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Sample records for subantarctic mode water

  1. Subantarctic mode water: distribution and circulation

    NASA Astrophysics Data System (ADS)

    Herraiz-Borreguero, Laura; Rintoul, Stephen Rich

    2011-01-01

    The subduction and export of subantarctic mode water (SAMW) as part of the overturning circulation play an important role in global heat, freshwater, carbon and nutrient budgets. Here, the spatial distribution and export of SAMW is investigated using Argo profiles and a climatology. SAMW is identified by a dynamical tracer: a minimum in potential vorticity. We have found that SAMW consists of several modes with distinct properties in each oceanic basin. This conflicts with the previous view of SAMW as a continuous water mass that gradually cools and freshens to the east. The circulation paths of SAMW were determined using (modified) Montgomery streamlines on the density surfaces corresponding with potential vorticity minima. The distribution of the potential vorticity minima revealed "hotspots" where the different SAMW modes subduct north of the Subantarctic Front. The subducted SAMWs follow narrow export pathways into the subtropical gyres influenced by topography. The export of warmer, saltier modes in these "hotspots" contributes to the circumpolar evolution of mode water properties toward cooler, fresher and denser modes in the east.

  2. How does Subantarctic Mode Water ventilate the Southern Hemisphere subtropics?

    NASA Astrophysics Data System (ADS)

    Jones, Daniel C.; Meijers, Andrew J. S.; Shuckburgh, Emily; Sallée, Jean-Baptiste; Haynes, Peter; McAufield, Ewa K.; Mazloff, Matthew R.

    2016-09-01

    In several regions north of the Antarctic Circumpolar Current (ACC), deep wintertime convection refreshes pools of weakly stratified subsurface water collectively referred to as Subantarctic Mode Water (SAMW). SAMW ventilates the subtropical thermocline on decadal timescales, providing nutrients for low-latitude productivity and potentially trapping anthropogenic carbon in the deep ocean interior for centuries. In this work, we investigate the spatial structure and timescales of mode water export and associated thermocline ventilation. We use passive tracers in an eddy-permitting, observationally-informed Southern Ocean model to identify the pathways followed by mode waters between their formation regions and the areas where they first enter the subtropics. We find that the pathways followed by the mode water tracers are largely set by the mean geostrophic circulation. Export from the Indian and Central Pacific mode water pools is primarily driven by large-scale gyre circulation, whereas export from the Australian and Atlantic pools is heavily influenced by the ACC. Export from the Eastern Pacific mode water pool is driven by a combination of deep boundary currents and subtropical gyre circulation. More than 50% of each mode water tracer reaches the subtropical thermocline within 50 years, with significant variability between pools. The Eastern Pacific pathway is especially efficient, with roughly 80% entering the subtropical thermocline within 50 years. The time required for 50% of the mode water tracers to leave the Southern Ocean domain varies significantly between mode water pools, from 9 years for the Indian mode water pool to roughly 40 years for the Central Pacific mode water pool.

  3. Mechanisms of subantarctic mode water upwelling in a hybrid-coordinate global GCM

    NASA Astrophysics Data System (ADS)

    Zuo, Hao; Naveira Garabato, Alberto C.; New, Adrian L.; Oschlies, Andreas

    This article presents an investigation of the global circulation and upwelling of subantarctic mode water (SAMW), which is thought to be key in the supply of nutrients to support biological production over much of the world ocean excluding the North Pacific. The HYbrid isopycnic-cartesian Coordinate Ocean general circulation Model (HYCOM) is configured to simulate the global ocean circulation for time scales of up to centuries and a SAMW-tracking online tracer experiment is conducted. The tracer re-emergence fluxes across the mixed layer base effected by a range of physical mechanisms and by numerical mixing terms in HYCOM are diagnosed and discussed. For the global ocean north of 30°S, entrainment due to surface buoyancy loss and/or wind-induced mechanical stirring accounts for almost one third of the total tracer re-emergence. Ekman upwelling and shear-induced mixing are especially significant in the tropical oceans, and account for 19% and 18% of the total tracer re-emergence, respectively. There is substantial regional variation in the relative importance of the various upwelling mechanisms. Special attention is devoted to understanding the contrasting circulations of SAMW in the North Pacific and North Atlantic oceans. The modest penetration of SAMW into the North Pacific is found to arise from the comparatively light density level that the SAMW core resides at in the South Pacific Ocean, which results in its being captured by the Equatorial Undercurrent and prevents it from entering the western boundary current of the North Pacific. In the North Atlantic, a new conceptual model of SAMW circulation and re-emergence is proposed with application to nutrient supply to the regional upper ocean. The model formulates SAMW re-emergence as a sequence of distinct processes following the seasonal cycle of the thermocline as a water column circulates around the subtropical and subpolar gyres of the North Atlantic.

  4. Model Comparison of Subantarctic Mode and Antarctic Intermediate Water In The Southeast Pacific During The Present And Last Glacial Maximum

    NASA Astrophysics Data System (ADS)

    Hartin, C. A.; Fine, R. A.; Clement, A. C.; Kamenkovich, I. V.; Peterson, L. C.

    2009-12-01

    Subantarctic Mode Water (SAMW) and Antarctic Intermediate Water (AAIW) are large volume mid-depth (400-1200 m) water masses, which transport heat, freshwater and CO2 into the Southern Hemisphere subtropical gyres and to the equatorial thermoclines. This study investigates variations in SAMW and AAIW properties and circulation in the southeast Pacific between the present and Last Glacial Maximum (LGM). Observations from the 1990s and 2000s and model output from NCAR CCSM3 climate model are compared. Under present climate conditions, some of the coldest SAMW and freshest AAIW are formed in the southeast Pacific Ocean. Presently, SAMW is formed equatorward of the Subantarctic Front (SAF) within deep mixed layers, while AAIW is formed just poleward of the SAF. During the LGM there was a fundamental reorganization of the ocean circulation. The model simulates an equatorward shift in the location of formation by approximately 7° between present day and the LGM. The model also simulates a fresher SAMW during the LGM, while AAIW is saltier by up to 1.5 psu. In addition, depth, equatorward extent and thickness have varied between the LGM and present. Comparisons of SAMW and AAIW under present day conditions and under extreme climate conditions (i.e. the LGM), can be used to shed light on how these important water masses will vary with future climate change.

  5. Comparison of Subantarctic Mode Water and Antarctic Intermediate Water formation rates in the South Pacific between NCAR-CCSM4 and observations

    NASA Astrophysics Data System (ADS)

    Hartin, Corinne A.; Fine, Rana A.; Kamenkovich, Igor; Sloyan, Bernadette M.

    2014-01-01

    Average formation rates for Subantarctic Mode Water (SAMW) and Antarctic Intermediate Water (AAIW) in the South Pacific are calculated from the National Center for Atmospheric Research Community Climate System Model version 4 (NCAR-CCSM4), using chlorofluorocarbon inventories (CFC-12). When compared to observations, CCSM4 accurately simulates the southeast Pacific as the main formation region for SAMW and AAIW. Formation rates for SAMW in CCSM4 are 3.4 sverdrup (Sv), about half of the observational rate, due in part to shallow mixed layers, a thinner SAMW layer, and insufficient meridional transport. A formation rate of 8.1 Sv for AAIW in CCSM4 is higher than observations due to higher inventories in the southwest and central Pacific and surface concentrations within CCSM4. Also, a lack of data in the southwest Pacific may bias the observational rate low. This model-observation comparison is useful for understanding the uptake and transport of other gases, e.g., CO2 by the model.

  6. Comparison of Subantarctic Mode Water and Antarctic Intermediate Water formation rates in the South Pacific between NCAR-CCSM4 and observations

    SciTech Connect

    Hartin, Corinne A.; Fine, Rana A.; Kamenkovich, Igor; Sloyan, Bernadette M.

    2014-01-28

    Average formation rates for Subantarctic Mode (SAMW) and Antarctic Intermediate Waters (AAIW) in the South Pacific are calculated from the National Center for Atmospheric Research Community Climate System Model version 4 (NCAR-CCSM4), using chlorofluorocarbon inventories. CFC-12 inventories and formation rates are compared to ocean observations. CCSM4 accurately simulates the southeast Pacific as the main formation region for SAMW and AAIW. CCSM4 formation rates for SAMW are 3.4 Sv, about half of the observational rate. Shallow mixed layers and a thinner SAMW in CCSM4 are responsible for lower formation rates. A formation rate of 8.1 Sv for AAIW in CCSM4 is higher than observations. Higher inventories in CCSM4 in the southwest and central Pacific, and higher surface concentrations are the main reasons for higher formation rates of AAIW. This comparison of model and observations is useful for understanding the uptake and transport of other gases, e.g., CO2 by the model.

  7. Species composition and biogeography of diatoms in antarctic and subantarctic (Argentine shelf) waters (37-76°S)

    NASA Astrophysics Data System (ADS)

    Olguín, Héctor F.; Alder, Viviana A.

    2011-03-01

    A large spatial scale study of the diatom species inhabiting waters from the subantarctic (Argentine shelf) to antarctic was made for the first time in order to understand the relationships between these two regions with regard to the fluctuations in diatom abundances in relation with environmental features, their floristic associations and the effect of the Polar Front as a biogeographic barrier. Species-specific diatom abundance, nutrient and chlorophyll- a concentration were assessed from 64 subsurface oceanographic stations carried out during the austral summer 2002, a period characterized by an anomalous sea-ice coverage corresponding to a "warm year". Significant relationships of both diatom density and biomass with chlorophyll- a (positive) and water temperature (negative) were found for the study area as a whole. Within the Subantarctic region, diatom density and biomass values were more uniform and significantly (in average: 35 and 11 times) lower than those of the Antarctic region, and did not correlate with chlorophyll- a. In antarctic waters, instead, biomass was directly related with chlorophyll- a, thus confirming the important contribution of diatoms to the Antarctic phytoplanktonic stock. A total of 167 taxa were recorded for the entire study area, with Chaetoceros and Thalassiosira being the best represented genera. Species richness was maximum in subantarctic waters (46; Argentine shelf) and minimum in the Antarctic region (21; Antarctic Peninsula), and showed a significant decrease with latitude. Floristic associations were examined both qualitatively (Jaccard Index) and quantitatively (correlation) by cluster analyses and results allowed differentiating a similar number of associations (12 vs. 13, respectively) and two main groups of stations. In the Drake Passage, the former revealed that the main floristic change was found at the Polar Front, while the latter reflected the Southern ACC Front as a main boundary, and yielded a higher number of

  8. Submesoscale dynamics at the Subantarctic Front in the Scotia Sea: Implications for vertical exchange and water mass transformation

    NASA Astrophysics Data System (ADS)

    Adams, K.; Hosegood, P. J.; Taylor, J. R.; Sallee, J. B.; Bachman, S.; Stamper, M. A.

    2016-02-01

    We present new results from the Surface Mixed Layer Evolution at Submesoscales (SMILES) cruise conducted in the Scotia Sea during May 2015. We aimed to (1) measure with submesoscale-resolving resolution the evolution of two different sites within the Subantarctic Front (SAF) with varying lateral buoyancy gradients and strain rates and (2) assess implications for upper ocean vertical exchange and water mass transformation. The first site was a cold filament that extended westward following the northward deflection of the SAF east of the Falkland Islands. Repeated towed CTD sections across the front, which was confined to the surface mixed layer (SML), were made in a Lagrangian reference frame whilst following a drogued drifter. The front oscillated with a near-inertial frequency, repeatedly slumping and returning to the vertical as horizontal current velocities exhibited upward phase propagation consistent with a downward propagating near inertial wave. We discuss the interaction between the wave and front, drawing upon microstructure data acquired over an inertial cycle. The second site was a strongly strained frontal region to the south (57oS) where the Polar and Subantarctic Fronts converge along the ACC. Intense subduction of surface waters to depths >400 m within a narrow region between the two fronts is observed in chlorophyll fluorescence and dissolved oxygen. Our observations focused on a northward meander in this frontal region and coincided with the precise moment that it evolved into a high chlorophyll, closed core eddy that we tracked post-cruise with drogued drifters and remote sensing for over 2 months. Using data from repeated Seasoar transects that sampled around the entire eddy and the trajectories of three drogued drifter triplets released in a cold water filament that demarcated the inner flank of the eddy periphery, we discuss the eddy generation mechanisms and role of submesoscale instabilities within the front that were apparent in the Seasoar

  9. On Hokusai's Great wave off Kanagawa: localization, linearity and a rogue wave in sub-Antarctic waters

    PubMed Central

    Dudley, J. M.; Sarano, V.; Dias, F.

    2013-01-01

    The Hokusai woodcut entitled The great wave off Kanagawa has been interpreted as an unusually large storm wave, likely to be classed as a rogue wave, and possibly generated from nonlinear wave dynamics (J. H. E. Cartwright and H. Nakamura, Notes Rec. R. Soc. 63, 119–135 (2009)). In this paper, we present a complementary discussion of this hypothesis, discussing in particular how linear and nonlinear mechanisms can both contribute to the emergence of rogue wave events. By making reference to the Great wave's simultaneous transverse and longitudinal localization, we show that the purely linear mechanism of directional focusing also predicts characteristics consistent with those of the Great wave. In addition, we discuss the properties of a particular rogue wave photographed on the open ocean in sub-Antarctic waters, which shows two-dimensional localization and breaking dynamics remarkably similar to Hokusai's depiction in the woodcut. PMID:24687148

  10. On Hokusai's Great wave off Kanagawa: localization, linearity and a rogue wave in sub-Antarctic waters.

    PubMed

    Dudley, J M; Sarano, V; Dias, F

    2013-06-20

    The Hokusai woodcut entitled The great wave off Kanagawa has been interpreted as an unusually large storm wave, likely to be classed as a rogue wave, and possibly generated from nonlinear wave dynamics (J. H. E. Cartwright and H. Nakamura, Notes Rec. R. Soc.63, 119-135 (2009)). In this paper, we present a complementary discussion of this hypothesis, discussing in particular how linear and nonlinear mechanisms can both contribute to the emergence of rogue wave events. By making reference to the Great wave's simultaneous transverse and longitudinal localization, we show that the purely linear mechanism of directional focusing also predicts characteristics consistent with those of the Great wave. In addition, we discuss the properties of a particular rogue wave photographed on the open ocean in sub-Antarctic waters, which shows two-dimensional localization and breaking dynamics remarkably similar to Hokusai's depiction in the woodcut.

  11. The skin of Commerson's dolphins (Cephalorhynchus commersonii) as a biomonitor of mercury and selenium in Subantarctic waters.

    PubMed

    Cáceres-Saez, Iris; Goodall, R Natalie P; Dellabianca, Natalia A; Cappozzo, H Luis; Ribeiro Guevara, Sergio

    2015-11-01

    The skin of bycaught Commerson's dolphins was tested for mercury (Hg) and selenium (Se) biomonitoring in Subantarctic environments. The correlation of levels detected in the skin with those found in internal tissues - lung, liver, kidney and muscle - was assessed to evaluate how skin represents internal Hg and Se distribution for monitoring purposes. Mercury in skin had a concentration range of 0.68-3.11 μg g(-1) dry weight (DW), while Se had a higher concentration range of 74.3-124.5 μg g(-1) DW. There was no significant correlation between selenium levels in any of the analyzed tissues. Thus, the skin selenium concentration did not reflect the tissular Se levels and did not provide information for biomonitoring. The lack of correlation is explained by the biological role of Se, provided that each tissue regulates Se levels according to physiological needs. However, the skin Hg level had significant positive correlation with the levels in internal tissues (ANOVA p<0.05), particularly with that of muscle (R(2)=0.79; ANOVA p=0.0008). Thus, this correlation permits the estimation of Hg content in muscle based on the multiplication of skin biopsy levels by a factor of 1.85. Mercury bioindication using skin biopsies is a non-lethal approach that allows screening of a large number of specimens with little disturbance and makes possible an adequate sampling strategy that produces statistically valid results in populations and study areas. The correlation between Hg levels in the skin and internal tissues supports the use of the epidermis of Commerson's dolphins for Hg biomonitoring in the waters of the Subantarctic, which is a poorly studied region regarding Hg levels, sources and processes.

  12. Bone-Eating Worms Spread: Insights into Shallow-Water Osedax (Annelida, Siboglinidae) from Antarctic, Subantarctic, and Mediterranean Waters

    PubMed Central

    Taboada, Sergi; Riesgo, Ana; Bas, Maria; Arnedo, Miquel A.; Cristobo, Javier; Rouse, Greg W.; Avila, Conxita

    2015-01-01

    Osedax, commonly known as bone-eating worms, are unusual marine annelids belonging to Siboglinidae and represent a remarkable example of evolutionary adaptation to a specialized habitat, namely sunken vertebrate bones. Usually, females of these animals live anchored inside bone owing to a ramified root system from an ovisac, and obtain nutrition via symbiosis with Oceanospirillales gamma-proteobacteria. Since their discovery, 26 Osedax operational taxonomic units (OTUs) have been reported from a wide bathymetric range in the Pacific, the North Atlantic, and the Southern Ocean. Using experimentally deployed and naturally occurring bones we report here the presence of Osedax deceptionensis at very shallow-waters in Deception Island (type locality; Antarctica) and at moderate depths near South Georgia Island (Subantarctic). We present molecular evidence in a new phylogenetic analysis based on five concatenated genes (28S rDNA, Histone H3, 18S rDNA, 16S rDNA, and cytochrome c oxidase I–COI–), using Maximum Likelihood and Bayesian inference, supporting the placement of O. deceptionensis as a separate lineage (Clade VI) although its position still remains uncertain. This phylogenetic analysis includes a new unnamed species (O. ‘mediterranea’) recently discovered in the shallow-water Mediterranean Sea belonging to Osedax Clade I. A timeframe of the diversification of Osedax inferred using a Bayesian framework further suggests that Osedax diverged from other siboglinids during the Middle Cretaceous (ca. 108 Ma) and also indicates that the most recent common ancestor of Osedax extant lineages dates to the Late Cretaceous (ca. 74.8 Ma) concomitantly with large marine reptiles and teleost fishes. We also provide a phylogenetic framework that assigns newly-sequenced Osedax endosymbionts of O. deceptionensis and O. ‘mediterranea’ to ribospecies Rs1. Molecular analysis for O. deceptionensis also includes a COI-based haplotype network indicating that individuals from

  13. Bone-Eating Worms Spread: Insights into Shallow-Water Osedax (Annelida, Siboglinidae) from Antarctic, Subantarctic, and Mediterranean Waters.

    PubMed

    Taboada, Sergi; Riesgo, Ana; Bas, Maria; Arnedo, Miquel A; Cristobo, Javier; Rouse, Greg W; Avila, Conxita

    2015-01-01

    Osedax, commonly known as bone-eating worms, are unusual marine annelids belonging to Siboglinidae and represent a remarkable example of evolutionary adaptation to a specialized habitat, namely sunken vertebrate bones. Usually, females of these animals live anchored inside bone owing to a ramified root system from an ovisac, and obtain nutrition via symbiosis with Oceanospirillales gamma-proteobacteria. Since their discovery, 26 Osedax operational taxonomic units (OTUs) have been reported from a wide bathymetric range in the Pacific, the North Atlantic, and the Southern Ocean. Using experimentally deployed and naturally occurring bones we report here the presence of Osedax deceptionensis at very shallow-waters in Deception Island (type locality; Antarctica) and at moderate depths near South Georgia Island (Subantarctic). We present molecular evidence in a new phylogenetic analysis based on five concatenated genes (28S rDNA, Histone H3, 18S rDNA, 16S rDNA, and cytochrome c oxidase I-COI-), using Maximum Likelihood and Bayesian inference, supporting the placement of O. deceptionensis as a separate lineage (Clade VI) although its position still remains uncertain. This phylogenetic analysis includes a new unnamed species (O. 'mediterranea') recently discovered in the shallow-water Mediterranean Sea belonging to Osedax Clade I. A timeframe of the diversification of Osedax inferred using a Bayesian framework further suggests that Osedax diverged from other siboglinids during the Middle Cretaceous (ca. 108 Ma) and also indicates that the most recent common ancestor of Osedax extant lineages dates to the Late Cretaceous (ca. 74.8 Ma) concomitantly with large marine reptiles and teleost fishes. We also provide a phylogenetic framework that assigns newly-sequenced Osedax endosymbionts of O. deceptionensis and O. 'mediterranea' to ribospecies Rs1. Molecular analysis for O. deceptionensis also includes a COI-based haplotype network indicating that individuals from Deception

  14. Annual cycles of deep-ocean biogeochemical export fluxes in subtropical and subantarctic waters, southwest Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Nodder, Scott D.; Chiswell, Stephen M.; Northcote, Lisa C.

    2016-04-01

    The annual cycles of particle fluxes derived from moored sediment trap data collected during 2000-2012 in subtropical (STW) and subantarctic waters (SAW) east of New Zealand are presented. These observations are the most comprehensive export flux time series from temperate Southern Hemisphere latitudes to date. With high levels of variability, fluxes in SAW were markedly lower than in STW, reflecting the picophytoplankton-dominated communities in the iron-limited, high nutrient-low chlorophyll SAW. Austral spring chlorophyll blooms in surface STW were near synchronous with elevated fluxes of bio-siliceous, carbonate, and organic carbon-rich materials to the deep ocean, probably facilitated by diatom and/or coccolithophorid sedimentation. Lithogenic fluxes were also high in STW, compared to SAW, reflecting proximity to the New Zealand landmass. In contrast, the highest biogenic fluxes in SAW occurred in spring when surface chlorophyll concentrations were low, while highest annual chlorophyll concentrations were in summer with no associated flux increase. We hypothesize that the high spring export in SAW results from subsurface chlorophyll accumulation that is not evident from remote-sensing satellites. This material was also rich in biogenic silica, perhaps related to the preferential export of diatoms and other silica-producing organisms, such as silicoflagellates and radiolarians. Organic carbon fluxes in STW are similar to that of other mesotrophic to oligotrophic waters (˜6-7 mg C m-2 d-1), whereas export from SAW is below the global average (˜3 mg C m-2 d-1). Regional differences in flux across the SW Pacific and Tasman region reflect variations in physical processes and ecosystem structure and function.

  15. The response of phytoplankton to iron enrichment in Sub-Antarctic HNLCLSi waters: Results from the SAGE experiment

    NASA Astrophysics Data System (ADS)

    Peloquin, Jill; Hall, Julie; Safi, Karl; Smith, Walker O., Jr.; Wright, Simon; van den Enden, Rick

    2011-03-01

    Areas of high nutrients and low chlorophyll a comprise nearly a third of the world's oceans, including the equatorial Pacific, the Southern Ocean and the Sub-Arctic Pacific. The SOLAS Sea- Air Gas Exchange (SAGE) experiment was conducted in late summer, 2004, off the east coast of the South Island of New Zealand. The objective was to assess the response of phytoplankton in waters with low iron and silicic acid concentrations to iron enrichment. We monitored the quantum yield of photochemistry ( Fv/ Fm) with pulse amplitude modulated fluorometry, chlorophyll a, primary productivity, and taxonomic composition. Measurements of Fv/ Fm indicated that the phytoplankton within the amended patch were relieved from iron stress ( Fv/ Fm approached 0.65). Although there was no significant difference between IN and OUT stations at points during the experiment, the eventual enhancement in chlorophyll a and primary productivity was twofold by the end of the 15-day patch occupation. However, no change in particulate carbon or nitrogen pools was detected. Enhancement in primary productivity and chlorophyll a were approximately equal for all phytoplankton size classes, resulting in a stable phytoplankton size distribution. Initial seed stocks of diatoms were extremely low, <1% of the assemblage based on HPLC pigment analysis, and did not respond to iron enrichment. The most dominant groups before and after iron enrichment were type 8 haptophytes and prasinophytes that were associated with ˜75% of chlorophyll a. Twofold enhancement of biomass estimated by flow cytometry was detected only in eukaryotic picoplankton, likely prasinophytes, type 8 haptophytes and/or pelagophytes. These results suggest that factors other than iron, such as silicic acid, light or physical disturbance limited the phytoplankton assemblage during the SAGE experiment. Furthermore, these results suggest that additional iron supply to the Sub-Antarctic under similar seasonal conditions and seed stock will most

  16. Redescription of Terebellides kerguelensis stat. nov. (Polychaeta: Trichobranchidae) from Antarctic and subantarctic waters

    NASA Astrophysics Data System (ADS)

    Parapar, Julio; Moreira, Juan

    2008-06-01

    During the Spanish Antarctic expeditions “Bentart” 1994, 1995 and 2003, a number of trichobranchid (Annelida: Polychaeta) specimens were collected and identified initially as Terebellides stroemii kerguelensis McIntosh, 1885, the only known species of the genus widely recognised as valid in Antarctic waters. In the framework of a worldwide revision of the genus Terebellides, a reconsideration of the taxonomic status of this subspecies of the boreal Terebellides stroemii Sars, 1835 is done through the examination of the syntypes of T. s. kerguelensis compared with recent descriptions of the nominal species from Norwegian waters and material from Icelandic waters. Thus, T. s. kerguelensis is regarded as a valid species, T. kerguelensis stat. nov., and redescribed designating a lectotype and paralectotypes. The species is mainly characterised by the presence of an anterior branchial extension (fifth lobe), lateral lappets in five anterior thoracic chaetigers, segmental organs in chaetigers 1, 4 and 5, and first thoracic acicular neurochaetae sharply bent with pointed tips. The biological role of the segmental organs, the presence and disposition of cilia in branchial lamellae and the finding of new structures located in dorsal part of thoracic notopodia are discussed.

  17. Particulate iron dynamics during FeCycle in subantarctic waters southeast of New Zealand

    NASA Astrophysics Data System (ADS)

    Frew, R. D.; Hutchins, D. A.; Nodder, S.; Sanudo-Wilhelmy, S.; Tovar-Sanchez, A.; Leblanc, K.; Hare, C. E.; Boyd, P. W.

    2006-03-01

    The FeCycle experiment provided an SF6 labeled mesoscale patch of high-nitrate low-chlorophyll (HNLC) water in austral summer 2003. These labeled waters enabled a comparison of the inventory of particulate iron (PFe) in the 45-m-deep surface mixed layer with the concurrent downward export flux of PFe at depths of 80 and 120 m. The partitioning of PFe between four size fractions (0.2-2, 2-5, 5-20, and >20 μm) was assessed, and PFe was mainly found in the >20-μm size fraction throughout FeCycle. Estimates of the relative contribution of the biogenic and lithogenic components to PFe were based on an Al:Fe molar ratio (0.18) derived following analysis of dust/soil from the nearest source of aerosol Fe: the semi-arid regions of Australia. The lithogenic component dominated each of the four PFe size fractions, with medians ranging from 68 to 97% of PFe during the 10-day experiment. The Fe:C ratios for mixed-layer particles were ˜40 μmol/mol. PFe export was ˜300 nmol m-2 d-1 at 80 m depth representing a daily loss of ˜1% from the mixed-layer PFe inventory. There were pronounced increases in the Fe:C particulate ratios with depth, with a five-fold increase from the surface mixed layer to 80 m depth, consistent with scavenging of the remineralized Fe by sinking particles and concurrent solubilization and loss of particulate organic carbon. Significantly, the lithogenic fraction of the sinking PFe intercepted at both 80 m and 120 m was >40% that is, there was an approximately twofold decrease in the proportion of lithogenic iron exported relative to that in the mixed-layer lithogenic iron inventory. This indicates that the transformation of lithogenic to biogenic PFe takes place in the mixed layer, prior to particles settling to depth. Moreover, the magnitude of lithogenic Fe supply from dust deposition into the waters southeast of New Zealand is comparable to that of the export of PFe from the mixed layer, suggesting that a large proportion of the deposited dust

  18. Biogeochemical iron budgets of the Southern Ocean south of Australia: Decoupling of iron and nutrient cycles in the subantarctic zone by the summertime supply

    NASA Astrophysics Data System (ADS)

    Bowie, Andrew R.; Lannuzel, Delphine; Remenyi, Tomas A.; Wagener, Thibaut; Lam, Phoebe J.; Boyd, Philip W.; Guieu, CéCile; Townsend, Ashley T.; Trull, Thomas W.

    2009-12-01

    Climate change is projected to significantly alter the delivery (stratification, boundary currents, aridification of landmasses, glacial melt) of iron to the Southern Ocean. We report the most comprehensive suite of biogeochemical iron budgets to date for three contrasting sites in subantarctic and polar frontal waters south of Australia. Distinct regional environments were responsible for differences in the mode and strength of iron supply mechanisms, with higher iron stocks and fluxes observed in surface northern subantarctic waters, where atmospheric iron fluxes were greater. Subsurface waters southeast of Tasmania were also enriched with particulate iron, manganese and aluminum, indicative of a strong advective source from shelf sediments. Subantarctic phytoplankton blooms are thus driven by both seasonal iron supply from southward advection of subtropical waters and by wind-blown dust deposition, resulting in a strong decoupling of iron and nutrient cycles. We discuss the broader global significance our iron budgets for other ocean regions sensitive to climate-driven changes in iron supply.

  19. Seasonal to decadal pH and fCO2 changes in the subtropical, sub-antarctic and polar waters of the SW Indian ocean

    NASA Astrophysics Data System (ADS)

    Lourantou, A.; Lo Monaco, C.; Brunet, C.; Ridame, C.; Metzl, N.

    2012-04-01

    Human-induced CO2 emissions are constantly increasing and the role of the ocean carbon sink becomes crucial for the global carbon budget (Peters et al., 2011). The Southern Ocean is a key area of carbon sink (Takahashi et al. 2009) and thus more susceptible to pH changes, according to model predictions (Orr et al., 2005; McNeil & Matear, 2008). Little is known from in situ observations. The SW Indian Ocean is being regularly visited in the framework of the OISO (Océan Indien Service d'Observation) program. This extended area is annually a carbon sink (Metzl, 2009; Lourantou and Metzl, 2011). Here we examine three distinct stations located south of the Polar Front (50°S, KERFIX station), in the frontal zone (40°S) and in the Subtropical Zone (30°S). These stations differ by their hydrological properties, their potential in assimilating atmospheric CO2 and their associated nutritional and ecosystem regime, from a HNLC -High Nutrient Low Chlorophyll- area (50°S), to a region of formation of Subantarctic Mode Waters (40°S), and oligotrophic waters in the north (30°S). By using CARINA (Key et al., 2010) and SOCAT (Pfeil et al., in prep.) databases, for the water column and surface waters, respectively, and the addition of recent OISO data, we computed the evolution of pH along depth and time (from 1978- 2010) at these stations. We present: (i) the temporal evolution of the rate of change of computed pH and fCO2 at the 3 stations from surface to deep waters; (ii) a comparison with anthropogenic carbon estimates, Cant (Touratier et al., 2007) and the change in measured Dissolved Inorganic Carbon, DIC; (iii) a comparison with the evolution of chlorophyll a concentrations. Based on these results, we discuss the dominant mechanisms responsible for the changes in pH observed at different depths and latitudes. For KERFIX station we also assess the distinction between seasonality and decadal evolution of biogeochemical parameters. Our first results point towards a

  20. Silicic acid enrichment of subantarctic surface water from continental inputs along the Patagonian archipelago interior sea (41-56°S)

    NASA Astrophysics Data System (ADS)

    Torres, Rodrigo; Silva, Nelson; Reid, Brian; Frangopulos, Máximo

    2014-12-01

    We estimated Si∗, the surplus or deficit of orthosilicic acid (DSi) relative to nitrate available for diatom growth, in the Chilean Patagonian Archipelago Interior Sea (PAIS). Si∗ and salinity were negatively correlated in the PAIS because of the mixing of high nitrate, low DSi subantarctic surface water and high DSi, low nitrate continental freshwater runoff. Both the slope and the intercept of this relationship decreased from northern to southern Patagonia, which was likely a consequence of reduced DSi inputs from several overlapping hydrological, biological and geological drivers along this gradient. In general, lower freshwater DSi concentrations were expected below 46°S, and a lower total DSi load was expected from reduced runoff below 51°S. The north-south decreasing DSi concentration trend may be linked to dilutions from a higher proportion of runoff in latitudes with higher precipitation rates (45-53°S), the transition to more resistant granitic rocks and glacial melt-water from the Northern and Southern Patagonia Ice Fields (46-51°S) and a reduced density of volcanoes active during the Holocene (48-56°S). The intensification of a southward DSi deficit may be a forcing factor involved in the reported southward reductions in plankton biomass and a more frequent occurrence of non-diatom blooms in southern PAIS.

  1. Annual Cycles of Deep-ocean, Biogeochemical Export Fluxes and Biological Pump Processes in Subtropical and Subantarctic Waters, Southwest Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Nodder, S.; Chiswell, S.; Northcote, L.

    2016-02-01

    One of the key aspects of the global carbon cycle is the efficiency and spatio-temporal variability of the biological pump. In this paper, the annual cycles of particle fluxes, derived from moored sediment trap data collected from 2000-12 in subtropical (STW) and subantarctic waters (SAW), east of New Zealand, are presented. These observations are the most comprehensive export flux time-series from temperate Southern Hemisphere latitudes to date. With high levels of variability, fluxes in SAW were markedly lower than in STW, reflecting the picophytoplankton-dominated communities in the iron-limited, high nutrient-low chlorophyll SAW. Austral spring chlorophyll blooms in surface STW were near-synchronous with elevated fluxes of bio-siliceous, carbonate and organic carbon-rich materials to the deep ocean, probably facilitated by diatom sedimentation. Lithogenic fluxes were also high in STW, compared to SAW, reflecting proximity to the New Zealand landmass. In contrast, the highest biogenic fluxes in SAW occurred in spring when surface chlorophyll concentrations were low, while highest annual chlorophyll concentrations were in summer with no associated flux increase. We hypothesize that the high spring export in SAW occurs from subsurface chlorophyll accumulations that are not evident from remote-sensing satellites. This material was also rich in biogenic silica, perhaps related to the preferential export of diatoms and other silica-producing organisms, such as silicoflagellates and radiolarians. Particle fluxes in STW are similar to that of other mesotrophic to oligotrophic waters ( 6-7 mgC m-2 d-1), whereas export from SAW is below global averages ( 3 mgC m-2 d-1), and is characterized by carbonate-dominated and prominent bio-siliceous deposition.

  2. INFLUENCE OF DIFFERENT WATER MASSES AND BIOLOGICAL ACTIVITY ON DIMETHYLSULPHIDE AND DIMETHYLSULPHONIOPROPIONATE IN THE SUBANTARCTIC ZONE OF THE SOUTHERN OCEAN DURING ACE-1

    EPA Science Inventory

    Measurements of salinity, temperature, phytoplankton biomass and speciation, dissolved nitrate, dimethylsulphide (DMS) in seawater and air, and dimethylsulphoniopropionate (DMSP), were made in the subantarctic zone of the Southern Ocean from 40|-54|S, and 140|-153|E during the So...

  3. INFLUENCE OF DIFFERENT WATER MASSES AND BIOLOGICAL ACTIVITY ON DIMETHYLSULPHIDE AND DIMETHYLSULPHONIOPROPIONATE IN THE SUBANTARCTIC ZONE OF THE SOUTHERN OCEAN DURING ACE-1

    EPA Science Inventory

    Measurements of salinity, temperature, phytoplankton biomass and speciation, dissolved nitrate, dimethylsulphide (DMS) in seawater and air, and dimethylsulphoniopropionate (DMSP), were made in the subantarctic zone of the Southern Ocean from 40|-54|S, and 140|-153|E during the So...

  4. On the formation, ventilation, and erosion of mode waters in the North Atlantic and Southern Oceans

    NASA Astrophysics Data System (ADS)

    Trossman, D. S.; Thompson, L.; Mecking, S.; Warner, M. J.

    2012-09-01

    The mean residence times, subduction rates, and formation rates of Subtropical Mode Water (STMW) and Subpolar Mode Water (SPMW) in the North Atlantic and Subantarctic Mode Water (SAMW) in the Southern Ocean are estimated by combining a model and observations of chlorofluorocarbon-11 (CFC-11) via Bayesian Model Averaging (BMA), a statistical technique that weights model estimates according to how close they agree with observations. Subduction rates are estimated in two different ways to investigate the non-advective contribution to thermocline ventilation, which in turn are compared to formation rate estimates. One subduction rate estimate is based on entrainment/detrainment velocities and the other subduction rate estimate allows ventilation to be both an advective and diffusive process instead of a purely advective one by using transit-time distributions (TTDs). It is found that the subduction of all three mode waters is mostly an advective process, but up to about one-third of STMW subduction likely owes to non-advective processes. Also, while the formation of STMW is mostly due to subduction, the formation of SPMW is mostly due to other processes. About half of the formation of SAMW is due to subduction and half is due to other processes. A combination of air-sea flux, acting on relatively short timescales, and turbulent mixing, acting on a wide range of timescales, is likely the dominant SPMW erosion mechanism. Air-sea flux is likely responsible for most STMW erosion, and turbulent mixing is likely responsible for most SAMW erosion.

  5. Kelp genes reveal effects of subantarctic sea ice during the Last Glacial Maximum.

    PubMed

    Fraser, Ceridwen I; Nikula, Raisa; Spencer, Hamish G; Waters, Jonathan M

    2009-03-03

    The end of the Last Glacial Maximum (LGM) dramatically reshaped temperate ecosystems, with many species moving poleward as temperatures rose and ice receded. Whereas reinvading terrestrial taxa tracked melting glaciers, marine biota recolonized ocean habitats freed by retreating sea ice. The extent of sea ice in the Southern Hemisphere during the LGM has, however, yet to be fully resolved, with most palaeogeographic studies suggesting only minimal or patchy ice cover in subantarctic waters. Here, through population genetic analyses of the widespread Southern Bull Kelp (Durvillaea antarctica), we present evidence for persistent ice scour affecting subantarctic islands during the LGM. Using mitochondrial and chloroplast genetic markers (COI; rbcL) to genetically characterize some 300 kelp samples from 45 Southern Ocean localities, we reveal a remarkable pattern of recent recolonization in the subantarctic. Specifically, in contrast to the marked phylogeographic structure observed across coastal New Zealand and Chile (10- to 100-km scales), subantarctic samples show striking genetic homogeneity over vast distances (10,000-km scales), with a single widespread haplotype observed for each marker. From these results, we suggest that sea ice expanded further and ice scour during the LGM impacted shallow-water subantarctic marine ecosystems more extensively than previously suggested.

  6. Kelp genes reveal effects of subantarctic sea ice during the Last Glacial Maximum

    PubMed Central

    Fraser, Ceridwen I.; Nikula, Raisa; Spencer, Hamish G.; Waters, Jonathan M.

    2009-01-01

    The end of the Last Glacial Maximum (LGM) dramatically reshaped temperate ecosystems, with many species moving poleward as temperatures rose and ice receded. Whereas reinvading terrestrial taxa tracked melting glaciers, marine biota recolonized ocean habitats freed by retreating sea ice. The extent of sea ice in the Southern Hemisphere during the LGM has, however, yet to be fully resolved, with most palaeogeographic studies suggesting only minimal or patchy ice cover in subantarctic waters. Here, through population genetic analyses of the widespread Southern Bull Kelp (Durvillaea antarctica), we present evidence for persistent ice scour affecting subantarctic islands during the LGM. Using mitochondrial and chloroplast genetic markers (COI; rbcL) to genetically characterize some 300 kelp samples from 45 Southern Ocean localities, we reveal a remarkable pattern of recent recolonization in the subantarctic. Specifically, in contrast to the marked phylogeographic structure observed across coastal New Zealand and Chile (10- to 100-km scales), subantarctic samples show striking genetic homogeneity over vast distances (10,000-km scales), with a single widespread haplotype observed for each marker. From these results, we suggest that sea ice expanded further and ice scour during the LGM impacted shallow-water subantarctic marine ecosystems more extensively than previously suggested. PMID:19204277

  7. Reconsidering connectivity in the sub-Antarctic.

    PubMed

    Moon, Katherine L; Chown, Steven L; Fraser, Ceridwen I

    2017-03-29

    Extreme and remote environments provide useful settings to test ideas about the ecological and evolutionary drivers of biological diversity. In the sub-Antarctic, isolation by geographic, geological and glaciological processes has long been thought to underpin patterns in the region's terrestrial and marine diversity. Molecular studies using increasingly high-resolution data are, however, challenging this perspective, demonstrating that many taxa disperse among distant sub-Antarctic landmasses. Here, we reconsider connectivity in the sub-Antarctic region, identifying which taxa are relatively isolated, which are well connected, and the scales across which this connectivity occurs in both terrestrial and marine systems. Although many organisms show evidence of occasional long-distance, trans-oceanic dispersal, these events are often insufficient to maintain gene flow across the region. Species that do show evidence of connectivity across large distances include both active dispersers and more sedentary species. Overall, connectivity patterns in the sub-Antarctic at intra- and inter-island scales are highly complex, influenced by life-history traits and local dynamics such as relative dispersal capacity and propagule pressure, natal philopatry, feeding associations, the extent of human exploitation, past climate cycles, contemporary climate, and physical barriers to movement. An increasing use of molecular data - particularly genomic data sets that can reveal fine-scale patterns - and more effective international collaboration and communication that facilitates integration of data from across the sub-Antarctic, are providing fresh insights into the processes driving patterns of diversity in the region. These insights offer a platform for assessing the ways in which changing dispersal mechanisms, such as through increasing human activity and changes to wind and ocean circulation, may alter sub-Antarctic biodiversity patterns in the future.

  8. Iron Fertilization in the Subantarctic South Pacific?

    NASA Astrophysics Data System (ADS)

    Winckler, G.; Anderson, R. F.; Schwartz, R.; Park, J.; Pahnke, K.; Martinez-Garcia, A.; Lamy, F.; Gersonde, R.

    2014-12-01

    The scarcity of iron limits marine export production and carbon uptake in about 25% of the global ocean where the concentration of major nutrients is high, yet phytoplankton growth is low. Of these, the Southern Ocean is the region where variations in iron availability can have the largest effect on Earth's carbon cycle through its fertilizing effect on marine ecosystems, both in the modern and in the past. Recent work in the Subantarctic South Atlantic (Martínez-Garcia et al., 2009, 2014, Anderson et al., 2014) suggests that dust-driven iron fertilization lowered atmospheric CO2 from about 225 ppm to 185 ppm in the latter half of each glacial cycle of the late Pleistocene, with the increase in Subantarctic productivity consuming a greater fraction of the surface nutrients and thus driving more storage of carbon in the ocean interior. The opposite effect, reduced iron fertilization, has been hypothesized to drive the 15-20 ppm increase during Heinrich Events in the last glacial cycle (Martínez -Garcia et al, 2014). The vast majority of the information we have so far is from observations in the Subantarctic Atlantic and therefore our current estimates of the role of the Southern Ocean in lowering CO2 rely critically on the assumed extrapolation of the results from the Atlantic Sector to the entire Southern Ocean. However, the Pacific Sector of the Southern Ocean not only accounts for the largest surface area of the Subantarctic Southern Ocean, but the deep Pacific Ocean also can be inferred - based on its volume - to have stored the largest fraction of carbon that was extracted from the atmosphere and from the terrestrial biosphere during glacial periods. Here we report first results from a set of cores from the Subantarctic Pacific (PS75, Lamy et al 2014), including a high-resolution sediment core (PS75/056-1) from the flank of the East Pacific Rise that allows to resolve millennial year variability over the past glacial cycle. We test how tightly dust and

  9. Role of the seasonal cycle in coupling climate and carbon cycling in the subantarctic zone

    NASA Astrophysics Data System (ADS)

    Monteiro, Pedro M. S.; Boyd, Philip; Bellerby, Richard

    2011-07-01

    Workshop on the Seasonal Cycle of the Carbon-Climate System in the Southern Ocean; Cape Town, South Africa, 23-25 August 2010; There is increasing evidence in the Southern Ocean that mesoscales and seasonal scales play an important role in the coupling of ocean carbon cycling and climate. The seasonal cycle is one of the strongest modes of variability in different components of the carbon cycle in the Southern Ocean. It is also the mode that couples climate forcing to ecosystem responses such as productivity and ultimately biogeochemical signals including carbon export. However, not only are these scales of coupling poorly understood, but also there appear to be important regional differences in the way they couple climate to carbon. With this as an overarching theme, a workshop in South Africa brought together scientists working in the Southern Ocean, the waters south of Australia, New Zealand, and South Africa. The importance of the Subantarctic Zone (SAZ) as a carbon sink made it an ideal system on which to focus the workshop.

  10. Deep Water Ambient Noise and Mode Processing

    DTIC Science & Technology

    2012-09-30

    Deep Water Ambient Noise and Mode Processing Kathleen E. Wage George Mason University Electrical and Computer Engineering Department 4400...UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) George Mason University Electrical and Computer Engineering Department 4400 University...analysis of the Church Opal data set showed that noise levels decreased substantially (on the order of 20 dB) below the critical depth [5]. This project

  11. Latitudinal and temporal distributions of diatom populations in the pelagic waters of the Subantarctic and Polar Frontal Zones of the Southern Ocean and their role in the biological pump

    NASA Astrophysics Data System (ADS)

    Rigual-Hernández, A. S.; Trull, T. W.; Bray, S. G.; Cortina, A.; Armand, L. K.

    2015-06-01

    The Subantarctic and Polar Frontal zones (SAZ and PFZ) represent a large portion of the total area of the Southern Ocean and serve as a strong sink for atmospheric CO2. These regions are central to hypotheses linking particle fluxes and climate change, yet multi-year records of modern flux and the organisms that control it are, for obvious reasons, rare. In this study, we examine two sediment trap records of the flux of diatoms and bulk components collected by two bottom-tethered sediment traps deployed at mesopelagic depths (~ 1 km) in the SAZ (two-year record) and in the PFZ (six-year record) along the 140° E meridian. These traps provide a direct measure of transfer below winter mixed layer depths, i.e. at depths where effective sequestration from the atmosphere occurs, in contrast to study of processes in the surface ocean. Total mass fluxes were about two-fold higher in the PFZ (24 ± 13 g m-2 yr-1) than in the SAZ (14 ± 2 g m-2 yr-1). Bulk chemical composition of the particle fluxes mirrored the composition of the distinct plankton communities of the surface layer, being dominated by carbonate in the SAZ and by biogenic silica in the PFZ. POC export was similar for the annual average at both sites (1.0 ± 0.1 and 0.8 ± 0.4 g m-2 yr-1, for the PFZ and SAZ, respectively), indicating that the particles in the SAZ were relatively POC rich. Seasonality in the particle export was more pronounced in the PFZ. Peak fluxes occurred during summer in the PFZ and during spring in the SAZ. The strong summer pulses in the PFZ are responsible for a large fraction of the variability in carbon sequestration from the atmosphere in this region. The latitudinal variation of the total diatom flux was found to be in line with the biogenic silica export with an annual flux of 31 ± 5.5 × 108 valves m-2 yr-1 at the PFZ compared to 0.5 ± 0.4 × 108 m-2 yr-1 of the SAZ. Fragilariopsis kerguelensis dominated the annual diatom export at both sites (43 at the SAZ and 59% in the PFZ

  12. Latitudinal and temporal distributions of diatom populations in the pelagic waters of the Subantarctic and Polar Frontal zones of the Southern Ocean and their role in the biological pump

    NASA Astrophysics Data System (ADS)

    Rigual-Hernández, A. S.; Trull, T. W.; Bray, S. G.; Cortina, A.; Armand, L. K.

    2015-09-01

    The Subantarctic and Polar Frontal zones (SAZ and PFZ) represent a large portion of the total area of the Southern Ocean and serve as a strong sink for atmospheric CO2. These regions are central to hypotheses linking particle fluxes and climate change, yet multi-year records of modern flux and the organisms that control it are, for obvious reasons, rare. In this study, we examine two sediment trap records of the flux of diatoms and bulk components collected by two bottom-tethered sediment traps deployed at mesopelagic depths (~ 1 km) in the SAZ (2-year record; July 1999-October 2001) and in the PFZ (6-year record; September 1997-February 1998, July 1999-August 2000, November 2002-October 2004 and December 2005-October 2007) along the 140° E meridian. These traps provide a direct measure of transfer below winter mixed layer depths, i.e. at depths where effective sequestration from the atmosphere occurs, in contrast to study of processes in the surface ocean. Total mass fluxes were about twofold higher in the PFZ (24 ± 13 g m-2 yr-1) than in the SAZ (14 ± 2 g m-2 yr-1). Bulk chemical composition of the particle fluxes mirrored the composition of the distinct plankton communities of the surface layer, being dominated by carbonate in the SAZ and by biogenic silica in the PFZ. Particulate organic carbon (POC) export was similar for the annual average at both sites (1.0 ± 0.1 and 0.8 ± 0.4 g m-2 yr-1 for the PFZ and SAZ, respectively), indicating that the particles in the SAZ were relatively POC rich. Seasonality in the particle export was more pronounced in the PFZ. Peak fluxes occurred during summer in the PFZ and during spring in the SAZ. The strong summer pulses in the PFZ are responsible for a large fraction of the variability in carbon sequestration from the atmosphere in this region. The latitudinal variation of the total diatom flux was found to be in line with the biogenic silica export with an annual flux of 31 ± 5.5 × 108 valves m-2 yr-1 at the PFZ

  13. Controls and variability of solute and sedimentary fluxes in Antarctic and sub-Antarctic Environments

    NASA Astrophysics Data System (ADS)

    Zwolinski, Zbigniew

    2015-04-01

    . Solute and sediment transport in the streams of analyzed environments are constrained by the relatively short water runoff season that typically lasts from a few weeks to maximum of four months during the austral summer, for Antarctic and sub-Antarctic regions respectively. Because of high intensity of mechanical and chemical weathering processes solute and sediment transport are rather high within Antarctic environments. Weathering rates on slopes and magnitude of fluvial transport in relatively short streams control the intensity of denudational processes. Both mechanical and chemical denudation varies highly through sub-Antarctic and Antarctic environments. To generate accurate predictions of fluvial and denudational processes we must fully understand the actual geoecological processes, which in some places are under rapid change, e.g., the Antarctic Peninsula and sub-Antarctic islands.

  14. Air-sea Fluxes and Mode Waters in an Eddy Resolving Ocean Data Assimilating Southern Ocean State Estimate (SOSE) (Invited)

    NASA Astrophysics Data System (ADS)

    Cerovecki, I.; Talley, L. D.; Mazloff, M. R.

    2010-12-01

    An eddy-permitting data assimilating system, the Southern Ocean State Estimate (SOSE), has been developed by Mazloff et al. (2010) to estimate the Southern Ocean circulation in years 2005 and 2006. We assess the accuracy of SOSE air-sea heat and freshwater flux estimates by comparing them to widely used flux products (the National Center for Environmental Prediction-National Center for Atmospheric Reanalysis 1 (NCEP1), European Centre for Medium-Range Weather Forecasts operational model) and to a recently developed flux product constructed by Large and Yeager (2009). SOSE and Large and Yeager (2009) estimates show remarkable similarity in the large scale pattern of air-sea fluxes when compared to the NCEP1 fields that SOSE uses as an initial guess and constraint. Having verified that the accuracy of SOSE air-sea buoyancy flux estimate is satisfactory, we use SOSE fluxes and three-dimensional oceanic fields to investigate Subantarctic Mode Water (SAMW) formation and destruction by diapycnal buoyancy exchange at the ocean surface and in the ocean interior as well as identify and quantify SAMW transport pathways. Surface buoyancy fluxes produce on average 6.9 +/-1.6 Sv of Southeast Indian SAMW (SEISAMW) and 4.8 +/- 2.2 Sv of East Pacific SAMW, averaged over years 2005 and 2006. This transformation is largely compensated by diapycnal mixing in the ocean interior where SAMW gets mostly transformed into denser water, especially in the Pacific sector of the Southern Ocean. There is also a net conversion of lighter thermocline water into SAMW in the ocean interior (occurring mostly in the Indian Ocean), which is part of the shallow overturning. The zonally integrated export of SAMW across 30S is thus relatively small and on average equals approximately 3.5 Sv of (SEISAMW) and 2.0 Sv of East Pacific SAMW.

  15. Draft Genome Sequence of Subantarctic Rhodococcus sp. Strain 1139

    PubMed Central

    Baker, Anthony L.; Charleston, Michael A.; Britz, Margaret L.

    2017-01-01

    ABSTRACT The draft genome sequence of subantarctic Rhodococcus sp. strain 1139 is reported here. The genome size is 7.04 Mb with high G+C content (62.3%) and it contains a large number of genes involved in lipid synthesis. This lipid synthesis system is characteristic of oleaginous Actinobacteria, which are of interest for biofuel production. PMID:28385836

  16. Dispersion Management of Propagating Waveguide Modes on the Water Surface

    NASA Astrophysics Data System (ADS)

    Fu, Shenhe; Zhou, Jianying; Li, Yongyao; Shemer, Lev; Arie, Ady

    2017-04-01

    We report on the theoretical and experimental study of the generation of propagating waveguide modes on the water surface. These propagating modes are modulated in the transverse direction in a manner that satisfies boundary conditions on the walls of the water tank. It is shown that the propagating modes possess both anomalous and normal dispersion regimes, in contrast to the extensively studied zero mode that, in the case of deep water, only has normal dispersion with a fixed frequency independent dispersion coefficient. Importantly, by using a carrier frequency at which the group velocity dispersion crosses zero, a linear nonspreading and shape-preserving wave packet is observed. By increasing the wave steepness, nonlinear effects become pronounced, thereby enabling the first observation of linearly chirped parabolic water wave pulses in the anomalous dispersion regime. This parabolic wave maintains its linear frequency chirp and does not experience wave breaking during propagation.

  17. Underwater Optics in Sub-Antarctic and Antarctic Coastal Ecosystems.

    PubMed

    Huovinen, Pirjo; Ramírez, Jaime; Gómez, Iván

    2016-01-01

    Understanding underwater optics in natural waters is essential in evaluating aquatic primary production and risk of UV exposure in aquatic habitats. Changing environmental conditions related with global climate change, which imply potential contrasting changes in underwater light climate further emphasize the need to gain insights into patterns related with underwater optics for more accurate future predictions. The present study evaluated penetration of solar radiation in six sub-Antarctic estuaries and fjords in Chilean North Patagonian region (39-44°S) and in an Antarctic bay (62°S). Based on vertical diffuse attenuation coefficients (Kd), derived from measurements with a submersible multichannel radiometer, average summer UV penetration depth (z1%) in these water bodies ranged 2-11 m for UV-B (313 nm), 4-27 m for UV-A (395 nm), and 7-30 m for PAR (euphotic zone). UV attenuation was strongest in the shallow Quempillén estuary, while Fildes Bay (Antarctica) exhibited the highest transparency. Optically non-homogeneous water layers and seasonal variation in transparency (lower in winter) characterized Comau Fjord and Puyuhuapi Channel. In general, multivariate analysis based on Kd values of UV and PAR wavelengths discriminated strongly Quempillén estuary and Puyuhuapi Channel from other study sites. Spatial (horizontal) variation within the estuary of Valdivia river reflected stronger attenuation in zones receiving river impact, while within Fildes Bay a lower spatial variation in water transparency could in general be related to closeness of glaciers, likely due to increased turbidity through ice-driven processes. Higher transparency and deeper UV-B penetration in proportion to UV-A/visible wavelengths observed in Fildes Bay suggests a higher risk for Antarctic ecosystems reflected by e.g. altered UV-B damage vs. photorepair under UV-A/PAR. Considering that damage repair processes often slow down under cool temperatures, adverse UV impact could be further

  18. Underwater Optics in Sub-Antarctic and Antarctic Coastal Ecosystems

    PubMed Central

    Huovinen, Pirjo; Ramírez, Jaime; Gómez, Iván

    2016-01-01

    Understanding underwater optics in natural waters is essential in evaluating aquatic primary production and risk of UV exposure in aquatic habitats. Changing environmental conditions related with global climate change, which imply potential contrasting changes in underwater light climate further emphasize the need to gain insights into patterns related with underwater optics for more accurate future predictions. The present study evaluated penetration of solar radiation in six sub-Antarctic estuaries and fjords in Chilean North Patagonian region (39–44°S) and in an Antarctic bay (62°S). Based on vertical diffuse attenuation coefficients (Kd), derived from measurements with a submersible multichannel radiometer, average summer UV penetration depth (z1%) in these water bodies ranged 2–11 m for UV-B (313 nm), 4–27 m for UV-A (395 nm), and 7–30 m for PAR (euphotic zone). UV attenuation was strongest in the shallow Quempillén estuary, while Fildes Bay (Antarctica) exhibited the highest transparency. Optically non-homogeneous water layers and seasonal variation in transparency (lower in winter) characterized Comau Fjord and Puyuhuapi Channel. In general, multivariate analysis based on Kd values of UV and PAR wavelengths discriminated strongly Quempillén estuary and Puyuhuapi Channel from other study sites. Spatial (horizontal) variation within the estuary of Valdivia river reflected stronger attenuation in zones receiving river impact, while within Fildes Bay a lower spatial variation in water transparency could in general be related to closeness of glaciers, likely due to increased turbidity through ice-driven processes. Higher transparency and deeper UV-B penetration in proportion to UV-A/visible wavelengths observed in Fildes Bay suggests a higher risk for Antarctic ecosystems reflected by e.g. altered UV-B damage vs. photorepair under UV-A/PAR. Considering that damage repair processes often slow down under cool temperatures, adverse UV impact could be

  19. Diatom and silicoflagellate biostratigraphy for the late Eocene: ODP 1090 (sub-Antarctic Atlantic)

    USGS Publications Warehouse

    Barron, John A.; Bukry, David B.; Gersonde, Rainer

    2014-01-01

    Abundant and well-preserved diatoms and silicofl agellate assemblages are documented through a complete late Eocene sequence, ODP Hole 1090B, recovered from the southern Agulhas Ridge in the sub-Antarctic South Atlantic. A sequence of Cestodiscus (diatom) species occurrence events involving C. pulchellus var. novazealandica, C. fennerae, C. antarcticus, C. convexus, C. trochus, and C. robustus is tied with paleomagnetic stratigraphy and provides the basis of proposing a new diatom zonation for the latest middle Eocene to early Oligocene (~37.6–33.4 Ma) of the sub-Antarctic South Atlantic. Comparison with previously published diatom occurrence charts suggested this zonation should be applicable throughout the low latitude regions of the world’s oceans. Silicofl agellates belong to the Dictyocha hexacantha and the overlying Corbisema apiculata Zones. The late Eocene succession of silicofl agellate species is dominated by Naviculopsis (20–60%). Naviculopsis constricta and N. foliacea dominate the D. hexacantha Zone, followed by the N. constricta, then N. biapiculata in the C. apiculata Zone. Cold-water Distephanus is most abundant in the latest Eocene along with N. biapiculata. The tops of zonal guide fossils Dictyocha hexacantha and Hannaites quadria (both 36.6 Ma) and Dictyocha spinosa (37.1 Ma) are tied with paleomagnetic stratigraphy.

  20. Permeable bio-reactive barriers to address petroleum hydrocarbon contamination at subantarctic Macquarie Island.

    PubMed

    Freidman, Benjamin L; Terry, Deborah; Wilkins, Dan; Spedding, Tim; Gras, Sally L; Snape, Ian; Stevens, Geoffrey W; Mumford, Kathryn A

    2017-05-01

    A reliance on diesel generated power and a history of imperfect fuel management have created a legacy of petroleum hydrocarbon contamination at subantarctic Macquarie Island. Increasing environmental awareness and advances in contaminant characterisation and remediation technology have fostered an impetus to reduce the environmental risk associated with legacy sites. A funnel and gate permeable bio-reactive barrier (PRB) was installed in 2014 to address the migration of Special Antarctic Blend diesel from a spill that occurred in 2002, as well as older spills and residual contaminants in the soil at the Main Power House. The PRB gate comprised of granular activated carbon and natural clinoptilolite zeolite. Petroleum hydrocarbons migrating in the soil water were successfully captured on the reactive materials, with concentrations at the outflow of the barrier recorded as being below reporting limits. The nutrient and iron concentrations delivered to the barrier demonstrated high temporal variability with significant iron precipitation observed across the bed. The surface of the granular activated carbon was largely free from cell attachment while natural zeolite demonstrated patchy biofilm formation after 15 months following PRB installation. This study illustrates the importance of informed material selection at field scale to ensure that adsorption and biodegradation processes are utilised to manage the environmental risk associated with petroleum hydrocarbon spills. This study reports the first installation of a permeable bio-reactive barrier in the subantarctic. Copyright © 2017 Elsevier Ltd. All rights reserved.

  1. Diatom and silicoflagellate biostratigraphy for the late Eocene: ODP 1090 (sub-Antarctic Atlantic)

    USGS Publications Warehouse

    Barron, John A.; Bukry, David B.; Gersonde, Rainer

    2014-01-01

    Abundant and well-preserved diatoms and silicofl agellate assemblages are documented through a complete late Eocene sequence, ODP Hole 1090B, recovered from the southern Agulhas Ridge in the sub-Antarctic South Atlantic. A sequence of Cestodiscus (diatom) species occurrence events involving C. pulchellus var. novazealandica, C. fennerae, C. antarcticus, C. convexus, C. trochus, and C. robustus is tied with paleomagnetic stratigraphy and provides the basis of proposing a new diatom zonation for the latest middle Eocene to early Oligocene (~37.6–33.4 Ma) of the sub-Antarctic South Atlantic. Comparison with previously published diatom occurrence charts suggested this zonation should be applicable throughout the low latitude regions of the world’s oceans. Silicofl agellates belong to the Dictyocha hexacantha and the overlying Corbisema apiculata Zones. The late Eocene succession of silicofl agellate species is dominated by Naviculopsis (20–60%). Naviculopsis constricta and N. foliacea dominate the D. hexacantha Zone, followed by the N. constricta, then N. biapiculata in the C. apiculata Zone. Cold-water Distephanus is most abundant in the latest Eocene along with N. biapiculata. The tops of zonal guide fossils Dictyocha hexacantha and Hannaites quadria (both 36.6 Ma) and Dictyocha spinosa (37.1 Ma) are tied with paleomagnetic stratigraphy.

  2. Transport of continental air to the subantarctic Indian Ocean

    NASA Technical Reports Server (NTRS)

    Balkanski, Yves J.; Jacob, Daniel J.

    1990-01-01

    The occurrence of high Rn-222 episodes (radonic storms) observed at three islands (Crozet, Kerguelen, and Amsterdam) in the subantarctic Indian Ocean is simulated using a three-dimensional chemical tracer model. The chemical tracer model is described and the simulated time series of Rn-222 concentrations at the three islands are compared to observations. The origin, seasonal frequencies, and periodicities of the storms are examined. It is found that the storms are due to fast boundary layer advection of air from South Africa, made possible by the conjunction of a subtropical high SE of Madagascar and a midlatitudes low off the southern tip of Africa. The implications of the results for the transport of continental air to the subantarctic Indian Ocean are discussed.

  3. Transport of continental air to the subantarctic Indian Ocean

    NASA Technical Reports Server (NTRS)

    Balkanski, Yves J.; Jacob, Daniel J.

    1990-01-01

    The occurrence of high Rn-222 episodes (radonic storms) observed at three islands (Crozet, Kerguelen, and Amsterdam) in the subantarctic Indian Ocean is simulated using a three-dimensional chemical tracer model. The chemical tracer model is described and the simulated time series of Rn-222 concentrations at the three islands are compared to observations. The origin, seasonal frequencies, and periodicities of the storms are examined. It is found that the storms are due to fast boundary layer advection of air from South Africa, made possible by the conjunction of a subtropical high SE of Madagascar and a midlatitudes low off the southern tip of Africa. The implications of the results for the transport of continental air to the subantarctic Indian Ocean are discussed.

  4. Submesoscale processes promote seasonal restratification in the Subantarctic Ocean

    NASA Astrophysics Data System (ADS)

    du Plessis, M.; Swart, S.; Ansorge, I. J.; Mahadevan, A.

    2017-04-01

    Traditionally, the mechanism driving the seasonal restratification of the Southern Ocean mixed layer (ML) is thought to be the onset of springtime warming. Recent developments in numerical modeling and North Atlantic observations have shown that submesoscale ML eddies (MLE) can drive a restratifying flux to shoal the deep winter ML prior to solar heating at high latitudes. The impact of submesoscale processes on the intraseasonal variability of the Subantarctic ML is still relatively unknown. We compare 5 months of glider data in the Subantarctic Zone to simulations of a 1-D mixing model to show that the magnitude of restratification of the ML cannot be explained by heat, freshwater, and momentum fluxes alone. During early spring, we estimate that periodic increases in the vertical buoyancy flux by MLEs caused small increases in stratification, despite predominantly down-front winds that promote the destruction of stratification. The timing of seasonal restratification was consistent between 1-D model estimates and the observations. However, during up-front winds, the strength of springtime stratification increased over twofold compared to the 1-D model, with a rapid shoaling of the MLD from >200 m to <100 m within a few days. The ML stratification is further modified under a negative Ekman buoyancy flux during down-front winds, resulting in the destruction of ML stratification and deepening of the MLD. These results propose the importance of submesoscale buoyancy fluxes enhancing seasonal restratification and mixing of the Subantarctic ML.

  5. Mode and Intermediate Waters in Earth System Models

    SciTech Connect

    Gnanadesikan, Anand; Sarmiento, Jorge L.

    2015-12-22

    This report describes work done as part of a joint Princeton-Johns Hopkins project to look at the impact of mode and intermediate waters in Earth System Models. The Johns Hopkins portion of this work focussed on the role of lateral mixing in ventilating such waters, with important implications for hypoxia, the uptake of anthropogenic carbon, the dynamics of El Nino and carbon pumps. The Johns Hopkins group also collaborated with the Princeton Group to help develop a watermass diagnostics framework.

  6. Identification of a wagging vibrational mode of water molecules at the water/vapor interface.

    PubMed

    Perry, Angela; Neipert, Christine; Ridley, Christina; Space, Brian; Moore, Preston B

    2005-05-01

    An improved time correlation function description of sum frequency generation (SFG) spectroscopy was applied to theoretically describe the water/vapor interface. The resulting spectra compare favorably in shape and relative magnitude to extant experimental results in the O-H stretching region of water. Further, the SFG spectra show a well-defined intermolecular mode at 875 cm(-1) that has significant intensity. The resonance is due to a wagging mode localized on a single water molecule. It represents a well-defined population of water molecules at the interface that, along with the free O-H modes, represent the dominant interfacial species.

  7. Surface destabilisation by the invasive burrowing engineer Mus musculus on a sub-Antarctic island

    NASA Astrophysics Data System (ADS)

    Eriksson, Bert; Eldridge, David J.

    2014-10-01

    Invasive species are known to have substantial trophic effects on ecosystems and ecosystem processes. The invasion of the house mouse (Mus musculus) onto sub-Antarctic islands has had a devastating effect on plants, invertebrates, and birds with substantial changes in ecosystem functions. Less well understood, however, are the nontrophic, geomorphic effects of mice resulting from their burrowing activities. We examined the extent of burrow construction by M. musculus across an area of about 20 ha on Marion Island and the effects of burrows on water flow and sediment movement. We recorded a density of 0.59 ± 0.48 (mean ± SD) burrows m- 2, with more burrows at lower altitudes and shallower slopes, and twice the density in the solifluction risers (0.86 ± 0.54 m- 2) than the intervening terraces or treads (0.40 ± 0.51 m- 2). Most burrows were dug horizontally into the slope and tended to extend about 20 cm deep before turning. A very conservative estimate of sediment removed from burrows from this depth is 2.4 t ha- 1. However, taking into account more detailed data on burrow morphology based on excavations, actual amounts may be closer to 8.4 t ha- 1. Average soil displacement rate for a single burrow, measured over 5 days, was 0.18 kg burrow- 1 day- 1. Burrows acted as conduits for water and warmer air. Stones at burrow entrances were moved eight times farther by water (10.4 cm) than those not associated with burrows. Similarly, temperatures adjacent to burrow entrances were 4.1 °C higher than sites 10 cm away. Together our data indicate that mice are having substantial deleterious and geomorphic effects on sub-Antarctic ecosystems through their burrowing. With lower rates of mouse mortality resulting from warmer climates predicted under global climate models, we can expect an increase in damage resulting from mouse activity.

  8. Postglacial Records of Southern Hemisphere Westerly Wind Variability From the New Zealand Subantarctic Auckland Islands

    NASA Astrophysics Data System (ADS)

    Moy, C. M.; Vandergoes, M.; Gilmer, G. J.; Nichols, J. E.; Dagg, B. J.; Wilson, G. S.; Browne, I. M.; Curtin, L. G.; Aebig, C.; McGlone, M.

    2015-12-01

    The strength and latitudinal position of the Southern Hemisphere westerly winds (SHWW) play a fundamental role in influencing mid latitude climate and carbon dioxide exchange between the Southern Ocean and the atmosphere. Despite their importance, our understanding of past changes in the SHWW is limited by few paleoclimate records from the modern wind maximum that are often not in agreement. The New Zealand subantarctic Auckland Islands are located within the core of the modern wind belt (50°S) where the ocean-atmospheric linkages between the Antarctic and middle latitudes are strong. In contrast to other subantarctic islands on the Campbell Plateau, the Auckland Islands have protected fjord sub-basins, deep lakes, and peatlands that are advantageous for the development of high-resolution paleoclimate records. We will present ongoing work towards the establishment of multi-proxy and multi-site reconstructions of past SHWW variability from the Auckland Islands. Modern process and paleoclimate results from two research cruises in 2014 and 2015 suggest that in lacustrine and fjord settings, the degree of water column mixing, the stable isotopic composition of n-alkanes and benthic foraminifera, the influx of terrestrial organic matter are good indicators of wind-induced mixing of the water column or precipitation-driven erosion within catchments. In ombrotrophic peatlands, hydrogen isotope ratios of specific organic molecules allow reconstructions of the hydrogen isotope ratios of precipitation, which is related to precipitation source area and the latitudinal position of the SHWW. Using macrofossil counts paired with abundances of leaf wax biomarkers, we are able to estimate the moisture balance at peatland coring sites. Early results indicate an overall strengthening of the SHWW at the Auckland Islands through the Holocene. We will discuss these results within the context of complimentary records developed from New Zealand and southern South America to ultimately

  9. Differences between 1999 and 2010 across the Falkland Plateau: fronts and water masses

    NASA Astrophysics Data System (ADS)

    Pérez-Hernández, M. Dolores; Hernández-Guerra, Alonso; Comas-Rodríguez, Isis; Benítez-Barrios, Verónica M.; Fraile-Nuez, Eugenio; Pelegrí, Josep L.; Naveira Garabato, Alberto C.

    2017-07-01

    Decadal differences in the Falkland Plateau are studied from the two full-depth hydrographic data collected during the ALBATROSS (April 1999) and MOC-Austral (February 2010) cruises. Differences in the upper 100 dbar are due to changes in the seasonal thermocline, as the ALBATROSS cruise took place in the austral fall and the MOC-Austral cruise in summer. The intermediate water masses seem to be very sensitive to the wind conditions existing in their formation area, showing cooling and freshening for the decade as a consequence of a higher Antarctic Intermediate Water (AAIW) contribution and of a decrease in the Subantarctic Mode Water (SAMW) stratum. The deeper layers do not exhibit any significant change in the water mass properties. The Subantarctic Front (SAF) in 1999 is observed at 52.2-54.8° W with a relative mass transport of 32.6 Sv. In contrast, the SAF gets wider in 2010, stretching from 51.1 to 57.2° W (the Falkland Islands), and weakening to 17.9 Sv. Changes in the SAF can be linked with the westerly winds and mainly affect the northward flow of Subantarctic Surface Water (SASW), SAMW and AAIW/Antarctic Surface Water (AASW). The Polar Front (PF) carries 24.9 Sv in 1999 (49.8-44.4° W), while in 2010 (49.9-49.2° W) it narrows and strengthens to 37.3 Sv.

  10. Failure mode and weakening effect of water on sandstone

    NASA Astrophysics Data System (ADS)

    Baud, Patrick; Zhu, Wenlu; Wong, Teng-Fong

    2000-07-01

    Previous studies have shown that brittle strength of a rock is generally reduced in the presence of water. However, for siliciclastic rocks, there is a paucity of data on the waterweakening behavior in the cataclastic flow regime. To compare the weakening effect of water in the brittle faulting and cataclastic flow regime, triaxial compression experiments were conducted on the Berea, Boise, Darley Dale, and Gosford sandstones (with nominal porosities ranging from 11% to 35%) under nominally dry and saturated conditions at room temperature. Inelastic behavior and failure mode of the nominal dry samples were qualitatively similar to those of water-saturated samples. At elevated pressures, shear localization was inhibited, and all the samples failed by strain hardening. The compactive yield strengths (associated with the onset of shear-enhanced compaction) in the saturated samples were lower than those in the dry samples deformed under comparable pressure conditions by 20% to 70%. The reductions of brittle strength in the presence of water ranged from 5% to 17%. The water-weakening effects were most and least significant in the Gosford and Berea sandstones, respectively. The relation between water weakening and failure mode is consistently explained by micromechanical models formulated on the basis that the specific surface energy in the presence of water is lowered than that in vacuum by the ratio λ. In accordance with the Hertzian fracture model the initial yield stress in the compactive cataclastic flow regime scales with the grain-crushing pressure, which is proportional to λ3/2. In the brittle faulting regime, damage mechanics models predict that the uniaxial compressive strength scales with λ1/2. In the presence of water the confined brittle strength is lower due to reductions of both the specific surface energy and friction coefficient.

  11. Interannual variability of Indian Ocean subtropical mode water subduction rate

    NASA Astrophysics Data System (ADS)

    Ma, Jie; Lan, Jian

    2016-08-01

    The interannual variation of Indian Ocean subtropical mode water (IOSTMW) subduction rate in the Southwest Indian Ocean from 1980 to 2007 is investigated in this paper based on Simple Ocean Data Assimilation (SODA) outputs. Climatology of subduction rate exceeds 75 m/year in the IOSTMW formation area. The renewal time of permanent pycnocline water mass based on the subduction rate is calculated for each density class: 3-6 years for IOSTMW (25.8 < σ θ < 26.2 kg m-3). Subduction rate in the Southwest Indian Ocean subtropical gyre exhibits a great year-to-year variability. This interannual variations of the IOSTMW subduction rate is primarily dominated by the lateral induction term, associated with the interannual variations of strong meridional gradient of winter mixed layer depth (MLD). The slope of the mixed layer depth in the mode water is closely linked to the large variations of deep late winter MLD in the mid-latitudes and negligible variations of shallow winter MLD in lower latitudes. It is further identified that the interannual variation of late winter MLD in this area is largely controlled by the latent and sensible heat flux components. The water volume of the permanent pycnocline in the IOSTMW distribution area is also found to show a significant interannual variability, and it is well correlated with the interannual variation of subduction rate.

  12. Interannual variability of Indian Ocean subtropical mode water subduction rate

    NASA Astrophysics Data System (ADS)

    Ma, Jie; Lan, Jian

    2017-06-01

    The interannual variation of Indian Ocean subtropical mode water (IOSTMW) subduction rate in the Southwest Indian Ocean from 1980 to 2007 is investigated in this paper based on Simple Ocean Data Assimilation (SODA) outputs. Climatology of subduction rate exceeds 75 m/year in the IOSTMW formation area. The renewal time of permanent pycnocline water mass based on the subduction rate is calculated for each density class: 3-6 years for IOSTMW (25.8 < σ θ < 26.2 kg m-3). Subduction rate in the Southwest Indian Ocean subtropical gyre exhibits a great year-to-year variability. This interannual variations of the IOSTMW subduction rate is primarily dominated by the lateral induction term, associated with the interannual variations of strong meridional gradient of winter mixed layer depth (MLD). The slope of the mixed layer depth in the mode water is closely linked to the large variations of deep late winter MLD in the mid-latitudes and negligible variations of shallow winter MLD in lower latitudes. It is further identified that the interannual variation of late winter MLD in this area is largely controlled by the latent and sensible heat flux components. The water volume of the permanent pycnocline in the IOSTMW distribution area is also found to show a significant interannual variability, and it is well correlated with the interannual variation of subduction rate.

  13. Characterization of SAR Mode Altimetry over Inland Water

    NASA Astrophysics Data System (ADS)

    Fabry, Pierre; Bercher, Nicolas

    2015-12-01

    Radar altimetry over the inland water domain is a difficult topic that still requires a lot of human expertise as well as manual editing and verifications. This is mainly due to the fact that inland water scenes are highly variable, both in space and time, which leads to a much broader range of radar signatures than in oceanography. The remark is particularly true for LRM altimetry and remains valid in many cases in SAR mode (SARM). In preparation for the operational Sentinel-3 mission and to better benefit from the improved SARM along-track resolution it is required to: 1. better characterize the SARM Individual Echoes, Multi-Look Stacks, 20Hz waveforms as well as the Range Integrated Power (RIP) over the inland water domain, 2. step toward processing schemes that account for the actual content of the illuminated scene. In this work, we introduce an automated technique to assess the water fraction within the Beam-limited Doppler footprint through its intersection area of with a water mask. This framework opens up new ways toward the automated characterization and processing of altimetry data based on regularly updated water masks.

  14. New Characterization of SAR Mode Altimetry Data over Inland Waters

    NASA Astrophysics Data System (ADS)

    Fabry, Pierre; Bercher, Nicolas

    2016-08-01

    Radar altimetry over the inland water domain is a difficult topic that still requires a lot of human expertise as well as manual editing and verifications. This is mainly due to the fact that inland water scenes are highly variable, both in space and time, which leads to a much broader range of radar signatures than in oceanography. The remark is particularly true for LRM altimetry and remains valid in many cases in SAR mode (SARM). In preparation for the operational Sentinel-3 mission and to better benefit from the improved SARM along-track resolution it is required to:1. better characterize the SARM Individual Echoes, Multi-Look Stacks, 20Hz waveforms as well as the Range Integrated Power (RIP) over the inland water domain,2. step toward processing schemes that account for the actual content of the illuminated scene.In this work, we introduce an automated technique to assess the water fraction within the Beam-limited Doppler footprint through its intersection area of with a water mask. This framework opens up new ways toward the automated characterization and processing of altimetry, in the future, thanks to regularly updated water masks.

