Science.gov

Sample records for 50-fm 91-m isobath

  1. 50 CFR 660.72 - Latitude/longitude coordinates defining the 50 fm (91 m) through 75 fm (137 m) depth contours.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 50 Wildlife and Fisheries 13 2014-10-01 2014-10-01 false Latitude/longitude coordinates defining.../longitude coordinates defining the 50 fm (91 m) through 75 fm (137 m) depth contours. Boundaries for RCAs are defined by straight lines connecting a series of latitude/longitude coordinates. This...

  2. 50 CFR 660.72 - Latitude/longitude coordinates defining the 50 fm (91 m) through 75 fm (137 m) depth contours.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 50 Wildlife and Fisheries 13 2012-10-01 2012-10-01 false Latitude/longitude coordinates defining.../longitude coordinates defining the 50 fm (91 m) through 75 fm (137 m) depth contours. Boundaries for RCAs are defined by straight lines connecting a series of latitude/longitude coordinates. This...

  3. 50 CFR 660.392 - Latitude/longitude coordinates defining the 50 fm (91 m) through 75 fm (137 m) depth contours.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 50 Wildlife and Fisheries 9 2010-10-01 2010-10-01 false Latitude/longitude coordinates defining.../longitude coordinates defining the 50 fm (91 m) through 75 fm (137 m) depth contours. Boundaries for RCAs are defined by straight lines connecting a series of latitude/longitude coordinates. This...

  4. 50 CFR 660.72 - Latitude/longitude coordinates defining the 50 fm (91 m) through 75 fm (137 m) depth contours.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 50 Wildlife and Fisheries 13 2013-10-01 2013-10-01 false Latitude/longitude coordinates defining.../longitude coordinates defining the 50 fm (91 m) through 75 fm (137 m) depth contours. Boundaries for RCAs are defined by straight lines connecting a series of latitude/longitude coordinates. This...

  5. 50 CFR 660.72 - Latitude/longitude coordinates defining the 50 fm (91 m) through 75 fm (137 m) depth contours.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 50 Wildlife and Fisheries 11 2011-10-01 2011-10-01 false Latitude/longitude coordinates defining.../longitude coordinates defining the 50 fm (91 m) through 75 fm (137 m) depth contours. Boundaries for RCAs are defined by straight lines connecting a series of latitude/longitude coordinates. This...

  6. 50 CFR 660.212 - Fixed gear fishery-prohibitions.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ..., subpart C): Thompson Seamount, President Jackson Seamount, Cordell Bank (50-fm (91-m) isobath), Harris... Davidson Seamount area (defined in § 660.75, subpart C). (d) Sablefish fisheries. (1) Take, retain,...

  7. 50 CFR 660.230 - Fixed gear fishery-management measures.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... Seamount, President Jackson Seamount, Cordell Bank (50 fm (91 m) isobath), Harris Point, Richardson Rock... Seamount EFH Area, which is defined by specific latitude and longitude coordinates at § 660.75. (e)...

  8. 50 CFR 660.230 - Fixed gear fishery-management measures.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... Seamount, President Jackson Seamount, Cordell Bank (50 fm (91 m) isobath), Harris Point, Richardson Rock... Seamount EFH Area, which is defined by specific latitude and longitude coordinates at § 660.75. (e)...

  9. 50 CFR 660.212 - Fixed gear fishery-prohibitions.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ..., subpart C): Thompson Seamount, President Jackson Seamount, Cordell Bank (50-fm (91-m) isobath), Harris... Davidson Seamount area (defined in § 660.75, subpart C). (d) Sablefish fisheries. (1) Take, retain,...

  10. 50 CFR 660.312 - Open access fishery-prohibitions.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ..., subpart C) within the EEZ in the following areas (defined in §§ 660.78 and 660.79): Thompson Seamount, President Jackson Seamount, Cordell Bank (50-fm (91-m) isobath), Harris Point, Richardson Rock, Scorpion... other gear that is deployed deeper than 500-fm (914-m), within the Davidson Seamount area (defined...

  11. On the nature of cross-isobath energy fluxes in topographically modified barotropic semidiurnal Kelvin waves

    NASA Astrophysics Data System (ADS)

    Zhang, Tianyi; Yankovsky, Alexander E.

    2016-05-01

    Continental shelf topography modifies a Kelvin wave into a hybrid Kelvin-edge wave with a nonzero across-isobath velocity and a phase speed that decreases with increasing wave number while the group velocity reaches a minimum at intermediate wave numbers. We model the modified semidiurnal Kelvin wave adjustment to alongshore changes in the shelf width. The model domain consists of two alongshore-uniform continental shelves of different widths adjoined through a 150 km long transition zone. The continental shelf and slope are adjacent to an ocean of a constant depth, allowing radiation of Poincaré waves. We consider three shelf widths of 150, 250, and 300 km, where properties of a zero mode at semidiurnal frequency change from Kelvin wave like to edge wave like. For each shelf width, a zero wave mode has its distinctive alongshore energy flux structure on the shelf. As the incident wave encounters a variable shelf width, the alongshore energy flux converges (diverges) on the shelf resulting in an offshore (onshore) energy flux over the continental slope. Furthermore, for a strongly convergent alongshore energy flux, the incident wave mode scatters into radiating Poincaré waves. On sufficiently wide shelves, a strong across-isobath energy flux comparable with the incident wave energy flux can be triggered even by relatively modest changes of shelf width. An energy flux divergence parameter De is defined, which scales with magnitude and direction of the energy flux across the continental slope. More than 50% of the incident energy flux scatters into modes radiating offshore when De is -1 or less.

  12. 15 CFR Appendix B to Subpart K of... - Line Representing the 50-Fathom Isobath Surrounding Cordell Bank

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 15 Commerce and Foreign Trade 3 2013-01-01 2013-01-01 false Line Representing the 50-Fathom Isobath Surrounding Cordell Bank B Appendix B to Subpart K of Part 922 Commerce and Foreign Trade... Cordell Bank National Marine Sanctuary Pt. 922, Subpt. K, App. B Appendix B to Subpart K of Part...

  13. 15 CFR Appendix B to Subpart K of... - Line Representing the 50-Fathom Isobath Surrounding Cordell Bank

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 15 Commerce and Foreign Trade 3 2014-01-01 2014-01-01 false Line Representing the 50-Fathom Isobath Surrounding Cordell Bank B Appendix B to Subpart K of Part 922 Commerce and Foreign Trade... Cordell Bank National Marine Sanctuary Pt. 922, Subpt. K, App. B Appendix B to Subpart K of Part...

  14. 15 CFR Appendix B to Subpart K of... - Line Representing the 50-Fathom Isobath Surrounding Cordell Bank

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 15 Commerce and Foreign Trade 3 2012-01-01 2012-01-01 false Line Representing the 50-Fathom Isobath Surrounding Cordell Bank B Appendix B to Subpart K of Part 922 Commerce and Foreign Trade... Cordell Bank National Marine Sanctuary Pt. 922, Subpt. K, App. B Appendix B to Subpart K of Part...

  15. 15 CFR Appendix B to Subpart K of... - Line Representing the 50-Fathom Isobath Surrounding Cordell Bank

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 15 Commerce and Foreign Trade 3 2011-01-01 2011-01-01 false Line Representing the 50-Fathom Isobath Surrounding Cordell Bank B Appendix B to Subpart K of Part 922 Commerce and Foreign Trade... Cordell Bank National Marine Sanctuary Pt. 922, Subpt. K, App. B Appendix B to Subpart K of Part...

  16. 15 CFR Appendix B to Subpart K of... - Line Representing the 50-Fathom Isobath Surrounding Cordell Bank

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 15 Commerce and Foreign Trade 3 2010-01-01 2010-01-01 false Line Representing the 50-Fathom Isobath Surrounding Cordell Bank B Appendix B to Subpart K of Part 922 Commerce and Foreign Trade... Cordell Bank National Marine Sanctuary Pt. 922, Subpt. K, App. B Appendix B to Subpart K of Part...

  17. Density-dependent variations of the along-isobath flow in the East Greenland Current from Fram Strait to Denmark Strait

    NASA Astrophysics Data System (ADS)

    Schlichtholz, Pawel

    2007-12-01

    The East Greenland Current (EGC) dynamically connects the Arctic Ocean to the North Atlantic on the western side of the Nordic Seas. Observations show that the speed of the EGC considerably varies along the East Greenland Slope (EGS). Here it is shown, using current meter data reported in the literature and climatological hydrographic fields, that velocity and transport variations along the EGS are supported by the cross-isobath component of the density-dependent geostrophic flow relative to the bottom. The relative flow impinging on (leaving) the EGS in a northern (southern) limb of the cyclonic circulation in the Nordic Seas strengthens (weakens) the along-isobath bottom geostrophic flow. Variations of the latter are clearly associated with along-isobath bottom density gradients. Current observations indicate an increase of the along-isobath bottom velocity from 79°N to 75°N equal to about 9 and 10 cm s-1 on the upper (1000 m isobath) and lower (2000 m isobath) EGS, respectively. Corresponding estimates based on bottom density distribution along the 1000 and 2000 m isobaths are grossly consistent with the observations given above though we obtain a higher increase (13 cm s-1) at 1000 m and lower increase (6 cm s-1) at 2000 m. Considering the variability of the system and the poor resolution of the observations we find this to be a very convincing result, demonstrating the power of the geostrophic approximation for such estimates.

  18. Eddy forced variations in on- and off-margin summertime circulation along the 1000-m isobath of the northern Gulf of Mexico, 2000-2003, and links with sperm whale distributions along the middle slope

    NASA Astrophysics Data System (ADS)

    Biggs, Douglas C.; Jochens, Ann E.; Howard, Matthew K.; DiMarco, Steven F.; Mullin, Keith D.; Leben, Robert R.; Muller-Karger, Frank E.; Hu, Chuanmin

    In summers 2000-2003, NOAA Ship Gordon Gunter and TAMU R/V Gyre dropped XBTs and logged ADCP data while carrying out visual and passive-acoustic surveys for sperm whales along the 1000-m isobath of the northern Gulf of Mexico. The ships also made CTD casts, particularly when/where the XBT and ADCP data indicated the ships were passing into or out of anticyclonic and/or cyclonic slope eddies. The fine-scale resolution of the ship surveys, when combined with the meso-scale resolution of remote sensing surveys of sea surface height and ocean color, document the summer-to-summer variability in the intensity and geographic location of Loop Current eddies, warm slope eddies, and areas of cyclonic circulation over this middle slope region of the northern Gulf of Mexico. These variations forced striking year-to-year differences in the locations along the 1000-m isobath where there was on-margin and off-margin flow, and in locations where sperm whales were encountered along the 1000-m isobath. For example, when there was on-margin flow into the Mississippi Canyon region in early summer 2003, sperm whales were very rarely seen or heard there. In contrast, later that summer and during other summers when flow was along-margin or off-margin there, sperm whales were locally abundant. In this report we describe how eddy-forced variations in on-margin and off-margin flow changed the meso-scale circulation along the 1000-m isobath, and we show that most sperm whales were encountered in regions of negative SSH and/or higher-than-average surface chlorophyll.

  19. 50 CFR 660.79 - EFH Conservation Areas off the Coast of California.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... to 40°27.53′ N. lat., 124°26.84′ W. long. (c) Mendocino Ridge. The boundary of the Mendocino Ridge... Conservation Area is located offshore of California′s Marin County defined by straight lines connecting all of... (91-m) isobath) EFH Conservation Area is located offshore of California′s Marin County defined...

  20. 50 CFR 660.399 - EFH Conservation Areas off the Coast of California.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... connecting back to 40°27.53′ N. lat., 124°26.84′ W. long. (c) Mendocino Ridge. The boundary of the Mendocino... Conservation Area is located offshore of California′s Marin County defined by straight lines connecting all of... (91-m) isobath) EFH Conservation Area is located offshore of California′s Marin County defined...

  1. 50 CFR 660.79 - EFH Conservation Areas off the Coast of California.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... to 40°27.53′ N. lat., 124°26.84′ W. long. (c) Mendocino Ridge. The boundary of the Mendocino Ridge... Conservation Area is located offshore of California′s Marin County defined by straight lines connecting all of... (91-m) isobath) EFH Conservation Area is located offshore of California′s Marin County defined...

  2. 50 CFR 660.330 - Open access fishery-management measures.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... coordinates at §§ 660.78 through 660.79: Thompson Seamount, President Jackson Seamount, Cordell Bank (50-fm... bottom contact gear is also prohibited within the Davidson Seamount EFH Area, which is defined...

  3. An analysis of the current deflection around Dongsha Islands in the northern South China Sea

    NASA Astrophysics Data System (ADS)

    Wang, Dongxiao; Wang, Qiang; Zhou, Weidong; Cai, Shuqun; Li, Li; Hong, Bo

    2013-01-01

    Based on the in situ data and ADCP observation in fall, it is found that a northeastward current at inter-middle level flows on the Northern South China Sea (NSCS) continental shelf. This current flows almost along the isobaths, and it deflects from the isobaths veering toward deep water when flowing over the Dongsha Islands. Geographic currents derived from the climatologic hydrography data (WOA01) and absolute dynamic topography (ADT) data confirm the deflection of the northeastward current on NSCS continent. A fine resolution regional ocean model which can well reproduce the large scale circulation in the NSCS is used to analyze the dynamic about the deflection. The vorticity term balances shows that JEBAR (Joint Effect of Baroclinicity and Relief) drives the water column to depart from the isobaths. To the east of the Dongsha Islands, the isopycnal is almost orthogonal to the isobaths. The joint effect of the topographic and the baroclinic effect supplies negative vorticity and drives the water column to deflect from the isobaths and veer to deeper water. Momentum analysis along the stream line shows that, when the sea water flows around the Dongsha islands, the pressure gradient along the isobath pushes the sea water to accelerate, and then the Coriolis force orthogonal to the isobath increases and overcomes the corresponding pressure gradient, which drives the water deflected from the isobath toward the deep sea.

  4. 50 CFR 665.799 - Area restrictions.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ....799 Wildlife and Fisheries FISHERY CONSERVATION AND MANAGEMENT, NATIONAL OCEANIC AND ATMOSPHERIC... Ocean Survey Chart Numbers 83116 and 83153; (2) Landward of the 50-fm (91.5-m) curve around Rose Atoll, as depicted on National Ocean Survey Chart Number 83484....

  5. 50 CFR 665.799 - Area restrictions.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ....799 Wildlife and Fisheries FISHERY CONSERVATION AND MANAGEMENT, NATIONAL OCEANIC AND ATMOSPHERIC... Ocean Survey Chart Numbers 83116 and 83153; (2) Landward of the 50-fm (91.5-m) curve around Rose Atoll, as depicted on National Ocean Survey Chart Number 83484....

  6. Amending reduced fish-meal feeds with marine lecithin, but not soy lecithin, improves the growth of juvenile cobia and may attenuate heightened responses to stress challenge.

    PubMed

    Trushenski, J; Schwarz, M; Pessoa, W V N; Mulligan, B; Crouse, C; Gause, B; Yamamoto, F; Delbos, B

    2013-02-01

    Sparing of marine resources in aquafeeds can be environmentally and economically advantageous; however, fish meal (FM) replacement can affect the production performance and physiological competence. Phospholipids are increasingly understood to be involved in maintaining growth and vigour in fish and may be deficient in reduced FM formulations. Accordingly, we evaluated the growth and stress tolerance of juvenile cobia fed typical (50% FM) or reduced FM feeds (12% FM) with or without phospholipid amendment [1% marine lecithin (12% FM + Marine PL) or soy lecithin (12% FM + Soy PL)] for 6 weeks in triplicate tanks (N = 3) in a recirculation aquaculture system. The 50% FM feed yielded significantly superior growth and growth efficiency in comparison with the 12% FM and 12% FM+ Soy PL feeds, but the 12% FM+ Marine PL feed yielded comparable results to 50% FM feed. A low-water stress challenge induced elevated plasma glucose, cortisol and lactate levels in all treatments. However, a significant interaction (diet × stress) effect suggested a lesser cortisol response among fish fed the 12% FM+ Marine PL and 50% FM diets. These findings demonstrate that growth performance and, perhaps, resilience of cobia raised on reduced FM feeds may be improved by the addition of marine-origin phospholipid to the diet. PMID:22106957

  7. A physical and biological context for Karenia brevis seed populations on the northwest Florida shelf during July 2009

    NASA Astrophysics Data System (ADS)

    McCulloch, Anita A.; Kamykowski, Daniel; Morrison, John M.; Thomas, Carrie J.; Pridgen, Katy Grabowski

    2013-07-01

    The current effort focuses on characterizing physical and biological conditions across the northwest Florida shelf during summer as they influence Karenia brevis distributions and phytoplankton/microphytobenthos community associations. Phytoplankton and benthic algal communities were examined in the context of cross-shelf hydrography and sediment conditions during July 2009 between the 20 and 65 m isobaths off Panama City, FL. A towed undulating profiler (SeaSciences Acrobat) mapped water column characteristics between near-surface and ˜1 m above the sediment. A CTD/rosette provided hydrographic profiles and collected water samples at 17 cross-shelf locations at selected depths for nutrient concentration, phytoplankton biomass determination, and chemotaxonomic and taxonomic phytoplankton identification. In addition, a CTD/rosette time series sample set was collected following a holey sock drogue set at ˜34 m along the ˜50 m isobath, and cores were collected at eight stations approximately along the 30, 40 and 55 m isobaths. Cross-shelf, a pycnocline existed at ˜10 m depth, the 1% light level penetrated to ˜45 m depth, and nitrate-nitrite (NO3-+NO2-) concentrations increased in the lower 10 m of the water column to the 50 m isobath and then below 40-m depth to the 65 m isobath. A chlorophyll a peak occurred near-bottom between the 25 and 35 m isobaths. Gyroxanthin dinoflagellates (GD) representing K. brevis occurred across the shelf in near-surface and near-bottom waters. Near-surface GD co-occurred with cyanophytes at low density in the upper 20 m of the water column where NO3-+NO2- concentrations were low. Above sediments in the euphotic zone, near-bottom GD were most abundant between the 25 and 35 m isobaths where the NO3-+NO2- concentrations were 1-4 µM and where microphytobenthos competed for nutrient sources. Below the euphotic zone, GD were present near-bottom to the 60 m isobath where NO3-+NO2- concentrations approached 6 µM. A pattern consistent with

  8. Dynamics of wind-driven upwelling off the northeastern coast of Hainan Island

    NASA Astrophysics Data System (ADS)

    Lin, Peigen; Cheng, Peng; Gan, Jianping; Hu, Jianyu

    2016-02-01

    Both observational and reanalysis sea surface temperature data reveal that upwelling occurs frequently off the northeastern coast of Hainan Island (downstream of the change in topography off Tongluo Cape), which cannot be attributed to the along-shelf wind alone. To identify dynamics of the upwelling, we conduct a numerical experiment using an idealized topography that is simplified from the actual topography off the eastern and northeastern coasts of Hainan Island. The result indicates that the upwelling downstream of the change in topography is associated with onshore cross-isobath transport. Analysis of the vertically integrated momentum balance shows that the upwelling-linked onshore transport is primarily intensified by the along-isobath barotropic pressure gradient force (PGT), but is weakened by the along-isobath baroclinic pressure gradient force (PGC). The along-isobath PGT is linked to the advection of relative vorticity, the bottom stress curl and the gradient of momentum flux in vorticity equation. On the other hand, the PGC-related process is diagnosed by potential vorticity (PV) balance. Similar to the negative PV term from wind stress, the negative PV terms of the joint effect of baroclinicity and relief and the baroclinic bottom pressure torque weaken the upwelling-linked onshore transport downstream of the change in topography. The onshore transport is enhanced by the positive PV from bottom stress. In addition, the cross-isobath forces play an important role in upwelling intensification in the shallow nearshore region.

  9. 29 CFR 1926.760 - Fall protection.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    .... (2) Perimeter safety cables. On multi-story structures, perimeter safety cables shall be installed at... more than two stories or 30 feet (9.1 m) above a lower level, whichever is less; (2) Have completed... in a CDZ shall be protected from fall hazards of more than two stories or 30 feet (9.1 m),...

  10. 29 CFR 1926.760 - Fall protection.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    .... (2) Perimeter safety cables. On multi-story structures, perimeter safety cables shall be installed at... more than two stories or 30 feet (9.1 m) above a lower level, whichever is less; (2) Have completed... in a CDZ shall be protected from fall hazards of more than two stories or 30 feet (9.1 m),...

  11. 29 CFR 1926.760 - Fall protection.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    .... (2) Perimeter safety cables. On multi-story structures, perimeter safety cables shall be installed at... more than two stories or 30 feet (9.1 m) above a lower level, whichever is less; (2) Have completed... in a CDZ shall be protected from fall hazards of more than two stories or 30 feet (9.1 m),...

  12. 29 CFR 1926.760 - Fall protection.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    .... (2) Perimeter safety cables. On multi-story structures, perimeter safety cables shall be installed at... more than two stories or 30 feet (9.1 m) above a lower level, whichever is less; (2) Have completed... in a CDZ shall be protected from fall hazards of more than two stories or 30 feet (9.1 m),...

  13. Zooplankton and Karenia brevis in the Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Lester, Kristen M.; Heil, Cynthia A.; Neely, Merry B.; Spence, Danylle N.; Murasko, Susan; Hopkins, Thomas L.; Sutton, Tracey T.; Burghart, Scott E.; Bohrer, Richard N.; Remsen, Andrew W.; Vargo, Gabriel A.; Walsh, John J.

    2008-01-01

    Blooms of the toxic dinoflagellate Karenia brevis are common in the Gulf of Mexico, yet no in situ studies of zooplankton and K. brevis have been conducted there. Zooplankton abundance and taxonomic composition at non-bloom and K. brevis bloom stations within the Ecology of Harmful Algal Blooms (ECOHAB) study area were compared. At non-bloom stations, the most abundant species of zooplankton were Parvocalanus crassirostris, Oithona colcarva, and Paracalanus quasimodo at the 5-m isobath and P. quasimodo, O. colcarva, and Oikopleura dioica at the 25-m isobath. There was considerable overlap in dominance of zooplankton species between the 5 and 25-m isobaths, with nine species contributing to 90% of abundance at both isobaths. At stations within K. brevis blooms however, Acartia tonsa, Centropages velificatus, Temora turbinata, Evadne tergestina, O. colcarva, O. dioica, and P. crassirostris were dominant. Variations in abundance between non-bloom and bloom assemblages were evident, including the reduction in abundance of three key species within K. brevis blooms.

  14. 40 CFR 435.44 - Effluent limitations guidelines representing the degree of effluent reduction attainable by the...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... in 40 CFR 125.30-125.32, any existing point source subject to this subpart must achieve the following... Chlorine Minimum of 1 mg/l maintained as close to this concentration as possible. Sanitary M91M...

  15. Seasonal hypoxia regulates macrobenthic function and structure in the Mississippi Bight.

    PubMed

    Rakocinski, Chet F; Menke, Daneen P

    2016-04-15

    Hypoxic conditions are escalating to the east of the Mississippi River within the Mississippi Bight. The objective of this study was to examine changes in macrobenthic function and structure relative to seasonal hypoxia over a 3.5year period at the 10m (Site 6) and 20m (Site 8) isobaths within the Mississippi Bight. Seasonal hypoxia acted as a regular periodic disturbance during the study period, although the magnitude and duration of hypoxia varied inter-annually. Macrobenthic metrics revealed seasonal hypoxia effects on secondary production potential and community maturity, which agrees with previous studies. In addition, metrics were notably higher at the 20m isobath during the latter half of the study period, following the Deepwater Horizon (DwH) oil spill. This study confirms hypoxia as a major driver affecting the function and structure of soft-bottom macrobenthos in the Mississippi Bight. PMID:26920427

  16. Self-advection of density perturbations on a sloping continental shelf

    SciTech Connect

    Ping-Tung Shaw; Csanady, G.T.

    1983-05-01

    Bottom water movement on the continental shelf is modeled by the nonlinear interaction between longshore bottom geostrophic flow and the density field. Bottom geostrophic velocity, subject to linear steady momentum equations with linear bottom friction, can be generated by along-isobath density variations over a sloping bottom. At the same time, the density field is slowly advected by the velocity field. Away from boundary layers, the interplay is governed by Burgers' equation, which shows the formation and self-propulsion of strong density gradients along an isobath. The direction of propagation of a dense water blob is to have shallow water on the right- (left-) hand side facing downstream in the Northern (Southern) Hemisphere. The propagation of a light water blob is opposite to that of a dense water blob.

  17. Multiple-scale temporal variations and fluxes near a hydrothermal vent over the Southwest Indian Ridge

    NASA Astrophysics Data System (ADS)

    Chen, Xiaodan; Liang, Chujin; Dong, Changming; Zhou, Beifeng; Liao, Guanghong; Li, Junde

    2015-12-01

    A deep-ocean mooring system was deployed 100 m away from an active hydrothermal vent over the Southwest Indian Ridge (SWIR), where the water depth is about 2,800 m. One year of data on ocean temperature 50 m away from the ocean floor and on velocities at four levels (44 m, 40 m, 36 m, and 32 m away from the ocean floor) were collected by the mooring system. Multiplescale variations were extracted from these data: seasonal, tidal, super-tidal, and eddy scales. The semidiurnal tide was the strongest tidal signal among all the tidal constituents in both currents and temperature. With the multiple-scale variation presented in the data, a new method was developed to decompose the data into five parts in terms of temporal scales: time-mean, seasonal, tidal, super-tidal, and eddy. It was shown that both eddy and tidal heat (momentum) fluxes were characterized by variation in the bottom topography: the tidal fluxes of heat and momentum in the along-isobath direction were much stronger than those in the cross-isobath direction. For the heat flux, eddy heat flux was stronger than tidal heat flux in the cross-isobath direction, while eddy heat flux was weaker in the along-isobath direction. For the momentum flux, the eddy momentum flux was weaker than tidal momentum flux in both directions. The eddy momentum fluxes at the four levels had a good relationship with the magnitude of mean currents: it increased with the mean current in an exponential relationship.

  18. Relationship between the distribution pattern of right whales, Eubalaena glacialis, and satellite-derived sea surface thermal structure in the Great South Channel

    NASA Astrophysics Data System (ADS)

    Brown, C. W.; Winn, H. E.

    1989-03-01

    Right whales (Eubalaena glacialis) were sighted during random aerial transects over the Great South Channel region located between Georges Bank and Cape Cod in April to July in 1979-1981, 1984 and 1985. Sightings were superimposed on satellite AVHRR (Advanced Very High Resolution Radiometer) imagery of the same or approximate date to describe the whale's distribution pattern in relation to the thermal front, the 100 m isobath and sea surface temperature (SST) characteristics within the region. The majority of whales occurred north of the thermal front in the warmer, more stratified waters of the Gulf of Maine. Within the Great South Channel region, whales are not limited to a given surface isotherm. As would be expected from a stratified water mass, SST at whale sightings in the Gulf of Maine did not differ significantly from the median SST of those waters, and the horizontal SST gradient at whale sightings was not higher than background values. The SST did differ significantly from the median SST of the entire area sampled. Whales are distributed non-randomly about, and are in close proximity to, the 100 m isobath and the thermal front. The results indicate that whales were not found in areas where surface signatures of upwelling on or at spatial scales greater than 1 km 2 are present. The proximity of whale sightings to the isobath and the front suggests that frontal features and/or associated phenomena play an important role in the distribution pattern of right whales in the Great South Channel region.

  19. Suspended sediment on the Amazon continental shelf, and its relationship to sedimentary processes

    SciTech Connect

    Nittrouer, C.A.; DeMaster, D.J.; Curtin, T.B.

    1985-01-01

    Suspended-sediment concentrations (SSC) commonly exceed 100 mg/1 on the inner shelf (<30 m water depth) near the mouth of the Amazon River. Vertical profiles of SSC generally reveal an exponential increase toward the sea bed, indicating resuspension of sediment. On the Amazon shelf, the presence of high SSC reflects the inhibition of sediment accumulation rather than the potential for accumulation. SSC becomes significant (>10 mg/1) landward of the 40-m isobath and generally increases toward shore, as a result of shoaling surface waves and intense tidal currents. A number of chemical components dissolved in river water and ocean water, whose removal is dependent on SSC, are concentrated in the sea bed in an along-shelf region centered about the 40-m isobath. Strong tidal currents create significant temporal variability of SSC on semi-diurnal time scales. The frequent resuspension and deposition of sediment causes physical mixing of the sea bed to dominate over biological mixing, and physical sedimentary structures to characterize much of the shelf. Suspended sediment is advected northwestward by the North Brazilian Coastal Current, with most of the transport occurring landward of the 10-m isobath.

  20. On the methods for the construction of seabed digital elevation models (using the example of the White Sea)

    NASA Astrophysics Data System (ADS)

    Nikiforov, S. L.; Koshel, S. M.; Frol, V. V.; Popov, O. E.; Levchenko, O. V.

    2015-03-01

    A digital elevation model (DEM) of the White Sea has been constructed based on navigational maps on different scales. The maps have been scanned, and their raster images have been processed. The isobaths have been vectorized, and attribute tables have been created. The vector layers have been transformed from map projections to geographical coordinates. The sheets have been edited and stapled. The geometry and attributes have been corrected. When constructing a DEM, it is important to choose an algorithm that will make it possible to maintain the bed forms expressed in the raw isobaths with maximum detail in the model. An original algorithm developed and implemented by the authors is used. It is based on the fast computation of the distances to the two nearest isobaths at different levels. Its main feature is the interpretation of the contour lines as linear vector objects. The comparison of the depths based on the constructed seabed DEM with depths measured during echo sounding in natural conditions shows their good agreement. Currently, not only the constructed seabed digital elevation model but also methodical and methodological bases of numerical simulations, including the new classification approaches to the terrain description, are relevant.

  1. High frequency sampling of the 1984 spring bloom within the mid-Atlantic Bight: Synoptic shipboard, aircraft, and in situ perspectives of the SEEP-I experiment

    NASA Technical Reports Server (NTRS)

    Walsh, J. J.; Wirick, C. D.; Pietrafesa, L. J.; Whitledge, T. E.; Hoge, F. E.; Swift, R. N.

    1986-01-01

    Moorings of current meters, thermistors, transmissometers, and fluorometers on the mid-Atlantic shelf, south of Long Island, suggest a cumulative seaward export of perhaps 0.35 g C/sq m/day between the 80 and 120 m isobaths during February-April 1984. Such a horizontal loss of algal carbon over the lower third of the water column would be 23 to 78% of the March-April 1984 primary production. This physical carbon loss is similar to daily grazing losses from zooplankton of 32-40% of the algal fixation of carbon. Metabolic demands of the benthos could be met by just the estimated fecal pellet flux, without direct consumption of algal carbon, while bacterioplankton needs could be served by excretory release of dissolved organic matter during photosynthesis. Sediment traps tethered 10 m off the bottom at the 120 m isobath and 50 m above the 500 m isobath caught as much as 0.16 to 0.26 g C /sq m/day during March-April 1984, in reasonable agreement with the flux estimated from the other moored instruments.

  2. Internal Tides in the Western Gulf of Maine During Summer:1996

    NASA Astrophysics Data System (ADS)

    Brown, W. S.; Yu, Z.

    2008-12-01

    The summer internal tide in Wilkinson Basin is described in terms of a set moored currents measured at depths of 4m, 80m, 150m and 220m respectively between late August and mid-October 1996. The summer mean currents at each level were about 3 cm/s and generally directed along-isobaths. Most of the current variance was due to the semidiurnal tides, with the external M2 tidal ellipses generally oriented across- isobath (310oT-130oT). The winter external tidal variability was removed from the total summer currents leaving a residual that is dominated by M2 surface-intensified internal tidal currents that are coherent with the external tide. The semidiurnal tidal band statistics explain a dominant M2 tidal response that consists of a strong depth-independent profile of nearly rectilinear external tidal currents oriented in the across-isobath direction (~320oT) plus a weaker of surface-intensified (i.e. depth-dependent or baroclinic) internal tidal currents that are coherent with the external tide. The current shear between 4m and 80m is consistent with the relatively shallow pycnocline. These internal tides are probably generated through the interaction of the external (or barotropic) tidal currents with the steep southeast-facing slope of Jeffrey's Bank. These highly nonlinear internal tidal waves (or sometimes called internal solitons) intermittently evolve into packets of higher frequency internal wave packets that are present in our 5-minute current records.

  3. Relative contributions of local wind and topography to the coastal upwelling intensity in the northern South China Sea

    NASA Astrophysics Data System (ADS)

    Wang, Dongxiao; Shu, Yeqiang; Xue, Huijie; Hu, Jianyu; Chen, Ju; Zhuang, Wei; Zu, TingTing; Xu, Jindian

    2014-04-01

    Topographically induced upwelling caused by the interaction between large-scale currents and topography was observed during four cruises in the northern South China Sea (NSCS) when the upwelling favorable wind retreated. Using a high-resolution version of the Princeton Ocean Model, we investigate relative contributions of local wind and topography to the upwelling intensity in the NSCS. The results show that the topographically induced upwelling is sensitive to alongshore large-scale currents, which have an important contribution to the upwelling intensity. The topographically induced upwelling is comparable with the wind-driven upwelling at surface and has a stronger contribution to the upwelling intensity than the local wind does at bottom in the near-shore shelf region. The widened shelf to the southwest of Shanwei and west of the Taiwan Banks intensifies the bottom friction, especially off Shantou, which is a key factor for topographically induced upwelling in terms of bottom Ekman transport and Ekman pumping. The local upwelling favorable wind enhances the bottom friction as well as net onshore transport along the 50 m isobath, whereas it has less influence along the 30 m isobath. This implies the local wind is more important in upwelling intensity in the offshore region than in the nearshore region. The contribution of local upwelling favorable wind on upwelling intensity is comparable with that of topography along the 50 m isobath. The effects of local upwelling favorable wind on upwelling intensity are twofold: on one hand, the wind transports surface warm water offshore, and as a compensation of mass the bottom current transports cold water onshore; on the other hand, the wind enhances the coastal current, and the bottom friction in turn increases the topographically induced upwelling intensity.

  4. The wind driven currents on the Middle Atlantic Bight inner shelf

    NASA Astrophysics Data System (ADS)

    Wong, Kuo-Chuin

    1999-05-01

    A set of month-long current meter data from two moorings deployed at the 20 and 30 m isobaths to the southeast of Atlantic City, New Jersey are examined to characterize the structure of the wind-induced subtidal currents in the Middle Atlantic Bight under summer time conditions. The wind stress and currents are dominated by variability at the 2-4 d time scales. The majority of the wind stress variance is oriented in the along-shelf direction (35°T), but the subtidal currents at both moorings also show substantial across-shelf variability, with the standard deviation of the across-shelf current component exceeding 50% of that of the along-shelf current component. Furthermore, there is an appreciable reduction in magnitude and a change in orientation of the subtidal current vector with depth. The currents from the mooring located at the 30 m isobath are significantly coherent with the wind stress, with surface current rotating clockwise and bottom current rotating anticlockwise of the wind. With an upwelling favorable wind, there is a significant offshore flow in the upper layer and an onshore flow in the lower layer, consistent with Ekman transport. The situation reverses with a downwelling favorable wind. The depth-averaged current is dominated by variability in the along-shelf direction. Wind stress and along-shelf surface slope are the leading terms in the depth-integrated along-shelf momentum balance, but bottom stress also plays an important role in the balance. The currents at the inner shelf mooring (20 m isobath) are much less coherent with the wind, particularly for the surface current. The reduced linear correlation between the wind and the observed subtidal current there may be caused by the influence of the buoyancy-driven coastal current originating from the Hudson River estuary to the north of the mooring site.

  5. Mean circulation in the coastal ocean off northeastern North America from a regional-scale ocean model

    NASA Astrophysics Data System (ADS)

    Chen, K.; He, R.

    2015-07-01

    A regional-scale ocean model was used to hindcast the coastal circulation over the Middle Atlantic Bight (MAB) and Gulf of Maine (GOM) from 2004 to 2013. The model was nested inside a data assimilative global ocean model that provided initial and open boundary conditions. Realistic atmospheric forcing, tides and observed river runoff were also used to drive the model. Hindcast solutions were compared against observations, which included coastal sea levels, satellite altimetry sea surface height, in situ temperature and salinity measurements in the GOM, and observed mean depth-averaged velocities. Good agreements with observations suggest that the hindcast model is capable of capturing the major circulation variability in the MAB and GOM. Time- and space-continuous hindcast fields were used to depict the mean circulation, along- and cross-shelf transport and the associated momentum balances. The hindcast confirms the presence of the equatorward mean shelf circulation, which varies from 2.33 Sv over the Scotian Shelf to 0.22 Sv near Cape Hatteras. Using the 200 m isobath as the shelf/slope boundary, the mean cross-shelf transport calculations indicate that the shelfbreak segments off the Gulf of Maine (including the southern flank of Georges Bank and the Northeast Channel) and Cape Hatteras are the major sites for shelf water export. The momentum analysis reveals that the along-shelf sea level difference from Nova Scotia to Cape Hatteras is about 0.36 m. The nonlinear advection, stress, and horizontal viscosity terms all contribute to the ageostrophic circulation in the along-isobath direction, whereas the nonlinear advection plays a dominant role in determining the ageostrophic current in the cross-isobath direction.

  6. Mean circulation in the coastal ocean off northeastern North America from a regional-scale ocean model

    NASA Astrophysics Data System (ADS)

    Chen, K.; He, R.

    2014-12-01

    A regional-scale ocean model was used to hindcast the coastal circulation over the Middle Atlantic Bight (MAB) and Gulf of Maine (GOM) from 2004 to 2013. The model was nested inside a data assimilative global ocean model that provided initial and open boundary conditions. Realistic atmospheric forcing, tides and observed river runoff were also used to drive the model. Hindcast solutions were compared against observations, which included coastal sea levels, satellite altimetry sea surface height, temperature and salinity time series in the GOM, glider transects in the MAB, and observed mean depth-averaged velocities by Lentz (2008a). Good agreements with observations suggest that the hindcast model is capable of capturing the major circulation variability in the MAB and GOM. Time- and space-continuous hindcast fields were used to depict the mean circulation, along- and cross-shelf transport and the associated momentum balances. The hindcast confirms the presence of the equatorward mean shelf circulation, which varies from 2.33 Sv at Scotian Shelf to 0.22 Sv near Cape Hatteras. Using the 200 m isobath as the shelf/slope boundary, the mean cross-shelf transport calculations indicate that the shelfbreak segments off the Gulf of Maine (including the southern flank of Georges Bank and the Northeast Channel) and Cape Hatteras are the major sites for shelf water export. The momentum analysis reveals that the along-shelf sea level difference from Nova Scotia to Cape Hatteras is about 0.36 m. The nonlinear advection, stress, and horizontal viscosity terms all contribute to the ageostrophic circulation in the along-isobath direction, whereas the nonlinear advection plays a dominant role in determining the ageostrophic current in the cross-isobath direction.

  7. Investigation of Northeastern North America Coastal Circulation Using a Nested Regional Circulation Hindcast Model

    NASA Astrophysics Data System (ADS)

    Chen, K.; He, R.

    2008-12-01

    A regional coastal circulation model was used to hindcast circulation over the middle Atlantic Bight (MAB) and Gulf of Maine (GOM) shelf from November 2003 to June 2008. Realistic atmospheric forcing, tidal harmonics and real-time river runoff data were used to drive the hindcast. In addition, this regional model was nested inside the data assimilative global HYCOM, which provides dynamically consistent and numerically accurate its initial and open boundary conditions. Model hindcast solutions were gauged against in situ observations, including coastal sea levels, satellite altimeter sea surface height, mooring observed temperature and salinity time series, glider hydrographic transects, and long term means of depth-averaged current analysis. Such data/model comparisons show the nested regional model is skillful in capturing major regional shelf circulation variability, lending confidence for using 4-year of time and space continuous hindcast fields (January 2004-December 2007) to depict shelf- wide circulation dynamics, along- and cross-shelf transport and the associated momentum balances. Model hindcast solutions confirm the existence of the equatorward shelf circulation with gradually decreased alongshore transport from north to south. Mean alongshelf current is characterized by a strong shelf-break jet, whereas the cross-shelf current is characterized by complex convergence and divergence on the shelf. Mean cross-shelf transports were estimated along 200-m isobath. Momentum balance analyses further nonlinear advection, stress and diffusion term all contribute to the ageostrophic circulation in the along- isobath directions, whereas in the across-isobath direction, the nonlinear advection is predominate. Our nested regional circulation model was also coupled with a 11-component ecosystem model. Some preliminary bio-physical modeling result will also be presented.

  8. Temporal and spatial distributions of dominant shrimp stocks and their relationship with the hydrological environment in the East China Sea

    NASA Astrophysics Data System (ADS)

    Lü, Huaqing; Song, Haitang; Bayly, Chris

    2007-10-01

    To provide a scientific and technological base for fishery administration, holding a moratorium on fishing, and combating habitat degradation, a shrimp stock survey was carried out in May, August, and November 1998 and in February 1999. The study was conducted in the area between 26°00' N and 33°00' N and to the west of 127°00' E in the East China Sea using a multi-sac trawl-net, with 115 stations being sampled. Up to 2001, we had found 121 species, which belong to 63 genera under 22 families, and 41 species are of high economic value and in great abundance. Nine shrimp species were of great economic importance, whose stock accounted for 76.8% of the demersal total. They were Parapenaeus fissuroides, Metapenaeopsis philippi, Palaemon gravieri, Metapenaeopsis barbata, Solenocera koelbeli, Solenocera crassicornis, Trachypenaeus curvirostris, Solenocera melantho and Parapenaeopsis hardwickii (listed in stock order). The nine species belong to the curythermal and eurysaline community and high thermal and high saline community, had different migration patterns and stocks, and their distribution patterns could be generally classified into three types: (1) dominating in the north or the south; (2) dominating to the north of and in the coast to the south of 30°00' N; and (3) dominating to the east of 60 m isobath, which were related to six water masses in the ECS near two lines, i.e., the 60 m isobath and 30°00'N latitudinal lines. Densely habited shrimps were found in all four seasons due to temperature and salinity frontiers and upwelling. The general stock density index was relatively higher in spring, summer, and autumn, when it surpassed 10 kg/h, while in winter, it was only 6.8 kg/h which might be caused by overfishing. According to the spawning areas of the nine species and their distribution patterns, to attain sustainable development of the shrimp fishery in the ECS, it is imperative to protect fishing areas and to hold a moratorium on catching to the west of

  9. Study of biological processes on the US North Atlantic slope and rise. Interim report November 1984-November 1985

    SciTech Connect

    Maciolek, N.; Hecker, B.; Butman, C.A.; Grassle, J.F.; Wade, W.B.

    1986-04-07

    Temporal and spatial variations in infaunal benthic community structure, grain-size composition of sediments, concentrations of hydrocarbons in sediments, and concentrations of total organic carbon, hydrogen, and nitrogen were studied at 14 stations over three sampling seasons. The station design also allowed comparison of gully and nongully environments, and canyon and noncanyon environments at several depths. Megafaunal populations were studied along a transect near the US/Canadian border and along the 2100-m isobath near Lydonia Canyon. Statistical analysis of the infauna indicated four major groups that corresponded to the four depth intervals sampled.

  10. Precise measurement of deuteron tensor analyzing powers with BLAST.

    PubMed

    Zhang, C; Kohl, M; Akdogan, T; Alarcon, R; Bertozzi, W; Booth, E; Botto, T; Calarco, J R; Clasie, B; Crawford, C; DeGrush, A; Dow, K; Farkhondeh, M; Fatemi, R; Filoti, O; Franklin, W; Gao, H; Geis, E; Gilad, S; Hasell, D; Karpius, P; Kolster, H; Lee, T; Maschinot, A; Matthews, J; McIlhany, K; Meitanis, N; Milner, R; Rapaport, J; Redwine, R; Seely, J; Shinozaki, A; Sindile, A; Širca, S; Six, E; Smith, T; Tonguc, B; Tschalär, C; Tsentalovich, E; Turchinetz, W; Xiao, Y; Xu, W; Zhou, Z-L; Ziskin, V; Zwart, T

    2011-12-16

    We report a precision measurement of the deuteron tensor analyzing powers T(20) and T(21) at the MIT-Bates Linear Accelerator Center. Data were collected simultaneously over a momentum transfer range Q=2.15-4.50 fm(-1) with the Bates Large Acceptance Spectrometer Toroid using a highly polarized deuterium internal gas target. The data are in excellent agreement with calculations in a framework of effective field theory. The deuteron charge monopole and quadrupole form factors G(C) and G(Q) were separated with improved precision, and the location of the first node of G(C) was confirmed at Q=4.19±0.05 fm(-1). The new data provide a strong constraint on theoretical models in a momentum transfer range covering the minimum of T(20) and the first node of G(C). PMID:22243068

  11. Macrolide-Resistant Mycoplasma pneumoniae, United States.

    PubMed

    Zheng, Xiaotian; Lee, Stella; Selvarangan, Rangaraj; Qin, Xuan; Tang, Yi-Wei; Stiles, Jeffrey; Hong, Tao; Todd, Kathleen; Ratliff, Amy E; Crabb, Donna M; Xiao, Li; Atkinson, T Prescott; Waites, Ken B

    2015-08-01

    Macrolide-resistant Mycoplasma pneumoniae (MRMP) is highly prevalent in Asia and is now being reported from Europe. Few data on MRMP are available in the United States. Using genotypic and phenotypic methods, we detected high-level MRMP in 13.2% of 91 M. pneumoniae--positive specimens from 6 US locations. PMID:26196107

  12. Macrolide-Resistant Mycoplasma pneumoniae, United States1

    PubMed Central

    Lee, Stella; Selvarangan, Rangaraj; Qin, Xuan; Tang, Yi-Wei; Stiles, Jeffrey; Hong, Tao; Todd, Kathleen; Ratliff, Amy E.; Crabb, Donna M.; Xiao, Li; Atkinson, T. Prescott; Waites, Ken B.

    2015-01-01

    Macrolide-resistant Mycoplasma pneumoniae (MRMP) is highly prevalent in Asia and is now being reported from Europe. Few data on MRMP are available in the United States. Using genotypic and phenotypic methods, we detected high-level MRMP in 13.2% of 91 M. pneumoniae­–positive specimens from 6 US locations. PMID:26196107

  13. Compost: a potential value-added product for dairy operations?

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The objective of this study was to evaluate the composting potential of various bedding materials that were previously used in experimental compost-bedded packs for dairy cows. Each material was placed in windrows (1.8 m high, 9.1 m long, and 2.3 m wide) from April 2007 to September 2007 and managed...

  14. Evaluation of partial water reuse systems used for Atlantic salmon smolt production at the White River National Fish Hatchery

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Eight of the existing 9.1 m (30 ft) diameter circular culture tanks at the White River National Fish Hatchery in Bethel, Vermont, were retrofitted and plumbed into two 8,000 L/min partial water reuse systems to help meet the region's need for Atlantic salmon (Salmo salar) smolt production. The part...

  15. Performance of a Zerovalent Iron Reactive Barrier for the Treatment of Arsenic in Groundwater: Part 1. Hydrogeochemical Studies

    EPA Science Inventory

    Developments and improvements of remedial technologies are needed to effectively manage arsenic contamination in groundwater at hazardous waste sites. In June 2005, a 9.1 m long, 14 m deep, and 1.8 to 2.4 m wide (in the direction of groundwater flow) pilot-scale permeable reacti...

  16. Oleic/Linoleic (O/L) acid ratios of Red River Runner peanut at three digging dates

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Peanut plots were established at Stillwater, OK in 2011. Each plot consisted of 4 rows each being 6.1 m in length and row spacing of 0.91 m. Plots were arranged in a randomized complete block design with five replications. Plots received a total of 69 cm of water (natural and sprinkler) during th...

  17. 78 FR 15669 - Marine Mammals: Alaska Harbor Seal Habitats

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-03-12

    ...) approach limit for humpback whales (Megaptera novaeangliae) in Hawaii (60 FR 3775, January 19, 1995). In... right whales (Eubalaena glacialis) closer than 500 yards (457 m) (62 FR 6729, February 13, 1997). In 2001, NMFS published a final rule (66 FR 29502, May 31, 2001) establishing a 100-yard (91-m)...

  18. Peanut, Cotton, and Corn Yield and Partial Net Income with Two Surface Drip Lateral Spacings

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Surface drip irrigation laterals were spaced next to crop rows (0.91 m) and in alternate row middles (1.83 m) to document crop yield and partial net economic returns compared with non-irrigated peanut (Arachis hypogaea), cotton (Gossypium hirsutum), and corn (Zea mays). A drip irrigation system was ...

  19. 29 CFR 1918.41 - Coaming clearances.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... hatch beams and hatch covers are not protected by a coaming at least 24-inch (.61 m) high, a taut... athwartship hatch beams, and at both ends of those hatches with fore and aft hatch beams, before intermediate deck hatch covers and hatch beams are removed or replaced. Exception: The three-foot (.91 m)...

  20. 29 CFR 1918.41 - Coaming clearances.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... hatch beams and hatch covers are not protected by a coaming at least 24-inch (.61 m) high, a taut... athwartship hatch beams, and at both ends of those hatches with fore and aft hatch beams, before intermediate deck hatch covers and hatch beams are removed or replaced. Exception: The three-foot (.91 m)...

  1. 29 CFR 1918.41 - Coaming clearances.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... hatch beams and hatch covers are not protected by a coaming at least 24-inch (.61 m) high, a taut... athwartship hatch beams, and at both ends of those hatches with fore and aft hatch beams, before intermediate deck hatch covers and hatch beams are removed or replaced. Exception: The three-foot (.91 m)...

  2. 29 CFR 1918.41 - Coaming clearances.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... hatch beams and hatch covers are not protected by a coaming at least 24-inch (.61 m) high, a taut... athwartship hatch beams, and at both ends of those hatches with fore and aft hatch beams, before intermediate deck hatch covers and hatch beams are removed or replaced. Exception: The three-foot (.91 m)...

  3. Antimicrobial, Antiparasitic and Cytotoxic Spermine Alkaloids from Albizia schimperiana

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Albizia schimperiana Oliv. (Leguminosae) is a tree distributed in the highland of Kenya, where it is used as a traditional medicine for the treatment of bacterial and parasitic infections, notably pneumonia and malaria, respectively. Bioassay guided isolation of the CH2Cl2–MeOH 1:1/ MeOH-H2O 9:1 (m...

  4. A modelling study of inter-annual variation of Kuroshio intrusion on the shelf of East China Sea

    NASA Astrophysics Data System (ADS)

    Li, Jiaxing; Wei, Hao; Zhang, Zhihua; Lu, Youyu

    2013-12-01

    Inter-annual variability of the Kuroshio water intrusion on the shelf of East China Sea (ECS) was simulated with a nested global and Northwest Pacific ocean circulation model. The model analysis reveals the influence of the variability of Kuroshio transport east of Taiwan on the intrusion to the northeast of Taiwan: high correlation ( r = 0.92) with the on-shore volume flux in the lower layer (50-200 m); low correlation ( r = 0.50) with the on-shore flux in the upper layer (0-50 m). Spatial distribution of correlations between volume fluxes and sea surface height suggests that inter-annual variability of the Kuroshio flux east of Taiwan and its subsurface water intruding to the shelf lag behind the sea surface height anomalies in the central Pacific at 162°E by about 14 months, and could be related to wind-forced variation in the interior North Pacific that propagates westward as Rossby waves. The intrusion of Kuroshio surface water is also influenced by local winds. The intruding Kuroshio subsurface water causes variations of temperature and salinity of bottom waters on the southern ECS shelf. The influence of the intruding Kuroshio subsurface water extends widely from the shelf slope northeast of Taiwan northward to the central ECS near the 60 m isobath, and northeastward to the region near the 90 m isobath.

  5. Frequent excitations of T waves by earthquakes in the South Mariana Arc

    NASA Astrophysics Data System (ADS)

    Chen, Po-Fei; Chen, Kai-Xun; Cheng, Hui-Yun

    2015-02-01

    We used broadband stations in Taiwan and on the Ryukyu Arc islands to investigate T waves induced by earthquakes in the Izu-Bonin-Mariana subduction zone. Of the 48 earthquakes that took place in 2005, 17 earthquakes exhibited T-wave signals consistent with predicted arrival times at stations. Of theses T-excited events, 13 were located in the South Mariana Arc, where the isobaths exhibit strong concave curvature, and were predominantly of normal faulting type. The energies of observed T waves were used quantitatively to evaluate the relative efficiency of receiver-side acoustic-elastic conversions by Gamma calculations. Results show that the steep slopes of offshore bathymetry together with nearly perpendicular angles of back azimuth relative to local isobaths are suitable conditions for T waves observations. In 2010, two clusters of repeated moderate earthquakes in the north and south ends of the Mariana Arc displayed stark contrasts in terms of T-wave excitations despite their normal faulting type. Examining of this discrepancy indicate that a specific curvature together with a specific radiation pattern accounts for the frequent excitations of T waves from shallow earthquakes in the South Mariana Arc.

  6. Phytoplankton community structure in local water types at a coastal site in north-western Bay of Bengal.

    PubMed

    Baliarsingh, S K; Srichandan, Suchismita; Lotliker, Aneesh A; Sahu, K C; Srinivasa Kumar, T

    2016-07-01

    A comprehensive analysis on seasonal distribution of phytoplankton community structure and their interaction with environmental variables was carried out in two local water types (type 1 < 30 m isobath and Type 2 > 30 m isobath) at a coastal site in north-western Bay of Bengal. Phytoplankton community was represented by 211 taxa (146 marine, 37 fresh, 2 brackish, 20 marine-fresh, and 6 marine-brackish-fresh) belonging to seven major groups including 45 potential bloom forming and 22 potential toxin producing species. The seasonal variability depicted enrichment of phytoplankton during pre-monsoon in both water types. Total phytoplankton abundance pattern observed with inter-annual shift during monsoon and post-monsoon period at both water types. In both water types, diatom predominance was observed in terms of species richness and abundance comprising of centric (82 sp.) and pennate (58 sp.) forms. Pennate diatoms, Thalassiothrix longissima and Skeletonema costatum preponderated in both the water types. The diatom abundance was higher in type 1 in comparison to type 2. In general, SiO4 found to fuel growth of the dominant phytoplankton group, diatom in both the water types despite comparative lower concentration of other macronutrients in type 2. PMID:27334343

  7. Tidal residual current and its role in the mean flow on the Changjiang Bank

    NASA Astrophysics Data System (ADS)

    Xuan, Jiliang; Yang, Zhaoqing; Huang, Daji; Wang, Taiping; Zhou, Feng

    2016-02-01

    The tidal residual current may play an important role in the mean flow in the Changjiang Bank region, in addition to other residual currents, such as the Taiwan Warm Current, the Yellow Sea Coastal Current, and the Yellow Sea Warm Current. In this paper, a detailed structure of the tidal residual current, in particular the meso-scale eddies, in the Changjiang Bank region is observed from model simulations, and its role in the mean flow is quantified using the well-validated Finite Volume Coastal Ocean Model. The tidal residual current in the Changjiang Bank region consists of two components: an anticyclonic regional-scale tidal residual circulation around the edge of the Changjiang Bank and some cyclonic meso-scale tidal residual eddies across the Changjiang Bank. The meso-scale tidal residual eddies occur across the Changjiang Bank and contribute to the regional-scale tidal residual circulation offshore at the northwest boundary and on the northeast edge of the Changjiang Bank, southeastward along the 50 m isobath. Tidal rectification is the major mechanism causing the tidal residual current to flow along the isobaths. Both components of the tidal residual current have significant effects on the mean flow. A comparison between the tidal residual current and the mean flow indicates that the contribution of the tidal residual current to the mean flow is greater than 50%.

  8. Double SST fronts observed from MODIS data in the East China Sea off the Zhejiang-Fujian coast, China

    NASA Astrophysics Data System (ADS)

    He, Shuangyan; Huang, Daji; Zeng, Dingyong

    2016-02-01

    We report a double coastal front system off the Zhejiang (Zhe) and Fujian (Min) Provinces in the East China Sea in winter. In addition to the well-known Zhe-Min offshore coastal front along 50 m isobath, a secondary near-shore coastal thermal front along 20 m isobath is also apparent in December and January. The fronts were observed by Moderate Resolution Imaging Spectroradiometer (MODIS) at monthly mean nighttime sea surface temperature (SST) during 2000-2013 in terms of SST gradients. Our results showed temporal and spatial variations of the two fronts as follows: (1) both offshore front and near-shore front often co-exist between 26.5°N and 29.5°N in December and between 28.0°N and 29.5°N in January. However, only the offshore front is apparent in November and February. (2) The near-shore front is narrow (4-16 km), while the offshore front is three to four times wider (16-48 km). (3) In contrast to the well-known offshore front which exists throughout the winter with a strong intensity, the near-shore front has a shorter lifetime with a weak intensity, and has been overlooked by previous studies. Finally, we proposed that the bottom bathymetric gradients may play an important role in the frontogenesis of the double fronts.

  9. Characterizing a Foraging Hotspot for Short-Finned Pilot Whales and Blainville’s Beaked Whales Located off the West Side of Hawai‘i Island by Using Tagging and Oceanographic Data

    PubMed Central

    Abecassis, Melanie; Polovina, Jeffrey; Baird, Robin W.; Copeland, Adrienne; Drazen, Jeffrey C.; Domokos, Reka; Oleson, Erin; Jia, Yanli; Schorr, Gregory S.; Webster, Daniel L.; Andrews, Russel D.

    2015-01-01

    Satellite tagging data for short-finned pilot whales (Globicephala macrorhynchus) and Blainville’s beaked whales (Mesoplodon densirostris) were used to identify core insular foraging regions off the Kona (west) Coast of Hawai‘i Island. Ship-based active acoustic surveys and oceanographic model output were used in generalized additive models (GAMs) and mixed models to characterize the oceanography of these regions and to examine relationships between whale density and the environment. The regions of highest density for pilot whales and Blainville’s beaked whales were located between the 1000 and 2500 m isobaths and the 250 and 2000 m isobaths, respectively. Both species were associated with slope waters, but given the topography of the area, the horizontal distribution of beaked whales was narrower and located in shallower waters than that of pilot whales. The key oceanographic parameters characterizing the foraging regions were bathymetry, temperature at depth, and a high density of midwater micronekton scattering at 70 kHz in 400–650 m depths that likely represent the island-associated deep mesopelagic boundary community and serve as prey for the prey of the whales. Thus, our results suggest that off the Kona Coast, and potentially around other main Hawaiian Islands, the deep mesopelagic boundary community is key to a food web that supports insular cetacean populations. PMID:26605917

  10. Maps Showing Distribution of Heavy Minerals on the South Texas Outer Continental Shelf

    USGS Publications Warehouse

    Shideler, Gerald L.; Flores, Romeo M.

    1976-01-01

    Heavy minerals constitute a natural resource which, under proper conditions, could have potential economic significance. The purpose of this report is to describe the heavy-mineral distribution in sea-floor sediments On the South Texas Outer Continental Shelf (OCS) within the northwestern Gulf of Mexico. The South Texas OCS encompasses approximately 24,500 sq km extending southward from Matagorda Bay to the U.S.-Mexico border (fig. 1). In a shoreward direction, the OCS extends from the 180-m isobath to the Federal-State water boundary (16.6 km offshore); however, the mineral distribution patterns presented in these maps have been extrapolated slightly shoreward of the l5-m isobath. This work was part of a regional environmental studies program in the South Texas OCS that was conducted in conjunction with the offshore petroleum-lease sales, under the auspices of the U.S. Bureau of Land Management. Some previous work on heavy minerals within the OCS had been done by van Andel and Poole (1960) and van Andel (1960); the fOrIner work was based on relatively few OCS samples and was part of a broader regional study of the northern Gulf of Mexico.

  11. A numerical analysis of landfall of the 1979 red tide of Karenia brevis along the west coast of Florida

    NASA Astrophysics Data System (ADS)

    Walsh, John J.; Haddad, Kenneth D.; Dieterle, Dwight A.; Weisberg, Robert H.; Li, Zhenjiang; Yang, Huijun; Muller-Karger, Frank E.; Heil, Cynthia A.; Bissett, W. Paul

    2002-01-01

    A simple ecological model, coupled to a primitive equation circulation model, is able to replicate the observed alongshore transport of the toxic dinoflagellate Karenia brevis on the West Florida shelf during a fall red tide in 1979. Initial land fall of these populations at the coast in our model matches shoreline data sets as well. The simulated vertical movement of K. brevis, in response to light-cued migration and nocturnal mixing, also mimics these aspects of the next fall red tide in 1980, suggesting that sunrise populations may provide the strongest surface signal, for detection of red tides by remote sensors aboard aircraft and satellites. Once a mature red tide is formed, a light-regulated maximal growth rate of 0.15 day -1, reflecting nutrient-limitation, and no other loss processes may be an adequate description of population dynamics above the 30-40 m isobaths, where blooms of K. brevis originate. Within shallow waters at the 10-m isobath, however, an apparent larger growth rate of 0.80 day -1—as a presumed consequence of frontal aggregations—must be offset by unknown processes of algal mortality. Likely candidates for cumulative, biomass-dependent losses are UV-B irradiation, microbial-induced lysis, and unselective grazing pressure from copepods, protozoans and heterotrophic dinoflagellates.

  12. Crystal alignments in the fast ice of Arctic Alaska

    SciTech Connect

    Weeks, W.F.; Gow, A.J.

    1980-02-20

    Field observations at 60 sites located in the fast or near-fast ice along a 1200-km stretch of the north coast of Alaska between the Bering Strait and Barter Island have shown that the great majority of the ice samples (95%) exhibit striking c axis alignments within the horizontal plane. In all cases the degree of preferred orientation increased with depth in the ice. Representative standard deviations around a mean direction in the horizontal plane are commonly less than +- 10/sup 0/ for samples collected near the bottom of the ice. At a given site the mean c axis direction X-bar/sub 0/ may vary as much as 20/sup 0/ with vertical location in the ice sheet. The c axis allignments in the nearshore region generally parallel the coast, with strong alignments occurring in the lagoon systems between the barrier islands and the coast and seaward of the barrier islands. In passes between islands and in entrances such as the opening to Kotzebue Sound the alignment is parallel to the channel. Only limited observations are available farther seaward over the inner (10- to 50-m isobaths) and outer (50-m isobath to shelf break) shelf regions. These indicate Ne-SW and E-W alignments, respectively, in the Beaufort Sea north of Prudhoe Bay.

  13. Characterizing a Foraging Hotspot for Short-Finned Pilot Whales and Blainville's Beaked Whales Located off the West Side of Hawai'i Island by Using Tagging and Oceanographic Data.

    PubMed

    Abecassis, Melanie; Polovina, Jeffrey; Baird, Robin W; Copeland, Adrienne; Drazen, Jeffrey C; Domokos, Reka; Oleson, Erin; Jia, Yanli; Schorr, Gregory S; Webster, Daniel L; Andrews, Russel D

    2015-01-01

    Satellite tagging data for short-finned pilot whales (Globicephala macrorhynchus) and Blainville's beaked whales (Mesoplodon densirostris) were used to identify core insular foraging regions off the Kona (west) Coast of Hawai'i Island. Ship-based active acoustic surveys and oceanographic model output were used in generalized additive models (GAMs) and mixed models to characterize the oceanography of these regions and to examine relationships between whale density and the environment. The regions of highest density for pilot whales and Blainville's beaked whales were located between the 1000 and 2500 m isobaths and the 250 and 2000 m isobaths, respectively. Both species were associated with slope waters, but given the topography of the area, the horizontal distribution of beaked whales was narrower and located in shallower waters than that of pilot whales. The key oceanographic parameters characterizing the foraging regions were bathymetry, temperature at depth, and a high density of midwater micronekton scattering at 70 kHz in 400-650 m depths that likely represent the island-associated deep mesopelagic boundary community and serve as prey for the prey of the whales. Thus, our results suggest that off the Kona Coast, and potentially around other main Hawaiian Islands, the deep mesopelagic boundary community is key to a food web that supports insular cetacean populations. PMID:26605917

  14. Observing Poleward Relaxation Flows Along the Central California Coast Using Gliders as Virtual Moorings

    NASA Astrophysics Data System (ADS)

    Washburn, L.; Aragon, D.; Haldeman, C.; Ohlmann, C.; Gotschalk, C.; Couto, N.; Miles, T. N.; Robbins, I.; Schofield, O.; Moline, M.; Kerfoot, J. M.

    2012-12-01

    Gliders and moorings were used in 2011 to observe warm propagating currents that follow relaxations of prevailing upwelling-favorable winds along the central CA coast. Additional measurements will occur in August and September 2012. We are experimenting with various sampling patterns to determine which best allow the gliders to maintain their horizontal positions in the presence of ambient coastal currents. The gliders, manufactured by Teledyne Webb, measure CTD variables and current velocity using externally mounted acoustic Doppler current profilers (ADCPs). ADCP data are processed following the method described by Todd et al. 2011. In September, 2011 two gliders were deployed offshore of Port San Luis, CA, first in 55 m water depth and then in 95 m. During their deployments within a 3-week period, the gliders observed the passage of a strong poleward relaxation flow. The flow followed a rapid decrease in equatorward wind stress from ~0.4 Pa to zero over 24 hr. Sequential warming at three moorings along the coast on the 15 m isobath revealed propagation of about 25 km/day. As the flow passed the gliders, alongshore currents reversed from ~0.15 m/s equatorward to ~0.3 m/s poleward over about 12 hours. ADCP-measured near-surface currents were consistent with simultaneous currents measured in the region by high frequency radar (~1 m depth). Near-surface temperatures at the gliders increased by 3 °C and near-surface salinity decreased by 0.25, consistent with source waters in the Southern California Bight. As of this writing two gliders are being prepared for deployment offshore of Pt. Sal, CA where two moorings have been deployed on the 15 m and 26 m isobaths. Soon after deployment, the gliders will profile around the mooring on the 26 m isobath to provide a validation data set for currents measured by the glider-mounted ADCPs. The gliders will then move offshore to measure poleward flow characteristics on the mid-shelf in water depths of 55m and 100 m. We also

  15. A 3-D prognostic numerical model study of the Georges Bank ecosystem. Part I: physical model1

    NASA Astrophysics Data System (ADS)

    Chen, Changsheng; Beardsley, Robert; Franks, Peter J. S.

    The influence of tidal forcing and tidal and wind mixing on circulation and stratification over Georges Bank and adjacent regions in the Gulf of Maine has been examined using the 3-D semi-implicit version of the Blumberg and Mellor (1987) primitive equation ocean-circulation model. The numerical domain covered the Gulf of Maine/Georges Bank region with an open boundary starting at the New Jersey coast and ending at the Nova Scotia coast, with increased spatial resolution over Georges Bank. Numerical experiments were conducted using both smoothed and non-smoothed high-resolution (15 s) bottom topography. The model was forced by specifying the M 2 elevation and phase on the open boundary, and several forms of the bottom roughness parameter zo were used. The model provided a reasonable simulation of the M 2 tidal elevations and currents. The model, when run as an initial value problem with early summer stratification, exhibited tidal mixing fronts around the 40-60 m isobath over Georges Bank and Nantucket Shoals, and 100-m isobath on Brown Bank. The formation of these tidal mixing fronts significantly enhanced the along-isobath tidal rectified current over Georges Bank and the other two shoal regions. A cool-water band developed within the frontal zone along the eastern and southern flanks of Georges Bank and Nantucket Shoal, and it became cooler owing to wind mixing and upwelling as a mean summer wind stress was added. Tidal mixing and turbulent dissipation varied in time asymmetrically over Georges Bank. Over Georges Bank, tidal mixing was generally characterized as a local 1-D balance between turbulent shear production and dissipation. The spatial structure of the tidal residual flow and local turbulent dissipation rate depended critically on the spatial resolution of the bottom topography and the spatial distribution of z0. Analysis of the 3-D momentum balance and the residual flow over the center of Georges Bank indicates that earlier results based on a 2-D cross

  16. Marine bird and cetacean associations with bathymetric habitats and shallow-water topographies: implications for trophic transfer and conservation

    NASA Astrophysics Data System (ADS)

    Yen, Peggy P. W.; Sydeman, William J.; Hyrenbach, K. David

    2004-09-01

    We investigated the aggregative response of marine birds and cetaceans to bathymetric features in central California over 4 years, 1996-1997 and 2001-2002. A total of 1700 km 2 of ocean habitat was surveyed over six cruises. We considered the distribution of the most abundant marine birds and mammals in relation to bathymetry. We focused our analyses on eight focal taxa: Cassin's auklet ( Ptychoramphus aleuticus), common murre ( Uria aalge), sooty shearwater ( Puffinus grieus), phalarope species (red, and red-necked: Phalaropus fulicaria, Phalaropus lobatus), Dall's porpoise ( Phocoenoides dalli), Pacific white-sided dolphin ( Lagenorhynchus obliquidens), humpback whale ( Megaptera novaeangliae), and Risso's dolphin ( Grampus griseus). We evaluated associations of top predators with seven bathymetric indices and three distance measurements to shallow-water topographies. The bathymetric descriptors included (1) median depth, (2) depth coefficient of variation, (3) contour index, and shortest distance to (4) the mainland, (5) the continental shelf-break (200-m isobath), (6) the continental slope (1000-m isobath), and (7) pelagic waters (3000-m isobath). The measurements of shallow water topographies included the shortest distance to: (8) the Cordell Bank seamount, (9) the Farallon Island Archipelago (a breeding colony for auklets and murres), and (10) Monterey Canyon. We documented two instances of spatial autocorrelation (for Cassin's auklet and common murre) at lags (distances) of 0-3 and 3-9 km, respectively, and accounted for this spatial pattern in analyses of habitat associations. We found similar relationships between cetaceans and bathymetric features at both interannual and weekly time scales. Seabirds revealed both persistent and variable relationships through time. For the resident breeding murres, we detected an interannual trend in habitat use, with these birds shifting their distribution offshore over time. Our study demonstrates that resident and

  17. Results of in vivo measurements of strontium-90 body-burden in Urals residents: analyses of data obtained 2006-2012

    SciTech Connect

    Tolstykh, E. I.; Bougrov, N. G.; Krivoshchapov, Victor A.; Shishkina, Elena A.; Shagina, N. B.; Degteva, M. O.; Anspaugh, L. R.; Napier, Bruce A.

    2012-06-01

    A part of the Urals territory was contaminated with 90Sr and 137Cs in the 1950s as a result of accidents at the "Mayak" Production Association. The paper describes the analysis of in vivo 90Sr measurements in Urals residents. The measurements were performed with the use of whole-body-counter SICH-9.1M in 2006-2012. Totally 5840 measurements for 4876 persons were performed from 2006 to 2012; maximal measured value was 24 kBq. Earlier, similar measurements were performed with SICH-9.1 (1974-1997). Comparison of the results obtained with SICH-9.1 and SICH-9.1M has shown a good agreement of the two data sets.

  18. Feeding flights of breeding double-crested cormorants at two Wisconsin colonies

    USGS Publications Warehouse

    Custer, T.W.; Bunck, C.

    1992-01-01

    Unmarked Double-crested Cormorants (Phalacrocorax auritus ) were followed by airplane from Cat Island and Spider Island, two nesting colonies in Wisconsin, to their first landing site. Cormorants flew an average of 2.0 km from Cat Island (maximum 40 km) and 2.4 km from Spider Island (maximum 12 km). The mean direction of landing sites differed seasonally for flights from Spider Island, but not from Cat Island, Cormorants generally landed in Green Bay or Lake Michigan and rarely landed in inland lakes or ponds. The most frequent water depth at landing sites for each colony was < 9.1 m. Water depths greater than or equal to 9.1 m were used less frequently than available within the maximum observed flight distance for each colony. The average flight speed for cormorants was 61 km/h.

  19. Bird population and habitat surveys in urban areas

    USGS Publications Warehouse

    DeGraaf, R.M.; Geis, A.D.; Healy, P.A.

    1991-01-01

    Breeding bird populations in six habitats in Columbia. MD, were studied to develop procedures suitable for measuring bird use of residential areas and to identify habitat characteristics that define the distribution of various common bird species. A procedure to measure bird use based on 4-min transect counts on plots measuring 91 m ? 91 m proved better than point counts. Transect counts reduced many of the problems associated with counting birds in urban areas, such as varying noise and visibility. Eighty percent of observations were recorded in the first 4 min. Habitat measurement procedures were examined also. It was found that a subsample of woody tree and shrub crown volumes made on 0.2 ha was highly correlated with similar measures made on 0.8-ha plots.

  20. Paleogeodynamics of the Bransfield Strait

    NASA Astrophysics Data System (ADS)

    Schreider, Al. A.

    2015-09-01

    The axes of zones split off between the northern continental slope of the Bransfield Basin and its southern slope belonging to the Antarctic Peninsula are reconstructed by determining the Euler poles and rotation angles that describe the splitting-off process. The revealed difference in the depths of joined isobaths of up to a hundred of meters reflects the different-scale slippage of peripheral parts of the continental crust from the main body of the Antarctic Peninsula along the plane of the through-lithosphere fracture. On the basis of paleogeodynamic reconstruction, it is possible to reconstruct also the initial bottom topography before the splitting off of the slipping fragments. It is shown that peripheral areas towered initially over the main surface of the shelf of the Antarctic Peninsula for many tens of meters. The locations of tectonic distortions along both borders of the strait due to transtension are reconstructed.

  1. Large-scale penetration of Gulf Stream water onto the continental shelf north of Cape Hatteras

    NASA Technical Reports Server (NTRS)

    Gawarkiewicz, Glen; Church, Thomas M.; Luther, George W., III; Ferdelman, Timothy G.; Caruso, Michael

    1992-01-01

    The presence of Gulf Stream water on the continental shelf as much as 60 km north of Cape Hatteras was observed during a hydrographic cruise in the summer of 1990. Gulf Stream water was concentrated at mid-depth between 10 and 30 m and penetrated the shelfbreak front which normally separates the shelf water from slope water and Gulf Stream water. Velocities of Gulf Stream water in the upper 110 m of the water column along the 1000 m isobath indicated a flow of 18 to 25 cm/s directed towards the northwest. Gulf Stream water on the shelf is considered to be associated with low values of fluorescence, transmissivity, and nutrient concentrations relative to adjacent shelf water.

  2. Cross-Shelf Exchange.

    PubMed

    Brink, K H

    2016-01-01

    Cross-shelf exchange dominates the pathways and rates by which nutrients, biota, and materials on the continental shelf are delivered and removed. This follows because cross-shelf gradients of most properties are usually far greater than those in the alongshore direction. The resulting transports are limited by Earth's rotation, which inhibits flow from crossing isobaths. Thus, cross-shelf flows are generally weak compared with alongshore flows, and this leads to interesting observational issues. Cross-shelf flows are enabled by turbulent mixing processes, nonlinear processes (such as momentum advection), and time dependence. Thus, there is a wide range of possible effects that can allow these critical transports, and different natural settings are often governed by different combinations of processes. This review discusses examples of representative transport mechanisms and explores possible observational and theoretical paths to future progress. PMID:26747520

  3. Insights into Mejerda basin hydrogeology, Tunisia

    NASA Astrophysics Data System (ADS)

    Guellala, Rihab; Tagorti, Mohamed Ali; Inoubli, Mohamed Hédi; Amri, Faouzi

    2012-09-01

    The present study concentrates on the interpretation of Vertical Electrical Soundings (VES) and well logs to understand the geometry and the functioning of the Ghardimaou multilayered aquifer, a potential target for water supply in the Mejerda basin (Tunisia). The analysis of isobath and isopach maps established in this study, shows a tectonic influence on the reservoirs structure; the Villafranchian folding and the NE-SW, and E-W normal faulting in the recent Quaternary created an aquifer system compartmentalized by raised and tilted blocks. Geoelectrical cross sections reveal that this structure influences the thickness of permeable formations and the groundwater circulation. These results will be useful for rationalizing the future hydrogeological research that will be undertaken in the Mejerda basin.

  4. Bathymetry and Acoustic Backscatter: Northern Santa Barbara Channel, Southern California

    USGS Publications Warehouse

    Dartnell, Pete; Finlayson, David; Conrad, Jamie; Cochrane, Guy; Johnson, Samuel

    2010-01-01

    In the summer of 2008, as part of the California Seafloor Mapping Program (CSMP) the U.S. Geological Survey, Coastal and Marine Geology mapped a nearshore region of the northern Santa Barbara Channel in Southern California (fig 1). The CSMP is a cooperative partnership between Federal and State agencies, Universities, and Industry to create a comprehensive coastal/marine geologic and habitat basemap series to support the Marine Life Protection Act (MLPA) inititive. The program is supported by the California Ocean Protection Council and the California Coastal Conservancy. The 2008 mapping collected high resolution bathymetry and acoustic backscatter data using a bathymetric side scan system within State waters from about the 10-m isobath out over 3-nautical miles. This Open-File Report provides these data in a number of different formats, as well as a summary of the mapping mission, maps of bathymetry and backscatter, and FGDC metadata.

  5. The impact of high-frequency current variability on dispersion off the eastern Antarctic Peninsula

    NASA Astrophysics Data System (ADS)

    TrasviñA, A.; Heywood, Karen J.; Renner, A. H. H.; Thorpe, S. E.; Thompson, A. F.; Zamudio, L.

    2011-11-01

    We present observations of high-frequency current variability on the continental shelf and the slope of the Antarctic Peninsula using Lagrangian surface drifters deployed as part of the Antarctic Drifter Experiment: Links to Isobaths and Ecosystems (ADELIE) project. Here we focus on high-frequency processes such as tides and inertial oscillations that are typically smoothed out of large-scale spatially averaged, and/or temporally averaged, observed current fields. We investigate the role that this class of motion plays in the transport of physical or biogeochemical properties. Lateral displacements on the shelf and slope are found to be larger than displacements in deeper waters where tidal currents are negligible. We apply this result in a parameterization of the lateral dispersion during an off-line drifter modeling study. The outcome is an improvement on the modeling of Lagrangian drifting particles compared with a standard random walk scheme.

  6. Polychlorinated biphenyl residues in some marine organisms from the Baie des Anglais (Baie-Comeau, Quebec, Saint-Lawrence Estuary

    SciTech Connect

    Delval, C.; Fournier, S.; Vigneault, Y.

    1986-12-01

    The main source of PCB's in the Baie des Anglais comes from a pseudo lagoon which is located upstream from the Anse au Moulin immediately below an aluminum plant. Organic matter in suspension coming from industrial wastes from baie-Comeau is likely responsible for the binding of PCB's. However due to hydrodynamic factors in the Baie des Anglais, contaminants stay only a short time in the littoral area and are evacuated to the southeast, where they accumulate at 80 m depth. Another source of contamination is the accumulation of dredging spoils at the entrance of the Anse au Moulin above the 40 m isobath. The contaminated sediments are resuspended by storm wave action. The work described in this paper was conducted in order to determine the extent of PCB bioaccumulation in two molluscs species (Mytilus edulis L. and Buccinum undatum L.) and two fish species (Clupea harengus harengus and Anguilla rostrata) from the Baie des Anglais (Baie-Comeau, Quebec).

  7. Studies of the inner shelf and coastal sedimentation environment of the Beaufort Sea from ERTS-A

    NASA Technical Reports Server (NTRS)

    Reimnitz, E. (Principal Investigator); Barnes, P. W.; Toimil, L. J.; Harden, D.

    1976-01-01

    The author has identified the following significant results. Shearing periodically occurs between the westward moving pack ice (3 to 10 km/d) within the Pacific Gyre and the fast ice along the coast, forming major grounded shear and pressure ridges between the 10 to 40 m isobaths. Ridges occur in patterns conforming to known shoals. The zone of grounded ridges, called stamukhi zone, protects the inner shelf and coast from marine energy and pack ice forces. Relatively undeformed fast ice grows inshore of the stamukhi zone. The boundary is explained in terms of pack ice drift and major promontories and shoals. Intense ice gaging, highly disrupted sediments, and landward migration of shoals suggest that much of the available marine energy is expended on the sea floor within the stamukhi zone. Naleds (products of river icings) on the North Slope are more abundant east than west of the Colville River. Their location, growth, and decay were studied from LANDSAT imagery.

  8. Topographic control of the cyclonic circulation in the southern Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Perez-Brunius, P.; García-Carrillo, P.; Dubranna, J.; Candela, J.; Sheinbaum, J.

    2011-12-01

    Until recently, the Bay of Campeche was the most undersampled area of the Gulf of Mexico. Three years of mooring and drifter observations of the upper-layer velocity field have greatly improved our understanding of the dynamics in this region. They show that the mean cyclonic circulation, previously reported in the literature, is a persistent feature that extends down to 800-1000m. The gyre's size and location appear determined by the particular configuration of the isobaths in the region, which consists of a deep basin to the west, and a shallower, gently sloping submarine fan to the east. Data suggest that the flow is equivalent barotropic, and that potential vorticity conservation explains the gyre's topographic control. Preliminary results indicate that the interaction of the gyre with Loop Current eddies and wind-stress curl variations can also be explained by this hypothesis.

  9. Uncertainty quantification and inference of Manning's friction coefficients using DART buoy data during the Tōhoku tsunami

    NASA Astrophysics Data System (ADS)

    Sraj, Ihab; Mandli, Kyle T.; Knio, Omar M.; Dawson, Clint N.; Hoteit, Ibrahim

    2014-11-01

    Tsunami computational models are employed to explore multiple flooding scenarios and to predict water elevations. However, accurate estimation of water elevations requires accurate estimation of many model parameters including the Manning's n friction parameterization. Our objective is to develop an efficient approach for the uncertainty quantification and inference of the Manning's n coefficient which we characterize here by three different parameters set to be constant in the on-shore, near-shore and deep-water regions as defined using iso-baths. We use Polynomial Chaos (PC) to build an inexpensive surrogate for the GEOCLAW model and employ Bayesian inference to estimate and quantify uncertainties related to relevant parameters using the DART buoy data collected during the Tōhoku tsunami. The surrogate model significantly reduces the computational burden of the Markov Chain Monte-Carlo (MCMC) sampling of the Bayesian inference. The PC surrogate is also used to perform a sensitivity analysis.

  10. A numerical model investigation of the formation and persistence of an erosion hotspot

    USGS Publications Warehouse

    Hansen, Jeff E.; Elias, Edwin; List, Jeffrey H.; Barnard, Patrick L.

    2011-01-01

    A Delft3D-SWAN coupled flow and wave model was constructed for the San Francisco Bight with high-resolution at 7 km-long Ocean Beach, a high-energy beach located immediately south of the Golden Gate, the sole entrance to San Francisco Bay. The model was used to investigate tidal and wave-induced flows, basic forcing terms, and potential sediment transport in an area in the southern portion of Ocean Beach that has eroded significantly over the last several decades. The model predicted flow patterns that were favorable for sediment removal from the area and net erosion from the surf-zone. Analysis of the forcing terms driving surf-zone flows revealed that wave refraction over an exposed wastewater outfall pipe between the 12 and 15 m isobaths introduces a perturbation in the wave field that results in erosion-causing flows. Modeled erosion agreed well with five years of topographic survey data from the area.

  11. Dynamics of the direct intrusion of Gulf Stream ring water onto the Mid-Atlantic Bight shelf

    NASA Astrophysics Data System (ADS)

    Zhang, Weifeng G.; Gawarkiewicz, Glen G.

    2015-09-01

    Onshore intrusions of offshore waters onto the Mid-Atlantic Bight shelf can greatly affect shelf circulation, biogeochemistry, and fisheries. Previous studies have concentrated on onshore intrusions of slope water. Here we present a direct intrusion of Gulf Stream warm-core ring water onto the shelf representing a previously unknown exchange process at the shelfbreak. Impingement of warm-core rings at the shelfbreak generates along-isobath intrusions that grow like Pinocchio's nose, extending hundreds of kilometers to the southwest. By combining satellite and Ocean Observatory Initiative Pioneer Array data and idealized numerical simulations, we discover that the intrusion results from topographically induced vorticity variation of the ring water, rather than from entrainment of the shelfbreak frontal jet. This intrusion of the Gulf Stream ring water has important biogeochemical implications and could facilitate migration of marine species across the shelfbreak barrier and transport low-nutrient surface Gulf Stream ring water to the otherwise productive shelfbreak region.

  12. Gulf stream meanders in the South Atlantic Bight 2: Momentum balances

    SciTech Connect

    Miller, J.L.; Lee, T.N.

    1995-04-15

    Gulf Stream meanders and their associated frontal eddies have been numerically simulated using a model tuned to the southern portion of the South Atlantic Bight. A run which produced events most similar to those observed in nature was identified, and the dynamics of a particular meander event were examined in detail. A complex array of momentum balances are obtained, and they vary with position within the feature. While the along-isobath flow is predominantly in geostrophic balance, several of the nonlinear advection terms in both horizontal momentum equations play important roles in the space-time development of the flow. In particular, the vertical advection of horizontal momentum as well as frictional dissipation are now recognized as important contributors to the dynamical balances in the vicinity of the steep continental slope. It would appear that the semigeostrophic equations constitute the simplest description of this system. 10 refs., 15 figs., 3 tabs.

  13. The nearshore benthic community of Kasatochi Island, one year after the 2008 volcanic eruption

    USGS Publications Warehouse

    Jewett, S.C.; Bodkin, J.L.; Chenelot, H.; Esslinger, G.G.; Hoberg, M.K.

