)

Kim, Jin-Hong; Lee, Jun-Seok; Lim, Jungshik; Seo, Jung-Kyo

2009-03-01

Narrow gap distance in cover-layer incident near-field recording (NFR) configuration causes a collision problem in the interface between a solid immersion lens and a disk surface. A polymer cover-layer with smooth surface results in a stable gap servo while a nanocomposite cover-layer with high refractive index shows a collision problem during the gap servo test. Even though a dielectric cover-layer, in which the surface is rougher than the polymer, supplements the mechanical properties, an unclear eye pattern due to an unstable gap servo can be obtained after a chemical mechanical polishing. Not only smooth surface but also good mechanical properties of cover-layer are required for the stable gap servo in the NFR.

Surface acoustic waves in one-dimensional piezoelectric-metallic phononic crystal: Effect of a cap layer.

PubMed

Alami, M; El Boudouti, E H; Djafari-Rouhani, B; El Hassouani, Y; Talbi, A

2018-06-18

We study the propagation of transverse acoustic waves associated with the surface of a semi-infinite superlattice (SL) composed of piezoelectric-metallic layers and capped with a piezoelectric layer. We present closed-form expressions for localized surface waves, the so-called Bleustein-Gulyaev (BG) waves depending on whether the cap layer is open-circuited or short-circuited. These expressions are obtained by means of the Green's function method which enables to deduce also the densities of states. These theoretical results are illustrated by a few numerical applications to SLs made of piezoelectric layers of hexagonal symmetry belonging to the 6 mm class such as PZT4 and ZnO in contact with metallic layers such as Fe, Al, Au, Cu and boron-doped-diamond. We demonstrate a rule about the existence of surface modes when considering two complementary semi-infinite SLs obtained by the cleavage of an infinite SL along a plane parallel to the piezoelectric layers. Indeed, when the surface layers are open-circuited, one obtains one surface mode per gap, this mode is associated with one of the two complementary SLs. However, when the surface layers are short-circuited, this rule is not fulfilled and one can obtain zero, one or two modes inside each gap of the two complementary SLs depending on the position of the plane where the cleavage is produced. We show that in addition to the BG surface waves localized at the surface of the cap layer, there may exist true guided waves and pseudo-guided waves (i.e. leaky waves) induced by the cap layer either inside the gaps or inside the bands of the SL respectively. Also, we highlight the possibility of existence of interface modes between the SL and a cap layer as well as an interaction between these modes and the BG surface mode when both modes fall in the same band gaps of the SL. The strength of the interaction depends on the width of the cap layer. Finally, we show that the electromechanical coupling coefficient (ECC) is very sensitive to the cap layer thickness, in particular we calculate and discuss the behavior of the ECC as a function of the adlayer thickness for the low velocity surface modes of the SL which exhibit the highest ECC values. The effect of the nature of the metallic layers inside the SL on the ECC is also investigated. The different surface modes discussed in this work should have applications in sensing applications. Copyright © 2018. Published by Elsevier B.V.

The effect of chloride ions on the corroded surface layer of 00Cr22Ni5Mo3N duplex stainless steel under cavitation.

PubMed

Wan, Tong; Xiao, Ning; Shen, Hanjie; Yong, Xingyue

2016-11-01

The effects of Cl(-) on the corroded surface layer of 00Cr22Ni5Mo3N duplex stainless steel under cavitation in chloride solutions were investigated using nanoindentation in conjunction with XRD and XPS. The results demonstrate that Cl(-) had a strong effect on the nano-mechanical properties of the corroded surface layer under cavitation, and there was a threshold Cl(-) concentration. Furthermore, a close relationship between the nano-mechanical properties and the cavitation corrosion resistance of 00Cr22Ni5Mo3N duplex stainless steel was observed. The degradation of the nano-mechanical properties of the corroded surface layer was accelerated by the synergistic effect between cavitation erosion and corrosion. A key factor was the adsorption of Cl(-), which caused a preferential dissolution of the ferrous oxides in the passive film layer on the corroded surface layer. Cavitation further promoted the preferential dissolution of the ferrous oxides in the passive film layer. Simultaneously, cavitation accelerated the erosion of the ferrite in the corroded surface layer, resulting in the degradation of the nano-mechanical properties of the corroded surface layer on 00Cr22Ni5Mo3N duplex stainless steel under cavitation. Copyright © 2016. Published by Elsevier B.V.

Assessment of surface turbulent fluxes using geostationary satellite surface skin temperatures and a mixed layer planetary boundary layer scheme

NASA Technical Reports Server (NTRS)

Diak, George R.; Stewart, Tod R.

1989-01-01

A method is presented for evaluating the fluxes of sensible and latent heating at the land surface, using satellite-measured surface temperature changes in a composite surface layer-mixed layer representation of the planetary boundary layer. The basic prognostic model is tested by comparison with synoptic station information at sites where surface evaporation climatology is well known. The remote sensing version of the model, using satellite-measured surface temperature changes, is then used to quantify the sharp spatial gradient in surface heating/evaporation across the central United States. An error analysis indicates that perhaps five levels of evaporation are recognizable by these methods and that the chief cause of error is the interaction of errors in the measurement of surface temperature change with errors in the assigment of surface roughness character. Finally, two new potential methods for remote sensing of the land-surface energy balance are suggested which will relay on space-borne instrumentation planned for the 1990s.

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.

Structural and lithographic study of northern coast ranges and Sacramento Valley, California

NASA Technical Reports Server (NTRS)

Rich, E. I. (Principal Investigator)

1973-01-01

The author has identified the following significant results. The analysis of the ERTS data has disclosed three potentially important linear systems within the northern coast ranges and Sacramento Valley, California. A preliminary geomorphic analysis of the northern coast ranges discloses that the geomorphic characteristics of the area underlain by the Coastal system are much different from those associated with the Central system in the core of the Coast Ranges. Within the Coastal system, or Coastal belt, the drainage networks are moderately fine-textured and have moderately high density. The area associated with the Central system seems to be underlain by an heterogeneous assemblage of rock types which vary in their resistance to erosion. The boundary between the Coastal and Central geomorphic regions is poorly defined and, in a few places, the two regions can be separated only approximately.

Observation of surface layering in a nonmetallic liquid

NASA Astrophysics Data System (ADS)

Mo, Haiding; Evmenenko, Guennadi; Kewalramani, Sumit; Kim, Kyungil; Dutta, Pulak; Ehrlich, Steven

2006-03-01

Non-monotonic density profiles (layers) have previously been observed at the free surfaces of many metallic liquids, but not in isotropic dielectric liquids. Whether the presence of an electron gas is necessary for surface layering has been the subject of debate. Until recently, MD simulations have suggested that layering at free liquid interface may be a generic phenomenon and is not limited to the metallic liquids^1. The theories predict that if normal liquids can be cooled down to temperatures low enough, layering structure should be observed experimentally. However, this is difficult for most molecular liquids because these liquids freeze well above the temperature necessary for observing the layering structure. By studying the surface structure of liquid TEHOS (tetrakis(2-ethylhexoxy)silane), which combines relatively low freezing point and high boiling point compared to that of most molecular liquids, we have observed the evidence of layering at the free interface of liquid TEHOS using x-ray reflectivity. When cooled to T/Tc 0.25 (well above the bulk freezing point, Tc is the critical temperature of TEHOS), the surface roughness drops sharply and density oscillations appear near the surface. Lateral ordering of the surface layers is liquid-like, just as at liquid metal surfaces. 1. E. Chac'on and P. Tarazona, Phys. Rev. Lett. 91 166103-1 (2003)

Protected electrode structures and methods

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

Mikhaylik, Yuriy V.; Laramie, Michael G.; Kopera, John Joseph Christopher

2017-08-08

An electrode structure and its method of manufacture are disclosed. The disclosed electrode structures may be manufactured by depositing a first release layer on a first carrier substrate. A first protective layer may be deposited on a surface of the first release layer and a first electroactive material layer may then be deposited on the first protective layer. The first release layer may have a low mean peak to valley surface roughness, which may enable the formation of a thin protective layer with a low mean peak to valley surface roughness.

Plasmon absorption modulator systems and methods

DOEpatents

Kekatpure, Rohan Deodatta; Davids, Paul

2014-07-15

Plasmon absorption modulator systems and methods are disclosed. A plasmon absorption modulator system includes a semiconductor substrate, a plurality of quantum well layers stacked on a top surface of the semiconductor substrate, and a metal layer formed on a top surface of the stack of quantum well layers. A method for modulating plasmonic current includes enabling propagation of the plasmonic current along a metal layer, and applying a voltage across the stack of quantum well layers to cause absorption of a portion of energy of the plasmonic current by the stack of quantum well layers. A metamaterial switching system includes a semiconductor substrate, a plurality of quantum well layers stacked on a top surface of the semiconductor substrate, and at least one metamaterial structure formed on a top surface of the stack of quantum well layers.

30 CFR 715.16 - Topsoil handling.

Code of Federal Regulations, 2010 CFR

2010-07-01

... as the surface soil layers. Where the A horizon is less than 6 inches, a 6-inch layer that includes... replaced as the surface soil layer. (3) Where necessary to obtain soil productivity consistent with... amounts and analyses as determined by soil tests shall be applied to the surface soil layer so that it...

30 CFR 715.16 - Topsoil handling.

Code of Federal Regulations, 2011 CFR

2011-07-01

... as the surface soil layers. Where the A horizon is less than 6 inches, a 6-inch layer that includes... replaced as the surface soil layer. (3) Where necessary to obtain soil productivity consistent with... amounts and analyses as determined by soil tests shall be applied to the surface soil layer so that it...

30 CFR 715.16 - Topsoil handling.

Code of Federal Regulations, 2014 CFR

2014-07-01

... as the surface soil layers. Where the A horizon is less than 6 inches, a 6-inch layer that includes... replaced as the surface soil layer. (3) Where necessary to obtain soil productivity consistent with... amounts and analyses as determined by soil tests shall be applied to the surface soil layer so that it...

30 CFR 715.16 - Topsoil handling.

Code of Federal Regulations, 2012 CFR

2012-07-01

... as the surface soil layers. Where the A horizon is less than 6 inches, a 6-inch layer that includes... replaced as the surface soil layer. (3) Where necessary to obtain soil productivity consistent with... amounts and analyses as determined by soil tests shall be applied to the surface soil layer so that it...

30 CFR 715.16 - Topsoil handling.

Code of Federal Regulations, 2013 CFR

2013-07-01

... as the surface soil layers. Where the A horizon is less than 6 inches, a 6-inch layer that includes... replaced as the surface soil layer. (3) Where necessary to obtain soil productivity consistent with... amounts and analyses as determined by soil tests shall be applied to the surface soil layer so that it...

Photo-stimulated low electron temperature high current diamond film field emission cathode

DOEpatents

Shurter,; Roger Philips, Devlin [Los Alamos, NM; David James, Moody [Santa Fe, NM; Nathan Andrew, Taccetti [Los Alamos, NM; Jose Martin, Russell [Santa Fe, NM; John, Steven [Los Alamos, NM

2012-07-24

An electron source includes a back contact surface having a means for attaching a power source to the back contact surface. The electron source also includes a layer comprising platinum in direct contact with the back contact surface, a composite layer of single-walled carbon nanotubes embedded in platinum in direct contact with the layer comprising platinum. The electron source also includes a nanocrystalline diamond layer in direct contact with the composite layer. The nanocrystalline diamond layer is doped with boron. A portion of the back contact surface is removed to reveal the underlying platinum. The electron source is contained in an evacuable container.

Geometry and significance of stacked gullies on the northern California slope

USGS Publications Warehouse

Field, M.E.; Gardner, J.V.; Prior, D.B.

1999-01-01

Recent geophysical surveys off northern California reveal patterns of gullies on the sea floor and preserved within continental-slope deposits that represent both erosional and aggradational processes. These surveys, conducted as part of the STRATAFORM project, combined multibeam bathymetry and backscatter with high-resolution seismic profiles. These data provide a new basis for evaluating gully morphology, distribution, and their significance to slope sedimentation and evolution. The continental margin off northern California exhibits an upper slope that has undergone both progradation and aggradation. The slope surface, which dips at <2??to 4.0??, contains a set of straight, evenly spaced, and parallel to sub-parallel gullies that begin at the 380-m isobath and extend onto the Eel and Klamath plateaus and into Trinity Canyon. The surface gullies are typically 100-m wide or more and only 1-2 m deep. The gullied slope is underlain by a sedimentary sequence that contains abundant buried gullies to subsurface depths of over 150 m. Although some of the buried gullies are distinctly erosional, most are part of the aggradational pattern responsible for the overall growth of the slope. The latest phase of gully erosion is marked by a gullied surface lying <20 m below the present-day sea floor. These erosional gullies locally truncate individual reflectors, have small depositional levees, and exhibit greater relief than do overlying gullies exposed on the sea floor. The older subsurface gullies document a period of widespread, but minor, erosion and downslope transport, presumably from a large, proximal sediment source. The cycles of downcutting and gully excavation are a minor part of the stratigraphic section, and are likely related to the combined influence of lower sea levels and higher sediment yields. During aggradation of the slope depositional sequences, sediment was draped over the gully features, producing sediment layers that mimic the underlying gully form. Consequently, gully morphology and geometries were preserved and migrated upwards with time. The processes that produce aggraded gully drape also resulted in laterally continuous strata and were most likely related to a period when the sediment source was dispersed from a more distal (10s of km) source, such as during present conditions. The draped sequences also contain a few new gullies, which indicates that gullies can be initiated at all or most stages of slope growth.

Solar cell with silicon oxynitride dielectric layer

DOEpatents

Shepherd, Michael; Smith, David D

2015-04-28

Solar cells with silicon oxynitride dielectric layers and methods of forming silicon oxynitride dielectric layers for solar cell fabrication are described. For example, an emitter region of a solar cell includes a portion of a substrate having a back surface opposite a light receiving surface. A silicon oxynitride (SiO.sub.xN.sub.y, 0

Surface Characterization of an Organized Titanium Dioxide Layer

NASA Astrophysics Data System (ADS)

Curtis, Travis

Soft lithographic printing techniques can be used to control the surface morphology of titanium dioxide layers on length scales of several hundred nanometers. Controlling surface morphology and volumetric organization of titanium dioxide electrodes can potentially be used in dye-sensitized solar cell devices. This thesis explores how layer-by-layer replication can lead to well defined, dimensionally controlled volumes and details how these control mechanisms influence surface characteristics of the semiconducting oxide.

Application of atomic force microscopy to microbial surfaces: from reconstituted cell surface layers to living cells.

PubMed

Dufrêne, Y F

2001-02-01

The application of atomic force microscopy (AFM) to probe the ultrastructure and physical properties of microbial cell surfaces is reviewed. The unique capabilities of AFM can be summarized as follows: imaging surface topography with (sub)nanometer lateral resolution; examining biological specimens under physiological conditions; measuring local properties and interaction forces. AFM is being used increasingly for: (i) visualizing the surface ultrastructure of microbial cell surface layers, including bacterial S-layers, purple membranes, porin OmpF crystals and fungal rodlet layers; (ii) monitoring conformational changes of individual membrane proteins; (iii) examining the morphology of bacterial biofilms, (iv) revealing the nanoscale structure of living microbial cells, including fungi, yeasts and bacteria, (v) mapping interaction forces at microbial surfaces, such as van der Waals and electrostatic forces, solvation forces, and steric/bridging forces; and (vi) probing the local mechanical properties of cell surface layers and of single cells.

Proximity charge sensing for semiconductor detectors

DOEpatents

Luke, Paul N; Tindall, Craig S; Amman, Mark

2013-10-08

A non-contact charge sensor includes a semiconductor detector having a first surface and an opposing second surface. The detector includes a high resistivity electrode layer on the first surface and a low resistivity electrode on the high resistivity electrode layer. A portion of the low resistivity first surface electrode is deleted to expose the high resistivity electrode layer in a portion of the area. A low resistivity electrode layer is disposed on the second surface of the semiconductor detector. A voltage applied between the first surface low resistivity electrode and the second surface low resistivity electrode causes a free charge to drift toward the first or second surface according to a polarity of the free charge and the voltage. A charge sensitive preamplifier coupled to a non-contact electrode disposed at a distance from the exposed high resistivity electrode layer outputs a signal in response to movement of free charge within the detector.

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

Simpson, John T.; Ivanov, Ilia N.; Shibata, Jason

An external covering and method of making an external covering for hiding the internal endoskeleton of a mechanical (e.g., prosthetic) device that exhibits skin-like qualities is provided. The external covering generally comprises an internal bulk layer in contact with the endoskeleton of the prosthetic device and an external skin layer disposed about the internal bulk layer. The external skin layer is comprised of a polymer composite with carbon nanotubes embedded therein. The outer surface of the skin layer has multiple cone-shaped projections that provide the external skin layer with superhydrophobicity. The carbon nanotubes are preferably vertically aligned between the innermore » surface and outer surface of the external skin layer in order to provide the skin layer with the ability to transmit heat. Superhydrophobic powders may optionally be used as part of the polymer composite or applied as a coating to the surface of the skin layer to enhance superhydrophobicity.« less

High efficiency replicated x-ray optics and fabrication method

DOEpatents

Barbee, Jr., Troy W.; Lane, Stephen M.; Hoffman, Donald E.

2001-01-01

Replicated x-ray optics are fabricated by sputter deposition of reflecting layers on a super-polished reusable mandrel. The reflecting layers are strengthened by a supporting multilayer that results in stronger stress-relieved reflecting surfaces that do not deform during separation from the mandrel. The supporting multilayer enhances the ability to part the replica from the mandrel without degradation in surface roughness. The reflecting surfaces are comparable in smoothness to the mandrel surface. An outer layer is electrodeposited on the supporting multilayer. A parting layer may be deposited directly on the mandrel before the reflecting surface to facilitate removal of the layered, tubular optic device from the mandrel without deformation. The inner reflecting surface of the shell can be a single layer grazing reflection mirror or a resonant multilayer mirror. The resulting optics can be used in a wide variety of applications, including lithography, microscopy, radiography, tomography, and crystallography.

Water resources of the Big Black River basin, Mississippi

USGS Publications Warehouse

Wasson, B.E.

1971-01-01

Abundant supplies of water of good quality are available in the Big Black River basin from either ground-water or surface-water sources. For 90 percent of the time flow in the lower part of the Big Black River below Pickens is not less than 85 cfs (cubic feet per second), and low flows of more than 5 cfs are available in five of the eastern tributary streams in the upper half of the basin. Chemical quality of water in the streams is excellent, except for impairment caused by pollution at several places. The Big Black River basin is underlain by several thousand feet of clay, silt, sand, gravel, and limestone. This sedimentary material is mostly loose to semiconsolidated and is stratified. The beds dip to the southwest at the rate of 20 to 50 feet per mile. The Big Black River flows southwestward but at a lower gradient; therefore, any specific formation is at a greater depth below the river the farther one goes down stream. The formations crop out in northwest-southeast trending belts. Most of the available ground water is contained in six geologic units; thickness of these individual units ranges from 100 to 1,000 feet. The aquifers overlap to the extent that a well drilled to the base of fresh water will, in most places, penetrate two or more aquifers. Well depths range from less than 10 to 2,400 feet. Water suitable for most needs can be obtained from the aquifers available at most localities. Dissolved-solids content of water within an aquifer increases down the dip. Also, generally the deeper a well is the higher will be the dissolved-solids content of the water. Shallow ground water (less than 200 ft deep) in the basin usually contains about 100 mg/l (milligrams per liter) of dissolved solids. Most water in the basin from more than 2,500 feet below land surface contains m ore than 1,000 mg/l of dissolved solids. In several areas fresh water is deeper than 2,500 feet, but near the mouth of the Big Black River brackish water is only about 300 feet below land surface. Practically all water pumped for man's use in the basin is from the ground (about 11 million gallons per day); however, a small amount of surface water is used for supplemental irrigation of row crops. Wells producing 500 to 1,000 gpm (gallons per minute) are not unusual in the basin. Most of the area is underlain by one or more aquifers from which a properly constructed well could produce as much as 2,000 gpm. All the towns in the area have sufficient ground water available to at least double or triple their ground-water pumpage.

On the origin of saline soils at Blackspring Ridge, Alberta, Canada

NASA Astrophysics Data System (ADS)

Stein, Richard; Schwartz, Franklin W.

1990-09-01

Problems of soil salinity occur at Blackspring Ridge, Alberta, in four different settings. The most seriously affected area is at the base of the ridge where salinity appears as severe salt crusting on the surface, salt-tolerant vegetation, and areas of poor or no crop production. Blackspring Ridge is a structural bedrock high that is underlain by Upper Cretaceous sediment of the Horseshoe Canyon Formation. Bedrock is overlain by fluvial, glacial, lacustrine, and aeolian sediment. Piezometric data indicate that groundwater is recharged on and along the upper flanks of Blackspring Ridge and discharges in southern parts of a lacustrine plain that surrounds the ridge. Hydraulic conductivity data, water-level fluctuations, stable isotopes, and hydrochemical data indicate that the fractured near-surface bedrock and overlying thin-drift sediment constitute a zone of active groundwater flow within which salts are generated and transported. Water discharging from this shallow system evaporates and forms saline areas at the base of the ridge. The most seriously affected areas on the lacustrine plain coincide with places where the water table is less than 1.5m from the ground surface. A high water table occurs locally because of the changing topology of geologic units, and lows in the topographic surface that focus groundwater and surface water flows. Some proportion of the shallow groundwater salinized by evaporation is also transported down the flow system where it mixes with unevaporated water. Surface water, from snowmelt and precipitation events, dissolves salt that was deposited at the surface by evaporating groundwater and redistributes the salt to areas of lower elevation.

The impact of surface chemistry on the performance of localized solar-driven evaporation system

PubMed Central

Yu, Shengtao; Zhang, Yao; Duan, Haoze; Liu, Yanming; Quan, Xiaojun; Tao, Peng; Shang, Wen; Wu, Jianbo; Song, Chengyi; Deng, Tao

2015-01-01

This report investigates the influence of surface chemistry (or wettability) on the evaporation performance of free-standing double-layered thin film on the surface of water. Such newly developed evaporation system is composed of top plasmonic light-to-heat conversion layer and bottom porous supporting layer. Under solar light illumination, the induced plasmonic heat will be localized within the film. By modulating the wettability of such evaporation system through the control of surface chemistry, the evaporation rates are differentiated between hydrophilized and hydrophobized anodic aluminum oxide membrane-based double layered thin films. Additionally, this work demonstrated that the evaporation rate mainly depends on the wettability of bottom supporting layer rather than that of top light-to-heat conversion layer. The findings in this study not only elucidate the role of surface chemistry of each layer of such double-layered evaporation system, but also provide additional design guidelines for such localized evaporation system in applications including desalination, distillation and power generation. PMID:26337561

The impact of surface chemistry on the performance of localized solar-driven evaporation system.

PubMed

Yu, Shengtao; Zhang, Yao; Duan, Haoze; Liu, Yanming; Quan, Xiaojun; Tao, Peng; Shang, Wen; Wu, Jianbo; Song, Chengyi; Deng, Tao

2015-09-04

This report investigates the influence of surface chemistry (or wettability) on the evaporation performance of free-standing double-layered thin film on the surface of water. Such newly developed evaporation system is composed of top plasmonic light-to-heat conversion layer and bottom porous supporting layer. Under solar light illumination, the induced plasmonic heat will be localized within the film. By modulating the wettability of such evaporation system through the control of surface chemistry, the evaporation rates are differentiated between hydrophilized and hydrophobized anodic aluminum oxide membrane-based double layered thin films. Additionally, this work demonstrated that the evaporation rate mainly depends on the wettability of bottom supporting layer rather than that of top light-to-heat conversion layer. The findings in this study not only elucidate the role of surface chemistry of each layer of such double-layered evaporation system, but also provide additional design guidelines for such localized evaporation system in applications including desalination, distillation and power generation.

The microstructure of the surface layer of magnesium laser alloyed with aluminum and silicon

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

Dziadoń, Andrzej

2016-08-15

The surface layer under analysis was formed as a result of diffusion bonding of a thin AlSi20 plate to a magnesium substrate followed by laser melting. Depending on the process parameters, the laser beam melted the AlSi20 plate only or the AlSi20 plate and a layer of the magnesium surface adjacent to it. Two types of microstructure of the remelted layer were thus analyzed. If the melting zone was limited to the AlSi20 plate, the microstructure of the surface layer was typical of a rapidly solidified hypereutectic Al–Si alloy. Since, however, the liquid AlSi20 reacted with the magnesium substrate, themore » following intermetallic phases formed: Al{sub 3}Mg{sub 2}, Mg{sub 17}Al{sub 12} and Mg{sub 2}Si. The microstructure of the modified surface layer of magnesium was examined using optical, scanning electron and transmission electron microscopy. The analysis of the surface properties of the laser modified magnesium revealed that the thin layer has a microstructure of a rapidly solidified Al–Si alloy offering good protection against corrosion. By contrast, the surface layer containing particles of intermetallic phases was more resistant to abrasion but had lower corrosion resistance than the silumin type layer. - Highlights: •A CO{sub 2} laser was used for surface alloying of Mg with AlSi20. •Before alloying, an AlSi20 plate was diffusion bonded with the Mg substrate. •The process parameters affected the alloyed layer microstructure and properties. •With melting limited to AlSi20, the layer had a structure of rapidly solidified AlSi20. •Mg–Al and Mg–Si phases were present when both the substrate and the plate were melted.« less

Semianalytical solutions for transport in aquifer and fractured clay matrix system

NASA Astrophysics Data System (ADS)

Huang, Junqi; Goltz, Mark N.

2015-09-01

A three-dimensional mathematical model that describes transport of contaminant in a horizontal aquifer with simultaneous diffusion into a fractured clay formation is proposed. A group of semianalytical solutions is derived based on specific initial and boundary conditions as well as various source functions. The analytical model solutions are evaluated by numerical Laplace inverse transformation and analytical Fourier inverse transformation. The model solutions can be used to study the fate and transport in a three-dimensional spatial domain in which a nonaqueous phase liquid exists as a pool atop a fractured low-permeability clay layer. The nonaqueous phase liquid gradually dissolves into the groundwater flowing past the pool, while simultaneously diffusing into the fractured clay formation below the aquifer. Mass transfer of the contaminant into the clay formation is demonstrated to be significantly enhanced by the existence of the fractures, even though the volume of fractures is relatively small compared to the volume of the clay matrix. The model solution is a useful tool in assessing contaminant attenuation processes in a confined aquifer underlain by a fractured clay formation.

Highway runoff in areas of karst topography.

DOT National Transportation Integrated Search

2004-01-01

Karst terrain is characterized by sinkholes, depressions, caves, and underground drainage, generally underlain by soluble rocks such as limestone and dolomite. Because natural filtration through soil is limited in karst areas, pollutants in highway s...

Stacked mechanical nanogenerator comprising piezoelectric semiconducting nanostructures and Schottky conductive contacts

DOEpatents

Wang, Zhong L [Marietta, GA; Xu, Sheng [Atlanta, GA

2011-08-23

An electric power generator includes a first conductive layer, a plurality of semiconducting piezoelectric nanostructures, a second conductive layer and a plurality of conductive nanostructures. The first conductive layer has a first surface from which the semiconducting piezoelectric nanostructures extend. The second conductive layer has a second surface and is parallel to the first conductive layer so that the second surface faces the first surface of the first conductive layer. The conductive nanostructures depend downwardly therefrom. The second conductive layer is spaced apart from the first conductive layer at a distance so that when a force is applied, the semiconducting piezoelectric nanostructures engage the conductive nanostructures so that the piezoelectric nanostructures bend, thereby generating a potential difference across the at semiconducting piezoelectric nanostructures and also thereby forming a Schottky barrier between the semiconducting piezoelectric nanostructures and the conductive nanostructures.

Highly improved passivation of c-Si surfaces using a gradient i a-Si:H layer

NASA Astrophysics Data System (ADS)

Lee, Soonil; Ahn, Jaehyun; Mathew, Leo; Rao, Rajesh; Zhang, Zhongjian; Kim, Jae Hyun; Banerjee, Sanjay K.; Yu, Edward T.

2018-04-01

Surface passivation using intrinsic a-Si:H (i a-Si:H) films plays a key role in high efficiency c-Si heterojunction solar cells. In this study, we demonstrate improved passivation quality using i a-Si:H films with a gradient-layered structure consisting of interfacial, transition, and capping layers deposited on c-Si surfaces. The H2 dilution ratio (R) during deposition was optimized individually for the interfacial and capping layers, which were separated by a transition layer for which R changed gradually between its values for the interfacial and capping layers. This approach yielded a significant reduction in surface carrier recombination, resulting in improvement of the minority carrier lifetime from 1480 μs for mono-layered i a-Si:H passivation to 2550 μs for the gradient-layered passivation approach.

Evaluation of parameterization for turbulent fluxes of momentum and heat in stably stratified surface layers

NASA Astrophysics Data System (ADS)

Sodemann, H.; Foken, Th.

2003-04-01

General Circulation Models calculate the energy exchange between surface and atmosphere by means of parameterisations for turbulent fluxes of momentum and heat in the surface layer. However, currently implemented parameterisations after Louis (1979) create large discrepancies between predictions and observational data, especially in stably stratified surface layers. This work evaluates a new surface layer parameterisation proposed by Zilitinkevich et al. (2002), which was specifically developed to improve energy flux predictions in stable stratification. The evaluation comprises a detailed study of important surface layer characteristics, a sensitivity study of the parameterisation, and a direct comparison to observational data from Antarctica and predictions by the Louis (1979) parameterisation. The stability structure of the stable surface layer was found to be very complex, and strongly influenced fluxes in the surface layer. The sensitivity study revealed that the new parameterisation depends strongly on the ratio between roughness length and roughness temperature, which were both observed to be very variable parameters. The comparison between predictions and measurements showed good agreement for momentum fluxes, but large discrepancies for heat fluxes. A stability dependent evaluation of selected data showed better agreement for the new parameterisation of Zilitinkevich et al. (2002) than for the Louis (1979) scheme. Nevertheless, this comparison underlines the need for more detailed and physically sound concepts for parameterisations of heat fluxes in stably stratified surface layers. Zilitinkevich, S. S., V. Perov and J. C. King (2002). "Near-surface turbulent fluxes in stable stratification: Calculation techniques for use in General Circulation Models." Q. J. R. Meteorol. Soc. 128(583): 1571--1587. Louis, J. F. (1979). "A Parametric Model of Vertical Eddy Fluxes in the Atmosphere." Bound.-Layer Meteor. 17(2): 187--202.

Response of terrestrial hydrology to climate and permafrost change for the 21st century as simulated by JSBACH offline experiments

NASA Astrophysics Data System (ADS)

Blome, Tanja; Hagemann, Stefan; Ekici, Altug; Beer, Christian

2015-04-01

Permafrost (PF) or perennially frozen ground is an important part of the terrestrial cryosphere; roughly one quarter of Earth's land surface is underlain by permafrost. As it is a thermal phenomenon, its characteristics are highly dependent on climatic factors. The impact of the currently observed warming, which is projected to persist during the coming decades due to anthropogenic CO2 input, certainly has effects for the vast permafrost areas of the high northern latitudes. The quantification of these effects, however, is scientifically still an open question. This is partly due to the complexity of the system, where several feedbacks are interacting between land and atmosphere, sometimes counterbalancing each other. In terms of hydrology, changes in permafrost characteristics may lead to contradicting effects. E.g., observations show that the deepening of the Active Layer (AL) can both decrease and increase soil moisture, depending on the specific conditions. For the investigation of hydrological changes in response to climatic and thus PF change, it is therefore necessary to use a model. To address this response of the terrestrial hydrology to projected changes for the 21st century, the global land surface model of the Max-Planck-Institute for Meteorology, JSBACH, was used to simulate several future climate scenarios. JSBACH recently has been equipped with important physical PF processes, such as the effects of freezing and thawing of soil water for both energy and water cycles, thermal properties depending on soil water and ice contents, and soil moisture movement being influenced by the presence of soil ice. In order to identify hydrological impacts originating solely in the physical forcing, experiments were conducted in an offline mode and with fixed vegetation cover. Feedback mechanisms, e.g. via the carbon cycle, were thus excluded. The uncertainty range arising through different Representative Concentration Pathways (RCPs) as well as through different GCMs was addressed through the use of combinations of two RCPs and two GCMs as driving data. Analysis will focus on hydrological variables and related quantities.

Potentiometric surfaces of the intermediate aquifer system, west-central Florida, May, 1993

USGS Publications Warehouse

Mularoni, R.A.