  15. Distribution, formation, and seasonal variability of Okhotsk Sea Mode Water

    NASA Astrophysics Data System (ADS)

    Gladyshev, Sergey; Talley, Lynne; Kantakov, Gennady; Khen, Gennady; Wakatsuchi, Masaaki

    2003-06-01

    Russian historical data and recently completed conductivity-temperature-depth surveys are used to examine the formation and spread in the deep Ohkotsk Sea of dense shelf water (DSW) produced in the Okhotsk Sea polynyas. Isopycnal analysis indicates that all of the main polynyas contribute to the ventilation at σθ < 26.80, including the Okhotsk Sea Mode Water (OSMW), which has densities σθ = 26.7-27.0. At densities greater than 26.9 σθ the northwest polynya is the only contributor to OSMW. (Although Shelikhov Bay polynyas produce the densest water with σθ > 27.1, vigorous tidal mixing leads to outflow of water with a density of only about 26.7 σθ). In the western Okhotsk Sea the East Sakhalin Current rapidly transports modified dense shelf water along the eastern Sakhalin slope to the Kuril Basin, where it is subject to further mixing because of the large anticyclonic eddies and tides. Most of the dense water flows off the shelves in spring. Their average flux does not exceed 0.2 Sv in summer and fall. The shelf water transport and water exchange with the North Pacific cause large seasonal variations of temperature at densities of 26.7-27.0 σθ (depths of 150-500 m) in the Kuril Basin, where the average temperature minimum occurs in April-May, and the average temperature maximum occurs in September, with a range of 0.2°-0.7°C. The average seasonal variations of salinity are quite small and do not exceed 0.05 psu. The Soya Water mixed by winter convection, penetrating to depths greater than 200 m, in the southern Kuril Basin also produces freezing water with density greater than 26.7 σθ. Using a simple isopycnal box model and seasonal observations, the OSMW production rate is seen to increase in summer up to 2.2 ± 1.7 Sv, mainly because of increased North Pacific inflow, and drops in winter to 0.2 ± 0.1 Sv. A compensating decrease in temperature in the Kuril Basin implies a DSW volume transport of 1.4 ± 1.1 Sv from February through May. The

  16. Larval development of the subantarctic king crabs Lithodes santolla and Paralomis granulosa reared in the laboratory

    NASA Astrophysics Data System (ADS)

    Calcagno, J. A.; Anger, K.; Lovrich, G. A.; Thatje, S.; Kaffenberger, A.

    2004-02-01

    The larval development and survival in the two subantarctic lithodid crabs Lithodes santolla (Jaquinot) and Paralomis granulosa (Molina) from the Argentine Beagle Channel were studied in laboratory cultures. In L. santolla, larval development lasted about 70 days, passing through three zoeal stages and the megalopa stage, with a duration of approximately 4, 7, 11 and 48 days, respectively. The larval development in P. granulosa is more abbreviated, comprising only two zoeal stages and the megalopa stage, with 6, 11 and 43 days' duration, respectively. In both species, we tested for effects of presence versus absence of food (Artemia nauplii) on larval development duration and survival rate. In P. granulosa, we also studied effects of different rearing conditions, such as individual versus mass cultures, as well as aerated versus unaerated cultures. No differences in larval development duration and survival were observed between animals subjected to those different rearing conditions. The lack of response to the presence or absence of potential food confirms, in both species, a complete lecithotrophic mode of larval development. Since lithodid crabs are of high economic importance in the artisanal fishery in the southernmost parts of South America, the knowledge of optimal rearing conditions for lithodid larvae is essential for future attempts at repopulating the collapsing natural stocks off Tierra del Fuego.

  17. Properties of the Subantarctic Front and Polar Front from the skewness of sea level anomaly

    NASA Astrophysics Data System (ADS)

    Shao, Andrew E.; Gille, Sarah T.; Mecking, Sabine; Thompson, LuAnne

    2015-07-01

    The region of the Southern Ocean that encompasses the Subantarctic Front (SAF) to the north and the Polar Front (PF) to the south contains most of the transport of the Antarctic Circumpolar Current. Here skewness of sea level anomaly (SLA) from 1992 to 2013 is coupled with a meandering Gaussian jetw model to estimate the mean position, meridional width, and the percent variance that each front contributes to total SLA variability. The SAF and PF have comparable widths (85 km) in the circumpolar average, but their widths differ significantly in the East Pacific Basin (85 and 60 km, respectively). Interannual variability in the positions of the SAF and PF are also estimated using annual subsets of the SLA data from 1993 to 2012. The PF position has enhanced variability near strong topographic features such as the Kerguelen Plateau, the Campbell Plateau east of New Zealand, and downstream of Drake Passage. Neither the SAF nor the PF showed a robust meridional trend over the 20 year period. The Southern Annular Mode was significantly correlated with basin-averaged SAF and PF positions in the East Pacific and with the PF south of Australia. A correlation between the PF and the basin-scale wind stress curl anomaly was also found in the western extratropical Pacific but not in other basins.

  18. Near-Surface Phytoplankton Pigment from the Coastal Zone Color Scanner in the Subantarctic Region Southeast of New Zealand

    NASA Technical Reports Server (NTRS)

    Banse, Karl; English, David C.

    1997-01-01

    Primarily based on satellite images, the phytoplankton concentration southeast (down- stream) of New Zealand in the High Nitrate - Low Chlorophyll (HNLC) Subantarctic water between the Subtropical Convergence (STC) and the Polar Front (PF) is believed to be higher than in the remainder of the Pacific Sector. Iron enrichment is assumed to be the reason, To study the question, near-surface phytoplankton pigment estimates from the Coastal Zone Color Scanner for up to 7 yr were reprocessed with particular attention to interference by clouds. Monthly mean images were created for the U,S. JGOFS Box along 170 deg W and means for individual dates calculated for 7 large areas between 170 deg E and 160 deg W, 45 deg and 58 deg S, well offshore of New Zealand and principally between and away from the STC and PF. The areal means are about as low as in other HNLC regions (most values between 0.1 and 0.4 or 0.5 mg/ sq m, with very few winter images; median of seasonal means, 0.26 mg/sq m) except at times near the STC, The higher means tend to occur in late summer and autumn, However, contrary to expectations, neither the PF nor the environs of the Subantarctic Front are distinguished by a zone of increased pigment. Also, of 24 spring-summer images of oceanic islands in mostly pigment-poor water, 17 yielded no recognizable elevated pigment; islands were 5 times surrounded by approximately doubled concentrations (ca 100 km in diameter), and 2 cases may have been associated with an extensive bloom. Inspection of offshore images showed concentrations of 1 greater than or equal to(up to 5) mg/sq m in rare patches of 65 to 200 km size on approximately one-tenth of the dates; such patches were not seen in Sub-antarctic waters of the eastern Pacific Sector. A case is made for Australian airborne iron supply being the cause that, presumably, would enhance large-celled phytoplankton. Since, however, the putative iron supply from the seabed around the oceanic islands or the near

  19. Near-Surface Phytoplankton Pigment from the Coastal Zone Color Scanner in the Subantarctic Region Southeast of New Zealand

    NASA Technical Reports Server (NTRS)

    Banse, Karl; English, David C.

    1997-01-01

    Primarily based on satellite images, the phytoplankton concentration southeast (down- stream) of New Zealand in the High Nitrate - Low Chlorophyll (HNLC) Subantarctic water between the Subtropical Convergence (STC) and the Polar Front (PF) is believed to be higher than in the remainder of the Pacific Sector. Iron enrichment is assumed to be the reason, To study the question, near-surface phytoplankton pigment estimates from the Coastal Zone Color Scanner for up to 7 yr were reprocessed with particular attention to interference by clouds. Monthly mean images were created for the U,S. JGOFS Box along 170 deg W and means for individual dates calculated for 7 large areas between 170 deg E and 160 deg W, 45 deg and 58 deg S, well offshore of New Zealand and principally between and away from the STC and PF. The areal means are about as low as in other HNLC regions (most values between 0.1 and 0.4 or 0.5 mg/ sq m, with very few winter images; median of seasonal means, 0.26 mg/sq m) except at times near the STC, The higher means tend to occur in late summer and autumn, However, contrary to expectations, neither the PF nor the environs of the Subantarctic Front are distinguished by a zone of increased pigment. Also, of 24 spring-summer images of oceanic islands in mostly pigment-poor water, 17 yielded no recognizable elevated pigment; islands were 5 times surrounded by approximately doubled concentrations (ca 100 km in diameter), and 2 cases may have been associated with an extensive bloom. Inspection of offshore images showed concentrations of 1 greater than or equal to(up to 5) mg/sq m in rare patches of 65 to 200 km size on approximately one-tenth of the dates; such patches were not seen in Sub-antarctic waters of the eastern Pacific Sector. A case is made for Australian airborne iron supply being the cause that, presumably, would enhance large-celled phytoplankton. Since, however, the putative iron supply from the seabed around the oceanic islands or the near

  20. Cryptic species diversity in sub-Antarctic islands: A case study of Lepidonotothen.

    PubMed

    Dornburg, Alex; Federman, Sarah; Eytan, Ron I; Near, Thomas J

    2016-11-01

    The marine fauna of the Southern Ocean is well known for an impressive adaptive radiation of fishes, the notothenioids. However, when compared to other marine areas, the frigid waters of the Southern Ocean also contain a seemingly large proportion of cryptic species. The documented instances of speciation in the absence of morphological change are largely observed in invertebrate taxa, in particular around peri- and sub-Antarctic islands such as South Georgia, which has been dubbed a cryptic species hotspot. This prevalence of cryptic species raises the question of how generalizable these patterns are for Antarctic vertebrates. Here we examine aspects of genotype and phenotype in an Antarctic notothenioid fish species, Lepidonotothen nudifrons, which is distributed in near shore habitats of the Antarctic Peninsula, South Orkney Islands, South Georgia, and the South Sandwich Islands. The results of our analyses show that L. nudifrons comprises two species. We highlight that cryptic species are phenomena not restricted to invertebrate lineages, raising the possibility that the species diversity of notothenioids and other Southern Ocean fishes is under-described. In addition, our findings raise several questions about the evolutionary origin and maintenance of morphological stasis in one of the most extreme habitats on earth. Copyright © 2016 Elsevier Inc. All rights reserved.

  1. Assessing Sub-Antarctic Zone primary productivity from fast repetition rate fluorometry

    NASA Astrophysics Data System (ADS)

    Cheah, Wee; McMinn, Andrew; Griffiths, F. Brian; Westwood, Karen J.; Wright, Simon W.; Molina, Ernesto; Webb, Jason P.; van den Enden, Rick

    2011-11-01

    In situ primary productivity (PP) in the Sub-Antarctic Zone (SAZ) and the Polar Frontal Zone (PFZ) south of Australia was estimated using fast repetition rate fluorometry (FRRF). FRRF-derived PP at Process station 3 (P3) southeast of Tasmania (46°S, 153°E) were higher than P1 in the southwest of Tasmania (46°S, 140°E) and P2 in the Polar Frontal Zone (54°S, 146°E). The FRRF-derived PP rates were well correlated with 14C-uptake rates from one-hour incubations ( r2=0.85, slope=1.23±0.05, p<0.01, n=85) but the relationship between both methods differed vertically and spatially. There was a linear relationship between FRRF-based PP and 14C-based PP under light-limited conditions in deeper waters. Under light-saturated conditions near the surface (0-45 m), the relationship was less clear. This was likely associated with the effects of physiological processes such as cyclic electron flow and the Mehler reaction, which are stimulated at high irradiance. Our results indicate that FRRF can be used to estimate photosynthesis rates in the SAZ and PFZ but to derive an accurate estimation of C-fixation requires a detailed understanding of the physiological properties of the cells and their response to oceanographic parameters under different environmental conditions.

  2. Carbon isotope offsets between benthic foraminifer species of the genus Cibicides (Cibicidoides) in the glacial sub-Antarctic Atlantic

    NASA Astrophysics Data System (ADS)

    Gottschalk, Julia; Vázquez Riveiros, Natalia; Waelbroeck, Claire; Skinner, Luke C.; Michel, Elisabeth; Duplessy, Jean-Claude; Hodell, David; Mackensen, Andreas

    2016-12-01

    Epibenthic foraminifer δ13C measurements are valuable for reconstructing past bottom water dissolved inorganic carbon δ13C (δ13CDIC), which are used to infer global ocean circulation patterns. Epibenthic δ13C, however, may also reflect the influence of 13C-depleted phytodetritus, microhabitat changes, and/or variations in carbonate ion concentrations. Here we compare the δ13C of two benthic foraminifer species, Cibicides kullenbergi and Cibicides wuellerstorfi, and their morphotypes, in three sub-Antarctic Atlantic sediment cores over several glacial-interglacial transitions. These species are commonly assumed to be epibenthic, living above or directly below the sediment-water interface. While this might be consistent with the small δ13C offset that we observe between these species during late Pleistocene interglacial periods (Δδ13C = -0.19 ± 0.31‰, N = 63), it is more difficult to reconcile with the significant δ13C offset that is found between these species during glacial periods (Δδ13C = -0.76 ± 0.44‰, N = 44). We test possible scenarios by analyzing Uvigerina spp. δ13C and benthic foraminifer abundances: (1) C. kullenbergi δ13C is biased to light values either due to microhabitat shifts or phytodetritus effects and (2) C. wuellerstorfi δ13C is biased to heavy values, relative to long-term average conditions, for instance by recording the sporadic occurrence of less depleted deepwater δ13CDIC. Neither of these scenarios can be ruled out unequivocally. However, our findings emphasize that supposedly epibenthic foraminifer δ13C in the sub-Antarctic Atlantic may reflect several factors rather than being solely a function of bottom water δ13CDIC. This could have a direct bearing on the interpretation of extremely light South Atlantic δ13C values at the Last Glacial Maximum.

  3. Climatic change and its ecological implications at a subantarctic island.

    PubMed

    Smith, V R; Steenkamp, Marianna

    1990-11-01

    Marion Island (47°S, 38°E) has one of the most oceanic climates on earth, with consistently low air temperatures, high precipitation, constantly high humidity, and low incident radiation. Since 1968 mean surface air temperature has increased significantly, by 0.025° C year(-1). This was strongly associated with corresponding changes in sea surface temperature but only weakly, or not at all, with variations in radiation and precipitation. We suggest that changing sealevel (atmospheric and oceanic) circulation patterns in the region underlie all of these changes. Sub-Antarctic terrestrial ecosystems are characterized by being species-poor and having a simple trophic structure. Marion Island is no exception and a scenario is presented of the implications of climatic change for the structure and functioning of its ecosystem. Primary production on the island is high and consequently the vegetation has a large annual requirement for nutrients. There are no macroherbivores and even the insects play only a small role as herbivores, so most of the energy and nutrients incorporated in primary production go through a detritus, rather than grazing, cycle. Ameliorating temperatures and increasing CO2 levels are expected to increase productivity and nutrient demand even further. However, most of the plant communities occur on soils which have especially low available levels of nutrients and nutrient mineralization from organic reserves is the main bottleneck in nutrient cycling and primary production. Increasing temperatures will not significantly enhance microbially-mediated mineralization rates since soil microbiological processes on the island are strongly limited by waterlogging, rather than by temperature. The island supports large numbers of soil macro-arthropods, which are responsible for most of the nutrient release from peat and litter. The activities of these animals are strongly temperature dependent and increasing temperature will result in enhanced nutrient

  4. Chromophoric DOM as a Tracer of North Atlantic Subtropical Mode Water Formation

    NASA Astrophysics Data System (ADS)

    Nelson, N. B.; McDonald, N.; Korol, O.; Siegel, D. A.; Carlson, C. A.

    2008-12-01

    Global surveys of chromophoric dissolved organic matter (CDOM) profiles have revealed that subtropical mode water layers represent a local minimum in the CDOM profile, reflecting their source in surface waters that have been bleached by solar radiation. Biogeochemical changes in CDOM below the surface layer have also been shown to be relatively slow, suggesting the use of CDOM as a semiconservative tracer of mode water formation. Estimates of CDOM formation rate in the mode water from concurrent measurements of CDOM and CFCs and salinity could be used to separate the biogeochemical signal from that of mixing. In this study, we examine mode water formation and transport using a 7-year record of CDOM concentrations in the subtropical mode water and sections from the CO2/CLIVAR Repeat Hydrography program. We used this in conjunction with hydrographic and biogeochemical data collected by the BATS and Repeat Hydrography programs, as well as nutrient data from the same sites. We found that profiles of CDOM concentrations at Bats tended to be inversely proportional to those of excess nitrogen (DINxs), reflecting remineralization throughout the water column. Furthermore, typical CDOM profiles were altered when the mode water was compressed due to factors such as eddies, indicating a need to consider such factors in characterizing CDOM distribution in areas where mode water exists.

  5. Development of a Regional Glycerol Dialkyl Glycerol Tetraether (GDGT) - Temperature Calibration for Antarctic and sub-Antarctic Lakes

    NASA Astrophysics Data System (ADS)

    Roberts, S. J.; Foster, L. C.; Pearson, E. J.; Steve, J.; Hodgson, D.; Saunders, K. M.; Verleyen, E.

    2016-12-01

    Temperature calibration models based on the relative abundances of sedimentary glycerol dialkyl glycerol tetraethers (GDGTs) have been used to reconstruct past temperatures in both marine and terrestrial environments, but have not been widely applied in high latitude environments. This is mainly because the performance of GDGT-temperature calibrations at lower temperatures and GDGT provenance in many lacustrine settings remains uncertain. To address these issues, we examined surface sediments from 32 Antarctic, sub-Antarctic and Southern Chilean lakes. First, we quantified GDGT compositions present and then investigated modern-day environmental controls on GDGT composition. GDGTs were found in all 32 lakes studied. Branched GDGTs (brGDGTs) were dominant in 31 lakes and statistical analyses showed that their composition was strongly correlated with mean summer air temperature (MSAT) rather than pH, conductivity or water depth. Second, we developed the first regional brGDGT-temperature calibration for Antarctic and sub-Antarctic lakes based on four brGDGT compounds (GDGT-Ib, GDGT-II, GDGT-III and GDGT-IIIb). Of these, GDGT-IIIb proved particularly important in cold lacustrine environments. Our brGDGT-Antarctic temperature calibration dataset has an improved statistical performance at low temperatures compared to previous global calibrations (r2=0.83, RMSE=1.45°C, RMSEP-LOO=1.68°C, n=36 samples), highlighting the importance of basing palaeotemperature reconstructions on regional GDGT-temperature calibrations, especially if specific compounds lead to improved model performance. Finally, we applied the new Antarctic brGDGT-temperature calibration to two key lake records from the Antarctic Peninsula and South Georgia. In both, downcore temperature reconstructions show similarities to known Holocene warm periods, providing proof of concept for the new Antarctic calibration model.

  6. VSCF calculations for the intra- and intermolecular vibrational modes of the water dimer and its isotopologs

    NASA Astrophysics Data System (ADS)

    Monteiro, João G. S.; Barbosa, André G. H.

    2016-11-01

    In this work we show how the VSCF method may be successfully used to describe all fundamental vibrational transitions of several isotopologs of water dimer. By expressing the normal mode displacements in terms of appropriate delocalized internal coordinates we are able to minimize the mode-mode coupling in the PES and thus yield PT2-VSCF frequencies in good agreement with the experiment. The use of curvilinear normal modes is of paramount importance to describe vibrational transitions of the very soft intermolecular modes. Within our approach the maximum calculated error for the (H2O)2 intermolecular frequencies are reduced from 311 cm-1 (Cartesian normal modes) to just 56 cm-1 (curvilinear normal modes). Plots of the diagonal intermolecular potential and of the vibrational wave function illustrate the remarkable effect of different coordinate systems. In conclusion, our PT2-VSCF calculations provide a fair anharmonic description of the fundamental transitions of water dimers.

  7. Intrusion of Fukushima-derived radiocaesium into subsurface water due to formation of mode waters in the North Pacific.

    PubMed

    Kaeriyama, Hideki; Shimizu, Yugo; Setou, Takashi; Kumamoto, Yuichiro; Okazaki, Makoto; Ambe, Daisuke; Ono, Tsuneo

    2016-02-26

    The Fukushima Dai-ichi Nuclear Power Plant accident in March 2011 released radiocaesium ((137)Cs and (134)Cs) into the North Pacific Ocean. Meridional transects of the vertical distribution of radiocaesium in seawater were measured along 147 °E and 155 °E in October-November 2012, 19 months after the accident. These measurements revealed subsurface peaks in radiocaesium concentrations at locations corresponding to two mode waters, Subtropical Mode Water and Central Mode Water. Mode water is a layer of almost vertically homogeneous water found over a large geographical area. Here we show that repeated formation of mode water during the two winter seasons after the Fukushima accident and subsequent outcropping into surface water transported radiocaesium downward and southward to subtropical regions of the North Pacific. The total amount of Fukushima-derived (134)Cs within Subtropical Mode Water, decay-corrected to April 2011, was estimated to be 4.2 ± 1.1 PBq in October-November 2012. This amount of (134)Cs corresponds to 22-28% of the total amount of (134)Cs released to the Pacific Ocean.

  8. Intrusion of Fukushima-derived radiocaesium into subsurface water due to formation of mode waters in the North Pacific

    PubMed Central

    Kaeriyama, Hideki; Shimizu, Yugo; Setou, Takashi; Kumamoto, Yuichiro; Okazaki, Makoto; Ambe, Daisuke; Ono, Tsuneo

    2016-01-01

    The Fukushima Dai-ichi Nuclear Power Plant accident in March 2011 released radiocaesium (137Cs and 134Cs) into the North Pacific Ocean. Meridional transects of the vertical distribution of radiocaesium in seawater were measured along 147 °E and 155 °E in October–November 2012, 19 months after the accident. These measurements revealed subsurface peaks in radiocaesium concentrations at locations corresponding to two mode waters, Subtropical Mode Water and Central Mode Water. Mode water is a layer of almost vertically homogeneous water found over a large geographical area. Here we show that repeated formation of mode water during the two winter seasons after the Fukushima accident and subsequent outcropping into surface water transported radiocaesium downward and southward to subtropical regions of the North Pacific. The total amount of Fukushima-derived 134Cs within Subtropical Mode Water, decay-corrected to April 2011, was estimated to be 4.2 ± 1.1 PBq in October–November 2012. This amount of 134Cs corresponds to 22–28% of the total amount of 134Cs released to the Pacific Ocean. PMID:26915424

  9. Intrusion of Fukushima-derived radiocaesium into subsurface water due to formation of mode waters in the North Pacific

    NASA Astrophysics Data System (ADS)

    Kaeriyama, Hideki; Shimizu, Yugo; Setou, Takashi; Kumamoto, Yuichiro; Okazaki, Makoto; Ambe, Daisuke; Ono, Tsuneo

    2016-02-01

    The Fukushima Dai-ichi Nuclear Power Plant accident in March 2011 released radiocaesium (137Cs and 134Cs) into the North Pacific Ocean. Meridional transects of the vertical distribution of radiocaesium in seawater were measured along 147 °E and 155 °E in October-November 2012, 19 months after the accident. These measurements revealed subsurface peaks in radiocaesium concentrations at locations corresponding to two mode waters, Subtropical Mode Water and Central Mode Water. Mode water is a layer of almost vertically homogeneous water found over a large geographical area. Here we show that repeated formation of mode water during the two winter seasons after the Fukushima accident and subsequent outcropping into surface water transported radiocaesium downward and southward to subtropical regions of the North Pacific. The total amount of Fukushima-derived 134Cs within Subtropical Mode Water, decay-corrected to April 2011, was estimated to be 4.2 ± 1.1 PBq in October-November 2012. This amount of 134Cs corresponds to 22-28% of the total amount of 134Cs released to the Pacific Ocean.

  10. Linkages between rapid climate variability and deep-sea benthic foraminifera in the deep Subantarctic South Atlantic during the last 95 kyr

    NASA Astrophysics Data System (ADS)

    Diz, Paula; Barker, Stephen

    2015-06-01

    We present a high-resolution record of benthic foraminifera fauna from a sediment core retrieved from the South Cape Basin (Subantarctic South Atlantic) spanning the last glacial cycle (95 kyr). Information provided by benthic foraminiferal assemblages together with paleoclimate proxies from the same core allow us to interpret changes in the style of primary production (episodic versus sustained) in relation to abrupt climate oscillations. Our results indicate that fluctuations in the abundance of the phytodetritus-related species, Epistominella exigua, are concomitant with millennial-scale high-latitude climate perturbations. Episodic phytoplankton blooms increased during a negative mode of the bipolar seesaw, irrespective of the magnitude of the perturbation (i.e., Heinrich stadial versus non-Heinrich stadial events). We provide a hypothesis linking the frequency and intensity of these events to atmospheric perturbations, interhemispheric climate variability, and millennial-scale changes in atmospheric CO2. A notable exception to the overall pattern is the generally high abundance of E. exigua across the globally synchronous onset of glacial marine oxygen isotope stage (MIS) 4, a period generally characterized by increased dustiness and low-quality organic carbon as inferred by the percentage of the nonphytodetritus species. This highlights the special characteristics governing the onset of MIS 4 in the Subantarctic.

  11. Submarine geology and geomorphology of active Sub-Antarctic volcanoes: Heard and McDonald Islands

    NASA Astrophysics Data System (ADS)

    Watson, S. J.; Coffin, M. F.; Whittaker, J. M.; Lucieer, V.; Fox, J. M.; Carey, R.; Arculus, R. J.; Bowie, A. R.; Chase, Z.; Robertson, R.; Martin, T.; Cooke, F.

    2016-12-01

    Heard and McDonald Islands (HIMI) are World Heritage listed sub-Antarctic active volcanic islands in the Southern Indian Ocean. Built atop the Kerguelen Plateau by Neogene-Quaternary volcanism, HIMI represent subaerial exposures of the second largest submarine Large Igneous Province globally. Onshore, processes influencing island evolution include glaciers, weathering, volcanism, vertical tectonics and mass-wasting (Duncan et al. 2016). Waters surrounding HIMI are largely uncharted, due to their remote location. Hence, the extent to which these same processes shape the submarine environment around HIMI has not been investigated. In early 2016, we conducted marine geophysical and geologic surveys around HIMI aboard RV Investigator (IN2016_V01). Results show that volcanic and sedimentary features prominently trend east-west, likely a result of erosion by the eastward flowing Antarctic Circumpolar Current and tidal currents. However, spatial patterns of submarine volcanism and sediment distribution differ substantially between the islands. >70 sea knolls surround McDonald Island suggesting substantial submarine volcanism. Geophysical data reveals hard volcanic seafloor around McDonald Island, whereas Heard Island is characterised by sedimentary sequences tens of meters or more thick and iceberg scours - indicative of glacial processes. Differences in submarine geomorphology are likely due to the active glaciation of Heard Island and differing rock types (Heard: alkali basalt, McDonald: phonolite), and dominant products (clastics vs. lava). Variations may also reflect different magmatic plumbing systems beneath the two active volcanoes (Heard produces larger volumes of more focused lava, whilst McDonald extrudes smaller volumes of more evolved lavas from multiple vents across the edifice). Using geophysical data, corroborated with new and existing geologic data, we present the first geomorphic map revealing the processes that shape the submarine environment around HIMI.

  12. Effectiveness of bioremediation of crude oil contaminated subantarctic intertidal sediment: the microbial response.

    PubMed

    Delille, D; Delille, B; Pelletier, E

    2002-08-01

    A field study was initiated in February 1996 in a remote sandy beach of The Grande Terre (Kerguelen Archipelago, 69 degrees 42 degrees E, 49 degrees 19 degrees S) with the objective of determining the long-term effects of some bioremediation agents on the biodegradation rate and the toxicity of oil residues under severe subantarctic conditions. A series of 10 experimental plots were settled firmly into sediment. Each plot received 2L of Arabian light crude oil and some of them were treated with bioremediation agents: slow release fertilizer Inipol EAP-22 (Elf Atochem) or fish composts. Plots were sampled on a regular basis over a 3-year period. A two-order of magnitude increase of saprophytic and hydrocarbon-utilizing microorganisms occurred during the first month of the experiment in all treated enclosures, but no clear differences appeared between the plots. Very high microbial populations were present during the experiment. Biodegradation within treated spots was faster than within the untreated ones and appeared almost complete after 6 months as indicated by the degradation index of aliphatic hydrocarbons within all plots. The analysis of interstitial water collected below the oily residues presented no toxicity. However, a high toxicity signal, using Microtox solid phase, appeared for all oiled sand samples with a noticeable reduction with time even if the toxicity signal remained present and strong after 311 days of oil exposition. As a conclusion, it is clear that the microbial response was rapid and efficient in spite of the severe weather conditions, and the rate of degradation was improved in presence of bioremediation agents. However, the remaining residues had a relatively high toxicity.

  13. Mode-distribution analysis of quasielastic neutron scattering and application to liquid water

    NASA Astrophysics Data System (ADS)

    Kikuchi, Tatsuya; Nakajima, Kenji; Ohira-Kawamura, Seiko; Inamura, Yasuhiro; Yamamuro, Osamu; Kofu, Maiko; Kawakita, Yukinobu; Suzuya, Kentaro; Nakamura, Mitsutaka; Arai, Masatoshi

    2013-06-01

    A quasielastic neutron scattering (QENS) experiment is a particular technique that endeavors to define a relationship between time and space for the diffusion dynamics of atoms and molecules. However, in most cases, analyses of QENS data are model dependent, which may distort attempts to elucidate the actual diffusion dynamics. We have developed a method for processing QENS data without a specific model, wherein all modes can be described as combinations of the relaxations based on the exponential law. By this method, we can obtain a distribution function B(Q,Γ), which we call the mode-distribution function (MDF), to represent the number of relaxation modes and distributions of the relaxation times in the modes. The deduction of MDF is based on the maximum entropy method and is very versatile in QENS data analysis. To verify this method, reproducibility was checked against several analytical models, such as that with a mode of distributed relaxation time, that with two modes closely located, and that represented by the Kohlrausch-Williams-Watts function. We report the first application to experimental data of liquid water. In addition to the two known modes, the existence of a relaxation mode of water molecules with an intermediate time scale has been discovered. We propose that the fast mode might be assigned to an intermolecular motion and the intermediate motion might be assigned to a rotational motion of the water molecules instead of to the fast mode.

  14. Investigation of IPCC AR4 coupled climate model North Atlantic mode water formation

    NASA Astrophysics Data System (ADS)

    Carman, Jessie C.; McClean, Julie L.

    The formation of mode waters in the North Atlantic was examined in the suite of ocean models that comprise the World Climate Research Programme (WCRP) Coupled Model Intercomparison Project phase 3 (CMIP3). We constructed model climatologies for 1980-1999 from the 20th century simulations, and compared their mode water properties (temperature, salinity, formation rate, volume, turnover time, heat content) with data. In these models, we found biases in both the properties of the mode waters and their formation rates. For Subpolar Mode Water (SPMW), property biases principally involved salinity errors; additionally, some models form SPMW in an anomalous region west of the British Isles, shifting the source location of waters entering the overturning cell and altering the Nordic Seas' involvement in the Meridional Overturning Circulation. For Subtropical Mode Water (STMW), property biases involved both salinity and temperature errors, while positioning of heat and water fluxes relative to the Gulf Stream and northwest Sargasso Sea influenced STMW formation rate. Deficiencies in STMW formation rate and volume produced a turnover time of 1-2 years, approximately half of that observed; these variations in mode water bulk properties imply variation in ocean heat storage and advection, and hence deficiencies in all the models' abilities to adequately respond to changes in climatic forcing.

  15. Ringin' the water bell: dynamic modes of curved fluid sheets

    NASA Astrophysics Data System (ADS)

    Kolinski, John; Aharoni, Hillel; Fineberg, Jay; Sharon, Eran

    2015-11-01

    A water bell is formed by fluid flowing in a thin, coherent sheet in the shape of a bell. Experimentally, a water bell is created via the impact of a cylindrical jet on a flat surface. Its shape is set by the splash angle (the separation angle) of the resulting cylindrically symmetric water sheet. The separation angle is altered by adjusting the height of a lip surrounding the impact point, as in a water sprinkler. We drive the lip's height sinusoidally, altering the separation angle, and ringin' the water bell. This forcing generates disturbances on the steady-state water bell that propagate forward and backward in the fluid's reference frame at well-defined velocities, and interact, resulting in the emergence of an interference pattern unique to each steady-state geometry. We analytically model these dynamics by linearizing the amplitude of the bell's response about the underlying curved geometry. This simple model predicts the nodal structure over a wide range of steady-state water bell configurations and driving frequencies. Due to the curved water bell geometry, the nodal structure is quite complex; nevertheless, the predicted nodal structure agrees extremely well with the experimental data. When we drive the bell beyond perturbative separation angles, the nodal locations surprisingly persist, despite the strikingly altered underlying water bell shape. At extreme driving amplitudes the water sheet assumes a rich variety of tortuous, non-convex shapes; nevertheless, the fluid sheet remains intact.

  16. Instantaneous normal mode analysis of the vibrational relaxation of the amide I mode of alanine dipeptide in water.

    PubMed

    Farag, Marwa H; Zúñiga, José; Requena, Alberto; Bastida, Adolfo

    2013-05-28

    Nonequilibrium Molecular Dynamics (MD) simulations coupled to instantaneous normal modes (INMs) analysis are used to study the vibrational relaxation of the acetyl and amino-end amide I modes of the alanine dipeptide (AlaD) molecule dissolved in water (D2O). The INMs are assigned in terms of the equilibrium normal modes using the Effective Atomic Min-Cost algorithm as adapted to make use of the outputs of standard MD packages, a method which is well suited for the description of flexible molecules. The relaxation energy curves of both amide I modes show multiexponential decays, in good agreement with the experimental findings. It is found that ~85%-90% of the energy relaxes through intramolecular vibrational redistribution. The main relaxation pathways are also identified. The rate at which energy is transferred into the solvent is similar for the acetyl-end and amino-end amide I modes. The conformational changes occurring during relaxation are investigated, showing that the populations of the alpha and beta region conformers are altered by energy transfer in such a way that it takes 15 ps for the equilibrium conformational populations to be recovered after the initial excitation of the AlaD molecule.

  17. Frontal Structure, Water Masses, and Circulation in the Crozet Basin

    NASA Astrophysics Data System (ADS)

    Park, Young-Hyang; Gamberoni, Lucien; Charriaud, Edwige

    1993-07-01

    Due to topographic steering by the Crozet and Kerguelen Plateaus, the Antarctic Circumpolar Current (ACC) core in the Crozet Basin area is shifted to its northernmost position in the Southern Ocean, along the southern limb of the South Indian subtropical gyre. Here the jet-like current is embedded within a narrow band (< 200 km) of the frontal zone which marks a sharp transition between subtropical and subantarctic waters, hugging the northern flanks of the Crozet and Kerguelen Plateaus. Adding to this topographic control, the confluence of the ACC and the Agulhas Return Current north of Crozet further intensifies downstream baroclinic shear strengths. Eastward transport associated with the Agulhas Return Current at the entrance of the Crozet Basin at 53°E is estimated as 35 Sv (1 Sv = 106 m3/s), most of which recirculating northward into the northern part of the basin before reaching Kerguelen-Amsterdam passage. About 75% of the ACC transport through Drake Passage pass through Kerguelen-Amsterdam passage, the quasi-totality of which being concentrated in the frontal zone composed of two merged fronts, the Subtropical and Subantarctic Fronts; the rest of the current passes south of Kerguelen. The Polar Front in this Crozet Basin area is not associated with any noticeable baroclinic shear and represents only a minor portion (5-7 Sv) of the ACC, in great contrast to that observed in the other sectors of the Southern Ocean. The Crozet Basin provides an important source for the formation and modification of water masses. Crozet Basin Mode Water formed locally just north of the ACC is of subtropical origin but shows significant zonal anomalies in its characteristics, with lighter mode (γθ > 26.5 kg/m3) in the western half of the basin and heavier mode (γθ < 26.7 kg/m3) in its eastern half. These different varieties of Crozet Basin Mode Water are closely correlated with the degree of exchange and mixing between subtropical and subantarctic waters along the

  18. Collaborative Project. Mode and Intermediate Waters in Earth System Models

    SciTech Connect

    Sarmiento, Jorge L.; Dufour, Carolina; Rodgers, Keith B.

    2015-12-16

    The focus of this grant was on diagnosing the physical mechanisms controlling upper ocean water mass formation and carbon distribution in Earth System Models (ESMs), with the goal of improving the physics that controls their formation.

  19. Mode-bifurcation upon pouring water into a cup that depends on the shape of the cup

    NASA Astrophysics Data System (ADS)

    Nakata, Satoshi; Yamada, Akiko; Kitahata, Hiroyuki

    2005-05-01

    Mode-bifurcation that included hysteresis was investigated when water was poured into a cup via a water faucet. Three modes, i.e., accumulation flow (mode I), scattering flow (mode II), and open and shut oscillatory flow (mode III), could be produced by laterally changing the distance between the center of the cup and the landing point of water poured at a constant flow rate. Hysteresis in mode-bifurcation was observed when the distance was changed depending on the initial location of the water poured into the cup. Pendulum flow was also observed when water was poured into a shallow cell. The essential features of this mode-switching were reproduced by a numerical calculation as a function of the landing point of the poured water using two-variable (the size of the water hollow and the pressure on the water surface) differential equations that included the nature of reversed flow.

  20. Impacts of aquatic macrophytes configuration modes on water quality.

    PubMed

    Liu, Jiakai; Liu, Jinglan; Zhang, Rong; Zou, Yuqi; Wang, Huihui; Zhang, Zhenming

    2014-01-01

    Constructed wetland technology is regarded as an important ecological restoration technology and used widely in sewage disposal. In order to give them a wider scope of application and to improve their performance in water restoration, the current experiment was designed. Four aquatic macrophytes (dwarf cattail (TM), yellow-flowered iris (WI), water shallot (ST) and watermifoil (MS)) were picked and planted in artificial floating islands (AFIs) in different configurations (TM + WI, ST + MS and TM + WI + MS) and two patterns, radiation pattern (RP) and annular pattern (AP), for a 60-day experiment. Then, water quality and growth were monitored every 10 days. The results indicate that the different configurations performed diversely on waste water purification. First, a composite plant configuration removed more pollutant than a single one with the same total increment of biomass. Second, the plant configuration of MS + ST was most effective in total nitrogen (TN), total phosphorus (TP) or PO4(3-) removal, and TM + IW + MS was good at chemical oxygen demand (COD) and NO3(-) removal. However, different patterns comprised from the same species had a certain effect on absorption of pollutants. Generally speaking, plant configurations with a RP were better than an AP in purification. Accordingly, these provided the methods for the pollution wetland restoration.

  1. Enhanced warming of the subtropical mode water in the North Pacific and North Atlantic

    NASA Astrophysics Data System (ADS)

    Sugimoto, Shusaku; Hanawa, Kimio; Watanabe, Tomowo; Suga, Toshio; Xie, Shang-Ping

    2017-09-01

    Over the past six decades, the subtropical surface ocean has warmed at rates close to those of global mean surface ocean temperature except in western boundary current regions where the surface warming is locally enhanced by a factor of two. Changes in the subsurface ocean, however, remain unclear because of lack of data. Compiling historical temperature measurements--some available for the first time--here we show that the subtropical mode water has warmed over the past six decades in both the North Pacific and North Atlantic. The rate of the warming is twice as large in the mode waters than at the surface. Subtropical mode waters are important water masses of vertically uniform temperature that are a few hundred metres thick and distributed widely in the main thermocline of the subtropical oceans. The enhanced warming of subtropical mode waters can be traced back to the surface warming in the formation regions along the western boundary current extensions. Furthermore, we detect increased temperature stratification and decreased dissolved oxygen in the subtropical mode waters. The latter change has clear implications for predicting biogeochemical responses to climate warming.

  2. Carbon export production in the subantarctic zone and polar front zone south of Tasmania

    NASA Astrophysics Data System (ADS)

    Jacquet, S. H. M.; Lam, P. J.; Trull, T.; Dehairs, F.

    2011-11-01

    We studied the water column distribution of total 234Th in subantarctic (SAZ) and polar front (PFZ) zone systems south of Tasmania during mid-austral summer 2007. The objective was to assess whether the observed zonal differences in biomass in this sector translated into variability of the carbon export and sequestration potential, and to identify possible causes inducing this variability. This study is part of a broader investigation focusing on macro- and micronutrient availability controlling ecosystem functioning in this area. Surface deficits in 234Th activities were observed at every station. 234Th export fluxes calculated from the 234Th activity deficits assuming steady state conditions showed higher 234Th export fluxes in the western than eastern SAZ, both of which were higher than those in the PFZ. 234Th fluxes sampled by free-drifting IRS and PPS-3 sediment traps at 150 and 170 m during short-term deployments (˜ 6 days) at the three process stations were significantly lower than those obtained by the 234Th-deficit method. Possible reasons for this discrepancy are discussed. Carbon export fluxes were calculated based on the total 234Th fluxes ( 234Th deficit method) and the C:Th ratio for the >54 μm particle size fraction from the appropriate export depth. The >54 μm C:Th ratio was significantly lower in the eastern SAZ than the western SAZ or PFZ, resulting in carbon export fluxes that were lowest in the eastern SAZ. Overall, export fluxes range from 3.6±1.5 to 13.2±3.1 mmol C m -2 d -1. Carbon export fluxes are compared with gross primary production, new production and mesopelagic remineralization fluxes obtained by others during the same cruise. Contrary to expectations, we found higher export production in the PFZ and the western SAZ where biomass and dissolved Fe were lower than in the eastern SAZ. Significant differences in community structure of both primary producers and consumers likely contributed to this difference between the three regions

  3. Iron fertilization of the Subantarctic ocean during the last ice age.

    PubMed

    Martínez-García, Alfredo; Sigman, Daniel M; Ren, Haojia; Anderson, Robert F; Straub, Marietta; Hodell, David A; Jaccard, Samuel L; Eglinton, Timothy I; Haug, Gerald H

    2014-03-21

    John H. Martin, who discovered widespread iron limitation of ocean productivity, proposed that dust-borne iron fertilization of Southern Ocean phytoplankton caused the ice age reduction in atmospheric carbon dioxide (CO2). In a sediment core from the Subantarctic Atlantic, we measured foraminifera-bound nitrogen isotopes to reconstruct ice age nitrate consumption, burial fluxes of iron, and proxies for productivity. Peak glacial times and millennial cold events are characterized by increases in dust flux, productivity, and the degree of nitrate consumption; this combination is uniquely consistent with Subantarctic iron fertilization. The associated strengthening of the Southern Ocean's biological pump can explain the lowering of CO2 at the transition from mid-climate states to full ice age conditions as well as the millennial-scale CO2 oscillations.

  4. Quantum Mode Selectivity of Plasmon-Induced Water Splitting on Gold Nanoparticles.

    PubMed

    Yan, Lei; Wang, Fangwei; Meng, Sheng

    2016-05-24

    Plasmon induced water splitting is a promising research area with the potential for efficient conversion of solar to chemical energy, yet its atomic mechanism is not well understood. Here, ultrafast electron-nuclear dynamics of water splitting on gold nanoparticles upon exposure to femtosecond laser pulses was directly simulated using real time time-dependent density functional theory (TDDFT). Strong correlation between laser intensity, hot electron transfer, and reaction rates has been identified. The rate of water splitting is dependent not only on respective optical absorption strength, but also on the quantum oscillation mode of plasmonic excitation. Odd modes are more efficient than even modes, owing to faster decaying into hot electrons whose energy matches well the antibonding orbital of water. This finding suggests photocatalytic activity can be manipulated by adjusting the energy level of plasmon-induced hot carriers, through altering the cluster size and laser parameter, to better overlap adsorbate unoccupied level in plasmon-assisted photochemistry.

  5. Extended hatching periods in the subantarctic lithodid crabs Lithodes santolla and Paralomis granulosa (Crustacea: Decapoda: Lithodidae)

    NASA Astrophysics Data System (ADS)

    Thatje, S.; Calcagno, J. A.; Lovrich, G. A.; Sartoris, F. J.; Anger, K.

    2003-06-01

    Temporal pattern of hatching was studied in the subantarctic lithodid crabs Lithodes santolla (Molina) and Paralomis granulosa (Jaquinot) from the Argentine Beagle Channel. In both species, larval hatching occurred in low daily numbers over an extended period of up to several weeks, depending on hatch size. Low daily hatching activity and low oxygen-consumption rates in freshly hatched P. granulosa larvae are discussed as life history adaptations to, and/or physiological constraints by, the environmental conditions of high latitudes.

  6. Soil biogeochemical toxicity end points for sub-Antarctic islands contaminated with petroleum hydrocarbons.

    PubMed

    Schafer, Alexis Nadine; Snape, Ian; Siciliano, Steven Douglas

    2007-05-01

    Sub-Antarctic islands have been subjected to petroleum hydrocarbon spills, yet no information is available regarding the toxicity of petroleum hydrocarbons to these subpolar soils. The purpose of the present study was to identify soil biogeochemical toxicity end points for petroleum hydrocarbon contamination in sub-Antarctic soil. Soil from Macquarie Island, a sub-Antarctic island south of Australia, was collected and exposed to 10 concentrations of Special Antarctic Blend (SAB) diesel fuel, ranging from 0 to 50,000 mg fuel/kg soil, for a 21-d period. The sensitivity of nitrification, denitrification, carbohydrate utilization, and total soil respiration to SAB fuel was assessed. Potential nitrification activity was the most sensitive indicator of SAB contamination assessed for nitrogen cycling, with an IC20 (concentration that results in a 20% change from the control response) of 190 mg fuel/ kg soil. Potential denitrification activity was not as sensitive to SAB contamination, with an IC20 of 950 mg fuel/kg soil for nitrous oxide production. Nitrous oxide consumption was unaffected by SAB contamination. Carbohydrate utilization (respiration caused by sucrose) was a more sensitive indicator (IC20, 16 mg fuel/kg soil) of SAB contamination than total respiration (IC20, 220 mg fuel/kg soil). However, total soil respiration was a more responsive measurement end point, increasing soil respiration over a 72-h period by 17 mg of CO2, compared to a change of only 2.1 mg of CO2 for carbohydrate utilization. Our results indicate that IC20s varied between 16 to 950 mg fuel/kg soil for Macquarie Island soil spiked with SAB diesel fuel. These results indicate that current cleanup levels derived from temperate zones may be too liberal for soil contamination in sub-Antarctic islands.

  7. Biological response to millennial variability of dust and nutrient supply in the Subantarctic South Atlantic Ocean.

    PubMed

    Anderson, Robert F; Barker, Stephen; Fleisher, Martin; Gersonde, Rainer; Goldstein, Steven L; Kuhn, Gerhard; Mortyn, P Graham; Pahnke, Katharina; Sachs, Julian P

    2014-07-13

    Fluxes of lithogenic material and fluxes of three palaeo-productivity proxies (organic carbon, biogenic opal and alkenones) over the past 100,000 years were determined using the (230)Th-normalization method in three sediment cores from the Subantarctic South Atlantic Ocean. Features in the lithogenic flux record of each core correspond to similar features in the record of dust deposition in the EPICA Dome C ice core. Biogenic fluxes correlate with lithogenic fluxes in each sediment core. Our preferred interpretation is that South American dust, most probably from Patagonia, constitutes a major source of lithogenic material in Subantarctic South Atlantic sediments, and that past biological productivity in this region responded to variability in the supply of dust, probably due to biologically available iron carried by the dust. Greater nutrient supply as well as greater nutrient utilization (stimulated by dust) contributed to Subantarctic productivity during cold periods, in contrast to the region south of the Antarctic Polar Front (APF), where reduced nutrient supply during cold periods was the principal factor limiting productivity. The anti-phased patterns of productivity on opposite sides of the APF point to shifts in the physical supply of nutrients and to dust as cofactors regulating productivity in the Southern Ocean. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

  8. Effects of nutrient and temperature on degradation of petroleum hydrocarbons in contaminated sub-Antarctic soil.

    PubMed

    Coulon, Frédéric; Pelletier, Emilien; Gourhant, Lénaick; Delille, Daniel

    2005-03-01

    Mesocosm studies using sub-Antarctic soil artificially contaminated with diesel or crude oil were conducted in Kerguelen Archipelago (49 degrees 21' S, 70 degrees 13' E) in an attempt to evaluate the potential of a bioremediation approach in high latitude environments. All mesocosms were sampled on a regular basis over six months period. Soils responded positively to temperature increase from 4 degrees C to 20 degrees C, and to the addition of a commercial oleophilic fertilizer containing N and P. Both factors increased the hydrocarbon-degrading microbial abundance and total petroleum hydrocarbons (TPH) degradation. In general, alkanes were faster degraded than polyaromatic hydrocarbons (PAHs). After 180 days, total alkane losses of both oils reached 77-95% whereas total PAHs never exceeded 80% with optimal conditions at 10 degrees C and fertilizer added. Detailed analysis of naphthalenes, dibenzothiophenes, phenanthrenes, and pyrenes showed a clear decrease of their degradation rate as a function of the size of the PAH molecules. During the experiment there was only a slight decrease in the toxicity, whereas the concentration of TPH decreased significantly during the same time. The most significant reduction in toxicity occurred at 4 degrees C. Therefore, bioremediation of hydrocarbon-contaminated sub-Antarctic soil appears to be feasible, and various engineering strategies, such as heating or amending the soil can accelerate hydrocarbon degradation. However, the residual toxicity of contaminated soil remained drastically high before the desired cleanup is complete and it can represent a limiting factor in the bioremediation of sub-Antarctic soil.

  9. Iron fertilization of the Subantarctic Ocean during the last ice age

    NASA Astrophysics Data System (ADS)

    Martinez-Garcia, A.

    2015-12-01

    Dust has the potential to modify global climate by influencing the radiative balance of the atmosphere and by supplying iron and other essential limiting micronutrients to the ocean. The scarcity of iron limits marine productivity and carbon uptake in one-quarter of the world ocean where the concentration of major nutrients (phosphorus and nitrogen) is perennially high. The Southern Ocean is the region where variations in iron availability can have the largest effect on Earth's carbon cycle through its fertilizing effect on marine ecosystems. Paleoceanographic records from the Subantarctic Atlantic have revealed a remarkable correlation between phytoplankton productivity and aeolian iron flux during glacial periods supporting the iron fertilization hypothesis. In addition, a recent study has shown that peak glacial times and millennial cold events were nearly universally associated not only with increases in dust flux and export production, but also with an increase in nutrient consumption (the last indicated by higher foraminifera-bound δ15N) (Martinez-Garcia et al. 2014). This combination of changes is uniquely consistent with ice age iron fertilization of the Subantarctic Atlantic. The strengthening of the biological pump associated with the observed increase in Subantarctic nutrient consumption during the high-dust intervals of the last two ice ages can explain up to ~40 ppm of the CO2 decrease that characterizes the transitions from mid-climate states to full ice age conditions. However, the impact of iron fertilization in other sectors of the Southern Ocean characterized by lower ice age dust fluxes than the Atlantic remains unclear. A series of recently published records from the Subantarctic Pacific indicate that dust deposition and marine export production were three times higher during glacial periods than during interglacials (Lamy et al. 2014). Here we present new measurements of foraminifera-bound nitrogen isotopes in a sediment core located in the

  10. Observing mesoscale eddy effects on mode-water subduction and transport in the North Pacific

    PubMed Central

    Xu, Lixiao; Li, Peiliang; Xie, Shang-Ping; Liu, Qinyu; Liu, Cong; Gao, Wendian

    2016-01-01

    While modelling studies suggest that mesoscale eddies strengthen the subduction of mode waters, this eddy effect has never been observed in the field. Here we report results from a field campaign from March 2014 that captured the eddy effects on mode-water subduction south of the Kuroshio Extension east of Japan. The experiment deployed 17 Argo floats in an anticyclonic eddy (AC) with enhanced daily sampling. Analysis of over 3,000 hydrographic profiles following the AC reveals that potential vorticity and apparent oxygen utilization distributions are asymmetric outside the AC core, with enhanced subduction near the southeastern rim of the AC. There, the southward eddy flow advects newly ventilated mode water from the north into the main thermocline. Our results show that subduction by eddy lateral advection is comparable in magnitude to that by the mean flow—an effect that needs to be better represented in climate models. PMID:26829888

  11. The hydrogen-bond network of water supports propagating optical phonon-like modes

    PubMed Central

    Elton, Daniel C.; Fernández-Serra, Marivi

    2016-01-01

    The local structure of liquid water as a function of temperature is a source of intense research. This structure is intimately linked to the dynamics of water molecules, which can be measured using Raman and infrared spectroscopies. The assignment of spectral peaks depends on whether they are collective modes or single-molecule motions. Vibrational modes in liquids are usually considered to be associated to the motions of single molecules or small clusters. Using molecular dynamics simulations, here we find dispersive optical phonon-like modes in the librational and OH-stretching bands. We argue that on subpicosecond time scales these modes propagate through water's hydrogen-bond network over distances of up to 2 nm. In the long wavelength limit these optical modes exhibit longitudinal–transverse splitting, indicating the presence of coherent long-range dipole–dipole interactions, as in ice. Our results indicate the dynamics of liquid water have more similarities to ice than previously thought. PMID:26725363

  12. Modes of elastic plates and shells in water driven by modulated radiation pressure of focused ultrasound

    NASA Astrophysics Data System (ADS)

    Marston, Philip L.; Daniel, Timothy D.; Abawi, Ahmad T.; Kirsteins, Ivars

    2015-11-01

    The modulated radiation pressure (MRP) of ultrasound has been used for decades to selectively excite low frequency modes associated with surface tension of fluid objects in water. Much less is known about the excitation of low frequency modes of less compliant metallic objects. Here we use MRP of focused ultrasound to excite resonant flexural vibrations of a circular metal plate in water. The source transducer was driven with a double-sideband suppressed carrier voltage as in. The response of the target (detected with a hydrophone) was at twice the modulation frequency and proportional to the square of the drive voltage. Since the radiation pressure of focused beams is spatially localized, mode shapes could be identified by scanning the source along the target while measuring the target's response. Additional measurements were done with an open-ended water-filled copper circular cylindrical shell in which resonant frequencies and mode shapes were also identified. These experiments show how focused ultrasound can be used to identify low-frequency modes of elastic objects without direct contact. Supported by ONR.

  13. The hydrogen-bond network of water supports propagating optical phonon-like modes

    DOE PAGES

    Elton, Daniel C.; Fernández-Serra, Marivi

    2016-01-04

    The local structure of liquid water as a function of temperature is a source of intense research. This structure is intimately linked to the dynamics of water molecules, which can be measured using Raman and infrared spectroscopies. The assignment of spectral peaks depends on whether they are collective modes or single-molecule motions. Vibrational modes in liquids are usually considered to be associated to the motions of single molecules or small clusters. Using molecular dynamics simulations, here we find dispersive optical phonon-like modes in the librational and OH-stretching bands. We argue that on subpicosecond time scales these modes propagate through water’smore » hydrogen-bond network over distances of up to 2 nm. In the long wavelength limit these optical modes exhibit longitudinal–transverse splitting, indicating the presence of coherent long-range dipole–dipole interactions, as in ice. Lastly, our results indicate the dynamics of liquid water have more similarities to ice than previously thought.« less

  14. The hydrogen-bond network of water supports propagating optical phonon-like modes

    SciTech Connect

    Elton, Daniel C.; Fernández-Serra, Marivi

    2016-01-04

    The local structure of liquid water as a function of temperature is a source of intense research. This structure is intimately linked to the dynamics of water molecules, which can be measured using Raman and infrared spectroscopies. The assignment of spectral peaks depends on whether they are collective modes or single-molecule motions. Vibrational modes in liquids are usually considered to be associated to the motions of single molecules or small clusters. Using molecular dynamics simulations, here we find dispersive optical phonon-like modes in the librational and OH-stretching bands. We argue that on subpicosecond time scales these modes propagate through water’s hydrogen-bond network over distances of up to 2 nm. In the long wavelength limit these optical modes exhibit longitudinal–transverse splitting, indicating the presence of coherent long-range dipole–dipole interactions, as in ice. Lastly, our results indicate the dynamics of liquid water have more similarities to ice than previously thought.

  15. Mode Water Formation via Cabbeling and Submesoscale Lateral Mixing at a Strained Thermohaline Front

    NASA Astrophysics Data System (ADS)

    Thomas, L. N.; Shakespeare, C. J.

    2014-12-01

    Mode waters play an important role in interannual climate variability through the temporary storage of heat and carbon in the ocean. The mechanisms explaining their formation are not well understood but appear to be shaped by the dynamics of the ocean fronts that mark their poleward extent. We explore a mode water formation mechanism that has a clear connection to fronts and involves cabbeling. Cabbeling refers to the process by which two water masses of equal density but different temperature and salinity are combined to create a new, denser water mass, as a result of nonlinearities in the equation of state for seawater. The work is motivated in part by recent observations of an extremely sharp, density-compensated front at the north wall of the Gulf Stream, the boundary between the subtropical and subpolar gyres. Here, the inter-gyre salinity/temperature difference is compressed into a span of a few kilometers, making the flow susceptible to cabbeling. The sharpness of the front is caused by frontogenetic strain, which is presumably balanced by submesoscale lateral mixing processes. We study this balance with a simple analytical model of a thermohaline front forced by uniform strain and derive a scaling for the amount of water mass transformation resulting from the ensuing cabbeling. The theory suggests that this mechanism could be responsible for persistent, hence significant, mode water formation. As such, it represents a submesoscale process that impacts the ocean on basin scales that should be resolved or parameterized in realistic numerical simulations.

  16. Reconstructing Export Production in the Subantarctic South Pacific during the Last Ice Age

    NASA Astrophysics Data System (ADS)

    Park, J. W.; Winckler, G.; Anderson, R. F.; Schwartz, R.; Lamy, F.; Gersonde, R.; Pahnke, K.

    2016-02-01

    Despite high concentration of major nutrients in the Southern Ocean, nutrient utilization is inefficient because the scarcity of iron limits phytoplankton growth and primary productivity. Input of eolian dust into the ocean may supply iron, leading to increased export production and nutrient utilization, and potentially affect the Earth's carbon cycle through its fertilizing effect on marine ecosystem. Recent studies (Martínez-Garcia et al., 2009, 2011, 2014) suggest that iron fertilization in the Subantarctic South Atlantic may have contributed to reducing atmospheric CO2 by 40ppm over the last glacial cycle. While most of current observations on the Southern Ocean come from the South Atlantic, the Pacific sector covers the largest surface area of the Southern Ocean, indicating its potential to store the largest fraction of carbon. Dust fluxes to the South Atlantic are generally stronger than those to the South Pacific, but the glacial-interglacial pattern of dust deposition is similar. A recent study (Lamy et al., 2014) suggests a threefold increase of dust deposition over glacial periods than over interglacial periods in the South Pacific, and show a correlation between dust records and preliminary export production. In this study, we examine a set of cores from the Subantarctic South Pacific at higher temporal resolution to observe variability of export production in response to changing dust flux. We present proxy records for paleoproductivity from excess Ba, biogenic opal and authigenic Uranium. The results will allow us to evaluate the importance of iron fertilization in the Subantarctic Pacific Ocean over glacial/interglacial timescale and its potential effect on the global carbon cycle.

  17. Mass loss and imbalance of glaciers along the Andes Cordillera to the sub-Antarctic islands

    NASA Astrophysics Data System (ADS)

    Mernild, Sebastian H.; Beckerman, Andrew P.; Yde, Jacob C.; Hanna, Edward; Malmros, Jeppe K.; Wilson, Ryan; Zemp, Micheal

    2015-10-01

    Here, we examine available glacier mass-balance records between 1993 and 2012 for Andes Cordillera, South America (6.5°N-45.8°S), and the sub-Antarctic islands around the northern tip of the Antarctic Peninsula (62.7°S-63.8°S) to determine their recent mass loss and imbalance with the present climate. The mean annual observed mass-balance Ba changed from - 620 ± 390 (1993-2002) to - 740 ± 240 kg m- 2 yr- 1 (2003-2012) and for this past decade showed a decrease in Ba from south to north. These glaciers had a mean accumulation area ratio of 0.42, which is below the AAR value for glaciers in equilibrium, reflecting mean area and volume imbalances of 23% and 27%, respectively. Glaciers in the northern part of Andes Cordillera are most out of balance with the present climate (33%), while glaciers on the sub-Antarctic islands are only slightly out of balance (4%). We identified a spatiotemporal cycle of Ba that distinguishes glaciers on the sub-Antarctic islands from glaciers in the Andes using an Empirical Orthogonal Function analysis. This analysis also revealed that South America should be divided into three individual glacier regions, and not two regions as earlier stated. Overall, the spatiotemporal cycles identified correlate to the multivariate El Niño Southern Oscillation Index instantaneously (zero-year lag-time) and to the Pacific Decadal Oscillation with an approximately eight-year lag-time.

  18. Critical indirect effects of climate change on sub-Antarctic ecosystem functioning.

    PubMed

    Louise Allan, E; William Froneman, P; Durgadoo, Jonathan V; McQuaid, Christopher D; Ansorge, Isabelle J; Richoux, Nicole B

    2013-09-01

    Sub-Antarctic islands represent critical breeding habitats for land-based top predators that dominate Southern Ocean food webs. Reproduction and molting incur high energetic demands that are sustained at the sub-Antarctic Prince Edward Islands (PEIs) by both inshore (phytoplankton blooms; "island mass effect"; autochthonous) and offshore (allochthonous) productivity. As the relative contributions of these sustenance pathways are, in turn, affected by oceanographic conditions around the PEIs, we address the consequences of climatically driven changes in the physical environment on this island ecosystem. We show that there has been a measurable long-term shift in the carbon isotope signatures of the benthos inhabiting the shallow shelf region of the PEIs, most likely reflecting a long-term decline in enhanced phytoplankton productivity at the islands in response to a climate-driven shift in the position of the sub-Antarctic Front. Our results indicate that regional climate change has affected the balance between allochthonous and autochthonous productivity at the PEIs. Over the last three decades, inshore-feeding top predators at the islands have shown a marked decrease in their population sizes. Conversely, population sizes of offshore-feeding predators that forage over great distances from the islands have remained stable or increased, with one exception. Population decline of predators that rely heavily on organisms inhabiting the inshore region strongly suggest changes in prey availability, which are likely driven by factors such as fisheries impacts on some prey populations and shifts in competitive interactions among predators. In addition to these local factors, our analysis indicates that changes in prey availability may also result indirectly through regional climate change effects on the islands' marine ecosystem. Most importantly, our results indicate that a fundamental shift in the balance between allochthonous and autochthonous trophic pathways within

  19. Seawater temperature effect on metal accumulation and toxicity in the subantarctic Macquarie Island isopod, Exosphaeroma gigas.

    PubMed

    Lewis, Alexander; King, Catherine K; Hill, Nicole A; Cooper, Ashley; Townsend, Ashley T; Mondon, Julie A

    2016-08-01

    Very little is currently known of subantarctic nearshore invertebrates' sensitivity to environmental metals and the role of temperature in this relationship. This study investigated Cu and Zn toxicity in the common subantarctic intertidal isopod, Exosphaeroma gigas, and the influence of temperature on Cu toxicity and bioaccumulation kinetics. Adult E. gigas are insensitive to Cu and Zn at concentrations of 3200 and 7400μg/L respectively in non-renewal tests at 5.5°C (ambient subtidal temperature) over 14days. Under renewed exposures over the same temperature and time period the LC50 for copper was 2204μg/L. A 10-fold increase in Cu body burden occurred relative to zinc, indicating E. gigas has different strategies for regulating the two metals. Copper toxicity and time to mortality both increased with elevated temperature. However, temperature did not significantly affect Cu uptake rate and efflux rate constants derived from biodynamic modelling at lower Cu concentrations. These results may be attributable to E. gigas being an intertidal species with physiological mechanisms adapted to fluctuating environmental conditions. Cu concentrations required to elicit a toxicity response indicates that E. gigas would not be directly threatened by current levels of Cu or Zn present in Macquarie Island intertidal habitats, with the associated elevated temperature fluctuations. This study provides evidence that the sensitivity of this subantarctic intertidal species to metal contaminants is not as high as expected, and which has significance for the derivation of relevant guidelines specific to this distinct subpolar region of the world. Copyright © 2016 Elsevier B.V. All rights reserved.

  20. Mesoscale eddy effects on the subduction of North Pacific mode waters

    NASA Astrophysics Data System (ADS)

    Xu, L.

    2016-02-01

    Eddy effects on the subduction of North Pacific mode waters are investigated by comparing observations and ocean general circulation models where eddies are either parameterized or resolved. The eddy resolving models produce results closer to observations than the non-eddy resolving model. There are large discrepancies in subduction patterns between eddy resolving and non-eddy resolving models. In the non-eddy resolving model, subduction on a given isopycnal is limited to the cross point between the mixed layer depth (MLD) front and the outcrop line whereas in eddy resolving models and observations, subduction takes place in a broader, zonally elongated band within the deep mixed layer region. Mesoscale eddies significantly enhance the total subduction rate, helping create remarkable peaks in the volume histogram that correspond to North Pacific subtropical mode water (STMW) and central mode water (CMW). Eddy-enhanced subduction preferentially occurs south of the winter mean outcrop. With an anticyclonic eddy to the west and a cyclonic eddy to the east, the outcrop line meanders south, and the thermocline/MLD shoals eastward. As eddies propagate westward, the MLD shoals, shielding the water of low potential vorticity from the atmosphere. The southward eddy flow then carries the subducted water mass into the thermocline. The eddy subduction processes revealed here have important implications for designing field observations and improving models.

  1. Predicting the occurrence of mixed mode failure associated with hydraulic fracturing, part 2 water saturated tests

    SciTech Connect

    Bauer, Stephen J.; Broome, Scott Thomas; Choens, Charles; Barrow, Perry Carl

    2015-09-14

    Seven water-saturated triaxial extension experiments were conducted on four sedimentary rocks. This experimental condition was hypothesized more representative of that existing for downhole hydrofracture and thus it may improve our understanding of the phenomena. In all tests the pore pressure was 10 MPa and confirming pressure was adjusted to achieve tensile and transitional failure mode conditions. Using previous work in this LDRD for comparison, the law of effective stress is demonstrated in extension using this sample geometry. In three of the four lithologies, no apparent chemo-mechanical effect of water is apparent, and in the fourth lithology test results indicate some chemo-mechanical effect of water.

  2. Response of North Pacific eastern subtropical mode water to greenhouse gas versus aerosol forcing

    NASA Astrophysics Data System (ADS)

    Li, Xiang; Luo, Yiyong

    2016-04-01

    Mode water is a distinct water mass characterized by a near vertical homogeneous layer or low potential vorticity, and is considered essential for understanding ocean climate variability. Based on the output of GFDL CM3, this study investigates the response of eastern subtropical mode water (ESTMW) in the North Pacific to two different single forcings: greenhouse gases (GHGs) and aerosol. Under GHG forcing, ESTMW is produced on lighter isopycnal surfaces and is decreased in volume. Under aerosol forcing, in sharp contrast, it is produced on denser isopycnal surfaces and is increased in volume. The main reason for the opposite response is because surface ocean-to-atmosphere latent heat flux change over the ESTMW formation region shoals the mixed layer and thus weakens the lateral induction under GHG forcing, but deepens the mixed layer and thus strengthens the lateral induction under aerosol forcing. In addition, local wind changes are also favorable to the opposite response of ESTMW production to GHG versus aerosol.

  3. Potential energy and vibrational levels for local modes in water and acetylene

    NASA Astrophysics Data System (ADS)

    Wright, James S.; Donaldson, D. J.

    1985-03-01

    MRD Cl calculations are given for the potential energy along local X-H streching modes in water and acetylene, out to near dissolution. The Cl data points are accurately fitted by Morse functions up to half the well depth, but generalized (five-parameter) Morse functions are required to fit the whole range of data. The implications for the traetment of vibrational overtone levels are discussed, including a comparison of several treatments. Agreement with experimentally derived mode spectra is good, as is the agreement with bond distances and thermochemistry.

  4. Aspects of reproductive ecology and benthic-pelagic coupling in the sub-antarctic sea cucumber Pseudostichopus mollis (Theel)

    NASA Astrophysics Data System (ADS)

    Morgan, Andrew; Neal, Lance

    2012-07-01

    For deeper regions of the continental shelf environmental cues entraining reproduction in echinoderms are often absent, which contributes to adoption of continuous reproduction, having larger eggs, and a lecithotrophic mode of larval development. In the present study the sub-Antarctic sea cucumber Pseudostichopus mollis from the family Synallactidae was obtained during June (winter) and September (spring) from a depth of approximately 300 m north of the Auckland Islands in an area abundant in biogenic sediments. Samples were processed for body indices and gonad development. Features characteristic of non-continuous reproduction were exhibited. Although a larger egg size was found (212±14 μm), two distinct winter cohorts of oocytes occurred (41-81 and 161-201 μm) and body wall weight fluctuations (7.6% increase in males and 27.5% reduction in females) coincided with changes in gonad indices between sample dates. For males gonad as a proportion of body wall weight decreased from 3.31±0.9 to 2.11±0.37% and for females it increased from 1.59±0.28 to 2.5±0.30%. For both sample dates the gonad of males maintained mature spermatozoa whereas female gonad shifted from mainly recovery and growth of oocytes to growth and advanced growth of mature oocytes. In habitats with low or variable food availability intermittent reproduction is predicted as resources are too low for a high reproductive effort and too erratic for synchrony. A pattern of reproduction where fluctuations in seasonal organic input into an accumulated benthic food source initiates and synchronises gametogenesis for future spawning is proposed.

  5. Iron-limitation and high light stress on phytoplankton populations from the Australian Sub-Antarctic Zone (SAZ)

    NASA Astrophysics Data System (ADS)

    Petrou, Katherina; Hassler, Christel S.; Doblin, Martina A.; Shelly, Kirsten; Schoemann, Véronique; van den Enden, Rick; Wright, Simon; Ralph, Peter J.

    2011-11-01

    The high nutrient low chlorophyll (HNLC) surface waters of the Southern Ocean are characterised by high concentrations of nitrate and phosphate, low concentrations of dissolved iron and deep vertical mixing. Future climate scenarios predict increased surface temperatures and ocean stratification in the region. These changes to vertical mixing will result in a slowdown of nutrient supply to surface waters and an increase in the integrated irradiance in the upper mixed layer. To investigate the influence of iron-limitation and high irradiance on phytoplankton growth and physiology, a 6-day shipboard incubation experiment was conducted during the Sub-Antarctic Zone Sensitivity to Environmental Change (SAZ Sense) voyage using phytoplankton populations from the upper mixed layer in the north-eastern SAZ region. Iron-limitation was induced with an organic siderophore and was compared with a 1 nM iron-enriched incubation and an unamended treatment (under silicate replete conditions). As expected, iron enrichment led to dominance by large diatoms and enhanced photosynthetic performance, while the iron-limited community showed a decline in total chl a and photochemical efficiency. Under the added stress of high light, the iron-limited community was able to cope with the shift from in situ (<150 μmol photons m -2 s -1) to incubation (mean=765 μmol photons m -2 s -1) irradiance by increasing the proportion of photoprotective pigments and diverting excess light energy via energy-dependent quenching ( qE). The responses to iron-limitation under high light showed that the phytoplankton community was able to acclimate to these conditions, but exhibited an overall decline in photosynthetic activity. Data presented here suggest the community shifts, in particular the decrease in diatoms, and the decline in photosynthetic performance of phytoplankton under low iron-high irradiance conditions has the potential to impact future ocean productivity and biogeochemical cycling.

  6. Initial report on methane and carbon dioxide emission dynamics from sub-Antarctic freshwater ecosystems: A seasonal study of a lake and a reservoir.

    PubMed

    Gerardo-Nieto, Oscar; Astorga-España, María Soledad; Mansilla, Andrés; Thalasso, Frederic

    2017-03-22

    The sub-Antarctic Magellanic ecoregion is a part of the world where ecosystems have been understudied and where the CH4 cycling and emissions in lakes has not ever been reported. To fill that knowledge gap, a lake and a reservoir located at 53°S were selected and studied during three campaigns equally distributed over one year. Among the parameters measured were CH4 and CO2 emissions, as well their dissolved concentrations in the water column, which were determined with high spatial resolution. No ebullition was observed and the CH4 flux ranged from 0.0094 to 4.47mmolm(-2)d(-1) while the CO2 flux ranged from -22.95 to 35.68mmolm(-2)d(-1). Dissolved CH4 concentrations varied over more than four orders of magnitude (0.025-128.75μmolL(-1)), and the dissolved carbon dioxide ranged from below the detection limit of our method (i.e., 0.15μmolL(-1)) to 379.09μmolL(-1). The high spatial resolution of the methods used enabled the construction of bathymetric maps, surface contour maps of CH4 and CO2 fluxes, and transect contour maps of dissolved oxygen, temperature, and dissolved greenhouse gases. Overall, both lakes were net greenhouse gas producers and were not significantly different from temperate lakes located at a similar northern latitudes (53°N), except that ebullition was never observed in the studied sub-Antarctic lakes.

  7. Is the Oceanography of the New Zealand Subantarctic Region Responding to the Tropics?

    NASA Astrophysics Data System (ADS)

    Forcen-Vazquez, A. N.

    2016-02-01

    The Campbell Plateau, south of New Zealand plays an important role in New Zealand's regional climate and its oceanography may have a significant impact on fluctuations in fish stocks and marine mammal populations. It is located between the Subtropical and Subantarctic Fronts and exhibits marked variability over long time scales. It has been previously assumed, because of its location, that the Campbell Plateau oceanography is driven by Subantarctic and polar processes. Recent analysis, presented here, suggests this in not the case, and instead forcing comes from the tropics and subtropics. This is supported by positive correlations of Sea Level Anomalies (SLA) and Sea Surface Temperature (SST) with the Southern Oscillation Index (SOI) with SOI leading changes on the Campbell Plateau by two months for SLA and seven months for SST. Here we will present evidence of the similarity between the Campbell Plateau and the Tasman Sea SLA trends which suggests a closer relationship with the subtropical region. Satellite collected SLA data and SST from the last two decades are investigated to understand trends and long-term variability over the Campbell Plateau and its relationship with the surrounding open ocean, and other potential remote drivers of variability.

  8. Texture-based classification of sub-Antarctic vegetation communities on Heard Island

    NASA Astrophysics Data System (ADS)

    Murray, Humphrey; Lucieer, Arko; Williams, Raymond

    2010-06-01

    This study was the first to use high-resolution IKONOS imagery to classify vegetation communities on sub-Antarctic Heard Island. We focused on the use of texture measures, in addition to standard multispectral information, to improve the classification of sub-Antarctic vegetation communities. Heard Island's pristine and rapidly changing environment makes it a relevant and exciting location to study the regional effects of climate change. This study uses IKONOS imagery to provide automated, up-to-date, and non-invasive means to map vegetation as an important indicator for environmental change. Three classification techniques were compared: multispectral classification, texture based classification, and a combination of both. Texture features were calculated using the Grey Level Co-occurrence Matrix (GLCM). We investigated the effect of the texture window size on classification accuracy. The combined approach produced a higher accuracy than using multispectral bands alone. It was also found that the selection of GLCM texture features is critical. The highest accuracy (85%) was produced using all original spectral bands and three uncorrelated texture features. Incorporating texture improved classification accuracy by 6%.

  9. Foraging Behavior of Subantarctic Fur Seals Supports Efficiency of a Marine Reserve’s Design

    PubMed Central

    Kirkman, Stephen P.; Yemane, Dawit G.; Lamont, Tarron; Meÿer, Michael A.; Pistorius, Pierre A.

    2016-01-01

    Foraging behaviour of marine top predators is increasingly being used to identify areas of ecological importance. This is largely enabled by the ability of many such species to forage extensively in search of prey that is often concentrated in oceanographically productive areas. To identify important habitat in the Southern Indian Ocean within and around South Africa’s Prince Edward Islands’ Marine Protected Area (MPA), satellite transmitters were deployed on 12 lactating Subantarctic fur seals Arctocephalus tropicalis at Prince Edward Island (PEI) itself. Switching state space models were employed to correct ARGOS tracks and estimate behavioural states for locations along predicted tracks, namely travelling or area restricted search (ARS). A random forest model showed that distance from the study colony, longitude and distance from the Subantarctic Front were the most important predictors of suitable foraging habitat (inferred from ARS). Model-predicted suitable habitat occurred within the MPA in relatively close access to the colony during summer and autumn, but shifted northwards concurrently with frontal movements in winter and spring. The association of ARS with the MPA during summer-autumn was highly significant, highlighting the effectiveness of the recently declared reserve’s design for capturing suitable foraging habitat for this and probably other marine top predator species. PMID:27163373

  10. Analysis of spurious oscillation modes for the shallow water and Navier-Stokes equations

    USGS Publications Warehouse

    Walters, R.A.; Carey, G.F.

    1983-01-01

    The origin and nature of spurious oscillation modes that appear in mixed finite element methods are examined. In particular, the shallow water equations are considered and a modal analysis for the one-dimensional problem is developed. From the resulting dispersion relations we find that the spurious modes in elevation are associated with zero frequency and large wave number (wavelengths of the order of the nodal spacing) and consequently are zero-velocity modes. The spurious modal behavior is the result of the finite spatial discretization. By means of an artificial compressibility and limiting argument we are able to resolve the similar problem for the Navier-Stokes equations. The relationship of this simpler analysis to alternative consistency arguments is explained. This modal approach provides an explanation of the phenomenon in question and permits us to deduce the cause of the very complex behavior of spurious modes observed in numerical experiments with the shallow water equations and Navier-Stokes equations. Furthermore, this analysis is not limited to finite element formulations, but is also applicable to finite difference formulations. ?? 1983.

  11. Chemical reactions of water molecules on Ru(0001) induced by selective excitation of vibrational modes

    SciTech Connect

    Mugarza, Aitor; Shimizu, Tomoko K.; Ogletree, D. Frank; Salmeron, Miquel

    2009-05-07

    Tunneling electrons in a scanning tunneling microscope were used to excite specific vibrational quantum states of adsorbed water and hydroxyl molecules on a Ru(0 0 0 1) surface. The excited molecules relaxed by transfer of energy to lower energy modes, resulting in diffusion, dissociation, desorption, and surface-tip transfer processes. Diffusion of H{sub 2}O molecules could be induced by excitation of the O-H stretch vibration mode at 445 meV. Isolated molecules required excitation of one single quantum while molecules bonded to a C atom required at least two quanta. Dissociation of single H{sub 2}O molecules into H and OH required electron energies of 1 eV or higher while dissociation of OH required at least 2 eV electrons. In contrast, water molecules forming part of a cluster could be dissociated with electron energies of 0.5 eV.