    2010-01-01

    A description is presented of the nearshore benthic community of Kasatochi Island 1012 months after a catastrophic volcanic eruption in 2008. The eruption extended the coastline of the island approximately 400 m offshore, mainly along the south, southeast, and southwest shores, to roughly the 20 m isobath. Existing canopy kelp of Eualaria (Alaria) fistulosa, as well as limited understory algal species and associated fauna (e.g., urchin barrens) on the hard substratum were apparently buried following the eruption. Samples and observations revealed the substrate around the island in 2009 was comprised almost entirely of medium and coarse sands with a depauperate benthic community, dominated by opportunistic pontogeneiid amphipods. Comparisons of habitat and biological communities with other nearby Aleutian Islands, as well as with the Icelandic volcanic island of Surtsey, confirm dramatic reductions in flora and fauna consistent with an early stage of recovery from a large-scale disturbance event. ?? 2010 Regents of the University of Colorado.

  14. Shoaling of nonlinear internal waves in Massachusetts Bay

    USGS Publications Warehouse

    Scotti, A.; Beardsley, R.C.; Butman, B.; Pineda, J.

    2008-01-01

    The shoaling of the nonlinear internal tide in Massachusetts Bay is studied with a fully nonlinear and nonhydrostatic model. The results are compared with current and temperature observations obtained during the August 1998 Massachusetts Bay Internal Wave Experiment and observations from a shorter experiment which took place in September 2001. The model shows how the approaching nonlinear undular bore interacts strongly with a shoaling bottom, offshore of where KdV theory predicts polarity switching should occur. It is shown that the shoaling process is dominated by nonlinearity, and the model results are interpreted with the aid of a two-layer nonlinear but hydrostatic model. After interacting with the shoaling bottom, the undular bore emerges on the shallow shelf inshore of the 30-m isobath as a nonlinear internal tide with a range of possible shapes, all of which are found in the available observational record. Copyright 2008 by the American Geophysical Union.

  15. Submarine processes of the middle Atlantic continental rise based on GLORIA imagery

    USGS Publications Warehouse

    Schlee, J.S.; Robb, James M.

    1991-01-01

    Approximately 6100 km of 3.5-kHz echo-sounding profiles was correlated with a GLORIA side-scan sonar image of the mid-Atlantic United States (34??N, 70??W) lower slope-upper continental rise. The image allows us to map the major erosional and depositional features and to identify major processes that have shaped the area. Interpretation of GLORIA imagery and echo-sounding profiles indicates that mass movement is the predominant process affecting sediment on the United States east coast mid-Atlantic slope and upper rise and that isobath-parallel sediment movement by geostrophic currents is restricted mainly to the lower continental rise. The mass-movement processes evident on the rise probably were most active during the Pleistocene, when sea level was lower and sediment input more active. -from Authors

  16. Assessing oil spill sensitivity in unsheltered coastal environments: A case study for Lithuanian-Russian coasts, South-eastern Baltic Sea.

    PubMed

    Depellegrin, Daniel; Pereira, Paulo

    2016-01-15

    This study presents a series of oil spill indexes for the characterization of physical and biological sensitivity in unsheltered coastal environments. The case study extends over 237 km of Lithuanian-Russian coastal areas subjected to multiple oil spill threats. Results show that 180 km of shoreline have environmental sensitivity index (ESI) of score 3. Natural clean-up processes depending on (a) shoreline sinuosity, (b) orientation and (c) wave exposure are favourable on 72 km of shoreline. Vulnerability analysis from pre-existing Kravtsovskoye D6 platform oil spill scenarios indicates that 15.1 km of the Curonian Spit have high impact probability. The highest seafloor sensitivity within the 20 m isobath is at the Vistula Spit and Curonian Spit, whereas biological sensitivity is moderate over the entire study area. The paper concludes with the importance of harmonized datasets and methodologies for transboundary oil spill impact assessment. PMID:26705575

  17. Downslope Eulerian mean flow associated with high-frequency current fluctuations observed on the outer continental shelf and upper slope along the northeastern United States continental margin: implications for sediment transport

    USGS Publications Warehouse

    Butman, B.

    1988-01-01

    Eulerian current measurements made 5-7 m above bottom at six stations along the United States east coast continental margin show a net downslope flow of 1-5 cm s-1. Although the scalar current speed decreases with water depth and toward the bottom, fluctuations in the cross-isobath flow were stronger and increasingly asymmetric near the bottom. Maximum downslope flow exceeded maximum upslope flow by a factor of two to three. The strength of the low-passed downslope flow was proportional to the upslope Reynolds flux of density as well as to the amplitude of the current fluctuations that have periods shorter than 30 h. These flow characteristics may be caused by differential vertical mixing in the bottom boundary layer where a stratified fluid flows upslope (unstable) and downslope (stable). The asymmetry in current strength clearly favors net downslope transport of sediments that move as bedload. ?? 1988.

  18. Rapid and widespread dispersal of flood sediment on the northern California margin

    USGS Publications Warehouse

    Wheatcroft, R.A.; Sommerfield, C.K.; Drake, D.E.; Borgeld, J.C.; Nittrouer, C.A.

    1997-01-01

    The dispersal of flood sediment from small river systems is a poorly studied, yet potentially important aspect of active continental-margin sedimentation. In January 1995, during a flood with a 30 yr return period, the Eel River (northern California) delivered an estimated 25 ?? 3 ?? 106 t (metric tons) of tine-grained (<62 ??m) sediment to the ocean. The flood formed a distinct layer on the sea bed that was centered on the 70 m isobath, extended for 30 km along shelf and 8 km across shelf, and was as thick as 8.5 cm, but contained only 6 ?? 106 t of sediment. Thus, 75% of the flood-derived sediment did not form a recount/able deposit, but was instead rapidly and widely dispersed over the continental margin. Stratigraphic models of, and compilations of sediment flux to, active continental margins need to take the dispersive nature of small river systems into account.

  19. Subinertial canyon resonance

    NASA Astrophysics Data System (ADS)

    Clarke, Allan J.; Van Gorder, Stephen

    2016-04-01

    Near the bottom of a narrow canyon currents that oscillate back and forth along the bottom slope hx in a stratified ocean of buoyancy frequency N do so with a natural internal gravitational frequency Nhx. From May 2012 to May 2013 Acoustic Doppler Current Profiler measurements were made at 715 m depth in the deep narrow part of the DeSoto Canyon south of Pensacola, Florida, in water with 2π/Nhx ≈ 2.5 days. Above the canyon the flow follows the large-scale isobaths, but beneath the canyon rim the current oscillates along the canyon axis with 2-3 day periodicity, and is much stronger than and uncorrelated with the overlying flow. A simple theoretical model explains the resonant response. Published observations from the Hudson and Gully canyons suggest that the strong subinertial current oscillations observed in these canyons occur close to the relevant local frequency Nhx, consistent with the proposed simple model physics.

  20. Near-surface circulation in the South China Sea during the winter monsoon

    NASA Astrophysics Data System (ADS)

    Centurioni, L. R.; Niiler, P. N.; Lee, D.-K.

    2009-03-01

    Original velocity measurements at 15 m depth from Surface Velocity Program drifters are used to calculate the circulation in the South China Sea during the Winter Monsoon. The Ekman currents are computed with a new method and subtracted from drifter's velocity to calculate the residual circulation, which is approximately in geostrophic balance. The Ekman flow is nearly zonal and comparable to the zonal geostrophic flow in the northern basin. The geostrophic flow is cyclonic and extends into the southern Luzon Strait. Strong jets occur south of Hainan, off Vietnam and, to the south, off peninsular Malaysia. The Vietnam jet is concentrated inshore of the 200 m isobath, with mean speeds in excess of 1 m s-1. The onshore Ekman transport and pumping velocity computed from the wind stress curl offer a qualitative explanation of the existence and behavior of such jets.

  1. Atlantic to Mediterranean Sea Level Difference Driven by Winds near Gibraltar Strait

    NASA Technical Reports Server (NTRS)

    Menemenlis, Dimitris; Fukumori, Ichiro; Lee, Tong

    2006-01-01

    Observations and numerical simulations show that winds near Gibraltar Strait cause an Atlantic Ocean to Mediterranean Sea sea level difference of 20 cm peak to peak with a 3-cm standard deviation for periods of days to years. Theoretical arguments and numerical experiments establish that this wind-driven sea level difference is caused in part by storm surges due to alongshore winds near the North African coastline on the Atlantic side of Gibraltar. The fraction of the Moroccan coastal current offshore of the 284-m isobath is deflected across Gibraltar Strait, west of Camarinal Sill, resulting in a geostrophic surface pressure gradient that contributes to a sea level difference at the stationary limit. The sea level difference is also caused in part by the along-strait wind setup, with a contribution proportional to the along-strait wind stress and to the length of Gibraltar Strait and adjoining regions and inversely proportional to its depth.

  2. Connectivity of the Apalachicola River flow variability and the physical and bio-optical oceanic properties of the northern West Florida Shelf

    NASA Astrophysics Data System (ADS)

    Morey, Steven L.; Dukhovskoy, Dmitry S.; Bourassa, Mark A.

    2009-05-01

    Maps of satellite-derived estimates of monthly averaged chlorophyll a concentration over the northern West Florida Shelf show interannual variations concentrated near the coastline, but also extending offshore over the shelf in a tongue-like pattern from the Apalachicola River during the late winter and early spring. These anomalies are significantly correlated with interannual variability in the flow rate of the Apalachicola River, which is linked to the precipitation anomalies over the watershed, over a region extending 150-200 km offshore out to roughly the 100 m isobath. This study examines the variability of the Apalachicola River and its impacts on the variability of water properties over the northern West Florida Shelf. A series of numerical model experiments show that episodic wind-driven offshore transport of the Apalachicola River plume is a likely physical mechanism for connecting the variability of the river discharge with oceanic variability over the middle and outer shelf.

  3. Transporting Fish Eggs, Larvae, Harmful Algal Blooms and Pollution Towards the Shore via Stokes' Drift.

    NASA Astrophysics Data System (ADS)

    Maksimova, E.; Clarke, A. J.

    2008-12-01

    Cross-shelf transport of particles is vital to the life cycles of many marine populations as well as the magnitude and distribution of harmful algal blooms (HABs) and pollution seen at the coast. To carry particles long distances currents must be in the same direction for a long time, i.e., for effective transport, the flows must be of low frequency. Low-frequency flows usually do not cross isobaths. An exception is the wind driven low-frequency flow in surface and bottom Ekman Layers. Another mechanism is the low-frequency transport of particles towards the shore via the Stokes' Drift due to surface gravity waves. This mechanism should be effective on most coastlines. Using wave measurements on the West Florida Shelf, we show that this mechanism is capable of transporting HABs, fish eggs, larvae and pollutants across the shelf there.

  4. Mechanism of the cysteine sulfenic acid O-sulfenylation of 1,3-cyclohexanedione.

    PubMed

    Freeman, Fillmore

    2014-04-21

    The density functionals B3LYP, B3PW91, M062X, and CAM-B3LYP with the 6-311+G(d,p) basis set predict the cysteine sulfenic acid O-sulfenylation of the s-cis-ketoenol tautomer of 1,3-cyclohexanedione proceeds through a cyclic 14-membered transition state structure containing three water molecules. PMID:24619216

  5. Enhancing alkaline hydrogen evolution reaction activity through Ni-Mn3O4 nanocomposites.

    PubMed

    Li, Xu; Liu, Peng Fei; Zhang, Le; Zu, Meng Yang; Yang, Yun Xia; Yang, Hua Gui

    2016-08-18

    Developing efficient, stable and cost-effective electrocatalysts towards hydrogen production in alkaline environments is vital to improve energy efficiency for water splitting. In this work, we prepared Ni-Mn3O4 nanocomposites on Ni foam which exhibit an excellent hydrogen evolution reaction catalytic activity with a current density (j) of 10 mA cm(-2) at an overpotential (η) of 91 mV and show good stability in an alkaline medium. PMID:27500290

  6. Soybean cultivar selection for Bioregenerative Life Support Systems (BLSSs) - Hydroponic cultivation

    NASA Astrophysics Data System (ADS)

    Paradiso, R.; Buonomo, R.; De Micco, V.; Aronne, G.; Palermo, M.; Barbieri, G.; De Pascale, S.

    2012-12-01

    Four soybean cultivars ('Atlantic', 'Cresir', 'Pr91m10' and 'Regir'), selected through a theoretical procedure as suitable for cultivation in BLSS, were evaluated in terms of growth and production. Germination percentage and Mean Germination Time (MGT) were measured. Plants were cultivated in a growth chamber equipped with a recirculating hydroponic system (Nutrient Film Technique). Cultivation was performed under controlled environmental conditions (12 h photoperiod, light intensity 350 μmol m-2 s-1, temperature regime 26/20 °C light/dark, relative humidity 65-75%). Fertigation was performed with a standard Hoagland solution, modified for soybean specific requirements, and EC and pH were kept at 2.0 dS m-1 and 5.5 respectively. The percentage of germination was high (from 86.9% in 'Cresir' to 96.8% in 'Regir')and the MGT was similar for all the cultivars (4.3 days). The growing cycle lasted from 114 in 'Cresir' to 133 days on average in the other cultivars. Differences in plant size were recorded, with 'Pr91m10' plants being the shortest (58 vs 106 cm). Cultivars did not differ significantly in seed yield (12 g plant-1) and in non edible biomass (waste), water consumption and biomass conversion efficiency (water, radiation and acid use indexes). 'Pr91m10' showed the highest protein content in the seeds (35.6% vs 33.3% on average in the other cultivars). Results from the cultivation experiment showed good performances of the four cultivars in hydroponics. The overall analysis suggests that 'Pr91m10' could be the best candidate for the cultivation in a BLSS, coupling the small plant size and the good yield with high resource use efficiency and good seed quality.

  7. 24 CFR 3280.703 - Minimum standards.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... Addendum Z21.47a-1990 and Z21.47b-1992. Household Cooking Gas Appliances—ANSI Z21.1-2000. Refrigerators... Addendum Z21.10.1a-2000. Household Electric Storage Tank Water Heaters, Tenth Edition—UL 174-1996, with..., Appliance Connector Valves and Hose End Valves—ANSI Z21.15/CGA 9.1-M97-1997. Standard for Gas...

  8. 24 CFR 3280.703 - Minimum standards.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... Addendum Z21.47a-1990 and Z21.47b-1992. Household Cooking Gas Appliances—ANSI Z21.1-2000. Refrigerators... Addendum Z21.10.1a-2000. Household Electric Storage Tank Water Heaters, Tenth Edition—UL 174-1996, with..., Appliance Connector Valves and Hose End Valves—ANSI Z21.15/CGA 9.1-M97-1997. Standard for Gas...

  9. Easily Assembled Reflector for Solar Concentrators

    NASA Technical Reports Server (NTRS)

    Bouquet, F. L.; Hasegawa, T.

    1982-01-01

    Reflectors for concentrating solar collectors are assembled quickly and inexpensively by method that employs precontoured supports, plastic film, and adhesive to form a segmented glass mirror. New method is self-focusing, and does not require skilled labor at any stage. Contoured ribs support film and mirror segments of reflector. Nine mirror segments are bonded to sheet. Combined mirror surface closely approximates a spherical surface with a radius of curvature of 36 inches (0.91 m).

  10. An irregular feather-edge and potential outcrop of marine gas hydrate along the Mauritanian margin

    NASA Astrophysics Data System (ADS)

    Davies, Richard J.; Yang, Jinxiu; Li, Ang; Mathias, Simon; Hobbs, Richard

    2015-08-01

    The dissociation of marine hydrate that surrounds continental margins is thought to be an agent for past and future climate change. As the water depth decreases landwards, the base of the hydrate stability zone progressively shallows until hydrate can occur at or immediately below the seabed where an increase in bottom water temperature can cause dissociation. But the true extent of these most vulnerable hydrate deposits is unknown. Here we use exceptional quality three-dimensional (3-D) seismic reflection imagery offshore of Mauritania that reveals a rare example of a bottom simulating reflection (BSR) that intersects the seabed and delineates the feather-edge of hydrate. The BSR intersects the seabed at the ∼636 m isobath but along the 32 km of the margin analysed, the intersection is highly irregular. Intersections and seismic evidence for hydrate less than ∼4.3 m below the seabed occur in seven small, localised areas that are 0.02-0.45 km2 in extent. We propose gas flux below the dipping base of the hydrate to these places has been particularly effective. The intersections are separated by recessions in the BSR where it terminates below the seabed, seawards of the 636 m isobath. Recessions are areas where the concentration of hydrate is very low or hydrate is absent. They are regions that have been bypassed by gas that has migrated landwards along the base of the hydrate or via hydraulic fractures that pass vertically through the hydrate stability zone and terminate at pockmarks at the seabed. An irregular feather-edge of marine hydrate may be typical of other margins.

  11. Quantitative morphology of a fringing reef tract from high-resolution laser bathymetry: Southern Molokai, Hawaii

    USGS Publications Warehouse

    Storlazzi, C.D.; Logan, J.B.; Field, M.E.

    2003-01-01

    High-resolution Scanning Hydrographic Operational Airborne Lidar Survey (SHOALS) laser-determined bathymetric data were used to define the morphology of spur-and-groove structures on the fringing reef off the south coast of Molokai, Hawaii. These data provide a basis for mapping and analyzing morphology of the reef with a level of precision and spatial coverage never before attained. An extensive fringing coral reef stretches along the central two-thirds of Molokai's south shore (???40 km); along the east and west ends there is only a thin veneer of living coral with no developed reef complex. In total, ???4800 measurements of spur-and-groove height and the distance between adjacent spur crests (wavelength) were obtained along four isobaths. Between the 5m and 15m isobaths, the mean spur height increased from 0.7 m to 1.6 m, whereas the mean wavelength increased from 71 m to 104 m. Reef flat width was found to exponentially decrease with increasing wave energy. Overall, mean spur-and-groove height and wavelength were shown to be inversely proportional to wave energy. In high-energy environments, spur-and-groove morphology remains relatively constant across all water depths. In low-energy environments, however, spur-and-groove structures display much greater variation; they are relatively small and narrow in shallow depths and develop into much larger and broader features in deeper water. Therefore, it appears that waves exert a primary control on both the small and large-scale morphology of the reef off south Molokai.

  12. Wind-driven coastal upwelling and westward circulation in the Yucatan shelf

    NASA Astrophysics Data System (ADS)

    Ruiz-Castillo, Eugenio; Gomez-Valdes, Jose; Sheinbaum, Julio; Rioja-Nieto, Rodolfo

    2016-04-01

    The wind-driven circulation and wind-induced coastal upwelling in a large shelf sea with a zonally oriented coast are examined. The Yucatan shelf is located to the north of the Yucatan peninsula in the eastern Gulf of Mexico. This area is a tropical shallow body of water with a smooth sloping bottom and is one of the largest shelves in the world. This study describes the wind-driven circulation and wind-induced coastal upwelling in the Yucatan shelf, which is forced by easterly winds throughout the year. Data obtained from hydrographic surveys, acoustic current profilers and environmental satellites are used in the analysis. Hydrographic data was analyzed and geostrophic currents were calculated in each survey. In addition an analytical model was applied to reproduce the currents. The results of a general circulation model were used with an empirical orthogonal function analysis to study the variability of the currents. The study area is divided in two regions: from the 40 m to the 200 m isobaths (outer shelf) and from the coast to the 40 m isobath (inner shelf). At the outer shelf, observations revealed upwelling events throughout the year, and a westward current with velocities of approximately 0.2 m s-1 was calculated from the numerical model output and hydrographic data. In addition, the theory developed by Pedlosky (2007) for a stratified fluid along a sloping bottom adequately explains the current's primary characteristics. The momentum of the current comes from the wind, and the stratification is an important factor in its dynamics. At the inner shelf, observations and numerical model output show a wind-driven westward current with maximum velocities of 0.20 m s-1. The momentum balance in this region is between local acceleration and friction. A cold-water band is developed during the period of maximum upwelling.

  13. Temporal and spatial variability of the sediment grain-size distribution on the Eel shelf: The flood layer of 1995

    USGS Publications Warehouse

    Drake, D.E.

    1999-01-01

    Sediment grain-size characteristics observed on the Eel shelf have been analyzed using a wet-sieving technique that minimizes breakage of aggregates. At several sites on the 70-m isobath north of the river, where a 1995 flood layer attained a maximum thickness of about 9 cm, replicate box cores were collected on seven cruises during February 1995 to January 1997. These samples provide a unique opportunity to follow the evolution of a flood layer over a two-year period as it was modified and gradually buried. One month after the flood, a layer of tan-colored, high-porosity sediment with up to 96% of its particles in the size range of 0-20 ??m had accumulated on the central part of the shelf, 7-30 km north of the river and principally between the 50-m and 90-m isobaths. Substantial coarsening of this layer occurred between February 1995 and May 1995, particularly along the southern and the landward edge of the deposit in water depths of <70 m. The early stage of coarsening was probably caused by physical reworking of the surface 0.5-cm of the deposit and by addition of new sediment from shallower regions of the shelf. Temporal changes in inventories of several grain-size fractions show that physical processes continued to add coarse sediment to the flood layer after May 1995, but the large increases in thickness of the surface mixed layer could only be attributed to bioturbation by a recovering, or seasonally fluctuating, benthic community. The 1995 flood layer has evolved from exhibiting limited variability and normal grading (i:e., upward fining) to a layer that (1) shows significant spatial variability on scales from centimeters to 10's of meters, (2) is substantially coarser owing to additions of sediment from the inner shelf, (3) is inversely graded (i.e., coarsens upward), and (4) is intensely bioturbated to depths of 4-5 cm.

  14. Mesoscale structure and oceanographic determinants of krill hotspots in the California Current: Implications for trophic transfer and conservation

    NASA Astrophysics Data System (ADS)

    Santora, Jarrod A.; Sydeman, William J.; Schroeder, Isaac D.; Wells, Brian K.; Field, John C.

    2011-12-01

    Krill (crustaceans of the family Euphausiacea) comprise an important prey field for vast array of fish, birds, and marine mammals in the California Current and other large marine ecosystems globally. In this study, we test the hypothesis that mesoscale spatial organization of krill is related to oceanographic conditions associated with coastal upwelling. To test this, we compiled a climatology of krill distributions based on hydroacoustic surveys off California in May-June each year between 2000 and 2009 (missing 2007). Approximately 53,000 km of ocean habitat was sampled, resulting in a comprehensive geo-spatial data set from the Southern California Bight to Cape Mendocino. We determined the location and characteristics of eight definite and two probable krill “hotspots” of abundance. Directional-dependence analysis revealed that krill hotspots were oriented in a northwest-southeast (135°) direction, corresponding to the anisotropy of the 200-2000 m isobath. Krill hotspots were disassociated (inversely correlated) with three upwelling centers, Point Arena, Point Sur, and Point Conception, suggesting that krill may avoid locations of strong offshore transport or aggregate downstream from these locations. While current fisheries management considers the entire coast out to the 2000 m isobath critical habitat for krill in this ecosystem, we establish here smaller scale structuring of this critical mid-trophic level prey resource. Identifying mesoscale krill hotspots and their oceanographic determinants is significant as these smaller ecosystem divisions may warrant protection to ensure key ecosystem functions (i.e., trophic transfer) and resilience. Furthermore, delineating and quantifying krill hotspots may be important for conservation of krill-predators in this system.

  15. Modeling study of upwelling processes over the Oregon shelf

    NASA Astrophysics Data System (ADS)

    Gan, J.; Allen, J. S.

    2002-12-01

    Time-dependent, three dimensional circulation on the continental shelf off Oregon is studied using the Princeton Ocean Model (POM). The objective is to investigate the flow dynamics, the across-shelf transport, and the nature of the small scale turbulence field associated with the temporal and spatial variability of upwelling on the Oregon shelf during summer 2001. The study applies forcing from observed winds and heat flux for May-August 2001. Model variables compare favorably with current, temperature, hydrographic and turbulence measurements from the 2001 Coastal Ocean Advances in Shelf Transport (COAST) field experiment. The results show that strong offshore transport occurs in the surface/bottom layers near the coast and over Heceta Bank during upwelling/relaxation, respectively. Opposite conditions occur, however, onshore of the 100 m isobath over the south-east region of the bank where northward currents associated with a cyclonic circulation are found. Relatively large values of across-barotropic-streamline transport are found at the outer edge of the bank along the 200 m isobath and off Cape Blanco. Analysis of the balance of terms in the equation for potential temperature reveals that decreasing water temperatures over the bank are caused mainly by across-shelf and vertical advection. Alongshore advection, however, leads to low-density water around the southeast edge of the bank. Relatively large values of turbulent kinetic energy (TKE) are found in both the surface and the bottom boundary layers, with the higher intensity near the coast and over the bank during upwelling. As the upwelling wind relaxes, the TKE weakens quickly at the surface while high values remain near the bottom during the development of northward currents as part of the pressure gradient driven relaxation response. In the time-averaged alongshore momentum equation, strong nonlinear advective effects balance a northward ageostrophic pressure gradient force over the bank contributing to

  16. Low-Frequency Response Following the Passage of Hurricane Andrew on the Texas-Louisiana Shelf

    NASA Astrophysics Data System (ADS)

    Pearce, S. M.; Smith, D. C.; Dimarco, S. F.

    2009-12-01

    During August 24th through 27th in 1992, Hurricane Andrew passed through the Gulf Of Mexico almost directly over several moorings on the easternmost Louisiana shelf portion of the Texas-Louisiana Shelf (LATEX) coastal ocean monitoring program. Examination of the current meter time-series showed the existence of fast moving, long shelf waves over the entire Texas-Louisiana shelf west of the storm passage for up to 12 days after direct forcing ceased. The LATEX program featured 31 moorings each with 3 current meters over the 10, 20, 50, and 200 meter isobaths in 5 cross sectional lines with additional coverage on the 200 meter isobath from the Louisiana-Mississippi River delta, to Corpus Christi, Texas. Additionally, several pressure records from LATEX and several NOAA historical coastal tide gauge data from Sabine Pass to Port Isabella, Texas were incorporated. Raw, 3-hour low pass filtered, and 40-hour low pass filtered versions of the current data were analyzed. The pressure data used were detided using a least squares fit, and the tidal records were detided using the NOAA predicted tides for that location. All data were analyzed using a wavelet analysis to determine the spectra over time. The analyzed data shows that the shelf response was largely dominated in the internal Kelvin wave mode. The wave propagated towards the west on the shelf at approximately 400 km/day. These results are contrasted and compared with wave modes predicted for coastal trapped wave solutions. The output of a coastal ocean model simulation using a forced wind field similar to the storm are also contrasted and compared with the observed data.

  17. The response of shelf waters to the passage of tropical cyclones—observations from the Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Halper, Fern B.; Schroeder, William W.

    1990-08-01

    Current meter data obtained from sites on the Alabama, west Florida, and Texas-Louisiana shelves during 1979 coincided with the passage of five tropical cyclones; hurricane Bob, tropical storm Claudette, tropical storm Elena, hurricane Frederic and hurricane Henri, and a sixth storm (hurricane David) which skirted the west Florida coast, although the eye remained east of the Florida penninsula. The observations suggest that along the Alabama shelf (25 m water depth), where the isobaths were essentially perpendicular to the path of the storms, hurricanes Bob and Frederic and tropical storm Claudette caused coastal set-up/set-down, resulting in a complex response. The observations from the west Florida shelf (31 m water depth), where storm paths generally paralleled the isobaths, suggest that the flows associated with hurricanes Frederic, David and possibly tropical storm Claudette were a combination of the storms setting water in motion as they moved through the Gulf of Mexico and local wind forcing. These observations are supported, in part, by the results of an empirical model developed by HOLLAND (1980, Monthly Weather Review, 108, 1212-1218) to estimate the winds associated with tropical cyclones. At the Texas mooring (100 m water depth), one storm, Claudette, passed nearly over the mooring, forcing the flow to a depth of 50 m below the surface. With the exception of hurricane Frederic at the Alabama shelf mooring, and tropical storm Claudette at the Texas mooring, a response to some of the tropical cyclones occurred even when the center of the storms passed over 200 km from the moorings.

  18. Records of sedimentary dynamics in the continental shelf and upper slope between Aveiro-Espinho (N Portugal)

    NASA Astrophysics Data System (ADS)

    Martins, Virgínia; Abrantes, Isabel; Grangeia, Carlos; Martins, Paula; Nagai, Renata; Sousa, Sílvia H. M.; Laut, Lazaro L. M.; Dias, João M. Alveirinho; Dias, João M.; da Silva, Eduardo Ferreira; Rocha, Fernando

    2012-08-01

    The sedimentary unconsolidated cover of the Aveiro-Espinho continental shelf and upper slope (NW Portugal) records a complex interplay of processes including wave energy and currents, fluvial input, sediment transport alongshore and cross-shelf, geological and oceanographic processes and sediment sources and sinks. In order to study this record, a set of surface sediment samples was studied. Sediment grain size and composition, as well as the mineralogical composition (by XRD) of the fine (< 63 μm) and clay (< 2 μm) fractions and benthic microfaunal (foraminifera) data were analysed. Cluster analysis applied to the sedimentological data (grain size, sediment composition and mineralogy) allowed the establishment of three main zones corresponding to the: inner-, mid- and outer-shelf/upper slope. On the inner-shelf, the sedimentary coverture is composed of siliciclastic fine to very fine sand, essentially comprising modern (immature) terrigenous particles. The sediment grain size, as well as mineralogical and microfaunal composition, denote the high energetic conditions of this sector in which the alongshore transport of sand is predominantly southward and occurs mostly during the spring-summer oceanographic regime, when the main river providing sediments to this area, the River Douro, undergoes periods of drought. This effect may emphasize the erosive character of this coastal sector at present, since the Ria de Aveiro provides the shelf with few sediments. On the mid-shelf, an alongshore siliciclastic band of coarse sand and gravel can be found between the 40 m and 60 m isobaths. This gravelly deposit includes relic sediments deposited during lower sea-level stands. This structure stays on the surface due to the high bottom energy, which promotes the remobilization of the fine-grained sediments, and/or events of sediments bypassing. Benthic foraminifera density and "Benthic Foraminifera High Productivity" (BFHP) proxy values are in general low, which is consistent

  19. Multibeam Bathymetry Mapping for U.S. UNCLOS Concerns: A Gold Mine for Marine Geology

    NASA Astrophysics Data System (ADS)

    Gardner, J. V.; Mayer, L. A.; Armstrong, A.

    2007-12-01

    Since 2003, the University of New Hampshire's Center for Coastal and Ocean Mapping-Joint Hydrographic Center has conducted mapping of several U.S. continental margins in areas where a potential exists for an extended continental shelf as defined under Article 76 of the United Nations Convention on the Law of the Sea. UNH was directed by Congress, through funding to NOAA, to map the bathymetry in areas in the Arctic Ocean, Bering Sea, Gulf of Alaska, Atlantic, Gulf of Mexico, Philippine Sea, and slopes of Kingman Reef and Palmyra Atoll. These new data can be used to accurately locate the 2500-m isobath and to determine the location of the maximum change in gradient at the base of the continental slopes. To achieve these objectives, the area between ~1000 m and ~5000 m isobaths are mapped. The program has mapped >900,000 km2 as of September 2007. The bathymetry data are collected with multibeam echosounders navigated with inertial-aided DGPS and are fully motion compensated. An integral part of the data collection is measurements of the sound-speed profile in the water column to correct for refraction. The data are fully processed at sea. Most cruises also collect 3.5-kHz high-resolution profiles and some have included gravity measurements. All processed bathymetry and associated acoustic backscatter data are immediately available one the web and the raw multibeam datagrams and processed gravity data are archived at NOAA/NGDC. The new data provide a wealth of new information on the geomorphology of the continental margins. The mapping discovered many new features on the U.S. margins, as well as better defined features known to exist but either poorly mapped or mapped with obsolete mapping technology. New features discovered during the surveys include an undiscovered seamount, christened Healy Seamount and a series of huge sediment ridges striking normal to the Barrow margin in the Arctic Ocean; a series of plateaus and ridges north of Bowers Ridge in the Bering Sea

  20. Use of the Frank sequence in pulsed EPR.

    PubMed

    Tseitlin, Mark; Quine, Richard W; Eaton, Sandra S; Eaton, Gareth R; Halpern, Howard J; Ardenkjaer-Larsen, J-H

    2011-04-01

    The Frank polyphase sequence has been applied to pulsed EPR of triarylmethyl radicals at 25 6 MHz (9.1 mT magnetic field), using 256 phase pulses. In EPR, as in NMR, use of a Frank sequence of phase steps permits pulsed FID signal acquisition with very low power microwave/RF pulses (ca. 1.5 mW in the application reported here) relative to standard pulsed EPR. A 0.2 mM aqueous solution of a triarylmethyl radical was studied using a 16 mm diameter cross-loop resonator to isolate the EPR signal detection system from the incident pulses. PMID:21371924

  1. Use of the Frank Sequence in Pulsed EPR

    PubMed Central

    Tseitlin, Mark; Quine, Richard W.; Eaton, Sandra S.; Eaton, Gareth R.; Halpern, Howard J.; Ardenkjaer-Larsen, J.-H.

    2011-01-01

    The Frank polyphase sequence has been applied to pulsed EPR of triarylmethyl radicals at 256 MHz (9.1 mT magnetic field), using 256 phase pulses. In EPR, as in NMR, use of a Frank sequence of phase steps permits pulsed FID signal acquisition with very low power microwave/RF pulses (ca. 1.5 mW in the application reported here) relative to standard pulsed EPR. A 0.2 mM aqueous solution of a triarylmethyl radical was studied using a 16 mm diameter cross loop resonator to isolate the EPR signal detection system from the incident pulses. PMID:21371924

  2. Neutral hydrogen observations of a large sample of galaxies

    SciTech Connect

    Fisher, J.R.; Tully, R.B.

    1981-10-01

    A sample of 1787 nearby galaxies has been observed in the 21 cm line with the NRAO 91 m and 43 m telescopes and the Bonn 100 m telescope. A total of 1171 galaxies were detected. The radio observations provide an accurate heliocentric velocity, an H I flux, and a line profile width for each detection. Literature optical magnitudes, dimensions, and morphological types are reduced to common systems and tabulated. Intrinsic luminosities, dimensions, H I masses, and total masses are determined, assuming distances derived from redshifts.

  3. Air-Operated Sump Pump

    NASA Technical Reports Server (NTRS)

    Nolt, Gary D.

    1988-01-01

    Pump removes liquid seepage from small, restricted area and against large pressure head. Developed for moving small amounts of water and oil from sump pit 85 ft (25.91 m) deep. Fits in space only 6 1/2 in. (16.5 cm) in diameter and 18 in. (45.7 cm) long. In discharge part of pumping cycle, air forces liquid out of pump chamber through pipe. During filling part of pumping cycle, water enters pump chamber from sump pit. Float in chamber next to pump chamber controls pressurization through timer and solenoid valve.

  4. A 1400-MHz survey of 1478 Abell clusters of galaxies

    NASA Technical Reports Server (NTRS)

    Owen, F. N.; White, R. A.; Hilldrup, K. C.; Hanisch, R. J.

    1982-01-01

    Observations of 1478 Abell clusters of galaxies with the NRAO 91-m telescope at 1400 MHz are reported. The measured beam shape was deconvolved from the measured source Gaussian fits in order to estimate the source size and position angle. All detected sources within 0.5 corrected Abell cluster radii are listed, including the cluster number, richness class, distance class, magnitude of the tenth brightest galaxy, redshift estimate, corrected cluster radius in arcmin, right ascension and error, declination and error, total flux density and error, and angular structure for each source.

  5. Meiofaunal abundances and faunal similarity on the continental rise off the coast of California

    NASA Astrophysics Data System (ADS)

    Rohal, Melissa; Thistle, David; Easton, Erin E.

    2014-11-01

    Metazoan meiofauna (e.g., nematodes, benthic copepods) play important roles in deep-sea sediment communities, but information as basic as standing stocks is not known for much of the world ocean. We therefore sampled six stations: one near the 2700-m isobath and one near the 3700-m isobath off northern, central, and southern California. We counted benthic copepods, both Desmoscolecidae and nondesmoscolecid nematodes, kinorhynchs, nauplii, and ostracods from multiple-corer samples. Nematodes from our 2700-m and 3700-m stations, and ostracods and nauplii from our 3700-m stations, were unusually abundant compared to those from other stations from comparable depths in the Pacific. Off California, the abundances of benthic copepods, kinorhynchs, and nondesmoscolecids at the 2700-m stations were significantly greater than those at the 3700-m stations. Abundance of benthic copepods was correlated with the percentage of medium sand in the sediment, so sediment texture could be important to them. That of kinorhynchs was correlated with the concentration of chloroplastic-pigment equivalents and percentage nitrogen, so consumable material from the euphotic zone could be important to them. In contrast to the usual pattern of decreasing abundance with depth, Desmoscolecidae abundance in the central region was greater at the 3700-m than at the 2700-m station. The three regions differed significantly in both kinorhynch and ostracod abundances, independently of depth. In the food-poor deep sea, animals are expected to be more abundant where food is plentiful. Unexpectedly, ostracod abundance was negatively correlated with all food variables. A possible explanation is that the natural enemies of ostracods are abundant where food is abundant. Multivariate faunal similarity at 2700 m differed significantly from that at 3700 m, independently of regions. Benthic copepods were most responsible for the difference. Regions also differed in multivariate faunal similarity independently of

  6. Arctic continental shelf morphology related to sea-ice zonation, Beaufort Sea, Alaska

    USGS Publications Warehouse

    Reimnitz, E.; Toimil, L.; Barnes, P.

    1978-01-01

    Landsat-1 and NOAA satellite imagery for the winter 1972-1973, and a variety of ice and sea-floor data were used to study sea-ice zonation and dynamics and their relation to bottom morphology and geology on the Beaufort Sea continental shelf of arctic Alaska. In early winter the location of the boundary between undeformed fast ice and westward-drifting pack ice of the Pacific Gyre is controlled by major coastal promontories. Pronounced linear pressure- and shear-ridges, as well as hummock fields, form along this boundary and are stabilized by grounding, generally between the 10- and 20-m isobaths. Slippage along this boundary occurs intermittently at or seaward of the grounded ridges, forming new grounded ridges in a widening zone, the stamukhi zone, which by late winter extends out to the 40-m isobath. Between intermittent events along the stamukhi zone, pack-ice drift and slippage is continuous along the shelf edge, at average rates of 3-10 km/day. Whether slippage occurs along the stamukhi zone or along the shelf edge, it is restricted to a zone several hundred meters wide, and ice seaward of the slip face moves at uniform rates without discernible drag effects. A causal relationship is seen between the spatial distribution of major ice-ridge systems and offshore shoals downdrift of major coastal promontories. The shoals appear to have migrated shoreward under the influence of ice up to 400 m in the last 25 years. The sea floor seaward of these shoals within the stamukhi zone shows high ice-gouge density, large incision depths, and a high degree of disruption of internal sedimentary structures. The concentration of large ice ridges and our sea floor data in the stamukhi zone indicate that much of the available marine energy is expended here, while the inner shelf and coast, where the relatively undeformed fast ice grows, are sheltered. There is evidence that anomalies in the overall arctic shelf profile are related to sea-ice zonation, ice dynamics, and bottom

  7. Cruise report; RV Coastal Surveyor Cruise C1-99; multibeam mapping of the Long Beach, California continental shelf; April 12 through May 19, 1999

    USGS Publications Warehouse

    Gardner, James V.; Hughes-Clarke, John E.; Mayer, Larry A.

    1999-01-01

    The greater Los Angeles area of California is home to more than 10 million people. This large population puts increased pressure on the adjacent offshore continental shelf and margin with activities such as ocean disposal for dredged spoils, explosive disposal, waste-water outfall, and commercial fishing. The increased utilization of the shelf and margin in this area has generated accelerated multi-disciplinary research efforts in all aspects of the environment of the coastal zone. Prior to 1996 there were no highly accurate base maps of the continental shelf and slope upon which the research activities could be located and monitored. In 1996, the United States Geological Survey (USGS) Pacific Seafloor Mapping Project began to address this problem by mapping the Santa Monica shelf and margin (Fig. 1) using a state-of-the-art, high-resolution multibeam sonar system (Gardner, et al., 1996; 1999). Additional seafloor mapping in 1998 provided coverage of the continental margin from south of Newport to the proximal San Pedro Basin northwest of Palos Verdes Peninsula (Gardner, et al., 1998) (Fig. 1). The mapping of the seafloor in the greater Los Angeles continental shelf and margin was completed with a 30-day mapping of the Long Beach shelf in April and May 1999, the subject of this report. The objective of Cruise C-1-99-SC was to completely map the broad continental shelf from the eastern end of the Palos Verdes Peninsula to the narrow shelf south of Newport Beach, from the break in slope at about 120-m isobath to the inner shelf at about the 10-m isobath. Mapping the Long Beach shelf was jointly funded by the U.S. Geological Survey and the County of Orange (CA) Sanitation District and was conducted under a Cooperative Agreement with the Ocean Mapping Group from the University of New Brunswick (OMG/UNB). The OMG/UNB contracted with C&C Technologies, Inc. of Lafayette, LA for use of the RV Coastal Surveyor and the latest evolution of high-resolution multibeam sonars, a

  8. Coupled physical/biogeochemical modeling including O2-dependent processes in the Eastern Boundary Upwelling Systems: application in the Benguela

    NASA Astrophysics Data System (ADS)

    Gutknecht, E.; Dadou, I.; Le Vu, B.; Cambon, G.; Sudre, J.; Garçon, V.; Machu, E.; Rixen, T.; Kock, A.; Flohr, A.; Paulmier, A.; Lavik, G.

    2013-06-01

    the poleward meridional advection of oxygen-depleted waters offshore of a 300 m isobath and by the biogeochemical activity inshore of this isobath, highlighting a spatial shift of dominant processes maintaining the minimum oxygen concentrations off Namibia. In the OMZ off Namibia, the magnitude of N2O outgassing and of N loss is comparable. Anammox contributes to about 20% of total N loss, an estimate lower than currently assumed (up to 50%) for the global ocean.

  9. Evolution of the Jiuduansha wetland and the impact of navigation works in the Yangtze Estuary, China

    NASA Astrophysics Data System (ADS)

    Li, Xing; Liu, J. Paul; Tian, Bo

    2016-01-01

    The estuarine wetlands in the Yangtze Estuary face increasing threats due to large-scale engineering projects and huge land requirements. As a Wetland National Nature Reserve and important stopover site for migratory shorebirds of the East Asian-Australasian Flyway, the Jiuduansha wetland, one of four main islands in the estuary, is of both national and international importance. Since 1998 the previously undisturbed wetland has been considerably modified by the adjacent Deep-water Navigation Channel project (DNC). In order to understand the role of the DNC for the evolution of the Jiuduansha wetland, we performed a diagnostic study from multiple perspectives, including deposition rate, area change, evolution track, geometric characteristics, and geomorphological change. By coupling GIS, geostatistics, and remote sensing techniques, this study demonstrates the impact of the DNC on the Jiuduansha wetland in a spatially explicit way. Multi-temporal bathymetric maps and Landsat images from before and after the DNC was constructed were adopted to conduct our study. We find that deposition has occurred in most parts of the wetland over the past almost 30 years, accounting for 67.3% of the total area. However, over 40% of the study area shows a decreasing trend in deposition rate. The spatial distribution of deposition-erosion patterns is closely linked to the DNC. We also find that the DNC has substantial effects on the evolution of the Jiuduansha wetland. The 0, 2, and 5 m isobaths in the Jiuduansha Shoal (JDS), as well as in the Jiangya Shoal (JYS), the Upper Shoal (US) and the Middle-Lower Shoal (MLS), show different response patterns to the DNC. Specifically, the south training jetty of the DNC has an "adsorption effect" on the JDS above the 2 m isobaths intersecting with it. As a result, the evolution track, geometric and geomorphological characteristics of the JDS were markedly altered in the short term. Our comprehensive analysis suggests that in the future, the

  10. Dispersal of Mississippi and Atchafalaya sediment on the Texas-Louisiana shelf: Model estimates for the year 1993

    NASA Astrophysics Data System (ADS)

    Xu, Kehui; Harris, Courtney K.; Hetland, Robert D.; Kaihatu, James M.

    2011-10-01

    A three-dimensional coupled hydrodynamic-sediment transport model for the Texas-Louisiana continental shelf was developed using the Regional Ocean Modeling System (ROMS) and used to represent fluvial sediment transport and deposition for the year 1993. The model included water and sediment discharge from the Mississippi River and Atchafalaya Bay, seabed resuspension, and suspended transport by currents. Input wave properties were provided by the Simulating WAves Nearshore (SWAN) model so that ROMS could estimate wave-driven bed stresses, critical to shallow-water sediment suspension. The model used temporally variable but spatially uniform winds, spatially variable seabed grain size distributions, and six sediment tracers from rivers and seabed. At the end of the year 1993, much of the modeled fluvial sediment accumulation was localized with deposition focused near sediment sources. Mississippi sediment remained within 20-40 km of the Mississippi Delta. Most Atchafalaya sediment remained landward of the 10-m isobath in the inner-most shelf south of Atchafalaya Bay. Atchafalaya sediment displayed an elongated westward dispersal pattern toward the Chenier Plain, reflecting the importance of wave resuspension and perennially westward depth-averaged currents in the shallow waters (<10 m). Due to relatively high settling velocities assumed for sediment from the Mississippi River as well as the shallowness of the shelf south of Atchafalaya Bay, most sediment traveled only a short distance before initial deposition. Little fluvial sediment could be transported into the vicinity of the "Dead Zone" (low-oxygen area) within a seasonal-annual timeframe. Near the Mississippi Delta and Atchafalaya Bay, alongshore sediment-transport fluxes always exceeded cross-shore fluxes. Estimated cumulative sediment fluxes next to Atchafalaya Bay were episodic and "stepwise-like" compared to the relatively gradual transport around the Mississippi Delta. During a large storm in March 1993

  11. Gulf Stream Marine Hydrokinetic Energy Observations for North Carolina

    NASA Astrophysics Data System (ADS)

    Muglia, M.; Edge, B.; Lowcher, C.

    2014-12-01

    North Carolina and Florida are likely the only two states on the US east coast that have practical access to energy extraction from the Gulf Stream. After leaving the Florida Straits, the Gulf Stream in the region offshore of Cape Hatteras, NC exhibits the least variability in position of any location on the east coast, while simultaneously being closest to land. These important characteristics have made this area the focus of observations to quantify the hydrokinetic energy that may be available from the Gulf Stream for the state of North Carolina. Three types of observations to quantify the energy resource off NC began in 2013. A 150 kHz Acoustic Doppler Current Profiler (ADCP) was moored on the 225 meter isobath at the location estimated to be best for energy extraction, and recovered after a 9-month continuous deployment. Another ADCP was moored in nearly the same location to continue observations, and will be retrieved this fall. Currents from the first deployment averaged 1.15 m/s, and the average Betz Power was 0.8 kW/m2 at a depth of 30 meters over the 9-month duration. Significant variability in current speed, and thus power, occurred over the deployment period. Additionally, current measurements from a vessel mounted 300 kHz ADCP were made from water depths of 100m to 1000 m on a cross-isobath transect that included the location of the ADCP mooring. Currents from the ship transects are still under evaluation and comparison with the 150 kHz ADCP mooring, and will provide valuable information about the spatial variability of the current and its dependence on depth. A coastal ocean radar was added to an existing radar network to provide hourly surface current measurements over the larger study area. Methods to use the relative vorticity in the surface currents to identify the shoreward front of the Gulf Stream are being developed and compared with existing frontal determinations such as Navy Gulf Stream frontal charts produced bi-daily. Frontal estimates are

  12. Habitat use and preferences of cetaceans along the continental slope and the adjacent pelagic waters in the western Ligurian Sea

    NASA Astrophysics Data System (ADS)

    Azzellino, A.; Gaspari, S.; Airoldi, S.; Nani, B.

    2008-03-01

    The physical habitat of cetaceans occurring along the continental slope in the western Ligurian Sea was investigated. Data were collected from two different sighting platforms, one of the two being a whale-watching boat. Surveys, conducted from May to October and from 1996 to 2000, covered an area of approximately 3000 km 2 with a mean effort of about 10,000 km year -1. A total of 814 sightings was reported, including all the species occurring in the area: Stenella coeruleoalba, Balaenoptera physalus, Physeter macrocephalus, Globicephala melas, Grampus griseus, Ziphius cavirostris, Tursiops truncatus, Delphinus delphis. A Geographic Information System was used to integrate sighting data to a set of environmental characteristics, which included bottom gradient, area between different isobaths, and length and linearity of the isobaths within a cell unit. Habitat use was analysed by means of a multi-dimensional scaling, MDS, analysis. Significant differences were found in the habitat preference of most of the species regularly occurring in the area. Bottlenose dolphin, Risso's dolphin, sperm whale and Cuvier's beaked whale were found strongly associated to well-defined depth and slope gradient characteristics of the shelf-edge and the upper and lower slope. The hypothesis of habitat segregation was considered for Risso's dolphin, sperm whale and Cuvier's beaked whale. Canonical discriminant functions using depth and slope as predictors outlined clear and not overlapping habitat preferences for Risso's dolphin and Cuvier's beaked whale, whereas a partial overlapping of the habitat of the other two species was observed for sperm whale. Such a partitioning of the upper and lower slope area may be the result of the common feeding habits and suggests a possible competition of these three species. A temporal segregation in the use of the slope area was also observed for sperm whales and Risso's dolphins. Fin whales, and the occasionally encountered common dolphin and long

  13. Sediment transport on the Palos Verdes shelf, California

    NASA Astrophysics Data System (ADS)

    Ferré, Bénédicte; Sherwood, Christopher R.; Wiberg, Patricia L.

    2010-04-01

    Sediment transport and the potential for erosion or deposition have been investigated on the Palos Verdes (PV) and San Pedro shelves in southern California to help assess the fate of an effluent-affected deposit contaminated with DDT and PCBs. Bottom boundary layer measurements at two 60-m sites in spring 2004 were used to set model parameters and evaluate a one-dimensional (vertical) model of local, steady-state resuspension, and suspended-sediment transport. The model demonstrated skill (Brier scores up to 0.75) reproducing the magnitudes of bottom shear stress, current speeds, and suspended-sediment concentrations measured during an April transport event, but the model tended to underpredict observed rotation in the bottom-boundary layer, possibly because the model did not account for the effects of temperature-salinity stratification. The model was run with wave input estimated from a nearby buoy and current input from four to six years of measurements at thirteen sites on the 35- and 65-m isobaths on the PV and San Pedro shelves. Sediment characteristics and erodibility were based on gentle wet-sieve analysis and erosion-chamber measurements. Modeled flow and sediment transport were mostly alongshelf toward the northwest on the PV shelf with a significant offshore component. The 95th percentile of bottom shear stresses ranged from 0.09 to 0.16 Pa at the 65-m sites, and the lowest values were in the middle of the PV shelf, near the Whites Point sewage outfalls where the effluent-affected layer is thickest. Long-term mean transport rates varied from 0.9 to 4.8 metric tons m -1 yr -1 along the 65-m isobaths on the PV shelf, and were much higher at the 35-m sites. Gradients in modeled alongshore transport rates suggest that, in the absence of a supply of sediment from the outfalls or PV coast, erosion at rates of ˜0.2 mm yr -1 might occur in the region southeast of the outfalls. These rates are small compared to some estimates of background natural sedimentation

  14. Active tectonic morphology and submarine deformation of the northern Gulf of Eilat/Aqaba from analyses of multibeam data

    NASA Astrophysics Data System (ADS)

    Tibor, Gideon; Niemi, Tina M.; Ben-Avraham, Zvi; Al-Zoubi, Abdallah; Sade, Ronnie A.; Hall, John K.; Hartman, Gal; Akawi, Emad; Abueladas, Abdelrahmem; Al-Ruzouq, Rami

    2010-12-01

    A high-resolution marine geophysical study was conducted during October-November 2006 in the northern Gulf of Aqaba/Eilat, providing the first multibeam imaging of the seafloor across the entire gulf head spanning both Israeli and Jordanian territorial waters. Analyses of the seafloor morphology show that the gulf head can be subdivided into the Eilat and Aqaba subbasins separated by the north-south-trending Ayla high. The Aqaba submarine basin appears starved of sediment supply, apparently causing erosion and a landward retreat of the shelf edge. Along the eastern border of this subbasin, the shelf is largely absent and its margin is influenced by the Aqaba Fault zone that forms a steep slope partially covered by sedimentary fan deltas from the adjacent ephemeral drainages. The Eilat subbasin, west of the Ayla high, receives a large amount of sediment derived from the extensive drainage basins of the Arava Valley (Wadi ’Arabah) and Yutim River to the north-northeast. These sediments and those entering from canyons on the south-western border of this subbasin are transported to the deep basin by turbidity currents and gravity slides, forming the Arava submarine fan. Large detached blocks and collapsed walls of submarine canyons and the western gulf margin indicate that mass wasting may be triggered by seismic activity. Seafloor lineaments defined by slope gradient analyses suggest that the Eilat Canyon and the boundaries of the Ayla high align along north- to northwest-striking fault systems—the Evrona Fault zone to the west and the Ayla Fault zone to the east. The shelf-slope break that lies along the 100 m isobath in the Eilat subbasin, and shallower (70-80 m isobaths) in the Aqaba subbasin, is offset by approx. 150 m along the eastern edge of the Ayla high. This offset might be the result of horizontal and vertical movements along what we call the Ayla Fault on the east side of the structure. Remnants of two marine terraces at 100 m and approx. 150 m water

  15. Active tectonic morphology and submarine deformation of the northern Gulf of Eilat/Aqaba from analyses of multibeam data

    NASA Astrophysics Data System (ADS)

    Tibor, Gideon; Niemi, Tina; Ben-Avraham, Zvi; Al-Zoubi, Abdallah; Sade, Ronnie; Hall, John; Hartman, Gal; Akawi, Emad; Abueladas, Abed; Al-Ruzouq, Rami

    2010-05-01

    A high-resolution marine geophysical study was conducted during October-November 2006 in the northern Gulf of Aqaba/Eilat (gulf head). The gulf head can be subdivided into the Eilat and Aqaba subbasins separated by the north-south-trending Ayla high. The Aqaba submarine basin appears starved of sediment supply, apparently causing erosion and a landward retreat of the shelf edge. Along the eastern border of this subbasin, the shelf is largely absent and its margin is influenced by the Aqaba fault zone that forms a steep slope partially covered by sedimentary fan deltas from the adjacent ephemeral drainages. The Eilat subbasin, west of the Ayla high, receives a large amount of sediment derived from the extensive drainage basins of the Arava Valley (Wadi 'Arabah) and Yutim River to the north-northeast. These sediments and those entering from canyons on the south-western border of this subbasin are transported to the deep basin by turbidity currents and gravity slides, forming the Arava submarine fan. Large detached blocks and collapsed walls of submarine canyons and the western gulf margin indicate that mass wasting may be triggered by seismic activity. Seafloor lineaments defined by slope gradient analyses suggest that the Eilat Canyon and the boundaries of the Ayla high align along north- to northwest-striking fault systems—the Evrona Fault Zone to the west and the Ayla Fault Zone to the east. The shelf-slope break that lies along the 100 m isobath in the Eilat subbasin, and shallower (70-80 m isobaths) in the Aqaba subbasin, is offset by approx. 150 m along the eastern edge of the Ayla high. This offset might be the result of horizontal and vertical movements along what we call the Ayla Fault on the east side of the structure. Remnants of two marine terraces at 100 m and approx. 150 m water depths line the southwest margin of the gulf. These terraces are truncated by faulting along their northern end. Fossil coral reefs, which have a similar

  16. School characteristics of mesopelagic fish at South Georgia

    NASA Astrophysics Data System (ADS)

    Saunders, Ryan A.; Fielding, Sophie; Thorpe, Sally E.; Tarling, Geraint A.

    2013-11-01

    In this paper, we describe the variation in myctophid schools characteristics at South Georgia using multi-frequency acoustic data collected annually between November 2007 and January 2012. We studied the relationship between the proximity of land and the distribution and schooling characteristics of myctophid fish. We also examined patterns in schooling behaviour in relation to oceanographic data. Fish schools were identified using a dual-frequency dB identification method (Sv120-38 kHz), where negative Sv120-38 kHz is indicative of gas-bearing organisms, such as swimbladdered fish. Available net data were used to provide information on the meosopelagic fish community in the region. School morphometrics (e.g. length, thickness, area) data were extracted and pooled according to their distance from the shore (0-30 km, 30-60 km, 60-90 km, 90-120 km). A total of 578 schools were detected in the survey region and there was high variation in school backscattering strength (NASC), length, height, perimeter, depth and horizontal distribution between surveys, including distinct inter-annual variation in these parameters when surveys were conducted in the same season (2009-2012). Schools were distributed predominantly on-shelf (0-500 m isobaths) during some summer surveys (2007 and 2012) and predominantly off-shelf on others (>500 m isobaths; 2009, 2010 and 2011). There was also evidence of bathymetric separation in the horizontal distribution of schools. Schools observed in the late-season in 2008 had the greatest NASC, largest height and the deepest depth distribution. Most schools occurred at depths between ˜60 and 300 m, but they did not occupy the same water masses during each survey. Schools became progressively thinner, shallower and acoustically weaker with increasing distance to land, whilst school length and perimeter increased correspondingly. The change in fish schooling behaviour between environments could be a response to a combination of local predatory

  17. Geophysical and Geotechnical Determination of Sand Resources on the Florida Atlantic Continental Shelf: Preliminary Results

    NASA Astrophysics Data System (ADS)

    Finkl, C. W.; Andrews, J. L.; Suthard, B. C.; Robertson, W.

    2007-12-01

    The State of Florida is committed to maintaining beaches to sustain beach width and protect coastal infrastructure. Nearshore sand resources must be identified and cataloged for potential beach nourishment projects in response to sea-level rise and increased tropical storm activity. Given the vast length of Florida coastline, application of a variety of remote sensing techniques are required for measuring large areas in a short amount of time. The study area encompasses a shelf area of about 2,053,220 ha (20,532 km2) from Miami to the Georgia State line (about 653 km shoreline length) and extends up to 27 km offshore to about the 45 m isobath offshore Jacksonville. The continental shelf along the east coast of the Florida peninsula contains a wide range of seafloor environments that lie above the Florida-Hatteras Slope on the shoreface and inner, middle, and outer shelf floors. This study used Airborne Laser Bathymetry (ALB), 3D digital terrain models based on reformatted NOAA bathymetric data, sidescan sonar, and seismic reflection profiling to map seafloor geomorphological conditions that range from coralline-algal reef systems to drowned karst, submerged paleo shorelines (drowned beach ridge plains), and buried paleo channels. Seatruthing of morphosedimentary features is achieved via jetprobe and vibracore surveys in the study of inter-reefal sand troughs, ebb-tidal deltas, transverse bars, shoals, sand waves, ridges, and banks. Preliminary results, which visualize seafloor topography as color-ramped morphoforms, indicate the presence of sedimentary deposits that may constitute viable sand resources for shore protection in the form of beach renourishment. Use of ALB and reformatted NOAA bathymetric data in the form of 3D terrain models permits classification of submarine landform topologies that was heretofore not possible using isobaths. The combination of multiple remote sensing methods showed the spatial distribution of morphosedimentary features and provided

  18. Climate-sensitive subsea permafrost and related gas expulsions on the South Kara Sea shelf. Field studies and modeling results.

    NASA Astrophysics Data System (ADS)

    Portnov, Alexey; Mienert, Jurgen; Serov, Pavel

    2015-04-01

    Thawing subsea permafrost controls methane release bearing a considerable impact on the climate-sensitive Arctic environment. Significant expulsion of methane into shallow Russian shelf areas may continue to rise into the atmosphere on the Arctic shelves in response to intense degradation of relict subsea permafrost. The release of formerly trapped gas, essentially methane, is linked to the permafrost evolution. Modeling of the permafrost at the West Yamal shelf allowed describing its evolution from the Late Pleistocene to Holocene. During the previous work we detected extensive emissions of free gas into the water column at the boundary between today's shallow water permafrost and deeper water non-permafrost areas. These gas expulsions formed seismic and hydro-acoustic anomalies on the high-resolution seismic records. We supposed that in the water depths <20m continuous ice-bearing permafrost plays a role of a seal through which gas can not migrate. We integrate 1D modeling results of relict permafrost distributions with these field data from the South Kara Sea. Modeling results suggest a highly-dynamic permafrost system that directly responds to even minor variations of lower and upper boundary conditions, e.g. heat flux from below and/or bottom water temperature changes from above. We present several scenarios of permafrost evolution and show that potentially minimal modern extent of the permafrost at the West Yamal shelf is limited by ~17 m isobaths, whereas maximal probable extent coincides with ~100 m isobaths. The model also predicts seaward tapering of relict permafrost with its maximal thickness 275-390 m near the shore line. We also present sensitivity analysis which define the wider range of modeling results depending on the changing input parameters (e.g. geothermal heat flux, bottom water temperature, porosity of the sediments). The model adapts well to corresponding field data, providing crucial information about the modern permafrost conditions

  19. Winter variability in the western Gulf of Maine: Part 1: Internal tides

    NASA Astrophysics Data System (ADS)

    Brown, W. S.

    2011-09-01

    During the winter 1997-1998, a field program was conducted in Wilkinson Basin-western Gulf of Maine-as part of a study of winter convective mixing. The field program consisted of (1) Wilkinson basin-scale hydrographic surveys, (2) a tight three-mooring array with ˜100 m separations measured temperature and conductivity at rates of 2-15 min and (3) a single pair of upward/downward-looking pair acoustic Doppler current profiling (ADCP) instruments measured currents with 8 m vertical resolution over the 270 m water column in north-central Wilkinson basin at a rate of 10 min. The moored array measurements below the mixed layer (˜100 m depth) between 11 January and 6 February 1998 were dominated by a combination of the relatively strong semidiurnal external (depth-independent or barotropic) tide; upon which were superposed a weaker phase-locked semidiurnal internal tide and a very weak water column mean currents of about 1 cm/s southward or approximately across the local isobaths. The harmonic analysis of a vertical average of the relatively uniform ADCP velocities in the well-mixed upper 123 m of the water column, defined the external tidal currents which were dominated by a nearly rectilinear, across-isobath (326°T) M 2 semidiurnal tidal current of about 15 cm/s. The depth-dependent residual current field, which was created by subtracting the external tidal current, consisted of (1) clockwise-rotating semidiurnal internal tidal currents of about 5 cm/s below the mixed layer; (2) clockwise-rotating inertial currents; and (3) a considerably less energetic subtidal current variability. The results from both frequency-domain empirical orthogonal function and tidal harmonic analyses of the of isotherm displacement series at each of the three moorings in the 100 m array mutually confirm an approximate east-northeastward phase propagation of the dominant M 2 semidiurnal internal tide across Wilkinson Basin. Further investigation supports the idea that this winter internal

  20. Measurement of excitation functions in alpha-induced reactions on yttrium

    NASA Astrophysics Data System (ADS)

    Shahid, Muhammad; Kim, Kwangsoo; Naik, Haladhara; Zaman, Muhammad; Kim, Guinyun; Yang, Sung-Chul; Song, Tae-Young

    2015-01-01

    The excitation functions of 89g,m,90,91m,92mNb,88,89Zr, and 87g,m,88,90m,91mY from alpha-induced reactions on 89Y were measured from their respective threshold to 45 MeV by using a stacked-foil activation technique at the MC-50 cyclotron of the Korean Institute of Radiological and Medical Sciences. The results were compared with the earlier reported data as well as with the theoretical values obtained from the TENDL-2013 library based on the TALYS1.6 code. Our measurements in the energy region from the threshold energy to 45 MeV are in general good agreement with the other experimental data and calculated results. The integral yields for thick target of the produced radionuclides were also deduced from their measured cross sections and the stopping power of 89Y. The measured excitation functions find importance in various practical applications including nuclear medicine and improvement of nuclear model calculations.

  1. Light Charged-Particle Production Activation Cross Sections of Zr Isotopes from 14 to 20 MeV

    SciTech Connect

    Semkova, V.; Plompen, A.J.M.; Smith, D.L.

    2005-05-24

    Results of new cross-section measurements are presented for the following neutron-induced reactions: 90Zr(n,{alpha})87mSr, 90Zr(n,p)90mY, 91Zr(n,p)91mY, 91Zr(n,x)90mY, 92Zr(n,p)92Y, 92Zr(n,x)91mY, 94Zr(n,{alpha})91Sr, and 94Zr(n,p)94Y in the energy range from 14 to 21 MeV. Use was made of the activation technique in combination with high-resolution {gamma}-ray spectrometry. The irradiations were carried out at the 7-MV Van de Graaff accelerator at IRMM, Geel. Quasi-monoenergetic neutrons were produced via the 3H(d,n)4He reaction at 1, 2, 3, and 4 MeV incident deuteron energy. Both natural and samples enriched in 90Zr, 91Zr, and 92Zr were used to enhance the reaction yield or to facilitate correction for interfering reactions leading to the same product. The measured results are compared with work by other authors, TALYS-0.57 and EMPIRE-II model calculations, and current evaluated data files. Cross sections for all of the investigated reactions have been measured for the first time above 16 MeV.

  2. Activation Cross-Sections for 14.2 MeV Neutrons on Molybdenum

    NASA Astrophysics Data System (ADS)

    Srinivasa Rao, C. V.; Lakshmana Das, N.; Thirumala Rao, B. V.; Rama Rao, J.

    1981-12-01

    Using the activation method, the cross-section for the following reactions on molybdenum were measured employing the mixed powder technique and Ge(Li) gamma-ray spectroscopy: 94Mo(n, 2n)93mMo, 3.5 ± 0.5 mbarn; 92Mo(n, 2n)91mMo, 19 ± 3 mbarn; 92Mo(n, 2n)91m+gMo, 226 ± 11 mbarn; 100Mo(n, p)100m2Nb, 9 ± 1 mbarn; 98Mo(n, p)98Nb, 10 ± 1 mbarn; 97Mo(n, p)97mNb, 5 ± 1 mbarn; 96Mo(n, p)96Nb, 12 ± 2 mbarn; 92Mo(n, α)89mZr, 2.1 ± 0.5 mbarn; and 92Mo(n, α)89m+gZr 24 ± 6 mbarn; the neutron energy was 14.2 ± 0.2 MeV. The experimental cross-sections were compared with the predictions of evaporation model and of different versions of pre-equilibrium model. The master equation approach appears to give satisfactory results.

  3. Frontal structures associated with coastal upwelling and ice-edge subduction events in southern Beaufort Sea during the Canadian Arctic Shelf Exchange Study

    NASA Astrophysics Data System (ADS)

    Sévigny, Caroline; Gratton, Yves; Galbraith, Peter S.

    2015-04-01

    The near-surface temperature structure in the southeastern Beaufort Sea is shown to have been largely dependent on frontal dynamics in spring 2004, which may be typical for the region. Easterly wind events generated coastal upwelling along the Cap Bathurst peninsula; a recurring event in that area. Further west, a large mesoscale anticyclone simultaneously developed and subsequently controlled the sea-surface circulation in the central Amundsen Gulf. Sharp temperature and density fronts were created at the surface at both eastern and western ends of the domain. Sampling north of Cape Bathurst and Cape Parry showed evidence of frontal intensification. Frontal features were detected near the 50-200 m isobaths, at the mouth of the gulf, where density-compensated near-surface intrusions driven by agesotrophic vertical circulation were identified. These warm water tongues intruded into the outcropping isopycnal layers, which dipped down between 5 and 25 m over the Mackenzie Shelf. They then crossed the density surfaces with an inverse slope consistent with N/f as predicted for quasi-geostrophic flows. The front event ended prior to the breakup of the landfast-ice bridge in late June with sea-surface temperature undergoing quick and widespread changes throughout the Amundsen Gulf.

  4. Marine heat flow measurements across subsea permafrost limit in the eastern Mackenzie Trough, Canadian Beaufort Sea

    NASA Astrophysics Data System (ADS)

    Kim, Y. G.; Hong, J. K.; Jin, Y. K.; Riedel, M.; Melling, H.; Kang, S. G.; Dallimore, S.

    2015-12-01

    Marine heat flow measurements using a 5 m-long Ewing-type heat probe were made during Korean icebreaker R/V Araon's Arctic expeditions (ARA04C in 2013 and ARA05B in 2014) to better know the shallow subsurface thermal structure in the eastern slope of Mackenzie Trough, the Canadian Beaufort Sea, in which associative geological processes of permafrost degradation and gas hydrate dissociation occur because of long-term warming since the Last Glacial Maximum. Heat flow in the continental slope was collected for the first time and is rather higher than those from deep boreholes (up to a few km below the seafloor) in the continental shelf. However, the smaller geothermal gradient and thermal conductivity were observed from sites along a transect line across permafrost limit on the eastern slope of the trough. It is noted that geothermal gradients are relatively constant in the vicinity of permafrost limit but are much smaller (even minus) only at deeper depths with positive bottom water temperature. Reason for such distribution is unclear yet. Based on observed geothermal gradient and bottom water temperature, permafrost table shown in subbottom profile seems to be controlled not by temperature. On the other hand, our finding of permafrost evidence on the other subbottom profile located landward may support that permafrost limit in the trough is along with ~100 m isobath.

  5. Geologic development and characteristics of the continental margins, Gulf of Mexico. Research report, 1983-1986

    SciTech Connect

    Coleman, J.M.; Prior, D.B.; Roberts, H.H.

    1986-01-01

    The continental slope of the Gulf Basin covers more than 500,000 sq km and consists of smooth and gently sloping surfaces, prominent escarpments, knolls, intraslope basins, and submarine canyons and channels. It is an area of extremely diverse topographic and sedimentologic conditions. The slope extends from the shelf break, roughly at the 200 m isobath, to the upper limit of the continental rise, at a depth of 2800 m. The most-complex province in the basin, and the one of most interest to the petroleum industry, is the Texas-Louisiana slope, occupying 120,000 sq km and in which bottom slopes range from < 1 deg to > 20 deg around the knolls and basins. The near-surface geology and topography of the slope are functions of the interplay between episodes of rapid shelf-edge and slope progradation and contemporaneous modification of the depositional sequence by diapirism. Development of discrete depo-centers throughout the Neogene results in rapid shelf-edge progradation, often in excess of 15-20 km/my. This rapid progradation of the shelf edge leads to development of thick wedges of sediment accumulation on the continental slope. Oversteeping, high pore pressures in rapidly deposited soft sediments and changes in eustatic sea level cause subaqueous slope instabilities such as landsliding and debris flows. Large scale features such as shelf edge separation scars and landslide related canyons often results from such processes.

  6. Geologic development and characteristics of continental margins, Gulf of Mexico

    SciTech Connect

    Coleman, J.M.; Prior, D.B.; Roberts, H.H.

    1986-09-01

    The continental slope of the Gulf basin covers more than 500,000 km/sup 2/ and consists of smooth and gently sloping surfaces, prominent escarpments, knolls, intraslope basins, and submarine canyons and channels. It is an area of extremely diverse topographic and sedimentologic conditions. The slope extends from the shelf break, roughly at the 200-m isobath, to the upper limit of the continental rise at a depth of 2800 m. The most complex province in the basin, and the one of most interest to the petroleum industry, is the Texas-Louisiana slope, occupying 120,000 km/sup 2/ and in which bottom slopes range from less than 1/sup 0/ to greater than 20/sup 0/ around the knolls and basins. The near-surface geology and topography of the slope is a function of the interplay between episodes of rapid shelf-edge and slope progradation and contemporaneous modification of the depositional sequence by diapirism. Development of discrete depocenters throughout the Neogene results in rapid shelf-edge progradation, often exceeding 15-20 km/m.y. This rapid progradation of the shelf edge leads to development of thick wedges of sediment accumulation on the continental slope. Slope oversteepening, high pore pressures in rapidly deposited soft sediments, and changes in eustatic sea level cause subaqueous slope instabilities such as landslides and debris flows. Large-scale features such as shelf-edge separation scars and landslide-related canyons often result from such processes.

  7. Manganese and copper fluxes from continental margin sediments

    SciTech Connect

    Heggie, D.; Klinkhammer, G.; Cullen, D.

    1987-05-01

    Total dissolvable Cu and Mn have been measured in sea water collected from the continental shelf of the eastern Bering Sea. Copper concentrations of <3 nmole kg/sup -1/ were measured over the shelf break but concentrations increased to >4 nmole kg/sup -1/ inshore of a hydrographic front over the 100 m isobath. Manganese concentrations also were low over the shelf break, <10 nmole kg/sup -1/, and increased systematically to concentrations >10 nmole kg/sup -1/ inshore of the hydrographic front. Depth distributions of Mn at all continental shelf stations showed gradients into the sediments, with concentrations typically >20 nmole kg/sup -1/ in a bottom layer extending about 30 m off the bottom. Benthic Cu and Mn fluxes are indicated by cross-shelf pore water profiles that show interfacial concentrations more than an order of magnitude greater than in bottom water. These data and the results of a model of metal transport across the shelf suggest that Cu and Mn fluxes, estimated at 2 and 18 nmole cm/sup -2/y/sup -1/, respectively, from continental shelf sediments may be one source of these metals to the deep sea.

  8. The cyclonic circulation in the Australian-Antarctic basin simulated by an eddy-resolving general circulation model

    NASA Astrophysics Data System (ADS)

    Aoki, Shigeru; Sasai, Yoshikazu; Sasaki, Hideharu; Mitsudera, Humio; Williams, Guy D.

    2010-06-01

    Flow structure in the Australian-Antarctic basin is investigated using an eddy-resolving general ocean circulation model and validated with iceberg and middepth float trajectories. A cyclonic circulation system between the Antarctic Circumpolar Current and Antarctic Slope Current consists of a large-scale gyre in the west (80-110° E) and a series of eddies in the east (120-150° E). The western gyre has an annual mean westward transport of 22 Sv in the southern limb. Extending west through the Princess Elizabeth Trough, 5 Sv of the gyre recirculates off Prydz Bay and joins the western boundary current off the Kerguelen Plateau. Iceberg trajectories from QuickScat and ERS-1/2 support this recirculation and the overall structure of the Antarctic Slope Current against isobath in the model. Argo float trajectories also reveal a consistent structure of the deep westward slope current. This study indicates the presence of a large cyclonic circulation in this basin, which is comparable to the Weddell and Ross gyres.

  9. Minimum distribution of subsea ice-bearing permafrost on the US Beaufort Sea continental shelf

    USGS Publications Warehouse

    Brothers, Laura L.; Hart, Patrick E.; Ruppel, Carolyn D.

    2012-01-01

    Starting in Late Pleistocene time (~19 ka), sea level rise inundated coastal zones worldwide. On some parts of the present-day circum-Arctic continental shelf, this led to flooding and thawing of formerly subaerial permafrost and probable dissociation of associated gas hydrates. Relict permafrost has never been systematically mapped along the 700-km-long U.S. Beaufort Sea continental shelf and is often assumed to extend to ~120 m water depth, the approximate amount of sea level rise since the Late Pleistocene. Here, 5,000 km of multichannel seismic (MCS) data acquired between 1977 and 1992 were examined for high-velocity (>2.3 km s−1) refractions consistent with ice-bearing, coarse-grained sediments. Permafrost refractions were identified along <5% of the tracklines at depths of ~5 to 470 m below the seafloor. The resulting map reveals the minimum extent of subsea ice-bearing permafrost, which does not extend seaward of 30 km offshore or beyond the 20 m isobath.

  10. A Seamless, High-Resolution, Coastal Digital Elevation Model (DEM) for Southern California

    USGS Publications Warehouse

    Barnard, Patrick L.; Hoover, Daniel

    2010-01-01

    A seamless, 3-meter digital elevation model (DEM) was constructed for the entire Southern California coastal zone, extending 473 km from Point Conception to the Mexican border. The goal was to integrate the most recent, high-resolution datasets available (for example, Light Detection and Ranging (Lidar) topography, multibeam and single beam sonar bathymetry, and Interferometric Synthetic Aperture Radar (IfSAR) topography) into a continuous surface from at least the 20-m isobath to the 20-m elevation contour. This dataset was produced to provide critical boundary conditions (bathymetry and topography) for a modeling effort designed to predict the impacts of severe winter storms on the Southern California coast (Barnard and others, 2009). The hazards model, run in real-time or with prescribed scenarios, incorporates atmospheric information (wind and pressure fields) with a suite of state-of-the-art physical process models (tide, surge, and wave) to enable detailed prediction of water levels, run-up, wave heights, and currents. Research-grade predictions of coastal flooding, inundation, erosion, and cliff failure are also included. The DEM was constructed to define the general shape of nearshore, beach and cliff surfaces as accurately as possible, with less emphasis on the detailed variations in elevation inland of the coast and on bathymetry inside harbors. As a result this DEM should not be used for navigation purposes.

  11. Inner shelf circulation patterns and nearshore flow reversal under downwelling and stratified conditions off a curved coastline

    NASA Astrophysics Data System (ADS)

    Sanay, Rosario; Yankovsky, Alexander; Voulgaris, George

    2008-08-01

    The role of a curved coastline and associated bathymetry in the development of downwelling circulation in a stratified inner shelf is examined through a number of numerical experiments. Different scenarios include constant versus variable wind-forcing and variations in bottom friction. The three-dimensional response of the shelf within the domain (embayment enclosed by capes) is associated with the generation of a velocity/pycnocline disturbance at the upstream cape and its subsequent downstream advection. This disturbance is more pronounced under variable wind conditions. Its downstream advection through the bay exhibits different patterns depending on the competition between inertia and bottom friction near the cape. When inertia dominates, the disturbance separates from the cape and travels downwind with an enhanced downstream flow offshore and a countercurrent inshore. The separation occurs at a low Rossby number (Ro ˜ 0.15), which is attributed to the positive curvature of the coastline forming the cape. When friction dominates, the advection path is constrained along the coastline, resulting in an alongshore temperature gradient and a transient thermal front running almost perpendicular to the coast/isobaths. Simulations with spatially variable bottom friction, with higher friction toward the coast, result in the generation of eddy-like features. The numerical results are in agreement with both observations and surface temperature imagery from Long Bay, South Carolina, an embayment enclosed by two capes, and emphasize the role that coastline and associated shelf morphology can play in enhancing cross-shelf transport and exchange.

  12. On whether azimuthal isotropy and alongshelf translational invariance are present in low-frequency acoustic propagation along the New Jersey shelfbreak.

    PubMed

    Lynch, James F; Emerson, Chris; Abbot, Philip A; Gawarkiewicz, Glen G; Newhall, Arthur E; Lin, Ying-Tsong; Duda, Timothy F

    2012-02-01

    To understand the issues associated with the presence (or lack) of azimuthal isotropy and horizontal (along isobath) invariance of low-frequency (center frequencies of 600 Hz and 900 Hz) acoustic propagation in a shelfbreak environment, a series of experiments were conducted under the Autonomous Wide-Aperture Cluster for Surveillance component of the Shallow Water 2006 experiment. Transmission loss data reported here were from two mobile acoustic sources executing (nearly) circular tracks transmitting to sonobuoy receivers in the circle centers, and from one 12.5 km alongshelf acoustic track. The circle radii were 7.5 km. Data are from September 8, 2006. Details of the acoustic and environmental measurements are presented. Simple analytic and computer models are used to assess the variability expected due to the ocean and seabed conditions encountered. A comparison of model results and data is made, which shows preliminary consistency between the data and the models, but also points towards further work that should be undertaken specifically in enlarging the range and frequency parameter space, and in looking at integrated transmission loss. PMID:22352604

  13. Development and application of Labrador Sea climatologies

    NASA Astrophysics Data System (ADS)

    Cetin, Nilgun

    2007-05-01

    Two yearly climatologies of the Labrador Sea are developed. One is based on the traditional geopotential coordinates, and the other employs isopycnal coordinates in the vertical. The analysis of the results show that the isopycnal climatology has more skill at describing the mean state of the Labrador Sea, without smoothing out important flow features such as strong boundary currents and fronts. Seasonal climatologies based on the isopycnal coordinates in the vertical are also developed to study seasonal variability of the Labrador Sea hydrography and freshwater and heat fluxes. The greatest seasonal variability is observed in winter, the season in which deep convective overturning takes place. By using the objective analysis technique which successfully represented the dynamics of the Labrador Sea, a pseudo time-series of water properties is developed to study their inter-annual variability. The contribution of the West Greenland Current to the interior Labrador Sea freshwater budget is found to be greater than that of the Labrador Current, even though the Labrador Current has a larger freshwater content. Diagnostic calculations show that the Labrador Current flows southward mostly parallel to the isobaths without much of its fresher waters ever crossing into the interior Labrador Sea.

  14. Diurnal trends in the mid-water biomass community of the Northwestern Hawaiian Islands observed acoustically

    NASA Astrophysics Data System (ADS)

    Lammers, Marc O.; Brainard, Russell E.; Au, Whitlow W. L.

    2004-10-01

    The nighttime mid-water biomass occurring near six banks in the Northwestern Hawaiian Islands was investigated using 38- and 120-kHz EK60 echosounders. Locations investigated included: French Frigate Shoals, Maro Reef, Lisianksi Island/Neva Shoals, Pearl and Hermes Atoll, Kure Atoll and Midway Atoll. Surveys were designed to sample transect lines parallel and normal to shore between 10 p.m. and 7 a.m. and once during daylight hours. A diurnal trend was found in the occurrence of mid-water sound scattering organisms at all six locations. Communities of organisms accumulate at night on the edges of each island between the 20- and 100-fathom isobaths. The highest densities of organisms restrict their horizontal movements to depths of 20 fathoms or deeper, but increases in biomass were also observed at shallower depths. The northern islands of Kure, Midway, and Pearl and Hermes Atolls exhibited patchier distributions than the southern islands. The composition of the biomass is presently unclear but resembles the mesopelagic boundary community found near the Main Hawaiian Islands. Simultaneous observations with the TOAD camera system revealed clouds of zooplankton mixed with small fish and other micronekton. The nightly influx of these organisms is likely a significant, though poorly understood, component of these islands ecosystems.

  15. Distribution and abundance of cetaceans in the north-central and western Gulf of Mexico. Final report. Volume 1. Executive summary

    SciTech Connect

    Davis, R.W.; Fargion, G.S.

    1996-05-24

    The purpose of the study was to determine the distribution and abundance of cetaceans in areas potentially affected by future oil and gas activities along the continental slope of the north-central and western Gulf of Mexico. This 3.75 year project commenced 1 October 1991 and finished 15 July 1995. The study area was bounded by the Florida-Alabama border, the Texas-Mexico border, and the 100 m and 2,000 m isobaths. Cetacean distribution and abundance were determined from seasonal aerial and shipboard visual surveys and shipboard acoustic surveys. In addition, hydrographic data were collected in situ and by satellite remote sensing to characterize cetacean habitat. Finally, tagging and tracking of sperm whales using satellite telemetry was attempted. This volume summarizes the results of the study. Cetaceans were observed throughout the study area during all four seasons. Nineteen species were identified, including two species (melon-headed whales and Fraser`s dolphins) previously thought to be rare in the Gulf. Pantropical spotted dolphins, bottlenose dolphins, clymene dolphins, striped dolphins, Atlantic spotted dolphins, and melon-headed whales were the most common small cetaceans and the sperm whale was the most common large cetacean. The mean annual abundance for all cetaceans was estimated to be 19,198. Although the study area had complex and dynamic oceanography, bottom depth was the only environmental variable which correlated to cetacean distribution.

  16. Distribution and abundance of cetaceans in the north-central and western Gulf of Mexico. Final report. Volume 3. Appendix C. Part 1

    SciTech Connect

    Davis, R.W.; Fargion, G.S.

    1996-05-24

    The purpose of the study was to determine the distribution and abundance of cetaceans in areas potentially affected by future oil and gas activities along the continental slope of the north-central and western Gulf of Mexico. This 3.75 year project commenced 1 October 1991 and finished 15 July 1995. The study area was bounded by the Florida-Alabama border, the Texas-Mexico border, and the 100 m and 2,000 m isobaths. Cetacean distribution and abundance were determined from seasonal aerial and shipboard visual surveys and shipboard acoustic surveys. In addition, hydrographic data were collected in situ and by satellite remote sensing to characterize cetacean habitat. Finally, tagging and tracking of sperm whales using satellite telemetry was attempted. Appendix C Part 1 contains the hydrographic data collected during TIO Cruises 1-4. Cetaceans were observed throughout the study area during all four seasons. Nineteen species were identified, including two species (melon-headed whales and Fraser`s dolphins) previously thought to be rare in the Gulf. Pantropical spotted dolphins, bottlenose dolphins, clymene dolphins, striped dolphins, Atlantic spotted dolphins, and melon-headed whales were the most common small cetaceans and the sperm whale was the most common large cetacean. The mean annual abundance for all cetaceans was estimated to be 19,198. Although the study area had complex and dynamic oceanography, bottom depth was the only environmental variable which correlated to cetacean distribution.