1994-01-01

The intermediate aquifer system underlies a 5000-sq-mi area including De Soto, Sarasota, Hardee, Manatee, and parts of Charlotte, Hillsborough, Highlands, and Polk Counties, Florida. It is overlain by the surf@cial aquifer system and underlain by the Floridan aquifer system. The potentiometric surface of the intermediate aquifer system was mapped by determining the altitude of water levels in a network of wells and represented on a map by contours that connect points of equal altitude. This map represents water-level conditions near the end of the spring dry season when ground- water withdrawals for agricultural use were high. The cumulative rainfall for the study area was 4.84 inches above normal for the period from June 1992 to May 1993. Hydrographs for selected wells indicated that the annual and seasonal fluctuations of the water levels were generally large (greater than 15 feet) in the central interior region where water demand for irrigation is high during the fall and spring. Seasonal fluctuations were smaller in the northern recharge area where water use is predominantly for public supply. Water levels measured in May 1993 for the composite intermediate aquifer potentiometric surface were lower than those measured in May or September 1992. A cone of depression exists in the potentiometric surface for the composite aquifer system at Warm Mineral Springs, which is a natural discharge point from this system.

Surface Morphology Transformation Under High-Temperature Annealing of Ge Layers Deposited on Si(100).

PubMed

Shklyaev, A A; Latyshev, A V

2016-12-01

We study the surface morphology and chemical composition of SiGe layers after their formation under high-temperature annealing at 800-1100 °C of 30-150 nm Ge layers deposited on Si(100) at 400-500 °C. It is found that the annealing leads to the appearance of the SiGe layers of two types, i.e., porous and continuous. The continuous layers have a smoothened surface morphology and a high concentration of threading dislocations. The porous and continuous layers can coexist. Their formation conditions and the ratio between their areas on the surface depend on the thickness of deposited Ge layers, as well as on the temperature and the annealing time. The data obtained suggest that the porous SiGe layers are formed due to melting of the strained Ge layers and their solidification in the conditions of SiGe dewetting on Si. The porous and dislocation-rich SiGe layers may have properties interesting for applications.

Monte Carlo simulations of ABC stacked kagome lattice films

NASA Astrophysics Data System (ADS)

Yerzhakov, H. V.; Plumer, M. L.; Whitehead, J. P.

2016-05-01

Properties of films of geometrically frustrated ABC stacked antiferromagnetic kagome layers are examined using Metropolis Monte Carlo simulations. The impact of having an easy-axis anisotropy on the surface layers and cubic anisotropy in the interior layers is explored. The spin structure at the surface is shown to be different from that of the bulk 3D fcc system, where surface axial anisotropy tends to align spins along the surface [1 1 1] normal axis. This alignment then propagates only weakly to the interior layers through exchange coupling. Results are shown for the specific heat, magnetization and sub-lattice order parameters for both surface and interior spins in three and six layer films as a function of increasing axial surface anisotropy. Relevance to the exchange bias phenomenon in IrMn3 films is discussed.

Antiferromagnetic MnN layer on the MnGa(001) surface

NASA Astrophysics Data System (ADS)

Guerrero-Sánchez, J.; Takeuchi, Noboru

2016-12-01

Spin polarized first principles total energy calculations have been applied to study the stability and magnetic properties of the MnGa(001) surface and the formation of a topmost MnN layer with the deposit of nitrogen. Before nitrogen adsorption, surface formation energies show a stable gallium terminated ferromagnetic surface. After incorporation of nitrogen atoms, the antiferromagnetic manganese terminated surface becomes stable due to the formation of a MnN layer (Mn-N bonding at the surface). Spin density distribution shows a ferromagnetic/antiferromagnetic arrangement in the first surface layers. This thermodynamically stable structure may be exploited to growth MnGa/MnN magnetic heterostructures as well as to look for exchange biased systems.

What's on the Surface? Physics and Chemistry of Delta-Doped Surfaces

NASA Technical Reports Server (NTRS)

Hoenk, Michael

2011-01-01

Outline of presentation: 1. Detector surfaces and the problem of stability 2. Delta-doped detectors 3. Physics of Delta-doped Silicon 4. Chemistry of the Si-SiO2 Interface 5. Physics and Chemistry of Delta-doped Surfaces a. Compensation b. Inversion c. Quantum exclusion. Conclusions: 1. Quantum confinement of electrons and holes dominates the behavior of delta-doped surfaces. 2. Stability of delta-doped detectors: Delta-layer creates an approx 1 eV tunnel barrier between bulk and surface. 3. At high surface charge densities, Tamm-Shockley states form at the surface. 4. Surface passivation by quantum exclusion: Near-surface delta-layer suppresses T-S trapping of minority carriers. 5. The Si-SiO2 interface compensates the surface 6. For delta-layers at intermediate depth, surface inversion layer forms 7. Density of Si-SiO2 interface charge can be extremely high (>10(exp 14)/sq cm)

Surface control alloy substrates and methods of manufacture therefor

DOEpatents

Fritzemeier, Leslie G.; Li, Qi; Rupich, Martin W.; Thompson, Elliott D.; Siegal, Edward J.; Thieme, Cornelis Leo Hans; Annavarapu, Suresh; Arendt, Paul N.; Foltyn, Stephen R.

2004-05-04

Methods and articles for controlling the surface of an alloy substrate for deposition of an epitaxial layer. The invention includes the use of an intermediate layer to stabilize the substrate surface against oxidation for subsequent deposition of an epitaxial layer.

Linking Dynamics of the Near-surface Flow to Deeper Boundary Layer Forcing in the Nocturnal Boundary Layer

DTIC Science & Technology

2012-06-01

Kaimal and Finnigan (1994), modified) Figure 2.2 illustrates the evolution from unstable CBL to a nocturnal Stable Bound- ary Layer ( SBL ) in the absence...mixed layer acts as a cap for the SBL . The SBL persists through the night until sunrise when surface heating resumes and a new unstable layer begins...to form at the surface, gradually returning to a CBL. 7 2.2.1 Dynamics of the stable boundary layer Because the SBL is stably stratified, buoyancy

Methods For Improving Polymeric Materials For Use In Solar Cell Applications

DOEpatents

Hanoka, Jack I.

2003-07-01

A method of manufacturing a solar cell module includes the use of low cost polymeric materials with improved mechanical properties. A transparent encapsulant layer is placed adjacent a rear surface of a front support layer. Interconnected solar cells are positioned adjacent a rear surface of the transparent encapsulant layer to form a solar cell assembly. A backskin layer is placed adjacent a rear surface of the solar cell assembly. At least one of the transparent encapsulant layer and the backskin layer are predisposed to electron beam radiation.

Methods For Improving Polymeric Materials For Use In Solar Cell Applications

DOEpatents

Hanoka, Jack I.

2001-11-20

A method of manufacturing a solar cell module includes the use of low cost polymeric materials with improved mechanical properties. A transparent encapsulant layer is placed adjacent a rear surface of a front support layer. Interconnected solar cells are positioned adjacent a rear surface of the transparent encapsulant layer to form a solar cell assembly. A backskin layer is placed adjacent a rear surface of the solar cell assembly. At least one of the transparent encapsulant layer and the backskin layer are predisposed to electron beam radiation.

The significance of pre-existing, deeply weathered crystalline rock in interpreting the effects of glaciation in the Minnesota River valley, U.S.A.

USGS Publications Warehouse

Patterson, C.J.; Boerboom, Terrence

1999-01-01

Minnesota is largely underlain by Precambrian crystalline bedrock that was weathered to an average depth of 30 m prior to Late Cretaceous time. The fresh-rock-weathered-rock interface is irregular, with as much as 45 m of relief. Weathering exploited joints, locally isolating meter-sized volumes of rock known as corestones. Variable amounts of residuum were removed through glaciation to leave (1) saprolite overlain by an in-situ Late Cretaceous soil profile; (2) partially eroded saprolite; and (3) undulating fresh rock surfaces (commonly mantled by rounded boulders) that display striae and glacial or fluvial polish. Significant subglacial erosion of fresh bedrock is not required to form smoothly undulating bedrock surfaces with closed depressions; they may also form through removal of weathered bedrock and exposure of the weathering front. Large rounded boulders are not always shaped during transport; they may represent chemically rounded corestones resting at or near the bedrock source. Unambiguous evidence for glacial erosion includes striae and streamlining of bedrock parallel to striae. Polish on rock can be created fluvially, and smoothed grooves and ridges in the rock may be chemically produced. Many rounded boulders found in glacial till and strewn on bedrock surfaces probably originated as corestones.

Ground-water hydrology of the central Raton Basin, Colorado and New Mexico

USGS Publications Warehouse

Geldon, Arthur L.

1989-01-01

The watersheds of the Purgatoire and Apishapa Rivers contain most of the public coal lands in the Raton Basin. The U.S. Geological Survey, in cooperation with the U.S. Bureau of Land Management, investigated the hydrogeology of this area from 1978 to 1982, inventorying 231 wells, 38 springs, and 6 mines, and collecting ground-water samples from 71 sites. The Raton Basin is an asymmetrical trough, containing 10,000 to 25,000 feet of sedimentary rocks that range in age from Pennsylvanian to Eocene. These rocks are intruded by Miocene igneous rocks, covered with Pleistocene and Holocene alluvium on pediments and in stream valleys, and underlain by Precambrian crystalline rocks. Bituminous coal occurs in the Vermejo and Raton Formations of Cretaceous and Paleocene age. Virtually all of the sedimentary rocks transmit water. Stream alluvium is the most productive aquifer. Bedrock aquifers have smaller yields but greater distribution. The principal bedrock aquifers are the Cuchara-Poison Canyon and the Raton-Vermejo-Trinidad. Other formations are nearly impermeable or too deep to be utilized economically. The Cuchara-Poison Canyon aquifer provides small, nonsustainable yields to wells. Sandstone and coal layers in the Raton-Vermejo-Trinidad aquifer provide small, sustainable yields, but many of these beds are lenticular and can be missed easily by wells. Water in alluvium typically is less mineralized than in bedrock but more susceptible to contamination. Sodium and calcium bicarbonate waters predominate in the area, but sodium chloride water commonly occurs in the Cuchara-Poison Canyon aquifer and may occur in the Pierre Shale. Plumes of sulfate-enriched water extend from coal mines into bedrock and alluvial aquifers. Dissolved-solids concentrations range from less than 500 milligrams per liter in calcium bicarbonate water to more than 1,500 milligrams per liter in sulfate and chloride waters. Much of the ground water is hard. Nitrogen is enriched in shallow ground water, and fluoride is enriched in deeper ground water. Levels of iron, manganese, zinc, and selenium locally exceed standards for domestic consumption. The Purgatoire River and its tributaries are predominantly gaining streams, but losing reaches occur. Water quality in streams is affected by tributary inflows, mine discharge, contact with and seepage from tailings, groundwater seepage, diversion ditches, and changes in stage. Ground water flows regionally from west to east and locally from stream divides to valleys. Depths to water vary from 500 feet beneath divides to less than 100 feet in valleys. Springs typically develop where valleys intersect the water table, at or below the contact between the Poison Canyon and Raton Formations, and in stream channels that are crossed by dikes or sills or underlain by shallow bedrock. Most of the water in regional circulation discharges into surface drainages before reaching the east side of the basin. Groundwater supplies probably are insufficient for expanded settlement and coal mining.

Landslides on Charon and not on Pluto

NASA Astrophysics Data System (ADS)

Beyer, Ross A.; Singer, Kelsi N.; Nimmo, Francis; Moore, Jeffrey M.; McKinnon, William B.; Schenk, Paul M.; Spencer, John R.; Weaver, Harold A.; Olkin, Catherine B.; Young, Leslie; Ennico, Kimberly; Stern, S. Alan; New Horizons Science Team

2016-10-01

Landslide features are observed on Charon but not on Pluto. This observation is another that reinforces the different strength regime of surface materials on the two bodies. Pluto's surface, although underlain by strong water ice, is primarily mantled with a variety of geologically weak ice species. Observations of these features indicate that they flow and move, but do so in a manner similar to glacial flow, and the strength and steepening required to precipitate a landslide simply isn't present in these materials under the pressure and temperature conditions on Pluto's surface. There are certainly areas of local mass-wasting, but no substantial landslide deposits. There are some locations on Pluto, notably along the fossae walls, and perhaps on the steeper montes surfaces that could have fostered landslides, but no landslide deposits have been observed nor are there obvious landslide alcoves that would have sourced them. The resolution of observations along the fossae may prevent identification there, and the toes of the steeper montes are embayed by geologically recent plains material which could be overlaying any landslide deposits.Charon, however, has a water-ice surface which exhibits many strength-dominated geologic features, and also exhibits landslide deposits. There are not many of these features and they are confined to the informally named Serenity Chasma, which has relatively steep, tall slopes, perfect for landslide initiation. We will discuss the physical characteristics of these landslide deposits and their context amongst other landslide features in the solar system.

High-sensitivity four-layer polymer fiber-optic evanescent wave sensor.

PubMed

Xin, Xin; Zhong, Nianbing; Liao, Qiang; Cen, Yanyan; Wu, Ruohua; Wang, Zhengkun

2017-05-15

We present a novel four-layer structure consisting of bottom, second, third, and surface layers in the sensing region, for a D-shaped step-index fiber-optic evanescent wave (FOEW) sensor. To reduce the background noise, the surface of the longitudinal section in the D-shaped region is coated with a light-absorbing film. We check the morphologies of the second and surface layers, examine the refractive indices (RIs) of the third and surface layers, and analyze the composition of the surface layer. We also investigate the effects of the thicknesses and RIs of the third and surface layers and the LA film on the light transmission and sensitivity of the FOEW sensors. The results highlight the very good sensitivity of the proposed FOEW sensor with a four-layer structure, which reached -0.077 (μg/l) -1 in the detection of the target antibody; the sensitivity of the novel FOEW sensor was 7.60 and 1.52 times better than that of a conventional sensor with a core-cladding structure and an FOEW sensor with a three-layer structure doped with GeO 2 . The applications of this high-sensitivity FOEW sensor can be extended to biodefense, disease diagnosis, and biomedical and biochemical analysis. Copyright © 2017 Elsevier B.V. All rights reserved.

Effect of elastic excitations on the surface structure of hadfield steel under friction

NASA Astrophysics Data System (ADS)

Kolubaev, A. V.; Ivanov, Yu. F.; Sizova, O. V.; Kolubaev, E. A.; Aleshina, E. A.; Gromov, V. E.

2008-02-01

The structure of the Hadfield steel (H13) surface layer forming under dry friction is examined. The deformation of the material under the friction surface is studied at a low slip velocity and a low pressure (much smaller than the yields stress of H13 steel). The phase composition and defect substructure on the friction surface are studied using scanning, optical, and diffraction electron microscopy methods. It is shown that a thin highly deformed nanocrystalline layer arises near the friction surface that transforms into a polycrystalline layer containing deformation twins and dislocations. The nanocrystalline structure and the presence of oxides in the surface layer and friction zone indicate a high temperature and high plastic strains responsible for the formation of the layer. It is suggested that the deformation of the material observed far from the surface is due to elastic wave generation at friction.

Process of producing a ceramic matrix composite article and article formed thereby

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

Corman, Gregory Scot; McGuigan, Henry Charles; Brun, Milivoj Konstantin

A CMC article and process for producing the article to have a layer on its surface that protects a reinforcement material within the article from damage. The method entails providing a body containing a ceramic reinforcement material in a matrix material that contains a precursor of a ceramic matrix material. A fraction of the reinforcement material is present and possibly exposed at a surface of the body. The body surface is then provided with a surface layer formed of a slurry containing a particulate material but lacking the reinforcement material of the body. The body and surface layer are heatedmore » to form the article by converting the precursor within the body to form the ceramic matrix material in which the reinforcement material is contained, and by converting the surface layer to form the protective layer that covers any fraction of the reinforcement material exposed at the body surface.« less

Process of producing a ceramic matrix composite article and article formed thereby

DOEpatents

Corman, Gregory Scot [Ballston Lake, NY; McGuigan, Henry Charles [Duanesburg, NY; Brun, Milivoj Konstantin [Ballston Lake, NY

2011-10-25

A CMC article and process for producing the article to have a layer on its surface that protects a reinforcement material within the article from damage. The method entails providing a body containing a ceramic reinforcement material in a matrix material that contains a precursor of a ceramic matrix material. A fraction of the reinforcement material is present and possibly exposed at a surface of the body. The body surface is then provided with a surface layer formed of a slurry containing a particulate material but lacking the reinforcement material of the body. The body and surface layer are heated to form the article by converting the precursor within the body to form the ceramic matrix material in which the reinforcement material is contained, and by converting the surface layer to form the protective layer that covers any fraction of the reinforcement material exposed at the body surface.

Changes of electrical conductivity of the metal surface layer by the laser alloying with foreign elements

NASA Astrophysics Data System (ADS)

Kostrubiec, Franciszek; Pawlak, Ryszard; Raczynski, Tomasz; Walczak, Maria

1994-09-01

Laser treatment of the surface of materials is of major importance for many fields technology. One of the latest and most significant methods of this treatment is laser alloying consisting of introducing foreign atoms into the metal surface layer during the reaction of laser radiation with the surface. This opens up vast possibilities for the modification of properties of such a layer (obtaining layers of increased microhardness, increased resistance to electroerosion in an electric arc, etc.). Conductivity of the material is a very important parameter in case of conductive materials used for electrical contacts. The paper presents the results of studies on change in electrical conductivity of the surface layer of metals alloyed with a laser. A comparative analysis of conductivity of base metal surface layers prior to and following laser treatment has been performed. Depending on the base metal and the alloying element, optical treatment parameters allowing a required change in the surface layer conductivity have been selected. A very important property of the contact material is its resistance to plastic strain. It affects the real value of contact surface coming into contact and, along with the material conductivity, determines contact resistance and the amount of heat generated in place of contact. These quantities are directly related to the initiation and the course of an arc discharge, hence they also affect resistance to electroerosion. The parameter that reflects plastic properties with loads concentrated on a small surface, as is the case with a reciprocal contact force of two real surfaces with their irregularities being in contact, is microhardness. In the paper, the results of investigations into microhardness of modified surface layers compared with base metal microhardness have been presented.

Characterization of chemical interactions during chemical mechanical polishing (CMP) of copper

NASA Astrophysics Data System (ADS)

Lee, Seung-Mahn

2003-10-01

Chemical mechanical polishing (CMP) has received much attention as an unique technique to provide a wafer level planarization in semiconductor manufacturing. However, despite the extensive use of CMP, it still remains one of the least understood areas in semiconductor processing. The lack of the fundamental understanding is a significant barrier to further advancements in CMP technology. One critical aspect of metal CMP is the formation of a thin surface layer on the metal surface. The formation and removal of this layer controls all the aspects of the CMP process, including removal rate, surface finish, etc. In this dissertation, we focus on the characterization of the formation and removal of the thin surface layer on the copper surface. The formation dynamics was investigated using static and dynamic electrochemical techniques, including potentiodynamic scans and chronoamperometry. The results were validated using XPS measurements. The mechanical properties of the surface layer were investigated using nanoindentation measurements. The electrochemical investigation showed that the thickness of the surface layer is controlled by the chemicals such as an oxidizer (hydrogen peroxide), a corrosion inhibitor (benzotriazole), a complexing agent (citric acid), and their concentrations. The dynamic electrochemical measurements indicated that the initial layer formation kinetics is unaffected by the corrosion inhibitors. The passivation due to the corrosion inhibitor becomes important only on large time scales (>200 millisecond). The porosity and the density of the chemically modified surface layer can be affected by additives of other chemicals such as citric acid. An optimum density of the surface layer is required for high polishing rate while at the same time maintaining a high degree of surface finish. Nanoindentation measurements indicated that the mechanical properties of the surface layer are strongly dependent on the chemical additives in the slurry. The CMP removal rates were found to be in good agreement with the initial reaction kinetics as well as the mechanical properties of the chemically modified surface layer. In addition, the material removal model based on the micro- and nano-scale interactions, which were measured experimentally, has been developed.

Enhanced magneto-optical imaging of internal stresses in the removed surface layer

NASA Astrophysics Data System (ADS)

Agalidi, Yuriy; Kozhukhar, Pavlo; Levyi, Sergii; Turbin, Dmitriy

2015-10-01

The paper describes a software method of reconstructing the state of the removed surface layer by visualising internal stresses in the underlying layers of the sample. Such a problem typically needs to be solved as part of forensic investigation that aims to reveal original marking of a sample with removed surface layer. For example, one may be interested in serial numbers of weapons or vehicles that had the surface layer of metal removed from the number plate. Experimental results of studying gradient internal stress fields in ferromagnetic sample using the NDI method of magneto-optical imaging (MOI) are presented. Numerical modelling results of internal stresses enclosed in the surface marking region are analysed and compared to the experimental results of magneto-optical imaging (MOI). MOI correction algorithm intended for reconstructing internal stress fields in the removed surface layer by extracting stresses retained by the underlying layers is described. Limiting ratios between parameters of a marking font are defined for the considered correction algorithm. Enhanced recognition properties for hidden stresses left by marking symbols are experimentally verified and confirmed.

Process for selectively patterning epitaxial film growth on a semiconductor substrate

DOEpatents

Sheldon, P.; Hayes, R.E.

1984-12-04

Disclosed is a process for selectively patterning epitaxial film growth on a semiconductor substrate. The process includes forming a masking member on the surface of the substrate, the masking member having at least two layers including a first layer disposed on the substrate and the second layer covering the first layer. A window is then opened in a selected portion of the second layer by removing that portion to expose the first layer thereunder. The first layer is then subjected to an etchant introduced through the window to dissolve the first layer a sufficient amount to expose the substrate surface directly beneath the window, the first layer being adapted to preferentially dissolve at a substantially greater rate than the second layer so as to create an overhanging ledge portion with the second layer by undercutting the edges thereof adjacent the window. The epitaxial film is then deposited on the exposed substrate surface directly beneath the window. Finally, an etchant is introduced through the window to dissolve the remainder of the first layer so as to lift-off the second layer and materials deposited thereon to fully expose the balance of the substrate surface.

Process for selectively patterning epitaxial film growth on a semiconductor substrate

DOEpatents

Sheldon, Peter; Hayes, Russell E.

1986-01-01

A process is disclosed for selectively patterning epitaxial film growth on a semiconductor substrate. The process includes forming a masking member on the surface of the substrate, the masking member having at least two layers including a first layer disposed on the substrate and the second layer covering the first layer. A window is then opened in a selected portion of the second layer by removing that portion to expose the first layer thereunder. The first layer is then subjected to an etchant introduced through the window to dissolve a sufficient amount of the first layer to expose the substrate surface directly beneath the window, the first layer being adapted to preferentially dissolve at a substantially greater rate than the second layer so as to create an overhanging ledge portion with the second layer by undercutting the edges thereof adjacent to the window. The epitaxial film is then deposited on the exposed substrate surface directly beneath the window. Finally, an etchant is introduced through the window to dissolve the remainder of the first layer so as to lift-off the second layer and materials deposited thereon to fully expose the balance of the substrate surface.

Using fluorescence spectroscopy to gain new insights into seasonal patterns of stream DOC concentrations in an alpine, headwater catchment underlain by discontinuous permafrost in Wolf Creek Research Basin, Yukon Territory, Canada

NASA Astrophysics Data System (ADS)

Shatilla, N. J.; Carey, S.; Tang, W.

2017-12-01

The Canadian subarctic is experiencing rapid climate warming resulting in decreased depth and duration of snowcover, decreased permafrost extent and time span of seasonal frozen ground resulting in increased active layer depth, and increased frequency and magnitude of rainfall events during the growing season. These changes challenge our conceptual models of permafrost hydrology as comparisons between recent and historical streamflow records show an emerging secondary post-freshet peak in flow in recent years along with enhanced winter flows. Long-term monitoring of Granger Creek (7.6km2), an alpine watershed underlain by discontinuous permafrost located within Wolf Creek Research Basin (176km2) in Yukon Territory, Canada provided a multi-decadal record of hydro-meteorological measurements. Granger Creek experienced warmer and wetter summers in 2015-6 compared to 2001-8, and an altered streamflow pattern with an earlier spring freshet and peak in dissolved organic carbon (DOC) concentrations. DOC concentrations post-freshet remained low at both the headwater and meso-catchment scale, which contradicts trends of increasing DOC concentrations observed in larger river systems. Hysteresis loops of sub-hourly measurements of streamflow, salinity and chromophoric dissolved organic matter (CDOM) were analyzed to provide new insights into how hydrological connectivity at the headwater scale affected the timing of solute release with supporting information from optical indices calculated from fluorescence spectroscopy. These indices provided a more nuanced view of catchment dynamics than the DOC concentrations. The composition and quality of DOM varied throughout the growing season with the delivery of older, terrestrially-derived material corresponding to high DOC concentrations at the onset of spring freshet when the catchment was initially being flushed. The origin and quality of stream DOM shifted throughout the rest of the season to newer, more easily mobilized DOM. Comparison of historical and current data show a shift from the freshet-driven primary flush of DOC from the system to an increasingly important mobilization of solutes at the end of the growing season that could begin impacting the quantity and quality of solutes exported in the subsequent spring.

Refining the link between the Holocene development of the Mississippi River Delta and the geologic evolution of Cat Island, MS: implications for delta-associated barrier islands

USGS Publications Warehouse

Miselis, Jennifer L.; Buster, Noreen A.; Kindinger, Jack G.

2014-01-01

The geologic evolution of barrier islands is profoundly influenced by the nature of the deposits underlying them. Many researchers have speculated on the origin and evolution of Cat Island in Mississippi, but uncertainty remains about whether or not the island is underlain completely or in part by deposits associated with the past growth of the Mississippi River delta. In part, this is due to a lack of comprehensive geological information offshore of the island that could augment previous stratigraphic interpretations based on terrestrial borings. An extensive survey of Cat Island and its surrounding waters was conducted, including shallow-water geophysics (e.g., high-resolution chirp seismic, side-scan sonar, and swath and single-beam bathymetry) and both terrestrial and marine vibracoring. High-resolution seismic data and vibracores from south and east of the island show two horizontally laminated silt units; marine radiocarbon dates indicate that they are St. Bernard delta complex (SBDC) deposits. Furthermore, seismic data reveal that the SBDC deposits taper off toward the southern shoreline of Cat Island and to the west, morphology consistent with the distal edge of a delta complex. The sedimentology and extent of each unit suggest that the lower unit may have been deposited during an earlier period of continuous river flow while the upper unit may represent reduced or sporadic river flow. OSL dates from the island platform (beneath beach ridge complexes) indicate three stages of terrestrial evolution: island emergence resulting from relative sea-level rise (~ 5400 ybp) island aggradation via littoral transport (~ 2500–4000 ybp) and island degradation due to delta-mediated changes in wave direction (present– ~ 3600 ybp). Finally, the combination of terrestrial and marine data shows that portions of Cat Island that are lower in elevation than the central part of the island are younger and are likely underlain by a thin layer of deltaic sediments. This underscores the potential for increased future vulnerability of barrier islands that develop adjacent to major river delta complexes.

Direct chemical vapor deposition of graphene on dielectric surfaces

DOEpatents

Zhang, Yuegang; Ismach, Ariel

2014-04-29

A substrate is provided that has a metallic layer on a substrate surface of a substrate. A film made of a two dimensional (2-D) material, such as graphene, is deposited on a metallic surface of the metallic layer. The metallic layer is dewet and/or removed to provide the film on the substrate surface.

Modification of surface oxide layers of titanium targets for increasing lifetime of neutron tubes

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

Zakharov, A. M., E-mail: zam@plasma.mephi.ru; Dvoichenkova, O. A.; Evsin, A. E.

The peculiarities of interaction of hydrogen ions with a titanium target and its surface oxide layer were studied. Two ways of modification of the surface oxide layers of titanium targets for increasing the lifetime of neutron tubes were proposed: (1) deposition of an yttrium oxide barrier layer on the target surface; (2) implementation of neutron tube work regime in which the target is irradiated with ions with energies lower than 1000 eV between high-energy ion irradiation pulses.

Boundary layer transition observations on a body of revolution with surface heating and cooling in water

NASA Astrophysics Data System (ADS)

Arakeri, V. H.

1980-04-01

Boundary layer flow visualization in water with surface heat transfer was carried out on a body of revolution which had the predicted possibility of laminar separation under isothermal conditions. Flow visualization was by in-line holographic technique. Boundary layer stabilization, including elimination of laminar separation, was observed to take place on surface heating. Conversely, boundary layer destabilization was observed on surface cooling. These findings are consistent with the theoretical predictions of Wazzan et al. (1970).

An Investigation of Instantaneous Plume Rise from Rocket Exhaust

DTIC Science & Technology

1996-12-01

METERS) TOP = 2973.48 BASE= 210.62 SIGMAR (AZ) AT THE SURFACE (DEGREES) 13.5054 SIGMER(EL) AT THE SURFACE (DEGREES) 2.9738 MET. WIND WIND LAYER WIND SPEED...SELECTED LAYER HEIGHT- (METERS) TOP = 2973.48 BASE= 210.62 SIGMAR (AZ) AT THE SURFACE (DEGREES) 13.6911 SIGMER(EL) AT THE SURFACE (DEGREES) 2.9738 MET...TIME (SECS) 368.08 FIRST MIXING LAYER HEIGHT- (METERS) TOP = 210.62 BASE= 0.00 SECOND SELECTED LAYER HEIGHT- (METERS) TOP = 2973.48 BASE= 210.62 SIGMAR

Fracture Characterization in the Astor Pass Geothermal Field, Nevada

NASA Astrophysics Data System (ADS)

Walsh, D. C.; Reeves, D. M.; Pohll, G.; Lyles, B. F.; Cooper, C. A.

2011-12-01

The Astor Pass geothermal field, near Pyramid Lake, NV, is under study as a site of potential geothermal energy production. Three wells have been completed in the graben of this typical Basin and Range geologic setting. Lithologies include a layer of unconsolidated sediment (basin fill) underlain by various tertiary volcanic units and granodiorite and metavolcanic basement rock. Characterization of fractures within the relatively impermeable rock matrix is being conducted for the three wells. Statistical analysis of fracture orientation, densities, and spacing obtained from borehole imaging logs is used to determine stress orientation and to generate a statistically equivalent Discrete Fracture Network (DFN) model. Fractures at depth are compared to fracture data collected in nearby outcrops of the same lithologic stratigraphy. Fracture geometry and density is correlated to mechanically discrete layers within the stratigraphy to test whether variations in fracturing can be attributed to variations in Young's modulus. Correlation of fracture geometry and densities with spinner flowmeter logs and distributed temperature sensor records are made in an effort to identify potential flowing fracture zones intersecting the borehole. Mean fracture aperture is obtained from open fracture counts and reservoir-scale transmissivity values (computed from a 30 day pump test) in the absence of readily available aperture data. The goal of this thorough fracture characterization is to create a physically relevant model which may be coupled with a multipurpose fluid flow and thermal simulator for investigation of geothermal reservoir behavior, particularly at the borehole scale.

Comparison of wetlands in different hydrogeological settings under conditions of extreme climate variability

USGS Publications Warehouse

Winter, T.; Rosenberry, D.; Kelly, E.; LaBaugh, J.

2005-01-01

Wetlands in the Cottonwood Lake area in North Dakota, USA, are underlain by poorly permeable till and have little groundwater input. Lakes and wetlands in the Shingobee River headwaters in Minnesota are underlain by permeable sand and have substantial groundwater input. Hydrological, chemical, and biological characteristics of these ecosystems have been monitored since 1977. Both sites experienced the second worst drought of the 20th century followed by the wettest period in more than a century. At Cottonwood Lake, plants that invaded the dry wetlands during the drought were flooded during the wet period and became a food source for animals. This resulted in successive substantial population increases and declines of plankton, invertebrates, amphibians and waterfowl. Substantial groundwater input buffered the lakes and wetlands in the Shingobee area against the changing water conditions. Only subtle changes in water chemistry and plankton populations were observed during the transition from drought to deluge.

Doped LZO buffer layers for laminated conductors

DOEpatents

Paranthaman, Mariappan Parans [Knoxville, TN; Schoop, Urs [Westborough, MA; Goyal, Amit [Knoxville, TN; Thieme, Cornelis Leo Hans [Westborough, MA; Verebelyi, Darren T [Oxford, MA; Rupich, Martin W [Framingham, MA

2010-03-23

A laminated conductor includes a metallic substrate having a surface, a biaxially textured buffer layer supported by the surface of the substrate, the biaxially textured buffer layer comprising LZO and a dopant for mitigating metal diffusion through the LZO, and a biaxially textured conductor layer supported by the biaxially textured buffer layer.