  12. Effect of physisorption and chemisorption of water on resonant modes of rolled-up tubular microcavities

    PubMed Central

    2013-01-01

    Both blue- and redshifts of resonant modes are observed in the rolled-up Y2O3/ZrO2 tubular microcavity during a conformal oxide coating process. Our investigation based on spectral analyses suggests that there are two competitive processes during coating: desorption of both chemically and physically absorbed water molecules and increase of the tube wall thickness. The redshift is due to the increase of the wall thickness and corresponding light confinement enhancement. On the other hand, desorption of water molecules by heating leads to a blueshift. The balance of these two factors produces the observed bi-directional shift of the modes while they both contribute to promoted quality factor after coating. PMID:24344644

  13. Damage classification of pipelines under water flow operation using multi-mode actuated sensing technology

    NASA Astrophysics Data System (ADS)

    Lee, Changgil; Park, Seunghee

    2011-11-01

    In a structure, several types of damage can occur, ranging from micro-cracking to corrosion or loose bolts. This makes identifying the damage difficult with a single mode of sensing. Therefore, a multi-mode actuated sensing system is proposed based on a self-sensing circuit using a piezoelectric sensor. In self-sensing-based multi-mode actuated sensing, one mode provides a wide frequency-band structural response from the self-sensed impedance measurement and the other mode provides a specific frequency-induced structural wavelet response from the self-sensed guided wave measurement. In this experimental study, a pipeline system under water flow operation was examined to verify the effectiveness and robustness of the proposed structural health monitoring approach. Different types of structural damage were inflicted artificially on the pipeline system. To classify the multiple types of structural damage, supervised learning-based statistical pattern recognition was implemented by composing a three-dimensional space using the damage indices extracted from the impedance and guided wave features as well as temperature variations. For a more systematic damage classification, several control parameters were optimized to determine an optimal decision boundary for the supervised learning-based pattern recognition. Further research issues are also discussed for real-world implementations of the proposed approach.

  14. Upper tropospheric water vapour variability at high latitudes - Part 1: Influence of the annular modes

    NASA Astrophysics Data System (ADS)

    Sioris, C. E.; Zou, J.; Plummer, D. A.; Boone, C. D.; McElroy, C. T.; Sheese, P. E.; Moeini, O.; Bernath, P. F.

    2015-08-01

    Seasonal and monthly zonal medians of water vapour in the upper troposphere and lower stratosphere (UTLS) are calculated for both Atmospheric Chemistry Experiment (ACE) instruments for the northern and southern high-latitude regions (60-90 and 60-90° S). Chosen for the purpose of observing high-latitude processes, the ACE orbit provides sampling of both regions in eight of 12 months of the year, with coverage in all seasons. The ACE water vapour sensors, namely MAESTRO (Measurements of Aerosol Extinction in the Stratosphere and Troposphere Retrieved by Occultation) and the Fourier Transform Spectrometer (ACE-FTS) are currently the only satellite instruments that can probe from the lower stratosphere down to the mid-troposphere to study the vertical profile of the response of UTLS water vapour to the annular modes. The Arctic oscillation (AO), also known as the northern annular mode (NAM), explains 64 % (r = -0.80) of the monthly variability in water vapour at northern high-latitudes observed by ACE-MAESTRO between 5 and 7 km using only winter months (January to March 2004-2013). Using a seasonal timestep and all seasons, 45 % of the variability is explained by the AO at 6.5 ± 0.5 km, similar to the 46 % value obtained for southern high latitudes at 7.5 ± 0.5 km explained by the Antarctic oscillation or southern annular mode (SAM). A large negative AO event in March 2013 produced the largest relative water vapour anomaly at 5.5 km (+70 %) over the ACE record. A similarly large event in the 2010 boreal winter, which was the largest negative AO event in the record (1950-2015), led to > 50 % increases in water vapour observed by MAESTRO and ACE-FTS at 7.5 km.

  15. Upper tropospheric water vapour variability at high latitudes - Part 1: Influence of the annular modes

    NASA Astrophysics Data System (ADS)

    Sioris, Christopher E.; Zou, Jason; Plummer, David A.; Boone, Chris D.; McElroy, C. Thomas; Sheese, Patrick E.; Moeini, Omid; Bernath, Peter F.

    2016-03-01

    Seasonal and monthly zonal medians of water vapour in the upper troposphere and lower stratosphere (UTLS) are calculated for both Atmospheric Chemistry Experiment (ACE) instruments for the northern and southern high-latitude regions (60-90° N and 60-90° S). Chosen for the purpose of observing high-latitude processes, the ACE orbit provides sampling of both regions in 8 of 12 months of the year, with coverage in all seasons. The ACE water vapour sensors, namely MAESTRO (Measurements of Aerosol Extinction in the Stratosphere and Troposphere Retrieved by Occultation) and the Fourier Transform Spectrometer (ACE-FTS) are currently the only satellite instruments that can probe from the lower stratosphere down to the mid-troposphere to study the vertical profile of the response of UTLS water vapour to the annular modes. The Arctic oscillation (AO), also known as the northern annular mode (NAM), explains 64 % (r = -0.80) of the monthly variability in water vapour at northern high latitudes observed by ACE-MAESTRO between 5 and 7 km using only winter months (January to March, 2004-2013). Using a seasonal time step and all seasons, 45 % of the variability is explained by the AO at 6.5 ± 0.5 km, similar to the 46 % value obtained for southern high latitudes at 7.5 ± 0.5 km explained by the Antarctic oscillation or southern annular mode (SAM). A large negative AO event in March 2013 produced the largest relative water vapour anomaly at 5.5 km (+70 %) over the ACE record. A similarly large event in the 2010 boreal winter, which was the largest negative AO event in the record (1950-2015), led to > 50 % increases in water vapour observed by MAESTRO and ACE-FTS at 7.5 km.

  16. [A new type water supplement mode of urban wetland park and its effects in purification and ecology].

    PubMed

    Zhang, Li; Zhu, Xiao-dong; Chen, Jie; Zhu, Zhao-li; Pan, Tao; Li, Yang-fan

    2008-12-01

    With the Rosebush Wetland Park in Changzhou as a case, a new type water supplement mode for urban wetland park, i.e., "vertical-flow plus horizontal-flow", was constructed, and its effects in water purification, ecology, and economic advantages were evaluated. The results showed that this water supplement mode could not only improve the landscape of the water bodies in urban wetland park, but also enhance their quality, making it satisfy the requirement for human full-body exposure. Furthermore, the operation cost of the mode was as lower as 5%-25% of direct municipal pipe-water supply and other routine technique solutions, suggesting that this water supplement mode had potential positive ecological effects and economic advantages.

  17. Non-equilibrium thermodynamics and collective vibrational modes of liquid water in an inhomogeneous electric field.

    PubMed

    Wexler, Adam D; Drusová, Sandra; Woisetschläger, Jakob; Fuchs, Elmar C

    2016-06-28

    In this experiment liquid water is subject to an inhomogeneous electric field (∇(2)Ea≈ 10(10) V m(2)) using a high voltage (20 kV) point-plane electrode system. Using interferometry it was found that the application of a strong electric field gradient to water generates local changes in the refractive index of the liquid, polarizes the surface and creates a downward moving electro-convective jet. A maximum temperature difference of 1 °C is measured in the immediate vicinity of the point electrode. Raman spectroscopy performed on water reveals an enhancement of the vibrational collective modes (3250 cm(-1)) as well as an increase in the local mode (3490 cm(-1)) energy. This bimodal enhancement indicates that the spectral changes are not due to temperature changes. The intense field gradient thus establishes an excited subpopulation of vibrational oscillators far from thermal equilibrium. Delocalization of the collective vibrational mode spatially expands this excited population beyond the microscale. Hindered rotational freedom due to electric field pinning of molecular dipoles retards the heat flow and generates a chemical potential gradient. These changes are responsible for the observed changes in the refractive index and temperature. It is demonstrated that polar liquids can thus support local non-equilibrium thermodynamic transient states critical to biochemical and environmental processes.

  18. Characterization of the faecal bacterial community of wild young South American (Arctocephalus australis) and Subantarctic fur seals (Arctocephalus tropicalis).

    PubMed

    Medeiros, Aline Weber; Giongo, Adriana; Valdez, Fernanda P; Blaese de Amorin, Derek; Tavares, Maurício; d'Azevedo, Pedro A; Franco, Ana Claudia; Frazzon, Jeverson; Frazzon, Ana P G

    2016-03-01

    The microbiota of wild marine mammals is poorly understood, perhaps due to the migratory habits of some species and the difficulty in obtaining samples. Using high-throughput sequencing, the present study examines the faecal bacterial community of wild young South American (Arctocephalus australis) and Subantarctic fur seals (A. tropicalis). Faecal samples from South American (n = 6) and Subantarctic fur seals (n = 4) found dead along the south coast of Brazil were collected. Sequences were assigned to taxa using the Ribosomal Database Project-Bayesian classifier. Diversity of the microbiota was assessed by categorization of sequence reads into operational taxonomic units. Results indicate that Firmicutes (88.556%-84.016%) was the predominant phylum in South American and Subantarctic fur seals. The distribution of Actinobacteria and Proteobacteria varied according to the fur seal species. Fusobacteria and Bacteroidetes represented less than 1% of the sequences. The most abundant order in both fur seals was Clostridiales (88.64% and 87.49%). Individual variable incidences were observed in the composition of family among the fur seals, though the families Lachnospiraceae, Peptostreptococcaceae, Ruminococcaceae and Coriobacteriaceae were more prevalent. This study provides insight into the faecal bacterial community of wild young South American and Subantarctic fur seals.

  19. Connection between the Eastern Subtropical Mode Water in the South Pacific Ocean and the ENSO cycle

    NASA Astrophysics Data System (ADS)

    Li, Z.

    2012-12-01

    Water subducted in the subtropics is intimately linked to the circulation in the Tropics through the interior mass communication and/or the western boundary, and could potentially affect climate variability on interannual and decadal time scales (Gu and Philander, 1997). The interior mass communication rate between the subtropical and equatorial ocean can be quantified in different ways. For example, Huang and Wang (2001) proposed a method of using the Sverdrup function to quantify the communication rate. Their method is used here to compute the meridional transport function below the Ekman layer in order to investigate the direct communication from the eastern STMW to the equatorial Pacific, and study the connection between the eastern STMW and the ENSO cycle. The western subtropical mode water, however, is less likely to directly participate in the subtropical-tropical exchange because they are mainly formed and confined to the recirculation region of the western subtropical gyre (Ladd and Thompson, 2000). The variability of the Subtropical Mode Water (STMW) formation in the South Pacific Ocean from 1980 to 2004 is investigated in this study, using a high-resolution numerical model and a 3D Lagrangian trajectory model. Variations of subduction rate in the mode waters are closely linked to the El Niño-Southern Oscillation (ENSO) cycle. The eastern STMW could potentially affect the ENSO cycle through the interior communication window that was identified from the virtual streamfunction. Its location and width closely related to the ENSO cycle. The deep westward penetration of the western edge of the window at the equatorial Pacific is evident during the 1998 La Niña event.; Zonal location of the interior communication window for eastern STMW, when the subducted water parcels reach the equatorial Pacific at 10oS. Solid gray (black) line represents the western (eastern) edge of the window.

  20. Millennial Scale Events Of The Last 40 Ky In The South Atlantic: From The Tropics To The Subantarctic

    NASA Astrophysics Data System (ADS)

    Vazquez Riveiros, N.; Waelbroeck, C.; Arz, H. W.; Gottschalk, J.; Skinner, L. C.; Dokken, T. M.

    2015-12-01

    We present sub-millennially resolved time series from core MD08-3167, retrieved at 23°S and 1950 m water depth on the Namibian margin during 2008 RETRO cruise. At present, this region is characterised by upwelling of waters from 150-500 m depth. Stable isotopes (d18O and d13C) and Mg/Ca were measured on the planktonic foraminifer Globigerina bulloides, which may be assumed to thrive in upwelled waters. Stable isotopes were also measured on the benthic foraminifer Cibicides wuellerstorfi. Core MD08-3167 records were dated based on 23 14C dates covering the last 30 ky. These records are compared with new and published surface and deep water records from cores from the North-East Brazil margin (MD09-3257, 4.3°S, 2340 m, and MD09-3256Q, 3.33°S, 3537 m; Burckel et al., 2015) and the South Atlantic (core MD07-3076Q, 44°S, 3770 m; Gottschalk et al., 2015). Our comparison of surface records indicates that sea surface temperature increases, in phase with Antarctic warming during the Younger Dryas (YD), Heinrich Stadial (HS) 1 and HS4, took place everywhere in the South Atlantic, form equatorial Brazil to the Subantarctic region. In addition, the planktonic d18O records from the Namibian margin indicate that rapid changes in surface ocean circulation and upwelling intensity took place in that region at the beginning of HS1, possibly in response to sea-ice retreat around Antarctica and/or changes in the intensity or position of the westerlies. The deep water records show that water mass ventilation during the YD and Heinrich stadials in the South Atlantic was very similar between 1800 and 2900 m, but a chemical divide seems to be present below this depth before HS1. The comparison of these records demonstrates that the large ocean circulation changes observed during the YD and HS1 (e.g., Waelbroeck et al., 2011) also prevailed during preceding Heinrich stadials and are thus not characteristic of terminations.

  1. Biogeochemical flux and phytoplankton succession: A year-long sediment trap record in the Australian sector of the Subantarctic Zone

    NASA Astrophysics Data System (ADS)

    Wilks, Jessica V.; Rigual-Hernández, Andrés S.; Trull, Thomas W.; Bray, Stephen G.; Flores, José-Abel; Armand, Leanne K.

    2017-03-01

    The Subantarctic Zone (SAZ) plays a crucial role in global carbon cycling as a significant sink for atmospheric CO2. In the Australian sector, the SAZ exports large quantities of organic carbon from the surface ocean, despite lower algal biomass accumulation in surface waters than other Southern Ocean sectors. We present the first analysis of diatom and coccolithophore assemblages and seasonality, as well as the first annual quantification of bulk organic components of captured material at the base of the mixed layer (500 m depth) in the SAZ. Sediment traps were moored in the SAZ southwest of Tasmania as part of the long-term SAZ Project for one year (September 2003 to September 2004). Annual mass flux at 500 m and 2000 m was composed mainly of calcium carbonate, while biogenic silica made up on average <10% of material captured in the traps. Organic carbon flux was estimated at 1.1 g m-2 y-1 at 500 m, close to the estimated global mean carbon flux. Low diatom fluxes and high fluxes of coccoliths were consistent with low biogenic silica and high calcium carbonate fluxes, respectively. Diatoms and coccoliths were identified to species level. Diatom and coccolithophore sinking assemblages reflected some seasonal ecological succession. A theoretical scheme of diatom succession in live assemblages is compared to successional patterns presented in sediment traps. This study provides a unique, direct measurement of the biogeochemical fluxes and their main biological carbon vectors just below the winter mixed layer depth at which effective sequestration of carbon occurs. Comparison of these results with previous sediment trap deployments at the same site at deeper depths (i.e. 1000, 2000 and 3800 m) documents the changes particle fluxes experience in the lower ;twilight zone; where biological processes and remineralisation of carbon reduce the efficiency of carbon sequestration.

  2. A Nonlinear Coupled-Mode System for Water Waves over a General Bathymetry

    NASA Astrophysics Data System (ADS)

    Athanassoulis, G. A.; Belibassakis, K. A.

    2003-04-01

    In the present work we consider the problem of non-linear gravity waves propagating over a general bathymetry. The simpler two dimensional problem (one horizontal dimension) is first examined. An essential feature of this problem is that the wave field is not spatially periodic. Extra difficulties are introduced by the fact that we wish to drop the assumptions of smallness of the free-surface and bottom slope. The interaction of free-surface gravity waves with uneven bottom topography requires, in principle, the solution of a complicated nonlinear boundary value problem. Under the assumptions of incompressibility and irrotationality, the problem of evolution of water waves, over a variable bathymetry region, admits of at least two different varia-tional formulations: A Hamiltonian one, proposed by Petrov (1964) and exploited further by Zakharov (1968) and various other authors thenceforth, and an unconstrained one, proposed by Luke (1967). Our main concern herewith is to develop a non-linear theory for the case of a smooth, generally shaped bathymetry, without imposing any mild-slope type assumptions neither on the free-surface nor on the bottom boundary. The present development is based on Luke's variational principle, in which the admissible fields are free of essential conditions, except, of course, for the smoothness and completeness (compatibility) prerequisites. The vertical structure of the wave field is exactly represented by means of a modal-type series expansion of the wave potential (Athanassoulis and Belibassakis 2000). This series expansion contains the usual propagating and evanescent modes, plus two additional modes, called the free-surface mode and the sloping-bottom mode, introduced in order to consistently treat the non-vertical end-conditions at the free-surface and the bottom boundaries. A similar technique has been successfully applied to the solution of the linearised (Athanassoulis and Belibassakis 1999) and the second-order (Belibassakis and

  3. Origin, formation and variability of the Subpolar Mode Water located over the Reykjanes Ridge

    NASA Astrophysics Data System (ADS)

    de Boisséson, E.; Thierry, V.; Mercier, H.; Caniaux, G.; Desbruyères, D.

    2012-12-01

    The origin and formation of the Subpolar Mode Water (SPMW) located over the Reykjanes Ridge in the North-Atlantic Ocean and the variability of its properties over the period 1966-2004 are investigated through the use of a global eddy-permitting (1/4°) ocean/sea-ice model and a Lagrangian analysis tool. The SPMW is fed by subtropical and subpolar waters advected by the branches of the North-Atlantic Current. The SPMW acquires its properties when its source waters enter the winter mixed layer in the Iceland Basin. The SPMW temperature variability is mainly explained by variations of the relative contributions of the subtropical and subpolar water transports to the total transport. Compared to the 1966-2004 mean, lower (higher) subtropical water relative transport contribution leads to colder (warmer) SPMW in the early 1990s (in the late 1960s and late 1990s). The intensity of the winter convection in the Iceland basin also influences the SPMW temperature through the amount of relatively cold intermediate waters of subtropical origin integrated in the SPMW layer. Strong convection partly explains the cold SPMW of the early 1990s. The large increase in the SPMW temperature in the late 1990s is due to both a decrease in the winter convection and an increase in the relative transport of the subtropical waters.

  4. Modes of targets in water excited and identified using radiation pressure of modulated focused ultrasound

    NASA Astrophysics Data System (ADS)

    Daniel, Timothy; Fortuner, Auberry; Abawi, Ahmad; Kirsteins, Ivars; Marston, Philip

    2016-11-01

    The modulated radiation pressure (MRP) of ultrasound has been widely used to selectively excite low frequency modes of fluid objects. We previously used MRP to excite less compliant metallic object in water including the low frequency modes of a circular metal plate in water. A larger focused ultrasonic transducer allows us to drive modes of larger more-realistic targets. In our experiments solid targets are suspended by strings or supported on sand and the modulated ultrasound is focused on the target's surface. Target sound emissions were recorded and a laser vibrometer was used to measure the surface velocity of the target to give the magnitude of the target response. The source transducer was driven with a doublesideband suppressed carrier voltage as in. By varying the modulation frequency and monitoring target response, resonant frequencies can be measured and compared to finite element models. We also demonstrate the radiation torque of a focused first-order acoustic vortex beam associated with power absorption in the Stokes layer adjacent to a sphere. Funded by ONR.

  5. Conformational Changes of Trialanine in Water Induced by Vibrational Relaxation of the Amide I Mode.

    PubMed

    Bastida, Adolfo; Zúñiga, José; Requena, Alberto; Miguel, Beatriz; Candela, María Emilia; Soler, Miguel Angel

    2016-01-21

    Most of the protein-based diseases are caused by anomalies in the functionality and stability of these molecules. Experimental and theoretical studies of the conformational dynamics of proteins are becoming in this respect essential to understand the origin of these anomalies. However, a description of the conformational dynamics of proteins based on mechano-energetic principles still remains elusive because of the intrinsic high flexibility of the peptide chains, the participation of weak noncovalent interactions, and the role of the ubiquitous water solvent. In this work, the conformational dynamics of trialanine dissolved in water (D2O) is investigated through Molecular Dynamics (MD) simulations combined with instantaneous normal modes (INMs) analysis both at equilibrium and after the vibrational excitation of the C-terminal amide I mode. The conformational equilibrium between α and pPII conformers is found to be altered by the intramolecular relaxation of the amide I mode as a consequence of the different relaxation pathways of each conformer which modify the amount of vibrational energy stored in the torsional motions of the tripeptide, so the α → pPII and pPII → α conversion rates are increased differently. The selectivity of the process comes from the shifts of the vibrational frequencies with the conformational changes that modify the resonance conditions driving the intramolecular energy flows.

  6. Ascidian fauna (Tunicata, Ascidiacea) of subantarctic and temperate regions of Chile.

    PubMed

    Turon, Xavier; Cañete, Juan I; Sellanes, Javier; Rocha, Rosana M; López-Legentil, Susanna

    2016-03-21

    We studied the ascidian fauna from two zones located in subantarctic (Punta Arenas, latitude 53º) and temperate Chile (Coquimbo, latitude 29º). The different oceanographic features of the two zones, with influence of the Humboldt Current in the north and the Cape Horn Current System and freshwater inputs in the south, led to markedly different ascidian faunas. A total of 22 species were recorded, with no shared species across the two areas (11 species each). The new species Polyzoa iosune is described, Lissoclinum perforatum is found for the first time in the Pacific Ocean, and Synoicum georgianum and Polyzoa minor are new to the Chilean fauna. The populations of Ciona in the Coquimbo area (formerly attributed to Ciona intestinalis) correspond to the species Ciona robusta. A total of 35 Cytochrome oxidase (COI) sequences of the standard barcode region have been obtained for 17 of the 22 species reported.

  7. Track analysis of Oribatid mites (Acari: Oribatida) of the Subantarctic subregion of South America.

    PubMed

    Ruiz, Érica V; Romano, Gonzalo M; Morrone, Juan J

    2016-06-23

    We analysed distributional data of 30 species of Oribatid mites of the Subantarctic subregion of southern South America in order to contribute to elucidate their biotic evolution. We constructed individual tracks for the species analysed, based on published and unpublished records. After superposing them we obtained six generalized tracks and five nodes. Four generalized tracks (T2, T3, T4 and T6) extend along and near the Andean ranges, whereas two generalized tracks (T1 and T5) may be artefacts caused by the lack of information. The generalized tracks and nodes show the complex relationships of the austral biota, as hypothesized in previous contributions based on other plant and animal taxa.

  8. Daily accumulation rates of marine debris on sub-Antarctic island beaches.

    PubMed

    Eriksson, Cecilia; Burton, Harry; Fitch, Stuart; Schulz, Martin; van den Hoff, John

    2013-01-15

    The worlds' oceans contain a large but unknown amount of plastic debris. We made daily collections of marine debris stranded at two sub-Antarctic islands to establish (a) physical causes of strandings, and (b) a sampling protocol to better estimate the oceans' plastic loading. Accumulation rates at some beaches were dependent on tide and onshore winds. Most of the 6389 items collected were plastic (Macquarie 95%, Heard 94%) and discarded or lost fishing gear comprised 22% of those plastic items. Stalked barnacles (Lepas spp.) were a regular attachment on Macquarie debris but not at Heard Island. The daily accumulation rate of plastic debris on Macquarie Island was an order of magnitude higher than that estimated from monthly surveys during the same 4 months in the previous 5 years. This finding suggests that estimates of the oceans' plastic loading are an order of magnitude too low.

  9. Different adaptations of Chinese winter-over expeditioners during prolonged Antarctic and sub-Antarctic residence

    NASA Astrophysics Data System (ADS)

    Chen, Nan; Wu, Quan; Li, Hao; Zhang, Tao; Xu, Chengli

    2016-05-01

    Prolonged residence in Antarctica is characterized by exposure to isolated, confined, and extreme (ICE) environment. Winter-over expeditioners at research stations often exhibit a complex of psychophysiological symptoms, which varied by stations and sociocultural backgrounds. To understand the different patterns of psychophysiological responses provoked by environmental stress, we conducted a longitudinal assessment of mood and endocrine function in two groups of Chinese expeditioners who were deployed to sub-Antarctic (Great Wall Station, 62°S, N = 12) and Antarctic (Zhongshan Station, 66°S, N = 16) from December 2003 to 2005. Measures of mood, thyroid function, the levels of plasma catecholamine, and circulating interleukins were obtained at departure from China, mid-winter (Antarctica), end of winter (Antarctica), and return to China, respectively. The Zhongshan Station crew experienced significant increases in fatigue, anger, tension, confusion, and decrease in free thyroxine (FT4), norepinephrine (NE), and epinephrine (E) during the winter, increase in thyrotropin (TSH) and total triiodothyronine (TT3) when returning, whereas their counterparts at Great Wall Station only experienced increased TT3 after deployment. Moreover, compared with the Great Wall Station crew, the Zhongshan Station crew exhibited greater increase in anger, greater decrease in FT4, total thyroxine (TT4), NE and E over the winter, and greater increase in TSH when returning. Chinese expeditioners who lived and worked at the Antarctic station and the sub-Antarctic station for over a year showed different change patterns in mood and endocrine hormones. Negative mood and endocrine dysfunction were positively associated with the severity of environment. The study is a supplement to scientific knowledge on psychophysiological variation under ICE environment, which has certain applied value for the development of preventive countermeasures or interventions.

  10. Spatial variation in plant interactions across a severity gradient in the sub-Antarctic.

    PubMed

    le Roux, Peter C; McGeoch, Melodie A

    2008-04-01

    The stress-gradient hypothesis predicts that the intensity of interspecific positive interactions increases along environmental severity (i.e. stress and disturbance) gradients faster than the intensity of negative interactions. This study is the first to test if the stress-gradient hypothesis is supported for a location in the climatically extreme and species-poor sub-Antarctic. To do so, we investigate the fine-scale spatial distribution of plant species across altitude- and aspect-related abiotic severity gradients on a scoria cone on Marion Island. A clear altitudinal severity gradient was observed across the scoria cone, with lower temperatures, stronger winds and greater soil movement at higher altitudes. The altitudinal severity gradient was matched by stronger interspecific spatial association between the four dominant species at higher altitudes and in areas of lower vegetation cover. This suggests that, relative to the intensity of competition, the intensity of facilitation is greater under more severe conditions, supporting the stress-gradient hypothesis at the community level (i.e. for multiple pairs of species) and corroborating its usefulness for predicting variation in plant interactions at high latitudes and altitudes. Furthermore, the directional intraspecific aggregation and interspecific association plant cover patterns found within the gradient suggest that protection from the prevailing wind and from burial by loose substrate are the dominant facilitative mechanisms. Thus, plants benefit from the presence of neighbours when they provide shelter and substrate stability, and the relative intensity of this positive interaction is greatest at higher altitudes, and varies between species pairs. This study, therefore, not only provides support for the stress-gradient hypothesis in the sub-Antarctic, but also demonstrates fine-scale directional spatial patterns between multiple species nested within the severity gradient.

  11. Different adaptations of Chinese winter-over expeditioners during prolonged Antarctic and sub-Antarctic residence.

    PubMed

    Chen, Nan; Wu, Quan; Li, Hao; Zhang, Tao; Xu, Chengli

    2016-05-01

    Prolonged residence in Antarctica is characterized by exposure to isolated, confined, and extreme (ICE) environment. Winter-over expeditioners at research stations often exhibit a complex of psychophysiological symptoms, which varied by stations and sociocultural backgrounds. To understand the different patterns of psychophysiological responses provoked by environmental stress, we conducted a longitudinal assessment of mood and endocrine function in two groups of Chinese expeditioners who were deployed to sub-Antarctic (Great Wall Station, 62°S, N = 12) and Antarctic (Zhongshan Station, 66°S, N = 16) from December 2003 to 2005. Measures of mood, thyroid function, the levels of plasma catecholamine, and circulating interleukins were obtained at departure from China, mid-winter (Antarctica), end of winter (Antarctica), and return to China, respectively. The Zhongshan Station crew experienced significant increases in fatigue, anger, tension, confusion, and decrease in free thyroxine (FT4), norepinephrine (NE), and epinephrine (E) during the winter, increase in thyrotropin (TSH) and total triiodothyronine (TT3) when returning, whereas their counterparts at Great Wall Station only experienced increased TT3 after deployment. Moreover, compared with the Great Wall Station crew, the Zhongshan Station crew exhibited greater increase in anger, greater decrease in FT4, total thyroxine (TT4), NE and E over the winter, and greater increase in TSH when returning. Chinese expeditioners who lived and worked at the Antarctic station and the sub-Antarctic station for over a year showed different change patterns in mood and endocrine hormones. Negative mood and endocrine dysfunction were positively associated with the severity of environment. The study is a supplement to scientific knowledge on psychophysiological variation under ICE environment, which has certain applied value for the development of preventive countermeasures or interventions.

  12. Impact of hydrocarbons from a diesel fuel on the germination and early growth of subantarctic plants.

    PubMed

    Macoustra, Gabriella K; King, Catherine K; Wasley, Jane; Robinson, Sharon A; Jolley, Dianne F

    2015-07-01

    Special Antarctic Blend (SAB) is a diesel fuel dominated by aliphatic hydrocarbons that is commonly used in Antarctic and subantarctic regions. The past and present use of SAB fuel at Australia's scientific research stations has resulted in multiple spills, contaminating soils in these pristine areas. Despite this, no soil quality guidelines or remediation targets have been developed for the region, primarily due to the lack of established indigenous test species and subsequent biological effects data. In this study, twelve plant species native to subantarctic regions were collected from Macquarie Island and evaluated to determine their suitably for use in laboratory-based toxicity testing, using germination success and seedling growth (shoot and root length) as endpoints. Two soil types (low and high organic carbon (OC)) were investigated to reflect the variable OC content found in soils on Macquarie Island. These soils were spiked with SAB fuel and aged for 14 days to generate a concentration series of SAB-contaminated soils. Exposure doses were quantified as the concentration of total petroleum hydrocarbons (TPH, nC9-nC18) on a soil dry mass basis. Seven species successfully germinated on control soils under laboratory conditions, and four of these species (Colobanthus muscoides Hook.f., Deschampsia chapmanii Petrie, Epilobium pendunculare A.Cunn. and Luzula crinita Hook.f.) showed a dose-dependent inhibition of germination when exposed to SAB-contaminated soils. Contaminated soils with low OC were generally more toxic to plants than high organic carbon soils. Increasing soil-TPH concentrations significantly inhibited shoot and root growth, and root length was identified as the most sensitive endpoint. Although the test species were tolerant to SAB-contaminated soils in germination assays, development of early life stages (up to 28 days) were generally more sensitive indicator of exposure effects, and may be more useful endpoints for future testing.

  13. Parametric Reconstruction of Water Vapour Accumulation Modes in the Western and the Eastern Mediterranean Basins

    NASA Astrophysics Data System (ADS)

    Palau, J. L.; Rovira, F.; Millan, M.

    2009-09-01

    The Mediterranean Sea acts as a source of heat and moisture for the surrounding regions, but not only because it is a closed and warm sea. The Mediterranean Basin is located in the mid-latitudes (i.e., high solar insolation), and it is almost completely surrounded by mountains. Moreover, from a meteorological point of view, the Mediterranean Basin can be regarded as two well-differentiated sub-basins: The Western Mediterranean Basin, where the prevailing synoptic conditions are associated with the Azores High Pressure system; and the Eastern Mediterranean Basin, which is under the influence of the Middle-East monsoon low-pressure system. The combination of all these features enables strong evapotranspiration with lower ventilation conditions (especially on the Western side) than in other geographical areas of the world (e.g., areas under the direct influence of the Atlantic Ocean). As a result, there are different water vapour "accumulation modes” on both sides of the Mediterranean Basin. The determination of the main atmospheric accumulation modes and their seasonal variability on both sides of the Mediterranean Basin is a relevant issue for integrating some of the feedbacks driving climate change, e.g., precipitation regimes, secondary pollutant production, ventilation conditions, etc. This study focuses on the total water vapour accumulation modes found on both sides of the Mediterranean Basin throughout the year. The data used in this study come from the most recent EOS satellite missions. Specifically, this investigation analyses the nine-year time series of water vapour data measured by the MODIS instrument (MODerate Resolution Imaging Spectroradiometer) on board the TERRA (EOS AM-1) satellite. Annual evolution (2000-2008) and seasonality of the total precipitable water column are analysed in both the Western and the Eastern Mediterranean Basins. After carrying out the parametric reconstruction of the water vapour time series, we have obtained their

  14. Four Years of North Pacific Mode Water Evolution: A Fukushima Tracer Perspective

    NASA Astrophysics Data System (ADS)

    Macdonald, Alison M.; Yoshida, Sachiko; Pike, Steven; Buesseler, Ken O.; Rypina, Irina I.; Jayne, Steven

    2017-04-01

    Here we presents the results of a investigation which uses the tracer information provided by the 2011 direct ocean release of radio-isotopes, (137Cs, 30-year half-life and 134Cs, 2-year half-life) from the Fukushima Daiichi nuclear power plant to better understand the pathways, mixing and transport of water in the North Pacific Ocean. The main focus is the analysis of cesium observations obtained from the spring 2015 CLIVAR/GO-SHIP occupation of the P16N line in the eastern North Pacific. Nearly four hundred 20 L radionuclide samples were obtained on this cruise between 29 April and 26 June 2015 covering the 152°W line from 3°N to the Alaskan Shelf off Kodiak (56.4°N), crossing the Alaska Gyre at 55°N and making a short (200 nm) line extending from the outer edge of U.S. EEZ coming into Seattle, just to the south of the Canadian border and Line-P. Samples include both profiles from the surface to 1000 m and surface/subsurface pairs that provide an average 1° latitude spacing along 152°W. A clear Fukushima signal is apparent from the surface down to 400 m. The core signal lies at between 0-200 m at about 40°N where Subtropical Mode Water density water outcrops. The densest waters with Fukushima isotopes lie at 440 m in the bottom density range of Dense-Central Mode Water. There is a weak, but detectable signal in the Alaska Current to the north off both Kodiak and Sitka. The deepest detectable 137Cs (weapon's testing) signals are found at and to the north of 45°N at 900-1000 m. There is detectable, background level 137Cs as far south as 3°N, but as of spring 2015 the southernmost 134C signal was found above 200 m at 30°N. This horizontal and vertical pattern of Fukushima radionuclides traces the path of mode waters from their formation regions in the western North Pacific to their outcrop in eastern basin over the four years since their release.

  15. STOMP Sparse Vegetation Evapotranspiration Model for the Water-Air-Energy Operational Mode

    SciTech Connect

    Ward, Anderson L.; White, Mark D.; Freeman, Eugene J.; Zhang, Z. F.

    2005-09-15

    The Water-Air-Energy (WAE) Operational Mode of the Subsurface Transport Over Multiple Phases (STOMP) numerical simulator solves the coupled conservation equations for water mass, air mass, and thermal energy in multiple dimensions. This addendum describes the theory, input file formatting, and application of a soil-vegetation-atmosphere transfer (SVAT) scheme for STOMP that is based on a sparse vegetation evapotranspiration model. The SVAT scheme is implemented as a boundary condition on the upper surface of the computational domain and has capabilities for simulating evaporation from bare surfaces as well as evapotranspiration from sparsely vegetated surfaces populated with single or multiple plant species in response to meteorological forcings. With this extension, the model calculates water mass, air mass and thermal energy across a boundary surface in addition to root-water transport between the subsurface and atmosphere. This mode represents the barrier extension of the WAE mode and is designated as STOMP-WAE-B. Input for STOMP-WAE-B is specified via three input cards and include: atmospheric conditions through the Atmospheric Conditions Card; time-invariant plant species data through the Plant Properties Card; and time varying plant species data through the Boundary Conditions Card. Two optional cards, the Observed Data and UCODE Control Cards allow use of STOMP-WAE with UCODE in an inverse mode to estimate model parameters. STOMP-WAE was validated by solving a number of test problems from the literature that included experimental observations as well as analytical or numerical solutions. Several of the UNSAT-H verification problems are included along with a benchmark simulation derived from a recently published intercode comparison for barrier design tools. Results show that STOMP is able to meet, and in most cases, exceed performance of other commonly used simulation codes without having to resort to may of their simplifying assumptions. Use of the fully

  16. Controlled cytotoxicity of plasma treated water formulated by open-air hybrid mode discharge

    NASA Astrophysics Data System (ADS)

    Lu, P.; Boehm, D.; Cullen, P.; Bourke, P.

    2017-06-01

    Plasma treated liquids (PTLs) provide a means to convey a broad range of effects of relevance for food, environmental, or clinical decontamination, plant growth promotion, and therapeutic applications. Devising the reactive species ingredients and controlling the biological response of PTLs are of great interest. We demonstrate an approach by using an open-air hybrid mode discharge (HMD) to control the principal reactive species composition within plasma treated water (PTW), which is then demonstrated to regulate the cytotoxicity of PTW. The cytotoxicity of HMD produced PTW demonstrates a non-monotonic change over the discharge time. Although hydrogen peroxide and nitrite are not the sole effectors for cell death caused by PTW, using them as principal reactive species indicators, cytotoxicity can be removed and/or enhanced by formulating their concentrations and composition through adjusting the discharge mode and time on-line during PTW generation without the addition of additional working gas or chemical scavengers. This work demonstrates that a hybrid mode discharge can be employed to generate a PTW formulation to control a biological response such as cytotoxicity. This provides insights into how plasma treated liquids may be harnessed for biological applications in a specific and controllable manner.

  17. Mode coupling theory and fragile to strong transition in supercooled TIP4P/2005 water

    NASA Astrophysics Data System (ADS)

    De Marzio, M.; Camisasca, G.; Rovere, M.; Gallo, P.

    2016-02-01

    We study by molecular dynamics simulations supercooled water with the TIP4P/2005 potential. This model is able to predict many properties of water in a large range of the thermodynamic space in agreement with experiments. We explore the dynamical behavior and, in particular, the self intermediate scattering function of the oxygen atoms. We find that the structural relaxation in the range of mild supercooling is in agreement with the Mode Coupling Theory (MCT). The ideal MCT crossover takes place at decreasing temperature with increasing density. Deviations from the MCT behavior are found upon further supercooling. A crossover from the MCT, fragile, regime to a strong, Arrhenius, regime is found and it is connected to the presence of a liquid-liquid phase transition and the Widom line emanating from the liquid-liquid critical point.

  18. Mode coupling and fragile to strong transition in supercooled TIP4P water

    NASA Astrophysics Data System (ADS)

    Gallo, P.; Rovere, M.

    2012-10-01

    We consider one of the most used model for water, the rigid four site TIP4P potential, and we study by molecular dynamics simulation the dynamical properties of the liquid upon supercooling. In the previous studies of the thermodynamics of the TIP4P model a liquid-liquid critical point (LLCP) located at the end of the coexistence between the low density liquid (LDL) and the high density liquid (HDL) of water was found. We present here the analysis of the self intermediate scattering functions in a large range of temperatures and densities and we show that the structural relaxation in the region of mild supercooling is in agreement with the predictions of the mode coupling theory. In the more deep supercooled region we observe that the α-relaxation time deviates from the mode coupling theory (MCT) trend and a crossover takes place from a fragile to a strong behavior upon crossing the Widom line emanating from the LLCP. The HDL and the LDL phases are associated with the fragile and the strong behavior, respectively.

  19. A short-term sink for atmospheric CO2 in subtropical mode water of the North Atlantic Ocean.

    PubMed

    Bates, Nicholas R; Pequignet, A Christine; Johnson, Rodney J; Gruber, Nicolas

    2002-12-05

    Large-scale features of ocean circulation, such as deep water formation in the northern North Atlantic Ocean, are known to regulate the long-term physical uptake of CO2 from the atmosphere by moving CO2-laden surface waters into the deep ocean. But the importance of CO2 uptake into water masses that ventilate shallower ocean depths, such as subtropical mode waters of the subtropical gyres, are poorly quantified. Here we report that, between 1988 and 2001, dissolved CO2 concentrations in subtropical mode waters of the North Atlantic have increased at a rate twice that expected from these waters keeping in equilibrium with increasing atmospheric CO2. This accounts for an extra 0.4-2.8 Pg C (1 Pg = 10(15) g) over this period (that is, about 0.03-0.24 Pg C yr(-1)), equivalent to 3-10% of the current net annual ocean uptake of CO2 (ref. 3). We suggest that the lack of strong winter mixing events, to greater than 300 m in depth, in recent decades is responsible for this accumulation, which would otherwise disturb the mode water layer and liberate accumulated CO2 back to the atmosphere. However, future climate variability (which influences subtropical mode water formation) and changes in the North Atlantic Oscillation (leading to a return of deep winter mixing events) may reduce CO2 accumulation in subtropical mode waters. We therefore conclude that, although CO2 uptake by subtropical mode waters in the North Atlantic--and possibly elsewhere--does not always represent a long-term CO2 sink, the phenomenon is likely to contribute substantially to interannual variability in oceanic CO2 uptake.

  20. Aerated biofilter with seasonally varied operation modes for the production of irrigation water.

    PubMed

    Meda, A; Cornel, P

    2010-01-01

    Water reuse for agricultural irrigation can contribute to the conservation of valuable water resources and opens the possibility to reuse the wastewater's nutrients (N and P) at the same time. As irrigation is usually limited to vegetation periods, effluent requirements for treated wastewater may vary seasonally. A process concept for wastewater treatment with variable operation modes for the seasonal production of nutrient-rich irrigation water and nutrient-poor discharge water is proposed. It is shown that a two-step process consisting of organics removal followed by biological aerated filters (biofilters) for nitrogen removal is a promising combination which allows a flexible and seasonally varied operation with a fast re-start of biological nitrification after shut-down periods. To date, there is no commonly accepted practice amongst operators to take biofilters out of service for periods of time while - at the same time - maintaining biological activity to enable a quick start-up. This paper shows that during shut-down periods the activity drop rate is the smallest if the filter bed is maintained flooded and without aeration; then a very quick re-start is possible.

  1. Failure Mode of the Water-filled Fractures under Hydraulic Pressure in Karst Tunnels

    NASA Astrophysics Data System (ADS)

    Dong, Xin; Lu, Hao; Huang, Houxu; Hao, Yiqing; Xia, Yuanpu

    2017-06-01

    Water-filled fractures continue to grow after the excavation of karst tunnels, and the hydraulic pressure in these fractures changes along with such growth. This paper simplifies the fractures in the surrounding rock as flat ellipses and then identifies the critical hydraulic pressure values required for the occurrence of tensile-shear and compression-shear failures in water-filled fractures in the case of plane stress. The occurrence of tensile-shear fracture requires a larger critical hydraulic pressure than compression-shear failure in the same fracture. This paper examines the effects of fracture strike and lateral pressure coefficient on critical hydraulic pressure, and identifies compression-shear failure as the main failure mode of water-filled fractures. This paper also analyses the hydraulic pressure distribution in fractures with different extensions, and reveals that hydraulic pressure decreases along with the continuous growth of fractures and cannot completely fill a newly formed fracture with water. Fracture growth may be interrupted under the effect of hydraulic tensile shear.

  2. Inferential monitoring of chlorinated solvents through Raman spectroscopic observation of the vibrational modes of water.

    PubMed

    Sinfield, Joseph V; Monwuba, Chike

    2016-02-01

    Recent improvements in diode laser, fiber optic, and data acquisition technology have rejuvenated interest in field applications of Raman spectroscopy in a wide range of settings. One such application involves the observation of chlorinated solvents to facilitate the practice of "monitored natural attenuation." In this context, this manuscript focuses on means to improve the sensitivity of in-situ Raman analysis of chlorinated solvents. In particular, the work explores the performance limits of a Time-Resolved Raman Spectroscopy (TRRS) system employed to observe chlorinated solvents in aqueous samples via laboratory tests conducted on both liquid standards of trichloroethylene (TCE) and simulated biodegraded field samples. Quantitative assessment of TCE in solution is carried out through both direct observation of TCE Raman functional groups (381 cm(-1) (δ skeletal), 840 cm(-1) (νCCl) and 1242 cm(-1) (δCH)) and indirect observation of the broad OH stretching (2700-3800 cm(-1)) Raman modes of water. Results from tests on simple solutions show that the TRRS system can detect TCE at aqueous concentrations as low as 70 ppm by directly monitoring the 381 cm(-1) TCE line, whereas observation of the OH stretching line of water (3393 cm(-1)) provides an indirect indication of TCE presence with nearly a 9× improvement in detection level. This unique and counterintuitive mechanism to detect the presence of chlorinated compounds in solution takes advantage of the influence of chlorine on the vibrational modes of water. This influence, which is believed to be attributed to the formation of hydrogen bonds and their resultant interactions with the solvation shell, may serve as a more sensitive and robust indication of the presence of aggregate chlorinated solvent contamination in aqueous systems. Tests performed on simulated biodegraded field samples demonstrate that the indirect detection mechanism is apparent even in complex samples representative of typical field

  3. Water reclamation from emulsified oily wastewater via effective forward osmosis hollow fiber membranes under the PRO mode.

    PubMed

    Han, Gang; de Wit, Jos S; Chung, Tai-Shung

    2015-09-15

    By using a novel hydrophilic cellulose acetate butyrate (CAB) as the membrane material for the hollow fiber substrate and modifying its outer surface by polydopamine (PDA) coating and inner surface by interfacial polymerization, we have demonstrated that the thin-film composite (TFC) membranes can be effectively used for sustainable water reclamation from emulsified oil/water streams via forward osmosis (FO) under the pressure retarded osmosis (PRO) mode. The newly developed TFC-FO hollow fiber membrane shows characteristics of high water flux, outstanding salt and oil rejection, and low fouling propensity. Under the PRO mode, the newly developed TFC-FO membrane exhibits a water flux of 37.1 L m(-2) h(-1) with an oil rejection of 99.9% using a 2000 ppm soybean oil/water emulsion as the feed and 1 M NaCl as the draw solution. Remarkable anti-fouling behaviors have also been observed. Under the PRO mode, the water flux decline is only 10% of the initial value even after a 12 h test for oil/water separation. The water flux of the fouled membrane can be effectively restored to 97% of the original value by water rinses on the fiber outer surface without using any chemicals. Furthermore, the flux declines are only 25% and 52% when the water recovery of a 2000 ppm soybean oil/water emulsion and a 2000 ppm petroleum oil/water emulsion containing 0.04 M NaCl reaches 82%, respectively. This study may not only provide insightful guidelines for the fabrication of effective TFC-FO membranes with high performance and low fouling behaviors for oily wastewater under the PRO mode but also add an alternative perspective to the design of new materials for water purification purposes. Copyright © 2015 Elsevier Ltd. All rights reserved.

  4. Generation of real-time mode high-resolution water vapor fields from GPS observations

    NASA Astrophysics Data System (ADS)

    Yu, Chen; Penna, Nigel T.; Li, Zhenhong

    2017-02-01

    Pointwise GPS measurements of tropospheric zenith total delay can be interpolated to provide high-resolution water vapor maps which may be used for correcting synthetic aperture radar images, for numeral weather prediction, and for correcting Network Real-time Kinematic GPS observations. Several previous studies have addressed the importance of the elevation dependency of water vapor, but it is often a challenge to separate elevation-dependent tropospheric delays from turbulent components. In this paper, we present an iterative tropospheric decomposition interpolation model that decouples the elevation and turbulent tropospheric delay components. For a 150 km × 150 km California study region, we estimate real-time mode zenith total delays at 41 GPS stations over 1 year by using the precise point positioning technique and demonstrate that the decoupled interpolation model generates improved high-resolution tropospheric delay maps compared with previous tropospheric turbulence- and elevation-dependent models. Cross validation of the GPS zenith total delays yields an RMS error of 4.6 mm with the decoupled interpolation model, compared with 8.4 mm with the previous model. On converting the GPS zenith wet delays to precipitable water vapor and interpolating to 1 km grid cells across the region, validations with the Moderate Resolution Imaging Spectroradiometer near-IR water vapor product show 1.7 mm RMS differences by using the decoupled model, compared with 2.0 mm for the previous interpolation model. Such results are obtained without differencing the tropospheric delays or water vapor estimates in time or space, while the errors are similar over flat and mountainous terrains, as well as for both inland and coastal areas.

  5. Spectroscopic identification of ethanol-water conformers by large-amplitude hydrogen bond librational modes

    SciTech Connect

    Andersen, J.; Wugt Larsen, R.; Heimdal, J.

    2015-12-14

    The far-infrared absorption spectra have been recorded for hydrogen-bonded complexes of water with ethanol embedded in cryogenic neon matrices at 2.8 K. The partial isotopic H/D-substitution of the ethanol subunit enabled by a dual inlet deposition procedure enables the observation and unambiguous assignment of the intermolecular high-frequency out-of-plane and the low-frequency in-plane donor OH librational modes for two different conformations of the mixed binary ethanol/water complex. The resolved donor OH librational bands confirm directly previous experimental evidence that ethanol acts as the O⋯HO hydrogen bond acceptor in the two most stable conformations. In the most stable conformation, the water subunit forces the ethanol molecule into its less stable gauche configuration upon dimerization owing to a cooperative secondary weak O⋯HC hydrogen bond interaction evidenced by a significantly blue-shift of the low-frequency in-plane donor OH librational band origin. The strong correlation between the low-frequency in-plane donor OH librational motion and the secondary intermolecular O⋯HC hydrogen bond is demonstrated by electronic structure calculations. The experimental findings are further supported by CCSD(T)-F12/aug-cc-pVQZ calculations of the conformational energy differences together with second-order vibrational perturbation theory calculations of the large-amplitude donor OH librational band origins.

  6. Comparison of different tracking algorithms analysing subantarctic cyclones: A contribution to the IMILAST programme

    NASA Astrophysics Data System (ADS)

    Grieger, Jens; Leckebusch, Gregor C.; Raible, Christoph C.; Rudeva, Irina; Simmonds, Ian

    2015-04-01

    Cyclones are a dominant feature of the mid- and high-latitude atmospheric circulation, however their definition is not straightforward as their characteristics are complex. Thus, a number of studies present different objective cyclone detection and tracking algorithms focusing on different aspects of what is thought to be the main characteristic of a cyclone. For example, studies use either the rotational character of cyclones by using the vorticity as main field to identify cyclones or the mass character by using the pressure field. In this study, 14 different objective identification and tracking algorithms are compared by analyzing subantarctic cyclones. This region is of especial interest because it hosts the greatest frequencies of cyclogenesis and cyclone occurrence across the whole Southern Hemisphere. The character of cyclones there are strongly influenced by the intense baroclinicity and the presence of the Antarctic massif. The study is part of the Intercomparison of Mid Latitude STorm diagnostics (IMILAST) project. As a common basis ERA-Interim reanalysis data between 1979-2008 is used. This contribution investigates the output of the different tracking algorithms for the representation of extra-tropical cyclones around Antarctica, and all cyclone tracks south of 60° S are selected. We focus on three sectors around Antarctica, namely East Antarctica, Amundsen-Bellingshausen Seas, and Weddell Sea, for a differentiated comparison of the different tracking methodologies. A track-to-track analysis allows the evaluation of differences and similarities of the methodologies for the representation of subantarctic cyclones. As known from similar studies for the entire Southern Hemisphere, absolute numbers of identified cyclone tracks differ significantly. This is also the case for all sectors around Antarctica. Differences are even more pronounced in austral winter (JJA) due to the different treatment of cyclone intensities by the numerous tracking methods

  7. Phytoremediation of hydrocarbon contaminants in subantarctic soils: an effective management option.

    PubMed

    Bramley-Alves, Jessica; Wasley, Jane; King, Catherine K; Powell, Shane; Robinson, Sharon A

    2014-09-01

    Accidental fuel spills on world heritage subantarctic Macquarie Island have caused considerable contamination. Due to the island's high latitude position, its climate, and its fragile ecosystem, traditional methods of remediation are unsuitable for on-site clean up. We investigated the tolerance of a subantarctic native tussock grass, Poa foliosa (Hook. f.), to Special Antarctic Blend (SAB) diesel fuel and its potential to reduce SAB fuel contamination via phytoremediation. Toxicity of SAB fuel to P. foliosa was assessed in an 8 month laboratory growth trial under growth conditions which simulated the island's environment. Single seedlings were planted into 1 L pots of soil spiked with SAB fuel at concentrations of 1000, 5 000, 10,000, 2000 and 40,000 mg/kg (plus control). Plants were harvested at 0, 2, 4 and 8 months and a range of plant productivity endpoints were measured (biomass production, plant morphology and photosynthetic efficiency). Poa foliosa was highly tolerant across all SAB fuel concentrations tested with respect to biomass, although higher concentrations of 20,000 and 40,000 mg SAB/kg soil caused slight reductions in leaf length, width and area. To assess the phytoremediation potential of P. foliosa (to 10 000 mg/kg), soil from the planted pots was compared with that from paired unplanted pots at each SAB fuel concentration. The effect of the plant on SAB fuel concentrations and the associated microbial communities found within the soil (total heterotrophs and hydrocarbon degraders) were compared between planted and unplanted treatments at the 0, 2, 4 and 8 month harvest periods. The presence of plants resulted in significantly less SAB fuel in soils at 2 months and a return to background concentration by 8 months. Microbes did not appear to be the sole driving force behind the observed hydrocarbon loss. This study provides evidence that phytoremediation using P. foliosa is a valuable remediation option for use at Macquarie Island, and may be

  8. Solving Two-Mode Shallow Water Equations Using Finite Volume Methods

    NASA Astrophysics Data System (ADS)

    Cheng, Y.

    2015-12-01

    We develop and study numerical methods for the two-mode shallow water equations recently proposed in [S. STECHMANN, A. MAJDA, and B. KHOUIDER, Theor. Comput. Fluid Dynamics, 22 (2008), pp. 407-432]. Designing a reliable numerical method for this system is a challenging task due to its conditional hyperbolicity and the presence of nonconservative terms. We present several numerical approaches — two operator splitting methods (based on either Roe-type upwind or central-upwind scheme), a central-upwind scheme and a path-conservative central-upwind scheme — and test their performance in a number of numerical experiments. The obtained results demonstrate that a careful numerical treatment of nonconservative terms is crucial for designing a robust and highly accurate numerical method. This is a joint work with M. J. Castro Díaz, A. Chertock and A. Kurganov.

  9. High frequency normal mode statistics in a shallow water waveguide: the effect of random linear internal waves.

    PubMed

    Raghukumar, Kaustubha; Colosi, John A

    2014-07-01

    Using transport theory and Monte Carlo numerical simulation, the statistical properties of mode propagation at a frequency of 1 kHz are studied in a shallow water environment with random sound-speed perturbations from linear internal waves. The environment is typical of summer conditions in the mid-Atlantic bight during the Shallow Water 2006 experiment. Observables of interest include the second and fourth moments of the mode amplitudes, which are relevant to full-field mean intensity and scintillation index. It is found that mode phase randomization has a strong adiabatic component while at the same time mode coupling rates are significant. As a consequence, a computationally efficient transport theory is presented, which models cross-mode correlation adiabatically, but accounts for mode coupling using the mode energy equations of Creamer [(1996). J. Acoust. Soc. Am. 99, 2825-2838]. The theory also has closed-form expressions for the internal wave scattering matrix and a correction for an edge effect. The hybrid transport theory is shown to accurately reproduce many statistical quantities from the Monte Carlo simulations.

  10. [Effects of different water-saving irrigation modes on chestnut growth and fruiting in drought hilly land].

    PubMed

    Tian, Shou-Le; Shen, Guang-Ning; Xu, Lin; Sun, Xiao-Li

    2012-03-01

    Taking the chestnut trees in a semi-arid and semi-humid hilly orchard of Tai' an, Shandong Province of East China as test objects, a field experiment was conducted to study the effects of different water-saving irrigation modes (pottery jar storing water, small hole storing water, and border irrigation with covering) on the soil moisture characteristics and the growth, fruiting, and development of chestnut roots. Comparing with the control (border irrigation), all the three water-saving irrigation modes could prolong the period of soil keeping moist, and the best effect came from pottery, jar treatment, with the soil keeping moist for 32 days, 13 days longer than the control. Under water-saving irrigations, the bearing branches length and number, leaf area and mass, and shoot mixed buds all increased obviously. Both pottery jar storing water and small hole storing water could irrigate deeper roots and induce root growth in deeper soil layers, and thus, relieve the drought stress on superficial roots. The three water-saving irrigation modes could increase chestnut yield markedly, with an increment of 18.8%, 16.5%, and 14.2%, respectively, as compared with the control.

  11. Understanding diversity patterns in bacterioplankton communities from a sub-Antarctic peatland.

    PubMed

    Quiroga, María Victoria; Valverde, Angel; Mataloni, Gabriela; Cowan, Don

    2015-06-01

    Bacterioplankton communities inhabiting peatlands have the potential to influence local ecosystem functions. However, most microbial ecology research in such wetlands has been done in ecosystems (mostly peat soils) of the Northern Hemisphere, and very little is known of the factors that drive bacterial community assembly in other regions of the world. In this study, we used high-throughput sequencing to analyse the structure of the bacterial communities in five pools located in a sub-Antarctic peat bog (Tierra del Fuego, Argentina), and tested for relationships between bacterial communities and environmental conditions. Bacterioplankton communities in peat bog pools were diverse and dominated by members of the Proteobacteria, Actinobacteria, Bacteroidetes and Verrucomicrobia. Community structure was largely explained by differences in hydrological connectivity, pH and nutrient status (ombrotrophic versus minerotrophic pools). Bacterioplankton communities in ombrotrophic pools showed phylogenetic clustering, suggesting a dominant role of deterministic processes in shaping these assemblages. These correlations between habitat characteristics and bacterial diversity patterns provide new insights into the factors regulating microbial populations in peatland ecosystems.

  12. Metagenomic Survey of Viral Diversity Obtained from Feces of Subantarctic and South American Fur Seals

    PubMed Central

    Kluge, Mariana; Campos, Fabrício Souza; Tavares, Maurício; de Amorim, Derek Blaese; Valdez, Fernanda Pedone; Giongo, Adriana; Roehe, Paulo Michel; Franco, Ana Claudia

    2016-01-01

    The Brazilian South coast seasonally hosts numerous marine species, observed particularly during winter months. Some animals, including fur seals, are found dead or debilitated along the shore and may harbor potential pathogens within their microbiota. In the present study, a metagenomic approach was performed to evaluate the viral diversity in feces of fur seals found deceased along the coast of the state of Rio Grande do Sul. The fecal virome of two fur seal species was characterized: the South American fur seal (Arctocephalus australis) and the Subantarctic fur seal (Arctocephalus tropicalis). Fecal samples from 10 specimens (A. australis, n = 5; A. tropicalis, n = 5) were collected and viral particles were purified, extracted and amplified with a random PCR. The products were sequenced through Ion Torrent and Illumina platforms and assembled reads were submitted to BLASTx searches. Both viromes were dominated by bacteriophages and included a number of potentially novel virus genomes. Sequences of picobirnaviruses, picornaviruses and a hepevirus-like were identified in A. australis. A rotavirus related to group C, a novel member of the Sakobuvirus and a sapovirus very similar to California sea lion sapovirus 1 were found in A. tropicalis. Additionally, sequences of members of the Anelloviridae and Parvoviridae families were detected in both fur seal species. This is the first metagenomic study to screen the fecal virome of fur seals, contributing to a better understanding of the complexity of the viral community present in the intestinal microbiota of these animals. PMID:26986573

  13. An estimate of the heat flow on the Meteor Rise, subantarctic South Atlantic

    SciTech Connect

    Nobes, D.C. ); Mienert, J. ); Mwenifumbo, C.J. )

    1991-04-10

    Heat flow determinations require more than one reliable temperature measurment to obtain an estimate of the temperature gradient, and subsequently the heat flow. Two temperature readings were taken on leg 114 of the Ocean Drilling Program, both in hole 704B on the Meteor Rise in the subantarctic South Atlantic. One of these readings appears to be reliable, but the other appears to be invalid. Because any temperature gradient and estimate of heat flow derived using these two readings will be questionable, the authors suggest a different approach to determine heat flow. They use the one reliable temperature measurement to calibrate the temperature derived from the induction resistivity log and the laboratory porosity measurements. The temperature and heat flow depend on the shape factor used in the modified Archie's law. The temperature gradient empirically obtained from the resistivity and porosity is 38 {plus minus} mK/m and the average heat flow is 64 {plus minus} 8 mW/m{sup 2}, which is consistent with the age of the Meteor Rise (approximately 60 to 65 Ma). These values are in agreement with the computed heat flow when they assume a simple linear temperature gradient through the sediment section.

  14. Palaeoecological signatures of vegetation change induced by herbivory regime shifts on subantarctic Enderby Island

    NASA Astrophysics Data System (ADS)

    Wood, Jamie R.; Wilmshurst, Janet M.; Turney, Chris S. M.; Fogwill, Christopher J.

    2016-02-01

    The stratigraphic relationships of palaeoecological proxies and use of changepoint analyses to determine the cause and effect relationships between past events has allowed a better understanding of the relative contributions of humans and environmental drivers to Late Quaternary extinctions and of their effects on terrestrial ecosystems. Few studies, however, have validated these approaches at localities where past interactions between vegetation communities and large herbivores are well-documented. Here, we use a peat core from subantarctic Enderby Island to present the first study tracing the spores of dung fungi alongside pollen at a site where the history of mammalian herbivore introductions (and subsequent eradication), and their effects on the vegetation, are precisely known. We find a strong connection between spore influx rates of the dung-fungus Sporormiella and PCA axis 1 of the pollen assemblages, suggesting that past vegetation change caused by herbivore introductions and eradications at the core site can be readily deduced from the palaeoecological record. The response of the vegetation community to the removal of herbivores was so rapid, however, that a difference in timing between changepoints relating to specific pollen taxa, the overall pollen community, and the decline of Sporormiella spores, could not be resolved in our record, despite a sampling resolution of <5 years. We suggest that further case-studies, spanning different vegetation and herbivore communities, are required to provide increased confidence in inferences drawn about cause-and-effect relationships using proxy changepoint offsets in palaeoecological records.

  15. Metagenomic Survey of Viral Diversity Obtained from Feces of Subantarctic and South American Fur Seals.

    PubMed

    Kluge, Mariana; Campos, Fabrício Souza; Tavares, Maurício; de Amorim, Derek Blaese; Valdez, Fernanda Pedone; Giongo, Adriana; Roehe, Paulo Michel; Franco, Ana Claudia

    2016-01-01

    The Brazilian South coast seasonally hosts numerous marine species, observed particularly during winter months. Some animals, including fur seals, are found dead or debilitated along the shore and may harbor potential pathogens within their microbiota. In the present study, a metagenomic approach was performed to evaluate the viral diversity in feces of fur seals found deceased along the coast of the state of Rio Grande do Sul. The fecal virome of two fur seal species was characterized: the South American fur seal (Arctocephalus australis) and the Subantarctic fur seal (Arctocephalus tropicalis). Fecal samples from 10 specimens (A. australis, n = 5; A. tropicalis, n = 5) were collected and viral particles were purified, extracted and amplified with a random PCR. The products were sequenced through Ion Torrent and Illumina platforms and assembled reads were submitted to BLASTx searches. Both viromes were dominated by bacteriophages and included a number of potentially novel virus genomes. Sequences of picobirnaviruses, picornaviruses and a hepevirus-like were identified in A. australis. A rotavirus related to group C, a novel member of the Sakobuvirus and a sapovirus very similar to California sea lion sapovirus 1 were found in A. tropicalis. Additionally, sequences of members of the Anelloviridae and Parvoviridae families were detected in both fur seal species. This is the first metagenomic study to screen the fecal virome of fur seals, contributing to a better understanding of the complexity of the viral community present in the intestinal microbiota of these animals.

  16. Tropical forcing of increased Southern Ocean climate variability revealed by a 140-year subantarctic temperature reconstruction

    NASA Astrophysics Data System (ADS)

    Turney, Chris S. M.; Fogwill, Christopher J.; Palmer, Jonathan G.; van Sebille, Erik; Thomas, Zoë; McGlone, Matt; Richardson, Sarah; Wilmshurst, Janet M.; Fenwick, Pavla; Zunz, Violette; Goosse, Hugues; Wilson, Kerry-Jayne; Carter, Lionel; Lipson, Mathew; Jones, Richard T.; Harsch, Melanie; Clark, Graeme; Marzinelli, Ezequiel; Rogers, Tracey; Rainsley, Eleanor; Ciasto, Laura; Waterman, Stephanie; Thomas, Elizabeth R.; Visbeck, Martin

    2017-03-01

    Occupying about 14 % of the world's surface, the Southern Ocean plays a fundamental role in ocean and atmosphere circulation, carbon cycling and Antarctic ice-sheet dynamics. Unfortunately, high interannual variability and a dearth of instrumental observations before the 1950s limits our understanding of how marine-atmosphere-ice domains interact on multi-decadal timescales and the impact of anthropogenic forcing. Here we integrate climate-sensitive tree growth with ocean and atmospheric observations on southwest Pacific subantarctic islands that lie at the boundary of polar and subtropical climates (52-54° S). Our annually resolved temperature reconstruction captures regional change since the 1870s and demonstrates a significant increase in variability from the 1940s, a phenomenon predating the observational record. Climate reanalysis and modelling show a parallel change in tropical Pacific sea surface temperatures that generate an atmospheric Rossby wave train which propagates across a large part of the Southern Hemisphere during the austral spring and summer. Our results suggest that modern observed high interannual variability was established across the mid-twentieth century, and that the influence of contemporary equatorial Pacific temperatures may now be a permanent feature across the mid- to high latitudes.

  17. Comparative mesocosm study of biostimulation efficiency in two different oil-amended sub-antarctic soils.

    PubMed

    Delille, Daniel; Coulon, Frédéric

    2008-08-01

    Biological treatment has become increasingly popular as a remediation method for soils and groundwater contaminated with petroleum hydrocarbon, chlorinated solvents, and pesticides. Bioremediation has been considered for application in cold regions such as Arctic and sub-Arctic climates and Antarctica. Studies to date suggest that indigenous microbes suitable for bioremediation exist in soils in these regions. This paper reports on two case studies at the sub-Antarctic Kerguelen Island in which indigenous bacteria were found that were capable of mineralizing petroleum hydrocarbons in soil contaminated with crude oil and diesel fuel. All results demonstrate a serious influence of the soil properties on the biostimulation efficiency. Both temperature elevation and fertilizer addition have a more significant impact on the microbial assemblages in the mineral soil than in the organic one. Analysis of the hydrocarbons remaining at the end of the experiments confirmed the bacterial observations. Optimum temperature seems to be around 10 degrees C in organic soil, whereas it was higher in mineral soil. The benefit of adding nutrients was much stronger in mineral than in the organic soil. Overall, this study suggests that biostimulation treatments were driven by soil properties and that ex situ bioremediation for treatment of cold contaminated soils will allow greater control over soil temperature, a limiting factor in cold climates.

  18. Effect of horizontal grid resolution on simulations of the subtropical mode water in the North Pacific

    NASA Astrophysics Data System (ADS)

    Lee, Ho Jin; Yeop Kim, Sang; Lee, Kyung Eun

    2016-04-01

    We investigate how the Subtopical Mode Water (STMW) can be simulated differently in the North Pacific using a global Ocean General Circulation Model (OGCM) with non-eddying and eddy permitting resolution. The OGCM used in this study is the MOM version 4.1 and has a total of 50 levels along the vertical direction with enhanced resolution near the surface. The CORE version 2 (normal year forcing) data derived from the air-sea flux climatology averaged over 60 years (1948-2007) are used to calculate heat, salt and momentum fluxes with a bulk formula at the sea surface. The sea surface salinity is restored to the climatological monthly mean surface salinity of the Polar Science Center Hydrographic Climatology on a 60-day timescale, to make up the fresh water flux at the sea surface. Two models that have horizontal resolutions of 1° and 1/4 °, respectively, are integrated during 50 years. The inter-annual variation of the STMW volume was well reproduced with the eddy-permitting grid resolution although the model was forced by a climatological atmospheric forcing. The annual formation and erosion volume of STMW varies by 7% and 9% of the mean volume, respectively.

  19. Microstructure and deformation mode of a stainless steel rupture disc exposed to sodium-water reaction

    SciTech Connect

    Sudha, C.; Parameswaran, P. Kishore, S.; Murthy, C. Meikanda; Rajan, M.; Vijayalakshmi, M.; Raghunathan, V.S.

    2008-08-15

    This paper deals with microstructural studies carried out on an austenitic stainless steel rupture disc which was exposed to sodium-water reaction. The rupture disc was part of a leak simulator put in a micro leak test section which was used to study the 'self wastage' of steam generator tubes. During micro leak testing, the rupture disc failed exhibiting a linear crack at a much lower pressure of 10 MPa rather than bursting open at the higher designed pressure of 15 MPa. The failed rupture disc revealed different microstructural features on the inner (steam exposed) and outer (sodium exposed) surfaces. Using microstructure as the signature, the temperature experienced by the rupture disc was predicted as {>=} 1273 K. Evidence for the exposure of the rupture disc to highly exothermic sodium-water reaction was obtained in the form of sodium rich debris, microcracks and deformation bands. Detailed transmission electron microscopy revealed the nature of deformation bands as deformation twins which is not a preferred failure mode for austenitic stainless steels.

  20. A Fast Iterated Conditional Modes Algorithm for Water-Fat Decomposition in MRI

    PubMed Central

    Huang, Fangping; Narayan, Sreenath; Wilson, David; Johnson, David; Zhang, Guo-Qiang

    2013-01-01

    Decomposition of water and fat in Magnetic Resonance Imaging (MRI) is important for biomedical research and clinical applications. In this paper, we propose a two-phased approach for the three-point water-fat decomposition problem. Our contribution consists of two components: (1) a background-masked Markov Random Field (MRF) energy model to formulate the local smoothness of field inhomogeneity; (2) a new Iterated Conditional Modes (ICM) algorithm accounting for high-performance optimization of the MRF energy model. The MRF energy model is integrated with background masking to prevent error propagation of background estimates as well as improve efficiency. The central component of our new ICM algorithm is the Stability Tracking (ST) mechanism intended to dynamically track iterative stability on pixels so that computation per iteration is performed only on instable pixels. The ST mechanism significantly improves the efficiency of ICM. We also develop a median-based initialization algorithm to provide good initial guesses for ICM iterations, and an adaptive gradient-based scheme for parametric configuration of the MRF model. We evaluate the robust of our approach with high-resolution mouse datasets acquired from 7-Tesla MRI. PMID:21402510

  1. Water dissociation on Ni(100), Ni(110), and Ni(111) surfaces: Reaction path approach to mode selectivity

    DOE PAGES

    Seenivasan, H.; Jackson, Bret; Tiwari, Ashwani K.

    2017-02-17

    We performed a comparative study of mode-selectivity of water dissociation on Ni(100), Ni(110), and Ni(111) surfaces at the same level of theory using a fully quantum approach based on the reaction path Hamiltonian. Calculations show that the barrier to water dissociation on the Ni(110) surface is significantly lower compared to its close-packed counterparts. Transition states for this reaction on all three surfaces involve the elongation of one of the O–H bonds. Furthermore, a significant decrease in the symmetric stretching and bending mode frequencies near the transition state is observed in all three cases and in the vibrational adiabatic approximation, excitationmore » of these softened modes results in a significant enhancement in reactivity. Inclusion of non-adiabatic couplings between modes results in the asymmetric stretching mode showing a similar enhancement of reactivity as the symmetric stretching mode. Dissociation probabilities calculated at a surface temperature of 300 K showed higher reactivity at lower collision energies compared to that of the static surface case, underlining the importance of lattice motion in enhancing reactivity. Mode selective behavior is similar on all the surfaces. Molecules with one-quantum of vibrational excitation in the symmetric stretch, at lower energies (up to 0.45 eV), are more reactive on Ni(110) than the Ni(100) and Ni(111) surfaces. But, the dissociation probabilities approach saturation on all the surfaces at higher incident energy values. Ultimately, Ni(110) is found to be highly reactive toward water dissociation among the low-index nickel surfaces owing to a low reaction barrier resulting from the openness and corrugation of the surface. These results show that the mode-selective behavior does not vary with different crystal facets of Ni qualitatively, but there is a significant quantitative effect.« less

  2. Water dissociation on Ni(100), Ni(110), and Ni(111) surfaces: Reaction path approach to mode selectivity

    NASA Astrophysics Data System (ADS)

    Seenivasan, H.; Jackson, Bret; Tiwari, Ashwani K.

    2017-02-01

    A comparative study of mode-selectivity of water dissociation on Ni(100), Ni(110), and Ni(111) surfaces is performed at the same level of theory using a fully quantum approach based on the reaction path Hamiltonian. Calculations show that the barrier to water dissociation on the Ni(110) surface is significantly lower compared to its close-packed counterparts. Transition states for this reaction on all three surfaces involve the elongation of one of the O-H bonds. A significant decrease in the symmetric stretching and bending mode frequencies near the transition state is observed in all three cases and in the vibrational adiabatic approximation, excitation of these softened modes results in a significant enhancement in reactivity. Inclusion of non-adiabatic couplings between modes results in the asymmetric stretching mode showing a similar enhancement of reactivity as the symmetric stretching mode. Dissociation probabilities calculated at a surface temperature of 300 K showed higher reactivity at lower collision energies compared to that of the static surface case, underlining the importance of lattice motion in enhancing reactivity. Mode selective behavior is similar on all the surfaces. Molecules with one-quantum of vibrational excitation in the symmetric stretch, at lower energies (up to ˜0.45 eV), are more reactive on Ni(110) than the Ni(100) and Ni(111) surfaces. However, the dissociation probabilities approach saturation on all the surfaces at higher incident energy values. Overall, Ni(110) is found to be highly reactive toward water dissociation among the low-index nickel surfaces owing to a low reaction barrier resulting from the openness and corrugation of the surface. These results show that the mode-selective behavior does not vary with different crystal facets of Ni qualitatively, but there is a significant quantitative effect.

  3. Highly sensitive dual-mode fluorescence detection of lead ion in water using aggregation-induced emissive polymers.

    PubMed

    Saha, Sukanta Kumar; Ghosh, Khama Rani; Gao, Jian Ping; Wang, Zhi Yuan

    2014-09-01

    A series of fluorene-based conjugated polymers containing the aggregation-induced emissive (AIE)-active tetraphenylethene and dicarboxylate pseudocrown as a receptor exhibits a unique dual-mode sensing ability for selective detection of lead ion in water. Fluorescence turn-off and turn-on detections are realized in 80%-90% and 20% water in tetrahydrofuran (THF), respectively, for lead ion with a concentration as low as 10(-8) m.

  4. Effects of surface water on protein dynamics studied by a novel coarse-grained normal mode approach.

    PubMed

    Zhou, Lei; Siegelbaum, Steven A

    2008-05-01

    Normal mode analysis (NMA) has received much attention as a direct approach to extract the collective motions of macromolecules. However, the stringent requirement of computational resources by classical all-atom NMA limits the size of the macromolecules to which the method is normally applied. We implemented a novel coarse-grained normal mode approach based on partitioning the all-atom Hessian matrix into relevant and nonrelevant parts. It is interesting to note that, using classical all-atom NMA results as a reference, we found that this method generates more accurate results than do other coarse-grained approaches, including elastic network model and block normal mode approaches. Moreover, this new method is effective in incorporating the energetic contributions from the nonrelevant atoms, including surface water molecules, into the coarse-grained protein motions. The importance of such improvements is demonstrated by the effect of surface water to shift vibrational modes to higher frequencies and by an increase in overlap of the coarse-grained eigenvector space (the motion directions) with that obtained from molecular dynamics simulations of solvated protein in a water box. These results not only confirm the quality of our method but also point out the importance of incorporating surface structural water in studying protein dynamics.

  5. Extensive lake sediment coring survey on Sub-Antarctic Indian Ocean Kerguelen Archipelago (French Austral and Antarctic Lands)

    NASA Astrophysics Data System (ADS)

    Arnaud, Fabien; Fanget, Bernard; Malet, Emmanuel; Poulenard, Jérôme; Støren, Eivind; Leloup, Anouk; Bakke, Jostein; Sabatier, Pierre

    2016-04-01

    Recent paleo-studies revealed climatic southern high latitude climate evolution patterns that are crucial to understand the global climate evolution(1,2). Among others the strength and north-south shifts of westerlies wind appeared to be a key parameter(3). However, virtually no lands are located south of the 45th South parallel between Southern Georgia (60°W) and New Zealand (170°E) precluding the establishment of paleoclimate records of past westerlies dynamics. Located around 50°S and 70°E, lost in the middle of the sub-Antarctic Indian Ocean, Kerguelen archipelago is a major, geomorphologically complex, land-mass that is covered by hundreds lakes of various sizes. It hence offers a unique opportunity to reconstruct past climate and environment dynamics in a region where virtually nothing is known about it, except the remarkable recent reconstructions based on a Lateglacial peatbog sequence(4). During the 2014-2015 austral summer, a French-Norwegian team led the very first extensive lake sediment coring survey on Kerguelen Archipelago under the umbrella of the PALAS program supported by the French Polar Institute (IPEV). Two main areas were investigated: i) the southwest of the mainland, so-called Golfe du Morbihan, where glaciers are currently absent and ii) the northernmost Kerguelen mainland peninsula so-called Loranchet, where cirque glaciers are still present. This double-target strategy aims at reconstructing various independent indirect records of precipitation (glacier advance, flood dynamics) and wind speed (marine spray chemical species, wind-borne terrigenous input) to tackle the Holocene climate variability. Despite particularly harsh climate conditions and difficult logistics matters, we were able to core 6 lake sediment sites: 5 in Golfe du Morbihan and one in Loranchet peninsula. Among them two sequences taken in the 4km-long Lake Armor using a UWITEC re-entry piston coring system by 20 and 100m water-depth (6 and 7m-long, respectively). One

  6. Multi-decadal uptake of carbon dioxide into subtropical mode water of the North Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Bates, N. R.