  17. Distribution and abundance of cetaceans in the north-central and western Gulf of Mexico. Final report. Volume 3. Appendix B

    SciTech Connect

    1996-05-24

    The purpose of the study was to determine the distribution and abundance of cetaceans in areas potentially affected by future oil and gas activities along the continental slope of the north-central and western Gulf of Mexico. This 3.75 year project commenced 1 October 1991 and finished 15 July 1995. The study area was bounded by the Florida-Alabama border, the Texas-Mexico border, and the 100 m and 2,000 m isobaths. Cetacean distribution and abundance were determined from seasonal aerial and shipboard visual surveys and shipboard acoustic surveys. In addition, hydrographic data were collected in situ and by satellite remote sensing to characterize cetacean habitat. Finally, tagging and tracking of sperm whales using satellite telemetry was attempted. Appendix B contains the hydrographic data collected during all four NMFS-SEFSC cruises. Cetaceans were observed throughout the study area during all four seasons. Nineteen species were identified, including two species (melon-headed whales and Fraser`s dolphins) previously thought to be rare in the Gulf. Pantropical spotted dolphins, bottlenose dolphins, clymene dolphins, striped dolphins, Atlantic spotted dolphins, and melon-headed whales were the most common small cetaceans and the sperm whale was the most common large cetacean. The mean annual abundance for all cetaceans was estimated to be 19,198. Although the study area had complex and dynamic oceanography, bottom depth was the only environmental variable which correlated to cetacean distribution.

  18. Distribution and abundance of cetaceans in the north-central and western Gulf of Mexico. Final report. Volume 3. Appendix C. Part 2

    SciTech Connect

    Davis, R.W.; Fargion, G.S.

    1996-05-24

    The purpose of the study was to determine the distribution and abundance of cetaceans in areas potentially affected by future oil and gas activities along the continental slope of the north-central and western Gulf of Mexico. This 3.75 year project commenced 1 October 1991 and finished 15 July 1995. The study area was bounded by the Florida-Alabama border, the Texas-Mexico border, and the 100 m and 2,000 m isobaths. Cetacean distribution and abundance were determined from seasonal aerial and shipboard visual surveys and shipboard acoustic surveys. In addition, hydrographic data were collected in situ and by satellite remote sensing to characterize cetacean habitat. Finally, tagging and tracking of sperm whales using satellite telemetry was attempted. Appendix C Part 2 contains the hydrogrpahic data collected during TIO Cruises 5-7. Cetaceans were observed throughout the study area during all four seasons. Nineteen species were identified, including two species (melon-headed whales and Fraser`s dolphins) previously thought to be rare in the Gulf. Pantropical spotted dolphins, bottlenose dolphins, clymene dolphins, striped dolphins, Atlantic spotted dolphins, and melon-headed whales were the most common small cetaceans and the sperm whale was the most common large cetacean. The mean annual abundance for all cetaceans was estimated to be 19,198. Although the study area had complex and dynamic oceanography, bottom depth was the only environmental variable which correlated to cetacean distribution.

  19. Distribution and abundance of cetaceans in the north-central and western Gulf of Mexico. Final report. Volume 2. Technical report

    SciTech Connect

    Davis, R.W.; Fargion, G.S.

    1996-05-24

    The purpose of the study was to determine the distribution and abundance of cetaceans in areas potentially affected by future oil and gas activities along the continental slope of the north-central and western Gulf of Mexico. This 3.75 year project commenced 1 October 1991 and finished 15 July 1995. The study area was bounded by the Florida-Alabama border, the Texas-Mexico border, and the 100 m and 2,000 m isobaths. Cetacean distribution and abundance were determined from seasonal aerial and shipboard visual surveys and shipboard acoustic surveys. In addition, hydrographic data were collected in situ and by satellite remote sensing to characterize cetacean habitat. Finally, tagging and tracking of sperm whales using satellite telemetry was attempted. This volume summarizes the results of the study. Cetaceans were observed throughout the study area during all four seasons. Nineteen species were identified, including two species (melon-headed whales and Fraser`s dolphins) previously thought to be rare in the Gulf. Pantropical spotted dolphins, bottlenose dolphins, clymene dolphins, striped dolphins, Atlantic spotted dolphins, and melon-headed whales were the most common small cetaceans and the sperm whale was the most common large cetacean. The mean annual abundance for all cetaceans was estimated to be 19,198. Although the study area had complex and dynamic oceanography, bottom depth was the only environmental variable which correlated to cetacean distribution.

  20. Bipohysical provinces and surface fronts in the western south atlantic

    NASA Astrophysics Data System (ADS)

    Saraceno, M.; Provost, C.; Piola, A.

    Biophysical Provinces in the Western South Atlantic are studied using 6 years (1998-2003) of sea surface color images from SeaWiFS and 10 years (1986-1995) of AVHRR data. Based on histogram analysis of monthly climatologies of both data sets the space-time variations of the limits of the Biophysical Provinces are investigated. The Zapiola Rise shows up as a local minimum in SST gradient magnitude and shows chlorophyll-a concentration values that are out of phase with the surroundings (minimum in austral spring). This result suggests that the corresponding region should be recognized as an independent Province from the South Subtropical Convergence Province. In addition, the motion of the Brazil-Malvinas is focused out. The surface expression of the Brazil-Malvinas front, present in both SST and SeaWiFS images is centered at 38°S. The surface front remains at the same location all year round with a north-south orientation, except in summer when it tends to pivot and have an east-west direction. This pivotal motion in summer leads to a 250 km long migration along the 1000 m isobath. The Brazil-Malvinas frontal motion is confronted to different model outputs.

  1. Atlantic marginal basins of Africa

    SciTech Connect

    Moore, G.T.

    1988-02-01

    The over 10,000-km long Atlantic margin of Africa is divisible into thirty basins or segments of the margin that collectively contain over 18.6 x 10/sup 6/ km/sup 3/ of syn-breakup and post-breakup sediments. Twenty of these basins contain a sufficiently thick volume of sediments to be considered prospects. These basins lie, at least partially, within the 200 m isobath. The distribution of source rocks is broad enough to give potential to each of these basins. The sedimentation patterns, tectonics, and timing of events differ from basin to basin and are related directly to the margin's complex history. Two spreading modes exist: rift and transform. Rifting dates from Late Triassic-Early Jurassic in the northwest to Early Cretaceous south of the Niger Delta. A complex transform fault system separated these two margins. Deep-water communication between the two basins became established in the middle Cretaceous. This Mesozoic-Cenozoic cycle of rifting and seafloor spreading has segmented the margin and where observable, basins tend to be bounded by these segments.

  2. Processing multi temporal Thematic Mapper data for mapping the submarine shelf of the Island Kerkennah

    NASA Astrophysics Data System (ADS)

    Katlane, Rim; Berges, Jean-Claude; Beltrando, Gérard; Zargouni, Fouad

    2014-05-01

    Gulf of Gabes in Tunisia is unique among Mediterranean coastal environments by shallow water extension and tide amplitude. Kerkennah islands, located in this this gulf, are characterized by a -10 m isobath few kilometers away from the shoreline and by a lithology composition dominated by smooth rocks (sandstone and mio-plocene clay). These features, combined with a sea level rise and an active subsidence, constitute major risk factors. Islands vulnerability is increased by sebkha (salted low lands) extension which accounts now for 45% of the total area. Thus assessing the littoral sea depth change is a key issue for risk monitoring. Our study relies on the 30 years archive of Landsat 5 TM sensor managed by GSFC/NASA. The depth assessment has been carried out by an empiric method based on TM1 channel which has the better water penetration properties (up to 25 m). We focused on summer period and selected images from July 1986, August 1987, June 2003 and July 2009. After a first step of data preprocessing to ensure data homogeneity, we produced sub-aquatic morphology change maps. The observed features (submarine channels enlargement, cells sinking) are consistent with the hypothesis of the ebb tide as the process leading phenomenon.

  3. Structure and variability of the Western Maine Coastal Current

    USGS Publications Warehouse

    Churchill, J.H.; Pettigrew, N.R.; Signell, R.P.

    2005-01-01

    Analyses of CTD and moored current meter data from 1998 and 2000 reveal a number of mechanisms influencing the flow along the western coast of Maine. On occasions, the Eastern Maine Coastal Current extends into the western Gulf of Maine where it takes the form of a deep (order 100 m deep) and broad (order 20 km wide) southwestward flow with geostrophic velocities exceeding 20 cm s -1. This is not a coastally trapped flow, however. In fields of geostrophic velocity, computed from shipboard-CTD data, the core of this current is roughly centered at the 100 m isobath and its onshore edge is no closer than 10 km from the coast. Geostrophic velocity fields also reveal a relatively shallow (order 10 m deep) baroclinic flow adjacent to the coast. This flow is also directed to the southwest and appears to be principally comprised of local river discharge. Analyses of moored current meter data reveal wind-driven modulations of the coastal flow that are consistent with expectations from simple theoretical models. However, a large fraction of the near-shore current variance does not appear to be directly related to wind forcing. Sea-surface temperature imagery, combined with analysis of the moored current meter data, suggests that eddies and meanders within the coastal flow may at times dominate the near-shore current variance. ?? 2005 Elsevier Ltd. All rights reserved.

  4. Slope currents around the Kerguelen Islands from demersal longline fishing records

    NASA Astrophysics Data System (ADS)

    Park, Young-Hyang; Gasco, Nicolas; Duhamel, Guy

    2008-05-01

    The Kerguelen Plateau constitutes a natural obstacle for the eastward progress of the Antarctic Circumpolar Current, especially around the Kerguelen Islands. However, there is little quantitative knowledge of the current field around the islands due to lack of long-term current measurements. We performed a systematic analysis of a total of 28917 points of fishing gear drifts from setting and recovery positions of demersal longlines deployed between 2002 and 2007 for Patagonian Toothfish (Dissostichus eleginoides) fisheries in Kerguelen waters. This enabled the construction of a realistic field of depth-averaged time-mean slope currents along the 1000 m isobath all around the Kerguelen Islands. The strongest depth-mean velocities of 25 cm s-1 are associated with the Polar Front, which rounds the islands from the south and flows northward along the inner continental slope immediately east of the islands, strongly supporting previous hydrographic evidence. These results demonstrate the potential for hitherto unexploited historic longline drift data from demersal fishing grounds to provide valuable quantitative information on the regional circulation.

  5. Feeding habits of the congeneric species Stellifer rastrifer and Stellifer brasiliensis (Acanthopterygii: Sciaenidae) co-occurring in the coast of the state of Santa Catarina, Brazil.

    PubMed

    Sabinson, L M; Rodrigues-Filho, J L; Peret, A C; Branco, J O; Verani, J R

    2015-05-01

    The objective of the present study was to investigate the feeding habits allowing the occurrence of the congeneric species Stellifer rastrifer and Stellifer brasiensis, collected on a seasonal basis, in the operating area of the artisanal seabob-shrimp trawl fishery in Porto Belo, an important fishing area on the southern Brazilian coast. Fish were collected seasonally from November 2009 to August 2010, in isobaths of 10, 20 and 30 m. Of the 450 stomachs analyzed, 194 belonged to Stellifer rastrifer and 242 to Stellifer brasiliensis. From the totality of analyzed stomachs 33.49% were empty and 66.52% had some content. Crustacea were the predominant food category in the diet of S. rastrifer and S. brasiliensis, and the shrimp Acetes americanus was the most frequent crustacean in stomachs of both studied species. The overlapping in the diet of the species was high, however when analyzing the overlap in each season it was found that it occurred only during spring and winter. Although the most important items in the diet of these species are the same, the intake of each alternates in time, suggesting a difference in predation pressure, which leads to less direct competition in a given time. PMID:26132027

  6. Source rock, maturity data indicate potential off Namibia

    SciTech Connect

    Bray, R.; Lawrence, S.; Swart, R.

    1998-08-10

    Namibia`s territorial waters occupy a large portion of West Africa`s continental shelf. The area to the 1,000 m isobath is comparable in size to the combined offshore areas of Gabon, Congo, Zaire, and Angola. Around half as much again lies in 1,000--2,500 m of water. The whole unlicensed part of this area will be open for bidding when the Third Licensing Round starts Oct. 1, 1998. Offshore Namibia is underexplored by drilling with only seven exploration wells drilled. Shell`s Kudu field represents a considerable gas resource with reserves of around 3 tcf and is presently the only commercial discovery.Namibia`s offshore area holds enormous exploration potential. Good quality sandstone reservoirs are likely to be distributed widely, and a number of prospective structural and stratigraphic traps have been identified. The recognition of Cretaceous marine oil-prone source rocks combined with the results of new thermal history reconstruction and maturity modeling studies are particularly significant in assessment of the oil potential. The paper discusses resource development and structures, oil source potential, maturity, and hydrocarbon generation.

  7. Namibia, practically unexplored, may have land, offshore potential

    SciTech Connect

    Light, M.P.R. ); Shimutwikeni, N. )

    1991-04-08

    Namibia became an independent nation in March 1990. Lying in southwestern Africa, it has an onshore area of 823,144 sq km with a coastline some 1,400 km long (Figs. 1,2). The offshore area, out to the 1,000 m isobath, is 340,000 sq km. This is equal to the combined offshore areas of Gabon, Congo, Zaire, and Angola. The hydrocarbon potential of this vast region is virtually unexplored because of political uncertainties that affected the country in the years until independence. Now, however, the country has a democratically elected government, political stability, and a positive and realistic attitude towards foreign investment. The authors describe the recently enacted petroleum legislation, taxation system, and hydrocarbon potential of Namibia. A licensing round (both offshore and onshore) has just been announced and will close Nov. 1, 1991. The new onshore and offshore blocks are shown. Through the activities of Namcor, the national petroleum corporation, and Intera ECL, Namibia is emerging as one of the few remaining countries of the world where truly giant fields could be found.

  8. Relative diffusion and dispersion at the Antarctic Peninsula: observations of pairs and triplets of drifters

    NASA Astrophysics Data System (ADS)

    Bandet, Marion D.; Thompson, Andrew F.; Heywood, Karen J.; Thorpe, Sally E.

    2010-05-01

    Forty surface drifters were deployed in 2007 at the tip of the Antarctic Peninsula as part of the ADELIE research project to map the near surface currents around the tip of the Antarctic Peninsula and to determine the role of these currents in the retention or dispersion of krill. Here we use the ADELIE drifters, together with 55 historical drifters that pass close to the Antarctic Peninsula, to evaluate the strength of advection and diffusion in this region. Relative eddy dispersion and diffusivities have been calculated using drifter pairs and triplets. The relative eddy diffusivity along and across isobaths is presented for various areas around the peninsula based on current paths and data availability. Combined together, the ADELIE and historical drifters provide a data set of up to 148 pairs for which we use a maximum initial separation varying between 15 and 60 km and a temporal resolution of 30 days. The triplets, although limited in number, allow the anisotropy of the diffusivity to be quantified. They provide insight into the stretching and straining deformations of krill or tracer patches. The results are compared with a previous analysis of the same data set using single drifters (Thompson et al. 2009, J. Phys. Oceanogr.). Data from ARGO floats deployed in the region will also be used to bring additional information about the flow structure in the vicinity of the Antarctic Peninsula.

  9. Response of Euphausia pacifica to small-scale shear in turbulent flow over a sill in a fjord

    PubMed Central

    Ianson, Debby; Allen, Susan E.; Mackas, David L.; Trevorrow, Mark V.; Benfield, Mark C.

    2011-01-01

    Zooplankton in the ocean respond to visual and hydro-mechanical cues such as small-scale shear in turbulent flow. In addition, they form strong aggregations where currents intersect sloping bottoms. Strong and predictable tidal currents over a sill in Knight Inlet, Canada, make it an ideal location to investigate biological behaviour in turbulent cross-isobath flow. We examine acoustic data (38, 120 and 200 kHz) collected there during the daylight hours, when the dominant zooplankters, Euphausia pacifica have descended into low light levels at ∼90 m. As expected, these data reveal strong aggregations at the sill. However, they occur consistently 10–20 m below the preferred light depth of the animals. We have constructed a simple model of the flow to investigate this phenomenon. Tracks of individual animals are traced in the flow and a variety of zooplankton behaviours tested. Our results indicate that the euphausiids must actively swim downward when they encounter the bottom boundary layer (bbl) to reproduce the observed downward shift in aggregation patterns. We suggest that this behaviour is cued by the small-scale shear in the bbl. Furthermore, this behaviour is likely to enhance aggregations found in strong flows at sills and on continental shelves. PMID:21954320

  10. New Regional-Scale Geophysical Observations of the Delmarva Peninsula, U.S.A. Inner Continental Shelf

    NASA Astrophysics Data System (ADS)

    Brothers, L. L.; Thieler, E. R.; Pendleton, E. A.; Foster, D. S.; Danforth, W. W.; Baldwin, W. E.; Ackerman, S. D.

    2014-12-01

    The Delmarva Peninsula is a 220-kilometer-long headland, spit and barrier island complex located in the central Mid-Atlantic Bight. This region's antecedent geology, sediment type and distribution, deposit geometry, and transport pathways are poorly constrained. Here we present preliminary findings from chirp and 16-channel boomer seismic reflection profiles, swath bathymetry, acoustic backscatter data and sediment samples collected in June-July, 2014, over 3220 km2 of the inner continental shelf. These co-located datasets characterize the broad-scale geologic framework of the central offshore Delmarva Peninsula, and also provide the geologic underpinnings to National Ocean Service (NOS) hydrographic bathymetry and previously unpublished acoustic backscatter data collected in the region between 2007 and 2011. The combined datasets extend 100 km along the coast from approximately the 8-m isobath to 30 km offshore in water depths up to ~ 30 m. They provide unprecedented resolution and spatial coverage of an inner continental shelf environment along the U.S. eastern seaboard. Analyses of these high-resolution datasets will improve understanding of inner continental shelf features and processes including: shoal massif origins, sand-ridge development, barrier-island system migration, shallow natural gas occurrence and distribution, paleochannel evolution, regional sea-level history and the role of antecedent geology in the central Delmarva coastal system. In addition to scientific insights, these data provide the foundation for a variety of management applications, such as sand resource, habitat, and coastal vulnerability assessments.

  11. Temperature, salinity, and density variability in the central Middle Atlantic Bight

    NASA Astrophysics Data System (ADS)

    Castelao, Renato; Glenn, Scott; Schofield, Oscar

    2010-10-01

    Four years of sustained glider observations are used to compute the seasonal cycle of hydrographic fields in the central Middle Atlantic Bight (MAB). Results reveal a large phase lag in near bottom temperatures, with peak values occurring in September at the inner shelf, in October at the mid shelf, and in November at the outer shelf. Unlike the northern MAB, the seasonal cycle explains over 70% of the near-surface salinity variability. At the inner shelf and offshore near the bottom, however, most of the variance is due to pulses in river discharge and to shifts in the position of the shelfbreak front. Cross-shelf density gradients inshore of the 60-m isobath are dominated by salinity during winter and spring, with temperature contributing significantly from August to October. This is because bottom waters near the coast are warm due to the deepening of the thermocline during fall, but offshore waters are still influenced by the cold pool. The vertical stratification seasonal variability is also large. Early in the year, stratification is small and entirely due to salinity. By May, salinity still dominates vertical gradients near the coast, but temperature and salinity contribute equally to the density stratification offshore. During summer, stratification is dominated by temperature. Temperature interannual variability was small during the sampling period, but surface salinity was anomalously low by 1.2 psu in summer 2006. The anomaly was due to larger than average discharge from the Hudson River in early summer during a period of strong upwelling favorable winds.

  12. Anisotropy of eddy variability in the global ocean

    NASA Astrophysics Data System (ADS)

    Stewart, K. D.; Spence, P.; Waterman, S.; Sommer, J. Le; Molines, J.-M.; Lilly, J. M.; England, M. H.

    2015-11-01

    The anisotropy of eddy variability in the global ocean is examined in geostrophic surface velocities derived from satellite observations and in the horizontal velocities of a 1/12° global ocean model. Eddy anisotropy is of oceanographic interest as it is through anisotropic velocity fluctuations that the eddy and mean-flow fields interact dynamically. This study is timely because improved observational estimates of eddy anisotropy will soon be available with Surface Water and Ocean Topography (SWOT) altimetry data. We find there to be good agreement between the characteristics and distributions of eddy anisotropy from the present satellite observations and model ocean surface. In the model, eddy anisotropy is found to have significant vertical structure and is largest close to the ocean bottom, where the anisotropy aligns with the underlying isobaths. The highly anisotropic bottom signal is almost entirely contained in the barotropic variability. Upper-ocean variability is predominantly baroclinic and the alignment is less sensitive to the underlying bathymetry. These findings offer guidance for introducing a parameterization of eddy feedbacks, based on the eddy kinetic energy and underlying bathymetry, to operate on the barotropic flow and better account for the effects of barotropic Reynolds stresses unresolved in coarse-resolution ocean models.

  13. A revised strategy for the monitoring and management of the galapagos sea cucumber Isostichopus fuscus (Aspidochirotida: Stichopodidae).

    PubMed

    Wolff, Matthias; Schuhbauer, Anna; Castrejón, Mauricio

    2012-06-01

    The brown sea cucumber fishery is active in the Galapagos Islands since the year 1991 after its collapse in mainland Ecuador. This paper analyzes the Galapagos Sea cucumber fishery over the past decade and the reasons for its management pitfalls and chronic over fishing, and proposes an improved strategy for estimating stock size and harvest potential. Based on the historical distribution of the fishing fleet and past fishery surveys, 15 macrozones were defined; their areas were estimated from the coastline to the 30m isobaths and the numbers of sample replicates per macrozone were calculated for a density estimate precision of +/-25%. Overall stock size was calculated by summing over all macrozones and was multiplied by 0.122 to obtain the annual quota. This multiplier was derived by inserting an exploitation rate of E=0.3 and a published natural mortality value of M=0.17 into Cadimas formula, thereby obtaining a more conservative precautionary quota estimate. Pre-fishery stock densities in 2009 were below the legal threshold value and the fishery remained closed. Mean densities were significantly lower in the deeper (>15m) than in the shallower (<15m) stratum, contrary to fishermen expectations. Through an empirical regression of (log) pre-fishery density versus subsequent annual catch for the period 1998-2008 we found that catches of most years greatly exceeded the here proposed quota explaining the collapsed nature of the stock. PMID:23894927

  14. Geologic report for the O'OTEC site off Kahe Point, Oahu, Hawaii

    SciTech Connect

    Normark, W.R.; Chase, T.E.; Wilde, P.; Hampton, M.A.; Gutmacher, C.E.; Seekins, B.A.; Johnson, K.H.

    1982-04-01

    The O'OTEC geologic survey provides the following points of information concerning development of the OTEC facilities of the Kahe Point: (1) the 1000 m isobath lies in the landward half of a gently sloping (10 to 20% grade) plateau that is generally sediment covered. The plateau extends as much as 15 km from the coast to a water depth of 1600 m. Although the plateau sediment cover locally displays a morphology and internal structure indicative of submarine sliding, or other types of mass movement, the age of movement or extent of internal disruption is not known. Thus, the geotechnical studies (Part B of this report by Winters and Lee) on the sediments recovered provide the only direct evaluation of the engineering properties of this sediment cover. (2) The more gently sloping plateau is separated from the shelf and coastal area by a steeper (30 to 90% grade) narrow slope that appears relatively free of sediment cover resolvable by acoustic profiling south of Maili Point. (3) The distribution of sediment type as mapped with the acoustic-reflection profiles does not show a simple relation to volcanic bedrock relief. The bathymetry basically reflects the volcanic surface because the resolvable sediment cover is generally less than 35 m.

  15. Distributions of the sea-surface temperature fronts in the Baltic Sea as derived from satellite imagery

    NASA Astrophysics Data System (ADS)

    Kahru, Matt; Håkansson, Bertil; Rud, Ove

    1995-05-01

    A 9-month time series of satellite infrared imagery was used to examine the sea surface temperature (SST) variability in the northern and central Baltic Sea. Objective multi-level edge detection techniques were applied to find sharp SST gradient areas known as fronts. The spatial distribution of frontal frequency was calculated over time periods from a few days to 9 months covering different thermal and wind conditions. The 9-month average frequency that a front is detected in a pixel of 1.1 x 1.1 km is up to 10% in certain areas whereas the median is around 2%. Large scale fronts are aligned to the coast and isobaths, and occur predominantly in areas of straight and uniformly sloping bottom topography. The major frontal areas are along the eastern coast of the Bothnian Sea and along the north-western coast of the Gulf of Finland. Low large-scale frontal frequency is characteristic to areas with highly structured bottom topography. The major mechanism of front generation is coastal upwelling, being complemented by coastal jets, eddies, differential heating and cooling, and water exchange between basins with different water characteristics. Filaments ("squirts") originating from upwelling areas are shown to be an important mechanism for transporting water and substances over long distances.

  16. Shipboard acoustic Doppler profiler velocity observations near Point Conception: Spring 1983

    NASA Astrophysics Data System (ADS)

    Barth, J. A.; Brink, K. H.

    1987-04-01

    During April 1983, shipboard Doppler acoustic log current profiles were collected in an effort to characterize the flow field near points Conception and Arguello, California. Subsurface velocity maps derived from these profiles have been used to describe spatial flow structures both on and off the shelf and to investigate flow variability as a function of time and of wind stress. Persistent westward flow out of the northern half of the Santa Barbara Channel and eastward flow into its southern half were observed regardless of the direction of the local wind stress. During one well-documented upwelling-favorable wind event, currents responded in the form of an energetic (maximum 21-m speeds of >60 cm s-1) offshore squirt of cold water. During weak or downwelling-favorable winds, currents continuous with the Santa Barbara Channel outflow were observed flowing to the northwest following the local isobaths before turning offshore west of Point Arguello. Evidence for wind forcing of current fluctuations nearshore between the points and north of Point Arguello was found. Lack of a thermal wind balance between directly measured velocity shear and horizontal density gradient was explained by the presence of large accelerations in the momentum equations. Lack of a consistent relation between velocity and temperature gradient illustrates the difficulty in estimating velocity from temperature information alone in this area.

  17. Seasonal and interannual changes of the Kuroshio intrusion onto the East China Sea Shelf

    NASA Astrophysics Data System (ADS)

    Wu, Chau-Ron; Hsin, Yi-Chia; Chiang, Tzu-Ling; Lin, Yong-Fu; Tsui, I.-Fong

    2014-08-01

    An advanced artificial neural network classification algorithm is applied to 20 years of multisatellite geostrophic velocity data to study the Kuroshio intrusion onto the southern shelf of the East China Sea. The results suggest that the on-shelf intrusion may occur year round, but winter intrusion events are more frequent than summer events. Both stronger intrusion (which is closely correlated to surface heat flux gradient) and weaker intrusion (which is correlated to wind forcing) occur during wintertime, but the former dominates in late winter while the latter prevails in early winter. There is a significant year-to-year variation of the winter on-shelf intrusion. Although on-shelf intrusion is the major characteristic of the region during wintertime, seldom intrusion events have been identified in the winters of 1997-1998 and 2002-2003. Two conditions are responsible for the cause of the nonintrusion events. During the two nonintrusion winters, the upstream Kuroshio transport anomaly is insignificant (the Kuroshio is not weakened) and no significant winter cooling off northeast Taiwan. Thus, the Kuroshio tends to flow along the shelf break following the 200 m isobath and on-shelf intrusion ceases. Those two nonintrusion events take place during the winters when both the Niño 3.4 index and the PDO index are large and positive.

  18. Modeling alongshore propagating tides and currents around West Maui, Hawaii and implications for transport using Delft3D.

    NASA Astrophysics Data System (ADS)

    Vitousek, S.; Fletcher, C. H.; Storlazzi, C. D.

    2006-12-01

    Nearshore currents are driven by a number of components including tides, waves winds and even internal tides. To adequately simulate transport of sand and other constituents, the realistic behavior of the dominant current-generating phenomena should be resolved. This often requires sufficient observations and calibration/validation efforts to achieve realistic modeling results. The work explores the capabilities of modeling the currents along West Maui. The West Maui coast has a propagating tide where the observed peak tidal currents, which are directed parallel to the coast, occur very closely to the peak tidal water levels. In 2003, the USGS collected an extensive set of current observations along West Maui, Hawaii, with the goal of better understanding transport mechanisms of sediment, larvae, pollutants and other particles in coral reef settings. The observations included vessel mounted ADCP surveys and an array seafloor instruments at the 10m isobath along the coast. A simple 2DH model of West Maui using Delft3D shows good comparison of the modeled and observed currents. Nearshore currents driven by waves and winds are also considered. During the data collection period a significant erosion event occurred within the study domain at Kaanapali Beach. This event undermined several trees on the shoreline and threatened resort infrastructure. In modeling the nearshore currents of this region we hope to determine the potential for sand transport and shoreline change to hindcast this event.

  19. Hanging canyons of Haida Gwaii, British Columbia, Canada: Fault-control on submarine canyon geomorphology along active continental margins

    NASA Astrophysics Data System (ADS)

    Harris, Peter T.; Barrie, J. Vaughn; Conway, Kim W.; Greene, H. Gary

    2014-06-01

    Faulting commonly influences the geomorphology of submarine canyons that occur on active continental margins. Here, we examine the geomorphology of canyons located on the continental margin off Haida Gwaii, British Columbia, that are truncated on the mid-slope (1200-1400 m water depth) by the Queen Charlotte Fault Zone (QCFZ). The QCFZ is an oblique strike-slip fault zone that has rates of lateral motion of around 50-60 mm/yr and a small convergent component equal to about 3 mm/yr. Slow subduction along the Cascadia Subduction Zone has accreted a prism of marine sediment against the lower slope (1500-3500 m water depth), forming the Queen Charlotte Terrace, which blocks the mouths of submarine canyons formed on the upper slope (200-1400 m water depth). Consequently, canyons along this margin are short (4-8 km in length), closely spaced (around 800 m), and terminate uniformly along the 1400 m isobath, coinciding with the primary fault trend of the QCFZ. Vertical displacement along the fault has resulted in hanging canyons occurring locally. The Haida Gwaii canyons are compared and contrasted with the Sur Canyon system, located to the south of Monterey Bay, California, on a transform margin, which is not blocked by any accretionary prism, and where canyons thus extend to 4000 m depth, across the full breadth of the slope.

  20. Recolonization of the intertidal and shallow subtidal community following the 2008 eruption of Alaska’s Kasatochi Volcano

    USGS Publications Warehouse

    Jewett, S.C.; Drew, Gary S.

    2014-01-01

    The intertidal and nearshore benthic communities of Kasatochi Island are described following a catastrophic volcanic eruption in 2008. Prior to the eruption, the island was surrounded by a dense bed of canopy-forming dragon kelp Eualaria fistulosa which supported a productive nearshore community. The eruption extended the coastline of the island approximately 400 m offshore to roughly the 20 m isobath. One year following the eruption a reconnaissance survey found the intertidal zone devoid of life. Subtidally, the canopy kelp, as well as limited understory algal species and associated benthic fauna on the hard substratum, were buried by debris from the eruption. The resulting substrate was comprised almost entirely of medium and coarse sands with a depauperate benthic community. Comparisons of habitat and biological communities with other nearby Aleutian Islands and the Icelandic submarine volcanic eruption of Surtsey confirm dramatic reductions in flora and fauna consistent with the initial stages of recovery from a large-scale disturbance event. Four and five years following the eruption brief visits revealed dramatic intertidal and subtidal recolonization of the flora and fauna in some areas. Signs of nesting and fledging of young pigeon guillemots Cepphus columba suggest that the recovery of the nearshore biota may have begun affecting higher trophic levels. Recolonization or lack thereof was tied to bathymetric changes from coastal and nearshore erosion over the study period.

  1. Results from the Elba HF-2003 experiment

    NASA Astrophysics Data System (ADS)

    Jensen, Finn; Pautet, Lucie; Porter, Michael; Siderius, Martin; McDonald, Vincent; Badiey, Mohsen; Kilfoyle, Dan; Freitag, Lee

    2004-11-01

    In October of 2003, a high-frequency propagation and acoustic communications experiment was conducted off the Italian island of Elba. The experiment followed closely a previous experiment off Kauai (Hawaii Islands). In particular, a 5 km propagation path along the 100-m isobath was selected. Relative to the Kauai Experiment, the Elba test was significant both in terms of what was similar and what was different. The experiment geometry was identical and a similar mixed layer structure was expected. However, since NURC has worked extensively in this area in past tests we were able to confidently select two sites, one with a very soft bottom and one with a very hard bottom. The comparison between measurements at the two sites in Elba and in Kauai is very illuminating in terms of the propagation conditions and the performance of the acoustic communications scheme. A final significant change was the inclusion of multiple input/multiple output (i.e. using source/receive arrays) communications schemes. We summarize preliminary results from this experiment.

  2. Physical mechanisms for the offshore detachment of the Changjiang Diluted Water in the East China Sea

    NASA Astrophysics Data System (ADS)

    Chen, Changsheng; Xue, Pengfei; Ding, Pingxing; Beardsley, R. C.; Xu, Qichun; Mao, Xianmou; Gao, Guoping; Qi, Jiahua; Li, Chunyan; Lin, Huichan; Cowles, Geoffrey; Shi, Maochong

    2008-02-01

    Physical mechanisms for the summertime offshore detachment of the Changjiang Diluted Water (CDW) into the East China Sea are examined using the high-resolution, unstructured-grid, Finite-Volume Coastal Ocean Model (FVCOM). The model results suggest that isolated low salinity water lens detected west of Cheju Island can be formed by (1) a large-scale adjustment of the flow field to the Changjiang discharge and (2) the detachment of anticyclonic eddies as a result of baroclinic instability of the CDW front. Adding the Changjiang discharge intensifies the clockwise vorticity of the subsurface current (originating from the Taiwan Warm Current) flowing along the 50-m isobath and thus drives the low-salinity water in the northern coastal area of the Changjiang mouth offshore over a submerged plateau that extends toward Cheju Island. Given a model horizontal resolution of less than 1.0 km, the CDW front becomes baroclinically unstable and forms a chain of anticyclonic and cyclonic eddies. The offshore detachment of anticyclonic eddies can carry the CDW offshore. This process is enhanced under northward winds as a result of the spatially nonuniform interaction of wind-induced Ekman flow and eddy-generated frontal density currents. Characteristics of the model-predicted eddy field are consistent with previous theoretical studies of baroclinic instability of buoyancy-driven coastal density currents and existing satellite imagery. The plume stability is controlled by the horizontal Ekman number. In the Changjiang, this number is much smaller than the criterion suggested by a theoretical analysis.

  3. A model-dye comparison experiment in the tidal mixing front zone on the southern flank of Georges Bank

    NASA Astrophysics Data System (ADS)

    Chen, Changsheng; Xu, Qichun; Houghton, Robert; Beardsley, Robert C.

    2008-02-01

    A process-oriented model-dye comparison experiment was conducted to examine the ability of a numerical ocean model to simulate the observed movement of dye across the tidal mixing front on the southern flank of Georges Bank during 22-26 May 1999. The experiment was made using the unstructured-grid Finite-Volume Coastal Ocean Model (FVCOM) with varying horizontal resolution. The results indicate that the observed cross-isobath movement of the dye patch was primarily controlled by meso-scale temporal and spatial variability of the water temperature and salinity fields. Onset of vertical stratification tended to slow down an upward stretching of the dye column and trapped the dye within the bottom mixed layer. To reach a convergent numerical solution that reproduced the observed lateral turbulent dispersion of dye, the FVCOM grid required a horizontal resolution of ˜500 m in the dye study region. Within the tidal mixing front of Georges Bank, the movement of the center of the dye patch was mainly driven by the ensemble velocity integrated over the dye volume, with a first-order contribution from vertical shear of the dye's horizontal velocity.

  4. An investigation of submarine groundwater-borne nutrient fluxes to the west Florida shelf and recurrent harmful algal blooms

    USGS Publications Warehouse

    Smith, Christopher G.; Swarzenski, Peter W.

    2012-01-01

    A cross-shelf, water-column mass balance of radon-222 (222Rn) provided estimates of submarine groundwater discharge (SGD), which were then used to quantify benthic nutrient fluxes. Surface water and groundwater were collected along a shore-normal transect that extended from Tampa Bay, Florida, across the Pinellas County peninsula, to the 10-m isobath in the Gulf of Mexico. Samples were analyzed for 222Rn and radium-223,224,226 (223,224,226Ra) activities as well as inorganic and organic nutrients. Cross-shore gradients of 222Rn and 223,224,226Ra activities indicate a nearshore source for these isotopes, which mixes with water characterized by low activities offshore. Radon-based SGD rates vary between 2.5 and 15 cm d-1 proximal to the shoreline and decrease offshore. The source of SGD is largely shallow exchange between surface and pore waters, although deeper groundwater cycling may also be important. Enrichment of total dissolved nitrogen and soluble reactive phosphorus in pore water combined with SGD rates results in specific nutrient fluxes comparable to or greater than estuarine fluxes from Tampa Bay. The significance of these fluxes to nearshore blooms of Karenia brevis is highlighted by comparison with prescribed nutrient demands for bloom maintenance and growth. Whereas our flux estimates do not indicate SGD and benthic fluxes as the dominant nutrient source to the harmful algal blooms, SGD-derived loads do narrow the deficit between documented nutrient supplies and bloom demands.

  5. Cross-shelf subtidal variability in San Pedro Bay during summer, 2001

    USGS Publications Warehouse

    Hamilton, P.; Noble, M.A.; Largier, J.; Rosenfeld, L.K.; Robertson, G.

    2006-01-01

    A total of 16 moorings were deployed across the San Pedro shelf, one of the two wider embayments in the Southern California Bight, from near the surfzone to the upper-slope. On the middle and outer shelf in the summer of 2001, the currents flowed strongly equatorward at the surface and had large vertical shears through the well-stratified water column. This equatorward flow differs from predominantly poleward flow found in previous studies of the coastal margin further west. In deeper water, near the shelf break, the shears were such that near-bottom flows were poleward and incorporated into the upper parts of the Southern California Undercurrent over the slope. Mid-shelf current fluctuations, with periods of 10-25 days, along with upwelling over the shelf, were not related to local winds, but were significantly correlated with the large-scale alongshore pressure gradient. Shorter period (???7-10 days) inner shelf alongshore currents, however, were significantly correlated with the alongshore wind at the shelf break. A CEOF analysis gives two significant modes, with the first mode dominant over the outer and middle shelf. The wind-forced second mode connects the inner shelf to the poleward undercurrent over the slope such that increases in the poleward flow over the slope are correlated with increases in the equatorward current inshore of the 15 m isobath.

  6. Low Frequency Seiche in a Large Bay

    NASA Astrophysics Data System (ADS)

    MacMahan, J. H.; Thornton, E. B.; Gallagher, E. L.; Reniers, A.

    2014-12-01

    Short-term observations of sea surface elevations (η) along the 10m isobath, and long-term observations inside and outside of a large bay (Monterey Bay, CA) were obtained to describe the nodal structure of the mode 0-3 seiches within the bay and the low frequency (<346 cpd) seiche forcing mechanism. The measured nodal pattern validates previous numerical estimates associated with a northern amplitude bias, though variability exists across the modal frequency band, particularly for mode 0 and 1. Low frequency oceanic η white noise within seiche frequency bands (24-69 cpd) provides a continuous forcing of the bay seiche with a η2 (variance) amplification of 16-40 for the different modes. The temporal variation of the oceanic η white noise is significantly correlated (R2=0.86) at the 95% confidence interval with the bay seiche η that varies seasonally. The oceanic η white noise is hypothesized as being from low frequency, free, infragravity waves that are forced by short waves. This work was funded by NPS, ONR, & NSF.

  7. Seasonal thermal fronts on the northern South China Sea shelf: Satellite measurements and three repeated field surveys

    NASA Astrophysics Data System (ADS)

    Jing, Zhiyou; Qi, Yiquan; Fox-Kemper, Baylor; Du, Yan; Lian, Shumin

    2016-03-01

    Seasonal thermal fronts associated with wind-driven coastal downwelling/upwelling in the northern South China Sea are investigated using satellite measurements and three repeated fine-resolution mapping surveys in winter, spring, and summer. The results show that vigorous thermal fronts develop over the broad shelf with variable widths and intensities in different seasons, which tend to be approximately aligned with the 20-100 m isobaths. Driven by the prevailing winter/summer monsoon, the band-shaped fronts were observed with a magnitude exceeding 0.1°C/km in the subsurface, and accompanied by energetic coastal downwelling/upwelling due to shoreward/offshore Ekman transport. The downward/upward tilting of seasonal thermoclines across the shelf exceeds 20 m, significantly contributing to the development of thermal fronts over the shelf. In addition, the diagnostic analysis of Potential Vorticity (PV) suggests that the summer frontal activities induced by the coastal upwelling are more stable to convection and symmetric instabilities in comparison to the winter fronts associated with downwelling-favorable monsoon forcing. This is primarily due to their essential differences in the upper ocean stratification and horizontal buoyancy gradients arising from wind forcing. At the same time, the coastal currents are substantially regulated by the seasonal winds. An expected lag correlation between the velocity from mooring measurements and alongshore wind stress is detected near the frontal region. These results indicate that seasonal wind forcing plays an important role in the frontal activities and coastal water transport over the shelf.

  8. Feature-oriented regional modeling of oceanic fronts

    NASA Astrophysics Data System (ADS)

    Gangopadhyay, Avijit; Robinson, Allan R.

    2002-11-01

    This paper outlines some important aspects of modeling oceanic fronts in the context of feature-oriented regional modeling for the deep sea and the Global Coastal Ocean. Previously developed forms of feature models for different types of fronts are presented in a generalized approach. The large-scale meandering frontal systems such as the Gulf Stream, Kuroshio and Brazil current can be represented by velocity-based feature models. Buoyancy forced coastal water mass fronts, such as the coastal currents, the tidal fronts, plume fronts, dense water fronts and inflow/outflow fronts can be represented by a generalized parameterized water mass feature model. The interface region of the deep ocean and the coastal region can be modeled by a melding of two water masses along and across a prescribed isobath in the form of a shelf-break front. Initialization and/or updating fields for a regional dynamical model can then be established in association with other available synoptic data sets via a feature-oriented strategic sampling approach for forecasting and dynamical balances. Example simulations from the western north Atlantic (WNA) and the strait of Sicily region are presented in support of the applicability of this approach for the Global Coastal Ocean. Simulations in the strait of Sicily region with fronts, eddies and background climatology help provide a perspective on dynamical processes in this region. Application of this methodology for rapid assessment of any regional ocean, based on limited data and resources is now possible.

  9. Characterizing benthic substrates of Santa Monica Bay with seafloor photography and multibeam sonar imagery.

    PubMed

    Edwards, Brian D; Dartnell, Peter; Chezar, Henry

    2003-01-01

    Seafloor photography from three cruises is combined with multibeam sonar imagery to characterize benthic substrates and associated fauna of Santa Monica Bay, California. The multibeam EM1000 imagery was collected in 1996. Two sampling cruises (in 1998 and 1999) provided photographs at 142 sites throughout the Bay; a final cruise (in 2000) collected still photographs and continuous video along nine transects on the mainland shelf from Pt. Dume to the Palos Verdes peninsula. Muddy substrates (typically low backscatter) were the predominant habitat throughout the Santa Monica Bay, from the 20 m isobath to the adjacent Santa Monica basin floor (780 m). Bioturbation was pervasive as evidenced by abundant open burrows, mounds, and faunal tracks and trails. Sandy substrates (typically intermediate to high backscatter) were restricted to the innermost mainland shelf and a narrow outer shelf band north of Santa Monica Canyon. Cobble and gravel substrates (high backscatter) were restricted to the innermost shelf south of El Segundo and limited parts of the shelf edge. Rocky substrates (high backscatter) with interspersed patches of sand and gravel occurred on the high-relief marginal plateau and along parts of the shelf break offshore of Malibu. PMID:12648949

  10. Geochemical behavior of dissolved manganese in the East China Sea: Seasonal variation, estuarine removal, and regeneration under suboxic conditions

    NASA Astrophysics Data System (ADS)

    Wang, Zhao-Wei; Ren, Jing-Ling; Jiang, Shuo; Liu, Su-Mei; Xuan, Ji-Liang; Zhang, Jing

    2016-02-01

    To better understand the geochemical cycle of dissolved manganese (Mn) in the East China Sea (ECS), the distribution of dissolved Mn across the ECS was investigated during three field studies in 2011 (May, August, and November). The concentration of dissolved Mn decreased across the ECS with distance from the coast. Mn-rich ECS shelf waters could export to the Kuroshio Waters, and had the potential to influence the northwest Pacific Ocean as well as the Japan Sea. The Kuroshio Waters were devoid of dissolved Mn, so its incursion could be tracked as it entered the ECS continental shelf region (approximately 50 m isobath). Seasonal variations of dissolved Mn in the ECS were significant, with the highest concentrations occurring in summer. Dissolved Mn in the Changjiang Estuary was nonconservative, and significant quantities were removed by net sorption onto suspended particulate matter. A model describing the sorption processes was applied to data for the Changjiang Estuary. Regeneration of dissolved Mn took place in near-bottom waters of the suboxic zone in August 2011, following extensive consumption of oxygen. The benthic flux of dissolved Mn was estimated based on Mn concentrations in the overlying waters and the near-bottom waters. A preliminary box model was established to develop a dissolved Mn budget for the ECS. Based on the dissolved Mn content in the ECS and the total input flux, a residence time of 76-350 days for dissolved Mn in the ECS was inferred.

  11. Regional synchrony of temperature variation and internal wave forcing along the Florida Keys reef tract

    NASA Astrophysics Data System (ADS)

    Leichter, James J.; Stokes, M. Dale; Vilchis, L. Ignacio; Fiechter, Jerome

    2014-01-01

    Analysis of 10 year temperature records collected along the Florida Keys reef tract (FLKRT) reveals strong, regional-scale synchrony in high-frequency temperature variation suggestive of internal wave forcing at predominately semidiurnal frequencies. In each year and at all sites, the amplitude of semidiurnal temperature variation was greatest from March to September, and markedly lower from October to February. Comparisons of the semidiurnal component of the temperature variation among sites suggest complex patterns in the arrival of internal waves, with highest cross correlation among closely spaced sites and synchrony in periods of enhanced internal wave activity across the length of the FLKRT, particularly in summer. The periods of enhanced semidiurnal temperature variation at the 20 and 30 m isobaths on the reef slopes appear to be associated with the dynamics of the Florida Current and the onshore movement of warm fronts preceding the passage of Florida Current frontal eddies. Regional-scale satellite altimetry observations suggest temporal linkages to sea surface height anomalies in the Loop Current (upstream of the Florida Current) and setup of the Tortugas Gyre. The synchronized forcing of cool water onto the reef slope sites across the FLKRT is likely to affect physiological responses to temperature variation in corals and other ectothermic organisms, as well as larval transport and nutrient dynamics with the potential for regionally coherent pulses of larvae and nutrients arriving on reef slopes across the FLKRT.

  12. The evolution of a thin phytoplankton layer in strong turbulence

    NASA Astrophysics Data System (ADS)

    Wang, Zhankun; Goodman, Louis

    2010-01-01

    Simultaneous and collocated spatial measurements of turbulence, fine structure, and chlorophyll a fields were made from the Autonomous Underwater Vehicle T-REMUS as a part of the Layered Organization in the Coastal Ocean (LOCO) experiment. The T-REMUS was operated in a cycling 5° yo-yo mode. Deployments were of 8 h duration and consisted of a series of across isobath legs, each of 2.5 km in extent. From the suite of sensors onboard the T-REMUS vehicle we are able to measure directly the turbulent eddy velocity, we=√{ɛ/N}, and turbulent Reynolds number, Re b=( ɛ/ vN2), in the vicinity of a thin chlorophyll a layer. Using the turbulent eddy velocity, we develop criteria for when phytoplankton will behave as passive Lagrangian tracers. The turbulent Reynolds number is used as an indicator of turbulence strength, with the criterion of Re b=200 the boundary between weak and strong turbulence. We present data for the case of a spatially extensive thin layer being advected into the T-REMUS LOCO site. Using the above criterion, we observe that thin chlorophyll a layers can exist and be embedded as passive Lagrangian tracers in both weak and strong turbulent conditions. During a time period of weak turbulence Re b<200 little diffusion occurs and the thin layer remains compact. Under strong turbulence Re b>200 the thin layer weakens and diffuses as it is advected through the experimental site.

  13. Observational evidence for tidal straining over a sloping continental shelf

    NASA Astrophysics Data System (ADS)

    Endoh, Takahiro; Yoshikawa, Yutaka; Matsuno, Takeshi; Wakata, Yoshinobu; Lee, Keun-Jong; Umlauf, Lars

    2016-04-01

    Straining of a horizontal density gradient by tidal currents acts to periodically produce and destroy near-bottom stratification, which has been shown to modulate turbulence in the bottom boundary layer (BBL). Previous observations of such periodic variations have been limited to the coastal ocean and estuaries, where horizontal density gradients are maintained by river runoff or differential heating. In the present study, we show evidence for the existence of tidal straining over the continental shelf, outside any regions of freshwater influence, where horizontal density gradients are likely to result from the projection of the interior vertical stratification onto sloping topography. Based on microstructure data obtained in the East China Sea, we demonstrate that the tidal current shear interacting with the cross-isobath density gradient results in semidiurnal switching between unstable and stable stratification in the lower part of the BBL. The cycle of turbulent dissipation is quarter-diurnal, corresponding to the semidiurnal variation of tidal current shear. In addition, a noticeable diurnal modulation in stratification as well as a significant diurnal cycle of turbulent dissipation are observed in the upper part of the BBL, where the time evolution of stratification is dominated by tidal advection, rather than tidal straining.

  14. Global distribution of naturally occurring marine hypoxia on continental margins

    NASA Astrophysics Data System (ADS)

    Helly, John J.; Levin, Lisa A.

    2004-09-01

    Hypoxia in the ocean influences biogeochemical cycling of elements, the distribution of marine species and the economic well being of many coastal countries. Previous delineations of hypoxic environments focus on those in enclosed seas where hypoxia may be exacerbated by anthropogenically induced eutrophication. Permanently hypoxic water masses in the open ocean, referred to as oxygen minimum zones, impinge on a much larger seafloor surface area along continental margins of the eastern Pacific, Indian and western Atlantic Oceans. We provide the first global quantification of naturally hypoxic continental margin floor by determining upper and lower oxygen minimum zone depth boundaries from hydrographic data and computing the area between the isobaths using seafloor topography. This approach reveals that there are over one million km 2 of permanently hypoxic shelf and bathyal sea floor, where dissolved oxygen is <0.5 ml l -1; over half (59%) occurs in the northern Indian Ocean. We also document strong variation in the intensity, vertical position and thickness of the OMZ as a function of latitude in the eastern Pacific Ocean and as a function of longitude in the northern Indian Ocean. Seafloor OMZs are regions of low biodiversity and are inhospitable to most commercially valuable marine resources, but support a fascinating array of protozoan and metazoan adaptations to hypoxic conditions.

  15. Recolonization of the intertidal and shallow subtidal community following the 2008 eruption of Alaska's Kasatochi Volcano

    NASA Astrophysics Data System (ADS)

    Jewett, S. C.; Drew, G. S.

    2014-03-01

    The intertidal and nearshore benthic communities of Kasatochi Island are described following a catastrophic volcanic eruption in 2008. Prior to the eruption, the island was surrounded by a dense bed of canopy-forming dragon kelp Eualaria fistulosa which supported a productive nearshore community. The eruption extended the coastline of the island approximately 400 m offshore to roughly the 20 m isobath. One year following the eruption a reconnaissance survey found the intertidal zone devoid of life. Subtidally, the canopy kelp, as well as limited understory algal species and associated benthic fauna on the hard substratum, were buried by debris from the eruption. The resulting substrate was comprised almost entirely of medium and coarse sands with a depauperate benthic community. Comparisons of habitat and biological communities with other nearby Aleutian Islands and the Icelandic submarine volcanic eruption of Surtsey confirm dramatic reductions in flora and fauna consistent with the initial stages of recovery from a large-scale disturbance event. Four and five years following the eruption brief visits revealed dramatic intertidal and subtidal recolonization of the flora and fauna in some areas. Signs of nesting and fledging of young pigeon guillemots Cepphus columba suggest that the recovery of the nearshore biota may have begun affecting higher trophic levels. Recolonization or lack thereof was tied to bathymetric changes from coastal and nearshore erosion over the study period.

  16. Minimum distribution of subsea ice-bearing permafrost on the U.S. Beaufort Sea continental shelf

    NASA Astrophysics Data System (ADS)

    Brothers, Laura L.; Hart, Patrick E.; Ruppel, Carolyn D.

    2012-08-01

    Starting in Late Pleistocene time (˜19 ka), sea level rise inundated coastal zones worldwide. On some parts of the present-day circum-Arctic continental shelf, this led to flooding and thawing of formerly subaerial permafrost and probable dissociation of associated gas hydrates. Relict permafrost has never been systematically mapped along the 700-km-long U.S. Beaufort Sea continental shelf and is often assumed to extend to ˜120 m water depth, the approximate amount of sea level rise since the Late Pleistocene. Here, 5,000 km of multichannel seismic (MCS) data acquired between 1977 and 1992 were examined for high-velocity (>2.3 km s-1) refractions consistent with ice-bearing, coarse-grained sediments. Permafrost refractions were identified along <5% of the tracklines at depths of ˜5 to 470 m below the seafloor. The resulting map reveals the minimum extent of subsea ice-bearing permafrost, which does not extend seaward of 30 km offshore or beyond the 20 m isobath.

  17. Multiple jets in the Malvinas Current

    NASA Astrophysics Data System (ADS)

    Piola, Alberto R.; Franco, Bárbara C.; Palma, Elbio D.; Saraceno, Martín

    2013-04-01

    The velocity structure of the Malvinas Current is described based on the analysis of high-resolution hydrographic data and direct current observations. The data show that though the current width exceeds 150 km, the flow is concentrated in two relatively narrow (~10-20 km) jets. Within these cores, the direct observations indicate surface velocities exceeding 0.5 m.s-1. Surface drifter, satellite-derived mean dynamic topography, and sea surface temperature data suggest that the high-velocity jets are also ubiquitous features of the time mean circulation. Both jets appear to be continuous features extending more than 900 km along the western slope of the Argentine Basin. These jets closely follow the 200 and 1400 m isobaths. Additional high-velocity cores are apparent in direct current measurements and hydrographic observations, but these features are weaker and not continuous along the slope. Though the Malvinas Current transport is mostly barotropic, baroclinic jets are also identified in relative geostrophic velocity sections. The baroclinic jets are colocated with the barotropic jets. Our results suggest that the main Malvinas Current core is located over a relatively flat portion of the bottom, referred to as the Perito Moreno terrace. This observation is in agreement with recent seismic and geological evidence suggesting that in geological time scales the Malvinas Current played a key role in the configuration of the bottom sediments over the western slope of the Argentine Basin.

  18. Accuracy of the spatial representation of the seafloor with bathymetric sidescan sonars

    NASA Astrophysics Data System (ADS)

    Cervenka, Pierre; Herzfeld, Ute Christina; de Moustier, Christian

    1994-12-01

    When isobath maps of the seafloor are constructed with a bathymetric sidescan sonar system the position of each sounding is derived from estimates of range and elevation. The location of each pixel forming the acoustic backscatter image is calculated from the same estimates. The accuracy of the resulting maps depends on the acoustic array geometry, on the performances of the acoustic signal processing, and on knowledge of other parameters including: the platform's navigation, the sonar transducer's attitude, and the sound rays' trajectory between the sonar and the seafloor. The relative importance of these factors in the estimation of target location is assesed. The effects of the platform motions (e.g. roll, pitch, yaw, sway, surge and heave) and of the uncertainties in the elevation angle measurements are analyzed in detail. The variances associated with the representation (orientation and depth) of a plane, rectangular patch of the seafloor are evaluated, depending on the geometry of the patch. The inverse problem is addressed. Its solution gives the lateral dimensions of the spatial filter that must be applied to the bathymetric data to obtain specified accuracies of the slopes and depths. The uncertainty in the estimate of elevation angle, mostly due to the acoustic noise, is found to bring the main error contribution in across-track slope estimates. It can also be critical for along-track slope estimates, overshadowing error contributions due to the platform's attitude. Numerical examples are presented.

  19. Analysis of measured broadband acoustic propagation using a parabolic equation approach

    NASA Astrophysics Data System (ADS)

    Gray, Mason; Knobles, D. P.; Koch, Robert

    2003-10-01

    A broadband parabolic equation (PE) approach is employed to simulate data taken from two Shallow Water Acoustic Measurement Instrument (SWAMI) bottom mounted horizontal line array (HLA) experiments in shallow water environments off the east coast of the U.S. and in the Gulf of Mexico. In both experiments the HLA was deployed along an isobath. Light bulbs were imploded at known depths and ranges in both the range-independent (array end fire) and range-dependent (array broadside) directions. For the east coast experimental data, the PE model is used to infer a seabed geoacoustic description in both the range-dependent and range-independent directions. Also, comparisons of modeled time series were made for the range-independent case with a broadband normal mode model to validate the PE calculations. In the Gulf of Mexico experiment, the sediment geoacoustic profile is well known from previous inversions and geophysical measurements. This known seabed description was used to simulate the range-dependent data. A broadband energy-conserving coupled mode approach is also employed to model the range-dependent propagation. This allows the physical mechanisms associated with range-dependent propagation to be examined in a quantitative manner for this shallow water environment. [Work supported by ONR.

  20. West Florida shelf response to upwelling favorable wind forcing: Kinematics

    NASA Astrophysics Data System (ADS)

    Li, Zhenjiang; Weisberg, Robert H.

    1999-06-01

    The barotropic responses of the west Florida continental shelf to idealized upwelling favorable alongshore and offshore wind stresses are studied using the three-dimensional, time-dependent, primitive equation Princeton Ocean Model (POM). When forced with uniform winds, the shelf circulation evolves quickly to a quasi steady state. A southeastward alongshore wind lowers sea level along the coast and drives a southeastward coastal jet with a relatively weak northwestward return flow farther offshore. A southwestward offshore wind lowers sea level along the west Florida coast and raises sea level along the Panhandle coast. Two independent circulation gyres are set up in association with these regionally different sea level distributions: an anticyclonic gyre off the west Florida coast consisting of a southeastward coastal jet and a broad return flow over the middle shelf and a cyclonic gyre off the Panhandle coast consisting of a strong northwestward coastal jet and an adjacent narrow southeastward undercurrent. These gyres are separated by the Big Bend region. In both cases (alongshore and offshore wind forcing) the circulations are fully three-dimensional, with opposing surface and bottom boundary layer flows accounting for the across-shelf transports. The shapes of the coastline and the isobaths are important determinants of the shelf-wide responses. Several locally maximum upwelling regions are identified for geometrical reasons. These include the Panhandle coast south of Apalachicola Bay, the west Florida coast south of Tampa Bay, along the Florida Keys, and at the shelf break where topographic Rossby waves are evident.

  1. Drifter observations of the Gulf of Maine Coastal Current

    NASA Astrophysics Data System (ADS)

    Manning, J. P.; McGillicuddy, D. J., Jr.; Pettigrew, N. R.; Churchill, J. H.; Incze, L. S.

    2009-04-01

    Two-hundred and twenty seven satellite-tracked drifters were deployed in the Gulf of Maine (GoM) from 1988 to 2007, primarily during spring and summer. The archive of tracks includes over 100,000 km logged thus far. Statistics such as transit times, mean velocities, response to wind events, and preferred pathways are compiled for various areas of the coastal GoM. We compare Lagrangian flow with Eulerian estimates from nearby moorings and evaluate drifter trajectories using Ekman theory and 3-D ocean circulation models. Results indicate that the Gulf of Maine Coastal Current is a strong and persistent feature centered on the 94±23 m isobath, but that particles: (a) deviate from the seasonal-mean core fairly regularly, and are often re-entrained; (b) follow a slower (9 cm/s), less-constrained path in the western portion off the coast of Maine relative to the eastern (16 cm/s) section; and (c) can be affected by wind events and small-scale baroclinic structures. Residence times calculated for each 1/2° grid cell throughout the GoM depict some regions (Eastern Maine and Western Nova Scotia) as being relatively steady, flow-through systems, while others (Penobscot, Great South Channel) have more variable, branching pathways. Travel times for drifters that are retained within the coastal current along the entire western side of the Gulf of Maine are typically less than two months (55 days).

  2. Structure and variability of the Western Maine Coastal Current

    NASA Astrophysics Data System (ADS)

    Churchill, James H.; Pettigrew, Neal R.; Signell, Richard P.

    2005-09-01

    Analyses of CTD and moored current meter data from 1998 and 2000 reveal a number of mechanisms influencing the flow along the western coast of Maine. On occasions, the Eastern Maine Coastal Current extends into the western Gulf of Maine where it takes the form of a deep (order 100 m deep) and broad (order 20 km wide) southwestward flow with geostrophic velocities exceeding 20 cm s -1. This is not a coastally trapped flow, however. In fields of geostrophic velocity, computed from shipboard-CTD data, the core of this current is roughly centered at the 100 m isobath and its onshore edge is no closer than 10 km from the coast. Geostrophic velocity fields also reveal a relatively shallow (order 10 m deep) baroclinic flow adjacent to the coast. This flow is also directed to the southwest and appears to be principally comprised of local river discharge. Analyses of moored current meter data reveal wind-driven modulations of the coastal flow that are consistent with expectations from simple theoretical models. However, a large fraction of the near-shore current variance does not appear to be directly related to wind forcing. Sea-surface temperature imagery, combined with analysis of the moored current meter data, suggests that eddies and meanders within the coastal flow may at times dominate the near-shore current variance.

  3. Boundary Layer Effects on Internal Wave Generation in a Stably Stratified Fluid

    NASA Astrophysics Data System (ADS)

    Eberly, Lauren; Vanderhoff, Julie

    2010-11-01

    Through a series of laboratory experiments we attempt to quantify internal wave generation due to flow over the rough topography of a continental slope. Although significant progress has been made in flow over rough topography, few experimental studies have been done where the topography is oriented at an angle to both the isobaths and flow. Laboratory investigation is critical as linear theory is not completely accurate in describing generated internal waves. The disparity between linear theory and physical observation is greatest when the wave amplitudes reach a critical level or when boundary layer separation occurs. Previous experimental work on bottom topography suggests that linear theory over predicts the amplitude of generated lee waves as it does not account for effects due to boundary layer separation. This study employs a series of experiments to analyze an approximately two-dimensional, stably stratified fluid undergoing tidal flow over a topographically rough, sloped shelf. The laboratory set up utilizes a corrugated slope towed through the fluid as the forcing mechanism behind internal wave generation. The waves are visualized using the Synthetic Schlieren technique. Results show decreased internal wave amplitude from that predicted by linear theory.

  4. Shipboard surveys of endangered cetaceans in the northwestern Gulf of Alaska. Final report

    SciTech Connect

    Brueggeman, J.J.; Green, G.A.; Tressler, R.W.; Chapman, D.G.

    1988-10-01

    Shipboard surveys were conducted during June-July 1987 along 2,034 nmi of trackline south of the Alaska Peninsula to determine the abundance and distribution of endangered whales and other marine mammals. There were 150 observations of humpback whales, 122 of finback whales, 351 of Dall porpoises, 101 of killer whales, 12 of minke whales, 3 of harbor porpoises, and 170 of pinnipeds and sea otters. Humpbacks were primarily associated with the 50- and 100-fathom isobaths, particularly near the Shelikof Strait submarine canyon and some banks. Humpbacks and finbacks were observed on one occasion feeding together, but their distribution generally did not overlap. The other species were widespread in the study area except for killer whales, which were observed together east of Kodiak Island. Abundance was estimated for humpbacks at 1,247 (+ or - 392 SE) and finbacks at 1,257 (+ or - 563 SE). Sample sizes were too small to estiamte abundance for the other species. These results are similar to those developed for this area in 1985.

  5. Contribution à l'étude d'une partie du bassin d'Essaouira (Maroc) par sismique réflexionContribution to part of the Essaouira Basin (Morocco) by seismic reflection

    NASA Astrophysics Data System (ADS)

    Jaffal, Mohammed; Kchikach, Azzouz; Lefort, Jean-Pierre; Hanich, Lahoucine

    A large number of seismic reflection lines and boreholes have been carried out in the Essaouira Basin by the oil industry. The present study concentrates on the reinterpretation of these data in the restricted area of Khemis Meskala, in order to better characterise the structure of the Cretaceous aquiferous system. The reflector corresponding to the bottom of the Vraconian formation has been identified on the different seismic sections. This horizon, which marks the base of the aquiferous system, was first digitised on time migration sections and then converted to depth sections using a suitable linear velocity law. The isobath map of the bottom of the Vraconian resulting from this study images the 3D geometrical structure of this horizon and shows that it is slightly folded in domes and basins. This document will be useful for rationalising the future hydrogeological researches that will be undertaken in the Khemis Meskala area. To cite this article: M. Jaffal et al., C. R. Geoscience 334 (2002) 229-234.

  6. Effects of fotemustine or dacarbasine on a melanoma cell line pretreated with therapeutic proton irradiation

    PubMed Central

    Ristić-Fira, Aleksandra M; Korićanac, Lela B; Žakula, Jelena J; Valastro, Lucia M; Iannolo, Gioacchin; Privitera, Giuseppe; Cuttone, Giacomo; Petrović, Ivan M

    2009-01-01

    Background Considering that HTB140 melanoma cells have shown a poor response to either protons or alkylating agents, the effects of a combined use of these agents have been analysed. Methods Cells were irradiated in the middle of the therapeutic 62 MeV proton spread out Bragg peak (SOBP). Irradiation doses were 12 or 16 Gy and are those frequently used in proton therapy. Four days after irradiation cells were treated with fotemustine (FM) or dacarbazine (DTIC). Drug concentrations were 100 and 250 μM, values close to those that produce 50% of growth inhibition. Cell viability, proliferation, survival and cell cycle distribution were assessed 7 days after irradiation that corresponds to more than six doubling times of HTB140 cells. In this way incubation periods providing the best single effects of drugs (3 days) and protons (7 days) coincided at the same time. Results Single proton irradiations have reduced the number of cells to ~50%. FM caused stronger cell inactivation due to its high toxicity, while the effectiveness of DTIC, that was important at short term, almost vanished with the incubation of 7 days. Cellular mechanisms triggered by proton irradiation differently influenced the final effects of combined treatments. Combination of protons and FM did not improve cell inactivation level achieved by single treatments. A low efficiency of the single DTIC treatment was overcome when DTIC was introduced following proton irradiation, giving better inhibitory effects with respect to the single treatments. Most of the analysed cells were in G1/S phase, viable, active and able to replicate DNA. Conclusion The obtained results are the consequence of a high resistance of HTB140 melanoma cells to protons and/or drugs. The inactivation level of the HTB140 human melanoma cells after protons, FM or DTIC treatments was not enhanced by their combined application. PMID:19358719

  7. Wind speeds in two tornadic storms and a tornado, deduced from Doppler Spectra

    SciTech Connect

    Zrnic, D.; Istok, M.

    1980-12-01

    Doppler spectra of a tornado were collected with a radar having a large unambiguous velocity range, +- 91 m s/sup -1/. Thus for the first time a presentation of nonaliased spectra was possible, showing direct measurement of radial velocities. By fitting the tornado model spectrum to data, the radius of maximum winds and tornado center location are deduced. Tornado spectral signature is defined as a double peak, symmetric with respect to the mean wind spectrum. Histograms of maximum measured wind speeds (from spectrum skirts) for two tornadic storms are obtained, and the histograms of velocity difference (between the left and right spectrum skirt) suggest that smaller scale turbulence (<500 m) is principally responsible for spectrum broadness.

  8. Rapid scanning all-reflective optical delay line for real-time optical coherence tomography.

    PubMed

    Liu, Xiumei; Cobb, Michael J; Li, Xingde

    2004-01-01

    We describe a dispersion-free high-speed scanning optical delay line that is suitable for real-time optical coherence tomography, in particular, when an ultrabroadband light source is used. The delay line is based on all-reflective optics consisting of two flat and one curved mirrors. We achieve optical path-length scanning by oscillating one of the two flat mirrors with a resonant galvanometer. The delay line is compact and easy to implement. A total scanning depth of 1.50 mm with an 89% duty ratio, a maximal scanning speed of approximately 9.1 m/s, and a 4.1-kHz repetition rate has been demonstrated. PMID:14719667

  9. Enzymatic Microreactors for the Determination of Ethanol by an Automatic Sequential Injection Analysis System

    NASA Astrophysics Data System (ADS)

    Alhadeff, Eliana M.; Salgado, Andrea M.; Cos, Oriol; Pereira, Nei; Valdman, Belkis; Valero, Francisco

    A sequential injection analysis system with two enzymatic microreactors for the determination of ethanol has been designed. Alcohol oxidase and horseradish peroxidase were separately immobilized on glass aminopropyl beads, and packed in 0.91-mL volume microreactors, working in line with the sequential injection analysis system. A stop flow of 120 s was selected for a linear ethanol range of 0.005-0.04 g/L±0.6% relative standard deviation with a throughput of seven analyses per hour. The system was applied to measure ethanol concentrations in samples of distilled and nondistilled alcoholic beverages, and of alcoholic fermentation with good performance and no significant difference compared with other analytical procedures (gas chromatography and high-performance liquid chromatography).

  10. Aspects of blast resistant masonry design

    SciTech Connect

    Volkman, D.E.

    1989-01-01

    Blast resistant design should be examined for building code incorporation, due to the potential of explosions occurring in an industrial society. Specifically, public and commercial structures of concrete masonry construction need additional building code criteria, since these buildings have high density populations to protect. Presently, blast resistant design is accomplished by using government published manuals, but these do not address industry standard construction. A design air blast load of 4.54 kg (10 lbs) of TNT, located 0.91 m (3 ft) above ground surface and 30.48 m (100 ft) from a structure should be considered standard criteria. This loading would be sufficient to protect against blast, resist progressive failure, and yet not be an economic impediment. Design details and adequate inspection must be observed to ensure blast resistant integrity. 10 refs., 3 figs., 1 tab.

  11. New activation cross section data on longer lived radio-nuclei produced in proton induced nuclear reaction on zirconium.

    PubMed

    Tárkányi, F; Ditrói, F; Takács, S; Hermanne, A; Al-Abyad, M; Yamazaki, H; Baba, M; Mohammadi, M A

    2015-03-01

    The excitation functions of (96)Nb, (95m)Nb, (95g)Nb, (92m)Nb, (91m)Nb, (90)Nb, (95)Zr, (89)Zr, (88)Zr, (86)Zr, (88)Y, (87m)Y, (87g)Y, (86)Y were measured up to 70MeV proton energy by using the stacked foil technique and the activation method. The new data were compared with the critically analyzed experimental data in the literature and with the TALYS based model results in TENDL-2013 library. The possible role of the investigated reactions in the production of medically relevant (90)Nb, (95m)Nb, (89)Zr, and (88)Y radionuclides is discussed. PMID:25579457

  12. Engineering report on drilling in the Black Hills, South Dakota

    SciTech Connect

    Abou-Zied, S.; Callihan, M.C.

    1980-01-01

    The Black Hills drilling project was conducted by Bendix Field Engineering Corporation (BFEC) in support of the US Department of Energy (DOE) National Uranium Resource Evaluation (NURE) program. The project consisted of five drill holes, ranging in depth from 365 feet (111.25 m) to 564 feet (171.90 m). A total of 2,211 feet (673.91 m) were drilled, all of which were cored. The objective of the project was to obtain subsurface data which would enable us to more accurately assess the favorability of the Precambrian Estes Conglomerate as a host of World Class uranium deposits. Drilling began on August 3, 1979, and concluded on September 7, 1979, with final site restoration and clean-up.

  13. The Effect of Widowhood on Husbands’ and Wives’ Physical Activity: The Cardiovascular Health Study

    PubMed Central

    Stahl, Sarah T.; Schulz, Richard

    2013-01-01

    This prospective study examined the effect of widowhood on physical activity by comparing widowed elders to health status-, age-, and sex-matched married controls. Participants included 396 married controls and 396 widows/widowers age 64 to 91 (M age = 72.7 years) who experienced the death of their spouse while participating in the Cardiovascular Health Study (CHS). Compared to married controls, widowed men, but not women, were more likely to increase their physical activity following the death of their spouse. However, this increased level of activity was not sustained and declines as time since spousal death passes. Moreover, during the year before spousal death, soon-to-be widowed men, but not women, increase their physical activity. Our results suggest that widowed men experience significant changes in physical activity and that the transition to widowhood contribute to these changes. PMID:23975417

  14. Okayama astrophysical observatory wide field camera

    NASA Astrophysics Data System (ADS)

    Yanagisawa, Kenshi; Shimizu, Yasuhiro; Okita, Kiichi; Kuroda, Daisuke; Koyano, Hisashi; Tsutsui, Hironori; Toda, Hiroyuki; Izumiura, Hideyuki; Yoshida, Michitoshi; Ohta, Kouji; Kawai, Nobuyuki; Yamamuro, Tomoyasu

    2014-08-01

    Okayama Astrophysical Observatory Wide Field Camera: OAOWFC is a near-infrared (0.9-2.5 μm) survey telescope, whose aperture is 0.91m. It works at Y, J, H, and Ks bands. The optics are consisted of forward Cassegrain and quasi Schmidt which yield the image circle of Φ 52 mm or Φ 1.3 deg at the focal plane. The overall F-ratio is F/2.51 which is one of the fastest among near infrared imagers in the world. A HAWAII-1 detector array placed at the focal plane cuts the central 0.48 deg. x 0.48 deg. with a pixel scale of 1.67 arcsec/pix. It will be used to survey the Galactic plane for variability and search for transients such as Gamma-ray burst afterglows optical counterpart of gravitational wave sources.

  15. Holographic modification of TiO2 nanostructure for enhanced charge transport in dye-sensitized solar cell

    NASA Astrophysics Data System (ADS)

    Lee, Jinsoo; Yoon, Junghwan; Jin, Minhea; Lee, Myeongkyu

    2012-08-01

    We show that the photocurrent and energy conversion efficiency of dye-sensitized solar cells can be greatly enhanced with holographic modification to the morphology of TiO2 electrode. The nanoporous electrode coated onto conducting glass was irradiated by three interfering laser beams at 1064 nm incident from the backside of the substrate. This generated two-dimensional periodic pillars of higher density in the electrode, through which the photoexcited electrons could be extracted more effectively. The cells fabricated with modified electrodes exhibited average photocurrent and efficiency of 17.14 mA/cm2 and 9.03%, while 14.91 mA/cm2 and 7.83% were obtained from the reference cells. It was attributed to the enhanced charge transport accompanied by the reduction of internal resistance of the electrode.

  16. Fabrication and characterization of a microaccelerometer based on resonant-tunneling diodes

    NASA Astrophysics Data System (ADS)

    Li, Mengwei; Deng, Tao; Du, Kang; Chu, WeiHang; Liu, Jun; Chen, Houjin; Liu, Zewen

    2016-01-01

    A microaccelerometer based on gallium arsenide (GaAs) resonant-tunneling diodes (RTDs) is demonstrated. The input acceleration signal can be transformed into an output electrical signal using the meso-piezoresistive effects of the RTDs located at the root of the detection beams. Finite element simulations were performed to design, analyze, and optimize the structures of the accelerometer. The accelerometer was fabricated using a combination of GaAs IC surface and bulk micromachining techniques. Vibrating tests and shock tests were conducted to investigate the accelerometer characteristics. The experimental results revealed that the sensitivity of the RTD accelerometer was 7.91 mV/g. The noise resolution was ˜1.264 mg/√Hz, and the working frequency was up to 3 kHz.

  17. Prototype spent-fuel canister design, analysis, and test

    SciTech Connect

    Leisher, W.B.; Eakes, R.G.; Duffey, T.A.

    1982-03-01

    Sandia National Laboratories was asked by the US Energy Research and Development Administration (now US Department of Energy) to design the spent fuel shipping cask system for the Clinch River Breeder Reactor Plant (CRBRP). As a part of this task, a canister which holds liquid sodium and the spent fuel assembly was designed, analyzed, and tested. The canister body survived the regulatory Type-B 9.1-m (30-ft) drop test with no apparent leakage. However, the commercially available metal seal used in this design leaked after the tests. This report describes the design approach, analysis, and prototype canister testing. Recommended work for completing the design, when funding is available, is included.

  18. The size distribution of the earth-approaching asteroids

    NASA Astrophysics Data System (ADS)

    Rabinowitz, D. L.

    1993-04-01

    The discovery circumstances of the first asteroids ever observed outside the earth's atmosphere but within the neighborhood of the earth-moon system are described. Four natural objects with diameters in the range 5-50 m were detected during a search for earth-approaching asteroids conducted each month at the 0.91-m Spacewatch Telescope at Kitt Peak. An additional 19 earth approachers with sizes in the range 50 m to 5 km were discovered. These obervations determine the cumulative flux of asteroids near earth as a function of absolute magnitude. For asteroids larger than about 100 m, a power-law dependence with exponent of about 0.9 is observed, consistent with their evolution from the main-belt population. At about 10 m, the flux is more than two orders of magnitude greater than this power-law extrapolation.

  19. Spinal injury in a U.S. Army light observation helicopter.

    PubMed

    Shanahan, D F; Mastroianni, G R

    1984-01-01

    All accident reports involving U.S. Army OH-58 series helicopters were analyzed to determine vertical and horizontal velocity change at impact and the relationship of this kinematic data to the production of spinal injury. This analysis determined that spinal injury is related primarily to vertical velocity change at impact and is relatively independent of horizontal velocity change. The dramatic increase in the rate of spinal injury occurring just above the design sink speed of the aircraft landing gear (3.7 m/s) suggests that the fuselage and seat provide little additional impact attenuation capability above that of the gear alone. It is concluded that if this aircraft were modified to provide protection to the occupants for impacts up to 9.1 m/s (30 ft/s), approximately 80% of all spinal injury incurred in survivable accidents could be substantially mitigated. The incorporation of energy absorbing seats is recommended. PMID:6696693

  20. Friction loss in straight pipes of unplasticized polyvinyl chloride.

    PubMed

    Iwasaki, T; Ojima, J

    1996-01-01

    In order to design proper ductwork for a local exhaust system, airflow characteristics were investigated in straight pipes of unplasticized polyvinyl chloride (PVC). A linear decrease in static pressure was observed downstream at points from the opening of the VU pipes (JIS K 6741) located at distances greater than 10 times the pipe diameter, for velocities ranging between 10.18-36.91 m/s. Roughness inside pipes with small diameters was found to be 0.0042-0.0056 mm and the friction factor was calculated on the basis of Colebrook's equation for an airflow transition zone. An extended friction chart was then constructed on the basis of the roughness value and the friction factor. This chart can be applied when designing a local exhaust system with the ducts of diameters ranging from 40 to 900 mm. The friction loss of the PVC pipe was found to be approximately 2/3 of that of a galvanized steel pipe. PMID:8768669

  1. FRAM 2 Single Channel Ambient Noise Statistics

    NASA Astrophysics Data System (ADS)

    Dwyer, R. F.

    1981-11-01

    This document describes the results of a statistical analysis study of FRAM II arctic under-ice ambient noise data. The specific data that were analyzed were recorded on 23-24 April 1980 from a pack ice camp in the Arctic Ocean, located at 86 deg N latitude, 25 deg W longitude. At this location, the bottom depth was approximately 4000 m. The measurement system consisted of a broadband omnidirectional hydrophone, suspended to a depth of 91 m from a sonobuoy located in a lead. Under the influence of arctic currents, the pack ice was slowly moving. This movement caused rifting and cracking of ice, which occurred, at times, throughout the experiments and represented a structured acoustic noise source. Both impulsive and burst noise were identified in the data and were probably created by tensile cracks and rubbing ice masses.

  2. Formulation optimization of palm kernel oil esters nanoemulsion-loaded with chloramphenicol suitable for meningitis treatment.

    PubMed

    Musa, Siti Hajar; Basri, Mahiran; Masoumi, Hamid Reza Fard; Karjiban, Roghayeh Abedi; Malek, Emilia Abd; Basri, Hamidon; Shamsuddin, Ahmad Fuad

    2013-12-01

    Palm kernel oil esters nanoemulsion-loaded with chloramphenicol was optimized using response surface methodology (RSM), a multivariate statistical technique. Effect of independent variables (oil amount, lecithin amount and glycerol amount) toward response variables (particle size, polydispersity index, zeta potential and osmolality) were studied using central composite design (CCD). RSM analysis showed that the experimental data could be fitted into a second-order polynomial model. Chloramphenicol-loaded nanoemulsion was formulated by using high pressure homogenizer. The optimized chloramphenicol-loaded nanoemulsion response values for particle size, PDI, zeta potential and osmolality were 95.33nm, 0.238, -36.91mV, and 200mOsm/kg, respectively. The actual values of the formulated nanoemulsion were in good agreement with the predicted values obtained from RSM. The results showed that the optimized compositions have the potential to be used as a parenteral emulsion to cross blood-brain barrier (BBB) for meningitis treatment. PMID:23974000

  3. Platinum-based nanocomposite electrodes for low-temperature solid oxide fuel cells with extended lifetime

    NASA Astrophysics Data System (ADS)

    Lee, Yoon Ho; Cho, Gu Young; Chang, Ikwhang; Ji, Sanghoon; Kim, Young Beom; Cha, Suk Won

    2016-03-01

    Due to its high catalytic activity and convenient fabrication procedure that uses physical vapor deposition (PVD), nanofabricated platinum (Pt) is widely used for low temperature operating solid oxide fuel cells (LT-SOFC). However, the poor thermal stability of nanofabricated Pt accelerates cell performance degradation. To solve this problem, we apply a thermal barrier coating and use the dispersion hardening process for the nanofabrication of Pt by sputter device. Through morphological and electrochemical data, GDC modified nano-porous Pt electrodes shows improved performance and thermal stability at the operating temperature of 500 °C. While the peak power density of pure Pt sample is 6.16 mW cm-2 with a performance degradation of 43% in an hour, the peak power density of the GDC modified Pt electrodes are in range of 7.42-7.91 mW cm-2 with a 7-16% of performance degradation.

  4. Vacuum deposition of iridium on large astronomical mirrors for use in the far UV

    NASA Technical Reports Server (NTRS)

    Herzig, H.; Spencer, R. S.

    1982-01-01

    An iridium coating has been deposited by electron-beam evaporation on a 0.91-m mirror which serves as the telescope primary of a sounding rocket instrument for far-UV spectrometry. The evaporation was carried out by applying 8 kV at 400 mA to the electron gun. Zone refined Ir of 99.99% purity was used, and the electron beam was electromagnetically swept over the surface of the evaporant. Under these conditions, deposition rates of 0.55 A/sec were achieved. The reflectance distribution achieved at a wavelength of 584 A was extremely uniform; the mean reflectance was 21.2% with a standard deviation of only 0.3%. This represents a substantial improvement over Al + MgF2 and Al + LiF coatings for applications involving multiple reflections and weak signals, as might be expected in a high-resolution spectrograph studying distant celestial objects.

  5. Submersible observations of an iceberg pit and scour on the Grand Banks of Newfoundland

    NASA Astrophysics Data System (ADS)

    Barrie, J. V.; Lewis, C. F. M.; Parrott, D. R.; Collins, W. T.

    1992-03-01

    An elongated sea bed depression (pit), 80 by 125 m and 10 m deep located on the Grand Banks of Newfoundland was identified on high resolution surficial geophysical survey lines and investigated using a manned submersible. The pit occurs at the termination of a long (greater than 3 km) iceberg scour, 1.5 m deep, and 80 m wide in 91 m of water. It is similar to other depressions in the region that indent the sea bed up to seven times deeper than the surrounding deepest iceberg furrows. The pit is interpreted to be the sea bed response to impact and loading by a rolling and grounding iceberg. The iceberg scour and pit appear to be of recent origin.

  6. Development of multiwavelength excitation light source for autofluorescence and photodynamic diagnosis systems

    NASA Astrophysics Data System (ADS)

    Kenar, Necla; Lim, H. S.; Mirzaaghasi, Amin

    2014-02-01

    New design of the excitation light source that can stably generate light with center wavelengths of 450nm, 530nm, 632.8nm and white light for auto-fluorescence(AF) and photodynamic diagnosis(PDD) of cancer in clinics in a single system is presented in this study. The light source consists of Xenon Lamp (300W), light guide module including motorize filter wheel equipped with optical filters with corresponding to wavelength bands, servo motor, motorize iris, a cooling system, power supply and optical transmission part for the output light. The transmission part of the light source was developed to collimate the light with desired wavelength into input of fiber optic. Output powers are obtained average 99.91 mW for 450+/-40 nm, 111.01 mW for 530+/-10nm, and 78.50 mW for 632.8+/-10nm.

  7. Transesterification of rapeseed oil for biodiesel production in trickle-bed reactors packed with heterogeneous Ca/Al composite oxide-based alkaline catalyst.