The effects of spatial inhomogeneities on flow through the endothelial surface layer.

PubMed

Leiderman, Karin M; Miller, Laura A; Fogelson, Aaron L

2008-05-21

Flow through the endothelial surface layer (the glycocalyx and adsorbed plasma proteins) plays an important but poorly understood role in cell signaling through a process known as mechanotransduction. Characterizing the flow rates and shear stresses throughout this layer is critical for understanding how flow-induced ionic currents, deformations of transmembrane proteins, and the convection of extracellular molecules signal biochemical events within the cell, including cytoskeletal rearrangements, gene activation, and the release of vasodilators. Previous mathematical models of flow through the endothelial surface layer are based upon the assumptions that the layer is of constant hydraulic permeability and constant height. These models also assume that the layer is continuous across the endothelium and that the layer extends into only a small portion of the vessel lumen. Results of these models predict that fluid shear stress is dissipated through the surface layer and is thus negligible near endothelial cell membranes. In this paper, such assumptions are removed, and the resultant flow rates and shear stresses through the layer are described. The endothelial surface layer is modeled as clumps of a Brinkman medium immersed in a Newtonian fluid. The width and spacing of each clump, hydraulic permeability, and fraction of the vessel lumen occupied by the layer are varied. The two-dimensional Navier-Stokes equations with an additional Brinkman resistance term are solved using a projection method. Several fluid shear stress transitions in which the stress at the membrane shifts from low to high values are described. These transitions could be significant to cell signaling since the endothelial surface layer is likely dynamic in its composition, density, and height.

Theoretical study of magnetic layers of nickel on copper; dead or alive?

NASA Astrophysics Data System (ADS)

Ernst, A.; Lueders, M.; Temmerman, W. M.; Szotek, Z.; van der Laan, G.

2000-07-01

We studied the persistence of magnetism in ultrathin nickel films on copper. Layer-dependent magnetic moments in Ni films on the (001), (110) and (111) surfaces of Cu have been calculated using the Korringa-Kohn-Rostoker Green's function method. The results show that, at temperature T = 0, a single nickel monolayer is ferromagnetic on Cu(001) and Cu(110) but magnetically `dead' on the more closely packed Cu(111) surface. Films of two and more layers of Ni are always ferromagnetic, with the magnetic moment enhanced in the surface layer but strongly reduced in the interface layer. Due to the short screening length, both the effect of the interface and that of the surface are confined to only a few atomic layers.

Electrical properties of surface and interface layers of the N- and In-polar undoped and Mg-doped InN layers grown by PA MBE

NASA Astrophysics Data System (ADS)

Komissarova, T. A.; Kampert, E.; Law, J.; Jmerik, V. N.; Paturi, P.; Wang, X.; Yoshikawa, A.; Ivanov, S. V.

2018-01-01

Electrical properties of N-polar undoped and Mg-doped InN layers and In-polar undoped InN layers grown by plasma-assisted molecular beam epitaxy (PA MBE) were studied. Transport parameters of the surface and interface layers were determined from the measurements of the Hall coefficient and resistivity as well as the Shubnikov-de Haas oscillations at magnetic fields up to 60 T. Contributions of the 2D surface, 3D near-interface, and 2D interface layers to the total conductivity of the InN films were defined and discussed to be dependent on InN surface polarity, Mg doping, and PA MBE growth conditions.

[A surface reacted layer study of titanium-zirconium alloy after dental casting].

PubMed

Zhang, Y; Guo, T; Li, Z; Li, C

2000-10-01

To investigate the influence of the mold temperature on the surface reacted layer of Ti-Zr alloy castings. Ti-Zr alloy was casted into a mold which was made of a zircon (ZrO2.SiO2) for inner coating and a phosphate-bonded material for outer investing with a casting machine (China) designed as vacuum, pressure and centrifuge. At three mold temperatures (room temperature, 300 degrees C, 600 degrees C) the Ti-Zr alloy was casted separately. The surface roughness of the castings was calculated by instrument of smooth finish (China). From the surface to the inner part the Knoop hardness and thickness in reacted layer of Ti-Zr alloy casting was measured. The structure of the surface reacted layer was analysed by SEM. Elemental analyses of the interfacial zone of the casting was made by element line scanning observation. The surface roughness of the castings was increased significantly with the mold temperature increasing. At a higher mold temperature the Knoop hardness of the reactive layer was increased. At the three mold temperature the outmost surface was very hard, and microhardness data decreased rapidly where they reached constant values. The thickness was about 85 microns for castings at room temperature and 300 degrees C, 105 microns for castings at 600 degrees C. From the SEM micrograph of the Ti-Zr alloy casting, the surface reacted layer could be divided into three different layers. The first layer was called non-structure layer, which thickness was about 10 microns for room temperature group, 20 microns for 300 degrees C and 25 microns for 600 degrees C. The second layer was characterized by coarse-grained acicular crystal, which thickness was about 50 microns for three mold temperatures. The third layer was Ti-Zr alloy. The element line scanning showed non-structure layer with higher level of element of O, Al, Si and Zr, The higher the mold temperature during casting, the deeper the Si permeating and in the second layer the element Si could also be found. The mold temperature is one of the major factors influencing to casting quality. In order to reduce the surface reacted layer of Ti-Zr alloy castings, the lower mold temperature and the investment without Si should be chosen.

Organic light emitting diode with light extracting layer

DOEpatents

Lu, Songwei

2016-06-14

A light extraction substrate includes a glass substrate having a first surface and a second surface. A light extraction layer is formed on at least one of the surfaces. The light extraction layer is a coating, such as a silicon-containing coating, incorporating nanoparticles.

Modification of the Atmospheric Boundary Layer by a Small Island: Observations from Nauru

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

Matthews, Stuart; Hacker, Jorg M.; Cole, Jason N.

2007-03-01

Nauru, a small island in the tropical pacific, generates plumes of clouds that may grow to several hundred km length. This study uses observations to examine the mesoscale disturbance of the marine atmospheric boundary layer by the island that produces these cloud streets. Observations of the surface layer were made from two ships in the vicinity of Nauru and from instruments on the island. The structure of the atmospheric boundary layer over the island was investigated using aircraft flights. Cloud production over Nauru was examined using remote sensing instruments. During the day the island surface layer was warmer than themore » marine surface layer and wind speed was lower than over the ocean. Surface heating forced the growth of a thermal internal boundary layer, above which a street of cumulus clouds formed. The production of clouds resulted in reduced downwelling shortwave irradiance at the island surface. A plume of warm-dry air was observed over the island which extended 15 – 20 km downwind.« less

Inversion layer solar cell fabrication and evaluation. [measurement of response of inversion layer solar cell to light of different wavelengths

NASA Technical Reports Server (NTRS)

Call, R. L.

1973-01-01

Silicon solar cells operating with induced junctions rather than diffused junctions have been fabricated and tested. Induced junctions were created by forming an inversion layer near the surface of the silicon by supplying a sheet of positive charge above the surface. This charged layer was supplied through three mechanisms: (1) applying a positive potential to a transparent electrode separated from the silicon surface by a dielectric, (2) contaminating the oxide layer with positive ions, and (3) forming donor surface states that leave a positive charge on the surface. A movable semi-infinite shadow delineated the extent of sensitivity of the cell due to the inversion region. Measurements of the response of the inversion layer cell to light of different wavelengths indicated it to be more sensitive to the shorter wavelengths of the sun's spectrum than conventional cells. The greater sensitivity occurs because of the shallow junction and the strong electric field at the surface.

Photocurrent generation in SnO2 thin film by surface charged chemisorption O ions

NASA Astrophysics Data System (ADS)

Lee, Po-Ming; Liao, Ching-Han; Lin, Chia-Hua; Liu, Cheng-Yi

2018-06-01

We report a photocurrent generation mechanism in the SnO2 thin film surface layer by the charged chemisorption O ions on the SnO2 thin film surface induced by O2-annealing. A critical build-in electric field in the SnO2 surface layer resulted from the charged O ions on SnO2 surface prolongs the lifetime and reduces the recombination probability of the photo-excited electron-hole pairs by UV-laser irradiation (266 nm) in the SnO2 surface layer, which is the key for the photocurrent generation in the SnO2 thin film surface layer. The critical lifetime of prolonged photo-excited electron-hole pair is calculated to be 8.3 ms.

Extractable Bacterial Surface Proteins in Probiotic–Host Interaction

PubMed Central

do Carmo, Fillipe L. R.; Rabah, Houem; De Oliveira Carvalho, Rodrigo D.; Gaucher, Floriane; Cordeiro, Barbara F.; da Silva, Sara H.; Le Loir, Yves; Azevedo, Vasco; Jan, Gwénaël

2018-01-01

Some Gram-positive bacteria, including probiotic ones, are covered with an external proteinaceous layer called a surface-layer. Described as a paracrystalline layer and formed by the self-assembly of a surface-layer-protein (Slp), this optional structure is peculiar. The surface layer per se is conserved and encountered in many prokaryotes. However, the sequence of the corresponding Slp protein is highly variable among bacterial species, or even among strains of the same species. Other proteins, including surface layer associated proteins (SLAPs), and other non-covalently surface-bound proteins may also be extracted with this surface structure. They can be involved a various functions. In probiotic Gram-positives, they were shown by different authors and experimental approaches to play a role in key interactions with the host. Depending on the species, and sometime on the strain, they can be involved in stress tolerance, in survival within the host digestive tract, in adhesion to host cells or mucus, or in the modulation of intestinal inflammation. Future trends include the valorization of their properties in the formation of nanoparticles, coating and encapsulation, and in the development of new vaccines. PMID:29670603

Plasmon Excitations of Multi-layer Graphene on a Conducting Substrate

PubMed Central

Gumbs, Godfrey; Iurov, Andrii; Wu, Jhao-Ying; Lin, M. F.; Fekete, Paula

2016-01-01

We predict the existence of low-frequency nonlocal plasmons at the vacuum-surface interface of a superlattice of N graphene layers interacting with conducting substrate. We derive a dispersion function that incorporates the polarization function of both the graphene monolayers and the semi-infinite electron liquid at whose surface the electrons scatter specularly. We find a surface plasmon-polariton that is not damped by particle-hole excitations or the bulk modes and which separates below the continuum mini-band of bulk plasmon modes. The surface plasmon frequency of the hybrid structure always lies below , the surface plasmon frequency of the conducting substrate. The intensity of this mode depends on the distance of the graphene layers from the conductor’s surface, the energy band gap between valence and conduction bands of graphene monolayer and, most importantly, on the number of two-dimensional layers. For a sufficiently large number of layers the hybrid structure has no surface plasmon. The existence of plasmons with different dispersion relations indicates that quasiparticles with different group velocity may coexist for various ranges of wavelengths determined by the number of layers in the superlattice. PMID:26883086

Surface-enhanced Raman medical probes and system for disease diagnosis and drug testing

DOEpatents

Vo-Dinh, T.

1999-01-26

A probe for a surface-enhanced Raman scattering spectrometer includes a member of optically transmissive material for receiving the excitation radiation from a laser and for carrying the radiation emitted from a specimen to a detector. An end of the member for placing against the specimen has a coating that produces surface enhancement of the specimen during Raman scattering spectroscopic analysis. Specifically the coating is formed by a first layer of microparticles on the member and a metal layer over the first layer. The first layer may form a microstructure surface over which a metal layer is applied. Alternatively the coating may be a material containing microparticles of a metal. An optional layer of a material may be applied to the metal layer to concentrate onto the probe compounds of analytical interest onto the probe. 39 figs.

Surface-enhanced raman medical probes and system for disease diagnosis and drug testing

DOEpatents

Vo-Dinh, Tuan

1999-01-01

A probe for a surface-enhanced Raman scattering spectrometer includes a member of optically transmissive material for receiving the excitation radiation from a laser and for carrying the radiation emitted from a specimen to a detector. An end of the member for placing against the specimen has a coating that produces surface enhancement of the specimen during Raman scattering spectroscopic analysis. Specifically the coating is formed by a first layer of microparticles on the member and a metal layer over the first layer. The first layer may form a microstructure surface over which a metal layer is applied. Alternatively the coating may be a material containing microparticles of a metal. An optional layer of a material may be applied to the metal layer to concentrate onto the probe compounds of analytical interest onto the probe.

Endothelial glycocalyx: permeability barrier and mechanosensor.

PubMed

Curry, F E; Adamson, R H

2012-04-01

Endothelial cells are covered with a polysaccharide rich layer more than 400 nm thick, mechanical properties of which limit access of circulating plasma components to endothelial cell membranes. The barrier properties of this endothelial surface layer are deduced from the rate of tracer penetration into the layer and the mechanics of red and white cell movement through capillary microvessels. This review compares the mechanosensor and permeability properties of an inner layer (100-150 nm, close to the endothelial membrane) characterized as a quasi-periodic structure which accounts for key aspects of transvascular exchange and vascular permeability with those of the whole endothelial surface layers. We conclude that many of the barrier properties of the whole surface layer are not representative of the primary fiber matrix forming the molecular filter determining transvascular exchange. The differences between the properties of the whole layer and the inner glycocalyx structures likely reflect dynamic aspects of the endothelial surface layer including tracer binding to specific components, synthesis and degradation of key components, activation of signaling pathways in the endothelial cells when components of the surface layer are lost or degraded, and the spatial distribution of adhesion proteins in microdomains of the endothelial cell membrane.

Viscous flow drag reduction; Symposium, Dallas, Tex., November 7, 8, 1979, Technical Papers

NASA Technical Reports Server (NTRS)

Hough, G. R.

1980-01-01

The symposium focused on laminar boundary layers, boundary layer stability analysis of a natural laminar flow glove on the F-111 TACT aircraft, drag reduction of an oscillating flat plate with an interface film, electromagnetic precipitation and ducting of particles in turbulent boundary layers, large eddy breakup scheme for turbulent viscous drag reduction, blowing and suction, polymer additives, and compliant surfaces. Topics included influence of environment in laminar boundary layer control, generation rate of turbulent patches in the laminar boundary layer of a submersible, drag reduction of small amplitude rigid surface waves, and hydrodynamic drag and surface deformations generated by liquid flows over flexible surfaces.

Method of depositing epitaxial layers on a substrate

DOEpatents

Goyal, Amit

2003-12-30

An epitaxial article and method for forming the same includes a substrate having a textured surface, and an electrochemically deposited substantially single orientation epitaxial layer disposed on and in contact with the textured surface. The epitaxial article can include an electromagnetically active layer and an epitaxial buffer layer. The electromagnetically active layer and epitaxial buffer layer can also be deposited electrochemically.

A model of the planetary boundary layer over a snow surface

NASA Technical Reports Server (NTRS)

Halberstam, I.; Melendez, R.

1979-01-01

A model of the planetary boundary layer over a snow surface has been developed. It contains the vertical heat exchange processes due to radiation, conduction, and atmospheric turbulence. Parametrization of the boundary layer is based on similarity functions developed by Hoffert and Sud (1976), which involve a dimensionless variable, dependent on boundary-layer height and a localized Monin-Obukhov length. The model also contains the atmospheric surface layer and the snowpack itself, where snowmelt and snow evaporation are calculated. The results indicate a strong dependence of surface temperatures, especially at night, on the bursts of turbulence which result from the frictional damping of surface-layer winds during periods of high stability, as described by Businger (1973). The model also shows the cooling and drying effect of the snow on the atmosphere, which may be the mechanism for air mass transformation in sub-Arctic regions.

Passivating Window/First Layer AR Coating for Space Solar Cells

NASA Technical Reports Server (NTRS)

Faur, Mircea; Faur, Maria; Bailey, S. G.; Flood, D. J.; Brinker, D. J.; Alterovitz, S. A.; Wheeler, D. R.; Matesscu, G.; Goradia, C.; Goradia, M.

2004-01-01

Chemically grown oxides, if well designed, offer excellent surface passivation of the emitter surface of space solar cells and can be used as effective passivating window/first layer AR coating. In this paper, we demonstrate the effectiveness of using a simple room temperature wet chemical technique to grow cost effective passivating layers on solar cell front surfaces after the front grid metallization step. These passivating layers can be grown both on planar and porous surfaces. Our results show that these oxide layers: (i) can effectively passivate the from the surface, (ii) can serve as an effective optical window/first layer AR coating, (iii) are chemically, thermally and UV stable, and (iv) have the potential of improving the BOL and especially the EOL efficiency of space solar cells. The potential of using this concept to simplify the III-V based space cell heterostructures while increasing their BOL and EOL efficiency is also discussed.

Stormwater infiltration and surface runoff pollution reduction performance of permeable pavement layers.

PubMed

Niu, Zhi-Guang; Lv, Zhi-Wei; Zhang, Ying; Cui, Zhen-Zhen

2016-02-01

In this paper, the laboratory-scale permeable pavement layers, including a surface permeable brick layer, coarse sand bedding layers (thicknesses = 2, 3.5, and 5 cm), and single-graded gravel sub-base layers (thicknesses = 15, 20, 25, and 30 cm), were built to evaluate stormwater infiltration and surface runoff pollution reduction performance. And, the infiltration rate (I) and concentrations of suspended solids (SS), total phosphorus (TP), chemical oxygen demand (COD), ammonia nitrogen, and total nitrogen (TN) were measured under the simulated rainfall intensity of 72.4 mm/h over duration of 60 min. The results indicate that the thickness factor primarily influences the infiltration rate and pollutant removal rate. The highest steady infiltration rate was for surface brick layer 51.0 mm/h, for 5-cm sand bedding layer 32.3 mm/h, and for 30-cm gravel sub-base layer 42.3 mm/h, respectively. The SS average removal rate was relative higher (79.8 ∼ 98.6 %) for all layers due to the interception and filtration. The average removal rates of TP and COD were for surface layer 71.2 and 24.1 %, for 5-cm bedding layer 54.8 and 9.0 %, and for 20-cm sub-base layer 72.2 and 26.1 %. Ammonia nitrogen and TN cannot steadily be removed by layers according to the experiment results. The optimal thickness of bedding sands was 5 cm, and that of sub-base gravels was 20 ∼ 30 cm.

Foam Core Particleboards with Intumescent FRT Veneer: Cone Calorimeter Testing With Varying Adhesives, Surface Layer Thicknesses, and Processing Conditions

Treesearch

Mark A. Dietenberger; Johannes Welling; Ali Shalbafan

2014-01-01

Intumescent FRT Veneers adhered to the surface of foam core particleboard to provide adequate fire protection were evaluated by means of cone calorimeter tests (ASTM E1354). The foam core particleboards were prepared with variations in surface layer treatment, adhesives, surface layer thicknesses, and processing conditions. Ignitability, heat release rate profile, peak...

Lower Crustal Strength Controls on Melting and Serpentinization at Magma-Poor Margins: Potential Implications for the South Atlantic

NASA Astrophysics Data System (ADS)

Ros, Elena; Pérez-Gussinyé, Marta; Araújo, Mario; Thoaldo Romeiro, Marco; Andrés-Martínez, Miguel; Morgan, Jason P.

2017-12-01

Rifted continental margins may present a predominantly magmatic continent-ocean transition (COT), or one characterized by large exposures of serpentinized mantle. In this study we use numerical modeling to show the importance of the lower crustal strength in controlling the amount and onset of melting and serpentinization during rifting. We propose that the relative timing between both events controls the nature of the COT. Numerical experiments for half-extension velocities <=10 mm/yr suggest there is a genetic link between margin tectonic style and COT nature that strongly depends on the lower crustal strength. Our results imply that very slow extension velocities (< 5 mm/yr) and a strong lower crust lead to margins characterized by large oceanward dipping faults, strong syn-rift subsidence and abrupt crustal tapering beneath the continental shelf. These margins can be either narrow symmetric or asymmetric and present a COT with exhumed serpentinized mantle underlain by some magmatic products. In contrast, a weak lower crust promotes margins with a gentle crustal tapering, small faults dipping both ocean- and landward and small syn-rift subsidence. Their COT is predominantly magmatic at any ultra-slow extension velocity and perhaps underlain by some serpentinized mantle. These margins can also be either symmetric or asymmetric. Our models predict that magmatic underplating mostly underlies the wide margin at weak asymmetric conjugates, whereas the wide margin is mainly underlain by serpentinized mantle at strong asymmetric margins. Based on this conceptual template, we propose different natures for the COTs in the South Atlantic.

Geologic map of the Fittstown 7.5΄ quadrangle, Pontotoc and Johnston Counties, Oklahoma

USGS Publications Warehouse

Lidke, David J.; Blome, Charles D.

2017-01-09

This 1:24,000-scale geologic map includes new geologic mapping as well as compilation and revision of previous geologic maps in the area. Field investigations were carried out during 2009–2011 that included mapping and investigations of the geology and hydrology of the Chickasaw National Recreation Area, Oklahoma, west of the map area.The Fittstown quadrangle is in Pontotoc and Johnston Counties in south-central Oklahoma, which is in the northeastern part of the Arbuckle Mountains. The Arbuckle Mountains are composed of a thick sequence of Paleozoic sedimentary rocks that overlie Lower Cambrian and Precambrian igneous rocks; these latter rocks are not exposed in the quadrangle. From Middle to Late Pennsylvanian time, the Arbuckle Mountains region was folded, faulted, and uplifted. Periods of erosion followed these Pennsylvanian mountain-building events, beveling this region and ultimately developing the current subtle topography that includes hills and incised uplands. The southern and northwestern parts of the Fittstown quadrangle are directly underlain by Lower Ordovician dolomite of the Arbuckle Group that has eroded to form an extensive, stream-incised upland containing the broad, gently southeast-plunging, Pennsylvanian-age Hunton anticline. The northeastern part of the map area is underlain by Middle Ordovician to Pennsylvanian limestone, shale, and sandstone units that predominantly dip northeast and form the northeastern limb of the Hunton anticline; this limb is cut by steeply dipping, northwest-southeast striking faults of the Franks fault zone. This limb and the Franks fault zone define the southwestern margin of the Franks graben, which is underlain by Pennsylvanian rocks in the northeast part of the map area.

Integrated assessment of groundwater - surface water exchange in the hillslope - riparian interface of a montane catchment

NASA Astrophysics Data System (ADS)

Scheliga, Bernhard; Tetzlaff, Doerthe; Nuetzmann, Gunnar; Soulsby, Chris

2016-04-01

Groundwater-surface water dynamics play an important role in runoff generation and the hydrologic connectivity between hillslopes and streams. Here, we present findings from a suite of integrated, empirical approaches to increase our understanding of groundwater-surface water interlinkages in a 3.2 km ^ 2 experimental catchment in the Scottish Highlands. The montane catchment is mainly underlain by granite and has extensive (70%) cover of glacial drift deposits which are up to 40 m deep and form the main aquifer in the catchment. Flat valley bottom areas fringe the stream channel and are characterised by peaty soils (0.5-4 m deep) which cover about 10% of the catchment and receive drainage from upslope areas. The transition between the hillslopes and riparian zone forms a critical interface for groundwater-surface water interactions that controls both the dynamics of riparian saturation and stream flow generation. We nested observations using wells to assess the groundwater - surface water transition, LiDAR surveys to explore the influence of micro-topography on shallow groundwater efflux and riparian wells to examine the magnitude and flux rates of deeper groundwater sources. We also used electrical resistivity surveys to assess the architecture and storage properties of drift aquifers. Finally, we used isotopic tracers to differentiate recharge sources and associated residence times as well as quantifying how groundwater dynamics affect stream flow. These new data have provided a novel conceptual framework for local groundwater - surface water exchange that is informing the development of new deterministic models for the site.

Layered surface structure of gas-atomized high Nb-containing TiAl powder and its impact on laser energy absorption for selective laser melting

NASA Astrophysics Data System (ADS)

Zhou, Y. H.; Lin, S. F.; Hou, Y. H.; Wang, D. W.; Zhou, P.; Han, P. L.; Li, Y. L.; Yan, M.

2018-05-01

Ti45Al8Nb alloy (in at.%) is designed to be an important high-temperature material. However, its fabrication through laser-based additive manufacturing is difficult to achieve. We present here that a good understanding of the surface structure of raw material (i.e. Ti45Al8Nb powder) is important for optimizing its process by selective laser melting (SLM). Detailed X-ray photoelectron spectroscopy (XPS) depth profiling and transmission electron microscopy (TEM) analyses were conducted to determine the surface structure of Ti45Al8Nb powder. An envelope structure (∼54.0 nm in thickness) was revealed for the powder, consisting of TiO2 + Nb2O5 (as the outer surface layer)/Al2O3 + Nb2O5 (as the intermediate layer)/Al2O3 (as the inner surface layer)/Ti45Al8Nb (as the matrix). During SLM, this layered surface structure interacted with the incident laser beam and improved the laser absorptivity of Ti45Al8Nb powder by ∼32.21%. SLM experiments demonstrate that the relative density of the as-printed parts can be realized to a high degree (∼98.70%), which confirms good laser energy absorption. Such layered surface structure with appropriate phase constitution is essential for promoting SLM of the Ti45Al8Nb alloy.

A thickness-weighted average perspective of force balance in an idealized circumpolar current

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

Ringler, Todd Darwin; Saenz, Juan Antonio; Wolfram, Jr., Phillip Justin

The exact, three-dimensional thickness-weighted averaged (TWA) Boussinesq equations are used to diagnose eddy-mean flow interaction in an idealized circumpolar current (ICC). The force exerted by mesoscale eddies on the TWA velocity is expressed as the divergence of the Eliassen-Palm flux tensor. Consistent with previous findings, the analysis indicates that the dynamically relevant definition of the ocean surface layer is comprised of the set of buoyancy coordinates that ever reside at the ocean surface at a given horizontal position. The surface layer is found to be a physically distinct object with a diabatic- and force-balance that is largely isolated from themore » underlying adiabatic region in the interior. Within the ICC surface layer, the TWA meridional velocity is southward/northward in the top/bottom half, and has a value near zero at the bottom. In the top half of the surface layer, the zonal forces due to wind stress and meridional advection of potential vorticity act to accelerate the TWA zonal velocity; equilibrium is obtained by eddies decelerating the zonal flow via a downward flux of eastward momentum that increases with depth. In the bottom half of the surface layer, the accelerating force of the wind stress is balanced by the eddy force and meridional advection of potential vorticity. The bottom of the surface layer coincides with the location where the zonal eddy force, meridional advection of potential vorticity and zonal wind stress force are all zero. The net meridional transport, S f, within the surface layer is a small residual of its southward and northward TWA meridional flows. Furthermore, the mean meridional gradient of surface-layer buoyancy is advected by S f to balance the surface buoyancy fluxs.« less

A thickness-weighted average perspective of force balance in an idealized circumpolar current

DOE PAGES

Ringler, Todd Darwin; Saenz, Juan Antonio; Wolfram, Jr., Phillip Justin; ...

2016-11-22

The exact, three-dimensional thickness-weighted averaged (TWA) Boussinesq equations are used to diagnose eddy-mean flow interaction in an idealized circumpolar current (ICC). The force exerted by mesoscale eddies on the TWA velocity is expressed as the divergence of the Eliassen-Palm flux tensor. Consistent with previous findings, the analysis indicates that the dynamically relevant definition of the ocean surface layer is comprised of the set of buoyancy coordinates that ever reside at the ocean surface at a given horizontal position. The surface layer is found to be a physically distinct object with a diabatic- and force-balance that is largely isolated from themore » underlying adiabatic region in the interior. Within the ICC surface layer, the TWA meridional velocity is southward/northward in the top/bottom half, and has a value near zero at the bottom. In the top half of the surface layer, the zonal forces due to wind stress and meridional advection of potential vorticity act to accelerate the TWA zonal velocity; equilibrium is obtained by eddies decelerating the zonal flow via a downward flux of eastward momentum that increases with depth. In the bottom half of the surface layer, the accelerating force of the wind stress is balanced by the eddy force and meridional advection of potential vorticity. The bottom of the surface layer coincides with the location where the zonal eddy force, meridional advection of potential vorticity and zonal wind stress force are all zero. The net meridional transport, S f, within the surface layer is a small residual of its southward and northward TWA meridional flows. Furthermore, the mean meridional gradient of surface-layer buoyancy is advected by S f to balance the surface buoyancy fluxs.« less

Adsorption of lysozyme to phospholipid and meibomian lipid monolayer films.

PubMed

Mudgil, Poonam; Torres, Margaux; Millar, Thomas J

2006-03-15

It is believed that a lipid layer forms the outer layer of the pre-ocular tear film and this layer helps maintain tear film stability by lowering its surface tension. Proteins of the aqueous layer of the tear film (beneath the lipid layer) may also contribute to reducing surface tension by adsorbing to, or penetrating the lipid layer. The purpose of this study was to compare the penetration of lysozyme, a tear protein, into films of meibomian lipids and phospholipids held at different surface pressures to determine if lysozyme were part of the surface layer of the tear film. Films of meibomian lipids or phospholipids were spread onto the surface of a buffered aqueous subphase. Films were compressed to particular pressures and lysozyme was injected into the subphase. Changes in surface pressure were monitored to determine adsorption or penetration of lysozyme into the surface film. Lysozyme penetrated a meibomian lipid film at all pressures tested (max=20 mN/m). It also penetrated phosphatidylglycerol, phosphatidylserine or phosphatidylethanolamine lipid films up to a pressure of 20 mN/m. It was not able to penetrate a phosphatidylcholine film at pressures >or=10 mN/m irrespective of the temperature being at 20 or 37 degrees C. However, it was able to penetrate it at very low pressures (<10 mN/m). Epifluorescence microscopy showed that the protein either adsorbs to or penetrates the lipid layer and the pattern of mixing depended upon the lipid at the surface. These results indicate that lysozyme is present at the surface of the tear film where it contributes to decreasing the surface tension by adsorbing and penetrating the meibomian lipids. Thus it helps to stabilize the tear film.

A streptavidin linker layer that functions after drying.

PubMed

Xia, Nan; Shumaker-Parry, Jennifer S; Zareie, M Hadi; Campbell, Charles T; Castner, David G

2004-04-27

The ability of streptavidin (SA) to simultaneously bind four biotins is often used in linker layers, where a biotinylated molecule is linked to a biotin-functionalized surface via SA. For biosensor and array applications, it is desirable that the SA linker layer be stable to drying and rehydration. In this study it was observed that a significant decrease in binding capacity of a SA layer occurred when that layer was dried. For this study a SA linker layer was constructed by binding SA to a biotin-containing alkylthiolate monolayer (BAT/OEG) self-assembled onto gold. Its stability after drying was investigated using surface plasmon resonance (SPR). Approximately a quarter of the SA layer was removed from the BAT/OEG surface upon drying and rehydration, suggesting disruption of SA-biotin binding when dry. This resulted in the dried SA layer losing approximately 40% of its biotinylated ferritin (BF) binding capacity. Coating the layer with trehalose before drying was found to inhibit the loss of SA from the BAT/OEG surface. SPR showed that the trehalose-protected SA linker layer retained approximately 91% of its original BF binding capacity after drying and rehydration. Atomic force microscopy, which was used to image individual surface-bound SA and BF molecules, qualitatively confirmed these observations.

