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Sample records for ace lake antarctica

  1. Low deuterium content of Lake Vanda, Antarctica

    USGS Publications Warehouse

    Ragotzkie, R.A.; Friedman, I.

    1965-01-01

    Lake Vanda in Victoria Land, Antarctica, is permanently ice-covered and permanently stratified, with warm, salty water near the bottom. Deuterium analyses of lake water from several levels indicate that the lake has a low deuterium content, and that it is stratified with respect to this isotope. This low deuterium content supports the evidence from the lake's ionic content that the saline layer is not of marine origin, and it indicates that evaporation from the ice surface has taken place. The stratification of the lake with respect to deuterium suggests that the upper and lower layers of water were formed at different times from different sources of glacial melt water.

  2. An integrative study of a meromictic lake ecosystem in Antarctica.

    PubMed

    Lauro, Federico M; DeMaere, Matthew Z; Yau, Sheree; Brown, Mark V; Ng, Charmaine; Wilkins, David; Raftery, Mark J; Gibson, John A E; Andrews-Pfannkoch, Cynthia; Lewis, Matthew; Hoffman, Jeffrey M; Thomas, Torsten; Cavicchioli, Ricardo

    2011-05-01

    In nature, the complexity and structure of microbial communities varies widely, ranging from a few species to thousands of species, and from highly structured to highly unstructured communities. Here, we describe the identity and functional capacity of microbial populations within distinct layers of a pristine, marine-derived, meromictic (stratified) lake (Ace Lake) in Antarctica. Nine million open reading frames were analyzed, representing microbial samples taken from six depths of the lake size fractionated on sequential 3.0, 0.8 and 0.1 μm filters, and including metaproteome data from matching 0.1 μm filters. We determine how the interactions of members of this highly structured and moderately complex community define the biogeochemical fluxes throughout the entire lake. Our view is that the health of this delicate ecosystem is dictated by the effects of the polar light cycle on the dominant role of green sulfur bacteria in primary production and nutrient cycling, and the influence of viruses/phage and phage resistance on the cooperation between members of the microbial community right throughout the lake. To test our assertions, and develop a framework applicable to other microbially driven ecosystems, we developed a mathematical model that describes how cooperation within a microbial system is impacted by periodic fluctuations in environmental parameters on key populations of microorganisms. Our study reveals a mutualistic structure within the microbial community throughout the lake that has arisen as the result of mechanistic interactions between the physico-chemical parameters and the selection of individual members of the community. By exhaustively describing and modelling interactions in Ace Lake, we have developed an approach that may be applicable to learning how environmental perturbations affect the microbial dynamics in more complex aquatic systems. PMID:21124488

  3. Molecular organic tracers of biogeochemical processes in a saline meromictic lake (Ace Lake)

    NASA Astrophysics Data System (ADS)

    Schouten, S.; Rijpstra, W. I. C.; Kok, M.; Hopmans, E. C.; Summons, R. E.; Volkman, J. K.; Sinninghe Damsté, J. S.

    2001-05-01

    The chemical structures, distribution and stable carbon isotopic compositions of lipids in a sediment core taken in meromictic Ace Lake (Antarctica) were analyzed to trace past biogeochemical cycling. Biomarkers from methanogenic archaea, methanotrophic bacteria and photosynthetic green sulfur bacteria were unambiguously assigned using organic geochemical understanding and by reference to what is known about the lake's present-day ecosystem. For instance, saturated and unsaturated 2,6,10,15,19-pentamethylicosane, archaeol and sn2-hydroxyarchaeol were derived from methanogenic archaea. Carotenoid analysis revealed chlorobactene and isorenieratene derived from the green-colored and brown-colored strains of the green sulfur bacteria (Chlorobiaceae); isotopic analyses showed that they were 13C-enriched. Phytenes appear to be derived from photoautotrophs that use the Calvin-Benson cycle, while phytane has a different source, possibly within the archaea. The most 13C-depleted compounds (ca. -55‰) identified were 4-methyl-5α-cholest-8(14)-en-3β-ol, identified using an authentic standard, and co-occurring 4-methylsteradienes: these originate from the aerobic methanotrophic bacterium Methylosphaera hansonii. Lipids of photoautotrophic origin, steranes and alkenones, are relatively depleted (ca. -28 to -36‰) whilst archaeal biomarkers are relatively enriched in 13C (ca. -17 to -25‰). The structural and carbon isotope details of sedimentary lipids thus revealed aspects of in situ biogeochemical processes such as methane generation and oxidation and phototrophic sulfide oxidation.

  4. ACE

    NASA Technical Reports Server (NTRS)

    Lumia, R.

    1999-01-01

    This document describes the progress made during the fourth year of the Center for Autonomous Control Engineering (ACE). We currently support 30 graduate students, 52 undergraduate students, 9 faculty members, and 4 staff members. Progress will be divided into two categories. The first category explores progress for ACE in general. The second describes the results of each specific project supported within ACE.

  5. Anaerobic psychrophiles from Lake Zub and Lake Untersee, Antarctica

    NASA Astrophysics Data System (ADS)

    Townsend, Alisa; Pikuta, Elena V.; Guisler, Melissa; Stahl, Sarah; Hoover, Richard B.