    PubMed

    Meng, Yong-Lu; Tian, Song-Jiang; Li, Shu-Fen; Wang, Bo-Yang; Zhang, Min-Hua

    2013-05-01

    A conventional trickle bed reactor and its modified type both packed with Ca/Al composite oxide-based alkaline catalysts were studied for biodiesel production by transesterification of rapeseed oil and methanol. The effects of the methanol usage and oil flow rate on the FAME yield were investigated under the normal pressure and methanol boiling state. The oil flow rate had a significant effect on the FAME yield for the both reactors. The modified trickle bed reactor kept over 94.5% FAME yield under 0.6 mL/min oil flow rate and 91 mL catalyst bed volume, showing a much higher conversion and operational stability than the conventional type. With the modified trickle bed reactor, both transesterification and methanol separation could be performed simultaneously, and glycerin and methyl esters were separated additionally by gravity separation. PMID:23558183

  8. Holographic modification of TiO{sub 2} nanostructure for enhanced charge transport in dye-sensitized solar cell

    SciTech Connect

    Lee, Jinsoo; Yoon, Junghwan; Jin, Minhea; Lee, Myeongkyu

    2012-08-15

    We show that the photocurrent and energy conversion efficiency of dye-sensitized solar cells can be greatly enhanced with holographic modification to the morphology of TiO{sub 2} electrode. The nanoporous electrode coated onto conducting glass was irradiated by three interfering laser beams at 1064 nm incident from the backside of the substrate. This generated two-dimensional periodic pillars of higher density in the electrode, through which the photoexcited electrons could be extracted more effectively. The cells fabricated with modified electrodes exhibited average photocurrent and efficiency of 17.14 mA/cm{sup 2} and 9.03%, while 14.91 mA/cm{sup 2} and 7.83% were obtained from the reference cells. It was attributed to the enhanced charge transport accompanied by the reduction of internal resistance of the electrode.

  9. Mass balance, meteorological, and runoff measurements at South Cascade Glacier, Washington, 1992 balance year

    USGS Publications Warehouse

    Krimmel, R.M.

    1993-01-01

    Values of winter snow accumulation and summer snow, firn, and ice ablation were measured at South Cascade Glacier, WA, to determine the winter and net balance for the 1992 balance year. The 1992 winter balance, averaged over the glacier, was 1.91 m, and the net balance was -2.01 m. This extremely negative balance continued a trend of negative balance years beginning in 1977. Air temperature (at 1,615 m and 1,867 m), barometric pressure, precipitation, and runoff from this glacier basin and an adjacent non-glacierized basin were also continuously measured. This report makes all these data, in tabular, graphical, and machine-readable forms, available to users.

  10. Performance enhancement of dye-sensitized solar cell with a TiCl4-treated TiO2 compact layer

    NASA Astrophysics Data System (ADS)

    Park, Jisuk; Lee, Myeongkyu

    2015-03-01

    We here show that an effective blocking layer for dye-sensitized solar cells (DSSCs) can be formed by spin coating a commercial TiO2 paste onto a conducting glass substrate. The spin-coated TiO2 layer was made more compact than the main absorption layer by TiCl4 treatment. DSSCs employing a compact layer exhibited an average current density and an efficiency of 19.09 mA/cm2 and 9.10%, respectively, while 16.91 mA/cm2 and 8.33% were obtained from unblocked reference cells. The enhanced DSSC performance is attributed to the increased electron lifetime. Intensity-modulated photovoltage spectroscopy and open-circuit voltage decay analysis showed that a TiCl4-treated compact layer substantially suppresses the charge recombination at the TiO2/substrate interface, thereby increasing the electron lifetime. [Figure not available: see fulltext.

  11. Effect of Substrate Temperature on Ti/TiO2 Layers Growth Using a Combined Sputtering/Sol-Gel Combustion Method.

    PubMed

    Kim, Sang-Gon; Sung, Youl-Moon; Shin, Hoon-Kyu

    2015-02-01

    A combined radio frequency sputtering/sol-gel combustion method was investigated in order to obtain optimum process condition for fabrication of a Titanium (Ti)/Titanium oxide (TiO2) films electrode of transparent conductive oxide-less dye-sensitized solar cells (TCO-less DSCs), Experimentally, the substrate temperature was changed from R.T. to 500 °C, and it was found that there existed an optimum value for efficient performance of the cell. The porous Ti layer with low sheet resistance (-2.5 Ω/sq.) can be prepared by substrate temperature 250 °C under RF power 300 W and Ar 8 mTorr. The efficiency (η) of the cell was 6.52% [FF: 0.76, VOC: 0.72 V, JSC: 11.91 mA/cm2]. PMID:26353715

  12. A two-dimensional simulation of tritium transport in the vadose zone at the Nevada Test site

    SciTech Connect

    Ross, W.C.; Wheatcraft, S.W.

    1994-09-01

    The site of a 0.75-kiloton underground nuclear explosion, the Cambric event, was selected for the study of radionuclide transport in the hydrologic environment. Water samples from RNM-2S, a well located 91 m from Cambric, have been analyzed for tritium and other radionuclides since the initiation of pumping. Water from RNM-2S flows to Frenchman Lake via an unlined canal. Flume data indicate canal transmission losses of approximately 2m{sup 3}/day/meter of canal. To determine if infiltrating canal water might be recirculated by RNM-2S, and therefore provide an additional radionuclide input to water samples collected at RNM-2S, a two-dimensional variably saturated solute transport computer model (SATURN, Huyakorn et al., 1983) was used to simulate the movement of tritium from the canal to the water table. Results indicate that recirculated canal water has not had a significant effect on the breakthrough of tritium at RNM-2S.

  13. Activation cross sections of deuteron induced reactions on niobium in the 30-50 MeV energy range

    NASA Astrophysics Data System (ADS)

    Ditrói, F.; Tárkányi, F.; Takács, S.; Hermanne, A.; Ignatyuk, A. V.

    2016-04-01

    Activation cross-sections of deuterons induced reactions on Nb targets were determined with the aim of different applications and comparison with theoretical models. We present the experimental excitation functions of 93Nb(d,x)93m,90Mo, 92m,91m,90Nb, 89,88Zr and 88,87m,87gY in the energy range of 30-50 MeV. The results were compared with earlier measurements and with the cross-sections calculated by means of the theoretical model codes ALICE-D, EMPIRE-D and TALYS (on-line TENDL-2014 and TENDL-2015 libraries). Possible applications of the radioisotopes are discussed in detail.

  14. Ethanol synthesis and water gas shift over bifunctional sulfide catalysts

    SciTech Connect

    Klier, K.; Herman, R.G.; Deemer, M.

    1992-12-01

    During this quarter, the surface areas of various catalysts were determined. The surface area of the catalyst tested last quarter was determined for the undoped catalyst, the doped catalyst before testing, and the doped catalyst after testing. These surface areas were then compared with ones reported earlier. After testing under high temperature and high pressure conditions for 551 hours, there was a loss of surface area. This might be due possibly to agglomeration of cesium formate on the surface. Higher surface area catalysts were also produced. Two samples of MoS[sub 2] were synthesized with surface areas of 96 m2/g and 91 m2/g. These were obtained by varying the heating rate of MoS[sub 3] and the calcination temperature.

  15. Ethanol synthesis and water gas shift over bifunctional sulfide catalysts. Technical progress report, September 1992--November 1992

    SciTech Connect

    Klier, K.; Herman, R.G.; Deemer, M.

    1992-12-01

    During this quarter, the surface areas of various catalysts were determined. The surface area of the catalyst tested last quarter was determined for the undoped catalyst, the doped catalyst before testing, and the doped catalyst after testing. These surface areas were then compared with ones reported earlier. After testing under high temperature and high pressure conditions for 551 hours, there was a loss of surface area. This might be due possibly to agglomeration of cesium formate on the surface. Higher surface area catalysts were also produced. Two samples of MoS{sub 2} were synthesized with surface areas of 96 m2/g and 91 m2/g. These were obtained by varying the heating rate of MoS{sub 3} and the calcination temperature.

  16. Results of a five-year program of multifrequency monitoring of low-frequency variable radio sources

    NASA Technical Reports Server (NTRS)

    Mitchell, K. J.; Dennison, Brian; Condon, J. J.; Altschuler, Daniel R.; Payne, H. E.; O'Dell, S. L.; Broderick, J. J.

    1994-01-01

    We present the results of a detailed multifrequency monitoring program of low-frequency variable radio sources. This consists of light curves at 318, 430, 606, 880, and 1400 MHz over a 5 year period. The observations were carried out with the Arecibo 305 m radiotelescope and the Green Bank 91 m radio telescope. The spectral characteristics of the variations confirm the general picture that at least two mechanisms are responsible. The first is clearly intrinsic evolution of synchrotron-emitting components as it is manifested by variations that appear first and most strongly at high frequencies, subsequently drifting to lower frequencies with diminished amplitude. The more common type of low-frequency variability, however, dominates at frequencies below approximately 800 MHz, while the variations near 1 GHz are often quite weak. This spectral property is strong evidence that these variations are interstellar refractive scintillation.

  17. Power spectral density of subsonic jet noise

    NASA Technical Reports Server (NTRS)

    Zaman, K. B. M. Q.; Yu, J. C.

    1985-01-01

    The power-spectrum density (PSD) of the far-field noise of a subsonic unheated axisymmetric jet is investigated by analysis of about 80 sets of published noise spectra and of spectra obtained using 12.7 and 25.4-mm-diameter compressed-air jets at exit velocities 66 and 104 m/s and 67 and 91 m/s, respectively, in the NASA Langley anechoic flow facility. The results are presented in tables and graphs and characterized in detail. Findings reported include Strouhal-number scaling of the PSD at theta = 30 deg or more, scaling with the product of the Helmholtz number and the Doppler factor at theta less than 30 deg, best collapse at source convection Mach number 0.5, variation of PSD amplitude as U to the 6.5th at theta = 90 deg, and no sharp PSD-amplitude variation at any critical Reynolds number.

  18. A Cryogenic test stand for LHC quadrupole magnets

    SciTech Connect

    R. J. Rabehl et al.

    2004-03-09

    A new test stand for testing LHC interaction region (IR) quadrupole magnets at the Fermilab Magnet Test Facility has been designed and operated. The test stand uses a double bath system with a lambda plate to provide the magnet with a stagnant bath of pressurized He II at 1.9 K and 0.13 MPa. A cryostated magnet 0.91 m in diameter and up to 13 m in length can be accommodated. This paper describes the system design and operation. Issues related to both 4.5 K and 1.9 K operations and magnet quenching are highlighted. An overview of the data acquisition and cryogenics controls systems is also included.

  19. Laithwaite's Heavy Spinning Disk Demonstration

    NASA Astrophysics Data System (ADS)

    Cross, Rod

    2014-09-01

    In 1974, Professor Eric Laithwaite demonstrated an unusually heavy gyroscope at a Royal Institution lecture in London. The demonstration was televised and can be viewed on YouTube.1 A recent version of the same experiment, together with partial explanations, attracted two million YouTube views in the first few months.2 In both cases, the gyroscope consisted of a 40-lb (18-kg) spinning disk on the end of a 3-ft (0.91-m) long axle. The most remarkable feature of the demonstration was that Laithwaite was able to lift the disk over his head with one hand, holding onto the far end of the axle. The impression was given that the 40-lb disk was almost weightless, or "as light as a feather" according to Laithwaite.

  20. Excitation functions for production of radioisotopes of niobium, zirconium and yttrium by irradiation of zirconium with deuterons

    NASA Astrophysics Data System (ADS)

    Tárkányi, F.; Hermanne, A.; Takács, S.; Ditrói, F.; Dityuk, A. I.; Shubin, Yu. N.

    2004-05-01

    Excitation functions of deuteron-induced reactions on natural zirconium were re-measured up to 50 MeV for the natZr(d,x) 90,91m,92m,95,96Nb, natZr(d,x) 88,89,95,97Zr and natZr(d,x) 86,87,88Y reactions. A physically accurate activation method on stacks of natural zirconium foils was used. The results were critically compared with a detailed compilation of earlier reported experimental data and with theoretical calculations. In the overlapping energy regions mainly acceptable agreement was found or our data complete the database where contradictory or scarce data were available. The possible alternative uses in medically relevant radionuclide production as well as applications in thin layer activation and dosimetry are discussed.

  1. Common denominator of three weather-related aircraft accidents. [due to thunderstorm related downburst

    NASA Technical Reports Server (NTRS)

    Fujita, T. T.; Caracena, F.

    1977-01-01

    Three aircraft accidents are analyzed to gain an understanding of thunderstorm-related downbursts, or extremely rapid downdrafts, which interfered with takeoff or landing maneuvers in each of the three cases. For the purposes of this study, downbursts are defined as having downward speeds greater than 3.6 m/sec at 91 m altitude, and diameters of 800 m or greater. Few of the strongest downdrafts investigated reach the intensity of a downburst. The downburst cells mature about 5-10 minutes after formation, and are generally no more than 3-4 miles in diameter at maturity. A spearhead echo is found to be associated with each of the downburst-caused accidents.

  2. Evaluation of Interferon Resistance in Newly Established Genotype 1b Hepatitis C Virus Cell Culture System

    PubMed Central

    Taniguchi, Miki; Tasaka-Fujita, Megumi; Nakagawa, Mina; Watanabe, Takako; Kawai-Kitahata, Fukiko; Otani, Satoshi; Goto, Fumio; Nagata, Hiroko; Kaneko, Shun; Nitta, Sayuri; Murakawa, Miyako; Nishimura-Sakurai, Yuki; Azuma, Seishin; Itsui, Yasuhiro; Mori, Kenichi; Yagi, Shintaro; Kakinuma, Sei; Asahina, Yasuhiro; Watanabe, Mamoru

    2016-01-01

    Background and Aims: The hepatitis C virus (HCV) genotype 1b is known to exhibit treatment resistance with respect to interferon (IFN) therapy. Substitution of amino acids 70 and 91 in the core region of the 1b genotype is a significant predictor of liver carcinogenesis and poor response to pegylated-IFN-α and ribavirin therapy. However, the molecular mechanism has not yet been clearly elucidated because of limitations of the HCV genotype 1b infectious model. Recently, the TPF1-M170T HCV genotype 1b cell culture system was established, in which the clone successfully replicates and infects Huh-7-derived Huh7-ALS32.50 cells. Therefore, the purpose of this study was to compare IFN resistance in various HCV clones using this system. Methods: HCV core amino acid substitutions R70Q and L91M were introduced to the TPF1-M170T clone and then transfected into Huh7-ALS32.50 cells. To evaluate the production of each virus, intracellular HCV core antigens were measured. Results were confirmed with Western blot analysis using anti-NS5A antibodies, and IFN sensitivity was subsequently measured. Results: Each clone was transfected successfully compared with JFH-1, with a significant difference in intracellular HCV core antigen (p < 0.05), an indicator of continuous HCV replication. Among all clones, L91M showed the highest increase in the HCV core antigen and HCV protein. There was no significant resistance against IFN treatment in core substitutions; however, IFN sensitivity was significantly different between the wildtype core and JFH-1 (p < 0.05). Conclusions: A novel genotype 1b HCV cell culture was constructed with core amino acid substitutions, which demonstrated IFN resistance of genotype 1b. This system will be useful for future analyses into the mechanisms of HCV genotype 1b treatment. PMID:27047766

  3. ZFP91-a newly described gene potentially involved in prostate pathology.

    PubMed

    Paschke, Lukasz; Rucinski, Marcin; Ziolkowska, Agnieszka; Zemleduch, Tomasz; Malendowicz, Witold; Kwias, Zbigniew; Malendowicz, Ludwik K

    2014-04-01

    In search for novel molecular targets in benign prostate hyperplasia (BPH), a PCR Array based screening of 84 genes was performed. Of those, expression of ZFP91 (ZFP91 zinc finger protein) was notably upregulated. Limited data concerning the function of ZFP91 product show that it is a potential transcription factor upregulated in human acute myelogenous leukemia and most recently found to be the non-canonical NF-κB pathway regulator. In order to test this finding on a larger number of samples, prostate specimens were obtained from patients undergoing adenomectomy for BPH (n = 21), and as a control, from patients undergoing radical cystectomy for bladder cancer (prostates unchanged pathologically, n = 18). Similar studies were performed on cultured human prostate cancer cell lines: LNCaP, DU145, 22Rv1, PC-3; as well as normal prostate epithelial cells-PrEC. Methods employed included: Human Obesity PCR Array (Qiagen), QPCR and Western blotting. QPCR studies confirmed significant overexpression of ZFP91 in BPH samples. On a protein level, however, comparison between normal and BPH prostates revealed insignificant differences. As for prostate cell lines examined, all expressed ZFP91 mRNA. Western blotting analysis showed markedly higher protein levels of ZFP91 in all cancer cell lines in comparison with normal (PrEC) cells. In conclusion, the upregulated ZFP91 mRNA in BPH, not accompanied by parallel changes in ZFP91 protein levels, together with ZFP91 protein abundance in prostate cancer cell lines suggest ZFP91 involvement in these prostate diseases. PMID:24272675

  4. The interaction between clothing and air weapon pellets.

    PubMed

    Wightman, G; Wark, K; Thomson, J

    2015-01-01

    Comparatively few studies have been carried out on air weapon injuries yet there are significant number of injuries and fatalities caused by these low power weapons because of their availability and the public perception that because they need no licence they are assumed to be safe. In this study ballistic gel was tested by Bloom and rupture tests to check on consistency of production. Two series of tests were carried out firing into unclothed gel blocks and blocks loosely covered by different items of clothing to simulate attire (tee shirt, jeans, fleece, and jacket). The damage to the clothing caused by different shaped pellets when fired at different ranges was examined. The apparent hole size was affected by the shape of pellet (round, pointed, flat and hollow point) and whether damage was predominantly caused by pushing yarn to one side or by laceration of the yarn through cutting or tearing. The study also compared penetration into clothed gel and unclothed gel under identical conditions, and loose clothing greatly reduced penetration. With loose clothing at 9.1 m range clothing reduced penetration to 50-70% of the penetration of unclothed gel but at 18.3m range only 7 out of 36 shots penetrated the gel. This cannot be accounted for by the energy loss at the longer range (3-7% reduction from 9.1 m to 18.3 m range in unclothed gels) and it is suggested that impulse may have a role to play. Shots that did not penetrate the gel were used to estimate the possible stopping time for the pellet (around 75 μs) and force (1700 N) or stress (100 MPa) required to bring the pellet to a halt. Even with these low energy projectiles, cloth fibres were entrained in the gel showing the potential for penetration of the body and subsequent infection. PMID:25460102

  5. 99mTc-labeled Therapeutic Inhaled Amikacin Loaded Liposomes

    PubMed Central

    Lee, Jae-Ho; Cheng, Kenneth T.; Malinin, Vladimir; Li, Zhili; Yao, Zhengsheng; Lee, Sung-Jin; Gould, Christine M.; Olivier, Kenneth N.; Chen, Clara; Perkins, Walter R.; Paik, Chang H.

    2014-01-01

    The radiolabeling of the liposome surface can be a useful tool for in vivo tracking of therapeutic drug loaded liposomes. We investigated radiolabeling therapeutic drug (i.e., an antibiotic, amikacin) loaded liposomes with 99mTc, nebulization properties of 99mTc-labeled liposomal amikacin for inhalation (99mTc-LAI), and its stability by size exclusion low pressure liquid chromatography (LPLC). LAI was reacted with 99mTc using SnCl2 dissolved in ascorbic acid as a reducing agent for 10 min at room temperature. The labeled products were then purified by anion exchange resin. The purified 99mTc-LAI in 1.5% NaCl solution was incubated at 4oC to assess its stability by LPLC. The purified 99mTc-LAI was subjected to studies with a clinically used nebulizer (PARI eFlow®) and the Anderson Cascade Impactor (ACI). The use of ascorbic acid at 0.91 mM resulted in a quantitative labeling efficiency. The LPLC profile showed that the liposomal peak of LAI detected by a UV monitor at both 200 nm and 254 nm overlapped with the radioactivity peak of 99mTc-LAI, indicating that 99mTc-LAI is suitable for tracing LAI. The ACI study demonstrated that the aerosol droplet size distribution determined gravimetrically was similar to that determined by radioactivity. The liposome surface labeling method using SnCl2 in 0.91mM ascorbic acid produced 99mTc-LAI with a high labeling efficiency and stability that are adequate to evaluate the deposition and clearance of inhaled LAI in the lung by gamma scintigraphy. PMID:23879241

  6. Lack of size selectivity for paddlefish captured in hobbled gillnets

    USGS Publications Warehouse

    Scholten, G.D.; Bettoli, P.W.

    2007-01-01

    A commercial fishery for paddlefish Polyodon spathula caviar exists in Kentucky Lake, a reservoir on the lower Tennessee River. A 152-mm (bar-measure) minimum mesh size restriction on entanglement gear was enacted in 2002 and the minimum size limit was increased to 864 mm eye-fork length to reduce the possibility of recruitment overfishing. Paddlefish were sampled in 2003-2004 using experimental monofilament gillnets with panels of 89, 102, 127, 152, 178, and 203-mm meshes and the efficacy of the mesh size restriction was evaluated. Following the standards of commercial gear used in that fishery, nets were "hobbled" (i.e., 128 m ?? 3.6 m nets were tied down to 2.4 m; 91 m ?? 9.1 m nets were tied down to 7.6 m). The mean lengths of paddlefish (Ntotal = 576 fish) captured in each mesh were similar among most meshes and bycatch rates of sublegal fish did not vary with mesh size. Selectivity curves could not be modeled because the mean and modal lengths of fish captured in each mesh did not increase with mesh size. Ratios of fish girth to mesh perimeter (G:P) for individual fish were often less than 1.0 as a result of the largest meshes capturing small paddlefish. It is unclear whether lack of size selectivity for paddlefish was because the gillnets were hobbled, the unique morphology of paddlefish, or the fact that they swim with their mouths agape when filter feeding. The lack of size selectivity by hobbled gillnets fished in Kentucky Lake means that managers cannot influence the size of paddlefish captured by commercial gillnet gear by changing minimum mesh size regulations. ?? 2006 Elsevier B.V. All rights reserved.

  7. Performance evaluation of a cable bolted yield-abutment gate road system at the Crandall Canyon No. 1 Mine, Genwal Resources, Inc., Huntington, Utah

    SciTech Connect

    Koehler, J.R.; DeMarco, M.J.; Marshall, R.J.; Fielder, J.

    1996-12-01

    Although two-entry yield pillar-based gate roads supported by wooden cribs have been commonly used throughout longwalling in the Wasatch Plateau/Roan Cliffs coalfield of central Utah, a three-entry yield-abutment gate road configuration was recently trialed in the Hiawatha Seam at the Genwal Resources (GRI) Crandall Canyon No. 1 Mine, near Huntington, UT. Pillar, entry, and cable bolt performance were monitored through second panel mining using a fairly extensive array of geomechanical instruments installed over a span of four crosscuts. Ground pressure and entry closure measurements confirmed that the 9.1-m-wide (30-ft) yield pillar was partially shielded from first panel longwall loads by the 36.6-m-wide (120-ft) abutment pillar, and consequently, experienced only minor yielding until the approach of the second panel face. Complete yielding of the 9.1-m-wide (30-ft) pillar occurred when the second panel was approximately 6.1 m (20 ft) in by the instrumentation site. Average cable bolt loads and differential roof sag remained low through second panel mining and tailgate entry ground conditions were excellent; however, very high ground pressures in the abutment and yield pillars, and second panel rib strongly suggest a high potential for coal bumps utilizing this gate road configuration at mining cover depths in excess of 396 to 457 m (1300 to 1500 ft). This conclusion is supported by the suspected occurrence of small coal bumps along the abutment pillar ribs, observed indirectly as fresh debris in the middle entry just behind the second face. This paper presents a case history developed from the geotechnical measurements and on-site observations of this unique application of a yield-abutment gate road configuration and cable support system in the Hiawatha Seam.

  8. Phytoplankton biomass, production and growth limitations on the Huanghe (Yellow River) continental shelf

    NASA Astrophysics Data System (ADS)

    Turner, R. Eugene; Rabalais, Nancy N.; Zhang, Zhi Nan

    1990-06-01

    We examined phytoplankton populations in coastal waters of the Huanghe (Yellow River) estuary during two cruises in the annual high and normal discharge periods: August 1986 and October 1987, respectively. Strong salinity, nutrient, and phytoplankton pigment concentration gradients occur along the 5 m isobath. Landward of these gradients the phytoplankton growth potential (PGP) appears strongly phosphorus-limited and light limitation of PGP, paradoxically, appears less significant than it does further offshore where the euphotic zone depth is greater. Phytoplankton pigments are sparse both in the river and far offshore, and the peak accumulation (9 μg l -1 chlorophyll a) is centered broadly between 20 and 25 ppt, thus straddling the region of the hypopycnal plume from the hyperpycnal plunge point to where Secchi disk depth exceeds 1 m. As the suspended matter falls out (sharply) near the 25 ppt isohaline, light conditions improve, the N:P ratio drops to below 100, and nitrate concentrations continue to decrease in an offshore direction. Phytoplankton production rates reach a maximum and large algal cells accumulate where the suspended particulate matter concentration drops to less than 10 mg l -1. Both phytoplankton biomass and production declines beyond approximately 32 ppt. Sedimentary pigment accumulations also increase going from land to sea. Phosphorus and nitrogen dominate the suite of nutrients tested to determine which nutrients limit PGP. Phosphorus is probably the major nutrient limiting phytoplankton growth (not necessarily biomass accumulation) in most of the Huanghe estuary. This conclusion is based on the very high N:P ratios of dissolved nutrients, the results of an extensive array of addition and deletion bioassay experiments, and the results of P addition experiments. Where trace metals and EDTA limit PGP, they are usually limiting in concert with other nutrients and do not act alone. Comparison with other large river plumes are made.

  9. Ascension Submarine Canyon, California - Evolution of a multi-head canyon system along a strike-slip continental margin

    USGS Publications Warehouse

    Nagel, D.K.; Mullins, H.T.; Greene, H. Gary

    1986-01-01

    Ascension Submarine Canyon, which lies along the strike-slip (transform) dominated continental margin of central California, consists of two discrete northwestern heads and six less well defined southeastern heads. These eight heads coalesce to form a single submarine canyon near the 2700 m isobath. Detailed seismic stratigraphic data correlated with 19 rock dredge hauls from the walls of the canyon system, suggest that at least one of the two northwestern heads was initially eroded during a Pliocene lowstand of sea level ???3.8 m.y. B.P. Paleogeographic reconstructions indicate that at this time, northwestern Ascension Canyon formed the distal channel of nearby Monterey Canyon and has subsequently been offset by right-lateral, strike-slip faulting along the San Gregorio fault zone. Some of the six southwestern heads of Ascension Canyon may also have been initially eroded as the distal portions of Monterey Canyon during late Pliocene-early Pleistocene sea-level lowstands (???2.8 and 1.75 m.y. B.P.) and subsequently truncated and offset to the northwest. There have also been a minimum of two canyon-cutting episodes within the past 750,000 years, after the entire Ascension Canyon system migrated to the northwest past Monterey Canyon. We attribute these late Pleistocene erosional events to relative lowstands of sea level 750,000 and 18,000 yrs B.P. The late Pleistocene and Holocene evolution of the six southeastern heads also appears to have been controlled by structural uplift of the Ascension-Monterey basement high at the southeastern terminus of the Outer Santa Cruz Basin. We believe that uplift of this basement high sufficiently oversteepened submarine slopes to induce gravitational instability and generate mass movements that resulted in the erosion of the canyon heads. Most significantly, though, our results and interpretations support previous proposals that submarine canyons along strike-slip continental margins can originate by tectonic trunction and lateral

  10. Impact of recirculation on the East Greenland Current in Fram Strait: Results from moored current meter measurements between 1997 and 2009

    NASA Astrophysics Data System (ADS)

    de Steur, L.; Hansen, E.; Mauritzen, C.; Beszczynska-Möller, A.; Fahrbach, E.

    2014-10-01

    Transports of total volume and water masses obtained from a mooring array in the East Greenland Current (EGC) in Fram Strait are presented for the period 1997-2009. The array in the EGC was moved along isobaths from 79°N to 78°50‧N in 2002 to line up with moorings in the eastern Fram Strait. Analysis of the time series at the two latitudes shows that associated with the southward move, the annual mean volume transport of the EGC increased from 5.8±1.8 Sv to 8.7±2.5 Sv, mostly related with an increase in barotropic flow. This suggests a recirculation of close to 3 Sv at 78°50‧N as a consequence of the large-scale wind-driven cyclonic gyre in the Nordic Seas. In addition, the volume transport at 78°50‧N showed a clear seasonal cycle which was absent at 79°N. Estimates of the wind-driven Sverdrup transport at two different latitudes show that the difference in total volume transport and seasonality can largely be explained by the wind-stress curl. However, weak transport in 2003 was only partially related with weak Sverdrup transport and coincided also with anomalously weak northerly winds. The stronger recirculation at 78°50‧N has also consequences for the observed Atlantic Water: there is significantly more Atlantic derived water present at the southerly latitude. In addition, the warm anomaly in Fram Strait between 2005 and 2007 doubled the amount of Recirculated Atlantic Water temporarily. Finally, we estimate that close to 2.7 Sv, or 50%, of Atlantic derived water recirculates in Fram Strait.

  11. Temperature-salinity distribution in the northeastern Atlantic from ship and Argo vertical casts

    NASA Astrophysics Data System (ADS)

    Bashmachnikov, I.; Neves, F.; Nascimento, Â.; Medeiros, J.; Ambar, I.; Dias, J.; Carton, X.

    2015-03-01

    The present study defines new interpolation functions for hydrological data. These functions are applied to generate climatological maps of temperature-salinity distribution with a 25 m depth interval and a 30 km space interval (MEDTRANS data set). The data undergo rigorous initial data quality control, having passed several filtering procedures. The gridding is done on neutral density surfaces, which allows better representation of thermohaline fronts for the same gridding radius. The multi-pass Barnes optimum interpolation procedure with spatially variable size of the gridding window is used. The shape of the window accounts for the dominant along-isobath direction of water mass transport over steeply sloping topography. A local ratio of topographic to planetary β-effects is used to define the shape of the window as a function of the relative importance of the topographic influence. The N/f ratio is applied to account for the baroclinic compensation decay of the topographic influence on water mass transport with the distance from the bottom. The gridded fields are available at the website of the Centre of Oceanography of the University of Lisbon (http://co.fc.ul.pt/en/data). The MEDTRANS climatology gives more details of the distribution of water characteristics in the subtropical northeastern Atlantic than other alternative climatologies and is able to reproduce a number of dynamic features described in the literature: the acceleration in the meanders of the Azores current; the cyclonic gyre in the Gulf of Cadiz; and the splitting and separation of the Mediterranean Water (MW) outflow in two veins near the Gorringe and Galicia banks. Seasonal climatologies, computed for the warm (May-October) and cold (November-April) seasons, reveal stronger zonal extension of the upper ocean patterns during the warm season, as compared to the cold one.

  12. Diel Vertical Dynamics of Gelatinous Zooplankton (Cnidaria, Ctenophora and Thaliacea) in a Subtropical Stratified Ecosystem (South Brazilian Bight).

    PubMed

    Nogueira Júnior, Miodeli; Brandini, Frederico Pereira; Codina, Juan Carlos Ugaz

    2015-01-01

    The diel vertical dynamics of gelatinous zooplankton in physically stratified conditions over the 100-m isobath (~110 km offshore) in the South Brazilian Bight (26°45'S; 47°33'W) and the relationship to hydrography and food availability were analyzed by sampling every six hours over two consecutive days. Zooplankton samples were taken in three depth strata, following the vertical structure of the water column, with cold waters between 17 and 13.1°C, influenced by the South Atlantic Central Water (SACW) in the lower layer (>70 m); warm (>20°C) Tropical Water in the upper 40 m; and an intermediate thermocline with a deep chlorophyll-a maximum layer (0.3-0.6 mg m-3). Two distinct general patterns were observed, emphasizing the role of (i) physical and (ii) biological processes: (i) a strong influence of the vertical stratification, with most zooplankton absent or little abundant in the lower layer. The influence of the cold SACW on the bottom layer apparently restricted the vertical occupation of most species, which typically inhabit epipelagic warm waters. Even among migratory species, only a few (Aglaura hemistoma, Abylopsis tetragona eudoxids, Beroe sp., Thalia democratica, Salpa fusiformis) crossed the thermocline and reached the bottom layer. (ii) A general tendency of partial migrations, with variable intensity depending on the different species and developmental stages; populations tended to be more widely distributed through the water column during daylight, and to become more aggregated in the upper layer during the night, which can be explained based on the idea of the "hunger-satiation hypothesis", maximizing feeding and minimizing the chances of being predated. PMID:26637179

  13. Interannual variability of wintertime temperature on the inner continental shelf of the Middle Atlantic Bight

    NASA Astrophysics Data System (ADS)

    Connolly, Thomas P.; Lentz, Steven J.

    2014-09-01

    The shallow depth of the inner continental shelf allows for rapid adjustment of the ocean to air-sea exchange of heat and momentum compared with offshore locations. Observations during 2001-2013 are used to evaluate the contributions of air-sea heat flux and oceanic advection to interannual variability of inner-shelf temperature in the Middle Atlantic Bight. Wintertime processes are important for interpreting regional interannual variability at nearshore locations since winter anomalies account for 69-77% of the variance of the annual anomalies and are correlated over broad along-shelf scales, from New England to North Carolina. At the Martha's Vineyard Coastal Observatory on the 12 m isobath, a heat budget is used to test the hypothesis that interannual differences in winter temperatures are due solely to air-sea heat flux. Bimonthly averages of air-sea heat flux are correlated with temporal changes in temperature, but overestimate the observed wintertime cooling. Velocity and satellite-derived temperature data show that interannual variability in wintertime surface cooling is partially compensated for by alongshore advection of warmer water from the west at this particular location. It is also shown that surface heat flux is a strong function of air-sea temperature difference. Because of this coupling between ocean and air temperatures in shallow water, along-shelf advection can significantly modify the surface heat flux at seasonal and interannual time scales. While along-shelf advection at relatively small (˜100 km) scales can be an important component of the heat budget over the inner shelf, interannual temperature variability is still largely determined by adjustment to large-scale air-temperature anomalies.

  14. Quantification of source uncertainties in Seismic Probabilistic Tsunami Hazard Analysis (SPTHA)

    NASA Astrophysics Data System (ADS)

    Selva, J.; Tonini, R.; Molinari, I.; Tiberti, M. M.; Romano, F.; Grezio, A.; Melini, D.; Piatanesi, A.; Basili, R.; Lorito, S.

    2016-06-01

    We propose a procedure for uncertainty quantification in Probabilistic Tsunami Hazard Analysis (PTHA), with a special emphasis on the uncertainty related to statistical modelling of the earthquake source in Seismic PTHA (SPTHA), and on the separate treatment of subduction and crustal earthquakes (treated as background seismicity). An event tree approach and ensemble modelling are used in spite of more classical approaches, such as the hazard integral and the logic tree. This procedure consists of four steps: (1) exploration of aleatory uncertainty through an event tree, with alternative implementations for exploring epistemic uncertainty; (2) numerical computation of tsunami generation and propagation up to a given offshore isobath; (3) (optional) site-specific quantification of inundation; (4) simultaneous quantification of aleatory and epistemic uncertainty through ensemble modelling. The proposed procedure is general and independent of the kind of tsunami source considered; however, we implement step 1, the event tree, specifically for SPTHA, focusing on seismic source uncertainty. To exemplify the procedure, we develop a case study considering seismic sources in the Ionian Sea (central-eastern Mediterranean Sea), using the coasts of Southern Italy as a target zone. The results show that an efficient and complete quantification of all the uncertainties is feasible even when treating a large number of potential sources and a large set of alternative model formulations. We also find that (i) treating separately subduction and background (crustal) earthquakes allows for optimal use of available information and for avoiding significant biases; (ii) both subduction interface and crustal faults contribute to the SPTHA, with different proportions that depend on source-target position and tsunami intensity; (iii) the proposed framework allows sensitivity and deaggregation analyses, demonstrating the applicability of the method for operational assessments.

  15. Bottom temperature and salinity distribution and its variability around Iceland

    NASA Astrophysics Data System (ADS)

    Jochumsen, Kerstin; Schnurr, Sarah M.; Quadfasel, Detlef

    2016-05-01

    The barrier formed by the Greenland-Scotland-Ridge (GSR) shapes the oceanic conditions in the region around Iceland. Deep water cannot be exchanged across the ridge, and only limited water mass exchange in intermediate layers is possible through deep channels, where the flow is directed southwestward (the Nordic Overflows). As a result, the near-bottom water masses in the deep basins of the northern North Atlantic and the Nordic Seas hold major temperature differences. Here, we use near-bottom measurements of about 88,000 CTD (conductivity-temperature-depth) and bottle profiles, collected in the period 1900-2008, to investigate the distribution of near-bottom properties. Data are gridded into regular boxes of about 11 km size and interpolated following isobaths. We derive average spatial temperature and salinity distributions in the region around Iceland, showing the influence of the GSR on the near-bottom hydrography. The spatial distribution of standard deviation is used to identify local variability, which is enhanced near water mass fronts. Finally, property changes within the period 1975-2008 are presented using time series analysis techniques for a collection of grid boxes with sufficient data resolution. Seasonal variability, as well as long term trends are discussed for different bottom depth classes, representing varying water masses. The seasonal cycle is most pronounced in temperature and decreases with depth (mean amplitudes of 2.2 °C in the near surface layers vs. 0.2 °C at depths > 500 m), while linear trends are evident in both temperature and salinity (maxima in shallow waters of +0.33 °C/decade for temperature and +0.03/decade for salinity).

  16. Diversity and Distribution Patterns of Cetaceans in the Subtropical Southwestern Atlantic Outer Continental Shelf and Slope.

    PubMed

    Di Tullio, Juliana Couto; Gandra, Tiago B R; Zerbini, Alexandre N; Secchi, Eduardo R

    2016-01-01

    Temporal and spatial patterns of cetacean diversity and distribution were investigated through eight ship-based surveys carried out during spring and autumn between 2009 and 2014 on the outer continental shelf (~150m) and slope (1500m) off southeastern and southern Brazil (~23°S to ~34°S). The survey area was divided into southeast and south areas according to their oceanographic characteristics. Twenty-one species were observed in 503 sightings. The overall number of species was similar between the two areas, though it was higher in the spring in the south area. Five species were dominant and diversity varied more seasonally than spatially. ANOVA and kernel analyses showed that overall cetacean densities were higher in spring compared to autumn. Physeter macrocephalus, the most frequent species, concentrated throughout the south area at depths over 1000m in both seasons. Despite the overlapped occurrence at a broader scale, small delphinids presented latitudinal and in-offshore gradients as well as seasonal variation in distribution patterns, which could indicate habitat partitioning between some species. Delphinus delphis was only recorded in the south and its density decreased in areas where the presence of Stenella frontalis increased, mainly beyond the 250m isobath. Densities of S. longirostris and S. attenuata increased in lower latitudes and beyond the shelf break. The large delphinids Tursiops truncatus and Globicephala melas formed mixed groups in many occasions and were observed along the study area around depths of 500m. Grampus griseus was twice as frequent in the south area and densities increased in waters deeper than 600m. As expected, densities of both small and large migratory whales were higher during spring, over the continental slope, in the southeast area. The results presented here provided strong evidence on the importance of the outer continental shelf and slope to a diverse community of cetaceans occurring in the subtropical Southwestern

  17. Geometry, lateral variability, and preservation of downlapped regressive shelf deposits, eastern Tyrrhenian Margin, Italy

    SciTech Connect

    Field, M.E. ); Trincardi, F. )

    1990-05-01

    The shelf of the eastern Tyrrhenian margin changes substantially in width, shelf-break depth, and sea-floor steepness over relatively short distances, largely due to marked lateral changes in geologic structure. Remnants of late Pleistocene prograded coastal deposits are locally preserved on the middle and outer parts of this complex shelf. Through the authors studies of these prograded deposits they recognize two major controls on the distribution, lateral extent, thickness, and preservation potential. First, prograded (downlapped) deposits formed only where the physiographic shelf break was deeper than the lowstand shoreline, thus providing accommodation space for the lowstand deposits. Second, the proximity and relative size of sediment sources and the local coastal dispersal system influenced the geometry of the deposit. Mid-shelf and shelf-margin bodies composed of seaward-steepening downlapping reflectors were deposited as thin-to-thick continuous prograding sheets over an irregular eroded shelf surface and onto the shelf edge during the last fall and lowstand of sea level. A dearth of sediment at the end of lowstand conditions led to a switch from deposition to erosion. During sea level rise, shoreface erosion produced a major marine erosional (ravinement) surface landward of the 120-m isobath, and much, and in many places all, of the downlapping deposit was removed. Preservation of downlapping deposits is largely a function of their thickness. Thick continuous deposits are common on the shelf edge, whereas on the mid-shelf only thin remnants are preserved locally where depressions or morphologic steps were present in the shelf surface.

  18. Sonograph mosaic of northern California and southern Oregon Exclusive Economic Zone

    SciTech Connect

    Cacchione, D.A.; Drake, D.E.; Clarke, S.H.; Masson, D.G.

    1985-02-01

    During June 15 to July 9, 1984, the third leg of the cooperative US Geological Survey-Institute of Oceanographic Sciences GLORIA survey of the conterminous US Exclusive Economic Zone (EEZ) collected digital acoustic data off northern California and southern Oregon. The region covered during leg 3 extends from the 200-m isobath westward to the 375-km (200-nmi) EEZ boundary and from about 39/sup 0/ to 43/sup 0/N. The survey used the IOS GLORIA long-range side-scan sonar, a 2-channel airgun seismic reflection system, and 3.5 kHz and 10 kHz high-resolution seismic systems. The GLORIA data were collected in a pattern that permitted overlapping coverage so that a mosaic of the sonographs could be constructed. These sonographs were slant-range and anamorphically corrected aboard ship, and a mosaic was constructed at a scale of 1:375,000. Among the most striking geomorphic features revealed in this segment of the EEZ is the Mendocino transform fault, which extends for more than 120 nmi along the northern base of the Mendocino fracture zone and delineates the southern boundary of the Gorda plate. Other features clearly revealed are the complex geometry of the Gorda rift valley, and the subparallel flanking ridges and dramatically deformed base of the continental slope at the eastern boundary of the Gorda plate. The data are presently being processed by image analytical techniques to enhance the fine-scale features such as sediment waves, slumps, and areas of differing sedimentary facies.

  19. Analysis of the northern South China Sea counter-wind current in winter using a data assimilation model

    NASA Astrophysics Data System (ADS)

    Xie, Jiping; Zhu, Jiang; Bertino, Laurent; Counillon, Francois

    2015-04-01

    The South China Sea Warm Current (SCSWC) has drawn considerable attentions in the past decade due to its characteristic of flowing against the wind direction along the coast of Southeast China during winter. Observational monitoring of the SCSWC is yet insufficient to firmly assess of the property of this current. Prior modeling attempts have been carried out in idealized or simplified framework, e.g., coarse resolution, unrealistic wind forcing, artificial bathymetry, and/or missing dynamical processes. It is still unclear to what extent the above approximations may affect the properties of the SCSWC. In this study, a state-of-the-art data assimilation system of the South China Sea has been integrated from 1993 to 2005. The system uses the Hybrid Ocean Model (HYCOM) with tidal forcing and is forced with realistic atmospheric forcing. In order to ensure a more realistic positioning of the mesoscale features, the system assimilates along-track altimetry data with the Ensemble Optimal Interpolation (EnOI) to investigate the properties of the SCSWC for the period 1996-2005. The properties of the SCSWC in winter time are investigated and found: the current mainly follows the 100 m isobaths and exists from immediately below the surface to the depth of 50 m with a baroclinic structure; the main core is located at 20-30 m depths and is composed of water warmer than the shelf water; and the width of the current is less than 100 km. Meanwhile, based on the daily output, it was shown that the current is highly transient in January. Additional simulations without tidal forcing and without assimilation suggest that the transient property of the current is mainly driven by the atmospheric forcing while the mesoscale eddies enhance its variability. On the contrary, tidal forcing seems to reduce the strength of the SCSWC, as expected from tidal rectifying of the current.

  20. Interannual to decadal temperature variability in the north-west Atlantic: Observations from the MV Oleander XBT line

    NASA Astrophysics Data System (ADS)

    Forsyth, J. S. T.; Andres, M.; Gawarkiwicz, G.

    2014-12-01

    Despite convincing evidence of deep ocean warming, temperature changes over the shelves have proven difficult to quantify as most long-term records lack the spatial and temporal resolution needed to resolve shelf variability. XBT data have been collected for 37 years along a repeat track from New Jersey to Bermuda from the MV Oleander providing the resolution necessary for shelf analysis. The XBT temperature data on the shelf (onshore of the 80 m isobath) were binned with 10 km horizontal and 5 m vertical resolution to produce monthly and annually averaged temperature sections. A climatology produced from the binned data identifies key seasonal temperature features consistent with previous climatologies, showing the utility of the XBT data. Annual spatially-averaged shelf temperatures have trended upwards since the beginning of the record in 1977 (0.025 C/yr), with recent trends (i.e., since 2002, 0.10 C/yr) substantially larger than the overall 37- year trend. Comparison of composite sections for the most anomalous years suggests that the interannual variability in the spatially-averaged temperatures is most heavily influenced by temperature anomalies near the shelf break. The spatially-averaged temperature anomalies are not correlated with annually-averaged coastal sea level anomalies from tide gauges at zero lag, which suggest that interannual variability in coastal sea level is not due to thermo steric effects. However, a strong positive correlation is found between 2-year lagged temperature anomalies and coastal sea level anomalies. This relationship is most pronounced for the shelf break temperature anomalies, with the strongest 2-year lag correlations found in winter and spring. Connections between the observed interannual to decadal temperature variability on the shelf and variability in the AMOC are being investigated in an ongoing effort to better understand open-ocean/shelf interactions in the Northwest Atlantic.

  1. Alongshore and cross-shore circulations and their response to winter monsoon in the western East China Sea

    NASA Astrophysics Data System (ADS)

    Huang, Daji; Zeng, Dingyong; Ni, Xiaobo; Zhang, Tao; Xuan, Jiliang; Zhou, Feng; Li, Jia; He, Shuangyan

    2016-02-01

    An array of four bottom-mounted acoustic Doppler current profilers (ADCPs) were deployed during the winter of 2008 (28 December 2008 to 12 March 2009) along a cross-shelf section in the western East China Sea to investigate the winter circulation and its response to wind. During the observation period, the observed subtidal currents exhibit coherent spatial structure and temporal variation in terms of their mean (seasonal), trend (intra-seasonal), and synoptic variability. The subtidal currents are polarized roughly in the alongshore direction parallel to local isobaths, and the weak cross-shore current is closely linked to the alongshore component. The temporal variation of the currents follows the rhythm of wind stress, sea level, and sea level difference at the synoptic scale. The mean currents are basically composed of two anti-parallel currents in the alongshore direction: the East China Sea coastal current (ECSCC) flows southwestward along the inner shelf and the Taiwan warm current (TWC) flows in the opposite direction along the outer-shelf. The strongest current occurs over the mid-shelf as a coastal jet. The intra-seasonal currents exhibit an expansion and intensification of the ECSCC along with shrinking and weakening the alongshore component of the TWC. There is a significant increase in onshore current particularly over the mid-shelf. The fluctuations of synoptic currents show a significant positive correlation with wind stress, and the fluctuations are negatively correlated with sea level and sea level difference. The coherent spatial structure of the currents indicates that the depth-independent column motion is related to the sea level difference through a barotropic pressure gradient. The vertical shear of currents is related to the density-related baroclinic pressure gradient in the whole water column and to the friction within the surface and bottom boundary layers.

  2. Spatial localization and mesoscale modulation of mixing and transformation of the Denmark Strait Overflow

    NASA Astrophysics Data System (ADS)

    Koszalka, Inga; Haine, Thomas; Magaldi, Marcello

    2015-04-01

    The Denmark Strait Overflow (DSO) is a major export route for dense waters from the Nordic Seas forming the North Atlantic Deep Water, an important element of the climate system. Mixing processes in the Irminger Basin determine volume transport and properties of the DSO but are poorly resolved by sparse observations which hinders development of DSO mixing parameterizations in global circulation models (GCMs). We employ a high resolution circulation model (horizontal grid spacing of 2km and 210 levels in the vertical) to investigate transformation and mixing in the DSO in the Irminger Basin and quantify the effect of mesoscale (10-100km) flows unresolved by GCMs. Both the warming rate derived from model Lagrangian particles and the Eulerian eddy temperature flux divergence show elevated values in about a 200km long and 50km wide corridor downstream of the Denmark Strait sill and between the shelf break and the 2000m isobath. In this region, the DSO warms by about 1K, which constitutes most of the transformation along the entire 700km pathway in the Irminger Basin. The horizontal and vertical mixing is modulated by dense water boluses and overlying cyclonic eddies that propagate together through the Irminger Basin (`beddies'). The passage of beddies increase the squared vertical shear of horizontal velocity by a factor of 3, correspond to increase in the vertical velocity by ten times and double the eddy heat flux divergence leading to a warming of the bottom (densest) waters and a cooling of the interface layer of the overflow plume and the ambient water above. There is a clear correlation between the speed in the nose of the plume, the eddy kinetic energy and the vertical shear in the horizontal flow. The modulation of mixing by the mesoscale variability and the attendant mixing localization should be included in future overflow parameterizations in global circulation models. A targeted field campaign to empirically test these conjectures is another high priority.

  3. Satellite-measured interannual variability of turbid river plumes off central-southern Chile: Spatial patterns and the influence of climate variability

    NASA Astrophysics Data System (ADS)

    Saldías, Gonzalo S.; Largier, John L.; Mendes, Renato; Pérez-Santos, Iván; Vargas, Cristian A.; Sobarzo, Marcus

    2016-08-01

    Ocean color imagery from MODIS (Moderate Resolution Imaging Spectroradiometer) onboard the Aqua platform is used to characterize the interannual variability of turbid river plumes off central-southern Chile. Emphasis is placed on the influence of climate fluctuations, namely El Niño Southern Oscillation (ENSO), the Pacific Decadal Oscillation (PDO), and the Antarctic Oscillation (AAO). Additional satellite data on wind, boat-based hydrographic profiles, and regional climate indices are used to identify the influence of climate variability on the generation of anomalous turbid river plumes. The evolution of salinity at a coastal station on the 90 m isobath between the Itata and Biobío Rivers shows a freshwater surface layer with salinity < 32.5 and 5-10 m thick during major plume events in 2002, 2005 and 2006. Surface salinity minima are correlated with peaks in turbidy from the normalized water leaving radiance at 555 nm (nLw(555)), both representing turbid river plumes. EOF analysis reveals that major turbid plume events occurred primarily during warm phases of the ENSO and PDO, and negative phases of the AAO, when storm tracks are further north. Anomalously large turbid plumes extend long distances offshore (∼ 70-80 km), and individual plumes coalesce into a continuous plume along the coast that covers the entire continental shelf. Season-specific correlation analyses reveal an increased influence of the AAO on river plumes south of Punta Lavapié in spring-summer (negative correlation). North of this major cape, ENSO and PDO indices have a dominant influence on plumes with positive correlations with the nLw(555) signal in winter (and negative in summer). We discuss the biogeochemical implications of plume events and the importance of long-term and high-resolution ocean color observations for studying the temporal evolution of river plumes.

  4. Pathways of shelf water export from the Hatteras shelf and slope

    NASA Astrophysics Data System (ADS)

    Churchill, James H.; Gawarkiewicz, Glen G.

    2012-08-01

    It has long been recognized that a massive flow of Middle Atlantic Bight (MAB) shelf water is exported to the deep ocean in the region near Cape Hatteras, North Carolina. We examine the details of this export using data from an extensive array of 26 moorings, deployed over the shelf and slope between Cape Hatteras and the Chesapeake Bay mouth (from 35° 27‧ to 36° 40‧ N) as part of the U.S. Department of Energy's Ocean Margins Program. Our analysis indicates that the flow of the MAB shelf-edge frontal jet, which typically extends over the MAB slope, falls victim to export over the length of the mooring array, essentially vanishing by the southern extreme of the array. By contrast, the flow of MAB shelf water entering the study region over the inner and middle shelf (to roughly the 40-m isobath) tends to experience very little loss over the extent of the OMP array. Based on our findings and those of previous studies, we hypothesize that this inner and middle shelf flow is diverted seaward upon encountering the Hatteras Front, which separates MAB and South Atlantic Bight shelf waters. Some fraction of this flow appears to return to the OMP array, moving northeastward over the upper slope en route to the deep ocean. Our analysis also suggests that the export of MAB shelf water is enhanced as the Gulf Stream approaches the shelf-edge near Diamond Shoals, a process we deem to be a high priority for future study.

  5. Diversity and Distribution Patterns of Cetaceans in the Subtropical Southwestern Atlantic Outer Continental Shelf and Slope

    PubMed Central

    Di Tullio, Juliana Couto; Gandra, Tiago B. R.; Zerbini, Alexandre N.; Secchi, Eduardo R.

    2016-01-01

    Temporal and spatial patterns of cetacean diversity and distribution were investigated through eight ship-based surveys carried out during spring and autumn between 2009 and 2014 on the outer continental shelf (~150m) and slope (1500m) off southeastern and southern Brazil (~23°S to ~34°S). The survey area was divided into southeast and south areas according to their oceanographic characteristics. Twenty-one species were observed in 503 sightings. The overall number of species was similar between the two areas, though it was higher in the spring in the south area. Five species were dominant and diversity varied more seasonally than spatially. ANOVA and kernel analyses showed that overall cetacean densities were higher in spring compared to autumn. Physeter macrocephalus, the most frequent species, concentrated throughout the south area at depths over 1000m in both seasons. Despite the overlapped occurrence at a broader scale, small delphinids presented latitudinal and in-offshore gradients as well as seasonal variation in distribution patterns, which could indicate habitat partitioning between some species. Delphinus delphis was only recorded in the south and its density decreased in areas where the presence of Stenella frontalis increased, mainly beyond the 250m isobath. Densities of S. longirostris and S. attenuata increased in lower latitudes and beyond the shelf break. The large delphinids Tursiops truncatus and Globicephala melas formed mixed groups in many occasions and were observed along the study area around depths of 500m. Grampus griseus was twice as frequent in the south area and densities increased in waters deeper than 600m. As expected, densities of both small and large migratory whales were higher during spring, over the continental slope, in the southeast area. The results presented here provided strong evidence on the importance of the outer continental shelf and slope to a diverse community of cetaceans occurring in the subtropical Southwestern

  6. Coastal ocean variability in the US Pacific Northwest region: seasonal patterns, winter circulation, and the influence of the 2009-2010 El Niño

    NASA Astrophysics Data System (ADS)

    Durski, Scott M.; Kurapov, Alexander L.; Allen, John S.; Kosro, P. Michael; Egbert, Gary D.; Shearman, R. Kipp; Barth, John A.

    2015-12-01

    A 2-km horizontal resolution ocean circulation model is developed for a large coastal region along the US Pacific Northwest (34-50N) to study how continental shelf, slope, and interior ocean variability influence each other. The model has been run for the time period September 2008-May 2011, driven by realistic surface momentum and heat fluxes obtained from an atmospheric model and lateral boundary conditions obtained from nesting in a global ocean model. The solution compares favorably to satellite measurements of sea surface temperature and sea surface height, observations of surface currents by high-frequency radars, mooring temperature time series, and glider temperature and salinity sections. The analysis is focused on the seasonal response of the coastal ocean with particular emphasis on the winter circulation patterns which have previously garnered relatively little attention. Interannual variability is examined through a comparison of the 2009-2010 winter influenced by El Niño and the winters in the preceding and following years. Strong northward winds combined with reduced surface cooling along the coast north of Cape Mendocino (40.4N) in winter 2009-2010, resulting in a vigorous downwelling season, characterized by relatively energetic northward currents and warmer ocean temperatures over the continental shelf and upper slope. An analysis of the time variability of the volume-averaged temperature and salinity in a coastal control volume (CV), that extends from 41 to 47N and offshore from the coast to the 200-m isobath, clearly shows relevant integrated characteristics of the annual cycle and the transitions between winter shelf circulation forced by northward winds and the summer circulation driven primarily by southward, upwelling-favorable winds. The analysis also reveals interesting interannual differences in these characteristics. In particular, the CV volume-average temperature remains notably warmer during January-March 2010 of the El Niño winter.

  7. Lagrangian flow observations of the Amazon River discharge into the North Atlantic

    NASA Astrophysics Data System (ADS)

    Limeburner, Richard; Beardsley, Robert C.; Soares, Ivan D.; Lentz, Steven J.; Candela, Julio

    1995-02-01

    Nine satellite-tracked drifters with near-surface drogues were launched in or near the mouth of the Amazon River on the north Brazil shelf during 1989-1991 at four different stages of river discharge. The drifters initially moved along shelf toward the northwest over the north Brazil shelf with mean speeds varying from 41 to 128 cm/s and a maximum along-shelf velocity of 197 cm/s. Many drifters experienced strong acceleration near 2°N between the 5-m and 20-m isobaths, caused in part by the sharp reduction in cross-shelf cross-sectional area near the shore-perpendicular Cabo Norte shoal. The drifter trajectories showed strong cross-shelf tidal variability in the flow field near the Amazon River mouth, and the largest low-frequency, along-shelf variability was located over the open shelf just north of Cabo Norte. Good visual correlation between drifter along-shelf velocity and along-shelf wind stress supports the dynamical model of Lentz (this issue) that subtidal fluctuations in near-surface along-shelf currents in the Amazon River Plume are strongly wind driven. Drifters left the north Brazil shelf after about 5 to 30 days. Three drifters moved northwestward parallel to the northeast coast of South America, crossed the shelf break near 8°N, and moved into deeper North Atlantic water where they began looping in anticyclonic eddies (often called retroflection eddies or loopers) with periods of approximately 11 days as they moved northwestward to the Caribbean Sea. Four drifters initially moved along shelf toward the northwest and then offshore between 3°N and 7°N, where they followed the retroflection of the North Brazil Current. Only one drifter entered the zonal current system that characterizes the equatorial Atlantic circulation.

  8. Effects of seasonal and interannual variability in along-shelf and cross-shelf transport on groundfish recruitment in the eastern Bering Sea

    NASA Astrophysics Data System (ADS)

    Vestfals, Cathleen D.; Ciannelli, Lorenzo; Duffy-Anderson, Janet T.; Ladd, Carol

    2014-11-01

    The Bering Sea responds rapidly to atmospheric perturbations and over the past several decades has experienced extreme variability in both its physical and biological characteristics. These changes can impact organisms that inhabit the region, particularly marine fishes, as normal current patterns to which reproductive habits are tuned can be disrupted, which, in turn, may influence recruitment and population dynamics. To understand the influence of ocean circulation on groundfish recruitment in the eastern Bering Sea, we examined transport along and across the Bering Slope derived from 23 years (1982-2004) of simulations from a Regional Ocean Modeling System (ROMS) ocean circulation model. We expected that changes in the strength and position of the Bering Slope Current (BSC) would affect recruitment in selected species (Pacific cod, walleye pollock, Greenland halibut, Pacific halibut, and arrowtooth flounder), and that circulation features along and across the shelf edge would be strongly influenced by atmospheric forcing. Variability in along-shelf transport at three transects along the path of the BSC, cross-shelf transport across the 100 and 200 m isobaths, and transport through Unimak Pass were examined. Strong seasonal and interannual variations in flow were observed, with transport typically highest during fall and winter months, coinciding with timing of spawning activity in the five species. Significant correlations were found between transport, BSC position, and groundfish recruitment. Pacific cod, in particular, benefitted from decreased along-shelf and on-shelf flow, while Pacific halibut recruitment increased in relation to increased on-shelf transport through southern canyons. The results of this study improve our understanding of variability in circulation and associated effects on groundfish recruitment in the eastern Bering Sea.

  9. Observations of storm-induced mixing and Gulf Stream Ring incursion over the southern flank of Georges Bank: Winter and summer 1997

    NASA Astrophysics Data System (ADS)

    Lee, Craig M.; Brink, Kenneth H.

    2010-08-01

    High-resolution hydrographic measurements collected along the southern edge of Georges Bank during March and June-July 1997 focused on characterizing processes that drive fluxes of material between the slope and bank. Wintertime sampling characterized changes driven by a strong storm. A Scotian Shelf crossover event produced a ribbon of anomalously fresh water along the bank's southern flank that was diluted during the storm. Comparison of prestorm and poststorm sections shows that over the bank changes in heat and salt inventories are consistent with those expected solely from local surface fluxes. In deeper waters, advective effects, likely associated with frontal motion and eddies, are clearly important. Summertime surveys resolve the development of a massive intrusion of Gulf Stream-like waters onto the bank. East of the intrusion, a thin extrusion of bank water is drawn outward by the developing ring, exporting fresher water at a rate of about 7 × 104 m3/s. A large-amplitude Gulf Stream meander appears to initiate the extrusion, but it quickly evolves, near the bank edge, into a warm core ring. Ring water intrudes to approximately the 80 m isobath, 40 km inshore from the bank edge. The intrusion process seems analogous to the development of Gulf Stream shingles (a hydrodynamic instability) in the South Atlantic Bight. It appears that, once the intruded water is established on the bank, it remains there and dissipates in place. Although the intrusion is an extremely dramatic event, it is probably not actually a major contributor to shelf edge exchanges over a seasonal time scale.

  10. Distribution and abundance of cetaceans in the north-central and western Gulf of Mexico. Final report. Volume 3. Appendix A

    SciTech Connect

    Davis, R.W.; Fargion, G.S.

    1996-05-24

    The purpose of the study was to determine the distribution and abundance of cetaceans in areas potentially affected by future oil and gas activities along the continental slope of the north-central and western Gulf of Mexico. This 3.75 year project commenced 1 October 1991 and finished 15 July 1995. The study area was bounded by the Florida-Alabama border, the Texas-Mexico border, and the 100 m and 2,000 m isobaths. Cetacean distribution and abundance were determined from seasonal aerial and shipboard visual surveys and shipboard acoustic surveys. In addition, hydrographic data were collected in situ and by satellite remote sensing to characterize cetacean habitat. Finally, tagging and tracking of sperm whales using satellite telemetry was attempted. Appendix A contains: the cetacean, trutle, and bird sighting data from all shipboard and aerial visual surveys; contact data from the shipboard acoustic survey; and the cetacean environmental profiles. Cetaceans were observed throughout the study area during all four seasons. Nineteen species were identified, including two species (melon-headed whales and Fraser`s dolphins) previously thought to be rare in the Gulf. Pantropical spotted dolphins, bottlenose dolphins, clymene dolphins, striped dolphins, Atlantic spotted dolphins, and melon-headed whales were the most common small cetaceans and the sperm whale was the most common large cetacean. The mean annual abundance for all cetaceans was estimated to be 19,198. Although the study area had complex and dynamic oceanography, bottom depth was the only environmental variable which correlated to cetacean distribution.

  11. Can Static Habitat Protection Encompass Critical Areas for Highly Mobile Marine Top Predators? Insights from Coastal East Africa

    PubMed Central

    Pérez-Jorge, Sergi; Pereira, Thalia; Corne, Chloe; Wijtten, Zeno; Omar, Mohamed; Katello, Jillo; Kinyua, Mark; Oro, Daniel; Louzao, Maite

    2015-01-01

    Along the East African coast, marine top predators are facing an increasing number of anthropogenic threats which requires the implementation of effective and urgent conservation measures to protect essential habitats. Understanding the role that habitat features play on the marine top predator’ distribution and abundance is a crucial step to evaluate the suitability of an existing Marine Protected Area (MPA), originally designated for the protection of coral reefs. We developed species distribution models (SDM) on the IUCN data deficient Indo-Pacific bottlenose dolphin (Tursiops aduncus) in southern Kenya. We followed a comprehensive ecological modelling approach to study the environmental factors influencing the occurrence and abundance of dolphins while developing SDMs. Through the combination of ensemble prediction maps, we defined recurrent, occasional and unfavourable habitats for the species. Our results showed the influence of dynamic and static predictors on the dolphins’ spatial ecology: dolphins may select shallow areas (5-30 m), close to the reefs (< 500 m) and oceanic fronts (< 10 km) and adjacent to the 100m isobath (< 5 km). We also predicted a significantly higher occurrence and abundance of dolphins within the MPA. Recurrent and occasional habitats were identified on large percentages on the existing MPA (47% and 57% using presence-absence and abundance models respectively). However, the MPA does not adequately encompass all occasional and recurrent areas and within this context, we propose to extend the MPA to incorporate all of them which are likely key habitats for the highly mobile species. The results from this study provide two key conservation and management tools: (i) an integrative habitat modelling approach to predict key marine habitats, and (ii) the first study evaluating the effectiveness of an existing MPA for marine mammals in the Western Indian Ocean. PMID:26186438

  12. Diel Vertical Dynamics of Gelatinous Zooplankton (Cnidaria, Ctenophora and Thaliacea) in a Subtropical Stratified Ecosystem (South Brazilian Bight)

    PubMed Central

    Nogueira Júnior, Miodeli; Brandini, Frederico Pereira; Codina, Juan Carlos Ugaz

    2015-01-01

    The diel vertical dynamics of gelatinous zooplankton in physically stratified conditions over the 100-m isobath (~110 km offshore) in the South Brazilian Bight (26°45’S; 47°33’W) and the relationship to hydrography and food availability were analyzed by sampling every six hours over two consecutive days. Zooplankton samples were taken in three depth strata, following the vertical structure of the water column, with cold waters between 17 and 13.1°C, influenced by the South Atlantic Central Water (SACW) in the lower layer (>70 m); warm (>20°C) Tropical Water in the upper 40 m; and an intermediate thermocline with a deep chlorophyll-a maximum layer (0.3–0.6 mg m-3). Two distinct general patterns were observed, emphasizing the role of (i) physical and (ii) biological processes: (i) a strong influence of the vertical stratification, with most zooplankton absent or little abundant in the lower layer. The influence of the cold SACW on the bottom layer apparently restricted the vertical occupation of most species, which typically inhabit epipelagic warm waters. Even among migratory species, only a few (Aglaura hemistoma, Abylopsis tetragona eudoxids, Beroe sp., Thalia democratica, Salpa fusiformis) crossed the thermocline and reached the bottom layer. (ii) A general tendency of partial migrations, with variable intensity depending on the different species and developmental stages; populations tended to be more widely distributed through the water column during daylight, and to become more aggregated in the upper layer during the night, which can be explained based on the idea of the “hunger-satiation hypothesis”, maximizing feeding and minimizing the chances of being predated. PMID:26637179

  13. Manganese, iron, and sulfur cycling in Louisiana continental shelf sediments

    NASA Astrophysics Data System (ADS)

    Devereux, Richard; Lehrter, John C.; Beddick, David L.; Yates, Diane F.; Jarvis, Brandon M.

    2015-05-01

    Sulfate reduction is considered the primary pathway for organic carbon remineralization on the northern Gulf of Mexico Louisiana continental shelf (LCS) where bottom waters are seasonally hypoxic, yet limited information is available on the importance of iron and manganese cycling in the region. Sedimentary manganese, iron, and sulfur cycling were investigated on the LCS using a combined chemical analysis and sediment diagenesis modeling approach. Three stations situated 320 km across the LCS along the 20 m isobath were sampled up to five times between the spring of 2006 and summer of 2007. Bottom water oxygen levels at the stations ranged from 203 mmol m-3 in spring to 2.5 mmol m-3 in summer. Porewater Mn and Fe2+ concentrations (up to 275 and 300 μmol L-1, respectively), sulfate reduction rates (1.0-8.4 mmol m-2 d-1), and the fraction of total oxalate extracted iron obtained as Fe(II) (0.25-0.52) differed between station and season. Sediments at station Z02 on the eastern LCS, south of Terrebonne Bay, had higher organic matter content and sulfate reduction rates than sediments at Z03, 160 km further west. Sulfate reduction rates were higher in summer than spring at station Z02 but not at Z03 where porewater Mn and Fe concentrations were highest in summer. Porewater Fe2+ concentrations, solid phase oxalate-extractable Fe concentrations, and sediment incubation experiments suggested iron reduction at Z03 may account for 20% or more of organic carbon remineralization. LCS Fe(III) concentrations decreased and sulfate reduction rates increased in model simulations by lowering interfacial dissolved oxygen levels and increasing the rates of organic matter deposited on the sediment surface. Results from this study demonstrate that LCS sedimentary metal oxide cycling may be more important in organic carbon mineralization pathways than previously recognized.

  14. [Shrimp community structure and its relationships with environmental factors in the Yellow Sea in summer].

    PubMed

    Pang, Zhi-wei; Li, Xian-sen; Ying, Yi-ping; Wu, Qiang; Luan, Qing-shan

    2015-11-01

    Based on the data collected from the bottom trawl survey in Yellow Sea, August, 2014, the community structure of shrimp assemblage and its relationships with environmental factors in summer was examined by using index of relative importance, ecological diversity indices and multivariate statistical analysis. A total of 20 shrimp species were captured, belonging to 3 orders, 10 families, 16 genera. The relative abundance of shrimp of all stations ranged from 13 to 45047 g · h(-1) and its mean value was 6838 g · h(-1). The dominant species was Crangon affinis, and the common species was Eualus sinensis. The rare species were Metapenaeopsis dalei, Palaemon gravieri and Oratosquilla oratoria. The ranges of Shannon diversity index (H) , Pielou' s evenness index (J) and the Margalef' s species richness index (D) of all stations of the shrimp community structure were 0.007-1.538, 0.101-1.138 and 0.006-0.947, respectively, and the mean values of H, Jand D were 0.391, 0.374 and 0.298, respectively. MDS and Cluster analyses revealed that two clusters of Group I named cold water mass group and Group II named coastal group, which were bounded by the 45 m isobaths, were identified for all the sampling stations. Significant difference was detected by ANOSIM analysis between Group I and Group II. BIOENV analysis indicated that bottom temperature and bottom salinity were the most important environmental factors for structuring the spatial distribution of the shrimp assemblage. Cold water mass group accounted for absolute advantage and Yellow Sea cold mass had a decisive influence on the distribution pattern of the shrimp community in the Yellow Sea in summer. PMID:26915210

  15. Mesoscale process-induced variation of the West India Coastal Current during the winter monsoon.

    PubMed

    Jineesh, V K; Muraleedharan, K R; Lix John, K; Revichandran, C; Hareesh Kumar, P V; Naveen Kumar, K R

    2015-08-01

    This manuscript presents the analysis of current meter records at Kollam and Kannur along the 20-m isobaths during November-December 2005. Currents in the coastal waters are strongly influenced by winds (both local and remote forcing), tides, propagation of coastal Kelvin and Rossby waves, etc. We hypothesize that the mesoscale (spatial scales of 10-500 km and temporal scale of 10-100 days) features in ocean are also competent to alter the characteristics of coastal currents to a large extent. Analysis of sea level anomaly from the merged altimeter data reveals the existence of a large anticyclonic eddy in the southeastern Arabian Sea during the winter monsoon. The eddy moves westward with an average speed of ∼15 km day(-1) corresponding to an increase in sea level amplitude up to 28 cm. Off southwest India, the poleward flow is along the western flank of this anticyclonic eddy and the geostrophic current completes the circulation around the eddy. The eastward component of the geostrophic current at the northern edge of the eddy is bifurcated at ∼9° N: one flowing towards north and the other towards south. Current meter records at station Kollam revealed a dominant southward current due to the bifurcated southward component. The bifurcated northward component coalesced with the poleward flow along the western flank of the anticyclonic eddy. At Kannur, a poleward flow along the coast is responsible for a predominant northward trend in the observed current pattern during the initial phase of observation. A reversal in the current direction is caused by the southward-flowing geostrophic current along the eastern flank of the subsequent anticyclonic eddy centered at 73.5° E and 13° N. The stations were located at the eastern periphery of these anticyclonic eddies, where the mesoscale features overwhelm the seasonal characteristics of the West India Coastal Current (WICC). PMID:26183151

  16. Distribution and relative abundance of humpback whales in relation to environmental variables in coastal British Columbia and adjacent waters

    NASA Astrophysics Data System (ADS)

    Dalla Rosa, Luciano; Ford, John K. B.; Trites, Andrew W.

    2012-03-01

    Humpback whales are common in feeding areas off British Columbia (BC) from spring to fall, and are widely distributed along the coast. Climate change and the increase in population size of North Pacific humpback whales may lead to increased anthropogenic impact and require a better understanding of species-habitat relationships. We investigated the distribution and relative abundance of humpback whales in relation to environmental variables and processes in BC waters using GIS and generalized additive models (GAMs). Six non-systematic cetacean surveys were conducted between 2004 and 2006. Whale encounter rates and environmental variables (oceanographic and remote sensing data) were recorded along transects divided into 4 km segments. A combined 3-year model and individual year models (two surveys each) were fitted with the mgcv R package. Model selection was based primarily on GCV scores. The explained deviance of our models ranged from 39% for the 3-year model to 76% for the 2004 model. Humpback whales were strongly associated with latitude and bathymetric features, including depth, slope and distance to the 100-m isobath. Distance to sea-surface-temperature fronts and salinity (climatology) were also constantly selected by the models. The shapes of smooth functions estimated for variables based on chlorophyll concentration or net primary productivity with different temporal resolutions and time lags were not consistent, even though higher numbers of whales seemed to be associated with higher primary productivity for some models. These and other selected explanatory variables may reflect areas of higher biological productivity that favor top predators. Our study confirms the presence of at least three important regions for humpback whales along the BC coast: south Dixon Entrance, middle and southwestern Hecate Strait and the area between La Perouse Bank and the southern edge of Juan de Fuca Canyon.

  17. Oscillation Responses to an Extreme Weather Event from a Deep Moored Observing System

    NASA Astrophysics Data System (ADS)

    Wang, Z.; Dimarco, S. F.; Stoessel, M. M.; Zhang, X.; Ingle, S.

    2011-12-01

    In June 2007 tropical Cyclone Gonu passed directly over an ocean observing system consisting of four, deep autonomous mooring stations along the 3000 m isobath in the northern Arabian Sea. Gonu was the largest cyclone known to have occurred in the Arabian Sea or to strike the Arabian Peninsula. The mooring system was designed by Lighthouse R & D Enterprises, Inc. and installed in cooperation with the Oman Ministry of Agriculture and Fisheries Wealth. The instruments on the moorings continuously recorded water velocities, temperature, conductivity, pressure, dissolved oxygen and turbidity at multiple depths and at hourly intervals during the storm. Near-inertial oscillations at all moorings from thermocline to seafloor are coincident with the arrival of Gonu. Sub-inertial oscillations with periods of 2-10 days are recorded at the post-storm relaxation stage of Gonu, primarily in the thermocline. These oscillations consist of warm, saline water masses, likely originating from the Persian Gulf. Prominent 12.7-day sub-inertial waves, measured at a station ~300 km offshore, are bottom-intensified and have characteristics of baroclinic, topographically-trapped waves. Theoretical results from a topographically-trapped wave model are in a good agreement with the observed 12.7-day waves. The wavelength of the 12.7-day waves is about 590 km calculated from the dispersion relationship. Further analysis suggests that a resonant standing wave is responsible for trapping the 12.7-day wave energy inside the Sea of Oman basin. The observational results reported here are the first measurements of deepwater responses to a tropical cyclone in the Sea of Oman/Arabian Sea. Our study demonstrates the utility of sustained monitoring for studying the impact of extreme weather events on the ocean.

  18. Distribution of diatoms and silicoflagellates in surface sediments of the Yellow Sea and offshore from the Changjiang River, China

    NASA Astrophysics Data System (ADS)

    Wang, Yanna; Liu, Dongyan; Di, Baoping; Shi, Yajun; Wang, Yujue

    2016-01-01

    The spatial distribution of siliceous microfossils (diatoms and silicoflagellates) in the surface sediments was mapped at 113 sites in the Yellow Sea and sea areas adjacent to the Changjiang (Yangtze) River, China. In total, 267 diatom taxa and two silicoflagellate species were identified from the sediments. The spatial variations in abundance and diversity were classified into three distinct geographic patterns using Q mode clustering: a south-north geographic pattern, a coastal-offshore pattern and a unique pattern in the Changjiang River mouth. The south-north geographic pattern was related to the spatial variations in sea temperature. Coscinodiscus oculatus, a warm-water species, indicated these variations by a gradual decrease in abundance from the south to the north. The coastal-offshore pattern was in response to the spatial variations in salinity. Cyclotella stylorum, Actinocyclus ehrenbergii and Dictyocha messanensis, the dominant brackish species in coastal waters, significantly decreased at the isobaths of approximately 30 m, where the salinity was higher than 31. Paralia sulcata and Podosira stelliger indicated the impact of the Yellow Sea Warm Current in the central Yellow Sea. The unique pattern in the Changjiang River mouth showed the highest species diversity but lower abundance, apparently because: freshwater input can significantly increase the proportion of brackish species; nutrients can supply the growth of phytoplankton; and high sedimentation rates can dilute the microfossil abundance in the sediments. Our results show that an integration of environmental factors (e.g., nutrient levels, sedimentation rate, sea temperature, salinity and water depth) determined the spatial characteristics of the siliceous microfossils in the surface sediments.

  19. Modeling and observations of high-frequency flow variability and internal waves at a Caribbean reef spawning aggregation site

    NASA Astrophysics Data System (ADS)

    Ezer, Tal; Heyman, William D.; Houser, Chris; Kjerfve, Björn

    2011-05-01

    The characteristics and forcing mechanisms of high-frequency flow variations (periods of minutes to days) were investigated near Gladden Spit, a reef promontory off the coast of Belize. Direct field observations and a high-resolution (50-m grid size) numerical ocean model are used to describe the flow variations that impact the initial dispersion of eggs and larvae from this site, which serves as a spawning aggregation site for many species of reef fishes. Idealized sensitivity model experiments isolate the role of various processes, such as internal waves, wind, tides, and large-scale flow variations. The acute horizontal curvature and steep topography of the reef intensify the flow, create small-scale convergence and divergence zones, and excite high-frequency oscillations and internal waves. Although the tides in this area are relatively small (˜10-cm amplitude), the model simulations show that tides can excite significant high-frequency flow variations near the reef, which suggests that the preference of fish to aggregate and spawn in the days following the time of full moon may not be coincidental. Even small variations in remote flows (2-5 cm s-1) due to say, meso-scale eddies, are enough to excite near-reef oscillations. Model simulations and the observations further suggest that the spawning site at the tip of the reef provides initial strong dispersion for eggs, but then the combined influence of the along-isobath flow and the westward wind will transport the eggs and larvae downstream of Gladden Spit toward less turbulent region, which may contribute to enhanced larval survival.

  20. Quantification of source uncertainties in Seismic Probabilistic Tsunami Hazard Analysis (SPTHA)

    NASA Astrophysics Data System (ADS)

    Selva, J.; Tonini, R.; Molinari, I.; Tiberti, M. M.; Romano, F.; Grezio, A.; Melini, D.; Piatanesi, A.; Basili, R.; Lorito, S.

    2016-03-01

    We propose a procedure for uncertainty quantification in Probabilistic Tsunami Hazard Analysis (PTHA), with a special emphasis on the uncertainty related to statistical modelling of the earthquake source in Seismic PTHA (SPTHA), and on the separate treatment of subduction and crustal earthquakes (treated as background seismicity). An event tree approach and ensemble modelling are used in spite of more classical approaches, such as the hazard integral and the logic tree. This procedure consists of four steps: 1) exploration of aleatory uncertainty through an event tree, with alternative implementations for exploring epistemic uncertainty; 2) numerical computation of tsunami generation and propagation up to a given offshore isobath; 3) (optional) site-specific quantification of inundation; 4) simultaneous quantification of aleatory and epistemic uncertainty through ensemble modelling. The proposed procedure is general and independent of the kind of tsunami source considered; however, we implement step 1), the event tree, specifically for SPTHA, focussing on seismic source uncertainty. To exemplify the procedure, we develop a case study considering seismic sources in the Ionian Sea (central-eastern Mediterranean Sea), using the coasts of Southern Italy as a target zone. The results show that an efficient and complete quantification of all the uncertainties is feasible even when treating a large number of potential sources and a large set of alternative model formulations. We also find that: i) treating separately subduction and background (crustal) earthquakes allows for optimal use of available information and for avoiding significant biases; ii) both subduction interface and crustal faults contribute to the SPTHA, with different proportions that depend on source-target position and tsunami intensity; iii) the proposed framework allows sensitivity and deaggregation analyses, demonstrating the applicability of the method for operational assessments.

  1. The offshore export of sand during exceptional discharge from California rivers

    USGS Publications Warehouse

    Warrick, Jonathan A.; Barnard, Patrick L.

    2012-01-01

    Littoral cells along active tectonic margins receive large inputs of sand and gravel from coastal watersheds and commonly lose this sediment to submarine canyons. One hypothesis is that the majority of coarse (sand and gravel) river sediment discharge will be emplaced within and immediately “resupply” local littoral cells. A competing hypothesis is that the infrequent, large floods that supply the majority of littoral sediment may discharge water-sediment mixtures within negatively buoyant hyperpycnal plumes that transport sediment offshore of the littoral cell. Here we summarize pre- and post-flood surveys of two wave-dominated California (United States) river deltas during record to near-record floods to help evaluate these hypotheses: the 1982–1983 delta at the San Lorenzo River mouth and the 2005 delta at the Santa Clara River mouth. Flood sedimentation at both deltas resulted in several meters of aggradation and hundreds of meters of offshore displacement of isobaths. One substantial difference between these deltas was the thick (>2 m) aggradation of sand on the inner shelf of the Santa Clara River delta that contained substantial amounts (∼50%) of littoral-grade sediment. Once deposited on the inner shelf, only a fraction (∼20%) of this river sand was observed to migrate toward the beach over the following 5 yr. Furthermore, simple hypopycnal plume behavior could not explain deposition of this sand on the inner shelf. Thus, during an exceptional flood a substantial amount of littoral-grade sand was exported offshore of the littoral system at the Santa Clara River mouth—likely from hyperpycnal plume processes—and was deposited on the inner shelf.

  2. The influence of wind forcing on across-shelf transport in the Florida Keys

    NASA Astrophysics Data System (ADS)

    Smith, Ned Philip

    2009-01-01

    Acoustic Doppler current profiles and current meter data are combined with wind observations to describe the transport of water leaving Florida Bay and moving onto the inner shelf on the Atlantic side of the Florida Keys. A 275-day study in the Long Key Channel reveals strong tidal exchanges, but the average ebb tide volume leaving Florida Bay is 19% greater than the average flood tide volume entering the bay. The long-term net outflow averages 472 m 3 s -1. Two studies in shelf waters describe the response to wind forcing during spring and summer months in 2004 and during fall and winter months in 2004-2005. During the spring-summer study, southeasterly winds have a distinct shoreward component, and a two-layer pattern appears. Surface layers move shoreward while near-bottom layers move seaward. During the winter study, the resultant wind direction is parallel to the Keys and to the local isobaths. The entire water column moves in a nearly downwind direction, and across-shelf transport is relatively small. During the summer wet season, Florida Bay water should be warmer, fresher, and thus less dense than Atlantic shelf waters. Ebbing bay water should move onto the shelf as a buoyant plume and be held close to the Keys by southeasterly winds. During the winter dry season, colder and saltier Florida Bay water should leave the tidal channels with relatively high density and be concentrated in the near-bottom layers. But little across-shelf flow occurs with northeasterly winds. The study suggests that seasonally changing wind forcing and hydrographic conditions serve to insulate the reef tract from the impact of low-quality bay water.

  3. Zooplankton and forage fish species off Peru: Large-scale bottom-up forcing and local-scale depletion

    NASA Astrophysics Data System (ADS)

    Ayón, Patricia; Swartzman, Gordon; Bertrand, Arnaud; Gutiérrez, Mariano; Bertrand, Sophie

    2008-10-01

    The Humboldt Current System, like all upwelling systems, has dramatic quantities of plankton-feeding fish, which suggested that their population dynamics may ‘drive’ or ‘control’ ecosystem dynamics. With this in mind we analysed the relationship between forage fish populations and their main prey, zooplankton populations. Our study combined a zooplankton sampling program (1961-2005) with simultaneous acoustic observations on fish from 40 pelagic surveys (1983-2005) conducted by the Peruvian Marine Research Institute (IMARPE) and landing statistics for anchoveta ( Engraulis ringens) and sardine ( Sardinops sagax) along the Peruvian coast from 1961 to 2005. The multi-year trend of anchoveta population abundance varied consistently with zooplankton biovolume trend, suggesting bottom-up control on anchovy at the population scale (since oceanographic conditions and phytoplankton production support the changes in zooplankton abundance). For a finer-scale analysis (km) we statistically modelled zooplankton biovolume as a function of geographical (latitude and distance from the 200-m isobath), environmental (sea surface temperature), temporal (year, month and time-of-day) and biological (acoustic anchovy and sardine biomass within 5 km of each zooplankton sample) covariates over all survey using both classification and regression trees (CART) and generalized additive models (GAM). CART showed local anchoveta density to have the strongest effect on zooplankton biovolume, with significantly reduced levels of biovolume for higher neighbourhood anchoveta biomass. Additionally, zooplankton biovolume was higher offshore than on the shelf. GAM results corroborated the CART findings, also showing a clear diel effect on zooplankton biovolume, probably due to diel migration or daytime net avoidance. Apparently, the observed multi-year population scale bottom-up control is not inconsistent with local depletion of zooplankton when anchoveta are locally abundant, since the

  4. Dissolved organic carbon fluxes in the Middle Atlantic Bight: An integrated approach based on satellite data and ocean model products

    NASA Astrophysics Data System (ADS)

    Mannino, Antonio; Signorini, Sergio R.; Novak, Michael G.; Wilkin, John; Friedrichs, Marjorie A. M.; Najjar, Raymond G.