Stability of surface and subsurface hydrogen on and in Au/Ni near-surface alloys

DOE PAGES

Celik, Fuat E.; Mavrikakis, Manos

2015-01-12

Periodic, self-consistent DFT-GGA (PW91) calculations were used to study the interaction of hydrogen atoms with the (111) surfaces of substitutional near-surface alloys (NSAs) of Au and Ni with different surface layer compositions and different arrangements of Au atoms in the surface layer. The effect of hydrogen adsorption on the surface and in the first and second subsurface layers of the NSAs was studied. Increasing the Au content in the surface layer weakens hydrogen binding on the surface, but strengthens subsurface binding, suggesting that the distribution of surface and subsurface hydrogen will be different than that on pure Ni(111). While themore » metal composition of the surface layer has an effect on the binding energy of hydrogen on NSA surfaces, the local composition of the binding site has a stronger effect. For example, fcc hollow sites consisting of three Ni atoms bind H nearly as strongly as on Ni(111), and fcc sites consisting of three Au atoms bind H nearly as weakly as on Au(111). Sites with one or two Au atoms show intermediate binding energies. The preference of hydrogen for three-fold Ni hollow sites alters the relative stabilities of different surface metal atom arrangements, and may provide a driving force for adsorbate-induced surface rearrangement.« less

Stability of Surface and Subsurface Hydrogen on and in Au/Ni Near-Surface Alloys

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

Celik, Fuat E.; Mavrikakis, Manos

2015-10-01

Periodic, self-consistent DFT-GGA (PW91) calculations were used to study the interaction of hydrogen atoms with the (111) surfaces of substitutional near-surface alloys (NSAs) of Au and Ni with different surface layer compositions and different arrangements of Au atoms in the surface layer. The effect of hydrogen adsorption on the surface and in the first and second subsurface layers of the NSAs was studied. Increasing the Au content in the surface layer weakens hydrogen binding on the surface, but strengthens subsurface binding, suggesting that the distribution of surface and subsurface hydrogen will be different than that on pure Ni(111). While themore » metal composition of the surface layer has an effect on the binding energy of hydrogen on NSA surfaces, the local composition of the binding site has a stronger effect. For example, fcc hollow sites consisting of three Ni atoms bind H nearly as strongly as on Ni(111), and fcc sites consisting of three Au atoms bind H nearly as weakly as on Au(111). Sites with one or two Au atoms show intermediate binding energies. The preference of hydrogen for three-fold Ni hollow sites alters the relative stabilities of different surface metal atom arrangements, and may provide a driving force for adsorbate-induced surface rearrangement.« less

Stability of surface and subsurface hydrogen on and in Au/Ni near-surface alloys

NASA Astrophysics Data System (ADS)

Celik, Fuat E.; Mavrikakis, Manos

2015-10-01

Periodic, self-consistent DFT-GGA (PW91) calculations were used to study the interaction of hydrogen atoms with the (111) surfaces of substitutional near-surface alloys (NSAs) of Au and Ni with different surface layer compositions and different arrangements of Au atoms in the surface layer. The effect of hydrogen adsorption on the surface and in the first and second subsurface layers of the NSAs was studied. Increasing the Au content in the surface layer weakens hydrogen binding on the surface, but strengthens subsurface binding, suggesting that the distribution of surface and subsurface hydrogen will be different than that on pure Ni(111). While the metal composition of the surface layer has an effect on the binding energy of hydrogen on NSA surfaces, the local composition of the binding site has a stronger effect. For example, fcc hollow sites consisting of three Ni atoms bind H nearly as strongly as on Ni(111), and fcc sites consisting of three Au atoms bind H nearly as weakly as on Au(111). Sites with one or two Au atoms show intermediate binding energies. The preference of hydrogen for three-fold Ni hollow sites alters the relative stabilities of different surface metal atom arrangements, and may provide a driving force for adsorbate-induced surface rearrangement.

Surface preparation of substances for continuous convective assembly of fine particles

DOEpatents

Rossi, Robert

2003-01-01

A method for producing periodic nanometer-scale arrays of metal or semiconductor junctions on a clean semiconductor substrate surface is provided comprising the steps of: etching the substrate surface to make it hydrophilic, forming, under an inert atmosphere, a crystalline colloid layer on the substrate surface, depositing a metal or semiconductor material through the colloid layer onto the surface of the substrate, and removing the colloid from the substrate surface. The colloid layer is grown on the clean semiconductor surface by withdrawing the semiconductor substrate from a sol of colloid particles.

Atomic Layer Deposition of Chemical Passivation Layers and High Performance Anti-Reflection Coatings on Back-Illuminated Detectors

NASA Technical Reports Server (NTRS)

Hoenk, Michael E. (Inventor); Greer, Frank (Inventor); Nikzad, Shouleh (Inventor)

2014-01-01

A back-illuminated silicon photodetector has a layer of Al2O3 deposited on a silicon oxide surface that receives electromagnetic radiation to be detected. The Al2O3 layer has an antireflection coating deposited thereon. The Al2O3 layer provides a chemically resistant separation layer between the silicon oxide surface and the antireflection coating. The Al2O3 layer is thin enough that it is optically innocuous. Under deep ultraviolet radiation, the silicon oxide layer and the antireflection coating do not interact chemically. In one embodiment, the silicon photodetector has a delta-doped layer near (within a few nanometers of) the silicon oxide surface. The Al2O3 layer is expected to provide similar protection for doped layers fabricated using other methods, such as MBE, ion implantation and CVD deposition.

Effect of surface wave propagation in a four-layered oceanic crust model

NASA Astrophysics Data System (ADS)

Paul, Pasupati; Kundu, Santimoy; Mandal, Dinbandhu

2017-12-01

Dispersion of Rayleigh type surface wave propagation has been discussed in four-layered oceanic crust. It includes a sandy layer over a crystalline elastic half-space and over it there are two more layers—on the top inhomogeneous liquid layer and under it a liquid-saturated porous layer. Frequency equation is obtained in the form of determinant. The effects of the width of different layers as well as the inhomogeneity of liquid layer, sandiness of sandy layer on surface waves are depicted and shown graphically by considering all possible case of the particular model. Some special cases have been deduced, few special cases give the dispersion equation of Scholte wave and Stoneley wave, some of which have already been discussed elsewhere.

Porous titania surfaces on titanium with hierarchical macro- and mesoporosities for enhancing cell adhesion, proliferation and mineralization.

PubMed

Han, Guang; Müller, Werner E G; Wang, Xiaohong; Lilja, Louise; Shen, Zhijian

2015-02-01

Titanium received a macroporous titania surface layer by anodization, which contains open pores with average pore diameter around 5 μm. An additional mesoporous titania top layer following the contour of the macropores, of 100-200 nm thickness and with a pore diameter of 10nm, was formed by using the evaporation-induced self-assembly (EISA) method with titanium (IV) tetraethoxide as the precursor. A coherent laminar titania surface layer was thus obtained, creating a hierarchical macro- and mesoporous surface that was characterized by high-resolution electron microscopy. The interfacial bonding between the surface layers and the titanium matrix was characterized by the scratch test that confirmed a stable and strong bonding of titania surface layers on titanium. The wettability to water and the effects on the osteosarcoma cell line (SaOS-2) proliferation and mineralization of the formed titania surface layers were studied systematically by cell culture and scanning electron microscopy. The results proved that the porous titania surface with hierarchical macro- and mesoporosities was hydrophilic that significantly promoted cell attachment and spreading. A synergistic role of the hierarchical macro- and mesoporosities was revealed in terms of enhancing cell adhesion, proliferation and mineralization, compared with the titania surface with solo scale topography. Copyright © 2014 Elsevier B.V. All rights reserved.

Near Surface Vapor Bubble Layers in Buoyant Low Stretch Burning of Polymethylmethacrylate

NASA Technical Reports Server (NTRS)

Olson, Sandra L.; Tien, J. S.

1999-01-01

Large-scale buoyant low stretch stagnation point diffusion flames over solid fuel (polymethylmethacrylate) were studied for a range of aerodynamic stretch rates of 2-12/ sec which are of the same order as spacecraft ventilation-induced stretch in a microgravity environment. An extensive layer of polymer material above the glass transition temperature is observed. Unique phenomena associated with this extensive glass layer included substantial swelling of the burning surface, in-depth bubble formation, and migration and/or elongation of the bubbles normal to the hot surface. The bubble layer acted to insulate the polymer surface by reducing the effective conductivity of the solid. The reduced in-depth conduction stabilized the flame for longer than expected from theory neglecting the bubble layer. While buoyancy acts to move the bubbles deeper into the molten polymer, thermocapillary forces and surface regression both act to bring the bubbles to the burning surface. Bubble layers may thus be very important in low gravity (low stretch) burning of materials. As bubbles reached the burning surface, monomer fuel vapors jetted from the surface, enhancing burning by entraining ambient air flow. Popping of these bubbles at the surface can expel burning droplets of the molten material, which may increase the fire propagation hazards at low stretch rates.

Measurement of the oxygen mass transfer through the air-water interface.

PubMed

Mölder, Erik; Mashirin, Alelxei; Tenno, Toomas

2005-01-01

Gas mass transfer through the liquid-gas interface has enormous importance in various natural and industrial processes. Surfactants or insoluble compounds adsorbed onto an interface will inhibit the gas mass transfer through the liquid-gas surface. This study presents a technique for measuring the oxygen mass transfer through the air-water interface. Experimental data obtained with the measuring device were incorporated into a novel mathematical model, which allowed one to calculate diffusion conduction of liquid surface layer and oxygen mass transfer coefficient in the liquid surface layer. A special measurement cell was constructed. The most important part of the measurement cell is a chamber containing the electrochemical oxygen sensor inside it. Gas exchange between the volume of the chamber and the external environment takes place only through the investigated surface layer. Investigated liquid was deoxygenated, which triggers the oxygen mass transfer from the chamber through the liquid-air interface into the liquid phase. The decrease of oxygen concentration in the cell during time was measured. By using this data it is possible to calculate diffusional parameters of the water surface layer. Diffusion conduction of oxygen through the air-water surface layer of selected wastewaters was measured. The diffusion conduction of different wastewaters was about 3 to 6 times less than in the unpolluted water surface. It was observed that the dilution of wastewater does not have a significant impact on the oxygen diffusion conduction through the wastewater surface layer. This fact can be explained with the presence of the compounds with high surface activity in the wastewater. Surfactants achieved a maximum adsorption and, accordingly, the maximum decrease of oxygen permeability already at a very low concentration of surfactants in the solution. Oxygen mass transfer coefficient of the surface layer of the water is found to be Ds/ls = 0.13 x 10(-3) x cm/s. A simple technique for measuring oxygen diffusion parameters through the air-water solution surface has been developed. Derived equations enable the calculation of diffusion parameters of the surface layer at current conditions. These values of the parameters permit one to compare the resistances of the gas-liquid interface to oxygen mass transfer in the case of adsorption of different substances on the surface layer. This simple technique may be used for a determination of oxygen permeability of different water-solution surface layers. It enables one to measure the resistance to the oxygen permeability of all inflowing wastewater surface layers in the wastewater treatment plant, and to initiate a preliminary cleaning of this wastewater if required. Similarly, we can measure oxygen permeability of natural waterbodies. Especially in the case of pollution, it is important to know to what extent the oxygen permeability of the water surface layer has been decreased. Based on the tehnique presented in this research, fieldwork equipment will be developed.

Theoretical study for heterojunction surface of NEA GaN photocathode dispensed with Cs activation

NASA Astrophysics Data System (ADS)

Xia, Sihao; Liu, Lei; Wang, Honggang; Wang, Meishan; Kong, Yike

2016-09-01

For the disadvantages of conventional negative electron affinity (NEA) GaN photocathodes activated by Cs or Cs/O, new-type NEA GaN photocathodes with heterojunction surface dispensed with Cs activation are investigated based on first-principle study with density functional theory. Through the growth of an ultrathin n-type GaN cap layer on p-type GaN emission layer, a p-n heterojunction is formed on the surface. According to the calculation results, it is found that Si atoms tend to replace Ga atoms to result in an n-type doped cap layer which contributes to the decreasing of work function. After the growth of n-type GaN cap layer, the atom structure near the p-type emission layer is changed while that away from the surface has no obvious variations. By analyzing the E-Mulliken charge distribution of emission surface with and without cap layer, it is found that the positive charge of Ga and Mg atoms in the emission layer decrease caused by the cap layer, while the negative charge of N atom increases. The conduction band moves downwards after the growth of cap layer. Si atom produces donor levels around the valence band maximum. The absorption coefficient of GaN emission layer decreases and the reflectivity increases caused by n-type GaN cap layer.

Characterization and use of crystalline bacterial cell surface layers

NASA Astrophysics Data System (ADS)

Sleytr, Uwe B.; Sára, Margit; Pum, Dietmar; Schuster, Bernhard

2001-10-01

Crystalline bacterial cell surface layers (S-layers) are one of the most common outermost cell envelope components of prokaryotic organisms (archaea and bacteria). S-layers are monomolecular arrays composed of a single protein or glycoprotein species and represent the simplest biological membranes developed during evolution. S-layers as the most abundant of prokaryotic cellular proteins are appealing model systems for studying the structure, synthesis, genetics, assembly and function of proteinaceous supramolecular structures. The wealth of information existing on the general principle of S-layers have revealed a broad application potential. The most relevant features exploited in applied S-layer research are: (i) pores passing through S-layers show identical size and morphology and are in the range of ultrafiltration membranes; (ii) functional groups on the surface and in the pores are aligned in well-defined positions and orientations and accessible for chemical modifications and binding functional molecules in very precise fashion; (iii) isolated S-layer subunits from a variety of organisms are capable of recrystallizing as closed monolayers onto solid supports (e.g., metals, polymers, silicon wafers) at the air-water interface, on lipid films or onto the surface of liposomes; (iv) functional domains can be incorporated in S-layer proteins by genetic engineering. Thus, S-layer technologies particularly provide new approaches for biotechnology, biomimetics, molecular nanotechnology, nanopatterning of surfaces and formation of ordered arrays of metal clusters or nanoparticles as required for nanoelectronics.

Analysis of self-assembly of S-layer protein slp-B53 from Lysinibacillus sphaericus.

PubMed

Liu, Jun; Falke, Sven; Drobot, Bjoern; Oberthuer, Dominik; Kikhney, Alexey; Guenther, Tobias; Fahmy, Karim; Svergun, Dmitri; Betzel, Christian; Raff, Johannes

2017-01-01

The formation of stable and functional surface layers (S-layers) via self-assembly of surface-layer proteins on the cell surface is a dynamic and complex process. S-layers facilitate a number of important biological functions, e.g., providing protection and mediating selective exchange of molecules and thereby functioning as molecular sieves. Furthermore, S-layers selectively bind several metal ions including uranium, palladium, gold, and europium, some of them with high affinity. Most current research on surface layers focuses on investigating crystalline arrays of protein subunits in Archaea and bacteria. In this work, several complementary analytical techniques and methods have been applied to examine structure-function relationships and dynamics for assembly of S-layer protein slp-B53 from Lysinibacillus sphaericus: (1) The secondary structure of the S-layer protein was analyzed by circular dichroism spectroscopy; (2) Small-angle X-ray scattering was applied to gain insights into the three-dimensional structure in solution; (3) The interaction with bivalent cations was followed by differential scanning calorimetry; (4) The dynamics and time-dependent assembly of S-layers were followed by applying dynamic light scattering; (5) The two-dimensional structure of the paracrystalline S-layer lattice was examined by atomic force microscopy. The data obtained provide essential structural insights into the mechanism of S-layer self-assembly, particularly with respect to binding of bivalent cations, i.e., Mg 2+ and Ca 2+ . Furthermore, the results obtained highlight potential applications of S-layers in the fields of micromaterials and nanobiotechnology by providing engineered or individual symmetric thin protein layers, e.g., for protective, antimicrobial, or otherwise functionalized surfaces.

Composite fuel cell membranes

DOEpatents

Plowman, K.R.; Rehg, T.J.; Davis, L.W.; Carl, W.P.; Cisar, A.J.; Eastland, C.S.

1997-08-05

A bilayer or trilayer composite ion exchange membrane is described suitable for use in a fuel cell. The composite membrane has a high equivalent weight thick layer in order to provide sufficient strength and low equivalent weight surface layers for improved electrical performance in a fuel cell. In use, the composite membrane is provided with electrode surface layers. The composite membrane can be composed of a sulfonic fluoropolymer in both core and surface layers.

Composite fuel cell membranes

DOEpatents

Plowman, Keith R.; Rehg, Timothy J.; Davis, Larry W.; Carl, William P.; Cisar, Alan J.; Eastland, Charles S.

1997-01-01

A bilayer or trilayer composite ion exchange membrane suitable for use in a fuel cell. The composite membrane has a high equivalent weight thick layer in order to provide sufficient strength and low equivalent weight surface layers for improved electrical performance in a fuel cell. In use, the composite membrane is provided with electrode surface layers. The composite membrane can be composed of a sulfonic fluoropolymer in both core and surface layers.

Modulating surface rheology by electrostatic protein/polysaccharide interactions.

PubMed

Ganzevles, Renate A; Zinoviadou, Kyriaki; van Vliet, Ton; Cohen, Martien A; de Jongh, Harmen H

2006-11-21

There is a large interest in mixed protein/polysaccharide layers at air-water and oil-water interfaces because of their ability to stabilize foams and emulsions. Mixed protein/polysaccharide adsorbed layers at air-water interfaces can be prepared either by adsorption of soluble protein/polysaccharide complexes or by sequential adsorption of complexes or polysaccharides to a previously formed protein layer. Even though the final protein and polysaccharide bulk concentrations are the same, the behavior of the adsorbed layers can be very different, depending on the method of preparation. The surface shear modulus of a sequentially formed beta-lactoglobulin/pectin layer can be up to a factor of 6 higher than that of a layer made by simultaneous adsorption. Furthermore, the surface dilatational modulus and surface shear modulus strongly (up to factors of 2 and 7, respectively) depend on the bulk -lactoglobulin/pectin mixing ratio. On the basis of the surface rheological behavior, a mechanistic understanding of how the structure of the adsorbed layers depends on the protein/polysaccharide interaction in bulk solution, mixing ratio, ionic strength, and order of adsorption to the interface (simultaneous or sequential) is derived. Insight into the effect of protein/polysaccharide interactions on the properties of adsorbed layers provides a solid basis to modulate surface rheological behavior.

The Synthesis, Structures, and Chemical Properties of Macrocyclic Ligands Covalently Bonded into Layered Arrays

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

Clearfield, Abraham

2014-11-01

In this part of the proposal we have concentrated on the surface functionalization of α-zirconium phosphate of composition Zr(O3POH)2•H2O. It is a layered compound that can be prepared as particles as small as 30 nm to single crystals in the range of cm. This compound is an ion exchanger with a capacity of 6.64 meq per gram. It finds use as a catalyst, proton conductor, sensors, biosensors, in kidney dialysis and drug delivery. By functionalizing the surface additional uses are contemplated as will be described. The layers consist of the metal, with 4+ charge, that is positioned slightly above andmore » below the mean layer plane and bridged by three of the four phosphate oxygens. The remaining POH groups point into the interlayer space creating double rows of POH groups but single arrays on the surface layers. The surface groups are reactive and we were able to bond silanes, isocyanates, epoxides, acrylates ` and phosphates to the surface POH groups. The layers are easily exfoliated or filled with ions by ion exchange or molecules by intercalation reactions. Highlights of our work include, in addition to direct functionalization of the surfaces, replacement of the protons on the surface with ions of different charge. This allows us to bond phosphates, biophosphates, phosphonic acids and alcohols to the surface. By variation of the ion charge of the ions that replace the surface protons, different surface structures are obtained. We have already shown that polymer fillers, catalysts and Janus particles may be prepared. The combination of surface functionalization with the ability to insert molecules and ions between the layers allow for a rich development of numerous useful other applications as well as nano-surface chemistry.« less

Marine Atmospheric Surface Layer and Its Application to Electromagnetic Wave Propagation

NASA Astrophysics Data System (ADS)

Wang, Q.

2015-12-01

An important application of the atmospheric surface layer research is to characterize the near surface vertical gradients in temperature and humidity in order to predict radar and radio communication conditions in the environment. In this presentation, we will give an overview of a new research initiative funded under the Office of Naval Research (ONR) Multi-University Research Initiative (MURI): the Coupled Air-Sea Processes and EM Ducting Research (CASPER). The objective is to fully characterize the marine atmospheric boundary layer (MABL) as an electromagnetic (EM) propagation environment with the emphasis of spatial and temporal heterogeneities and surface wave/swell effects, both of which contravene the underlying assumptions of Monin-Obukhov Similarity Theory (MOST) used in coupled environmental forecast models. Furthermore, coastal variability in the inversion atop the MABL presents a challenge to forecast models and also causes practical issues in EM prediction models. These issues are the target of investigation of CASPER. CASPER measurement component includes two major field campaigns: CASPER-East (2015 Duck, NC) and CASPER-West (2018 southern California). This presentation will show the extensive measurements to be made during the CASPER -East field campaign with the focus on the marine atmospheric surface layer measurements with two research vessels, two research aircraft, surface flux buoy, wave gliders, ocean gliders, tethered balloons, and rawinsondes. Unlike previous research on the marine surface layer with the focus on surface fluxes and surface flux parameterization, CASPER field campaigns also emphasize of the surface layer profiles and the validation of the surface layer flux-profile relationship originally derived over land surfaces. Results from CASPER pilot experiment and preliminary results from CASPER-East field campaign will be discussed.

The influence of upper-crust lithology on topographic development in the central Coast Ranges of California

USGS Publications Warehouse

Garcia, A.F.; Mahan, S.A.

2012-01-01

A fundamental geological tenet is that as landscapes evolve over graded to geologic time, geologic structures control patterns of topographic distribution in mountainous areas such that terrain underlain by competent rock will be higher than terrain underlain by incompetent rock. This paper shows that in active orogens where markedly weak and markedly strong rocks are juxtaposed along contacts that parallel regional structures, relatively high topography can form where strain is localized in the weak rock. Such a relationship is illustrated by the topography of the central Coast Ranges between the Pacific coastline and the San Andreas fault zone (SAFZ), and along the length of the Gabilan Mesa (the "Gabilan Mesa segment" of the central Coast Ranges). Within the Gabilan Mesa segment, the granitic upper crust of the Salinian terrane is in contact with the accretionary-prism m??lange upper crust of the Nacimiento terrane along the inactive Nacimiento fault zone. A prominent topographic lineament is present along most of this lithologic boundary, approximately 50 to 65. km southwest of the SAFZ, with the higher topography formed in the m??lange on the southwest side of the Nacimiento fault. This paper investigates factors influencing the pattern of topographic development in the Gabilan Mesa segment of the central Coast Ranges by correlating shortening magnitude with the upper-crust compositions of the Salinian and Nacimiento terranes. The fluvial geomorphology of two valleys in the Gabilan Mesa, which is within the Salinian terrane, and alluvial geochronology based on optically-stimulated luminescence (OSL) age estimates, reveal that the magnitude of shortening accommodated by down-to-the-southwest tilting of the mesa since 400ka is less than 1 to 2m. Our results, combined with those of previous studies, indicate that at least 63% to 78% of late-Cenozoic, northeast-southwest directed, upper-crustal shortening across the Gabilan Mesa segment has been accommodated within the Nacimiento terrane. This is significant because perpendicular to orogenic strike the Nacimiento terrane constitutes less than 1/4 of the distance between the coast and the SAFZ, and the other 3/4 (or greater) of the distance between the coast and the SAFZ is underlain by the granitic upper crust of the Salinian terrane. We propose that strain and mountain building are localized within the Nacimiento terrane because it consists predominantly of the relatively weak Franciscan Complex m??lange, and because the upper crust of the Salinian terrane is composed of relatively strong granitic rocks. Our hypothesis is supported by the distribution of post-seismic surface uplift associated with the 2003, 6.5M W San Simeon earthquake, which mimics the topography of the southwestern part of the Gabilan Mesa segment of the central Coast Ranges. ?? 2011 Elsevier B.V.

Ceramic coatings on smooth surfaces

NASA Technical Reports Server (NTRS)

Miller, R. A. (Inventor); Brindley, W. J. (Inventor); Rouge, C. J. (Inventor)

1991-01-01

A metallic coating is plasma sprayed onto a smooth surface of a metal alloy substitute or on a bond coating. An initial thin ceramic layer is low pressure sprayed onto the smooth surface of the substrate or bond coating. Another ceramic layer is atmospheric plasma sprayed onto the initial ceramic layer.

Optical Tamm states in one-dimensional superconducting photonic crystal

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

El Abouti, O.; El Boudouti, E. H.; IEMN, UMR-CNRS 8520, UFR de Physique, Université de Lille 1, 59655 Villeneuve d'Ascq

2016-08-15

In this study, we investigate localized and resonant optical waves associated with a semi-infinite superlattice made out of superconductor-dielectric bilayers and terminated with a cap layer. Both transverse electric and transverse magnetic waves are considered. These surface modes are analogous to the so-called Tamm states associated with electronic states found at the surface of materials. The surface guided modes induced by the cap layer strongly depend on whether the superlattice ends with a superconductor or a dielectric layer, the thickness of the surface layer, the temperature of the superconductor layer as well as on the polarization of the waves. Differentmore » kinds of surface modes are found and their properties examined. These structures can be used to realize the highly sensitive photonic crystal sensors.« less

Compositions of surface layers formed on amalgams in air, water, and saline.

PubMed

Hanawa, T; Gnade, B E; Ferracane, J L; Okabe, T; Watari, F

1993-12-01

The surface layers formed on both a zinc-free and a zinc-containing dental amalgam after polishing and aging in air, water, or saline, were characterized using x-ray photoelectron spectroscopy (XPS) to determine the compositions of the surface layers which might govern the release of mercury from amalgam. The XPS data revealed that the formation of the surface layer on the zinc-containing amalgam was affected by the environment in which the amalgam was polished and aged, whereas that on the zinc-free amalgam was not affected. In addition, among the elements contained in amalgam, zinc was the most reactive with the environment, and was preferentially dissolved from amalgam into water or saline. Mercury atoms existed in the metallic state in the surface layer.

Effect of non-equilibrium flow chemistry and surface catalysis on surface heating to AFE

NASA Technical Reports Server (NTRS)

Stewart, David A.; Henline, William D.; Chen, Yih-Kanq

1991-01-01

The effect of nonequilibrium flow chemistry on the surface temperature distribution over the forebody heat shield on the Aeroassisted Flight Experiment (AFE) vehicle was investigated using a reacting boundary-layer code. Computations were performed by using boundary-layer-edge properties determined from global iterations between the boundary-layer code and flow field solutions from a viscous shock layer (VSL) and a full Navier-Stokes solution. Surface temperature distribution over the AFE heat shield was calculated for two flight conditions during a nominal AFE trajectory. This study indicates that the surface temperature distribution is sensitive to the nonequilibrium chemistry in the shock layer. Heating distributions over the AFE forebody calculated using nonequilibrium edge properties were similar to values calculated using the VSL program.

Rough SERS substrate based on gold coated porous silicon layer prepared on the silicon backside surface

NASA Astrophysics Data System (ADS)

Dridi, H.; Haji, L.; Moadhen, A.

2017-04-01

We report in this paper a novel method to elaborate rough Surface Enhanced Raman Scattering (SERS) substrate. A single layer of porous silicon was formed on the silicon backside surface. Morphological characteristics of the porous silicon layer before and after gold deposition were influenced by the rough character (gold size). The reflectance measurements showed a dependence of the gold nano-grains size on the surface nature, through the Localized Surface Plasmon (LSP) band properties. SERS signal of Rhodamine 6G used as a model analyte, adsorbed on the rough porous silicon layer revealed a marked enhancement of its vibrational modes intensities.

Portable heatable container

NASA Technical Reports Server (NTRS)

Yang, L. C. (Inventor)

1980-01-01

A container is provided which can be designed to heat its outer surface to sterilize it, or to heat its inner surface and any contents therewithin. In a container that self sterilizes its outer surface, the container includes a combustible layer of thermite-type pyrotechnic material which can be ignited to generate considerable heat, and a thin casing around the combustible layer which is of highly thermally conductive materials such as aluminum which can be heated to a high temperature by the ignited combustible layer. A buffer layer which may be of metal, lies within the combustible layer, and a layer of insulation such as Teflon lies within the buffer layer to insulate the contents of the container from the heat.

Portable heatable container

NASA Astrophysics Data System (ADS)

Yang, L. C.

1980-03-01

A container is provided which can be designed to heat its outer surface to sterilize it, or to heat its inner surface and any contents therewithin. In a container that self sterilizes its outer surface, the container includes a combustible layer of thermite-type pyrotechnic material which can be ignited to generate considerable heat, and a thin casing around the combustible layer which is of highly thermally conductive materials such as aluminum which can be heated to a high temperature by the ignited combustible layer. A buffer layer which may be of metal, lies within the combustible layer, and a layer of insulation such as Teflon lies within the buffer layer to insulate the contents of the container from the heat.

Encapsulant Material For Solar Cell Module And Laminated Glass Applications

DOEpatents

Hanoka, Jack I.

2000-09-05

An encapsulant material includes a layer of metallocene polyethylene disposed between two layers of ionomer. More specifically, the layer of metallocene polyethylene is disposed adjacent a rear surface of the first ionomer layer, and a second layer of ionomer is disposed adjacent a rear surface of the layer of metallocene polyethylene. The encapsulant material can be used in solar cell module and laminated glass applications.

Using Ground Measurements to Examine the Surface Layer Parameterization Scheme in NCEP GFS

NASA Astrophysics Data System (ADS)

Zheng, W.; Ek, M. B.; Mitchell, K.

2017-12-01

Understanding the behavior and the limitation of the surface layer parameneterization scheme is important for parameterization of surface-atmosphere exchange processes in atmospheric models, accurate prediction of near-surface temperature and identifying the role of different physical processes in contributing to errors. In this study, we examine the surface layer paramerization scheme in the National Centers for Environmental Prediction (NCEP) Global Forecast System (GFS) using the ground flux measurements including the FLUXNET data. The model simulated surface fluxes, surface temperature and vertical profiles of temperature and wind speed are compared against the observations. The limits of applicability of the Monin-Obukhov similarity theory (MOST), which describes the vertical behavior of nondimensionalized mean flow and turbulence properties within the surface layer, are quantified in daytime and nighttime using the data. Results from unstable regimes and stable regimes are discussed.

Microporous structure with layered interstitial surface treatment, and method and apparatus for preparation thereof

NASA Technical Reports Server (NTRS)

Koontz, Steven L. (Inventor)

1994-01-01

A microporous structure with layered interstitial surface treatments, and method and apparatus for preparation thereof is presented. The structure is prepared by sequentially subjecting a uniformly surface-treated structure to atomic oxygen treatment to remove an outer layer of surface treatment to a generally uniform depth, and then surface treating the so exposed layer with another surface treating agent. The atomic oxygen/surface treatment steps may optionally be repeated, each successive time to a lesser depth, to produce a microporous structure having multilayered surface treatments. The apparatus employs at least one side arm from a main atomic oxygen-containing chamber. The side arm has characteristic relaxation times such that a uniform atomic oxygen dose rate is delivered to a specimen positioned transversely in the side arm spaced from the main gas chamber.

Microporous structure with layered interstitial surface treatment, and method and apparatus for preparation thereof

NASA Technical Reports Server (NTRS)

Koontz, Steven L. (Inventor)

1992-01-01

A microporous structure with layered interstitial surface treatments, and the method and apparatus for its preparation are disclosed. The structure is prepared by sequentially subjecting a uniformly surface treated structure to atomic oxygen treatment to remove an outer layer of surface treatment to a generally uniform depth, and then surface treating the so exposed layer with another surface treating agent. The atomic oxygen/surface treatment steps may optionally be repeated, each successive time to a lesser depth, to produce a microporous structure having multilayered surface treatments. The apparatus employs at least one side arm from a main oxygen-containing chamber. The side arm has characteristic relaxation times such that a uniform atomic oxygen dose rate is delivered to a specimen positioned transversely in the side arm spaced from the main gas chamber.

Boundary-layer exchange by bubble: A novel method for generating transient nanofluidic layers

NASA Astrophysics Data System (ADS)

Jennissen, Herbert P.

2005-10-01

Unstirred layers (i.e., Nernst boundary layers) occur on every dynamic solid-liquid interface, constituting a diffusion barrier, since the velocity of a moving liquid approaches zero at the surface (no slip). If a macromolecule-surface reaction rate is higher than the diffusion rate, the Nernst layer is solute depleted and the reaction rate becomes mass-transport limited. The thickness of a Nernst boundary layer (δN) generally lies between 5 and 50μm. In an evanescent wave rheometer, measuring fibrinogen adsorption to fused silica, we made the fundamental observation that an air bubble preceding the sample through the flow cell abolishes the mass-transport limitation of the Nernst diffusion layer. Instead exponential kinetics are found. Experimental and simulation studies strongly indicate that these results are due to the elimination of the Nernst diffusion layer and its replacement by a dynamic nanofluidic layer (δν) maximally 200-300nm thick. It is suggested that the air bubble leads to a transient boundary-layer separation into a novel nanoboundary layer on the surface and the bulk fluid velocity profile separated by a vortex sheet with an estimated lifetime of 30-60s. A bubble-induced boundary-layer exchange from the Nernst to the nanoboundary layer and back is obtained, giving sufficient time for the measurement of unbiased exponential surface kinetics. Noteworthy is that the nanolayer can exist at all and displays properties such as (i) a long persistence and resistance to dissipation by the bulk liquid (boundary-layer-exchange-hysteresis) and (ii) a lack of solute depletion in spite of boundary-layer separation. The boundary-layer-exchange by bubble (BLEB) method therefore appears ideal for enhancing the rates of all types of diffusion-limited macromolecular reactions on surfaces with contact angles between 0° and 90° and only appears limited by slippage due to nanobubbles or an air gap beneath the nanofluidic layer on very hydrophobic surfaces. The possibility of producing nanoboundary layers without any nanostructuring or nanomachining should also be useful for fundamental physical studies in nanofluidics.