    2012-07-01

    Natural climate variability impacts the multi-decadal uptake of anthropogenic carbon dioxide (Cant) into the North Atlantic Ocean subpolar and subtropical gyres. Previous studies have shown that there is significant uptake of CO2 into subtropical mode water (STMW) of the North Atlantic. STMW forms south of the Gulf Stream in winter and constitutes the dominant upper-ocean water mass in the subtropical gyre of the North Atlantic Ocean. Observations at the Bermuda Atlantic Time-series Study (BATS) site near Bermuda show an increase in dissolved inorganic carbon (DIC) of +1.51 ± 0.08 μmol kg-1 yr-1 between 1988 and 2011, but also an increase in ocean acidification indicators such as pH at rates (-0.0022 ± 0.0002 yr-1) higher than the surface ocean (Bates et al., 2012). It is estimated that the sink of CO2 into STMW was 0.985 ± 0.018 Pg C (Pg = 1015 g C) between 1988 and 2011 (70 ± 1.8% of which is due to uptake of Cant). The sink of CO2 into the STMW is 20% of the CO2 uptake in the North Atlantic Ocean between 14°-50° N (Takahashi et al., 2009). However, the STMW sink of CO2 was strongly coupled to the North Atlantic Oscillation (NAO), with large uptake of CO2 into STMW during the 1990s during a predominantly NAO positive phase. In contrast, uptake of CO2 into STMW was much reduced in the 2000s during the NAO neutral/negative phase. Thus, NAO induced variability of the STMW CO2 sink is important when evaluating multi-decadal changes in North Atlantic Ocean CO2 sinks.

  7. Influence of photo- and thermal bleaching on pre-irradiation low water peak single mode fibers

    NASA Astrophysics Data System (ADS)

    Yin, Jianchong; Wen, Jianxiang; Luo, Wenyun; Xiao, Zhongyin; Chen, Zhenyi; Wang, Tingyun

    2011-12-01

    Reducing the radiation-induced transmission loss in low water peak single mode fiber (LWP SMF) has been investigated by using photo-bleaching method with 980nm pump light source and using thermal-bleaching method with temperature control system. The results show that the radiation-induced loss of pre-irradiation optical fiber can be reduced effectively with the help of photo-bleaching or thermal-bleaching. Although the effort of photo-bleaching is not as significant as thermal-bleaching, by using photo-bleaching method, the loss of fiber caused by radiation-induced defects can be reduced best up to 49% at 1310nm and 28% at 1550nm in low pre-irradiation condition, the coating of the fiber are not destroyed, and the rehabilitating time is just several hours, while self-annealing usually costs months' time. What's more, the typical high power LASER for photo-bleaching can be 980nm pump Laser Diode, which is very accessible.

  8. Estimates of late Quaternary mode and intermediate water silicic acid concentration in the Pacific Southern Ocean

    NASA Astrophysics Data System (ADS)

    Rousseau, Jonathon; Ellwood, Michael J.; Bostock, Helen; Neil, Helen

    2016-04-01

    The Southern Ocean plays a critical role in the exchange of carbon between the ocean and atmosphere over glacial-interglacial timescales. Hypotheses used to explain late Quaternary variations in atmospheric carbon dioxide (CO2) implicate changes in the nutrient dynamics and circulation of the Southern Ocean. Here we present silicon isotope (δ30Si) records of late Quaternary sponges and diatoms from the NZ-sector of the Southern Ocean. Analysis of our sponge δ30Si records strongly suggests that the silicic acid concentration at mode and intermediate depths was higher during the LGM and the deglacial period compared to the present day. Our diatom δ30Si record suggests biological productivity near of the Polar Front was greater during the deglacial period, but not significantly different during the LGM compared to the present day. Taking our dataset in context with other regional paleoceanographic records, we interpret the predicted elevation in LGM and deglacial silicic acid concentration to reflect a shoaling of water masses during the LGM and 'leakage' of excess Southern Ocean dissolved silicon during the deglacial period.

  9. Surface charge mapping of solid surfaces in water by pulsed-force-mode atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Miyatani, T.; Okamoto, S.; Rosa, A.; Marti, O.; Fujihira, M.

    We have studied the lateral distribution of charges on various surfaces in water by measuring the electrical double layer forces between a Si3N4 atomic force microscope (AFM) tip and the surfaces. By increasing the pH of the solution around the isoelectric point (IEP) of Si3N4 of approximately 6, the charge on the Si3N4 AFM tip was changed from positive to negative. The surface charges of the samples were also controlled by the pH of the solution in which the sample oxides were dipped. When the samples were electronically conductive, the surface charge was controlled by the electrode potentials. When the sample surface was heterogeneous in terms of the isoelectric point or point of zero charge (pzc), the surface charge was changed from one place to the other. As a heterogeneous oxide sample, a quartz plate patterned with alumina was used. The lateral charge distributions on such surfaces were mapped by pulsed-force-mode AFM. The lateral resolution of the present method was found to be approximately 20 nm.

  10. Millennial-scale variability in dust deposition, marine export production, and nutrient consumption in the glacial subantarctic ocean (Invited)

    NASA Astrophysics Data System (ADS)

    Martinez-Garcia, A.; Sigman, D. M.; Anderson, R. F.; Ren, H. A.; Hodell, D. A.; Straub, M.; Jaccard, S.; Eglinton, T. I.; Haug, G. H.

    2013-12-01

    Based on the limitation of modern Southern Ocean phytoplankton by iron and the evidence of higher iron-bearing dust fluxes to the ocean during ice ages, it has been proposed that iron fertilization of Southern Ocean phytoplankton contributed to the reduction in atmospheric CO2 during ice ages. In the Subantarctic zone of the Atlantic Southern Ocean, glacial increases in dust flux and export production have been documented, supporting the iron fertilization hypothesis. However, these observations could be interpreted alternatively as resulting from the equatorward migration of Southern Ocean fronts during ice ages if the observed productivity rise was not accompanied by an increase in major nutrient consumption. Here, new 230Th-normalized lithogenic and opal fluxes are combined with high-resolution biomarker measurements to reconstruct millennial-scale changes in dust deposition and marine export production in the subantarctic Atlantic over the last glacial cycle. In the same record foraminifera-bound nitrogen isotopes are used to reconstruct ice age changes in surface nitrate utilization, providing a comprehensive test of the iron fertilization hypothesis. Elevation in foraminifera-bound δ15N, indicating more complete nitrate consumption, coincides with times of surface cooling and greater dust flux and export production. These observations indicate that the ice age Subantarctic was characterized by iron fertilized phytoplankton growth. The resulting strengthening of the Southern Ocean's biological pump can explain the ~40 ppm lowering of CO2 that characterizes the transitions from mid-climate states to full ice age conditions as well as the millennial-scale atmospheric CO2 fluctuations observed within the last ice age

  11. Evolution of ozone depletion on Antarctic and sub-Antarctic regions (1979-2012)

    NASA Astrophysics Data System (ADS)

    Diaz, S. B.; Paladini, A. A.; Deferrari, G. A.; Vrsalovic, J.

    2013-08-01

    At the middle eighties, strong stratospheric ozone depletion during spring was discovered over Antarctica. Since then, the scientific community has put large efforts in performing studies directed to evaluate the magnitude and consequences of this depletion and to take the necessary measures to revert the situation to the scenarios before 1970. In 1987, the Montreal Protocol established a list of ozone depleting products and faced out policies. As consequence of these restrictions on ozone depleting substances, the ozone layer should start to recover in the 21st century. In order to study the evolution of the Antarctic ozone depletion, we analyzed the ozone hole area and mass deficit and seasonal total ozone column (TOC) minimum. We also performed a seasonal and bi-monthly analysis for TOC time series (1979-2012), at twenty Antarctic and Sub-Antarctic stations. The number of days inside the vortex (TOC below 220DU) per season (September-December) and for September-October and November-December were analyzed, fitting the time series with a second degree polynomial According to this study, ozone hole area would have peaked between 2001 and 2002 (R=0.91, p<0.01), while the minimum TOC would have occurred between 2000 and 2001(R=0.91, p<0.01). Mass deficit is only provided since 2005 and it showed a decrease since then, although ot statistically significant as consequence of the short time series. From the 20 analyzed stations, 80% showed that the number of days per season inside the vortex peaked between 2000 and 2003 and for 55% of the stations the number of days inside the vortex for September-October peaked between 1999 and 2004.

  12. Diverse Bacterial Groups Contribute to the Alkane Degradation Potential of Chronically Polluted Subantarctic Coastal Sediments

    SciTech Connect

    Guibert, Lilian M.; Loviso, Claudia L.; Borglin, Sharon; Jansson, Janet K.; Dionisi, Hebe M.; Lozada, Mariana

    2015-11-07

    We aimed to gain insight into the alkane degradation potential of microbial communities from chronically polluted sediments of a subantarctic coastal environment using a combination of metagenomic approaches. A total of 6178 sequences annotated as alkane-1-monooxygenases (EC 1.14.15.3) were retrieved from a shotgun metagenomic dataset that included two sites analyzed in triplicate. The majority of the sequences binned with AlkB described in Bacteroidetes (32 ± 13 %) or Proteobacteria (29 ± 7 %), although a large proportion remained unclassified at the phylum level. Operational taxonomic unit (OTU)-based analyses showed small differences in AlkB distribution among samples that could be correlated with alkane concentrations, as well as with site-specific variations in pH and salinity. A number of low-abundance OTUs, mostly affiliated with Actinobacterial sequences, were found to be only present in the most contaminated samples. On the other hand, the molecular screening of a large-insert metagenomic library of intertidal sediments from one of the sampling sites identified two genomic fragments containing novel alkB gene sequences, as well as various contiguous genes related to lipid metabolism. Both genomic fragments were affiliated with the phylum Planctomycetes, and one could be further assigned to the genus Rhodopirellula due to the presence of a partial sequence of the 23S ribosomal RNA (rRNA) gene. This work highlights the diversity of bacterial groups contributing to the alkane degradation potential and reveals patterns of functional diversity in relation with environmental stressors in a chronically polluted, high-latitude coastal environment. In addition, alkane biodegradation genes are described for the first time in members of Planctomycetes.

  13. Diverse Bacterial Groups Contribute to the Alkane Degradation Potential of Chronically Polluted Subantarctic Coastal Sediments.

    PubMed

    Guibert, Lilian M; Loviso, Claudia L; Borglin, Sharon; Jansson, Janet K; Dionisi, Hebe M; Lozada, Mariana

    2016-01-01

    We aimed to gain insight into the alkane degradation potential of microbial communities from chronically polluted sediments of a subantarctic coastal environment using a combination of metagenomic approaches. A total of 6178 sequences annotated as alkane-1-monooxygenases (EC 1.14.15.3) were retrieved from a shotgun metagenomic dataset that included two sites analyzed in triplicate. The majority of the sequences binned with AlkB described in Bacteroidetes (32 ± 13 %) or Proteobacteria (29 ± 7 %), although a large proportion remained unclassified at the phylum level. Operational taxonomic unit (OTU)-based analyses showed small differences in AlkB distribution among samples that could be correlated with alkane concentrations, as well as with site-specific variations in pH and salinity. A number of low-abundance OTUs, mostly affiliated with Actinobacterial sequences, were found to be only present in the most contaminated samples. On the other hand, the molecular screening of a large-insert metagenomic library of intertidal sediments from one of the sampling sites identified two genomic fragments containing novel alkB gene sequences, as well as various contiguous genes related to lipid metabolism. Both genomic fragments were affiliated with the phylum Planctomycetes, and one could be further assigned to the genus Rhodopirellula due to the presence of a partial sequence of the 23S ribosomal RNA (rRNA) gene. This work highlights the diversity of bacterial groups contributing to the alkane degradation potential and reveals patterns of functional diversity in relation with environmental stressors in a chronically polluted, high-latitude coastal environment. In addition, alkane biodegradation genes are described for the first time in members of Planctomycetes.

  14. At-sea distribution and habitat use in king penguins at sub-Antarctic Marion Island.

    PubMed

    Pistorius, Pierre; Hindell, Mark; Crawford, Robert; Makhado, Azwianewi; Dyer, Bruce; Reisinger, Ryan

    2017-06-01

    King penguins make up the bulk of avian biomass on a number of sub-Antarctic islands where they have a large functional effect on terrestrial and marine ecosystems. The same applies at Marion Island where a substantial proportion of the world population breeds. In spite of their obvious ecological importance, the at-sea distribution and behavior of this population has until recently remained entirely unknown. In addressing this information deficiency, we deployed satellite-linked tracking instruments on 15 adult king penguins over 2 years, April 2008 and 2013, to study their post-guard foraging distribution and habitat preferences. Uniquely among adult king penguins, individuals by and large headed out against the prevailing Antarctic Circumpolar Current, foraging to the west and southwest of the island. On average, individuals ventured a maximum distance of 1,600 km from the colony, with three individuals foraging close to, or beyond, 3,500 km west of the colony. Birds were mostly foraging south of the Antarctic Polar Front and north of the southern boundary of the Antarctic Circumpolar Current. Habitat preferences were assessed using boosted regression tree models which indicated sea surface temperate, depth, and chorophyll a concentration to be the most important predictors of habitat selection. Interestingly, king penguins rapidly transited the eddy-rich area to the west of Marion Island, associated with the Southwest Indian Ocean Ridge, which has been shown to be important for foraging in other marine top predators. In accordance with this, the king penguins generally avoided areas with high eddy kinetic energy. The results from this first study into the behavioral ecology and at-sea distribution of king penguins at Marion Island contribute to our broader understanding of this species.

  15. Determinants of individual foraging specialization in large marine vertebrates, the Antarctic and subantarctic fur seals.

    PubMed

    Kernaléguen, Laëtitia; Arnould, John P Y; Guinet, Christophe; Cherel, Yves

    2015-07-01

    The degree of individual specialization in resource use differs widely among wild populations where individuals range from fully generalized to highly specialized. This interindividual variation has profound implications in many ecological and evolutionary processes. A recent review proposed four main ecological causes of individual specialization: interspecific and intraspecific competition, ecological opportunity and predation. Using the isotopic signature of subsampled whiskers, we investigated to what degree three of these factors (interspecific and intraspecific competition and ecological opportunity) affect the population niche width and the level of individual foraging specialization in two fur seal species, the Antarctic and subantarctic fur seals (Arctocephalus gazella and Arctocephalus tropicalis), over several years. Population niche width was greater when the two seal species bred in allopatry (low interspecific competition) than in sympatry or when seals bred in high-density stabilized colonies (high intraspecific competition). In agreement with the niche variation hypothesis (NVH), higher population niche width was associated with higher interindividual niche variation. However, in contrast to the NVH, all Antarctic females increased their niche width during the interbreeding period when they had potential access to a wider diversity of foraging grounds and associated prey (high ecological opportunities), suggesting they all dispersed to a similar productive area. The degree of individual specialization varied among populations and within the annual cycle. Highest levels of interindividual variation were found in a context of lower interspecific or higher intraspecific competition. Contrasted results were found concerning the effect of ecological opportunity. Depending on seal species, females exhibited either a greater or lower degree of individual specialization during the interbreeding period, reflecting species-specific biological constraints

  16. Long Term Trends in Subantarctic Nutrient Consumption: Evidence from Sedimentary and Diatom-Bound Nitrogen Isotopes

    NASA Astrophysics Data System (ADS)

    Bedsole, P.

    2014-12-01

    It has been proposed that the long term increase in Subantarctic opal export during glacial periods, centered around 1 Ma, is related to enhanced iron deposition and, potentially, carbon dioxide drawdown. New bulk sedimentary and diatom-bound nitrogen isotope records are used in combination with opal accumulation data from ODP Site 1090 to investigate controls on export production over the last 3 Ma. Sedimentary nitrogen content tracks opal during periods of high iron accumulation, especially after ~1 Ma. Bulk sedimentary nitrogen isotope trends are negatively correlated with sedimentary N-content and opal accumulation. This may be signal weaker nutrient consumption during times of high production, perhaps as a result of enhanced vertical nutrient supply. Alternatively, this variation in bulk, where high values occur in organic poor intervals, is consistent with other evidence for nitrogen isotopic alteration during periods of low export to the seafloor. The diatom-bound nitrogen isotope record does not have a clear relationship with opal or iron accumulation. A long term shift in the diatom-bound N isotope values is apparent, where the average diatom-bound δ15N from 0.5-1 Ma is 4.4 ‰, and from 2-2.6 Ma is 5.9 ‰. This decrease may reflect long-term changes in nitrate availability. A first order comparison to planktonic/benthic carbon isotopic gradients suggests that enhanced vertical mixing may explain the observed productivity peaks and lower overall diatom-bound N isotope values in the interval centered around 1 Ma.

  17. Toxicity of diesel contaminated soils to the subantarctic earthworm Microscolex macquariensis.

    PubMed

    Mooney, Thomas J; King, Catherine K; Wasley, Jane; Andrew, Nigel R

    2013-02-01

    Several fuel spills have occurred on subantarctic Macquarie Island (54°30' S 158°57' E) associated with storing fuel and generating power for the island's research station. The Australian Antarctic Division began full-scale, on-site remediation of these sites in 2009. To develop appropriate target concentrations for remediation, acute and chronic tests were developed with the endemic earthworm, Microscolex macquariensis, using avoidance, survival, and reproduction as endpoints. Uncontaminated low (3%), medium (11%), and high (38-48%) carbon content soils from Macquarie Island were used to examine the influence of soil carbon on toxicity. Soils were spiked with Special Antarctic Blend (SAB) diesel and used either immediately to simulate a fresh spill or after four weeks to simulate an aged spill. Earthworms were sensitive to fresh SAB, with significant avoidance at 181 mg/kg; acute 14-d survival median lethal concentration (LC50) of 103 mg/kg for low carbon soil; and juvenile production median effective concentration (EC50) of 317 mg/kg for high carbon soil. Earthworms were less sensitive to aged SAB than to fresh SAB in high carbon soil for juvenile production (EC50 of 1,753 and 317 mg/kg, respectively), but were more sensitive for adult survival (LC50 of 2,322 and 1,364 mg/kg, respectively). Using M. macquariensis as a surrogate for soil quality, approximately 50 to 200 mg SAB/kg soil would be a sufficiently protective remediation target.

  18. Soil Calcium Availability Influences Shell Ecophenotype Formation in the Sub-Antarctic Land Snail, Notodiscus hookeri

    PubMed Central

    Charrier, Maryvonne; Marie, Arul; Guillaume, Damien; Bédouet, Laurent; Le Lannic, Joseph; Roiland, Claire; Berland, Sophie; Pierre, Jean-Sébastien; Le Floch, Marie; Frenot, Yves; Lebouvier, Marc

    2013-01-01

    Ecophenotypes reflect local matches between organisms and their environment, and show plasticity across generations in response to current living conditions. Plastic responses in shell morphology and shell growth have been widely studied in gastropods and are often related to environmental calcium availability, which influences shell biomineralisation. To date, all of these studies have overlooked micro-scale structure of the shell, in addition to how it is related to species responses in the context of environmental pressure. This study is the first to demonstrate that environmental factors induce a bi-modal variation in the shell micro-scale structure of a land gastropod. Notodiscus hookeri is the only native land snail present in the Crozet Archipelago (sub-Antarctic region). The adults have evolved into two ecophenotypes, which are referred to here as MS (mineral shell) and OS (organic shell). The MS-ecophenotype is characterised by a thick mineralised shell. It is primarily distributed along the coastline, and could be associated to the presence of exchangeable calcium in the clay minerals of the soils. The Os-ecophenotype is characterised by a thin organic shell. It is primarily distributed at high altitudes in the mesic and xeric fell-fields in soils with large particles that lack clay and exchangeable calcium. Snails of the Os-ecophenotype are characterised by thinner and larger shell sizes compared to snails of the MS- ecophenotype, indicating a trade-off between mineral thickness and shell size. This pattern increased along a temporal scale; whereby, older adult snails were more clearly separated into two clusters compared to the younger adult snails. The prevalence of glycine-rich proteins in the organic shell layer of N. hookeri, along with the absence of chitin, differs to the organic scaffolds of molluscan biominerals. The present study provides new insights for testing the adaptive value of phenotypic plasticity in response to spatial and temporal

  19. Microbial biomass and basal respiration in Sub-Antarctic and Antarctic soils in the areas of some Russian polar stations

    NASA Astrophysics Data System (ADS)

    Abakumov, E.; Mukhametova, N.

    2014-03-01

    Antarctica is the unique place for pedological investigations. Soils of Antarctica have been studied intensively during the last century. Antarctic logistic provides the possibility to scientists access the terrestrial landscapes mainly in the places of polar stations. That is why the main and most detailed pedological investigations were conducted in Mc Murdo Valleys, Transantarctic Mountains, South Shetland Islands, Larsemann hills and Schirmacher Oasis. Investigations were conducted during the 53rd and 55th Russian Antarctic expeditions on the base of soil pits and samples collected in Sub-Antarctic and Antarctic regions. Soils of diverse Antarctic landscapes were studied with aim to assess the microbial biomass level, basal respiration rates and metabolic activity of microbial communities. The investigation conducted shows that soils of Antarctic are quite different in profile organization and carbon content. In general, Sub-Antarctic soils are characterized by more developed humus (sod) organo-mineral horizons as well as the upper organic layer. The most developed organic layers were revealed in peat soils of King-George Island, where its thickness reach even 80 cm. These soils as well as soils under guano are characterized by the highest amount of total organic carbon (TOC) 7.22-33.70%. Coastal and continental soils of Antarctic are presented by less developed Leptosols, Gleysols, Regolith and rare Ornhitosol with TOC levels about 0.37-4.67%. The metabolic ratios and basal respiration were higher in Sub-Antarctic soils than in Antarctic ones which can be interpreted as result of higher amounts of fresh organic remnants in organic and organo-mineral horizons. Also the soils of King-George island have higher portion of microbial biomass (max 1.54 mg g-1) than coastal (max 0.26 mg g-1) and continental (max 0.22 mg g-1) Antarctic soils. Sub-Antarctic soils mainly differ from Antarctic ones in increased organic layers thickness and total organic carbon content

  20. On the possibility of representing an acoustic field in shallow water as the sum of normal modes and quasimodes

    NASA Astrophysics Data System (ADS)

    Grigor'ev, V. A.; Petnikov, V. G.

    2016-11-01

    Using the example of a shallow-water acoustic waveguide with a homogeneous water layer of constant thickness H lying on a homogeneous fluid absorbing half-space (bottom), we obtain estimates of distance r from a source, for which it is possible to ignore the continuous spectrum for the mode description of the depth dependence of the intensity of a low-frequency sound field in the bottom layer. We have compared two discrete representations of the field using (1) the total set of normal modes and (2) the total set of normal modes and quasimodes. It is shown that in the case when there is at least one normal mode in the channel, additional allowance for quasimodes makes it possible by an order of magnitude to approximate the boundary of applicability of mode theory and on average establish it at a level of r H or less. We explain the functional dependences of the contribution of the continuous spectrum to the total field on the waveguide parameters and find the conditions of its minimization. We present examples of description of the field in the bottom, where the advantage of using quasimodes at short distances is also demonstrated.

  1. High-frequency normal-mode statistics in shallow water: the combined effect of random surface and internal waves.

    PubMed

    Raghukumar, Kaustubha; Colosi, John A

    2015-05-01

    In an earlier article, the statistical properties of mode propagation were studied at a frequency of 1 kHz in a shallow water environment with random sound-speed perturbations from linear internal waves, using a hybrid transport theory and Monte Carlo numerical simulations. Here, the analysis is extended to include the effects of random linear surface waves, in isolation and in combination with internal waves. Mode coupling rates for both surface and internal waves are found to be significant, but strongly dependent on mode number. Mode phase randomization by surface waves is found to be dominated by coupling effects, and therefore a full transport theory treatment of the range evolution of the cross mode coherence matrix is needed. The second-moment of mode amplitudes is calculated using transport theory, thereby providing the mean intensity while the fourth-moment is calculated using Monte Carlo simulations, which provides the scintillation index. The transport theory results for second-moment statistics are shown to closely reproduce Monte Carlo simulations. Both surface waves and internal waves strongly influence the acoustic field fluctuations.

  2. New water soluble heterometallic complex showing unpredicted coordination modes of EDTA

    SciTech Connect

    Mudsainiyan, R.K. Jassal, A.K.; Chawla, S.K.

    2015-10-15

    A mesoporous 3D polymeric complex (I) having formula ([Zr(IV)O-μ{sup 3}-(EDTA)Fe(III)OH]·H{sub 2}O){sub n} has been crystallized and characterized by various techniques. Single-crystal X-ray diffraction analysis revealed that complex (I) crystallized in chiral monoclinic space group Cc (space group no. 9) with unexpected coordination modes of EDTA and mixture of two transition metal ions. In this complex, the coordination number of Zr(IV) ion is seven where four carboxylate oxygen atoms, two nitrogen atoms, one oxide atom are coordinating with Zr(IV). Fe(III) is four coordinated and its coordination environment is composed of three different carboxylic oxygen atoms from three different EDTA and one oxygen atom of –OH group. The structure consists of 4-c and 16-c (2-nodal) net with new topology and point symbol for net is (3{sup 36}·4{sup 54}·5{sup 30})·(3{sup 6}). TGA study and XRPD pattern showed that the coordination polymer is quite stable even after losing water molecule and –OH ion. Quenching behavior in fluorescence of ligand is observed by complexation with transition metal ions is due to n–π⁎ transition. The SEM micrograph shows the morphology of complex (I) exhibits spherical shape with size ranging from 50 to 280 nm. The minimum N{sub 2} (S{sub BET}=8.7693 m{sup 2}/g) and a maximum amount of H{sub 2} (high surface area=1044.86 m{sup 2}/g (STP)) could be adsorbed at 77 K. From DLS study, zeta potential is calculated i.e. −7.94 shows the negative charges on the surface of complex. Hirshfeld surface analysis and fingerprint plots revealed influence of weak or non bonding interactions in crystal packing of complex. - Graphical abstract: The complex (I) crystallized with unexpected coordination modes of EDTA having 4-c, 16-c net with new topology and point symbol is (3{sup 36}·4{sup 54}·5{sup 30})·(3{sup 6}). TGA study and XRPD pattern proved its stability with high preference of H{sub 2} uptake by complex. - Highlights: • 3D complex

  3. New water soluble heterometallic complex showing unpredicted coordination modes of EDTA

    NASA Astrophysics Data System (ADS)

    Mudsainiyan, R. K.; Jassal, A. K.; Chawla, S. K.

    2015-10-01

    A mesoporous 3D polymeric complex (I) having formula {[Zr(IV)O-μ3-(EDTA)Fe(III)OH]·H2O}n has been crystallized and characterized by various techniques. Single-crystal X-ray diffraction analysis revealed that complex (I) crystallized in chiral monoclinic space group Cc (space group no. 9) with unexpected coordination modes of EDTA and mixture of two transition metal ions. In this complex, the coordination number of Zr(IV) ion is seven where four carboxylate oxygen atoms, two nitrogen atoms, one oxide atom are coordinating with Zr(IV). Fe(III) is four coordinated and its coordination environment is composed of three different carboxylic oxygen atoms from three different EDTA and one oxygen atom of -OH group. The structure consists of 4-c and 16-c (2-nodal) net with new topology and point symbol for net is (336·454·530)·(36). TGA study and XRPD pattern showed that the coordination polymer is quite stable even after losing water molecule and -OH ion. Quenching behavior in fluorescence of ligand is observed by complexation with transition metal ions is due to n-π* transition. The SEM micrograph shows the morphology of complex (I) exhibits spherical shape with size ranging from 50 to 280 nm. The minimum N2 (SBET=8.7693 m2/g) and a maximum amount of H2 (high surface area=1044.86 m2/g (STP)) could be adsorbed at 77 K. From DLS study, zeta potential is calculated i.e. -7.94 shows the negative charges on the surface of complex. Hirshfeld surface analysis and fingerprint plots revealed influence of weak or non bonding interactions in crystal packing of complex.

  4. Extraction and stability of pesticide multiresidues from natural water on a mixed-mode admicellar sorbent.

    PubMed

    Luque, Noelia; Rubio, Soledad

    2012-07-27

    The suitability of a mixed-mode sorbent made up of admicelles of sodium dodecyl sulphate (SDS) and tetrabutylammonium (TBA) to extract and preserve pesticides from river and underground water was assessed. Pesticides belonging to different structural groups (i.e. triazines, carbamates, phenylureas, anilides, chloroacetanilides, organophosphorus and phenoxyacids), most of them well known by their instability, were selected for this purpose. Extraction of pesticides with the admicellar sorbent was optimized. Percolation of 250 mL of sample through the SPE cartridge, elution with 1 mL of methanol (neutral and basic pesticides) or 2 mL of 0.3M NaOH:methanol (90:10, v/v) (acidic pesticides) and direct analysis of the extract by liquid chromatography/UV detection, permitted to obtain method detection limits in the range 2-60 ng L(-1). Their degradation on the SPE cartridges after sample percolation was investigated under a variety of experimental conditions, namely darkness, natural illumination and different temperatures (room temperature, 4 °C and -20 °C) for 3 months. Under darkness, most of pesticides were stable for 1 month at room temperature and 3 months at 4 °C. Only atriazine and clorfenvinfos did not follow this general behaviour. No influence of matrix components on the stabilization of pesticides in the admicellar sorbent was observed. The stabilizing capability of surfactant aggregates surpassed that of C18 and black carbon and was similar to that obtained in some polymeric materials, which have the disadvantage of requiring large volumes of solvents for analyte elution. The stabilization of pesticides on the admicellar sorbent was long enough to permit easy shipping and storage of the cartridges in monitorization campaigns.

  5. Identification, characterization and modulation of ferritin-H in the sub-Antarctic Notothenioid Eleginops maclovinus challenged with Piscirickettsia salmonis.

    PubMed

    Martínez, D; Oyarzún, R; Vargas-Lagos, C; Pontigo, J P; Soto-Dávila, M; Saravia, J; Romero, A; Núñez, J J; Yáñez, A J; Vargas-Chacoff, L

    2017-03-21

    Ferritin is a major iron storage protein essential not only in the infectious process, but also in any circumstance generating oxidative stress. In this study, the cDNA coding sequence of ferritin-H was obtained from the sub-Antarctic Notothenioid fish Eleginops maclovinus through transcriptomic analysis of the head kidney. This sequence contained a 534 bp open reading frame that coded for a 177 amino acid protein with a molecular weight of 20,786.2 Da and a theoretical pI of 5.56. The protein displayed a region of iron putative response elements in the 5'UTR, two putative ferritin iron-binding region signatures, and seven characteristic amino acids with ferroxidase functions. Phylogenetic analysis related this sequence to ferritin-H sequences of other Antarctic Notothenioid fish, sharing 96.61% similarity. Constitutive gene expression analysis in different organs revealed increased ferritin-H gene expression in the gills, spleen, muscle, and liver. After infection with two bacterial strains of Piscirickettsia salmonis (LF-89 and Austral-005), ferritin-H was differentially expressed depending on bacterial strain and tissue. This study provides relevant information towards understanding the iron metabolism of a sub-Antarctic Notothenioid fish.

  6. Isolation and molecular identification of free-living amoebae of the genus Naegleria from Arctic and sub-Antarctic regions.

    PubMed

    De Jonckheere, Johan F

    2006-07-01

    Twenty-three freshwater samples with sediment taken from two regions in the Arctic, Spitzbergen and Greenland, and one region in sub-Antarctica, Ile de la Possession, were cultured for amoebae at 37 degrees C and room temperature (RT). Only two samples yielded amoebae at 37 degrees C and the two isolates were identified from their morphological features to belong to the genus Acanthamoeba. Vahlkampfiid amoebae were isolated from 11 samples at RT. Morphological analysis of the cysts identified all 11 isolates as belonging to the genus Naegleria, although only about half of them (45%) transformed into flagellates. Ribosomal DNA sequence analysis demonstrated that these isolates represent novel species and that N. antarctica, N. dobsoni and N. chilensis are their closest relatives. Not surprisingly, these three species also grow at lower temperatures (<37 degrees C) than the majority of described Naegleria spp. Two of the eight new species were found in both Arctic and sub-Antarctic regions, and other new species from the Arctic are closely related to new species from the sub-Antarctic. Therefore, it seems the Naegleria gene pool present in the polar regions is different from that found in temperate and tropical regions.

  7. Mapping Sub-Antarctic Cushion Plants Using Random Forests to Combine Very High Resolution Satellite Imagery and Terrain Modelling

    PubMed Central

    Bricher, Phillippa K.; Lucieer, Arko; Shaw, Justine; Terauds, Aleks; Bergstrom, Dana M.

    2013-01-01

    Monitoring changes in the distribution and density of plant species often requires accurate and high-resolution baseline maps of those species. Detecting such change at the landscape scale is often problematic, particularly in remote areas. We examine a new technique to improve accuracy and objectivity in mapping vegetation, combining species distribution modelling and satellite image classification on a remote sub-Antarctic island. In this study, we combine spectral data from very high resolution WorldView-2 satellite imagery and terrain variables from a high resolution digital elevation model to improve mapping accuracy, in both pixel- and object-based classifications. Random forest classification was used to explore the effectiveness of these approaches on mapping the distribution of the critically endangered cushion plant Azorellamacquariensis Orchard (Apiaceae) on sub-Antarctic Macquarie Island. Both pixel- and object-based classifications of the distribution of Azorella achieved very high overall validation accuracies (91.6–96.3%, κ = 0.849–0.924). Both two-class and three-class classifications were able to accurately and consistently identify the areas where Azorella was absent, indicating that these maps provide a suitable baseline for monitoring expected change in the distribution of the cushion plants. Detecting such change is critical given the threats this species is currently facing under altering environmental conditions. The method presented here has applications to monitoring a range of species, particularly in remote and isolated environments. PMID:23940805

  8. Mapping sub-antarctic cushion plants using random forests to combine very high resolution satellite imagery and terrain modelling.

    PubMed

    Bricher, Phillippa K; Lucieer, Arko; Shaw, Justine; Terauds, Aleks; Bergstrom, Dana M

    2013-01-01

    Monitoring changes in the distribution and density of plant species often requires accurate and high-resolution baseline maps of those species. Detecting such change at the landscape scale is often problematic, particularly in remote areas. We examine a new technique to improve accuracy and objectivity in mapping vegetation, combining species distribution modelling and satellite image classification on a remote sub-Antarctic island. In this study, we combine spectral data from very high resolution WorldView-2 satellite imagery and terrain variables from a high resolution digital elevation model to improve mapping accuracy, in both pixel- and object-based classifications. Random forest classification was used to explore the effectiveness of these approaches on mapping the distribution of the critically endangered cushion plant Azorella macquariensis Orchard (Apiaceae) on sub-Antarctic Macquarie Island. Both pixel- and object-based classifications of the distribution of Azorella achieved very high overall validation accuracies (91.6-96.3%, κ = 0.849-0.924). Both two-class and three-class classifications were able to accurately and consistently identify the areas where Azorella was absent, indicating that these maps provide a suitable baseline for monitoring expected change in the distribution of the cushion plants. Detecting such change is critical given the threats this species is currently facing under altering environmental conditions. The method presented here has applications to monitoring a range of species, particularly in remote and isolated environments.

  9. Wetting mode transition of nanoliter scale water droplets during evaporation on superhydrophobic surfaces with random roughness structure

    NASA Astrophysics Data System (ADS)

    Furuta, Tsutomu; Isobe, Toshihiro; Sakai, Munetoshi; Matsushita, Sachiko; Nakajima, Akira

    2012-01-01

    During evaporation, shape changes of nanoliter-scale (80-100 nL) water droplets were evaluated on two superhydrophobic surfaces with different random roughness (nm-coating, μm-coating). The square of the contact radius and the square of the droplet height decreased linearly with evaporation time. However, trend changes were observed at around 170 s (nm-coating) and around 150 s (μm-coating) suggesting a wetting mode transition. The calculated droplet radii for the wetting mode transition from the average roughness distance and the average roughness height of these surface structures were approximately equal to the experimental values at these trend changes. A certain level of correlation between the roughness size and droplet radius at the wetting mode transition was confirmed on surfaces with random roughness.

  10. Foraging behaviour of Lesser Sheathbills Chionis minor exploiting invertebrates on a sub-Antarctic island.

    PubMed

    Burger, Alan E

    1982-02-01

    During winter (May through October) many Lesser Sheathbills Chionis minor at Marion Island in the sub-Antarctic were obliged to leave their preferred foraging habitat in penguin colonies to forage for invertebrates on the island's coastal plain. The study describes factors affecting feeding success, time budgets and predation risk of the sheathbills which exploited these small, patchily dispersed prey. The birds appeared to select prey ≧1 mm in diameter, and ignore smaller, common invertebrates.Sheathbills were highly selective of foraging habitat. During 17 censuses made through the winter, 97% of the 1,504 birdsightings were at only eight of the 19 available vegetation types. Multiple regression analysis revealed that prey density was the most important criterion in habitat preference, followed by plant canopy height and distance of the habitat from the sea. These variables accounted for 78% of the variance of habitat use. Focal-animal observations in a sample of habitats showed that feeding success was correlated with prey density and distance from the sea. Tall vegetation impeded the locomotion and foraging of sheathbills. The sheathbills reduced predation risk from skuas Catharacta lonnbergi and travelling time by foraging near the shore. The spatial distribution of prey within vegetation types was apparently unimportant in habitat selection.During winter 83% of the sheathbills in the study foraged communally and 98% roosted communally. Flocks occurred only on good quality habitat and flocking probably facilitated habitat selection. Feeding success increased initially with increasing flock size but decreased in flocks greater than 15 birds, which was attributed to localized prey deletions. The sheathbills spent 88% of the daytime foraging; and feeding, looking around and walking comprised 99% of foraging time. Feeding time increased with increasing flock size, looking around decreased but walking was unaffected. Aggression was rare, was unaffected by flock

  11. Surface greenhouse gas fluxes downwind of a penguin colony in the maritime sub-Antarctic

    NASA Astrophysics Data System (ADS)

    Drewer, Julia; Braban, Christine F.; Tang, Y. Sim; Anderson, Margaret; Skiba, Ute M.; Dragosits, Ulrike; Trathan, Phil

    2015-12-01

    The relationship between ammonia (NH3) concentrations downwind from a penguin colony and local surface greenhouse gas (GHG) fluxes was investigated on the remote sub-Antarctic Bird Island (54°00‧S, 38°03‧W) during summer 2010 (November and December). A Macaroni penguin (Eudyptes chrysolophus) colony (40,000 pairs) at Goldcrest Point is a large point source of NH3 on the island and a measurement transect of 23 m, 36 m, 70 m, 143 m and 338 m was set up downwind from the colony. Atmospheric NH3 concentrations measured by passive diffusion samplers declined from 23 μg m-3 close to the colony to less than 1 μg m-3 338 m downwind. As increased nitrogen (N) deposition can affect soil carbon (C) and N cycling, it can therefore potentially influence GHG and nitric oxide (NO) emission rates. However, in this study, a clear correlation between surface GHG fluxes and atmospheric NH3 concentrations could not be established. Average fluxes for nitrous oxide (N2O), methane (CH4) and carbon dioxide (CO2) over the entire transect and the eight week study period ranged from 7 to 23 μg N2O-N m-2 h-1, -5.5-245 μg CH4 m-2 h-1, and CO2 respiration rates averaged 2.2 μmol m-2 s-1. Laboratory studies using intact soil cores from the transect also did not show any significant correlation between atmospheric NH3 concentrations and N2O, NO, CH4 emissions or CO2 respiration rates. Overall, fluxes measured in the laboratory study reflected the high variability measured in the field. Large changes in soil depth along the transect, due to the topography of the island, possibly influenced fluxes more than NH3 concentration and seabirds appeared to have a more localised input (e.g. ground nesting birds). However, warmer temperatures might have a large potential to increase GHG fluxes in this ecosystem. This study confirms that GHG fluxes do occur in these ornithogenic ecosystems, however, the scale of the impact remains largely unquantified due to high uncertainties and high spatial

  12. CLIVAR Mode Water Dynamics Experiment (CLIMODE) Fall 2005 R/V Oceanus Voyage 419, November 9, 2005 - November 27, 2005

    DTIC Science & Technology

    2006-02-01

    processes responsible for the formation and dissipation of North Atlantic subtropical mode water, also called Eighteen Degree Water (EDW). Among these...Anchor Position CUMODE I 2000 4000 SURVEY POS. 2 N 38 20.677 30()0 W 6448.195* 2000 SURVEY ROSA )1000 LU 0+ ANCHOR OVER -1000- W 6446.954 -4000...duration days Distance from actual waterline to buoy deck m 36 0 D M 4; 0 3 010- & LAA 3 7,? 2r-W-- -Z Z -7 {J (Y ~ -3 -. p -e 3 A e 𔃽 N -l N -. 37c ~ 7 w w

  13. Evaluation of neural network modeing to calculate well-watered leaf temperature of wine grape

    USDA-ARS?s Scientific Manuscript database

    Mild to moderate water stress is desirable in wine grape for controlling vine vigor and optimizing fruit yield and quality, but precision irrigation management is hindered by the lack of a reliable method to easily quantify and monitor vine water status. The crop water stress index (CWSI) that effec...

  14. Slow relaxation mode in concentrated oil-in-water microemulsions consisting of repulsive droplets

    NASA Astrophysics Data System (ADS)

    Hattori, Y.; Ushiki, H.; Courbin, L.; Panizza, P.

    2007-02-01

    The present contribution reports on the observation of two diffusive relaxation modes in a concentrated microemulsion made of repulsive droplets. These two modes can be interpreted in the frame of Weissman’s and Pusey’s theoretical pioneering works. The fast mode is associated to the collective diffusion of droplets whereas the slow one corresponds to the relaxation of droplet concentration fluctuations associated with composition and/or size. We show that (i) repulsive interactions considerably slow down the latter and (ii) a generalized Stokes Einstein relationship between its coefficient of diffusion and the Newtonian viscosity of the solutions, similar to the Walden’s rule for electrolytes, holds for concentrated microemulsion systems made of repulsive droplets.

  15. Libration induced stretching mode excitation for pump-probe spectroscopy in pure liquid water.

    PubMed

    Amir, Wafa; Gallot, Guilhem; Hache, François

    2004-10-22

    We developed an experimental approach to study pure liquid water in the infrared and avoid thermal effects. This technique is based on libration induced stretching excitation of water molecules. A direct correspondence between frequencies within the libration and OH stretching bands is demonstrated. Energy diffusion is studied in pure liquid water by measuring wave packet dynamics of OH stretching vibrator with infrared femtosecond spectroscopy. Wave packet dynamics reveals ultrafast energy dynamics and reflects 130 fs intermolecular energy transfer between water vibrators. Energy diffusion is almost two orders of magnitude faster than self diffusion in water.

  16. Coupled mode transport theory for sound transmission through an ocean with random sound speed perturbations: coherence in deep water environments.

    PubMed

    Colosi, John A; Chandrayadula, Tarun K; Voronovich, Alexander G; Ostashev, Vladimir E

    2013-10-01

    Second moments of mode amplitudes at fixed frequency as a function of separations in mode number, time, and horizontal distance are investigated using mode-based transport equations and Monte Carlo simulation. These second moments are used to study full-field acoustic coherence, including depth separations. Calculations for low-order modes between 50 and 250 Hz are presented using a deep-water Philippine Sea environment. Comparisons between Monte Carlo simulations and transport theory for time and depth coherence at frequencies of 75 and 250 Hz and for ranges up to 500 km show good agreement. The theory is used to examine the accuracy of the adiabatic and quadratic lag approximations, and the range and frequency scaling of coherence. It is found that while temporal coherence has a dominant adiabatic component, horizontal and vertical coherence have more equal contributions from coupling and adiabatic effects. In addition, the quadratic lag approximation is shown to be most accurate at higher frequencies and longer ranges. Last the range and frequency scalings are found to be sensitive to the functional form of the exponential decay of coherence with lag, but temporal and horizontal coherence show scalings that fall quite close to the well-known inverse frequency and inverse square root range laws.

  17. Single longitudinal mode diamond Raman laser in the eye-safe spectral region for water vapor detection.

    PubMed

    Lux, Oliver; Sarang, Soumya; Williams, Robert J; McKay, Aaron; Mildren, Richard P

    2016-11-28

    We report a narrowband and tunable diamond Raman laser generating eye-safe radiation suitable for water vapor detection. Frequency conversion of a tunable pump laser operating from 1063 to 1066 nm to the second order Stokes component in an external standing-wave cavity yielded 7 W of multimode output power in the wavelength range from 1483 to 1488 nm at a conversion efficiency of 21%. Stable single longitudinal mode operation was achieved over the whole tuning range at low power (0.1 W), whereas incorporation of a volume Bragg grating as an output coupler enabled much higher stable power to be attained (0.5 W). A frequency stability of 40 MHz was obtained over a minute without active cavity stabilization. It was found that mode stability is aided via seeding of the second Stokes by four-wave mixing, which leads to a doubling of the mode-hopping interval. The laser was employed for the detection of water vapor in ambient air, demonstrating its potential for remote sensing applications.

  18. Relationship between height and width of resonance peaks in a whispering gallery mode resonator immersed in water and sucrose solutions

    NASA Astrophysics Data System (ADS)

    Teraoka, Iwao; Yao, Haibei; Huiyi Luo, Natalie

    2017-06-01

    We employed a recently developed whispering gallery mode (WGM) dip sensor made of silica to obtain spectra for many resonance peaks in water and solutions of sucrose at different concentrations and thus having different refractive indices (RI). The apparent Q factor was estimated by fitting each peak profile in the busy resonance spectrum by a Lorentzian or a sum of Lorentzians. A plot of the Q factor as a function the peak height for all the peaks analyzed indicates a straight line with a negative slope as the upper limit, for each of water and the solutions. A coupling model for a resonator and a pair of fiber tapers to feed and pick up light, developed here, supports the presence of the upper limit. We also found that the round-trip attenuation of WGM was greater than the one estimated from light absorption by water, and the difference increased with the concentration of sucrose.

  19. Changes in meridional fluxes and water properties in the Southern Hemisphere subtropical oceans between 1992/1995 and 2003/2004

    NASA Astrophysics Data System (ADS)

    Katsumata, K.; Fukasawa, M.

    2011-04-01

    substantial seasonal or higher-frequency variations are filtered out by comparing the water properties on neutral density surfaces. Along the South Pacific P06 line, Subantarctic Mode Water on γ = 26.8 (the neutral density surface of 1026.8 kg m -3) becomes cooler and fresher by up to 0.2 °C and 0.04 psu (practical salinity unit). The property changes are largest in the Chile Basin and smallest in the Tasman Sea. In the deep Southwest Pacific Basin, a small but statistically significant freshening of 0.002 psu was found in the Circumpolar Deep Water ( γ = 28.11). Along the South Atlantic A10 line, Subantarctic Mode Water and Antarctic Intermediate Water were found warmer and saltier to the east of the Mid-Atlantic Ridge (e.g. by 0.2 °C and 0.05 psu on γ = 26.8; 0.1 °C and 0.02 psu on γ = 27.4). North Atlantic Deep Water and Antarctic Bottom Water were found warmer and saltier particularly in the Argentine Basin (e.g. by 0.02 °C and 0.004 psu on γ = 28.0; 0.01 °C and 0.002 psu on γ = 28.2). Along the south Indian I03/I04 lines, Subantarctic Mode Water was found warmer and saltier to the west of 95°E (e.g. by 0.2 °C and 0.05 psu on γ = 26.8) and cooler and fresher to the east (e.g. a difference of -0.2 °C and -0.05 psu on γ = 26.8).

  20. Data Collection Plan to Populate the Light Water Reactor Sustainability Failure Mode Degradation Library

    SciTech Connect

    Magdy S. Tawfik; Binh T. Pham; Vivek Agarwal; Nancy J. Lybeck

    2011-09-01

    Interest in implementing advanced Prognostic Health Management (PHM) systems in commercial nuclear power plants (NPPs) has increased rapidly in recent years, with an overarching goal of implementing of improving the safety, reliability, and economics/profitability of the aging nuclear fleet and extending their service life in the most cost-effective manner. The PHM system utilizes prognostic tools to estimate the remaining useful life (RUL) of a component or system of components based on current and predicted operating conditions. An effective implementation of the PHM system will anticipate and identify unique age-dependent degradation modes to provide early warning of emerging problems. Selection of the components and structures to be monitored is a crucial step for successful PHM implementation in NPPs. A selection framework is recommended for risk significant components (both safety-related and non-safety related) based on the Fussell-Vesely (F-V) Importance Measure and the Risk Achievement Worth (RAW) measure. For the selected components, a failure mode degradation library will be developed consisting of data corresponding to different failure/degradation modes. In lieu of constructing an expensive scaled test facility, several data sources are identified for populating the failure mode degradation library, including various national laboratories, universities, agencies, and industries.

  1. Intersexual differences in the diving behaviour of foraging subantarctic cormorant (Phalacrocorax albiventer) and Japanese cormorant (P. filamentosus).

    PubMed

    Kato, A; Watanuki, Y; Shaughnessy, P; Le Maho, Y; Naito, Y

    1999-07-01

    Cormorants feed by feet-propelled diving. How cormorants optimize foraging is of a particular interest in relation to the understanding of the feeding strategies of diving birds, as well as within the debate about cormorants' impact on sustainable resources. Using microdata loggers that recorded diving depth, we investigated the foraging strategy of males and females of subantarctic cormorants, which inhabit cold regions, and of Japanese cormorants, which live in the northern temperate zone. For both species, males and females daily spent the same amount of time submerged, and apparently captured the same amount of fish. However, males dived deeper and longer, which could be explained by their 15-20% larger body mass and may minimize potential competition for food.

  2. Contrasting nurse plants and nurse rocks: The spatial distribution of seedlings of two sub-Antarctic species

    NASA Astrophysics Data System (ADS)

    Haussmann, N. S.; McGeoch, M. A.; Boelhouwers, J. C.

    2010-05-01

    Positive plant interactions, such as those associated with nurse plants, have been suggested to dominate over negative interactions in environments with high abiotic stress. Here we demonstrate that the sub-Antarctic cushion plant species, Azorella selago (Apiaceae), positively affects the distribution of both its own seedlings and those of the perennial grass, Agrostis magellanica (Poaceae). As a result of the light weight and small size of seeds of both species, coupled with strong winds experienced in the study area, we consider it unlikely that these patterns are the result of very localized seed dispersal from the study cushions themselves. Instead, we suggest that both cushions and rocks act as seed traps, trapping seeds dispersed by wind, runoff and/or downslope sediment transport through frost creep. In addition, increased A. selago seedling numbers around cushions, but not around rocks, suggest that cushions provide a biological nurse effect, such as improving soil nutrient status or providing mychorrizae, to seedlings of their own kind.

  3. Temporal and spatial variation in mercury concentrations in some albatrosses and petrels from the sub-Antarctic

    SciTech Connect

    Thompson, D.R.; Furness, R.W.; Lewis, S.A. )

    1993-01-01

    Mercury concentrations in albatrosses and some other large procellariiforms are very much higher than found in other groups of seabirds. Analysis of mercury concentrations in feather samples collected prior to 1950 and after this date showed slight, but significant, increased in three out of ten sub-Antarctic procellariiform species. The lack of widespread and pronounced increases in mercury concentrations in procellariiforms between these periods may indicate that industrial and agricultural emissions of mercury in the southern hemisphere have been relatively minor and the high concentrations are predominantly due to natural processes. Mercury concentrations were relatively consistent between body feathers of individuals, and showed no variation related to adult age (in years). Within species, mercury concentrations tended to be highest in New Zealand populations and lowest in Falkland Island and South Georgia populations. Mercury concentrations also varied among species, but not in a way that could be related to diet. 27 refs., 1 fig., 3 tabs.

  4. Evaluation of dual-mode rainwater harvesting system to mitigate typhoon-induced water shortage in Taiwan.

    PubMed

    Islam, M M; Chou, F N-F; Liaw, C-H

    2010-01-01

    The water shortage of today's world is one of the most challenging problems and the world is looking for the best solution to reduce it. Some human made causes and also natural causes are liable for the shortage of the existing water supply system. In Taiwan, especially during typhoon, the turbidity of raw water increases beyond the treatment level and the plant cannot supply required amount of water. To make the system effective, a couple of days are needed and the shortage occurs. The purpose of this study is to solve this emergency shortage problem. A dual-mode Rainwater Harvesting System (RWHS) was designed for this study as a supplement to the existing water supply system to support some selected non-potable components such as toilet and urinal flushing of an elementary school. An optimal design algorithm was developed using YAS (yield after spillage) and YBS (yield before spillage) release rules. The study result proved that an optimum volume of tank can solve the emergency water shortage properly. The system was found to be more reliable in Taipei area than that of Tainan area. The study also discovered that a government subsidy would be needed to promote the system in Taiwan.

  5. The impact of water column variability on horizontal wave number estimation and mode based geoacoustic inversion results.

    PubMed

    Becker, Kyle M; Frisk, George V

    2008-02-01

    The influence of water column variability on low-frequency, shallow water geoacoustic inversion results is considered. The data are estimates of modal eigenvalues obtained from measurements of a point source acoustic field using a horizontal aperture array in the water column. The inversion algorithm is based on perturbations to a background waveguide model with seabed properties consistent with the measured eigenvalues. Water column properties in the background model are assumed to be known, as would be obtained from conductivity, temperature, and depth measurements. The scope of this work in addressing the impact of water column variability on inversion is twofold. Range-dependent propagation effects as they pertain to eigenvalue estimation are first considered. It is shown that mode coupling is important even for weak internal waves and can enhance modal eigenvalue estimates. Second, the effect of the choice of background sound speed profile in the water column is considered for its impact on the estimated bottom acoustic properties. It is shown that a range-averaged sound velocity profile yields the best geoacoustic parameter estimates.

  6. Gene flow and hybridization between numerically imbalanced populations of two duck species on the subantarctic island of South Georgia.

    PubMed

    McCracken, Kevin G; Wilson, Robert E; Martin, Anthony R

    2013-01-01

    Hybridization is common between species of animals, particularly in waterfowl (Anatidae). One factor shown to promote hybridization is restricted mate choice, which can occur when 2 species occur in sympatry but one is rare. According to the Hubbs principle, or "desperation hypothesis," the rarer species is more likely to mate with heterospecifics. We report the second of 2 independent examples of hybridization between 2 species of ducks inhabiting island ecosystems in the Subantarctic and South Atlantic Ocean. Yellow-billed pintails (Anas georgica) and speckled teal (Anas flavirostris) are abundant in continental South America, where they are sympatric and coexist in mixed flocks. But on South Georgia, an isolated island in the Subantarctic, the pintail population of approximately 6000 pairs outnumbers a small breeding population of speckled teal 300∶1. Using 6 genetic loci (mtDNA and 5 nuclear introns) and Bayesian assignment tests coupled with coalescent analyses, we identified hybrid-origin speckled teal alleles in 2 pintails on South Georgia. While it is unclear whether introgression has also occurred into the speckled teal population, our data suggest that this hybridization was not a recent event, but occurred some time ago. We also failed to identify unequivocal evidence of introgression in a much larger sample of pintails and speckled teal from Argentina using a 3-population "Isolation-with-Migration" coalescent analysis. Combined with parallel findings of hybridization between these same 2 duck species in the Falkland Islands, where population ratios are reversed and pintails are outnumbered by speckled teal 1:10, our results provide further support for the desperation hypothesis, which predicts that scarcity in one population and abundance of another will often lead to hybridization. While the South Georgia pintail population appears to be thriving, it's possible that low density of conspecific mates and inverse density dependence (Allee effect) may be

  7. Gene Flow and Hybridization between Numerically Imbalanced Populations of Two Duck Species on the Subantarctic Island of South Georgia

    PubMed Central

    McCracken, Kevin G.; Wilson, Robert E.; Martin, Anthony R.

    2013-01-01

    Hybridization is common between species of animals, particularly in waterfowl (Anatidae). One factor shown to promote hybridization is restricted mate choice, which can occur when 2 species occur in sympatry but one is rare. According to the Hubbs principle, or "desperation hypothesis," the rarer species is more likely to mate with heterospecifics. We report the second of 2 independent examples of hybridization between 2 species of ducks inhabiting island ecosystems in the Subantarctic and South Atlantic Ocean. Yellow-billed pintails (Anas georgica) and speckled teal (Anas flavirostris) are abundant in continental South America, where they are sympatric and coexist in mixed flocks. But on South Georgia, an isolated island in the Subantarctic, the pintail population of approximately 6000 pairs outnumbers a small breeding population of speckled teal 300∶1. Using 6 genetic loci (mtDNA and 5 nuclear introns) and Bayesian assignment tests coupled with coalescent analyses, we identified hybrid-origin speckled teal alleles in 2 pintails on South Georgia. While it is unclear whether introgression has also occurred into the speckled teal population, our data suggest that this hybridization was not a recent event, but occurred some time ago. We also failed to identify unequivocal evidence of introgression in a much larger sample of pintails and speckled teal from Argentina using a 3-population "Isolation-with-Migration" coalescent analysis. Combined with parallel findings of hybridization between these same 2 duck species in the Falkland Islands, where population ratios are reversed and pintails are outnumbered by speckled teal 1:10, our results provide further support for the desperation hypothesis, which predicts that scarcity in one population and abundance of another will often lead to hybridization. While the South Georgia pintail population appears to be thriving, it's possible that low density of conspecific mates and inverse density dependence (Allee effect) may be

  8. Mode-specific vibrational energy relaxation of amide I' and II' modes in N-methylacetamide/water clusters: intra- and intermolecular energy transfer mechanisms.

    PubMed

    Zhang, Yong; Fujisaki, Hiroshi; Straub, John E

    2009-04-02

    The mode-specific vibrational energy relaxation of the amide I' and amide II' modes in NMA-d(1)/(D(2)O)(n) (n = 0-3) clusters were studied using the time-dependent perturbation theory at the B3LYP/aug-cc-pvdz level. The amide modes were identified for each cluster based on the potential energy distribution of each mode. The vibrational population relaxation time constants were derived for the amide I' and II' modes. Results for the amide I' mode relaxation of NMA-d(1)/(D(2)O)(3) agree well with previous experimental results. The energy relaxation pathways were identified, and both intra- and intermolecular mechanisms were found to be important. The amide II' mode was identified in the energy transfer pathways from the excited amide I' mode of NMA-d(1)/(D(2)O)(n) (n = 1-3) clusters. The modes associated with methyl group deformation were found to play a role in the mechanism of energy transfer from both excited amide I' and II' modes. The kinetics of energy flow in the cluster were examined by solving a master equation describing the vibrational energy relaxation process from excited system mode as a multistep reaction with the third order Fermi resonance parameters as the reaction rate constants. The intramolecular energy transfer mechanism was found to dominate the short time energy flow dynamics, whereas the intermolecular mechanism was found to be dominant at longer times.

  9. Evaluation of genotoxic effects of surface waters using a battery of bioassays indicating different mode of action.

    PubMed

    Han, Yingnan; Li, Na; Oda, Yoshimitsu; Ma, Mei; Rao, Kaifeng; Wang, Zijian; Jin, Wei; Hong, Gang; Li, Zhiguo; Luo, Yi

    2016-11-01

    With the burgeoning contamination of surface waters threatening human health, the genotoxic effects of surface waters have received much attention. Because mutagenic and carcinogenic compounds in water cause tumors by different mechanisms, a battery of bioassays that each indicate a different mode of action (MOA) is required to evaluate the genotoxic effects of contaminants in water samples. In this study, 15 water samples from two source water reservoirs and surrounding rivers in Shijiazhuang city of China were evaluated for genotoxic effects. Target chemical analyses of 14 genotoxic pollutants were performed according to the Environmental quality standards for surface water of China. Then, the in vitro cytokinesis-block micronucleus (CBMN) assay, based on a high-content screening technique, was used to detect the effect of chromosome damage. The SOS/umu test using strain TA1535/pSK1002 was used to detect effects on SOS repair of gene expression. Additionally, two other strains, NM2009 and NM3009, which are highly sensitive to aromatic amines and nitroarenes, respectively, were used in the SOS/umu test to avoid false negative results. In the water samples, only two of the genotoxic chemicals listed in the water standards were detected in a few samples, with concentrations that were below water quality standards. However, positive results for the CBMN assay were observed in two river samples, and positive results for the induction of umuC gene expression in TA1535/pSK1002 were observed in seven river samples. Moreover, positive results were observed for NM2009 with S9 and NM3009 without S9 in some samples that had negative results using the strain TA1535/pSK1002. Based on the results with NM2009 and NM3009, some unknown or undetected aromatic amines and nitroarenes were likely in the source water reservoirs and the surrounding rivers. Furthermore, these compounds were most likely the causative pollutants for the genotoxic effect of these water samples. Therefore

  10. Classification, mode of action and production strategy of xylanase and its application for biofuel production from water hyacinth.

    PubMed

    Uday, Uma Shankar Prasad; Choudhury, Payel; Bandyopadhyay, Tarun Kanti; Bhunia, Biswanath

    2016-01-01

    Xylanases are classified under glycoside hydrolase families which represent one of the largest groups of commercial enzymes. Depolymerizing xylan molecules into monomeric pentose units involves the synergistic action of mainly two key enzymes which are endo-β-xylanase and β-xylosidase. Xylanases are different with respect to their mode of action, substrate specificities, biochemical properties, 3D structure and are widely produced by a spectrum of bacteria and fungi. Currently, large scale production of xylanase can be produced through the application of genetic engineering tool which allow fast identification of novel xylanase genes and their genetic variations makes it an ideal enzymes. Due to depletion of fossil fuel, there is urgent need to find out environment friendly and sustainable energy sources. Therefore, utilisation of cheap lignocellulosic materials along with proper optimisation of process is most important for cost efficient ethanol production. Among, various types of lignocellulosic substances, water hyacinth, a noxious aquatic weed, has been found in many tropical. Therefore, the technological development for biofuel production from water hyacinth is becoming commercially worthwhile. In this review, the classification and mode of action of xylanase including genetic regulation and strategy for robust xylanase production have been critically discussed from recent reports. In addition various strategies for cost effective biofuel production from water hyacinth including chimeric proteins design has also been critically evaluated. Copyright © 2015 Elsevier B.V. All rights reserved.

  11. Surface modes of a sessile water drop: An optical tweezer based study

    NASA Astrophysics Data System (ADS)

    Ghosh, Shankar; Sharma, Prerna; Bhattacharya, S.

    2007-11-01

    A high-precision method to study the dynamics of two-fluid interfaces using an optical tweezer and a phase-sensitive detection technique are described. The disturbances set up at the interface are studied by analyzing the motion of an optically trapped particle in the bulk of the fluid, i.e., away from the interface. The usefulness of the technique is demonstrated for the well-known problem of a horizontally vibrated sessile liquid drop. The vibrational modes of the liquid drop excited by sinusoidally vibrating the support in a horizontal plane appear as resonances in the motion of the trapped particle. The nature of the resonance is studied in detail by measuring the real part, the imaginary part, and the phase response of the motion of the particle as a function of the "effective" size of the liquid drop. Excellent quantitative agreement with the theoretically predicted values of the eigenfrequencies and damping of the surface modes is obtained.

  12. Surface modes of a sessile water drop: an optical tweezer based study.

    PubMed

    Ghosh, Shankar; Sharma, Prerna; Bhattacharya, S

    2007-11-01

    A high-precision method to study the dynamics of two-fluid interfaces using an optical tweezer and a phase-sensitive detection technique are described. The disturbances set up at the interface are studied by analyzing the motion of an optically trapped particle in the bulk of the fluid, i.e., away from the interface. The usefulness of the technique is demonstrated for the well-known problem of a horizontally vibrated sessile liquid drop. The vibrational modes of the liquid drop excited by sinusoidally vibrating the support in a horizontal plane appear as resonances in the motion of the trapped particle. The nature of the resonance is studied in detail by measuring the real part, the imaginary part, and the phase response of the motion of the particle as a function of the "effective" size of the liquid drop. Excellent quantitative agreement with the theoretically predicted values of the eigenfrequencies and damping of the surface modes is obtained.

  13. Observation of the low frequency vibrational modes of bacteriophage M13 in water by Raman spectroscopy

    PubMed Central

    Tsen, KT; Dykeman, Eric C; Sankey, Otto F; Lin, Nien-Tsung; Tsen, Shaw-Wei D; Kiang, Juliann G

    2006-01-01

    Background Recently, a technique which departs radically from conventional approaches has been proposed. This novel technique utilizes biological objects such as viruses as nano-templates for the fabrication of nanostructure elements. For example, rod-shaped viruses such as the M13 phage and tobacco mosaic virus have been successfully used as biological templates for the synthesis of semiconductor and metallic nanowires. Results and discussion Low wave number (≤ 20 cm-1) acoustic vibrations of the M13 phage have been studied using Raman spectroscopy. The experimental results are compared with theoretical calculations based on an elastic continuum model and appropriate Raman selection rules derived from a bond polarizability model. The observed Raman mode has been shown to belong to one of the Raman-active axial torsion modes of the M13 phage protein coat. Conclusion It is expected that the detection and characterization of this low frequency vibrational mode can be used for applications in nanotechnology such as for monitoring the process of virus functionalization and self-assembly. For example, the differences in Raman spectra can be used to monitor the coating of virus with some other materials and nano-assembly process, such as attaching a carbon nanotube or quantum dots. PMID:16995944

  14. Shift in failure modes in foam core sandwich composites subject to repeated slamming on water

    NASA Astrophysics Data System (ADS)

    Figueroa, Evaristo; Shafiq, Basir

    2013-06-01

    A test program designed and carried out to mimic the repeated impact of the bow section of fast-moving small boats on the ocean surface provided some unique observations in terms of failure mode transition. Damage progression and modes of failure were evaluated for two types of sandwich composites with comparable global strength and stiffness but different foam density and facesheet strength. Testing was performed on flat rectangular specimens that contained symmetric semi-elliptical edge flaws produced near the end of the specimen held by the rotating cam. Type 1 specimens (softer core/stronger facesheet) consistently failed by interface and through-the-thickness core shear, independent of the flaw size. In contrast, a gradual decrease in flaw size in Type 2 specimens (denser core/weaker facesheet) produced a striking transition in the mode of failure from local buckling in the vicinity of the flaw site along with exponentially increasing lifetime, to interface shear failure at the free end accompanied by a dramatic drop in lifetime. The lifetime of Type 2 specimens was more than two orders of magnitude greater than that of Type 1 specimens.

  15. Bottom attenuation estimation using sound intensity fluctuations due to mode coupling by nonlinear internal waves in shallow water.

    PubMed

    Grigorev, Valery A; Katsnelson, Boris G; Lynch, James F

    2016-11-01

    Analyses of fluctuations of low frequency signals (300 ± 30 Hz) propagating in shallow water in the presence of nonlinear internal waves (NIWs) in the Shallow Water 2006 experiment are carried out. Signals were received by a vertical line array at a distance of ∼20 km from the source. A NIW train was moving totally inside of the acoustic track, and the angle between the wave front of the NIW and the acoustic track in the horizontal plane was ∼10°. It is shown that the spectrum of the sound intensity fluctuations contains peaks corresponding to the coupling of pairs of propagating modes. Analysis of spectra at different hydrophone depths, and also summed over depth allows the authors to estimate attenuation in the bottom sediments.

  16. Non-invasive assessment of leaf water status using a dual-mode microwave resonator.

    PubMed

    Dadshani, Said; Kurakin, Andriy; Amanov, Shukhrat; Hein, Benedikt; Rongen, Heinz; Cranstone, Steve; Blievernicht, Ulrich; Menzel, Elmar; Léon, Jens; Klein, Norbert; Ballvora, Agim

    2015-01-01

    The water status in plant leaves is a good indicator for the water status in the whole plant revealing stress if the water supply is reduced. The analysis of dynamic aspects of water availability in plant tissues provides useful information for the understanding of the mechanistic basis of drought stress tolerance, which may lead to improved plant breeding and management practices. The determination of the water content in plant tissues during plant development has been a challenge and is currently feasible based on destructive analysis only. We present here the application of a non-invasive quantitative method to determine the volumetric water content of leaves and the ionic conductivity of the leaf juice from non-invasive microwave measurements at two different frequencies by one sensor device. A semi-open microwave cavity loaded with a ceramic dielectric resonator and a metallic lumped-element capacitor- and inductor structure was employed for non-invasive microwave measurements at 150 MHz and 2.4 Gigahertz on potato, maize, canola and wheat leaves. Three leaves detached from each plant were chosen, representing three developmental stages being representative for tissue of various age. Clear correlations between the leaf- induced resonance frequency shifts and changes of the inverse resonator quality factor at 2.4 GHz to the gravimetrically determined drying status of the leaves were found. Moreover, the ionic conductivity of Maize leaves, as determined from the ratio of the inverse quality factor and frequency shift at 150 MHz by use of cavity perturbation theory, was found to be in good agreement with direct measurements on plant juice. In conjunction with a compact battery- powered circuit board- microwave electronic module and a user-friendly software interface, this method enables rapid in-vivo water amount assessment of plants by a handheld device for potential use in the field.

  17. Crystallization, preliminary X-ray diffraction studies and Raman microscopy of the major haemoglobin from the sub-Antarctic fish Eleginops maclovinus in the carbomonoxy form

    PubMed Central

    Merlino, Antonello; Vitagliano, Luigi; Balsamo, Anna; Nicoletti, Francesco P.; Howes, Barry D.; Giordano, Daniela; Coppola, Daniela; di Prisco, Guido; Verde, Cinzia; Smulevich, Giulietta; Mazzarella, Lelio; Vergara, Alessandro

    2010-01-01

    The blood of the sub-Antarctic fish Eleginops maclovinus (Em) contains three haemoglobins. The major haemoglobin (Hb1Em) displays the Root effect, a drastic decrease in the oxygen affinity and a loss of cooperativity at acidic pH. The carbomonoxy form of HbEm1 has been crystallized in two different crystal forms, orthorhombic (Ortho) and hexagonal (Hexa), and high-resolution diffraction data have been collected for both forms (1.45 and 1.49 Å resolution, respectively). The high-frequency resonance Raman spectra collected from the two crystal forms using excitation at 514 nm were almost indistinguishable. Hb1Em is the first sub-Antarctic fish Hb to be crystallized and its structural characterization will shed light on the molecular mechanisms of cold adaptation and the role of the Root effect in fish haemoglobins. PMID:21045316

  18. Influence of water conductivity on particular electrospray modes with dc corona discharge — optical visualization approach

    NASA Astrophysics Data System (ADS)

    Pongrác, Branislav; Kim, Hyun-Ha; Negishi, Nobuaki; Machala, Zdenko

    2014-08-01

    The effect of water conductivity on electrospraying of water was studied in combination with positive DC corona discharge generated in air. We used a point-to-plane geometry of electrodes with a hollow syringe needle anode opposite to the metal mesh cathode. We employed total average current measurements and high-speed camera fast time-resolved imaging. We visualized the formation of a water jet (filament) and investigated corona discharge behavior for various water conductivities. Depending on the conductivity, various jet properties were observed: pointy, prolonged, and fast spreading water filaments for lower conductivity; in contrast to rounder, broader, and shorter quickly disintegrating filaments for higher conductivity. The large acceleration values (4060 m/s2 and 520 m/s2 for 2 μS/cm and 400 μS/cm, respectively) indicate that the process is mainly governed by the electrostatic force. In addition, with increasing conductivity, the breakdown voltage for corona-to-spark transition was decreasing.

  19. Correlation between shape, evaporation mode and mobility of small water droplets on nanorough fibres.

    PubMed

    Funk, C S; Winzer, B; Peukert, W

    2014-03-01

    The dynamic wetting behaviour and the mobility of droplets on fibres is a very important factor in coating processes, textile fabrication, in self-cleaning processes and in the filtration of fluids. In principal, filter regeneration depends on the mobility of the droplets on the fibre surface. Mobile droplets tend to coalesce which greatly simplifies their removal from the filter. In this contribution mobility analyses of water droplets on monofilaments in air are performed. Studies of droplet evaporation on pure PET fibres and on nanorough fibres coated with SiO2 nanoparticles of diameters between 6 nm and 50 nm in a hydrophilic binder system were done. We show that the mobility of water droplets correlates with the droplet conformation which in turn is determined by the droplet-fibre interface. We demonstrate that fibre coatings can be used to tailor the conformation and mobility of water droplets. The smaller the nanoparticle diameters in the coating are, the smaller are the contact angles between water droplets and fibre and the better is the mobility of the droplets on the fibre. Our results allow a fast optimization of the fibre surface properties which are directly influencing the contact angle, the mobility and the coalescence of water droplets and thus filter regeneration.

  20. Directional Analysis of Sub-Antarctic Climate Change on South Georgia 1905-2009

    NASA Astrophysics Data System (ADS)

    Sakamoto Ferranti, Emma Jayne; Solera Garcia, Maria Angeles; Timmis, Roger James; Gerrard McKenna, Paul; Whyatt, James Duncan

    2010-05-01

    Directional analysis has been used to study changes in the sub-polar climate of the mountainous and glacierised sub-Antarctic island of South Georgia (54-55°S, 36-38°W). Significantly for climate change studies, South Georgia lies in the Scotia Sea between polar and temperate latitudes, and approximately 1000 km northeast and downwind of the Antarctic Peninsula - one of the fastest-warming regions on Earth (Vaughan et al., 2001). South Georgia was chosen for directional analysis because its climate is substantially advected by predominantly westerly circulations, and because it has a long (since 1905) meteorological record from King Edward Point (KEP) on its eastern side. Additional shorter records from Bird Island at the northwest tip of South Georgia allow comparison between windward (Bird Island) and leeward (KEP) climate regimes. The variation of mountain barrier heights with direction from KEP allows climate changes to be studied under different amounts of orographic influence (from ~700 m to ~2200 m). Records of glacier advance and retreat provide further independent evidence of climate change for comparison with the meteorological record. Directional climate analysis is based on a series of monthly-mean pressure fields defining the orientation and strength of synoptic-scale air-mass advection over the Scotia Sea. These fields are used to define directional climatologies for six 30° sectors with bearings from 150-180° to 300-330°; these sectors encompass 99% of recorded months since 1905. The climatologies summarise the frequencies of air masses from each sector, and the accompanying temperatures and precipitation. The 6 sectors can be broadly associated with 4 air-mass types and source regions: (i) sectors 150-210° advect cold polar maritime air that originated over the Antarctic continent before passing over the Weddell Sea, (ii) sectors 210-270° advect warmer, more stable polar maritime air from the Bellingshausen Sea/Antarctic Peninsula region

  1. Single-mode lasing from colloidal water-soluble CdSe/CdS quantum dot-in-rods.

    PubMed

    Di Stasio, Francesco; Grim, Joel Q; Lesnyak, Vladimir; Rastogi, Prachi; Manna, Liberato; Moreels, Iwan; Krahne, Roman

    2015-03-18

    Core-shell CdSe/CdS nanocrystals are a very promising material for light emitting applications. Their solution-phase synthesis is based on surface-stabilizing ligands that make them soluble in organic solvents, like toluene or chloroform. However, solubility of these materials in water provides many advantages, such as additional process routes and easier handling. So far, solubilization of CdSe/CdS nanocrystals in water that avoids detrimental effects on the luminescent properties poses a major challenge. This work demonstrates how core-shell CdSe/CdS quantum dot-in-rods can be transferred into water using a ligand exchange method employing mercaptopropionic acid (MPA). Key to maintaining the light-emitting properties is an enlarged CdS rod diameter, which prevents potential surface defects formed during the ligand exchange from affecting the photophysics of the dot-in-rods. Films made from water-soluble dot-in-rods show amplified spontaneous emission (ASE) with a similar threshold (130 μJ/cm(2)) as the pristine material (115 μJ/cm(2)). To demonstrate feasibility for lasing applications, self-assembled microlasers are fabricated via the "coffee-ring effect" that display single-mode operation and a very low threshold of ∼10 μJ/cm(2). The performance of these microlasers is enhanced by the small size of MPA ligands, enabling a high packing density of the dot-in-rods.

  2. Isotope effects in liquid water probed by transmission mode x-ray absorption spectroscopy at the oxygen K-edge

    NASA Astrophysics Data System (ADS)

    Schreck, Simon; Wernet, Philippe

    2016-09-01

    The effects of isotope substitution in liquid water are probed by x-ray absorption spectroscopy at the O K-edge as measured in transmission mode. Confirming earlier x-ray Raman scattering experiments, the D2O spectrum is found to be blue shifted with respect to H2O, and the D2O spectrum to be less broadened. Following the earlier interpretations of UV and x-ray Raman spectra, the shift is related to the difference in ground-state zero-point energies between D2O and H2O, while the difference in broadening is related to the difference in ground-state vibrational zero-point distributions. We demonstrate that the transmission-mode measurements allow for determining the spectral shapes with unprecedented accuracy. Owing in addition to the increased spectral resolution and signal to noise ratio compared to the earlier measurements, the new data enable the stringent determination of blue shift and broadening in the O K-edge x-ray absorption spectrum of liquid water upon isotope substitution. The results are compared to UV absorption data, and it is discussed to which extent they reflect the differences in zero-point energies and vibrational zero-point distributions in the ground-states of the liquids. The influence of the shape of the final-state potential, inclusion of the Franck-Condon structure, and differences between liquid H2O and D2O resulting from different hydrogen-bond environments in the liquids are addressed. The differences between the O K-edge absorption spectra of water from our transmission-mode measurements and from the state-of-the-art x-ray Raman scattering experiments are discussed in addition. The experimentally extracted values of blue shift and broadening are proposed to serve as a test for calculations of ground-state zero-point energies and vibrational zero-point distributions in liquid H2O and D2O. This clearly motivates the need for new calculations of the O K-edge x-ray absorption spectrum of liquid water.

  3. Isotope effects in liquid water probed by transmission mode x-ray absorption spectroscopy at the oxygen K-edge.

    PubMed

    Schreck, Simon; Wernet, Philippe

    2016-09-14

    The effects of isotope substitution in liquid water are probed by x-ray absorption spectroscopy at the O K-edge as measured in transmission mode. Confirming earlier x-ray Raman scattering experiments, the D2O spectrum is found to be blue shifted with respect to H2O, and the D2O spectrum to be less broadened. Following the earlier interpretations of UV and x-ray Raman spectra, the shift is related to the difference in ground-state zero-point energies between D2O and H2O, while the difference in broadening is related to the difference in ground-state vibrational zero-point distributions. We demonstrate that the transmission-mode measurements allow for determining the spectral shapes with unprecedented accuracy. Owing in addition to the increased spectral resolution and signal to noise ratio compared to the earlier measurements, the new data enable the stringent determination of blue shift and broadening in the O K-edge x-ray absorption spectrum of liquid water upon isotope substitution. The results are compared to UV absorption data, and it is discussed to which extent they reflect the differences in zero-point energies and vibrational zero-point distributions in the ground-states of the liquids. The influence of the shape of the final-state potential, inclusion of the Franck-Condon structure, and differences between liquid H2O and D2O resulting from different hydrogen-bond environments in the liquids are addressed. The differences between the O K-edge absorption spectra of water from our transmission-mode measurements and from the state-of-the-art x-ray Raman scattering experiments are discussed in addition. The experimentally extracted values of blue shift and broadening are proposed to serve as a test for calculations of ground-state zero-point energies and vibrational zero-point distributions in liquid H2O and D2O. This clearly motivates the need for new calculations of the O K-edge x-ray absorption spectrum of liquid water.