    2016-02-01

    Continental margins play an important role in global carbon cycle, accounting for 15-21% of the global marine primary production. Since carbon fluxes across continental margins from land to the open ocean are not well constrained, we undertook a study to develop satellite algorithms to retrieve dissolved organic carbon (DOC) and combined these satellite data with physical circulation model products to quantify the shelf boundary fluxes of DOC for the U.S. Middle Atlantic Bight (MAB). Satellite DOC was computed through seasonal relationships of DOC with colored dissolved organic matter absorption coefficients, which were derived from an extensive set of in situ measurements. The multiyear time series of satellite-derived DOC stocks (4.9 Teragrams C; Tg) shows that freshwater discharge influences the magnitude and seasonal variability of DOC on the continental shelf. For the 2010-2012 period studied, the average total estuarine export of DOC into the MAB shelf is 0.77 Tg C yr-1 (year). The integrated DOC tracer fluxes across the shelf boundaries are 12.1 Tg C yr-1 entering the MAB from the southwest alongshore boundary, 18.5 Tg C yr-1 entering the MAB from the northeast alongshore boundary, and 29.0 Tg C yr-1 flowing out of the MAB across the entire length of the 100 m isobath. The magnitude of the cross-shelf DOC flux is quite variable in time (monthly) and space (north to south). The highly dynamic exchange of water along the shelf boundaries regulates the DOC budget of the MAB at subseasonal time scales.

  5. Sedimentary processes on the Bengal continental shelf as revealed by clay-size mineralogy

    NASA Astrophysics Data System (ADS)

    Segall, M. P.; Kuehl, S. A.

    1992-04-01

    Shelf sediment dispersal seaward of the Ganges-Brahmaputra river system is examined during January/February (low discharge) through analysis of sediment cores and surface grab samples for clay-size mineralogy. Illite is the dominant mineral in surficial sediments landward of the 50-m isobath, comprising >40% of the clay-size assemblage. Kaolinite concentrations of surficial sediments generally are greater than 20% throughout the area; however, very high abundances occur off Bhola Island (25-33%) and the Chittagong coast (34-39%), probably as a result of extensive shoreline erosion of cultivated areas enriched in kaolinite. Smectite and illite/smectite concentrations, reflecting input from distributaries of the Ganges, are enriched on the western inner shelf and along the western margin of the "Swatch of No Ground", a major submarine canyon west of the present river mouth. Although surficial chlorite abundances on the inner shelf in water depths <20m generally are low to negligible (<5%), mid-shelf abundances range from 5 to 13% with the highest concentrations near the head of the submarine canyon. These high concentrations probably reflect sediment dispersal to the mid-shelf region during the high-discharge season (May-October) when chlorite-enriched sediments from the nearby Himalayas are discharged by the river. During low discharge, chlorite-poor sediments are concentrated on the inner shelf and do not dilute the "relict" chlorite signal which is preserved offshore. Downcore zones of high chlorite concentrations east of the submarine canyon indicate that at least part of the high-discharge signal is preserved in the sedimentary record. Chlorite is depleted west of the canyon, suggesting that the "Swatch of No Ground" presently interrupts the westward along-shelf transport of riverine sediments.

  6. Sedimentological conditions and sediment transport pathways in the nearshore zone of the Russian part of South-Eastern Baltic Sea

    NASA Astrophysics Data System (ADS)

    Dorokhova, Evgenia

    2016-04-01

    The sediment transport pathways and sedimentological conditions are identified on the South-Eastern Baltic Sea coastal zone (Russian part) up to the depth of 30 m on the base of grain size analysis of recent marine sediments. The interrelations between grain size statistical parameters of 971 sediment samples are used. The two independent approaches that discussed in the literature are applied: 1) the sediment trend analysis, based on spatial variations of sediment grain size parameters from sample to sample (McLaren, 1981) and 2) the population anomalies method, which allows to determine the sedimentation conditions (erosion, transit or accumulation) from the deviations of sediments grain size parameters in each sampling place from the average values in investigation area (Baraniecki and Racinowski, 1996). Taking into account that the sediment grain size composition achieve its constant in calm period of reduced storm influence and that the all samples were taking during summer season, the obtained sedimentation pattern present the long-time annual average of sediment transport pathways in the investigated area. The results show that the sediment accumulation under the wave influence prevails up to the depth of 5 m. The continuous accumulation zone breaks in erosion where the shore line changes its direction. Seaward of the accumulation zone the sediment transit area extends and interrupts by zones of erosion and accumulation up to the depth of 20 m. Sediment transport here occurs in hydrodynamic circulation cells within bays along the Sambian peninsula north coast. The erosion zones serves as sediment source on the underwater shore slope. The north-eastern direction of sediment transport exist along the straightened coast of Curonian spit according to prevail west winds. Deeper there are zones of transit and "slowly" sediment accumulation up to the depth of 30 m. The seaward and isobaths parallel sediment transport pathways are obtained in these zones. The work

  7. New Thought on the Agulhas Current

    NASA Astrophysics Data System (ADS)

    Meyer, A. A.; Lutjeharms, J. R.; Whittle, C.; Weeks, S.; Roy, C.

    2002-12-01

    A more complete understanding of the fundamental dynamics of the Agulhas Current Proper is evolving rapidly because of new discoveries. The discovery of the Agulhas Undercurrent (Beal and Bryden, 1997) had a profound effect on the overall estimate of the Agulhas Current transport. Also, the discovery of Schouten et al. (2002) that Mozambique Channel Eddies are responsible for the formation of Natal Pulses, which in turn is significantly related to the Indian-Atlantic Interocean leakage of water masses, had a profound effect on how the Agulhas Current System is now perceived. These new insights, historical hydrographic data, and satellite remote sensed data contributed to the formulation of 3 hypotheses on the fundamental dynamics of the Agulhas Current Proper. Hypothesis one: Directly north of the Delagoa Bight the Mozambique Channel Eddies encounter the most northern extend of the shallow Agulhas Current and interact with the seaward side of this Western Boundary Current to form the Delagoa Pulse, obtaining its required cyclonicity from the Delagoa Bight Lee Eddy. Hypothesis two: Water masses of the Agulhas Undercurrent and Red Sea Water are upwelled within the Delagoa Bight Lee eddy which forms the southward propagating Delagoa Pulse. Hence, parts of the Agulhas Undercurrent are transported back into the Atlantic Ocean via a fast-track (10 to 20 km/day) mechanism, the Delagoa Pulse. Hypothesis three: Delagoa Pulses act as mechanisms for the injection of upwelled Agulhas Undercurrent water masses and Red Sea Water onto the eastern Agulhas Bank, supplying a semi-continuous density flow along the 100 m isobath. This density current originates from the Indian Ocean sector of the Agulhas Bank at the Port Alfred Upwelling Cell, feeds the cold bottom ridge, rounds the Alphard Banks, and enters the Atlantic Ocean sector of the Agulhas Bank. The physical and chemical properties of the density flow coined the Lutjeharms (Indian-Atlantic Interocean secondary leakage) Return

  8. 3D cartographic modeling of the Alpine arc

    NASA Astrophysics Data System (ADS)

    Vouillamoz, Naomi; Sue, Christian; Champagnac, Jean-Daniel; Calcagno, Philippe

    2012-12-01

    We built a 3D cartography of the Alpine arc, a highly non-cylindrical mountain belt, using the 3D GeoModeller of the BRGM (French geological survey). The model allows to handle the large-scale 3D structure of seventeen major crustal units of the belt (from the lower crust to the sedimentary cover nappes), and two main discontinuities (the Insubric Line and the Crustal Penninic Front). It provides a unique document to better understand their structural relationships and to produce new sections. The study area comprises the western Alpine arc, from the Jura to the Northwest, up to the Bergell granite intrusion and the Lepontine Dome to the East, and is limited to the South by the Ligurian basin. The model is limited vertically 10 km above sea level at the top, and the moho interface at the bottom. We discarded the structural relationships between the Alps sensus stricto and the surrounding geodynamic systems such as the Rhine graben or the connection with the Apennines. The 3D-model is based on the global integration of various data such as the DEM of the Alps, the moho isobaths, the simplified geological and tectonic maps of the belt, the crustal cross-sections ECORS-CROP and NFP-20, and complementary cross-sections specifically built to precise local complexities. The database has first been integrated in a GIS-project to prepare their implementation in the GeoModeller, by homogenizing the different spatial referencing systems. The global model is finally interpolated from all these data, using the potential field method. The final document is a new tri-dimensional cartography that would be used as input for further alpine studies.

  9. 3D cartography of the Alpine Arc

    NASA Astrophysics Data System (ADS)

    Vouillamoz, N.; Sue, C.; Champagnac, J. D.; Calcagno, P.

    2012-04-01

    We present a 3D cartography of the alpine arc, a highly non-cylindrical mountain belt, built using the 3D GeoModeller of the BRGM (French geological survey). The model allows to handle the large-scale 3D structure of seventeen major crustal units of the belt (from the lower crust to the sedimentary cover nappes), and two main discontinuities (the Insubric line and the Crustal Penninic Front). It provides a unique document to better understand their structural relationships and to produce new sections. The study area comprises the western alpine arc, from the Jura to the Northwest, up to the Bergell granite intrusion and the Lepontine Dome to the East, and is limited to the South by the Ligurian basin. The model is limited vertically 10 km above sea level at the top, and the moho interface at the bottom. We discarded the structural relationships between the Alps sensus stricto and the surrounding geodynamic systems such as the Rhine graben or the connection with the Apennines. The 3D-model is based on the global integration of various data such as the DEM of the Alps, the moho isobaths, the simplified geological and tectonic maps of the belt, the crustal cross-sections ECORS-CROP and NFP-20, and complementary cross-sections specifically built to precise local complexities. The database has first been integrated in a GIS-project to prepare their implementation in the GeoModeller, by homogenizing the different spatial referencing systems. The global model is finally interpolated from all these data, using the potential field method. The final document is a new tri-dimentional cartography that would be used as input for further alpine studies.

  10. Dolomite as a tracer for sediment transport and deposition on the northwestern Adriatic continental shelf (Adriatic Sea, Italy)

    NASA Astrophysics Data System (ADS)

    Ravaioli, Mariangela; Alvisi, Francesca; Vitturi, Laura Menegazzo

    2003-09-01

    Surface sediments of the Northern and Middle Adriatic shelf were studied during five cruises, from 1977 to 1990, in order to map the distribution of Ca and Mg carbonates in bottom sediments of the Adriatic Sea. The aim of this work was to trace the preferential depositional areas of sediments derived from Italian rivers by distinguishing among the contributions from northeastern Italian rivers, the Po and Apenninic streams. The pattern distribution of dolomite concentration proved to be a good tracer of the alongshore transport of particulate material from the Northern toward the Middle and Southern Adriatic. Moreover, dolomite and textural sedimentary parameters such as grain size distributions discriminate between local, recent sources, and regional, older sources of bottom sedimentary material. The analysis of the main pathways of sediment transfer between different shelf compartments shows that a huge amount of material is transferred from north to south. This occurs in two main shelf sectors: along the Romagna coast, sediments moving inside the belt delimited by the 20 m isobaths are influenced by the local river input and minor coastal gyres, whereas offshore sediments, coming from the northern Adriatic Sea, are transported southward by the Northern Adriatic Coastal Current (NACC); along the Marche and Abruzzo coasts, the "local" belt extends offshore on the outer shelf. In order to obtain a quantitative estimate of sediment accumulation of fine sediments of Northern Adriatic origin along the shelf sectors, a mass budget was calculated for bulk sediments and for dolomite contributions. The budget shows that the amount of sediment transferred between adjacent boxes is always of the order of 50% of the fluvial input to the sea.

  11. Fluctuations of Gulf Stream frontal position between Cape Hatteras and the Straits of Florida

    SciTech Connect

    Miller, J.L. )

    1994-03-15

    Low-frequency variations in the onshore/offshore position of the Gulf Stream thermal front have been examined at 10 cross-isobath transects spaced along the South Atlantic Bight between the Straits of Florida and Cape Hatteras. The data were obtained from the U.S. Navy's frontal analysis charts for the 12-year period, 1976-1988. A time domain empirical orthogonal function (EOF) analysis revealed two modes of fluctuation about the mean Gulf Stream Position, which together explain the well-known [open quotes]weakly and strongly deflected[close quotes] frontal position states which occur on timescales of a few months in the vicinity of the Charleston Bump. Analyses of fluctuations at the annual period revealed a 3-month phase lag between frontal position, as shown by the most significant time domain EOF mode, and volume transport through the Straits of Florida. In addition, frequency domain EOF and cross-spectral analysis of frontal position revealed annual waves which appear to propagate to the south (north) in the region south (north) of the bump. For transect pairs having significant coherence and nonzero phase estimates, the phase speed and wavelength were about 10 cm/s southward (7 cm/s northward) and 3000 km (2000 km) in the southern (northern) region. This suggests an annual generation of a perturbation in the vicinity of the bump which radiates away as a long annual wave and which may be related to, or part of, the mechanism which produces the annual modulation of Gulf Stream transport. 11 refs., 9 figs., 1 tab.

  12. Preliminary Seismic Probabilistic Tsunami Hazard Map for Italy

    NASA Astrophysics Data System (ADS)

    Lorito, Stefano; Selva, Jacopo; Basili, Roberto; Grezio, Anita; Molinari, Irene; Piatanesi, Alessio; Romano, Fabrizio; Tiberti, Mara Monica; Tonini, Roberto; Bonini, Lorenzo; Michelini, Alberto; Macias, Jorge; Castro, Manuel J.; González-Vida, José Manuel; de la Asunción, Marc

    2015-04-01

    We present a preliminary release of the first seismic probabilistic tsunami hazard map for Italy. The map aims to become an important tool for the Italian Department of Civil Protection (DPC), as well as a support tool for the NEAMTWS Tsunami Service Provider, the Centro Allerta Tsunami (CAT) at INGV, Rome. The map shows the offshore maximum tsunami elevation expected for several average return periods. Both crustal and subduction earthquakes are considered. The probability for each scenario (location, depth, mechanism, source size, magnitude and temporal rate) is defined on a uniform grid covering the entire Mediterranean for crustal earthquakes and on the plate interface for subduction earthquakes. Activity rates are assigned from seismic catalogues and basing on a tectonic regionalization of the Mediterranean area. The methodology explores the associated aleatory uncertainty through the innovative application of an Event Tree. Main sources of epistemic uncertainty are also addressed although in preliminary way. The whole procedure relies on a database of pre-calculated Gaussian-shaped Green's functions for the sea level elevation, to be used also as a real time hazard assessment tool by CAT. Tsunami simulations are performed using the non-linear shallow water multi-GPU code HySEA, over a 30 arcsec bathymetry (from the SRTM30+ dataset) and the maximum elevations are stored at the 50-meter isobath and then extrapolated through the Green's law at 1 meter depth. This work is partially funded by project ASTARTE - Assessment, Strategy And Risk Reduction for Tsunamis in Europe - FP7-ENV2013 6.4-3, Grant 603839, and by the Italian flagship project RITMARE.

  13. Variability of the internal tide on the southern Monterey Bay continental shelf and associated bottom boundary layer sediment transport

    NASA Astrophysics Data System (ADS)

    Rosenberger, K. J.; Storlazzi, C. D.; Cheriton, O. M.; McPhee-Shaw, E. E.

    2014-12-01

    A 6-month deployment of instrumentation from April to October 2012 in 90 m water depth near the outer edge of the mid-shelf mud belt in southern Monterey Bay, California, reveals the relative importance of internal tides on the resuspension and transport of seabed sediment. Observations consisted of time-series measurements of water-column currents, temperature and salinity, and near-bed currents and suspended matter. The internal tide accounted for 15-25% of the water-column current variance and the barotropic tide accounted for up to 35%. The subtidal flow showed remarkably little shear and was dominated by the 7-14 day band, which is associated with relaxations in the dominant equatorward winds typical of coastal California in the spring and summer. Upwelling and relaxation events resulted in strong near-bed flows and accounted for almost half of the current stress on the seafloor (not accounting for wave orbital velocities), and may have driven along-shelf geostrophic flow during steady state conditions. Several elevated suspended particulate matter (SPM) events occurred within 3 m of the bed and were generally associated with higher, long-period surface waves. However, these peaks in SPM did not coincide with the predicted resuspension events from the modeled combined wave-current shear stress, indicating that the observed SPM at our site was most likely resuspended elsewhere and advected along-isobath. Sediment flux is almost equal in magnitude in the alongshore and cross-shore directions. Instances of wave-current shear stress that exceeded the threshold of resuspension for the silty-clays common at these water depths only occurred when near-bed orbital velocities due to long-period surface waves coincided with vigorous near-bed currents associated with the internal tide or upwelling/relaxation events. Thus, the internal tide and upwelling/relaxation dynamics are important in the transport of sediment during the relatively quiescent summer months.

  14. Spring 2009 water mass distribution, mixing and transport in the southern Adriatic after a low production of winter dense waters

    NASA Astrophysics Data System (ADS)

    Rice, Ana E.; Book, Jeffrey W.; Carniel, Sandro; Russo, Aniello; Schroeder, Katrin; Wood, Warren T.

    2013-08-01

    Enhanced mixing of North Adriatic Dense Water (NAdDW) occurs in a strong frontal region as this cold and fresh intermediate water enters the southern Adriatic basin and meets warm and salty Modified Levantine Intermediate Water (MLIW) coming from the Ionian Sea. This study examines how NAdDW was mixed and transformed as it traveled southward from the Gargano to the Bari region and investigates the pathway and intrusion patterns of MLIW in late winter/spring 2009. Hydrographic data are analyzed to compute source water fractions via a least-squares analysis method and combined with ADCP data to compute source water volume fluxes. Results show that despite an anomalous low year for NAdDW production in the Adriatic, a warmer, fresher and lighter version of traditional NAdDW (i.e. 2009 NAdDW) endured its journey from Gargano to Bari. In the Gargano region, 2009 NAdDW (with fractions up to 80-90%) traveled southward in a non-continuous thin, dense vein between 35 m and 100 m isobaths, with diluted cores (>50%) extending to 140 m depth, and with fluxes of -0.05 Sv, to the southeast, south of Palagruz˘a Sill. Near the sill, 2009 NAdDW was further mixed and diluted with MLIW and surface water. By the time it reached the Bari region, the 2009 NAdDW fraction in the water column was reduced to about 20%. MLIW intrusions observed over the Sill and in northern sections of the study area suggest a splitting of MLIW pathways (stemming from the main South Adriatic rim pathway) towards the central Adriatic. Source water fraction results combined with velocity and seismic oceanography data show that eddies in the study area are one mechanism for the generation of MLIW intrusions towards the northwest.

  15. Upwelling and downwelling induced by mesoscale circulation in the DeSoto Canyon region

    NASA Astrophysics Data System (ADS)

    Nguyen, T. T.; Chassignet, E.; Morey, S. L.; Dukhovskoy, D. S.

    2014-12-01

    Ocean dynamics are complex over irregular topography areas, and the northeastern Gulf of Mexico, specifically the DeSoto Canyon region, is a challenge for modelers and oceanographers. Vertical movement of waters, especially upwelling, is observed to take place over the canyon's head and along the coast; however, it is not well understood. We focus on upwelling/downwelling processes induced by the Loop Current and its associated eddy field using multi-decadal Hybrid Coordinate Ocean Model simulations. The Loop Current, part of the Gulf Stream, can develop northward into the Gulf through the Yucatan Channel and exit through the Florida Straits. It can reach the continental slope of the study domain and directly depress the isopycnals. Cyclonic eddies in front of the Loop Current also induce upwelling underneath. On the other hand, the Loop Current sometimes impinges on the West Florida Shelf and generates a high pressure disturbance, which travels northward along the shelf into the study region. Consequently, large-scale downwelling occurs across the continental slopes. Our analysis of sea surface height shows that the Loop Current pressure disturbance tends to propagate along the shallow isobaths of 100 to 300 m in the topographic wave direction from south of the West Florida Shelf to the Mississippi Delta. In addition, after shedding a large anticyclonic eddy, the Loop Current retracts southward and can touch the southeastern corner of the West Florida Shelf. This can result in a higher pressure disturbance, and therefore stronger large-scale downwelling in the DeSoto Canyon region.

  16. Bathymetric and regional changes in benthic macrofaunal assemblages on the deep Eastern Brazilian margin, SW Atlantic

    NASA Astrophysics Data System (ADS)

    Bernardino, Angelo Fraga; Berenguer, Vanessa; Ribeiro-Ferreira, Venina P.

    2016-05-01

    Deep-sea continental slopes have valuable mineral and biological resources in close proximity to diverse, undersampled and fragile marine benthic ecosystems. The eastern Brazilian Continental Margin (19.01°S to 21.06°S, 37.88°W to 40.22°W) is an important economic region for both fishing and oil industries, but is poorly understood with respect to the structure of the soft-sediment benthic fauna, their regional distribution and their bathymetric patterns. To identify spatial and temporal patterns of benthic macrofaunal assemblages on the slope (400 to 3000 m), the Espirito Santo Basin Assessment Project (AMBES, coordinated by Cenpes-Petrobras) sampled 42 stations across the Brazilian Eastern Slope during both Summer 2012 and Winter 2013. We found a significant decrease in macrofaunal abundance at the 400 m isobath along the slope near the northern region of the Espirito Santo Basin, suggesting benthic responses to upwelling events towards the south in Campos Basin and southern Espirito Santo Basin. The taxonomic diversity and assemblage composition also changed significantly across depth zones with mid-slope peaks of diversity at 1000-1300 m. In general, macrofaunal assemblages were strongly related to slope depth, suggesting a strong influence of productivity gradients and water mass distribution on this oligotrophic margin. Sediment grain size was marginally important to macrofaunal composition on the upper slope. In general, macrofaunal assemblages on the slope of Espirito Santo Basin are similar to other areas of the SE Brazilian margin, but regional changes in response to productivity and depth need to be considered for management strategies in the face of increasing economic activities off-shore.

  17. Seasonal variability in satellite-measured surface chlorophyll in the Patagonian Shelf

    NASA Astrophysics Data System (ADS)

    Rivas, Andrés L.; Dogliotti, Ana Inés; Gagliardini, Domingo A.

    2006-04-01

    Six years (January 1998—December 2003) of SeaWiFS ocean color satellite data are used to estimate monthly climatological means and to present the near-surface chlorophyll-a seasonal evolution in the Patagonian Shelf. The southern part of the shelf presents elevated chlorophyll concentrations from spring through autumn, while the northern part shows three regions with particular characteristics. The external region, bordering the 200 m isobath, presents elevated concentrations from spring through autumn supported by the nutrient-rich waters from the Malvinas (Falkland) Current. The central region presents a typical pattern of temperate regions, characterized by two well-defined maxima, a stronger spring bloom and a weaker fall bloom, and low chlorophyll values throughout summer (scarce availability of nutrients) and winter (light being the limiting factor). Even though the displacement direction of the spring and fall blooms do not agree with previous information reported in the literature, they are interpreted based on the heat exchange in the air-sea interface that controls the development and erosion of the seasonal thermocline. Finally, the coastal region presents less-marked seasonal variability and isolated small areas with elevated concentrations associated with frontal areas are observed. The spatial mean chlorophyll evolution, averaged over the whole shelf (less than 200 m depth), shows a marked annual cycle with high values from spring to autumn, supporting the importance of frontal regions as a fertilization mechanism. An increasing trend in chlorophyll concentrations, within the 6 years analyzed here (in the order of 23%), is apparent based on an increasing of the maximum annual values. From the comparison with in situ data it can be concluded that satellite information reproduces the spatial patterns of chlorophyll fields obtained from more classical data, while differences exist in absolute values obtained from both methodologies.

  18. Molecular Characterization of Water Column Microbial Populations within the Northern Gulf of Mexico Hypoxic Zone

    NASA Astrophysics Data System (ADS)

    Mills, H. J.; Reese, B. K.; Romero, B.

    2012-12-01

    The Gulf of Mexico hypoxic zone displays spatial and temporal variability on seasonal, diurnal, and hourly timescales. The highly dynamic geochemistry can be a result of physical and chemical factors as well as pelagic microbial populations. As part of an ongoing project to determine the mechanisms controlling hypoxia and understand the biological factors within this region, shifts in the composition of the metabolically active microbial populations within the water column were characterized. Understanding these shifts provide information on microbial populations that have the potential to decrease oxygen concentrations through respiration and increase oxygen through photosynthesis. Temporal and spatial variations of metabolically active microbial populations were investigated along a well-studied 20 m isobath extending east of Terrebonne Bay to a location offshore from the Atchafalaya Bay. An RNA-based molecular characterization of the microbial population was used to determine the distribution of the metabolically active lineages. Bacterial SSU rRNA were pyrosequenced (Roche 454 FLX) providing over 700,000 sequences with an average read length of more than 400 bases. Known photosynthetic lineages varied in frequency of detection at depth and time of sampling, as was expected. Additional lineages with the capacity for suboxic metabolic processes were detected mid-water column associated with hypoxic water formation. These data suggest hypoxic conditions persist long enough in the mid-water to promote a physiological response within the microbial populations. In addition, temporal switches between photosynthesis and respiration should be considered when analyzing the extent of hypoxia. The techniques used provide a unique view of the biological mechanisms controlling hypoxia within the northern Gulf of Mexico.

  19. Cleavage of a Gulf of Mexico Loop Current eddy by a deep water cyclone

    NASA Astrophysics Data System (ADS)

    Biggs, D. C.; Fargion, G. S.; Hamilton, P.; Leben, R. R.

    1996-09-01

    Eddy Triton, an anticyclonic eddy shed by the Loop Current in late June 1991, drifted SW across the central Gulf of Mexico in the first 6 months of 1992, along the ``southern'' of the three characteristic drift paths described by Vukovich and Crissman [1986] from their analyses of 13 years of advanced very high resolution radiometer sea surface temperature data. An expendable bathythermograph (XBT) and conductivity-temperature-depth (CTD) transect of opportunity through Triton at eddy age 7 months in January 1992 found that eddy interior stood 23 dyn. cm higher than periphery; this gradient drove an anticyclonic swirl transport of 9-10 Sv relative to 800 dbar. At eddy age 9-10 months and while this eddy was in deep water near 94°W, it interacted with a mesoscale cyclonic circulation and was cleaved into two parts. The major (greater dynamic centimeters) piece drifted NW to end up in the ``eddy graveyard'' in the NW corner of the gulf, while the minor piece drifted SW and reached the continental margin of the western gulf off Tuxpan. This southern piece of Eddy Triton then turned north to follow the 2000-m isobath to about 24°N and later coalesced with what remained of the major fragment. Because Eddy Triton's cleavage took place just before the start of marine mammals (GulfCet) and Louisiana-Texas physical oceanography (LATEX) field programs, the closely spaced CTD, XBT, and air dropped XBT (AXBT) data that were gathered on the continental margin north of 26°N in support of these programs allow a detailed look at the northern margin of the larger fragment of this eddy. Supporting data from the space-borne altimeters on ERS 1 and TOPEX/POSEIDON allow us to track both pieces of Eddy Triton in the western Gulf and follow their spin down in dynamic height, coalescence, and ultimate entrainment in January 1993 into another anticyclonic eddy (Eddy U).

  20. Moored observation of abyssal flow and temperature near a hydrothermal vent on the Southwest Indian Ridge

    NASA Astrophysics Data System (ADS)

    Liao, Guanghong; Zhou, Beifeng; Liang, Chujin; Zhou, Huaiyang; Ding, Tao; Wang, Yuan; Dong, Changming

    2016-01-01

    Four moorings were deployed near "Dragon Flag," an active hydrothermal vent in the valley of the Southwest Indian Ridge. The goal was to examine the variability of currents and temperature, which will guide the trajectory of spreading plumes. The mean current was cross-isobath, and the circulation was characterized by a submesoscale circulation. Observed currents also showed fluctuations with periods of 1-15 days. The inferred phase speed and wavelength for the wave with a period of 4.4 day are 10.4 km d-1 and 45.8km, respectively, which are consistent with the topographic Rossby wave theory. The persistent warming tendency with corresponding variation of salinity based on background θ-S properties may be caused by background circulation and divergence of the water column. The warming or cooling episodes were most likely as signatures of isopycnal surface depression or uplifting induced by the moving of mesoscale eddies. Well-resolved rotary spectra exhibited important nonlinear interactions between inertial and semidiurnal tide in the velocity and temperature records. Amplification of near-inertial currents in the near bottom is also exposed. These discoveries provided new evidence for the nonlinear interaction and trapped near-inertial waves by the ridge, which occurred in the deep ocean of the Southern Hemisphere. Such nonlinear interaction may represent a significant energy loss pathway for the internal waves, and part of the decay of such motion would likely result in increased mixing to maintain the abyssal stratification. Enhanced near-inertial motions can play a major role for the local advection of hydrothermal plumes.

  1. Shelf response to intense offshore wind

    NASA Astrophysics Data System (ADS)

    Grifoll, Manel; Aretxabaleta, Alfredo L.; Espino, Manuel

    2015-09-01

    Cross and along-shelf winds drive cross-shelf transport that promotes the exchange of tracers and nutrients to the open sea. The shelf response to cross-shelf winds is studied in the north shelf of the Ebro Delta (Mediterranean Sea), where those winds are prevalent and intense. Offshore winds in the region exhibit strong intensities (wind stress larger than 0.8 Pa) during winter and fall. The monthly average flow observed in a 1 year current meter record at 43.5 m was polarized following the isobaths with the along-shelf variability being larger than the cross-shelf. Prevalent southwestward along-shelf flow was induced by the three-dimensional regional response to cross-shelf winds and the coastal constraint. Seaward near-surface velocities occurred predominantly during offshore wind events. During intense wind periods, the surface cross-shelf water transport exceeded the net along-shelf transport. During typically stratified seasons, the intense cross-shelf winds resulted in a well-defined two-layer flow and were more effective at driving offshore transport than during unstratified conditions. While transfer coefficients between wind and currents were generally around 1%, higher cross-shelf transfer coefficients were observed in the near-inertial band. The regional extent of the resulting surface cold water during energetic cross-shelf winds events was concentrated around the region of the wind jet. Cross-shelf transport due to along-shelf winds was only effective during northeast wind events. During along-shelf wind conditions, the transport was estimated to be between 10 and 50% of the theoretical Ekman transport.

  2. Observations of sediment transport on the continental shelf off the mouth of the Waiapu River, New Zealand: Evidence for current-supported gravity flows

    NASA Astrophysics Data System (ADS)

    Ma, Yanxia; Wright, L. Donelson; Friedrichs, Carl T.

    2008-03-01

    Instrumented tripods deployed at depths of 40 and 60 m on the shelf off the mouth of the Waiapu River on the east coast of New Zealand's North Island recorded data on waves, currents, and sediment fluxes from May 22 to August 10, 2004. Three major flood events and several wave events occurred during the deployment. Data from acoustic Doppler velocimeters and profilers revealed that downslope sediment fluxes accompanied a flood event of late June, during which near-bed downslope current speeds approached 0.5 m s -1. The most pronounced downslope transport within the benthic layer occurred the day after peak flood but coincided with strong isobath-parallel currents. Suspended sediment concentrations about 1 m above the bed were on the order of 2-4 g l -1 at times of maximum seaward flow. Suspension of freshly discharged sediment within the hyperpycnal layer over much of the profile was maintained by the high bed stresses associated with the strong benthic currents, in contrast to the wave-supported sediment gravity flows recently reported on other river-nourished shelf systems. Nonetheless, observed concentrations and velocities were largely consistent with the dynamics of critically stratified sediment gravity flows based on equations previously applied elsewhere to wave-supported cases. Despite lower concentrations in current-supported gravity currents, the greater thickness results in similar total loads. In further contrast to earlier results, our data suggest that as sediment off the Waiapu flowed into deeper water across the seaward steepening bottom profile, auto-suspension may have aided in thickening and accelerating the gravity current.

  3. Diffuse Deformation Across the Southern Mariana Margin: Possible Effects of Water on Large-Scale Lithospheric Rheology

    NASA Astrophysics Data System (ADS)

    Martinez, F.; Sleeper, J. D.

    2012-12-01

    The southern Mariana margin is extending in an approximately E-W direction at about 45 mm/yr above the subducting Pacific slab. We use earthquake locations, shallow- and new deep-towed side-scan sonar imagery together with compiled multibeam bathymetry to document the nature of the tectonic and volcanic deformation. A well-defined and magmatically robust spreading center takes up part of this extension along the northern part of the southern margin. However, it does not intersect the trench. Instead the spreading center curves westward and becomes a diffuse zone of volcanism extending to the western end of the back-arc basin. The approximately E-W oriented fabric of this diffuse volcanic zone suggest it is taking up a southerly-directed extensional component associated with southward trench rollback in this area. The main E-W oriented extension in the southern margin appears to be distributed broadly across the margin to the south, as indicated by ~N-S-oriented seafloor fabric and the distribution of earthquakes in this area. Near the outer margin, deep-towed side-scan sonar data to near the 6000 m isobath image possible isolated volcanic emplacements within an otherwise tectonized terrain. Possible ~E-W oriented mullion structures are also imaged suggesting low angle tectonic deformation within the margin. The transition of the organized spreading center to a diffuse volcano-tectonic zone and the broadly distributed deformation in the entire southern margin may be consequences of the high water content in the mantle wedge and overlying lithosphere predicted here. Hydrous and therefore weak subduction margin lithosphere may not be able to localize the narrow plate boundary zones characteristic of extension in oceanic lithosphere.

  4. Tropical atlantic water within the Benguela upwelling system at 27°S

    NASA Astrophysics Data System (ADS)

    Gordon, Arnold L.; Bosley, Kathryn T.; Aikman, Frank

    1995-01-01

    A CTD-O2 and ADCP section across the African Atlantic continental margin near 27°S, obtained during R.R.S. Discovery cruise 165B in May 1987, reveals the water mass structure and associated velocity field of the shelf and upper slope of the Benguela upwelling system. Continental shelf water upwelling within the Benguela Current is drawn from the 12°C (about 200 m) level. The upwelling water is drawn from oxygen depleted, tropical South Atlantic thermocline water that is advected along the shelf floor by a southward flowing subsurface current. Lower thermocline and intermediate water from the tropical South Atlantic are also observed flowing southward over the continental slope. Tropical Atlantic water generally resides north of the Angola-Benguela Front at 16°S. A narrow band of upwelled water is observed well seaward of the shelf, along the western edge of a large Agulhas eddy, indicating that Agulhas eddies play a role in stirring eastern boundary upwelled water into the ocean interior. These eddies also draw into the interior tropical Atlantic water found over the upper continental slope. The net transport between the 120 and 350 isobaths as measured by the ship-mounted ADCP, referenced to the sea floor, is 0.9 × 106 m3 s-1 1 to the south, with 1.6 × 106 m3 s-1 of southward flowing tropical Atlantic water and 0.7 × 106 m3 s-1 of northward flowing upwelled surface water. The tropical thermocline water mass advected to the south is not observed offshore within the northward flowing Benguela Current, in an unaltered state, thus the 0.9 × 106 m3 s-1 must feed shelf upwelling south of 27°S, implying a net offshore flux of upwelled water between Ld¨eritz (26°) and Cape Columbine (33°S).

  5. Prediction of the fate of p,p'-DDE in sediment on the Palos Verdes shelf, California, USA

    USGS Publications Warehouse

    Sherwood, C.R.; Drake, D.E.; Wiberg, P.L.; Wheatcroft, R.A.

    2002-01-01

    Long-term (60-yr) predictions of vertical profiles of p,p???-DDE concentrations in contaminated bottom sediments on the Palos Verdes shelf were calculated for three locations along the 60-m isobath using a numerical solution of the one-dimensional advection-diffusion equation. The calculations incorporated the following processes: sediment deposition (or erosion), depth-dependent solid-phase biodiffusive mixing, in situ diagenetic transformation, and loss of p,p???-DDE across the sediment-water interface by two mechanisms (resuspension of sediments by wave action and subsequent loss of p,p???-DDE to the water column by desorption, and desorption from sediments to porewater and subsequent molecular diffusion to the water column). A combination of field measurements, laboratory analyses, and calculations with supporting models was used to set parameters for the model. The model explains significant features observed in measurements made every 2 years from 1981 to 1997 by the County Sanitation Districts of Los Angeles (LACSD). Analyses of available data suggest that two sites northwest of the Whites Point sewage outfalls will remain depositional, even as particulate supply from the sewage-treatment plant and nearby Portuguese Bend Landslide decreases. At these sites, model predictions for 1991-2050 indicate that most of the existing inventory of p,p???-DDE will remain buried and that surface concentrations will gradually decrease. Analyses of data southeast of the outfalls suggest that erosion is likely to occur somewhere on the southeast edge of the existing effluent-affected deposit, and model predictions for such a site showed that erosion and biodiffusion will reintroduce the p,p???-DDE to the upper layer of sediments, with subsequent increases in surface concentrations and loss to the overlying water column.

  6. Stratification effects on the plankton of the subtropical Canary Current

    NASA Astrophysics Data System (ADS)

    Schmoker, Claire; Hernández-León, Santiago

    2013-12-01

    The Canary Current has experienced a progressive warming and a decrease in productivity over the last decades. In order to study the effect of stratification in these waters, we conducted a weekly sampling at one station (28°04‧N 15°21‧E) located ∼3 nmi offshore in the 100 m isobath, at the edge of the island shelf of Gran Canaria Island (Canary Islands). The sampling was performed over two and a half years, from January 2005 to June 2007, covering the most productive season in subtropical waters, the so-called late winter bloom, three times. The variables measured were temperature, chlorophyll a (Chl a), heterotrophic and autotrophic prokaryotes, pico-, nano-, micro- and mesozooplankton biomass. During 2005, the mixing of the water column started in January, while in 2007 the mixing period was delayed one month. Between years, temperature showed an increase of 0.5 °C, and Chl a decreased to half of the initial concentration (from ∼0.50 to ∼0.25 mg Chl a m-3). Autotrophic picoplankton and heterotrophic prokaryotes decreased between 2005 and 2007. However, neither nanoflagellates nor microplankton showed this decrease. The mesozooplankton biomass outburst lasted for three months in 2005, two in 2006, and only one month in 2007. Contrary to previously hypothesized size relationships, we did not observe an increase in the contribution of autotrophic picoplankton to total phytoplankton during periods of higher stability of the water column, but the opposite. We explain this surprising finding by possible top-down effects and by the success of motile morphotypes of algae (i.e., small dinoflagellates) under stable, nutrient-limited, conditions. Overall, the results suggest that small inter-annual differences in temperature, resulting in a tendency towards more stratified waters, give rise to important changes in the structure of the pelagic ecosystem in subtropical waters through a combination of bottom-up and top-down effects.

  7. Estimation of extreme marine hydrodynamic variables in western Laizhou Bay

    NASA Astrophysics Data System (ADS)

    Dai, Yanchen; Qiao, Lulu; Xu, Jishang; Zhou, Chunyan; Ding, Dong; Bi, Wei

    2015-06-01

    Laizhou Bay and its adjacent waters are of great importance to China's marine oil and gas development. It is therefore crucial to estimate return-period values of marine environmental variables in this region to ensure the safety and success of maritime engineering and maritime exploration. In this study, we used numerical simulations to estimate extreme wave height, sea current velocity and sea-level height in western Laizhou Bay. The results show that the sea-level rise starts at the mouth of the bay, increases toward west/southwest, and reaches its maximum in the deepest basin of the bay. The 100-year return-period values of sea level rise can reach 3.4-4.0 m in the western bay. The elevation of the western part of the Qingdong Oil Field would remain above the sea surface during extreme low sea level, while the rest of the oil field would be 1.6-2.4 m below the sea surface. The return-period value of wave height is strongly affected by water depth; in fact, its spatial distribution is similar to the isobath's. The 100-year return-period values of effective wave height can be 6 m or higher in the central bay and be more than 1 m in the shallow water near shore. The 100-year return-period values of current velocity is about 1.2-1.8 m s-1 in the Qingdong Oil Field. These results provide scientific basis for ensuring construction safety and reducing construction cost.

  8. Deep current measurements at 38°N east of Japan

    NASA Astrophysics Data System (ADS)

    Fujio, Shinzou; Yanagimoto, Daigo

    2005-02-01

    Deep currents east of Japan were investigated using direct current measurements and hydrographic observations. Current data, recorded for 9 months along 38°N, showed a pair of currents, one southward and the other northward, flowing along local isobaths above the western and eastern flanks. respectively, of the Japan Trench. Geostrophic velocities calculated from conductivity-temperature-depth (CTD) data showed a similar velocity pattern to the current measurements. The transports referring to the mean current velocities were estimated. Below 2000 m, the deep transports above the trench were southward 5.5 Sv and northward 13.5 Sv, and the boundary was at the deepest point of the trench. The mean current measured above the abyssal plain to the east of the trench was westward at 38°N. Since the bottom water properties above the eastern flank of the trench were colder and more saline than those on the abyssal plain, the westward current does not enter the trench but rather is expected to turn northward just east of the trench. Its northward transport was estimated to be 6.2 Sv, and the total northward transport was estimated to be 19.7 Sv at 38°N. A pair of oppositely flowing deep currents is confirmed in the Japan Trench. While the transports were similar to those of the Izu-Ogasawara and Kuril-Kamchatka trenches, whose ends connect with the Japan Trench, the current structure resembles that at the Izu-Ogasawara Trench rather than that at the Kuril-Kamchatka Trench.

  9. Vertical and horizontal particle transport in the coastal waters of a large lake: An assessment by sediment trap and thorium-234 measurements

    NASA Astrophysics Data System (ADS)

    Waples, James T.; Klump, J. Val

    2013-10-01

    The horizontal and vertical flux of particulate material in the nearshore of southern Lake Michigan (0-40 m) was estimated with the naturally occurring radionuclide 234Th. Horizontal fluxes of 234Th supplemented apparent vertical fluxes of 234Th in the water column (based on local 234Th/238U disequilibria) by a factor of 7-14, reinforcing the importance of lateral transport in coastal environments. Calculated onshore transport of particulate material across the 40 m isobath was as high as 1.1 × 106 kg km-1 d-1, and exceeds estimates of terrigenous (riverine and bluff erosion) loading. Estimates of onshore flux of organic carbon exceeded areal primary productivity by as much as ˜300%, and should be considered in nearshore carbon budgets. Bottom-tethered sediment traps (placed 5 m above the bottom) measured sedimentation rates that were ˜1 order of magnitude lower than 234Th derived mass fluxes from the water column and ˜2 orders of magnitude lower than 234Th derived mass fluxes to the lakebed. We ascribe this difference to under collecting by the sediment trap either because of trap hydrodynamics or flux occurring below the trap capture plane. Cross-shore fluxes showed a periodicity of ˜4 days and correlated strongly with a topographic vorticity wave that is present throughout the year in southern Lake Michigan. The impact of this wave (as a driver of bidirectional cross-shore flux) on biogeochemical cycling and both nearshore and offshore food webs has not yet been explicitly considered.

  10. Subsea Permafrost Mapped Across the U.S. Beaufort Sea Using Multichannel Seismic Data

    NASA Astrophysics Data System (ADS)

    Brothers, L.; Hart, P. E.; Ruppel, C. D.

    2011-12-01

    Circum-Arctic continental shelves at water depths less than ~100 m were subaerial permafrost prior to the onset of sea-level rise starting in the late Pleistocene. Rapid transgression and the resulting temperature increase at the sediment surface have led to thawing of the inundated permafrost, landward retreat of the leading edge of the permafrost, and dissociation of permafrost-associated gas hydrates. Past numerical modeling has shown that gas hydrate dissociation is particularly pronounced at the permafrost-to-no permafrost transition offshore. On the U.S. Beaufort margin, subsea permafrost has never been systematically mapped, and the best insights about permafrost and associated gas hydrate have been based on a limited number of offshore boreholes and numerical studies, with sometimes contrasting predictions of the permafrost's seaward extent. We bring together 5370 km of multichannel seismic (MCS) data acquired during various proprietary exploration industry and public domain government surveys between 1977 and 1992 to map a velocity anomaly diagnostic of submerged permafrost along 500 km of the US Beaufort coastline. These high-velocity (>~2.8 km/s) refractions (HVR), which are evident in prestack MCS shot records, reveal laterally continuous layers of shallow, ice-bonded, coarse-grained sediments beneath the inner continental shelf. The HVR occur in less than 5% of the tracklines, and calculated HVR depths range from 60 to 350 m below seafloor. The velocity anomaly is not observed seaward of the 20 m isobath, and is only found within 30 km of the current shoreline. These results can be used to: 1) create a map of the minimum distribution of remaining US Beaufort shelf subsea permafrost; 2) reconcile discrepancies between model-predicted and borehole-verified offshore permafrost distribution; and 3) constrain where to expect hydrate dissociation.

  11. Tectonic context of fluid venting at the toe of the eastern Nankai accretionary prism: Evidence for a shallow detachment fault

    NASA Astrophysics Data System (ADS)

    Chamot-Rooke, N.; Lallemant, S. J.; Le Pichon, X.; Henry, P.; Sibuet, M.; Boulègue, J.; Foucher, J.-P.; Furuta, T.; Gamo, T.; Glaçon, G.; Kobayashi, K.; Kuramoto, S.; Ogawa, Y.; Schultheiss, P.; Segawa, J.; Takeuchi, A.; Tarits, P.; Tokuyama, H.

    1992-04-01

    During the Kaiko-Nankai diving cruise the peak of the venting activity was located near the top of the very first anticline. The most prominent morphological feature between the mid-slope (3870 m) and the apex of the fold (3770 m) is a 20 m high cliff cutting through subhorizontal massive mudstones affected by numerous joints. The trend of this scarp is oblique to the fold axis and structurally controlled along two sharply defined NNE-SSE and E-W directions. Fresh talus and blocks found locally suggest active tectonics and recent erosion. Intense deformation is evident from strongly tilted strata restricted to the base of the cliff that we interpret as an upslope thrust. At the scale of Seabeam mapping, this thrust can be followed eastward for more than 5 km along the 3820 m isobath. Two seismic lines recorded during one of the pre-site surveys show deformation at shallow depth, including small-scale folding and thrusting affecting only the wedge-shaped top sequence. Deeper layers can be traced continuously below this sequence. We conclude that the boundary between the "piggy-back" basin and the frontal fold turbidites acts as a shallow detachment fault, and interpret the base of the cliff as the outcrop of the fault. Dense colonies ofCalyptogena clams and strongly nonlinear thermal gradients locate the major peak of fluid activity at the edge of the plateau above the main cliff. Scattered biological colonies as well as white bacterial mats and cemented chimneys were also found in a narrow belt along the base of the cliff. Fluid activity is thus closely related to the shallow detachment fault, fluid being expelled both at the outcrop of the fault and above it through the overlying strata, possibly using the very dense joint network.

  12. Mediterranean subsurface circulation estimated from Argo data in 2003-2009

    NASA Astrophysics Data System (ADS)

    Menna, M.; Poulain, P. M.

    2009-11-01

    Data from 38 Argo profiling floats are used to describe the subsurface Mediterranean currents for the period 2003-2009. These floats were programmed to execute 5-day cycles, to drift at a neutral parking depth of 350 m and measure temperature and salinity profiles from either 700 or 2000 m up to the surface. At the end of each cycle the floats remained at the sea surface for about 6 h, enough time to be localised and transmit the data to the Argos satellite system. The Argos positions were used to determine the float surface and subsurface displacements. At the surface, the float motion was approximated by a linear displacement and inertial motion. Subsurface velocities estimates were used to investigate the Mediterranean circulation at 350 m, to compute the pseudo-Eulerian statistics and to study the influence of bathymetry on the subsurface currents. Maximum speeds, as large as 33 cm/s, were found northeast of the Balearic Islands (Western basin) and in the Ierapetra eddy (Eastern basin). Typical speeds in the main along-slope currents (Liguro-Provençal-Catalan, Algerian and Libyo-Egyptian Currents) were ~20 cm/s. In the best sampled regions, the pseudo-Eulerian statistics show typical subsurface circulation pathways which can be related to the motion of Levantine Intermediate Water. In general our results agree with the qualitative subsurface circulation schemes proposed in the literature, except in the southern Ionian where we found westward-flowing subsurface currents. Fluctuating currents appeared to be usually larger than the mean flow. Subsurface currents were found to be essentially parallel to the isobaths over most of the areas characterized by strong bathymetry gradients, in particular, in the vicinity of the continental slopes.

  13. Mediterranean intermediate circulation estimated from Argo data in 2003-2010

    NASA Astrophysics Data System (ADS)

    Menna, M.; Poulain, P. M.

    2010-03-01

    Data from 38 Argo profiling floats are used to describe the intermediate Mediterranean currents for the period October 2003-January 2010. These floats were programmed to execute 5-day cycles, to drift at a neutral parking depth of 350 m and measure temperature and salinity profiles from either 700 or 2000 m up to the surface. At the end of each cycle the floats remained at the sea surface for about 6 h, enough time to be localised and transmit the data to the Argos satellite system. The Argos positions were used to determine the float surface and intermediate displacements. At the surface, the float motion was approximated by a linear displacement and inertial motion. Intermediate velocities estimates were used to investigate the Mediterranean circulation at 350 m, to compute the pseudo-Eulerian statistics and to study the influence of bathymetry on the intermediate currents. Maximum speeds, as large as 33 cm/s, were found northeast of the Balearic Islands (western basin) and in the Ierapetra eddy (eastern basin). Typical speeds in the main along-slope currents (Liguro-Provençal-Catalan, Algerian and Libyo-Egyptian Currents) were ~20 cm/s. In the central and western part of Mediterranean basin, the pseudo-Eulerian statistics show typical intermediate circulation pathways which can be related to the motion of Levantine Intermediate Water. In general our results agree with the qualitative intermediate circulation schemes proposed in the literature, except in the southern Ionian where we found westward-flowing intermediate currents. Fluctuating currents appeared to be usually larger than the mean flow. Intermediate currents were found to be essentially parallel to the isobaths over most of the areas characterized by strong bathymetry gradients, in particular, in the vicinity of the continental slopes.

  14. Formation and variability of the Lofoten basin vortex in a high-resolution ocean model

    NASA Astrophysics Data System (ADS)

    Volkov, Denis L.; Kubryakov, Arseny A.; Lumpkin, Rick

    2015-11-01

    The Lofoten Basin of the Norwegian Sea is characterized by a local maximum of eddy kinetic energy and it is an important transit region for the warm and saline Atlantic waters on their way towards the Arctic Ocean. Eddies are generated by the Norwegian Atlantic Current and propagate anticlockwise around the center of the basin. In situ and satellite observations have discovered a rather small (with a radius of a few tens of km), but strong quasi-permanent anticyclonic vortex that resides in the center of the Lofoten Basin near 3°E, 69.8°N. The objective of this paper is to understand how and why the vortex is formed and to investigate what processes support its stability and drive its variability. To achieve this objective, we have conducted three high-resolution numerical experiments with the mean horizontal grid spacing of 18 km, 9 km, and 4 km. The Lofoten Vortex did not form in the 18-km experiment. The most realistic (compared to available observations) simulation of the vortex is provided by the 4-km experiment, which better reproduces eddy variability in the region. The experiments thus provide experimental evidence of the importance of eddies in the formation and stability of the vortex. We demonstrate how anticyclonic eddies, that are usually stronger and more numerous in the basin than cyclonic eddies, contribute to the intensification of the Lofoten Vortex. The Lofoten Vortex itself is not stationary and drifts cyclonically within the area bounded by approximately the 3250 m isobath. The analysis of the barotropic vorticity budget in the 4-km experiment shows that the advection of the relative vorticity gradient by eddies is the main mechanism that drives the variability of the Lofoten Vortex. The direct impact of wind/buoyancy forcing is found to be small to negligible.

  15. Environmental Variability, Bowhead Whale Distributions, and Inupiat Subsistence Whaling in the Coastal Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Ashjian, C. J.; Campbell, R. G.; George, J. C.; Moore, S. E.; Okkonen, S. R.; Sherr, B. F.; Sherr, E. B.

    2006-12-01

    The annual migration of bowhead whales (Balaena mysticetus) past Barrow, Alaska has provided subsistence hunting opportunities to Native whalers for centuries. Bowheads regularly feed along the Arctic coast near Barrow in autumn, presumably to utilize recurrent aggregations of their zooplankton prey (e.g., copepods, euphausiids). Oceanographic field-sampling on the narrow continental shelf near Barrow and in Elson Lagoon was conducted during mid-August to mid-September of 2005 and 2006 to describe the different water mass types and plankton communities, to identify exchange of water and material between the shelf and lagoon and offshore, and to identify biological and physical mechanisms of plankton aggregation. High spatial resolution profiles of temperature, salinity, fluorescence, optical backscatter, and C-DOM were collected using an Acrobat undulating towed vehicle in the lagoon and across the shelf from near-shore to the ~150 m isobath. Discrete sampling for nutrients, chlorophyll a, and phytoplankton, and microzooplankton and mesozooplankton abundance and composition was conducted in distinct water types and across frontal boundaries identified from the high-resolution data. The distributions of bowhead whales were documented using aerial surveys. Inter-annual and shorter-term (days to weeks) variability in the distribution of water masses and intrinsic biological properties was observed. Distinct hydrographic and biological-chemical regions were located across the shelf that may contribute to the formation of bowhead whale prey aggregations. The lagoon system is an important interface between the ocean and land and may be critical to the formation of nearshore bowhead whale prey aggregations. Results from the field sampling will be coupled to biological-physical modeling and retrospective analyses to understand the response of this complex environment-whale-human system to climate variability.

  16. Radiation stress gradients across the surf zone for hurricane wave forcing: theory and observations

    NASA Astrophysics Data System (ADS)

    Mulligan, R. P.; Bowen, A. J.; Hanson, J. L.; Hathaway, K. K.

    2012-12-01

    Wave breaking is a non-linear, turbulent and chaotic phenomenon that is the overwhelmingly dominant physical process acting along beaches and coasts exposed to surface waves during storms. The breaking process causes large rates of wave energy dissipation over short distances and the momentum that is exchanged with the mean flow is the dominant forcing for currents and water level changes across nearshore region. Inside the surf zone, this can outweigh other flow forcing mechanisms such as winds and tides by several orders of magnitude. We examine Eulerian observations from six sensor sites the USACE FRF cross-shore array for several large hurricane wave events with wide surf zones, to elucidate the nearshore balance of momentum under storm conditions. Under such strong wave forcing, observations of longshore currents up to 2 m/s and mean cross-shore flows up to 0.3 m/s near the 5 m isobath are presented for wave events that impacted the U.S. Atlantic coast in 2009-2011 including Hurricanes Bill, Earl and Irene. An investigation of the mass flux and momentum terms across the surf zone indicates that the radiation stress gradient in the cross-shore direction can exceed the momentum that can be balanced by the pressure gradient and results in significant bottom stress term and thus an offshore directed cross-shore flow. The mean cross-shore flow contributes to advection of alongshore momentum and although small when integrated across the whole surf zone, is locally important especially near the outer edge of the surf zone.

  17. Hydrographic Conditions At The Carbonate Mound Locations In The NE Atlantic

    NASA Astrophysics Data System (ADS)

    van Weering, T.; de Hass, H.; White, M.; de Stigter, H.

    As part of the component 5th framework projects that form part of the OMARC clus- ter, hydrographic measurements have been made in the region of the deep water car- bonate mounds provinces of the NE Atlantic. These mounds are located at depths 600-1000m depth along the continental slopes of the Porcupine Sea Bight and Bank and the SE Rockall Bank. These regions correspond to the vertical and horizontal boundaries of the intermediate water masses that occupy the region, providing differ- ent hydrographic regimes between mound locations,. In addition there is a large vari- ability in temperature/salinity conditions and both characteristics have implications for the distribution of mound fauna. The deep water coral associated with carbonate mound structures coincide with strong benthic current activity and this is confirmed from benthic current measurements from landers and current meters at the SE Rockall and NW Porcupine Bank mound loca- tions. Near seabed currents are strong, with a typical mean speed of 20cm/s and a max- imum in excess of 50cm/s. At the SE Rockall Bank site, a mean SW along isobath flow is measured, whilst at the NW Porcupine mound location, a poleward slope current is measured. Bottom Ekman dynamics is apparent with a changes in near seabed verti- cal stratification related to changes to overlying slope current strength. Strong diurnal variability is found at the Rockall Bank site, providing strong cross-slope currents. The diurnal current forcing over both the Rockall and Porcupine Banks may result in enclosed circulation patterns over the banks and retention of organic material supplied to the mounds. In contrast, currents at the Hovland and Magellan mound sites in the northern Porcupine Sea Bight, where there are numerous buried mounds, are relatively low.

  18. Fault mirrors along carbonate faults: Formation and destruction during shear experiments

    NASA Astrophysics Data System (ADS)

    Siman-Tov, Shalev; Aharonov, Einat; Boneh, Yuval; Reches, Ze'ev

    2015-11-01

    Glossy, light reflective surfaces are commonly exposed in carbonate fault-zones. It was suggested that such surfaces, recently termed Fault Mirrors (FMs), form during seismic slip. Ultramicroscopic analyses indicate that FMs are highly smooth and composed of a cohesive thin layer of nano-size grains. We explore here mechanisms of formation and destruction of FMs by shear experiments that were conducted on three types of limestone which were sheared at wide range of slip-velocities of v = 0.001- 0.63 m /s, and normal stress up to 1.57 MPa. The experiments showed that FMs started to develop as local patches when the slip velocity exceeded a critical value of 0.07 m/s. The area coverage by FM patches increases systematically with increasing velocity, reaching in a few cases ∼100% coverage. The measured quasi-steady-state friction coefficient, μss, was inversely correlated with the FM coverage: μss ∼ 0.8 for no-FM, at v < 0.07 m /s, and μss ∼ 0.4 for 50% FM coverage at v ∼ 0.6 m /s. Further, in a series of slip-velocity alternation between low and high values, the FMs which formed at a high-velocity stage were destroyed during a subsequent low-velocity stage. Our analyses of the experimental thermal conditions and ultramicroscopy imaging of the FMs suggest that the FMs form by sintering of gouge nanograins during shear. We propose that formation/destruction of FMs in high/low slip-velocity reflects a competition between brittle and ductile processes: FMs form in a ductile mode, and are destroyed by brittle wear. Shear heating during high velocity leads to ductile deformation and sintering so that FM construction rate exceeds brittle FM destruction rate. Based on our results, we suggest that, at least for shallow faults, the presence of extensive FM coverage along natural carbonate faults indicates that the fault segment slipped at seismic velocities and experienced dynamic weakening.

  19. Passive treatment of acid mine drainage in down-flow limestone systems

    SciTech Connect

    Watzlaf, G.R.

    1997-12-31

    Passive down-flow systems, consisting of compost and/or limestone layers, may be well suited for treatment of acidic mine drainage containing ferric iron and/or aluminum. Two columns were constructed and operated in the laboratory. The first column simulated a downward, vertical-flow anaerobic wetland, also referred to as successive alkalinity-producing systems (SAPS), and has received mine drainage for 97 weeks. The 0.16-m diameter column was vertically oriented and (from bottom to top) consisted of a 0.30-m thick layer of limestone, a 0.76-m thick layer of spent mushroom compost, and 0.91 m of free standing water. Water flowed vertically downward through the system. A second column, filled with only limestone, received water from the same source as the first column. This limestone column contained a 1.06-m thick layer of limestone and 0.91 m of free standing water and has received water for 55 weeks. Actual acid mine drainage (pH = 3.1, acidity = 200 mg/L (as CaCO{sub 3}), SO{sub 4}{sup 2-} = 600 mg/L, Total Fe = 10 mg/L, Mn = 14 mg/L, and Al = 18 mg/L) was collected every two weeks from a nearby abandoned deep mine and applied to these columns at a rate of 3.8 mL/min. For the compost/limestone column, effluent pH remained above 6.2 (6.2-7.9); however, pH at a depth of 0.38 m in the compost (halfway) dropped to < 4 after 28 weeks (net acidic). At the bottom of the compost pH remained > 4.5 for all 97 weeks. Alkalinity was generated by a combination of limestone dissolution and sulfate reduction. Over the 97 week period, the column generated an average of 330 mg/L of alkalinity, mostly due to limestone dissolution. Bacterial sulfate reduction displayed an ever decreasing trend, initially accounting for more than 200 mg/L of alkalinity and after 40 weeks only accounting for about 50 mg/L.

  20. An operational global ocean forecast system and its applications

    NASA Astrophysics Data System (ADS)

    Mehra, A.; Tolman, H. L.; Rivin, I.; Rajan, B.; Spindler, T.; Garraffo, Z. D.; Kim, H.

    2012-12-01

    A global Real-Time Ocean Forecast System (RTOFS) was implemented in operations at NCEP/NWS/NOAA on 10/25/2011. This system is based on an eddy resolving 1/12 degree global HYCOM (HYbrid Coordinates Ocean Model) and is part of a larger national backbone capability of ocean modeling at NWS in strong partnership with US Navy. The forecast system is run once a day and produces a 6 day long forecast using the daily initialization fields produced at NAVOCEANO using NCODA (Navy Coupled Ocean Data Assimilation), a 3D multi-variate data assimilation methodology. As configured within RTOFS, HYCOM has a horizontal equatorial resolution of 0.08 degrees or ~9 km. The HYCOM grid is on a Mercator projection from 78.64 S to 47 N and north of this it employs an Arctic dipole patch where the poles are shifted over land to avoid a singularity at the North Pole. This gives a mid-latitude (polar) horizontal resolution of approximately 7 km (3.5 km). The coastline is fixed at 10 m isobath with open Bering Straits. This version employs 32 hybrid vertical coordinate surfaces with potential density referenced to 2000 m. Vertical coordinates can be isopycnals, often best for resolving deep water masses, levels of equal pressure (fixed depths), best for the well mixed unstratified upper ocean and sigma-levels (terrain-following), often the best choice in shallow water. The dynamic ocean model is coupled to a thermodynamic energy loan ice model and uses a non-slab mixed layer formulation. The forecast system is forced with 3-hourly momentum, radiation and precipitation fluxes from the operational Global Forecast System (GFS) fields. Results include global sea surface height and three dimensional fields of temperature, salinity, density and velocity fields used for validation and evaluation against available observations. Several downstream applications of this forecast system will also be discussed which include search and rescue operations at US Coast Guard, navigation safety information

  1. Environmental geology of Harrison Bay, northern Alaska

    USGS Publications Warehouse

    Craig, J.D.; Thrasher, G.P.

    1982-01-01

    The surficial and shallow subsurface geology of Harrison Bay on the Beaufort Sea coast was mapped as part of the U.S. Geological Survey's prelease evaluation for Outer Continental Shelf (OCS) Oil and Gas Lease Sale 71. During the 1980 summer season, approximately 1600 km of multisensored, high-resolution geophysical profile data were collected along a rectangular grid with 4.8 km line spacing. Interpretation of these data is presented on five maps showing bathymetry, sea-floor microrelief, ice-gouge characteristics, Holocene sediment thickness, and geologic structure to depths of approximately 1000 m. On a broad scale, the seafloor is shallow and almost flat, although microrelief features produced by sediment transport and ice-gouge processes typically vary up to several meters in amplitude. Microrelief bedforms related to hydraulic processes are predominant in water depths less than 12 m. Microrelief caused by ice gouging generally increases with water depth, reaching a maximum of 2 m or more in water depths beyond the 20 m isobath. This intensely gouged area lies beneath the shear zone between the seasonal landfast ice and the mobile polar ice pack. The thickness of recent (Holocene) sediment increases offshore, from 2 m near the Colville River delta to 30 m or more on the outer shelf. The thin Holocene layer is underlain by a complex horizon interpreted to be the upper surface of a Pleistocene deposit similar in composition to the present Arctic Coastal Plain. The base of the inferred Pleistocene section is interpreted to be a low-angle unconformity 100 m below sea level. Beneath this Tertiary-Quaternary unconformity, strata are interpreted to be alluvial fan-delta plain deposits corresponding to the Colville Group and younger formations of Late Cretaceous to Tertiary age. Numerous high-angle faults downthrown to the north trend across the survey area. With few exceptions, these faults terminate at or below the 100 m unconformity, suggesting that most tectonism

  2. Tidal forcing, energetics, and mixing near the Yermak Plateau

    NASA Astrophysics Data System (ADS)

    Fer, I.; Müller, M.; Peterson, A. K.

    2015-03-01

    The Yermak Plateau (YP), located northwest of Svalbard in Fram Strait, is the final passage for the inflow of warm Atlantic Water into the Arctic Ocean. The region is characterized by the largest barotropic tidal velocities in the Arctic Ocean. Internal response to the tidal flow over this topographic feature locally contributes to mixing that removes heat from the Atlantic Water. Here, we investigate the tidal forcing, barotropic-to-baroclinic energy conversion rates, and dissipation rates in the region using observations of oceanic currents, hydrography, and microstructure collected on the southern flanks of the plateau in summer 2007, together with results from a global high-resolution ocean circulation and tide model simulation. The energetics (depth-integrated conversion rates, baroclinic energy fluxes and dissipation rates) show large spatial variability over the plateau and are dominated by the luni-solar diurnal (K1) and the principal lunar semidiurnal (M2) constituents. The volume-integrated conversion rate over the region enclosing the topographic feature is approximately 1 GW and accounts for about 50% of the M2 and approximately all of the K1 conversion in a larger domain covering the entire Fram Strait extended to the North Pole. Despite the substantial energy conversion, internal tides are trapped along the topography, implying large local dissipation rates. An approximate local conversion-dissipation balance is found over shallows and also in the deep part of the sloping flanks. The baroclinic energy radiated away from the upper slope is dissipated over the deeper isobaths. From the microstructure observations, we inferred lower and upper bounds on the total dissipation rate of about 0.5 and 1.1 GW, respectively, where about 0.4-0.6 GW can be attributed to the contribution of hot spots of energetic turbulence. The domain-integrated dissipation from the model is close to the upper bound of the observed dissipation, and implies that almost the entire

  3. The Angola Current and its seasonal variability as observed at 11°S

    NASA Astrophysics Data System (ADS)

    Kopte, Robert; Brandt, Peter; Dengler, Marcus; Claus, Martin; Greatbatch, Richard J.

    2016-04-01

    The eastern boundary circulation off the coast of Angola has been described only sparsely to date. The region off Angola, which connects the equatorial Atlantic and the Angola-Benguela upwelling regime, is of particular interest to understand the relative importance of transient equatorial versus local forcing of the observed variability in the coastal upwelling region. For the first time multi-year velocity observations of the Angola Current at 11°S are available. From July 2013 to November 2015 a bottom shield equipped with an ADCP had been deployed at 500m water depth, accompanied by a mooring sitting on the 1200m-isobath with an ADCP being installed at 500m depth. Both upward-looking instruments measured the current speed up to about 50m below the sea surface. During the deployment period the Angola Current was characterized by a weak southward mean flow of 5-8 cm/s at 50m depth (slightly stronger at the in-shore mooring position), with the southward current penetrating down to about 200m depth. The alongshore velocity component reveals a pronounced seasonal variability. It is dominated by 120-day, semi-annual, and annual oscillations with distinct baroclinic structures. Here we apply a reduced gravity model of the tropical Atlantic for the first five baroclinic modes forced with interannually varying wind stress to investigate the seasonal variability along the equatorial and coastal waveguides. In the equatorial Atlantic the 120-day, semi-annual, and annual oscillations are associated with resonant basin modes of the 1st, 2nd, and 4th baroclinic mode, respectively. These basin modes are composed of equatorial Kelvin and Rossby waves as well as coastally trapped waves. The reduced gravity model is further used to study the respective role of the remote equatorial forcing, more specifically the influence of equatorial basin modes via coastally trapped waves, and the local forcing for the observed seasonal variability and associated baroclinic structure of the

  4. Observations of second baroclinic mode internal solitary waves on the continental slope of the northern South China Sea

    NASA Astrophysics Data System (ADS)

    Yang, Yiing Jang; Fang, Ying Chih; Chang, Ming-Huei; Ramp, Steven R.; Kao, Chih-Chung; Tang, Tswen Yung

    2009-10-01

    A temperature and current velocity mooring, located on the upper continental slope of the northern South China Sea, recorded a number of second baroclinic mode (mode 2) internal solitary waves (ISWs). These types of waves are seldom observed in nature. The mode 2 ISWs typically showed upward (downward) displacement of isotherms in the upper (lower) water column and three layers of eastward, westward, and eastward current from the uppermost to bottommost portions of a wave. In summer, westward-propagating mode 2 ISWs were observed only occasionally. These waves generally appeared after mode 1 ISWs, a feature that may relate to the diurnal tide with a period of approximately 24 hours. The displacement of isotherms induced by mode 2 ISWs was 20 ± 14 m at 75 m and -22 ± 15 m at 240 m, and the characteristic time scale was approximately 8.0 ± 4.3 min. In winter, mode 2 ISWs were more active but mode 1 ISWs were rarely observed. Isotherm displacement by mode 2 ISWs in winter was 30 ± 18 m at 75 m and -26 ± 16 m at 240 m, and the average characteristic time scale was 6.9 ± 4.6 min. The mode 2 ISWs thus had larger amplitudes and smaller time scales in winter than they did in summer. The observed vertical temperature profile also showed notable seasonal change. The thermocline was shallow in summer and deep in winter. In winter, vertical temperature profiles indicated that the main thermocline was located near middepth over the upper continental slope near the 350 m isobath. Mode 1 ISWs were more active in summer than in winter, reflecting the larger Ursell numbers for mode 1 ISWs in summer. Among mode 2 ISWs in summer, 90% appeared after mode 1 ISWs. These results suggest that mode 2 ISWs could be related to mode 1 ISWs. In contrast, mode 2 ISWs were more active in winter than in summer, with larger mode 2 Ursell numbers also found in winter. Among winter mode 2 ISWs, 72% appeared without mode 1 ISWs. Mode 2 ISWs in winter could be related to the main thermocline

  5. In situ acoustic and laboratory ultrasonic sound speed and attenuation measured in heterogeneous soft seabed sediments: Eel River shelf, California

    USGS Publications Warehouse

    Gorgas, T.J.; Wilkens, R.H.; Fu, S.S.; Neil, Frazer L.; Richardson, M.D.; Briggs, K.B.; Lee, H.

    2002-01-01

    We compared in situ and laboratory velocity and attenuation values measured in seafloor sediments from the shallow water delta of the Eel River, California. This region receives a substantial volume of fluvial sediment that is discharged annually onto the shelf. Additionally, a high input of fluvial sediments during storms generates flood deposits that are characterized by thin beds of variable grain-sizes between the 40- and 90-m isobaths. The main objectives of this study were (1) to investigate signatures of seafloor processes on geoacoustic and physical properties, and (2) to evaluate differences between geoacoustic parameters measured in situ at acoustic (7.5 kHz) and in the laboratory at ultrasonic (400 kHz) frequencies. The in situ acoustic measurements were conducted between 60 and 100 m of water depth. Wet-bulk density and porosity profiles were obtained to 1.15 m below seafloor (m bsf) using gravity cores of the mostly cohesive fine-grained sediments across- and along-shelf. Physical and geoacoustic properties from six selected sites obtained on the Eel margin revealed the following. (1) Sound speed and wet-bulk density strongly correlated in most cases. (2) Sediment compaction with depth generally led to increased sound speed and density, while porosity and in situ attenuation values decreased. (3) Sound speed was higher in coarser- than in finer-grained sediments, on a maximum average by 80 m s-1. (4) In coarse-grained sediments sound speed was higher in the laboratory (1560 m s-1) than in situ (1520 m s-1). In contrast, average ultrasonic and in situ sound speed in fine-grained sediments showed only little differences (both approximately 1480 m s-1). (5) Greater attenuation was commonly measured in the laboratory (0.4 and 0.8 dB m-1 kHz-1) than in situ (0.02 and 0.65 dB m-1 kHz-1), and remained almost constant below 0.4 m bsf. We attributed discrepancies between laboratory ultrasonic and in situ acoustic measurements to a frequency dependence of

  6. Tidally-driven exchange at the European shelf break

    NASA Astrophysics Data System (ADS)

    Spingys, Carl; Williams, Ric; Hopkins, Jo; Green, Mattias; Sharples, Jonathan

    2015-04-01

    The exchange across the shelf break is restricted as the topographic slope limits the geostrophic flow to following isobaths, meaning the exchange between the open ocean and shelf seas is dependent on processes that break the assumptions in geostrophy, by for by not being in steady state. Using the thickness-weighted volume transport, usually invoked in the open ocean, we show that the covariance of thickness and velocity can drive a volume transport across the shelf break, usually referred to as the bolus transport. We propose that the internal tide drives a covariance resulting in a transport of both volume and tracers, analogous to the Stokes Drift. Whilst these transports are smaller than the mean velocity they can make a substantial contribution to the cross shelf component. Support for the theoretical framework is provided by a series of near shelf break moorings in the Celtic Sea and Malin Shelf deployed in the summers of 2012 and 2013 respectively, under the FASTNEt project. The thickness-weighted volume transports have been calculated for each of the moorings, including the bolus transport. The strength of this transport is strongly dependant on the strength of the internal tide, with the highly energetic Celtic Sea showing an on shelf bottom layer transport velocity of order 1 cm s-1, whereas the less energetic Malin Shelf shows a bottom layer transport velocity of order 0.01 - 0.1 cm s-1. These are comparable to the bolus velocities predicted by simple two layer linear internal wave theory. The mooring bolus transport also shows an M4 period, equivalent to the product of two M2 periods, reinforcing that the bolus transport is tidally-driven. These bottom layer transports can make a significant contribution to the lateral supply of nutrients required to support the enhanced productivity in shelf seas. Integrating the bottom layer transports from the moorings to the whole of the Celtic Sea shelf break gives a total volume transport of approximately 1 Sv or

  7. Current surges and seabed erosion near the shelf break in the Canadian Beaufort Sea: A response to wind and ice motion stress

    NASA Astrophysics Data System (ADS)

    Forest, Alexandre; Osborne, Philip D.; Curtiss, Gregory; Lowings, Malcolm G.

    2016-08-01

    Estimating the erosion potential of seabed sediments and the magnitude of the resulting suspended load in relation to current dynamics near the shelf break is a key issue for better understanding shelf-slope sediment transport. On the outer Mackenzie Shelf (Canadian Beaufort Sea, Arctic Ocean), a thin and discontinuous veneer of recent surficial clays overlie old glaciomarine sediments that further pinch out at the shelf edge. Gas and fluid venting is known to underlie part of sediment instability in the area, but recent mooring-based measurements also indicate that sediments near the shelf break are recurrently remobilized by strong subsurface currents. Here, we relate storms to the development of current surges that resulted in the abrupt resuspension of sediments at two locations along the shelf break. Near-bottom concentrations of suspended sediments were estimated using the acoustic backscatter of high-frequency acoustic Doppler current profilers deployed from September 2011 to September 2013 as part of the Beaufort Regional Environmental Assessment (BREA) program. Near-bottom currents near the shelf edge (140 to 150 m isobaths) were characterized by recurring episodes of elevated velocities (instantaneous speeds up to ~ 40-50 cm s-1) that were extensions of current surges (~ 60-80 cm s-1) occurring in the core of the shelfbreak jet located at ca. 90-120 m. Sudden peaks in suspended sediments (above 100 g m-3) corresponded closely with current surges in the near-bottom boundary layer (< 10 m) implying the local erosion of surficial sediments and the rapid advection or redeposition of the resuspended sediments. A range of apparent threshold velocities from 18 to 36 cm s-1 was calculated based on the relationship between suspended sediment concentrations and near-bottom current speeds. Two meteorological scenarios were identified to explain the current surges underlying these erosion events at the shelf edge: (1) Pacific or Arctic-born low pressure systems that

  8. Characteristic ichthyoplankton taxa in the separation zone of the East Australian Current: Larval assemblages as tracers of coastal mixing

    NASA Astrophysics Data System (ADS)

    Syahailatua, Augy; Roughan, Moninya; Suthers, Iain M.

    2011-03-01

    Ichthyoplankton assemblages were compared between regions dominated by the oligotrophic East Australian Current (EAC) and the inner-shelf waters off southeastern Australia, to determine if the early life history of fish was related to the separation of the EAC from the coast, producing different water masses as well as characteristic taxa. Samples were collected at the surface and in sub-surface waters, at 50 and 100 m isobath stations, during two summer research voyages in November 1998 and January 1999. On both voyages the study region was characterized by coastal and EAC waters in the north (˜31°S), and in the south by topographically induced upwelling (˜31°S), associated with narrowing of the continental shelf and separation of the EAC from the coast. Among the 111 families of larval fish, we observed distinctive assemblages of ichthyoplankton associated with the two different water masses. A greater abundance of the Carangidae, Labridae, Lutjanidae, Microcanthidae, Myctophidae and Scombridae was associated with the nutrient poor EAC water mass, while the Callionymidae, Clupeidae, Platycephalidae and Sillaginidae were mostly found in the cooler and/or fresher inner-shelf water mass. We assessed these patterns with opportunistic samples from an unusual, wind-driven upwelling event in the north (˜31°S) earlier in the November voyage. The relative abundance of these 10 characteristic families distinguished this wind-driven upwelling event from the subsequent relaxation and predominance of the EAC assemblage at this location just 6 d later. Distinctive and abundant families such as larval clupeids, relative to larval carangids, could be a useful marker of inner-shelf, EAC and mixed water masses in the absence of robust hydrographic data. This and related studies indicate contrast in early life histories of Sardinops sagax and Trachurus spp., which appear to spawn respectively in the inner-shelf and outer-shelf waters. The post-flexion stages of S. sagax

  9. Near-bottom temperature and salinity evolution around Iceland, 1975-2007

    NASA Astrophysics Data System (ADS)

    Jochumsen, Kerstin; Schnurr, Sarah; Quadfasel, Detlef

    2015-04-01

    The near-bottom water masses in the deep basins of the northern North Atlantic and the Nordic Seas hold major temperature differences due to the barrier formed by the Greenland-Scotland-Ridge (GSR). Deep water exchanges across the ridge are prohibited, and only limited water mass exchange in intermediate layers is possible through deep channels, where the flow is southwestward (the Nordic Overflows). The shallow surface layers exhibit warm and saline water flowing north-eastwards across most of the ridge, only at the western GSR (along the east Greenland coast) cold and fresh water is transported southwestward. Several studies have indicated that the GSR or the environmental conditions connected to the influence of the ridge system shape the species distribution and composition of particular benthic groups in this region. Species distribution models (SDMs), which use spatial environmental variables, can lead to a better understanding of species distributions within the marine environment. Additionally, these models provide an estimate of the response of the marine ecosystem and species distributions to climate change. Hence, spatial environmental variables, known to have an influence on the distribution of species (e.g. temperature, salinity, sediment type), are needed to create realistic SDMs. Here we use near-bottom measurements of about 88,000 CTD (conductivity-temperature-depth) and bottle profiles, collected in the period 1975-2007. The data is gridded into regular boxes of about 11 km size and interpolated following isobaths. We derive average spatial temperature and salinity distributions in the region around Iceland, showing the influence of the GSR on the near-bottom properties. The spatial distribution of standard deviation is used to compare local variability, which is enhanced near water mass fronts. These spatial property distributions can provide the basis for SDM modelling. Finally, property changes within the last 30 years are presented using time

  10. Late winter oceanography off the Sabrina and BANZARE coast (117-128°E), East Antarctica

    NASA Astrophysics Data System (ADS)

    Williams, G. D.; Meijers, A. J. S.; Poole, A.; Mathiot, P.; Tamura, T.; Klocker, A.

    2011-05-01

    We report on the late winter oceanography observed beneath the Antarctic sea ice offshore from the Sabrina and BANZARE coast of Wilkes Land, East Antarctica (117-128°E) in September-October 2007 during the Sea Ice Physics and Ecosystem eXperiment (SIPEX). A pilot program using specifically designed 'through-ice' conductivity-temperature-depth (CTD) and acoustic Doppler current profiling (ADCP) systems was conducted to opportunistically measure water mass properties and ocean currents at major ice stations. Additional water mass properties across the survey region were collected from Ice-Argo floats deployed during the voyage north of the 3000 m isobath. The mean drift of the floats was along the slope to the west with the Antarctic Slope Current. Vertical profiles of the potential temperature reveal the deepest (˜350-400m) winter mixed layer (WML) in the western sector of the survey northwest of the Dalton Iceberg Tongue polynya. The meridional structure of the Antarctic Slope Front, i.e. the monotonic shoaling of the WML across the upper continental slope, is found to be similar to the previous observations in summer. A strong bottom-intensified intrusion of modified Circumpolar Deep Water (mCDW) as warm as 0 °C was detected beneath the fast ice south of the continental shelf break at 118°E. An mCDW intrusion of similar strength was detected near this location in the austral summer of 1996. We hypothesise that there is a persistent supply of mCDW and associated ocean heat flux to this region of the continental shelf that is capable of migrating to the grounding lines of the nearby Totten Glacier and Moscow University Ice Shelf. There was no detection of locally formed dense shelf water capable of forming Antarctic Bottom Water at the shelf break locations sampled despite the number of minor polynyas across this region. Ocean current measurements, limited to a maximum period of 24 h and 50-100 m depth by the relative scarcity of backscatter, found increased

  11. Variability of the internal tide on the southern Monterey Bay continental shelf and associated bottom boundary layer sediment transport

    NASA Astrophysics Data System (ADS)

    Rosenberger, Kurt J.; Storlazzi, Curt D.; Cheriton, Olivia M.

    2016-06-01

    A 6-month deployment of instrumentation from April to October 2012 in 90 m water depth near the outer edge of the mid-shelf mud belt in southern Monterey Bay, California, reveals the importance regional upwelling on water column density structure, potentially accounting for the majority of the variability in internal tidal energy flux across the shelf. Observations consisted of time-series measurements of water-column currents, temperature and salinity, and near-bed currents and suspended matter. The internal tide accounted for 15-25% of the water-column current variance and the barotropic tide accounted for up to 35%. The subtidal flow showed remarkably little shear and was dominated by the 7-14 day band, which is associated with relaxations in the dominant equatorward winds typical of coastal California in the spring and summer. Upwelling and relaxation events resulted in strong near-bed flows and accounted for almost half of the current stress on the seafloor (not accounting for wave orbital velocities), and may have driven along-shelf geostrophic flow during steady state conditions. Several elevated suspended particulate matter (SPM) events occurred within 3 m of the bed and were generally associated with higher, long-period surface waves. However, these peaks in SPM did not coincide with the predicted resuspension events from the modeled combined wave-current shear stress, indicating that the observed SPM at our site was most likely resuspended elsewhere and advected along-isobath. Sediment flux was almost equal in magnitude in the alongshore and cross-shore directions. Instances of wave-current shear stress that exceeded the threshold of resuspension for the silty-clays common at these water depths only occurred when near-bed orbital velocities due to long-period surface waves coincided with vigorous near-bed currents associated with the internal tide or upwelling/relaxation events. Thus upwelling/relaxation dynamics are primarily responsible for variability

  12. Monsoon-ocean coupled modes in the South China Sea and their linkage with the eastern Indian Ocean-western Pacific warm pool

    NASA Astrophysics Data System (ADS)

    Huang, Fei; Yang, Yuxing; Huang, Jian

    2008-02-01

    Monsoon-ocean coupled modes in the South China Sea (SCS) were investigated by a combined singular value decomposition (CSVD) analysis based on sea surface temperature (SST) and sea surface wind stress (SWS) fields from SODA (Simple Ocean Data Assimilation) data spanning the period of 1950 1999. The coupled fields achieved the maximum correlation when the SST lagged SWS by one month, indicating that the SCS coupled system mainly reflected the response of the SST to monsoon forcing. Three significant coupled modes were found in the SCS, accounting for more than 80% of the cumulative squared covariance fraction. The first three SST spatial patterns from CSVD were: (I) the monopole pattern along the isobaths in the SCS central basin; (II) the north-south dipole pattern; and (III) the west-east seesaw pattern. The expansion coefficient of the SST leading mode showed interdecadal and interannual variability and correlation with the Indo-Pacific warm pool (IPWP), suggesting that the SCS belongs to part of the IPWP at interannual and interdecadal time scales. The second mode had a lower correlation coefficient with the warm pool index because its main period was at intra-annual time scales instead of the interannual and interdecadal scales with the warm pools. The third mode had similar periods to those of the leading mode, but lagged the eastern Indian Ocean warm pool (EIWP) and western Pacific warm pool (WPWP) by five months and one year respectively, implying that the SCS response to the warm pool variation occurred from the western Pacific to the eastern Indian Ocean, which might have been related to the variation of Indonesian throughflow. All three modes in the SCS had more significant correlations with the EIWP, which means the SCS SST varied much more coherently with the EIWP than the WPWP, suggesting that the SCS belongs mostly to part of the EIWP. The expansion coefficients of the SCS SST modes all had negative correlations with the Niño3 index, which they lag

  13. Estimating Heat Transfer from Grotto Mound, NEPTUNE Canada Cabled Observatory, Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Rona, P. A.; Bemis, K. G.; Xu, G.