Effect of a multi-layer infection control barrier on the micro-hardness of a composite resin

PubMed Central

HWANG, In-Nam; HONG, Sung-Ok; LEE, Bin-Na; HWANG, Yun-Chan; OH, Won-Mann; CHANG, Hoon-Sang

2012-01-01

Objective The aim of this study was to evaluate the effect of multiple layers of an infection control barrier on the micro-hardness of a composite resin. Material and Methods One, two, four, and eight layers of an infection control barrier were used to cover the light guides of a high-power light emitting diode (LED) light curing unit (LCU) and a low-power halogen LCU. The composite specimens were photopolymerized with the LCUs and the barriers, and the micro-hardness of the upper and lower surfaces was measured (n=10). The hardness ratio was calculated by dividing the bottom surface hardness of the experimental groups by the irradiated surface hardness of the control groups. The data was analyzed by two-way ANOVA and Tukey's HSD test. Results The micro-hardness of the composite specimens photopolymerized with the LED LCU decreased significantly in the four- and eight-layer groups of the upper surface and in the two-, four-, and eight-layer groups of the lower surface. The hardness ratio of the composite specimens was <80% in the eight-layer group. The micro-hardness of the composite specimens photopolymerized with the halogen LCU decreased significantly in the eight-layer group of the upper surface and in the two-, four-, and eight-layer groups of the lower surface. However, the hardness ratios of all the composite specimens photopolymerized with barriers were <80%. Conclusions The two-layer infection control barrier could be used on high-power LCUs without decreasing the surface hardness of the composite resin. However, when using an infection control barrier on the low-power LCUs, attention should be paid so as not to sacrifice the polymerization efficiency. PMID:23138746

Microstructure and properties of 17-4PH steel plasma nitrocarburized with a carrier gas containing rare earth elements

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

Liu, R.L., E-mail: ruiliangliu@126.com; Yan, M.F., E-mail: yanmufu@hit.edu.cn; Wu, Y.Q.

2010-01-15

The effect of rare earth addition in the carrier gas on plasma nitrocarburizing of 17-4PH steel was studied. The microstructure and crystallographically of the phases in the surface layer as well as surface morphology of the nitrocarburized specimens were characterized by optical microscope, X-ray diffraction and scanning tunneling microscope, respectively. The hardness of the surface layer was measured by using a Vickers hardness test. The results show that the incorporation of rare earth elements in the carrier gas can increase the nitrocarburized layer thickness up to 55%, change the phase proportion in the nitrocarburized layer, refine the nitrides in surfacemore » layer, and increase the layer hardness above 100HV. The higher surface hardening effect after rare earth addition is caused by improvement in microstructure and change in the phase proportion of the nitrocarburized layer.« less

Buffer architecture for biaxially textured structures and method of fabricating same

DOEpatents

Norton, David P.; Park, Chan; Goyal, Amit

2004-04-06

The invention relates to an article with an improved buffer layer architecture comprising a substrate having a metal surface, and an epitaxial buffer layer on the surface of the substrate. The epitaxial buffer layer comprises at least one of the group consisting of ZrO.sub.2, HfO.sub.2, and compounds having at least one of Ca and a rare earth element stabilizing cubic phases of ZrO.sub.2 and/or HfO.sub.2. The article can also include a superconducting layer deposited on the epitaxial buffer layer. The article can also include an epitaxial capping layer between the epitaxial buffer layer and the superconducting layer. A method for preparing an epitaxial article comprises providing a substrate with a metal surface, depositing on the metal surface an epitaxial buffer layer comprising at least one material selected from the group consisting of ZrO.sub.2, HfO.sub.2, and compounds having at least one of Ca and a rare earth element stabilizing cubic phases of at least one of ZrO.sub.2 and HfO.sub.2. The epitaxial layer depositing step occurs in a vacuum with a background pressure of no more than 1.times.10.sup.-5 Torr. The method can further comprise depositing a superconducting layer on the epitaxial layer, and depositing an epitaxial capping layer between the epitaxial buffer layer and the superconducting layer.

Control of the surface quality parameters of machine components during static pulsed treatment

NASA Astrophysics Data System (ADS)

Komkov, V. A.; Rabinskii, L. N.; Kokoreva, O. G.; Kuprikov, N. M.

2016-12-01

A technique is developed to determine the homogeneity of the structure in a surface layer subjected to strain hardening. Static pulsed treatment is found to be one of the most effective surface plastic deformation methods that can be used to control the uniformity of hardening a surface layer. This treatment makes it possible to create a hardened surface layer to a depth of 10 mm with a homogeneous or heterogeneous structure.

Structural properties and diffusion processes of the Cu 3Au (0 0 1) surface

NASA Astrophysics Data System (ADS)

Wang, Fang; Zhang, Jian-Min; Zhang, Yan; Ji, Vincent

2010-09-01

The surface relaxation and surface energy of both the mixed AuCu and pure Cu terminated Cu 3Au (0 0 1) surfaces are simulated and calculated by using the modified analytical embedded-atom method. We find that the mixed AuCu termination is energetically preferred over the pure Cu termination thereby the mono-vacancy diffusion is also investigated in the topmost few layers of the mixed AuCu terminated Cu 3Au (0 0 1) surface. In the mixed AuCu terminated surface the relaxed Au atoms are raised above Cu atoms for 0.13 Å in the topmost layer. All the surface atoms displace outwards, this effect occurs in the first three layers and changes the first two inter-layer spacing. For mono-vacancy migration in the first layer, the migration energies of Au and Cu mono-vacancy via two-type in-plane displace: the nearest neighbor jump (NNJ) and the second nearest neighbor jump (2NNJ), are calculated and the results show that the NNJ requires a much lower energy than 2NNJ. For the evolution of the energy requirements for successive nearest neighbor jumps (SNNJ) along three different paths: circularity, zigzag and beeline, we find that the circularity path is preferred over the other two paths due to its minimum energy barriers and final energies. In the second layer, the NN jumps in intra- and inter-layer of the Cu mono-vacancy are investigated. The calculated energy barriers and final energies show that the vacancy prefer jump up to a proximate Cu site. This replacement between the Cu vacancy in the second layer and Cu atom in the first layer is remunerative for the Au atoms enrichment in the topmost layer.

Recycling inflow method for simulations of spatially evolving turbulent boundary layers over rough surfaces

NASA Astrophysics Data System (ADS)

Yang, Xiang I. A.; Meneveau, Charles

2016-01-01

The technique by Lund et al. to generate turbulent inflow for simulations of developing boundary layers over smooth flat plates is extended to the case of surfaces with roughness elements. In the Lund et al. method, turbulent velocities on a sampling plane are rescaled and recycled back to the inlet as inflow boundary condition. To rescale mean and fluctuating velocities, appropriate length scales need be identified and for smooth surfaces, the viscous scale lν = ν/uτ (where ν is the kinematic viscosity and uτ is the friction velocity) is employed for the inner layer. Different from smooth surfaces, in rough wall boundary layers the length scale of the inner layer, i.e. the roughness sub-layer scale ld, must be determined by the geometric details of the surface roughness elements and the flow around them. In the proposed approach, it is determined by diagnosing dispersive stresses that quantify the spatial inhomogeneity caused by the roughness elements in the flow. The scale ld is used for rescaling in the inner layer, and the boundary layer thickness δ is used in the outer region. Both parts are then combined for recycling using a blending function. Unlike the blending function proposed by Lund et al. which transitions from the inner layer to the outer layer at approximately 0.2δ, here the location of blending is shifted upwards to enable simulations of very rough surfaces in which the roughness length may exceed the height of 0.2δ assumed in the traditional method. The extended rescaling-recycling method is tested in large eddy simulation of flow over surfaces with various types of roughness element shapes.

Surface Modification Enhanced Reflection Intensity of Quartz Crystal Microbalance Sensors upon Molecular Adsorption.

PubMed

Kojima, Taisuke

2018-01-01

Molecular adsorption on a sensing surface involves molecule-substrate and molecule-molecule interactions. Combining optical systems and a quartz crystal microbalance (QCM) on the same sensing surface allows the quantification of such interactions and reveals the physicochemical properties of the adsorbed molecules. However, low sensitivity of the current reflection-based techniques compared to the QCM technique hinders the quantitative analysis of the adsorption events. Here, a layer-by-layer surface modification of a QCM sensor is studied to increase the optical sensitivity. The intermediate layers of organic-inorganic molecules and metal-metal oxide were explored on a gold (Au) surface of a QCM sensor. First, polyhedral oligomeric silsesquioxane-derivatives that served as the organic-inorganic intermediate layer were synthesized and modified on the Au-QCM surface. Meanwhile, titanium oxide, fabricated by anodic oxidation of titanium, was used as a metal-metal oxide intermediate layer on a titanium-coated QCM surface. The developed technique enabled interrogation of the molecular adsorption owing to the enhanced optical sensitivity.

Thermal oxidation of single crystal aluminum antimonide and materials having the same

DOEpatents

Sherohman, John William; Yee, Jick Hong; Coombs, III, Arthur William; Wu, Kuang Jen J.

2012-12-25

In one embodiment, a method for forming a non-conductive crystalline oxide layer on an AlSb crystal includes heat treating an AlSb crystal in a partial vacuum atmosphere at a temperature conducive for air adsorbed molecules to desorb, surface molecule groups to decompose, and elemental Sb to evaporate from a surface of the AlSb crystal and exposing the AlSb crystal to an atmosphere comprising oxygen to form a crystalline oxide layer on the surface of the AlSb crystal. In another embodiment, a method for forming a non-conductive crystalline oxide layer on an AlSb crystal includes heat treating an AlSb crystal in a non-oxidizing atmosphere at a temperature conducive for decomposition of an amorphous oxidized surface layer and evaporation of elemental Sb from the AlSb crystal surface and forming stable oxides of Al and Sb from residual surface oxygen to form a crystalline oxide layer on the surface of the AlSb crystal.

Role of humidity in reducing the friction of graphene layers on textured surfaces

NASA Astrophysics Data System (ADS)

Li, Zheng-yang; Yang, Wen-jing; Wu, Yan-ping; Wu, Song-bo; Cai, Zhen-bing

2017-05-01

A multiple-layer graphene was prepared on steel surface to reduce friction and wear. A graphene-containing ethanol solution was dripped on the steel surface, and several layers of graphene flakes were deposited on the surface after ethanol evaporated. Tribological performance of graphene-contained surface (GCS) was induced by reciprocating ball against plate contact in different RH (0% (dry nitrogen), 30%, 60%, and 90%). Morphology and wear scar were analyzed by OM, 2D profile, SEM, Raman spectroscopy, and XPS. Results show that GCS can substantially reduce the wear and coefficient of friction (COF) in 60% relative humidity (RH). Low COF occurs due to graphene layer providing a small shear stress on the friction interface. Meanwhile, conditions of high RH and textured surface could make the low COF persist for a longer time. High moisture content can stabilize and protect the graphene C-network from damage due to water dissociative chemisorption with carbon dangling bonds, and the textured surface was attributed to release graphene layer stored in the dimple.

Mercapto-based coupling agent for improved thermophotovoltaic device back surface reflector adhesion and reflectance

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

Wernsman, Bernard; Fiedor, Joseph N.; Irr, Lawrence G.

2016-10-04

A back surface reflector (BSR) is described. The BSR includes a reflecting layer, a substrate and an adhesion layer between the reflecting layer and the substrate. The adhesion layer includes 3-mercaptopropyl (trimethoxy) silane (a.k.a. Merc).

Modeling the surface of Campylobacter fetus: protein surface layer stability and resistance to cationic antimicrobial peptides.

PubMed

Roberts, James M D; Graham, Lori L; Quinn, Bonnie; Pink, David A

2013-03-01

Campylobacter fetus is a Gram negative bacterium recognized for its virulence in animals and humans. This bacterium possesses a paracrystalline array of high molecular weight proteins known as surface-layer proteins covering its cell surface. A mathematical model has been made of the outer membrane of this bacterium, both with its surface-layer proteins (S+) and without (S-). Monte Carlo computer simulation was used to understand the stability of the surface-layer protein structure as a function of ionic concentration. The interactions of an electrically-charged antimicrobial agent, the cationic antimicrobial peptide protamine, with surface-layer proteins and with the lipopolysaccharides of the outer membrane were modeled and analyzed. We found that (1) divalent ions stabilize the surface-layer protein array by reducing the fluctuations perpendicular and parallel to the membrane plane thereby promoting adhesion to the LPS region. This was achieved via (2) divalent ions bridging the negatively-charged LPS Core. The effect of this bridging is to bring individual Core regions closer together so that the O-antigens can (3) increase their attractive van der Waals interactions and "collapse" to form a surface with reduced perpendicular fluctuations. These findings provide support for the proposal of Yang et al. [1]. (4) No evidence for a significant increase in Ca(2+) concentration in the region of the surface-layer protein subunits was observed in S+ simulations compared to S- simulations. (5) We predicted the trends of protamine MIC tests performed on C. fetus and these were in good agreement with our experimental results. Copyright © 2012 Elsevier B.V. All rights reserved.

Surface-Layer (S-Layer) Proteins Sap and EA1 Govern the Binding of the S-Layer-Associated Protein BslO at the Cell Septa of Bacillus anthracis

PubMed Central

Kern, Valerie J.; Kern, Justin W.; Theriot, Julie A.; Schneewind, Olaf

2012-01-01

The Gram-positive pathogen Bacillus anthracis contains 24 genes whose products harbor the structurally conserved surface-layer (S-layer) homology (SLH) domain. Proteins endowed with the SLH domain associate with the secondary cell wall polysaccharide (SCWP) following secretion. Two such proteins, Sap and EA1, have the unique ability to self-assemble into a paracrystalline layer on the surface of bacilli and form S layers. Other SLH domain proteins can also be found within the S layer and have been designated Bacillus S-layer-associated protein (BSLs). While both S-layer proteins and BSLs bind the same SCWP, their deposition on the cell surface is not random. For example, BslO is targeted to septal peptidoglycan zones, where it catalyzes the separation of daughter cells. Here we show that an insertional lesion in the sap structural gene results in elongated chains of bacilli, as observed with a bslO mutant. The chain length of the sap mutant can be reduced by the addition of purified BslO in the culture medium. This complementation in trans can be explained by an increased deposition of BslO onto the surface of sap mutant bacilli that extends beyond chain septa. Using fluorescence microscopy, we observed that the Sap S layer does not overlap the EA1 S layer and slowly yields to the EA1 S layer in a growth-phase-dependent manner. Although present all over bacilli, Sap S-layer patches are not observed at septa. Thus, we propose that the dynamic Sap/EA1 S-layer coverage of the envelope restricts the deposition of BslO to the SCWP at septal rings. PMID:22609927

Sintered wire cesium dispenser photocathode

DOEpatents

Montgomery, Eric J; Ives, R. Lawrence; Falce, Louis R

2014-03-04

A photoelectric cathode has a work function lowering material such as cesium placed into an enclosure which couples a thermal energy from a heater to the work function lowering material. The enclosure directs the work function lowering material in vapor form through a low diffusion layer, through a free space layer, and through a uniform porosity layer, one side of which also forms a photoelectric cathode surface. The low diffusion layer may be formed from sintered powdered metal, such as tungsten, and the uniform porosity layer may be formed from wires which are sintered together to form pores between the wires which are continuous from the a back surface to a front surface which is also the photoelectric surface.

Heat transfer and phase transitions of water in multi-layer cryolithozone-surface systems

NASA Astrophysics Data System (ADS)

Khabibullin, I. L.; Nigametyanova, G. A.; Nazmutdinov, F. F.

2018-01-01

A mathematical model for calculating the distribution of temperature and the dynamics of the phase transfor-mations of water in multilayer systems on permafrost-zone surface is proposed. The model allows one to perform calculations in the annual cycle, taking into account the distribution of temperature on the surface in warm and cold seasons. A system involving four layers, a snow or land cover, a top layer of soil, a layer of thermal-insulation materi-al, and a mineral soil, is analyzed. The calculations by the model allow one to choose the optimal thickness and com-position of the layers which would ensure the stability of structures built on the permafrost-zone surface.

Structured wafer for device processing

DOEpatents

Okandan, Murat; Nielson, Gregory N

2014-05-20

A structured wafer that includes through passages is used for device processing. Each of the through passages extends from or along one surface of the structured wafer and forms a pattern on a top surface area of the structured wafer. The top surface of the structured wafer is bonded to a device layer via a release layer. Devices are processed on the device layer, and are released from the structured wafer using etchant. The through passages within the structured wafer allow the etchant to access the release layer to thereby remove the release layer.

Structured wafer for device processing

DOEpatents

Okandan, Murat; Nielson, Gregory N

2014-11-25

A structured wafer that includes through passages is used for device processing. Each of the through passages extends from or along one surface of the structured wafer and forms a pattern on a top surface area of the structured wafer. The top surface of the structured wafer is bonded to a device layer via a release layer. Devices are processed on the device layer, and are released from the structured wafer using etchant. The through passages within the structured wafer allow the etchant to access the release layer to thereby remove the release layer.

Electroless atomic layer deposition

DOEpatents

Robinson, David Bruce; Cappillino, Patrick J.; Sheridan, Leah B.; Stickney, John L.; Benson, David M.

2017-10-31

A method of electroless atomic layer deposition is described. The method electrolessly generates a layer of sacrificial material on a surface of a first material. The method adds doses of a solution of a second material to the substrate. The method performs a galvanic exchange reaction to oxidize away the layer of the sacrificial material and deposit a layer of the second material on the surface of the first material. The method can be repeated for a plurality of iterations in order to deposit a desired thickness of the second material on the surface of the first material.

The stability boundary of group-III transition metal diboride ScB 2 (0 0 0 1) surfaces

NASA Astrophysics Data System (ADS)

Zhao, Hui; Qin, Na

2012-01-01

Experimental observations and theoretical investigations exhibit that a group-IV(V) transition metal diboride (0 0 0 1) surface is terminated with a 1 × 1 TM(B) layer. As to a group-III transition metal diboride, we have investigated the stability boundary of ScB2 (0 0 0 1) surfaces using first principles total energy plane-wave pseudopotential method based on density functional theory. The Mulliken charge population analysis shows that Sc atoms in the second layer cannot provide B atoms in the first layer with sufficient electrons to form a complete graphene-like boron layer. We also found that the charge transfer between the first and the second layer for the B-terminated surface is more than that for Sc-terminated surface. It elucidates the reason that the outermost interlayer spacing contract more strongly in the B-terminated surface than in the Sc-terminated surface. The surface energies of both terminated ScB2 (0 0 0 1) surfaces as a function of the chemical potential of B are also calculated to check the relative stability of the two surface structures.

Surface plasmon dispersion engineering via double-metallic AU/AG layers for nitride light-emitting diodes

DOEpatents

Tansu, Nelson; Zhao, Hongping; Zhang, Jing; Liu, Guangyu

2014-04-01

A double-metallic deposition process is used whereby adjacent layers of different metals are deposited on a substrate. The surface plasmon frequency of a base layer of a first metal is tuned by the surface plasmon frequency of a second layer of a second metal formed thereon. The amount of tuning is dependent upon the thickness of the metallic layers, and thus tuning can be achieved by varying the thicknesses of one or both of the metallic layers. In a preferred embodiment directed to enhanced LED technology in the green spectrum regime, a double-metallic Au/Ag layer comprising a base layer of gold (Au) followed by a second layer of silver (Ag) formed thereon is deposited on top of InGaN/GaN quantum wells (QWs) on a sapphire/GaN substrate.

Black carbon solar absorption suppresses turbulence in the atmospheric boundary layer.

PubMed

Wilcox, Eric M; Thomas, Rick M; Praveen, Puppala S; Pistone, Kristina; Bender, Frida A-M; Ramanathan, Veerabhadran

2016-10-18

The introduction of cloud condensation nuclei and radiative heating by sunlight-absorbing aerosols can modify the thickness and coverage of low clouds, yielding significant radiative forcing of climate. The magnitude and sign of changes in cloud coverage and depth in response to changing aerosols are impacted by turbulent dynamics of the cloudy atmosphere, but integrated measurements of aerosol solar absorption and turbulent fluxes have not been reported thus far. Here we report such integrated measurements made from unmanned aerial vehicles (UAVs) during the CARDEX (Cloud Aerosol Radiative Forcing and Dynamics Experiment) investigation conducted over the northern Indian Ocean. The UAV and surface data reveal a reduction in turbulent kinetic energy in the surface mixed layer at the base of the atmosphere concurrent with an increase in absorbing black carbon aerosols. Polluted conditions coincide with a warmer and shallower surface mixed layer because of aerosol radiative heating and reduced turbulence. The polluted surface mixed layer was also observed to be more humid with higher relative humidity. Greater humidity enhances cloud development, as evidenced by polluted clouds that penetrate higher above the top of the surface mixed layer. Reduced entrainment of dry air into the surface layer from above the inversion capping the surface mixed layer, due to weaker turbulence, may contribute to higher relative humidity in the surface layer during polluted conditions. Measurements of turbulence are important for studies of aerosol effects on clouds. Moreover, reduced turbulence can exacerbate both the human health impacts of high concentrations of fine particles and conditions favorable for low-visibility fog events.

Black carbon solar absorption suppresses turbulence in the atmospheric boundary layer

PubMed Central

Wilcox, Eric M.; Thomas, Rick M.; Praveen, Puppala S.; Pistone, Kristina; Bender, Frida A.-M.; Ramanathan, Veerabhadran

2016-01-01

The introduction of cloud condensation nuclei and radiative heating by sunlight-absorbing aerosols can modify the thickness and coverage of low clouds, yielding significant radiative forcing of climate. The magnitude and sign of changes in cloud coverage and depth in response to changing aerosols are impacted by turbulent dynamics of the cloudy atmosphere, but integrated measurements of aerosol solar absorption and turbulent fluxes have not been reported thus far. Here we report such integrated measurements made from unmanned aerial vehicles (UAVs) during the CARDEX (Cloud Aerosol Radiative Forcing and Dynamics Experiment) investigation conducted over the northern Indian Ocean. The UAV and surface data reveal a reduction in turbulent kinetic energy in the surface mixed layer at the base of the atmosphere concurrent with an increase in absorbing black carbon aerosols. Polluted conditions coincide with a warmer and shallower surface mixed layer because of aerosol radiative heating and reduced turbulence. The polluted surface mixed layer was also observed to be more humid with higher relative humidity. Greater humidity enhances cloud development, as evidenced by polluted clouds that penetrate higher above the top of the surface mixed layer. Reduced entrainment of dry air into the surface layer from above the inversion capping the surface mixed layer, due to weaker turbulence, may contribute to higher relative humidity in the surface layer during polluted conditions. Measurements of turbulence are important for studies of aerosol effects on clouds. Moreover, reduced turbulence can exacerbate both the human health impacts of high concentrations of fine particles and conditions favorable for low-visibility fog events. PMID:27702889

Scintillator reflective layer coextrusion

DOEpatents

Yun, Jae-Chul; Para, Adam

2001-01-01

A polymeric scintillator has a reflective layer adhered to the exterior surface thereof. The reflective layer comprises a reflective pigment and an adhesive binder. The adhesive binder includes polymeric material from which the scintillator is formed. A method of forming the polymeric scintillator having a reflective layer adhered to the exterior surface thereof is also provided. The method includes the steps of (a) extruding an inner core member from a first amount of polymeric scintillator material, and (b) coextruding an outer reflective layer on the exterior surface of the inner core member. The outer reflective layer comprises a reflective pigment and a second amount of the polymeric scintillator material.

Core-shell fuel cell electrodes

DOEpatents

Adzic, Radoslav; Bliznakov, Stoyan; Vukmirovic, Miomir

2017-07-25

Embodiments of the disclosure relate to electrocatalysts. The electrocatalyst may include at least one gas-diffusion layer having a first side and a second side, and particle cores adhered to at least one of the first and second sides of the at least one gas-diffusion layer. The particle cores includes surfaces adhered to the at least one of the first and second sides of the at least one gas-diffusion layer and surfaces not in contact with the at least one gas-diffusion layer. Furthermore, a thin layer of catalytically atoms may be adhered to the surfaces of the particle cores not in contact with the at least one gas-diffusion layer.

Analysis and Modeling of Boundary Layer Separation Method (BLSM).

PubMed

Pethő, Dóra; Horváth, Géza; Liszi, János; Tóth, Imre; Paor, Dávid

2010-09-01

Nowadays rules of environmental protection strictly regulate pollution material emission into environment. To keep the environmental protection laws recycling is one of the useful methods of waste material treatment. We have developed a new method for the treatment of industrial waste water and named it boundary layer separation method (BLSM). We apply the phenomena that ions can be enriched in the boundary layer of the electrically charged electrode surface compared to the bulk liquid phase. The main point of the method is that the boundary layer at correctly chosen movement velocity can be taken out of the waste water without being damaged, and the ion-enriched boundary layer can be recycled. Electrosorption is a surface phenomenon. It can be used with high efficiency in case of large electrochemically active surface of electrodes. During our research work two high surface area nickel electrodes have been prepared. The value of electrochemically active surface area of electrodes has been estimated. The existence of diffusion part of the double layer has been experimentally approved. The electrical double layer capacity has been determined. Ion transport by boundary layer separation has been introduced. Finally we have tried to estimate the relative significance of physical adsorption and electrosorption.

SHARAD Finds Voluminous CO2 Ice Sequestered in the Martian South Polar Layered Deposits

NASA Astrophysics Data System (ADS)

Phillips, R. J.; Davis, B. J.; Byrne, S.; Campbell, B. A.; Carter, L. M.; Haberle, R. M.; Holt, J. W.; Kahre, M. A.; Nunes, D. C.; Plaut, J. J.; Putzig, N. E.; Smith, I. B.; Smrekar, S. E.; Tanaka, K. L.; Titus, T. N.

2010-12-01

The SHARAD instrument on the Mars Reconnaissance Orbiter (MRO) mission has carried out systematic radar soundings of the layered deposits at both martian polar regions. While well-organized sets of radar reflectors are ubiquitous in the North Polar Layered Deposits, those in the South Polar Layered Deposits (SPLD) are limited to specific regions, and it is difficult to map SPLD-wide radar stratigraphy. What is evident in the radar observations are four regional reflection-free zones (RFZ) distinguished qualitatively by their radar characteristics. They are up to a kilometer in thickness and extend downward from near the surface. One such zone (RFZ3) occurs beneath the South Polar Residual Cap (SPRC), which is composed of ~5 m of solid CO2 underlain by an apparently thin layer of water ice. Using a correlation technique, we inverted for the real permittivity, ɛ', on each of 41 usable SHARAD orbits over RFZ3. The results were mean values of ɛ' = 2.0 or 2.1, with a σ of 0.2. A secondary technique based on the “smoothest” solution gave similar results. These values are exceptionally close to the laboratory-measured permittivity value of bulk CO2 ice [Pettinelli et al., 2003] and distant from the bulk water ice value (ɛ' = 3.15); water ice is the dominant volatile in the SPLD. An alternative hypothesis for ɛ' = 2.0-2.1 is that the RFZ3 material is porous water ice, but this can be strongly discounted based on theoretical and empirical models of ɛ' of porous water ice vs. thickness. By the same arguments, the proposed CO2 material also cannot be very porous, and ɛ' should be close to the bulk value. With the permittivity estimates, radar time delays were converted to depth, and for RFZ3 a mean thickness of 210-220 m and a volume of 4,200-4,400 km3 result. This is unlikely to be the entire volume because MRO’s orbital inclination precludes SHARAD sounding poleward of ~87°S, where RFZ3 appears to extend. We do find a very good spatial correlation of RFZ3 with the stratigraphic unit (named “Aa3”) immediately beneath the SPRC [Kolb et al., 2006] and use this geologic unit as a basis for extrapolation, yielding a volume estimate range of 9,500 to 12,500 km3. For comparison, the CO2 in the SPRC is estimated to be < 380 km3 [Thomas et al., 2009]. The equivalent atmospheric pressure of the extrapolated RFZ3 volume is 4-5 mbar, competing in magnitude with the current atmospheric pressure of 6-7 mbar. We have searched the past million year orbit history of Mars for periods when insolation at the south pole would likely render the proposed CO2 mass unstable and are carrying out GCM simulations to evaluate the climate regime at those times with 10-12 mbar of CO2 in the atmosphere. The other three reflection-free zones may also contain a component of CO2, but the reflector geometry is not favorable for estimating permittivity.

In Vitro Characterization of the Two-Stage Non-Classical Reassembly Pathway of S-Layers

PubMed Central

Breitwieser, Andreas; Iturri, Jagoba; Toca-Herrera, Jose-Luis; Sleytr, Uwe B.; Pum, Dietmar

2017-01-01

The recombinant bacterial surface layer (S-layer) protein rSbpA of Lysinibacillus sphaericus CCM 2177 is an ideal model system to study non-classical nucleation and growth of protein crystals at surfaces since the recrystallization process may be separated into two distinct steps: (i) adsorption of S-layer protein monomers on silicon surfaces is completed within 5 min and the amount of bound S-layer protein sufficient for the subsequent formation of a closed crystalline monolayer; (ii) the recrystallization process is triggered—after washing away the unbound S-layer protein—by the addition of a CaCl2 containing buffer solution, and completed after approximately 2 h. The entire self-assembly process including the formation of amorphous clusters, the subsequent transformation into crystalline monomolecular arrays, and finally crystal growth into extended lattices was investigated by quartz crystal microbalance with dissipation (QCM-D) and atomic force microscopy (AFM). Moreover, contact angle measurements showed that the surface properties of S-layers change from hydrophilic to hydrophobic as the crystallization proceeds. This two-step approach is new in basic and application driven S-layer research and, most likely, will have advantages for functionalizing surfaces (e.g., by spray-coating) with tailor-made biological sensing layers. PMID:28216572

Emergence of a Stern Layer from the Incorporation of Hydration Interactions into the Gouy-Chapman Model of the Electrical Double Layer.

PubMed

Brown, Matthew A; Bossa, Guilherme Volpe; May, Sylvio

2015-10-27

In one of the most commonly used phenomenological descriptions of the electrical double layer, a charged solid surface and a diffuse region of mobile ions are separated from each other by a thin charge-depleted Stern layer. The Stern layer acts as a capacitor that improves the classical Gouy-Chapman model by increasing the magnitude of the surface potential and limiting the maximal counterion concentration. We show that very similar Stern-like properties of the diffuse double layer emerge naturally from adding a nonelectrostatic hydration repulsion to the electrostatic Coulomb potential. The interplay of electrostatic attraction and hydration repulsion of the counterions and the surface leads to the formation of a diffuse counterion layer that remains well separated from the surface. In addition, hydration repulsions between the ions limit and control the maximal ion concentration and widen the width of the diffuse double layer. Our mean-field model, which we express in terms of electrostatic and hydration potentials, is physically consistent and conceptually similar to the classical Gouy-Chapman model. It allows the incorporation of ion specificity, accounts for hydration properties of charged surfaces, and predicts Stern layer properties, which we analyze in terms of the effective size of the hydrated counterions.