    2009-08-01

    The study of samples from Antarctica 2008 and 2009 expeditions organized and successfully conducted by Richard Hoover led to the isolation of diverse anaerobic strains with psychrotolerant and psychrophilic physiology. Due to the fact that Lake Untersee has never been subject to microbiological study, this work with the samples has significant and pioneering impact to the knowledge about the biology of this unique ecosystem. Also, the astrobiological significance for the study of these ecosystems is based on new findings of ice covered water systems on other bodies of our solar system. Anaerobic psychrotolerant strain LZ-22 was isolated from a frozen sample of green moss with soils around the rhizosphere collected near Lake Zub in Antarctica. Morphology of strain LZ-22 was observed to be motile, rod shaped and spore-forming cells with sizes 1 x 5-10 μm. This new isolate is a mesophile with the maximum temperature of growth at 40°C. Strain LZ-22 is able to live on media without NaCl and in media with up to 7 % (w/v) NaCl. It is catalase negative and grows only on sugars with the best growth rate being on lactose. The strain is a neutrophile and grows between pH 5 and 9.0 with the optimum at 7.8. Another two strains UL7-96mG and LU-96m7P were isolated from deep water samples of Lake Untersee. Proteolytic strain LU-96m7P had a truly psychrophilic nature and refused to grow at room temperature. Sugarlytic strain UL7-96mG was found to be psychrotolerant, but its rate of growth at 3°C was very high compared with other mesophiles. Two homoacetogenic psychrophilic strains A7AC-96m and AC-DS7 were isolated and purified from samples of Lake Untersee; both of them are able to grow chemolithotrophically on H2+CO2. In the presence of lactate, these strains are able to grow only at 0-18 °C, and growth at 22 °C was observed only with yeast extract stimulation. In this paper, physiological and morphological characteristics of novel psychrophilic and psychrotolerant isolates

  6. Anaerobic Psychrophiles from Lake Zub and Lake Untersee, Antarctica

    NASA Technical Reports Server (NTRS)

    Townsend, Alisa; Pikuta, Elena V.; Guisler, Melissa; Stahl, Sarah; Hoover, Richard B.

    2009-01-01

    The study of samples from Antarctica 2008 and 2009 expeditions organized and successfully conducted by Richard Hoover led to the isolation of diverse anaerobic strains with psychrotolerant and psychrophilic physiology. Due to the fact that Lake Untersee has never been subject to microbiological study, this work with the samples has significant and pioneering impact to the knowledge about the biology of this unique ecosystem. Also, the astrobiological significance for the study of these ecosystems is based on new findings of ice covered water systems on other bodies of our solar system. Anaerobic psychrotolerant strain LZ-22 was isolated from a frozen sample of green moss with soils around the rhizosphere collected near Lake Zub in Antarctica. Morphology of strain LZ-22 was observed to be motile, rod shaped and spore-forming cells with sizes 1 x 5-10 micron. This new isolate is a mesophile with the maximum temperature of growth at 40C. Strain LZ-22 is able to live on media without NaCl and in media with up to 7% (w/v) NaCl. It is catalase negative and grows only on sugars with the best growth rate being on lactose. The strain is a neutrophile and grows between pH 5 and 9.0 with the optimum at 7.8. Another two strains UL7-96mG and LU-96m7P were isolated from deep water samples of Lake Untersee. Proteolytic strain LU-96m7P had a truly psychrophilic nature and refused to grow at room temperature. Sugarlytic strain UL7-96mG was found to be psychrotolerant, but its rate of growth at 3C was very high compared with other mesophiles. Two homoacetogenic psychrophilic strains A7AC-96m and AC-DS7 were isolated and purified from samples of Lake Untersee; both of them are able to grow chemolithotrophically on H2+CO2. In the presence of lactate, these strains are able to grow only at 0-18C, and growth at 22C was observed only with yeast extract stimulation. In this paper, physiological and morphological characteristics of novel psychrophilic and psychrotolerant isolates from

  7. Topographic and hydrological controls on Subglacial Lake Ellsworth, West Antarctica

    NASA Astrophysics Data System (ADS)

    Vaughan, David G.; Rivera, Andrés; Woodward, John; Corr, Hugh F. J.; Wendt, Jens; Zamora, Rodrigo

    2007-09-01

    Subglacial Lake Ellsworth (SLE) was identified using reconnaissance data collected in the 1970s, here we present more detailed surveys. SLE lies beneath 3.2 km of ice in a subglacial valley in West Antarctica. It has an area of only ~18 km2, is dissimilar to the large tectonically-controlled lakes beneath East Antarctica and is a strong candidate for in situ exploration. Our analysis indicates that the ice above SLE is floating on a fluid whose density is 950-1013 kg m-3. This could indicate freshwater, but certainly precludes seawater, or high salt, acid, or clathrate content. The water in the lake is unlikely to be produced solely by local melt; it is more likely delivered via subglacial drainage. Our surveys show no identifiable hydrological barrier to outflow, meaning SLE is effectively full; new water entering the lake is likely balanced by outflow, which would drain into another lake that we have also identified.

  8. Hydrological Controls on Ecosystem Dynamics in Lake Fryxell, Antarctica

    PubMed Central

    Rytel, Alexander L.; Lyons, W. Berry; McKnight, Diane M.; Jaros, Christopher; Gooseff, Michael N.; Priscu, John C.

    2016-01-01

    The McMurdo Dry Valleys constitute the largest ice free area of Antarctica. The area is a polar desert with an annual precipitation of ∼ 3 cm water equivalent, but contains several lakes fed by glacial melt water streams that flow from four to twelve weeks of the year. Over the past ∼20 years, data have been collected on the lakes located in Taylor Valley, Antarctica as part of the McMurdo Dry Valley Long-Term Ecological Research program (MCM-LTER). This work aims to understand the impact of climate variations on the biological processes in all the ecosystem types within Taylor Valley, including the lakes. These lakes are stratified, closed-basin systems and are perennially covered with ice. Each lake contains a variety of planktonic and benthic algae that require nutrients for photosynthesis and growth. The work presented here focuses on Lake Fryxell, one of the three main lakes of Taylor Valley; it is fed by thirteen melt-water streams. We use a functional regression approach to link the physical, chemical, and biological processes within the stream-lake system to evaluate the input of water and nutrients on the biological processes in the lakes. The technique has been shown previously to provide important insights into these Antarctic lacustrine systems where data acquisition is not temporally coherent. We use data on primary production (PPR) and chlorophyll-A (CHL)from Lake Fryxell as well as discharge observations from two streams flowing into the lake. Our findings show an association between both PPR, CHL and stream input. PMID:27441705