    2012-12-01

    Heat flux is a fundamental property of a seafloor hydrothermal system that relates to magnitude of sub-seafloor heat source and biosphere conditions, to distribution and style of seafloor venting and benthic biota, to chemical flux, plume formation, and dispersal of biological matter in the water column. We are working to estimate heat flux from Grotto mound, the site of the NEPTUNE Canada Cabled Observatory in the Main Endeavour Field on the Juan de Fuca Ridge. The mound is formed of two sulfide edifices that lie between ~2190 and 2180 m isobaths: 1) an elliptical edifice with major NE-SW-trending axis ~30 m long and minor axis ~ 14 m wide (area ~ 330 m2); 2) a columnar edifice ~ 10 m in diameter and 10 m high (area ~80 m2) named the North Tower, situated across a narrow (~5 m wide) saddle (area ~40 m2) at the W end of the elliptical edifice. Several black smokers discharge relatively small plumes at the E end of the elliptical edifice. A cluster of vigorous black smokers discharge from the top of North Tower and merge to form a large plume. Patchy diffuse flow occurs in areas around all of the black smokers and in the saddle between the two edifices. We are in process of measuring heat flux from components of hydrothermal discharge on Grotto mound, as follows: 1) for smokers on the North Tower an integrated heat flux of 28-55 MW is calculated based on temperature measurements in the initial 20 m rise of the plume assuming that the highest temperatures measured are closest to those of the plume centerline ; 2) for smokers on the E end of the elliptical edifice based on measurements of flow rate from video and acoustic Doppler phase shift, video of vent diameters, and in situ temperature measurements; 3) for discharge from flanges on some chimneys based on video of flow and in situ temperature measurements; 4) for diffuse flow based on area measured by Acoustic Scintillation Thermography and direct measurements of temperature and flow rate. We are evaluating

  14. Improvement to the International Bathymetric Chart of the Arctic Ocean (IBCAO): Updating the Data Base and the Grid Model

    NASA Astrophysics Data System (ADS)

    Jakobsson, M.

    2001-12-01

    has been produced as well, with a resolution of 1' x 1' for compatibility with the global grid of bathymetry that is now under construction by a working group operating under the auspices of the General Bathymetric Chart of the Oceans (GEBCO). New products include a suite of bathymetric contours derived from the grid at depths ranging from 20 metres to 5000 metres, and poster-sized Postscript maps showing isobaths printed over a shaded relief background. These latest developments reflect a commitment to maintain IBCAO as a `live' product for the foreseeable future, with periodic upgrades to improve its quality and usefulness. >http://www.ngdc.noaa.gov/mgg/bathymetry/arctic/arctic.html

  15. Dramatic beach and nearshore morphological changes due to extreme flooding at a wave-dominated river mouth (Invited)

    NASA Astrophysics Data System (ADS)

    Barnard, P. L.; Warrick, J. A.

    2009-12-01

    Direct observations of major floods which input large volumes of sediment into littoral systems generally are rare due to the scarcity of large events and the difficulty of obtaining appropriate data. To understand the importance of infrequent, high-discharge river floods on the long-term morphodynamics of a coastal system, we combine 16 years of pre-flood survey data with three years of post-flood data to characterize morphologic changes at a wave-dominated river mouth. This study provides in-depth morphological analysis of coastal response to an extremely rare flooding event; the highest discharge on record for the Santa Clara River (CA, USA) which occurred in January 2005. This event injected ~5 million m3 of littoral-grade sediment into the Santa Barbara Littoral Cell (SBLC), producing rapid and extreme beach and nearshore morphologic evolution. The sediment load produced by the event is an order of magnitude larger than both the average annual river loads and the annual alongshore littoral transport in this portion of the SBLC. Over 170 m of local shoreline (mean high water (MHW)) progradation was observed as result of the flood, followed by 3 years of rapid local shoreline retreat. Linear regression-determined shoreline change rates of up to -45 m a-1 were observed on the subaerial beach (MHW) and -114 m a-1 on the submarine delta (6 m isobath). Starting approximately 1 km downdrift of the river mouth, shoreline progradation persisted throughout the three-year post-flood monitoring period, with rates of up to +19 m a-1. Post-flood bathymetric surveys show nearshore (0 to 12 m depth) erosion on the delta exceeding 400 m3/m a-1, more than an order of magnitude higher than mean seasonal cross-shore sediment transport rates in the region. Changes were not constant with depth, however; sediment accumulation and subsequent erosion on the delta were greatest at -5 to -8 m, and accretion in downdrift areas was greatest above -2 m. Simple “one-line” shoreline

  16. Transient tidal eddy motion in the western Gulf of Maine, part 1: Primary structure

    NASA Astrophysics Data System (ADS)

    Brown, W. S.; Marques, G. M.

    2013-07-01

    High frequency radar-derived surface current maps of the Great South Channel (GSC) in the western Gulf of Maine in 2005 revealed clockwise (CW) and anticlockwise (ACW) eddy motion associated with the strong regional tidal currents. To better elucidate the kinematics and dynamics of these transient tidal eddy motions, an observational and modeling study was conducted during the weakly stratified conditions of winter 2008-2009. Our moored bottom pressure and ADCP current measurements in 13m depth were augmented by historical current measurements in about 30m in documenting the dominance of highly polarized M2 semidiurnal currents in our nearshore study region. The high-resolution finite element coastal ocean model (QUODDY) - forced by the five principal tidal constituents - produced maps depicting the formation and evolution of the CW and ACW eddy motions that regularly follow maximum ebb and flood flows, respectively. Observation versus model current comparison required that the model bottom current drag coefficient be set to at an unusually high Cd=0.01 - suggesting the importance of form drag in the study region. The observations and model results were consistent in diagnosing CW or ACW eddy motions that (a) form nearshore in the coastal boundary layer (CBL) for about 3h after the respective tidal current maxima and then (b) translate southeastward across the GSC along curved 50m isobath at speeds of about 25m/s. Observation-based and model-based momentum budget estimates were consistent in showing a first order forced semidiurnal standing tidal wave dynamics (like the adjacent Gulf of Maine) which was modulated by adverse pressure gradient/bottom stress forcing to generate the eddy motions. Observation-based estimates of terms in the transport vorticity budget showed that in the shallower Inner Zone subregion (average depth=23m) that the diffusion of nearshore vorticity was dominant in feeding the growth of eddy motion vorticity; while in the somewhat deeper

  17. Modelisation of Circulation On The French Guiana Continental Shelf

    NASA Astrophysics Data System (ADS)

    Chevalier, C.; Dekeyser, I.; Ramamonjiarisoa, A.; Baklouti, M.; van Nieuwerberg, V.

    The continental shelf which extends more over than 1000 km to the north-west of the mouth of the Amazon river is an usual oceanographic environment : the entire area is influenced by fresh water flowing from the Amazon. The current on the shelf inter- acts with the strong, shallow Guiana Current along the outer shelf area. The prevailing trade winds across the area impose surface stresses. The tidal influence is also signif- icant with a diminishing amplitude from the Amazon to the north. This combination results in a persistent long-shore current flowing north-westward in the shallow wa- ter along the shore. In particular on French Guiana continental shelf, the combination of significant stratification, great coastal current just out of the shelf, influence of the wind and strong tidal component presents an interesting process for study. The purpose of this study is to look into the circulation that develops under these interacting forces. For that, we develop a numerical model of the circulation on the French Guiana shelf. Nowadays, in the bibliography, it seems to be the first numerical study on this area. This work is included in the Programme National dSEnvironnement Côtier (PNEC) in French Guiana. Simulations described the coastal currents, the salinity and temperature evolution on the shelf under the influence of rivers discharging in the shelf and the effect of north- eastward wind on the circulation. The current is parallel to the coast and the highest velocities are in the middle of the shelf, the maximum intensity is located at the surface and reached speed of 1m/s. The fresh water discharged by rivers extends alongshore near the coast, to about 30m-isobath, whereas the fresh water coming from the Ama- zon spreads out essentially in the middle of the shelf. The halocline is situated few meters (between 2 and 5 m) under the surface, with a lower salinity at the south-east boundary which is 20 and which is 25 at the north-west boundary, whereas, the

  18. Benthic community structure on the U.S. South Atlantic slope off the Carolinas: Spatial heterogeneity in a current-dominated system

    NASA Astrophysics Data System (ADS)

    Blake, James A.; Frederick Grassle, J.

    higher than in previously published accounts. The faunal assemblage at each station was consistent over 2 years in that samples from one station were always more similar to one another than to any other station. Stations grouped into upper slope, middle slope, lower slope and continental rise assemblages; the upper slope stations were the most variable, both in density and community composition. Transect differences in types of sediment and macrofaunal communities along and across isobaths, indicated considerable regional heterogeneity.

  19. Spatio-temporal distribution patterns of the epibenthic community in the coastal waters of Suriname

    NASA Astrophysics Data System (ADS)

    Willems, Tomas; De Backer, Annelies; Wan Tong You, Kenneth; Vincx, Magda; Hostens, Kris

    2015-10-01

    This study aimed to characterize the spatio-temporal patterns of the epibenthic community in the coastal waters of Suriname. Data were collected on a (bi)monthly basis in 2012-2013 at 15 locations in the shallow (<40 m) coastal area, revealing three spatially distinct species assemblages, related to clear gradients in some environmental parameters. A species-poor coastal assemblage was discerned within the muddy, turbid-water zone (6-20 m depth), dominated by Atlantic seabob shrimp Xiphopenaeus kroyeri (Crustacea: Penaeoidea). Near the 30 m isobath, sediments were much coarser (median grain size on average 345±103 μm vs. 128±53 μm in the coastal assemblage) and water transparency was much higher (on average 7.6±3.5 m vs. 2.4±2.1 m in the coastal assemblage). In this zone, a diverse offshore assemblage was found, characterized by brittle stars (mainly Ophioderma brevispina and Ophiolepis elegans) and a variety of crabs, sea stars and hermit crabs. In between both zones, a transition assemblage was noted, with epibenthic species typically found in either the coastal or offshore assemblages, but mainly characterized by the absence of X. kroyeri. Although the epibenthic community was primarily structured in an on-offshore gradient related to depth, sediment grain size and sediment total organic carbon content, a longitudinal (west-east) gradient was apparent as well. The zones in the eastern part of the Suriname coastal shelf seemed to be more widely stretched along the on-offshore gradient. Although clear seasonal differences were noted in the environmental characteristics (e.g. dry vs. rainy season), this was not reflected in the epibenthic community structure. X. kroyeri reached very high densities (up to 1383 ind 1000 m-²) in the shallow coastal waters of Suriname. As X. kroyeri is increasingly exploited throughout its range, the current study provides the ecological context for its presence and abundance, which is crucial for an ecosystem approach and the

  20. Abyssal θ-S Observations at Hawaii Ocean Time-series Station ALOHA

    NASA Astrophysics Data System (ADS)

    Lukas, R.; Santiago-Mandujano, F.; Fumar, C.; McCoy, D.; Deppe, R. W.; Gum, J.; Snyder, J.; Chee, B.; Howe, B. M.; Potemra, J. T.; Duennebier, F. K.

    2014-12-01

    Abyssal θ-S variations observed since June 2011 by the ALOHA Cabled Observatory (ACO) reveal a potential temperature range of 0.025°C, and a salinity range of more than 0.0025 g kg-1. The very large temperature range is associated with episodic cold events (Lukas et al.2001; Alford et al. 2011). The salinity range, while not large in absolute terms, is an order of magnitude larger than the precision of the Sea-Bird Microcat. The absolute salinity is calibrated against simultaneous Hawaii Ocean Time-series (HOT) full-depth CTD profiles that have an accuracy of ~10-3 g kg-1. A slow drift of the SBE-37 conductivity sensor is seen, along with a sudden offset that may have been caused by a nearby glass ball implosion. θ-S variations are dominated by changes in density that are associated with dynamic processes. Large cooling events are associated with increases of salinity ultimately deriving from the neighboring Maui Deep. The slopes of these excursions in θ-S space are consistent with the slopes of HOT CTD depth profiles, suggesting that these are vertical changes due either to gravity currents associated with cold, salty overflow events from the Maui Deep, or to internal seiches within the Kauai Deep. θ-S variations that are nearly isopycnal are also seen during the slow recovery from a major cooling event in 2011. This may be due to diapycnal mixing with fresher waters above the controlling sill depth. It cannot be ruled out that some apparent salinity changes may be associated with sediment resuspension events, with subsequent deviations from the PSS-78 empirical relationship between conductivity, salinity, temperature and pressure. ADCP records show large vacillations of along- and cross-isobath flow. Large vertical current variations are measured that are correlated with horizontal flows, likely due to the bottom slope, even after minimizing correlations to account for the unknown orientation of the ADCP. The primary conclusion is that abyssal dynamics

  1. Baffin Island and West Greenland Current Systems in northern Baffin Bay

    NASA Astrophysics Data System (ADS)

    Münchow, Andreas; Falkner, Kelly K.; Melling, Humfrey

    2015-03-01

    data averaged along isobaths during NAO-positive years reveals a baroclinic circulation in Baffin Bay more intense than 2003 with stronger southward flow of fresher Arctic waters along Baffin Island and stronger northward inflow of saltier Atlantic waters along Greenland. During negative NAO years this cyclonic circulation weakens as evidenced by a 1979 synoptic survey of the hydrography along Baffin Island.

  2. Habitat Distribution on the Inner Continental Shelf of Northern South Carolina Based on Sidescan Sonar and Submarine Video Data

    NASA Astrophysics Data System (ADS)

    Ojeda, G. Y.; Gayes, P. T.; van Dolah, R. F.; Schwab, W. C.

    2002-12-01

    Assessment of the extent and variability of benthic habitats is an important mission of biologists and marine scientists, and has supreme relevance in monitoring and maintaining the offshore resources of coastal nations. Mapping `hard bottoms', in particular, is of critical importance because these are the areas that support sessile benthic habitats and associated fisheries. To quantify the extent and distribution of habitats offshore northern South Carolina, we used a spatially quantitative approach that involved textural analysis of side scan sonar images and training of an artificial neural network classifier. This approach was applied to a 2 m-pixel image mosaic of sonar data collected by the USGS in 1999 and 2000. The entire mosaic covered some 686 km2 and extended between the ~6 m and ~10+ m isobaths off the Grand Strand region of South Carolina. Bottom video transects across selected sites provided 2,119 point observations which were used for image-to-ground control as well as training of the neural network classifier. A sensitivity study of 52 space-domain textural features indicated that 12 of them provided reasonable discriminating power between two end-member bottom types: hard bottom and sand. The selected features were calculated over 5 by 5 pixel windows of the image where video point observations existed. These feature vectors were then fed to a 3-layer neural network classifier, trained with a Levenberg-Marquardt backpropagation algorithm. Registration and display of the output habitat map were performed in GIS. Results of our classification indicate that outcropping Tertiary and Cretaceous strata are exposed over a significant portion of northern South Carolina's inner shelf, consistent with a sediment-starved margin type. The combined surface extent classified as hard bottom was 405 km2 -or 59 % of the imaged area-, while only 281 km2 -or 41 % of the area were classified as sand. In addition, our results provided constraints on the spatial

  3. Ocean dynamic processes causing spatially heterogeneous distribution of sedimentary caesium-137 massively released from the Fukushima Daiichi Nuclear Power Plant

    NASA Astrophysics Data System (ADS)

    Higashi, H.; Morino, Y.; Furuichi, N.; Ohara, T.

    2015-12-01

    Massive amounts of anthropogenic radiocaesium 137Cs that were released into the environment by the Fukushima Daiichi Nuclear Power Plant accident in March 2011 are widely known to have extensively migrated to Pacific Ocean sediment off of eastern Japan. Several recent reports have stated that the sedimentary 137Cs is now stable with a remarkably heterogeneous distribution. The present study elucidates ocean dynamic processes causing this heterogeneous sedimentary 137Cs distribution in and around the shelf off Fukushima and adjacent prefectures. We performed a numerical simulation of oceanic 137Cs behaviour for about 10 months after the accident, using a comprehensive dynamic model involving advection-diffusion transport in seawater, adsorption and desorption to and from particulate matter, sedimentation and suspension on and from the bottom, and vertical diffusion transport in the sediment. A notable simulated result was that the sedimentary 137Cs significantly accumulated in a swath just offshore of the shelf break (along the 50-100 m isobath) as in recent observations, although the seabed in the entire simulation domain was assumed to have ideal properties such as identical bulk density, uniform porosity, and aggregation of particles with a single grain diameter. This result indicated that the heterogeneous sedimentary 137Cs distribution was not necessarily a result of the spatial distribution of 137Cs sediment adsorptivity. The present simulation suggests that the shape of the swath is mainly associated with spatiotemporal variation between bottom shear stress in the shallow shelf (< 50 m depths) and that offshore of the shelf break. In a large part of the shallow shelf, the simulation indicated that strong bottom friction suspending particulate matter from the seabed frequently occurred via a periodic spring tide about every 2 weeks and via occasional strong wind. The sedimentary 137Cs thereby could hardly stay on the surface of the seabed with the result that

  4. Subtidal currents over the central California slope: Evidence for offshore veering of the undercurrent and for direct, wind-driven slope currents

    USGS Publications Warehouse

    Noble, M.A.; Ramp, S.R.

    2000-01-01

    In February 1991, an array of six current-meter moorings was deployed for one year across the central California outer shelf and slope. The main line of the array extended 30 km offshore of the shelf break, out to water depths of 1400 m. A more sparsely-instrumented line, displaced 30 km to the northwest, extended 14 km offshore. Though shorter, the northern line spanned similar water depths because the gradient of the topography steepened in the northern region. A poleward flow pattern, typical of the California undercurrent, was seen across both lines in the array over most of the year. The poleward flow was surface intensified. In general, the portion of the undercurrent that crossed the southern line had larger amplitudes and penetrated more deeply into the water column than the portion that crossed the northern line. Transport over the year ranged from 0 to 2.5 Sverdrups (Sv) poleward across the southern line; 0 to 1 Sv poleward across the northern line. We suggest the difference in transport was caused by topographic constraints, which tended to force the poleward flow offshore of the northern measurement sites. The slope of the topography steepened too abruptly to allow the poleward flow to follow isobaths when currents were strong. When current velocities lessened, a more coherent flow pattern was seen across both lines in the array. In general, the poleward flow patterns in the undercurrent were not affected by local winds or by the local alongshore pressure gradient. Nor was a strong seasonal pattern evident. Rather unexpectedly, a small but statistically significant fraction of the current variance over the mid- and outer slope was driven by the surface wind stress. An alongshelf wind stress caused currents to flow along the slope, parallel to the wind field, down to depths of 400 m below the surface and out to distances of 2 Rossby radii past the shelf break. The transfer functions were weak, 3-4 cm/s per dyn cm-2, but comparable to wind-driven current

  5. On dense water formation in shelves of the Aegean Sea during the year 1987

    NASA Astrophysics Data System (ADS)

    Salusti, Ettore; Bellacicco, Marco; Anagnostou, Christos; Rinaldi, Eleonora; Tripsanas, Efthymios

    2015-04-01

    We here investigate the role of the rather virgin year 1987, when some modern data are available but before the main EMT event. A combination of field, satellite and numerical model temperature and salinity data from PROTHEUS, as well as a coupled ocean-atmosphere model, are used to implement theoretical models. After its formation over a sloping shelf of some important points in the Aegean Sea, due to the strong cold winter winds, a dense water patch can either have a dramatic downflow or can start a slow geostrophic descent along shelves and then following isobaths, best described by streamtube models. The most important, among these shelves characterized by a strong air sea interaction, have been identified from satellite data. The Northernmost shelves are those north of the island of Samothrace and in the Northern Thermaikos Gulf. In agreement with the field measuraments of Georgopoulos et al. (1987) also the shallow shelf between Limnos and Goceada was a source of very dense water, as well as thr shelf between Lesbos and the Turkish coast. Most probably also the shelves around the Cycladic Plateau were affected by strong winds and contributed to the Aegean Sea deep water formation. In addition, other theoretical models of wind-induced coastal upwelling allow to infer temperature and salinity information of dense water dynamics along the shallow coasts and shelves of the Aegean Sea. All this allows a heuristic application of classical T/S diagrams to estimate Northern Aegean dense water evolution and spreading, that nicely supports the early ideas of Zervakis et al. (2000). A complex situation about the Cycladic Plateau dynamics is also analyzed in correlation with sediment locations. Indeed seismic-reflection profiles confirm the presence of a contourite location along the northeast Cyclades Plateau shelves. All this interestingly opens novel prospective about the dense water coastal formation shelves. In synthesis such field, numerical and satellite data

  6. Storm Bed Imprinting on the Northern California Shelf: Interaction of Fluvial and Marine Processes.

    NASA Astrophysics Data System (ADS)

    Swift, D. J.; Fan, S.; Niedoroda, A. W.; Reed, C.; Borgeld, J. C.; Crockett, J. S.

    2001-05-01

    Seismic records and cores from ONR's STRATAFORM program indicate that the Holocene deposits on the northern California shelf consist of a succession of back-stepping, storm-generated event beds, deposited as sediment undergoes cross-shelf dispersal from intermittently flooding river mouths. The beds are modified to varying degrees by secondary processes (gravity transport, bioturbation). Box core observations show that there is "mud line" on the shelf surface at approximately the 45 m isobath. Long cores show that within the 3-dimensional sediment body, nearshore sand beds intertongue with offshore mud beds beneath this line. However, numerical simulations suggest a more complex relationship. Instead of intertonguing, most event beds begin as sand beds in the nearshore sand deposit, pass through an interbedded zone, and enter the offshore mud deposit as mud beds. Event stratification is difficult to discern both seaward and landward of the transitional zone, mainly because the Cutoff Percentage has been exceeded in these areas (percent thickness of an upward-fining bed which must be preserved to observe grain size contrast). There are thus three facies bodies present, an Amalgamated Sand Facies on the inner shelf (sand beds on sand beds), an Interbedded Sand and Mud Facies on the central shelf, and an offshore Laminated or Bioturbated Mud Facies. Several other parameters are useful for defining these facies. The degree of condensation (extent to which each bed has cannibalized its predecessor) can be measured by the Reworking Ratio (ratio of mean annual resuspension depth to deposition per event). This value decreases seaward across the shelf to a minimum in the Interbedded Facies in response to decreasing wave energy flux into the sea floor. It then increases seaward across the outer shelf, as the decrease in available sediment becomes more important. The standard deviation of bed thickness is (in part) a measure of variation in storm intensity, and is a

  7. Nature of decadal-scale sediment accumulation on the western shelf of the Mississippi River delta

    NASA Astrophysics Data System (ADS)

    Reide Corbett, D.; McKee, Brent; Allison, Mead

    2006-11-01

    accumulation rates indicates that 40-50% of the sediment delivered by the river is transported out of the study region. Sediment is moved to distal regions of the shelf/slope through two different mechanisms. Along-isobath sediment movement occurs by normal resuspension processes west of the delta, whereas delivery of sediments south and southwest of the delta may be also be influenced by mass movement events on varying timescales.

  8. Steric contribution to the long-term sea level variations within the Gulf of Cadiz continental shelf

    NASA Astrophysics Data System (ADS)

    Laiz, Irene; Tejedor, Begoña; Gómez-Enri, Jesús; Aboitiz, Alazne; Villares, Pilar

    2015-04-01

    The response of the long-term coastal sea level variations to the steric contribution has been explored within the Gulf of Cadiz (GoC) for the period 1997-2008 using tide gauge data as well as altimeter-derived sea level anomaly maps (AVISO). In order to remove the atmospheric pressure contribution, tide gauge data were corrected using the inverted barometer (IB) method. The AVISO maps were initially de-corrected using the Dynamic Atmospheric Correction product and then corrected using the same IB method. Steric height (ssh) time series were computed by combining a high resolution climatology (0.1° x 0.1°) with monthly maps of AVHRR sea surface temperature considering a reference depth of 500 m at the open ocean and the bottom depth for shallower areas. In order to evaluate the steric effect on the long-term sea level changes, four types of steric contribution were defined: (1) The ssh values interpolated to the AVISO grid resolution were considered as the local steric effect. (2) The open ocean steric effect was computed by averaging all the steric heights corresponding to grid points located over the 500 m isobath and deeper. (3) The Eastern / Western continental shelf steric contribution was obtained by averaging over those grid points located within each continental shelf. (4) Finally, a basin-wide steric effect was computed by averaging the steric heights all over the GoC. The potential contribution of each of the defined steric effects on the pressure-adjusted sea level was evaluated. The open ocean contribution explained the highest percentage of variance all over the basin with the exception of the western shelf, where the best results were obtained with the local contribution, supporting the idea that the cell of cyclonic circulation found off Cape San Vicente is a local quasi-permanent feature. The fact that the open ocean steric effect explained the highest percentage of variance within the eastern shelf suggested that the deep ocean thermosteric

  9. 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

  10. Temporal and spatial variations of sea surface temperature in the East China Sea

    NASA Astrophysics Data System (ADS)

    Tseng, Chente; Lin, Chiyuan; Chen, Shihchin; Shyu, Chungzen

    2000-03-01

    Sea surface temperature of the East China Sea (ECS) were analyzed using the NOAA/AVHRR SST images. These satellite images reveal surface features of ECS including mainly the Kuroshio Current, Kuroshio Branch Current, Taiwan Warm Current, China coastal water, Changjiang diluted water and Yellow Sea mixed cold water. The SST of ECS ranges from 27 to 29°C in summer; some cold eddies were found off northeast Taiwan and to the south of Changjiang mouth. SST anomalies at the center of these eddies were about 2-5°C. The strongest front usually occurs in May each year and its temperature gradient is about 5-6°C over a cross-shelf distance of 30 nautical miles. The Yellow Sea mixed cold water also provides a contrast from China Coastal waters shoreward of the 50 m isobath; cross-shore temperature gradient is about 6-8°C over 30 nautical miles. The Kuroshio intrudes into ECS preferably at two locations. The first is off northeast Taiwan; the subsurface water of Kuroshio is upwelled onto the shelf while the main current is deflected seaward. The second site is located at 31°N and 128°E, which is generally considered as the origin of the Tsushima Warm Current. More quantitatively, a 2-year time series of monthly SST images is examined using EOF analysis to determine the spatial and temporal variations in the northwestern portion of ECS. The first spatial EOF mode accounts for 47.4% of total spatial variance and reveals the Changjiang plume and coastal cold waters off China. The second and third EOF modes account for 16.4 and 9.6% of total variance, respectively, and their eigenvector images show the intrusion of Yellow Sea mixed cold waters and the China coastal water. The fourth EOF mode accounts for 5.4% of total variance and reveals cold eddies around Chusan Islands. The temporal variance EOF analysis is less revealing in this study area.

  11. Gulf Stream marine hydrokinetic energy resource characterization off Cape Hatteras, North Carolina

    NASA Astrophysics Data System (ADS)

    Muglia, M.; He, R.; Lowcher, C.; Bane, J.; Gong, Y.; Taylor, P.

    2015-12-01

    The Gulf Stream off North Carolina has current velocities that approach 3 m/s and an average volume transport of 90 Sv (1 Sv= 106 m3/s) off of Cape Hatteras, making it the most abundant MHK (Marine Hydrokinetic Energy) resource for the state. Resource availability at a specific location depends primarily on the variability in Gulf Stream position, which is least offshore of Cape Hatteras after the stream exits the Florida Straits. Proximity to land and high current velocities in relatively shallow waters on the shelf slope make this an optimal location to quantify the MHK energy resource for NC. 3.5 years of current measurements beginning in August of 2013 from a moored 150 kHz ADCP (Acoustic Doppler Current Profiler) at an optimal location for energy extraction quantify the available energy resource and its variability, and establish the skill of a Mid-Atlantic Bight and South Atlantic Bight Regional Ocean Model in predicting the MHK energy resource. The model agrees well with long-term observed current averages and with weekly to monthly fluctuations in the current speeds. Model and observations over the first 9 months of the ADCP deployment period both averaged 1.15 m/s thirty meters below the surface. The model under estimates observed current speeds for the higher frequency current fluctuations of days to weeks. Comparisons between the model and ADCP observed currents, and velocity derived power density over the entire 3.5 years of observations demonstrate the significant inter-annual variability in power density. Shipboard 300 kHz ADCP cross-stream transects and hourly surface currents measurements off Cape Hatteras from a network of land based HF (high frequency) radars further quantify available MHK energy and assess model skill. Cross-stream transects were made with a vessel-mounted 300 kHz ADCP on a line from the 100-1000m isobaths, and measured currents in the top 100m. These measurements demonstrate the variability in the resource with water depth, and

  12. Understanding Nearshore Processes Of a Large Arctic Delta Using Combined Seabed Mapping, In Situ Observations, Remote Sensing and Modeling

    NASA Astrophysics Data System (ADS)

    Solomon, S. M.; Couture, N. J.; Forbes, D. L.; Hoque, A.; Jenner, K. A.; Lintern, G.; Mulligan, R. P.; Perrie, W. A.; Stevens, C. W.; Toulany, B.; Whalen, D.

    2009-12-01

    storm events, waves attenuate rapidly inshore of the 3 m isobath. Entrainment of fine material and rapid flocculation due to the presence of brackish water may induce the transient formation of high density suspensions near the seabed which contributes to this rapid attenuation. The relatively poor performance of shallow water wave models (e.g. SWAN) in very shallow depths during storm simulations appears to be related to inaccurate formulations for wave attenuation in this environment.

  13. Field observation and analysis of wave-current-sediment movement in Caofeidian Sea area in the Bohai Bay, China

    NASA Astrophysics Data System (ADS)

    Zuo, Li-qin; Lu, Yong-jun; Wang, Ya-ping; Liu, Huai-xiang

    2014-06-01

    In order to study the mechanism of flow-sediment movement, it is essential to obtain measured data of water hydrodynamic and sediment concentration process with high spatial and temporal resolution in the bottom boundary layer (BBL). Field observations were carried out in the northwest Caofeidian sea area in the Bohai Bay. Near 2 m isobath (under the lowest tidal level), a tripod system was installed with AWAC (Acoustic Wave And Current), ADCP (Acoustic Doppler Current Profilers), OBS-3A (Optical Backscatter Point Sensor), ADV (Acoustic Doppler Velocimeters), etc. The accurate measurement of the bottom boundary layer during a single tidal period was carried out, together with a long-term sediment concentration measurement under different hydrological conditions. All the measured data were used to analyze the characteristics of wave-current-sediment movement and the BBL. Analysis was performed on flow structure, shear stress, roughness, eddy viscosity and other parameters of the BBL. Two major findings were made. Firstly, from the measured data, the three-layer distribution model of the velocity profiles and eddy viscosities in the wave-current BBL are proposed in the observed sea area; secondly, the sediment movement is related closely to wind-waves in the muddy coast area where sediment is clayey silt: 1) The observed suspended sediment concentration under light wind conditions is very low, with the peak value generally smaller than 0.1 kg/m3 and the average value being 0.03 kg/m3; 2) The sediment concentration increases continuously under the gales over 6-7 in Beaufort scale, under a sustained wind action. The measured peak sediment concentration at 0.4 m above the seabed is 0.15-0.32 kg/m3, and the average sediment concentration during wind-wave action is 0.08-0.18 kg/m3, which is about 3-6 times the value under light wind conditions. The critical wave height signaling remarkable changes of sediment concentration is 0.5 m. The results show that the suspended

  14. Perspectives for Expanded Ocean Observing on the Southeast Florida Shelf and between Cuba and the Bahamas and the US

    NASA Astrophysics Data System (ADS)

    Soloviev, A.; Dodge, R. E.; Proni, J.

    2012-12-01

    A long term ocean observing system was established on the Southeast Florida shelf near Ft. Lauderdale by the Nova Southeastern University Oceanographic Center (NSUOC) in late 1990s as a cooperative agreement between the NSU Oceanographic Center and USF College of Marine Science. The system has been supported and upgraded during a number of projects funded by the US federal government and private industries. Currently it consists of two ADCP moorings deployed at 240 m and 11 m isobath and coastal meteorological station and primarily serves to support the Office of Naval Research and other Federal agencies projects. During active observational phases, the area is monitored using the new generation of synthetic aperture radar (SAR) satellites (TerraSAR-X, Cosmo SkyMed, ALOS PALSAR, RADARSAT 2). The NSUOC Ocean observing system is a component of SECOORA, which has been integrating coastal and ocean observing data in the Southeast United States as a part of IOOS. In this paper we overview the results obtained during more than a decade of observations and discuss perspectives for expanded ocean observing on the Southeast Florida Shelf and between Cuba, Bahamas and US. Increased ocean observations are needed of the major western boundary current, known as the Loop Current in the Gulf of Mexico and the Florida Current in the Straits Florida. This ocean current occurs to the west and north of Cuba and along the southeast US. Observations will provide better understanding of the processes that maintain, and account for, the current variability and will be useful in myriad practical applications. A major application is the need to monitor the occurrence of, and to forecast entrainment, trajectories, and detrainment of, potential oil spills that may propagate from Cuban drilling sites located along the north coast of Cuba as well as from proposed drilling in the Bahamas. Such ocean observation information can be used as input for operational response models and result in best

  15. Variability of the internal tide on the southern Monterey Bay continental shelf and associated bottom boundary layer sediment transport

    USGS Publications Warehouse

    Rosenberger, Kurt; Storlazzi, Curt; Cheriton, Olivia

    2016-01-01

    A 6-month deployment of instrumentation from April to October 2012 in 90 m water depth near the outer edge of the mid-shelf mud belt in southern Monterey Bay, California, reveals the importance regional upwelling on water column density structure, potentially accounting for the majority of the variability in internal tidal energy flux across the shelf. Observations consisted of time-series measurements of water-column currents, temperature and salinity, and near-bed currents and suspended matter. The internal tide accounted for 15–25% of the water-column current variance and the barotropic tide accounted for up to 35%. The subtidal flow showed remarkably little shear and was dominated by the 7–14 day band, which is associated with relaxations in the dominant equatorward winds typical of coastal California in the spring and summer. Upwelling and relaxation events resulted in strong near-bed flows and accounted for almost half of the current stress on the seafloor (not accounting for wave orbital velocities), and may have driven along-shelf geostrophic flow during steady state conditions. Several elevated suspended particulate matter (SPM) events occurred within 3 m of the bed and were generally associated with higher, long-period surface waves. However, these peaks in SPM did not coincide with the predicted resuspension events from the modeled combined wave–current shear stress, indicating that the observed SPM at our site was most likely resuspended elsewhere and advected along-isobath. Sediment flux was almost equal in magnitude in the alongshore and cross-shore directions. Instances of wave–current shear stress that exceeded the threshold of resuspension for the silty-clays common at these water depths only occurred when near-bed orbital velocities due to long-period surface waves coincided with vigorous near-bed currents associated with the internal tide or upwelling/relaxation events. Thus upwelling/relaxation dynamics are primarily responsible for

  16. Preliminary mooring results at the entrance to the Gulf of California from May to November 2004.

    NASA Astrophysics Data System (ADS)

    Mascarenhas, A. S.; Collins, C. A.; Castro, R.; Navarro, L. F.; Blanco, R.

    2005-05-01

    The preliminary results of two moorings at the entrance to the Gulf of California, from May to November 2004 are discussed. The mooring M1 (23o 28.58' N, 109o 23.34' W), off Cabo Pulmo, Baja California consisted of a ADCP workhorse broadband at 118 m and three MicroCats at 40, 79 and 118 m respectively. The mooring M2 (24o 02.15'N, 107o 51.40' W), off El Dorado, Sinaloa, consisted of a ADP Sontek 250 (KHz) at 115 m and also three MicroCats at 38, 77 and 115 m respectively. The low passed filtered pressures at the three depths in each site are highly coherent while the coherence between the pressures on opposite sides of the entrance at three depths is low, being high only at the diurnal and semidiurnal tidal frequencies. The pressure record at the three depths in the El Dorado side was dominated by two events that occurred on June 10 and October 23, 2004. The first event was preceded by an increase in salinity of about .30 at 40 m, as well as small increases at 80 and 120 m, all of which were associated to an increase in pressure, suggesting an intrusion of a saline vortex. The coherence of temperature and salinity measured at the two moorings was low indicating the difference in changes of thermohaline characteristics. The along shelf current direction was chosen as the principal axes for each current time series (Cabo Pulmo and El Dorado). As expected, the principal axes were aligned with the local isobaths on each shelf. On the Sinaloa shelf (El Dorado), the currents were strongly oriented along the shelf. Along shelf currents were stronger and less variable on the Baja California shelf (Cabo Pulmo). At El Dorado, with the exception of the strong event periods mentioned above when the current reached 0.5 ms-1, flow was weaker and more variable; periods of strong outlfow lasted for about 8 days. The vertically averaged flow at both sides of the entrance to the Gulf was directed out of the Gulf most of the time. This suggests that the persistent cyclonic

  17. Offshore permafrost decay and massive seabed methane escape in water depths >20 m at the South Kara Sea shelf

    NASA Astrophysics Data System (ADS)

    Portnov, A.; Mienert, J.; Cherkashov, G. A.

    2013-12-01

    We study the West-Yamal Shelf in the Kara Sea, offshore Western Russia. We present new high-resolution seismic data (2-16 kHz) and gas geochemical data from 2012 cruises. In high-resolution seismic data, we found extensive acoustic anomalies in the water column, which we interpreted to be gas (bubble) flares rising from the seafloor. These anomalies were widespread throughout the study area, but seemed to be limited to water depths > 20 meters below sea level (mbsl). One seepage site in ~6m water depth released gas that reached almost to the sea surface. The hydroacoustic anomalies are limited by the 20 m isobaths, and it may be controlled by the extension of permafrost that is still present below the seafloor at these depths providing an impermeable layer through which gas and other fluids cannot migrate. We detected acoustically transparent zones in sediments in the upper 2-5 meters below seafloor (mbsf). We interpret these acoustic anomalies to record the presence of free gas. Deeper seismic data show that acoustic anomalies in sediments near the seafloor are connected to gas chimneys that extend to depths >2000 mbsf. This suggests that gas is migrating from deeper hydrocarbon reservoirs and therefore it has very likely a thermogenic origin. In addition to the more widespread and disperse acoustically transparent zones, we discovered two prominent transparent mounds that are 1.5-2 km in diameter and that are elevated 10-15 meters above the seafloor. These features bear striking resemblance to the pingo-like features (PLF) that have been studied on the Beaufort Shelf (e.g. Shearer et al., 1971; Paull et al., 2007), and Pechora Sea (Rokos, 2009). Tentative results of numerical modelling estimate the thickness of permafrost, which was during the last sea level regression 170-300 meters thick. Based on the model of permafrost melting we state, that continuous sub-seabed permafrost may extend to water depths of ~20 m offshore creating a seal through which gas cannot

  18. Methane Release and Pingo-Like Feature Across the South kara Sea Shels, an Area of Thawing Offshore Permafrost

    NASA Astrophysics Data System (ADS)

    Serov, P.; Portnov, A.; Mienert, J.

    2015-12-01

    Thawing subsea permafrost controls methane release from the Russian Arctic shelf having a considerable impact on the climate-sensitive Arctic environment. Our recent studies revealed extensive gas release over an area of at least 7500 km2and presence of pingo-like features (PLFs), showing severe methane leakage, in the South Kara Sea in water depths >20m (Serov et al., 2015). Specifically, we detected shallow methane ebullition sites expressed in water column acoustic anomalies (gas flares and gas fronts) and areas of increased dissolved methane concentrations in bottom water, which might be sufficient sources of carbon for seawater-atmosphere exchange. A study of nature and source of leaking gas was focused on two PLFs, which are acoustically transparent circular mounds towering 5-9 m above the surrounding seafloor. One PLF (PLF 2) connects to biogenic gas from deeper sources, which is reflected in δ13CCH4 values ranging from -55,1‰ to -88,0‰ and δDCH4values varied from -175‰ to -246‰. Low organic matter content (0.52-1.69%) of seafloor sediments restricts extensive in situ methane production. The formation of PLF 2 is directly linked to the thawing of subsea permafrost and, possibly, decomposition of permafrost related gas hydrates. High accumulations of biogenic methane create the necessary forces to push the remaining frozen layers upwards and, therefore, form a topographic feature. We speculate that PLF 1, which shows ubiquitously low methane concentrations, is either a relict submerged terrestrial pingo, or a PLF lacking the necessary underlying methane accumulations. Our model of glacial-interglacial permafrost evolution supports a scenario in which subsea permafrost tapers seaward and pinches out at 20m isobaths, controlling observed methane emissions and development of PLFs. Serov. P., A. Portnov, J. Mienert, P. Semenov, and P. Ilatovskaya (2015), Methane release from pingo-like features across the South Kara Sea shelf, an area of thawnig

  19. Across-shore variability in plankton layering and abundance associated with physical forcing in Monterey Bay, California

    NASA Astrophysics Data System (ADS)

    Sevadjian, J. C.; McManus, M. A.; Ryan, J.; Greer, A. T.; Cowen, R. K.; Woodson, C. B.

    2014-01-01

    The purpose of this study was to further our understanding of the role of the coastal physical oceanographic environment as a dynamic and constantly evolving habitat for plankton. Over a 3-week period in the summer of 2010, an array of moorings were deployed and shipboard and autonomous underwater vehicle (AUV) surveys were conducted to investigate the association between physical processes and plankton distributions over the Monterey Bay, California inner shelf. Acoustic backscatter, chlorophyll-a fluorescence, and high-resolution zooplankton imagery data collected during the shipboard surveys were used to map the distributions of phytoplankton and zooplankton; and profiles of temperature, salinity, oxygen, and nitrate from the AUV characterized the physical and chemical environment. A synthesis of underway and moored time series data provided insight into the histories of water masses in the area, and facilitated tracking of internal wave groups as they propagated towards shore. A near-bottom intrusion of recently-upwelled water was found to be strongly influenced by the diurnal tide, resulting in daily across-shelf excursions past the mooring array at the 20-m isobath. Behind the leading edge of the intrusion, the water column was highly stratified in temperature, salinity, oxygen, and nitrate; and thin layers of phytoplankton and zooplankton persisted at the upper boundary of the intrusion. In ambient waters shoreward of the intrusion, stratification was weak; copepod, appendicularian, and gelatinous zooplankton abundances were relatively low; and phytoplankton and acoustic backscatter were broadly distributed throughout the lower half of the water column. The arrival of two shoreward-propagating internal wave groups observed during the shipboard survey corresponded with disparate responses in plankton distribution. In the wake of the first wave group, phytoplankton and zooplankton layers thinned or converged; in the wake of the second wave group, an eight

  20. 7Be as a tracer of flood sedimentation on the northern California continental margin

    USGS Publications Warehouse

    Sommerfield, C. K.; Nittrouer, C. A.; Alexander, C. R.

    1999-01-01

    Sediment inventories of the cosmogenic radionuclide 7Be (t1/2=53 d) were measured on the Eel River shelf and slope (northern California continental margin) to investigate sedimentation processes associated with coastal river flooding. Seabed coring shortly after major riverflow events in 1995 and 1997 documented a shelf-wide flood deposit, and subsequent radionuclide studies determined 7Be to be a powerful tracer of fine-grained river sediment. In addition, distinctive signatures of 234Th and 210Pb were observed in oceanic flood deposits and provided additional information regarding depositional processes. During the 1995–1997 monitoring period, 7Be was present (2–35 dpm cm-2) in shelf and slope sediments only after periods of high rainfall and river runoff during the winter months. It is suggested that fluvial input was the primary source of 7Be in shelf sediments after the floods. 7Be sediment inventories and sediment-trap fluxes determined after the 1997 flood revealed that fine-grained fluvial sediments were rapidly (within one month) broadcast over the continental margin, to the 500 m isobath. Dispersal was apparently facilitated by energetic storm waves, which resuspended and redistributed some fraction of the suspended load residing on the shelf prior to accretion as flood deposits. These observations illustrate that floods are an important sedimentary process for modern environments of the Eel shelf and slope, and perhaps for other fluviomarine sedimentary systems of the northern California continental margin. Ratios of the 210Pb sediment-accumulation rate (100 yr average) to the 7Be deposition rate (1–2 month average) for shelf sites illustrate the episodic nature of shelf sedimentation, and suggest that a minimum of 3–30 depositional events complete the most recent stratigraphic record. This observation is consistent with the magnetude and frequency of fluvial sediment input, as Eel River floods with return periods of 3–33 yr (3% of the time of

  1. Dissipation Rate of Turbulent Kinetic Energy in Diel Vertical Migrations: Comparison of ANSYS Fluent Model to Measurements

    NASA Astrophysics Data System (ADS)

    Dean, Cayla; Soloviev, Alexander; Hirons, Amy; Frank, Tamara; Wood, Jon

    2015-04-01

    Recent studies suggest that diel vertical migrations of zooplankton may have an impact on ocean mixing, though details are not completely clear. A strong sound scattering layer of zooplankton undergoing diel vertical migrations was observed in Saanich Inlet, British Colombia, Canada by Kunze et al. (2006). In this study, a shipboard 200-kHz echosounder was used to track vertical motion of the sound scattering layer, and microstructure profiles were collected to observe turbulence. An increase of dissipation rate of turbulent kinetic energy by four to five orders of magnitude was measured during diel vertical migrations of zooplankton in one case (but not observed during other cases). A strong sound scattering layer undergoing diel vertical migration was also observed in the Straits of Florida via a bottom mounted acoustic Doppler current profiler at 244 m isobath. A 3-D non-hydrostatic computational fluid dynamics model with Lagrangian particle injections (a proxy for migrating zooplankton) via a discrete phase model was used to simulate the effect of diel vertical migrations on the turbulence for both Saanich Inlet and the Straits of Florida. The model was initialized with idealized (but based on observation) density and velocity profiles. Particles, with buoyancy adjusted to serve as a proxy for vertically swimming zooplankton, were injected to simulate diel vertical migration cycles. Results of models run with extreme concentrations of particles showed an increase in dissipation rate of turbulent kinetic energy of approximately five orders of magnitude over background turbulence during migration of particles in both Saanich Inlet and the Straits of Florida cases (though direct relation of the turbulence produced by buoyant particles and swimming organisms isn't straightforward). This increase was quantitatively consistent, with turbulence measurements by Kunze et al. (2006). When 10 times fewer particles were injected into the model, the effect on dissipation

  2. AUV Mapping and ROV Exploration of Los Frailes Submarine Canyon, Cabo Pulmo National Marine Park, Baja California Sur, Mexico

    NASA Astrophysics Data System (ADS)

    Troni, G.; Caress, D. W.; Graves, D.; Thomas, H. J.; Thompson, D.; Barry, J. P.; Aburto-Oropeza, O.; Johnson, A. F.; Lundsten, L.

    2015-12-01

    Los Frailes submarine canyon is located at the south boundary of the Cabo Pulmo National Marine Park on the southeast tip of the Baja California Peninsula. During the Monterey Bay Aquarium Research Institute (MBARI) 2015 Gulf of California expedition we used an autonomous underwater vehicle (AUV) to map this canyon from 50 m to 450 m depths, and then explored the canyon with a small remotely operated vehicle (ROV). This three day R/V Rachel Carson cruise was a collaboration with the Center for Marine Biodiversity and Conservation at Scripps Institution of Oceanography and the Centro para la Biodiversidad Marina y la Conservación in La Paz. The MBARI AUV D. Allan B. collected high resolution bathymetry, sidescan, and subbottom profiles of Los Frailes submarine canyon and part of the north Cabo Pulmo deep reef. In order to safely generate a 1-m lateral resolution multibeam bathymetry map in the nearshore high relief terrain, the mapping operations consisted of an initial short survey following the 100-m isobath followed by a series of short, incremental AUV missions located on the deep edge of the new AUV bathymetry. The MBARI Mini-ROV was used to explore the submarine canyon within the detailed map created by the MBARI AUV. The Mini-ROV is a 1.2-m-long, 350 kg, 1,500-m-depth-rated ROV designed and constructed by MBARI. It is controlled by six 600-watt thrusters and is equipped with a high-definition video camera and navigation sensors. This small ROV carries less accurate, lower cost navigation sensors than larger vehicles. We implemented new algorithms to localize combining Doppler velocity log sensor data and low-cost MEMS-based inertial sensor data with sporadic ultra-short baseline position measurements to provide a high accuracy position estimation. The navigation performance allowed us to colocate the ROV video imagery with the 1-m resolution bathymetric map of the submarine canyon. Upper Los Frailes Canyon is rugged and, aside from small sand pockets along

  3. Observations of large-amplitude cross-shore internal bores near the shelf break, Santa Monica Bay, CA

    USGS Publications Warehouse

    Noble, M.A.; Xu, J. P.

    2003-01-01

    Two sets of moorings were deployed along a cross-shelf transect in central Santa Monica bay for four months in the winter of 1998-1999. Both sites had an array of instruments attached to tripods set on the seafloor to monitor currents over the entire water column, surface waves, near-bed temperature, water clarity and suspended sediment. A companion mooring had temperature sensors spaced approximately 10 m apart to measure temperature profiles between the surface and the seafloor. One array was deployed in 70 m of water at a site adjacent to the shelf break, just northwest of a major ocean outfall. The other was deployed on the mid shelf in 35 m of water approximately 6 km from the shelf break site. The subtidal currents in the region flowed parallel to the isobaths with fluctuating time scales around 10 days, a typical coastal-ocean pattern. However, during the falling phase of the barotropic spring tide, sets of large-amplitude, sheared cross-shore current pulses with a duration of 2-5 h were observed at the shelf break site. Currents in these pulses flowed exclusively offshore in a thin layer near the bed with amplitudes reaching 30-40 cm/s. Simultaneously, currents with amplitudes around 15-20 cm/s flowed exclusively onshore in the thicker layer between the offshore flow layer and the sea surface. The net offshore transport was about half the onshore transport. Near-surface isotherms were depressed 30-40 m. These pulses were likely internal bores generated by tidal currents. Bed stresses associated with these events exceeded 3 dynes/cm2. These amplitudes are large enough to resuspend and transport not only fine-grained material, but also medium to coarse sands from the shelf toward the slope. Consequently, the seafloor over the shelf break was swept clear of fine sediments. The data suggest that the internal bores dissipate and are reduced in amplitude as they propagate across this relatively narrow shelf. There is evidence that they reach the 35 m site, but

  4. The influence of Congo River discharges in the surface and deep layers of the Gulf of Guinea

    NASA Astrophysics Data System (ADS)

    Vangriesheim, Annick; Pierre, Catherine; Aminot, Alain; Metzl, Nicolas; Baurand, François; Caprais, Jean-Claude

    2009-12-01

    The main feature of the Congo-Angola margin in the Gulf of Guinea is the Congo (ex-Zaire) deep-sea fan composed of a submarine canyon directly connected to the Congo River, a channel and a [sediment] lobe area. During the multi-disciplinary programme called BIOZAIRE conducted by Ifremer from 2000 to 2005, two CTD-O 2 sections with discrete water column samples were performed (BIOZAIRE3 cruise: 2003-2004) to study the influence of the Congo River discharges, both in the surface layer and in the deep and near-bottom layers. The surface layer water is greatly diluted with river water that has a heavy particle load. The deep layer is affected by episodic turbidity currents that flow in the deep Congo channel and reach deep areas far from the coast. Previous studies revealed deep anomalies in oxygen (deficit) and nutrient (excess) concentrations at ˜4000 m depth and assumed that they resulted from mineralisation of the particulate organic matter from the Congo River. The BIOZAIRE3 sections were designed to explore these phenomena in more detail near the Congo channel. Oxygen and nutrients were measured as well as additional parameters, including stable isotopes of oxygen and carbon, dissolved inorganic carbon and pH. For the surface layer, the effect of the Congo River was studied with reference to salinity. Deviations from the theoretical dilution of various inorganic solutes suggested the occurrence of mineralisation and consumption processes. For the deep layer, the network of CTD-O 2 stations gave a more detailed description of the deep anomalies than in previous studies. From the east-west section, anomalies appeared on the bottom at 4000 m depth and became slightly shallower when they spread to the west. They were also present north and south on the bottom along the 4000 m isobath. In these deep waters, the decrease in the δ 13C values of dissolved inorganic carbon confirmed that the mineralisation of organic matter plays a role in generating these anomalies

  5. Ship Shoal as a prospective borrow site for barrier island restoration, coastal south-central Louisiana, Usa: Numerical wave modeling and field measurements of hydrodynamics and sediment transport

    USGS Publications Warehouse

    Stone, G.W.; Pepper, D.A.; Xu, Jie; Zhang, X.

    2004-01-01

    Ship Shoal, a transgressive sand body located at the 10 m isobath off south-central Louisiana, is deemed a potential sand source for restoration along the rapidly eroding Isles Dernieres barrier chain and possibly other sites in Louisiana. Through numerical wave modeling we evaluate the potential response of mining Ship Shoal on the wave field. During severe and strong storms, waves break seaward of the western flank of Ship Shoal. Therefore, removal of Ship Shoal (approximately 1.1 billion m3) causes a maximum increase of the significant wave height by 90%-100% and 40%-50% over the shoal and directly adjacent to the lee of the complex for two strong storm scenarios. During weak storms and fair weather conditions, waves do not break over Ship Shoal. The degree of increase in significant wave height due to shoal removal is considerably smaller, only 10%-20% on the west part of the shoal. Within the context of increasing nearshore wave energy levels, removal of the shoal is not significant enough to cause increased erosion along the Isles Dernieres. Wave approach direction exerts significant control on the wave climate leeward of Ship Shoal for stronger storms, but not weak storms or fairweather. Instrumentation deployed at the shoal allowed comparison of measured wave heights with numerically derived wave heights using STWAVE. Correlation coefficients are high in virtually all comparisons indicating the capability of the model to simulate wave behavior satisfactorily at the shoal. Directional waves, currents and sediment transport were measured during winter storms associated with frontal passages using three bottom-mounted arrays deployed on the seaward and landward sides of Ship Shoal (November, 1998-January, 1999). Episodic increases in wave height, mean and oscillatory current speed, shear velocity, and sediment transport rates, associated with recurrent cold front passages, were measured. Dissipation mechanisms included both breaking and bottom friction due to

  6. Small-scale distribution of deep-sea demersal nekton and other megafauna in the Charlie-Gibbs Fracture Zone of the Mid-Atlantic Ridge

    NASA Astrophysics Data System (ADS)

    Felley, J. D.; Vecchione, M.; Wilson, R. R., Jr.

    2008-01-01

    Videotapes from manned submersibles diving in the area of the Charlie-Gibbs Fracture Zone of the Mid-Atlantic Ridge were used to investigate the distribution of fishes, large crustaceans, epifaunal and sessile organisms, and environmental features along a series of transects. Submersibles MIR 1 and MIR 2 conducted paired dives in an area of mixed sediment and rock (beginning depth ca. 3000 m) and on a large pocket of abyssal-like sediments (depth ca. 4000 m). In the shallower area, the submersibles passed over extremely heterogeneous terrain with a diversity of nekton, epifaunal forms and sessile forms. In the first pair of dives, MIR 1 rose along the Mid-Atlantic Ridge from 3000 to 1700 m, while MIR 2 remained near the 3000 m isobath. Nekton seen in these relatively shallow dives included large and small macrourids (genus Coryphaenoides), shrimp (infraorder Penaeidea), Halosauropsis macrochir, Aldrovandia sp., Antimora rostrata, and alepocephalids. The last two were more characteristic of the upper areas of the slope reached by MIR 1, as it rose along the Mid-Atlantic Ridge to depths less than 3000 m. Distributions of some forms seemed associated with depth and/or the presence of hard substrate. Sessile organisms such as sponges and large cnidaria were more likely to be found in rocky areas. The second pair of dives occurred in an abyssal area and the submersibles passed over sediment-covered plains, with little relief and many fewer countable organisms and features. The most evident of these were holes, mounds, small cerianthid anemones, small macrourids and the holothurian Benthodytes sp. A few large macrourids and shrimp also were seen in these deeper dives, as well as squat lobsters ( Munidopsis sp.). Sponges and larger cnidaria were mostly associated with a few small areas of rocky substrate. Holes and mounds showed distributions suggesting large-scale patterning. Over all dives, most sessile and epifaunal forms showed clumped distributions. However, large

  7. Spatial variability of shelf sediments in the STRATAFORM natural laboratory, Northern California

    USGS Publications Warehouse

    Goff, J.A.; Wheatcroft, R.A.; Lee, H.; Drake, D.E.; Swift, D.J.P.; Fan, S.

    2002-01-01

    The "Correlation Length Experiment", an intensive box coring effort on the Eel River shelf (Northern California) in the summer of 1997, endeavored to characterize the lateral variability of near-surface shelf sediments over scales of meters to kilometers. Coring focused on two sites, K60 and S60, separated by ??? 15 km along the 60 m isobath. The sites are near the sand-to-mud transition, although K60 is sandier owing to its proximity to the Eel River mouth. Nearly 140 cores were collected on dip and strike lines with core intervals from < 10m to 1 km. Measurements on each core included bulk density computed from gamma-ray attenuation, porosity converted from resistivity measurements, and surficial grain size. Grain size was also measured over the full depth range within a select subset of cores. X-radiograph images were also examined. Semi-variograms were computed for strike, dip, and down-hole directions at each site. The sand-to-mud transition exerts a strong influence on all measurements: on average, bulk density increases and porosity decreases with regional increases in mean grain size. Analysis of bulk density measurements indicates very strong contrasts in the sediment variability at K60 and S60. No coherent bedding is seen at K60; in the strike direction, horizontal variability is "white" (fully uncorrelated) from the smallest scales examined (a few meters) to the largest (8 km), with a variance equal to that seen within the cores. In contrast, coherent bedding exists at S60 related to the preservation of the 1995 flood deposit. A correlatable structure is found in the strike direction with a decorrelation distance of ??? 800 m, and can be related to long-wavelength undulations in the topography and/or thickness of the flood layer or overburden. We hypothesize that the high degree of bulk density variability at K60 is a result of more intense physical reworking of the seabed in the sandier environment. Without significant averaging, the resistivity

  8. The influence of shelfbreak forcing on the alongshelf penetration of the Danube buoyant water, Black sea

    NASA Astrophysics Data System (ADS)

    Yankovsky, Alexander E.; Lemeshko, Evgeny M.; Ilyin, Yuriy P.

    2004-06-01

    The buoyancy-driven coastal current propagating along the western coast in the Black Sea is forced by the discharge of several major European rivers including the Danube, Dnepr and South Bug. In this study, we present observational evidence that the buoyant water alongshelf penetration is strongly affected by shelfbreak mesoscale features associated with the Rim Current dynamics. The Rim Current is a major element of the Black Sea general circulation, typically following isobaths over the upper-to-middle slope. Two hydrographic surveys conducted in 1992 and 1994 have been chosen among available archive data for the detailed analysis. In both years, though Danube buoyant discharge was similar prior to the beginning of shipboard observations (varying around 7000 m 3 s -1), the buoyant water exhibited very different downstream (that is, in the direction of Kelvin wave) penetration. In 1992, it spread all the way around the southwestern corner of the Black Sea basin and then further eastward past the Bosporus Strait. In contrast, its downstream penetration was blocked in 1994 and buoyant water did not even reach Cape Kaliakra on the Bulgarian coast. This difference was related to the shelfbreak processes. In 1992, the cyclonic meander of the Rim Current merged with the coastal buoyant water thus promoting its advection from Cape Kaliakra downstream. In 1994, a strong anticyclone in the southwestern corner of the Black Sea completely blocked the propagation of a buoyancy-driven current past Cape Kaliakra. In addition, another anticyclone in the northwestern part of the sea advected buoyant water offshore to the central area of the northwestern shelf. The positions of anticyclonic eddies during a period of observations was confirmed by remote sensing data. As these and other examples indicate, coastal buoyancy driven currents can be effectively blocked and dispersed offshore by the shelfbreak anticyclones if the shelf width allows their interaction with buoyant water

  9. Size distribution of particles and zooplankton across the shelf-basin system in Southeast Beaufort Sea: combined results from an Underwater Vision Profiler and vertical net tows

    NASA Astrophysics Data System (ADS)

    Forest, A.; Stemmann, L.; Picheral, M.; Burdorf, L.; Robert, D.; Fortier, L.; Babin, M.

    2011-11-01

    The size distribution and mean spatial trends of large particles (>100 μm, in equivalent spherical diameter, ESD) and mesozooplankton were investigated across the Mackenzie Shelf (Southeast Beaufort Sea, Arctic Ocean) in July-August 2009. Our main objective was to combine results from an Underwater Vision Profiler 5 (UVP5) and traditional net tows (200 μm mesh size) to characterize the structural diversity and functioning of the Arctic shelf-basin ecosystem and to assess the large-scale correspondence between the two methodological approaches. The core dataset comprised 154 UVP5 profiles and 29 net tows conducted in the shelf (<100 m isobath), slope (100-1000 m) and basin (>1000 m) regions of the study area. The mean abundance of total particles and zooplankton in the upper water column (<75 m depth) declined exponentially with increasing distance from shore. Vertical and latitudinal patterns in total particle concentration followed those of chlorophyll-a (chl-a) concentration, with maximum values between 30 and 70 m depth. Based on the size-spectra derived from the UVP5 dataset, living organisms (0.1-10 mm ESD) accounted for an increasingly large proportion of total particle abundance (from 0.1% to > 50 %) when progressing offshore and as the ESD of particles was increasing. Both the UVP5 and net tows determined that copepods dominated the zooplankton community (~78-94 % by numbers) and that appendicularians were generally the second most abundant group (~1-11 %). The vertical distribution patterns of copepods and appendicularians indicated a close association between primary production and the main grazers. Manual taxonomic counts and ZooScan image analyses shed further light on the size-structure and composition of the copepod community - which was dominated at ~95 % by a guild of 10 typical taxa. The size distributions of copepods, as evaluated with the 3 methods (manual counts, ZooScan and UVP5), showed consistent patterns co-varying in the same order of

  10. Size distribution of particles and zooplankton across the shelf-basin system in southeast Beaufort Sea: combined results from an Underwater Vision Profiler and vertical net tows

    NASA Astrophysics Data System (ADS)

    Forest, A.; Stemmann, L.; Picheral, M.; Burdorf, L.; Robert, D.; Fortier, L.; Babin, M.

    2012-04-01

    The size distribution and mean spatial trends of large particles (>100 μm, in equivalent spherical diameter, ESD) and mesozooplankton were investigated across the Mackenzie Shelf (southeast Beaufort Sea, Arctic Ocean) in July-August 2009. Our main objective was to combine results from an Underwater Vision Profiler 5 (UVP5) and traditional net tows (200 μm mesh size) to characterize the structural diversity and functioning of the Arctic shelf-basin ecosystem and to assess the large-scale correspondence between the two methodological approaches. The core dataset comprised 154 UVP5 profiles and 29 net tows conducted in the shelf (<100 m isobath), slope (100-1000 m) and basin (>1000 m) regions of the study area. The mean abundance of total particles and zooplankton in the upper water column (<75 m depth) declined exponentially with increasing distance from shore. Vertical and latitudinal patterns in total particle concentration followed those of chlorophyll a (chl a) concentration, with maximum values between 30 and 70 m depth. Based on the size-spectra derived from the UVP5 dataset, living organisms (0.1-10 mm ESD) accounted for an increasingly large proportion of total particle abundance (from 0.1 % to >50 %) when progressing offshore and as the ESD of particles was increasing. Both the UVP5 and net tows determined that copepods dominated the zooplankton community (~78-94 % by numbers) and that appendicularians were generally the second most abundant group (~1-11 %). The vertical distribution patterns of copepods and appendicularians indicated a close association between primary production and the main grazers. Manual taxonomic counts and ZooScan image analyses shed further light on the size-structure and composition of the copepod community - which was dominated at ~95 % by a guild of 10 typical taxa. The size distributions of copepods, as evaluated with the 3 methods (manual counts, ZooScan and UVP5), showed consistent patterns co-varying in the same order of

  11. Depositional sequences in a foreland basin (north-western domain of the continental Duero basin, Spain)

    NASA Astrophysics Data System (ADS)

    Herrero, Antonio; Alonso-Gavilán, Gaspar; Colmenero, Juan Ramón

    2010-01-01

    The Cenozoic record of the north-western domain of the Duero basin is articulated at the surface through a set of continental depositional sequences called, from base to top, the Vegaquemada sequence, the Candanedo sequence, and the Barrillos sequence. These depositional sequences were deposited in continental sedimentary environments. The deposition of the first sequence occurred through a fluvial system with floodplains cut by low-sinuosity channels. The Vegaquemada sequence was developed between the Middle Eocene and the Early Agenian. The second sequence was formed by a set of highly efficient transport alluvial fans that evolved laterally towards fluvial systems with low-sinuosity fluvial channels and an extensive floodplain, where several types of palaeosols were formed. This sequence developed between the Early Agenian and the Late Vallesian. The third unit-the Barrillos sequence (between the Late Vallesian and the Turolian/Ruscinian transition), was generated by a set of highly efficient transport alluvial fans dominated by low-sinuosity fluvial channels. In subsurface geology, seismic and well data are used to rebuild the stratigraphic architecture. The two basal depositional sequences can be identified with two seismic units: the Palaeogene Seismic Unit (PgSU) and the Neogene Seismic Unit (NgSU), respectively. In the present work, we obtained the isovelocity, isochron, and isobath maps for the top and base of the two Cenozoic units. The Palaeozoic (PzSU) and Mesozoic (MzSU) seismic units are found under these two units. Through study of the logs of the various boreholes, it was only possible to analyse the upper 700 m of the Candanedo Sequence (NgSU), without encompassing the total thickness of the unit. Several middle-order sequences were differentiated, in general showing a sequential fining-upwards evolutionary character. Additionally, for the boreholes analysed two main types of electrofacies were identified, both representing fluvial channels and

  12. Additional Investigations of Ice Shape Sensitivity to Parameter Variations

    NASA Technical Reports Server (NTRS)

    Miller, Dean R.; Potapczuk, Mark G.; Langhals, Tammy J.

    2006-01-01

    A second parameter sensitivity study was conducted at the NASA Glenn Research Center's Icing Research Tunnel (IRT) using a 36 in. chord (0.91 m) NACA-0012 airfoil. The objective of this work was to further investigate the feasibility of using ice shape feature changes to define requirements for the simulation and measurement of SLD and appendix C icing conditions. A previous study concluded that it was feasible to use changes in ice shape features (e.g., ice horn angle, ice horn thickness, and ice shape mass) to detect relatively small variations in icing spray condition parameters (LWC, MVD, and temperature). The subject of this current investigation extends the scope of this previous work, by also examining the effect of icing tunnel spray-bar parameter variations (water pressure, air pressure) on ice shape feature changes. The approach was to vary spray-bar water pressure and air pressure, and then evaluate the effects of these parameter changes on the resulting ice shapes. This paper will provide a description of the experimental method, present selected experimental results, and conclude with an evaluation of these results.

  13. Preparation and evaluation of naringenin-loaded sulfobutylether-β-cyclodextrin/chitosan nanoparticles for ocular drug delivery.

    PubMed

    Zhang, Ping; Liu, Xin; Hu, Wenjing; Bai, Yan; Zhang, Liangke

    2016-09-20

    The aim of this study was to prepare and characterize the naringenin-loaded sulfobutylether-β-cyclodextrin/chitosan nanoparticles (Nag-CD/CS-NPs) and evaluate their potential for the topical ophthalmic delivery. Naringenin was first complexed with sulfobutylether-β-cyclodextrin (SBE-β-CD), which can significantly enhance the solubility of poorly soluble drugs. Then, nanoparticles were prepared by ionic gelation of chitosan with SBE-β-CD, and their in vitro and vivo properties were investigated, respectively. The resulting nanoparticles showed an average size of 446.4±112.8nm and zeta potential of +22.5±4.91mV with predominant spherical in shape. The FT-IR and DSC confirmed the formation of Nag-CD/CS-NPs. The in vitro release study indicated that Nag-CD/CS-NPs achieved moderate sustained-release effect, and the in vivo study revealed that the prepared nanoparticles was nonirritating to rabbit's eye and had better ability to prolong the residence time than the naringenin suspension, which can significantly increase naringenin bioavailability in the aqueous humor. In conclusion, the developed CD/CS nanoparticles offer a potential alternative for the ocular administration of poorly soluble drugs. PMID:27261746

  14. Development Status of the NASA 30-cm Ion Thruster and Power Processor

    NASA Technical Reports Server (NTRS)

    Sovey, James S.; Haag, Thomas W.; Hamley, John A.; Mantenieks, Maris A.; Patterson, Michael J.; Pinero, Luis R.; Rawlin, Vincent K.; Kussmaul, Michael T.; Manzella, David H.; Myers, Roger M.

    1994-01-01

    Xenon ion propulsion systems are being developed by NASA Lewis Research Center and the Jet Propulsion Laboratory to provide flight qualification and validation for planetary and earth-orbital missions. In the ground-test element of this program, light-weight (less than 7 kg), 30 cm diameter ion thrusters have been fabricated, and preliminary design verification tests have been conducted. At 2.3 kW, the thrust, specific impulse, and efficiency were 91 mN, 3300 s, and 0.65, respectively. An engineering model thruster is now undergoing a 2000 h wear-test. A breadboard power processor is being developed to operate from an 80 V to 120 V power bus with inverter switching frequencies of 50 kHz. The power processor design is a pathfinder and uses only three power supplies. The projected specific mass of a flight unit is about 5 kg/kW with an efficiency of 0.92 at the full-power of 2.5 kW. Preliminary integration tests of the neutralizer power supply and the ion thruster have been completed. Fabrication and test of the discharge and beam/accelerator power stages are underway.

  15. Relationship of Ordovician and Silurian reservoir development to unconformities at Midland farms and Inez fields, Andrews County, Texas

    SciTech Connect

    Mear, C.E.; Becher, J.W.

    1986-03-01

    Hydrocarbons are being produced at Midland Farms and Inez fields from Ellenburger dolomites and Fusselman limestones. Reservoirs developed there during Ordovician and Silurian periods of minor folding and faulting, followed by regional uplift and subaerial exposure of the carbonates. Vuggy, cavernous, and solution-enlarged fracture porosity was developed in the Lower Ordovician Ellenburger dolomites prior to deposition of the overlying Middle Ordovician shales of the Simpson Group. Vuggy and cavernous porosity developed in the Lower Silurian Fusselman crinoid-ostracod-pellet packstones and grainstones before deposition of the overlying Silurian Wristen shales. Montoya siliceous limestones of Late Ordovician age were truncated during a period of pre-Silurian erosion, but porosity development is not indicated in Montoya rock cuttings. Only minor amounts of porosity developed in the Lower to Middle Devonian Thirty-one packstones and wackestones as a result of uplift and erosion in the Middle Devonian. Regional compression during the post-Mississippian enhanced doubly plunging anticlines now having up to 91 m (300 ft) of closure at the Ellenburger through Thirty-one formations at Midland Farms and Inez fields. Fractures may have developed in Paleozoic limestones during this period of folding, but reservoir enhancement appears to have resulted only in the Ellenburger dolomites. Representative porosity measurements of the Ellenburger and Fusselman pay zones cannot be made from wireline log calculations, due to the fractured, vuggy, and cavernous nature of the porosity.

  16. SUBSTELLAR-MASS COMPANIONS TO THE K-GIANTS HD 240237, BD +48 738, AND HD 96127

    SciTech Connect

    Gettel, S.; Wolszczan, A.; Niedzielski, A.; Nowak, G.; Adamow, M.; Zielinski, P.; Maciejewski, G. E-mail: alex@astro.psu.edu

    2012-01-20

    We present the discovery of substellar-mass companions to three giant stars by the ongoing Penn State-Torun Planet Search conducted with the 9.2 m Hobby-Eberly Telescope. The most massive of the three stars, K2-giant HD 240237, has a 5.3 M{sub J} minimum mass companion orbiting the star at a 746 day period. The K0-giant BD +48 738 is orbited by a {>=}0.91 M{sub J} planet which has a period of 393 days and shows a nonlinear, long-term radial velocity (RV) trend that indicates a presence of another, more distant companion, which may have a substellar mass or be a low-mass star. The K2-giant HD 96127 has a {>=}4.0 M{sub J} mass companion in a 647 day orbit around the star. The two K2-giants exhibit a significant RV noise that complicates the detection of low-amplitude, periodic variations in the data. If the noise component of the observed RV variations is due to solar-type oscillations, we show, using all the published data for the substellar companions to giants, that its amplitude is anti-correlated with stellar metallicity.

  17. New Cascadia subduction zone tsunami inundation modeling to guide relocation of coastal infrastucture for Indian tribes on the northern Washington coast

    NASA Astrophysics Data System (ADS)

    Walsh, T. J.; LeVeque, R. J.; Adams, L. M.; Schelling, J.; Gonzalez, F. I.; Cakir, R.

    2015-12-01

    There have been advances in understanding the potential for great tsunamigenic earthquakes on the Cascadia Subduction Zone, motivating an effort to update the assessment of tsunami hazards on the Washington coast. Fine resolution (1/3 arc-second) digital elevation models (DEMs) of the Strait of Juan de Fuca and northern Olympic Peninsula have recently been made available, and coastal Indian tribes (Quinault, Hoh, and Quileute) have made plans to move important infrastructure out of their tsunami hazard zones. We have made numerical simulations of tsunamis incident on the Quinault, Hoh, Quileute, and Makah Reservations and adjacent coast with the GeoClaw numerical model [http://depts.washington.edu/clawpack/geoclaw/] for a local tsunami generated by a 9.1M Cascadia Subduction Zone earthquake, designated L1 by Witter and others (DOGAMI Special Paper 43). This scenario is estimated to have `2% probability of nonexceedance in 50 years, which would be comparable to the International Building Code standard for seismic loading on structures of high importance, and provides appropriate guidance to the affected communities for siting of their significant infrastructure.

  18. Tobacco Smoking Habits Among First Year Medical Students, University of Prishtina, Kosovo: Cross-sectional Study

    PubMed Central

    Çuperjani, Frederik; Elezi, Shkëlzen; Lila, Albert; Daka, Qëndresë; Dakaj, Qëndrim; Gashi, Sanije

    2015-01-01

    Introduction: Tobacco smoking remains the leading causes of preventable morbidity and mortality in the world, requiring intensified national and international public health response. World Health Organization (WHO) has urged health professional organizations to encourage and support their members to be models for not using tobacco products and promote tobacco-free culture. Healthcare students are the future authority of the health society, they are in a position to play a vital role and have impact on social norms related to smoking. Aim: To determine the prevalence of tobacco smoking among healthcare students of Medical Faculty, University of Prishtina in Kosovo, so that recommendations can be made for its cessation among healthcare providers and thereafter the community. Materials and methods: Descriptive cross-sectional study was conducted using self-administrated questionnaire prepared for this purpose. A total of 284 first year healthcare students of Medical Faculty, University of Prishtina in Kosovo were enrolled in the study. The data were analyzed using SPSS 22. Results: All respondents completed the questionnaire, giving a response rate of 100% (general medicine=180, dentistry = 104). The prevalence of students who have ever smoked was 53.2%. However, only 8.9% (9.1% M vs. 8.7% F) of the general medicine students and 5.8% (4.8% M vs. 6.5% F) of dentistry students declared that smoke tobacco every day. Overall, the research shows that the prevalence of occasional smokers among medical students in Kosova is quite high. PMID:26236164

  19. Radar imaging of glaciovolcanic stratigraphy, Mount Wrangell caldera, Alaska - Interpretation model and results

    NASA Technical Reports Server (NTRS)

    Clarke, Garry K. C.; Cross, Guy M.; Benson, Carl S.

    1989-01-01

    Glaciological measurements and an airborne radar sounding survey of the glacier lying in Mount Wrangell caldera raise many questions concerning the glacier thermal regime and volcanic history of Mount Wrangell. An interpretation model has been developed that allows the depth variation of temperature, heat flux, pressure, density, ice velocity, depositional age, and thermal and dielectric properties to be calculated. Some predictions of the interpretation model are that the basal ice melting rate is 0.64 m/yr and the volcanic heat flux is 7.0 W/sq m. By using the interpretation model to calculate two-way travel time and propagation losses, radar sounding traces can be transformed to give estimates of the variation of power reflection coefficient as a function of depth and depositional age. Prominent internal reflecting zones are located at depths of approximately 59-91m, 150m, 203m, and 230m. These internal reflectors are attributed to buried horizons of acidic ice, possibly intermixed with volcanic ash, that were deposited during past eruptions of Mount Wrangell.

  20. Statistical and geostatistical features of streambed hydraulic conductivities in the Platte River, Nebraska

    NASA Astrophysics Data System (ADS)

    Chen, Xunhong

    2005-09-01

    This paper presents streambed hydraulic conductivities of the Platte River from south-central to eastern Nebraska. The hydraulic conductivities were determined from river channels using permeameter tests. The vertical hydraulic conductivities ( K v ) from seven test sites along this river in south-central Nebraska belong to one statistical population. Its mean value is 40.2 m/d. However, the vertical hydraulic conductivities along four transects of the Ashland test site in eastern Nebraska have lower mean values, are statistically different from the K v values in south-central Nebraska, and belong to two different populations with mean values of 20.7 and 9.1 m/d, respectively. Finer sediments carried from the Loup River and Elkhorn River watersheds to the eastern reach of the Platte River lowers the vertical hydraulic conductivity of the streambed. Correlation coefficients between water depth and K v values along a test transect indicates a positive correlation a larger K v usually occurs in the part of channel with deeper water. Experimental variograms derived from the vertical hydraulic conductivities for several transects across the channels of the Platte River show periodicity of spatial correlation, which likely result from periodic variation of water depth across the channels. The sandy to gravelly streambed contains very local silt and clay layers; spatially continuous low-permeability streambed was not observed in the river channels. The horizontal hydraulic conductivities were larger than the vertical hydraulic conductivities for the same test locations.

  1. Room-Temperature Fabrication of a Flexible Thermoelectric Generator Using a Dry-Spray Deposition System

    NASA Astrophysics Data System (ADS)

    Song, Dae-Seob; Choi, Jung-Oh; Ahn, Sung-Hoon

    2016-04-01

    We present a flexible thermoelectric (TE) generator with titanium dioxide (TiO2), antimony (Sb), and tellurium (Te) powders fabricated by a nanoparticle deposition system (NPDS). NPDS is a novel low-energy consumption dry-spray method that enables the deposition of inorganic materials on substrates at room temperature and under low vacuum. TiO2 nanopowders were dispersed on a TE powder for improved adhesion between TE films and the substrate. Film morphologies were investigated using field-emission scanning electron microscopy, and the phase structure was analyzed by x-ray diffraction. A TE leg, deposited with 3 wt.% TiO2 content, had the largest Seebeck coefficient of approximately 160 μV/K. The prototype TE generator consisted of 16 TE legs linked by silver interconnects over an area of 20 mm × 60 mm. The prototype produced a voltage of 48.91 mV and a maximum power output of 0.18 μW from a temperature gradient of 20 K. The values are comparable to that of conventional methods. These results suggest that flexible TE generators can be fabricated by energy efficient methods, although internal and contact resistances must be decreased.

  2. Measurement of nitrogen in the body using a commercial PGNAA system--phantom experiments.

    PubMed

    Chichester, D L; Empey, E

    2004-01-01

    An industrial prompt-gamma neutron activation analysis (PGNAA) system, originally designed for the real-time elemental analyses of bulk coal on a conveyor belt, has been studied to examine the feasibility of using such a system for body composition analysis. Experiments were conducted to measure nitrogen in a simple, tissue equivalent phantom comprised of 2.7 wt% of nitrogen. The neutron source for these experiments was 365 MBq (18.38 microg) of 252Cf located within an engineered low Z moderator and it yielded a dose rate in the measurement position of 3.91 mSv/h; data were collected using a 2780 cm(3) NaI(Tl) cylindrical detector with a digital signal processor and a 512 channel MCA. Source, moderator and detector geometries were unaltered from the system's standard configuration, where they have been optimized for considerations such as neutron thermalization, measurement sensitivity and uniformity, background radiation and external dose minimization. Based on net counts in the 10.8 MeV PGNAA nitrogen photopeak and its escape peaks the dose dependent nitrogen count rate was 11,600 counts/mSv with an uncertainty of 3.0% after 0.32 mSv (4.9 min), 2.0% after 0.74 mSv (11.4 min) and 1.0% after 3.02 mSv (46.4 min). PMID:14687637

  3. Sources of low-arsenic groundwater in the Bengal Basin: investigating the influence of the last glacial maximum palaeosol using a 115-km traverse across Bangladesh

    NASA Astrophysics Data System (ADS)

    Hoque, M. A.; McArthur, J. M.; Sikdar, P. K.

    2014-05-01

    Pollution of groundwater in the Bengal Basin (Bangladesh and West Bengal, India) by arsenic (As) puts at risk the health of more than 100 million consumers. Using 1,580 borehole lithological logs and published hydrochemistry on 2,387 wells, it was predicted that low-As (<10 μg/L) groundwater exists, in palaeo-interfluvial aquifers of brown sand capped by a protective palaeosol, beneath at least 45,000 km2 of the Bengal Basin. The aquifers were predicted to be at a depth of as little as 25 m below ground level (mbgl), and typically no more than 50 mbgl. The predictions were confirmed along an east-west traverse 115 km in length (i.e. across half of Bangladesh) by drilling 28 new boreholes to 91-m depth to reveal subsurface sedimentology, and by mapping As distribution in groundwater. The aquifers identified occur at typically <40 mbgl and so are accessible with local drilling methods. A protective palaeosol that caps the palaeo-interfluvial aquifers prevents downward movement into them of As-polluted groundwater present in shallower palaeo-channel aquifers and ensures that the palaeo-interfluvial aquifers will yield low-As groundwater for the foreseeable future. Their use, in place of the shallower As-polluted palaeo-channel aquifers, would rapidly mitigate the health risks from consumption of As-polluted groundwater.

  4. Efficacy of Two Larvasonic™ Units Against Culex Larvae and Effects on Common Aquatic Nontarget Organisms in Harris County, Texas.

    PubMed

    Fredregill, Chris L; Motl, Greg C; Dennett, James A; Bueno, Rudy; Debboun, Mustapha

    2015-12-01

    The Larvasonic™ Field Arm Mobile Wetlands Unit and SD-Mini were tested for efficacy against Culex larvae, and effects on aquatic nontarget organisms (NTO). The Field Arm provided 84.61% to 100% control of caged Culex larvae out to 0.91-m distance in shallow ditches and 60.45% control of Culex larvae at 0.61-m without any effects to caged NTO. Slow ditch treatment achieved 77.35% control compared to fast treatment (20.42%), whereas 77.65% control was obtained along edges of a neglected swimming pool, compared to near the middle (23.97%). In bucket tests, the SD-Mini provided >97% control of Culex and 85.35% reduction of immature giant water bugs, which decreased slightly (83.45%) over the monitoring period, which was not significantly different from cannibalistic damselflies (62.80%), with reduction of both being significantly higher than other NTO tested. There was a small (0.37%) reduction of dragonflies (naiads), due to cannibalism. Both Larvasonic units could effectively augment conventional larvicide operations in smaller areas without causing resistance within mosquito populations or harming NTO when used properly. PMID:26675460

  5. Rapid assessment of renal reserve in young adults by cystatin C

    PubMed Central

    FUHRMAN, DANA Y.; MAIER, PAULA S.; SCHWARTZ, GEORGE J.

    2014-01-01

    Background The kidney can increase glomerular filtration rate (GFR) in response to a protein load (renal reserve). In a pilot study of healthy young adults we examined renal reserve using changes in serum cystatin C (cysC). Methods Glomerular filtration rate was obtained using iohexol single slope plasma disappearance. To stimulate GFR, subjects ingested a beefburger containing 60 grams of protein. CysC was measured by immunonephelometry before and 125–141 minutes after protein loading. Results All subjects were found to have a normal iohexol plasma disappearance GFR with a mean of 104.6 ± 9.9 mL/min per 1.73 m2. CysC decreased in each subject after the meat meal. Baseline cysC-based estimated GFR was 98.1 ± 9.1 mL/min per 1.73 m2 with a mean increase of 12.0 ± 5.2 (p = 0.0003). Conclusions Our study showed a consistent decrease in serum cysC and increase in cysC-based estimated GFR following a protein load in young adults. Further studies are needed using renal clearance methods to confirm that cysC accurately determines renal reserve in patients with and without chronic kidney disease. PMID:23461550

  6. SEMICONDUCTOR INTEGRATED CIRCUITS: A fully integrated UHF RFID reader SoC for handheld applications in the 0.18 μm CMOS process

    NASA Astrophysics Data System (ADS)

    Jingchao, Wang; Chun, Zhang; Zhihua, Wang

    2010-08-01

    A low cost fully integrated single-chip UHF radio frequency identification (RFID) reader SoC for short distance handheld applications is presented. The SoC integrates all building blocks—including an RF transceiver, a PLL frequency synthesizer, a digital baseband and an MCU—in a 0.18 μm CMOS process. A high-linearity RX front-end is designed to handle the large self-interferer. A class-E power amplifier with high power efficiency is also integrated to fulfill the function of a UHF passive RFID reader. The measured maximum output power of the transmitter is 20.28 dBm and the measured receiver sensitivity is -60 dBm. The digital baseband including MCU core consumes 3.91 mW with a clock of 10 MHz and the analog part including power amplifier consumes 368.4 mW. The chip has a die area of 5.1 × 3.8 mm2 including pads.