Formation mechanism of photo-induced nested wrinkles on siloxane-photomonomer hybrid film

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

Suzuki, Kazumasa; International Laboratory of Materials Science and Nanotechnology; Laboratorio di Scienz

Nested wrinkle structures, hierarchical surface wrinkles of different periodicities of sub-μm and tens-μm, have been fabricated on a siloxane-photomonomer hybrid film via a photo-induced surface polymerization of acrylamide. The formation mechanism of the nested wrinkle structures is examined based on a time-dependent structure observation and chemical composition analyses. In-situ observation of the evolving surface structure showed that sub-μm scale wrinkles first formed, subsequently the tens-μm scale ones did. In-situ FT-IR analysis indicated that the nested wrinkles formation took place along with the development of siloxane network of under layer. A cross sectional observation of the film revealed that the filmmore » was composed of three layers. FT-IR spectra of the film revealed that the surface and interior layers were polyacrylamide rich layer and siloxane-polymer rich layer, respectively. The intermediate layer formed as a diffusion layer by migration of acrylamide from interior to the surface. These three layers have different chemical compositions and therefore different mechanical characteristics, which allows the wrinkle formation. Shrinkage of siloxane-polymer interior layers, as a result of polycondensation of siloxane network, induced mechanical instabilities at interlayers, to form the nested wrinkle structures.« less

Understanding the Growth Mechanism of GaN Epitaxial Layers on Mechanically Exfoliated Graphite

NASA Astrophysics Data System (ADS)

Li, Tianbao; Liu, Chenyang; Zhang, Zhe; Yu, Bin; Dong, Hailiang; Jia, Wei; Jia, Zhigang; Yu, Chunyan; Gan, Lin; Xu, Bingshe; Jiang, Haiwei

2018-04-01

The growth mechanism of GaN epitaxial layers on mechanically exfoliated graphite is explained in detail based on classic nucleation theory. The number of defects on the graphite surface can be increased via O-plasma treatment, leading to increased nucleation density on the graphite surface. The addition of elemental Al can effectively improve the nucleation rate, which can promote the formation of dense nucleation layers and the lateral growth of GaN epitaxial layers. The surface morphologies of the nucleation layers, annealed layers and epitaxial layers were characterized by field-emission scanning electron microscopy, where the evolution of the surface morphology coincided with a 3D-to-2D growth mechanism. High-resolution transmission electron microscopy was used to characterize the microstructure of GaN. Fast Fourier transform diffraction patterns showed that cubic phase (zinc-blend structure) GaN grains were obtained using conventional GaN nucleation layers, while the hexagonal phase (wurtzite structure) GaN films were formed using AlGaN nucleation layers. Our work opens new avenues for using highly oriented pyrolytic graphite as a substrate to fabricate transferable optoelectronic devices.

Understanding the Growth Mechanism of GaN Epitaxial Layers on Mechanically Exfoliated Graphite.

PubMed

Li, Tianbao; Liu, Chenyang; Zhang, Zhe; Yu, Bin; Dong, Hailiang; Jia, Wei; Jia, Zhigang; Yu, Chunyan; Gan, Lin; Xu, Bingshe; Jiang, Haiwei

2018-04-27

The growth mechanism of GaN epitaxial layers on mechanically exfoliated graphite is explained in detail based on classic nucleation theory. The number of defects on the graphite surface can be increased via O-plasma treatment, leading to increased nucleation density on the graphite surface. The addition of elemental Al can effectively improve the nucleation rate, which can promote the formation of dense nucleation layers and the lateral growth of GaN epitaxial layers. The surface morphologies of the nucleation layers, annealed layers and epitaxial layers were characterized by field-emission scanning electron microscopy, where the evolution of the surface morphology coincided with a 3D-to-2D growth mechanism. High-resolution transmission electron microscopy was used to characterize the microstructure of GaN. Fast Fourier transform diffraction patterns showed that cubic phase (zinc-blend structure) GaN grains were obtained using conventional GaN nucleation layers, while the hexagonal phase (wurtzite structure) GaN films were formed using AlGaN nucleation layers. Our work opens new avenues for using highly oriented pyrolytic graphite as a substrate to fabricate transferable optoelectronic devices.

Photovoltaic device comprising compositionally graded intrinsic photoactive layer

DOEpatents

Hoffbauer, Mark A; Williamson, Todd L

2013-04-30

Photovoltaic devices and methods of making photovoltaic devices comprising at least one compositionally graded photoactive layer, said method comprising providing a substrate; growing onto the substrate a uniform intrinsic photoactive layer having one surface disposed upon the substrate and an opposing second surface, said intrinsic photoactive layer consisting essentially of In.sub.1-xA.sub.xN,; wherein: i. 0.ltoreq.x.ltoreq.1; ii. A is gallium, aluminum, or combinations thereof; and iii. x is at least 0 on one surface of the intrinsic photoactive layer and is compositionally graded throughout the layer to reach a value of 1 or less on the opposing second surface of the layer; wherein said intrinsic photoactive layer is isothermally grown by means of energetic neutral atom beam lithography and epitaxy at a temperature of 600.degree. C. or less using neutral nitrogen atoms having a kinetic energy of from about 1.0 eV to about 5.0 eV, and wherein the intrinsic photoactive layer is grown at a rate of from about 5 nm/min to about 100 nm/min.

The Effects of Tidal Dissipation on the Thermal Evolution of Triton

NASA Astrophysics Data System (ADS)

Gaeman, J.; Hier-Majumder, S.; Roberts, J. H.

2009-12-01

This work explores the coupled structural, thermal, and orbital evolution of Neptune's icy satellite, Triton. Recent geyser activity, ridge formation, and volatile transport, observed on Triton's surface, indicate possible activity within Triton's interior [1,2]. Triton is hypothesized to have been captured from an initially heliocentric orbit. During the circularization of Triton's orbit following its capture by Neptune, intense tidal heating likely contributed to the formation of a subsurface ocean [3]. Although the time of Triton's capture is not exactly known, it is likely that the event took place earlier in the history of our solar system, when the probability of binary capture was higher [4, 5]. This work examines the thermal evolution of Triton by employing a coupled tidal and two-phase thermal evolution model, for both an early and late capture scenario. Thermal evolution of a solid crust underlain by an H2O-NH3 mushy layer is driven by the evolution of tidal heating, as Triton's orbital eccentricity evolves following its capture. The governing equations for tidal heating are solved using the propagator matrix method [6, 7], while the governing equation for the coupled crust-multiphase layer thermal evolution were numerically solved using a finite volume discretization. The results indicate that the existence of a subsurface ocean is strongly dependent on ammonia content as larger concentrations of ammonia influence liquidus temperature and density contrast between solid and liquid phases [8]. Preliminary results indicate that an ocean likely exists for compositions containing a relatively high percentage of ammonia for both early and late capture of the satellite. In contrast, the subsurface ocean freezes completely for lower ammonia content. [1] Brown, R. H., Kirk, R. L. (1994). Journal of Geophysical Research 99, 1965-981. [2] Prockter, L. M., Nimmo, F., Pappalardo, R. T. (2005). Geophysical Research Letters 32, L14202. [3] Ross, M. N., Schubert, G. (1990). Geophysical Research Letters 17, 1749-752. [4] Agnor, C. B., Hamilton, D. P. (2006). Nature 441, 192-94. [5] Schenk, P. M., Zahnle, K. (2007). Icarus 192, 135-49. [6] Roberts, J. H., Nimmo, F. (2008). Icarus 194, 675-689. [7] Sabadini, R., Vermeersen, B., (2004). Global Dynamics of the Earth. Kluwer Academic Publishers. [8] Hogenboom, D. L., Kargel, J. S., Concolmagno, G. J., Holden, T. C., Lee, L., Buyyounouski, M. (1997). Icarus 128, 171-80.

Improved Modeling of Surface Layer Parameters in a AGCM Using Refined Vertical Resolution in the Surface Layer

NASA Astrophysics Data System (ADS)

Shin, H. H.; Zhao, M.; Ming, Y.; Chen, X.; Lin, S. J.

2017-12-01

Surface layer (SL) parameters in atmospheric models - such as 2-m air temperature (T2), 10-m wind speed (U10), and surface turbulent fluxes - are computed by applying the Monin-Obukhov Similarity Theory (MOST) to the lowest model level height (LMH) in the models. The underlying assumption is that LMH is within surface layer height (SLH), but most AGCMs hardly meet the condition in stable boundary layers (SBLs) over land. To assess the errors in modeled SL parameters caused by this, offline computations of the MOST are performed with different LMHs from 1 to 100 m, for an idealized SBL case with prescribed surface parameters (surface temperature, roughness length and Obukhov length), and vertical profiles of temperature and winds. The results show that when LMH is higher than SLH, T2 and U10 are underestimated by O(1 K) and O(1 m/s), respectively, and the biases increase as LMH increases. Based on this, the refined vertical resolution with an additional layer in the SL is applied to the GFDL AGCM, and it reduces the systematic cold biases in T2 and the systematic underestimation of U10.

CWEX: Crop/wind-energy experiment: Observations of surface-layer, boundary-layer and mesoscale interactions with a wind farm

USDA-ARS?s Scientific Manuscript database

Large wind turbines perturb mean and turbulent wind characteristics, which modify fluxes between the vegetated surface and the lower boundary layer. While simulations have suggested that wind farms could create significant changes in surface fluxes of heat, momentum, moisture, and CO2 over hundreds ...

Crop/Wind-energy Experiment (CWEX): Observations of surface-layer, boundary-layer and mesoscale interactions with a wind farm

USDA-ARS?s Scientific Manuscript database

Perturbations of mean and turbulent wind characteristics by large wind turbines modify fluxes between the vegetated surface and the lower boundary layer. While simulations have suggested that wind farms could significantly change surface fluxes of heat, momentum, moisture, and CO2 over hundreds of s...

Treated and Untreated foam core particleboards with intumescent veneer

Treesearch

Mark A. Dietenberger; Ali Shalbafan; Johannes Welling; Charles Boardman

2013-01-01

The effectiveness of treatments for the surface layer of novel foam core particleboards was evaluated by means of Cone calorimeter tests, Foam cote particleboards with variations of surface layer treatment, adhesives, and surface layer thicknesses under similar processing conditions were used to produce the test specimen for the Cone calorimeter tests. Ignitability,...

Cone Calorimeter Analysis of FRT Intumescent and Untreated Foam Core Particleboards

Treesearch

Mark A. Dietenberger; Ali Shalbafan; Johannes Welling; Charles Boardman

2012-01-01

The effectiveness of treatments of the surface layer of novel foam core particleboards were evaluated by means of Cone calorimeter tests. Foam core particleboards with variations of surface layer treatment, adhesives and surface layer thicknesses under similar processing conditions were used to produce the test specimen for the Cone calorimeter tests. Ignitability,...

Formation of a Crack-Free, Hybrid Skin Layer with Tunable Surface Topography and Improved Gas Permeation Selectivity on Elastomers Using Gel–Liquid Infiltration Polymerization

DOE PAGES

Wang, Mengyuan; Gorham, Justin M.; Killgore, Jason P.; ...

2017-07-31

Surface modifications of elastomers and gels are crucial for emerging applications such as soft robotics and flexible electronics, in large part because they provide a platform to control wettability, adhesion, and permeability. Current surface modification methods via ultraviolet-ozone (UVO) and/or O2 plasma, atomic layer deposition (ALD), plasmas deposition, and chemical treatment impart a dense polymer or inorganic layer on the surface that is brittle and easy to fracture at low strain levels. This paper presents a new method, based on gel–liquid infiltration polymerization, to form hybrid skin layers atop elastomers. The method is unique in that it allows for controlmore » of the skin layer topography, with tunable feature sizes and aspect ratios as high as 1.8 without fracture. Unlike previous techniques, the skin layer formed here dramatically improves the barrier properties of the elastomer, while preserving skin layer flexibility. Furthermore, the method is versatile and likely applicable to most interfacial polymerization systems and network polymers on flat and patterned surfaces.« less

Formation of a Crack-Free, Hybrid Skin Layer with Tunable Surface Topography and Improved Gas Permeation Selectivity on Elastomers Using Gel–Liquid Infiltration Polymerization

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

Wang, Mengyuan; Gorham, Justin M.; Killgore, Jason P.

Surface modifications of elastomers and gels are crucial for emerging applications such as soft robotics and flexible electronics, in large part because they provide a platform to control wettability, adhesion, and permeability. Current surface modification methods via ultraviolet-ozone (UVO) and/or O2 plasma, atomic layer deposition (ALD), plasmas deposition, and chemical treatment impart a dense polymer or inorganic layer on the surface that is brittle and easy to fracture at low strain levels. This paper presents a new method, based on gel–liquid infiltration polymerization, to form hybrid skin layers atop elastomers. The method is unique in that it allows for controlmore » of the skin layer topography, with tunable feature sizes and aspect ratios as high as 1.8 without fracture. Unlike previous techniques, the skin layer formed here dramatically improves the barrier properties of the elastomer, while preserving skin layer flexibility. Furthermore, the method is versatile and likely applicable to most interfacial polymerization systems and network polymers on flat and patterned surfaces.« less

Loss of the Endothelial Glycocalyx Links Albuminuria and Vascular Dysfunction

PubMed Central

Ferguson, Joanne K.; Burford, James L.; Gevorgyan, Haykanush; Nakano, Daisuke; Harper, Steven J.; Bates, David O.; Peti-Peterdi, Janos

2012-01-01

Patients with albuminuria and CKD frequently have vascular dysfunction but the underlying mechanisms remain unclear. Because the endothelial surface layer, a meshwork of surface-bound and loosely adherent glycosaminoglycans and proteoglycans, modulates vascular function, its loss could contribute to both renal and systemic vascular dysfunction in proteinuric CKD. Using Munich-Wistar-Fromter (MWF) rats as a model of spontaneous albuminuric CKD, multiphoton fluorescence imaging and single-vessel physiology measurements revealed that old MWF rats exhibited widespread loss of the endothelial surface layer in parallel with defects in microvascular permeability to both water and albumin, in both continuous mesenteric microvessels and fenestrated glomerular microvessels. In contrast to young MWF rats, enzymatic disruption of the endothelial surface layer in old MWF rats resulted in neither additional loss of the layer nor additional changes in permeability. Intravenous injection of wheat germ agglutinin lectin and its adsorption onto the endothelial surface layer significantly improved glomerular albumin permeability. Taken together, these results suggest that widespread loss of the endothelial surface layer links albuminuric kidney disease with systemic vascular dysfunction, providing a potential therapeutic target for proteinuric kidney disease. PMID:22797190

Plasmonic enhancement of second-harmonic generation of dielectric layer embedded in metal-dielectric-metal structure

NASA Astrophysics Data System (ADS)

Kang, Byungjun; Imakita, Kenji; Fujii, Minoru; Hayashi, Shinji

2018-03-01

The enhancement of second-harmonic generation from a dielectric layer embedded in a metal-dielectric-metal structure upon excitation of surface plasmon polaritons is demonstrated experimentally. The metal-dielectric-metal structure consisting of a Gex(SiO2)1-x layer sandwiched by two Ag layers was prepared, and the surface plasmon polaritons were excited in an attenuated total reflection geometry. The measured attenuated total reflection spectra exhibited two reflection dips corresponding to the excitation of two different surface plasmon polariton modes. Strong second-harmonic signals were observed under the excitation of these surface plasmon polariton modes. The results demonstrate that the second-harmonic intensity of the Gex(SiO2)1-x layer is highly enhanced relative to that of the single layer deposited on a substrate. Under the excitation of one of the two surface plasmon polariton modes, the estimated enhancement factor falls in a range between 39.9 and 171, while under the excitation of the other surface plasmon polariton mode, it falls in a range between 3.96 and 84.6.

Vortex Flows in the Liquid Layer and Droplets on a Vibrating Flexible Plate

NASA Astrophysics Data System (ADS)

Aleksandrov, Vladimir; Kopysov, Sergey; Tonkov, Leonid

2018-02-01

In certain conditions, in the layers and droplets of a liquid on a vibrating rectangular flexible plate, vortex flows are formed simultaneously with the excitation of capillary oscillations on the free surface of the liquid layers and droplets. Capillary oscillations in the form of two-dimensional standing waves form Faraday ripples on the free surface of the liquid layer. On the surface of the vibrating droplets, at the excitation of capillary oscillations a light spot reflected from a spotlight source moves along a trajectory in the form of a Lissajous figure observed with a microscope. When vortex flows visualized with graphite microparticles appear in the layer and droplets of a transparent liquid, the trajectory of the light spot on the layer and droplet surface is a two-dimensional trajectory in the form of an ellipse or a saddle. This indicates that the generation of the vortex flows in a liquid at vibrations is due to capillary oscillations in the orthogonally related directions. In the liquid layer and droplets on the surface of the flexible plate, the vibrations of which are generated by bending vibrations, the vortex flows appear due to the plate vibrations and the capillary oscillations of the surface of a layer or a droplet of the liquid. On the free surface of the liquid, the capillary waves, which are parametrically excited by the plate bending vibrations, are additionally modulated by the same bending vibrations in the transverse direction.

Holocene paleoenvironments of Northeast Iowa

USGS Publications Warehouse

Baker, R.G.; Bettis, E. Arthur; Schwert, D.R.; Horton, D.G.; Chumbley, C.A.; Gonzalez, Luis A.; Reagan, M.K.

1996-01-01

This paper presents the biotic. sedimentary, geomorphic, and climatic history of the upper part of the Roberts Creek Basin, northeastern Iowa for the late-glacial and Holocene, and compares these records with a C-O isotopic sequence from Coldwater Cave. 60 km northwest of Roberts Creek. The biotic record (pollen, vascular plant and bryophyle macrofossils. and insects) is preserved in floodplain alluvium that underlies three constructional surfaces separated by low scarps. Each surface is underlain by a lithologically and temporally distinct alluvial fill. The highest surface is underlain by the Gunder Member of the Deforest Formation, dating from 11 000 to 4000 yr BP; beneath the intermediate level is the Roberts Creek Member, dating from 4000 to 400 yr BP; and the lowest level is underlain by the Camp Creek Member, deposited during the last 380 yr. Pollen and plant macrofossils in the alluvial fill show that a typical late-glacial spruce forest was replaced by Quercus and Ulmus in the early Holocene. This early-to-middle Holocene forest became dominated by mesic elements such as Acer saccharum, Tilia americana, Ostrya virginiana, and Carpinus caroliniana as late as 5500 yr BP; in contrast, the closest sites to the west and north were at their warmest and driest and were covered by prairie vegetation between 6500 and 5500 yr BP. After 5500 yr BP, the forest in the Roberts Creek area was replaced by prairie, as indicated by a rich assemblage of plant macrofossils, although only Ambrosia and Poaceae became abundant in the pollen record. The return of Quercus ??? 3000 BP (while nonarboreal pollen percentages remained relatively high) indicates that oak savanna prevailed with little change until settlement time. The bryophyte assemblages strongly support the vascular plant record. Rich fen species characteristic of boreal habitats occur only in the late-glacial. They are replaced by a number of deciduous-forest elements when early-to-middle Holocene forests were present, but mosses of forest habitats completely disappear when prairie became dominant. A few deciduousforest taxa return during the late-Holocene, when oak savanna prevailed. The C-O isotopic record from stalagmite "s" in Coldwater Cave indicates a relatively stable environment from ??? 8000 to 5100 yr BP, when the 813C values indicate a change in vegetation dominated by C3 (predominantly forest) to C4 (predominantly prairie) plants. About 4900 yr BP, the rise in 18O values indicates a temperature increase of ??? 1.5??C. The fact that the vegetational change suggested by the ??13C values preceded the temperature increase suggests that fire may have been an important factor in converting forest to prairie. Abundant charred seeds and other plant material at Roberts Creek 4830 yr BP support this hypothesis. The 18O values remain constant from ???5100 to ???3000 yr BP. but the ??13C values gradually rise, indicating that soil formed under forest takes at least 2000 yr for its carbon to reach equilibrium after replacement by prairie vegetation. The return of oak to form savanna is reflected in the gradual decline of ??13C values in the last 3000 yr BP: O isotopic values drop sharply by ??? 1??C ??? 2800 yr BP and then were relatively stable. In contrast to the vegetational and isotopic records, the insect assemblages suggest little change in the local environments throughout most of the Holocene. All of the beetle taxa presently occur in eastern Iowa. The relative stability through the Holocene indicates that both open grassland and riparian woodland elements were present throughout. Settlement, land clearing, and land cultivation by EuroAmericans in the region caused rapid erosion of the upland landscape, the deposition of 1-2 m of sediment across the floodplain, a replacement of the native vegetation with ruderal species, a decimation of the native insect fauna, and a degradation of water quality in the stream. These changes in the landscape, vegetation, and insect faunas

Quantifying the Impact of Background Atmospheric Stability on Air-Ice-Ocean Interactions the Arctic Ocean During the Fall Freeze-Up

NASA Astrophysics Data System (ADS)

Guest, P. S.; Persson, O. P. G.; Blomquist, B.; Fairall, C. W.

2016-02-01

"Background" stability refers to the effect of vertical virtual temperature variations above the surface layer on fluxes within the surface layer. This is different from the classical surface layer stability quantified by the Obhukhov length scale. In most locations, changes in the background stability do not have a significant direct impact on surface fluxes. However in polar regions, where there is usually a strong low-level temperature inversion capping the boundary layer, changes in background stability can have big impacts on surface fluxes. Therefore, in the Arctic, there is potential for a positive feedback effect between ice cover and surface wind speed (and momentum flux) due to the background stability effects. As the surface becomes more ice free, heat fluxes from the surface weaken the temperature inversion which in turn increases the surface wind speed which further increases the surface turbulent heat fluxes and removes more sea ice by melting or advection. It is not clear how important feedbacks involving the background stability are during the fall freeze up of the Arctic Ocean; that will be the focus of this study. As part of an ONR-sponsored cruise in the fall of 2015 to examine sea state and boundary layer processes in the Beaufort Sea on the R/V Sikuliaq, the authors will perform a variety of surface layer and upper level atmospheric measurements of temperature, humidity and wind vector using ship platform instruments, radiosonde weather balloons, tethered balloons, kites, and miniature quad-rotor unmanned aerial vehicles. In addition, the authors will deploy a full suite of turbulent and radiational flux measurements from the vessel. These measurements will be used to quantify the impact of changing surface conditions on atmospheric structure and vice-versa. The goal is to directly observe how the surface and atmosphere above the surface layer interact and feedback with each other through radiational and turbulent fluxes.

Role of SiC substrate surface on local tarnishing of deposited silver mirror stacks

NASA Astrophysics Data System (ADS)

Limam, Emna; Maurice, Vincent; Seyeux, Antoine; Zanna, Sandrine; Klein, Lorena H.; Chauveau, Grégory; Grèzes-Besset, Catherine; Savin De Larclause, Isabelle; Marcus, Philippe

2018-04-01

The role of the SiC substrate surface on the resistance to the local initiation of tarnishing of thin-layered silver stacks for demanding space mirror applications was studied by combined surface and interface analysis on model stack samples deposited by cathodic magnetron sputtering and submitted to accelerated aging in gaseous H2S. It is shown that suppressing the surface pores resulting from the bulk SiC material production process by surface pretreatment eliminates the high aspect ratio surface sites that are imperfectly protected by the SiO2 overcoat after the deposition of silver. The formation of channels connecting the silver layer to its environment through the failing protection layer at the surface pores and locally enabling H2S entry and Ag2S growth as columns until emergence at the stack surface is suppressed, which markedly delays tarnishing initiation and thereby preserves the optical performance. The results revealed that residual tarnishing initiation proceeds by a mechanism essentially identical in nature but involving different pathways short circuiting the protection layer and enabling H2S ingress until the silver layer. These permeation pathways are suggested to be of microstructural origin and could correspond to the incompletely coalesced intergranular boundaries of the SiO2 layer.

Ionization chamber dosimeter

DOEpatents

Renner, Tim R.; Nyman, Mark A.; Stradtner, Ronald

1991-01-01

A method for fabricating an ion chamber dosimeter collecting array of the type utilizing plural discrete elements formed on a uniform collecting surface which includes forming a thin insulating layer over an aperture in a frame having surfaces, forming a predetermined pattern of through holes in the layer, plating both surfaces of the layer and simultaneously tilting and rotating the frame for uniform plate-through of the holes between surfaces. Aligned masking and patterned etching of the surfaces provides interconnects between the through holes and copper leads provided to external circuitry.

Surface modification of active material structures in battery electrodes

DOEpatents

Erickson, Michael; Tikhonov, Konstantin

2016-02-02

Provided herein are methods of processing electrode active material structures for use in electrochemical cells or, more specifically, methods of forming surface layers on these structures. The structures are combined with a liquid to form a mixture. The mixture includes a surface reagent that chemically reacts and forms a surface layer covalently bound to the structures. The surface reagent may be a part of the initial liquid or added to the mixture after the liquid is combined with the structures. In some embodiments, the mixture may be processed to form a powder containing the structures with the surface layer thereon. Alternatively, the mixture may be deposited onto a current collecting substrate and dried to form an electrode layer. Furthermore, the liquid may be an electrolyte containing the surface reagent and a salt. The liquid soaks the previously arranged electrodes in order to contact the structures with the surface reagent.

Method for producing highly reflective metal surfaces

DOEpatents

Arnold, Jones B.; Steger, Philip J.; Wright, Ralph R.

1983-01-01

The invention is a novel method for producing mirror surfaces which are extremely smooth and which have high optical reflectivity. The method includes electrolessly depositing an amorphous layer of nickel on an article and then diamond-machining the resulting nickel surface to increase its smoothness and reflectivity. The machined nickel surface then is passivated with respect to the formation of bonds with electrodeposited nickel. Nickel then is electrodeposited on the passivated surface to form a layer of electroplated nickel whose inside surface is a replica of the passivated surface. The electroplated nickel layer then is separated from the passivated surface. The mandrel then may be re-passivated and provided with a layer of electrodeposited nickel, which is then recovered from the mandrel providing a second replica. The mandrel can be so re-used to provide many such replicas. As compared with producing each mirror-finished article by plating and diamond-machining, the new method is faster and less expensive.

Boundary Layer Flow Over a Moving Wavy Surface

NASA Astrophysics Data System (ADS)

Hendin, Gali; Toledo, Yaron

2016-04-01

Boundary Layer Flow Over a Moving Wavy Surface Gali Hendin(1), Yaron Toledo(1) January 13, 2016 (1)School of Mechanical Engineering, Tel-Aviv University, Israel Understanding the boundary layer flow over surface gravity waves is of great importance as various atmosphere-ocean processes are essentially coupled through these waves. Nevertheless, there are still significant gaps in our understanding of this complex flow behaviour. The present work investigates the fundamentals of the boundary layer air flow over progressive, small-amplitude waves. It aims to extend the well-known Blasius solution for a boundary layer over a flat plate to one over a moving wavy surface. The current analysis pro- claims the importance of the small curvature and the time-dependency as second order effects, with a meaningful impact on the similarity pattern in the first order. The air flow over the ocean surface is modelled using an outer, inviscid half-infinite flow, overlaying the viscous boundary layer above the wavy surface. The assumption of a uniform flow in the outer layer, used in former studies, is now replaced with a precise analytical solution of the potential flow over a moving wavy surface with a known celerity, wavelength and amplitude. This results in a conceptual change from former models as it shows that the pressure variations within the boundary layer cannot be neglected. In the boundary layer, time-dependent Navier-Stokes equations are formulated in a curvilinear, orthogonal coordinate system. The formulation is done in an elaborate way that presents additional, formerly neglected first-order effects, resulting from the time-varying coordinate system. The suggested time-dependent curvilinear orthogonal coordinate system introduces a platform that can also support the formulation of turbulent problems for any surface shape. In order to produce a self-similar Blasius-type solution, a small wave-steepness is assumed and a perturbation method is applied. Consequently, a novel self-similar solution is obtained from the first order set of equations. A second order solution is also obtained, stressing the role of small curvature on the boundary layer flow. The proposed model and solution for the boundary layer problem overlaying a moving wavy surface can also be used as a base flow for stability problems that can develop in a boundary layer, including phases of transitional states.

Preliminary Results of the Permafrost Carbon Study in the Lower Kolyma Lowland (Eastern Siberia) Based on Drilling Record

NASA Astrophysics Data System (ADS)

Spektor, V. V.; Kholodov, A. L.; Bulygina, E. B.; Andreeva, V.; Broderick, D.; Spawn, S.; Natali, S.; Davydova, A.

2012-12-01

In 2012, the Polaris Project (thepolarisproject.org, Director R.M. Holmes) has conducted the permafrost drilling on the Kolyma Lowland for a complex study of permafrost carbon as a potential source for microbial decomposition. In July 2012, the first two boreholes, 15.1 and 13.4 m in depth, were drilled. The first borehole (BH 12/1) was drilled in the stratum of ice complex (yedoma) on the local watershed near the Schuch'e lake in the vicinity of the town Chersky (N68°44.7' E161°23'). The depth of active layer is 45 cm. The permafrost to the depth of 15.1 m represents grey and brown silts with predominant homogeneous structure. Silts contain numerous thread-like roots, scarce plant macrofossils, and in places are colored with unclear spots of ferrugination. Cryostructure is mainly pore ice or thin lense-like ice layers. Wedge ice is observed in the interval 12.5-12.9 m. The moisture volumetric percentage of silts varies along the stratum, mainly, between 40-50%. The organic content, defined in every 20 cm of the core as a loss on ignition, varies between 2-4%. The second borehole (BH 12/2), located in the Pleistocene Park (N68°30.8' E161°30') was drilled through modern floodplain sediments (0-0.6 m) of the Kolyma River with polygonal network at the surface, underlain by peat (0.6-1.3 m), silt deposits of thermokarst lake (1.3-12.0 m), and river grey sands (12.0-13.4 m). The active layer thickness is 65 cm. The cryostructure is predominantly lattice-like. Silts contain modern wedge ice at the depth of 2.5-2.7 m. Mollusk shells and large amount of plant macrofossils are observed in the interval 5.7-8.0 m. The organic content in the thermokarst deposits varies in average within 2-3 %, but is about 1% in the underlying river sands. To investigate permafrost carbon, samples for microbial and enzyme activities, as well as samples of trapped gases were collected from different horizons of frozen cores. Samples for palynological, diatom, and lithological analyses, as well as for absolute age AMS 14C and isotopes O16/O18, and D were collected for reconstructing paleoclimate and paleogeographic conditions of organic matter accumulation and preservation. As a part of the TSP Program (Thermal State Permafrost), both boreholes were equipped with loggers for temperature measurements at 3,5,10, and 15 m and 3,4,10, and 13 m for the BH 12/1 and 12/2 correspondingly. To evaluate the role of landscape conditions on the thermal regime of permafrost and active layer dynamics terrestrial survey near the boreholes was conducted.

Composite neutron absorbing coatings for nuclear criticality control

DOEpatents

Wright, Richard N.; Swank, W. David; Mizia, Ronald E.

2005-07-19

Thermal neutron absorbing composite coating materials and methods of applying such coating materials to spent nuclear fuel storage systems are provided. A composite neutron absorbing coating applied to a substrate surface includes a neutron absorbing layer overlying at least a portion of the substrate surface, and a corrosion resistant top coat layer overlying at least a portion of the neutron absorbing layer. An optional bond coat layer can be formed on the substrate surface prior to forming the neutron absorbing layer. The neutron absorbing layer can include a neutron absorbing material, such as gadolinium oxide or gadolinium phosphate, dispersed in a metal alloy matrix. The coating layers may be formed by a plasma spray process or a high velocity oxygen fuel process.

Drivers of surface moisture flux variations in northern terrestrial regions

NASA Astrophysics Data System (ADS)

Fischer, R.; Walsh, J. E.

2017-12-01

The wetness of the high-latitude land surface is strongly dependent on the difference between precipitation (P) and evapotranspiration (ET). Variations of ET over daily, seasonal and interannual timescales are poorly documented, as are their relationships to key drivers. A combination of regional climate model output and eddy covariance measurements from five flux tower sites in Alaska are used to test the hypothesis that temperature is the key driver of ET in tundra regions underlain by permafrost, while precipitation plays a greater role in boreal forest areas. At the tundra sites, both the flux tower data and the model simulations show that daily and warm-season totals of ET are largely temperature driven, although daily ET also shows a negative correlation with P. At the boreal forest sites, P is the main driver of year-to-year variations of the seasonally integrated net moisture flux, although ET does not correlate strongly with either P or T. A short period of negative P-ET typically occurs during the warm season in the flux tower data. The model depicts a stronger hydrologic cycle (larger P, larger ET) relative to the measurements at all the sites.

Evidence of a Transition Layer between the Free Surface and the Bulk.

PubMed

Ogieglo, Wojciech; Tempelman, Kristianne; Napolitano, Simone; Benes, Nieck E

2018-03-15

The free surface, a very thin layer at the interface between polymer and air, is considered the main source of the perturbations in the properties of ultrathin polymer films, i.e., nanoconfinement effects. The structural relaxation of such a layer is decoupled from the molecular dynamics of the bulk. The free surface is, in fact, able to stay liquid even below the temperature where the polymer resides in the glassy state. Importantly, this surface layer is expected to have a very sharp interface with the underlying bulk. Here, by analyzing the penetration of n-hexane into polystyrene films, we report on the existence of a transition region, not observed by previous investigations, extending for 12 nm below the free surface. The presence of such a layer permits reconciling the behavior of interfacial layers with current models and has profound implications on the performance of ultrathin membranes. We show that the expected increase in the flux of the permeating species is actually overruled by nanoconfinement.

The nanostructure and microstructure of SiC surface layers deposited by MWCVD and ECRCVD

NASA Astrophysics Data System (ADS)

Dul, K.; Jonas, S.; Handke, B.