  9. Hydrological Controls on Ecosystem Dynamics in Lake Fryxell, Antarctica.

    PubMed

    Herbei, Radu; Rytel, Alexander L; Lyons, W Berry; McKnight, Diane M; Jaros, Christopher; Gooseff, Michael N; Priscu, John C

    2016-01-01

    The McMurdo Dry Valleys constitute the largest ice free area of Antarctica. The area is a polar desert with an annual precipitation of ∼ 3 cm water equivalent, but contains several lakes fed by glacial melt water streams that flow from four to twelve weeks of the year. Over the past ∼20 years, data have been collected on the lakes located in Taylor Valley, Antarctica as part of the McMurdo Dry Valley Long-Term Ecological Research program (MCM-LTER). This work aims to understand the impact of climate variations on the biological processes in all the ecosystem types within Taylor Valley, including the lakes. These lakes are stratified, closed-basin systems and are perennially covered with ice. Each lake contains a variety of planktonic and benthic algae that require nutrients for photosynthesis and growth. The work presented here focuses on Lake Fryxell, one of the three main lakes of Taylor Valley; it is fed by thirteen melt-water streams. We use a functional regression approach to link the physical, chemical, and biological processes within the stream-lake system to evaluate the input of water and nutrients on the biological processes in the lakes. The technique has been shown previously to provide important insights into these Antarctic lacustrine systems where data acquisition is not temporally coherent. We use data on primary production (PPR) and chlorophyll-A (CHL)from Lake Fryxell as well as discharge observations from two streams flowing into the lake. Our findings show an association between both PPR, CHL and stream input. PMID:27441705

  10. Discovery of large conical stromatolites in Lake Untersee, Antarctica.

    PubMed

    Andersen, D T; Sumner, D Y; Hawes, I; Webster-Brown, J; McKay, C P

    2011-05-01

    Lake Untersee is one of the largest (11.4 km(2)) and deepest (>160 m) freshwater lakes in East Antarctica. Located at 71°S the lake has a perennial ice cover, a water column that, with the exception of a small anoxic basin in the southwest of the lake, is well mixed, supersaturated with dissolved oxygen, alkaline (pH 10.4) and exceedingly clear. The floor of the lake is covered with photosynthetic microbial mats to depths of at least 100 m. These mats are primarily composed of filamentous cyanophytes and form two distinct macroscopic structures, one of which--cm-scale cuspate pinnacles dominated by Leptolyngbya spp.--is common in Antarctica, but the second--laminated, conical stromatolites that rise up to 0.5 m above the lake floor, dominated by Phormidium spp.--has not previously been reported in any modern environment. The laminae that form the conical stromatolites are 0.2-0.8 mm in thickness consisting of fine clays and organic material; carbon dating implies that laminations may occur on near decadal timescales. The uniformly steep sides (59.6 ± 2.5°) and the regular laminar structure of the cones suggest that they may provide a modern analog for growth of some of the oldest well-described Archean stromatolites. Mechanisms underlying the formation of these stromatolites are as yet unclear, but their growth is distinct from that of the cuspate pinnacles. The sympatric occurrence of pinnacles and cones related to microbial communities with distinct cyanobacterial compositions suggest that specific microbial behaviors underpin the morphological differences in the structures. PMID:21504538

  11. Lake Hoare, Antarctica: sedimentation through a thick perennial ice cover

    NASA Technical Reports Server (NTRS)

    Squyres, S. W.; Andersen, D. W.; Nedell, S. S.; Wharton, R. A. Jr; Wharton RA, J. r. (Principal Investigator)

    1991-01-01

    Lake Hoare in the Dry Valleys of Antarctica is covered with a perennial ice cover more than 3 m thick, yet there is a complex record of sedimentation and of growth of microbial mats on the lake bottom. Rough topography on the ice covering the lake surface traps sand that is transported by the wind. In late summer, vertical conduits form by melting and fracturing, making the ice permeable to both liquid water and gases. Cross-sections of the ice cover show that sand is able to penetrate into and apparently through it by descending through these conduits. This is the primary sedimentation mechanism in the lake. Sediment traps retrieved from the lake bottom indicate that rates of deposition can vary by large amounts over lateral scales as small as 1 m. This conclusion is supported by cores taken in a 3 x 3 grid with a spacing of 1.5 m. Despite the close spacing of the cores, the poor stratigraphic correlation that is observed indicates substantial lateral variability in sedimentation rate. Apparently, sand descends into the lake from discrete, highly localized sources in the ice that may in some cases deposit a large amount of sand into the lake in a very short time. In some locations on the lake bottom, distinctive sand mounds have been formed by this process. They are primary sedimentary structures and appear unique to the perennially ice-covered lacustrine environment. In some locations they are tens of centimetres high and gently rounded with stable slopes; in others they reach approximately 1 m in height and have a conical shape with slopes at angle of repose. A simple formation model suggests that these differences can be explained by local variations in water depth and sedimentation rate. Rapid colonization of fresh sand surfaces by microbial mats composed of cyanobacteria, eukaryotic algae, and heterotrophic bacteria produces a complex intercalation of organic and sandy layers that are a distinctive form of modern stromatolites.