  7. Potentiometric Urea Biosensor Based on an Immobilised Fullerene-Urease Bio-Conjugate

    PubMed Central

    Saeedfar, Kasra; Heng, Lee Yook; Ling, Tan Ling; Rezayi, Majid

    2013-01-01

    A novel method for the rapid modification of fullerene for subsequent enzyme attachment to create a potentiometric biosensor is presented. Urease was immobilized onto the modified fullerene nanomaterial. The modified fullerene-immobilized urease (C60-urease) bioconjugate has been confirmed to catalyze the hydrolysis of urea in solution. The biomaterial was then deposited on a screen-printed electrode containing a non-plasticized poly(n-butyl acrylate) (PnBA) membrane entrapped with a hydrogen ionophore. This pH-selective membrane is intended to function as a potentiometric urea biosensor with the deposition of C60-urease on the PnBA membrane. Various parameters for fullerene modification and urease immobilization were investigated. The optimal pH and concentration of the phosphate buffer for the urea biosensor were 7.0 and 0.5 mM, respectively. The linear response range of the biosensor was from 2.31 × 10−3 M to 8.28 × 10−5 M. The biosensor's sensitivity was 59.67 ± 0.91 mV/decade, which is close to the theoretical value. Common cations such as Na+, K+, Ca2+, Mg2+ and NH4+ showed no obvious interference with the urea biosensor's response. The use of a fullerene-urease bio-conjugate and an acrylic membrane with good adhesion prevented the leaching of urease enzyme and thus increased the stability of the urea biosensor for up to 140 days. PMID:24322561

  8. Large-scale traveling ionospheric disturbances observed using GPS receivers over high-latitude and equatorial regions

    NASA Astrophysics Data System (ADS)

    Idrus, Intan Izafina; Abdullah, Mardina; Hasbi, Alina Marie; Husin, Asnawi; Yatim, Baharuddin

    2013-09-01

    This paper presents the first results of large-scale traveling ionospheric disturbances (LSTIDs) observation during two moderate magnetic storm events on 28 May 2011 (SYM-H∼ -94 nT and Dst∼-80 nT) and 6 August 2011 (SYM-H∼-126 nT and Dst∼-113 nT) over the high-latitude region in Russia, Sweden, Norway, Iceland and Greenland and equatorial region in the Peninsular Malaysia using vertical total electron content (VTEC) from the Global Positioning System (GPS) observations measurement. The propagation of the LSTID signatures in the GPS TEC measurements over Peninsular Malaysia was also investigated using VTEC map. The LSTIDs were found to propagate both equatorward and poleward directions during these two events. The results showed that the LSTIDs propagated faster at high-latitude region with an average phase velocity of 1074.91 m/s than Peninsular Malaysia with an average phase velocity of 604.84 m/s. The LSTIDs at the high-latitude region have average periods of 150 min whereas the ones observed over Peninsular Malaysia have average periods of 115 min. The occurrences of these LSTIDs were also found to be the subsequent effects of substorm activities in the auroral region. To our knowledge, this is the first result of observation of LSTIDs over Peninsular Malaysia during the 24th solar cycle.

  9. Low cost composite materials for wind energy conversion systems

    SciTech Connect

    Weingart, O.

    1980-01-01

    Structural Composites Industries, Inc. (SCI) is developing new composite filament winding technology for low cost production of wind turbine generators (WTG). During 1977 the SCI TFT process was used to fabricate a 9072 kg (20,000 lb) filament-wound D-spar for a NASA/DOE 46 m (150 ft) composite wind turbine blade. In 1978 SCI designed a composite blade for the 91 m (300 ft) dia. NASA/DOE MOD-2 WTG. For the past year SCI has been under contract to NASA-Lewis Research Center to design and build two low cost 18 m (60 ft) blades for the 38 m (125 ft) dia. MOD-OA and to assess the applicability of the techniques developed for larger and smaller blades. SCI is also developing and constructing a 4-kW small wind energy conversion system (SWECS) for Rockwell International using low cost composites for the 9 m (31 ft) dia. rotor blades, 15 m (50 ft) tower and nacelle.

  10. Modeling Based Structural Insights into Biodegradation of the Herbicide Diuron by Laccase-1 from Ceriporiopsis subvermispora

    PubMed Central

    Vieira, Ana Carolina; Marschalk, Cidnei; Biavatti, Débora Carina; Lorscheider, Carla Andréia; Peralta, Rosane Marina; Seixas, Flavio Augusto Vicente

    2015-01-01

    The herbicide diuron (3-(3,4-dichlorophenyl)-1,1-dimethylurea) is used in many agricultural crops and non-crop areas worldwide, leading to the pollution of the aquatic environment by soil leaching. White rot fungi and its lignin modifying enzymes, peroxidases and laccases, are responsible for its degradation. Therefore, it is of interest to explore the potential use of Ceriporiopsis subvermispora laccase (CersuLac1) in the biotransformation of this herbicide by using its enzyme laccase. However, the structure of laccase from Ceriporiopsis subvermispora is still unknown. Hence, a model of laccase was constructed using homology modeling. The model was further used to dock p-methylbenzoate in the presence of four copper ions to analyze molecular basis of its binding and interaction. The ligand-protein interaction is stereo-chemically favorable in nature. The presence of the single protonated Lys457 was necessary for catalysis, being coordinated by a cupper ion. The best pose of diuron on CersuLac1 has a theoretical Ki of 2.91 mM. This is comparable to the KM values for laccases from other organisms with similar compounds. Thus, we document the insights for the potential use of laccase from Ceriporiopsis subvermispora in the biotransfrormation of diuron. PMID:26124565

  11. Surface waves generated by shallow underwater explosions

    NASA Technical Reports Server (NTRS)

    Falade, A.; Holt, M.

    1978-01-01

    Surface water waves generated by surface and near surface point explosions are calculated. Taking the impulse distribution imparted at the water surface by the explosion as the overriding mechanism for transferring energy of the explosive to surface wave motion, the linearized theory of Kranzer and Keller is used to obtain the wave displacement in the far field. The impulse distribution is obtained by integrating the pressure wave over an appropriate time interval on a horizontal surface just beneath the undisturbed water surface. For surface explosions, a modified form of the similarity method first used by Collins and Holt is used to obtain the flow field. In the case of submerged explosions, the flow field is estimated by making necessary modifications to Sedov's similarity solution to account for the venting that accompanies the interaction of the leading (blast) wave with the ocean surface. Surface waves generated by a charge at six depths of placement (0.15 m, 0.30 m, 0.61 m, 0.91 m, 1.37 m, 3.05 m) are considered in addition to surface explosions. The results seem to support the existence of an upper critical depth phenomenon (of the type already established for chemical explosions) for point (nuclear) explosions.

  12. The effect of hardhats on head and neck response to vertical impacts from large construction objects.

    PubMed

    Suderman, Bethany L; Hoover, Ryan W; Ching, Randal P; Scher, Irving S

    2014-12-01

    We evaluated the effectiveness of hardhats in attenuating head acceleration and neck force in vertical impacts from large construction objects. Two weight-matched objects (lead shot bag and concrete block) weighing 9.1 kg were dropped from three heights (0.91 m, 1.83 m and 2.74 m) onto the head of a 50th percentile male Hybrid III anthropomorphic test device (ATD). Two headgear conditions were tested: no head protection and an ANSI Type-I, Class-E hardhat. A third headgear condition (snow sport helmet) was tested at 1.83 m for comparison with the hardhat. Hardhats significantly reduced the resultant linear acceleration for the concrete block impacts by 70-95% when compared to the unprotected head condition. Upper neck compression was also significantly reduced by 26-60% with the use of a hardhat when compared to the unprotected head condition for the 0.91 and 1.83 m drop heights for both lead shot and concrete block drop objects. In this study we found that hardhats can be effective in reducing both head accelerations and compressive neck forces for large construction objects in vertical impacts. PMID:25215927

  13. Experimental assessment of theory for refraction of sound by a shear layer

    NASA Technical Reports Server (NTRS)

    Schlinker, R. H.; Amiet, R. K.

    1978-01-01

    The refraction angle and amplitude changes associated with sound transmission through a circular, open-jet shear layer were studied in a 0.91 m diameter open jet acoustic research tunnel. Free stream Mach number was varied from 0.1 to 0.4. Good agreement between refraction angle correction theory and experiment was obtained over the test Mach number, frequency and angle measurement range for all on-axis acoustic source locations. For off-axis source positions, good agreement was obtained at a source-to-shear layer separation distance greater than the jet radius. Measureable differences between theory and experiment occurred at a source-to-shear layer separation distance less than one jet radius. A shear layer turbulence scattering experiment was conducted at 90 deg to the open jet axis for the same free stream Mach numbers and axial source locations used in the refraction study. Significant discrete tone spectrum broadening and tone amplitude changes were observed at open jet Mach numbers above 0.2 and at acoustic source frequencies greater than 5 kHz. More severe turbulence scattering was observed for downstream source locations.

  14. An Experimental Investigation of Wind- and Mechanically Generated Short Wavelength Spilling Breakers

    NASA Astrophysics Data System (ADS)

    Diorio, J. D.; Liu, X.; Duncan, J. H.

    2006-11-01

    Short wavelength spilling breakers are studied in a wind wave tank that is 12.8 m long and 1.15 m wide and 0.91 m deep. The crest profile histories during breaking are measured with a photographic technique that employs a high-speed digital movie camera, a laser light sheet, and fluorescent dye. The photographic system is mounted on an instrument carriage that is set to move along the tank in phase with the crests of the breaking waves. In the first step in the experiment, breakers generated by the wind are measured at three wind speeds and three fetches at each wind speed. In the second step in the experiment, a mechanical wave maker is used without wind to generate a wave train consisting of a dominant wave and two unstable sidebands. The amplitudes and frequencies of these wave components are adjusted to create breakers at the various fetches and dominant wave frequencies found in the wind wave experiments. The similarities and differences between the ripple patterns at the crest during breaking between the wind wave and mechanical wave cases are discussed.

  15. Time-variable Aluminum Absorption in the Polar AR Ursae Majoris, and an Updated Estimate for the Mass of the White Dwarf

    NASA Astrophysics Data System (ADS)

    Bai, Yu; Justham, Stephen; Liu, JiFeng; Guo, JinCheng; Gao, Qing; Gong, Hang

    2016-09-01

    We present spectra of the extreme polar AR Ursae Majoris (AR UMa), which display a clear Al i absorption doublet, alongside spectra taken less than a year earlier in which that feature is not present. Re-examination of earlier SDSS spectra indicates that the Al i absorption doublet was also present ≈8 years before our first non-detection. We conclude that this absorbing material is unlikely to be on the surface of either the white dwarf (WD) or the donor star. We suggest that this Al i absorption feature arises in circumstellar material, perhaps produced by the evaporation of asteroids as they approach the hot WD. The presence of any remaining reservoir of rocky material in AR UMa might help to constrain the prior evolution of this unusual binary system. We also apply spectral decomposition to find the stellar parameters of the M dwarf companion, and attempt to dynamically measure the mass of the WD in AR UMa by considering both the radial velocity curves of the H β emission line and the Na i absorption line. Thereby we infer a mass range for the WD in AR UMa of 0.91 M ⊙ < M WD < 1.24 M ⊙.

  16. Relationship between collapse history and ore distribution in Sage Breccia pipe, northwestern Arizona

    SciTech Connect

    Brown, N.A.; Mead, R.H.; McMurray, J.M. )

    1989-09-01

    The Sage pipe is similar to other collapse breccia pipes in northern Arizona which have their beginnings in cave systems in the Redwall Limestone. Stoping of successively younger units caused the upward propagation of the pipe and provided the pipe-filling breccia. The Sage pipe extends at least 2,500 ft (762 m) vertically; the horizontal dimensions range from 100 to 300 ft (30.5-91 m), depending on variations in the adjoining host stratigraphy. The composition and distribution of breccia facies suggest a complex collapse history and variability in the mechanics of collapse. Rock failure took place both by block stoping and by decementation of sandstone and siltstone followed by flow of unconsolidated grains. The resulting breccias range from matrix to fragment-dominated, to sand flow breccia resulting from flow of individual grains. Episodic secondary collapse or readjustment within the breccia pile complicated facies distribution. Paragenetic studies indicate multiple periods of mineralization at Sage resulting in enrichment in an extensive suite of elements. Ore-grade uranium mineralization extends vertically for nearly 700 ft (213 m). Lateral distribution of the ore is variable and is directly related to breccia facies distribution. In generally, the more permeable breccias tend to be the most highly mineralized. Fracture, intergranular, and interfragment permeability were important to mineral distribution. Breccia continuity or plumbing was also important to lateral and vertical mineral distribution.

  17. A high-sensitivity search for extraterrestrial intelligence at lambda 18 cm

    NASA Technical Reports Server (NTRS)

    Tarter, J.; Cuzzi, J.; Black, D.; Clark, T.

    1980-01-01

    A targeted high-sensitivity search for narrow-band signals near a wavelength of 18 cm has been conducted using the 91-m radiotelescope of the National Radio Astronomy Observatory. The search included 201 nearby solar-type stars and achieved a frequency resolution of 5.5 Hz over a 1.4-MHz bandwidth. This high spectral resolution was obtained through a non-real-time reduction procedure using a Mark I VLBI recording terminal in conjunction with the CDC 7600 computational facility at the NASA-Ames Research Center. This is the first high-resolution search for narrow-band signals in this wavelength regime. To date it is the most sensitive search per unit observing time of any search strategy which does not postulate a unique magic frequency. Data show no evidence for narrow-band signals due to extraterrestrial intelligence at a 12-standard-deviation upper limit on signal strength of 1.1 x 10 to the -23rd W/sq m.

  18. A novel separation and calibration method for DVL and compass error in dead reckoning navigation systems

    NASA Astrophysics Data System (ADS)

    Zhang, Yanshun; Guo, Yajing; Yang, Tao; Li, Chunyu; Wang, Zhanqing

    2016-06-01

    The scale factor error δ C of the Doppler velocity log (DVL) and the heading angle error δ \\psi of a compass are so integrated in dead reckoning (DR) navigation systems that it is difficult to separate them. This paper aims to solve this problem by putting forward an online separation and calibration method for δ C and δ \\psi based on an ‘arc and linear’ trajectory. This method introduces the high-accuracy location information of a long base line (LBL) acoustic positioning system. At first, the relationship between the displacements on the ‘arc’ trajectory in directions of east and north, output by the LBL and DR systems, serves to judge the carrier direction and calibrate δ C . And then by compensating δ C , the displacement on the ‘linear’ trajectory is used to calibrate δ \\psi . Finally, a semi-physical simulation experiment is conducted to test and verify this calibration method to see how effective and accurate it is. Experimental results show that after calibration the residual error ratios of δ C and δ \\psi are 8.24% and 3.70% respectively. Therefore, online calibration of δ C and δ \\psi is realized effectively. What’s more, when the DR system is working alone in 400 s, this method reduces position error by up to 93.39%, from 18.91 m to 1.25 m.

  19. Lipase Production in Solid-State Fermentation Monitoring Biomass Growth of Aspergillus niger Using Digital Image Processing

    NASA Astrophysics Data System (ADS)

    Dutra, Julio C. V.; da Terzi, Selma C.; Bevilaqua, Juliana Vaz; Damaso, Mônica C. T.; Couri, Sônia; Langone, Marta A. P.; Senna, Lilian F.

    The aim of this study was to monitor the biomass growth of Aspergillus niger in solid-state fermentation (SSF) for lipase production using digital image processing technique. The strain A. niger 11T53A14 was cultivated in SSF using wheat bran as support, which was enriched with 0.91% (m/v) of ammonium sulfate. The addition of several vegetable oils (castor, soybean, olive, corn, and palm oils) was investigated to enhance lipase production. The maximum lipase activity was obtained using 2% (m/m) castor oil. In these conditions, the growth was evaluated each 24 h for 5 days by the glycosamine content analysis and digital image processing. Lipase activity was also determined. The results indicated that the digital image process technique can be used to monitor biomass growth in a SSF process and to correlate biomass growth and enzyme activity. In addition, the immobilized esterification lipase activity was determined for the butyl oleate synthesis, with and without 50% v/v hexane, resulting in 650 and 120 U/g, respectively. The enzyme was also used for transesterification of soybean oil and ethanol with maximum yield of 2.4%, after 30 min of reaction.

  20. Carbon-coated Li3V2(PO4)3 as insertion type electrode for lithium-ion hybrid electrochemical capacitors: An evaluation of anode and cathodic performance

    NASA Astrophysics Data System (ADS)

    Satish, Rohit; Aravindan, Vanchiappan; Ling, Wong Chui; Madhavi, Srinivasan

    2015-05-01

    We first report the possible utilization of carbon-coated Li3V2(PO4)3 (LVP-C) phase as insertion type anode and cathode in Lithium-ion hybrid electrochemical capacitor (Li-HEC) applications with activated carbon (AC) counter electrode. Conventional sol-gel technique is utilized to prepare LVP-C and characterized by various techniques like powder X-ray diffraction, field emission scanning electron microscopy and high resolution transmission electron microscopy. Li-cycling studies are performed in half-cell assembly to evaluate the optimum mass loading for the fabrication of Li-HEC. A reversible capacity of ∼125 and ∼91 mAh g-1 is noted (current density of 100 mA g-1) when LVP-C is employed as cathode (3-4.3 V vs. Li) and anode (1-3 V vs. Li), respectively. Li-HEC is constructed in an organic electrolyte and tested in two configurations, using LVP-C as positive electrode and AC as the negative electrode (LVP-C/AC) and the second one composed of AC as the positive electrode and LVP-C as the negative electrode (AC/LVP-C). The LVP-C/AC and AC/LVP-C Li-HECs delivered maximum energy densities of ∼27 and ∼25 Wh kg-1, respectively.

  1. Large quaternary landslides in the central appalachian valley and ridge province near Petersburg, West Virginia

    NASA Astrophysics Data System (ADS)

    Scott Southworth, C.

    1988-12-01

    Geological mapping and photointerpretation of side-looking airborne radar images and color-infrared aerial photographs reveal two large Quaternary landslides in the Valley and Ridge province of the central Appalachians near Petersburg, W. Va. The Elkhorn Mountain rock avalanche occurs on the thrust-faulted northwestern flank of the Elkhorn Mountain anticlinorium. A minimum of 7 × 10 6 m 3 of quartzite colluvium was transported more than 3 km from a 91 m high escarpment of Silurian Tuscarora Quartzite. The extensively vegetated deposit may owe, in part, its transport and weathering to periglacial conditions during the Pleistocene. In contrast, the Gap Mountain rock block slide is a single allochthonous block that is 1.2 km long, 0.6 km wide, and at least 60 m thick. The 43 × 10 6 m 3 block is composed of limestone of the Helderberg Group and the Oriskany Sanstone of Early Devonian age. Planar detachment probably occurred along a dissolution bedding plane near the Shriver Chert and the Oriskany Sandstone contact. Failure probably was initiated by downcutting of the South Branch Potomac River during the Pleistocene. Landslides of this magnitude suggest accelerated erosion during periglacial climates in the Pleistocene. The recognition of these large slope failures may provide evidence of paleoclimatic conditions and, thereby, increase our understanding of the geomorphologic development of the Valley and Ridge province.

  2. Characterization and prediction of spatial variability of unsaturated hydraulic properties in a field soil: Las Cruces, New Mexico

    SciTech Connect

    Yeh, T.C.J.; Greenholtz, D.E.; Nash, M.S.; Wierenga, P.J.

    1991-12-31

    A 91-m transect was set up in an irrigated field near Las Cruces, New Mexico to investigate the spatial variability of unsaturated soil properties. A total of 455 sampling points were monitored along a grid consisting of 91 stations placed 1 m apart by 5 depths per station. Post-irrigation soil water tension and water content measurements were recorded over 45 days at 11 time periods. The instantaneous profile was used to estimate the unsaturated hydraulic conductivity at the 455 sampling points. Fifty soil samples were also taken for analyzing sand, silt, and clay content distributions. The spatial and temporal variability of soil water tension and water content were investigated along with the spatial variability of parameters of an unsaturated hydraulic conductivity model. Results of the analysis show that spatial variation in soil water tension and water content is consistent with the soil texture spatial variability. In addition, the spatial distribution of the estimated parameter value of unsaturated hydraulic conductivity reflects the soil texture distribution. Using the statistics of the estimated hydraulic parameter values, a stochastic soil water tension model was employed to reproduce the variability of observed soil water tension. Although many assumptions were made, the results of the simulation appear promising.

  3. Characterization and prediction of spatial variability of unsaturated hydraulic properties in a field soil: Las Cruces, New Mexico

    SciTech Connect

    Yeh, T.C.J.; Greenholtz, D.E. . Dept. of Hydrology and Water Resources); Nash, M.S. . Dept. of Crop and Soil Sciences); Wierenga, P.J. . Dept. of Soil and Water Science)

    1991-01-01

    A 91-m transect was set up in an irrigated field near Las Cruces, New Mexico to investigate the spatial variability of unsaturated soil properties. A total of 455 sampling points were monitored along a grid consisting of 91 stations placed 1 m apart by 5 depths per station. Post-irrigation soil water tension and water content measurements were recorded over 45 days at 11 time periods. The instantaneous profile was used to estimate the unsaturated hydraulic conductivity at the 455 sampling points. Fifty soil samples were also taken for analyzing sand, silt, and clay content distributions. The spatial and temporal variability of soil water tension and water content were investigated along with the spatial variability of parameters of an unsaturated hydraulic conductivity model. Results of the analysis show that spatial variation in soil water tension and water content is consistent with the soil texture spatial variability. In addition, the spatial distribution of the estimated parameter value of unsaturated hydraulic conductivity reflects the soil texture distribution. Using the statistics of the estimated hydraulic parameter values, a stochastic soil water tension model was employed to reproduce the variability of observed soil water tension. Although many assumptions were made, the results of the simulation appear promising.

  4. Photoactivation of the p-nucleus 92Mo with bremsstrahlung at ELBE

    NASA Astrophysics Data System (ADS)

    Erhard, M.; Grosse, E.; Junghans, A. R.; Klug, J.; Nair, C.; Rusev, G.; Schilling, K. D.; Schwengner, R.; Wagner, A.

    2010-01-01

    In nuclear network calculations especially the p-nucleus 92Mo is frequently underproduced. Since experimental data of the photodisintegration of 92Mo so far do not exist, it was necessary to measure the reaction yields with the photoactivation method using the brems-strahlung facility ELBE at FZ Dresden-Rossendorf. Also the reaction 100Mo(γ,n) could be tested while irradiating Mo samples of natural composition. The photon fluence was measured with nuclear resonance fluorescence (NRF) of strong and well-known transitions in 11B. As a normalization standard the photoactivation reaction 197Au(γ,n) was used. For the 65 s half-life of 91mMo a fast pneumatic delivery was used. The photoactivation yields of the (γ,p) and (γ,n) reactions are compared to yield integrals of the bremsstrahlung spectral shape folded with the cross sections derived from Hauser-Feshbach nuclear model calculations using the TALYS program and cross sections from earlier experiments.

  5. The deep-water species of Halimeda Lamouroux (Halimedaceae, Chlorophyta) from San Salvador Island, Bahamas: species composition, distribution and depth records

    NASA Astrophysics Data System (ADS)

    Blair, Stephen M.; Norris, James N.

    1988-03-01

    Caribbean species of Halimeda from the steep slopes of San Salvador Island, Bahamas, were collected along vertical transects between 25 and 255 m, on the northeast, northwest, west, southwest and south sides of the island, using the Harbor Branch Oceanographic Institution's submersible Johnson Sea Link I. The characteristics delineating species (segment and utricle size) were assessed for selected species, and the depth and western Atlantic distributions of the species reviewed. Halimeda copiosa was found to show a variation of surface utricle diameter with depth, with the deeper plants having 15% larger diameter utricles than the shallower plants. Of the seven species, one variety and one form of Halimeda studied from our submersible dive sites, H. copiosa, H. cryptica and H. gracilis grew to the greatest depths, from 120 to 150-m depths. H. lacrimosa var. globosa was found growing to 91 m, and H. tuna f. platydisca and H. discoidea to a depth of 73 m. Those of lesser depth, to 61 m, were H. goreauii, H. tuna f. tuna and H. lacrimosa var. lacrimosa. These represent substantial increases in depth distribution of the nine taxa found.

  6. A groundwater flow and transport model of long-term radionuclide migration in central Frenchman flat, Nevada test site

    SciTech Connect

    Kwicklis, Edward Michael; Becker, Naomi M; Ruskauff, Gregory; De Novio, Nicole; Wilborn, Bill

    2010-11-10

    A set of groundwater flow and transport models were created for the Central Testing Area of Frenchman Flat at the former Nevada Test Site to investigate the long-term consequences of a radionuclide migration experiment that was done between 1975 and 1990. In this experiment, radionuclide migration was induced from a small nuclear test conducted below the water table by pumping a well 91 m away. After radionuclides arrived at the pumping well, the contaminated effluent was discharged to an unlined ditch leading to a playa where it was expected to evaporate. However, recent data from a well near the ditch and results from detailed models of the experiment by LLNL personnel have convincingly demonstrated that radionuclides from the ditch eventually reached the water table some 220 m below land surface. The models presented in this paper combine aspects of these detailed models with concepts of basin-scale flow to estimate the likely extent of contamination resulting from this experiment over the next 1,000 years. The models demonstrate that because regulatory limits for radionuclide concentrations are exceeded only by tritium and the half-life of tritium is relatively short (12.3 years), the maximum extent of contaminated groundwater has or will soon be reached, after which time the contaminated plume will begin to shrink because of radioactive decay. The models also show that past and future groundwater pumping from water supply wells within Frenchman Flat basin will have negligible effects on the extent of the plume.

  7. Ion source and injection line for high intensity medical cyclotron

    SciTech Connect

    Jia, XianLu Guan, Fengping; Yao, Hongjuan; Zhang, TianJue; Yang, Jianjun; Song, Guofang; Ge, Tao; Qin, Jiuchang

    2014-02-15

    A 14 MeV high intensity compact cyclotron, CYCIAE-14, was built at China Institute of Atomic Energy (CIAE). An injection system based on the external H− ion source was used on CYCIAE-14 so as to provide high intensity beam, while most positron emission tomography cyclotrons adopt internal ion source. A beam intensity of 100 μA/14 MeV was extracted from the cyclotron with a small multi-cusp H− ion source (CIAE-CH-I type) and a short injection line, which the H− ion source of 3 mA/25 keV H− beam with emittance of 0.3π mm mrad and the injection line of with only 1.2 m from the extraction of ion source to the medial plane of the cyclotron. To increase the extracted beam intensity of the cyclotron, a new ion source (CIAE-CH-II type) of 9.1 mA was used, with maximum of 500 μA was achieved from the cyclotron. The design and test results of the ion source and injection line optimized for high intensity acceleration will be given in this paper.

  8. Blue, Green, and Amber InGaN/GaN Light-Emitting Diodes on Semipolar {11\\bar{2}2} GaN Bulk Substrates

    NASA Astrophysics Data System (ADS)

    Funato, Mitsuru; Ueda, Masaya; Kawakami, Yoichi; Narukawa, Yukio; Kosugi, Takao; Takahashi, Masayoshi; Mukai, Takashi

    2006-07-01

    We demonstrate the fabrication of blue, green, and amber InGaN/GaN light-emitting diodes (LEDs) on semipolar {11\\bar{2}2} bulk GaN substrates. The {11\\bar{2}2}GaN substrates used in this study are produced by cutting out from a c-oriented GaN bulk crystal grown by hydride vapor epitaxy. The LEDs have a dimension of 320 × 320 μm2 and are packed in an epoxide resin. The output power and external quantum efficiency (EQE) at a driving current of 20 mA are 1.76 mW and 3.0%, respectively, for the blue LED, 1.91 mW and 4.1% for the green LED, and 0.54 mW and 1.3% for the amber LED. The maximum output powers obtained with a maximum current of 200 mA are 19.0 mW (blue), 13.4 mW (green), and 1.9 mW (amber), while the maximum EQEs are 4.0% at 140 mA (blue), 4.9% at 0.2 mA (green), and 1.6% at 1 mA (amber). It is confirmed that the emission light is polarized along the [1\\bar{1}00] direction, reflecting the low crystal symmetry of the {11\\bar{2}2} plane.

  9. LDEF Interplanetary Dust Experiment - Techniques for identification and study of long-lived orbital debris clouds

    NASA Technical Reports Server (NTRS)

    Singer, S. F.; Oliver, J. P.; Weinberg, J. L.; Cooke, W. J.; Montague, N. L.; Mulholland, J. D.; Wortman, J. J.; Kassel, P. C.; Kinard, W. H.

    1991-01-01

    The Long Duration Exposure Facility (LDEF) is a 12-sided, 4.3-m-diameter, 9.1-m-long cylinder designed and built by NASA Langley to carry experiments for extended periods in space. The LDEF was first placed in orbit by the Shuttle Challenger on 7 April 1984 and recovered by the Shuttle Columbia in January 1990, only days before it was expected to burn up in the earth's atmosphere. The Interplanetary Dust Experiment (IDE) was designed to detect impacts of extra-terrestrial particles and orbital debris. The IDE detectors (which covered about 1 sq m of the surface of LDEF) were sensitive to particles ranging in size from about 0.2 to 100 microns. Data were recorded for 11.5 months before the supply of magnetic tape was exhausted. Examination of the LDEF IDE dataset shows that impacts often occurred in 'bursts', during which numerous impacts occurred in a short time (typically 3-5 min) at a rate much greater than the average impact rate. In several cases, such events reoccurred each time the LDEF returned to the same point in its orbit. Such multi-orbit event sequences were found to extend for as many as 25 or more orbits.

  10. Fuel dispersal modeling for aircraft-runway impact scenarios

    SciTech Connect

    Tieszen, S.R.

    1995-11-01

    A fuel dispersal model for C-141 transport accidents was developed for the Defense Nuclear Agency`s Fuel Fire Technology Base Program to support Weapon System Safety Assessments. The spectrum of accidents resulting from aircraft impact on a runway was divided into three fuel dispersal regimes: low, intermediate, and high-velocity impact. Sufficient data existed in the accident, crash test, and fuel-filled bomb literature to support development of a qualitative framework for dispersal models, but not quantitative models for all regimes. Therefore, a test series at intermediate scale was conducted to generate data on which to base the model for the high-velocity regime. Tests were conducted over an impact velocity range from 12 m/s to 91 m/s and angles of impact from 22.5{degrees} to 67.5{degrees}. Dependent variables were area covered by dispersed fuel, amount of mass in that area, and location of the area relative to the impact line. Test results showed that no liquid pooling occurred for impact velocities greater than 61 m/s, independent of the angle of impact. Some pooling did occur at lower velocities, but in no test was the liquid-layer thickness greater than 5.25 mm.

  11. How Search for Meaning Interacts with Complex Categories of Meaning in Life and Subjective Well-Being?

    PubMed

    Damásio, Bruno Figueiredo; Koller, Sílvia Helena

    2015-01-01

    This study sought to assess how the search for meaning interacts with crisis of meaning and with different categories of meaning in life (meaningfulness, crisis of meaning, existential indifference, and existential conflict). Furthermore, the moderation role of search for meaning between the relation of categories of meaning and subjective well-being (SWB) was also evaluated. Participants included 3,034 subjects (63.9% women) ranging in age from 18 to 91 (M = 33.90; SD = 15.01) years old from 22 Brazilian states. Zero-order correlations and a factorial MANOVA were implemented. Positive low correlations were found for search for meaning and crisis of meaning (r = .258; p < .001). Search for meaning presented a small-effect size moderation effect on the relation of the different categories of meaning with subjective happiness, F(6, 3008) = 2.698, p < .05; η2 = .004, but not for satisfaction with life, F(6, 3008) = .935, p = .47; η2 = .002. The differences on the levels of subjective happiness of those inserted in existential indifferent and conflicting categories differ depending on the levels of search for meaning. Further directions for future studies are proposed. PMID:26054413

  12. The Average Body Surface Area of Adult Cancer Patients in the UK: A Multicentre Retrospective Study

    PubMed Central

    Sacco, Joseph J.; Botten, Joanne; Macbeth, Fergus; Bagust, Adrian; Clark, Peter

    2010-01-01

    The majority of chemotherapy drugs are dosed based on body surface area (BSA). No standard BSA values for patients being treated in the United Kingdom are available on which to base dose and cost calculations. We therefore retrospectively assessed the BSA of patients receiving chemotherapy treatment at three oncology centres in the UK between 1st January 2005 and 31st December 2005. A total of 3613 patients receiving chemotherapy for head and neck, ovarian, lung, upper GI/pancreas, breast or colorectal cancers were included. The overall mean BSA was 1.79 m2 (95% CI 1.78–1.80) with a mean BSA for men of 1.91 m2 (1.90–1.92) and 1.71 m2 (1.70–1.72) for women. Results were consistent across the three centres. No significant differences were noted between treatment in the adjuvant or palliative setting in patients with breast or colorectal cancer. However, statistically significant, albeit small, differences were detected between some tumour groups. In view of the consistency of results between three geographically distinct UK cancer centres, we believe the results of this study may be generalised and used in future costings and budgeting for new chemotherapy agents in the UK. PMID:20126669

  13. Origin of coal seam structures, Sullivan County, Indiana

    SciTech Connect

    Adams, S.C.; Kullerud, G.

    1983-09-01

    Structures of Pennsylvanian coal seams in Sullivan County, Indiana, reflect deeper structural components, of which regional dip is dominant. Other components of structure result form differential compaction. The effects of these components are characterized by their closure, size, shape, and orientation. (1) The Mississippian unconformity surface is characterized by parallel valley with up to 300 ft (91 m) of local relief. (2) The composite lower Pennsylvanian section below the Seelyville Coal has variable sandstone content. Some paleovalleys are filled with multistory sandstones, and others with claystone. (3) Silurian pinnacle reefs from small, circular features with a diameter of 1 to 2 mi (1.5 to 3 km) and closures of 25 tio 50 ft (8 to 15 m) on Pennsylvanian coal seams, 50 ft (15 m) on the Aux Vases Shale, and 150 ft (45 m) on the New Albany Shale. (4) The distributions and standard deviations of thicknesses, dips, and grain size of the sedimentary rocks between the coal seams demonstrate that seams above the Seelyville Coal were deposited in parallel and have concordant modern structures. Specific facies between seams have limited influence on the overall structure. Coal structures in the Illinois basin can be defined by a drilling program that penetrates only 150 ft (45 m) of Pennsylvanian strata. Below the Seelyville Coal, units examined demonstrate basin-margin convergence.

  14. Isolation and functional characterization of crustacean larval salt gland.

    PubMed

    Lowy, R J; Conte, F P

    1985-06-01

    A batch method for isolating viable salt glands from the naupliar brine shrimp (Artemia salina) has been developed. This protocol produces a final preparation consisting of approximately 185 isolated salt glands, representing 1 X 10(4) secretory cells/g wet wt nauplii, with a final purity of 88%. Assays of cell integrity and function indicate good retention of in situ characteristics. Vital dye was excluded by 95% of the cells for at least 24 h. The O2 consumption rate was 22.7 nM O2 X min-1 X mg protein-1 and could be altered predictably by compounds known to affect oxidative phosphorylation and ion transport. The specific activity of the Na+-K+-ATPase in the salt gland, measured here for the first time, was 9.1 mM Pi X h-1 X mg protein-1. This is a substantial proportion of the body total, 17%, as expected for an active ion-transporting epithelium. PMID:2988351

  15. Preparation and characteristics of biosilica derived from marine diatom biomass of Nitzschia closterium and Thalassiosira

    NASA Astrophysics Data System (ADS)

    Qi, Yarong; Wang, Xin; Cheng, Jay Jiayang

    2016-06-01

    In this study, biosilica of high purity was successfully prepared from marine diatom (Nitzschia closterium and Thalassiosira) biomass using an optimized novel method with acid washing treatment followed by thermal treatment of the biomass. The optimal condition of the method was 2% diluted HCl washing and baking at 600°C. The SiO2 contents of N. closterium biosilica and Thalassiosira biosilica were 92.23% and 91.52%, respectively, which were both higher than that of diatomite biosilica. The SiO2 morphologies of both biosilica are typical amorphous silica. Besides, N. closterium biosilica possessed micropores and fibers with a surface area of 59.81m2/g. And Thalassiosira biosilica possessed a mesoporous hierarchical skeleton with a surface area of 9.91m2/g. The results suggest that the biosilica samples obtained in this study present highly porous structures. The prepared porous biosilica material possesses great potential to be used as drug delivery carrier, biosensor, biocatalyst as well as adsorbent in the future.

  16. Cloning, Expression and 3D Structure Prediction of Chitinase from Chitinolyticbacter meiyuanensis SYBC-H1

    PubMed Central

    Hao, Zhikui; Wu, Hangui; Yang, Meiling; Chen, Jianjun; Xi, Limin; Zhao, Weijie; Yu, Jialin; Liu, Jiayang; Liao, Xiangru; Huang, Qingguo

    2016-01-01

    Two CHI genes from Chitinolyticbacter meiyuanensis SYBC-H1 encoding chitinases were identified and their protein 3D structures were predicted. According to the amino acid sequence alignment, CHI1 gene encoding 166 aa had a structural domain similar to the GH18 type II chitinase, and CHI2 gene encoding 383 aa had the same catalytic domain as the glycoside hydrolase family 19 chitinase. In this study, CHI2 chitinase were expressed in Escherichia coli BL21 cells, and this protein was purified by ammonium sulfate precipitation, DEAE-cellulose, and Sephadex G-100 chromatography. Optimal activity of CHI2 chitinase occurred at a temperature of 40 °C and a pH of 6.5. The presence of metal ions Fe3+, Fe2+, and Zn2+ inhibited CHI2 chitinase activity, while Na+ and K+ promoted its activity. Furthermore, the presence of EGTA, EDTA, and β-mercaptoethanol significantly increased the stability of CHI2 chitinase. The CHI2 chitinase was active with p-NP-GlcNAc, with the Km and Vm values of 23.0 µmol/L and 9.1 mM/min at a temperature of 37 °C, respectively. Additionally, the CHI2 chitinase was characterized as an N-acetyl glucosaminidase based on the hydrolysate from chitin. Overall, our results demonstrated CHI2 chitinase with remarkable biochemical properties is suitable for bioconversion of chitin waste. PMID:27240345

  17. Development of reactive artificial liner using recycled materials. 2. Chemical transport properties.

    PubMed

    Chin, Johnnie Y; Asavanich, Pitch; Moon, Kyong-Whan; Park, Jae K

    2013-07-01

    Volatile organic compounds (VOCs) have so far been found to permeate through geomembranes within days and potentially pollute the surrounding groundwater if no sufficient depth of underlain soil barrier existed In order to cope with the fast breakthrough of VOCs through high-density polyethylene (HDPE) geomembrane in the composite liner system, a composite material made of recycled materials was proposed and its mechanical properties were analyzed in a previous study. This artificial liner was composed of crumb rubber, organo-clay, silica fume and epoxy binder together with an environmentally-friendly solvent recycled from paper pulping, and dimethyl sulfoxide as a plasticizer. In this study, the new artificial liner and a typical HDPE geomembrane were tested to compare their abilities to mitigate the movement of VOCs, specifically partition coefficient, diffusion coefficient and mass fluxes. It was found that this new artificial liner had 2-3 orders of magnitude less VOC mass flux than the HDPE geomembrane. The new artificial liner is thought to have a great potential for containing VOCs, even with a thickness of 2.5 cm, and as a substitute for the clay liner. The cost of installing the artificial liner was estimated to be $13.78/m(2). This is lower than the current geomembrane-related price of $19.70-26.91/m(2). The new liner might give a new perspective in future liner design and alleviate the concerning issue of groundwater pollution caused by landfill leachate, which might contain highly mobile VOCs. PMID:23628903

  18. Preliminary Investigation of Ice Shape Sensitivity to Parameter Variations

    NASA Technical Reports Server (NTRS)

    Miller, Dean R.; Potapczuk, Mark G.; Langhals, Tammy J.

    2005-01-01

    A parameter sensitivity study was conducted at the NASA Glenn Research Center's Icing Research Tunnel (IRT) using a 36 in. chord (0.91 m) NACA-0012 airfoil. The objective of this preliminary work was to investigate the feasibility of using ice shape feature changes to define requirements for the simulation and measurement of SLD icing conditions. It was desired to identify the minimum change (threshold) in a parameter value, which yielded an observable change in the ice shape. Liquid Water Content (LWC), drop size distribution (MVD), and tunnel static temperature were varied about a nominal value, and the effects of these parameter changes on the resulting ice shapes were documented. The resulting differences in ice shapes were compared on the basis of qualitative and quantitative criteria (e.g., mass, ice horn thickness, ice horn angle, icing limits, and iced area). This paper will provide a description of the experimental method, present selected experimental results, and conclude with an evaluation of these results, followed by a discussion of recommendations for future research.

  19. Lipase production in solid-state fermentation monitoring biomass growth of aspergillus niger using digital image processing.

    PubMed

    Dutra, Júlio C V; da C Terzi, Selma; Bevilaqua, Juliana Vaz; Damaso, Mônica C T; Couri, Sônia; Langone, Marta A P; Senna, Lilian F

    2008-03-01

    The aim of this study was to monitor the biomass growth of Aspergillus niger in solid-state fermentation (SSF) for lipase production using digital image processing technique. The strain A. niger 11T53A14 was cultivated in SSF using wheat bran as support, which was enriched with 0.91% (m/v) of ammonium sulfate. The addition of several vegetable oils (castor, soybean, olive, corn, and palm oils) was investigated to enhance lipase production. The maximum lipase activity was obtained using 2% (m/m) castor oil. In these conditions, the growth was evaluated each 24 h for 5 days by the glycosamine content analysis and digital image processing. Lipase activity was also determined. The results indicated that the digital image process technique can be used to monitor biomass growth in a SSF process and to correlate biomass growth and enzyme activity. In addition, the immobilized esterification lipase activity was determined for the butyl oleate synthesis, with and without 50% v/v hexane, resulting in 650 and 120 U/g, respectively. The enzyme was also used for transesterification of soybean oil and ethanol with maximum yield of 2.4%, after 30 min of reaction. PMID:18401753

  20. A new thermal vacuum facility at the Martin Marietta Waterton plant

    NASA Astrophysics Data System (ADS)

    Watson, Robert N.; Bonn, John W.

    1992-11-01

    A new thermal-vacuum facility has been recently completed at the Martin Marietta Waterton plant near Denver, Colorado. The facility was designed, fabricated, installed, and tested as a turn-key project by Pitt-Des Moines Inc. and CVI Inc. The chamber has a 5.49 M by 6.10 M (18 ft by 20 ft) flat floor and a half-cylindrical roof with a diameter of 5.49 M (18 ft). Both ends of the chamber have full cross section doors, with one equipped with translating motors for horizontal motion. The chamber is provided with four 0.91 M (36 inches) cryopumps to obtain an ultimate pressure of 9 x 10(exp -8) Torr (Clean-Dry-Empty). The thermal shroud is designed to operate at a maximum of -179 C (-290 F) with an internal heat input of 316 MJ/Hr (300,000 BTU/Hr) using liquid nitrogen. The shroud is also designed to operate at any temperature between -156 C (-250 F) and 121 C (+250 F) using gaseous nitrogen, and heat or cool at a rate of 1.1 C (2 F) per minute.

  1. An Experimental Study of the Droplets Produced by a Plunging Breaker

    NASA Astrophysics Data System (ADS)

    Wang, D.; Liu, X.; Duncan, J. H.

    2011-11-01

    The dynamics of droplets generated by plunging breakers are experimentally studied in a wave tank that is 12 m long and 1.22 m wide with a water depth of 0.91 m. Breakers with various breaking intensity are generated from a packet of dispersively focused waves with average frequency of 1.15 Hz by varying the amplitude of wave maker motion. The sizes and motions of droplets at various positions relative the wave crest are measured with a cinematic shadowgraph technique, while the profile histories of the breaking wave crest along the center plane of the tank are simultaneously measured with a cinematic laser-induced fluorescence technique. Droplets are primarily created when strong turbulence is generated after the plunging jet impacts with the front face of the wave and when large air bubbles, entrapped during the plunging process, rise to the free surface and pop. The diameters and velocities of the droplets across one horizontal plane at an elevation just above the wave crest height are measured. The surface roughnesses of the breaking waves are estimated from the measured wave crest profile histories. The correlation between the flux of droplets and the surface roughness is investigated. Supported by the National Science Foundation, Division of Ocean Sciences, Grant OCE0751853.

  2. Steady-state wear and friction in boundary lubrication studies

    NASA Technical Reports Server (NTRS)

    Loomis, W. R.; Jones, W. R., Jr.

    1980-01-01

    A friction and wear study was made at 20 C to obtain improved reproducibility and reliability in boundary lubrication testing. Ester-base and C-ether-base fluids were used to lubricate a pure iron rider in sliding contact with a rotating M-50 steel disk in a friction and wear apparatus. Conditions included loads of 1/2 and 1 kg and sliding velocities of 3.6 to 18.2 m/min in a dry air atmosphere and stepwise time intervals from 1 to 250 min for wear measurements. The wear rate results were compared with those from previous studies where a single 25 min test period was used. Satisfactory test conditions for studying friction and wear in boundary lubrication for this apparatus were found to be 1 kg load; sliding velocities of 7.1 to 9.1 m/min (50 rpm disk speed); and use of a time stepwise test procedure. Highly reproducible steady-state wear rates and steady-state friction coefficients were determined under boundary conditions. Wear rates and coefficients of friction were constant following initially high values during run-in periods.

  3. CHARACTERIZATION AND EVALUATION OF CAUSTIC WASH TANK AND SOLVENT HOLD TANK SAMPLES FROM MCU FROM AUGUST TO SEPTEMBER 2011

    SciTech Connect

    Fondeur, F.; Fink, S.

    2012-08-01

    During processing of Salt Batches 3 and 4 in the Modular Caustic-Side Solvent Extraction Unit (MCU), the decontamination efficiency for cesium declined from historical values and from expectations based on laboratory testing. This report documents efforts to analyze samples of solvent and process solutions from MCU in an attempt to understand the cause of the reduced performance and to recommend mitigations. CWT Solutions from MCU from the time period of variable decontamination factor (DF) performance which covers from April 2011 to September 2011 (during processing of Salt Batch 4) were examined for impurities using chromatography and spectroscopy. The results indicate that impurities were found to be of two types: aromatic containing impurities most likely from Modifier degradation and aliphatic type impurities most likely from Isopar{reg_sign} L and tri-n-octylamine (TOA) degradation. Caustic washing the Solvent Hold Tank (SHT) solution with 1M NaOH improved its extraction ability as determined from {sup 22}Na uptake tests. Evidence from this work showed that pH variance in the aqueous solutions within the range of 1M nitric acid to 1.91M NaOH that contacted the solvent samples does not influence the analytical determination of the TOA concentration by GC-MS.

  4. Carbon-encapsulated LiMn2O4 spheres prepared using a polymer microgel reactor for high-power lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Zhang, Honglai; Li, Zhaohui; Yu, Shishun; Xiao, Qizhen; Lei, Gangtie; Ding, Yanhuai

    2016-01-01

    Carbon-encapsulated LiMn2O4 (LMO@C) spheres were prepared using polymer microgel reactor, in which Mn2+ ions are hydrolyzed in situ to form Mn(OH)2, and followed by annealing at a high temperature. The LMO@C spheres are constructed with the spinel LiMn2O4 nanospheres that embedded in a porous carbon matrix uniformly. Owing to possessing three-dimensional (3D) electron-conductive and 3D ion-conductive networks, the LMO@C spheres exhibit high rate capability. They can deliver the specific capacities of 142, 137, 126, 107, and 91 mAh g-1 at the rates of 0.1C, 1C, 5C, 10C, and 20C (1C = 148 mA g-1), respectively. Owing to carbon encapsulation, the LMO@C spheres can retain 80% of the initial capacity at 1C rate after 1000 cycles at 25 °C, displaying stable cycling performance. The results suggest that the LMO@C spheres are promising cathode materials for high-power lithium-ion batteries.

  5. A PUFs-based hardware authentication BLAKE algorithm in 65 nm CMOS

    NASA Astrophysics Data System (ADS)

    Zhang, Yuejun; Wang, Pengjun; Zhang, Xuelong; Weng, Xinqian; Yu, Zhiyi

    2016-06-01

    This paper presents a hardware authentication BLAKE algorithm based on physical unclonable functions (PUFs) in Taiwan Semiconductor Manufacturing Company low-power 65 nm CMOS. To support hardware authentication feature, PUFs have been organised in BLAKE algorithm as the salt value. The trials table method is used to improve the robust of PUFs, resulting in approximately 100% stability against supply voltage variations form 0.7 V to 1.6 V. By discussing the G-function of BLAKE algorithm, the hardware implementation is considered for acceleration, resulting in significant performance improvements. The die occupies 2.62 mm2 and operates maximum frequency 1.0 GHz at 1.6 V. Measured results show that PUFs have great random characteristic and the authentication chip dissipates an average power of 91 mW under typical condition at 1.2 V and 780 MHz. In comparison with other works, the PUFs-based BLAKE algorithm has hardware authentication feature and improves throughput about 45%.

  6. The effect of forward speed on J85 engine noise from suppressor nozzles as measured in the NASA-Ames 40- by 80-foot wind tunnel

    NASA Technical Reports Server (NTRS)

    Atencio, A., Jr.

    1977-01-01

    An investigation to determine the effect of forward speed on the exhaust noise from a conical ejector nozzle and three suppressor nozzles mounted behind a J85 engine was performed in a 40- by 80-foot wind tunnel. The nozzles were tested at three engine power settings and at wind tunnel forward speeds up to 91 m/sec (300 ft/sec). In addition, outdoor static tests were conducted to determine (1) the differences between near field and far field measurements, (2) the effect of an airframe on the far field directivity of each nozzle, and (3) the relative suppression of each nozzle with respect to the baseline conical ejector nozzle. It was found that corrections to near field data are necessary to extrapolate to far field data and that the presence of the airframe changed the far field directivity as measured statically. The results show that the effect of forward speed was to reduce the noise from each nozzle more in the area of peak noise, but the change in forward quadrant noise was small or negligible. A comparison of wind tunnel data with available flight test data shows good agreement.

  7. Real-Time Digital Data-Acquisition System for determining load characteristics. Volume 2. Operating, programming, and maintenance instructions. Final report

    SciTech Connect

    Podesto, B.; Lapointe, A.; Larose, G.; Robichaud, Y.; Vaillancourt, C.

    1981-03-01

    The work sponsored under this contract included the design and construction of a Real-Time Digital Data Acquisition System (RTDDAS) to be used in substations for on-site recording and pre-processing load response data. The gathered data can be partially processed on site to compute the apparent, active and reactive powers, voltage and current rms values, and instantaneous values of phase voltages and currents. On-site processing capability is provided for rapid monitoring of the field data to ensure that the test setup is suitable. Production analysis of field data is accomplished off-line on a central computer from data recorded on a dual-density (800/1600) magnetic tape which is IBM-compatible. Parallel channels of data can be recorded at a variable rate from 480 to 9000 samples per second per channel. The RTDDAS is housed in a 9.1 m (30-ft) trailer which is shielded from electromagnetic interference and protected by isolators from switching surges; therefore, it can operate safely in a high-voltage substation environment where the tests must sometimes be performed. Information pertaining to the installation, software operation, and maintenance of the RTDDAS designed by IREQ is presented. A list of supporting documentation supplied by Data General Corporation is given.

  8. Deglacial and lake level fluctuation history recorded in cores, Beaver Lake, Upper Peninsula, Michigan

    USGS Publications Warehouse

    Fisher, Timothy G.; Whitman, Richard L.

    1999-01-01

    Sediment cores collected from the littoral and pelagic zones of Beaver Lake, Michigan record fluctuations in the water level of Lake Superior. Beaver Lake is a small 300 ha lake in Pictured Rocks National Lakeshore (PRNL) now separated from Lake Superior by a dune-capped barrier bar. Cores were collected using a vibracorer from a lake-ice platform in February 1997. A 2.85 m long core in 10 m of water contains well-sorted sand, rhythmites, peat, interbedded sand and gyttja, and is capped with 1 m of massive gyttja. A 9480 BP AMS age from the basal sand provides a minimum deglacial date for the area. Further analysis indicates a sand-dominated depositional environment from a low lake stand at approximately 8500 BP to present. An approximate 8800 BP red to gray sediment color transition records either the cessation of meltwater input from Lake Agassiz or receding ice, while a younger similarly colored transition, 6600 BP in age, likely records sediment reworking in the coastal zone. Four AMS ages on peat range from 8520 to 7340 BP and are indicative of the Houghton low phase. Burial of the peat by stratified sand and gyttja after 7340 BP indicates a rising lake level. Peat at a higher level in the lake basin, encountered in shallow littoral cores, ranges in age from 6800 to 6420 BP, which estimates a 0.91 m rise/century in lake level to the Nipissing level by 5000 BP.

  9. [Adsorptive Stabilization of Soil Cr (VI) Using HDTMA Modified Montmorillonite].

    PubMed

    2016-03-15

    A series of organo-montomorillonites were prepared using Na-montomorillonite and hexadecyl trimethyl ammonium bromide (HDTMA). The organo-montomorillonites were then investigated for the remediation of Cr(VI) contaminated soils. FT-IR, XRD, SEM and N2 -BET, CEC, Zeta potential measurement were conducted to understand the structural changes of montmorillonites as different amounts of HDTMAs were added as modifier. The characterization results indicated that the clay interlayer spacing distance increased from 1. 25 nm to 2. 13 nm, the clay surface roughness decreased, the clay surface area reduced from 38.91 m² · g⁻¹ to 0.42 m² · g⁻¹, the clay exchangeable cation amount reduced from 62 cmol · kg⁻¹ to 9.9 cmol · kg⁻¹ and the clay surface charge changed from -29.1 mV to 5.59 mV as the dosage of HDTMA in montmorillonite was increased. The TCLP (toxicity characteristic leaching procedure) was used to evaluate the leachate toxicity of Cr(VI). The effects of the initial soil Cr(VI) concentration, montmorillonites dosage, reaction time and HDTMA modification amount were investigated, respectively. The results revealed that modification of montmorillonites would manifest an attenuated physical adsorptive effect and an enhanced electrostatic adsorptive effect on Cr(VI), suggesting electrostatic effect was the major force that resulted in improved Cr(VI) adsorption onto HDTMA modified montmorillonites. PMID:27337898

  10. Cloning, Expression and 3D Structure Prediction of Chitinase from Chitinolyticbacter meiyuanensis SYBC-H1.

    PubMed

    Hao, Zhikui; Wu, Hangui; Yang, Meiling; Chen, Jianjun; Xi, Limin; Zhao, Weijie; Yu, Jialin; Liu, Jiayang; Liao, Xiangru; Huang, Qingguo

    2016-01-01

    Two CHI genes from Chitinolyticbacter meiyuanensis SYBC-H1 encoding chitinases were identified and their protein 3D structures were predicted. According to the amino acid sequence alignment, CHI1 gene encoding 166 aa had a structural domain similar to the GH18 type II chitinase, and CHI2 gene encoding 383 aa had the same catalytic domain as the glycoside hydrolase family 19 chitinase. In this study, CHI2 chitinase were expressed in Escherichia coli BL21 cells, and this protein was purified by ammonium sulfate precipitation, DEAE-cellulose, and Sephadex G-100 chromatography. Optimal activity of CHI2 chitinase occurred at a temperature of 40 °C and a pH of 6.5. The presence of metal ions Fe(3+), Fe(2+), and Zn(2+) inhibited CHI2 chitinase activity, while Na⁺ and K⁺ promoted its activity. Furthermore, the presence of EGTA, EDTA, and β-mercaptoethanol significantly increased the stability of CHI2 chitinase. The CHI2 chitinase was active with p-NP-GlcNAc, with the Km and Vm values of 23.0 µmol/L and 9.1 mM/min at a temperature of 37 °C, respectively. Additionally, the CHI2 chitinase was characterized as an N-acetyl glucosaminidase based on the hydrolysate from chitin. Overall, our results demonstrated CHI2 chitinase with remarkable biochemical properties is suitable for bioconversion of chitin waste. PMID:27240345

  11. Surfactant effects on cumulative drop size distributions produced by air bubbles bursting on a non-quiescent free surface

    NASA Astrophysics Data System (ADS)

    Parmar, K.; Liu, X.; Duncan, J. H.

    2013-11-01

    The generation of droplets when air bubbles travel upwards from within a liquid and burst at a free surface is studied experimentally. The bubbles are generated in a glass water tank that is 0.91 m long and 0.46 m wide with a water depth of 0.5 m. The tank is equipped with an acrylic box at its bottom that creates the bubble field using filtered air injected through an array of 180 hypodermic needles (0.33 mm ID). Two different surface conditions are created by using clean water and a 0.4% aqueous solution of Triton X-100 surfactant. Measurements of the bubble diameters as they approach the free surface are obtained with diffuse light shadowgraph images. The range of bubble diameters studied is 2.885 mm to 3.301 mm for clean water and 2.369 mm to 3.014 mm for the surfactant solution. A laser-light high-speed cinematic shadowgraph system is employed to record and measure the diameters and motions of the droplets at the free surface. This system can measure droplets with diameters <= 50 μm. The results show a clear distinction between the droplet distributions obtained in clean water and the surfactant solution. A bimodal droplet distribution is observed for clean water with at least two dominating peaks. For the surfactant solution, a single distribution peak is seen. This work is supported by the National Science Foundation, Division of Ocean Sciences.

  12. The solar hydrogen from sea water using Cu/TiO2

    NASA Astrophysics Data System (ADS)

    Selvaraj, Baraniruben A./l.; Kait, Chong Fai; Bustam, M. Azmi; Nurlaela, Ela

    2012-09-01

    H2 production from water under visible light radiation has great potential for sustainable energy supply. The incorporation of 10 wt% Cu onto TiO2 via precipitation method in the presence of glycerol, followed by activation at 180°C and 200°C, was investigated for H2 production from sea water under visible light radiation. The photocatalysts were also characterized using Fourier Transform Infrared Spectroscopy (FTIR), powder X-Ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), temperature-programmed reduction (TPR) and diffuse reflectance UV-visible spectrophotometry (DR-UV-Vis). Results indicated that photocatalyst calcined at 180°C for 30 min displayed the best performance for H2 production (9.1 mL) compared to TiO2 which produced merely 4.4 mL H2. The bandgap energy of this photocatalyst was lower (3.10 eV) compare to that for TiO2 (3.16 eV). Details of the synthesis procedure, photocatalysts characterization, and photoreaction are presented in this paper.

  13. Improving the performance of quantum dot sensitized solar cells through CdNiS quantum dots with reduced recombination and enhanced electron lifetime.

    PubMed

    Gopi, Chandu V V M; Venkata-Haritha, Mallineni; Seo, Hyunwoong; Singh, Saurabh; Kim, Soo-Kyoung; Shiratani, Masaharu; Kim, Hee-Je

    2016-05-28

    To make quantum dot-sensitized solar cells (QDSSCs) competitive, we investigated the effect of Ni(2+) ion incorporation into a CdS layer to create long-lived charge carriers and reduce the electron-hole recombination. The Ni(2+)-doped CdS (simplified as CdNiS) QD layer was introduced to a TiO2 surface via the simple successive ionic layer adsorption and reaction (SILAR) method in order to introduce intermediate-energy levels in the QDs. The effects of different Ni(2+) concentrations (5, 10, 15, and 20 mM) on the physical, chemical, and photovoltaic properties of the QDSSCs were investigated. The Ni(2+) dopant improves the light absorption of the device, accelerates the electron injection kinetics, and reduces the charge recombination, which results in improved charge transfer and collection. The 15% CdNiS cell exhibits the best photovoltaic performance with a power conversion efficiency (η) of 3.11% (JSC = 8.91 mA cm(-2), VOC = 0.643 V, FF = 0.543) under one full sun illumination (AM 1.5 G). These results are among the best achieved for CdS-based QDSSCs. Electrochemical impedance spectroscopy (EIS) and open circuit voltage decay (OCVD) measurements confirm that the Ni(2+) dopant can suppress charge recombination, prolong the electron lifetime, and improve the power conversion efficiency of the cells. PMID:27111597

  14. Variation in energy metabolism and water flux of free-ranging male lace monitors, Varanus varius (Squamata: Varanidae).

    PubMed

    Guarino, Fiorenzo; Georges, Arthur; Green, Brian

    2002-01-01

    The energy and water used by Varanus varius correlated with changes in weather, activity, and possibly the availability of prey. In summer, CO(2) production and water influx rates were high (0.147 mL CO(2) g(-1) h(-1) and 23.6 mL H(2)O kg(-1) d(-1)) but substantially lower during autumn (0.053 mL CO(2) g(-1) h(-1) and 9.1 mL H(2)O kg(-1) d( -1)) and winter (0.016 mL CO(2) g(-1) h(-1) and 2.4 mL H(2)O kg(-1) d(-1)), increasing again in spring (0.052 mL CO(2) g(-1) h(-1) and 7.9 mL H(2)O kg(-1) d(-1)). The summer-winter difference represented more than a ninefold reduction in energy expenditure and water flux. However, individual V. varius could manipulate their energy and water requirements by up to sixfold during the summer period by regulating activity. Although we found no adaptive benefits of increased or decreased level of activity, we did find that larger animals moved more frequently and over greater distances than smaller animals. We hypothesise that V. varius regulates its activity on the basis of the trade-off between energy expenditure through activity and energy acquisition through foraging. PMID:12177832

  15. Clonal variation in survival and growth of hybrid poplar and willow in an in situ trial on soils heavily contaminated with petroleum hydrocarbons.

    PubMed

    Zalesny, Ronald S; Bauer, Edmund O; Hall, Richard B; Zalesny, Jill A; Kunzman, Joshua; Rog, Chris J; Riemenschneider, Don E

    2005-01-01

    Species and hybrids between species belonging to the genera Populus (poplar) and Salix (willow) have been used successfully for phytoremediation of contaminated soils. Our objectives were to: 1) evaluate the potential for establishing genotypes of poplar and willow on soils heavily contaminated with petroleum hydrocarbons and 2) identify promising genotypes for potential use in future systems. We evaluated height, diameter, and volume after first year budset by testing 20 poplar clones and two willow clones. Unrooted cuttings, 20 cm long, were planted in randomized complete blocks at 0.91- x 0.91-m spacing at Gary, IN, USA (41.5 degrees N, 87.3 degrees W). Four commercial poplar clones (NM6, DN5, DN34, and DN182) were planted as 20- and 60-cm cuttings. Sixty-cm cuttings exhibited greater height and diameter than 20-cm cuttings; however, we recommend continued use and testing of different combinations of genotype and cutting length. We identified promising genotypes for potential use in future systems and we recommend allocating the majority of resources into commercial poplar clones, given their generalist growth performance. However, further utilization and selection of experimental clones is needed. Specific clones rather than genomic groups should be selected based on the geographic location and soil conditions of the site. PMID:16285410

  16. Contrail radiative forcing over the Northern Hemisphere from 2006 Aqua MODIS data

    NASA Astrophysics Data System (ADS)

    Spangenberg, Douglas A.; Minnis, Patrick; Bedka, Sarah T.; Palikonda, Rabindra; Duda, David P.; Rose, Fred G.