  4. Malvinas-slope water intrusions on the northern Patagonia continental shelf

    NASA Astrophysics Data System (ADS)

    Piola, A. R.; Martínez Avellaneda, N.; Guerrero, R. A.; Jardón, F. P.; Palma, E. D.; Romero, S. I.

    2010-03-01

    The Patagonia continental shelf located off southeastern South America is bounded offshore by the Malvinas Current, which extends northward from northern Drake Passage (~55° S) to nearly 38° S. The transition between relatively warm-fresh shelf waters and Subantarctic Waters from the western boundary current is characterized by a thermohaline front extending nearly 2500 km. We use satellite derived sea surface temperature, and chlorophyll-a data combined with hydrographic and surface drifter data to document the intrusions of slope waters onto the continental shelf near 41° S. These intrusions create vertically coherent localized negative temperature and positive salinity anomalies extending onshore about 150 km from the shelf break. The region is associated with a center of action of the first mode of non-seasonal sea surface temperature variability and also relatively high chlorophyll-a variability, suggesting that the intrusions are important in promoting the local development of phytoplankton. The generation of slope water penetrations at this location may be triggered by the inshore excursion of the 100 m isobath, which appears to steer the Malvinas Current waters over the outer shelf.

  5. Malvinas-slope water intrusions on the northern Patagonia continental shelf

    NASA Astrophysics Data System (ADS)

    Piola, A. R.; Avellaneda, N. M.; Guerrero, R. A.; Jardón, F. P.; Palma, E. D.; Romero, S. I.

    2009-12-01

    The Patagonia continental shelf located off southeastern South America is bounded offshore by the Malvinas Current, which extends northward from northern Drake Passage (~55° S) to nearly 38° S. The transition between relatively warm-fresh shelf waters and Subantarctic Waters from the western boundary current is characterized by a thermohaline front extending nearly 2500 km. We use satellite derived sea surface temperature, and chlorophyll-a data combined with hydrographic and surface drifter data to document the intrusions of slope waters onto the continental shelf near 41° S. These intrusions create vertically coherent localized negative temperature and positive salinity anomalies extending onshore about 150 km from the shelf break. The region is associated with a center of action of the first mode of non-seasonal sea surface temperature variability and also relatively high chlorophyll-a variability, suggesting that the intrusions are important in promoting the local development of phytoplankton. The generation of slope water penetrations at this location may be triggered by the inshore excursion of the 100 m isobath, which appears to steer the Malvinas Current waters over the outer shelf.

  6. Validation of GPS atmospheric water vapor with WVR data in satellite tracking mode

    NASA Astrophysics Data System (ADS)

    Shangguan, M.; Heise, S.; Bender, M.; Dick, G.; Ramatschi, M.; Wickert, J.

    2015-01-01

    Slant-integrated water vapor (SIWV) data derived from GPS STDs (slant total delays), which provide the spatial information on tropospheric water vapor, have a high potential for assimilation to weather models or for nowcasting or reconstruction of the 3-D humidity field with tomographic techniques. Therefore, the accuracy of GPS STD is important, and independent observations are needed to estimate the quality of GPS STD. In 2012 the GFZ (German Research Centre for Geosciences) started to operate a microwave radiometer in the vicinity of the Potsdam GPS station. The water vapor content along the line of sight between a ground station and a GPS satellite can be derived from GPS data and directly measured by a water vapor radiometer (WVR) at the same time. In this study we present the validation results of SIWV observed by a ground-based GPS receiver and a WVR. The validation covers 184 days of data with dry and wet humidity conditions. SIWV data from GPS and WVR generally show good agreement with a mean bias of -0.4 kg m-2 and an rms (root mean square) of 3.15 kg m-2. The differences in SIWV show an elevation dependent on an rms of 7.13 kg m-2 below 15° but of 1.76 kg m-2 above 15°. Nevertheless, this elevation dependence is not observed regarding relative deviations. The relation between the differences and possible influencing factors (elevation angles, pressure, temperature and relative humidity) are analyzed in this study. Besides the elevation, dependencies between the atmospheric humidity conditions, temperature and the differences in SIWV are found.

  7. A role for oxygen delivery and extracellular magnesium in limiting cold tolerance of the sub-antarctic stone crab Paralomis granulosa?

    PubMed

    Wittmann, Astrid C; Pörtner, Hans O; Sartoris, Franz J

    2012-01-01

    A low capacity for regulation of extracellular Mg(2+) has been proposed to exclude reptant marine decapod crustaceans from temperatures below 0°C and thus to exclude them from the high Antarctic. To test this hypothesis and to elaborate the underlying mechanisms in the most cold-tolerant reptant decapod family of the sub-Antarctic, the Lithodidae, thermal tolerance was determined in the crab Paralomis granulosa (Decapoda, Anomura, Lithodidae) using an acute stepwise temperature protocol (-1°, 1°, 4°, 7°, 10°, and 13°C). Arterial and venous oxygen partial pressures (Po(2)) in hemolymph, heartbeat and ventilation beat frequencies, and hemolymph cation composition were measured at rest and after a forced activity (righting) trial. Scopes for heartbeat and ventilation beat frequencies and intermittent heartbeat and scaphognathite beat rates at rest were evaluated. Hemolymph [Mg(2+)] was experimentally reduced from 30 mmol L(-1) to a level naturally observed in Antarctic caridean shrimps (12 mmol L(-1)) to investigate whether the animals remain more active and tolerant to cold (-1°, 1°, and 4°C). In natural seawater, righting speed was significantly slower at -1° and 13°C, compared with acclimation temperature (4°C). Arterial and venous hemolymph Po(2) increased in response to cooling even though heartbeat and ventilation beat frequencies as well as scopes decreased. At rest, ionic composition of the hemolymph was not affected by temperature. Activity induced a significant increase in hemolymph [K(+)] at -1° and 1°C. Reduction of hemolymph [Mg(2+)] did not result in an increase in activity, an increase in heartbeat and ventilation beat frequencies, or a shift in thermal tolerance to lower temperatures. In conclusion, oxygen delivery in this cold-water crustacean was not acutely limiting cold tolerance, and animals may have been constrained more by their functional capacity and motility. In contrast to earlier findings in temperate and subpolar brachyuran

  8. Diel variation of chlorophyll- a fluorescence, phytoplankton pigments and productivity in the Sub-Antarctic and Polar Front Zones south of Tasmania, Australia

    NASA Astrophysics Data System (ADS)

    Doblin, Martina A.; Petrou, Katherina L.; Shelly, Kirsten; Westwood, Karen; van den Enden, Rick; Wright, Simon; Griffiths, Brian; Ralph, Peter J.

    2011-11-01

    Marine primary production is a fundamental measure of the ocean's capacity to convert carbon dioxide to particulate organic carbon for the marine foodweb, and as such is an essential variable used in ecosystem and biogeochemical models to assess trophic dynamics and carbon cycling. The Sub-Antarctic Zone (SAZ) is a major sink for atmospheric carbon and exhibits large gradients in ocean conditions on both temporal and spatial scales. In this dynamic system, an understanding of small-scale temporal changes is critical for modelling primary production at larger scales. Thus, we investigated diel effects on maximum quantum yield of PSII ( FV/ FM), photosynthetic pigment pools and primary productivity in the western (Diel 1) and eastern SAZ region (Diel 3) south of Tasmania, Australia, and compared this to a station at the polar front (Diel 2). Phytoplankton in the eastern SAZ had the greatest diel response, with cells showing decreased FV/ FM and increased biosynthesis and transformation of xanthophyll and other photoprotective pigments during the day, but only in the surface waters (0 and 10 m). Diel responses diminished by 30 m. Cells in the western SAZ had similar responses across the depths sampled, increasing their FV/ FM during the night and increasing their xanthophyll pigment content during the day. Phytoplankton at the polar front (Diel 2) showed intermediate diel-related variations in photophysiology, with xanthophyll conversion and increases in photoprotective pigments during the day but constant FV/ FM. These diel changes at all sampling stations had little impact on carbon fixation rates, although cells sampled from the deep chlorophyll maximum at the polar front had significantly lower maximum carbon fixation and minimum saturating irradiance ( Ek) compared to the other depths and stations. Considering the oceanographic context, cells at Diel 1 and 2 received less light and were more deeply mixed than cells at Diel 3, causing a dampening of the diel

  9. X-Ray Computed-Tomography Imaging of Preferential Mode of Gas Migration through Water-Saturated Sediments

    NASA Astrophysics Data System (ADS)

    Seol, Y.; Choi, J.; Rosenbaum, E.; Boswell, R. M.; Juanes, R.

    2011-12-01

    Field observations suggest that gas transport through water-saturated soft sediment is an essential component of seafloor dynamics, and that it exerts a fundamental control on natural gas seeps, the creation of pockmarks in the ocean floor, and the growth and form of gas hydrates. In this study, we use controlled experiments and computed tomography (CT) imaging to investigate the preferential mode of gas migration in three-dimensional samples of water-saturated silica-sand, silica-silt, kaolin-clay, as well as multi-layered sediments. Our experimental system allows independent control of radial and axial confining stresses and pore pressure while performing continuous x-ray CT scanning. The CT image analysis of the gas migration provides the first experimental confirmation, in three-dimensional systems, that capillary invasion preferentially occurs in coarse-grained sediments whereas grain displacement and conduit openings are dominant in fine-grained sediments [1]. Our findings rationalize prior field observations and pore-scale modeling results which suggest the strong control of grain size and sediment mechanics on the nature of gas invasion into water-filled porous media. These data provide critical experimental evidence to explain the means by which conduits for the transit of methane gas may be established through the gas hydrate stability zone in oceanic sediments, and cause large episodic releases of carbon into the deep ocean.

  10. Mode of inheritance for biochemical traits in genetically engineered cotton under water stress

    PubMed Central

    Abid, Muhammad Ali; Malik, Waqas; Yasmeen, Azra; Qayyum, Abdul; Zhang, Rui; Liang, Chengzhen; Guo, Sandui; Ashraf, Javaria

    2016-01-01

    Drought is an abiotic environmental stress that can significantly reduce crop productivity. We examined the mode of inheritance for different biochemical traits including total soluble proteins, chlorophyll a, chlorophyll b, total chlorophyll, carotenoids, total phenolic contents and enzymatic antioxidants (superoxide dismutase, peroxidase and catalase), and their relationship with Bacillus thuringiensis (Bt) toxin under control and drought conditions. Eight genetically diverse cotton genotypes were selfed for two generations to ensure homozygosity. Fifteen F1 hybrids were developed by crossing five non-Bt female lines with three Bt male testers. The F1 hybrids and eight parents were finally evaluated under control (100 % field capacity (FC)) and drought (50 % FC) conditions in 2013. The biochemical traits appeared to be controlled by non-additive gene action with low narrow sense heritability estimates. The estimates of general combining ability and specific combining ability for all biochemical traits were significant under control and drought conditions. The genotype-by-trait biplot analysis showed the better performance of Bt cotton hybrids when compared with their parental genotypes for various biochemical traits under control and drought conditions. The biplot and path coefficient analyses revealed the prevalence of different relationships between Cry1Ac toxin and biochemical traits in the control and drought conditions. In conclusion, biochemical traits could serve as potential biochemical markers for breeding Bt cotton genotypes without compromising the optimal level of Bt toxin. PMID:26839284

  11. Mechanical and thermal friability of coals and modes of water bonding

    SciTech Connect

    Hauserman, W.B.; Tye, C.

    1984-01-01

    The laboratory method developed to define mechanical and thermal friabilities of coals shows repeatable and consistent results. The method shows promise for prediction of a coal's behavior in various handling and thermal operations. This method is valid only if coals are compared with their intrinsic moisture intact, mine-fresh from an un-weathered surface; any predrying, however gentle, significantly reduces their friability. For this method to be valid, samples must consist of +1 in. (+2.5 cm) lumps, which must be uniform and representative of the vein, since significant variation occurs between different lithotypes. Intrinsic moisture, entrained in or bound to the coal is a positive factor contributing to the coal's structural integrity. Simply removing the moisture, with no concurrent damage by thermal expansion, substantially weakens to the coal. Differential calorimetry is a simple, effective method of determining comparative heats of wetting when a porous solid is immersed in a liquid. This exthermic heat is directly proportional to the specific surface of the solid. The only firm conclusion to be drawn from the friability and dielectric data together is that both are simple, numerical techniques to characterize and compare coals with respect to their mechanical structure and modes of intrinsic moisture attachment. Each provides sets of several variables, whose full significance can only be established after expanding the data base to include more coals. The accomplishment to date consists of demonstratng that such data are possible. 26 references, 3 tables, 16 figures.

  12. Mode of inheritance for biochemical traits in genetically engineered cotton under water stress.

    PubMed

    Abid, Muhammad Ali; Malik, Waqas; Yasmeen, Azra; Qayyum, Abdul; Zhang, Rui; Liang, Chengzhen; Guo, Sandui; Ashraf, Javaria

    2016-02-02

    Drought is an abiotic environmental stress that can significantly reduce crop productivity. We examined the mode of inheritance for different biochemical traits including total soluble proteins, chlorophyll a, chlorophyll b, total chlorophyll, carotenoids, total phenolic contents and enzymatic antioxidants (superoxide dismutase, peroxidase and catalase), and their relationship with Bacillus thuringiensis (Bt) toxin under control and drought conditions. Eight genetically diverse cotton genotypes were selfed for two generations to ensure homozygosity. Fifteen F1 hybrids were developed by crossing five non-Bt female lines with three Bt male testers. The F1 hybrids and eight parents were finally evaluated under control (100 % field capacity (FC)) and drought (50 % FC) conditions in 2013. The biochemical traits appeared to be controlled by non-additive gene action with low narrow sense heritability estimates. The estimates of general combining ability and specific combining ability for all biochemical traits were significant under control and drought conditions. The genotype-by-trait biplot analysis showed the better performance of Bt cotton hybrids when compared with their parental genotypes for various biochemical traits under control and drought conditions. The biplot and path coefficient analyses revealed the prevalence of different relationships between Cry1Ac toxin and biochemical traits in the control and drought conditions. In conclusion, biochemical traits could serve as potential biochemical markers for breeding Bt cotton genotypes without compromising the optimal level of Bt toxin.

  13. Microbial biomass and basal respiration of selected Sub-Antarctic and Antarctic soils in the areas of some Russian polar stations

    NASA Astrophysics Data System (ADS)

    Abakumov, E.; Mukhametova, N.

    2014-07-01

    Antarctica is a unique place for soil, biological, and ecological investigations. Soils of Antarctica have been studied intensively during the last century, when different national Antarctic expeditions visited the sixth continent with the aim of investigating nature and the environment. Antarctic investigations are comprised of field surveys mainly in the terrestrial landscapes, where the polar stations of different countries are situated. That is why the main and most detailed soil surveys were conducted in the McMurdo Valleys, Transantarctic Mountains, South Shetland Islands, Larsemann Hills and the Schirmacher Oasis. Our investigations were conducted during the 53rd and 55th Russian Antarctic expeditions in the base of soil pits, and samples were collected in Sub-Antarctic and Antarctic regions. Sub-Antarctic or maritime landscapes are considered to be very different from Antarctic landscapes due to differing climatic and geogenic conditions. Soils of diverse zonal landscapes were studied with the aim of assessing the microbial biomass level, basal respiration rates and metabolic activity of microbial communities. This investigation shows that Antarctic soils are quite diverse in profile organization and carbon content. In general, Sub-Antarctic soils are characterized by more developed humus (sod) organo-mineral horizons as well as by an upper organic layer. The most developed organic layers were revealed in peat soils of King George Island, where its thickness reach, in some cases, was 80 cm. These soils as well as soils formed under guano are characterized by the highest amount of total organic carbon (TOC), between 7.22 and 33.70%. Coastal and continental Antarctic soils exhibit less developed Leptosols, Gleysols, Regolith and rare Ornhitosol, with TOC levels between 0.37 and 4.67%. The metabolic ratios and basal respiration were higher in Sub-Antarctic soils than in Antarctic ones, which can be interpreted as a result of higher amounts of fresh organic

  14. Docking Prediction of a Water Soluble Porphyrin and Tubulin Assisted with Resonance Raman and Vibrational Mode Analysis

    NASA Astrophysics Data System (ADS)

    McMicken, Brady; Brancaleon, Lorenzo; Thomas, Robert; Parker, James

    2015-03-01

    The ability to modify protein conformation by controlling its partial unfolding may have practical applications such as diminishing its function or blocking its activity. One method used to induce partial unfolding of a protein involves the use of a photosensitizer non-covalently bound to a protein that triggers photochemical reactions upon irradiation leading to protein conformational changes. We are investigating the photoinduced conformational changes of tubulin mediated by a bound water-soluble porphyrin that acts as a photosensitizer. Analysis of how tubulin conformational changes affect its function including polymeric assembly forming microtubules is of interest to uncover the mechanism responsible for the structural change. Our approach to better understand the conformational change, we first plan to discover the binding location between the porphyrin and protein. Use of vibrational mode analysis using density functional theory and resonance Raman experiments targeting the porphyrin molecule will be used to correlate Raman peaks with vibrational modes. The relative intensities of the porphyrin bound to tubulin can be used to calculate the equilibrium geometry observed from Raman spectra. These data will provide the relative distortion of the porphyrin when bound to tubulin, which will subsequently be used in docking simulations to find the most likely binding configuration.

  15. Instantaneous normal modes, resonances, and decay channels in the vibrational relaxation of the amide I mode of N-methylacetamide-D in liquid deuterated water.

    PubMed

    Bastida, Adolfo; Soler, Miguel Angel; Zúñiga, José; Requena, Alberto; Kalstein, Adrián; Fernández-Alberti, Sebastián

    2010-06-14

    A nonequilibrium molecular dynamics (MD) study of the vibrational relaxation of the amide I mode of deuterated N-methylacetamide (NMAD) in aqueous (D(2)O) solution is carried out using instantaneous normal modes (INMs). The identification of the INMs as they evolve over time, which is necessary to analyze the energy fluxes, is made by using a novel algorithm which allows us to assign unequivocally each INM to an individual equilibrium normal mode (ENM) or to a group of ENMs during the MD simulations. The time evolution of the energy stored in each INM is monitored and the occurrence of resonances during the relaxation process is then investigated. The decay of the amide I mode, initially excited with one vibrational quantum, is confirmed to fit well to a biexponential function, implying that the relaxation process involves at least two mechanisms with different rate constants. By freezing the internal motions of the solvent, it is shown that the intermolecular vibration-vibration channel to the bending modes of the solvent is closed. The INM analysis reveals then the existence of a major and faster decay channel, which corresponds to an intramolecular vibrational redistribution process and a minor, and slower, decay channel which involves the participation of the librational motions of the solvent. The faster relaxation pathway can be rationalized in turn using a sequential kinetic mechanism of the type P-->M+L-->L, where P (parent) is the initially excited amide I mode, and M (medium) and L (low) are specific midrange and lower-frequency NMAD vibrational modes, respectively.

  16. Tempo and mode of the multiple origins of salinity tolerance in a water beetle lineage.

    PubMed

    Arribas, Paula; Andújar, Carmelo; Abellán, Pedro; Velasco, Josefa; Millán, Andrés; Ribera, Ignacio

    2014-02-01

    Salinity is one of the most important drivers of the distribution, abundance and diversity of organisms. Previous studies on the evolution of saline tolerance have been mainly centred on marine and terrestrial organisms, while lineages inhabiting inland waters remain largely unexplored. This is despite the fact that these systems include a much broader range of salinities, going from freshwater to more than six times the salinity of the sea (i.e. >200 g/L). Here, we study the pattern and timing of the evolution of the tolerance to salinity in an inland aquatic lineage of water beetles (Enochrus species of the subgenus Lumetus, family Hydrophilidae), with the general aim of understanding the mechanisms by which it was achieved. Using a time-calibrated phylogeny built from five mitochondrial and two nuclear genes and information about the salinity tolerance and geographical distribution of the species, we found that salinity tolerance appeared multiple times associated with periods of global aridification. We found evidence of some accelerated transitions from freshwater directly to high salinities, as reconstructed with extant lineages. This, together with the strong positive correlation found between salinity tolerance and aridity of the habitats in which species are found, suggests that tolerance to salinity may be based on a co-opted mechanism developed originally for drought resistance. © 2013 John Wiley & Sons Ltd.

  17. Effect of CaCO3(S) nucleation modes on algae removal from alkaline water.

    PubMed

    Choi, Jin Yong; Kinney, Kerry A; Katz, Lynn E

    2016-02-29

    The role of calcite heterogeneous nucleation was studied in a particle coagulation treatment process for removing microalgae from water. Batch experiments were conducted with Scenedesmus sp. and Chlorella sp. in the presence and absence of carbonate and in the presence and absence of Mg to delineate the role of CaCO3(S) nucleation on microalgae removal. The results indicate that effective algae coagulation (e.g., up to 81 % algae removal efficiency) can be achieved via heterogeneous nucleation with CaCO3(S); however, supersaturation ratios between 120 and 200 are required to achieve at least 50% algae removal, depending on ion concentrations. Algae removal was attributed to adsorption of Ca(2+) onto the cell surface which provides nucleation sites for CaCO3(S) precipitation. Bridging of calcite particles between the algal cells led to rapid aggregation and formation of larger flocs. However, at higher supersaturation conditions, algae removal was diminished due to the dominance of homogeneous nucleation of CaCO3(S). Removal of algae in the presence of Ca(2+) and Mg(2+) required higher supersaturation values; however, the shift from heteronucleation to homonucleation with increasing supersaturation was still evident. The results suggest that water chemistry, pH, ionic strength, alkalinity and Ca(2+) concentration can be optimized for algae removal via coagulation-sedimentation.

  18. The backscattering characteristics of wetland vegetation and water-level changes detection using multi-mode SAR: A case study

    NASA Astrophysics Data System (ADS)

    Zhang, Meimei; Li, Zhen; Tian, Bangsen; Zhou, Jianmin; Tang, Panpan

    2016-03-01

    A full understanding of the backscattering characteristics of wetlands is necessary for the analysis of the hydrological conditions. In this study, a temporal set of synthetic aperture radar (SAR) imagery, acquired at different frequencies, polarizations and incidence angles over the coastal wetlands of the Liaohe River Delta, China, were used to characterize seasonal variations in radar backscattering coefficient for reed marshes and rice fields. The combination of SAR backscattering intensity and an optical-based normalized difference vegetation index (NDVI) for long time series can provide additional insight into vegetation structural and its hydrological states. After identifying the factors that induce the backscattering and scattering mechanism changes, detailed analysis of L-band ALOS PALSAR interferometric SAR (InSAR) imagery was conducted to study water-level changes under different environmental conditions. In addition, ENVISAT altimetry was used to validate the accuracy of the water-level changes estimated using the InSAR technique-this is an effective tool instead of sparsely distributed gauge stations for the validation. Our study demonstrates that L-band SAR data with horizontal polarization is particularly suitable for the extraction of water-level changes in the study area; however, vertically-polarized C-band data may also be useful where the density of herbaceous vegetation is low at the initial stage. It is also shown that integrated analysis of the backscattering mechanism and interferometric characteristics using multi-mode SAR can considerably enhance the reliability of the water-level retrieval scheme and better capture the spatial distribution of hydrological patterns.

  19. Pleistocene refugia and polytopic replacement of diploids by tetraploids in the Patagonian and Subantarctic plant Hypochaeris incana (Asteraceae, Cichorieae).

    PubMed

    Tremetsberger, Karin; Urtubey, Estrella; Terrab, Anass; Baeza, Carlos M; Ortiz, María Angeles; Talavera, María; König, Christiane; Temsch, Eva M; Kohl, Gudrun; Talavera, Salvador; Stuessy, Tod F

    2009-09-01

    We report the phylogeographic pattern of the Patagonian and Subantarctic plant Hypochaeris incana endemic to southeastern South America. We applied amplified fragment length polymorphism (AFLP) and chloroplast DNA (cpDNA) analysis to 28 and 32 populations, respectively, throughout its distributional range and assessed ploidy levels using flow cytometry. While cpDNA data suggest repeated or simultaneous parallel colonization of Patagonia and Tierra del Fuego by several haplotypes and/or hybridization, AFLPs reveal three clusters corresponding to geographic regions. The central and northern Patagonian clusters (approximately 38-51 degrees S), which are closer to the outgroup, contain mainly tetraploid, isolated and highly differentiated populations with low genetic diversity. To the contrary, the southern Patagonian and Fuegian cluster (approximately 51-55 degrees S) contains mainly diploid populations with high genetic diversity and connected by high levels of gene flow. The data suggest that H. incana originated at the diploid level in central or northern Patagonia, from where it migrated south. All three areas, northern, central and southern, have similar levels of rare and private AFLP bands, suggesting that all three served as refugia for H. incana during glacial times. In southern Patagonia and Tierra del Fuego, the species seems to have expanded its populational system in postglacial times, when the climate became warmer and more humid. In central and northern Patagonia, the populations seem to have become restricted to favourable sites with increasing temperature and decreasing moisture and there was a parallel replacement of diploids by tetraploids in local populations.

  20. Habitat phenotyping of two sub-Antarctic flies by metabolic fingerprinting: evidence for a species outside its home?

    PubMed

    Laparie, M; Bical, R; Larvor, V; Vernon, P; Frenot, Y; Renault, D

    2012-08-01

    Metabolic fingerprinting can elucidate rearrangements of metabolic networks in organisms exposed to various environmental conditions. Maintenance of organismal performance occurs by alterations in metabolic fluxes and pathways, resulting in habitat-specific metabolic signatures. Several insects of sub-Antarctic Islands, including the wingless flies Anatalanta aptera and Calycopteryx moseleyi, are exposed to saline organic matter accumulated along littoral margins. However, C. moseleyi has long been considered restricted to a habitat of lower salinity, the Kerguelen cabbage. High C. moseleyi densities identified in saline decaying seaweeds are intriguing, and may involve osmoregulatory adjustments including accumulation of osmoprotectants. In the present work, we examined quantitative metabotypes (metabolic phenotypes) among wild C. moseleyi individuals from seaweeds versus non-saline Kerguelen cabbages. They were compared to metabotypes from wild A. aptera, a common fly on seaweed. Statistical procedures designed to magnify between-class differences failed to clearly separate C. moseleyi metabotypes from cabbage and seaweed, despite contrasted morphotypes, diets, and salinities. A. aptera exhibited higher glycerol, inositol, trehalose, and other osmoprotectants concentrations that may enhance its performance under saline environments. Seaweed may represent a secondary niche in C. moseleyi, promoted by the marked reduction in Kerguelen cabbage frequency subsequent to climate change, and herbivorous pressures caused by rabbit invasion.

  1. Major advance of South Georgia glaciers during the Antarctic Cold Reversal following extensive sub-Antarctic glaciation

    NASA Astrophysics Data System (ADS)

    Graham, Alastair G. C.; Kuhn, Gerhard; Meisel, Ove; Hillenbrand, Claus-Dieter; Hodgson, Dominic A.; Ehrmann, Werner; Wacker, Lukas; Wintersteller, Paul; Dos Santos Ferreira, Christian; Römer, Miriam; White, Duanne; Bohrmann, Gerhard

    2017-03-01

    The history of glaciations on Southern Hemisphere sub-polar islands is unclear. Debate surrounds the extent and timing of the last glacial advance and termination on sub-Antarctic South Georgia in particular. Here, using sea-floor geophysical data and marine sediment cores, we resolve the record of glaciation offshore of South Georgia through the transition from the Last Glacial Maximum to Holocene. We show a sea-bed landform imprint of a shelf-wide last glacial advance and progressive deglaciation. Renewed glacier resurgence in the fjords between c. 15,170 and 13,340 yr ago coincided with a period of cooler, wetter climate known as the Antarctic Cold Reversal, revealing a cryospheric response to an Antarctic climate pattern extending into the Atlantic sector of the Southern Ocean. We conclude that the last glaciation of South Georgia was extensive, and the sensitivity of its glaciers to climate variability during the last termination more significant than implied by previous studies.

  2. Landscape mapping at sub-Antarctic South Georgia provides a protocol for underpinning large-scale marine protected areas

    NASA Astrophysics Data System (ADS)

    Hogg, Oliver T.; Huvenne, Veerle A. I.; Griffiths, Huw J.; Dorschel, Boris; Linse, Katrin

    2016-10-01

    Global biodiversity is in decline, with the marine environment experiencing significant and increasing anthropogenic pressures. In response marine protected areas (MPAs) have increasingly been adopted as the flagship approach to marine conservation, many covering enormous areas. At present, however, the lack of biological sampling makes prioritising which regions of the ocean to protect, especially over large spatial scales, particularly problematic. Here we present an interdisciplinary approach to marine landscape mapping at the sub-Antarctic island of South Georgia as an effective protocol for underpinning large-scale (105-106  km2) MPA designations. We have developed a new high-resolution (100 m) digital elevation model (DEM) of the region and integrated this DEM with bathymetry-derived parameters, modelled oceanographic data, and satellite primary productivity data. These interdisciplinary datasets were used to apply an objective statistical approach to hierarchically partition and map the benthic environment into physical habitats types. We assess the potential application of physical habitat classifications as proxies for biological structuring and the application of the landscape mapping for informing on marine spatial planning.

  3. Landscape mapping at sub-Antarctic South Georgia provides a protocol for underpinning large-scale marine protected areas.

    PubMed

    Hogg, Oliver T; Huvenne, Veerle A I; Griffiths, Huw J; Dorschel, Boris; Linse, Katrin

    2016-10-03

    Global biodiversity is in decline, with the marine environment experiencing significant and increasing anthropogenic pressures. In response marine protected areas (MPAs) have increasingly been adopted as the flagship approach to marine conservation, many covering enormous areas. At present, however, the lack of biological sampling makes prioritising which regions of the ocean to protect, especially over large spatial scales, particularly problematic. Here we present an interdisciplinary approach to marine landscape mapping at the sub-Antarctic island of South Georgia as an effective protocol for underpinning large-scale (10(5)-10(6)  km(2)) MPA designations. We have developed a new high-resolution (100 m) digital elevation model (DEM) of the region and integrated this DEM with bathymetry-derived parameters, modelled oceanographic data, and satellite primary productivity data. These interdisciplinary datasets were used to apply an objective statistical approach to hierarchically partition and map the benthic environment into physical habitats types. We assess the potential application of physical habitat classifications as proxies for biological structuring and the application of the landscape mapping for informing on marine spatial planning.

  4. Major advance of South Georgia glaciers during the Antarctic Cold Reversal following extensive sub-Antarctic glaciation

    PubMed Central

    Graham, Alastair G. C.; Kuhn, Gerhard; Meisel, Ove; Hillenbrand, Claus-Dieter; Hodgson, Dominic A.; Ehrmann, Werner; Wacker, Lukas; Wintersteller, Paul; dos Santos Ferreira, Christian; Römer, Miriam; White, Duanne; Bohrmann, Gerhard

    2017-01-01

    The history of glaciations on Southern Hemisphere sub-polar islands is unclear. Debate surrounds the extent and timing of the last glacial advance and termination on sub-Antarctic South Georgia in particular. Here, using sea-floor geophysical data and marine sediment cores, we resolve the record of glaciation offshore of South Georgia through the transition from the Last Glacial Maximum to Holocene. We show a sea-bed landform imprint of a shelf-wide last glacial advance and progressive deglaciation. Renewed glacier resurgence in the fjords between c. 15,170 and 13,340 yr ago coincided with a period of cooler, wetter climate known as the Antarctic Cold Reversal, revealing a cryospheric response to an Antarctic climate pattern extending into the Atlantic sector of the Southern Ocean. We conclude that the last glaciation of South Georgia was extensive, and the sensitivity of its glaciers to climate variability during the last termination more significant than implied by previous studies. PMID:28303885

  5. Response of Phytoplankton Photophysiology to Varying Environmental Conditions in the Sub-Antarctic and Polar Frontal Zone

    PubMed Central

    Cheah, Wee; McMinn, Andrew; Griffiths, F. Brian; Westwood, Karen J.; Wright, Simon W.; Clementson, Lesley A.

    2013-01-01

    Climate-driven changes are expected to alter the hydrography of the Sub-Antarctic Zone (SAZ) and Polar Frontal Zone (PFZ) south of Australia, in which distinct regional environments are believed to be responsible for the differences in phytoplankton biomass in these regions. Here, we report how the dynamic influences of light, iron and temperature, which are responsible for the photophysiological differences between phytoplankton in the SAZ and PFZ, contribute to the biomass differences in these regions. High effective photochemical efficiency of photosystem II (/0.4), maximum photosynthesis rate (), light-saturation intensity (), maximum rate of photosynthetic electron transport (1/), and low photoprotective pigment concentrations observed in the SAZ correspond to high chlorophyll and iron concentrations. In contrast, phytoplankton in the PFZ exhibits low / ( 0.2) and high concentrations of photoprotective pigments under low light environment. Strong negative relationships between iron, temperature, and photoprotective pigments demonstrate that cells were producing more photoprotective pigments under low temperature and iron conditions, and are responsible for the low biomass and low productivity measured in the PFZ. As warming and enhanced iron input is expected in this region, this could probably increase phytoplankton photosynthesis in this region. However, complex interactions between the biogeochemical processes (e.g. stratification caused by warming could prevent mixing of nutrients), which control phytoplankton biomass and productivity, remain uncertain. PMID:23977242

  6. Investigation into the impact of storms on sustaining summer primary productivity in the Sub-Antarctic Ocean

    NASA Astrophysics Data System (ADS)

    Nicholson, Sarah-Anne; Lévy, Marina; Llort, Joan; Swart, Sebastiaan; Monteiro, Pedro M. S.

    2016-09-01

    In the Sub-Antarctic Ocean elevated phytoplankton biomass persists through summer at a time when productivity is expected to be low due to iron limitation. Biological iron recycling has been shown to support summer biomass. In addition, we investigate an iron supply mechanism previously unaccounted for in iron budget studies. Using a 1-D biogeochemical model, we show how storm-driven mixing provides relief from phytoplankton iron limitation through the entrainment of iron beneath the productive layer. This effect is significant when a mixing transition layer of strong diffusivities (kz > 10-4 m2 s-1) is present beneath the surface-mixing layer. Such subsurface mixing has been shown to arise from interactions between turbulent ocean dynamics and storm-driven inertial motions. The addition of intraseasonal mixing yielded increases of up to 60% in summer primary production. These results stress the need to acquire observations of subsurface mixing and to develop the appropriate parameterizations of such phenomena for ocean-biogeochemical models.

  7. Response of phytoplankton photophysiology to varying environmental conditions in the Sub-Antarctic and Polar Frontal Zone.

    PubMed

    Cheah, Wee; McMinn, Andrew; Griffiths, F Brian; Westwood, Karen J; Wright, Simon W; Clementson, Lesley A

    2013-01-01

    Climate-driven changes are expected to alter the hydrography of the Sub-Antarctic Zone (SAZ) and Polar Frontal Zone (PFZ) south of Australia, in which distinct regional environments are believed to be responsible for the differences in phytoplankton biomass in these regions. Here, we report how the dynamic influences of light, iron and temperature, which are responsible for the photophysiological differences between phytoplankton in the SAZ and PFZ, contribute to the biomass differences in these regions. High effective photochemical efficiency of photosystem II (F'(q)/F'(m)0.4), maximum photosynthesis rate (P(B)(max)), light-saturation intensity (E(k)), maximum rate of photosynthetic electron transport (1/[Symbol: see text]PSII), and low photoprotective pigment concentrations observed in the SAZ correspond to high chlorophyll a and iron concentrations. In contrast, phytoplankton in the PFZ exhibits low F'(q)/F'(M) (~ 0.2) and high concentrations of photoprotective pigments under low light environment. Strong negative relationships between iron, temperature, and photoprotective pigments demonstrate that cells were producing more photoprotective pigments under low temperature and iron conditions, and are responsible for the low biomass and low productivity measured in the PFZ. As warming and enhanced iron input is expected in this region, this could probably increase phytoplankton photosynthesis in this region. However, complex interactions between the biogeochemical processes (e.g. stratification caused by warming could prevent mixing of nutrients), which control phytoplankton biomass and productivity, remain uncertain.

  8. Major advance of South Georgia glaciers during the Antarctic Cold Reversal following extensive sub-Antarctic glaciation.

    PubMed

    Graham, Alastair G C; Kuhn, Gerhard; Meisel, Ove; Hillenbrand, Claus-Dieter; Hodgson, Dominic A; Ehrmann, Werner; Wacker, Lukas; Wintersteller, Paul; Dos Santos Ferreira, Christian; Römer, Miriam; White, Duanne; Bohrmann, Gerhard

    2017-03-17

    The history of glaciations on Southern Hemisphere sub-polar islands is unclear. Debate surrounds the extent and timing of the last glacial advance and termination on sub-Antarctic South Georgia in particular. Here, using sea-floor geophysical data and marine sediment cores, we resolve the record of glaciation offshore of South Georgia through the transition from the Last Glacial Maximum to Holocene. We show a sea-bed landform imprint of a shelf-wide last glacial advance and progressive deglaciation. Renewed glacier resurgence in the fjords between c. 15,170 and 13,340 yr ago coincided with a period of cooler, wetter climate known as the Antarctic Cold Reversal, revealing a cryospheric response to an Antarctic climate pattern extending into the Atlantic sector of the Southern Ocean. We conclude that the last glaciation of South Georgia was extensive, and the sensitivity of its glaciers to climate variability during the last termination more significant than implied by previous studies.

  9. Landscape mapping at sub-Antarctic South Georgia provides a protocol for underpinning large-scale marine protected areas

    PubMed Central

    Hogg, Oliver T.; Huvenne, Veerle A. I.; Griffiths, Huw J.; Dorschel, Boris; Linse, Katrin

    2016-01-01

    Global biodiversity is in decline, with the marine environment experiencing significant and increasing anthropogenic pressures. In response marine protected areas (MPAs) have increasingly been adopted as the flagship approach to marine conservation, many covering enormous areas. At present, however, the lack of biological sampling makes prioritising which regions of the ocean to protect, especially over large spatial scales, particularly problematic. Here we present an interdisciplinary approach to marine landscape mapping at the sub-Antarctic island of South Georgia as an effective protocol for underpinning large-scale (105–106  km2) MPA designations. We have developed a new high-resolution (100 m) digital elevation model (DEM) of the region and integrated this DEM with bathymetry-derived parameters, modelled oceanographic data, and satellite primary productivity data. These interdisciplinary datasets were used to apply an objective statistical approach to hierarchically partition and map the benthic environment into physical habitats types. We assess the potential application of physical habitat classifications as proxies for biological structuring and the application of the landscape mapping for informing on marine spatial planning. PMID:27694889

  10. Water filtration rate and infiltration/accumulation of low density lipoproteins in 3 different modes of endothelial/smooth muscle cell co-cultures.

    PubMed

    Ding, ZuFeng; Fan, YuBo; Deng, XiaoYan

    2009-11-01

    Using different endothelial/smooth muscle cell co-culture modes to simulate the intimal structure of blood vessels, the water filtration rate and the infiltration/accumulation of LDL of the cultured cell layers were studied. The three cell culture modes of the study were: (i) The endothelial cell monolayer (EC/Phi); (ii) endothelial cells directly co-cultured on the smooth muscle cell monolayer (EC-SMC); (iii) endothelial cells and smooth muscle cells cultured on different sides of a Millicell-CM membrane (EC/SMC). It was found that under the same condition, the water filtration rate was the lowest for the EC/SMC mode and the highest for the EC/Phi mode, while the infiltration/accumulation of DiI-LDLs was the lowest in the EC/Phi mode and the highest in the EC-SMC mode. It was also found that DiI-LDL infiltration/accumulation in the cultured cell layers increased with the increasing water filtration rate. The results from the in vitro model study therefore suggest that the infiltration/accumulation of the lipids within the arterial wall is positively correlated with concentration polarization of atherogenic lipids, and the integrity of the endothelium plays an important role in the penetration and accumulation of atherogenic lipids in blood vessel walls.

  11. Southern Ocean Circumpolar Deep Water warming: isopycnal mixing vs overturning as drivers of change

    NASA Astrophysics Data System (ADS)

    Meijers, Andrew; Farneti, Riccardo; Meredith, Michael

    2017-04-01

    Using an adiabatic as possible coordinate system we examine temperature and salinity trends in the three primary repeat hydrography sections that cross the Antarctic Circumpolar Current (ACC). These are the SR1b south of South America, Good Hope south of South Africa, and SR3 south of Australia. A similar pattern of change over the last 20 years is seen in all three, with cooling and freshening in the Subantarctic Mode Water (SAMW) and Antarctic Intermediate Water (AAIW) layers and warming and salinification in the upper Circumpolar Deep Water (CDW). We compare this fingerprint of change with the results from an eddy permitting general circulation model perturbation experiment forced by a near doubling in zonal wind stress with a corresponding increase of around 15% in the residual overturning circulation. A disparate fingerprint in temperature and salinity in the model to that observed suggests that the observed increase in zonal winds over the last 20 years has not driven a change in the residual overturning circulation. Instead we present analysis based on the observed climatic trend and background property gradients to argue that increased winter water temperatures in the outcropping zones are driving CDW warming via isopycnal mixing.

  12. Self-Powered Dual-Mode Amenity Sensor Based on the Water-Air Triboelectric Nanogenerator.

    PubMed

    Wang, Hao; Wu, Han; Hasan, Dihan; He, Tianyiyi; Shi, Qiongfeng; Lee, Chengkuo

    2017-10-10

    A water-air triboelectric nanogenerator (WATENG) is presented for CO2 sensing application. During the operation of WATENG, two independent charge transfers can be used to characterize the effect of force and humidity, respectively. Thus, the structure of WATENG provides a capability to eliminate these two major interferences in a triboelectric self-powered sensor. With the aid of the polyethylenimine (PEI) coating, WATENG can be used for CO2 sensing in both static and dynamic conditions. In static condition with a stable CO2 concentration, the CO2 sensing is characterized with respect to different relative humidity, and the sensing range can be up to 6000 ppm. In dynamic CO2 sensing of a pulse gas spray, due to the fast recovery of PEI surface reaction, the sensing range of dynamic situation can be broadened to 30,000 ppm. The self-powered and portable feature of WATENG is preferable as a self-powered amenity sensor for the construction of internet of the things (IoT) sensor networks in the future.

  13. Aligning Experimental and Theoretical Anisotropic B-Factors: Water Models, Normal-Mode Analysis Methods, and Metrics

    PubMed Central

    2014-01-01

    The strength of X-ray crystallography in providing the information for protein dynamics has been under appreciated. The anisotropic B-factors (ADPs) from high-resolution structures are invaluable in studying the relationship among structure, dynamics, and function. Here, starting from an in-depth evaluation of the metrics used for comparing the overlap between two ellipsoids, we applied normal-mode analysis (NMA) to predict the theoretical ADPs and then align them with experimental results. Adding an extra layer of explicitly treated water on protein surface significantly improved the energy minimization results and better reproduced the anisotropy of experimental ADPs. In comparing experimental and theoretical ADPs, we focused on the overlap in shape, the alignment of dominant directions, and the similarity in magnitude. The choices of water molecules, NMA methods, and the metrics for evaluating the overlap of ADPs determined final results. This study provides useful information for exploring the physical basis and the application potential of experimental ADPs. PMID:24673391

  14. MR-monitored focused ultrasound using the acoustic-coupling water bath as an intrinsic high-mode dielectric resonator.

    PubMed

    Webb, A G

    2014-06-01

    The conventional set-up for MR-monitored focused ultrasound surgery includes a piezoelectric transducer and an acoustic-coupling water bath integrated into the MR patient table; a large surface RF coil is placed close to the patient or, alternatively, the body coil is used as the MR receiver. Potential disadvantages of this approach are that the body coil has low sensitivity because of its low filling factor and the local RF coil can interfere with and cause reflections of the ultrasound irradiation. In this article, a completely new approach is presented, in which an MR transmit/receive coil is not needed at all. Instead, the dimensions of the water bath are adjusted so that a high-order dielectric mode is excited, resulting in efficient MR excitation and reception at the transducer focal point. An example of monitoring ultrasound-mediated heating in a phantom is shown on a 7-T human system, although the new method can also be applied at lower fields. Copyright © 2014 John Wiley & Sons, Ltd.

  15. Pressurised hot water extraction in continuous flow mode for thermolabile compounds: extraction of polyphenols in red onions.

    PubMed

    Liu, Jiayin; Sandahl, Margareta; Sjöberg, Per J R; Turner, Charlotta

    2014-01-01

    Extraction and analysis of labile compounds in complex sample matrices, such as plants, is often a big analytical challenge. In this work, the use of a "green and clean" pressurised hot water extraction (PHWE) approach performed in continuous flow mode is explored. Experimental data for extraction and degradation kinetics of selected compounds were utilised to develop a continuous flow extraction (CFE) method targeting thermolabile polyphenols in red onions, with detection by high-performance liquid chromatography (HPLC)-diode array detection (DAD)-mass spectrometry (MS). Water containing ethanol and formic acid was used as extraction solvent. Method performance was focused on extraction yield with minimal analyte degradation. By adjusting the flow rate of the extraction solvent, degradation effects were minimised, and complete extraction could be achieved within 60 min. The CFE extraction yields of the polyphenols investigated were 80-90 % of the theoretically calculated quantitative yields and were significantly higher than the yields obtained by conventional methanol extraction and static batch extraction (70-79 and 58-67 % of the theoretical yields, respectively). The precision of the developed method was lower than 8 % expressed as relative standard deviation.

  16. Identification of developmentally toxic drinking water disinfection byproducts and evaluation of data relevant to mode of action

    SciTech Connect

    Colman, Joan; Rice, Glenn E.; Wright, J. Michael; Hunter, E. Sidney; Teuschler, Linda K.; Lipscomb, John C.; Hertzberg, Richard C.; Simmons, Jane Ellen; Fransen, Margaret; Osier, Mark; Narotsky, Michael G.

    2011-07-15

    Reactions between chemicals used to disinfect drinking water and compounds present in source waters produce chemical mixtures containing hundreds of disinfection byproducts (DBPs). Although the results have been somewhat inconsistent, some epidemiological studies suggest associations may exist between DBP exposures and adverse developmental outcomes. The potencies of individual DBPs in rodent and rabbit developmental bioassays suggest that no individual DBP can account for the relative risk estimates reported in the positive epidemiologic studies, leading to the hypothesis that these outcomes could result from the toxicity of DBP mixtures. As a first step in a mixtures risk assessment for DBP developmental effects, this paper identifies developmentally toxic DBPs and examines data relevant to the mode of action (MOA) for DBP developmental toxicity. We identified 24 developmentally toxic DBPs and four adverse developmental outcomes associated with human DBP exposures: spontaneous abortion, cardiovascular defects, neural tube defects, and low birth weight infancy. A plausible MOA, involving hormonal disruption of pregnancy, is delineated for spontaneous abortion, which some epidemiologic studies associate with total trihalomethane and bromodichloromethane exposures. The DBP data for the other three outcomes were inadequate to define key MOA steps.

  17. Directly assessing uncertainty in designing the optimal operation of water resources systems by batch mode reinforcement learning

    NASA Astrophysics Data System (ADS)

    Biizzi, S.; Castelletti, A.; Pianosi, F.

    2012-04-01

    Optimal operating policies for water resources systems are obtained as the solution to a maximization/minimization problem, where the objective function is the operation target and the model of the physical system is the constraint set. Just as in any model-based analysis, the robustness and reliability of the result largely depend on the accuracy of the model. In water resource system applications this is a limitation since, despite the advances in data availability, systems understanding and computing facilities, still the characterization of most of these systems is affected by strong model uncertainties, including input, parameter and structural uncertainty. Traditionally, uncertainty estimation is evaluated via Monte Carlo methods: each source of uncertainty is given a statistical description (e.g. probability distribution function) and by random sampling from these distributions and repeated optimization and/or simulation uncertainty is propagated through the model. By doing so, the probability distribution of the objective function is derived for a given policy as well as a set of different policies, each one optimal for a different realization of the uncertain input. The approach is rather straightforward, though high resource demanding and then its effective application in real problems often unfeasible. In this paper we propose a novel optimization method that derives, just in one run, the set of optimal operating policies (and associated objective values) for all possible realizations of an uncertain variable in the model. The method is an extension of the Fitted-Q Iteration method, a model-free batch-mode reinforcement algorithm and it is demonstrated by application to a real water reservoir system. The case study is the Hoa Binh reservoir in Northern Vietnam, whose optimal operation is designed and assessed as a function of the uncertainty related to the evaporation rate of the reservoir model. It demonstrates the relevance of uncertainty in

  18. Atomic force microscopy on phase-control pulsed force mode in water: Imaging and force analysis on a rhodium-octaethylporphyrin layer on highly oriented pyrolytic graphite

    NASA Astrophysics Data System (ADS)

    Maeda, Yasushi; Yamazaki, Shin-ichi; Kohyama, Masanori

    2014-06-01

    We developed phase-control pulsed force mode (p-PFM) as the operation mode for atomic force microscopy (AFM). The p-PFM allowed us to observe soft or weakly adsorbed materials in a liquid environment using a conventional AFM apparatus, and allowed for force curve mapping (FCM) after offline data processing. We applied the p-PFM to a rhodium-octaethylporphyrin (RhOEP) layer on highly oriented pyrolytic graphite (HOPG), which is applicable to anode catalysts of fuel cells. The RhOEP/HOPG system was stably observed in water by this mode. In the p-PFM image, we found both large and small protrusions, which were not observed in the dynamic force mode, in air. The detailed force analysis suggested that these protrusions are nanobubbles located on the HOPG substrate exposed in holes or pits of the RhOEP layer.

  19. [Myxomatosis in the sub-antarctic islands of Kerguelen, without vectors, thirty years after its introduction].

    PubMed

    Chapuis, J L; Chantal, J; Bijlenga, G

    1994-02-01

    Myxoma virus was introduced into the Kerguelen archipelago in 1955-1956. Thirty years after its introduction, the virus is present in most areas inhabited by rabbits. Rabbit fleas and mosquitoes are absent from this group of islands and the disease is transmitted by contact. The timing of the beginning of new myxomatosis outbreaks, the absence of real epizootics as well as the higher percentage of infected males over females are specific observations in favour of this mode of transmission. The majority of 34 isolates tested between 1984 and 1988 are of intermediate virulence (Grades IIIA-IIIB). In these conditions, the impact of myxomatosis virus on rabbit populations estimated on two sites is low. Myxomatosis therefore plays only a minor role in the regulation of rabbit populations.

  20. Low-frequency broadband sound source localization using an adaptive normal mode back-propagation approach in a shallow-water ocean.

    PubMed

    Lin, Ying-Tsong; Newhall, Arthur E; Lynch, James F

    2012-02-01

    A variety of localization methods with normal mode theory have been established for localizing low frequency (below a few hundred Hz), broadband signals in a shallow water environment. Gauss-Markov inverse theory is employed in this paper to derive an adaptive normal mode back-propagation approach. Joining with the maximum a posteriori mode filter, this approach is capable of separating signals from noisy data so that the back-propagation will not have significant influence from the noise. Numerical simulations are presented to demonstrate the robustness and accuracy of the approach, along with comparisons to other methods. Applications to real data collected at the edge of the continental shelf off New Jersey, USA are presented, and the effects of water column fluctuations caused by nonlinear internal waves and shelfbreak front variability are discussed.

  1. Soil invertebrate community change over fuel-contaminated sites on a subantarctic island: An ecological field-based line of evidence for site risk assessment.

    PubMed

    Wasley, Jane; Mooney, Thomas J; King, Catherine K

    2016-04-01

    A number of fuel spills, of both recent and historic origins, have occurred on World Heritage-listed subantarctic Macquarie Island. Sites contaminated by mainly diesel fuels are undergoing remediation by the Australian Antarctic Division. The risks posed by these sites are being managed using a "weight of evidence" approach, for which this study provides a preliminary line of evidence for the ecological assessment component of this site management decision framework. This knowledge is pertinent, given the absence of environmental guidelines for fuel contaminants in subantarctic ecosystems. We provide a field-based, site-specific ecological risk assessment for soil invertebrate communities across the fuel spill sites, before the commencement of in situ remediation activities. Springtails (Collembola) were the most abundant taxa. Springtail community patterns showed only limited correlations with the level of fuel contamination at the soil surface, even when elevated levels occurred in the substratum layers. Of the environmental variables measured, community patterns were most strongly correlated with vegetation cover. We identify a suite of 6 species that contribute most to the community dynamics across these sites. A subset of these we propose as useful candidates for future development of single-species toxicity tests: Folsomotoma punctata, Cryptopygus caecus, Cryptopygus antarcticus and Parisotoma insularis. Findings from this study advance our understanding of soil invertebrate community dynamics within these contaminated sites, directly contributing to the improved management and restoration of the sites. Not only does this study provide an important line of evidence for the island's ecological risk assessment for fuel contaminants, it also enhances our understanding of the potential impact of fuels at other subantarctic islands.

  2. Acclimation effects on thermal tolerances of springtails from sub-Antarctic Marion Island: indigenous and invasive species.

    PubMed

    Slabber, Sarette; Worland, M Roger; Leinaas, Hans Petter; Chown, Steven L

    2007-02-01

    Collembola are abundant and functionally significant arthropods in sub-Antarctic terrestrial ecosystems, and their importance has increased as a consequence of the many invasive alien species that have been introduced to the region. It has also been predicted that current and future climate change will favour alien over indigenous species as a consequence of more favourable responses to warming in the former. It is therefore surprising that little is known about the environmental physiology of sub-Antarctic springtails and that few studies have explicitly tested the hypothesis that invasive species will outperform indigenous ones under warmer conditions. Here we present thermal tolerance data on three invasive (Pogonognathellus flavescens, Isotomurus cf. palustris, Ceratophysella denticulata) and two indigenous (Cryptopygus antarcticus, Tullbergia bisetosa) species of springtails from Marion Island, explicitly testing the idea that consistent differences exist between the indigenous and invasive species both in their absolute limits and the ways in which they respond to acclimation (at temperatures from 0 to 20 degrees C). Phenotypic plasticity is the first in a series of ways in which organisms might respond to altered environments. Using a poorly explored, but highly appropriate technique, we demonstrate that in these species the crystallization temperature (Tc) is equal to the lower lethal temperature. We also show that cooling rate (1 degree C min(-1); 0.1 degrees C min(-1); 0.5 degrees C h(-1) from 5 to -1 degrees C followed by 0.1 degrees C min(-1)) has little effect on Tc. The indigenous species typically have low Tcs (c. -20 to -13 degrees C depending on the acclimation temperature), whilst those of the invasive species tend to be higher (c. -12 to -6 degrees C) at the lower acclimation temperatures. However, Ceratophysella denticulata is an exception with a low Tc (c. -20 to -18 degrees C), and in P. flavescens acclimation to 20 degrees C results in a

  3. The δ15N of nitrate in the Southern Ocean: Consumption of nitrate in surface waters

    NASA Astrophysics Data System (ADS)

    Sigman, D. M.; Altabet, M. A.; McCorkle, D. C.; Francois, R.; Fischer, G.

    1999-12-01

    We report nitrogen isotope data for nitrate from transects of hydrocast and surface samples collected in the eastern Indian and Pacific sectors of the Southern Ocean, focusing here on the data from the upper water column to study the effect of nitrate consumption by phytoplankton. The δ15N of nitrate increases by 1-2‰ from deep water into the Antarctic summertime surface layer, due to kinetic isotopic fractionation during nitrate uptake. Estimation of the nitrate uptake isotope effect from Antarctic depth profiles yields values in the range of 5-6‰ in east Indian sector and 4-5‰ in the east Pacific sector. Surface transect data from the Pacific sector also yield values of 4-5‰. The major uncertainty in the profile-based estimation of the isotope effect involves the δ15N of nitrate from the temperature minimum layer below the summertime Antarctic surface layer, which deviates significantly from the predictions of simple models of isotope fractionation. For the Subantarctic surface, it is possible to distinguish between nitrate supplied laterally from the surface Antarctic and nitrate supplied vertically from the Subantarctic thermocline because of the distinctive relationships between the δ15N and concentration of nitrate in these two potential sources. Our Subantarctic samples, collected during the summer and fall, indicate that nitrate is supplied to the Subantarctic surface largely by northward transport of Antarctic surface water. Isotopic data from the Pacific sector of the Subantarctic suggest an isotope effect of 4.5‰, indistinguishable from the Antarctic estimates in this sector.

  4. Satellite Tagging and Biopsy Sampling of Killer Whales at Subantarctic Marion Island: Effectiveness, Immediate Reactions and Long-Term Responses

    PubMed Central

    Reisinger, Ryan R.; Oosthuizen, W. Chris; Péron, Guillaume; Cory Toussaint, Dawn; Andrews, Russel D.; de Bruyn, P. J. Nico

    2014-01-01

    Remote tissue biopsy sampling and satellite tagging are becoming widely used in large marine vertebrate studies because they allow the collection of a diverse suite of otherwise difficult-to-obtain data which are critical in understanding the ecology of these species and to their conservation and management. Researchers must carefully consider their methods not only from an animal welfare perspective, but also to ensure the scientific rigour and validity of their results. We report methods for shore-based, remote biopsy sampling and satellite tagging of killer whales Orcinus orca at Subantarctic Marion Island. The performance of these methods is critically assessed using 1) the attachment duration of low-impact minimally percutaneous satellite tags; 2) the immediate behavioural reactions of animals to biopsy sampling and satellite tagging; 3) the effect of researcher experience on biopsy sampling and satellite tagging; and 4) the mid- (1 month) and long- (24 month) term behavioural consequences. To study mid- and long-term behavioural changes we used multievent capture-recapture models that accommodate imperfect detection and individual heterogeneity. We made 72 biopsy sampling attempts (resulting in 32 tissue samples) and 37 satellite tagging attempts (deploying 19 tags). Biopsy sampling success rates were low (43%), but tagging rates were high with improved tag designs (86%). The improved tags remained attached for 26±14 days (mean ± SD). Individuals most often showed no reaction when attempts missed (66%) and a slight reaction–defined as a slight flinch, slight shake, short acceleration, or immediate dive–when hit (54%). Severe immediate reactions were never observed. Hit or miss and age-sex class were important predictors of the reaction, but the method (tag or biopsy) was unimportant. Multievent trap-dependence modelling revealed considerable variation in individual sighting patterns; however, there were no significant mid- or long-term changes following

  5. Characterization of MHC class I and II genes in a subantarctic seabird, the blue petrel, Halobaena caerulea (Procellariiformes).

    PubMed

    Strandh, Maria; Lannefors, Mimi; Bonadonna, Francesco; Westerdahl, Helena

    2011-10-01

    The great polymorphism observed in the major histocompatibility complex (MHC) genes is thought to be maintained by pathogen-mediated selection possibly combined with MHC-disassortative mating, guided by MHC-determined olfactory cues. Here, we partly characterize the MHC class I and II B of the blue petrel, Halobaena caerulea (Procellariiformes), a bird with significant olfactory abilities that lives under presumably low pathogen burdens in Subantarctica. Blue petrels are long-lived, monogamous birds which suggest the necessity of an accurate mate choice process. The species is ancestral to songbirds (Passeriformes; many MHC loci), although not to gamefowls (Galliformes; few MHC loci). Considering the phylogenetic relationships and the low subantarctic pathogen burden, we expected few rather than many MHC loci in the blue petrel. However, when we analysed partial MHC class I and class II B cDNA and gDNA sequences we found evidence for as many as at least eight MHC class I loci and at least two class II B loci. These class I and II B sequences showed classical MHC characteristics, e.g. high nucleotide diversity, especially in putative peptide-binding regions where signatures of positive selection was detected. Trans-species polymorphism was found between MHC class II B sequences of the blue petrel and those of thin-billed prion, Pachyptila belcheri, two species that diverged ∼25 MYA. The observed MHC allele richness in the blue petrel may well serve as a basis for mate choice, especially since olfactory discrimination of MHC types may be possible in this species.

  6. Habitat associations and distribution of the hyperbenthic shrimp, Nauticaris marionis, around the sub-Antarctic Prince Edward Islands

    NASA Astrophysics Data System (ADS)

    Haley, Craig; von der Meden, Charles; Atkinson, Lara; Reed, Cecile

    2017-09-01

    The association of organisms with particular habitats and habitat-forming organisms, can strongly influence species distributions, interactions and wider ecosystem services. At the sub-Antarctic Prince Edward Islands, the caridean shrimp Nauticaris marionis is a principal part of the benthic ecosystem, occurring between ca. 50 m and 600 m. Its role as a trophic link between the primary productivity and higher predators is established, but little is understood of its in situ habitat usage and associations or of how these structure patterns of abundance. We investigated these aspects directly using a benthic camera sled, sampling 27 stations between 50 m and 500 m. Substratum type was characterised, and estimates of percentage cover of the 13 main groups of habitat-forming epibenthic taxa were made, alongside absolute counts of N. marionis within 'digital quadrats' drawn from 300 m transects. The distribution of N. marionis was influenced by depth, substratum type and overall biogenic cover, being limited to habitats between 50 and 160 m depth on mud or gravel substrata only, and having > 50% biogenic cover. The presence/absence of N. marionis related to significantly different epibenthic assemblages (termed biogenic habitats), but this effect was contingent on depth. Likewise, densities of N. marionis were significantly affected by biogenic habitat type, identifying an association with two biogenic habitat groups, one dominated by red-algae, the other by structurally complex bryozoan species. These associations likely relate to the structural complexity of the two habitat groups, rather than the specific taxa involved. The apparent absence of N. marionis at depths > 160 m contrasts with earlier records and poses questions about the trophic importance of the shrimp in deeper habitats.

  7. Satellite tagging and biopsy sampling of killer whales at subantarctic Marion Island: effectiveness, immediate reactions and long-term responses.

    PubMed

    Reisinger, Ryan R; Oosthuizen, W Chris; Péron, Guillaume; Cory Toussaint, Dawn; Andrews, Russel D; de Bruyn, P J Nico

    2014-01-01

    Remote tissue biopsy sampling and satellite tagging are becoming widely used in large marine vertebrate studies because they allow the collection of a diverse suite of otherwise difficult-to-obtain data which are critical in understanding the ecology of these species and to their conservation and management. Researchers must carefully consider their methods not only from an animal welfare perspective, but also to ensure the scientific rigour and validity of their results. We report methods for shore-based, remote biopsy sampling and satellite tagging of killer whales Orcinus orca at Subantarctic Marion Island. The performance of these methods is critically assessed using 1) the attachment duration of low-impact minimally percutaneous satellite tags; 2) the immediate behavioural reactions of animals to biopsy sampling and satellite tagging; 3) the effect of researcher experience on biopsy sampling and satellite tagging; and 4) the mid- (1 month) and long- (24 month) term behavioural consequences. To study mid- and long-term behavioural changes we used multievent capture-recapture models that accommodate imperfect detection and individual heterogeneity. We made 72 biopsy sampling attempts (resulting in 32 tissue samples) and 37 satellite tagging attempts (deploying 19 tags). Biopsy sampling success rates were low (43%), but tagging rates were high with improved tag designs (86%). The improved tags remained attached for 26±14 days (mean ± SD). Individuals most often showed no reaction when attempts missed (66%) and a slight reaction-defined as a slight flinch, slight shake, short acceleration, or immediate dive-when hit (54%). Severe immediate reactions were never observed. Hit or miss and age-sex class were important predictors of the reaction, but the method (tag or biopsy) was unimportant. Multievent trap-dependence modelling revealed considerable variation in individual sighting patterns; however, there were no significant mid- or long-term changes following

  8. Dispersal in the sub-Antarctic: king penguins show remarkably little population genetic differentiation across their range.

    PubMed

    Clucas, Gemma V; Younger, Jane L; Kao, Damian; Rogers, Alex D; Handley, Jonathan; Miller, Gary D; Jouventin, Pierre; Nolan, Paul; Gharbi, Karim; Miller, Karen J; Hart, Tom

    2016-10-13

    Seabirds are important components of marine ecosystems, both as predators and as indicators of ecological change, being conspicuous and sensitive to changes in prey abundance. To determine whether fluctuations in population sizes are localised or indicative of large-scale ecosystem change, we must first understand population structure and dispersal. King penguins are long-lived seabirds that occupy a niche across the sub-Antarctic zone close to the Polar Front. Colonies have very different histories of exploitation, population recovery, and expansion. We investigated the genetic population structure and patterns of colonisation of king penguins across their current range using a dataset of 5154 unlinked, high-coverage single nucleotide polymorphisms generated via restriction site associated DNA sequencing (RADSeq). Despite breeding at a small number of discrete, geographically separate sites, we find only very slight genetic differentiation among colonies separated by thousands of kilometers of open-ocean, suggesting migration among islands and archipelagos may be common. Our results show that the South Georgia population is slightly differentiated from all other colonies and suggest that the recently founded Falkland Island colony is likely to have been established by migrants from the distant Crozet Islands rather than nearby colonies on South Georgia, possibly as a result of density-dependent processes. The observed subtle differentiation among king penguin colonies must be considered in future conservation planning and monitoring of the species, and demographic models that attempt to forecast extinction risk in response to large-scale climate change must take into account migration. It is possible that migration could buffer king penguins against some of the impacts of climate change where colonies appear panmictic, although it is unlikely to protect them completely given the widespread physical changes projected for their Southern Ocean foraging grounds

  9. Multi-mode humidity sensing with water-soluble copper phthalocyanine for increased sensitivity and dynamic range.

    PubMed

    Muckley, Eric S; Jacobs, Christopher B; Vidal, Keith; Lavrik, Nickolay V; Sumpter, Bobby G; Ivanov, Ilia N

    2017-08-30

    Aqueous solubility of copper phthalocyanine-3,4',4″,4″'-tetrasulfonic acid tetrasodium salt (CuPcTs) enables fabrication of flexible electronic devices by low cost inkjet printing. We (1) investigate water adsorption kinetics on CuPcTs for better understanding the effects of relative humidity (RH) on hydrophilic phthalocyanines, and (2) assess CuPcTs as a humidity-sensing material. Reaction models show that H2O undergoes 2-site adsorption which can be represented by a pair of sequentially-occurring pseudo-first order reactions. Using high frequency (300-700 THz) and low frequency (1-8 MHz) dielectric spectroscopy combined with gravimetric measurements and principal component analysis, we observe that significant opto-electrical changes in CuPcTs occur at RH ≈ 60%. The results suggest that rapid H2O adsorption takes place at hydrophilic sulfonyl/salt groups on domain surfaces at low RH, while slow adsorption and diffusion of H2O into CuPcTs crystallites leads to a mixed CuPcTs-H2O phase at RH > 60%, resulting in high frequency dielectric screening of the film by water and dissociation of Na(+) from CuPc(SO3(-))4 ions. The CuPcTs-H2O interaction can be tracked using a combination of gravimetric, optical, and electrical sensing modes, enabling accurate ( ± 2.5%) sensing in the ~0-95% RH range with a detection limit of less than 0.1% RH.

  10. Road-Mapping the Way Forward for Sentinel-3 STM SAR-Mode Waveform Retracking over Water Surfaces

    NASA Astrophysics Data System (ADS)

    Benveniste, Jérôme; Cotton, David; Dinardo, Salvatore; Lucas, Bruno Manuel; Martin-Puig, Cristina; Ray, Chris; Clarizia, Maria Paola; Gommenginger, Christine

    2013-04-01

    In the framework of the preparation activities for the Sentinel-3 Topography Mission, ESA launched an R&D project on SAR Altimetry and Applications over Ocean, Coastal zones and Inland waters. The main objective was to design a novel processing algorithm over ocean surface that would run in the Sentinel-3 ground segment to provide unprecedented quality altimeter measurements over ocean surfaces when in SAR mode. Also coastal zones and inland waters were the targets of research to derive new models and re-trackers for these difficult measurements. Innovative physically based models have been developed for near-nadir ocean altimetric waveforms in SAR-Mode and subsequently implemented in prototype ocean SAR re-trackers to perform the validation. A Detailed Processing Model Document was delivered for implementation in the Sentinel-3 Topography Mission Ground Segment. In this paper, we present the approach used to date within SAMOSA and the heritage behind the latest SAMOSA2 model. The SAMOSA2 model offers a complete description of SAR altimeter echoes from ocean surfaces, expressed in the form of maps of reflected power in delay and Doppler space. SAMOSA2 is able to account for an elliptical antenna pattern, mispointing errors in roll and yaw, errors in range cell migration correction, surface scattering pattern, non-linear ocean wave statistics and spherical Earth surface effects. SAMOSA2 addresses some of the known limitations of the earlier SAMOSA1 model, in particular with regards to sensitivity to mispointing. Due to its truly comprehensive character, the full SAMOSA2 model is a complicated semi-analytical formulation that still relies on some numerical integrations. The need for numerical integrations significantly impacts the computation time and raises problems of numerical stability once implemented operationally in a re-tracker scheme. This has potentially serious implications that could prevent the implementation of SAMOSA2 in operational re-tracker schemes

  11. Imaging Elastic Properties of Soft Materials Immersed in Water Using Force Modulation Mode in Atomic Force Microscopy

    NASA Astrophysics Data System (ADS)

    Haga, Hisashi; Sasaki, Shigeo; Morimoto, Mayumi; Kawabata, Kazushige; Ito, Etsuro; Abe, Kazuhiro; Sambongi, Takashi

    1998-06-01

    Using the force modulation mode in atomic force microscopy (AFM), we have succeeded in imaging elastic properties of agar gels immersed in water.The elastic images of agar have been captured simultaneously with the topographic images.Stiffer grains of agar whose size is about 200 nm can be clearly seen in the elastic image of 3.0% agar, while they are not so visible in the case of 1.5% agar.These grains probably correspond to aggregation of agar which cannot be observed in the topographic images.We also measured force-versus-distance curves using AFM to confirm that the absolute values of elastic modulus (Young's modulus) of agar coincide with the bulk values measured using the conventional stress-strain method.The estimated values of the elastic moduli with the AFM were 40 and 90 kPa for 1.5% and 3.0% agar gels, respectively.These are in good agreement with the respective bulk values of 30 and 80 kPa obtained using the conventional method.

  12. Community differentiation and population enrichment of Sargasso Sea bacterioplankton in the euphotic zone of a mesoscale mode-water eddy.

    PubMed

    Nelson, Craig E; Carlson, Craig A; Ewart, Courtney S; Halewood, Elisa R

    2014-03-01

    Eddies are mesoscale oceanographic features (∼ 200 km diameter) that can cause transient blooms of phytoplankton by shifting density isoclines in relation to light and nutrient resources. To better understand how bacterioplankton respond to eddies, we examined depth-resolved distributions of bacterial populations across an anticyclonic mode-water eddy in the Sargasso Sea. Previous work on this eddy has documented elevated phytoplankton productivity and diatom abundance within the eddy centre with coincident bacterial productivity and biomass maxima. We illustrate bacterial community shifts within the eddy centre, differentiating populations uplifted along isopycnals from those enriched or depleted at horizons of enhanced bacterial and primary productivity. Phylotypes belonging to the Roseobacter, OCS116 and marine Actinobacteria clades were enriched in the eddy core and were highly correlated with pigment-based indicators of diatom abundance, supporting developing hypotheses that members of these clades associate with phytoplankton blooms. Typical mesopelagic clades (SAR202, SAR324, SAR406 and SAR11 IIb) were uplifted within the eddy centre, increasing bacterial diversity in the lower euphotic zone. Typical surface oligotrophic clades (SAR116, OM75, Prochlorococcus and SAR11 Ia) were relatively depleted in the eddy centre. The biogeochemical context of a bloom-inducing eddy provides insight into the ecology of the diverse uncultured bacterioplankton dominating the oligotrophic oceans.

  13. Nanosecond Pulsed Discharges in Liquid Phase: Optical diagnostics of positive versus negative modes of initiation in water

    NASA Astrophysics Data System (ADS)

    Seepersad, Yohan; Fridman, Alexander; Dobrynin, Danil; Applied Physics Group Team

    2013-09-01

    Recent work on nanosecond pulsed discharges in liquids has shown the possibility of producing plasma directly in the liquid phase without bubble formation or heating of the liquid. Paramount to understanding the physical processes leading to this phenomenon is a thorough understanding of the way these discharges behave under various conditions. This work explores the development of nanosecond pulsed discharges in water, for both positively and negatively applied pulses in a pin-to-plane configuration. Time resolved nanosecond ICCD imaging is used to trace the development of the discharge for applied voltages up to 24 kV. From the results we are able to identify breakdown thresholds at which discharge is initiated for both modes. At voltages below the critical breakdown value, Schlieren and shadowgraphy techniques are used to investigate perturbations in the liquid layers near the electrode tip as a consequence of these fat rising pulses. This work was supported by Defense Advanced Research Projects Agency (grant #DARPA-BAA-11-31).

  14. Mode of action of dopamine in inducing hyperglycemia in the fresh water edible crab, Oziothelphusa senex senex.

    PubMed

    Swetha, Ch; Sainath, S B; Reddy, P Sreenivasula

    2014-11-01

    The objective of this study was to investigate the mode of action of dopamine in regulating hemolymph sugar level in the fresh water edible crab, Oziothelphusa senex senex. Injection of dopamine produced hyperglycemia in a dose-dependent manner in intact crabs but not in eyestalkless crabs. Administration of dopamine resulted in a significant decrease in total carbohydrates and glycogen levels with a significant increase in glycogen phosphorylase activity levels in hepatopancreas and muscle of intact crabs, indicating dopamine-induced glycogenolysis resulting in hyperglycemia. Bilateral eyestalk ablation resulted in significant increase in the total carbohydrates and glycogen levels with a significant decrease in the activity levels of phosphorylase in the hepatopancreas and muscle of the crabs. Eyestalk ablation resulted in significant decrease in hemolymph hyperglycemic hormone levels. The levels of hyperglycemic hormone in the hemolymph of dopamine injected crabs were significantly higher than in control crabs. However, no significant changes in the levels of hemolymph hyperglycemic hormone and sugar and tissue carbohydrate and phosphorylase activity were observed in dopamine injected eyestalk ablated crabs when compared with eyestalk ablated crabs. These results support an earlier hypothesis in crustaceans that dopamine acts as a neurotransmitter and induces hyperglycemia by triggering the release of hyperglycemic hormone in the crab, O. senex senex. © 2014 Wiley Periodicals, Inc.

  15. Effect of the mode of incorporation on the disintegrant properties of acid modified water and white yam starches

    PubMed Central

    Odeku, Oluwatoyin A.; Akinwande, Babatunde L.

    2011-01-01

    Acid modified starches obtained from two species of yam tubers namely white yam – Dioscorearotundata L. and water yam – D. alata L. DIAL2 have been investigated as intra- and extra-granular disintegrants in paracetamol tablet formulations. The native starches were modified by acid hydrolysis and employed as disintegrant at concentrations of 5 and 10% w/w and their disintegrant properties compared with those of corn starch BP. The tensile strength and drug release properties of the tablets, assessed using the disintegration and dissolution (t50 and t80 – time required for 50% and 80% of paracetamol to be released) times, were evaluated. The results showed that the tensile strength and the disintegration and dissolution times of the tablets decreased with increase in the concentration of the starch disintegrants. The acid modified yam starches showed better disintegrant efficiency than corn starch in the tablet formulations. Acid modification appeared to improve the disintegrant efficiency of the yam starches. Furthermore, tablets containing starches incorporated extragranularly showed faster disintegration but lower tensile strength than those containing starches incorporated intragranularly. This emphasizes the importance of the mode of incorporation of starch disintegrant. PMID:23960789

  16. Effect of the mode of incorporation on the disintegrant properties of acid modified water and white yam starches.

    PubMed

    Odeku, Oluwatoyin A; Akinwande, Babatunde L

    2012-04-01

    Acid modified starches obtained from two species of yam tubers namely white yam - Dioscorea rotundata L. and water yam - D. alata L. DIAL2 have been investigated as intra- and extra-granular disintegrants in paracetamol tablet formulations. The native starches were modified by acid hydrolysis and employed as disintegrant at concentrations of 5 and 10% w/w and their disintegrant properties compared with those of corn starch BP. The tensile strength and drug release properties of the tablets, assessed using the disintegration and dissolution (t 50 and t 80 - time required for 50% and 80% of paracetamol to be released) times, were evaluated. The results showed that the tensile strength and the disintegration and dissolution times of the tablets decreased with increase in the concentration of the starch disintegrants. The acid modified yam starches showed better disintegrant efficiency than corn starch in the tablet formulations. Acid modification appeared to improve the disintegrant efficiency of the yam starches. Furthermore, tablets containing starches incorporated extragranularly showed faster disintegration but lower tensile strength than those containing starches incorporated intragranularly. This emphasizes the importance of the mode of incorporation of starch disintegrant.

  17. Formation and conversion of defect centers in low water peak single mode optical fiber induced by gamma rays irradiation

    SciTech Connect

    Wen, J. X.; Luo, W. Y.; Xiao, Z. Y.; Wang, T. Y.; Chen, Z. Y.; Zeng, X. L.

    2010-02-15

    The formation and conversion processes of defect centers in low water peak single mode optical (LWPSM) fiber irradiated with gamma rays were investigated at room temperature using electron spin resonance. Germanium electron center (GEC) and self-trapped hole center (STH) occur when the fibers are irradiated with 1 and 5 kGy cumulative doses, respectively. With the increase in irradiation doses, the GEC defect centers disappear, and new defect centers such as E{sup '} centers (Si and Ge) and nonbridge oxygen hole centers (NBOHCs) generate. The generation of GEC and STH is attributed to the electron transfer, which is completely balanced. This is the main reason that radiation-induced attenuation (RIA) of the LWPSM fiber is only 10 dB/km at communication window. The new defect centers come from the conversion of GEC and STH to E{sup '} centers and NBOHC, and the conversion processes cause bond cleavage, which is the root cause that the RIA of the LWPSM fiber significantly increases up to 180 dB/km at working window. Furthermore, the concentration of new defect centers is saturated easily even by increasing cumulative doses.