  12. Growth of modern branched columnar stromatolites in Lake Joyce, Antarctica.

    PubMed

    Mackey, T J; Sumner, D Y; Hawes, I; Jungblut, A D; Andersen, D T

    2015-07-01

    Modern decimeter-scale columnar stromatolites from Lake Joyce, Antarctica, show a change in branching pattern during a period of lake level rise. Branching patterns correspond to a change in cyanobacterial community composition as preserved in authigenic calcite crystals. The transition in stromatolite morphology is preserved by mineralized layers that contain microfossils and cylindrical molds of cyanobacterial filaments. The molds are composed of two populations with different diameters. Large diameter molds (>2.8 μm) are abundant in calcite forming the oldest stromatolite layers, but are absent from younger layers. In contrast, <2.3 μm diameter molds are common in all stromatolites layers. Loss of large diameter molds corresponds to the transition from smooth-sided stromatolitic columns to branched and irregular columns. Mold diameters are similar to trichome diameters of the four most abundant living cyanobacteria morphotypes in Lake Joyce: Phormidium autumnale morphotypes have trichome diameters >3.5 μm, whereas Leptolyngbya antarctica, L. fragilis, and Pseudanabaena frigida morphotypes have diameters <2.3 μm. P. autumnale morphotypes were only common in mats at <12 m depth. Mats containing abundant P. autumnale morphotypes were smooth, whereas mats with few P. autumnale morphotypes contained small peaks and protruding bundles of filaments, suggesting that the absence of P. autumnale morphotypes allowed small-scale topography to develop on mats. Comparisons of living filaments and mold diameters suggest that P. autumnale morphotypes were present early in stromatolite growth, but disappeared from the community through time. We hypothesize that the mat-smoothing behavior of P. autumnale morphotypes inhibited nucleation of stromatolite branches. When P. autumnale morphotypes were excluded from the community, potentially reflecting a rise in lake level, short-wavelength roughness provided nuclei for stromatolite branches. This growth history provides a

  13. Climatological observations and predicted sublimation rates at Lake Hoare, Antarctica.

    USGS Publications Warehouse

    Clow, G.D.; McKay, C.P.; Simmons, G.M., Jr.; Wharton, R.A., Jr.

    1988-01-01

    In December 1985, an automated meteorological station was established at Lake Hoare in the dry valley region of Antarctica. Here, we report on the first year-round observations available for any site in Taylor Valley. This dataset augments the year-round data obtained at Lake Vanda (Wright Valley) by winter-over crews during the late 1960s and early 1970s. The mean annual solar flux at Lake Hoare was 92 W m-2 during 1986, the mean air temperature -17.3 degrees C, and the mean 3-m wind speed 3.3 m s-1. The local climate is controlled by the wind regime during the 4-month sunless winter and by seasonal and diurnal variations in the incident solar flux during the remainder of the year. Temperature increases of 20 degrees-30 degrees C are frequently observed during the winter due to strong fo??hn winds descending from the Polar Plateau. A model incorporating nonsteady molecular diffusion into Kolmogorov-scale eddies in the interfacial layer and similarity-theory flux-profiles in the surface sublayer, is used to determine the rate of ice sublimation from the acquired meteorological data. Despite the frequent occurrence of strong winter fo??hns, the bulk of the annual ablation occurs during the summer due to elevated temperatures and persistent moderate winds. The annual ablation from Lake Hoare is estimated to have been 35.0 +/- 6.3 cm for 1986.

  14. Chitinase genes in lake sediments of Ardley Island, Antarctica.

    PubMed

    Xiao, Xiang; Yin, Xuebin; Lin, Jian; Sun, Liguang; You, Ziyong; Wang, Peng; Wang, Fengping

    2005-12-01

    A sediment core spanning approximately 1,600 years was collected from a lake on Ardley Island, Antarctica. The sediment core had been greatly influenced by penguin guano. Using molecular methods, the chitinolytic bacterial community along the sediment core was studied over its entire length. Primers targeting conserved sequences of the catalytic domains of family 18 subgroup A chitinases detected group A chitinases from a wide taxonomic range of bacteria. Using quantitative competitive PCR (QC-PCR), chitinase gene copies in each 1-cm section of the whole sediment column were quantified. QC-PCR determination of the chitinase gene copies indicated significant correlation with phosphorus and total organic carbon concentration, suggesting a historical connection between chitinase gene copies and the amount of penguin guano input into the lake sediment. Most of the chitinase genes cloned from the historic sediment core were novel. Analysis of the chitinase gene diversity in selected sediment layers and in the fresh penguin deposits indicated frequent shifts in the chitinolytic bacterial community over time. Sequence analysis of the 16S rRNA genes of chitinolytic bacteria isolated from the lake sediment revealed that the isolates belonged to Janthinobacterium species, Stenotrophomonas species of gamma-Proteobacteria, Cytophaga species of the Cytophaga-Flexibacter-Bacteroides group, and Streptomyces and Norcardiopsis species of Actinobacteria. Chitinase gene fragments were cloned and sequenced from these cultivated chitinolytic bacteria. The phylogeny of the chitinase genes obtained from the isolates did not correspond well to that of the isolates, suggesting acquisition via horizontal gene transfer. PMID:16332766

  15. Evolution of dissolved organic matter under lake ice in Lake Hoare, Antarctica

    NASA Astrophysics Data System (ADS)

    Ebert, J.; Castendyk, D.; McKnight, D. M.

    2013-12-01

    DOM is present in all aquatic ecosystems on Earth and plays an important role in the global carbon cycle. DOM is comprised of a complex, heterogeneous mixture of organic compounds derived from both microbial and terrestrial sources and is analyzed using fluorescence spectroscopy. Lake Hoare, located in the McMurdo Dry Valleys, Antarctica is a perennially ice covered lake that occupies a 4-km-long, closed-basin fed by a diurnal meltwater stream called Andersen Creek, runoff from the Canada Glacier, and overflow from an adjacent pond. Previous studies in Antarctica suggest that DOM evolves under lake ice as a function of solar radiation and biological processes. This study explores the evolution of DOM in Andersen Creek and Lake Hoare water measured over a 4-hour time period in mid-summer 2013 in response to changes in stream discharge, solar radiation, water temperature, and biological activity. Water samples were collected from 15 ice boreholes and 5 ice-free stream locations between 19:30 and 18:30 hours on 17 December, and again between 23:30 hours and 00:30 hours. Four boreholes in the perennial lake ice were sampled at two depths: (1) immediately below lake ice and (2) one meter below lake ice. All samples were analyzed using a Horiba-Jorbin Yvon Fluoromax 4 fluorometer and were blank, Raman, and inner-filter corrected. Indices were calculated from the resulting excitation emission matrices (EEMs). Samples were then analyzed using a biogeochemically diverse model, which gives information regarding the properties of DOM. Preliminary fluorescence index (FI) values show spatial and temporal variability, with higher FI values shown in stream samples than in lake samples. This could indicate higher microbial activity in stream water than below perennial lake ice. For shore ice boreholes near the stream inlet, the humification index (HIX) decreased with time suggesting that incoming stream water is less humified than lake water. In-lake processes are more likely to