    2013-02-01

    Abstract Radiative forcing due to linear-shaped jet contrails is calculated over the Northern Hemisphere for four seasonal months using 2006 Aqua Moderate-resolution Imaging Spectroradiometer cloud and contrail property retrieval data in a radiative transfer model. The 4 month mean shortwave, longwave, and net radiative forcings normalized to 100% contrail cover are -5.7, 14.2, and 8.5 Wm-2. Mean total net forcing over the northern half of the globe varies from 9.1 mW m-2 during October to 12.1 mW m-2 in January and is only representative at 01:30 and 13:30 LT in nonpolar regions. In some dense flight traffic corridors, the mean net forcing approaches 80 mW m-2. Scaling the 4 month average of 10.6 mW m-2 to the Southern Hemisphere air traffic yields global mean net forcing of 5.7 mW m-2, which is smaller than most model estimates. Nighttime net forcing is 3.6 times greater than during daytime, when net forcing is greatest over low clouds. Effects from contrail cirrus clouds that evolve from linear contrails are not considered in these results.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3996072','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3996072"><span id="translatedtitle">Peripheral dose measurements in cervical cancer radiotherapy: a comparison of volumetric modulated arc therapy and step-and-shoot IMRT techniques</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p></p> <p>2014-01-01</p> <p>Purpose The aim of this study was to investigate the peripheral doses resulting from volumetric modulated arc therapy (VMAT) and intensity modulated radiotherapy (IMRT) techniques in cervical cancer radiotherapy. Methods Nine patients with cervical cancer had treatment planned with both VMAT and IMRT. A specially designed phantom was used for this study, with ion chambers placed at interest points approximating the position of the breast, thyroid, and lens. The peripheral doses at the phantom interest points were measured and compared between the VMAT and IMRT techniques. Results VMAT provides a potential dosimetric advantage compared with IMRT. The mean (± standard deviation) peripheral dose to the breast point for 1 fraction (2 Gy) during VMAT measured 5.13 ± 0.96 mGy, compared with 9.04 ± 1.50 mGy for IMRT. At the thyroid and lens interest points, the mean (± standard deviation) peripheral dose during VMAT was 2.19 ± 0.33 and 2.16 ± 0.28 mGy, compared with 7.07 ± 0.76 and 6.97 ± 0.<span class="hlt">91</span> <span class="hlt">m</span>Gy for IMRT, respectively. VMAT reduced the monitor units used by 28% and shortened the treatment delivery time by 54% compared with IMRT. Conclusion While the dosimetric results are similar for both techniques, VMAT results in a lower peripheral dose to the patient and reduces the monitor-unit usage and treatment delivery time compared with IMRT. PMID:24555547</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26674593','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26674593"><span id="translatedtitle">Crystal phase competition by addition of a second metal cation in solid solution metal-organic frameworks.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Castillo-Blas, C; Snejko, N; de la Peña-O'Shea, V A; Gallardo, J; Gutiérrez-Puebla, E; Monge, M A; Gándara, F</p> <p>2016-03-14</p> <p>Herein we report a synthetic study focused on the preparation of solid-solution metal-organic frameworks, MOFs, with the use of two kinds of linkers. In particular, we have explored the system composed by zinc, cobalt, 1,2,4-triazole and 4,4′-hexafluoroisopropylidenebisbenzoic acid (H2hfipbb). During this study, four new MOFs have been isolated, denoted TMPF-88 [M3(hfipbb)2(triazole)2(H2O)], TMPF-90 [M2(triazole)3(OCH2CH3)], TMPF-<span class="hlt">91</span> [<span class="hlt">M</span>2(hfipbb)(triazole)2(H2O)] and TMPF-95 [M5(hfipbb)4(triazole)2(H2O)] (TMPF = transition metal polymeric framework, M = Zn, Co, or mixture of them). The study demonstrates that the addition of a second metal element during the MOF synthesis has a major effect in the formation of new phases, even at very high Zn/Co metal ratios. Furthermore, we show that during the MOF formation reaction, there is a competition among different crystal phases, where kinetically favoured phases of various compositions crystallize in short reaction times, precluding the formation of the pure solid-solution phases of other energetically more stable MOFs. PMID:26674593</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/840300','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/840300"><span id="translatedtitle">A high average current DC GaAs photocathode gun for ERLs and FELs</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>C. Hernandez-Garcia; T. Siggins; S. Benson; D. Bullard; H. F. Dylla; K. Jordan; C. Murray; G. R. Neil; Michelle D. Shinn; R. Walker</p> <p>2005-05-01</p> <p>The Jefferson Lab (JLab) 10 kW IR Upgrade FEL DC GaAs photocathode gun is presently the highest average current electron source operational in the U.S., delivering a record 9.1 mA CW, 350 kV electron beam with 122 pC/bunch at 75 MHz rep rate. Pulsed operation has also been demonstrated with 8 mA per pulse (110 pC/bunch) in 16 ms-long pulses at 2 Hz rep rate. Routinely the gun delivers 5 mA CW and pulse current at 135 pC/bunch for FEL operations. The Upgrade DC photocathode gun is a direct evolution of the DC photocathode gun used in the previous JLab 1 kW IR Demo FEL. Improvements in the vacuum conditions, incorporation of two UHV motion mechanisms (a retractable cathode and a photocathode shield door) and a new way to add cesium to the GaAs photocathode surface have extended its lifetime to over 450 Coulombs delivered between re-cesiations (quantum efficiency replenishment). With each photocathode activation quantum efficiencies above 6% are routinely achieved. The photocathode activation and performance will be described in detail.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70026765','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70026765"><span id="translatedtitle">Heat flow in the SAFOD pilot hole and implications for the strength of the San Andreas Fault</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Williams, C.F.; Grubb, F.V.; Galanis, S.P., Jr.</p> <p>2004-01-01</p> <p>Detailed thermal measurements have been acquired in the 2.2-km-deep SAFOD pilot hole, located 1.8 km west of the SAF near Parkfield, California. Heat flow from the basement section of the borehole (770 to 2160 m) is <span class="hlt">91</span> <span class="hlt">m</span>W m-2, higher than the published 74 mW m -2 average for the Parkfield area. Within the resolution of the measurements, heat flow is constant across faults that intersect the borehole, suggesting that fluid flow does not alter the conductive thermal regime. Reanalysis of regional heat flow reveals an increase in heat flow along the SAF northwest of Parkfield. This transition corresponds to a shallowing base of seismicity and a change in fault behavior near the northern terminus of the M6 1966 Parkfield earthquake rupture. The persistence of elevated heat flow in the Coast Ranges to the west appears to rule out frictional heating on the SAF as the source of the SAFOD value.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_22 --> <div id="page_23" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="441"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/15054200','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/15054200"><span id="translatedtitle">Development and application of an integrated system for monitoring ethanol content of fuels.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Alhadeff, Eliana M; Salgado, Andrea M; Pereira, Nei; Valdman, Belkis</p> <p>2004-01-01</p> <p>An automated flow injection analysis (FIA) system for quantifying ethanol was developed using alcohol oxidase, horseradish peroxidase, 4-amino-phenazone, and phenol. A colorimetric detection method was developed using two different methods of analysis, with free and immobilized enzymes. The system with free enzymes permitted analysis of standard ethanol solution in a range of 0.05-1.0 g of ethanol/L without external dilution, a sampling frequency of 15 analyses/h, and relative SD of 3.5%. A new system was designed consisting of a microreactor with a 0.<span class="hlt">91</span>-<span class="hlt">m</span>L internal volume filled with alcohol oxidase immobilized on glass beads and an addition of free peroxidase, adapted in an FIA line, for continued reuse. This integrated biosensor-FIA system is being used for quality control of biofuels, gasohol, and hydrated ethanol. The FIA system integrated with the microreactor showed a calibration curve in the range of 0.05-1.5 g of ethanol/L, and good results were obtained compared with the ethanol content measured by high-performance liquid chromatography and gas chromatography standard methods. PMID:15054200</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26590824','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26590824"><span id="translatedtitle">Expression and localization of GPR91 and GPR99 in murine organs.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Diehl, Julia; Gries, Barbara; Pfeil, Uwe; Goldenberg, Anna; Mermer, Petra; Kummer, Wolfgang; Paddenberg, Renate</p> <p>2016-05-01</p> <p>Energy substrates and metabolic intermediates are proven ligands of a growing number of G-protein coupled receptors. In 2004, GPR91 and GPR99 were identified as receptors for the citric acid cycle intermediates, succinate and α-ketoglutarate, respectively. GPR91 seems to act as a first responder to local stress and GPR99 participates in the regulation of the acid-base balance through an intrarenal paracrine mechanism. However, a systematic analysis of the distribution of both receptors in mouse organs is still missing. The aim of this study was to examine the expression of GPR91 and GPR99 in a large number of different murine organs both at mRNA and protein level. Whereas GPR<span class="hlt">91</span> <span class="hlt">m</span>RNA was detectable in almost all organs, GPR99 mRNA was mainly expressed in neuronal tissues. Widespread expression of GPR91 was also detected at the protein level by western blotting and immunohistochemistry. In addition to neuronal cells, GPR99 protein was found in renal intercalated cells and epididymal narrow cells. Double-labeling immunohistochemistry demonstrated the colocalization of GPR99 with the B1 subunit isoform of vacuolar H(+)-ATPases which is expressed only by a very limited number of cell types. In summary, our detailed expression analysis of GPR91 and GPR99 in murine tissues will allow a more directed search for additional functions of both receptors. PMID:26590824</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AIPC.1728b0223D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AIPC.1728b0223D"><span id="translatedtitle">ZnO/CdS bi-layer nanostructures photoelectrode for dye-sensitized solar cells</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dalal, Paresh V.; Deshpande, Milind P.; Solanki, Bharat G.; Soni, Saurabh S.</p> <p>2016-05-01</p> <p>Simple chemical deposition method for the synthesis of ZnO/CdS bilayer photoelectrode on fluorine doped tin oxide (FTO) coated glass substrate in aqueous medium at low temperature (< 373K) is described. The different preparative parameters such as deposition time, bath temperature, concentration of precursor solution and, pH of the bath etc. were optimized. Nanograined ZnO was deposited on FTO coated glass substrates by dip-coating method, whereas CdS nanorods were successfully synthesized on pre-deposited ZnO film by Chemical Bath Deposition (CBD) method. The Photovoltaic properties of FTO/ZnO/CdS bilayer photo electrodes were also studied. A maximum short circuit current density of 9.1 mA cm-2 and conversion efficiency 1.05% are observed for ZnO/CdS_10min. Layer, which supports fast electron injection kinetics due to hetero structured nanorod, while minimum values of 0.53mA cm-2 and 0.01% respectively are observed for only ZnO deposited layer.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70017926','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70017926"><span id="translatedtitle">Climatic impact on isovolumetric weathering of a coarse-grained schist in the northern Piedmont Province of the central Atlantic states</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Cleaves, E.T.</p> <p>1993-01-01</p> <p>The possible impact of periglacial climates on the rate of chemical weathering of a coarse-grained plagioclase-muscovite-quartz schist has been determined for a small watershed near Baltimore, Maryland. The isovolumetric chemical weathering model formulated from the geochemical mass balance study of the watershed shows that the weathering front advances at a velocity of 9.1 m/m.y., if the modern environmental parameters remain the same back through time. However, recent surficial geological mapping demonstrates that periglacial climates have impacted the area. Such an impact significantly affects two key chemical weathering parameters, the concentration of CO2 in the soil and groundwater moving past the weathering front. Depending upon the assumptions used in the model, the rate of saprolitization varies from 2.2 to 5.3 m/m.y. The possible impact of periglacial processes suggested by the chemical weathering rates indicates a need to reconsider theories of landscape evolution as they apply to the northern Piedmont Province of the mid-Atlantic states. I suggest that from the Late Miocene to the present that the major rivers have become incised in their present locations; this incision has enhanced groundwater circulation and chemical weathering such that crystalline rocks beneath interfluvial areas remain mantled by saprolite; and the saprolite mantle has been partially stripped as periglacial conditions alternate with humid-temperate conditions. ?? 1993.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19940031343','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19940031343"><span id="translatedtitle">National Maglev initiative: California line electric utility power system requirements</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Save, Phil</p> <p>1994-01-01</p> <p>The electrical utility power system requirements were determined for a Maglev line from San Diego to San Francisco and Sacramento with a maximum capacity of 12,000 passengers an hour in each direction at a speed of 300 miles per hour, or one train every 30 seconds in each direction. Basically the Maglev line requires one 50-MVA substation every 12.5 miles. The need for new power lines to serve these substations and their voltage levels are based not only on equipment loading criteria but also on limitations due to voltage flicker and harmonics created by the Maglev system. The resulting power system requirements and their costs depend mostly on the geographical area, urban or suburban with 'strong' power systems, or mountains and rural areas with 'weak' power systems. A reliability evaluation indicated that emergency power sources, such as a 10-MW battery at each substation, were not justified if sufficient redundancy is provided in the design of the substations and the power lines serving them. With a cost of $5.6 M per mile, the power system requirements, including the 12-kV DC cables and the inverters along the Maglev line, were found to be the second largest cost component of the Maglev system, after the cost of the guideway system ($9.1 M per mile), out of a total cost of $23 M per mile.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27287153','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27287153"><span id="translatedtitle">Multi-loaded ceramic beads/matrix scaffolds obtained by combining ionotropic and freeze gelation for sustained and tuneable vancomycin release.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hess, Ulrike; Mikolajczyk, Gerd; Treccani, Laura; Streckbein, Philipp; Heiss, Christian; Odenbach, Stefan; Rezwan, Kurosch</p> <p>2016-10-01</p> <p>For a targeted release against bacteria-associated bone diseases (osteomyelitis) ceramic beads with a high drug loading capacity, loaded with vancomycin as model antibiotic, are synthesized as drug carrier and successfully incorporated in an open porous hydroxyapatite matrix scaffold via freeze gelation to prevent bead migration at the implantation site and to extend drug release. We demonstrate that the quantity of loaded drug by the hydroxyapatite and β-tricalcium phosphate beads, produced by ionotropic gelation, as well as drug release can be tuned and controlled by the selected calcium phosphate powder, sintering temperature, and high initial vancomycin concentrations (100mg/ml) used for loading. Bead pore volume up to 68mm(3)/g, with sufficiently large open pores (pore size of up to 650nm with open porosity of 72%) and high surface area (<span class="hlt">91</span><span class="hlt">m</span>(2)/g) account likewise for a maximum drug loading of 236mg/g beads or 26mg/sample. Multi-drug loading of the beads/matrix composite can further increase the maximum loadable amount of vancomycin to 37mg/sample and prolong release and antibacterial activity on Bacillus subtilis up to 5days. The results confirmed that our approach to incorporate ceramic beads as drug carrier for highly increased drug load in freeze-gelated matrix scaffolds is feasible and may lead to a sustained drug release and antibacterial activity. PMID:27287153</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26124565','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26124565"><span id="translatedtitle">Modeling Based Structural Insights into Biodegradation of the Herbicide Diuron by Laccase-1 from Ceriporiopsis subvermispora.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Vieira, Ana Carolina; Marschalk, Cidnei; Biavatti, Débora Carina; Lorscheider, Carla Andréia; Peralta, Rosane Marina; Seixas, Flavio Augusto Vicente</p> <p>2015-01-01</p> <p>The herbicide diuron (3-(3,4-dichlorophenyl)-1,1-dimethylurea) is used in many agricultural crops and non-crop areas worldwide, leading to the pollution of the aquatic environment by soil leaching. White rot fungi and its lignin modifying enzymes, peroxidases and laccases, are responsible for its degradation. Therefore, it is of interest to explore the potential use of Ceriporiopsis subvermispora laccase (CersuLac1) in the biotransformation of this herbicide by using its enzyme laccase. However, the structure of laccase from Ceriporiopsis subvermispora is still unknown. Hence, a model of laccase was constructed using homology modeling. The model was further used to dock p-methylbenzoate in the presence of four copper ions to analyze molecular basis of its binding and interaction. The ligand-protein interaction is stereo-chemically favorable in nature. The presence of the single protonated Lys457 was necessary for catalysis, being coordinated by a cupper ion. The best pose of diuron on CersuLac1 has a theoretical Ki of 2.<span class="hlt">91</span> <span class="hlt">m</span>M. This is comparable to the KM values for laccases from other organisms with similar compounds. Thus, we document the insights for the potential use of laccase from Ceriporiopsis subvermispora in the biotransfrormation of diuron. PMID:26124565</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26090472','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26090472"><span id="translatedtitle">Total Antioxidant Status in Type 2 Diabetic Patients in Palestine.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kharroubi, Akram T; Darwish, Hisham M; Akkawi, Mutaz A; Ashareef, Abdelkareem A; Almasri, Zaher A; Bader, Khaldoun A; Khammash, Umaiyeh M</p> <p>2015-01-01</p> <p>The objective of this study was to compare the level of total antioxidant status (TAS) in type 2 diabetic and normal Palestinian subjects as well as the major factors influencing TAS levels. A sample of convenience composed of 212 type 2 diabetic and 208 normal subjects above the age of 40 were recruited. Only 9.8% of the subjects had normal body mass index (BMI) levels (<25), 29% were overweight (≥25 to <30), and 61.2% were obese (≥30). The mean levels of TAS were significantly higher in diabetic compared to control subjects (2.18 versus 1.84 mM Trolox, P = 0.001) and in hypertensive subjects compared to subjects with normal blood pressure (BP). Mean TAS levels were higher in obese compared to nonobese subjects (2.12 versus 1.85 mM Trolox, P = 0.001). Mean TAS levels were similarly higher in subjects with high fasting plasma glucose (FPG) compared to normal FPG (2.19 versus 1.90 mM Trolox) and high HbA1c (≥6.5%) compared to HbA1c < 6.5% (2.14 versus 1.<span class="hlt">91</span> <span class="hlt">m</span>M Trolox). Multivariate analysis revealed that only diabetic status (P = 0.032) and the level of education (P = 0.036) were significantly associated with TAS. In conclusion diabetic patients had 18.5% increase in TAS levels compared to control subjects. PMID:26090472</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/20614784','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/20614784"><span id="translatedtitle">Paper sludge as a feasible soil amendment for the immobilization of Pb2+.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>He, Xiaojia; Yao, Lei; Liang, Zhu; Ni, Jinren</p> <p>2010-01-01</p> <p>The possibility of amending Pb2+ contaminated soil (S) with paper sludge (P) was investigated through adsorption and desorption experiments. The adsorption process of Pb2+ in soil containing paper sludge (SP) could be well described by pseudo second-order kinetic model and the Langmuir isotherm model. After P addition, the equilibrium time decreased greatly (from 28 to 8 hr) and the Pb2+ maximum adsorbed amount (Qmax) increased by a factor of more than three to 102.04 mg/g. Qmax reached its maximum as S:P was 9:1 (m/m) after 10 days contact between S and P. Moreover, Pb2+ adsorbed amount increased with the rise of pH during the adsorption process. Desorption experiments indicated that Pb2+ adsorption in SP was irreversible. The metal ion fraction was analyzed with Energy Dispersive Spectrometer and Environmental Scan Electron Microscope. As a result, the addition of P to soil was found to induce a decrease in the mobile forms. The Pb2+ complexes formation in the presence of carbonates was the main adsorption mechanism. Overall, the paper sludge could be one of the promising soil amendments for the remediation of soil with Pb2+ contamination. PMID:20614784</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19930006418','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19930006418"><span id="translatedtitle">A new thermal vacuum facility at the Martin Marietta Waterton plant</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Watson, Robert N.; Bonn, John W.</p> <p>1992-01-01</p> <p>A new thermal-vacuum facility has been recently completed at the Martin Marietta Waterton plant near Denver, Colorado. The facility was designed, fabricated, installed, and tested as a turn-key project by Pitt-Des Moines Inc. and CVI Inc. The chamber has a 5.49 M by 6.10 M (18 ft by 20 ft) flat floor and a half-cylindrical roof with a diameter of 5.49 M (18 ft). Both ends of the chamber have full cross section doors, with one equipped with translating motors for horizontal motion. The chamber is provided with four 0.<span class="hlt">91</span> <span class="hlt">M</span> (36 inches) cryopumps to obtain an ultimate pressure of 9 x 10(exp -8) Torr (Clean-Dry-Empty). The thermal shroud is designed to operate at a maximum of -179 C (-290 F) with an internal heat input of 316 MJ/Hr (300,000 BTU/Hr) using liquid nitrogen. The shroud is also designed to operate at any temperature between -156 C (-250 F) and 121 C (+250 F) using gaseous nitrogen, and heat or cool at a rate of 1.1 C (2 F) per minute.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19950016593','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19950016593"><span id="translatedtitle">The effect of sensor spacing on wind measurements at the Shuttle Landing Facility</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Merceret, Francis J.</p> <p>1995-01-01</p> <p>This document presents results of a field study of the effect of sensor spacing on the validity of wind measurements at the Space Shuttle landing Facility (SLF). Standard measurements are made at one second intervals from 30 foot (9.1m) towers located 500 feet (152m) from the SLF centerline. The centerline winds are not exactly the same as those measured by the towers. This study quantifies the differences as a function of statistics of the observed winds and distance between the measurements and points of interest. The field program used logarithmically spaced portable wind towers to measure wind speed and direction over a range of conditions. Correlations, spectra, moments, and structure functions were computed. A universal normalization for structure functions was devised. The normalized structure functions increase as the 2/3 power of separation distance until an asymptotic value is approached. This occurs at spacings of several hundred feet (about 100m). At larger spacings, the structure functions are bounded by the asymptote. This enables quantitative estimates of the expected differences between the winds at the measurement point and the points of interest to be made from the measured wind statistics. A procedure is provided for making these estimates.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19960004072','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19960004072"><span id="translatedtitle">The effect of sensor sheltering and averaging techniques on wind measurements at the Shuttle Landing Facility</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Merceret, Francis J.</p> <p>1995-01-01</p> <p>This document presents results of a field study of the effect of sheltering of wind sensors by nearby foliage on the validity of wind measurements at the Space Shuttle Landing Facility (SLF). Standard measurements are made at one second intervals from 30-feet (9.1-m) towers located 500 feet (152 m) from the SLF centerline. The centerline winds are not exactly the same as those measured by the towers. A companion study, Merceret (1995), quantifies the differences as a function of statistics of the observed winds and distance between the measurements and points of interest. This work examines the effect of nearby foliage on the accuracy of the measurements made by any one sensor, and the effects of averaging on interpretation of the measurements. The field program used logarithmically spaced portable wind towers to measure wind speed and direction over a range of conditions as a function of distance from the obstructing foliage. Appropriate statistics were computed. The results suggest that accurate measurements require foliage be cut back to OFCM standards. Analysis of averaging techniques showed that there is no significant difference between vector and scalar averages. Longer averaging periods reduce measurement error but do not otherwise change the measurement in reasonably steady flow regimes. In rapidly changing conditions, shorter averaging periods may be required to capture trends.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004JSSCh.177..793S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004JSSCh.177..793S"><span id="translatedtitle">Mechanochemical-hydrothermal synthesis of calcium phosphate powders with coupled magnesium and carbonate substitution</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Suchanek, Wojciech L.; Byrappa, Kullaiah; Shuk, Pavel; Riman, Richard E.; Janas, Victor F.; TenHuisen, Kevor S.</p> <p>2004-03-01</p> <p>Magnesium- and carbonate-substituted calcium phosphate powders (Mg-, CO 3-CaP) with various crystallinity levels were prepared at room temperature via a heterogeneous reaction between MgCO 3/Ca(OH) 2 powders and an (NH 4) 2HPO 4 solution using the mechanochemical-hydrothermal route. X-ray diffraction, infrared spectroscopy, and thermogravimetric analysis were performed. It was determined that the powders containing both Mg 2+ and CO 32- ions were incorporated uniformly into an amorphous calcium phosphate phase while in contrast, the as-prepared powder free of these dopants was crystalline phase-pure, stoichiometric hydroxyapatite. Dynamic light scattering revealed that the average particle size of the room temperature Mg-, CO 3-CaP powders was in the range of 482 nm-700 nm with a specific surface area between 53 and <span class="hlt">91</span> <span class="hlt">m</span> 2/g. Scanning electron microscopy confirmed that the Mg-, CO 3-CaP powders consisted of agglomerates of equiaxed, ≈20-35 nm crystals.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/6503983','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/6503983"><span id="translatedtitle">Development of Miocene-Pliocene reef trend, St. Croix, U. S. Virgin Islands</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Gill, I.; Eby, D.E.; Hubbard, D.K.; Frost, S.H.</p> <p>1988-01-01</p> <p>The Miocene-Pliocene reef trend on St. Croix, U.S. Virgin Islands, rims the present southern western coasts of the island and includes accompanying lagoonal and forereef facies. The reef trend was established on a foram-algal bank facies that represents basinal shallowing from the deep-water pelagic and hemipelagic facies of the Miocene Kingshill Limestone. Information on facies distribution and thickness is derived from rock exposures and 22 test wells drilled to a maximum depth of <span class="hlt">91</span> <span class="hlt">m</span>. The greatest thickness of the reef facies exists in a subsidiary graben on the south coast of St. Croix. The thickness of the reef section in this locality is due to preservation of the section in a downdropped block. Reef faunas include extant corals, as well as several extinct genera. Extant corals (e.g. Montastrea annularis, Diploria sp., and Porites porites) and extinct corals (e.g., Stylophora affinis, Antillea bilobata, and Thysanus sp.) are the main reef frame-builders. Coralline algea and large benthic foraminifera are significant contributors to the sediments both prior to and during scleractinian reef growth. Dolomitization and calcite cementation occur prominantly in an area corresponding to a Holocene lagoon. The spatial distribution of the dolomite suggests that the lagoon is a Tertiary feature directly related to the dolomitization process. Stable isotopic values suggest dolomitization of fluids of elevated salinity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/2507527','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/2507527"><span id="translatedtitle">Sodium dependence of acetate formation by the acetogenic bacterium Acetobacterium woodii.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Heise, R; Müller, V; Gottschalk, G</p> <p>1989-10-01</p> <p>Growth of Acetobacterium woodii on fructose was stimulated by Na+; this stimulation was paralleled by a shift of the acetate-fructose ratio from 2.1 to 2.7. Growth on H2-CO2 or on methanol plus CO2 was strictly dependent on the presence of sodium ions in the medium. Acetate formation from formaldehyde plus H2-CO by resting cells required Na+, but from methanol plus H2-CO did not. This is analogous to H2-CO2 reduction to methane by Methanosarcina barkeri, which involves a sodium pump (V. Müller, C. Winner, and G. Gottschalk, Eur. J. Biochem. 178:519-525, 1988). This suggests that the reduction of methylenetetrahydrofolate to methyltetrahydrofolate is the Na+-requiring reaction. A sodium gradient (Na+ out/Na+ in = 32, delta pNa = -<span class="hlt">91</span> <span class="hlt">m</span>V) was built up when resting cells of A. woodii were incubated under H2-CO2. Acetogenesis was inhibited when the delta pNa was dissipated by monensin. PMID:2507527</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016Nanot..27I5605N&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016Nanot..27I5605N&link_type=ABSTRACT"><span id="translatedtitle">Anodic Ag/TiO2 nanotube array formation in NaOH/fluoride/ethylene glycol electrolyte as a photoanode for dye-sensitized solar cells</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nyein, Nyein; Kian Tan, Wai; Kawamura, Go; Matsuda, Astunori; Lockman, Zainovia</p> <p>2016-09-01</p> <p>Self-organized, 23 μm-thick anodic TiO2 nanotube (TNT) arrays were formed in sodium hydroxide/fluoride/ethylene glycol (EG) electrolyte at 60 V for 60 min. The presence of sodium hydroxide (NaOH) in the fluoride/EG electrolyte accelerates the formation of the TiO2 nanotube arrays. The anodic film was then decorated with silver nanoparticles (Ag NPs) by the photodeposition process and used as a photoanode in a rear-side-illuminated dye-sensitized solar cell. The Ag NPs decorated TNT arrays, with the former having diameters of 10–30 nm formed from 0.2 M of Ag-precursor solution and exhibiting the highest photoconversion efficiency (η) of 3.7% and a short-circuit current density of 12.2 mA cm‑2 compared to η = 3% and short-circuit current density of 9.1 mA cm‑2 for a sample without Ag NPs. The increase in η is thought to be due to the surface plasmon resonance and excess electrons from the nanoparticles.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27456036','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27456036"><span id="translatedtitle">Anodic Ag/TiO2 nanotube array formation in NaOH/fluoride/ethylene glycol electrolyte as a photoanode for dye-sensitized solar cells.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Nyein, Nyein; Tan, Wai Kian; Kawamura, Go; Matsuda, Astunori; Lockman, Zainovia</p> <p>2016-09-01</p> <p>Self-organized, 23 μm-thick anodic TiO2 nanotube (TNT) arrays were formed in sodium hydroxide/fluoride/ethylene glycol (EG) electrolyte at 60 V for 60 min. The presence of sodium hydroxide (NaOH) in the fluoride/EG electrolyte accelerates the formation of the TiO2 nanotube arrays. The anodic film was then decorated with silver nanoparticles (Ag NPs) by the photodeposition process and used as a photoanode in a rear-side-illuminated dye-sensitized solar cell. The Ag NPs decorated TNT arrays, with the former having diameters of 10-30 nm formed from 0.2 M of Ag-precursor solution and exhibiting the highest photoconversion efficiency (η) of 3.7% and a short-circuit current density of 12.2 mA cm(-2) compared to η = 3% and short-circuit current density of 9.1 mA cm(-2) for a sample without Ag NPs. The increase in η is thought to be due to the surface plasmon resonance and excess electrons from the nanoparticles. PMID:27456036</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22348534','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22348534"><span id="translatedtitle">The binary white dwarf LHS 3236</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Harris, Hugh C.; Dahn, Conard C.; Canzian, Blaise; Guetter, Harry H.; Levine, Stephen E.; Luginbuhl, Christian B.; Monet, Alice K. B.; Stone, Ronald C.; Subasavage, John P.; Tilleman, Trudy; Walker, Richard L.; Dupuy, Trent J.; Liu, Michael C.; Hartkopf, William I.; Ireland, Michael J.; Leggett, S. K.</p> <p>2013-12-10</p> <p>The white dwarf LHS 3236 (WD1639+153) is shown to be a double-degenerate binary, with each component having a high mass. Astrometry at the U.S. Naval Observatory gives a parallax and distance of 30.86 ± 0.25 pc and a tangential velocity of 98 km s{sup –1}, and reveals binary orbital motion. The orbital parameters are determined from astrometry of the photocenter over more than three orbits of the 4.0 yr period. High-resolution imaging at the Keck Observatory resolves the pair with a separation of 31 and 124 mas at two epochs. Optical and near-IR photometry give a set of possible binary components. Consistency of all data indicates that the binary is a pair of DA stars with temperatures near 8000 and 7400 K and with masses of 0.93 and 0.<span class="hlt">91</span> <span class="hlt">M</span> {sub ☉}; also possible is a DA primary and a helium DC secondary with temperatures near 8800 and 6000 K and with masses of 0.98 and 0.69 M {sub ☉}. In either case, the cooling ages of the stars are ∼3 Gyr and the total ages are <4 Gyr. The combined mass of the binary (1.66-1.84 M {sub ☉}) is well above the Chandrasekhar limit; however, the timescale for coalescence is long.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27217363','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27217363"><span id="translatedtitle">The effect of locust bean gum (LBG)-based edible coatings carrying biocontrol yeasts against Penicillium digitatum and Penicillium italicum causal agents of postharvest decay of mandarin fruit.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Parafati, Lucia; Vitale, Alessandro; Restuccia, Cristina; Cirvilleri, Gabriella</p> <p>2016-09-01</p> <p>Strains belonging to Wickerhamomyces anomalus, Metschnikowia pulcherrima and Aureobasidium pullulans species were tested in vitro as biocontrol agents (BCAs) against the post-harvest pathogenic molds Penicillium digitatum and Penicillium italicum. Moreover, studies aimed at screening the antifungal activity of selected yeast strains in vivo conditions against P. digitatum and P. italicum, and investigated the efficacy of a polysaccharidic matrix, locust bean gum (LBG), enriched with the tested BCAs, in controlling postharvest decays in artificially inoculated mandarins. The population dynamics of BCAs on wounds and the magnitude of peroxidase (POD) and superoxide dismutase (SOD) in fruit tissues were also investigated after treatments of mandarins with antagonistic yeasts. W. anomalus BS<span class="hlt">91</span>, <span class="hlt">M</span>. pulcherrima MPR3 and A. pullulans PI1 provided excellent control of postharvest decays caused by P. digitatum and P. italicum on mandarins, both when the yeasts were used alone and in combination with LBG, which enhanced the yeast cell viability over time. Finally, the increased activity of POD and lower decrease in SOD activity in response to BCAs application in mandarin fruits confirmed their involvement in the biocontrol mechanism. PMID:27217363</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20110012880&hterms=index&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dindex','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20110012880&hterms=index&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dindex"><span id="translatedtitle">Measuring Effective Leaf Area Index, Foliage Profile, and Stand Height in New England Forest Stands Using a Full-Waveform Ground-Based Lidar</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Zhao, Feng; Yang, Xiaoyuan; Schull, Mithcell A.; Roman-Colon, Miguel O.; Yao, Tian; Wang, Zhuosen; Zhang, Qingling; Jupp, David L. B.; Lovell, Jenny L.; Culvenor, Darius; Newnham, Glenn J.; Richardson, Andrew D.; Ni-Meister, Wenge; Schaaf, Crystal L.; Woodcock, Curtis E.; Strahler, Alan H.</p> <p>2011-01-01</p> <p>Effective leaf area index (LAI) retrievals from a scanning, ground-based, near-infrared (1064 nm) lidar that digitizes the full return waveform, the Echidna Validation Instrument (EVI), are in good agreement with those obtained from both hemispherical photography and the Li-Cor LAI-2000 Plant Canopy Analyzer. We conducted trials at 28 plots within six stands of hardwoods and conifers of varying height and stocking densities at Harvard Forest, Massachusetts, Bartlett Experimental Forest, New Hampshire, and Howland Experimental Forest, Maine, in July 2007. Effective LAI values retrieved by four methods, which ranged from 3.42 to 5.25 depending on the site and method, were not significantly different ( b0.1 among four methods). The LAI values also matched published values well. Foliage profiles (leaf area with height) retrieved from the lidar scans, although not independently validated, were consistent with stand structure as observed and as measured by conventional methods. Canopy mean top height, as determined from the foliage profiles, deviated from mean RH100 values obtained from the Lidar Vegetation Imaging Sensor (LVIS) airborne large-footprint lidar system at 27 plots by .0.<span class="hlt">91</span> <span class="hlt">m</span> with RMSE=2.04 m, documenting the ability of the EVI to retrieve stand height. The Echidna Validation Instrument is the first realization of the Echidna lidar concept, devised by Australia's Commonwealth Scientific and Industrial Research Organization (CSIRO), for measuring forest structure using full-waveform, ground-based, scanning lidar.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_23 --> <div id="page_24" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="461"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19850008682','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19850008682"><span id="translatedtitle">Shuttle/Centaur project perspective</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Muckley, E. T.</p> <p>1984-01-01</p> <p>The shuttle/Centaur vehicle is being developed as an expendable, cryogenic high energy upper stage for use with the National Space Transportation System (NSTS). The stage is expected to meet the demands of a wide range of users. The shuttle/Centaur will be a modification of the highly successful Centaur stage, used extensively with the Atlas and Titan boosters since 1966 to launch planetary, geosynchronous and Earth orbital missions. The design changes required for use with the NSTS are described. These are primarily related to: (1) tank resizing to take advantage of the orbiter payload bay dimensions; (2) provisions for physically adopting Centaur to the orbiter; and, (3) accommodating safety requirements of the manned NSTS. The expected performance capabilities of two versions of the shuttle/Centaur are also described. The initial version, designated G-prime, is the larger of the two, with a length of about 9.1m (30 ft.). This vehicle will be used to launch the Galileo and International Solar Polar Mission to Jupiter in May 1986.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012JPS...213..233C&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012JPS...213..233C&link_type=ABSTRACT"><span id="translatedtitle">Study of a Li-air battery having an electrolyte solution formed by a mixture of an ether-based aprotic solvent and an ionic liquid</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cecchetto, Laura; Salomon, Mark; Scrosati, Bruno; Croce, Fausto</p> <p>2012-09-01</p> <p>Recent studies have clearly demonstrated that cyclic and linear carbonates are unstable when used in rechargeable Li-air batteries employing aprotic solvents mostly due to the cathodic formation of superoxide during the oxygen reduction reaction. In particular, it has been ascertained that nucleophilic attack by superoxide anion radical, O2-rad , at O-alkyl carbon is a common mechanism of decomposition of organic carbonates. Moreover, theoretical calculations showed that ether chemical functionalities are stable against nucleophilic substitution induced by superoxide. Aim of this study is to report on a new electrolyte solution for Li-air battery formed by a mixture of an ether-based aprotic solvent with an ionic liquid (IL). The IL-based electrolyte was obtained by mixing the pure ionic liquid N-methyl-(n-butyl) pyrrolidinium bis(trifluoromethane sulfonyl) imide (here denoted as PYR14TFSI) to a 0.<span class="hlt">91</span> <span class="hlt">M</span> solution of lithium triflate (LiCF3SO3) in tetra ethylene glycol dimethyl etcher (TEGDME). We observed that the presence of IL beneficially affects the kinetics and the reversibility of the oxygen reactions involved at the cathode. The most significant result being a lower overvoltage for the charge reaction, compared to a Li/air cell containing the same electrolyte solution without IL.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19950056069&hterms=continuum+begin&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dcontinuum%2Bbegin','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19950056069&hterms=continuum+begin&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dcontinuum%2Bbegin"><span id="translatedtitle">A multifrequency radio continuum and IRAS faint source survey of markarian galaxies</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Bicay, M. D.; Kojoian, G.; Seal, J.; Dickinson, D. F.; Malkan, M. A.</p> <p>1995-01-01</p> <p>Results are presented from a multifrequency radio continumm survey of Markarian galaxies (MRKs) and are supplemented by IRAS infrared data from the Faint Source Survey. Radio data are presented for 899 MRKs observed at nu = 4.755 GHz with the National Radio Astronomy Observatory (NRAO)-Green Bank 300 foot (<span class="hlt">91</span> <span class="hlt">m</span>) telescope, including nearly 88% of those objects in Markarian lists VI-XIV. In addition, 1.415 GHz measurements of 258 MRKs, over 30% of the MRKs accessible from the National Aeronomy and Ionosphere Center (NAIC)-Arecibo, are reported. Radio continuum observations of smaller numbers of MRKs were made at 10.63 GHz and at 23.1 GHz and are also presented. Infrared data from the IRAS Faint Source Survey (Ver. 2) are presented for 944 MRKs, with reasonably secure identifications extracted from the NASA/IPAC Extragalactic Database. MRKs exhibit the same canonical infrared characteristics as those reported for various other galaxy samples, that is well-known enhancement of the 25 micrometer/60 micrometer color ratio among Seyfert MRKs, and a clear tendency for MRKs with warmer 60 micrometer/100 micrometer colors to also possess cooler 12 micrometer/25 micrometer colors. In addition, non-Seyfert are found to obey the well-documented infrared/radio luminosity correlation, with the tightest correlation seen for starburst MRKs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014ApPhL.105k3904S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014ApPhL.105k3904S"><span id="translatedtitle">Enhancement of current collection in epitaxial lift-off InAs/GaAs quantum dot thin film solar cell and concentrated photovoltaic study</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sogabe, Tomah; Shoji, Yasushi; Mulder, Peter; Schermer, John; Tamayo, Efrain; Okada, Yoshitaka</p> <p>2014-09-01</p> <p>We report the fabrication of a thin film InAs/GaAs quantum dot solar cell (QD cell) by applying epitaxial lift-off (ELO) approach to the GaAs substrate. We confirmed significant current collection enhancement (˜0.<span class="hlt">91</span> <span class="hlt">m</span>A/cm2) in the ELO-InAs QD cell within the wavelength range of 700 nm-900 nm when compared to the ELO-GaAs control cell. This is almost six times of the sub-GaAs bandgap current collection (˜0.16 mA/cm2) from the wavelength range of 900 nm and beyond, we also confirmed the ELO induced resonance cavity effect was able to increase the solar cell efficiency by increasing both the short circuit current and open voltage. The electric field intensity of the resonance cavity formed in the ELO film between the Au back reflector and the GaAs front contact layer was analyzed in detail by finite-differential time-domain (FDTD) simulation. We found that the calculated current collection enhancement within the wavelength range of 700 nm-900 nm was strongly influenced by the size and shape of InAs QD. In addition, we performed concentrated light photovoltaic study and analyzed the effect of intermediate states on the open voltage under varied concentrated light intensity for the ELO-InAs QD cell.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25113864','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25113864"><span id="translatedtitle">Evaluating the physical demands on firefighters using track-type stair descent devices to evacuate mobility-limited occupants from high-rise buildings.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Mehta, Jay P; Lavender, Steven A; Hedman, Glenn E; Reichelt, Paul A; Park, Sanghyun; Conrad, Karen M</p> <p>2015-01-01</p> <p>The physical demands on firefighting personnel were investigated when using different types of track-type stair descent devices designed for the emergency evacuation of high rise buildings as a function of staircase width and evacuation urgency. Twelve firefighters used five track-type stair descent devices during simulated urgent and non-urgent evacuations. The devices were evaluated under two staircase width conditions (1.12, and 1.32 m), and three devices were also evaluated under a narrower staircase condition (0.<span class="hlt">91</span> <span class="hlt">m</span>). Dependent measures included electromyographic (EMG) data, spine motion, heart rates, Borg Scale ratings, task durations and descent velocities. Stair descent speeds favored the devices that had shorter fore/aft dimensions when moving through the landing. EMG results indicated that there were tradeoffs due to design features, particularly on the landings where the physical demands tended to be greater. On the landings, devices that could be rolled on four wheels reduced the deltoid and bicep activation levels. PMID:25113864</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2951758','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2951758"><span id="translatedtitle">An International Randomized Multicenter Comparison of Nasal Potential Difference Techniques</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Solomon, George M.; Konstan, Michael W.; Wilschanski, Michael; Billings, Joanne; Sermet-Gaudelus, Isabelle; Accurso, Frank; Vermeulen, François; Levin, Elina; Hathorne, Heather; Reeves, Ginger; Sabbatini, Gina; Hill, Aubrey; Mayer-Hamblett, Nicole; Ashlock, Melissa; Clancy, John Paul</p> <p>2010-01-01</p> <p>Background: The transepithelial nasal potential difference (NPD) is used to assess cystic fibrosis transmembrane conductance regulator (CFTR) activity. Unreliability, excessive artifacts, and lack of standardization of current testing systems can compromise its use as a diagnostic test and outcome measure for clinical trials. Methods: To determine whether a nonperfusing (agar gel) nasal catheter for NPD measurement is more reliable and less susceptible to artifacts than a continuously perfusing nasal catheter, we performed a multicenter, randomized, crossover trial comparing a standardized NPD protocol using an agar nasal catheter with the same protocol using a continuously perfusing catheter. The data capture technique was identical in both protocols. A total of 26 normal adult subjects underwent NPD testing at six different centers. Results: Artifact frequency was reduced by 75% (P < .001), and duration was less pronounced using the agar catheter. The measurement of sodium conductance was similar between the two catheter methods, but the agar catheter demonstrated significantly greater CFTR-dependent hyperpolarization, because Δ zero Cl- + isoproterenol measurements were significantly more hyperpolarized with the agar catheter (224.2 ± 12.9 mV with agar vs 18.2 ± 9.1 mV with perfusion, P < .05). Conclusions: The agar nasal catheter approach demonstrates superior reliability compared with the perfusion nasal catheter method for measurement of NPD. This nonperfusion catheter method should be considered for adoption as a standardized protocol to monitor CFTR activity in clinical trials. PMID:20472865</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27478013','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27478013"><span id="translatedtitle">Alpha-synuclein (SNCA) polymorphisms exert protective effects on memory after mild traumatic brain injury.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Shee, Kevin; Lucas, Alexandra; Flashman, Laura A; Nho, Kwangsik; Tsongalis, Gregory J; McDonald, Brenna C; Saykin, Andrew J; McAllister, Thomas W; Rhodes, C Harker</p> <p>2016-09-01</p> <p>Problems with attention and short-term learning and memory are commonly reported after mild traumatic brain injury (mTBI). Due to the known relationships between α-synuclein (SNCA), dopaminergic transmission, and neurologic deficits, we hypothesized that SNCA polymorphisms might be associated with cognitive outcome after mTBI. A cohort of <span class="hlt">91</span> <span class="hlt">m</span>TBI patients one month after injury and 86 healthy controls completed a series of cognitive tests assessing baseline intellectual function, attentional function, and memory, and was genotyped at 13 common single nucleotide polymorphisms (SNPs) in the SNCA gene. Significant differences in two memory measures (p=0.001 and 0.002), but not baseline intellectual function or attentional function tasks, were found between the mTBI group and controls. A highly significant protective association between memory performance and SNCA promoter SNP rs1372525 was observed in the mTBI patients (p=0.006 and 0.029 for the long and short delay conditions of the California Verbal Learning Tests, respectively), where the presence of at least one copy of the A (minor) allele was protective after mTBI. These results may help elucidate the pathophysiology of cognitive alterations after mTBI, and thus warrant further investigation. PMID:27478013</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70048675','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70048675"><span id="translatedtitle">Spatial distribution of pelagic fish larvae in the northern main basin of Lake Huron</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Roseman, Edward F.; O'Brien, Timothy P.</p> <p>2013-01-01</p> <p>Larval fish occurrence in inshore and offshore zones in the northern main basin of Lake Huron was assessed during 2007 as part of a larger ecological examination of Lake Huron foodwebs and habitats. Day and night collections using neuston and conical nets at inshore (1.5–15 m depths) and offshore (37 and <span class="hlt">91</span> <span class="hlt">m</span> depths) locations at De Tour and Hammond Bay to assess the abundance, phenology, and spatial distribution of pelagic ichthyoplankton during spring and early summer were made. In general, densities of larval fishes were higher at De Tour than Hammond Bay during daytime neuston net collections, with the exception of Longnose Sucker, which were only collected at Hammond Bay. Lake Whitefish, Burbot, and Rainbow Smelt dominated inshore catches in early spring with Cisco, Deepwater Sculpin, Emerald Shiner, Bloater, Slimy Sculpin, Ninespine Stickleback, and Yellow Perch larvae also collected. Nighttime nearshore and offshore sampling revealed that Rainbow Smelt and Burbot larvae were present in relatively high abundances compared to inshore densities. Concentrations of larvae of deepwater demersal fishes such as Lake Whitefish and Deepwater Sculpin suggest that inshore zones in northern Lake Huron are important nursery habitats emphasizing a critical production and recruitment linkage between inshore and deepwater zones.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/23848426','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/23848426"><span id="translatedtitle">Atorvastatin is beneficial for muscle reinnervation after complete sciatic nerve section in rats.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Cloutier, Frédéric-Charles; Rouleau, Dominique M; Hébert-Davies, Jonah; Beaumont, Pierre H; Beaumont, Eric</p> <p>2013-12-01</p> <p>Nerve regeneration and functional recovery are often incomplete after peripheral neurotmetic lesion. Atorvastatin has been shown to be neuroprotective after transient ischaemia or traumatic injury. The aim of this study was to establish if systemic administration of Atorvastatin could improve functional muscle reinnervation after complete sciatic nerve section. Sixteen female Sprague-Dawley rats were used in this study. After a complete right sciatic nerve section, end-to-end microsuture repair was performed and fibrin glue was added. Three groups were studied: (1) sutures (S) + fibrin glue (F) only + saline administration for 14 days; (2) S+F+Atorvastatin administration for 14 days; and (3) uninjured nerve. Five months later, the sciatic nerve and the gastrocnemius muscle were isolated to perform in vivo electrophysiological measurements. Better kinematics was observed in atorvastatin-treated rats 5 months after its administration. Indeed, a larger excursion of the hip-ankle-toe angle during walking was observed. This effect was associated with the preservation of electromyographic activity (2.<span class="hlt">91</span> <span class="hlt">m</span>V vs 0.77 mV) and maximal muscle force (85.1 g vs 28.6 g) on stimulation of the proximal nerve section. Five months after a neurotmetic lesion, the recovery is incomplete when using suture and fibrin glue only. Furthermore, the systemic administration of Atorvastatin for 14 days after lesion was beneficial in improving locomotion capability associated with the re-establishment of muscle strength and EMG activity. PMID:23848426</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009GeCoA..73.4199S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009GeCoA..73.4199S"><span id="translatedtitle">An attenuated total reflectance IR study of silicic acid adsorbed onto a ferric oxyhydroxide surface</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Swedlund, Peter J.; Miskelly, Gordon M.; McQuillan, A. James</p> <p>2009-07-01</p> <p>Silicic acid (H 4SiO 4) can have significant effects on the properties of iron oxide surfaces in both natural and engineered aquatic systems. Understanding the reactions of H 4SiO 4 on these surfaces is therefore necessary to describe the aquatic chemistry of iron oxides and the elements that associate with them. This investigation uses attenuated total reflectance infrared spectroscopy (ATR-IR) to study silicic acid in aqueous solution and the products formed when silicic acid adsorbs onto the surface of a ferrihydrite film in 0.01 M NaCl at pH 4. A spectrum of 1.66 mM H 4SiO 4 at pH 4 (0.01 M NaCl) has an asymmetric Si-O stretch at 939 cm -1 and a weak Si-O-H deformation at 1090 cm -1. ATR-IR spectra were measured over time (for up to 7 days) for a ferrihydrite film (≈1 mg) approaching equilibrium with H 4SiO 4 at concentrations between 0.044 and 0.<span class="hlt">91</span> <span class="hlt">m</span>M. Adsorbed H 4SiO 4 had a broad spectral feature between 750 and 1200 cm -1 but the shape of the spectra changed as the amount of H 4SiO 4 adsorbed on the ferrihydrite increased. When the solid phase Si/Fe mole ratio was less than ≈0.01 the ATR-IR spectra had a maximum intensity at 943 cm -1 and the spectral shape suggests that a monomeric silicate species was formed via a bidentate linkage. As the solid phase Si/Fe mole ratio increased to higher values a discrete oligomeric silicate species was formed which had maximum intensity in the ATR-IR spectra at 1001 cm -1. The spectrum of this species suggests that it is larger than a dimer and it was tentatively identified as a cyclic tetramer. A small amount of a polymeric silica phase with a broad spectral feature centered at ≈1110 cm -1 was also observed at high surface coverage. The surface composition was estimated from the relative contribution of each species to the area of the ATR-IR spectra using multivariate curve resolution with alternating least squares. For a ferrihydrite film approaching equilibrium with 0.044, 0.14, 0.40 and 0.<span class="hlt">91</span> <span class="hlt">m</span>M H 4SiO 4 the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25841963','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25841963"><span id="translatedtitle">Stall cleanliness and stall temperature of two different freestall bases.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wadsworth, B A; Stone, A E; Clark, J D; Ray, D L; Bewley, J M</p> <p>2015-06-01</p> <p>The objective of this study was to describe the differences in freestall cleanliness and stall temperature between a barn with Dual Chamber Cow Waterbeds (DCCW; Advanced Comfort Technology, Reedsburg, WI) and a barn with rubber-filled mattresses at the University of Kentucky Coldstream Dairy Research Farm from January 18, 2012, to May 3, 2013. Stall cleanliness was measured twice weekly (n=134) by the same 2 observers using a 0.<span class="hlt">91</span> <span class="hlt">m</span>×0.<span class="hlt">91</span> <span class="hlt">m</span> wire grid containing 128 equally sized rectangles (10.16 cm×5.08 cm). This grid was centered at the rear portion of the stall; a rectangle that was visibly wet or had any amount of feces present was defined as a dirty rectangle. Weekly stall temperature (n=66) was measured by the same observer during a.m. milkings in the same predetermined stalls. Feces and wet sawdust were removed from the stalls before stall temperatures were acquired. Temperatures were obtained using a handheld thermometer at 30.48 cm above the stall base as determined via dual laser measurements. Stall temperature was measured on the front, middle, and back of the stall first with clean sawdust and then with the sawdust removed from the stall and wiped clean with a towel. Daily temperature-humidity index (THI) was calculated using Kentucky climate data calculated through the University of Kentucky College of Agriculture via a data logger, located 5.63 km from the Coldstream Dairy Farm. Stall cleanliness was not different between the DCCW barn (26.09±0.89 rectangles) and the rubber-filled mattress barn (23.70±0.89 rectangles). Mean THI throughout the study was 64.39±0.82. Stall temperature was different among THI categories. Temperature-humidity index categories 1 (coldest), 2, 3, and 4 (warmest) had THI ranges of 22.94 to 50.77, 50.77 to 64.88, 64.88 to 78.75, and 78.75 to 101.59, respectively. Stall temperatures (°C; least squares means±SE) were 2.26±0.30, 8.86±0.30, 15.52±0.30, and 20.95±0.30 for THI categories 1 to 4, respectively. Stalls with</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013Nanos...5.7867C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013Nanos...5.7867C"><span id="translatedtitle">Yolk-shelled cathode materials with extremely high electrochemical performances prepared by spray pyrolysis</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Choi, Seung Ho; Hong, Young Jun; Kang, Yun Chan</p> <p>2013-08-01</p> <p>A facile, continuous preparation process of yolk-shell-structured lithium-metal oxide powders without a template for use as cathode materials in lithium ion batteries is introduced for the first time. Single and double-shelled LiNi0.5Mn1.5O4 yolk-shell powders as the first target materials are prepared directly by spray pyrolysis from a spray solution with sucrose, at a short residence time of 4 s. Fast combustion and contraction of a carbon-mixed oxide composite intermediate, formed from a micro-sized droplet inside a hot wall reactor maintained at 700 °C, produces the yolk-shell powders. The yolk-shell structure of the precursor powders directly prepared by spray pyrolysis is well maintained even at a high post-treatment temperature of 750 °C. The yolk-shell LiNi0.5Mn1.5O4 powders delivered a 1000th high discharge capacity of 108 mA h g-1 at 10 C. The discharge capacities are as high as 103, 95, and <span class="hlt">91</span> <span class="hlt">m</span>A h g-1 at extremely high discharge rates of 100, 200, and 300 C and the corresponding specific energy densities are 420, 370, and 328 W h kg-1. The capacity retention at a constant discharge rate of 200 C is 90% after 500 cycles.A facile, continuous preparation process of yolk-shell-structured lithium-metal oxide powders without a template for use as cathode materials in lithium ion batteries is introduced for the first time. Single and double-shelled LiNi0.5Mn1.5O4 yolk-shell powders as the first target materials are prepared directly by spray pyrolysis from a spray solution with sucrose, at a short residence time of 4 s. Fast combustion and contraction of a carbon-mixed oxide composite intermediate, formed from a micro-sized droplet inside a hot wall reactor maintained at 700 °C, produces the yolk-shell powders. The yolk-shell structure of the precursor powders directly prepared by spray pyrolysis is well maintained even at a high post-treatment temperature of 750 °C. The yolk-shell LiNi0.5Mn1.5O4 powders delivered a 1000th high discharge capacity of 108 m</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMED13A0769H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMED13A0769H"><span id="translatedtitle">Physical Hydraulic Model of Side-Channel Spillway of Lambuk DAM, Bali</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Harifa, A. C.; Sholichin, M.; Othman, F. B.</p> <p>2013-12-01</p> <p>The spillway is among the most important structures of a dam project. A spillway is designed to prevent overtopping of a dam at a place that is not designed for overtopping. Side-channel spillways are commonly used to release water flow from a reservoir in places where the sides are steep and have a considerable height above the dam. Experimental results were collected with a hydraulic model of the side-channel spillway for releasing the peak overflow of Lambuk Dam. This dam is, located on the Lambuk River, which is a tributary of the Yeh Hoo River ~ 34.6 km north of Denpasar on the island of Bali. The bituminous geomembrane faced dam is 24 m in height, with a 35-m wide spillway. The length of the side channel is 35 m long, with 58 m of transition channel, 67.37 m of chuteway channel and 22.71 m of stilling basin. The capacity of the spillway is 231.<span class="hlt">91</span> <span class="hlt">m</span>3/s and the outlet works capacity is 165.28 m3/s. The reservoir is designed for irrigation and water supply. The purpose of this study was to optimize the designed of the structure and to ensure its safe operation. In hydraulic model may help the decision-makers to visualize the flow field before selecting a ';suitable' design. The hydraulic model study was performed to ensure passage of the maximum discharge at maximum reservoir capacity; to study the spillway approach conditions, water surface profiles, and flow patterns in the chuteway; and to reveal potential demerits of the proposed hydraulic design of various structures and explore solutions. The model was constructed at 1 : 40 scale, Reservoir topography was modeled using concrete, the river bed using sand and some gravel, the river berm using concrete, and the spillway and channel using Plexiglas. Water was measured using Rectangular contracted weir. Design floods (with return period in year) were Q2 = 111.40 m3/s, Q5 = 136.84 m3/s, Q10 = 159.32 m3/s, Q25 = 174.61 m3/s, Q50 = 185.13 m3/s, Q100 = 198.08 m3/s, Q200 = 210.55 m3/s, Q1000 = 231.<span class="hlt">91</span> <span class="hlt">m</span>3/s and the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014Nanos...613854D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014Nanos...613854D"><span id="translatedtitle">Incorporation of Cl into sequentially deposited lead halide perovskite films for highly efficient mesoporous solar cells</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dharani, Sabba; Dewi, Herlina Arianita; Prabhakar, Rajiv Ramanujam; Baikie, Tom; Shi, Chen; Yonghua, Du; Mathews, Nripan; Boix, Pablo P.; Mhaisalkar, Subodh G.</p> <p>2014-10-01</p> <p>Organic-inorganic lead halide perovskites have been widely used as absorbers on mesoporous TiO2 films as well as thin films in planar heterojunction solar cells, yielding very high photovoltaic conversion efficiencies. Both the addition of chloride and sequential deposition methods were successfully employed to enhance the photovoltaic performance. Here, both approaches are combined in a sequential method by spincoating PbCl2 + PbI2 on a mesoporous TiO2 film followed by the perovskite transformation. The role of Cl in determining the optical, electrical, structural and morphological properties is correlated with the photovoltaic performance. The highest photovoltaic efficiency of 14.15% with the Voc, FF and Jsc being 1.09 V, 0.65 and 19.<span class="hlt">91</span> <span class="hlt">m</span>A cm-2 respectively was achieved with 10 mol% of PbCl2 addition due to an increase of the film conductivity induced by a better perovskite morphology. This is linked to an improvement of the hysteresis and reproducibility of the solar cells.Organic-inorganic lead halide perovskites have been widely used as absorbers on mesoporous TiO2 films as well as thin films in planar heterojunction solar cells, yielding very high photovoltaic conversion efficiencies. Both the addition of chloride and sequential deposition methods were successfully employed to enhance the photovoltaic performance. Here, both approaches are combined in a sequential method by spincoating PbCl2 + PbI2 on a mesoporous TiO2 film followed by the perovskite transformation. The role of Cl in determining the optical, electrical, structural and morphological properties is correlated with the photovoltaic performance. The highest photovoltaic efficiency of 14.15% with the Voc, FF and Jsc being 1.09 V, 0.65 and 19.<span class="hlt">91</span> <span class="hlt">m</span>A cm-2 respectively was achieved with 10 mol% of PbCl2 addition due to an increase of the film conductivity induced by a better perovskite morphology. This is linked to an improvement of the hysteresis and reproducibility of the solar cells. Electronic</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22221419','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22221419"><span id="translatedtitle">Decommissioning an Active Historical Reactor Facility at the Savannah River Site - 13453</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Bergren, Christopher L.; Long, J. Tony; Blankenship, John K.; Adams, Karen M.</p> <p>2013-07-01</p> <p>The Savannah River Site (SRS) is an 802 square-kilometer United States Department of Energy (US DOE) nuclear facility located along the Savannah River near Aiken, South Carolina, where Management and Operations are performed by Savannah River Nuclear Solutions (SRNS). In 2004, DOE recognized SRS as structure within the Cold War Historic District of national, state and local significance composed of the first generation of facilities constructed and operated from 1950 through 1989 to produce plutonium and tritium for our nation's defense. DOE agreed to manage the SRS 105-C Reactor Facility as a potentially historic property due to its significance in supporting the U.S. Cold War Mission and for potential for future interpretation. This reactor has five primary areas within it, including a Disassembly Basin (DB) that received irradiated materials from the reactor, cooled them and prepared the components for loading and transport to a Separation Canyon for processing. The 6,317 square meter area was divided into numerous work/storage areas. The walls between the individual basin compartments have narrow vertical openings called 'slots' that permit the transfer of material from one section to another. Data indicated there was over 830 curies of radioactivity associated with the basin sediments and approximately 9.1 M liters of contaminated water, not including a large quantity of activated reactor equipment, scrap metal, and debris on the basin floor. The need for an action was identified in 2010 to reduce risks to personnel in the facility and to eliminate the possible release of contaminants into the environment. The release of DB water could potentially migrate to the aquifer and contaminate groundwater. DOE, its regulators [U. S. Environmental Protection Agency (USEPA)-Region 4 and the South Carolina Department of Health and Environmental Control (SCDHEC)] and the SC Historical Preservation Office (SHPO) agreed/concurred to perform a non-time critical removal action for the In Situ Decommissioning (ISD) of the 105-C Disassembly Basin. ISD consisted of stabilization/isolation of remaining contaminated water, sediment, activated reactor equipment, and scrap metal by filling the DB with underwater non-structural grout to the appropriate (-4.877 meter) grade-level, thence with dry area non-structural grout to the final -10 centimeter level. The roof over the DB was preserved due to its potential historical significance and to prevent the infiltration of precipitation. Forced evaporation was the form of treatment implemented to remove the approximately 9.1 M liters of contaminated basin water. Using specially formulated grouts, irradiated materials and sediment were treated by solidification/isolation thus reducing their mobility, reducing radiation exposure and creating an engineered barrier thereby preventing access to the contaminants. Grouting provided a low permeability barrier to minimize any potential transport of contaminants to the aquifer. Efforts were made to preserve the historical significance of the Reactor in accordance with the National Historic Preservation Act. ISD provides a cost effective means to isolate and contain residual radioactivity from past nuclear operations allowing natural radioactive decay to reduce hazards to manageable levels. This method limits release of radiological contamination to the environment, minimizes radiation exposure to workers, prevents human/animal access to the hazardous substances, and allows for ongoing monitoring of the decommissioned facility. Field construction was initiated in August 2011; evaporator operations commenced January 2012 and ended July 2012 with over 9 M liters of water treated/removed. Over 8,525 cubic meters of grout were placed, completing in August 2012. The project completed with an excellent safety record, on schedule and under budget. (authors)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1000062','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1000062"><span id="translatedtitle">FIELD TEST INSTRUCTION 100-NR-2 OPERABLE UNIT DESIGN OPTIMIZATION STUDY FOR SEQUESTRATION OF SR-90 SATURATED ZONE APATITE PERMEABLE REACTIVE BARRIER EXTENSION</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>BOWLES NA</p> <p>2010-10-06</p> <p>The objective of this field test instruction is to provide technical guidance for aqueous injection emplacement of an extension apatite permeable reactive barrier (PRE) for the sequestration of strontium-90 (Sr-90) using a high concentration amendment formulation. These field activities will be conducted according to the guidelines established in DOE/RL-2010-29, 100-NR-2 Design Optimization Study, hereafter referred to as the DOS. The DOS supports the Federal Facility Agreement Consent Order (EPA et al., 1989), Milestone M-16-06-01, and 'Complete Construction of a Permeable Reactive Barrier at 100-N.' Injections of apatite precursor chemicals will occur at an equal distance intervals on each end of the existing PRE to extend the PRB from the existing <span class="hlt">91</span> <span class="hlt">m</span> (300 ft) to at least 274 m (900 ft). Field testing at the 100-N Area Apatite Treatability Test Site, as depicted on Figure 1, shows that the barrier is categorized by two general hydrologic conceptual models based on overall well capacity and contrast between the Hanford and Ringold hydraulic conductivities. The upstream portion of the original barrier, shown on Figure 1, is characterized by relatively low overall well specific capacity. This is estimated from well development data and a lower contrast in hydraulic conductivity between the Hanford formation and Ringold Formations. Comparison of test results from these two locations indicate that permeability contrast between the Hanford formation and Ringold Formation is significantly less over the upstream one-third of the barrier. The estimated hydraulic conductivity for the Hanford formation and Ringold Formation over the upstream portion of the barrier based on observations during emplacement of the existing <span class="hlt">91</span> <span class="hlt">m</span> (300 ft) PRB is approximately 12 and 10 m/day (39 and 32 ft/day), respectively (PNNL-17429). However, these estimates should be used as a rough guideline only, as significant variability in hydraulic conductivity is likely to be observed in the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012GeCoA..80...14S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012GeCoA..80...14S"><span id="translatedtitle">A re-evaluation of the use of branched GDGTs as terrestrial biomarkers: Implications for the BIT Index</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Smith, Richard W.; Bianchi, Thomas S.; Li, Xinxin</p> <p>2012-03-01</p> <p>This study examines estimates of soil organic matter content (%OMsoil) in marine sediments based on the branched/isoprenoid tetraether (BIT) Index, and suggests a new calculation method based on branched GDGT (brGDGT) concentrations. Four sediment cores were collected in 2008 at the 20 m <span class="hlt">isobath</span> of the Louisiana Continental Shelf. Glycerol dialkyl glycerol tetraether (GDGTs) and cupric oxide (CuO) oxidation products were analyzed down to ˜20 cm depth to examine terrestrially-derived organic matter. BIT Indices ranged from 0.50 to 0.03, and correlated poorly with lignin (mg S, V, and C phenols 10 g-1 sediment; ∑810) and 3,5-dihydroxybenzoic acid (μg 3,5-Bd g-1 sediment; 3,5:g) concentrations, which ranged from 0.01 to 0.87 mg g-1 and 0.00 (below detection limit) to 1.39 μg g-1, respectively. By calculating mass normalized core-lipid branched GDGT (brGDGT) and crenarchaeol mass abundances with the assistance of a surrogate standard, it was shown that overall, large variations in sedimentary crenarchaeol concentrations were responsible for vertical distributions of BIT Indices, due to the relatively smaller range of brGDGT concentrations. brGDGT concentrations produced stronger correlations with terrestrial CuO oxidation products than the BIT Index, which correlated strongly with crenarchaeol concentrations. Variations in the BIT Index may therefore reflect changes in the delivery of marine-derived organic matter to sediments in regions with large seasonal or decadal shifts in productivity, such as stratified continental shelves. An in depth look at conversions of the BIT Index to percent soil organic matter using a binary mixing model with a marine BIT value of 0 and a terrestrial BIT value of 1 (%OMsoil = BIT Index * 100) used in recent literature reveals that this method results in non-linear mixing of marine and terrestrial end-members, and the shape of the mixing line is based on sedimentary crenarchaeol concentrations. An alternative approach is to use</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003JGRC..108.3190W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003JGRC..108.3190W"><span id="translatedtitle">Phytoplankton response to intrusions of slope water on the West Florida Shelf: Models and observations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Walsh, John J.; Weisberg, Robert H.; Dieterle, Dwight A.; He, Ruoying; Darrow, Brian P.; Jolliff, Jason K.; Lester, Kristen M.; Vargo, Gabriel A.; Kirkpatrick, Gary J.; Fanning, Kent A.; Sutton, Tracey T.; Jochens, Ann E.; Biggs, Douglas C.; Nababan, Bisman; Hu, Chuanmin; Muller-Karger, Frank E.</p> <p>2003-06-01</p> <p>Previous hypotheses had suggested that upwelled intrusions of nutrient-rich Gulf of Mexico slope water onto the West Florida Shelf (WFS) led to formation of red tides of Karenia brevis. However, coupled biophysical models of (1) wind- and buoyancy-driven circulation, (2) three phytoplankton groups (diatoms, K. brevis, and microflagellates), (3) these slope water supplies of nitrate and silicate, and (4) selective grazing stress by copepods and protozoans found that diatoms won in one 1998 case of no light limitation by colored dissolved organic matter (CDOM). The diatoms lost to K. brevis during another CDOM case of the models. In the real world, field data confirmed that diatoms were indeed the dominant phytoplankton after massive upwelling in 1998, when only a small red tide of K. brevis was observed. Over a 7-month period of the CDOM-free scenario the simulated total primary production of the phytoplankton community was ˜1.8 g C m-2 d-1 along the 40-m <span class="hlt">isobath</span> of the northern WFS, with the largest accumulation of biomass on the Florida Middle Ground (FMG). Despite such photosynthesis, these models of the WFS yielded a net source of CO2 to the atmosphere during spring and summer and suggested a small sink in the fall. With diatom losses of 90% of their daily carbon fixation to herbivores the simulation supported earlier impressions of a short, diatom-based food web on the FMG, where organic carbon content of the surficial sediments is tenfold those of the surrounding seabeds. Farther south, the simulated near-bottom pools of ammonium were highest in summer, when silicon regeneration was minimal, leading to temporary Si limitation of the diatoms. Termination of these upwelled pulses of production by diatoms and nonsiliceous microflagellates mainly resulted from nitrate exhaustion in the model, however, mimicking most del15PON observations in the field. Yet, the CDOM-free case of the models failed to replicate the observed small red tide in December 1998, tagged</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015BGD....1212713H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015BGD....1212713H"><span id="translatedtitle">Ocean dynamic processes causing spatially heterogeneous distribution of sedimentary caesium-137 massively released from the Fukushima Dai-ichi Nuclear Power Plant</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Higashi, H.; Morino, Y.; Furuichi, N.; Ohara, T.</p> <p>2015-08-01</p> <p>Massive amounts of anthropogenic radiocaesium 137Cs that was released into the environment by the Fukushima Dai-ichi Nuclear Power Plant accident on March 2011 are widely known to have extensively migrated to Pacific oceanic sediment off of east Japan. Several recent reports have stated that the sedimentary 137Cs is now stable with a remarkably heterogeneous distribution. The present study elucidates ocean dynamic processes causing this heterogeneous sedimentary 137Cs distribution in and around the shelf off Fukushima and adjacent prefectures. We performed a numerical simulation of oceanic 137Cs behaviour for about 10 months after the accident, using a comprehensive dynamic model involving advection-diffusion transport in seawater, adsorption and desorption to and from particulate matter, sedimentation and suspension on and from the bottom, and vertical diffusion transport in the sediment. A notable simulated result was that the sedimentary 137Cs significantly accumulated in a swath just offshore of the shelf break (along the 50-100 m <span class="hlt">isobath</span>) as in recent observations, although the seabed in the entire simulation domain was assumed to have ideal properties such as identical bulk density, uniform porosity, and aggregation of particles with a single grain diameter. This result indicated that the heterogeneous sedimentary 137Cs distribution was not necessarily a result of the spatial distribution of 137Cs sediment adsorptivity. The present simulation suggests that the shape of the swath is mainly associated with spatiotemporal variation between bottom shear stress in the shallow shelf (< 50 m depths) and that offshore of the shelf break. In a large part of the shallow shelf, the simulation indicated that strong bottom friction suspending particulate matter from the seabed frequently occurred via a periodic spring tide about every 2 weeks and via occasional strong wind. The sedimentary 137Cs thereby could hardly stay on the surface of the seabed with the result that</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004AGUFMOS44A..06S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004AGUFMOS44A..06S"><span id="translatedtitle">Development of the Holocene Clinoform in the Gulf of Papua</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Slingerland, R.; Milliman, J. D.; Driscoll, N. W.; Walsh, J. P.; Keen, T. R.</p> <p>2004-12-01</p> <p> of these variations in clinoform growth and stratal geometry are presently uncertain but may reflect temporal variations in climate, coastal circulation, or longer-term Holocene changes in sea level. Computed annual circulation of the GoP in response to trade wind and monsoon conditions shows that the flow fields are significantly different. During trade winds sediment particle paths on the clinoform top are obliquely offshore to the east. A zone of convergence lies near the 25-m <span class="hlt">isobath</span> along the clinoform face, where offshore-directed waters on the shelf meet onshore-directed bottom waters climbing the clinoform face, possibly localizing sediment deposition there. During monsoon conditions average bottom flow is landward on the modern clinoform top and minimal over much of the slipface, suggesting that variations in sediment type at the bed level may be circulation related and seasonal.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_24 --> <div id="page_25" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active"><span>25</span></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="481"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.usgs.gov/bul/b2202-f/','USGSPUBS'); return false;" href="http://pubs.usgs.gov/bul/b2202-f/"><span id="translatedtitle">The Sirte Basin province of Libya; Sirte-Zelten total petroleum system</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Ahlbrandt, Thomas S.</p> <p>2001-01-01</p> <p> in the Early Cre-taceous and syn-rift sedimentary filling during Cretaceous through Eocene time, and post-rift deposition in the Oligocene and Miocene. Multiple reservoirs are charged largely by verti-cally migrating hydrocarbons along horst block faults from Upper Cretaceous source rocks that occupy structurally low posi-tions in the grabens. Evaporites in the middle Eocene, mostly post-rift, provide an excellent seal for the Sirte-Zelten hydrocarbon system. The offshore part of the Sirte Basin is complex, with subduction occurring to the northeast of the province boundary, which is drawn at the 2,000-meter <span class="hlt">isobath</span>. Possible petroleum systems may be present in the deep offshore grabens on the Sirte Rise such as those involving Silurian and Eocene rocks; however, potential of these systems remains speculative and was not assessed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016EGUGA..1810746A&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016EGUGA..1810746A&link_type=ABSTRACT"><span id="translatedtitle">Mercury in sediments from shelf and continental slope at Campos Basin near Rio de Janeiro, Brazil</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Araujo, Beatriz; Hintelmann, Holger; Dimock, Brian; Gomes de Almeida, Marcelo; Falcão, Ana Paula; de Rezende, Carlos Eduardo</p> <p>2016-04-01</p> <p>Mercury (Hg) is a global pollutant due to its ability to undergo long-range transport from source regions to remote parts of the world, and its ubiquitous presence in aquatic ecosystems. The Hg isotope ratios could be an effective tool for tracing the sources and process of Hg in the environment. This study aimed to establish the distribution of mercury in surface sediments of three transects (25- 3000m water depth) in continental shelf and slope in Campos Basin-RJ-Brazil, using the Hg isotopes to understand the geochemical processes relating to Hg cycling that occur in a subtropical coastal environment. The study area was divided into three transects: A (located to the south and close to a upwelling area), D (located opposite the mouth of the Paraiba do Sul River) and I (located north near the top of Vitória-ES). Sampling <span class="hlt">isobaths</span> were 25, 50, 75, 100, 150, 400, 700, 1000, 1300, 1900, 2500 and 3000m. The Total Hg, MMHg and Hg stable isotopes were determined based on EPA Method 1631, EPA method 1630 and Foucher and Hintelmann (2006), respectively. The silt/clay ranged from 0.05 to 95%, and the organic carbon (OC) from 0.07 to 1.43 % for all transects. THg and MMHg concentrations in the shelf were 11.9 ± 7.2 (1.7- 22.2) ng.g‑1 and 0.15 ± 0.12 (0.02 - 0.40) ng.g‑1; in the slope 30.3 ± 9.2 (11.6 - 51.6) ng.g‑1 and 0.13 ± 0.06 (0.03 -0.29) ng.g‑1 , respectively. The δ202Hg and Δ199Hg varied from -0.32 to -1.85 ‰ (-0.79 ± 0.44‰) and -0.41 to 0.09 ‰ (-0.03 ± 0.12 ‰) for all transects, respectively. The delta values between both regions are significantly different, the shelf region showed δ202Hg from -0.59 to -2.19 ‰ (mean: -1.52 ±0.65) and Δ199Hg from - 0.53 to 0.08 ‰ (mean: -0.27 ±0.55) and the slope region were observed δ202Hg values from -0.32 to -1.82 ‰ (mean: -0.73 ±0.39 ‰ n=18) and gΔ199Hg from -0.23 to 0.09‰ (mean: -0.02 ±0.08‰ n=5). The slope appears to be enriched with heavier isotopes compared to the shelf, however</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..16..112W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..16..112W"><span id="translatedtitle">Soft sediment deformation associated with the passage of North Atlantic Deep water through the deep Ariel Graben, Mozambique Ridge southwest Indian Ocean.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wiles, Errol; Green, Andrew; Watkeys, Mike; Jokat, Wilfried; Krocker, Ralph</p> <p>2014-05-01</p> <p>Interactions between bottom water currents and seafloor sediments are well known. Bottom current generated bedforms are varied both morphologicaly and sedimentologicaly. Sediment transport and deposition, associated with bottom water circulation, plays a significant role is sculpting seafloor morphology in all ocean basins. Indeed, bedforms have been used to great effect to define the presence, direction and strength of bottom water circulation globally. Here we present new multibeam swath bathymetry and high frequency seismic data from the Natal Valley and Mozambique Ridge, southwest Indian Ocean. These data show a deep (-3200 m) channel-like feature (Ariel Graben, situated at 28° 30"S on the Mozambique Ridge) connecting the northern Natal Valley to the Mozambique Basin. A distinct W - E change in seafloor morphology and seismic character is noted moving from the Natal Valley through the Ariel Graben. The northern flank of the graben exhibits smooth plastered drifts which give way to undulating seafloor in the east. The plastered drifts are characterised by distinct bottom echoes, with several discontinuous sub-bottom reflections. In contrast, the undulating seafloor is characterised by distinct hyperbolic echoes, with occasional indistinct sub-bottom reflectors. The W - E orientated undulations are straight crested, parallel / sub-parallel to the local <span class="hlt">isobaths</span>. Wavelength is variable, ranging from 600 m to 1200 m. Cross-sectional symmetry of these features varies from symmetrical to asymmetrical, with board crests and narrow troughs. When asymmetrical, the lower (south-facing) limb is the longer (511.76 m average) than the upper (north-facing) limb (323.53 m average). The lower limbs are also steeper than the upper limbs; calculated averages being 3.80° and 1.55°, respectively. Overall, the slope on which the undulations are found, is south-facing with a gradient of 1.54°, however, the area affected by undulations is slightly steeper (average slope of 1.75</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2001AGUFMOS32B0482E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2001AGUFMOS32B0482E"><span id="translatedtitle">The Coupled Boundary Layers and Air-Sea Transfer (CBLAST) Experiments at the Martha's Vineyard Coastal Observatory</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Edson, J. B.</p> <p>2001-12-01</p> <p>The Woods Hole Oceanographic Institution (WHOI) completed the initial phase of the Martha's Vineyard Coastal Observatory (MVCO) in July of 2001. The MVCO is being using to monitor coastal atmospheric and oceanic processes. Specifically, the observatory is expected to: - Provide continuous long-term observations for climate studies. - Provide a reliable system and rugged sensors that allow opportunistic sampling of extreme events. - Provide a local climatology for intensive, short duration field campaigns. - Further facilitate regional studies of coastal processes by providing infrastructure that supports easy access to power and data. This talk provides an example of the last two objectives using the low wind component of the Office of Naval Research's (ONR) Coupled Boundary Layers and Air-Sea Transfer (CBLAST) program. CBLAST-LOW has been designed to investigate air-sea interaction and coupled atmospheric and oceanic boundary layer dynamics at low wind speeds where the dynamic processes are driven and/or strongly modulated by thermal forcing. This effort is being carried out by scientists at WHOI, NPS, NOAA, NRL, Rutgers, UW/APL, JH/APL, OSU, NCAR, and other institutions, and includes observational and modeling components. The MVCO is providing observations and infrastructure in support of several intensive operating periods in the summers of 2001, 2002, and possibly 2003. During these periods, the observational network around the observatory was and will be greatly expanded using traditional oceanographic moorings and bottom mounted instrumentation, innovative 2- and 3-D moored and drifting arrays, survey ships, AUVs, satellite remote sensing, and heavily instrumented aircraft. In addition, the MVCO cabled components will be extended out to the 20-m <span class="hlt">isobath</span> where we plan to deploy a 35-m tower. The tower will be instrumented from 15-m above the ocean surface to the ocean bottom with instruments capable of directly measuring the momentum, heat, and radiative</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AGUFMOS43A0984J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUFMOS43A0984J"><span id="translatedtitle">Version 2.0 of the International Bathymetric Chart of the Arctic Ocean: A new Database for Oceanographers and Mapmakers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jakobsson, M.; Macnab, R.; Edwards, M.; Schenke, H.; Hatzky, J.</p> <p>2007-12-01</p> <p>The International Bathymetric Chart of the Arctic Ocean (IBCAO) was first released to the public after its introduction at the American Geophysical Union (AGU) Fall Meeting in 1999 (Jakobsson et al., 2000). This first release consisted of a Digital Bathymetric Model (DBM) on a Polar stereographic projection with grid cell spacing of 2.5 x 2.5 km derived from an accumulated database of all available bathymetric data at the time of compilation. The IBCAO bathymetric database included soundings collected during past and modern expeditions as well as digitized <span class="hlt">isobaths</span> and depth soundings from published maps. Compared to previous bathymetric maps of the Arctic Ocean, the first released IBCAO compilation was based upon a significantly enhanced database, particularly in the high Arctic. For example, de-classified echo soundings acquired during US and British submarine cruises between 1958 and 1988 were included as well as soundings from icebreaker cruises conducted by Sweden and Germany at the end of the last century. Despite the newly available data in 1999, there were still large areas of the Arctic Ocean where publicly available data were completely absent. Some of these areas had been mapped by Russian agencies, and since these observations were not available to IBCAO, depth contours from the bathymetric contour map published by the Head Department of Navigation and Hydrography (HDNO) (Naryshkin, 1999) were digitized and incorporated in the database. The new IBCAO Version 2.0 comprises the largest update since the first release; moreover, the grid spacing has been decreased to 2 x 2 km. Numerous multibeam data sets that were collected by ice breakers, e.g. USCGC Healy, R/V James Clarke Ross, R/V Polarstern, IB Oden, now form part of the database, as do the swath bathymetric observations acquired during the 1999 SCICEX expedition. The portrayal of the Eastern Arctic Basin is vastly improved due to e.g. the Arctic Mid Ocean Ridge Expedition 2001 (AMORE) and Arctic</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010EGUGA..1212992N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010EGUGA..1212992N"><span id="translatedtitle">Holocene morphologic changes offshore the Quarteira region, Algarve, south Portugal</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Noiva, João.; Duarte, Henrique; Terrinha, Pedro; Gonçalves, Daniela</p> <p>2010-05-01</p> <p>A 160 km long SPARKER single channel seismic reflection survey was acquired in November 2008 on the shallow continental shelf of south Portugal to investigate the recent tectonics of the S.Marcos - Quarteira Fault (SMQF) and of the Carcavai Fault. The NW-SE trending S.Marcos - Quarteira Fault (SMQF) can be traced on the onshore-offshore region of south Portugal for an extension of 160 km. It is a Variscan (Hercynian) orogenic thrust that was inverted as an extensional fault during the Mesozoic rifting in south Portugal, during which it played a major role in the segmentation of the Algarve Basin. The SMQF was re-inverted as a transpressive fault during the Paleogene-Miocene compression and folding and thrusting of Pleistocene terrigenous strata attest for its present day tectonic activity. The Carcavai fault trends NE-SW, intersects the SMQF. The Carcavai fault also played the role of rift fault during the Mesozoic and was inverted as a thrust during the Cenozoic compression. The mapping of both SMQ and Carcavai Faults offshore south Portugal attests for a complex interaction between the two in what concerns the Holocene and tectonics and paleogeography. The Carcavai Fault accommodates most of the Pliocene-Quaternary compression on its hanging-wall, whilst the SMQF takes up the deformation on the foot-wall of the Carcavai Fault. In what refers the early Holocene paleogeography, the interpretation of the seismic profiles shows the existence of two sedimentary bodies of possible Holocene age separated by a peninsula that consists of Pliocene-Pleistocene prograding clastics that make up the present day coastal cliff. This peninsula is parallel to the present day coastline, which is also parallel to the SMQF. The two bodies have different seismic facies. The offshore Holocene displays fairly continuous reflections, whilst the internal Holocene is made up of more discontinuous reflections. The <span class="hlt">isobaths</span> map of the base of the external Holocene unit shows a smooth gently</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016EGUGA..1815151C&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016EGUGA..1815151C&link_type=ABSTRACT"><span id="translatedtitle">Metal mobility in river and sea sediments affected by mine drainage (Sestri Levante, Italy)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Consani, Sirio; Capello, Marco; Cutroneo, Laura; Vagge, Greta; Zuccarelli, Andrea; Carbone, Cristina</p> <p>2016-04-01</p> <p>The Gromolo Torrent is a metal-polluted Apennine streamflow located near Sestri Levante (Liguria, Italy). It springs from the Monte Rocca Grande (850 m a.s.l.), and flows for 11.5 km through the Gromolo Valley before flowing into the Ligurian Sea. Inside the Gromolo basin is located the abandoned Fe-Cu mine of Libiola, which was the most important sulfide deposit of the Ligurian Apennines. In this mining site, extensive Acid Mine Drainage (AMD) processes are active, both inside the mine tunnels and in the sulfide rich waste-rock dumps; the solutions generated are characterised by low pH values and high amounts of dissolved SO42-, Fe, and other chemical elements such as Cu, Zn, Pb, Al, Co, and Ni. Moreover, exstensively precipitation of Fe and Cu-rich secondary minerals occurs both as soft crusts inside the mine adits and as loose suspensions associated with overland flow of mine drainage. AMD waters flowed into the uncontaminated Gromolo Torrent where abundant precipitation of amorphous Fe(III)-oxy-hydroxides occurred. The marine study area is characterised by the presence of the headland of Sestri Levante with two bays, the western one named "Baia delle Favole". The dynamics of the area is dominated by a permanent north-westward off-shore current flowing approximately along <span class="hlt">isobath</span>, and an eastward counter-current along the north coast with a resulting drift of the coastal materials from the West to Est towards "Baia delle Favole". The bottom sediment are principally characterised by coarse materials, mostly consisting of fine sand, with a percentage of the fine sediment increasing inside the bay, where the dynamics is low. The aims of this work are to 1) evaluate the metal mobility of colloidal river precipitates for about 7 km up to its mouth in the Ligurian Sea; 2) verify the contamination state of the marine bottom sediments off the mouth of the Gromolo Torrent ("Baia delle Favole" of Sestri Levante), and 3) identify the main sources and diffusion ways of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AGUSMOS51D..06M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUSMOS51D..06M"><span id="translatedtitle">Fine Resolution Termohaline Structure Of The Yuctatan Coastal Sea</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Marino-Tapia, I.; Enriquez-Ortiz, C.; Capurro, L.; Euan-Avila, J.</p> <p>2007-05-01</p> <p>In the Yucatan peninsula there are a variety processes that drastically affect the thermohaline structure of the coastal seas. Some of these include hyperhaline lagoons that export salt to the ocean, upwelling events that propagate to the coast, persistent submarine groundwater discharges, and very high evaporation rates caused by the intense solar radiation. On July 2006 a fine resolution oceanographic campaign was performed on the Yucatan coast to study the detailed structure of thermohaline processes and currents from the shore to the 10 m <span class="hlt">isobath</span>. A total of sixty nine transects that cover the entire northern stretch of the Yucatan coast were made. The transects extend seven kilometers in the offshore direction and have an alongshore spacing of 5 km. The temperature and salinity characteristics of the water column were monitored with a SEABIRD SBE 19 CTD performing profiles every 500 m along each transect. Ocean currents were measures along the same transect using a 1.5 MHz Acoustic Doppler Profiler (Sontek). The results clearly show the effects of coastal lagoons on the adjoining sea, with net salt export associated with hyperhaline lagoons (e.g. Ria Lagartos) or more estuarine influence of lagoons such as Celestun, where groundwater discharges play the role of rivers on the estuary. An assessment of this influence on the coastal ocean will be presented. It is well known the meteor impact at the end of the Cretacic era at Chicxulub, Yucatan, generated a crater with multiple rings which is evident from horizontal gravity gradients of the Yucatan mainland, and that associated with the outer ring there is a high concentration of cenotes (sinkholes) (Pope et al. 1991; Hildebrand, et al. 1995). It has also been shown that groundwater flows along this cenote ring towards the ocean, and the zones where the ring intersects the coast (Celestun and Dzilam Bravo) have impressive geologic features known as `submarine water springs' where freshwater springs as a fountain</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..1513513C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..1513513C"><span id="translatedtitle">Southern Dobrogea coastal potable water sources and Upper Quaternary Black Sea level changes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Caraivan, Glicherie; Stefanescu, Diana</p> <p>2013-04-01</p> <p> Maximum (MIS 2), the shoreline retreats eastwards, reaching the 100-120 m <span class="hlt">isobaths</span>. In these conditions, the surface drainage base level was very low. Phreatic nape closely followed the river valleys dynamics. Mean depth aquifer discharged on the inner shelf , where Sarmatian limestones outcrop. The deep aquifer discharge was restricted by the Capidava- Ovidiu Fault to the north-east and by a presumed seawards longitudinal Fault. This process enabled the migration of the prehistoric human communities, from Asia to Europe, who established settlements on the newly created alluvial plain on the western Black Sea shelf. The Holocene Transgression (MIS 1) determined a sea level rise up to the modern one, and probably higher. Under the pressure of these environmental changes, the Neolithic settlements slowly retreated upstream. During the Greek colonization, the rising sea level caused the salinisation of the previous drinking water phreatic sources. In these conditions, in the Roman Age, a new hydraulic infrastructure had to be developed, using aqueducts for available inland water delivery.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1997PhDT.......279H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1997PhDT.......279H"><span id="translatedtitle">Teledetection passive et processus decisionnel a reference spatiale: Application a l'aquaculture en milieu marin</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Habbane, Mohamed</p> <p></p> <p> parametres sont compares deux a deux par rapport a la carte preliminaire regionale d'indices du potentiel maricole pour determiner leur poids relatif. La carte finale produite avec ces parametres du niveau 2 presente un secteur ou les indices du potentiel maricole sont de 0,5 a 0,75. Ce secteur longe la cote et epouse les <span class="hlt">isobathes</span> de 10 a 30 m de profondeur. L'effet de la profondeur d'eau semble avoir jouer un role important. Le secteur de potentiel maricole de 0,25 a 0,5 est toujours present et couvre une superficie d'environ 426 kmsp2. L'etude necessitera toujours un suivi des conditions environnementales prevalant dans la region. Ce suivi peut etre effectue a l'aide d'un outil de vision aerospatiale (capteurs de teledetection) et d'analyse spatio-temporelle (SIG-PDRS). (Abstract shortened by UMI.)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMOS11D1676W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMOS11D1676W"><span id="translatedtitle">Study on the linear sand ridges on shelf of the East China Sea</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>WU, Z.; Jin, X.; Li, M.; Shang, J.; Li, S.</p> <p>2013-12-01</p> <p>The linear sand ridges (LSR) revealed by newest multi-beam echo soundings bathymetric data (MBES) are distributed extensively on shelf of the East China Sea (ECS). It is not only a kind of ubiquitous geological phenomenon on tide-dominated shelf but also a key step in paleo-environment evolvement history of the ECS. Based on the MBES, high-resolution single-channel seismic profiles, analyzed results of boreholes and numerical simulation of paleo-tidal current fields, the distribution, 3D fine structures , space-time spreading regulars and developing tendencies of the LSR on ECS shelf were studied by quantitative synthetic statistical analysis method. The relationship between LSR and paleo-tidal current field, sea-level curve and the evolution stages of LSR such as formation, growth and buried stages were discussed. The strikes of LSR on ECS shelf emerge at a normal distribution. The azimuth of N155°E is the central point and the azimuth of N125°E,N130°E,N140°E and N180°E are convergent points respectively for the normal distribution. The LSR are aggregating in the centre part of ECS shelf, rarefying at the north and south part, dispersing and bifurcating to the east, aggregating and converging to the west. The LSR on ECS shelf are distributed landward to the <span class="hlt">isobath</span> of 60m, and seaward to the water depth of 120m at northeast and 150m at southwest. Immature LSR are firstly observed at water depth of 130-180m in the southwestern depressions. Lithology analysis and dating of 4 boreholes and 12 cores have indicated that the widely distributed transgressive sand layers with high content of shell debris which formed in the early to middle Holocene are the main compositions of the LSR on the ECS shelf. The top boundaries of buried LSR in unit 14 are distinguished, and a 3D map of these buried LSR in local area is reconstructed. The features such as length, width, height and strikes of these buried LSR are analyzed quantitatively and compared with those of LSR in unit</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..16.5096B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..16.5096B"><span id="translatedtitle">Advanced interpretation of ground motion using Persistent Scatterer Interferometry technique: the Alto Guadalentín Basin (Spain) case of study</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bonì, Roberta; Herrera, Gerardo; Meisina, Claudia; Notti, Davide; Zucca, Francesco; Bejar, Marta; González, Pablo; Palano, Mimmo; Tomás, Roberto; Fernandez, José; Fernández-Merodo, José; Mulas, Joaquín; Aragón, Ramón; Mora, Oscar</p> <p>2014-05-01</p> <p> were compared with some predisposing and trigger factors as geological units, <span class="hlt">isobaths</span> of Plio-Quaternary filling, soft soil thickness and piezometric level. The PSI data were compared with measurement obtained by two GPS station located near the Lorca city: the value of deformation detected by satellites and ground-based tools are well correlated. The results are the following: a) the subsidence processes are related to soft soil thickness distribution; b) land subsidence rates shows that the area interested by the higher value is the same over the monitored period, a deceleration rate of subsidence has been recorded during the period 2011- 2012; c) the deformation rates are not correlated with the piezometric level trend, a delay time between piezometric level variations and ground deformations is evident. References González, P. J. & Fernández, J.,(2011) Drought-driven transient aquifer compaction imaged using multitemporal satellite radar interferometry. Geology 39, pp. 551-554.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010EGUGA..12.7766B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010EGUGA..12.7766B"><span id="translatedtitle">A comparison study of North Adriatic Dense Water descent using observations in March, 2006 and March, 2009</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Book, Jeffrey W.; Carniel, Sandro; Bergamasco, Andrea; Bortoluzzi, Giovanni; Hobbs, Richard; Matić, Frano; Rixen, Michel; Russo, Aniello; Schroeder, Katrin; Wood, Warren</p> <p>2010-05-01</p> <p>North Adriatic Dense Water (NAdDW) forms on the Adriatic shallow shelf, travels southeastward along the Italian slope in a dense vein near the 100 m <span class="hlt">isobath</span>, and then descends with mixing after it crosses the Palagruža Sill. As it can be much denser than the surrounding water masses, this descent could take the form of cascading especially at the topographic interruption of the Bari Canyon system. Two recent observational programs gathered data on this process in winters with strikingly different NAdDW conditions. The DART06A international collaborative cruise in March 2006 occurred during a period of strong NAdDW production and export to the southeast, as evidenced by bottom potential densities exceeding 29.7 kg/m3 along the sill observed by the 12 time-series moorings that spanned it. Further south, both upstream and offshore of the Bari Canyon system, observed temperature/salinity relationships from CTDs show mixing connections between waters deeper than 600 m (densities of 29.3 kg/m3 and 29.4 kg/m3) on the Italian slope and spatially unconnected waters at 100 m depth on the nearby coastal shelf (densities > 29.4 kg/m3). The AdriaSeismic09 international cruise in March 2009 was organized to examine the spatial pathways and evolution of NAdDW near the sill and canyons, but encountered a period of weak or absent NAdDW production and export. CTDs show that in March 2009 the northern source vein at 100 m depth was present but lower in density (maximum at 29.2 kg/m3) and was therefore not able to sink in bulk below the slightly denser surrounding waters. However, a thin layer of this water was found descending down the slope near the sill in a bottom-boundary layer through use of the new technique of seismic oceanography. This technique can image vertical thermal gradients with horizontal and vertical resolutions as fine as 7 meters all the way to the bottom. The temperature-salinity measurements from the two winters show that the bulk of 2009 water was lighter by a</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.6066Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.6066Z"><span id="translatedtitle">Supercritical turbidity-current bedforms in the northeastern continental slope, South China Sea</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhong, Guangfa; Kuang, Zenggui; Cartigny, Matthieu J. B.; Guo, Yiqun; Wang, Liaoliang</p> <p>2015-04-01</p> <p> the South Taiwan Shoal canyon, the southwestern flank of the Dongsha canyon, and outside of the mouth of the West Penghu canyon, respectively. The sediment waves are 2.8-7.2 km in wavelength and 30-60 m in wave height, and migrate upslope, and align parallel to local <span class="hlt">isobaths</span> and orthogonal or oblique to the canyon trends. All these lines of evidence point to an overspilling or off-stripping turbidity current origin of the sediment waves. Further research suggests that the sediment waves are composed of various types of supercritical flow bedforms, including antidunes, chutes-and-pools, and possibly cyclic steps. Discoveries of the supercritical flow bedforms provide crucial evidence for turbidity current activities in the canyons. This work was funded by the National Natural Science Foundation of China (grants 91028003 and 41076020).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015EGUGA..17.3568N&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015EGUGA..17.3568N&link_type=ABSTRACT"><span id="translatedtitle">Geomorphologic Structures on the South Cretan Margin, Greece</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nomikou, Paraskevi; Lykousis, Vasilis; Alexandri, Matina; Rousakis, Grigoris; Sakellariou, Dimitris; Lampridou, Danai; Alves, Tiago; Ballas, Dionysios</p> <p>2015-04-01</p> <p>Geomorphologic Structures on the South Cretan Margin, Greece Nomikou P.1, Lykousis V.2, Alexandri M.2, Rousakis G.2, Sakellariou D.2, Lampridou D.1 , Alves T.3, Ballas D.2 1University of Athens, Department of Geology and Geoenvironment, Panepistimioupoli Zografou, 15784 Athens, Greece. 2Inst. of Oceanography, Hellenic Centre for Marine Research, Anavyssos, Greece. 33D Seismic Laboratory, School of Earth and Ocean Sciences, Cardiff University, Main Building-Park Place, CF10 3AT Cardiff, UK. The swath bathymetric survey of the South Cretan Margin has been conducted during the HERMES-1 (May-June 2005) and HERMES-2 (September-October 2005) cruises onboard R/V "AEGAEO" using the 20 kHz, SEABEAM 2120 system. High-resolution multibeam bathymetry outlines in unprecedented detail the shape and the morphological features of the region. One of the most dominant geomorphological structures of the southwest Cretan slope is the submarine Samaria Canyon (Western Cretan Trough) which is characterized by high relief steep walls and V-shaped cross sections. Despite the fact that the trough trends predominantly northeastward, with a central axis oriented from east to west, the head displays a north-trending hook termination on the continental shelf. The minimum depth of its axis is 1400 m and the thalweg ranges from 1500 to 3500m. In addition, abrupt alternation in the axial trend of the canyon is observed, accompanied by sharp changes in axial gradient and in the geometry of the canyon profile ending in a flat area of 3600 m depth. From Paleochora up to Sindonia, numerous small canyons trending N-S crosscut the steep Cretan southern margin, that reaches the 2000 m <span class="hlt">isobath</span>. These are transversal to the main direction E-W of the slope. Furthermore, the detailed bathymetric map reveals the morphology of several troughs bounded by steep flanks. Their flat bottom may reach up to 3000m water depth. The most characteristic one, Ptolemy trough (eastern South Cretan Trough), is located in</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1814188G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1814188G"><span id="translatedtitle">3D free-air gravity anomaly modeling for the Southeast Indian Ridge</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Girolami, Chiara; Heyde, Ingo; Rinaldo Barchi, Massimiliano; Pauselli, Cristina</p> <p>2016-04-01</p> <p> the relation between the density and the seismic P-wave velocity VP. We choose the velocity data from the scientific literature. We found that the "layer-cake" model does not explain the measured anomalies satisfyingly and lateral density changes have to be considered for the area beneath the ridge axis. Accordingly we reduced the density values of the lower crust and the upper mantle beneath the axial ridge introducing in the model two additional bodies called partial melted crust and anomalous mantle. Finally we present <span class="hlt">isobaths</span> maps of the anomalous mantle which highlight the lateral heterogeneity of the oceanic crust beneath the ridge axis. In particular there are areas characterized by crustal thickening related to magmatic accretion and areas of crustal thinning related to depleted accretion of the mantle which can lead to the exposure of OCCs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004JGRC..109.5031W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004JGRC..109.5031W"><span id="translatedtitle">Decadal shifts in biophysical forcing of Arctic marine food webs: Numerical consequences</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Walsh, John J.; Dieterle, Dwight A.; Maslowski, Wieslaw; Whitledge, Terry E.</p> <p>2004-05-01</p> <p>Fall case studies of three-dimensional circulation, plankton, and benthos models explored the consequences of interannual changes in ice cover and water motion on carbon/nitrogen cycling by the end of September within the Chukchi/Beaufort Seas. The coupled model scenarios were those of reduced (greater) northward flow, colder (warmer) temperatures, and more (less) extensive ice cover over the preceding ˜60 days of August and September during the negative (positive), anticyclonic (cyclonic) phase of the Arctic Oscillation in 1980 (1989). On the inner Chukchi shelf, stronger flows in 1989 advected nitrate and silicate stocks of Pacific origin ˜130 km farther northwest toward Wrangel Island than in 1980. Yet an increase of the total net photosynthesis by the diatom-dominated phytoplankton community over both shelves in 1989 was mainly the result of less ice cover of the cyclonic period, with a concomittant increase of POC influxes of phytodetritus and fecal pellets to the sediments. In terms of present shelf export, the model's separate pools of ˜65 umol DOC kg-1 and 1 ug chl l-1, or ˜4 umol POC kg-1, at a depth of 60 m above the 2000-m <span class="hlt">isobath</span> of the Beaufort Sea in September 1989, matched the sum of ˜70 umol TOC kg--1 sampled there by submarine in September 1997. Accordingly, most of the simulated Chukchi shelf was a weak sink of atmospheric CO2 in both September 1980 and 1989, reflecting a net fall export of particulate and dissolved debris. Within the cyclonic case of strong flows in 1989, a surface pCO2 of 248 uatm was also simulated in September at 155°W on the Beaufort shelf, where ˜250 uatm was measured there in September 2000. Here, farther away from the Pacific source of nutrients for enhanced photosynthesis, the model's estimate of surface sea water fugacity in a weaker flow regime was only 375 uatm of pCO2 at the same location in September 1980, when typically outgassing would have instead prevailed, despite increasing atmospheric pCO2 values, i</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010AGUFMOS43A1602M&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010AGUFMOS43A1602M&link_type=ABSTRACT"><span id="translatedtitle">Near-bed environmental conditions influencing cold-water coral growth on Viosca Knoll, Gulf of Mexico</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mienis, F.; Duineveld, G.; Davies, A. J.; Weering, T. V.; Ross, S.; Roberts, M.; Seim, H.</p> <p>2010-12-01</p> <p>During recent decades research has shown that cold-water coral (CWC) ecosystems are widely distributed on the margins of the Atlantic Ocean, representing the most species rich ecosystems in the upper bathyal zone. On the European continental margin and the continental slope from North Carolina to Florida, CWCs have formed large reef and mound structures. Presently detailed studies on the environmental constraints in CWC areas are limited to the NE Atlantic. This is the first study showing long-term environmental variability in a CWC habitat in the West Atlantic. The most extensive CWC area known in the Gulf of Mexico is found on the Viosca Knoll (480 m), located in the vicinity of the Mississippi River. This source dominates sedimentation patterns, discharging large amounts of sediments and dispersing organic matter and nutrients. In the coral area, CTD transects were made and benthic landers were deployed for a period of 12 months to identify near-bed environmental conditions, seasonal variability and the forcing mechanisms of particle supply. The importance of studying the functioning of deep water ecosystems was underpinned by the recent Deepwater Horizon oil spill, which might pose a risk for the CWC ecosystems. CTD transects showed an oxygen minimum zone at the depth of the corals. Long term deployments of landers revealed intra-annual temperature (6.5-11.6 °C) and salinity fluctuations, which co-vary during the year. Food supply appears not to be driven by surface processes due to low fluorescence (except for two periods in April and June), but an indirect mechanism of transport may be a 24 hour diel vertical migration of zooplankton. The average current speed in the area varies at around 8 cms-1, whilst peak current speeds were recorded up to 38 cms-1. East-west currents are strongest in the area corresponding with flow along <span class="hlt">isobaths</span>. During westward flow, the amount of particles in the water column increases, while during eastward flow clearer water is</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010EGUGA..1211830P&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010EGUGA..1211830P&link_type=ABSTRACT"><span id="translatedtitle">Geophysical exploration of the Southeast Tyrrhenian Sea (Italy): Seamounts batimetries</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Passaro, Salvatore; Milano, Girolamo</p> <p>2010-05-01</p> <p> characteristics are found on the summit of the Marsili and Palinuro seamounts, that are the major features of the Southeast Tyrrhenian Sea. The morphology of the Marsili Seamount shows a linear summit region, approximately bounded by the 1000 meters <span class="hlt">isobath</span>, stretches about 20 km along the main axis of the volcanic complex. Throughout the summit framework, crater-like items are not identifiable whereas cone-like items are revealed. The morphology of the Palinuro seamount reveals a very articulated summit consisting in a group of overlapped and/or coalescent volcanic cones inside collapsed calderas. Relic domes of calderic collapses are identifiable both in the western and in the central sectors of the Palinuro Seamount. The continuation of the Palinuro seamount toward the mainland is marked by the Glabro seamount. Magnetic data constrain the interpretation of several volcanic features detected on both the Palinuro and the Marsili seamounts.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1993JGR....98.4775K&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1993JGR....98.4775K&link_type=ABSTRACT"><span id="translatedtitle">A numerical study of sediment transport and event bed genesis during tropical strom Delia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Keen, Timothy R.; Slingerland, Rudy L.</p> <p>1993-03-01</p> <p>Some event beds (tempestites) are thought to be emplaced on shallow marine shelves by the combined action of strong coastal currents and high waves during fairly short-lived storms. To test this hypothesis, a storm sedimentation system has been constructed from six numerical models describing a cyclonic wind field, three-dimensional coastal circulation, wind waves generated over the continental shelf, the combined effect of steady and oscillatory currents within the benthic boundary layer, suspended and bed load transport of sediment, and conservation of the seafloor. This model system is used to hindcast winds, currents, waves, and resulting sedimentation during Tropical Storm Delia, which passed over the Texas-Louisiana shelf on September 3-4, 1973. Sensitivity to the initial substrate is investigated in four experiments using uniform silt, uniform sand, a mud line at the 20-m <span class="hlt">isobath</span>, and a simplified modern sediment distribution. Modeled coastal currents are vertically uniform and do not reveal the structure predicted by the mid-latitude geostrophic storm circulation model, because the predicted depth of the wind-mixed layer is greater than the water depth over the shelf. Shelf currents in excess of 2 m/s flow predominantly along the coast to the southwest during most of the storm, driven by the wind stress and the trapped coastal wave which peaks at 180 cm near Galveston. Significant wave heights reach 8 m on the outer shelf but are less than 4 m over the inner shelf. These waves combine with steady currents to produce bed shear velocities which locally exceed 20 cm/s. The region of highest stresses always lies to the right of the storm track (viewed down the path) and moves across the shelf with the eye of the storm. Three general sediment transport paths are evident: (1) onshore transport of finer sediment over the outer shelf to the right of the storm track, (2) westward-directed along-shelf transport of predominantly fine sediment between approximately 40</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active"><span>25</span></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_25 --> <center> <div class="footer-extlink text-muted"><small>Some links on this page may take you to non-federal websites. 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