  18. Why does Antarctic sea-ice and Southern Ocean surface water appear to be oblivious to global warming?

    NASA Astrophysics Data System (ADS)

    England, M. H.; Purich, A.

    2016-12-01

    Despite global warming, total Antarctic sea-ice coverage has overall increased during the past three-four decades. In contrast, the majority of CMIP5 models simulate a decline. In addition, Southern Ocean surface waters have largely cooled over the past 50 years, in stark contrast to almost all historical CMIP5 simulations. For the most part Subantarctic Surface Waters have cooled and freshened while waters to the north of the ACC have warmed and increased in salinity. It remains unclear (1) to what extent Antarctic sea-ice expansion is due to natural variability vs. anthropogenic forcing of the Southern Annular Mode (via increasing greenhouse gases and/or ozone depleting substances), (2) what the respective role of surface buoyancy fluxes is compared to internal ocean circulation changes, (3) how much of the cooling trends might have been mitigated by ocean eddy fluxes, and (4) what the implications are for interior water masses, carbon uptake, and the global ocean thermohaline circulation. In this talk I will discuss possible causes for the observed trends in surface hydrographic properties over the Southern Ocean, with a focus on both Antarctic sea-ice expansion and sea surface cooling. I will also outline the main reasons why climate models for the most part miss these trends.

  19. Carbon cycling fed by methane seepage at the shallow Cumberland Bay, South Georgia, sub-Antarctic

    NASA Astrophysics Data System (ADS)

    Geprägs, Patrizia; Torres, Marta E.; Mau, Susan; Kasten, Sabine; Römer, Miriam; Bohrmann, Gerhard

    2016-04-01

    Recent studies have suggested that the marine contribution of methane from shallow regions and melting marine-terminating glaciers may have been underestimated. Here we report on methane sources and potential sinks associated with methane seeps in Cumberland Bay, South Georgia's largest fjord system. The average organic carbon content in the upper 8 m of the sediment is around 0.65 wt %; this observation combined with Parasound data suggest that the methane gas accumulations probably originate from peat-bearing sediments currently located several tens of meters below the seafloor. Only one of our cores indicates upward advection; instead most of the methane is transported via diffusion. Sulfate and methane flux estimates indicate that a large fraction of methane is consumed by anaerobic oxidation of methane (AOM). Carbon cycling at the sulfate-methane transition (SMT) results in a marked fractionation of the δ13C-CH4 from an estimated source value of -65‰ to a value as low as -96‰ just below the SMT. Methane concentrations in sediments are high, especially close to the seepage sites (˜40 mM); however, concentrations in the water column are relatively low (max. 58 nM) and can be observed only close to the seafloor. Methane is trapped in the lowermost water mass; however, measured microbial oxidation rates reveal very low activity with an average turnover of 3.1 years. We therefore infer that methane must be transported out of the bay in the bottom water layer. A mean sea-air flux of only 0.005 nM/m2 s confirms that almost no methane reaches the atmosphere.

  20. Road-mapping the Way Forward for Sentinel-3 Topography Mission SAR-Mode waveform Retracking over water surfaces

    NASA Astrophysics Data System (ADS)

    Benveniste, Jérôme; Gommenginger, Christine; Dinardo, Salvatore; Martin-Puig, MCristina; Lucas, Bruno Manuel; Cotton, David; Ray, Chris

    2012-07-01

    In the framework of the ESA SAMOSA Project (SAR Altimetry Studies and Applications over Ocean, Coastal zones and Inland waters), innovative physically based models have been developed for near-nadir ocean altimetric waveforms in SAR-Mode and subsequently implemented in prototype ocean SAR retrackers. In this paper, we present the approach used to date within SAMOSA and the heritage behind the latest SAMOSA2 model. The SAMOSA2 model offers a complete description of SAR altimeter Echoes from ocean surfaces, expressed in the form of maps of reflected power in delay and Doppler space. SAMOSA2 is able to account for an elliptical antenna pattern, mispointing errors in elevation and azimuth, errors in range cell migration correction, surface scattering pattern, non-linear ocean wave statistics and spherical Earth surface effects. SAMOSA2 addresses some of the known limitations of the earlier SAMOSA1 model, in particular with regards to sensitivity to mispointing. Due to its truly comprehensive character, the full SAMOSA2 model is a complicated semi-analytical formulation that still relies on some numerical integrations. The need for numerical integrations negatively impacts the computation time and raises problems of numerical stability once implemented operationally in a re-tracker scheme. This has potentially serious implications that could prevent future implementation of SAMOSA2 in operational re-tracker schemes for future SAR altimeters. However, since the ultimate goal of the SAMOSA project is to deliver to the Sentinel-3 Surface Topography Mission Product and Algorithm Development (S-3 STM PAD) a Detailed Processing Model of a SAR ocean waveform re-tracker based on the best SAMOSA model to operationally retrack Sentinel-3 STM SAR-Mode L1b waveforms, the need for the full mathematical complexity of the SAMOSA2 model is currently being evaluated. With this in mind, the SAMOSA team is assessing a number of simplifications that can transform the SAMOSA2 model into an

  1. Ancient mitochondrial genome reveals unsuspected taxonomic affinity of the extinct Chatham duck (Pachyanas chathamica) and resolves divergence times for New Zealand and sub-Antarctic brown teals.

    PubMed

    Mitchell, Kieren J; Wood, Jamie R; Scofield, R Paul; Llamas, Bastien; Cooper, Alan

    2014-01-01

    The Chatham duck (Pachyanas chathamica) represented one of just three modern bird genera endemic to the Chatham archipelago (situated ~850 km east of New Zealand) but became extinct soon after humans first settled the islands (c. 13th-15th centuries AD). The taxonomic affinity of the Chatham duck remains largely unresolved; previous studies have tentatively suggested placements within both Tadornini (shelducks) and Anatini (dabbling ducks). Herein, we sequence a partial mitochondrial genome (excluding the D-loop) from the Chatham duck and discover that it was a phenotypically-divergent species within the genus Anas (Anatini). This conclusion is further supported by a re-examination of osteological characters. Our molecular analyses convincingly demonstrate that the Chatham duck is the most basal member of a sub-clade comprising the New Zealand and sub-Antarctic brown teals (the brown teal [A. chlorotis], Auckland Island teal [A. aucklandica] and Campbell Island teal [A. nesiotis]). Molecular clock calculations based on an ingroup fossil calibration support a divergence between the Chatham duck and its sister-taxa that is consistent with the estimated time of emergence of the Chatham Islands. Additionally, we find that mtDNA divergence between the two sub-Antarctic teal species (A. aucklandica and A. nesiotis) significantly pre-dates the last few glacial cycles, raising interesting questions about the timing of their dispersal to these islands, and the recent phylogeographic history of brown teal lineages in the region. Copyright © 2013 Elsevier Inc. All rights reserved.

  2. Metagenomics reveals the high polycyclic aromatic hydrocarbon-degradation potential of abundant uncultured bacteria from chronically polluted subantarctic and temperate coastal marine environments.

    PubMed

    Loviso, C L; Lozada, M; Guibert, L M; Musumeci, M A; Sarango Cardenas, S; Kuin, R V; Marcos, M S; Dionisi, H M

    2015-08-01

    To investigate the potential to degrade polycyclic aromatic hydrocarbons (PAHs) of yet-to-be-cultured bacterial populations from chronically polluted intertidal sediments. A gene variant encoding the alpha subunit of the catalytic component of an aromatic-ring-hydroxylating oxygenase (RHO) was abundant in intertidal sediments from chronically polluted subantarctic and temperate coastal environments, and its abundance increased after PAH amendment. Conversely, this marker gene was not detected in sediments from a nonimpacted site, even after a short-term PAH exposure. A metagenomic fragment carrying this gene variant was identified in a fosmid library of subantarctic sediments. This fragment contained five pairs of alpha and beta subunit genes and a lone alpha subunit gene of oxygenases, classified as belonging to three different RHO functional classes. In silico structural analysis suggested that two of these oxygenases contain large substrate-binding pockets, capable of accepting high molecular weight PAHs. The identified uncultured micro-organism presents the potential to degrade aromatic hydrocarbons with various chemical structures, and could represent an important member of the PAH-degrading community in these polluted coastal environments. This work provides valuable information for the design of environmental molecular diagnostic tools and for the biotechnological application of RHO enzymes. © 2015 The Society for Applied Microbiology.

  3. Nutritional Immunity Triggers the Modulation of Iron Metabolism Genes in the Sub-Antarctic Notothenioid Eleginops maclovinus in Response to Piscirickettsia salmonis.

    PubMed

    Martínez, Danixa; Oyarzún, Ricardo; Pontigo, Juan Pablo; Romero, Alex; Yáñez, Alejandro J; Vargas-Chacoff, Luis

    2017-01-01

    Iron deprivation is a nutritional immunity mechanism through which fish can limit the amount of iron available to invading bacteria. The aim of this study was to evaluate the modulation of iron metabolism genes in the liver and brain of sub-Antarctic notothenioid Eleginops maclovinus challenged with Piscirickettsia salmonis. The specimens were inoculated with two P. salmonis strains: LF-89 (ATCC(®) VR-1361™) and Austral-005 (antibiotic resistant). Hepatic and brain samples were collected at intervals over a period of 35 days. Gene expression (by RT-qPCR) of proteins involved in iron storage, transport, and binding were statistically modulated in infected fish when compared with control counterparts. Specifically, the expression profiles of the transferrin and hemopexin genes in the liver, as well as the expression profiles of ferritin-M, ferritin-L, and transferrin in the brain, were similar for both experimental groups. Nevertheless, the remaining genes such as ferritin-H, ceruloplasmin, hepcidin, and haptoglobin presented tissue-specific expression profiles that varied in relation to the injected bacterial strain and sampling time-point. These results suggest that nutritional immunity could be an important immune defense mechanism for E. maclovinus against P. salmonis injection. This study provides relevant information for understanding iron metabolism of a sub-Antarctic notothenioid fish.

  4. [History of Polish botanical and mycological researches on sheets of land of Antarctic and Sub-Antarctic in the years 1977-2009].

    PubMed

    Köhler, Piotr; Olech, Maria

    2011-01-01

    The work includes a description of the period from the moment of setting up Polish Polar Station on King George Island (1977) to the end of International Polar Year IV in 2009. Researches on flower plants focused, among others, on plants' morphology, morphological composition of the pollen and anatomical ultra-structure of the leaves. There were also carried out biochemical and other searches for the internal mutability. Within physiological studies one concentrated on the problem of reaction to temperature stress. Biological researches focused mainly on solving taxonomic and bio-geographic problems. Finally, were published several monographs and, among others, the first in history complete description of moss' flora of the whole of Antarctic (2008). Research works over algae included also such issues as floristics, bio-geography, taxonomy and ecology (for instance, the rookery's impact on distribution of algae, or the influence of inanimate factors on dynamics of condensing the Diatoma in different water and soil-bound tanks). Up till now, within mycological investigations has been identified a variety of lichen fungi that for the most part of Antarctic are a novelty. There were scientifically described new for science genera and species of Western Antarctic. Lichenological studies were made in the field of taxonomy, geography, lichenometry, biochemistry of lichens, lichenoindication, ecophysiology and from the point of analysis of base metals' content. There were also described new for science species. Since 1991, were published the results of searches for the base metals' content and vestigial chemical elements in lichens' thallus. Ecophysiological researches concerned both micro-climatic conditions' impact on primary production and lichens' adaptation to a very cold climate. One discovered a mechanism of two-phase hydratization/dehydratization of lichens' thallus. On the ground of palaeobotanical analyzes was reconstructed a development of flora in Western

  5. Local stochastic subgrid-scale modeling for a one dimensional shallow water model using stochastic mode reduction

    NASA Astrophysics Data System (ADS)

    Zacharuk, Matthias; Dolaptchiev, Stamen; Achatz, Ulrich; Timofeyev, Ilya

    2017-04-01

    Due to the finite spatial resolution in numerical atmospheric models, subgrid-scale (SGS) processes arise. A SGS parameterization of these excluded processes might improve the model on all scales. In this study we present a model derived parameterization of these processes for the one dimensional shallow water equations. To parameterize the SGS processes we choose the MTV stochastic mode reduction (Majda, Timofeyev, Vanden-Eijnden 2001, A mathematical framework for stochastic climate models. Commun. Pure Appl. Math., 54:891-974). For this the model is separated into fast and slow processes. Using the statistics of the fast processes, a SGS parameterization is found. To identify fast processes the state vector of the model is separated into two state vectors. One vector is the average of the full model state vector in a coarse grid cell. The other describes SGS processes which are defined as the deviation of the full state vector from the coarse cell average. If the SGS vector decorrelates faster in time than the coarse grid vector, the stochastic MTV SGS parameterization can be derived from the model equation, which is the advantage of this method compared to others. So far the method was successfully applied on the Burgers-equation (Dolaptchiev et al. 2013, Stochastic closure for local averages in the finite-difference discretization of the forced Burgers equation. Theor. Comp. Fluid Dyn., 27:297-317). To apply the method onto the one the dimensional shallow water equations, we choose a local approach of the fine variable self-interactions. With this, we are able to derive a local SGS parameterization using MTV's method leading to a closed model wrt. the coarse variable. We show, that this model is able to fix the energy decrease for high wave numbers which appears at the coarse resolution model with neglected SGS parameterization. In the future we plan to extend the model to two dimensions and multiple layers. Perspectively, the method can be used to derive a

  6. Influence of pressure on the low-frequency vibrational modes of lysozyme and water: a complementary inelastic neutron scattering and molecular dynamics simulation study.

    PubMed

    Lerbret, Adrien; Hédoux, Alain; Annighöfer, Burkhard; Bellissent-Funel, Marie-Claire

    2013-02-01

    We performed complementary inelastic neutron scattering (INS) experiments and molecular dynamics (MD) simulations to study the influence of pressure on the low-frequency vibrational modes of lysozyme in aqueous solution in the 1 atm-6 kbar range. Increasing pressure induces a high-frequency shift of the low-frequency part (<10 meV = 80 cm(-1)) of the vibrational density of states (VDOS), g(ω), of both lysozyme and water that reveals a stiffening of the interactions ascribed to the reduction of the protein and water volumes. Accordingly, high pressures increase the curvature of the free energy profiles of the protein quasiharmonic vibrational modes. Furthermore, the nonlinear influence of pressure on the g(ω) of lysozyme indicates a change of protein dynamics that reflects the nonlinear pressure dependence of the protein compressibility. An analogous dynamical change is observed for water and stems from the distortion of its tetrahedral structure under pressure. Moreover, our study reveals that the structural, dynamical, and vibrational properties of the hydration water of lysozyme are less sensitive to pressure than those of bulk water, thereby evidencing the strong influence of the protein surface on hydration water.

  7. Dynamic absorption and scattering of water and hydrogel during high-repetition-rate (>100 MHz) burst-mode ultrafast-pulse laser ablation

    PubMed Central

    Qian, Zuoming; Covarrubias, Andrés; Grindal, Alexander W.; Akens, Margarete K.; Lilge, Lothar; Marjoribanks, Robin S.

    2016-01-01

    High-repetition-rate burst-mode ultrafast-laser ablation and disruption of biological tissues depends on interaction of each pulse with the sample, but under those particular conditions which persist from previous pulses. This work characterizes and compares the dynamics of absorption and scattering of a 133-MHz repetition-rate, burst-mode ultrafast-pulse laser, in agar hydrogel targets and distilled water. The differences in energy partition are quantified, pulse-by-pulse, using a time-resolving integrating-sphere-based device. These measurements reveal that high-repetition-rate burst-mode ultrafast-laser ablation is a highly dynamical process affected by the persistence of ionization, dissipation of plasma plume, neutral material flow, tissue tensile strength, and the hydrodynamic oscillation of cavitation bubbles. PMID:27375948

  8. [The origin of polyploid genomes of bluegrasses Poa L. and gene flow between Northern Pacific and sub-Antarctic islands].

    PubMed

    Rodionov, A V; Nosov, N N; Kim, E S; Machs, E M; Punina, E O; Probatova, N S

    2010-12-01

    ) (=Ncoraepoa chonotica) (2n = 42) was found to be related to Arctagrostis, Festucella, and Hookerochloa, being at the same time quite distant from the other species of the genus Poa. Polymorphic in chromosome number highly polyploid species of Northern Hemisphere, P. arctica (2n = 42 to 106), P. turneri (2n = 42, 63 to 64), and P. smirnovii (2n = 42, 70) (sect. Malacanthae) are relative to a large group of tetraploid (2n = 28) endemic bluegrass species from New Zealand and sub-Antarctic islands (P. novae-zelandiae and allied species).

  9. Librational modes of the water molecules in barium and strontium halide monohydrates, MX 2 · 1H 2O (M = Ba, Sr; X = Cl, Br, I)

    NASA Astrophysics Data System (ADS)

    Lutz, H. D.; Christian, H.

    1983-09-01

    The IR and Raman spectra of the isotypic alkaline earth halide monohydrates, MX 2 · 1H 2O, with M = Sr, Ba and X = Cl, Br, I, and of deuterated samples are presented for the range 200-700 cm -1 and discussed in terms of normal modes, assignment, coupling, correlation with structure data, and temperature dependence of both the H 2O (D 2O) and the HDO librational modes. The normal modes of the out-of-plane librations of HDO molecules are of the wagging and twisting type rather than H and D out-of-plane vibrations [4], at least for water molecules with C2v or nearly C2v symmetry. Thus the observed H 2O/HDO isotopic shifts can be used as a criterion for assigning the H 2O librations. The librational modes of the halide monohydrates (with tetrahedrally coordinated water oxygen atoms) are found in the order ν Rγ ≫ ν Rt ≫ ν Rr. The intensities of the IR and Raman spectra are in the order Rγ ≫ Rr ≫ Rt (or ˜ Rt in the case of strongly distorted H 2O molecules) and Rt ≫ Rr ≫ Rγ, respectively. Correlations of the H 2O librational modes with structural or bonding data are restricted by frequency shifts due to vibrational coupling and by the fact that the oxygen and the hydrogen atoms of the water molecules are generally affected in a different manner by bond interactions. However, in the case of the twisting vibrations, there are clear correlations with both the size of the metal ions, i.e. increase of ν Rt with decreasing size, and the intermolecular bonding of the hydrogen atoms, as shown by the OH stretching frequencies, i.e. increase of ν Rt with decreasing ν OH.

  10. Nonlinear evolution of high frequency R-mode waves excited by water group ions near comets - Computer experiments

    NASA Technical Reports Server (NTRS)

    Kojima, H.; Matsumoto, H.; Omura, Y.; Tsurutani, B. T.

    1989-01-01

    An ion beam resonates with R-mode waves at a high-frequency RH mode and a low-frequency RL mode. The nonlinear evolution of ion beam-generated RH waves is studied here by one-dimensional hybrid computer experiments. Both wave-particle and subsequent wave-wave interactions are examined. The competing process among coexisting RH and RL mode beam instabilities and repeated decay instabilities triggered by the beam-excited RH mode waves is clarified. It is found that the quenching of the RH instability is not caused by a thermal spreading of the ion beam, but by the nonlinear wave-wave coupling process. The growing RH waves become unstable against the decay instability. This instability involves a backward-traveling RH electromagnetic wave and a forward-traveling longitudinal sound wave. The inverse cascading process is found to occur faster than the growth of the RL mode. Wave spectra decaying from the RH waves weaken as time elapses and the RL mode waves become dominant at the end of the computer experiment.

  11. Development of an on-line mixed-mode gel liquid chromatography×reversed phase liquid chromatography method for separation of water extract from Flos Carthami.

    PubMed

    Wang, Yu-Qing; Tang, Xu; Li, Jia-Fu; Wu, Yun-Long; Sun, Yu-Ying; Fang, Mei-Juan; Wu, Zhen; Wang, Xiu-Min; Qiu, Ying-Kun

    2017-10-13

    A novel on-line comprehensive two-dimensional liquid chromatography (2D-LC) method by coupling mixed-mode gel liquid chromatography (MMG-LC) with reversed phase liquid chromatography (RPLC) was developed. A mixture of 17 reference compounds was used to study the separation mechanism. A crude water extract of Flos Carthami was applied to evaluate the performance of the novel 2D-LC system. In the first dimension, the extract was eluted with a gradient of water/methanol over a cross-linked dextran gel Sephadex LH-20 column. Meanwhile, the advantages of size exclusion, reversed phase partition and adsorption separation mechanism were exploited before further on-line reversed phase purification on the second dimension. This novel on-line mixed-mode Sephadex LH-20×RPLC method provided higher peak resolution, sample processing ability (2.5mg) and better orthogonality (72.9%) versus RPLC×RPLC and hydrophilic interaction liquid chromatography (HILIC)×RPLC. To the best of our knowledge, this is the first report of a mixed-mode Sephadex LH-20×RPLC separation method with successful applications in on-line mode, which might be beneficial for harvesting targets from complicated medicinal plants. Copyright © 2017 Elsevier B.V. All rights reserved.

  12. Sea spray production by bag breakup mode of fragmentation of the air-water interface at strong and hurricane wind

    NASA Astrophysics Data System (ADS)

    Troitskaya, Yuliya; Kandaurov, Alexander; Ermakova, Olga; Kozlov, Dmitry; Sergeev, Daniil; Zilitinkevich, Sergej

    2016-04-01

    Sea sprays is a typical element of the marine atmospheric boundary layer (MABL) of large importance for marine meteorology, atmospheric chemistry and climate studies. They are considered as a crucial factor in the development of hurricanes and severe extratropical storms, since they can significantly enhance exchange of mass, heat and momentum between the ocean and the atmosphere. This exchange is directly provided by spume droplets with the sizes from 10 microns to a few millimeters mechanically torn off the crests of a breaking waves and fall down to the ocean due to gravity. The fluxes associated with the spray are determined by the rate of droplet production at the surface quantified by the sea spray generation function (SSGF), defined as the number of spray particles of radius r produced from the unit area of water surface in unit time. However, the mechanism of spume droplets' formation is unknown and empirical estimates of SSGF varied over six orders of magnitude; therefore, the production rate of large sea spray droplets is not adequately described and there are significant uncertainties in estimations of exchange processes in hurricanes. Experimental core of our work comprise laboratory experiments employing high-speed video-filming, which have made it possible to disclose how water surface looks like at extremely strong winds and how exactly droplets are torn off wave crests. We classified events responsible for spume droplet, including bursting of submerged bubbles, generation and breakup of "projections" or liquid filaments (Koa, 1981) and "bag breakup", namely, inflating and consequent blowing of short-lived, sail-like pieces of the water-surface film, "bags". The process is similar to "bag-breakup" mode of fragmentation of liquid droplets and jets in gaseous flows. Basing on statistical analysis of results of these experiments we show that the main mechanism of spray-generation is attributed to "bag-breakup mechanism On the base of general principles

  13. Ventilation of The Thermocline In The Atlantic Ocean: Effects of Model Resolution On The Formation of Subtropical Mode Waters and The Associated Uptake of Anthropogenic Trace Gases

    NASA Astrophysics Data System (ADS)

    Czeschel, L.; Böning, C. W.; Beismann, J. O.; Biastoch, A.; Völker, C.

    The ocean takes up a large fraction of the perturbation CO2 that enters the atmosphere by human activity. A realistic representation of this uptake in numerical models is essential for future climate studies. The processes that are mainly responsible for the uptake are deep water formation in polar regions and ventilation of water masses be- tween the wind-mixed layer and the pycnocline. Earlier studies with coarse resolution models seem to underestimate this uptake mainly in the subtropics. In the present study, we investigate the ventilation of the thermocline and the related formation of mode waters in the subtropics using numerical models of the Atlantic Ocean which have been developed as part of the FLAME (Family of Linked Atlantic Model Experiments) hierarchy. We use a variety of models differing in horizontal res- olution (4/3, 1/3, 1/12) and mixing parameterisation. In comparison to climatologi- cal WOCE data, the coarse-resolution model underestimates the formation of subtrop- ical mode waters (STMW). The eddy-permitting and eddy-resolving models suggest that an increase of the grid resolution causes a significant increase of STMW forma- tion. The eddy-permitting configuration gives a more realistic mode water volume, but the eddy-resolving model is needed to simulate spatial structure and thickness of the STMW layer as observed. Because of the direct ventilation of these water masses, the bigger STMW volume leads to a larger uptake of CFCs and anthropogenic CO2 in the subtropics. In contrast, the coarse-resolution model (with properties similar to global ocean cycle models) takes up significantly less anthr. CO2 than the eddy-permitting version.

  14. Intermediate water 14C evidence for the mechanism of deglacial CO2 increase

    NASA Astrophysics Data System (ADS)

    Marchitto, T. M.; Lehman, S. J.; Ortiz, J. D.; van Geen, A.

    2006-12-01

    Carbon sequestration in the ocean is widely considered to be the proximate cause of glacial CO2 lowering. The 14C activity of the atmosphere during the last glacial period appears to have been too high to be explained by increased cosmogenic production alone, implying that exchange of CO2 with the deep ocean must have been reduced. In other words, there must have been a relatively isolated deep ocean carbon reservoir. Likewise there was a sharp drop in atmospheric 14C activity coincident with the Termination I atmospheric CO2 increase, suggesting that the deep isolated reservoir, and therefore the carbon released from the ocean, was extremely depleted in 14C. Both the CO2 and 14C changes occurred in step with Antarctic warming, implicating the Southern Ocean as the main locus of carbon release. We therefore hypothesize that 14C-depleted waters should have spread to the intermediate/upper ocean via Antarctic Intermediate Water and Subantarctic Mode Water during the last deglaciation. We show that at ~700 m water depth off of southern Baja California, very 14C-depleted waters appeared in two stages during the last deglaciation, closely coincident with the atmospheric CO2 rise. The spectral reflectance record from our sediment core bears a remarkable resemblance to Greenland ice δ 18O, allowing us to assign calendar ages to our samples. Radiocarbon activity of paleo-waters is then calculated by age-correcting our benthic foraminiferal 14C measurements. During most of the 40,000 year record, intermediate water activity was ~100-200‰ lower than the atmosphere (like today), but during deglaciation this depletion increased to as much as 450‰. We suggest that this transient drop reflects the mixing of `old' carbon to the Southern Ocean surface, with spreading to the North Pacific via Antarctic Intermediate Water.

  15. Local stochastic subgrid-scale modeling for a one dimensional shallow water model using stochastic mode reduction

    NASA Astrophysics Data System (ADS)

    Zacharuk, Matthias; Stamen, Dolaptchiev; Ulrich, Achatz; Ilya, Timofeyev

    2016-04-01

    Due to the finite spatial resolution in numerical atmospheric models subgrid-scale (SGS) processes are excluded. A SGS parameterization of these excluded processes might improve the model on all scales. To parameterize the SGS processes we choose the MTV stochastic mode reduction (Majda, Timofeyev, Vanden-Eijnden 2001, A mathematical framework for stochastic climate models. Commun. Pure Appl. Math., 54:891-974). For this the model is separated into fast and slow processes. Using the statistics of the fast processes, a SGS parameterization is found. To identify fast processes the state vector of the model is separated into two state vectors. One vector is the average of the full model state vector in a coarse grid cell. The other describes SGS processes which are defined as the deviation of the full state vector from the coarse cell average. If the SGS vector decorrelates faster in time than the coarse grid vector, the interactions of SGS processes in the equation of the SGS processes are replaced by a local Ornstein-Uhlenbeck process. Afterwards the MTV SGS parameterization can be derived. This method was successfully applied on the Burgers-equation (Dolaptchiev et al. 2013, Stochastic closure for local averages in the finite-difference discretization of the forced Burgers equation. Theor. Comp. Fluid Dyn., 27:297-317). In this study we consider a more atmosphere like model and choose a model of the one dimensional shallow water equations (SWe). It will be shown, that the fine state vector decorrelates faster than the coarse state vector. Due to the non-polynomial form of the SWe in flux formulation an approximation of all 1/h (h = fluid depth) terms needs to be done, except of the interactions between coarse state vector to coarse state vector. It will be shown, that this approximation has only minor impact on the model results. In the following the model with the local Ornstein-Uhlenbeck process approximation of SGS interactions is analyzed and compared to the

  16. Subsurface new production in the northwestern subtropical North Pacific fueled by nutrients from the Subtropical Mode Water

    NASA Astrophysics Data System (ADS)

    Suga, T.; Sukigara, C.; Saino, T.; Toyama, K.; Yanagimoto, D.; Hanawa, K.; Shikama, N.; Tsubono, K.; Kobayashi, T.; Hosoda, S.; Hibiya, T.; Furuichi, N.

    2010-12-01

    Substantial sustained subsurface new production during summer in the northwestern subtropical North Pacific is demonstrated, with its mechanism being proposed, based on observation by a profiling float and a synoptic survey by a research vessel. The profiling float equipped with a fluorometer, a dissolved oxygen (DO) sensor, and temperature and salinity sensors was deployed in the Subtropical Mode Water (STMW) formation region. It acquired quasi-Lagrangian, 5-day-interval time-series records from March to July 2006. The time-series distribution of chlorophyll showed a sustained and sizable subsurface maximum at 50-100 m, just above the upper boundary of the STMW, throughout early summer (May-July). The DO concentration in the lower euphotic zone (50-100 m) had been supersaturated in the same period but did not show a net increment. On the other hand, the DO concentration at 100-150 m near the upper edge of the STMW, which was below the euphotic zone, decreased very slightly, in spite of expected oxygen consumption by organisms at least as large as that appearing at 150-300 m. These small temporal variations of dissolved oxygen in the lower euphotic zone and near the upper edge of the STMW are explained by downward oxygen transport due to large diffusion near the top of the STMW. The estimated diffusivity based on an assumption of the large downward transport of oxygen is 1.5 × 10-4 m-2 s-1. The upward nitrate transport into the euphotic zone by the same diffusion is estimated to be 0.7 mmol N m-2 d-1 with using vertical profiles of nitrates obtained by ship-board measurements in the vicinity of the float. Assuming all of the transported nitrate be used for photosynthesis by the phytoplankton, the net community production is estimated to be 4.8 mmol C m-2 d-1. The large diffusivity near the top of the STMW is possibly associated with an abrupt decrease in buoyancy frequency there, which may prevents downward transmission of internal waves generated in the surface

  17. Evidence of silicic acid leakage to the tropical Atlantic via Antarctic Intermediate Water during Marine Isotope Stage 4

    NASA Astrophysics Data System (ADS)

    Griffiths, James D.; Barker, Stephen; Hendry, Katharine R.; Thornalley, David J. R.; van de Flierdt, Tina; Hall, Ian R.; Anderson, Robert F.

    2013-06-01

    Antarctic Intermediate Water (AAIW) and Subantarctic Mode Water (SAMW) are the main conduits for the supply of dissolved silicon (silicic acid) from the deep Southern Ocean (SO) to the low-latitude surface ocean and therefore have an important control on low-latitude diatom productivity. Enhanced supply of silicic acid by AAIW (and SAMW) during glacial periods may have enabled tropical diatoms to outcompete carbonate-producing phytoplankton, decreasing the relative export of inorganic to organic carbon to the deep ocean and lowering atmospheric pCO2. This mechanism is known as the "silicic acid leakage hypothesis" (SALH). Here we present records of neodymium and silicon isotopes from the western tropical Atlantic that provide the first direct evidence of increased silicic acid leakage from the Southern Ocean to the tropical Atlantic within AAIW during glacial Marine Isotope Stage 4 ( 60-70 ka). This leakage was approximately coeval with enhanced diatom export in the NW Atlantic and across the eastern equatorial Atlantic and provides support for the SALH as a contributor to CO2 drawdown during full glacial development.

  18. [Effects of water and nitrogen management modes on the leaf photosynthetic characters and yield formation of cotton with under-mulch drip irrigation].

    PubMed

    Luo, Hong-Hai; Zhang, Hong-Zhi; Tao, Xian-Ping; Zhang, Ya-Li; Zhang, Wang-feng

    2013-02-01

    Taking different genotype cotton varieties as test materials, a soil column culture experiment was conducted to study the effects of water and nitrogen management modes on the photosynthetic characters and yield formation of cotton with under-mulch drip irrigation in Xinjiang, Northwest China. Under the management mode W4N2, i.e., pre-sowing irrigation + limited drip irrigation before full-flowering + abundant drip irrigation after full-flowering in combining with basal 20% N + topdressing 80% N, the chlorophyll content, net photosynthetic rate (Pn), stomatal conductance (gs) , actual photochemical efficiency of photosystem II (Psi PSII), and photochemical quenching coefficient (qp) at full-flowering stage all decreased significantly, the non-photochemical quenching (NPQ) increased, and the aboveground dry matter accumulation was inhibited, as compared with those under common drip irrigation. From full-flowering stage to boll-opening stage, the chlorophyll content, gs, Pn, Psi PSII, and qp increased with increasing water and nitrogen supply, and the aboveground dry matter accumulation was enhanced by compensation, which benefited the translocation and distribution of photosynthates to seed cotton. Under the fertilization mode of basal 20% N + topdressing 80% N, the seed cotton yield of Xinluzaol3 was the highest in treatment pre-sowing irrigation + common drip irrigation (W3), but that of Xinluzao43 was the highest in treatment pre-sowing irrigation + limited drip irrigation before full-flowering + abundant drip irrigation after full-flowering (W4). It was concluded that under the condition of pre-sowing irrigation, to appropriately decrease the water and nitrogen supply before full-flowering stage and increase the water and nitrogen supply at middle and late growth stages could extend the active photosynthesis duration and promote the photosynthates allocation to reproductive organ, which would fully exploit the yield-increasing potential of cotton with under

  19. Observed Temporal and Spatial Variability in the Marine Environment at the Sub-Antarctic Prince Edward Islands - Evidence of a Changing Climate?

    NASA Astrophysics Data System (ADS)

    Asdar, S.; Deshayes, J.; Ansorge, I. J.

    2016-02-01

    The sub-Antarctic Prince Edward Islands (PEI) (47°S,38°E) are classified as isolated, hostile, impoverished regions, in which the terrestrial and marine ecosystems are relatively simple and extremely sensitive to perturbations. Their location between the Sub-Antarctic Front (SAF) and the Antarctic Polar Front (APF), bordering the Antarctic Circumpolar Current (ACC) provides an ideal natural laboratory for studying how organisms, ecological processes and ecosystems respond to a changing ocean climate in the Southern Ocean. Recent studies have proposed that climate changes reported at the PEI may correspond in time to a southward shift of the ACC and in particular of the SAF. This southward migration in the geographic position is likely to coincide with dramatic changes in the distribution of species and total productivity of this region. This study focuses on the inter-comparison of observations available at these islands. Using spectral analysis which is a study of the frequency domain characteristics of a process, we first determine the dominant characteristics of both the temporal and spatial variability of physical and biogeochemical properties. In doing so the authors are able to determine whether and how these indices of variability interact with one another in order to understand better the mechanisms underpinning this variability, i.e. the seasonal zonal migrations associated with the SAF. Additionally, we include in our analysis recent data from 2 ADCP moorings deployed between the islands from 2014 to 2015. These in-situ observations of circulation and hydrography in the vicinity of the islands provide a unique opportunity to establish a better understanding of how large scale climatic variability may impact local conditions, and more importantly its influence on the fragile ecosystem surrounding the PEI.

  20. Similar metabolic rate-temperature relationships after acclimation at constant and fluctuating temperatures in caterpillars of a sub-Antarctic moth.

    PubMed

    Chown, Steven L; Haupt, Tanya M; Sinclair, Brent J

    2016-02-01

    Temperature compensation in whole-animal metabolic rate is one of the responses thought, controversially, to characterize insects from low temperature environments. Temperature compensation may either involve a change in absolute values of metabolic rates or a change in the slope of the metabolic rate - temperature relationship. Moreover, assessments of compensation may be complicated by animal responses to fluctuating temperatures. Here we examined whole animal metabolic rates, at 0 °C, 5 °C, 10 °C and 15 °C, in caterpillars of the sub-Antarctic moth, Pringleophaga marioni Viette (Tineidae), following one week acclimations to 5 °C, 10 °C and 15 °C, and fluctuating temperatures of 0-10 °C, 5-15 °C, and 10-20 °C. Over the short term, temperature compensation was found following acclimation to 5 °C, but the effect size was small (3-14%). By comparison with caterpillars of 13 other lepidopteran species, no effect of temperature compensation was present, with the relationship between metabolic rate and temperature having a Q10 of 2 among species, and no effect of latitude on temperature-corrected metabolic rate. Fluctuating temperature acclimations for the most part had little effect compared with constant temperatures of the same mean value. Nonetheless, fluctuating temperatures of 5-15 °C resulted in lower metabolic rates at all test temperatures compared with constant 10 °C acclimation, in keeping with expectations from the literature. Absence of significant responses, or those of large effect, in metabolic rates in response to acclimation, may be a consequence of the unpredictable temperature variation over the short-term on sub-Antarctic Marion Island, to which P. marioni is endemic.

  1. The dissociative chemisorption of water on Ni(111): Mode- and bond-selective chemistry on metal surfaces

    SciTech Connect

    Farjamnia, Azar; Jackson, Bret

    2015-06-21

    A fully quantum approach based on an expansion in vibrationally adiabatic eigenstates is used to explore the dissociative chemisorption of H{sub 2}O, HOD, and D{sub 2}O on Ni(111). For this late barrier system, excitation of both the bending and stretching modes significantly enhances dissociative sticking. The vibrational efficacies vary somewhat from mode-to-mode but are all relatively close to one, in contrast to methane dissociation, where the behavior is less statistical. Similar to methane dissociation, the motion of lattice atoms near the dissociating molecule can significantly modify the height of the barrier to dissociation, leading to a strong variation in dissociative sticking with substrate temperature. Given a rescaling of the barrier height, our results are in reasonable agreement with measurements of the dissociative sticking of D{sub 2}O on Ni(111), for both laser-excited molecules with one or two quanta of excitation in the antisymmetric stretch and in the absence of laser excitation. Even without laser excitation, the beam contains vibrationally excited molecules populated at the experimental source temperature, and these make significant contributions to the sticking probability. At high collision energies, above the adiabatic barrier heights, our results correlate with these barrier heights and mode softening effects. At lower energies, dissociative sticking occurs primarily via vibrationally nonadiabatic pathways. We find a preference for O–H over O–D bond cleavage for ground state HOD molecules at all but the highest collision energies, and excitation of the O–H stretch gives close to 100% O–H selectivity at lower energies. Excitation of the O–D stretch gives a lower O–D cleavage selectivity, as the interaction with the surface leads to energy transfer from the O–D stretch into the O–H bond, when mode softening makes these vibrations nearly degenerate.

  2. Fabrication of porous ethyl cellulose microspheres based on the acetone-glycerin-water ternary system: Controlling porosity via the solvent-removal mode.

    PubMed

    Murakami, Masahiro; Matsumoto, Akihiro; Watanabe, Chie; Kurumado, Yu; Takama, Masashi

    2015-08-01

    Porous ethyl cellulose (EC) microspheres were prepared from the acetone-glycerin-water ternary system using an oil/water (O/W)-type emulsion solvent extraction method. The O/ W type emulsion was prepared using acetone dissolved ethyl cellulose as an oil phase and aqueous glycerin as a water phase. The effects of the different solvent extraction modes on the porosity of the microspheres were investigated. The specific surface area of the porous EC microspheres was estimated by the gas adsorption method. When the solvent was extracted rapidly by mixing the emulsion with water instantaneously, porous EC microspheres with a maximum specific surface area of 40.7±2.1 m2/g were obtained. On the other hand, when water was added gradually to the emulsion, the specific surface area of the fabricated microspheres decreased rapidly with an increase in the infusion period, with the area being 25-45% of the maximum value. The results of an analysis of the ternary phase diagram of the system suggested that the penetration of water and glycerin from the continuous phase to the dispersed phase before solidification affected the porosity of the fabricated EC microspheres.

  3. [Effects of different water harvesting modes on alfalfa planting in semi-arid areas of Northwest China].

    PubMed

    Huo, Hai-Li; Wang, Qi; Zhang, En-He; Shi, Shang-Li; Ren, Xiang; Wang, He-Ling; Wang, Tian-Tao; Liu, Qing-Lin

    2013-10-01

    A field experiment with complete random design was conducted to investigate the effects of different mulching materials [common plastic film (CMR), biodegradable mulch film (BMR), and soil crust (SR)] and different ratios of furrow to ridge (60 cm:30 cm, 60 cm:45 cm, and 60 cm:60 cm) on the runoff efficiency, soil water storage, soil water content, and hay yield and water use efficiency of alfalfa in semiarid areas of the Loess Plateau. The runoff efficiency in treatments SR, BMR, and CMR was 32.0%, 90.7%, and 96.4%, respectively. In the early growth period of alfalfa (from April to June) , the soil water storage between the treatments had no significant difference, but in the late growth period (from July to September), the soil water storage in CMR and BMR was significantly higher than that in SR. The soil water storage in SR was significantly higher than that in traditional planting (TP). At budding stage, the soil water storage in TP, SR, BMR, and CMR was 223.27, 248.56, and 277. 81, and 284.16 mm, respectively. In the whole growth period, the hay yield of alfalfa in TP, SR, BMR, and CMR was 4112.1, 3397.5, 4317.8, and 4523.8 kg x hm(-2), and the water use efficiency was 11.08, 10.48, 14.56, and 14.95 kg x mm(-1) x hm(-2), respectively. The ratio of furrow to ridge had no significant effects on the water use efficiency in the same treatments. When the ratio of furrow to ridge was 60 cm:44 cm, the hay yield in CMR and BMR reached the maximum.

  4. Acoustic mode coupling induced by shallow water nonlinear internal waves: sensitivity to environmental conditions and space-time scales of internal waves.

    PubMed

    Colosi, John A

    2008-09-01

    While many results have been intuited from numerical simulation studies, the precise connections between shallow-water acoustic variability and the space-time scales of nonlinear internal waves (NLIWs) as well as the background environmental conditions have not been clearly established analytically. Two-dimensional coupled mode propagation through NLIWs is examined using a perturbation series solution in which each order n is associated with nth-order multiple scattering. Importantly, the perturbation solution gives resonance conditions that pick out specific NLIW scales that cause coupling, and seabed attenuation is demonstrated to broaden these resonances, fundamentally changing the coupling behavior at low frequency. Sound-speed inhomogeneities caused by internal solitary waves (ISWs) are primarily considered and the dependence of mode coupling on ISW amplitude, range width, depth structure, location relative to the source, and packet characteristics are delineated as a function of acoustic frequency. In addition, it is seen that significant energy transfer to modes with initially low or zero energy involves at least a second order scattering process. Under moderate scattering conditions, comparisons of first order, single scattering theoretical predictions to direct numerical simulation demonstrate the accuracy of the approach for acoustic frequencies upto 400 Hz and for single as well as multiple ISW wave packets.

  5. Description of Pseudingolfiella possessionis n. sp. (Crustacea, Amphipoda) from sub-Antarctic Île de La Possession, Crozet archipelago: the second freshwater amphipod known from the Antarctic biome, a human introduction of Gondwanan ancestry?

    PubMed

    Smet, Willem H De

    2015-03-31

    A new species of freshwater amphipod, Pseudingolfiella possessionis n. sp. (Senticaudata, Pseudingolfiellidae), is described from the submerged moss vegetation of small brooklets at sub-Antarctic Île de La Possession, Crozet archipelago. It constitutes the second freshwater amphipod species known for the sub-Antarctic and Antarctic region, and the fourth member of the genus. The main characters distinguishing it from all congeners are: the spine on the posterior margin of the dactylus, incisor and lamina mobilis of mandible each with 5 teeth, the setation of the maxilliped, the vestigial second article of pleopod 3 in the female, the undulate and laterally notched posterolateral margin of the external ramus of uropods 1 and 2 in the male, the spinulate dorsomedian projection of the telson.

  6. An assessment of BWR (boiling water reactor) Mark III containment challenges, failure modes, and potential improvements in performance

    SciTech Connect

    Schroeder, J.A.; Pafford, D.J.; Kelly, D.L.; Jones, K.R.; Dallman, F.J. )

    1991-01-01

    This report describes risk-significant challenges posed to Mark III containment systems by severe accidents as identified for Grand Gulf. Design similarities and differences between the Mark III plants that are important to containment performance are summarized. The accident sequences responsible for the challenges and the postulated containment failure modes associated with each challenge are identified and described. Improvements are discussed that have the potential either to prevent or delay containment failure, or to mitigate the offsite consequences of a fission product release. For each of these potential improvements, a qualitative analysis is provided. A limited quantitative risk analysis is provided for selected potential improvements. 21 refs., 5 figs., 46 tabs.

  7. Development of a new sorptive extraction method based on simultaneous direct and headspace sampling modes for the screening of polycyclic aromatic hydrocarbons in water samples.

    PubMed

    Triñanes, Sara; Pena, Ma Teresa; Casais, Ma Carmen; Mejuto, Ma Carmen

    2015-01-01

    A new straightforward and inexpensive sample screening method for both EPA and EU priority polycyclic aromatic hydrocarbons (PAHs) in water has been developed. The method is based on combined direct immersion and headspace (DIHS) sorptive extraction, using low-cost disposable material, coupled to ultraperformance liquid chromatography with fluorescence and UV detection (UPLC-FD-UV). Extraction parameters, such as the sampling mode, extraction time and ionic strength were investigated in detail and optimized. Under optimized conditions, water samples (16 mL) were concentrated in silicone disks by headspace (HS) and direct immersion (DI) modes simultaneously, at room temperature for 9h for the majority of the 24 studied compounds. Ultrasound-assisted desorption of extracted analytes in acetonitrile was carried out also at room temperature. The optimized chromatographic method provided a good linearity (R≥0.9991) and a broad linear range for all studied PAHs. The proposed analytical procedure exhibited a good precision level with relative standard deviations below 15% for all analytes. Quantification limits between 0.7 and 2.3 µg L(-1) and 0.16 and 3.90 ng L(-1) were obtained for compounds analyzed by UV (acenaphtylene, cyclopenta[c,d]pyrene and benzo[j]fluoranthene) and fluorescence, respectively. Finally, the proposed method was applied to the determination of PAHs in different real tap, river and wastewater samples.

  8. Simultaneous spectral and temporal analyses of kinetic energies in nonequilibrium systems: theory and application to vibrational relaxation of O-D stretch mode of HOD in water.

    PubMed

    Jeon, Jonggu; Lim, Joon Hyung; Kim, Seongheun; Kim, Heejae; Cho, Minhaeng

    2015-05-28

    A time series of kinetic energies (KE) from classical molecular dynamics (MD) simulation contains fundamental information on system dynamics. It can also be analyzed in the frequency domain through Fourier transformation (FT) of velocity correlation functions, providing energy content of different spectral regions. By limiting the FT time span, we have previously shown that spectral resolution of KE evolution is possible in the nonequilibrium situations [Jeon and Cho, J. Chem. Phys. 2011, 135, 214504]. In this paper, we refine the method by employing the concept of instantaneous power spectra, extending it to reflect an instantaneous time-correlation of velocities with those in the future as well as with those in the past, and present a new method to obtain the instantaneous spectral density of KE (iKESD). This approach enables the simultaneous spectral and temporal resolution of KE with unlimited time precision. We discuss the formal and novel properties of the new iKESD approaches and how to optimize computational methods and determine parameters for practical applications. The method is specifically applied to the nonequilibrium MD simulation of vibrational relaxation of the OD stretch mode in a hydrated HOD molecule by employing a hybrid quantum mechanical/molecular mechanical (QM/MM) potential. We directly compare the computational results with the OD band population relaxation time profiles extracted from the IR pump-probe measurements for 5% HOD in water. The calculated iKESD yields the OD bond relaxation time scale ∼30% larger than the experimental value, and this decay is largely frequency-independent if the classical anharmonicity is accounted for. From the integrated iKESD over intra- and intermolecular bands, the major energy transfer pathways were found to involve the HOD bending mode in the subps range, then the internal modes of the solvent until 5 ps after excitation, and eventually the solvent intermolecular modes. Also, strong hydrogen

  9. Dual-mode spectral convertors as a simple approach for the enhancement of hematite's solar water splitting efficiency

    NASA Astrophysics Data System (ADS)

    Atabaev, Timur Sh.; Vu, Hong Ha Thi; Ajmal, Muhammad; Kim, Hyung-Kook; Hwang, Yoon-Hwae

    2015-06-01

    Storing solar energy via a chemical fuel of hydrogen from water splitting represents a clean alternative for petroleum fuel. Thus, it is highly desirable for the production of hydrogen using environment-friendly and cost-effective methods. Most photoelectrodes used for this conversion are semiconductor materials whose band gaps match the UV and visible radiation of solar energy. However, further improvement in electrodes performance may be possible by improving photoabsorption efficiency in near-infrared region. This report represents our attempt to utilize IR photons for water splitting, and thus, spectral convertors were incorporated within the hematite nanorods (NRs) grown directly on a FTO glass. The results demonstrate that incorporation of spectral convertors within the hematite NRs leads to higher efficiency and performance in solar water splitting, because the convertors enable harvesting more photons both at UV and IR regions than conventional hematite.

  10. [Effects of tillage mode on water use efficiency and yield of summer maize under different simulated rainfalls].

    PubMed

    Chen, Yu; Wen, Xiao-xia; Liao, Yun-cheng

    2013-08-01

    Based on the tillage practices of summer maize and the rainfall pattern in Northwest China, and by using self-made simulated rainfall device, a field experiment was conducted on the effects of plowing, no-tillage, and no-tillage plus mulching on the water use efficiency (WUE) and yield of summer maize under rainfalls 250, 350 and 450 mm from June to September, 2010. Compared with plowing, no-tillage increased the WUE and yield under rainfall 250 mm by 26% and 16.5% and under rainfall 350 mm by 17.6% and 6.1%, respectively. Under rainfall 450 mm, the water storage was smaller in treatment no-tillage than in treatment plowing, and the WUE and yield in treatment no-tillage were 1.1% and 0.6% lower than those in treatment plowing, respectively. No-tillage plus mulching overcame the disadvantage of no-tillage in lesser water-storing under sufficient rainfall than plowing. Under the three rainfalls, no-tillage plus mulching could effectively inhibit the soil evaporation between plants, decrease the invalid water consumption of bare soil, and increase the soil water storage and the rate of evapotranspiration to water consumption. Compared with plowing, no-tillage plus mulching increased the WUE and yield under rainfall 250 mm by 48.6% and 32.9%, under rainfall 350 mm by 51.6% and 27.1%, and under 450 mm rainfall by 23.7% and 13.1%, respectively. In sum, relative to plowing, no-tillage showed its superiority in increasing WUE and yield under rainfalls 250 and 350 mm, whereas no-tillage plus mulching increased the WUE and yield significantly under rainfalls 250 and 450 mm.

  11. Energy, structure and vibrational modes of small water clusters by a simple many-body potential mimicking polarisation effects

    NASA Astrophysics Data System (ADS)

    Bingham, R. J.; Ballone, P.

    2013-12-01

    An empirical many-body model potential able to mimic polarisation effects is applied to compute cohesive, structural and vibrational properties of water clusters with up to 12 H2O molecules. The model introduces local coordination functions to account for the variation of charges and other intra- and inter-molecular force constants upon formation of hydrogen bonds among water molecules. The potential is tuned to fit the results of state of the art density functional computations, and it is shown to accurately reproduce cohesive energies, bond lengths and vibrational properties of clusters. Moreover, it reproduces the marked increase of the molecular dipole moment with increasing water-water coordination. At variance from traditional polarisable models, the energy is an explicit function of the atomic coordinates, and does not require the minimisation of the electrostatic energy or the equalisation of the electron chemical potential, and thus is suitable for large-scale simulations in materials science and in bio-chemistry/bio-physics.

  12. Experimental investigation on the photovoltaic-thermal solar heat pump air-conditioning system on water-heating mode

    SciTech Connect

    Fang, Guiyin; Hu, Hainan; Liu, Xu

    2010-09-15

    An experimental study on operation performance of photovoltaic-thermal solar heat pump air-conditioning system was conducted in this paper. The experimental system of photovoltaic-thermal solar heat pump air-conditioning system was set up. The performance parameters such as the evaporation pressure, the condensation pressure and the coefficient of performance (COP) of heat pump air-conditioning system, the water temperature and receiving heat capacity in water heater, the photovoltaic (PV) module temperature and the photovoltaic efficiency were investigated. The experimental results show that the mean photovoltaic efficiency of photovoltaic-thermal (PV/T) solar heat pump air-conditioning system reaches 10.4%, and can improve 23.8% in comparison with that of the conventional photovoltaic module, the mean COP of heat pump air-conditioning system may attain 2.88 and the water temperature in water heater can increase to 42 C. These results indicate that the photovoltaic-thermal solar heat pump air-conditioning system has better performances and can stably work. (author)

  13. Assessing fuel spill risks in polar waters: Temporal dynamics and behaviour of hydrocarbons from Antarctic diesel, marine gas oil and residual fuel oil.

    PubMed

    Brown, Kathryn E; King, Catherine K; Kotzakoulakis, Konstantinos; George, Simon C; Harrison, Peter L

    2016-09-15

    As part of risk assessment of fuel oil spills in Antarctic and subantarctic waters, this study describes partitioning of hydrocarbons from three fuels (Special Antarctic Blend diesel, SAB; marine gas oil, MGO; and intermediate grade fuel oil, IFO 180) into seawater at 0 and 5°C and subsequent depletion over 7days. Initial total hydrocarbon content (THC) of water accommodated fraction (WAF) in seawater was highest for SAB. Rates of THC loss and proportions in equivalent carbon number fractions differed between fuels and over time. THC was most persistent in IFO 180 WAFs and most rapidly depleted in MGO WAF, with depletion for SAB WAF strongly affected by temperature. Concentration and composition remained proportionate in dilution series over time. This study significantly enhances our understanding of fuel behaviour in Antarctic and subantarctic waters, enabling improved predictions for estimates of sensitivities of marine organisms to toxic contaminants from fuels in the region. Copyright © 2016 Elsevier Ltd. All rights reserved.

  14. Modes of sediment transport in channelized water flows with ramifications to the erosion of the Martian outflow channels

    NASA Technical Reports Server (NTRS)

    Komar, P. D.

    1980-01-01

    The paper discusses application to Martian water flows of the criteria that determine which grain-size ranges are transported as bed load, suspension, and wash load. The results show nearly all sand-sized material and finer would have been transported as wash load and that basalt pebbles and even cobbles could have been transported at rapid rates of suspension. An analysis of the threshold of sediment motion on Mars further indicates that the flows would have been highly competent, the larger flows having been able to transport boulder-sized material. Comparisons with terrestrial rivers which transport hyperconcentration levels of sediments suggest that the Martian water flows could have achieved sediment concentrations up to 70% in weight. Although it is possible that flows could have picked up enough sediment to convert to pseudolaminar mud flows, they probably remained at hyperconcentration levels and fully turbulent in flow character.

  15. Oil removal from water by sorption on hydrophobic cotton fibers. 2. Study of sorption properties in dynamic mode.

    PubMed

    Deschamps, Gerald; Caruel, Herve; Borredon, Marie-Elisabeth; Albasi, Claire; Riba, Jean-Pierre; Bonnin, Christophe; Vignoles, Christian

    2003-11-01

    The recovery of oil from an oil-in-water emulsion, during a flow through a bed of cotton rendered hydrophobic by acylation of cellulose was defined by sorption and coalescence phenomena. During percolation, the column "hold-up" (difference between injected and rejected oil) became constant at the equilibrium volume, i.e., as soon as the instant oil concentration in the effluent (C) was equal to the oil concentration in the initial emulsion (C0). This equilibrium permitted the measurement of the cotton sorption capacity (SC), which increased with C0 up to the cotton saturation. The oil-water separation improved at a lower temperature, lower flow, a deeper medium, and larger oil drops. The system was modeled as a piston flow-through in order to generalize the results.

  16. Water-jet dissector for endoscopic submucosal dissection in an animal study: outcomes of the continuous and pulsed modes.

    PubMed

    Lepilliez, Vincent; Robles-Medranda, Carlos; Ciocirlan, Mihai; Lukashok, Hannah; Chemali, Marwan; Langonnet, Stephan; Chesnais, Sabrina; Hervieu, Valerie; Ponchon, Thierry

    2013-08-01

    Endoscopic submucosal dissection (ESD) allows en bloc resection of early neoplastic lesions of gastrointestinal tract. Lesions are lifted by submucosal fluid injection before circumferential incision and dissection. High-pressure fluid injection using water jet (WJ) technology is already used for lifting and dissection in surgery. The study was designed to assess WJ for ESD submucosal lifting and dissection. An experimental, randomized comparative, "in vivo" nonsurvival animal study on 12 pigs was designed. Stomach mucosal areas were delineated and resected using three ESD techniques: technique A-syringe injection and IT knife dissection; technique B-WJ continuous injection and IT knife dissection; technique C-WJ injection and WJ pulsed dissection. Injection and dissection speeds and complications rates were assessed. Water jet continuous injection is faster than syringe injection (B faster than A, p = 0.001 and B nonsignificantly faster than C, p = 0.06). IT knife dissection is significantly faster after WJ continuous injection (B faster than A, p = 0.003). WJ pulsed dissection is significantly slower than IT knife dissection (C slower than A and B, both p < 0.001). The overall procedure speed was significantly higher and the immediate bleedings rate was significantly lower for technique B than A and C (overall procedure speed p = 0.001, immediate bleedings p = 0.032 and 0.038 respectively). There were no perforations with any technique. Water jet fluid continuous injection speeds up ESD, whereas pulsed WJ dissection does not.

  17. Water- and nitrogen-dependent alterations in the inheritance mode of transpiration efficiency in winter wheat at the leaf and whole-plant level.

    PubMed

    Ratajczak, Dominika; Górny, Andrzej G

    2012-11-01

    The effects of contrasting water and nitrogen (N) supply on the observed inheritance mode of transpiration efficiency (TE) at the flag-leaf and whole-season levels were examined in winter wheat. Major components of the photosynthetic capacity of leaves and the season-integrated efficiency of water use in vegetative and grain mass formation were evaluated in parental lines of various origins and their diallel F(2)-hybrids grown in a factorial experiment under different moisture and N status of the soil. A broad genetic variation was mainly found for the season-long TE measures. The variation range in the leaf photosynthetic indices was usually narrow, but tended to slightly enhance under water and N shortage. Genotype-treatment interaction effects were significant for most characters. No consistency between the leaf- and season-long TE measures was observed. Preponderance of additivity-dependent variance was mainly identified for the season-integrated TE and leaf CO(2) assimilation rate. Soil treatments exhibited considerable influence on the phenotypic expression of gene action for the residual leaf measures. The contribution of non-additive gene effects and degree of dominance tended to increase in water- and N-limited plants, especially for the leaf transpiration rate and stomatal conductance. The results indicate that promise exists to improve the season-integrated TE. However, selection for TE components should be prolonged for later hybrid generations to eliminate the masking of non-additive causes. Such evaluation among families grown under sub-optimal water and nitrogen supply seems to be the most promising strategy in winter wheat.

  18. Assessing acute toxicity of effluent from a textile industry and nearby river waters using sulfur-oxidizing bacteria in continuous mode.

    PubMed

    Gurung, Anup; Hassan, Sedky H A; Oh, Sang-Eun

    2011-10-01

    Bioassays are becoming an important tool for assessing the toxicity of complex mixtures of substances in aquatic environments in which Daphnia magna is routinely used as a test organism. Bioassays outweigh physicochemical analyses and are valuable in the decision-making process pertaining to the final discharge of effluents from wastewater treatment plants as they measure the total effect of the discharge which is ecologically relevant. In this study, the aquatic toxicity of a textile plant effluent and river water downstream from the plant were evaluated with sulfur-oxidizing bacterial biosensors in continuous mode. Collected samples were analysed for different physicochemical parameters and 1,4-dioxane was detected in the effluent. The effluent contained a relatively high chemical oxygen demand of 60 mg L(-1), which exceeded the limit set by the Korean government for industrial effluent discharges. Results showed that both the effluent and river waters were toxic to sulfur-oxidizing bacteria. These results show the importance of incorporating bioassays to detect toxicity in wastewater effluents for the sustainable management of water resources.

  19. An assessment of BWR (boiling water reactor) Mark-II containment challenges, failure modes, and potential improvements in performance

    SciTech Connect

    Kelly, D.L.; Jones, K.R.; Dallman, R.J. ); Wagner, K.C. )

    1990-07-01

    This report assesses challenges to BWR Mark II containment integrity that could potentially arise from severe accidents. Also assessed are some potential improvements that could prevent core damage or containment failure, or could mitigate the consequences of such failure by reducing the release of fission products to the environment. These challenges and improvements are analyzed via a limited quantitative risk/benefit analysis of a generic BWR/4 reactor with Mark II containment. Point estimate frequencies of the dominant core damage sequences are obtained and simple containment event trees are constructed to evaluate the response of the containment to these severe accident sequences. The resulting containment release modes are then binned into source term release categories, which provide inputs to the consequence analysis. The output of the consequences analysis is used to construct an overall base case risk profile. Potential improvements and sensitivities are evaluated by modifying the event tree spilt fractions, thus generating a revised risk profile. Several important sensitivity cases are examined to evaluate the impact of phenomenological uncertainties on the final results. 75 refs., 25 figs., 65 tabs.

  20. GFS water vapor forecast error evaluated over the 2009-2010 West Coast cool season using the MET/MODE object analyses package

    NASA Astrophysics Data System (ADS)

    Clark, W. L.; Sukovich, E.; Tollerud, E. I.; Jensen, T.; Yuan, H.; Wick, G. A.; Bullock, R.; Hmt-Dtc Collaboration Project

    2010-12-01

    Research over the last decade and a half confirms that the vast majority of West Coast cool-season extreme precipitation events are due to the landfall of intense wind-driven streams of concentrated water vapor associated with extratropical cyclones called atmospheric rivers (ARs). Accurate prediction of the effects of ARs as they come ashore depends on accurate numeric modeling of integrated water vapor (IWV) over the Northeast Pacific (NEP). Quantifying the uncertainty in this forecast field is an important step toward understanding the causes of uncertainty in West Coast extreme event forecasts. To this end GFS (Global Forecast System) model output obtained in real time of the fields needed to calculate IWV were archived and analyzed. GFS was used because it is well known, it covers our area of interest, and the output is readily available to the community. To estimate forecast uncertainties we used an object-based method that allows quantitative comparisons of object location, size, shape, and intensity. In particular, we used MODE, the Method for Object-based Diagnostic Evaluation. MODE is an object-based verification tool from the MET (Model Evaluation Tools) package developed and supported by the Developmental Testbed Center (DTC). This package of verification tools is readily available and intended to provide the community with a common software package incorporating the latest advances in forecast verification. We describe results from two studies conducted as part of the Hydrometeorology Testbed (HMT)—DTC collaboration project. The studies are based upon Northeast Pacific (NEP) data collected during the 2009-2010 cool season. In the first study we focus on verifying GFS-analysis IWV against satellite-observed IWV throughout the NEP. Specifically, IWV GFS analysis objects are compared with 12-hour composite, satellite-derived Special Sensor Microwave/Imager (SSM/I) observational objects. Then we incorporate MODE object attributes related to object

  1. CLIVAR Mode Water Dynamics Experiment (CLIMODE), Fall 2006 R/V Oceanus Voyage 434, November 16, 2006-December 3, 2006

    DTIC Science & Technology

    2007-12-01

    2006 12/6/2006 531 16:39:26 16:31:45 WND 345 Flooded _ _ WND 217 12/8/2006 12/8/2006 5702 - 1/2 tsp water 11:52:40 11:52:00 inside PRC 502 12/7/2006 12...NOK314 Wr 5/r Achor hockl ( 17" Glass Uaile ou 3/811 Mooring Chain 3/" Aco hcl NO M. 3/16" Wre (3 11/ Ancoathd. L5k KigLik 7/6 Anhr hdd M. 3h16" Wire 7/8

  2. Design and evaluation of a detunable water-based quadrature HEM11 mode dielectric resonator as a new type of volume coil for high field MRI.

    PubMed

    Aussenhofer, Sebastian A; Webb, Andrew G

    2012-10-01

    An annular dielectric resonator made from distilled water has been designed to operate in degenerate quadrature HEM11 modes at 298.1 MHz (7 Tesla). The circularly polarized B1+ field has a high degree of homogeneity throughout a sample placed within the annulus. The sensitivity of the resonator was measured to be essentially identical to that of an eight-rung high-pass birdcage resonator with the same physical dimensions. High resolution in vivo images have been obtained from the human wrist. A new method of electronically detuning the resonator has also been evaluated. The design is extremely simple and rapid to build, with direct applicability to very high field imaging and also potential integration into human and animal hybrid position emission tomography (PET)/MRI and single-photon emission computed tomography (SPECT)/MRI systems due to the lack of conductor attenuation-induced artifacts in the reconstructed nuclear medicine images.

  3. Direction finding and suppression of vector-scalar sound signals in shallow water taking into account their correlation and mode structure

    NASA Astrophysics Data System (ADS)

    Belov, A. I.; Kuznetsov, G. N.

    2016-05-01

    The correlation of low-frequency sound signals from towed tonal low-frequency sources at the output of the scalar and vector channels is studied in shallow water. The correlation of the scalar field and signal received by a horizontally oriented vector receiver on average is 0.92-0.99; correlation with the signal received by a vertical vector receiver decreases to 0.66-85. When scalar fields or horizontal projections of the vibration velocity vector with application of the aperture synthesis algorithm are used, 3-5 normal waves are isolated; when the vertical component is used, 7-9 modes. It is demonstrated that the high signal correlation ensures direction-finding accuracy and suppression of strongly noise-emitting moving sources by 20-30 dB or more if the cardioid is directed at the source according to the zone of the minimum.

  4. New findings and a new species of the genus Ammothea (Pycnogonida, Ammotheidae), with an updated identification key to all Antarctic and sub-Antarctic species

    NASA Astrophysics Data System (ADS)

    Cano-Sánchez, E.; López-González, P. J.

    2014-03-01

    Specimens of the pycnogonid genus Ammothea collected during the Polarstern cruise XXIII/8 (23 November 2006-30 January 2007) were studied. Nine species were recognized in this collection: Ammothea bentartica, A. bicorniculata, A. carolinensis, A. clausi, A. longispina, A. minor, A. spinosa, A. striata and A. tibialis. Three of them ( A. bentartica, A. bicorniculata and A. tibialis) are reported for the second time, enlarging their known geographical and bathymetric range. In the present contribution, the observed morphological variability of all collected Ammothea species is described and discussed. For the identification and description of the material, different museum specimens were consulted. Among them, we have consulted part of the Discovery collection housed at the Natural History Museum in London. That material was initially identified by Isabella Gordon, a reputed author in the field of pycnogonid taxonomy. A new species, based on a museum specimen previously highly confused in the literature, is proposed in the present contribution as Ammothea isabellae n. sp. The new taxon is compared with its closest congeners, especially with A. longispina and A. stylirostris. Finally, we propose an updated dichotomous key to species covering all currently known Antarctic and sub-Antarctic Ammothea species.

  5. Recovering Greater Fungal Diversity from Pristine and Diesel Fuel Contaminated Sub-Antarctic Soil Through Cultivation Using Both a High and a Low Nutrient Media Approach

    PubMed Central

    Ferrari, Belinda C.; Zhang, Chengdong; van Dorst, Josie

    2011-01-01

    Novel cultivation strategies for bacteria are widespread and well described for recovering greater diversity from the “hitherto” unculturable majority. While similar approaches have not yet been demonstrated for fungi it has been suggested that of the 1.5 million estimated species less than 5% have been recovered into pure culture. Fungi are known to be involved in many degradative processes, including the breakdown of petroleum hydrocarbons, and it has been speculated that in Polar Regions they contribute significantly to bioremediation of contaminated soils. Given the biotechnological potential of fungi there is a need to increase efforts for greater species recovery, particularly from extreme environments such as sub-Antarctic Macquarie Island. In this study, like the yet-to-be cultured bacteria, high concentrations of nutrients selected for predominantly different fungal species to that recovered using a low nutrient media. By combining both media approaches to the cultivation of fungi from contaminated and non-contaminated soils, 91 fungal species were recovered, including 63 unidentified species. A preliminary biodegradation activity assay on a selection of isolates found that a high proportion of novel and described fungal species from a range of soil samples were capable of hydrocarbon degradation and should be characterized further. PMID:22131985

  6. Isomer morphology and vibrational mode dependence of the coupling between an excess electron and small water networks.

    NASA Astrophysics Data System (ADS)

    Johnson, Mark

    2006-03-01

    Negatively charged water clusters are presently the subject of intense study because of their promise to unravel the surprisingly complex dynamics of the hydrated electron. We focus on the use of vibrational spectroscopy to establish the morphologies and local binding motifs of the water networks that bind an electron. Here we will discuss the rearrangement pathways of the H-bond network in the elementary act of free electron accommodation, where we use argon-mediated population modulation to isolate the geometries of the neutral cluster precursors. We then obtain isomer-selective vibrational spectra of the anions that produced, where we correlate the local binding motifs with the overall electron binding energies. Finally, in the small cluster limit, we reveal how different intramolecular vibrational motions interact with the diffuse electron cloud by analysis of the resulting ``Fano'' lineshapes when vibrations are embedded in the electron continuum. These interactions vary by over an order of magnitude for various ``free OH'' bands. The implications of these observations on the extrapolation to bulk behavior will be considered in light of the trends displayed by the cluster properties up n=30 or so.

  7. Simultaneous measurement in mass and mass/mass mode for accurate qualitative and quantitative screening analysis of pharmaceuticals in river water.

    PubMed

    Martínez Bueno, M J; Ulaszewska, Maria M; Gomez, M J; Hernando, M D; Fernández-Alba, A R

    2012-09-21

    A new approach for the analysis of pharmaceuticals (target and non-target) in water by LC-QTOF-MS is described in this work. The study has been designed to assess the performance of the simultaneous quantitative screening of target compounds, and the qualitative analysis of non-target analytes, in just one run. The features of accurate mass full scan mass spectrometry together with high MS/MS spectral acquisition rates - by means of information dependent acquisition (IDA) - have demonstrated their potential application in this work. Applying this analytical strategy, an identification procedure is presented based on library searching for compounds which were not included a priori in the analytical method as target compounds, thus allowing their characterization by data processing of accurate mass measurements in MS and MS/MS mode. The non-target compounds identified in river water samples were ketorolac, trazodone, fluconazole, metformin and venlafaxine. Simultaneously, this strategy allowed for the identification of other compounds which were not included in the library by screening the highest intensity peaks detected in the samples and by analysis of the full scan TOF-MS, isotope pattern and MS/MS spectra - the example of loratadine (histaminergic) is described. The group of drugs of abuse selected as target compounds for evaluation included analgesics, opioids and psychostimulants. Satisfactory results regarding sensitivity and linearity of the developed method were obtained. Limits of detection for the selected target compounds were from 0.003 to 0.01 μg/L and 0.01 to 0.5 μg/L, in MS and MS/MS mode, respectively - by direct sample injection of 100 μL. Copyright © 2012 Elsevier B.V. All rights reserved.

  8. Decadal-scale variability of the core layer temperature of North Pacific Transition Region Mode Water: Influence of the quasi-stationary jet

    NASA Astrophysics Data System (ADS)

    Sugimoto, S.; Ueno, H.; Hoshi, N.

    2016-12-01

    Repeated hydrographic surveys at 155°E conducted by the T/S Oshoro-maru of Hokkaido University of Japan in spring (May/June) of 1989-2010 reveal a dominant decadal-scale ( 10 years) variation of core-layer temperature and salinity of the North Pacific Transition Region Mode Water (TRMW), a water mass with core characterized by potential temperature of 4-8°C, salinity of 33.5-34.0, and potential density of 26.4-26.7 kg m-3. An ocean heat content budget analysis based on historical temperature profiles and atmospheric reanalysis data shows that the observed decadal-scale variation of the core-layer temperature is not explained by variations in air-sea heat exchange and Ekman heat advection. The satellite-derived dataset and historical temperature-salinity profiles reveal that changes in the Kuroshio Extension (KE) path state, that is, stable state with the two quasi-stationary meanders and unstable state characterized by a convoluted path, are responsible for the formation of temperature-salinity anomalies in the TRMW formation region (40-44°N, 153-162°E). Meso-scale eddies that detach northward from the KE in the unstable path state form warmer-saltier conditions in the Kuroshio-Oyashio Confluence region. The warm-salty water is transported northward into the transition region by the quasi-stationary jet flowing from the subtropics to the subarctic, which induces an increase in temperature and salinity in the TRMW formation region, and this results in a peak in temperature and salinity a few years after the arrival of the warm-salty water in the formation region.

  9. The influence of water/air cooling on collateral tissue damage using a diode laser with an innovative pulse design (micropulsed mode)-an in vitro study.

    PubMed

    Beer, F; Körpert, W; Buchmair, A G; Passow, H; Meinl, A; Heimel, P; Moritz, A

    2013-05-01

    Since the diode laser is a good compromise for the daily use in dental offices, finding usage in numerous dental indications (e.g., surgery, periodontics, and endodontics), the minimization of the collateral damage in laser surgery is important to improve the therapeutical outcome. The aim of this study was to investigate the effect of water/air cooling on the collateral thermal soft tissue damage of 980-nm diode laser incisions. A total of 36 mechanically executed laser cuts in pork liver were made with a 980-nm diode laser in micropulsed mode with three different settings of water/air cooling and examined by histological assessment to determine the area and size of carbonization, necrosis, and reversible tissue damage as well as incision depth and width. In our study, clearly the incision depth increased significantly under water/air cooling (270.9 versus 502.3 μm-test group 3) without significant changes of incision width. In test group 2, the total area of damage was significantly smaller than in the control group (in this group, the incision depth increases by 65 %). In test group 3, the total area of damage was significantly higher (incision depth increased by 85 %), but the bigger part of it represented a reversible tissue alteration leaving the amount of irreversible damage almost the same as in the control group. This first pilot study clearly shows that water/air cooling in vitro has an effect on collateral tissue damage. Further studies will have to verify, if the reduced collateral damage we have proved in this study can lead to accelerated wound healing. Reduction of collateral thermal damage after diode laser incisions is clinically relevant for promoted wound healing.

  10. The quantum nature of the OH stretching mode in ice and water probed by neutron scattering experiments

    SciTech Connect

    Senesi, Roberto; Flammini, Davide; Kolesnikov, Alexander I; Murray, Eamonn D.; Galli, Giulia; Andreani, Carla

    2013-01-01

    The OH stretching vibrational spectrum of water was measured in a wide range of temperatures across the triple point, 269 K < T < 296 K, using Inelastic Neutron Scattering (INS). The hydrogen projected density of states and the proton mean kinetic energy, _OH, were determined for the first time within the framework of a harmonic description of the proton dynamics. We found that in the liquid the value of _OH is nearly constant as a function of T, indicating that quantum effects on the OH stretching frequency are weakly dependent on temperature. In the case of ice, ab initio electronic structure calculations, using non-local van der Waals functionals, provided _OH values in agreement with INS experiments. We also found that the ratio of the stretching (_OH) to the total (_exp) kinetic energy, obtained from the present measurements, increases in going from ice, where hydrogen bonding is the strongest, to the liquid at ambient conditions and then to the vapour phase, where hydrogen bonding is the weakest. The same ratio was also derived from the combination of previous deep inelastic neutron scattering data, which does not rely upon the harmonic approximation, and the present measurements. We found that the ratio of stretching to the total kinetic energy shows a minimum in the metastable liquid phase. This finding suggests that the strength of intermolecular interactions increases in the supercooled phase, with respect to that in ice, contrary to the accepted view that supercooled water exhibits weaker hydrogen bonding than ice.

  11. A highly sensitive protocol for the determination of Hg(2+) in environmental water using time-gated mode.

    PubMed

    Huang, Dawei; Niu, Chenggang; Zeng, Guangming; Wang, Xiaoyu; Lv, Xiaoxiao

    2015-01-01

    In this paper, a sensitive time-gated fluorescent sensing strategy for mercury ions (Hg(2+)) monitoring is developed based on Hg(2+)-mediated thymine (T)-Hg(2+)-T structure and the mechanism of fluorescence resonance energy transfer from Mn-doped CdS/ZnS quantum dots to graphene oxide. The authors employ two T-rich single-stranded DNA (ssDNA) as the capture probes for Hg(2+), and one of them is modified with Mn-doped CdS/ZnS quantum dots. The addition of Hg(2+) makes the two T-rich ssDNA hybrids with each other to form stable T-Hg(2+)-T coordination chemistry, which makes Mn-doped CdS/ZnS quantum dots far away from the surface of graphene oxide. As a result, the fluorescence signal is increased obviously compared with that without Hg(2+). The time-gated fluorescence intensities are linear with the concentrations of Hg(2+) in the range from 0.20 to 10 nM with a limit of detection of 0.11 nM. The detection limit is much lower than the U.S. Environmental Protection Agency limit of the concentration of Hg(2+) for drinking water. The time-gated fluorescent sensing strategy is specific for Hg(2+) even with interference by other metal ions based on the results of selectivity experiments. Importantly, the proposed sensing strategy is applied successfully to the determination of Hg(2+) in environmental water samples.

  12. Water equivalent hydrogen estimates from the first 200 sols of Curiosity's traverse (Bradbury Landing to Yellowknife Bay): Results from the Dynamic Albedo of Neutrons (DAN) passive mode experiment

    NASA Astrophysics Data System (ADS)

    Tate, C. G.; Moersch, J.; Jun, I.; Ming, D. W.; Mitrofanov, I.; Litvak, M.; Behar, A.; Boynton, W. V.; Deflores, L.; Drake, D.; Ehresmann, B.; Fedosov, F.; Golovin, D.; Hardgrove, C.; Harshman, K.; Hassler, D. M.; Kozyrev, A. S.; Kuzmin, R.; Lisov, D.; Malakhov, A.; Milliken, R.; Mischna, M.; Mokrousov, M.; Nikiforov, S.; Sanin, A. B.; Starr, R.; Varenikov, A.; Vostrukhin, A.; Zeitlin, C.