  16. Subglacial Lake Whillans, West Antarctica; Solute Dynamics and Fluxes to the Ross Sea

    NASA Astrophysics Data System (ADS)

    Skidmore, M. L.; Michaud, A. B.; Achberger, A.; Barbante, C.; Christner, B. C.; Mikucki, J.; Mitchell, A. C.; Priscu, J. C.; Purcell, A. M.; van Gelder, W.; Vick-Majors, T.

    2014-12-01

    Subglacial Lake Whillans is located beneath the Whillans Ice Stream in West Antarctica. The lake is situated beneath 800 m of ice and ~ 70 km upstream of the grounding line where Whillans Ice Stream terminates into the Ross Sea. Subglacial Lake Whillans is a shallow lake and a component of a complex subglacial hydrological system that may resemble a large wetland along the Siple Coast of West Antarctica. Subglacial Lake Whillans drains and refills on a sub-decadal time scale discharging water towards the Ross Sea. Water and sediment samples were recovered from the lake, using clean access drilling technologies, in January, 2013. Isotopic analysis of the lake waters indicates basal meltwater from the ice sheet as the dominant water source. Geochemical analysis of the lake water reveals it is freshwater with mineral weathering as a significant solute source, with a minor contribution from sea water likely from relict marine sediments. Subglacial hydrothermal activity upstream may also contribute solutes. Nutrients N and P are present at micromolar concentrations. Sediment porewaters from shallow cores (~ 40 cm depth) of the subglacial lake sediments indicate increasing solute concentration with depth, with up to ~ five times greater solute concentrations than in the lake water. The waters and sediment contain metabolically active organisms which are likely involved in elemental cycling within the lake system. Here we will discuss solute sources to the lake, solute dynamics within the lake waters and sediment, and the fluxes of solute and nutrients to the Ross Sea and their implications for these marine ecosystems.

  17. Ice cover, landscape setting, and geological framework of Lake Vostok, East Antarctica

    USGS Publications Warehouse

    Studinger, M.; Bell, R.E.; Karner, G.D.; Tikku, A.A.; Holt, J.W.; Morse, D.L.; David, L.; Richter, T.G.; Kempf, S.D.; Peters, M.E.; Blankenship, D.D.; Sweeney, R.E.; Rystrom, V.L.

    2003-01-01

    Lake Vostok, located beneath more than 4 km of ice in the middle of East Antarctica, is a unique subglacial habitat and may contain microorganisms with distinct adaptations to such an extreme environment. Melting and freezing at the base of the ice sheet, which slowly flows across the lake, controls the flux of water, biota and sediment particles through the lake. The influx of thermal energy, however, is limited to contributions from below. Thus the geological origin of Lake Vostok is a critical boundary condition for the subglacial ecosystem. We present the first comprehensive maps of ice surface, ice thickness and subglacial topography around Lake Vostok. The ice flow across the lake and the landscape setting are closely linked to the geological origin of Lake Vostok. Our data show that Lake Vostok is located along a major geological boundary. Magnetic and gravity data are distinct east and west of the lake, as is the roughness of the subglacial topography. The physiographic setting of the lake has important consequences for the ice flow and thus the melting and freezing pattern and the lake's circulation. Lake Vostok is a tectonically controlled subglacial lake. The tectonic processes provided the space for a unique habitat and recent minor tectonic activity could have the potential to introduce small, but significant amounts of thermal energy into the lake. ?? 2002 Elsevier Science B.V. All rights reserved.

  18. Subglacial Lake CECs: Discovery and in situ survey of a privileged research site in West Antarctica

    NASA Astrophysics Data System (ADS)

    Rivera, Andrés.; Uribe, José; Zamora, Rodrigo; Oberreuter, Jonathan

    2015-05-01

    We report the discovery and on-the-ground radar mapping of a subglacial lake in Antarctica, that we have named Lake CECs (Centro de Estudios Científicos) in honor of the institute we belong to. It is located in the central part of the West Antarctic Ice Sheet, right underneath the Institute Ice Stream and Minnesota Glacier ice divide, and has not experienced surface elevation changes during the last 10 years. The ratio between the area of the subglacial lake and that of its feeding basin is larger than those for either subglacial lakes Ellsworth or Whillans, and it has a depth comparable to that of Ellsworth and greater than that of Whillans. Its ice thickness is ˜600 m less than that over Ellsworth. The lake is very likely a system with long water residence time. The recent finding of microbial life in Lake Whillans emphasizes the potential of Subglacial Lake CECs for biological exploration.

  19. Tracking human footprints in Antarctica through passive sampling of polycyclic aromatic hydrocarbons in inland lakes.