2017-12-01

Scanning electron microscopy (SEM) and Atomic force microscopy (AFM) have been used to investigate ex-situ the surface topography of SiC layers deposited on Si(100) by Microwave Chemical Vapour Deposition (MWCVD) -S1,S2 layers and Electron Cyclotron Resonance Chemical Vapor Deposition (ECRCVD) - layers S3,S4, using silane, methane, and hydrogen. The effects of sample temperature and gas flow on the nanostructure and microstructure have been investigated. The nanostructure was described by three-dimensional surface roughness analysis based on digital image processing, which gives a tool to quantify different aspects of surface features. A total of 13 different numerical parameters used to describe the surface topography were used. The scanning electron image (SEM) of the microstructure of layers S1, S2, and S4 was similar, however, layer S3 was completely different; appearing like grains. Nonetheless, it can be seen that no grain boundary structure is present in the AFM images.

Cooptimization of Adhesion and Power Conversion Efficiency of Organic Solar Cells by Controlling Surface Energy of Buffer Layers.

PubMed

Lee, Inhwa; Noh, Jonghyeon; Lee, Jung-Yong; Kim, Taek-Soo

2017-10-25

Here, we demonstrate the cooptimization of the interfacial fracture energy and power conversion efficiency (PCE) of poly[N-9'-heptadecanyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)] (PCDTBT)-based organic solar cells (OSCs) by surface treatments of the buffer layer. The investigated surface treatments of the buffer layer simultaneously changed the crack path and interfacial fracture energy of OSCs under mechanical stress and the work function of the buffer layer. To investigate the effects of surface treatments, the work of adhesion values were calculated and matched with the experimental results based on the Owens-Wendt model. Subsequently, we fabricated OSCs on surface-treated buffer layers. In particular, ZnO layers treated with poly[(9,9-bis(3'-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] (PFN) simultaneously satisfied the high mechanical reliability and PCE of OSCs by achieving high work of adhesion and optimized work function.

A theoretical analysis of the current-voltage characteristics of solar cells. [and their energy conversion efficiency

NASA Technical Reports Server (NTRS)

Dunbar, P. M.; Hauser, J. R.

1976-01-01

Various mechanisms which limit the conversion efficiency of silicon solar cells were studied. The effects of changes in solar cell geometry such as layer thickness on performance were examined. The effects of various antireflecting layers were also examined. It was found that any single film antireflecting layer results in a significant surface loss of photons. The use of surface texturing techniques or low loss antireflecting layers can enhance by several percentage points the conversion efficiency of silicon cells. The basic differences between n(+)-p-p(+) and p(+)-n-n(+) cells are treated. A significant part of the study was devoted to the importance of surface region lifetime and heavy doping effects on efficiency. Heavy doping bandgap reduction effects are enhanced by low surface layer lifetimes, and conversely, the reduction in solar cell efficiency due to low surface layer lifetime is further enhanced by heavy doping effects. A series of computer studies is reported which seeks to determine the best cell structure and doping levels for maximum efficiency.

Oxidation of InP nanowires: a first principles molecular dynamics study.

PubMed

Berwanger, Mailing; Schoenhalz, Aline L; Dos Santos, Cláudia L; Piquini, Paulo

2016-11-16

InP nanowires are candidates for optoelectronic applications, and as protective capping layers of III-V core-shell nanowires. Their surfaces are oxidized under ambient conditions which affects the nanowire physical properties. The majority of theoretical studies of InP nanowires, however, do not take into account the oxide layer at their surfaces. In this work we use first principles molecular dynamics electronic structure calculations to study the first steps in the oxidation process of a non-saturated InP nanowire surface as well as the properties of an already oxidized surface of an InP nanowire. Our calculations show that the O 2 molecules dissociate through several mechanisms, resulting in incorporation of O atoms into the surface layers. The results confirm the experimental observation that the oxidized layers become amorphous but the non-oxidized core layers remain crystalline. Oxygen related bonds at the oxidized layers introduce defective levels at the band gap region, with greater contributions from defects involving In-O and P-O bonds.

Electronically shielded solid state charged particle detector

DOEpatents

Balmer, D.K.; Haverty, T.W.; Nordin, C.W.; Tyree, W.H.

1996-08-20

An electronically shielded solid state charged particle detector system having enhanced radio frequency interference immunity includes a detector housing with a detector entrance opening for receiving the charged particles. A charged particle detector having an active surface is disposed within the housing. The active surface faces toward the detector entrance opening for providing electrical signals representative of the received charged particles when the received charged particles are applied to the active surface. A conductive layer is disposed upon the active surface. In a preferred embodiment, a nonconductive layer is disposed between the conductive layer and the active surface. The conductive layer is electrically coupled to the detector housing to provide a substantially continuous conductive electrical shield surrounding the active surface. The inner surface of the detector housing is supplemented with a radio frequency absorbing material such as ferrite. 1 fig.

Electronically shielded solid state charged particle detector

DOEpatents

Balmer, David K.; Haverty, Thomas W.; Nordin, Carl W.; Tyree, William H.

1996-08-20

An electronically shielded solid state charged particle detector system having enhanced radio frequency interference immunity includes a detector housing with a detector entrance opening for receiving the charged particles. A charged particle detector having an active surface is disposed within the housing. The active surface faces toward the detector entrance opening for providing electrical signals representative of the received charged particles when the received charged particles are applied to the active surface. A conductive layer is disposed upon the active surface. In a preferred embodiment, a nonconductive layer is disposed between the conductive layer and the active surface. The conductive layer is electrically coupled to the detector housing to provide a substantially continuous conductive electrical shield surrounding the active surface. The inner surface of the detector housing is supplemented with a radio frequency absorbing material such as ferrite.

[A review on research of land surface water and heat fluxes].

PubMed

Sun, Rui; Liu, Changming

2003-03-01

Many field experiments were done, and soil-vegetation-atmosphere transfer(SVAT) models were stablished to estimate land surface heat fluxes. In this paper, the processes of experimental research on land surface water and heat fluxes are reviewed, and three kinds of SVAT model(single layer model, two layer model and multi-layer model) are analyzed. Remote sensing data are widely used to estimate land surface heat fluxes. Based on remote sensing and energy balance equation, different models such as simplified model, single layer model, extra resistance model, crop water stress index model and two source resistance model are developed to estimate land surface heat fluxes and evapotranspiration. These models are also analyzed in this paper.

Combined friction force microscopy and quantum chemical investigation of the tribotronic response at the propylammonium nitrate-graphite interface.

PubMed

Li, H; Atkin, R; Page, A J

2015-06-28

The energetic origins of the variation in friction with potential at the propylammonium nitrate-graphite interface are revealed using friction force microscopy (FFM) in combination with quantum chemical simulations. For boundary layer lubrication, as the FFM tip slides energy is dissipated via (1) boundary layer ions and (2) expulsion of near-surface ion layers from the space between the surface and advancing tip. Simulations reveal how changing the surface potential changes the ion composition of the boundary and near surface layer, which controls energy dissipation through both pathways, and thus the friction.

Extending the Diffuse Layer Model of Surface Acidity Constant Behavior: IV. Diffuse Layer Charge/Potential Relationships

EPA Science Inventory

Most current electrostatic surface complexation models describing ionic binding at the particle/water interface rely on the use of Poisson - Boltzmann (PB) theory for relating diffuse layer charge densities to diffuse layer electrostatic potentials. PB theory is known to contain ...

Contact mechanics for layered materials with randomly rough surfaces.

PubMed

Persson, B N J

2012-03-07

The contact mechanics model of Persson is applied to layered materials. We calculate the M function, which relates the surface stress to the surface displacement, for a layered material, where the top layer (thickness d) has different elastic properties than the semi-infinite solid below. Numerical results for the contact area as a function of the magnification are presented for several cases. As an application, we calculate the fluid leak rate for laminated rubber seals.

Surface Phenomena During Plasma-Assisted Atomic Layer Etching of SiO2.

PubMed

Gasvoda, Ryan J; van de Steeg, Alex W; Bhowmick, Ranadeep; Hudson, Eric A; Agarwal, Sumit

2017-09-13

Surface phenomena during atomic layer etching (ALE) of SiO 2 were studied during sequential half-cycles of plasma-assisted fluorocarbon (CF x ) film deposition and Ar plasma activation of the CF x film using in situ surface infrared spectroscopy and ellipsometry. Infrared spectra of the surface after the CF x deposition half-cycle from a C 4 F 8 /Ar plasma show that an atomically thin mixing layer is formed between the deposited CF x layer and the underlying SiO 2 film. Etching during the Ar plasma cycle is activated by Ar + bombardment of the CF x layer, which results in the simultaneous removal of surface CF x and the underlying SiO 2 film. The interfacial mixing layer in ALE is atomically thin due to the low ion energy during CF x deposition, which combined with an ultrathin CF x layer ensures an etch rate of a few monolayers per cycle. In situ ellipsometry shows that for a ∼4 Å thick CF x film, ∼3-4 Å of SiO 2 was etched per cycle. However, during the Ar plasma half-cycle, etching proceeds beyond complete removal of the surface CF x layer as F-containing radicals are slowly released into the plasma from the reactor walls. Buildup of CF x on reactor walls leads to a gradual increase in the etch per cycle.

Evidence of a reduction reaction of oxidized iron/cobalt by boron atoms diffused toward naturally oxidized surface of CoFeB layer during annealing

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

Sato, Soshi, E-mail: sato.soshi@cies.tohoku.ac.jp; Honjo, Hiroaki; Niwa, Masaaki

2015-04-06

We have investigated the redox reaction on the surface of Ta/CoFeB/MgO/CoFeB magnetic tunnel junction stack samples after annealing at 300, 350, and 400 °C for 1 h using angle-resolved X-ray photoelectron spectroscopy for precise analysis of the chemical bonding states. At a capping tantalum layer thickness of 1 nm, both the capping tantalum layer and the surface of the underneath CoFeB layer in the as-deposited stack sample were naturally oxidized. By comparison of the Co 2p and Fe 2p spectra among the as-deposited and annealed samples, reduction of the naturally oxidized cobalt and iron atoms occurred on the surface of the CoFeB layer.more » The reduction reaction was more significant at higher annealing temperature. Oxidized cobalt and iron were reduced by boron atoms that diffused toward the surface of the top CoFeB layer. A single CoFeB layer was prepared on SiO{sub 2}, and a confirmatory evidence of the redox reaction with boron diffusion was obtained by angle-resolved X-ray photoelectron spectroscopy analysis of the naturally oxidized surface of the CoFeB single layer after annealing. The redox reaction is theoretically reasonable based on the Ellingham diagram.« less

Electron affinity of cubic boron nitride terminated with vanadium oxide

NASA Astrophysics Data System (ADS)

Yang, Yu; Sun, Tianyin; Shammas, Joseph; Kaur, Manpuneet; Hao, Mei; Nemanich, Robert J.

2015-10-01

A thermally stable negative electron affinity (NEA) for a cubic boron nitride (c-BN) surface with vanadium-oxide-termination is achieved, and its electronic structure was analyzed with in-situ photoelectron spectroscopy. The c-BN films were prepared by electron cyclotron resonance plasma-enhanced chemical vapor deposition employing BF3 and N2 as precursors. Vanadium layers of ˜0.1 and 0.5 nm thickness were deposited on the c-BN surface in an electron beam deposition system. Oxidation of the metal layer was achieved by an oxygen plasma treatment. After 650 °C thermal annealing, the vanadium oxide on the c-BN surface was determined to be VO2, and the surfaces were found to be thermally stable, exhibiting an NEA. In comparison, the oxygen-terminated c-BN surface, where B2O3 was detected, showed a positive electron affinity of ˜1.2 eV. The B2O3 evidently acts as a negatively charged layer introducing a surface dipole directed into the c-BN. Through the interaction of VO2 with the B2O3 layer, a B-O-V layer structure would contribute a dipole between the O and V layers with the positive side facing vacuum. The lower enthalpy of formation for B2O3 is favorable for the formation of the B-O-V layer structure, which provides a thermally stable surface dipole and an NEA surface.

Study on dynamic deformation synchronized measurement technology of double-layer liquid surfaces

NASA Astrophysics Data System (ADS)

Tang, Huiying; Dong, Huimin; Liu, Zhanwei

2017-11-01

Accurate measurement of the dynamic deformation of double-layer liquid surfaces plays an important role in many fields, such as fluid mechanics, biomechanics, petrochemical industry and aerospace engineering. It is difficult to measure dynamic deformation of double-layer liquid surfaces synchronously for traditional methods. In this paper, a novel and effective method for full-field static and dynamic deformation measurement of double-layer liquid surfaces has been developed, that is wavefront distortion of double-wavelength transmission light with geometric phase analysis (GPA) method. Double wavelength lattice patterns used here are produced by two techniques, one is by double wavelength laser, and the other is by liquid crystal display (LCD). The techniques combine the characteristics such as high transparency, low reflectivity and fluidity of liquid. Two color lattice patterns produced by laser and LCD were adjusted at a certain angle through the tested double-layer liquid surfaces simultaneously. On the basis of the refractive indexes difference of two transmitted lights, the double-layer liquid surfaces were decoupled with GPA method. Combined with the derived relationship between phase variation of transmission-lattice patterns and out-of plane heights of two surfaces, as well as considering the height curves of the liquid level, the double-layer liquid surfaces can be reconstructed successfully. Compared with the traditional measurement method, the developed method not only has the common advantages of the optical measurement methods, such as high-precision, full-field and non-contact, but also simple, low cost and easy to set up.

Structural features of the adsorption layer of pentacene on the graphite surface and the PMMA/graphite hybrid surface

NASA Astrophysics Data System (ADS)

Fadeeva, A. I.; Gorbunov, V. A.; Litunenko, T. A.

2017-08-01

Using the molecular dynamics and the Monte Carlo methods, we have studied the structural features and growth mechanism of the pentacene film on graphite and polymethylmethacrylate /graphite surfaces. Monolayer capacity and molecular area, optimal angles between the pentacene molecules and graphite and PMMA/graphite surfaces as well as the characteristic angles between the neighboring pentacene molecules in the adsorption layer were estimated. It is shown that the orientation of the pentacene molecules in the film is determined by a number of factors, including the surface concentration of the molecules, relief of the surface, presence or absence of the polymer layer and its thickness. The pentacene molecules adsorbed on the graphite surface keep a horizontal position relative to the long axis at any surface coverage/thickness of the film. In the presence of the PMMA layer on the graphite, the increase of the number of pentacene molecules as well as the thickness of the PMMA layer induce the change of molecular orientation from predominantly horizontal to vertical one. The reason for such behavior is supposed to be the roughness of the PMMA surface.

Tuning the magnetism of the top-layer FeAs on BaFe2As2 (001): First-principles study

NASA Astrophysics Data System (ADS)

Zhang, Bing-Jing; Liu, Kai; Lu, Zhong-Yi

2018-04-01

Magnetism may play an important role in inducing the superconductivity in iron-based superconductors. As a prototypical system, the surface of BaFe2As2 provides a good platform for studying related magnetic properties. We have designed systematic first-principles calculations to clarify the surface magnetism of BaFe2As2 (001), which previously has received little attention in comparison with surface structures and electronic states. We find that the surface environment has an important influence on the magnetic properties of the top-layer FeAs. For As-terminated surfaces, the magnetic ground state of the top-layer FeAs is in the staggered dimer antiferromagnetic (AFM) order, distinct from that of the bulk, while for Ba-terminated surfaces the collinear (single-stripe) AFM order is the most stable, the same as that in the bulk. When a certain coverage of Ba or K atoms is deposited onto the As-terminated surface, the calculated energy differences among different AFM orders for the top-layer FeAs on BaFe2As2 (001) can be much reduced, indicating enhanced spin fluctuations. To compare our results with available scanning tunneling microscopy (STM) measurements, we have simulated the STM images of several structural/magnetic terminations. Astonishingly, when the top-layer FeAs is in the staggered dimer AFM order, a stripe pattern appears in the simulated STM image even when the surface Ba atoms adopt a √{2 }×√{2 } structure, while a √{2 }×√{2 } square pattern comes out for the 1 ×1 full As termination. Our results suggest: (i) the magnetic state at the BaFe2As2 (001) surface can be quite different from that in the bulk; (ii) the magnetic properties of the top-layer FeAs can be tuned effectively by surface doping, which may likely induce superconductivity at the surface layer; (iii) both the surface termination and the AFM order in the top-layer FeAs can affect the STM image of BaFe2As2 (001), which needs to be taken into account when identifying the surface termination.

Frontolysis by surface heat flux in the Agulhas Return Current region with a focus on mixed layer processes: observation and a high-resolution CGCM

NASA Astrophysics Data System (ADS)

Ohishi, Shun; Tozuka, Tomoki; Komori, Nobumasa

2016-12-01

Detailed mechanisms for frontogenesis/frontolysis of the Agulhas Return Current (ARC) Front, defined as the maximum of the meridional sea surface temperature (SST) gradient at each longitude within the ARC region (40°-50°E, 55°-35°S), are investigated using observational datasets. Due to larger (smaller) latent heat release to the atmosphere on the northern (southern) side of the front, the meridional gradient of surface net heat flux (NHF) is found throughout the year. In austral summer, surface warming is weaker (stronger) on the northern (southern) side, and thus the NHF tends to relax the SST front. The weaker (stronger) surface warming, at the same time, leads to the deeper (shallower) mixed layer on the northern (southern) side. This enhances the frontolysis, because deeper (shallower) mixed layer is less (more) sensitive to surface warming. In austral winter, stronger (weaker) surface cooling on the northern (southern) side contributes to the frontolysis. However, deeper (shallower) mixed layer is induced by stronger (weaker) surface cooling on the northern (southern) side and suppresses the frontolysis, because the deeper (shallower) mixed layer is less (more) sensitive to surface cooling. Therefore, the frontolysis by the NHF becomes stronger (weaker) through the mixed layer processes in austral summer (winter). The cause of the meridional gradient of mixed layer depth is estimated using diagnostic entrainment velocity and the Monin-Obukhov depth. Furthermore, the above mechanisms obtained from the observation are confirmed using outputs from a high-resolution coupled general circulation model. Causes of model biases are also discussed.

Method of Fabricating Schottky Barrier solar cell

NASA Technical Reports Server (NTRS)

Stirn, R. J.; Yeh, Y. C. M. (Inventor)

1982-01-01

On a thin substrate of low cost material with at least the top surface of the substrate being electrically conductive is deposited a thin layer of heavily doped n-type polycrystalline germanium, with crystalline sizes in the submicron range. A passivation layer may be deposited on the substrate to prevent migration of impurities into the polycrystalline germanium. The polycrystalline germanium is recrystallized to increase the crystal sizes in the germanium layer to not less than 5 micros to serve as a base layer on which a thin layer of gallium arsenide is vapor epitaxially grown to a selected thickness. A thermally-grown oxide layer of a thickness of several tens of angstroms is formed on the gallium arsenide layer. A metal layer, of not more about 100 angstroms thick, is deposited on the oxide layer, and a grid electrode is deposited to be in electrical contact with the top surface of the metal layer. An antireflection coating may be deposited on the exposed top surface of the metal layer.

Analysis of modern and Pleistocene hydrologic exchange between Saginaw Bay (Lake Huron) and the Saginaw Lowlands area

USGS Publications Warehouse

Hoaglund, J. R.; Kolak, J.J.; Long, D.T.; Larson, G.J.

2004-01-01

Two numerical models, one simulating present groundwater flow conditions and one simulating ice-induced hydraulic loading from the Port Huron ice advance, were used to characterize both modern and Pleistocene groundwater exchange between the Michigan Basin and near-surface water systems of Saginaw Bay (Lake Huron) and the surrounding Saginaw Lowlands area. These models were further used to constrain the origin of saline, isotopically light groundwater, and porewater from the study area. Output from the groundwater-flow model indicates that, at present conditions, head in the Marshall aquifer beneath Saginaw Bay exceeds the modern lake elevation by as much as 21 m. Despite this potential for flow, simulated groundwater discharge through the Saginaw Bay floor constitutes only 0.028 m3 s-1 (???1 cfs). Bedrock lithology appears to regulate the rate of groundwater discharge, as the portion of the Saginaw Bay floor underlain by the Michigan confining unit exhibits an order of magnitude lower flux than the portion underlain by the Saginaw aquifer. The calculated shoreline discharge of groundwater to Saginaw Bay is also relatively small (1.13 m3 s-1 or ???40 cfs) because of low gradients across the Saginaw Lowlands area and the low hydraulic conductivities of lodgement tills and glacial-lake clays surrounding the bay. In contrast to the present groundwater flow conditions, the Port Huron ice-induced hydraulic-loading model generates a groundwater-flow reversal that is localized to the region of a Pleistocene ice sheet and proglacial lake. This area of reversed vertical gradient is largely commensurate with the distribution of isotopically light groundwater presently found in the study area. Mixing scenarios, constrained by chloride concentrations and ??18O values in porewater samples, demonstrate that a mixing event involving subglacial recharge could have produced the groundwater chemistry currently observed in the Saginaw Lowlands area. The combination of models and mixing scenarios indicates that structural control is a major influence on both the present and Pleistocene flow systems.

Channeling at the base of the lithosphere during the lateral flow of plume material beneath flow line hot spots

NASA Astrophysics Data System (ADS)

Sleep, Norman H.

2008-08-01

Chains of volcanic edifices lie along flow lines between plume-fed hot spots and the thin lithosphere at ridge axes. Discovery and Euterpe/Musicians Seamounts are two examples. An attractive hypothesis is that buoyant plume material flows along the base of the lithosphere perpendicular to isochrons. The plume material may conceivably flow in a broad front or flow within channels convectively eroded into the base to the lithosphere. A necessary but not sufficient condition for convective channeling is that the expected stagnant-lid heat flow for the maximum temperature of the plume material is comparable to the half-space surface heat flow of the oceanic lithosphere. Two-dimensional and three-dimensional numerical calculations confirm this inference. A second criterion for significant convective erosion is that it needs to occur before the plume material thins by lateral spreading. Scaling relationships indicate spreading and convection are closely related. Mathematically, the Nusselt number (ratio of convective to conductive heat flow in the plume material) scales with the flux (volume per time per length of flow front) of the plume material. A blob of unconfined plume material thus spreads before the lithosphere thins much and evolves to a slowly spreading and slowly convecting warm region in equilibrium with conduction into the base of the overlying lithosphere. Three-dimensional calculations illustrate this long-lasting (and hence observable) state of plume material away from its plume source. A different flow domain occurs around a stationary hot plume that continuously supplies hot material. The plume convectively erodes the overlying lithosphere, trapping the plume material near its orifice. The region of lithosphere underlain by plume material grows toward the ridge axis and laterally by convective thinning of the lithosphere at its edges. The hottest plume material channels along flow lines. Geologically, the regions of lithosphere underlain by either warm or hot plume material are likely to extend laterally away from the volcanic edifices whether or not channeling occurs.

Predicted liquefaction in the greater Oakland area and northern Santa Clara Valley during a repeat of the 1868 Hayward Fault (M6.7-7.0) earthquake

USGS Publications Warehouse

Holzer, Thomas L.; Noce, Thomas E.; Bennett, Michael J.

2010-01-01

Probabilities of surface manifestations of liquefaction due to a repeat of the 1868 (M6.7-7.0) earthquake on the southern segment of the Hayward Fault were calculated for two areas along the margin of San Francisco Bay, California: greater Oakland and the northern Santa Clara Valley. Liquefaction is predicted to be more common in the greater Oakland area than in the northern Santa Clara Valley owing to the presence of 57 km2 of susceptible sandy artificial fill. Most of the fills were placed into San Francisco Bay during the first half of the 20th century to build military bases, port facilities, and shoreline communities like Alameda and Bay Farm Island. Probabilities of liquefaction in the area underlain by this sandy artificial fill range from 0.2 to ~0.5 for a M7.0 earthquake, and decrease to 0.1 to ~0.4 for a M6.7 earthquake. In the greater Oakland area, liquefaction probabilities generally are less than 0.05 for Holocene alluvial fan deposits, which underlie most of the remaining flat-lying urban area. In the northern Santa Clara Valley for a M7.0 earthquake on the Hayward Fault and an assumed water-table depth of 1.5 m (the historically shallowest water level), liquefaction probabilities range from 0.1 to 0.2 along Coyote and Guadalupe Creeks, but are less than 0.05 elsewhere. For a M6.7 earthquake, probabilities are greater than 0.1 along Coyote Creek but decrease along Guadalupe Creek to less than 0.1. Areas with high probabilities in the Santa Clara Valley are underlain by young Holocene levee deposits along major drainages where liquefaction and lateral spreading occurred during large earthquakes in 1868 and 1906.

A New Kinetic Simulation Model with Self-Consistent Calculation of Regolith Layer Charging for Moon-Plasma Interactions

NASA Astrophysics Data System (ADS)

Han, D.; Wang, J.

2015-12-01

The moon-plasma interactions and the resulting surface charging have been subjects of extensive recent investigations. While many particle-in-cell (PIC) based simulation models have been developed, all existing PIC simulation models treat the surface of the Moon as a boundary condition to the plasma flow. In such models, the surface of the Moon is typically limited to simple geometry configurations, the surface floating potential is calculated from a simplified current balance condition, and the electric field inside the regolith layer cannot be resolved. This paper presents a new full particle PIC model to simulate local scale plasma flow and surface charging. A major feature of this new model is that the surface is treated as an "interface" between two mediums rather than a boundary, and the simulation domain includes not only the plasma but also the regolith layer and the bedrock underneath it. There are no limitations on the surface shape. An immersed-finite-element field solver is applied which calculates the regolith surface floating potential and the electric field inside the regolith layer directly from local charge deposition. The material property of the regolith layer is also explicitly included in simulation. This new model is capable of providing a self-consistent solution to the plasma flow field, lunar surface charging, the electric field inside the regolith layer and the bedrock for realistic surface terrain. This new model is applied to simulate lunar surface-plasma interactions and surface charging under various ambient plasma conditions. The focus is on the lunar terminator region, where the combined effects from the low sun elevation angle and the localized plasma wake generated by plasma flow over a rugged terrain can generate strongly differentially charged surfaces and complex dust dynamics. We discuss the effects of the regolith properties and regolith layer charging on the plasma flow field, dust levitation, and dust transport.

Surface Brillouin scattering study of the surface excitations in amorphous silicon layers produced by ion bombardment

NASA Astrophysics Data System (ADS)

Zhang, X.; Comins, J. D.; Every, A. G.; Stoddart, P. R.; Pang, W.; Derry, T. E.

1998-11-01

Thin amorphous silicon layers on crystalline silicon substrates have been produced by argon-ion bombardment of (001) silicon surfaces. Thermally induced surface excitations characteristic of this example of a soft-on-hard system have been investigated by surface Brillouin scattering (SBS) as a function of scattering-angle and amorphous-layer thickness. At large scattering angles or for sufficiently large layer thickness, a second peak is present in the SBS spectrum near the low-energy threshold for the continuum of bulk excitations of the system. The measured spectra are analyzed on the basis of surface elastodynamic Green's functions, which successfully simulate their detailed appearance and identify the second peak as either a Sezawa wave (true surface wave) or a pseudo-Sezawa wave (attenuated surface wave) depending on the scattering parameters. The attributes of the pseudo-Sezawa wave are described; these include its asymmetrical line shape and variation in intensity with k∥d (the product of the surface excitation wave vector and the layer thickness), and its emergence as the Sezawa wave from the low-energy side of the Lamb shoulder at a critical value of k∥d. Furthermore, the behavior of a pronounced minimum in the Lamb shoulder near the longitudinal wave threshold observed in the experiments is reported and is found to be in good agreement with the calculated spectra. The elastic constants of the amorphous silicon layer are determined from the velocity dispersion of the Rayleigh surface acoustic wave and the minimum in the Lamb shoulder.

Properties of Surface-Modification Layer Generated by Atomic Hydrogen Annealing on Poly(ethylene naphthalate) Substrate

NASA Astrophysics Data System (ADS)

Heya, Akira; Matsuo, Naoto

2008-01-01

The surface of a poly(ethylene naphthalate) (PEN) substrate was modified by atomic hydrogen annealing (AHA). In this method, a PEN substrate was exposed to atomic hydrogen generated by cracking hydrogen molecules on heated tungsten wire. The properties of the surface-modification layer by AHA were evaluated by spectroscopic ellipsometry. It is found that the thickness of the modified layer was 5 nm and that the modification layer has a low refractive index compared with the PEN substrate. The modification layer relates to the reduction reaction of the PEN substrate by AHA.

Use of chemical mechanical polishing in micromachining

DOEpatents

Nasby, Robert D.; Hetherington, Dale L.; Sniegowski, Jeffry J.; McWhorter, Paul J.; Apblett, Christopher A.

1998-01-01

A process for removing topography effects during fabrication of micromachines. A sacrificial oxide layer is deposited over a level containing functional elements with etched valleys between the elements such that the sacrificial layer has sufficient thickness to fill the valleys and extend in thickness upwards to the extent that the lowest point on the upper surface of the oxide layer is at least as high as the top surface of the functional elements in the covered level. The sacrificial oxide layer is then polished down and planarized by chemical-mechanical polishing. Another layer of functional elements is then formed upon this new planarized surface.

Method for improving performance of high temperature superconductors within a magnetic field

DOEpatents

Wang, Haiyan; Foltyn, Stephen R.; Maiorov, Boris A.; Civale, Leonardo

2010-01-05

The present invention provides articles including a base substrate including a layer of an oriented cubic oxide material having a rock-salt-like structure layer thereon; and, a buffer layer upon the oriented cubic oxide material having a rock-salt-like structure layer, the buffer layer having an outwardly facing surface with a surface morphology including particulate outgrowths of from 10 nm to 500 run in size at the surface, such particulate outgrowths serving as flux pinning centers whereby the article maintains higher performance within magnetic fields than similar articles without the necessary density of such outgrowths.

Meta-structure and tunable optical device including the same

DOEpatents

Han, Seunghoon; Papadakis, Georgia Theano; Atwater, Harry

2017-12-26

A meta-structure and a tunable optical device including the same are provided. The meta-structure includes a plurality of metal layers spaced apart from one another, an active layer spaced apart from the plurality of metal layers and having a carrier concentration that is tuned according to an electric signal applied to the active layer and the plurality of metal layers, and a plurality of dielectric layers spaced apart from one another and each having one surface contacting a metal layer among the plurality of metal layers and another surface contacting the active layer.

Density functional theory simulation of titanium migration and reaction with oxygen in the early stages of oxidation of equiatomic NiTi alloy.

PubMed

Nolan, Michael; Tofail, Syed A M

2010-05-01

The biocompatibility of NiTi shape memory alloys (SMA) has made possible applications in self-expandable cardio-vascular stents, stone extraction baskets, catheter guide wires and other invasive and minimally invasive biomedical devices. The NiTi intermetallic alloy spontaneously forms a thin passive layer of TiO(2), which provides its biocompatibility. The oxide layer is thought to form as the Ti in the alloy surface reacts with oxygen, resulting in a depletion of Ti in the subsurface region - experimental evidence indicates formation of a Ni-rich layer below the oxide film. In this paper, we study the initial stages of oxide growth on the (110) surface of the NiTi alloy to understand the formation of alloy/oxide interface. We initially adsorb atomic and molecular oxygen on the (110) surface and then successively add O(2) molecules, up to 2 monolayer of O(2). Oxygen adsorption always results in a large energy gain. With atomic oxygen, Ti is pulled out of the surface layer leaving behind a Ni-rich subsurface region. Molecular O(2), on the other hand adsorbs dissociatively and pulls a Ti atom farther out of the surface layer. The addition of further O(2) up to 1 monolayer is also dissociative and results in complete removal of Ti from the initial surface layer. When further O(2) is added up to 2 monolayer, Ti is pulled even further out of the surface and a single thin layer of composition O-Ti-O is formed. The electronic structure shows that the metallic character of the alloy is unaffected by interaction with oxygen and formation of the oxide layer, consistent with the oxide layer being a passivant. Copyright 2010 Elsevier Ltd. All rights reserved.

P-type surface effects for thickness variation of 2um and 4um of n-type layer in GaN LED

NASA Astrophysics Data System (ADS)

Halim, N. S. A. Abdul; Wahid, M. H. A.; Hambali, N. A. M. Ahmad; Rashid, S.; Ramli, M. M.; Shahimin, M. M.