    2015-12-01

    The Dynamic Albedo of Neutrons (DAN) experiment on the Mars Science Laboratory (MSL) rover Curiosity is designed to detect neutrons to determine hydrogen abundance within the subsurface of Mars (Mitrofanov, I.G. et al. [2012]. Space Sci. Rev. 170, 559-582. http://dx.doi.org/10.1007/s11214-012-9924-y; Litvak, M.L. et al. [2008]. Astrobiology 8, 605-613. http://dx.doi.org/10.1089/ast.2007.0157). While DAN has a pulsed neutron generator for active measurements, in passive mode it only measures the leakage spectrum of neutrons produced by the Multi-Mission Radioisotope Thermoelectric Generator (MMRTG) and Galactic Cosmic Rays (GCR). DAN passive measurements provide better spatial coverage than the active measurements because they can be acquired while the rover is moving. Here we compare DAN passive-mode data to models of the instrument's response to compositional differences in a homogeneous regolith in order to estimate the water equivalent hydrogen (WEH) content along the first 200 sols of Curiosity's traverse in Gale Crater, Mars. WEH content is shown to vary greatly along the traverse. These estimates range from 0.5 ± 0.1 wt.% to 3.9 ± 0.2 wt.% for fixed locations (usually overnight stops) investigated by the rover and 0.6 ± 0.2 wt.% to 7.6 ± 1.3 wt.% for areas that the rover has traversed while continuously acquiring DAN passive data between fixed locations. Estimates of WEH abundances at fixed locations based on passive mode data are in broad agreement with those estimated at the same locations using active mode data. Localized (meter-scale) anomalies in estimated WEH values from traverse measurements have no particular surface expression observable in co-located images. However at a much larger scale, the hummocky plains and bedded fractured units are shown to be distinct compositional units based on the hydrogen content derived from DAN passive measurements. DAN passive WEH estimates are also shown to be consistent with geologic models inferred from other

  13. Water-soluble inorganic ions in airborne particulates from the nano to coarse mode: a case study of aerosol episodes in southern region of Taiwan.

    PubMed

    Chang, Li-Peng; Tsai, Jiun-Horng; Chang, Kai-Lun; Lin, Jim Juimin

    2008-06-01

    In 2004, airborne particulate matter (PM) was collected for several aerosol episodes occurring in the southern region of Taiwan. The particulate samples were taken using both a MOUDI (Micro-orifice Uniform Deposit Impactor) and a nano-MOUDI sampler. These particulate samples were analyzed for major water-soluble ionic species with an emphasis to characterize the mass concentrations and distributions of these ions in the ambient ultrafine (PM0.1, diameter <0.1 microm) and nano mode (PMnano, diameter <0.056 microm) particles. Particles collected at the sampling site (the Da-Liao station) on the whole exhibited a typical tri-modal size distribution on mass concentration. The mass concentration ratios of PMnano/PM2.5, PM0.1/PM2.5, and PM1/PM2.5 on average were 1.8, 2.9, and 71.0%, respectively. The peak mass concentration appeared in the submicron particle mode (0.1 microm < diameter <1.0 microm). Mass fractions (percentages) of the three major water-soluble ions (nitrate, sulfate, and ammonium) as a group in PMnano, PM0.1, PM1, and PM2.5 were 18.4, 21.7, 50.0, and 50.7%, respectively. Overall, results from this study supported the notion that secondary aerosols played a significant role in the formation of ambient submicron particulates (PM0.1-1). Particles smaller than 0.1 microm were essentially basic, whereas those greater than 2.5 microm were neutral or slightly acidic. The neutralization ratio (NR) was close to unity for airborne particles with diameters ranging from 0.18 to 1 microm. The NRs of these airborne particles were found strongly correlated with their sizes, at least for samples taken during the aerosol episodes under study. Insofar as this study is exploratory in nature, as only a small number of particulate samples were used, there appears to be a need for further research into the chemical composition, source contribution, and formation of the nano and ultrafine mode airborne particulates.

  14. Water

    MedlinePlus

    ... www.girlshealth.gov/ Home Nutrition Nutrition basics Water Water Did you know that water makes up more ... to drink more water Other drinks How much water do you need? top Water is very important, ...

  15. ZnO-PLLA Nanofiber Nanocomposite for Continuous Flow Mode Purification of Water from Cr(VI)

    PubMed Central

    Burks, T.; Akthar, F.; Saleemi, M.; Avila, M.; Kiros, Y.

    2015-01-01

    Nanomaterials of ZnO-PLLA nanofibers have been used for the adsorption of Cr(VI) as a prime step for the purification of water. The fabrication and application of the flexible ZnO-PLLA nanofiber nanocomposite as functional materials in this well-developed architecture have been achieved by growing ZnO nanorod arrays by chemical bath deposition on synthesized electrospun poly-L-lactide nanofibers. The nanocomposite material has been tested for the removal and regeneration of Cr(IV) in aqueous solution under a “continuous flow mode” by studying the effects of pH, contact time, and desorption steps. The adsorption of Cr(VI) species in solution was greatly dependent upon pH. SEM micrographs confirmed the successful fabrication of the ZnO-PLLA nanofiber nanocomposite. The adsorption and desorption of Cr(VI) species were more likely due to the electrostatic interaction between ZnO and Cr(VI) ions as a function of pH. The adsorption and desorption experiments utilizing the ZnO-PLLA nanofiber nanocomposite have appeared to be an effective nanocomposite in the removal and regeneration of Cr(VI) species. PMID:26681961

  16. Selective determination of antimycotic drugs in environmental water samples by mixed-mode solid-phase extraction and liquid chromatography quadrupole time-of-flight mass spectrometry.

    PubMed

    Casado, J; Rodríguez, I; Ramil, M; Cela, R

    2014-04-25

    The suitability of mixed-mode (reversed-phase and cationic exchange) solid-phase extraction (SPE) for the selective concentration of basic antimycotic drugs (belonging to triazole, imidazole and allylamine chemical classes) in environmental water samples has been demonstrated for first time. The use of a sequential elution protocol, allowing the removal of neutral and acidic interferences before analytes extraction, led to a significant reduction of matrix effects, during electrospray ionization (ESI), in comparison with results reported for reversed-phase sorbents. In combination with liquid chromatography (LC) quadrupole time-of-flight (QTOF) mass spectrometry (MS) determination, the developed method attained limits of quantification (LOQs) comprised between 2 and 15ngL(-1). After internal surrogate correction, accurate results (in most cases, recoveries ranged between 75 and 117%) were obtained for spiked aliquots of raw and treated wastewater, as well as river water, using quantification against calibration standard solutions in methanol (2% in NH3). Accurate, scan MS/MS spectra allowed the unambiguous identification of target compounds in environmental samples; furthermore, the information contained in MS spectra was used for the screening of additional antimycotics in the processed samples. Fluconazole, ketoconazole, miconazole and clotrimazole were measured in wastewater samples at concentrations up to 200ngL(-1). The screening capabilities of the LC-QTOF-MS system permitted to identify the systematic presence of climbazole in the processed samples. Copyright © 2014 Elsevier B.V. All rights reserved.

  17. Sea-air CO2 flux in the North Atlantic subtropical gyre: Role and influence of Sub-Tropical Mode Water formation

    NASA Astrophysics Data System (ADS)

    Andersson, Andreas J.; Krug, Lilian A.; Bates, Nicholas R.; Doney, Scott C.

    2013-07-01

    The uptake of atmospheric carbon dioxide (CO2) into the mid-latitudes of the North Atlantic Ocean through the production of wintertime Sub-Tropical Mode Water (STMW) also known as Eighteen Degree Water (EDW) is poorly quantified and constrained. Nonetheless, it has been proposed that the EDW could serve as an important short-term sink of anthropogenic CO2. The objective of the present investigation was to determine sea-air CO2 gas exchange rates and seawater CO2 dynamics during wintertime formation of EDW in the North Atlantic Ocean. During 2006 and 2007, several research cruises were undertaken as part of the CLIMODE project across the northwest Atlantic Ocean with the intent to study the pre-conditioning, formation, and the evolution of EDW. Sea-air CO2 exchange rates were calculated based on measurements of atmospheric pCO2, surface seawater pCO2 and wind speed with positive values denoting a net flux from the surface ocean to the atmosphere. Average sea-air CO2 flux calculated along cruise tracks in the formation region equaled -18±6 mmol CO2 m-2 d-1 and -14±9 mmol CO2 m-2 d-1 in January of 2006 and March of 2007, respectively. Average sea-air CO2 flux in newly formed outcropping EDW in February and March of 2007 equaled -28±10 mmol CO2 m-2 d-1. These estimates exceeded previous flux estimates in this region by 40-185%. The magnitude of CO2 flux was mainly controlled by the observed variability in wind speed and ΔpCO2 with smaller changes owing to variability in sea surface temperature. Small but statistically significant difference (4.1±2.6 μmol kg-1) in dissolved inorganic carbon (DIC) was observed in two occurrences of newly formed EDW in February and March of 2007. This difference was explained either by differences in the relative contribution from different water masses involved in the initial formation process of EDW or temporal changes owing to sea-air CO2 exchange (˜25%) and vertical and/or lateral mixing (˜75%) with water masses high in DIC

  18. Terrestrial and submarine evidence for the extent and timing of the Last Glacial Maximum and the onset of deglaciation on the maritime-Antarctic and sub-Antarctic islands

    NASA Astrophysics Data System (ADS)

    Hodgson, Dominic A.; Graham, Alastair G. C.; Roberts, Stephen J.; Bentley, Michael J.; Cofaigh, Colm Ó.; Verleyen, Elie; Vyverman, Wim; Jomelli, Vincent; Favier, Vincent; Brunstein, Daniel; Verfaillie, Deborah; Colhoun, Eric A.; Saunders, Krystyna M.; Selkirk, Patricia M.; Mackintosh, Andrew; Hedding, David W.; Nel, Werner; Hall, Kevin; McGlone, Matt S.; Van der Putten, Nathalie; Dickens, William A.; Smith, James A.

    2014-09-01

    This paper is the maritime and sub-Antarctic contribution to the Scientific Committee for Antarctic Research (SCAR) Past Antarctic Ice Sheet Dynamics (PAIS) community Antarctic Ice Sheet reconstruction. The overarching aim for all sectors of Antarctica was to reconstruct the Last Glacial Maximum (LGM) ice sheet extent and thickness, and map the subsequent deglaciation in a series of 5000 year time slices. However, our review of the literature found surprisingly few high quality chronological constraints on changing glacier extents on these timescales in the maritime and sub-Antarctic sector. Therefore, in this paper we focus on an assessment of the terrestrial and offshore evidence for the LGM ice extent, establishing minimum ages for the onset of deglaciation, and separating evidence of deglaciation from LGM limits from those associated with later Holocene glacier fluctuations. Evidence included geomorphological descriptions of glacial landscapes, radiocarbon dated basal peat and lake sediment deposits, cosmogenic isotope ages of glacial features and molecular biological data. We propose a classification of the glacial history of the maritime and sub-Antarctic islands based on this assembled evidence. These include: (Type I) islands which accumulated little or no LGM ice; (Type II) islands with a limited LGM ice extent but evidence of extensive earlier continental shelf glaciations; (Type III) seamounts and volcanoes unlikely to have accumulated significant LGM ice cover; (Type IV) islands on shallow shelves with both terrestrial and submarine evidence of LGM (and/or earlier) ice expansion; (Type V) Islands north of the Antarctic Polar Front with terrestrial evidence of LGM ice expansion; and (Type VI) islands with no data. Finally, we review the climatological and geomorphological settings that separate the glaciological history of the islands within this classification scheme.

  19. Variability in eastern equatorial Pacific intermediate water circulation during the last glacial termination: the impact of high latitude climate on equatorial stratification

    NASA Astrophysics Data System (ADS)

    Bova, S. C.; Herbert, T.; Mojarro, A.

    2013-12-01

    The eastern equatorial Pacific (EEP) is linked directly to the Southern High latitudes through an oceanic tunneling system that transports Antarctic Intermediate Water (AAIW) and Subantarctic Mode Water (SAMW) directly into the equatorial and Peru Margin upwelling systems (Toggweiler et al. 1991). These intermediate water masses form within the subantarctic zone and flow north, propagating signals of high latitude climate to the low latitude ocean (Kessler 2006). Their heat and salinity content are transported conservatively along their flow path and the high nutrient content of these waters support up to three-fourths of all biological production north of 30°S (Fiedler and Talley 2006, Sarmiento et al. 2004). Thus, variations in the physio-chemical properties and/or transport of these water masses into the low latitude thermocline have vast implications for oceanic heat transport, primary production, and global nutrient cycles (e.g CO2 and N). Here we assess the physio-chemical response of these Southern Ocean intermediate waters to high latitude forcing during the last glacial termination and the impact of these changes on EEP subsurface structure. Alkenone sea surface temperature reconstructions and benthic foraminiferal stable isotopic records from four rapidly accumulating sediment cores from the EEP cold tongue document variation in temperature and salinity gradients at three intermediate water depths (370, 600, and 1000 m). Our records provide evidence for substantial change in water column structure during the last glacial termination. Regional stratification decreased significantly during the deglacial (11-18 ka) relative to the last glacial period and the Holocene due to asynchronous warming of the EEP water column. Deglacial warming began first at 1000 m depth at ~18.2 ka, in phase with southern hemisphere temperatures, while surface warming experienced a 1-2 kyr delay. Additionally, we observe a convergence of oxygen and carbon isotopes across

  20. Sub-Antarctic glacier extensions in the Kerguelen region (49°S, Indian Ocean) over the past 24,000 years constrained by 36Cl moraine dating

    NASA Astrophysics Data System (ADS)

    Jomelli, Vincent; Mokadem, Fatima; Schimmelpfennig, Irene; Chapron, Emmanuel; Rinterknecht, Vincent; Favier, Vincent; Verfaillie, Deborah; Brunstein, Daniel; Legentil, Claude; Michel, Elisabeth; Swingedouw, Didier; Jaouen, Alain; Aumaitre, Georges; Bourlès, Didier L.; Keddadouche, Karim

    2017-04-01

    Similar to many other regions in the world, glaciers in the southern sub-polar regions are currently retreating. In the Kerguelen Islands (49°S, 69°E), the mass balance of the Cook Ice Cap (CIC), the largest ice cap in this region, experienced dramatic shrinking between 1960 and 2013 with retreat rates among the highest in the world. This observation needs to be evaluated in a long-term context. However, data on the past glacier extents are sparse in the sub-Antarctic regions. To investigate the deglaciation pattern since the Last Glacial Maximum (LGM) period, we present the first 13 cosmogenic 36Cl surface exposure ages from four sites in the Kerguelen Islands. The 36Cl ages from erratic and moraine boulders span from 24.4 ± 2.7 ka to 0.3 ± 0.1 ka. We combined these ages with existing glacio-marine radiocarbon ages and bathymetric data to document the temporal and spatial changes of the island's glacial history. Ice began to retreat on the main island before 24.4 ± 2.7 ka until around the time of the Antarctic Cold Reversal (ACR) period (∼14.5-12.9 ka), during which the Bontemps moraine was formed by the advance of a CIC outlet glacier. Deglaciation continued during the Holocene probably until 3 ka with evidence of minor advances during the last millennium. This chronology is in pace with major changes in δ18O in a recent West Antarctica ice core record, showing that Kerguelen Islands glaciers are particularly sensitive and relevant to document climate change in the southern polar regions.

  1. The seasonal succession of zooplankton in the Southern Ocean south of Australia, part II: The Sub-Antarctic to Polar Frontal Zones

    NASA Astrophysics Data System (ADS)

    Hunt, Brian P. V.; Hosie, Graham W.

    2006-07-01

    Between October 2001 and March 2002 six transects were completed at monthly intervals in the Sub-Antarctic Zone (SAZ) and Inter-Sub-Antarctic Front Zone (ISAFZ)/Polar Frontal Zone (PFZ) in the Southern Ocean south of Australia. Zooplankton were collected with a Continuous Plankton Recorder and NORPAC net and multivariate analysis was used to analyse the seasonal succession of communities. Despite strong, seasonally consistent, biogeographic differences between the SAZ and ISAFZ/PFZ, community structure in all zones was dominated by a suite of common taxa. These included the ubiquitous Oithona similis, foraminiferans and appendicularians (Core taxa), occurring in >97% of samples and contributing an average of 75% to total sample abundance, and Calanus simillimus, Rhincalanus gigas, Ctenocalanus citer, Clausocalanus brevipes, Clausocalanus laticeps, Oithona frigida, Limacina spp. and chaetognaths (Summer taxa), present in >57% of samples and occurring at seasonally high densities. Because of the dominance of the Core and Summer taxa, the seasonal succession was most clearly evident as a change in zooplankton densities. In October densities averaged <15 ind m -3, rising to 52 ind m -3 (max=92 ind m -3) in November, and subsequently increasing slowly through to January (ave=115 ind m -3; max=255 ind m -3). Densities peaked abruptly in February (ave=634 ind m -3; max=1593 ind m -3), and remained relatively high in March (ave=193 ind m -3; max=789 ind m -3). A latitudinal lag in seasonal development was observed with peak densities occurring first in the SAZ (February) and then in the ISAFZ/PFZ (March). The seasonal community succession was strongly influenced by species population cycles. The role of zooplankton in biogeochemical cycling in the SAZ and ISAFZ/PFZ was discussed in the light of past sediment trap data collected from the study area.

  2. Viral-mediated lysis of microbes and carbon release in the sub-Antarctic and Polar Frontal zones of the Australian Southern Ocean.

    PubMed

    Evans, Claire; Pearce, Imojen; Brussaard, Corina P D

    2009-11-01

    Viral production was determined in the sub-Antarctic zone (SAZ) to the southwest and southeast of Tasmania and in the Polar Frontal zone (PFZ) of the Australian sector of the Southern Ocean during Austral summer (January-February 2007). Concentrations of viruses were the lowest (6.6 x 10(9) particles l(-1)) in the PFZ and the highest (2.1 x 10(10) particles l(-1)) in the eastern SAZ where nutrient input from the East Australian Current (EAC) sustained higher concentrations of bacteria and bacterial production relative to the west. Rates of viral production in the PFZ (1.8 x 10(10) viruses l(-1) day(-1)) were lower than those in the western SAZ (2.5 x 10(10) viruses l(-1) day(-1)). Viral production in the eastern SAZ (2.2 x 10(11) viruses l(-1) day(-1)) was the highest recorded and was approximately one order of magnitude higher than at the other sites. In the western SAZ and PFZ, the percentage of available bacterial biomass lysed by viruses was similar (23.5% and 23% respectively) equating to the release of 3.3 and 2.3 microg carbon l(-1) day(-1) respectively (assuming a burst size of 50 viruses host(-1)). In the eastern SAZ the potential bacterial biomass lysed was higher (on average 40%) and corresponded to the release of 26.5 microg carbon l(-1) day(-1). These findings suggest the importance of the viral shunt in carbon cycling within these regions.

  3. Comparison of toxicogenomics and traditional approaches to inform mode of action and points of departure in human health risk assessment of benzo[a]pyrene in drinking water

    PubMed Central

    Labib, Sarah; Bourdon-Lacombe, Julie; Kuo, Byron; Buick, Julie K.; Lemieux, France; Williams, Andrew; Halappanavar, Sabina; Malik, Amal; Luijten, Mirjam; Aubrecht, Jiri; Hyduke, Daniel R.; Fornace, Albert J.; Swartz, Carol D.; Recio, Leslie; Yauk, Carole L.

    2015-01-01

    Toxicogenomics is proposed to be a useful tool in human health risk assessment. However, a systematic comparison of traditional risk assessment approaches with those applying toxicogenomics has never been done. We conducted a case study to evaluate the utility of toxicogenomics in the risk assessment of benzo[a]pyrene (BaP), a well-studied carcinogen, for drinking water exposures. Our study was intended to compare methodologies, not to evaluate drinking water safety. We compared traditional (RA1), genomics-informed (RA2) and genomics-only (RA3) approaches. RA2 and RA3 applied toxicogenomics data from human cell cultures and mice exposed to BaP to determine if these data could provide insight into BaP's mode of action (MOA) and derive tissue-specific points of departure (POD). Our global gene expression analysis supported that BaP is genotoxic in mice and allowed the development of a detailed MOA. Toxicogenomics analysis in human lymphoblastoid TK6 cells demonstrated a high degree of consistency in perturbed pathways with animal tissues. Quantitatively, the PODs for traditional and transcriptional approaches were similar (liver 1.2 vs. 1.0 mg/kg-bw/day; lung 0.8 vs. 3.7 mg/kg-bw/day; forestomach 0.5 vs. 7.4 mg/kg-bw/day). RA3, which applied toxicogenomics in the absence of apical toxicology data, demonstrates that this approach provides useful information in data-poor situations. Overall, our study supports the use of toxicogenomics as a relatively fast and cost-effective tool for hazard identification, preliminary evaluation of potential carcinogens, and carcinogenic potency, in addition to identifying current limitations and practical questions for future work. PMID:25605026

  4. Comparison of toxicogenomics and traditional approaches to inform mode of action and points of departure in human health risk assessment of benzo[a]pyrene in drinking water.

    PubMed

    Moffat, Ivy; Chepelev, Nikolai L; Labib, Sarah; Bourdon-Lacombe, Julie; Kuo, Byron; Buick, Julie K; Lemieux, France; Williams, Andrew; Halappanavar, Sabina; Malik, Amal I; Luijten, Mirjam; Aubrecht, Jiri; Hyduke, Daniel R; Fornace, Albert J; Swartz, Carol D; Recio, Leslie; Yauk, Carole L

    2015-01-01

    Toxicogenomics is proposed to be a useful tool in human health risk assessment. However, a systematic comparison of traditional risk assessment approaches with those applying toxicogenomics has never been done. We conducted a case study to evaluate the utility of toxicogenomics in the risk assessment of benzo[a]pyrene (BaP), a well-studied carcinogen, for drinking water exposures. Our study was intended to compare methodologies, not to evaluate drinking water safety. We compared traditional (RA1), genomics-informed (RA2) and genomics-only (RA3) approaches. RA2 and RA3 applied toxicogenomics data from human cell cultures and mice exposed to BaP to determine if these data could provide insight into BaP's mode of action (MOA) and derive tissue-specific points of departure (POD). Our global gene expression analysis supported that BaP is genotoxic in mice and allowed the development of a detailed MOA. Toxicogenomics analysis in human lymphoblastoid TK6 cells demonstrated a high degree of consistency in perturbed pathways with animal tissues. Quantitatively, the PODs for traditional and transcriptional approaches were similar (liver 1.2 vs. 1.0 mg/kg-bw/day; lungs 0.8 vs. 3.7 mg/kg-bw/day; forestomach 0.5 vs. 7.4 mg/kg-bw/day). RA3, which applied toxicogenomics in the absence of apical toxicology data, demonstrates that this approach provides useful information in data-poor situations. Overall, our study supports the use of toxicogenomics as a relatively fast and cost-effective tool for hazard identification, preliminary evaluation of potential carcinogens, and carcinogenic potency, in addition to identifying current limitations and practical questions for future work.

  5. Spatio-temporal variation in the strength and mode of selection acting on major histocompatibility complex diversity in water vole (Arvicola terrestris) metapopulations.

    PubMed

    Oliver, Matthew K; Lambin, Xavier; Cornulier, Thomas; Piertney, Stuart B

    2009-01-01

    Patterns of spatio-temporal genetic variation at a class II major histocompatibility complex (MHC) locus and multiple microsatellite loci were analysed within and between three water vole metapopulations in Scotland, UK. Comparisons of MHC and microsatellite spatial genetic differentiation, based on standardised tests between two demographically asynchronous zones within a metapopulation, suggested that spatial MHC variation was affected by balancing selection, directional selection and random genetic drift, but that the relative effects of these microevolutionary forces vary temporally. At the metapopulation level, between-year differentiation for MHC loci was significantly correlated with that of microsatellites, signifying that neutral factors such as migration and drift were primarily responsible for overall temporal genetic change at the metapopulation scale. Between metapopulations, patterns of genetic differentiation implied that, at large spatial scales, MHC variation was primarily affected by directional selection and drift. Levels of MHC heterozygosity in excess of Hardy-Weinberg expectations were consistent with overdominant balancing selection operating on MHC variation within metapopulations. However, this effect was not constant among all samples, indicating temporal variation in the strength of selection relative to other factors. The results highlight the benefit of contrasting variation at MHC with neutral markers to separate the effects of stochastic and deterministic microevolutionary forces, and add to a growing body of evidence showing that the mode and relative strength of selection acting on MHC diversity varies both spatially and temporally.

  6. Water

    MedlinePlus

    ... lead in it. For homes served by public water systems, data on lead in tap water may be available ... Many public water authorities have websites that include data on drinking water quality, including results of lead testing. Links to ...

  7. Inherent calibration of a blue LED-CE-DOAS instrument to measure iodine oxide, glyoxal, methyl glyoxal, nitrogen dioxide, water vapour and aerosol extinction in open cavity mode

    NASA Astrophysics Data System (ADS)

    Thalman, R.; Volkamer, R.

    2010-12-01

    The combination of Cavity Enhanced Absorption Spectroscopy (CEAS) with broad-band light sources (e.g. Light-Emitting Diodes, LEDs) lends itself to the application of cavity enhanced Differential Optical Absorption Spectroscopy (CE-DOAS) to perform sensitive and selective point measurements of multiple trace gases and aerosol extinction with a single instrument. In contrast to other broad-band CEAS techniques, CE-DOAS relies only on the measurement of relative intensity changes, i.e. does not require knowledge of the light intensity in the absence of trace gases and aerosols (I0). We have built a prototype LED-CE-DOAS instrument in the blue spectral range (420-490 nm) to measure nitrogen dioxide (NO2), glyoxal (CHOCHO), methyl glyoxal (CH3COCHO), iodine oxide (IO), water vapour (H2O) and oxygen dimers (O4). We demonstrate the first direct detection of methyl glyoxal, and the first CE-DOAS detection of CHOCHO and IO. The instrument is further inherently calibrated for light extinction from the cavity by observing O4 or H2O (at 477 nm and 443 nm) and measuring the pressure, relative humidity and temperature independently. This approach is demonstrated by experiments where laboratory aerosols of known size and refractive index were generated and their extinction measured. The measured extinctions were then compared to the theoretical extinctions calculated using Mie theory (3-7 × 10-7cm-1). Excellent agreement is found from both the O4 and H2O retrievals. This enables the first inherently calibrated CEAS measurement at blue wavelengths in open cavity mode, and eliminates the need for sampling lines to supply air to the cavity, i.e., keep the cavity enclosed and/or aerosol free. Measurements in open cavity mode are demonstrated for CHOCHO, CH3COCHO, NO2, H2O and aerosol extinction. Our prototype LED-CE-DOAS provides a low cost, yet research grade innovative instrument for applications in simulation chambers and in the open atmosphere.

  8. Inherent calibration of a novel LED-CE-DOAS instrument to measure iodine oxide, glyoxal, methyl glyoxal, nitrogen dioxide, water vapour and aerosol extinction in open cavity mode

    NASA Astrophysics Data System (ADS)

    Thalman, R.; Volkamer, R.

    2010-06-01

    The combination of Cavity Enhanced Absorption Spectroscopy (CEAS) with broad-band light sources (e.g. Light-Emitting Diodes, LEDs) lends itself to the application of cavity enhanced Differential Optical Absorption Spectroscopy (CE-DOAS) to perform sensitive and selective point measurements of multiple trace gases and aerosol extinction with a single instrument. In contrast to other broad-band CEAS techniques, CE-DOAS relies only on the measurement of relative intensity changes, i.e. does not require knowledge of the light intensity in the absence of trace gases and aerosols (I0). We have built a prototype LED-CE-DOAS instrument in the blue spectral range (420-490 nm) to measure nitrogen dioxide (NO2), glyoxal (CHOCHO), methyl glyoxal (CH3COCHO), iodine oxide (IO), water vapour (H2O) and oxygen dimers (O4). We demonstrate the first CEAS detection of methyl glyoxal, and the first CE-DOAS detection of CHOCHO and IO. A further innovation consists in the measurement of extinction losses from the cavity, e.g. due to aerosols, at two wavelengths by observing O4 (477 nm) and H2O (443 nm) and measuring the pressure, relative humidity and temperature independently. This approach is demonstrated by experiments where laboratory aerosols of known size and refractive index were generated and their extinction measured. The measured extinctions were then compared to the theoretical extinctions calculated using Mie theory (3-7×10-7 cm-1). Excellent agreement is found from both the O4 and H2O retrievals. This enables the first inherently calibrated CEAS measurement in open cavity mode (mirrors facing the open atmosphere), and eliminates the need for sampling lines to supply air to the cavity, and/or keep the cavity enclosed and aerosol free. Measurements in open cavity mode are demonstrated for CHOCHO, CH3COCHO, NO2, H2O and aerosol extinction at 477 nm and 443 nm. Our prototype LED-CE-DOAS provides a low cost, yet research grade innovative instrument for applications in simulation

  9. Diversity and extracellular enzymatic activities of yeasts isolated from King George Island, the sub-Antarctic region

    PubMed Central

    2012-01-01

    Background Antarctica has been successfully colonized by microorganisms despite presenting adverse conditions for life such as low temperatures, high solar radiation, low nutrient availability and dryness. Although these “cold-loving” microorganisms are recognized as primarily responsible for nutrient and organic matter recycling/mineralization, the yeasts, in particular, remain poorly characterized and understood. The aim of this work was to study the yeast microbiota in soil and water samples collected on King George Island. Results A high number of yeast isolates was obtained from 34 soil and 14 water samples. Molecular analyses based on rDNA sequences revealed 22 yeast species belonging to 12 genera, with Mrakia and Cryptococcus genera containing the highest species diversity. The species Sporidiobolus salmonicolor was by far the most ubiquitous, being identified in 24 isolates from 13 different samples. Most of the yeasts were psychrotolerant and ranged widely in their ability to assimilate carbon sources (consuming from 1 to 27 of the 29 carbon sources tested). All species displayed at least 1 of the 8 extracellular enzyme activities tested. Lipase, amylase and esterase activity dominated, while chitinase and xylanase were less common. Two yeasts identified as Leuconeurospora sp. and Dioszegia fristingensis displayed 6 enzyme activities. Conclusions A high diversity of yeasts was isolated in this work including undescribed species and species not previously isolated from the Antarctic region, including Wickerhamomyces anomalus, which has not been isolated from cold regions in general. The diversity of extracellular enzyme activities, and hence the variety of compounds that the yeasts may degrade or transform, suggests an important nutrient recycling role of microorganisms in this region. These yeasts are of potential use in industrial applications requiring high enzyme activities at low temperatures. PMID:23131126

  10. Satellite remote sensing of the island mass effect on the Sub-Antarctic Kerguelen Plateau, Southern Ocean

    NASA Astrophysics Data System (ADS)

    Jena, Babula

    2016-09-01

    The presence of the Kerguelen Plateau and surrounding bathymetric features has a strong influence on the persistently eastward flowing Antarctic Circumpolar Current (ACC), resulting in enhancement of surface chlorophyll-a (Chl- a) in the downstream section of the plateau along the polar front (PF). The phenomenon is reported in this paper as the island mass effect (IME). Analysis of climatological Chl- a datasets from Aqua- Moderate Resolution Imaging Spectroradiometer (Aqua- MODIS) and Sea-viewing Wide Field-of-view Sensor (SeaWiFS) shows distinct bloomy plumes (Chl- a>0.5 mg/m3) during austral spring-summer spreading as far as ~1800 km offshore up to 98°E along the downstream of the north Kerguelen Plateau (NKP). Similar IME phenomena is apparent over the south Kerguelen Plateau (SKP) with the phytoplankton bloom extending up to 96.7°E, along the southern boundary of ACC. The IME phenomena are pronounced only during austral spring-summer period with the availability of light and sedimentary source of iron from shallow plateau to sea surface that fertilizes the mixed layer. The NKP bloom peaks with a maximum areal extent of 1.315 million km2 during December, and the SKP bloom peaks during January with a time lag of one month. The blooms exist for at least 4 months of a year and are significant both as the base of regional food web and for regulating the biogeochemical cycle in the Southern Ocean. Even though the surface water above the Kerguelen Plateau is rich in Chl- a, an exception of an oligotrophic condition dominated between NKP and SKP due to apparent intrusion of iron limited low phytoplankton regime waters from the Enderby basin through the northeastward Fawn Trough Current.

  11. Mixed-mode acrylamide-based continuous beds bearing tert-butyl groups for capillary electrochromatography synthesized via complexation of N-tert-butylacrylamide with a water-soluble cyclodextrin. Part I: Retention properties.

    PubMed

    Al-Massaedh, Ayat Allah; Pyell, Ute

    2016-12-16

    With the aim to improve the understanding of morphology and efficiency properties, we investigate in this series the impact of the complex formation constant of the hydrophobic monomer with respect to statistically methylated-β-cyclodextrin (Me-β-CD) on the electrochromatographic properties of highly crosslinked amphiphilic mixed-mode acrylamide-based monolithic stationary phases. Based on our previous work on amphiphilic mixed-mode monolithic stationary phases for capillary electrochromatography (CEC) using N-(1-adamantyl)acrylamide (Ad-AAm) as hydrophobic monomer that forms an extremely strong water-soluble inclusion complex with Me-β-CD, we now selected N-tert-butylacrylamide (NTBA) as hydrophobic monomer forming an inclusion complex with Me-β-CD with a much lower value of the formation constant. Mixed-mode monolithic stationary phases are synthesized by in-situ free radical copolymerization of cyclodextrin-solubilized N-tert-butylacrylamide, a water soluble crosslinker (piperazinediacrylamide), a hydrophilic neutral monomer (methacrylamide), and a negatively charged monomer (vinylsulfonic acid) in aqueous medium in bind silane pre-treated fused silica capillaries. The synthesized monolithic stationary phases have both hydrophobic and hydrophilic moieties and can be employed in the reversed-phase mode, in the normal-phase mode, in a mixed-mode or in the hydrophilic interaction liquid chromatography (HILIC) mode (depending on the composition of the mobile phase and on the properties of the solute). Morphology and retention properties of this new type of stationary phase are compared to those reported in our previous series. With a homologues series of alkylphenones it is confirmed that the hydrophobicity (methylene selectivity αmeth) of the stationary phase is strongly dependent on the type of hydrophobic monomer employed. The studies reveal a significant influence of the formation constant of the involved host-guest inclusion complex on the morphology (i

  12. Controls on mesopelagic particle fluxes in the Sub-Antarctic and Polar Frontal Zones in the Southern Ocean south of Australia in summer—Perspectives from free-drifting sediment traps

    NASA Astrophysics Data System (ADS)

    Ebersbach, Friederike; Trull, Thomas W.; Davies, Diana M.; Bray, Stephen G.

    2011-11-01

    The SAZ-Sense project examined ecosystem controls on Southern Ocean carbon export during austral summer (January-February 2007) at three locations: P1 in the low biomass Subantarctic Zone (SAZ) west of Tasmania, P3 in a region of elevated biomass in the SAZ east of Tasmania fuelled by enhanced iron supply, and P2 in High-Nutrient/Low Chlorophyll (HNLC) Polar Frontal Zone (PFZ) waters south of P1 and P3. Sinking particles were collected using (i) a cylindrical time-series (PPS3/3) trap for bulk geochemical fluxes, (ii) indented rotating sphere (IRS) traps operated as in-situ settling columns to determine the flux distribution across sinking-rate fractions, and (iii) cylindrical traps filled with polyacrylamide gels to obtain intact particles for image analysis. Particulate organic carbon (POC) flux at 150 m (PPS3/3 trap) was highest at P1, lower at P2, and lowest at P3 (3.3±1.8, 2.1±0.9, and 0.9±0.4 mmol m -2 d -1, respectively). Biogenic silica (BSi) flux was very low in the SAZ (0.2±0.2 and 0.02±0.005 mmol m -2 d -1 at P1 and P3, respectively) and much higher in the PFZ (2.3±0.5 mmol m -2 d -1 at P2). Hence, the high biomass site P3 did not exhibit a correspondingly high flux of either POC or BSi. Separation of sinking-rate fractions with the IRS traps (at 170 and 320 m depth) was only successful at the PFZ site P2, where a relatively uniform distribution of flux was observed with ˜1/3 of the POC sinking faster than 100 m d -1 and 1/3 sinking slower than 10 m d -1. Analysis of thousands of particles collected with the gel traps (at 140, 190, 240, and 290 m depth) enabled us to identify 5 different categories: fluff-aggregates (low-density porous or amorphous aggregates), faecal-aggregates (denser aggregates composed of different types of particles), cylindrical and ovoid faecal pellets, and isolated phyto-cells (chains and single cells). Faecal-aggregates dominated the flux at all sites, and were larger in size at P1 in comparison to P3. The PFZ site P2

  13. First evidence of widespread active methane seepage in the Southern Ocean, off the sub-Antarctic island of South Georgia

    NASA Astrophysics Data System (ADS)

    Römer, M.; Torres, M.; Kasten, S.; Kuhn, G.; Graham, A. G. C.; Mau, S.; Little, C. T. S.; Linse, K.; Pape, T.; Geprägs, P.; Fischer, D.; Wintersteller, P.; Marcon, Y.; Rethemeyer, J.; Bohrmann, G.

    2014-10-01

    An extensive submarine cold-seep area was discovered on the northern shelf of South Georgia during R/V Polarstern cruise ANT-XXIX/4 in spring 2013. Hydroacoustic surveys documented the presence of 133 gas bubble emissions, which were restricted to glacially-formed fjords and troughs. Video-based sea floor observations confirmed the sea floor origin of the gas emissions and spatially related microbial mats. Effective methane transport from these emissions into the hydrosphere was proven by relative enrichments of dissolved methane in near-bottom waters. Stable carbon isotopic signatures pointed to a predominant microbial methane formation, presumably based on high organic matter sedimentation in this region. Although known from many continental margins in the world's oceans, this is the first report of an active area of methane seepage in the Southern Ocean. Our finding of substantial methane emission related to a trough and fjord system, a topographical setting that exists commonly in glacially-affected areas, opens up the possibility that methane seepage is a more widespread phenomenon in polar and sub-polar regions than previously thought.

  14. Effect of aerial exposure on the antioxidant status in the subantarctic stone crab Paralomis granulosa (Decapoda: Anomura).

    PubMed

    Romero, M Carolina; Ansaldo, Martín; Lovrich, Gustavo A

    2007-01-01

    In Tierra del Fuego (Southern South America), the stone or false king crab, Paralomis granulosa represents one of the most important crab fisheries. After capture, animals are kept in baskets and exposed to dryness for several hours, when the water flow through the gills is interrupted. As a consequence a concomitant increase of reactive oxygen species begins, triggering oxidative stress. The aim of this study was to determine oxidative stress and antioxidant enzyme activities due to air exposure in different tissues of P. granulosa. Fifty crabs (carapace length >82 mm) were captured in Beagle Channel (54 degrees 50'S, 68 degrees 20'W) during winter 2004. Five groups of 10 crabs each were exposed to dryness at 6 degrees C for 0, 3, 6, 12 or 24 h, respectively. Activity of superoxide dismutase (SOD), catalase (CAT), glutathione S transferase (GST) protein and lipid oxidation were measured in gills, muscle, hepatopancreas and haemolymph samples. Almost all analyzed tissues showed antioxidant enzymes activity, which varied with time of air exposure. The maximum enzyme activity was measured after 6 h of air exposure. Protein oxidation levels varied significantly in gills. Lipid peroxidation levels increased significantly in muscle and hepatopancreas. The critical time of air exposure probably occurs at 6 h. Thereafter animals were unable to induce the synthesis of antioxidant enzymes or proteins. This should be taken into account to minimize the stress generated by the commercial capture process.

  15. Comparative HPLC methods for β-blockers separation using different types of chiral stationary phases in normal phase and polar organic phase elution modes. Analysis of propranolol enantiomers in natural waters.

    PubMed

    Morante-Zarcero, Sonia; Sierra, Isabel

    2012-03-25

    The enantioselectivities of β-blockers (propranolol, metoprolol, atenolol and pindolol) on four different types of chiral stationary phases (CSPs): Chiralpak AD-H, Lux Cellulose-1, Chirobiotic T and Sumichiral OA-4900 were compared using polar organic (PO) elution mode and normal phase (NP) elution mode. Method optimizations were demonstrated by modifying parameters such as organic modifier composition (ethanol, 2-propanol and acetonitrile) and basic mobile phase additives (triethylamine, diethylamine, ethanolamine, and buthylamine). In normal phase elution mode with Lux Cellulose-1, the four pairs of enantiomers can be separated in the same run in gradient elution mode. Additionally, a simple chiral HPLC-DAD method using a newly commercialized polysaccharide-based CSP by Phenomenex (Lux Cellulose-1) in NP elution mode for enantioselective determination of propranolol in water samples by highly selective molecularly imprinted polymers extraction was validated. The optimized conditions were a mobile phase composed by n-hexane/ethanol/DEA (70/30/0.3, v/v/v) at a flow rate of 1.0 mL min(-1) and 25 °C. The method is selective, precise and accurate and was found to be linear in the range of 0.125-50 μg mL(-1) (R(2)>0.999) with a method detection limit (MLD) of 0.4 μg mL(-1) for both enantiomers. Recoveries achieved with both enantiomers ranged from 97 to 109%.

  16. Dissolved Iron in the Australian Sector of the Southern Ocean During Spring: Implications for the Seasonal Cycle of Iron in Antarctic Surface Waters

    NASA Astrophysics Data System (ADS)

    Sedwick, P. N.; Bowie, A. R.; Ussher, S. J.; Mackey, D. J.; Trull, T. W.; Worsfold, P. J.

    2002-12-01

    Colorimetric flow injection analysis was used to measure dissolved iron (<0.4 μm, dFe) in upper-ocean (<400 m depth) water samples collected from the CLIVAR SR3 section (~142°E) between Tasmania and Antarctica in November-December 2001. These are the first such data for this region during austral spring, and include results from two stations occupied in melting pack ice, as well as one station near the 61°S SOIREE site, occupied twice. Combining these new results with data from a March 1998 cruise and the February 1999 SOIREE campaign allows us to infer seasonal (spring-fall) changes in dFe concentrations in surface waters of our study region, assuming interannual variability is small. The data suggest a seasonal drawdown of ~0.1-0.2 nM dFe in the Subantarctic Zone waters (~47°S); a seasonal accumulation of ~0.1 nM dFe in near-surface (~25 m) waters and a drawdown of ~0.05 nM dFe in deeper (~50-300 m) waters of the Subantarctic Front (~51°S); and little or no seasonal dFe drawdown (~0.05 nM or less) in surface waters south of the Subantarctic Front, where dFe concentrations were uniformly low (~0.1 nM). Thus, if winter mixing provides a significant vertical resupply of dFe to Antarctic surface waters, our results suggest that most of this winter reserve of dissolved iron is removed from the upper water column very early in the growing season. In addition, our new data provide no evidence of significant iron inputs to surface waters from melting sea ice, which may explain the lack of ice-edge algal blooms in this sector of the Southern Ocean, as inferred from ocean-color satellite images.

  17. Water

    USGS Publications Warehouse

    Leopold, Luna Bergere; Baldwin, Helene L.

    1962-01-01

    What do you use water for?If someone asked you this question you would probably think right away of water for drinking. Then you would think of water for bathing, brushing teeth, flushing the toilet. Your list would get longer as you thought of water for cooking, washing the dishes, running the garbage grinder. Water for lawn watering, for play pools, for swimming pools, for washing the car and the dog. Water for washing machines and for air conditioning. You can hardly do without water for fun and pleasure—water for swimming, boating, fishing, water-skiing, and skin diving. In school or the public library, you need water to wash your hands, or to have a drink. If your home or school bursts into flames, quantities of water are needed to put it out.In fact, life to Americans is unthinkable without large supplies of fresh, clean water. If you give the matter a little thought, you will realize that people in many countries, even in our own, may suffer from disease and dirt simply because their homes are not equipped with running water. Imagine your own town if for some reason - an explosion, perhaps - water service were cut off for a week or several weeks. You would have to drive or walk to a neighboring town and bring water back in pails. Certainly if people had to carry water themselves they might not be inclined to bathe very often; washing clothes would be a real chore.Nothing can live without water. The earth is covered by water over three-fourths of its surface - water as a liquid in rivers, lakes and oceans, and water as ice and snow on the tops of high mountains and in the polar regions. Only one-quarter of our bodies is bone and muscle; the other three-fourths is made of water. We need water to live, and so do plants and animals. People and animals can live a long time without food, but without water they die in a few days. Without water, everything would die, and the world would turn into a huge desert.

  18. Automatic determination of important mode-mode correlations in many-mode vibrational wave functions.

    PubMed

    König, Carolin; Christiansen, Ove

    2015-04-14

    We introduce new automatic procedures for parameterizing vibrational coupled cluster (VCC) and vibrational configuration interaction wave functions. Importance measures for individual mode combinations in the wave function are derived based on upper bounds to Hamiltonian matrix elements and/or the size of perturbative corrections derived in the framework of VCC. With a threshold, this enables an automatic, system-adapted way of choosing which mode-mode correlations are explicitly parameterized in the many-mode wave function. The effect of different importance measures and thresholds is investigated for zero-point energies and infrared spectra for formaldehyde and furan. Furthermore, the direct link between important mode-mode correlations and coordinates is illustrated employing water clusters as examples: Using optimized coordinates, a larger number of mode combinations can be neglected in the correlated many-mode vibrational wave function than with normal coordinates for the same accuracy. Moreover, the fraction of important mode-mode correlations compared to the total number of correlations decreases with system size. This underlines the potential gain in efficiency when using optimized coordinates in combination with a flexible scheme for choosing the mode-mode correlations included in the parameterization of the correlated many-mode vibrational wave function. All in all, it is found that the introduced schemes for parameterizing correlated many-mode vibrational wave functions lead to at least as systematic and accurate calculations as those using more standard and straightforward excitation level definitions. This new way of defining approximate calculations offers potential for future calculations on larger systems.

  19. Hardware Assisted ROP Detection Mode (HARD Mode)

    DTIC Science & Technology

    2013-08-01

    Distribution A. Cleared for public release; unlimited distribution. USAFA-CN-2013-457 Hardware Assisted ROP Detection Mode (HARD Mode) NATHANIEL HART...457 This report, "Hardware Assisted ROP Detection Mode (HARD Mode)" is presented as a competent treatment of the subj ect, worthy of publication. The...Technical 20120810-20121215 Hardware Assisted ROP Detection Mode (HARD Mode) NATHANIEL HART MICHAEL WINSTEAD MARTIN CARLISLE RODNEY LYKINS MICHAEL

  20. Tsunami normal modes with solid earth and atmospheric coupling and inversion of the TEC data to estimate tsunami water height in the case of the Queen Charlotte tsunami.

    NASA Astrophysics Data System (ADS)

    Rakoto, V.; Lognonne, P. H.; Rolland, L.

    2016-12-01

    Large underwater earthquakes (Mw > 7) can transmit part of their energy to the surrounding ocean through large sea-floor motions, generating tsunamis that propagate over long distances. The forcing effect of long period ocean surface vibrations due to tsunami waves on the atmosphere trigger atmospheric internal gravity waves (IGWs) that induce ionospheric disturbances when they reach the upper atmosphere. In this poster, we study the IGWs associated to tsunamis using a normal modes 1D modeling approach. Our model is first applied to the case of the October 2012 Haida Gwaii tsunami observed offshore Hawaii. We found three resonances between tsunami modes and the atmospheric gravity modes occurring around 1.5 mHz, 2 mHz and 2.5 mHz, with a large fraction of the energy of the tsunami modes transferred from the ocean to the atmosphere. At theses frequencies, the gravity branches are interacting with the tsunami one and have large amplitude in the ocean. As opposed to the tsunami, a fraction of their energy is therefore transferred from the atmosphere to the ocean. We also show that the fundamental of the gravity waves should arrive before the tsunami due to higher group velocity below 1.6 mHz. We demonstrate that only the 1.5 mHz resonance of the tsunami mode can trigger observable ionospheric perturbations, most often monitored using GPS dual-frequency measurements. Indeed, we show that the modes at 2 mHz and 2.5 mHz are already evanescent at the height of the F2 peak and have little energy in the ionosphere. This normal modes modeling offers a novel and comprehensive study of the transfer function from a propagating tsunami to the upper atmosphere. In particular, we can invert the perturbed TEC data induced by a tsunami in order to estimate the amplitude of the tsunami waveform using a least square method. This method has been performed in the case of the Haida Gwaii tsunami. The results showed a good agreement with the measurement of the dart buoy.

  1. Using stable isotopes (δ^{18}O and δ$D) of gypsum hydration water to unravel the mode of gypsum speleothem formation in semi-arid caves

    NASA Astrophysics Data System (ADS)

    Gázquez, Fernando; Calaforra, Jose Maria; Evans, Nicholas P.; Hodell, David A.

    2016-04-01

    Subaerial gypsum speleothems form during the evaporation of calcium-sulfate-rich solutions in caves. The evaporation of infiltration water is the widely accepted mechanism to explain precipitation of gypsum speleothems; i.e., the dissolution of gypsum host-rock (e.g. Messinian marine gypsum) supplies Ca2+ and SO42- ions to cave waters and subsequent evaporation leads to gypsum saturation. However, water condensation actively occurs in caves of semi-arid regions and plays a key role in subaerial cave speleogenesis and recharge of aquifers in low-rainfall environments. To date, water condensation in karstic environments has not been considered as an important factor in gypsum speleothem formation. We collected speleothem samples from the upper passages of Covadura Cave in the gypsum karst of Sorbas (Almeria, SE Spain). This cave is located in a temperate (annual mean temperature of 19.5oC), semi-arid region (

  2. Mixed-mode solid-phase extraction coupled with liquid chromatography tandem mass spectrometry to determine phenoxy acid, sulfonylurea, triazine and other selected herbicides at nanogram per litre levels in environmental waters.

    PubMed

    Zhang, Pei; Bui, Anhduyen; Rose, Gavin; Allinson, Graeme

    2014-01-17

    The method presented uses a mixed-mode anion exchange SPE and liquid chromatography tandem mass spectrometry to analyze 5 sulfonylurea, 8 phenoxy acid, 12 triazine and 6 other herbicides in environmental waters. The mixed-mode SPE cartridge is able to retain a wide range of herbicides with acidic-neutral-basic characteristics, particularly the highly polar and acidic compounds clopyralid, dicamba and picloram. The neutral and basic herbicides can be effectively eluted with methanol, after which the acidic herbicides can be eluted using acidified methanol. The method has achieved an LOD of 0.7-3ng/L for the sulfonylureas, 4-12ng/L for the phenoxy acids and 0.4-30ng/L for the triazine and additional herbicides, with recoveries in the range 76-107%, 73-126%, and 65-104%, respectively. The precision of the method, calculated as relative standard deviation (RSD), was below 10% for both sulfonylurea and phenoxy acid herbicides, and less than 20% for the remaining herbicides. The developed method was used to determine the concentration of target herbicides in a range of environmental waters, and many of the target herbicides were detected at ng/L level.

  3. Rapid Oxic/Anoxic Changes in the Sediment-Water Interface During the Eocene- Oligocene Transition

    NASA Astrophysics Data System (ADS)

    Nicholas, C. J.; O'Halloran, A.; Goodhue, R.

    2008-12-01

    The Eocene-Oligocene Transition (EOT) refers to a 500 kyr period of time, which includes the Eocene- Olicgocene Boundary, stretching from 33.5-34.0 Ma (Pearson et al. 2008). It includes all of the changes associated with the expansion of Antarctic glaciation and the concurrent changes in marine fauna and productivity, as well as any physical oceanographic changes that occurred. Shallow-level drilling recovered cores from southern Tanzania and Java, Indonesia. The cores sampled outer-shelf to slope, organic-rich marine clays which show excellent preservation of microfossils and a very low thermal maturity. As the drill sites are from either side of the Indian Ocean, at approximately 10° south of the equator, the comparison of results from these sites will allow insights into the global or regional nature of oceanic signals. Results from the Tanzanian cores have highlighted rapid oscillations in the oxic/anoxic nature of the sediment-water interface throughout the EOT. This is currently interpreted as a direct result of changes occurring in the ocean currents surrounding Antarctica. In the present, Sub-Antarctic Mode Waters (SAMW) deliver high-latitude climatic signals to the tropical Indian Ocean (Dunkley Jones et al., 2008). We suggest that during the EOT these Antarctic currents were in an infantile state, switching on and off during the transitional period, until cooling reached a stable state and the currents were able to fully establish. This could have caused the oxygenation state of the Indian Ocean bottom waters to oscillate during the EOT, only being oxygenated in a stable way after 33.5 Ma. However, the cores from Java will help us verify whether these signals are global or regional in nature. Recent studies have indicated that the heightened productivity of the time is more global than regional, and does not occur just in the high latitudes around Antarctica. Preliminary results from Indonesia indicate that the same increase in productivity was occurring

  4. Investigating the impacts of DNA binding mode and sequence on thermodynamic quantities and water exchange values for two small molecule drugs.

    PubMed

    Kenney, Rachael M; Buxton, Katherine E; Glazier, Samantha

    2016-09-01

    Doxorubicin and nogalamycin are antitumor antibiotics that interact with DNA via intercalation and threading mechanisms, respectively. Because the importance of water, particularly its impact on entropy changes, has been established in other biological processes, we investigated the role of water in these two drug-DNA binding events. We used the osmotic stress method to calculate the number of water molecules exchanged (Δnwater), and isothermal titration calorimetry to measure Kbinding, ΔH, and ΔS for two synthetic DNAs, poly(dA·dT) and poly(dG·dC), and calf thymus DNA (CT DNA). For nogalamycin, Δnwater<0 for CT DNA and poly(dG·dC). For doxorubicin, Δnwater>0 for CT DNA and Δnwater<0 for poly(dG·dC). For poly(dA·dT), Δnwater~0 with both drugs. Net enthalpy changes were always negative, but net entropy changes depended on the drug. The effect of water exchange on the overall sign of entropy change appears to be smaller than other contributions. Copyright © 2016 Elsevier B.V. All rights reserved.

  5. DNA binding, DNA cleavage and cytotoxicity studies of a new water soluble copper(II) complex: The effect of ligand shape on the mode of binding

    NASA Astrophysics Data System (ADS)

    Kashanian, Soheila; Khodaei, Mohammad Mehdi; Roshanfekr, Hamideh; Shahabadi, Nahid; Mansouri, Ghobad

    2012-02-01

    The interaction of native calf thymus DNA (CT-DNA) with [Cu(ph 2phen)(phen-dione)Cl]Cl was studied at physiological pH by spectrophotometric, spectrofluorometric, circular dichroism, and viscometric techniques. Considerable hypochromicity and red shift are observed in the UV absorption band of the Cu complex. Binding constants ( Kb) of DNA with the complex were calculated at different temperatures. Thermodynamic parameters, enthalpy and entropy changes were calculated according to Van't Hoff equation, which indicated that reaction is predominantly enthalpically driven. All these results indicate that Cu(II) complex interacts with CT-DNA via intercalative mode. Also, this new complex induced cleavage in pUC18 plasmid DNA as indicated in gel electrophoresis and showed excellent antitumor activity against K562 (human chronic myeloid leukemia) and human T lymphocyte carcinoma-Jurkat cell lines.

  6. Anti-diabetic effect of balanced deep-sea water and its mode of action in high-fat diet induced diabetic mice.

    PubMed

    Ha, Byung Geun; Shin, Eun Ji; Park, Jung-Eun; Shon, Yun Hee

    2013-10-29

    In this study, we investigated the effects of balanced deep-sea water (BDSW) on hyperglycemia and glucose intolerance in high-fat diet (HFD)-induced diabetic C57BL/6J mice. BDSW was prepared by mixing deep-sea water (DSW) mineral extracts and desalinated water to give a final hardness of 500-2000. Mice given an HFD with BDSW showed lowered fasting plasma glucose levels compared to HFD-fed mice. Oral and intraperitoneal glucose tolerance tests showed that BDSW improves impaired glucose tolerance in HFD-fed mice. Histopathological evaluation of the pancreas showed that BDSW recovers the size of the pancreatic islets of Langerhans, and increases the secretion of insulin and glucagon in HFD-fed mice. Quantitative reverse transcription polymerase chain reaction results revealed that the expression of hepatic genes involved in glucogenesis, glycogenolysis and glucose oxidation were suppressed, while those in glucose uptake, β-oxidation, and glucose oxidation in muscle were increased in mice fed HFD with BDSW. BDSW increased AMP-dependent kinase (AMPK) phosphorylation in 3T3-L1 pre- and mature adipocytes and improved impaired AMPK phosphorylation in the muscles and livers of HFD-induced diabetic mice. BDSW stimulated phosphoinositol-3-kinase and AMPK pathway-mediated glucose uptake in 3T3-L1 adipocytes. Taken together, these results suggest that BDSW has potential as an anti-diabetic agent, given its ability to suppress hyperglycemia and improve glucose intolerance by increasing glucose uptake.

  7. Anti-Diabetic Effect of Balanced Deep-Sea Water and Its Mode of Action in High-Fat Diet Induced Diabetic Mice

    PubMed Central

    Ha, Byung Geun; Shin, Eun Ji; Park, Jung-Eun; Shon, Yun Hee

    2013-01-01

    In this study, we investigated the effects of balanced deep-sea water (BDSW) on hyperglycemia and glucose intolerance in high-fat diet (HFD)-induced diabetic C57BL/6J mice. BDSW was prepared by mixing deep-sea water (DSW) mineral extracts and desalinated water to give a final hardness of 500–2000. Mice given an HFD with BDSW showed lowered fasting plasma glucose levels compared to HFD-fed mice. Oral and intraperitoneal glucose tolerance tests showed that BDSW improves impaired glucose tolerance in HFD-fed mice. Histopathological evaluation of the pancreas showed that BDSW recovers the size of the pancreatic islets of Langerhans, and increases the secretion of insulin and glucagon in HFD-fed mice. Quantitative reverse transcription polymerase chain reaction results revealed that the expression of hepatic genes involved in glucogenesis, glycogenolysis and glucose oxidation were suppressed, while those in glucose uptake, β-oxidation, and glucose oxidation in muscle were increased in mice fed HFD with BDSW. BDSW increased AMP-dependent kinase (AMPK) phosphorylation in 3T3-L1 pre- and mature adipocytes and improved impaired AMPK phosphorylation in the muscles and livers of HFD-induced diabetic mice. BDSW stimulated phosphoinositol-3-kinase and AMPK pathway-mediated glucose uptake in 3T3-L1 adipocytes. Taken together, these results suggest that BDSW has potential as an anti-diabetic agent, given its ability to suppress hyperglycemia and improve glucose intolerance by increasing glucose uptake. PMID:24172214

  8. Modes of metal toxicity and impaired branchial ionoregulation in rainbow trout exposed to mixtures of Pb and Cd in soft water.

    PubMed

    Birceanu, Oana; Chowdhury, M Jasim; Gillis, Patricia L; McGeer, James C; Wood, Chris M; Wilkie, Michael P

    2008-09-29

    Models such as the Biotic Ligand Model (BLM) predict how natural organic matter (NOM) and competing ions (e.g., Ca(2+), H(+) and Na(+)) affect metal bioavailability and toxicity in aquatic organisms. However, such models focus upon individual metals, not metal mixtures. This study determined whether Pb and Cd interact at the gill of rainbow trout (Oncorhynchus mykiss) when trout were exposed to environmentally relevant concentrations of these metals (Cd<100 nmol L(-1); Pb<500 nmol L(-1)) in soft (<100 micromol Ca(2+)L(-1)), moderately acidic (pH 6.0) water. The 96-h LC50 for Pb was 482 nmol L(-1), indicating that Pb was one-order of magnitude more toxic in soft, acidic water than in harder, circumneutral pH waters. The LC50 for Cd alone was also low, 6.7 nmol L(-1). Surprisingly, fish acclimated to soft water had multiple populations of Pb-gill and Cd-gill binding sites. A low capacity, high affinity population of Pb-gill binding sites had a B(max) of 18.2 nmol g(-1) wet weight (ww) and apparent K(Pb-gill)=7.05, but a second low affinity population could not be saturated up to free Pb concentrations approaching 4000 nmol L(-1). Two populations of Cd-gill binding sites were characterized: a high affinity, low capacity population with an apparent K(Cd-gill)=7.33 and B(max)=1.73 nmol g(-1) ww, and a low affinity, high capacity population with an apparent K(Cd-gill)=5.86, and B(max)=13.7 nmol g(-1) ww. At low concentrations, Cd plus Pb accumulation was less than additive because Cd out-competed Pb for gill binding sites, which were likely apical Ca(2+)-channels. While disturbances to Ca(2+) influx were caused by Cd alone, Pb alone had no effect. However, Pb exacerbated Cd-induced disturbances to Ca(2+) influx demonstrating that, although Pb- plus Cd-gill binding was less than additive due to competition, the effects (ionic disturbances) were more than additive (synergistic). Pb was also likely binding to intracellular targets, such as branchial carbonic anhydrase

  9. Manipulation of polystyrene nanoparticles on a silicon wafer in the peak force tapping mode in water: pH-dependent friction and adhesion force

    SciTech Connect

    Schiwek, Simon; Stark, Robert W. E-mail: dietz@csi.tu-darmstadt.de; Dietz, Christian E-mail: dietz@csi.tu-darmstadt.de; Heim, Lars-Oliver

    2015-03-14

    The friction force between nanoparticles and a silicon wafer is a crucial parameter for cleaning processes in the semiconductor industry. However, little is known about the pH-dependency of the friction forces and the shear strength at the interface. Here, we push polystyrene nanoparticles, 100 nm in diameter, with the tip of an atomic force microscope and measure the pH-dependency of the friction, adhesion, and normal forces on a silicon substrate covered with a native silicon dioxide layer. The peak force tapping mode was applied to control the vertical force on these particles. We successively increased the applied load until the particles started to move. The main advantage of this technique over single manipulation processes is the achievement of a large number of manipulation events in short time and in a straightforward manner. Geometrical considerations of the interaction forces at the tip-particle interface allowed us to calculate the friction force and shear strength from the applied normal force depending on the pH of an aqueous solution. The results clearly demonstrated that particle removal should be performed with a basic solution at pH 9 because of the low interaction forces between particle and substrate.

  10. Preliminary results of field mapping of methane plumes offshore of Coal Oil Point, California with a RESON 7125 multibeam sonar in water-column mode

    NASA Astrophysics Data System (ADS)

    Finlayson, D. P.; Hatcher, G.; Lorenson, T. D.; Greinert, J.; Maillard, E.; Weirathmueller, M.; Leifer, I.

    2010-12-01

    From June 17 - 23 2010, the U. S. Geological Survey (USGS) in collaboration with the Bureau of Ocean Energy Management Regulation and Enforcement(BOEMRE), the Royal Netherlands Institute for Sea Research (NIOZ) , RESON Inc. and the University of California, Santa Barbara(UCSB) conducted a comprehensive marine-seep gas-plume mapping study offshore of Coal Oil Point, California. The ultimate goal of the experiment is to quantify the amount of methane emitted from natural seeps using multibeam sonar, with results calibrated using field measurements of aqueous and atmospheric methane in the seep fields. Success will lead to better estimates of natural marine methane contributions to the global methane budget. We mapped selected seeps, some twice, with a pole-mounted RESON 7125 multibeam with a 10-degree forward rake. Other equipment included a Benthos Stingray ROV equipped with high-definition video cameras and in situ gas sampling apparatus, Niskin bottles for water column sampling of dissolved methane, and a Picarro G1301 cavity ringdown spectrometer for mapping atmospheric methane concentrations. This paper focuses primarily on the data reduction and data visualization strategies employed while processing the more than 1.2 TB of raw water column data collected by the multibeam system over several high-output oil and gas seep areas. Water depths ranged from about 30 to 80m. Turnkey software solutions for processing these data are currently unavailable so most of the processing code was developed in-house by the USGS. The main challenge in processing the sonar water-column data is ray-tracing the large volume of data, with each ping containing more than 4500 times as many samples as a conventional multibeam ping. We employed two strategies to make processing tractable on conventional workstations: (1) decimate the raw data based on desired output resolution before ray-tracing; and (2) design the ray-tracing program to run in parallel on multi-core workstations

  11. Lipid production of microalga Chlorella sorokiniana CY1 is improved by light source arrangement, bioreactor operation mode and deep-sea water supplements.

    PubMed

    Chen, Chun-Yen; Chang, Hsin-Yueh

    2016-03-01

    Microalgae-based biodiesel has been recognized as a sustainable and promising alternative to fossil diesel. High lipid productivity of microalgae is required for economic production of biodiesel from microalgae. This study was undertaken to enhance the growth and oil accumulation of an indigenous microalga Chlorella sorokiniana CY1 by applying engineering strategies using deep-sea water as the medium. First, the microalga was cultivated using LED as the immersed light source, and the results showed that the immersed LED could effectively enhance the oil/lipid content and final microalgal biomass concentration to 53.8% and 2.5 g/l, respectively. Next, the semi-batch photobioreactor operation with deep-sea water was shown to improve lipid content and microalgal growth over those from using batch and continuous cultures under similar operating conditions. The optimal replacement ratio was 50%, resulting in an oil/lipid content and final biomass concentration of 61.5% and 2.8 g/l, respectively. A long-term semi-batch culture utilizing 50%-replaced medium was carried out for four runs. The final biomass concentration and lipid productivity were 2.5 g/L and 112.2 mg/L/d, respectively. The fatty acid composition of the microalgal lipids was predominant by palmitic acid, stearic acid, oleic acid and linoleic acid, and this lipid quality is suitable for biodiesel production. This demonstrates that optimizing light source arrangement, bioreactor operation and deep-sea water supplements could effectively promote the lipid production of C. sorokiniana CY1 for the applications in microalgae-based biodiesel industry. Copyright © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. In-tube solid-phase microextraction coupled by in valve mode to capillary LC-DAD: Improving detectability to multiresidue organic pollutants analysis in several whole waters.

    PubMed

    Campíns-Falcó, P; Verdú-Andrés, J; Sevillano-Cabeza, A; Herráez-Hernández, R; Molins-Legua, C; Moliner-Martinez, Y

    2010-04-16

    A simple and fast capillary chromatographic method has been developed to identify and quantify organic pollutants at sub-ppb levels in real water samples. The major groups of pesticides (organic halogens, organic phosphorous, and organic nitrogen compounds), some hydrocarbons (polycyclic aromatic hydrocarbons), phthalates and some phenols such as phenol and bisphenol A (endocrine disruptors) were included in this study. The procedure was based on coupling, in-tube solid-phase microextraction (IT-SPME) by using a conventional GC capillary column (95% methyl-5% phenyl substituted backbone, 80cmx0.32mm i.d., 3microm film thickness) in the injection valve to capillary liquid chromatography with diode array detection. A comparative study between the IT-SPME manifold and a column-switching device using a C(18) column (35mmx0.5mm i.d., 5microm particle size) has been performed. The IT-SPME procedure was optimal, it allows reaching limits of detection (LODs) between 0.008 and 0.2microg/L. No matrix effect was found and recoveries between 70 and 116% were obtained. The precision of the method was good, and the achieved intra- and inter-day variation coefficients were between 2 and 30%. This procedure has been applied to the screening analysis of 28 compounds in whole waters from several points of the Mediterranean coast (Valencia Community, Spain).

  13. [Effects of plastic film mulching and rain harvesting modes on chlorophyll fluorescence characteristics, yield and water use efficiency of dryland maize].

    PubMed

    Li, Shang-Zhong; Fan, Ting-Lu; Wang, Yong; Zhao, Gang; Wang, Lei; Tang, Xiao-Ming; Dang, Yi; Zhao, Hui

    2014-02-01

    The differences on chlorophyll fluorescence parameters, yield and water use efficiency of dryland maize were compared among full plastic film mulching on double ridges and planting in catchment furrows (FFDRF), half plastic film mulching on double ridges and planting in catchment furrows (HFDRF), plastic film mulching on ridge and planting in film-side (FS), and flat planting with no plastic film mulching (NM) under field conditions in dry highland of Loess Plateau in 2007-2012. The results showed that fluorescence yield (Fo), the maximum fluorescence yield (Fm), light-adapted fluorescence yield when PS II reaction centers were totally open (F), light-adapted fluorescence yield when PS II reaction centers closed (Fm'), the maximal photochemical efficiency of PS II (Fv/Fm), the actual photochemical efficiency of PS II in the light (Phi PS II), the relative electron transport rate (ETR), photochemical quenching (qP) and non-photochemical quenching (qN) in maize leaves of FFDRF were higher than that of control (NM), and the value of 1-qP was lower than that of control, at 13:00, chlorophyll fluorescence parameters values of FFDRF was significantly higher than control, which were increased by 5.3%, 56.8%, 10.7%, 36.3%, 23.6%, 56.7%, 64.4%, 45.5%, 23.6% and -55.6%, respectively, compared with the control. Yield and water use efficiency of FFDRF were the highest in every year no matter dry year, normal year, humid year and hail disaster year. Average yield and water use efficiency of FFDRF were 12,650 kg x hm(-2) and 40.4 kg x mm(-1) x hm(-2) during 2007-2012, increased by 57.8% and 61.6% compared with the control, respectively, and also significantly higher compared with HFDRF and PS. Therefore, it was concluded that FFDRF had significantly increased the efficiency of light energy conversion and improved the production capacity of dryland maize.

  14. A la Mode II.

    ERIC Educational Resources Information Center

    Stowe, Richard A.

    This paper describes two modes of educational decision-making: Mode I, in which the instructor makes such decisions as what to teach, to whom, when, in what order, at what pace, and at what complexity level; and Mode II, in which the learner makes the decisions. While Mode I comprises most of what is regarded as formal education, the learner in…

  15. List mode multichannel analyzer

    DOEpatents

    Archer, Daniel E.; Luke, S. John; Mauger, G. Joseph; Riot, Vincent J.; Knapp, David A.

    2007-08-07

    A digital list mode multichannel analyzer (MCA) built around a programmable FPGA device for onboard data analysis and on-the-fly modification of system detection/operating parameters, and capable of collecting and processing data in very small time bins (<1 millisecond) when used in histogramming mode, or in list mode as a list mode MCA.

  16. Host-guest chemistry of a water-soluble pillar[5]arene: evidence for an ionic-exchange recognition process and different complexation modes.

    PubMed

    Gómez, Borja; Francisco, Vitor; Fernández-Nieto, Fernando; Garcia-Rio, Luis; Martín-Pastor, M; Paleo, M Rita; Sardina, F Javier

    2014-09-15

    The complexation of an anionic guest by a cationic water-soluble pillararene is reported. Isothermal titration calorimetry (ITC), (1)H NMR, (1)H and (19)F DOSY, and STD NMR experiments were performed to characterize the complex formed under aqueous neutral conditions. The results of ITC and (1)H NMR analyses showed the inclusion of the guest inside the cavity of the pillar[5]arene, with the binding constant and thermodynamic parameters influenced by the counter ion of the macrocycle. NMR diffusion experiments showed that although a fraction of the counter ions are expelled from the host cavity by exchange with the guest, a complex with both counter ions and the guest inside the pillararene is formed. The results also showed that at higher concentrations of guest in solution, in addition to the inclusion of one guest molecule in the cavity, the pillararene can also form an external complex with a second guest molecule.

  17. Metal-ion effects on the polarization of metal-bound water and infrared vibrational modes of the coordinated metal center of Mycobacterium tuberculosis pyrazinamidase via quantum mechanical calculations.

    PubMed

    Salazar-Salinas, Karim; Baldera-Aguayo, Pedro A; Encomendero-Risco, Jimy J; Orihuela, Melvin; Sheen, Patricia; Seminario, Jorge M; Zimic, Mirko

    2014-08-28

    Mycobacterium tuberculosis pyrazinamidase (PZAse) is a key enzyme to activate the pro-drug pyrazinamide (PZA). PZAse is a metalloenzyme that coordinates in vitro different divalent metal cofactors in the metal coordination site (MCS). Several metals including Co(2+), Mn(2+), and Zn(2+) are able to reactivate the metal-depleted PZAse in vitro. We use quantum mechanical calculations to investigate the Zn(2+), Fe(2+), and Mn(2+) metal cofactor effects on the local MCS structure, metal-ligand or metal-residue binding energy, and charge distribution. Results suggest that the major metal-dependent changes occur in the metal-ligand binding energy and charge distribution. Zn(2+) shows the highest binding energy to the ligands (residues). In addition, Zn(2+) and Mn(2+) within the PZAse MCS highly polarize the O-H bond of coordinated water molecules in comparison with Fe(2+). This suggests that the coordination of Zn(2+) or Mn(2+) to the PZAse protein facilitates the deprotonation of coordinated water to generate a nucleophile for catalysis as in carboxypeptidase A. Because metal ion binding is relevant to enzymatic reaction, identification of the metal binding event is important. The infrared vibrational mode shift of the C═Nε (His) bond from the M. tuberculosis MCS is the best IR probe to metal complexation.

  18. Two-color terahertz interferometer based on the frequency-splitted orthogonal polarization modes of the water vapor laser and designed for measuring the electron density profile in the L-2M stellarator

    SciTech Connect

    Letunov, A. A.; Logvinenko, V. P.; Zav'yalov, V. V.

    2008-03-15

    An upgraded diagnostics for measuring the electron density profile in the L-2M stellarator is proposed. The existing diagnostics employs an interferometer based on an HCN laser with a mechanical frequency shifter and unmagnetized InSb detectors cooled with liquid helium. It is proposed to replace the HCN laser with a water vapor laser operating simultaneously at two wavelengths (220 and 118 {mu}m). Being equipped with an anisotropic exit mirror, the water vapor laser allows the generation of orthogonally polarized, frequency-splitted modes at each of these wavelengths with a frequency difference of several tens of kilohertzs. Such a scheme makes it possible to get rid of the mechanical frequency shifter. Moreover, simultaneous measurements at two wavelengths allow one to reliably separate the phase increments introduced by the plasma electron component and by variations in the lengths of the interferometer arms. To take full advantage of this scheme, specially developed cryogenic receivers consisting of Ge and InSb photodetectors placed one after another will be used. To increase the response of the system near {lambda} = 220 {mu}m, the InSb detector is placed in a Almost-Equal-To 0.55-T magnetic field.

  19. Metal-Ion Effects on the Polarization of Metal-Bound Water and Infrared Vibrational Modes of the Coordinated Metal Center of Mycobacterium tuberculosis Pyrazinamidase via Quantum Mechanical Calculations

    PubMed Central

    2014-01-01

    Mycobacterium tuberculosis pyrazinamidase (PZAse) is a key enzyme to activate the pro-drug pyrazinamide (PZA). PZAse is a metalloenzyme that coordinates in vitro different divalent metal cofactors in the metal coordination site (MCS). Several metals including Co2+, Mn2+, and Zn2+ are able to reactivate the metal-depleted PZAse in vitro. We use quantum mechanical calculations to investigate the Zn2+, Fe2+, and Mn2+ metal cofactor effects on the local MCS structure, metal–ligand or metal–residue binding energy, and charge distribution. Results suggest that the major metal-dependent changes occur in the metal–ligand binding energy and charge distribution. Zn2+ shows the highest binding energy to the ligands (residues). In addition, Zn2+ and Mn2+ within the PZAse MCS highly polarize the O–H bond of coordinated water molecules in comparison with Fe2+. This suggests that the coordination of Zn2+ or Mn2+ to the PZAse protein facilitates the deprotonation of coordinated water to generate a nucleophile for catalysis as in carboxypeptidase A. Because metal ion binding is relevant to enzymatic reaction, identification of the metal binding event is important. The infrared vibrational mode shift of the C=Nε (His) bond from the M. tuberculosis MCS is the best IR probe to metal complexation. PMID:25055049

  20. Evidence for Two Modes of Water Release in Comet 103P/Hartley 2: Distributions of Column Density, Rotational Temperature, and Ortho-Para Ratio

    NASA Astrophysics Data System (ADS)

    Bonev, Boncho; Villanueva, G. L.; Paganini, L.; DiSanti, M. A.; Gibb, E. L.; Keane, J. V.; Meech, K. J.; Combi, M. R.; Mumma, M. J.

    2012-10-01

    We acquired high-resolution near-infrared spectra of H2O emission from comet 103P/Hartley-2 using NIRSPEC at Keck 2. Long-slit spectroscopy can directly probe the inner comae of comets via spectrally and spatially resolved measurements. This capability strengthens the quantitative view of conditions within the closest 200 km from the cometary nucleus, thereby providing direct constraints for models of density and temperature distributions in this collisionally dominated region of the coma. The near-Earth approach of comet 103P/Hartley 2 in 2010 presented an especially interesting opportunity to investigate the near-nucleus region of an active comet with substantial extended (vs. nuclear) release of water. We present spatially resolved measurements of rotational temperature and column density and discuss insights into the nature of volatile release. We also present spatially resolved measurements of the H2O ortho-para ratio (OPR). We compare these measurements with OPRs retrieved by various techniques during the 1998 and 2010 apparitions. We gratefully acknowledge support by the NSF Astronomy and Astrophysics Research Grants Program (PI/co-PI Bonev/Gibb), by the NASA Astrobiology Institute (PI: Meech, PI: Mumma), by the NASA Postdoctoral Program (Fellow: Paganini), and by NASA's Planetary Astronomy (PI: DiSanti; PI: Mumma; PI: Villanueva), Planetary Atmospheres (PI: Combi; PI: DiSanti; PI: Villanueva), and Discovery (PI: Meech) Programs. NOAO (through the Telescope System Instrumentation Program funded by NSF) and the University of Hawaii granted Keck-2 telescope time for this investigation.

  1. Evidence for two modes of water release in Comet 103P/Hartley 2: Distributions of column density, rotational temperature, and ortho-para ratio

    NASA Astrophysics Data System (ADS)

    Bonev, Boncho P.; Villanueva, Geronimo L.; Paganini, Lucas; DiSanti, Michael A.; Gibb, Erika L.; Keane, Jacqueline V.; Meech, Karen J.; Mumma, Michael J.