    PubMed

    Yao, Yao; Meng, Xiang-Zhou; Wu, Chen-Chou; Bao, Lian-Jun; Wang, Feng; Wu, Feng-Chang; Zeng, Eddy Y

    2016-06-01

    Freely dissolved polycyclic aromatic hydrocarbons (PAHs) were monitored in seven inland lakes of Antarctica by a polyethylene (PE)-based passive sampling technique, with the objective of tracking human footprints. The measured concentrations of PAHs were in the range of 14-360 ng L(-1) with the highest values concentrated around the Russian Progress II Station, indicating the significance of human activities to the loading of PAHs in Antarctica. The concentrations of PAHs in the inland lakes were in the upper part of the PAHs levels in aquatic environments from remote and background regions across the globe. The composition profiles of PAHs indicated that PAHs in the inland lakes were derived mainly from local oil spills, which was corroborated by a large number of fuel spillage reports from ship and plane crash incidents in Antarctica during recent years. Clearly, local human activities, rather than long-range transport, are the dominant sources of PAH contamination to the inland lakes. Finally, the present study demonstrates the efficacy of PE-based passive samplers for investigating PAHs in the aquatic environment of Antarctica under complex field conditions. PMID:26946176

  20. The helium isotopic chemistry of Lake Bonney, Taylor Valley, Antarctica: Timing of late holocene climate change in Antarctica

    USGS Publications Warehouse

    Poreda, R.J.; Hunt, A.G.; Berry, Lyons W.; Welch, K.A.

    2004-01-01

    To better understand the long-term climate history of Antarctica, we studied Lake Bonney in Taylor Valley, Southern Victoria Land (78?? S). Helium isotope ratios and He, Ne, Ar and N2 concentration data, obtained from hydrocasts in the East (ELB) and West (WLB) Lobesof Lake Bonney, provided important constraints on the lake's Holocene evolution. Based on very low concentrations of Ar and N2 in the ELB bottom waters, ELB was free of ice until 200 ?? 50 years ago. After which, low salinity water flowing over the sill from WLB to ELB, covered ELB and formed a perennial ice cover, inhibiting the exchange of gases with the atmosphere. In contrast to the ELB, the WLB retained an ice cover through the Holocene. The brine in the WLB bottom waters has meteoric N2 and Ar gas concentrations indicating that it has not been significantly modified by atmospheric exchange or ice formation. The helium concentrations in the deep water of WLB are the highest measured in non-thermal surface water. By fitting a diffusional loss to the 3He/4He, helium, and Cl profiles, we calculate a time of ???3000 years for the initiation of flow over the sill separating the East and West Lobes. To supply this flux of helium to the lake, a helium-rich sediment beneath the lake must be providing the helium by diffusion. If at any time during the last million years the ice cover left WLB, there would be insufficient helium available to provide the current flux to WLB. The variations in water levels in Lake Bonney can be related to climatic events that have been documented within the Southern Victoria Land region and indicate that the lakes respond significantly to regional and, perhaps, global climate forcing. ?? 2004 Kluwer Academic Publishers.

  1. Antarctica

    Atmospheric Science Data Center

    2013-04-16

    ... Twilight in Antarctica, February 24, 2000 . Nearly 15 times every 24 hours, the Terra spacecraft, traveling southward, crosses from ... D.C. The Terra spacecraft is managed by NASA's Goddard Space Flight Center, Greenbelt, MD. The MISR data were obtained from the NASA Langley ...

  2. Geomicrobiology of subglacial ice above Lake Vostok, Antarctica

    USGS Publications Warehouse

    Priscu, J.C.; Adams, E.E.; Lyons, W.B.; Voytek, M.A.; Mogk, D.W.; Brown, R.L.; McKay, C.P.; Takacs, C.D.; Welch, K.A.; Wolf, C.F.; Kirshtein, J.D.; Avci, R.

    1999-01-01

    Data from ice 3590 meters below Vostok Station indicate that the ice was accredit from liquid water associated with Lake Vostok. Microbes were observed at concentrations ranging from 2.8 x 103 to 3.6 x 104 cells per milliliter; no biological incorporation of selected organic substrates or bicarbonate was detected. Bacterial 165 ribosomal DNA genes revealed low diversity in the gene population. The phylotypes were closely related to extant members of the alpha- and beta-Proteobacteria and the Actinomycetes. Extrapolation of the data from accretion ice to Lake Vostok implies that Lake Vostok may support a microbial population, despite more than 106 years of isolation from the atmosphere.

  3. Physical and chemical characteristics of the Subglacial Lake Whillans sediment cores, Whillans Ice Stream, West Antarctica

    NASA Astrophysics Data System (ADS)

    Hodson, T. O.; Powell, R. D.

    2013-12-01

    Sediment recovered from Subglacial Lake Whillans (SLW) is well-homogenized, structureless diamict; typical subglacial till. Based on theoretical estimates, the basal ice above SLW should be below the pressure melting point preventing melt-out of debris from basal ice. Therefore, the lake floor diamict likely formed through deformation while the ice stream was grounded at the drill site. Using satellite altimetry, Fricker, et al. (2007) inferred that SLW experiences short (~7 month) discharge events, lowering the ice surface and lake water level by between 1 and 4 m. The lake 'lowstands' are separated by longer periods of gradual recharge, but over the period of a lowstand the ice stream is suspected to touch down and couple with the lake floor, potentially shearing new till into the lake. The lack of sorted sediment or erosional lags indicates water flow during discharge/recharge events has had a low current velocity with quiescent conditions in the lake. The most notable variability in the cores is a uniformly weak, critical porosity horizon extending to ~50 cm depth above more consolidated till. We interpret the weak upper horizon as the product of shear deformation and decreasing effective pressure experienced during the final stages of grounding prior to a lake recharge event (see generally, the undrained plastic bed model of Tulaczyk et al. (2000)). The presence of this weak layer illustrates the importance of hydrology in modulating till rheology and is an example of how subglacial sediments can preserve archives of hydrologic conditions at the glacial bed. Fricker, H.A., T. Scambos, R. Bindschadler and L. Padman. 2007. An active subglacial water system in West Antarctica mapped from space. Science, 315(5818), 1544-1548. Tulaczyk S, Kamb WB, Engelhardt HF. 2000. Basal mechanics of Ice Stream B, West Antarctica. 2. Undrained plastic bed model. J. Geophys. Res. 105:483-94.