2017-09-01

The internal quantum efficiency of III-Nitrides group, GaN light-emitting diode (LED) has been considerably limited due to the insufficient hole injection and this is caused by the lack of performance p-type doping and low hole mobility. The low hole mobility makes the hole less energetic, thus reduced the performance operation of GaN LED itself. The internal quantum efficiency of GaN-based LED with surface roughness (texture) can be changed by texture size, density, and thickness of GaN film or by the combined effects of surface shape and thickness of GaN film. Besides, due to lack of p-type GaN, attempts to look forward the potential of GaN LED relied on the thickness of n-type layer and surface shape of p-type GaN layer. This work investigates the characteristics of GaN LED with undoped n-GaN layer of different thickness and the surface shape of p-type layer. The LEDs performance is significantly altered by modifying the thickness and shape. Enhancement of n-GaN layer has led to the annihilation of electrical conductivity of the chip. Different surface geometry governs the emission rate extensively. Internal quantum efficiency is also predominantly affected by the geometry of n-GaN layer which subjected to the current spreading. It is recorded that the IQE droop can be minimized by varying the thickness of the active layer without amplifying the forward voltage. Optimum forward voltage (I-V), total emission rate relationship with the injected current and internal quantum efficiency (IQE) for 2,4 µm on four different surfaces of p-type layer are also reported in this paper.

Observations of the Evolution of Turbulent Dissipation within the Ocean Surface Boundary Layer: an OSMOSIS study

NASA Astrophysics Data System (ADS)

Lucas, N. S.; Allen, J.; Belcher, S. E.; Boyd, T.; Brannigan, L.; Inall, M.; Palmer, M.; Polton, J.; Rippeth, T. P.

2016-02-01

This study presents a new 9.5 day dataset showing the evolution of the Ocean Surface Boundary Layer (OSBL) and dissipation of turbulence kinetic energy (TKE), carried out as part of OSMOSIS[i], at a location in the North East Atlantic Ocean in September 2012. The TKE dissipation measurements were made using three methods; (i) repeated profiling between 100m and the surface by an Ocean Microstructure glider, (ii) three series of profiles made using a loosely tethered velocity microstructure glider and (iii) a moored pulse-pulse coherent high frequency ADCP. Supporting measurements show the evolution of the water column structure, including surface wave measurements from a TRIAXYS wave buoy. This data shows two distinct regimes; the first, spanning 4 days with relatively low winds, displays a distinct diurnal cycle with the deepening of the active mixing layer during the night which shoaled during the day. The second spanned a significant storm, (with maximum winds speeds reaching 20 m s-1 and significant wave heights reaching 6 m), during which, rather than a deepening of the mixed layer as predicted by classical theory, the primary effect was a broadening of the transition layer, similar to that found by Dohan and Davies (2011). During the storm, significant dissipation was observed throughout the surface mixed layer and into the transition layer, driving fluxes of heat downwards through the base of the surface mixed layer. [i] Ocean Surface Mixing and Submesoscale Interaction Study Dohan, K. & Davis, R.E., 2011. Mixing in the Transition Layer during Two Storm Events. Journal of Physical Oceanography. 41 (1). pp. 42-66.

Method and closing pores in a thermally sprayed doped lanthanum chromite interconnection layer

DOEpatents

Singh, Prabhakar; Ruka, Roswell J.

1995-01-01

A dense, substantially gas-tight electrically conductive interconnection layer is formed on an air electrode structure of an electrochemical cell by (A) providing an air electrode surface; (B) forming on a selected portion of the electrode surface, a layer of doped LaCrO.sub.3 particles doped with an element or elements selected from Ca, Sr, Ba, Mg, Co, Ni, Al and mixtures thereof by thermal spraying doped LaCrO.sub.3 particles, either by plasma arc spraying or flame spraying; (C) depositing a mixture of CaO and Cr.sub.2 O.sub.3 on the surface of the thermally sprayed layer; and (D) heating the doped LaCrO.sub.3 layer coated with CaO and Cr.sub.2 O.sub.3 surface deposit at from about 1000.degree. C. to 1200.degree. C. to substantially close the pores, at least at a surface, of the thermally sprayed doped LaCrO.sub.3 layer. The result is a dense, substantially gas-tight, highly doped, electrically conductive interconnection material bonded to the electrode surface. A solid electrolyte layer can be applied to the nonselected portion of the air electrode. A fuel electrode can be applied to the solid electrolyte, to form an electrochemical cell, for example for generation of electrical power.

Method and closing pores in a thermally sprayed doped lanthanum chromite interconnection layer

DOEpatents

Singh, P.; Ruka, R.J.

1995-02-14

A dense, substantially gas-tight electrically conductive interconnection layer is formed on an air electrode structure of an electrochemical cell by (A) providing an air electrode surface; (B) forming on a selected portion of the electrode surface, a layer of doped LaCrO{sub 3} particles doped with an element or elements selected from Ca, Sr, Ba, Mg, Co, Ni, Al and mixtures thereof by thermal spraying doped LaCrO{sub 3} particles, either by plasma arc spraying or flame spraying; (C) depositing a mixture of CaO and Cr{sub 2}O{sub 3} on the surface of the thermally sprayed layer; and (D) heating the doped LaCrO{sub 3} layer coated with CaO and Cr{sub 2}O{sub 3} surface deposit at from about 1,000 C to 1,200 C to substantially close the pores, at least at a surface, of the thermally sprayed doped LaCrO{sub 3} layer. The result is a dense, substantially gas-tight, highly doped, electrically conductive interconnection material bonded to the electrode surface. A solid electrolyte layer can be applied to the nonselected portion of the air electrode. A fuel electrode can be applied to the solid electrolyte, to form an electrochemical cell, for example for generation of electrical power. 5 figs.

Soro West: A non-seismically defined, fault cut-off prospect in the Papuan Fold and Thrust Belt, Papua New Guinea

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

Robinson, W.F.; Swift, C.M. Jr.

Soro West is a fault cut-off prospect located in the frontal portion of the Papuan Fold and Thrust Belt. Prospective Toro and Imburu sandstones are interpreted to be in the hanging wall of the Soro Thrust. Truncation against the thrust, both updip and through lateral ramps, provides the trapping mechanism. The Soro West Prospect was defined using geological, geochemical, remote sensing, and geophysical data. The definition and location of the trap is a primary risk and work was focused on this aspect. Surface geological data (lithology, strikes, and dips) topography and synthetic aperture radar imagery were incorporated into the evaluation.more » Statistical curvature analysis techniques helped define the shape of the structure and the locations of the lateral ramps. Strontium isotope analyses of Darai Limestone surface samples refined erosional levels using a locally-derived reference curve. Severe karst precludes the acquisition of coherent surface seismic data, so the primary geophysical tool used was magnetotellurics (MT). A detailed, pre-survey feasibility study defined expected responses from alternative structural models. The MT data demonstrated that the limestone at surface is underlain by thick conductive clastics and not another Darai Limestone sheet. The data also constrained the range of fault cut-off positions significantly. Multiple, three-dimensionally consistent, restorable alternative structural models were created using results from all analyses. These led to a positive assessment of the prospect and an exploratory test is to be drilled in 1996.« less

Observing the seasonal cycle of the upper ocean in the Ross Sea, Antarctica, with autonomous profiling floats

NASA Astrophysics Data System (ADS)

Porter, D. F.; Springer, S. R.; Padman, L.; Fricker, H. A.; Bell, R. E.

2017-12-01

The upper layers of the Southern Ocean where it meets the Antarctic ice sheet undergoes a large seasonal cycle controlled by surface radiation and by freshwater fluxes, both of which are strongly influenced by sea ice. In regions where seasonal sea ice and icebergs limit use of ice-tethered profilers and conventional moorings, autonomous profiling floats can sample the upper ocean. The deployment of seven Apex floats (by sea) and six ALAMO floats (by air) provides unique upper ocean hydrographic data in the Ross Sea close to the Ross Ice Shelf front. A novel choice of mission parameters - setting parking depth deeper than the seabed - limits their drift, allowing us to deploy the floats close to the ice shelf front, while sea ice avoidance algorithms allow the floats to to sample through winter under sea ice. Hydrographic profiles show the detailed development of the seasonal mixed layer close to the Ross front, and interannual variability of the seasonal mixed layer and deeper water masses on the central Ross Sea continental shelf. After the sea ice breakup in spring, a warm and fresh surface mixed layer develops, further warming and deepening throughout the summer. The mixed layer deepens, with maximum temperatures exceeding 0ºC in mid-February. By March, the surface energy budget becomes negative and sea ice begins to form, creating a cold, saline and dense surface layer. Once these processes overcome the stable summer stratification, convection erodes the surface mixed layer, mixing some heat downwards to deeper layers. There is considerable interannual variability in the evolution and strength of the surface mixed layer: summers with shorter ice-free periods result in a cooler and shallower surface mixed layer, which accumulates less heat than the summers with longer ice-free periods. Early ice breakup occurred in all floats in 2016/17 summer, enhancing the absorbed solar flux leading to a warmer surface mixed layer. Together, these unique measurements from autonomous profilers provide insight into the hydrographic state of the Ross Sea at the start of the spring period of sea-ice breakup, and how ocean mixing and sea ice interact to initiate the summer open-water season.

Epitaxial growth of silicon for layer transfer

DOEpatents

Teplin, Charles; Branz, Howard M

2015-03-24

Methods of preparing a thin crystalline silicon film for transfer and devices utilizing a transferred crystalline silicon film are disclosed. The methods include preparing a silicon growth substrate which has an interface defining substance associated with an exterior surface. The methods further include depositing an epitaxial layer of silicon on the silicon growth substrate at the surface and separating the epitaxial layer from the substrate substantially along the plane or other surface defined by the interface defining substance. The epitaxial layer may be utilized as a thin film of crystalline silicon in any type of semiconductor device which requires a crystalline silicon layer. In use, the epitaxial transfer layer may be associated with a secondary substrate.

Core-shell fuel cell electrodes

DOEpatents

Adzic, Radoslav; Bliznakov, Stoyan; Vukmirovic, Miomir

2017-12-26

Embodiments of the disclosure relate to membrane electrode assemblies. The membrane electrode assembly may include at least one gas-diffusion layer having a first side and a second side, and particle cores adhered to at least one of the first and second sides of the at least one gas-diffusion layer. The particle cores includes surfaces adhered to the at least one of the first and second sides of the at least one gas-diffusion layer and surfaces not in contact with the at least one gas-diffusion layer. Furthermore, a thin layer of catalytically atoms may be adhered to the surfaces of the particle cores not in contact with the at least one gas-diffusion layer.

Generating Inviscid and Viscous Fluid-Flow Simulations over an Aircraft Surface Using a Fluid-Flow Mesh

NASA Technical Reports Server (NTRS)

Rodriguez, David L. (Inventor); Sturdza, Peter (Inventor)

2013-01-01

Fluid-flow simulation over a computer-generated aircraft surface is generated using inviscid and viscous simulations. A fluid-flow mesh of fluid cells is obtained. At least one inviscid fluid property for the fluid cells is determined using an inviscid fluid simulation that does not simulate fluid viscous effects. A set of intersecting fluid cells that intersects the aircraft surface are identified. One surface mesh polygon of the surface mesh is identified for each intersecting fluid cell. A boundary-layer prediction point for each identified surface mesh polygon is determined. At least one boundary-layer fluid property for each boundary-layer prediction point is determined using the at least one inviscid fluid property of the corresponding intersecting fluid cell and a boundary-layer simulation that simulates fluid viscous effects. At least one updated fluid property for at least one fluid cell is determined using the at least one boundary-layer fluid property and the inviscid fluid simulation.

A stable lithium-rich surface structure for lithium-rich layered cathode materials

PubMed Central

Kim, Sangryun; Cho, Woosuk; Zhang, Xiaobin; Oshima, Yoshifumi; Choi, Jang Wook

2016-01-01

Lithium ion batteries are encountering ever-growing demand for further increases in energy density. Li-rich layered oxides are considered a feasible solution to meet this demand because their specific capacities often surpass 200 mAh g−1 due to the additional lithium occupation in the transition metal layers. However, this lithium arrangement, in turn, triggers cation mixing with the transition metals, causing phase transitions during cycling and loss of reversible capacity. Here we report a Li-rich layered surface bearing a consistent framework with the host, in which nickel is regularly arranged between the transition metal layers. This surface structure mitigates unwanted phase transitions, improving the cycling stability. This surface modification enables a reversible capacity of 218.3 mAh g−1 at 1C (250 mA g−1) with improved cycle retention (94.1% after 100 cycles). The present surface design can be applied to various battery electrodes that suffer from structural degradations propagating from the surface. PMID:27886178

Implementation of a diffusion convection surface evolution model in WallDYN

NASA Astrophysics Data System (ADS)

Schmid, K.

2013-07-01

In thermonuclear fusion experiments with multiple plasma facing materials the formation of mixed materials is inevitable. The formation of these mixed material layers is a dynamic process driven the tight interaction between transport in the plasma scrape off layer and erosion/(re-) deposition at the surface. To track this global material erosion/deposition balance and the resulting formation of mixed material layers the WallDYN code has been developed which couples surface processes and plasma transport. The current surface model in WallDYN cannot fully handle the growth of layers nor does it include diffusion. However at elevated temperatures diffusion is a key process in the formation of mixed materials. To remedy this shortcoming a new surface model has been developed which, for the first time, describes both layer growth/recession and diffusion in a single continuous diffusion/convection equation. The paper will detail the derivation of the new surface model and compare it to TRIDYN calculations.

Covalent attachment of a bioactive hyperbranched polymeric layer to titanium surface for the biomimetic growth of calcium phosphates

PubMed Central

Tsiourvas, D.; Arkas, M.; Diplas, S.; Mastrogianni, E.

2010-01-01

This work is investigating the chemical grafting on Ti surface of a polymer/calcium phosphate coating of improved adhesion for enhanced bioactivity. For this purpose, a whole new methodology was developed based on covalently attaching a hyperbranched poly(ethylene imine) layer on Ti surface able to promote calcium phosphate formation in a next deposition stage. This was achieved through an intermediate surface silanization step. The research included optimization both of the reaction conditions for covalently grafting the intermediate organosilicon and the subsequent hyperbranched poly(ethylene imine) layers, as well as of the conditions for the mechanical and chemical pretreatment of Ti surface before coating. The reaction steps were monitored employing FTIR and XPS analyses, whereas the surface morphology and structure of the successive coating layers were studied by SEM combined with EDS. The analysis confirmed the successful grafting of the hybrid layer which demonstrated very good ability for hydroxyapatite growth in simulated body fluid. PMID:21069559

Covalent attachment of a bioactive hyperbranched polymeric layer to titanium surface for the biomimetic growth of calcium phosphates.

PubMed

Tsiourvas, D; Tsetsekou, A; Arkas, M; Diplas, S; Mastrogianni, E

2011-01-01

This work is investigating the chemical grafting on Ti surface of a polymer/calcium phosphate coating of improved adhesion for enhanced bioactivity. For this purpose, a whole new methodology was developed based on covalently attaching a hyperbranched poly(ethylene imine) layer on Ti surface able to promote calcium phosphate formation in a next deposition stage. This was achieved through an intermediate surface silanization step. The research included optimization both of the reaction conditions for covalently grafting the intermediate organosilicon and the subsequent hyperbranched poly(ethylene imine) layers, as well as of the conditions for the mechanical and chemical pretreatment of Ti surface before coating. The reaction steps were monitored employing FTIR and XPS analyses, whereas the surface morphology and structure of the successive coating layers were studied by SEM combined with EDS. The analysis confirmed the successful grafting of the hybrid layer which demonstrated very good ability for hydroxyapatite growth in simulated body fluid.

Doped Y.sub.2O.sub.3 buffer layers for laminated conductors

DOEpatents

Paranthaman, Mariappan Parans [Knoxville, TN; Schoop, Urs [Westborough, MA; Goyal, Amit [Knoxville, TN; Thieme, Cornelis Leo Hans [Westborough, MA; Verebelyi, Darren T [Oxford, MA; Rupich, Martin W [Framingham, MA

2007-08-21

A laminated conductor includes a metallic substrate having a surface, a biaxially textured buffer layer supported by the surface of the metallic substrate, the biaxially textured buffer layer comprising Y.sub.2O.sub.3 and a dopant for blocking cation diffusion through the Y.sub.2O.sub.3, and a biaxially textured conductor layer supported by the biaxially textured buffer layer.

Titanium modified with layer-by-layer sol-gel tantalum oxide and an organodiphosphonic acid: a coating for hydroxyapatite growth.

PubMed

Arnould, C; Volcke, C; Lamarque, C; Thiry, P A; Delhalle, J; Mekhalif, Z

2009-08-15

Titanium and its alloys are widely used in surgical implants due to their appropriate properties like corrosion resistance, biocompatibility, and load bearing. Unfortunately when metals are used for orthopedic and dental implants there is the possibility of loosening over a long period of time. Surface modification is a good way to counter this problem. A thin tantalum oxide layer obtained by layer-by-layer (LBL) sol-gel deposition on top of a titanium surface is expected to improve biocorrosion resistance in the body fluid, biocompatibility, and radio-opacity. This elaboration step is followed by a modification of the tantalum oxide surface with an organodiphosphonic acid self-assembled monolayer, capable of chemically binding to the oxide surface, and also improving hydroxyapatite growth. The different steps of this proposed process are characterized by surfaces techniques like contact angle, X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM).

THE ROLE OF WATER IN PROTOPLASMIC PERMEABILITY AND IN ANTAGONISM

PubMed Central

Osterhout, W. J. V.

1956-01-01

The behavior of the cell depends to a large extent on the permeability of the outer non-aqueous surface layer of the protoplasm. This layer is immiscible with water but may be quite permeable to it. It seems possible that a reversible increase or decrease in permeability may be due to a corresponding increase or decrease in the water content of the non-aqueous surface layer. Irreversible increase in permeability need not be due primarily to increase in the water content of the surface layer but may be caused chiefly by changes in the protoplasm on which the surface layer rests. It may include desiccation, precipitation, and other alterations. An artificial cell is described in which the outer protoplasmic surface layer is represented by a layer of guaiacol on one side of which is a solution of KOH + KCl representing the external medium and on the other side is a solution of CO2 representing the protoplasm. The K+ unites with guaiacol and diffuses across to the artificial protoplasm where its concentration becomes higher than in the external solution. The guaiacol molecule thus acts as a carrier molecule which transports K+ from the external medium across the protoplasmic surface. The outer part of the protoplasm may contain relatively few potassium ions so that the outwardly directed potential at the outer protoplasmic surface may be small but the inner part of the protoplasm may contain more potassium ions. This may happen when potassium enters in combination with carrier molecules which do not completely dissociate until they reach the vacuole. Injury and recovery from injury may be studied by measuring the movements of water into and out of the cell. Metabolism by producing CO2 and other acids may lower the pH and cause local shrinkage of the protoplasm which may lead to protoplasmic motion. Antagonism between Na+ and Ca++ appears to be due to the fact that in solutions of NaCl the surface layer takes up an excessive amount of water and this may be prevented by the addition of suitable amounts of CaCl2. In Nitella the outer non-aqueous surface layer may be rendered irreversibly permeable by sharply bending the cell without permanent damage to the inner non-aqueous surface layer surrounding the vacuole. The formation of contractile vacuoles may be imitated in non-living systems. An extract of the sperm of the marine worm Nereis which contains a highly surface-active substance can cause the egg to divide. It seems possible that this substance may affect the surface layer of the egg and cause it to take up water. A surface-active substance has been found in all the seminal fluids examined including those of trout, rooster, bull, and man. Duponol which is highly surface-active causes the protoplasm of Spirogyra to take up water and finally dissolve but it can be restored to the gel state by treatment with Lugol solution (KI + I). The transition from gel to sol and back again can be repeated many times in succession. The behavior of water in the surface layer of the protoplasm presents important problems which deserve careful examination. PMID:13346047

S-Layer Protein-Based Biosensors.

PubMed

Schuster, Bernhard

2018-04-11

The present paper highlights the application of bacterial surface (S-) layer proteins as versatile components for the fabrication of biosensors. One technologically relevant feature of S-layer proteins is their ability to self-assemble on many surfaces and interfaces to form a crystalline two-dimensional (2D) protein lattice. The S-layer lattice on the surface of a biosensor becomes part of the interface architecture linking the bioreceptor to the transducer interface, which may cause signal amplification. The S-layer lattice as ultrathin, highly porous structure with functional groups in a well-defined special distribution and orientation and an overall anti-fouling characteristics can significantly raise the limit in terms of variety and the ease of bioreceptor immobilization, compactness of bioreceptor molecule arrangement, sensitivity, specificity, and detection limit for many types of biosensors. The present paper discusses and summarizes examples for the successful implementation of S-layer lattices on biosensor surfaces in order to give a comprehensive overview on the application potential of these bioinspired S-layer protein-based biosensors.

Chemical Patterning by Mechanical Removal of Aqueous Polymers

NASA Astrophysics Data System (ADS)

Barnett, Katherine; Knoebel, Jodi; Davis, Robert C.

2006-10-01

We are developing a new method for micro and nanoscale patterning of lipids and proteins on solid surfaces. A layer of polyethylene glycol (PEG) teminated polyallyl amine (PAA) was initially applied to a mica surface. The PEG surface is a low adhesion surface for proteins. Following polymer deposition an Atomic Force Microscope (AFM) tip was used to remove the polymer layer in desired regions. AFM imaging of the surface after mechanical polymer removal shows squares of exposed MICA surrounded by the PEG surface. The clean mica regions are now available for specific adsorption of lipid or protein layers.

Soil-landscape development and late Quaternary environmental change in coastal Estremadura, Portugal

NASA Astrophysics Data System (ADS)

Daniels, Michael; Haws, Jonathan; Benedetti, Michael; Bicho, Nuno

2015-04-01

This poster integrates soil-landscape analysis with archaeological survey and paleoenvironmental reconstruction. Soils in surface and buried contexts in Estremadura, Portugal, provide evidence of landscape stability and instability, relative age relationships between landforms, and general paleoenvironmental conditions during the late Quaternary. These factors provide insight into the distribution and condition of Paleolithic archaeological sites and help understand the record of human settlement in the region. Late Pleistocene and Holocene dunes extend inland approximately 10 km from coastal source regions. Surface soils in Holocene dunes under maritime pine (Pinus pinaster) forest exhibit A, E, C/Bh and A, C horizon sequences and classify as Quartzipsamments. Surface soils in late Pleistocene dunes exhibit A, E, Bh, Bhs, Bs horizon sequences and classify as Haplorthods. Both Pleistocene and Holocene dunes commonly bury a heavily weathered soil formed in calcareous sandstone. The boundary between underlying buried soils and overlying surface soils is characterized by a lag deposit of medium to coarse, moderately-rounded gravels, underlain immediately by subsurface Bt and Bss horizons. The lag deposit and absence of buried A horizons both indicate intense and/or prolonged surface erosion prior to burial by late Quaternary dunes. Soil-geomorphic relationships therefore suggest at least two distinct episodes of dune emplacement and subsequent landscape stability following an extensive episode late Pleistocene landscape instability and soil erosion. A conceptual model of soil-landscape evolution through the late Quaternary and Holocene results from the integration of soil profile data, proxy paleoenvironmental data, and the partial record of human settled as revealed in the archaeological record.

Ablation layers to prevent pitting in laser peening

DOEpatents

Hackel, Lloyd A

2016-08-09

A hybrid ablation layer that comprises a separate under layer is applied to a material to prevent pitting resulting from laser peening. The underlayer adheres to the surface of the workpiece to be peened and does not have bubbles and voids that exceed an acceptable size. One or more overlayers are placed over and in contact with the underlayer. Any bubbles formed under the over layers are insulated from the surface to be peened. The process significantly reduces the incidence of pits on peened surfaces.

Towards a delimitation of southwestern Nigeria into hydrological regions

NASA Astrophysics Data System (ADS)

Ogunkoya, O. O.

1988-05-01

Fifteen third-order drainage basins (1:50,000) on the Basement Complex rocks of southwestern Nigeria are classified into hydrological regions using hydrologic response parameters of average daily mean specific discharge ( QA); daily mean specific discharges equalled or exceeded 90% ( Q90), 50% ( Q50) and 10% ( Q10) of the study period; variability index of flow ( VI); recession constant ( K) of flow from peak discharge at the end of the rainy season to minimum discharge in the dry season; total annual runoff ( RO); total runoff within the dry season ( DSRO); dry season runoff as a percentage of total annual runoff (% DSRO); runoff coefficient ( ROC); and, number of days during the study period when there was no flow ( NFD). An ordination technique and a classification algorithm derived from cluster analysis technique and incorporating the analysis of variance (ANOVA) tests to determine the level of significance of the homogeneity of derived classes, were used to classify the fifteen basins into five hydrologically homogeneous regions. The constituent basins of each region were observed to share common basin geology. It was observed that those drainage basins having at least 50% of their basin area underlain by quartzitic rocks form two groups and have the most desirable or optimal hydrologic response patterns, desirability or optimality being in terms of ability to potentially meet water resource development requirements (i.e. high perennial discharge, low variability and large groundwater contribution to stream flow). The basins predominantly underlain by granite-gneisses and amphibolitic rocks have much poorer hydrologic response patterns. Hydrological regionalization in southwestern Nigeria appears to be influenced by drainage basin geology while percentage area of the basin underlain by massive quartzites could be used as an index of occurrence of desirable hydrologic response pattern.

Controls and variability of solute and sedimentary fluxes in Arctic and sub-Arctic Environments

NASA Astrophysics Data System (ADS)

Dixon, John

2015-04-01

Six major factors consistently emerge as controls on the spatial and temporal variability in sediment and solute fluxes in cold climates. They are climatic, geologic, physiographic or relief, biologic, hydrologic, and regolith factors. The impact of these factors on sediment and solute mass transfer in Arctic and sub-Arctic environments is examined. Comparison of non-glacierized Arctic vs. subarctic drainage basins reveals the effects of these controls. All drainage basins exhibit considerable variability in rates of sediment and solute fluxes. For the non-glacierized drainage basins there is a consistent increase in sediment mass transfer by slope processes and fluvial processes as relief increases. Similarly, a consistent increase in sediment mass transfer by slope and fluvial processes is observed as total precipitation increases. Similar patterns are also observed with respect to solute transport and relief and precipitation. Lithologic factors are most strongly observed in the contrast between volcanic vs. plutonic igneous bedrock substrates. Basins underlain by volcanic rocks display greater mass transfers than those underlain by plutonic rocks. Biologic influences are most strongly expressed by variations in extent of vegetation cover and the degree of human interference, with human impacted basins generating greater fluxes. For glacierized basins the fundamental difference to non-glacierized basins is an overall increase in mean annual mass transfers of sediment and a generally smaller magnitude solute transfer. The principal role of geology is observed with respect to lithology. Catchments underlain by limestone demonstrate substantially greater solute mass transfers than sediment transfer. The influence of relief is seen in the contrast in mass transfers between upland and lowland drainage basins with upland basins generating greater sediment and solute transfers than lowland basins. For glacierized basins the effects of biology and regolith appear to be largely overridden by the hydrologic impacts of glacierization.

InP solar cell with window layer

NASA Technical Reports Server (NTRS)

Jain, Raj K. (Inventor); Landis, Geoffrey A. (Inventor)

1994-01-01

The invention features a thin light transmissive layer of the ternary semiconductor indium aluminum arsenide (InAlAs) as a front surface passivation or 'window' layer for p-on-n InP solar cells. The window layers of the invention effectively reduce front surface recombination of the object semiconductors thereby increasing the efficiency of the cells.

Cloud and boundary layer interactions over the Arctic sea-ice in late summer

NASA Astrophysics Data System (ADS)

Shupe, M. D.; Persson, P. O. G.; Brooks, I. M.; Tjernström, M.; Sedlar, J.; Mauritsen, T.; Sjogren, S.; Leck, C.

2013-05-01

Observations from the Arctic Summer Cloud Ocean Study (ASCOS), in the central Arctic sea-ice pack in late summer 2008, provide a detailed view of cloud-atmosphere-surface interactions and vertical mixing processes over the sea-ice environment. Measurements from a suite of ground-based remote sensors, near surface meteorological and aerosol instruments, and profiles from radiosondes and a helicopter are combined to characterize a week-long period dominated by low-level, mixed-phase, stratocumulus clouds. Detailed case studies and statistical analyses are used to develop a conceptual model for the cloud and atmosphere structure and their interactions in this environment. Clouds were persistent during the period of study, having qualities that suggest they were sustained through a combination of advective influences and in-cloud processes, with little contribution from the surface. Radiative cooling near cloud top produced buoyancy-driven, turbulent eddies that contributed to cloud formation and created a cloud-driven mixed layer. The depth of this mixed layer was related to the amount of turbulence and condensed cloud water. Coupling of this cloud-driven mixed layer to the surface boundary layer was primarily determined by proximity. For 75% of the period of study, the primary stratocumulus cloud-driven mixed layer was decoupled from the surface and typically at a warmer potential temperature. Since the near-surface temperature was constrained by the ocean-ice mixture, warm temperatures aloft suggest that these air masses had not significantly interacted with the sea-ice surface. Instead, back trajectory analyses suggest that these warm airmasses advected into the central Arctic Basin from lower latitudes. Moisture and aerosol particles likely accompanied these airmasses, providing necessary support for cloud formation. On the occasions when cloud-surface coupling did occur, back trajectories indicated that these air masses advected at low levels, while mixing processes kept the mixed layer in equilibrium with the near-surface environment. Rather than contributing buoyancy forcing for the mixed-layer dynamics, the surface instead simply appeared to respond to the mixed-layer processes aloft. Clouds in these cases often contained slightly higher condensed water amounts, potentially due to additional moisture sources from below.

Cloud and boundary layer interactions over the Arctic sea ice in late summer

NASA Astrophysics Data System (ADS)

Shupe, M. D.; Persson, P. O. G.; Brooks, I. M.; Tjernström, M.; Sedlar, J.; Mauritsen, T.; Sjogren, S.; Leck, C.

2013-09-01

Observations from the Arctic Summer Cloud Ocean Study (ASCOS), in the central Arctic sea-ice pack in late summer 2008, provide a detailed view of cloud-atmosphere-surface interactions and vertical mixing processes over the sea-ice environment. Measurements from a suite of ground-based remote sensors, near-surface meteorological and aerosol instruments, and profiles from radiosondes and a helicopter are combined to characterize a week-long period dominated by low-level, mixed-phase, stratocumulus clouds. Detailed case studies and statistical analyses are used to develop a conceptual model for the cloud and atmosphere structure and their interactions in this environment. Clouds were persistent during the period of study, having qualities that suggest they were sustained through a combination of advective influences and in-cloud processes, with little contribution from the surface. Radiative cooling near cloud top produced buoyancy-driven, turbulent eddies that contributed to cloud formation and created a cloud-driven mixed layer. The depth of this mixed layer was related to the amount of turbulence and condensed cloud water. Coupling of this cloud-driven mixed layer to the surface boundary layer was primarily determined by proximity. For 75% of the period of study, the primary stratocumulus cloud-driven mixed layer was decoupled from the surface and typically at a warmer potential temperature. Since the near-surface temperature was constrained by the ocean-ice mixture, warm temperatures aloft suggest that these air masses had not significantly interacted with the sea-ice surface. Instead, back-trajectory analyses suggest that these warm air masses advected into the central Arctic Basin from lower latitudes. Moisture and aerosol particles likely accompanied these air masses, providing necessary support for cloud formation. On the occasions when cloud-surface coupling did occur, back trajectories indicated that these air masses advected at low levels, while mixing processes kept the mixed layer in equilibrium with the near-surface environment. Rather than contributing buoyancy forcing for the mixed-layer dynamics, the surface instead simply appeared to respond to the mixed-layer processes aloft. Clouds in these cases often contained slightly higher condensed water amounts, potentially due to additional moisture sources from below.

Solder for oxide layer-building metals and alloys

DOEpatents

Kronberg, James W.

1992-01-01

A low temperature solder and method for soldering an oxide layer-building metal such as aluminum, titanium, tantalum or stainless steel. The comosition comprises tin and zinc; germanium as a wetting agent; preferably small amounts of copper and antimony; and a grit, such as silicon carbide. The grit abrades any oxide layer formed on the surface of the metal as the germanium penetrates beneath and loosens the oxide layer to provide good metal-to-metal contact. The germanium comprises less than aproximatley 10% by weight of the solder composition so that it provides sufficient wetting action but does not result in a melting temperature above approximately 300.degree. C. The method comprises the steps rubbing the solder against the metal surface so the grit in the solder abrades the surface while heating the surface until the solder begins to melt and the germanium penetrates the oxide layer, then brushing aside any oxide layer loosened by the solder.