    2013-02-01

    This paper presents long-slit spectra of H2O emission from the inner coma of Comet 103P/Hartley 2, acquired with NIRSPEC/Keck 2 during the comet's close approach to Earth in 2010. On UT 19.6 October 2010 the slit was oriented nearly orthogonal to the projected (in the plane of the sky) Sun-comet line, and the H2O rotational temperature and column density showed similar spatial distributions as a function of projected distance from the nucleus. On UT 22.5 October, the slit was oriented along the Sun-comet line, and the rotational temperatures revealed pronounced asymmetry while the column densities were nearly symmetric about the nucleus. We suggest this dichotomy reflects two qualitatively different mechanisms of volatile release, which introduce distinct rotational distributions in the sublimated material. Future modeling can test this hypothesis. We also report new retrievals of water nuclear spin species (ortho, para) in this comet, and we present the ortho-to-para ratio (OPR) for various projected nucleocentric distances. Our most precise individual measurement is OPR = 2.59 ± 0.13, corresponding to a nuclear spin temperature (Tspin) of 31 ± 3 K. A weighted mean of five independent measurements provides OPR = 2.79 ± 0.13 (T=37-4+8K). Hartley 2 is the first comet for which the OPR has been measured in multiple apparitions. Our values (in 2010) are in good agreement with those obtained two apparitions earlier by the Infrared Space Observatory. Since the comet lost a substantial amount of material between 1998 and 2010, we see no evidence for variation of the OPR with depth in the nucleus. Further discussion of the advantages, assumptions, and biases introduced by various approaches when quantifying nuclear spin species (observing techniques, models and model parameters, sources of uncertainty) would likely aid in interpreting the OPRs measured in cometary volatiles.

  2. Ultrasound-assisted dispersive liquid-liquid microextraction combined with gas chromatography-mass spectrometry in negative chemical ionization mode for the determination of polybrominated diphenyl ethers in water.

    PubMed

    Zhang, Qian; Liang, Tao; Guan, Lili

    2013-04-01

    A simple and economical method for the determination of eight polybrominated diphenyl ethers (BDE-28, 47, 99, 100,153,154,183, and 209) in water was developed. This method involves the use of ultrasound-assisted dispersive liquid-liquid microextraction combined with GC-MS in negative chemical ionization mode. Various parameters affecting the extraction efficiency, including the type and volume of extraction and dispersive solvents, salt concentration, extraction time, and ultrasonic time, were investigated. A volume of 1.0 mL of acetone (dispersive solvent) containing 10 μL tetrachloroethylene (extraction solvent) was injected into 5.0 mL of water samples and then emulsified by ultrasound for 2.0 min to produce the cloudy solution. Under the optimal condition, the enrichment factors for the eight PBDEs were varied from 845- to 1050-folds. Good linearity was observed in the range of 1.0-200 ng L(-1) for BDE-28, 47, 99, and 100; 5.0-200 ng L(-1) for BDE-153, 154, and 183; and 5.0-500 ng L(-1) for BDE-209. The RSD values were in the range of 2.5-8.4% (n = 5) and the LODs ranged from 0.40 to 2.15 ng L(-1) (S/N = 3). The developed method was applied for the determination of eight BPDEs in the river and lake water samples, and the mean recoveries at spiking levels of 5.0 and 50.0 ng L(-1) were in the range of 70.6-105.1%.

  3. Large mode radius resonators

    NASA Technical Reports Server (NTRS)

    Harris, Michael R.

    1987-01-01

    Resonator configurations permitting operation with large mode radius while maintaining good transverse mode discrimination are considered. Stable resonators incorporating an intracavity telescope and unstable resonator geometries utilizing an output coupler with a Gaussian reflectivity profile are shown to enable large radius single mode laser operation. Results of heterodyne studies of pulsed CO2 lasers with large (11mm e sup-2 radius) fundamental mode sizes are presented demonstrating minimal frequency sweeping in accordance with the theory of laser-induced medium perturbations.

  4. Few-mode fibers for mode division multiplexing transmission

    NASA Astrophysics Data System (ADS)

    Kubota, Hirokazu; Morioka, Toshio

    2012-01-01

    A study is presented of the fiber properties needed to achieve 10-mode multiplexing transmission. A combination of MIMO processing with optical LP mode separation is proposed to prevent the need for massive MIMO computation. The impact of mode crosstalk, differential mode delay, and the mode dependent loss of the few-mode fibers on mode multiplexing are discussed.

  5. Integrated mode converter for mode division multiplexing

    NASA Astrophysics Data System (ADS)

    Perez-Galacho, Diego; Alonso-Ramos, Carlos Alberto; Marris-Morini, Delphine; Vakarin, Vladyslav; Le Roux, Xavier; Ortega-Moñux, Alejandro; Wangüemert-Perez, Juan Gonzalo; Vivien, Laurent

    2016-05-01

    The ever growing demands of bandwidth in optical communication systems are making traditional Wavelength Division Multiplexing (WDM) based systems to reach its limit. In order to cope with future bandwidth demand is necessary to use new levels of orthogonality, such as the waveguide mode or the polarization state. Mode Division Multiplexing (MDM) has recently attracted attention as a possible solution to increase aggregate bandwidth. In this work we discuss the proposition a of mode converter that can cover the whole C-Band of optical communications. The Mode Converter is based on two Multimode Interference (MMI) couplers and a phase shifter. Insertion loss (IL) below 0.2 dB and Extinction ratio (ER) higher than 20 dB in a broad bandwidth range of 1.5 μm to 1.6 μm have been estimated. The total length of the device is less than 30 μm.

  6. Free-living and particle-associated prokaryote metabolism in giant kelp forests: Implications for carbon flux in a sub-Antarctic coastal area

    NASA Astrophysics Data System (ADS)

    Schapira, Mathilde; McQuaid, Christopher D.; Froneman, Pierre W.

    2012-06-01

    Extensive beds of large subtidal kelps are characteristic of many temperate and subpolar coastlines. They provide habitats for a wide range of other species and are sites of high primary production that generate large quantities of water-borne particles and dissolved organic compounds that support distinctive communities of prokaryotes. We measured prokaryotic metabolism along transects from the shore to the outside of three giant kelp forests (Macrocystis pyrifera) located in the shelf waters of the Prince Edward Islands (Southern Ocean). Abundance, heterotrophic production (PHP), respiration rates (R-ETS) and growth efficiencies (PGE) were investigated within the particle-associated (PA) and the free-living (FL) communities. Temperature, salinity and inorganic nutrient concentrations indicated distinct hydrological differences among the kelp forests that were related to different levels of freshwater input through island run-off. In contrast, detritus and particulate organic matter concentrations showed a common pattern, decreasing from the near-shore to offshore at all sampling sites, suggesting the retention of organically enriched water masses inshore of the kelp forests. While FL and PA abundances did not differ significantly along transects, FL and PA-PHP and PGE all varied significantly across the kelp forests, following the same pattern across each forest. PA-PGE was significantly higher than FL-PGE in the near-shore waters and farther offshore, while FL-PGE was higher or equal to PA-PGE inside the kelp. This shift can be interpreted in terms of gradients in both the age and origins of organic material across the kelp forests. Higher PA-PGE implies that a larger fraction of organic carbon on colonized particles is converted into prokaryotic biomass and so becomes available to higher trophic levels inshore and offshore of M. pyrifera forests than inside the kelp bed. In contrast, low PA-PGE suggests that a large quantity of carbon passes through the PA

  7. Microbe biogeography tracks water masses in a dynamic oceanic frontal system.

    PubMed

    Djurhuus, Anni; Boersch-Supan, Philipp H; Mikalsen, Svein-Ole; Rogers, Alex D

    2017-03-01

    Dispersal limitation, not just environmental selection, plays an important role in microbial biogeography. The distance-decay relationship is thought to be weak in habitats where dispersal is high, such as in the pelagic environment, where ocean currents facilitate microbial dispersal. Most studies of microbial community composition to date have observed little geographical heterogeneity on a regional scale (100 km). We present a study of microbial communities across a dynamic frontal zone in the southwest Indian Ocean and investigate the spatial structure of the microbes with respect to the different water masses separated by these fronts. We collected 153 samples of free-living microorganisms from five seamounts located along a gradient from subtropical to subantarctic waters and across three depth layers: (i) the sub-surface chlorophyll maximum (approx. 40 m), (ii) the bottom of the euphotic zone (approx. 200 m), and (iii) the benthic boundary layer (300-2000 m). Diversity and abundance of microbial operational taxonomic units (OTUs) were assessed by amplification and sequencing of the 16S rRNA gene on an Illumina MiSeq platform. Multivariate analyses showed that microbial communities were structured more strongly by depth than by latitude, with similar phyla occurring within each depth stratum across seamounts. The deep layer was homogeneous across the entire survey area, corresponding to the spread of Antarctic intermediate water. However, within both the sub-surface layer and the intermediate depth stratum there was evidence for OTU turnover across fronts. The microbiome of these layers appears to be divided into three distinct biological regimes corresponding to the subantarctic surface water, the convergence zone and subtropical. We show that microbial biogeography across depth and latitudinal gradients is linked to the water masses the microbes persist in, resulting in regional patterns of microbial biogeography that correspond to the regional

  8. Microbe biogeography tracks water masses in a dynamic oceanic frontal system

    PubMed Central

    Mikalsen, Svein-Ole; Rogers, Alex D.

    2017-01-01

    Dispersal limitation, not just environmental selection, plays an important role in microbial biogeography. The distance–decay relationship is thought to be weak in habitats where dispersal is high, such as in the pelagic environment, where ocean currents facilitate microbial dispersal. Most studies of microbial community composition to date have observed little geographical heterogeneity on a regional scale (100 km). We present a study of microbial communities across a dynamic frontal zone in the southwest Indian Ocean and investigate the spatial structure of the microbes with respect to the different water masses separated by these fronts. We collected 153 samples of free-living microorganisms from five seamounts located along a gradient from subtropical to subantarctic waters and across three depth layers: (i) the sub-surface chlorophyll maximum (approx. 40 m), (ii) the bottom of the euphotic zone (approx. 200 m), and (iii) the benthic boundary layer (300–2000 m). Diversity and abundance of microbial operational taxonomic units (OTUs) were assessed by amplification and sequencing of the 16S rRNA gene on an Illumina MiSeq platform. Multivariate analyses showed that microbial communities were structured more strongly by depth than by latitude, with similar phyla occurring within each depth stratum across seamounts. The deep layer was homogeneous across the entire survey area, corresponding to the spread of Antarctic intermediate water. However, within both the sub-surface layer and the intermediate depth stratum there was evidence for OTU turnover across fronts. The microbiome of these layers appears to be divided into three distinct biological regimes corresponding to the subantarctic surface water, the convergence zone and subtropical. We show that microbial biogeography across depth and latitudinal gradients is linked to the water masses the microbes persist in, resulting in regional patterns of microbial biogeography that correspond to the regional

  9. Modes of log gravity

    SciTech Connect

    Bergshoeff, Eric A.; Rosseel, Jan; Hohm, Olaf; Townsend, Paul K.

    2011-05-15

    The physical modes of a recently proposed D-dimensional 'critical gravity', linearized about its anti-de Sitter vacuum, are investigated. All 'log mode' solutions, which we categorize as 'spin-2' or 'Proca', arise as limits of the massive spin-2 modes of the noncritical theory. The linearized Einstein tensor of a spin-2 log mode is itself a 'nongauge' solution of the linearized Einstein equations whereas the linearized Einstein tensor of a Proca mode takes the form of a linearized general coordinate transformation. Our results suggest the existence of a holographically dual logarithmic conformal field theory.

  10. Comparison of the effects of hexavalent chromium in the alimentary canal of F344 rats and B6C3F1 mice following exposure in drinking water: implications for carcinogenic modes of action.

    PubMed

    Thompson, Chad M; Proctor, Deborah M; Suh, Mina; Haws, Laurie C; Hébert, Charles D; Mann, Jill F; Shertzer, Howard G; Hixon, J Gregory; Harris, Mark A

    2012-01-01

    Exposure to high concentrations of hexavalent chromium (Cr[VI]) in drinking water is reported to induce oral mucosa tumors in F344 rats and intestinal tumors in B6C3F1 mice. To investigate the modes of action underlying these tumors, 90-day drinking water studies (with interim necropsy at day 8) were conducted with concentrations of 0.1-182 mg/l Cr(VI), administered as 0.3-520 mg/l sodium dichromate dihydrate. Blood and tissue samples were analyzed for chromium content, oxidative stress, iron levels, and gross and microscopic lesions. Results for the F344 rats are described herein and compared with results from B6C3F1 mice published previously. After 90 days of exposure, total chromium concentrations in the rat and mouse oral mucosae were comparable, yet significant dose-dependent decreases in the reduced-to-oxidized glutathione ratio (GSH/GSSG) were observed only in rats. In the duodenum, changes in GSH/GSSG were only observed in mice. Levels of 8-hydroxydeoxyguanosine were not increased in the oral or duodenal mucosae of either species. Glutathione levels were increased in the duodenum but decreased in the jejunum of both species, indicating potential differential responses in the intestinal segments. Histiocytic infiltration was observed in the duodenum of both species, yet duodenal cytokines were repressed in mice but increased in rats. Serum and bone marrow iron levels were more decreased in rats than mice. Collectively, these data suggest that Cr(VI)-induced carcinogenesis in the rodent alimentary canal involves oxidative stress; however, differences in histopathology, cytokines, and iron status suggest potential contributions from other factors as well.

  11. Comparison of the Effects of Hexavalent Chromium in the Alimentary Canal of F344 Rats and B6C3F1 Mice Following Exposure in Drinking Water: Implications for Carcinogenic Modes of Action

    PubMed Central

    Thompson, Chad M.; Proctor, Deborah M.; Suh, Mina; Haws, Laurie C.; Hébert, Charles D.; Mann, Jill F.; Shertzer, Howard G.; Hixon, J. Gregory; Harris, Mark A.

    2012-01-01

    Exposure to high concentrations of hexavalent chromium (Cr[VI]) in drinking water is reported to induce oral mucosa tumors in F344 rats and intestinal tumors in B6C3F1 mice. To investigate the modes of action underlying these tumors, 90-day drinking water studies (with interim necropsy at day 8) were conducted with concentrations of 0.1–182 mg/l Cr(VI), administered as 0.3–520 mg/l sodium dichromate dihydrate. Blood and tissue samples were analyzed for chromium content, oxidative stress, iron levels, and gross and microscopic lesions. Results for the F344 rats are described herein and compared with results from B6C3F1 mice published previously. After 90 days of exposure, total chromium concentrations in the rat and mouse oral mucosae were comparable, yet significant dose-dependent decreases in the reduced-to-oxidized glutathione ratio (GSH/GSSG) were observed only in rats. In the duodenum, changes in GSH/GSSG were only observed in mice. Levels of 8-hydroxydeoxyguanosine were not increased in the oral or duodenal mucosae of either species. Glutathione levels were increased in the duodenum but decreased in the jejunum of both species, indicating potential differential responses in the intestinal segments. Histiocytic infiltration was observed in the duodenum of both species, yet duodenal cytokines were repressed in mice but increased in rats. Serum and bone marrow iron levels were more decreased in rats than mice. Collectively, these data suggest that Cr(VI)-induced carcinogenesis in the rodent alimentary canal involves oxidative stress; however, differences in histopathology, cytokines, and iron status suggest potential contributions from other factors as well. PMID:22011396

  12. Tuning vibrational mode localization with frequency windowing

    NASA Astrophysics Data System (ADS)

    Cheng, Xiaolu; Talbot, Justin J.; Steele, Ryan P.

    2016-09-01

    Local-mode coordinates have previously been shown to be an effective starting point for anharmonic vibrational spectroscopy calculations. This general approach borrows techniques from localized-orbital machinery in electronic structure theory and generates a new set of spatially localized vibrational modes. These modes exhibit a well-behaved spatial decay of anharmonic mode couplings, which, in turn, allows for a systematic, a priori truncation of couplings and increased computational efficiency. Fully localized modes, however, have been found to lead to unintuitive mixtures of characteristic motions, such as stretches and bends, and accordingly large bilinear couplings. In this work, a very simple, tunable localization frequency window is introduced, in order to realize the transition from normal modes to fully localized modes. Partial localization can be achieved by localizing only pairs of modes within this traveling frequency window, which allows for intuitive interpretation of modes. The optimal window size is suggested to be a few hundreds of wave numbers, based on small- to medium-sized test systems, including water clusters and polypeptides. The new sets of partially localized coordinates retain their spatial coupling decay behavior while providing a reduced number of potential energy evaluations for convergence of anharmonic spectra.

  13. Streaming tearing mode

    NASA Technical Reports Server (NTRS)

    Shigeta, M.; Sato, T.; Dasgupta, B.

    1985-01-01

    The magnetohydrodynamic stability of streaming tearing mode is investigated numerically. A bulk plasma flow parallel to the antiparallel magnetic field lines and localized in the neutral sheet excites a streaming tearing mode more strongly than the usual tearing mode, particularly for the wavelength of the order of the neutral sheet width (or smaller), which is stable for the usual tearing mode. Interestingly, examination of the eigenfunctions of the velocity perturbation and the magnetic field perturbation indicates that the streaming tearing mode carries more energy in terms of the kinetic energy rather than the magnetic energy. This suggests that the streaming tearing mode instability can be a more feasible mechanism of plasma acceleration than the usual tearing mode instability.

  14. Deep Water Ambient Noise and Mode Processing

    DTIC Science & Technology

    2014-09-30

    tomography sources. In 2009 the DVLA also recorded segments of ambient sound during time periods when the tomography sources were not transmitting. In our... designed to null out the largest interferers, 1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Report...Measurements of the vertical structure of ocean noise are important for understanding noise generation and propagation and for designing sonar signal

  15. [Soil and water losses and phosphorus output at the places between ridges in sloping peanut land under different planting modes in Yimeng mountainous area of Shandong Province, East China].

    PubMed

    Li, Jian-Hua; Yu, Xing-Xiu; Liu, Qian-Jin; Wu, Yuan-Zhi

    2012-12-01

    Taking the typical land use type, sloping Arachis hypogaea land, in Yimeng mountainous area of Shandong as study object, an in-situ fixed-point field experiment was conducted to study the characteristics of soil and water losses and phosphorus output at the places between ridges in the sloping land under different planting modes (Arachis hypogaea + Cynodon dactylon, I; A. hypogae + Melilotus officinalis, II; A. hypogaea + Lolium multiflorum, III; A. hypogaea + Trifolium repens, IV; A. hypogaea + blank control, V). Planting grasses at the places between ridges could effectively decrease the soil and water losses. The runoff was 55.1%-61.3% of the control, and decreased in the order of II > I > IV> III. The sediment loss was 3.4% -32.3% of the control, and decreased in the order of IV > II > I > 11. A. hypogaea + L. multiflorum was effective in storing water and retaining sediment. During the early period of planting L. multiflorum, the sediment loss was more affected by rainfall and presented a fluctuated variation, but in late period, the sediment loss decreased continuously and performed more stable, and accordingly, the sediment retention increased continuously. Planting grasses effectively decreased the output of phosphorus, with the decrease of total phosphorus (TP) output being 52.8%-75.3% of the control, and was in the order of I > II > IV > III. As compared with the control, planting grasses decreased 27.5% -67.0% of the output of particle phosphorus (PP), but relatively increased the output of dissolvable phosphorus (DP). A. hypogaea + L. multiflorum had the best effect in decreasing the output of phosphorus, with the outputs of TP and PP being 58.4% and 27.5% of the control, respectively. In the growth period of the vegetations, the losses of different phosphorus forms differed, and the dissolvable inorganic phosphorus was the main form of the output of DP during whole rain season. After the peanut harvested, the output of different phosphorus forms in the

  16. Single-Mode VCSELs

    NASA Astrophysics Data System (ADS)

    Larsson, Anders; Gustavsson, Johan S.

    The only active transverse mode in a truly single-mode VCSEL is the fundamental mode with a near Gaussian field distribution. A single-mode VCSEL produces a light beam of higher spectral purity, higher degree of coherence and lower divergence than a multimode VCSEL and the beam can be more precisely shaped and focused to a smaller spot. Such beam properties are required in many applications. In this chapter, after discussing applications of single-mode VCSELs, we introduce the basics of fields and modes in VCSELs and review designs implemented for single-mode emission from VCSELs in different materials and at different wavelengths. This includes VCSELs that are inherently single-mode as well as inherently multimode VCSELs where higher-order modes are suppressed by mode selective gain or loss. In each case we present the current state-of-the-art and discuss pros and cons. At the end, a specific example with experimental results is provided and, as a summary, the most promising designs based on current technologies are identified.

  17. Ordinary electromagnetic mode instability

    NASA Technical Reports Server (NTRS)

    Cheng, C. Z.

    1974-01-01

    The instability of the ordinary electromagnetic mode propagating perpendicular to an external magnetic field is studied for a single-species plasma with ring velocity distribution. The marginal instability boundaries for both the purely growing mode and the propagating growing modes are calculated from the instability criteria. The dispersion characteristics for various sets of plasma parameters are also given. The typical growth rates are of the order of the cyclotron frequency.

  18. Dual-Mode Combustor

    NASA Technical Reports Server (NTRS)

    Trefny, Charles J (Inventor); Dippold, Vance F (Inventor)

    2013-01-01

    A new dual-mode ramjet combustor used for operation over a wide flight Mach number range is described. Subsonic combustion mode is usable to lower flight Mach numbers than current dual-mode scramjets. High speed mode is characterized by supersonic combustion in a free-jet that traverses the subsonic combustion chamber to a variable nozzle throat. Although a variable combustor exit aperture is required, the need for fuel staging to accommodate the combustion process is eliminated. Local heating from shock-boundary-layer interactions on combustor walls is also eliminated.

  19. Asymmetric Bessel modes.

    PubMed

    Kotlyar, V V; Kovalev, A A; Soifer, V A

    2014-04-15

    We propose a new, three-parameter family of diffraction-free asymmetric elegant Bessel modes (aB-modes) with an integer and fractional orbital angular momentum (OAM). The aB-modes are described by the nth-order Bessel function of the first kind with complex argument. The asymmetry degree of the nonparaxial aB-mode is shown to depend on a real parameter c≥0: when c=0, the aB-mode is identical to a conventional radially symmetric Bessel mode; with increasing c, the aB-mode starts to acquire a crescent form, getting stretched along the vertical axis and shifted along the horizontal axis for c≫1. On the horizontal axis, the aB-modes have a denumerable number of isolated intensity zeros that generate optical vortices with a unit topological charge of opposite sign on opposite sides of 0. At different values of the parameter c, the intensity zeros change their location on the horizontal axis, thus changing the beam's OAM. An isolated intensity zero on the optical axis generates an optical vortex with topological charge n. The OAM per photon of an aB-mode depends near-linearly on c, being equal to ℏ(n+cI1(2c)/I0(2c)), where ℏ is the Planck constant and In(x) is a modified Bessel function.

  20. SAMPEX special pointing mode

    NASA Technical Reports Server (NTRS)

    Markley, F. Landis; Flatley, Thomas W.; Leoutsakos, Theodore

    1995-01-01

    A new pointing mode has been developed for the Solar, Anomalous, and Magnetospheric Particle Explorer (SAMPEX) spacecraft. This pointing mode orients the instrument boresights perpendicular to the field lines of the Earth's magnetic field in regions of low field strength and parallel to the field lines in regions of high field strength, to allow better characterization of heavy ions trapped by the field. The new mode uses magnetometer signals and is algorithmically simpler than the previous control mode, but it requires increased momentum wheel activity. It was conceived, designed, tested, coded, uplinked to the spacecraft, and activated in less than seven months.

  1. Seasonal characteristics of size-fractionated phytoplankton community and fate of photosynthesized carbon in a sub-Antarctic area (Straits of Magellan)

    NASA Astrophysics Data System (ADS)

    Decembrini, Franco; Bergamasco, Alessandro; Mangoni, Olga

    2014-08-01

    Phytoplankton community size drives the rates of biogenic carbon and the overall structure and dynamics of the marine pelagic food web. The Straits of Magellan, an inland passage between the Pacific and Atlantic Oceans, can be separated into three main sub-basins: the western-Pacific, the V-shaped central zone, and the eastern-Atlantic. To provide insights into the food structure of the phytoplankton community, size-fractionated chlorophyll a concentration and primary production rates were measured across the three sectors of the Magellan Straits in four periods between 1989 and 1995 in the Straits. Phytoplanktonic biomass and production ratios provided ecological insights into the food web structure, including the relevance of grazing in its largest fraction. The micro-phytoplanktonic fraction (> 10 μm) in the Pacific sub-basin is significantly less abundant than in the Central and Atlantic ones. Conversely, the lowest abundance of the pico-fraction (< 2.0 μm) is encountered in the Atlantic sub-basin. The observed patterns agree with the diffusion of smaller-size fractions from the western towards the easternmost sector of the Straits, and suggest that the largest phytoplankton tend to accumulate in the inner stretch of the Straits, being constrained by a clockwise gyre generated by tidal phases or partially spilling out into the Atlantic sector. The most active grazing activities occur in the Central sub-basin during the spring bloom and appear even stronger in summer. Our results pinpoint also that the basic levels of the planktonic food web rely on the nanophytoplankton (10-2 μm) fraction, which is the main contributor to the continuum multivorous food web. When external energy (e.g. nutrient pulses from land freshwater and water mixing) enters the system, the structure of the plankton in the Straits shifts towards the herbivorous food web and is characterized by the presence of large-size diatoms. This dynamics keeps the system in a persistent mesotrophic

  2. Difference in dose-volumetric data between the analytical anisotropic algorithm, the dose-to-medium, and the dose-to-water reporting modes of the Acuros XB for lung stereotactic body radiation therapy.

    PubMed

    Mampuya, Wambaka A; Nakamura, Mitsuhiro; Hirose, Yoshinori; Kitsuda, Kenji; Ishigaki, Takashi; Mizowaki, Takashi; Hiraoka, Masahiro

    2016-09-08

    The purpose of this study was to evaluate the difference in dose-volumetric data between the analytical anisotropic algorithms (AAA) and the two dose reporting modes of the Acuros XB, namely, the dose to water (AXB_Dw) and dose to medium (AXB_Dm) in lung stereotactic body radiotherapy (SBRT). Thirty-eight plans were generated using the AXB_Dm in Eclipse Treatment Planning System (TPS) and then recalculated with the AXB_Dw and AAA, using identical beam setup. A dose of 50 Gy in 4 fractions was prescribed to the isocenter and the planning target volume (PTV) D95%. The isocenter was always inside the PTV. The following dose-volumetric parameters were evaluated; D2%, D50%, D95%, and D98% for the internal target volume (ITV) and the PTV. Two-tailed paired Student's t-tests determined the statistical significance. Although for most of the parameters evaluated, the mean differences observed between the AAA, AXB_Dm, and AXB_Dw were statistically significant (p < 0.05), absolute differences were rather small, in general less than 5% points. The maximum mean difference was observed in the ITV D50% between the AXB_Dm and the AAA and was 1.7% points under the isocenter prescription and 3.3% points under the D95 prescription. AXB_Dm produced higher values than AXB_Dw with differences ranging from 0.4 to 1.1% points under isocenter prescription and 0.0 to 0.7% points under the PTV D95% prescription. The differences observed under the PTV D95% prescription were larger compared to those observed for the isocenter prescription between AXB_Dm and AAA, AXB_Dm and AXB_Dw, and AXB_Dw and AAA. Although statistically significant, the mean differences between the three algorithms are within 3.3% points.

  3. Tearing Modes in Tokamaks

    SciTech Connect

    White, R. B.

    2008-05-14

    This lecture gives a basic introduction to magnetic pound elds, magnetic surface destruction, toroidal equilibrium and tearing modes in a tokamak, including the linear and nonlinear development of these modes and their modi pound cation by current drive and bootstrap current, and sawtooth oscillations and disruptions.

  4. Mode decomposition evolution equations

    PubMed Central

    Wang, Yang; Wei, Guo-Wei; Yang, Siyang

    2011-01-01

    Partial differential equation (PDE) based methods have become some of the most powerful tools for exploring the fundamental problems in signal processing, image processing, computer vision, machine vision and artificial intelligence in the past two decades. The advantages of PDE based approaches are that they can be made fully automatic, robust for the analysis of images, videos and high dimensional data. A fundamental question is whether one can use PDEs to perform all the basic tasks in the image processing. If one can devise PDEs to perform full-scale mode decomposition for signals and images, the modes thus generated would be very useful for secondary processing to meet the needs in various types of signal and image processing. Despite of great progress in PDE based image analysis in the past two decades, the basic roles of PDEs in image/signal analysis are only limited to PDE based low-pass filters, and their applications to noise removal, edge detection, segmentation, etc. At present, it is not clear how to construct PDE based methods for full-scale mode decomposition. The above-mentioned limitation of most current PDE based image/signal processing methods is addressed in the proposed work, in which we introduce a family of mode decomposition evolution equations (MoDEEs) for a vast variety of applications. The MoDEEs are constructed as an extension of a PDE based high-pass filter (Europhys. Lett., 59(6): 814, 2002) by using arbitrarily high order PDE based low-pass filters introduced by Wei (IEEE Signal Process. Lett., 6(7): 165, 1999). The use of arbitrarily high order PDEs is essential to the frequency localization in the mode decomposition. Similar to the wavelet transform, the present MoDEEs have a controllable time-frequency localization and allow a perfect reconstruction of the original function. Therefore, the MoDEE operation is also called a PDE transform. However, modes generated from the present approach are in the spatial or time domain and can be

  5. Mode decomposition evolution equations.

    PubMed

    Wang, Yang; Wei, Guo-Wei; Yang, Siyang

    2012-03-01

    Partial differential equation (PDE) based methods have become some of the most powerful tools for exploring the fundamental problems in signal processing, image processing, computer vision, machine vision and artificial intelligence in the past two decades. The advantages of PDE based approaches are that they can be made fully automatic, robust for the analysis of images, videos and high dimensional data. A fundamental question is whether one can use PDEs to perform all the basic tasks in the image processing. If one can devise PDEs to perform full-scale mode decomposition for signals and images, the modes thus generated would be very useful for secondary processing to meet the needs in various types of signal and image processing. Despite of great progress in PDE based image analysis in the past two decades, the basic roles of PDEs in image/signal analysis are only limited to PDE based low-pass filters, and their applications to noise removal, edge detection, segmentation, etc. At present, it is not clear how to construct PDE based methods for full-scale mode decomposition. The above-mentioned limitation of most current PDE based image/signal processing methods is addressed in the proposed work, in which we introduce a family of mode decomposition evolution equations (MoDEEs) for a vast variety of applications. The MoDEEs are constructed as an extension of a PDE based high-pass filter (Europhys. Lett., 59(6): 814, 2002) by using arbitrarily high order PDE based low-pass filters introduced by Wei (IEEE Signal Process. Lett., 6(7): 165, 1999). The use of arbitrarily high order PDEs is essential to the frequency localization in the mode decomposition. Similar to the wavelet transform, the present MoDEEs have a controllable time-frequency localization and allow a perfect reconstruction of the original function. Therefore, the MoDEE operation is also called a PDE transform. However, modes generated from the present approach are in the spatial or time domain and can be

  6. Zero-mode waveguides

    DOEpatents

    Levene, Michael J.; Korlach, Jonas; Turner, Stephen W.; Craighead, Harold G.; Webb, Watt W.

    2007-02-20

    The present invention is directed to a method and an apparatus for analysis of an analyte. The method involves providing a zero-mode waveguide which includes a cladding surrounding a core where the cladding is configured to preclude propagation of electromagnetic energy of a frequency less than a cutoff frequency longitudinally through the core of the zero-mode waveguide. The analyte is positioned in the core of the zero-mode waveguide and is then subjected, in the core of the zero-mode waveguide, to activating electromagnetic radiation of a frequency less than the cut-off frequency under conditions effective to permit analysis of the analyte in an effective observation volume which is more compact than if the analysis were carried out in the absence of the zero-mode waveguide.

  7. Excursions through KK modes

    SciTech Connect

    Furuuchi, Kazuyuki

    2016-07-07

    In this article we study Kaluza-Klein (KK) dimensional reduction of massive Abelian gauge theories with charged matter fields on a circle. Since local gauge transformations change position dependence of the charged fields, the decomposition of the charged matter fields into KK modes is gauge dependent. While whole KK mass spectrum is independent of the gauge choice, the mode number depends on the gauge. The masses of the KK modes also depend on the field value of the zero-mode of the extra dimensional component of the gauge field. In particular, one of the KK modes in the KK tower of each massless 5D charged field becomes massless at particular values of the extra-dimensional component of the gauge field. When the extra-dimensional component of the gauge field is identified with the inflaton, this structure leads to recursive cosmological particle productions.

  8. Excursions through KK modes

    NASA Astrophysics Data System (ADS)

    Furuuchi, Kazuyuki

    2016-07-01

    In this article we study Kaluza-Klein (KK) dimensional reduction of massive Abelian gauge theories with charged matter fields on a circle. Since local gauge transformations change position dependence of the charged fields, the decomposition of the charged matter fields into KK modes is gauge dependent. While whole KK mass spectrum is independent of the gauge choice, the mode number depends on the gauge. The masses of the KK modes also depend on the field value of the zero-mode of the extra dimensional component of the gauge field. In particular, one of the KK modes in the KK tower of each massless 5D charged field becomes massless at particular values of the extra-dimensional component of the gauge field. When the extra-dimensional component of the gauge field is identified with the inflaton, this structure leads to recursive cosmological particle productions.

  9. Coupled seismoacoustic modes on the seafloor

    NASA Astrophysics Data System (ADS)

    Butler, Rhett; Lomnitz, Cinna

    2002-05-01

    Wave-to-wave coupling arises when an acoustic pulse selects a Rayleigh mode of the same speed and both travel together swapping energy across an interface [Ewing et al., 1957]. A distinctive signal is observed at the Hawaii-2 Observatory for purely oceanic paths from earthquakes on the Blanco and Mendocino Fracture Zones, off the coast of North America. The signal appears to be a composite of undispersed higher Rayleigh modes propagating along the ocean floor both in the sediments and in the water. The new coupled modes are identified by their frequency composition and their phase and group velocities. Seismoacoustic coupling at the seafloor is conditioned on (a) the presence of a low-velocity interface at the ocean floor, and (b) the wavelength of the Rayleigh component being shorter than the depth of the water layer.

  10. Mode II fatigue crack propagation.

    NASA Technical Reports Server (NTRS)

    Roberts, R.; Kibler, J. J.

    1971-01-01

    Fatigue crack propagation rates were obtained for 2024-T3 bare aluminum plates subjected to in-plane, mode I, extensional loads and transverse, mode II, bending loads. These results were compared to the results of Iida and Kobayashi for in-plane mode I-mode II extensional loads. The engineering significance of mode I-mode II fatigue crack growth is considered in view of the present results. A fatigue crack growth equation for handling mode I-mode II fatigue crack growth rates from existing mode I data is also discussed.

  11. Difference in dose-volumetric data between the analytical anisotropic algorithm, the dose-to-medium, and the dose-to-water reporting modes of the Acuros XB for lung stereotactic body radiation therapy.

    PubMed

    Mampuya, Wambaka A; Nakamura, Mitsuhiro; Hirose, Yoshinori; Ishigaki, Takashi; Mizowaki, Takashi; Hiraoka, Masahiro

    2016-09-01

    The purpose of this study was to evaluate the difference in dose-volumetric data between the analytical anisotropic algorithms (AAA) and the two dose reporting modes of the Acuros XB, namely, the dose to water (AXB-Dw) and dose to medium (AXB-Dm) in lung stereotactic body radiotherapy (SBRT). Thirty-eight plans were generated using the AXB-Dm in Eclipse Treatment Planning System (TPS) and then recalculated with the AXB-Dw and AAA, using identical beam setup. A dose of 50 Gy in 4 fractions was prescribed to the isocenter and the planning target volume (PTV) D95%. The isocenter was always inside the PTV. The following dose-volumetric parameters were evaluated; D2%, D50%, D95%, and D98% for the internal target volume (ITV) and the PTV. Two-tailed paired Student's t-tests determined the statistical significance. Although for most of the parameters evaluated, the mean differences observed between the AAA, AXB-Dmand AXB-Dw were statistically significant (p<0.05), absolute differences were rather small, in general less than 5% points. The maximum mean difference was observed in the ITV D50% between the AXB-Dm and the AAA and was 1.7% points under the isocenter prescription and 3.3% points under the D95 prescription. AXB-Dm produced higher values than AXB-Dw with differences ranging from 0.4 to 1.1% points under isocenter prescription and 0.0 to 0.7% points under the PTV D95% prescription. The differences observed under the PTV D95% prescription were larger compared to those observed for the isocenter prescription between AXB-Dm and AAA, AXB-Dm and AXB-Dw, and AXB-Dw and AAA. Although statistically significant, the mean differences between the three algorithms are within 3.3% points. PACS number(s): 87.55.x, 87.55.D-, 87.55.dk.

  12. Supersymmetric mode converters

    NASA Astrophysics Data System (ADS)

    Heinrich, Matthias; Miri, Mohammad-Ali; Stützer, Simon; Nolte, Stefan; Szameit, Alexander; Christodoulides, Demetrios N.

    2015-08-01

    In recent years, the ever-increasing demand for high-capacity transmission systems has driven remarkable advances in technologies that encode information on an optical signal. Mode-division multiplexing makes use of individual modes supported by an optical waveguide as mutually orthogonal channels. The key requirement in this approach is the capability to selectively populate and extract specific modes. Optical supersymmetry (SUSY) has recently been proposed as a particularly elegant way to resolve this design challenge in a manner that is inherently scalable, and at the same time maintains compatibility with existing multiplexing strategies. Supersymmetric partners of multimode waveguides are characterized by the fact that they share all of their effective indices with the original waveguide. The crucial exception is the fundamental mode, which is absent from the spectrum of the partner waveguide. Here, we demonstrate experimentally how this global phase-matching property can be exploited for efficient mode conversion. Multimode structures and their superpartners are experimentally realized in coupled networks of femtosecond laser-written waveguides, and the corresponding light dynamics are directly observed by means of fluorescence microscopy. We show that SUSY transformations can readily facilitate the removal of the fundamental mode from multimode optical structures. In turn, hierarchical sequences of such SUSY partners naturally implement the conversion between modes of adjacent order. Our experiments illustrate just one of the many possibilities of how SUSY may serve as a building block for integrated mode-division multiplexing arrangements. Supersymmetric notions may enrich and expand integrated photonics by versatile optical components and desirable, yet previously unattainable, functionalities.

  13. Mode Gaussian beam tracing

    NASA Astrophysics Data System (ADS)

    Trofimov, M. Yu.; Zakharenko, A. D.; Kozitskiy, S. B.

    2016-10-01

    A mode parabolic equation in the ray centered coordinates for 3D underwater sound propagation is developed. The Gaussian beam tracing in this case is constructed. The test calculations are carried out for the ASA wedge benchmark and proved an excellent agreement with the source images method in the case of cross-slope propagation. But in the cases of wave propagation at some angles to the cross-slope direction an account of mode interaction becomes necessary.

  14. First reconstruction of last millennium flooding activity on Kerguelen archipelago (50°S, sub-Antarctic Indian Ocean) from Lake Armor sediment: implications for southern hemisphere cyclonic circulation changes

    NASA Astrophysics Data System (ADS)

    Arnaud, F.; Révillon, S.; Poulenard, J.; Boone, D.; Heirman, K.

    2009-04-01

    Subantarctic Indian Ocean, above 50°S, is one the places in the world where past atmospheric circulation patterns remain completely unknown. This is an important lack in scientific knowledge of past climate changes as this region is one of the key places of the climate machine. In particular, we do not know the impact of Holocene climate variability on extreme south cyclonic circulation. Lake Armor is a fjord-type lake, 98m maximum depth, located on the eastern edge of Kerguelen mainland central plateau. A first reconnaissance survey, including seismic imaging and short cores retrieving, was led here in November 2006. Seismic and bathymetric data reveal the existence of two depocentres submitted to river inputs (Heirman et al., 2007 ; Arnaud et al., 2007). The southern one is submitted to strong underwater currents and is not suited for paleoclimate reconstruction. On the contrary, the northern one exhibits finely stratified Holocene deposits which were cored in the aim of reconstructing the evolution of river floods on Kerguelen archipelago. We led on the retrieved short cores a high resolution sedimentological study, including micro-grainsize, colour, physical properties (Geotek multi-track sensor), and geochemistry (XRF core scanning, major and trace elemental composition, infrared spectrometry). In the case of lake sediments in which detrital inputs are diluted by an autochthonous biogenic fraction, such an approach permits a high resolution reconstruction of flood history (Arnaud et al., 2005; Arnaud, 2005), taking account of both sediment source and river activity evolutions. Using an XRF core scanner, we established high resolution geochemical profiles on a short 14C-dated core, spanning the last 1200 years. We here interpret the Si/Rb ratio as an indicator of biogenic silica abundance, in opposition to Rubidium-bearing detrital inputs. We hence evidenced a series of high and low terrigenous inputs, corresponding to high and low flooding activity

  15. Physically constrained maximum likelihood mode filtering.

    PubMed

    Papp, Joseph C; Preisig, James C; Morozov, Andrey K

    2010-04-01

    Mode filtering is most commonly implemented using the sampled mode shapes or pseudoinverse algorithms. Buck et al. [J. Acoust. Soc. Am. 103, 1813-1824 (1998)] placed these techniques in the context of a broader maximum a posteriori (MAP) framework. However, the MAP algorithm requires that the signal and noise statistics be known a priori. Adaptive array processing algorithms are candidates for improving performance without the need for a priori signal and noise statistics. A variant of the physically constrained, maximum likelihood (PCML) algorithm [A. L. Kraay and A. B. Baggeroer, IEEE Trans. Signal Process. 55, 4048-4063 (2007)] is developed for mode filtering that achieves the same performance as the MAP mode filter yet does not need a priori knowledge of the signal and noise statistics. The central innovation of this adaptive mode filter is that the received signal's sample covariance matrix, as estimated by the algorithm, is constrained to be that which can be physically realized given a modal propagation model and an appropriate noise model. Shallow water simulation results are presented showing the benefit of using the PCML method in adaptive mode filtering.

  16. Arctic Ocean Centennial-Scale Rossby modes

    NASA Astrophysics Data System (ADS)

    Petersen, M.; Hjorth, P.; Schmith, T.

    2009-04-01

    The Arctic Ocean has a characteristic stable stratification with fresh and cold water occupying the upper few hundred meters and with warm and more saline Atlantic waters underneath. These water masses are separated by the cold halocline. The stability of the cold halocline regulates the upward directed turbulent heat flux from the Atlantic water to the Arctic water. Since this heat flux is an important part of the ocean energy budget it is important for the large scale sea ice formation and melting. Due to the sable vertical stratification combined with its almost circular symmetry the Arctic Ocean may support internal Rossby modes. In this study we investigate these modes in a theoretical framework. We apply the free surface two layer model with a linear damping on the sphere and solve this in idealised geometries. We solve this system numerically by a finite difference scheme based on the Arakawa C-grid. We find that solutions to the system have a damping time scale comparable to the propagation time scale, both in the order of a few centuries. Furthermore, this damping time scale is rather independent of the local damping coefficient. For a circular symmetric geometry the amplitude is zero at the boundary. Interestingly, for a more realistic sector-geometry we find finite amplitudes at the borders. We interpret this in the model as anomalies in the halocline height being exported as fresh water anomalies via the Fram Strait where they further south they may modulate deep water formation and strength of the thermohaline circulation.

  17. Pressurized hot water extraction with on-line fluorescence monitoring: a comparison of the static, dynamic, and static-dynamic modes for the removal of polycyclic aromatic hydrocarbons from environmental solid samples.

    PubMed

    Morales-Muñoz, S; Luque-García, J L; Luque de Castro, M D

    2002-08-15

    A comparison of the feasibility of the three operational modes of pressurized hot solvent extraction (PHSE) (namely, static, where a fixed extractant volume is used; dynamic, where the extractant continually flows through the sample; and static-dynamic mode, which consists of a combination of the two previous modes) for the extraction of polycyclic aromatic hydrocarbons (PAHs) from environmental solid samples (such as soil, sediment, trout, and sardine) has been performed. In all cases, a sodium dodecyl sulfate (SDS) aqueous solution was used as leaching agent. The use of a flow injection manifold between the extractor and a molecular fluorescence detector allowed real-time on-line fluorescence monitoring of the PAHs extracted from the samples, thus working as a screening system and providing qualitative and semiquantitative information on the target analytes extracted from both natural and spiked samples. The on-line monitoring option allowed the extraction kinetics to be monitored and the end of the leaching step to be determined independently of the sample matrix, thereby reducing extraction times. Efficiencies close to 100% have been provided by the three modes, which differ in the extraction time required for total removal of the target compounds. The time needed for the dynamic mode was shorter than that for the static mode. However, the establishment of a static extraction step prior to dynamic extraction was the key to shorten the time required for complete extraction. The method has been applied to a certified reference material (CRM 524, BCR, industrial soil/organics) for quality assurance/validation.

  18. Two-mode coupling model in a few mode fiber

    NASA Astrophysics Data System (ADS)

    Kaliteevskiy, N. A.; Korolev, A. E.; Koreshkov, K. S.; Nazarov, V. N.; Sterlingov, P. M.

    2013-06-01

    A phenomenological two-mode coupling model in few mode fibers (FMF) is developed. It uses a mode coupling coefficient and the differential modal delay as the input parameters and the split-step approach. The model is consistent with the experimental results demonstrating distributed mode coupling effects in FMF and may be used for multipath interference estimation based on statistical analysis of fluctuations.

  19. Whispering Bloch modes

    PubMed Central

    Craster, R. V.

    2016-01-01

    We investigate eigenvalue problems for the planar Helmholtz equation in open systems with a high order of rotational symmetry. The resulting solutions have similarities with the whispering gallery modes exploited in photonic micro-resonators and elsewhere, but unlike these do not necessarily require a surrounding material boundary, with confinement instead resulting from the geometry of a series of inclusions arranged in a ring. The corresponding fields exhibit angular quasi-periodicity reminiscent of Bloch waves, and hence we refer to them as whispering Bloch modes (WBMs). We show that if the geometry of the system is slightly perturbed such that the rotational symmetry is broken, modes with asymmetric field patterns can be observed, resulting in field enhancement and other potentially desirable effects. We investigate the WBMs of two specific geometries first using expansion methods and then by applying a two-scale asymptotic scheme. PMID:27493564

  20. Violin plate modes.

    PubMed

    Gough, Colin

    2015-01-01

    As the first step toward developing a generic model for the acoustically radiating vibrational modes of the violin and related instruments, the modes of both freely supported and edge-constrained top and back plates have been investigated as functions of shape, arching height, elastic anisotropy, the f-holes and associated island area, thickness graduations, and the additional boundary constraints of the ribs, soundpost, and bass-bar present in the assembled instrument. Comsol shell structure finite element software has been used as a quasi-experimental tool, with physical and geometric properties varied smoothly, often over several orders of magnitude, allowing the development of the plate modes to be followed continuously from those of an initially square plate to those of doubly-arched, guitar-shaped, orthotropic plates and their dependence on all the above factors.

  1. Whispering-mode waveguide

    NASA Astrophysics Data System (ADS)

    Kurnit, N. A.

    Properties of a relatively new type of waveguide structure of potential use of confining infrared radiation to a small mode volume over long path lengths are reviewed. A single guiding surface with curvature radius rho and band radius R allows propagation of a near-grazing incidence whispering mode of transverse width approximately (lambda square root of rho R/pi) sup 1/2 and radial width approximately 1/2 (sq lambda R)/sup 1/3. For sufficiently large rho, the loss per revolution for TE mode propagation is approximately pi A/sub N/, where A/sub N/ is the normal-incidence reflection loss. Results on a number of prototype structures in general agreement with these considerations are described.

  2. Infernal Fishbone Mode

    SciTech Connect

    Ya.I. Kolesnichenko; V.S. Marchenko; R.B. White

    2003-02-11

    A new kind of fishbone instability associated with circulating energetic ions is predicted. The considered instability is essentially the energetic particle mode; it is characterized by m/n not equal to 1 (m and n are the poloidal and toroidal mode numbers, respectively). The mode is localized inside the flux surface where the safety factor (q) is q* = m/n, its amplitude being maximum near q*. The instability arises in plasmas with small shear inside the q* surface and q(0) > 1. A possibility to explain recent experimental observations of the m = 2 fishbone oscillations accompanied by strong changes of the neutron emission during tangential neutral-beam injection in the National Spherical Torus Experiment [M. Ono, et al., Nucl. Fusion 40 (2000) 557] is shown.

  3. Multi-mode horn

    NASA Technical Reports Server (NTRS)

    Neilson, Jeffrey M. (Inventor)

    2002-01-01

    A horn has an input aperture and an output aperture, and comprises a conductive inner surface formed by rotating a curve about a central axis. The curve comprises a first arc having an input aperture end and a transition end, and a second arc having a transition end and an output aperture end. When rotated about the central axis, the first arc input aperture end forms an input aperture, and the second arc output aperture end forms an output aperture. The curve is then optimized to provide a mode conversion which maximizes the power transfer of input energy to the Gaussian mode at the output aperture.

  4. Study Mode Negotiation.

    ERIC Educational Resources Information Center

    Vasan, Mani Le; Sargunan, Rajeswary

    This paper outlines a model of study mode negotiation between clients and English Language Training providers that has been developed at the University of Malaya, specifically related to English language writing skills as taught to corporate clients. Negotiation is used to reach decisions concerning the goals and methodology of learning to ensure…

  5. Thermodynamics of Radiation Modes

    ERIC Educational Resources Information Center

    Pina, Eduardo; de la Selva, Sara Maria Teresa

    2010-01-01

    We study the equilibrium thermodynamics of the electromagnetic radiation in a cavity of a given volume and temperature. We found three levels of description, the thermodynamics of one mode, the thermodynamics of the distribution of frequencies in a band by summing over the frequencies in it and the global thermodynamics by summing over all the…

  6. Mode conversion in ITER

    NASA Astrophysics Data System (ADS)

    Jaeger, E. F.; Berry, L. A.; Myra, J. R.

    2006-10-01

    Fast magnetosonic waves in the ion cyclotron range of frequencies (ICRF) can convert to much shorter wavelength modes such as ion Bernstein waves (IBW) and ion cyclotron waves (ICW) [1]. These modes are potentially useful for plasma control through the generation of localized currents and sheared flows. As part of the SciDAC Center for Simulation of Wave-Plasma Interactions project, the AORSA global-wave solver [2] has been ported to the new, dual-core Cray XT-3 (Jaguar) at ORNL where it demonstrates excellent scaling with the number of processors. Preliminary calculations using 4096 processors have allowed the first full-wave simulations of mode conversion in ITER. Mode conversion from the fast wave to the ICW is observed in mixtures of deuterium, tritium and helium3 at 53 MHz. The resulting flow velocity and electric field shear will be calculated. [1] F.W. Perkins, Nucl. Fusion 17, 1197 (1977). [2] E.F. Jaeger, L.A. Berry, J.R. Myra, et al., Phys. Rev. Lett. 90, 195001-1 (2003).

  7. Thermodynamics of Radiation Modes

    ERIC Educational Resources Information Center

    Pina, Eduardo; de la Selva, Sara Maria Teresa

    2010-01-01

    We study the equilibrium thermodynamics of the electromagnetic radiation in a cavity of a given volume and temperature. We found three levels of description, the thermodynamics of one mode, the thermodynamics of the distribution of frequencies in a band by summing over the frequencies in it and the global thermodynamics by summing over all the…

  8. Single mode communication link

    NASA Astrophysics Data System (ADS)

    Cole, Stephen R.; Reid, D. C.; Carpenter, R.

    1990-02-01

    Optical fiber transmission has many features which make it very attractive for military applications. Furthermore, single mode fiber is superior to multimode fiber in terms of bandwidth, attenuation, radiation resistance and cost. The benefits of single mode optical fiber transmission can be further enhanced with the use of wavelength division multiplexing (WDM) technology in which multiple, independent optical signals may be simultaneously transmitted over a single fiber. This permits single fiber transmission of mixed signal traffic (e.g., digital data, voice, video, analog, etc.) as well as parallel digital traffic characteristic of computer data transfer. In addition, this technology creates new system design options and architectural flexibility for local area networks (LANs). This technical report describes the design and development of the critical element for implementing such a communications link - a 16 channel single mode WDM. Specifically, it describes the development and performance of a grating-based single mode WDM system suitable for use with single longitudinal lasers (e.g., distributed feedback lasers (DFB's)). The 16 channel WDM features channels with 3 dB bandwidths of 2.4 nM and separation of 7.2 nM. Any particular channel can be set to a precise wavelength due to the mechanical design features. End-to-End system channel insertion losses of 12.5 dB have been achieved with adjacent channel crosstalk of better than -25 dB.

  9. Alternative Modes of Inquiry.

    ERIC Educational Resources Information Center

    Friedlander, Frank

    1982-01-01

    Suggests that research on small group behavior, in a wide variety of settings, will be enhanced by rethinking alternative modes of enquiry, e.g., a focus on induction, a study of whole systems of human enterprise, the utilization of subjective experience, and trans-causal thinking. (Author/RC)

  10. Two Modes of Sexuality.

    ERIC Educational Resources Information Center

    Firestone, Robert W.

    This paper describes the essential difference between two modes of sexual relating: (1) a personal, outward style of interaction that is the natural extension of affection, tenderness, and companionship between two people; and (2) an impersonal, inward, more masturbatory expression in which sex is used primarily as a narcotic. The origins of…

  11. Theories and Modes

    ERIC Educational Resources Information Center

    Apsche, Jack A.

    2005-01-01

    In his work on the Theory of Modes, Beck (1996) suggested that there were flaws with his cognitive theory. He suggested that though there are shortcomings to his cognitive theory, there were not similar shortcomings to the practice of Cognitive Therapy. The author suggests that if there are shortcomings to cognitive theory the same shortcomings…

  12. Vibrational modes of nanolines

    NASA Astrophysics Data System (ADS)

    Heyliger, Paul R.; Flannery, Colm M.; Johnson, Ward L.

    2008-04-01

    Brillouin-light-scattering spectra previously have been shown to provide information on acoustic modes of polymeric lines fabricated by nanoimprint lithography. Finite-element methods for modeling such modes are presented here. These methods provide a theoretical framework for determining elastic constants and dimensions of nanolines from measured spectra in the low gigahertz range. To make the calculations feasible for future incorporation in inversion algorithms, two approximations of the boundary conditions are employed in the calculations: the rigidity of the nanoline/substrate interface and sinusoidal variation of displacements along the nanoline length. The accuracy of these approximations is evaluated as a function of wavenumber and frequency. The great advantage of finite-element methods over other methods previously employed for nanolines is the ability to model any cross-sectional geometry. Dispersion curves and displacement patterns are calculated for modes of polymethyl methacrylate nanolines with cross-sectional dimensions of 65 nm × 140 nm and rectangular or semicircular tops. The vibrational displacements and dispersion curves are qualitatively similar for the two geometries and include a series of flexural, Rayleigh-like, and Sezawa-like modes. This paper is a contribution of the National Institute of Standards and Technology and is not subject to copyright in the United States.

  13. List-mode likelihood

    PubMed Central

    Barrett, Harrison H.; White, Timothy; Parra, Lucas C.

    2010-01-01

    As photon-counting imaging systems become more complex, there is a trend toward measuring more attributes of each individual event. In various imaging systems the attributes can include several position variables, time variables, and energies. If more than about four attributes are measured for each event, it is not practical to record the data in an image matrix. Instead it is more efficient to use a simple list where every attribute is stored for every event. It is the purpose of this paper to discuss the concept of likelihood for such list-mode data. We present expressions for list-mode likelihood with an arbitrary number of attributes per photon and for both preset counts and preset time. Maximization of this likelihood can lead to a practical reconstruction algorithm with list-mode data, but that aspect is covered in a separate paper [IEEE Trans. Med. Imaging (to be published)]. An expression for lesion detectability for list-mode data is also derived and compared with the corresponding expression for conventional binned data. PMID:9379247

  14. Synthesize Modes and Correlate

    SciTech Connect

    Mayes, Randall Lee; Hensley, Daniel P.

    2005-10-01

    SMAC is an automated experimental modal parameter extraction package which determines the natural frequencies of vibration, viscous damping ratios and mode shapes from experimental accelerance frequency response functions (FRFs). It is written in the MATLAB interpretive matrix language and has a graphical user interface.

  15. Reactor water cleanup system

    DOEpatents

    Gluntz, Douglas M.; Taft, William E.

    1994-01-01

    A reactor water cleanup system includes a reactor pressure vessel containing a reactor core submerged in reactor water. First and second parallel cleanup trains are provided for extracting portions of the reactor water from the pressure vessel, cleaning the extracted water, and returning the cleaned water to the pressure vessel. Each of the cleanup trains includes a heat exchanger for cooling the reactor water, and a cleaner for cleaning the cooled reactor water. A return line is disposed between the cleaner and the pressure vessel for channeling the cleaned water thereto in a first mode of operation. A portion of the cooled water is bypassed around the cleaner during a second mode of operation and returned through the pressure vessel for shutdown cooling.

  16. Reactor water cleanup system

    DOEpatents

    Gluntz, D.M.; Taft, W.E.

    1994-12-20

    A reactor water cleanup system includes a reactor pressure vessel containing a reactor core submerged in reactor water. First and second parallel cleanup trains are provided for extracting portions of the reactor water from the pressure vessel, cleaning the extracted water, and returning the cleaned water to the pressure vessel. Each of the cleanup trains includes a heat exchanger for cooling the reactor water, and a cleaner for cleaning the cooled reactor water. A return line is disposed between the cleaner and the pressure vessel for channeling the cleaned water thereto in a first mode of operation. A portion of the cooled water is bypassed around the cleaner during a second mode of operation and returned through the pressure vessel for shutdown cooling. 1 figure.

  17. Antarctic jaws: cephalopod prey of sharks in Kerguelen waters

    NASA Astrophysics Data System (ADS)

    Cherel, Yves; Duhamel, Guy

    2004-01-01

    Only five species of sharks have been recorded in the Southern Ocean, where their biology is essentially unknown. We investigated the feeding habits of the three commonest species from stomach content analysis of specimens taken as bycatches of the fishery targeting the Patagonian toothfish ( Dissostichus eleginoides) in upper slope waters of the Kerguelen Archipelago. The three species prey upon a diversity of fishes and cephalopods. They segregate by feeding on different species of squids of different sizes. The small lanternsharks ( Etmopterus cf. granulosus; 0.3 m on average) feed on small-sized Mastigoteuthis psychrophila, while the large porbeagles ( Lamna nasus; 1.9 m) feed on small-sized histioteuthids ( Histioteuthis atlantica and H. eltaninae) and on medium-sized juvenile ommastrephids of the genus Todarodes. Finally, the huge sleeper sharks ( Somniosus cf. microcephalus; 3.9 m) prey upon large-sized cephalopods ( Kondakovia longimana and Taningia danae) and giant squids ( Mesonychoteuthis hamiltoni and Architeuthis dux). Thus sleeper shark is a fish with sperm whale-like feeding habits and, hence, the second top predator known to science to rely significantly on giant squids. Prey species and biology indicate that porbeagles are pelagic predators in the entire water column, while sleeper sharks are mainly benthic top predators and scavengers. The present study also underlines the diversity and biomass of the poorly known cephalopod fauna, including giant squids, occurring in outer shelf and upper slope waters surrounding subantarctic islands.

  18. Regional modeling of the water masses and circulation annual variability at the Southern Brazilian Continental Shelf

    NASA Astrophysics Data System (ADS)

    Mendonça, L. F.; Souza, R. B.; Aseff, C. R. C.; Pezzi, L. P.; Möller, O. O.; Alves, R. C. M.

    2017-02-01

    The Southern Brazilian Continental Shelf (SBCS) is one of the more productive areas for fisheries in Brazilian waters. The water masses and the dynamical processes of the region present a very seasonal behavior that imprint strong effects in the ecosystem and the weather of the area and its vicinity. This paper makes use of the Regional Ocean Modeling System (ROMS) for studying the water mass distribution and circulation variability in the SBCS during the year of 2012. Model outputs were compared to in situ, historical observations and to satellite data. The model was able to reproduce the main thermohaline characteristics of the waters dominating the SBCS and the adjacent region. The mixing between the Subantarctic Shelf Water and the Subtropical Shelf Water, known as the Subtropical Shelf Front (STSF), presented a clear seasonal change in volume. As a consequence of the mixing and of the seasonal oscillation of the STSF position, the stability of the water column inside the SBCS also changes seasonally. Current velocities and associated transports estimated for the Brazil Current (BC) and for the Brazilian Coastal Current (BCC) agree with previous measurements and estimates, stressing the fact that the opposite flow of the BCC occurring during winter in the study region is about 2 orders of magnitude smaller than that of the BC. Seasonal maps of simulated Mean Kinetic Energy and Eddy Kinetic Energy demonstrate the known behavior of the BC and stressed the importance of the mean coastal flow off Argentina throughout the year.

  19. Carbon dioxide along WOCE line A14: Water masses characterization and anthropogenic entry

    SciTech Connect

    Rios, A F; Alvarez-Salgado, X A; Perez, F F; Bingler, Linda S; Aristegui, J; Memery, L

    2003-04-22

    The meridional WOCE line A14, just east of the South Atlantic Mid-Atlantic Ridge, was surveyed during the austral summer of 1995 from 4°N to 45°S. Full-depth profiles of pH, total alkalinity (TA), and total inorganic carbon (CT) were measured, allowing a test of the internal consistency of the CO2 system parameters. The correlation between CT measured and calculated from pH and TA was very good (r2 = 0.998), with an insignificant average difference of 0.1 μ3.0 μmol kg-1 (n = 964 data). CO2 certified reference materials (CRMs) and a collection of selected samples subsequently analyzed at the Scripps Institution of Oceanography were used to assess the accuracy of our measurements at sea with satisfactory results. The three measured CO2 system variables were then used to identify the characteristic array of zonal flows throughout the South Atlantic intersected by A14. Equatorial, subequatorial, subtropical, and subantarctic domains were identified at the depth range of the surface water, South Atlantic Central Water (SACW), Antarctic Intermediate Water (AAIW), Upper Circumpolar Water (UCPW), North Atlantic Deep Water (NADW) and Antarctic Bottom Water (AABW). The nonconservative CO2 system parameters (pH, TA, CT) have been useful in identifying the transition from aged subequatorial to ventilated subtropical surface, central and intermediate waters. They have been identified as good tracers of the zonal circulation of NADW, with marked flows at the equator, 13°S, and 22°S (the "Namib Col Current") and the sharp transition from UNADW to UCPW at 23°S. The anthropogenic CO2 inventory (CANT) was estimated and compared with CFC-derived apparent ages for different water masses along A14. The anthropogenic entry reached maximum in the relatively young and ventilated subantarctic and subtropical domains where AAIW was the most efficient CO2 trap. The calculated annual rate of CANT entry by AAIW was 0.82 μmol kg-1 y-1, in agreement with the annual rate estimated from

  20. Mechanisms of mineral membrane fouling growth modulated by pulsed modes of current during electrodialysis: evidences of water splitting implications in the appearance of the amorphous phases of magnesium hydroxide and calcium carbonate.

    PubMed

    Cifuentes-Araya, Nicolás; Astudillo-Castro, Carolina; Bazinet, Laurent

    2014-07-15

    Experiments revealed the fouling nature evolutions along different electrodialysis (ED) trials, and how it disappears when current pulsation acts repetitively on the interfaces of ion-exchange membranes (IEMs). Fouling was totally controlled on the diluate side of cation-exchange membrane (CEM) by the repetitive pulsation frequency of the higher on-duty ratios applied. They created steady water splitting proton-barriers that neutralized OH(-) leakage through the membrane, decreasing the interfacial pH, and fouling of the concentrate side. The anion-exchange membrane (AEM) on the diluate side was similarly protected, but it was fouled once water splitting OH(-) generation became either intense enough or excessively weak. Interestingly, amorphous magnesium hydroxide (AMH) stemmed on the CEM-diluate side from brucite under intense water splitting OH(-) generation, and/or strong OH(-) leakage electromigration through the membrane. Water dissociation and overlimiting current regimes triggered drastic water molecule removal from crystal lattices through an accelerated cascade water splitting reaction. Also, amorphous calcium carbonate (ACC) appeared on CEM under intense water splitting reaction, and disappeared once intense OH(-) leakage was allowed by the water splitting proton-barrier dissipation. Our findings have implications for membrane fouling control, as well as for the understanding of the growth behavior of CaCO3 and Mg(OH)2 species on electromembrane interfaces. Copyright © 2014 Elsevier Inc. All rights reserved.

  1. Normal mode sound field of a directional radiator

    NASA Astrophysics Data System (ADS)

    Zhang, R.; Zhu, B.

    1987-12-01

    In this paper, the sound field of a general type of directional radiator in a stratified medium is treated, and the concept of directivity is applied to calculation of the normal modes. The result shows that the normal mode field of a directional radiator can be obtained by supplementing the normal mode expression of an omnidirectional point source with the directional excitation function, which is dependent on the position and directivity of the radiator. In addition, the normal mode fields of radiators with vertical-symmetrical, vertical-antisymmetrical, single-sided and sharp directivities are calculated, respectively. For a vertical line array in a homogeneous water layer, if the source distribution is proportional to the eigenfunction of some normal mode, the zeros of the directional excitation function correspond precisely to the directions of the eigenrays of other normal modes.

  2. Dual mode laser velocimeter

    NASA Technical Reports Server (NTRS)

    Gunter, William D., Jr. (Inventor); Donaldson, Ralph W. (Inventor); Anderson, Alma G., Jr. (Inventor)

    1987-01-01

    Described is a laser Doppler velocimeter (LDV) which is capable of operating with a small focus diameter for analyzing fluid flows at low velocity with high spatial resolution, or with a larger focus diameter to measure fluid flows at higher velocities accurately. More particularly, this is an LDV in which a simple reversal of a lens pair will allow it to operate in the two focus diameter modes.

  3. Modes of Learning.

    ERIC Educational Resources Information Center

    Partridge, Susan

    This literature review is divided into two parts. The first part is a survey of materials in the William S. Gray Collection at the University of Chicago that deal with modes of learning. The studies reviewed range from the 1930s to the 1960s. The second part of the paper extends the review to studies published during the 1970s. Each section of the…

  4. Whispering Gallery Mode Thermometry.

    PubMed

    Corbellini, Simone; Ramella, Chiara; Yu, Lili; Pirola, Marco; Fernicola, Vito

    2016-10-29

    This paper presents a state-of-the-art whispering gallery mode (WGM) thermometer system, which could replace platinum resistance thermometers currently used in many industrial applications, thus overcoming some of their well-known limitations and their potential for providing lower measurement uncertainty. The temperature-sensing element is a sapphire-crystal-based whispering gallery mode resonator with the main resonant modes between 10 GHz and 20 GHz. In particular, it was found that the WGM around 13.6 GHz maximizes measurement performance, affording sub-millikelvin resolution and temperature stability of better than 1 mK at 0 °C. The thermometer system was made portable and low-cost by developing an ad hoc interrogation system (hardware and software) able to achieve an accuracy in the order of a few parts in 10⁸ in the determination of resonance frequencies. Herein we report the experimental assessment of the measurement stability, repeatability and resolution, and the calibration of the thermometer in the temperature range from -74 °C to 85 °C. The combined standard uncertainty for a single temperature calibration point is found to be within 5 mK (i.e., comparable with state-of-the-art for industrial thermometry), and is mainly due to the employed calibration setup. The uncertainty contribution of the WGM thermometer alone is within a millikelvin.

  5. Whispering Gallery Mode Thermometry

    PubMed Central

    Corbellini, Simone; Ramella, Chiara; Yu, Lili; Pirola, Marco; Fernicola, Vito

    2016-01-01

    This paper presents a state-of-the-art whispering gallery mode (WGM) thermometer system, which could replace platinum resistance thermometers currently used in many industrial applications, thus overcoming some of their well-known limitations and their potential for providing lower measurement uncertainty. The temperature-sensing element is a sapphire-crystal-based whispering gallery mode resonator with the main resonant modes between 10 GHz and 20 GHz. In particular, it was found that the WGM around 13.6 GHz maximizes measurement performance, affording sub-millikelvin resolution and temperature stability of better than 1 mK at 0 °C. The thermometer system was made portable and low-cost by developing an ad hoc interrogation system (hardware and software) able to achieve an accuracy in the order of a few parts in 109 in the determination of resonance frequencies. Herein we report the experimental assessment of the measurement stability, repeatability and resolution, and the calibration of the thermometer in the temperature range from −74 °C to 85 °C. The combined standard uncertainty for a single temperature calibration point is found to be within 5 mK (i.e., comparable with state-of-the-art for industrial thermometry), and is mainly due to the employed calibration setup. The uncertainty contribution of the WGM thermometer alone is within a millikelvin. PMID:27801868

  6. Combined mode I and mode II fracture of monolithic ceramics

    NASA Technical Reports Server (NTRS)

    Tikare, Veena; Choi, Sung R.

    1993-01-01

    The mode I, mode II, and combined mode I-mode II fracture behaviors of a coarse-grained silicon nitride, a fine-grained silicon nitride, and an alumina were investigated. These ceramics were fractured from two types of fracture initiating flaws: small surface flaws and large single edge precracks. The small surface flaws were introduced by Knoop indentation in flexural samples at various angles to the tensile stress direction and fractured in four-point bending. The samples with large precracks were fractured in the asymmetric four-point-bend geometry. The mixed-mode fracture toughness values obtained from the two flaw configurations were in good agreement with each other. All three ceramics displayed very similar mixed-mode fracture behavior, although their microstructures were not similar. Comparison of experimental data to mixed-mode fracture theories revealed that the minimum strain energy density theory best described the mixed-mode fracture behavior of all three ceramics.

  7. Probing plasmonic breathing modes optically

    SciTech Connect

    Krug, Markus K. Reisecker, Michael; Hohenau, Andreas; Ditlbacher, Harald; Trügler, Andreas; Hohenester, Ulrich; Krenn, Joachim R.

    2014-10-27

    The confinement of surface plasmon modes in flat nanoparticles gives rise to plasmonic breathing modes. With a vanishing net dipole moment, breathing modes do not radiate, i.e., they are optically dark. Having thus escaped optical detection, breathing modes were only recently revealed in silver nanodisks with electron energy loss spectroscopy in an electron microscope. We show that for disk diameters >200 nm, retardation induced by oblique optical illumination relaxes the optically dark character. This makes breathing modes and thus the full plasmonic mode spectrum accessible to optical spectroscopy. The experimental spectroscopy data are in excellent agreement with numerical simulations.

  8. The different modes of hydro-economic analysis (Invited)

    NASA Astrophysics Data System (ADS)

    Harou, J. J.; Binions, O.; Erfani, T.

    2013-12-01

    In the face of growing water demands, climate change and spatial and temporal water access variability, accurately assessing the economic impacts of proposed water resource management changes is useful. The objective of this project funded by UK Water Industry Research was to present and demonstrate a framework for identifying and using the ';value of water' to enable water utilities and their regulators to make better decisions. A hydro-economic model can help evaluate water management options in terms of their hydrological and economic impact at different locations throughout a catchment over time. In this talk we discuss three modes in which hydro-economic models can be implemented: evaluative, behavioral and prescriptive. In evaluation mode economic water demand and benefit functions are used to post-process water resource management model results to assess the economic impacts (over space and time) of a policy under consideration. In behavioral hydro-economic models users are represented as agents and the economics is used to help predict their actions. In prescriptive mode optimization is used to find the most economically efficient management actions such as allocation patterns or source selection. These three types of hydro-economic analysis are demonstrated on a UK watershed (Great River Ouse) that includes 97 different water abstractors from amongst the public water supply, agriculture, industry and energy plant cooling sectors. The following issues under dry and normal historical conditions were investigated: Supply/demand investment planning, societal cost of environmental flows, water market prices, and scarcity-sensitive charges for water rights. The talk discusses which hydro-economic modeling mode is used to study each of these issues and why; example results are shown and discussed. The topic of how hydro-economic models can be built and deployed effectively is covered along with how existing water utility operational and planning tools can be

  9. Constraining primordial vector mode from B-mode polarization

    SciTech Connect

    Saga, Shohei; Ichiki, Kiyotomo; Shiraishi, Maresuke E-mail: maresuke.shiraishi@pd.infn.it

    2014-10-01

    The B-mode polarization spectrum of the Cosmic Microwave Background (CMB) may be the smoking gun of not only the primordial tensor mode but also of the primordial vector mode. If there exist nonzero vector-mode metric perturbations in the early Universe, they are known to be supported by anisotropic stress fluctuations of free-streaming particles such as neutrinos, and to create characteristic signatures on both the CMB temperature, E-mode, and B-mode polarization anisotropies. We place constraints on the properties of the primordial vector mode characterized by the vector-to-scalar ratio r{sub v} and the spectral index n{sub v} of the vector-shear power spectrum, from the Planck and BICEP2 B-mode data. We find that, for scale-invariant initial spectra, the ΛCDM model including the vector mode fits the data better than the model including the tensor mode. The difference in χ{sup 2} between the vector and tensor models is Δχ{sup 2} = 3.294, because, on large scales the vector mode generates smaller temperature fluctuations than the tensor mode, which is preferred for the data. In contrast, the tensor mode can fit the data set equally well if we allow a significantly blue-tilted spectrum. We find that the best-fitting tensor mode has a large blue tilt and leads to an indistinct reionization bump on larger angular scales. The slightly red-tilted vector mode supported by the current data set can also create O(10{sup -22})-Gauss magnetic fields at cosmological recombination. Our constraints should motivate research that considers models of the early Universe that involve the vector mode.

  10. Constraining primordial vector mode from B-mode polarization

    NASA Astrophysics Data System (ADS)

    Saga, Shohei; Shiraishi, Maresuke; Ichiki, Kiyotomo

    2014-10-01

    The B-mode polarization spectrum of the Cosmic Microwave Background (CMB) may be the smoking gun of not only the primordial tensor mode but also of the primordial vector mode. If there exist nonzero vector-mode metric perturbations in the early Universe, they are known to be supported by anisotropic stress fluctuations of free-streaming particles such as neutrinos, and to create characteristic signatures on both the CMB temperature, E-mode, and B-mode polarization anisotropies. We place constraints on the properties of the primordial vector mode characterized by the vector-to-scalar ratio rv and the spectral index nv of the vector-shear power spectrum, from the Planck and BICEP2 B-mode data. We find that, for scale-invariant initial spectra, the ΛCDM model including the vector mode fits the data better than the model including the tensor mode. The difference in χ2 between the vector and tensor models is Δχ2 = 3.294, because, on large scales the vector mode generates smaller temperature fluctuations than the tensor mode, which is preferred for the data. In contrast, the tensor mode can fit the data set equally well if we allow a significantly blue-tilted spectrum. We find that the best-fitting tensor mode has a large blue tilt and leads to an indistinct reionization bump on larger angular scales. The slightly red-tilted vector mode supported by the current data set can also create Script O(10-22)-Gauss magnetic fields at cosmological recombination. Our constraints should motivate research that considers models of the early Universe that involve the vector mode.

  11. Instantaneous Normal Modes and the Protein Glass Transition

    SciTech Connect

    Schultz, Roland; Krishnan, Marimuthu; Daidone, Isabella; Smith, Jeremy C

    2009-01-01

    In the instantaneous normal mode method, normal mode analysis is performed at instantaneous configurations of a condensed-phase system, leading to modes with negative eigenvalues. These negative modes provide a means of characterizing local anharmonicities of the potential energy surface. Here, we apply instantaneous normal mode to analyze temperature-dependent diffusive dynamics in molecular dynamics simulations of a small protein (a scorpion toxin). Those characteristics of the negative modes are determined that correlate with the dynamical (or glass) transition behavior of the protein, as manifested as an increase in the gradient with T of the average atomic mean-square displacement at 220 K. The number of negative eigenvalues shows no transition with temperature. Further, although filtering the negative modes to retain only those with eigenvectors corresponding to double-well potentials does reveal a transition in the hydration water, again, no transition in the protein is seen. However, additional filtering of the protein double-well modes, so as to retain only those that, on energy minimization, escape to different regions of configurational space, finally leads to clear protein dynamical transition behavior. Partial minimization of instantaneous configurations is also found to remove nondiffusive imaginary modes. In summary, examination of the form of negative instantaneous normal modes is shown to furnish a physical picture of local diffusive dynamics accompanying the protein glass transition.

  12. Solar p-Modes Modulated by Interior g-Modes

    NASA Astrophysics Data System (ADS)

    Lou, Yu-Qing

    2001-08-01

    The process by which frequency modulations of solar p-modes with shorter periods (~5 minutes) occur because of the presence of solar interior g-modes with longer periods (greater than a few hours approximately) is studied. The key results of a model analysis are given. In addition to the effects of stochastic excitation, this modulation by g-modes would give rise to fine spectral structures in the form of frequency sideband peaks closely packed around individual p-modes (with narrow frequency intervals on the order of g-mode frequencies) rather than of separate g-mode spectral power peaks in the low-frequency bands. For those p-modes of low degree that penetrate deep into the solar interior, this effect of frequency modulation by interior g-modes (if they exist) should be more pronounced. Observationally, individual p-modes usually contain numerous fine peaks that have to be somehow modeled (or smoothed) in order to estimate p-mode frequencies, amplitudes, and line widths, etc. By carefully weeding out noises of various origins in high-resolution p-mode frequency spectra, one might be able to extract the desired signals of g-modes trapped in the solar interior that have so far evaded the scrutiny of advanced helioseismological experiments.

  13. A Summary of Publications on the Development of Mode-of-Action Information and Statistical Tools for Evaluating Health Outcomes from Drinking Water Disinfection By-Product (DBP) Exposures

    EPA Science Inventory

    Chemical contaminants are formed as a consequence of chemical disinfection of public drinking waters. Chemical disinfectants, which are used to kill harmful microorganisms, react with natural organic matter (NOM), bromide, iodide, and other compounds, forming complex mixtures...

  14. A Summary of Publications on the Development of Mode-of-Action Information and Statistical Tools for Evaluating Health Outcomes from Drinking Water Disinfection By-Product (DBP) Exposures

    EPA Science Inventory

    Chemical contaminants are formed as a consequence of chemical disinfection of public drinking waters. Chemical disinfectants, which are used to kill harmful microorganisms, react with natural organic matter (NOM), bromide, iodide, and other compounds, forming complex mixtures...

  15. I-mode for ITER?

    NASA Astrophysics Data System (ADS)

    Whyte, D. G.; Marmar, E.; Hubbard, A.; Hughes, J.; Dominguez, A.; Greenwald, M.

    2011-10-01

    I-mode is a recently explored confinement regime that features a temperature pedestal and H-mode energy confinement, yet with L-mode particle confinement and no density pedestal nor large ELMs. Experiments on Alcator