  4. Carbon dioxide and methane fluxes in the littoral zones of two lakes, east Antarctica

    NASA Astrophysics Data System (ADS)

    Zhu, Renbin; Liu, Yashu; Xu, Hua; Huang, Tao; Sun, Jianjun; Ma, Erdeng; Sun, Liguang

    2010-01-01

    During the summertime of 2007/2008, carbon dioxide (CO 2) and methane (CH 4) fluxes across air-water interface were investigated in the littoral zones of Lake Mochou and Lake Tuanjie, east Antarctica, using a static chamber technique. The mean fluxes of CO 2 and CH 4 were -70.8 mgCO 2 m -2 h -1 and 144.6 μgCH 4 m -2 h -1, respectively, in the littoral zone of Lake Mochou; The mean fluxes were -36.9 mgCO 2 m -2 h -1 and 109.8 μgCH 4 m -2 h -1, respectively, in the littoral zone of Lake Tuanjie. Their fluxes showed large temporal and spatial dynamics. The CO 2 fluxes showed a significantly negative correlation with daily total radiation (DTR) and a weakly negative correlation with air temperature and water temperature, indicating that sunlight intensity controlled the magnitude of CO 2 fluxes from the open lakes. The CH 4 fluxes significantly correlated with local air temperature, water table and total dissolved solids (TDS), indicating that they were the predominant factors influencing CH 4 fluxes. Summertime CO 2 budgets in the littoral zones of Lake Mochou and Lake Tuanjie were estimated to be -152.9 gCO 2 m -2 and -79.7 gCO 2 m -2, respectively, and net CH 4 emissions were estimated to be 312.3 mgCH 4 m -2 and 237.2 mgCH 4 m -2, respectively. Our results show that shallow, open, alga-rich lakes might be strong summertime CO 2 absorbers and small CH 4 emitters during the open water in coastal Antarctica.

  5. Diversity of bacterial communities in the lakes of Schirmacher Oasis, Antarctica

    NASA Astrophysics Data System (ADS)

    Mojib, Nazia; Huang, Jonathan; Hoover, Richard B.; Pikuta, Elena V.; Storrie-Lombardi, Michael; Sattler, Birgit; Andersen, Dale; Bej, Asim K.

    2009-08-01

    Extreme conditions such as low temperature, aridness, low availability of organic matter, high salinity and UV-radiation in terrestrial Antarctica are key factors limiting the habitation of biotic communities and ecosystem dynamics. In recent studies, it has been discovered that the bacterial communities are highly diverse and distributed widely in the extreme ecosystem of Antarctica. Besides available morphometric data, geology, and thermal profile, limited study on the microbial identification, phylogenetic analysis, diversity and distribution of microorganisms in different lakes of Schirmacher Oasis in East Antarctica has been reported. The objective of this study was to assess the microbial biodiversity and distribution using culture-independent and culture-dependent methodologies based upon bacterial 16S rRNA gene analysis in three categories of lakes, i.e., the land-locked (L), epi-shelf (E), and pro-glacial (P) lakes in Schirmacher Oasis. The water and ice samples were collected during the 2008 Tawani International Scientific Expedition. Direct culturing of the samples on R2A agar media exhibited a wide variety of pigmented bacteria. Two of the pigmented bacteria that were cultured belong to the genera, Hymenobacter, and Flavobacterium. Cultureindependent methodology of one of the land-locked lakes L27C identified a rich microbial diversity consisting of six different phyla of bacteria. The majority of bacteria (56%) belong to the Class γ-proteobacteria within the phylum Proteobacteria. Within the Class γ-proteobacteria, Acinetobacter dominated (48%) the total microbial load. Characterization of the microbial diversity within the three different types of Antarctic lakes is important because it will help give us a better understanding of the survival mechanisms and the functionality of these bacteria in extremely cold and harsh Antarctic ecosystems.

  6. Active Lakes of the Recovery Ice Stream, East Antarctica: A Bedrock-Controlled Subglacial Hydrological System

    NASA Astrophysics Data System (ADS)

    Fricker, H. A.; Scambos, T. A.; Bell, R. E.; Carter, S. P.

    2014-12-01

    A connected system of active sub-glacial lakes was revealed beneath the Recovery Ice Stream, East Antarctica by ICESat laser altimetry acquired from 2003 to 2008. Here we combine repeat-track analysis of ICESat (2003-2009), Operation IceBridge laser altimetry and radio-echo sounding (RES; 2011 and 2012), and MODIS image differencing (2009-2011) to learn more about the surface and bedrock topographic setting of the lakes and the constraints on water flow through the system. IceBridge data reveal a ~1500 m deep, ~1000 km long bedrock trough under the main trunk of Recovery Ice Stream. We extend the lake activity time series to 2012 for the three lower lakes using IceBridge data: one lake underwent a large deflation between 2009 and 2011; another lake, which had been continuously filling between 2003 and 2010, started to drain after 2011. Hydrologic connections among the lakes appear to be direct and responsive. We reproduce the lake activity using a simple subglacial water model. The hydrologic system beneath Recovery Ice Stream is controlled by unusually pronounced bedrock topography (and not ice surface topography, as is the case for most Antarctic systems studied to date). We discuss potential causes of non-steady hydrologic behavior in major Antarctic catchments.

  7. Ground-based thermal imaging of lava lakes at Erebus volcano, Antarctica

    NASA Astrophysics Data System (ADS)

    Calkins, J.; Oppenheimer, C.; Kyle, P. R.

    2008-11-01

    Mount Erebus, a large intraplate stratovolcano dominating Ross Island, Antarctica, hosts the world's only active phonolite lava lakes. The main manifestation of activity at Erebus volcano in December 2004 was as the presence of two convecting lava lakes within an inner crater. The long-lived Ray Lake, ~ 1400 m 2 in area, was the site of up to 10 small Strombolian eruptions per day. A new but short-lived, ~ 1000-1200 m 2 lake formed at Werner vent in December 2004 sourced by lava flowing from a crater formed in 1993 by a phreatic eruption. We measured the radiative heat flux from the two lakes in December 2004 using a compact infrared (IR) imaging camera. Daily thermal IR surveys from the Main Crater rim provide images of the lava lake surface temperatures and identify sites of upwelling and downwelling. The radiative heat outputs calculated for the Ray and Werner Lakes are 30-35 MW and 20 MW, respectively. We estimate that the magma flux needed to sustain the combined heat loss is ~ 250-710 kg s - 1 , that the minimum volume of the magma reservoir is 2 km 3, and that the radius of the conduit feeding the Ray lake is ~ 2 m.

  8. Metal dynamics in Lake Vanda (Wright Valley, Antarctica)

    NASA Technical Reports Server (NTRS)

    Green, W. J.; Ferdelman, T. G.; Canfield, D. E.; DeVincenzi, D. L. (Principal Investigator)

    1989-01-01

    Data are reported for Mn, Fe, Co, Ni, Cu and Cd in the Onyx River, and for Mn, Co, Ni, Cu and Cd in Lake Vanda, a closed-basin Antarctic lake. Oxic water concentrations for Co, Ni, Cu and Cd were quite low and approximate pelagic ocean values. Scavenging of these metals by sinking particles is strongly indicated. Deep-lake profiles reveal a sharp peak in the concentrations of Mn, Fe and Co at the oxic-anoxic boundary at 60 m. Maxima for Ni, Cu and Cd occur higher in the water column, in the vicinity of a Mn submaximum, suggesting early release of these metals from sinking manganese oxide-coated particles. A rough steady-state model leads to the conclusion that there is a large downward flux of Mn into the deep lake and that this flux is sufficient to explain the annual loss of Co, Ni, Cu and Cd. A pronounced geochemical separation between Fe and Mn apparently occurs in this system--Fe being best lost in near-shore environments and Mn being lost in deeper waters. Comparison of metal residence times in Lake Vanda with those in the oceans shows that in both systems Mn, Fe and Co are much more reactive than Ni, Cu and Cd. Energetically favorable inclusion of the more highly charged metals, Mn(IV), Fe(III) and Co(III), into oxide-based lattices is a plausible explanation.

  9. Changes in ice cover thickness and lake level of Lake Hoare, Antarctica - Implications for local climatic change

    NASA Technical Reports Server (NTRS)

    Wharton, Robert A., Jr.; Mckay, Christopher P.; Clow, Gary D.; Andersen, Dale T.; Simmons, George M., Jr.; Love, F. G.

    1992-01-01

    Results are reported from 10 years of ice-thickness measurements at perennially ice-covered Lake Hoare in southern Victoria Land, Antarctica. The ice cover of this lake had been thinning steadily at a rate exceeding 20 cm/yr during the last decade but seems to have recently stabilized at a thickness of 3.3 m. Data concerning lake level and degree-days above freezing are presented to show the relationship between peak summer temperatures and the volume of glacier-derived meltwater entering Lake Hoare each summer. From these latter data it is inferred that peak summer temperatures have been above 0 C for a progressively longer period of time each year since 1972. Possible explanations for the thinning of the lake ice are considered. The thickness of the ice cover is determined by the balance between freezing during the winter and ablation that occurs all year but maximizes in summer. It is suggested that the term most likely responsible for the change in the ice cover thickness at Lake Hoare is the extent of summer melting, consistent with the rising lake levels.

  10. Physical processes in Subglacial Lake Whillans, West Antarctica: Inferences from sediment cores

    NASA Astrophysics Data System (ADS)

    Hodson, T. O.; Powell, R. D.; Brachfeld, S. A.; Tulaczyk, S.; Scherer, R. P.

    2016-06-01

    The hydrologic system beneath the Antarctic Ice Sheet is thought to influence both the dynamics and distribution of fast flowing ice streams, which discharge most of the ice lost by the ice sheet. Despite considerable interest in understanding this subglacial network and its affect on ice flow, in situ observations from the ice sheet bed are exceedingly rare. Here we describe the first sediment cores recovered from an active subglacial lake. The lake, known as Subglacial Lake Whillans, is part of a broader, dynamic hydrologic network beneath the Whillans Ice Stream in West Antarctica. Even though "floods" pass through the lake, the lake floor shows no evidence of erosion or deposition by flowing water. By inference, these floods must have insufficient energy to erode or transport significant volumes of sediment coarser than silt. Consequently, water flow beneath the region is probably incapable of incising continuous channels into the bed and instead follows preexisting subglacial topography and surface slope. Sediment on the lake floor consists of till deposited during intermittent grounding of the ice stream following flood events. The fabrics within the till are weaker than those thought to develop in thick deforming beds suggesting subglacial sediment fluxes across the ice plain are currently low and unlikely to have a large stabilizing effect on the ice stream's grounding zone.

  11. Airborne Gravimetry and Laser Altimetry over Lake Vostok, East Antarctica

    NASA Astrophysics Data System (ADS)

    Richter, T. G.; Kempf, S. D.; Holt, J. W.; Morse, D. L.; Blankenship, D. D.; Peters, M. E.

    2002-05-01

    In response to an NSF-OPP proposal from Lamont Doherty Earth Observatory (R. Bell and M. Studinger) to study Lake Vostok, a team from the University of Texas Institute for Geophysics (UTIG) conducted the first comprehensive aerogeophysical survey of Lake Vostok during the 2000/01 austral summer. A Twin Otter was instrumented for measurements of gravity, magnetics, ice thickness, and surface elevation. The survey grid was 165 x 330 km (line spacing 7.5 km with 11.25 km and 22.5 km tie-lines), augmented by 12 regional lines extending 180 - 440 km from the primary grid. The remote polar location, high altitude, and extreme cold presented significant technical and physiological challenges, but the survey was completed successfully in 36 flights over 26 days, and has resulted in excellent geophysical data sets. We describe here the acquisition and reduction of the gravity field and ice-surface elevation data sets. Gravimetry and laser altimetry both require high-quality, precise positioning for use in data reduction. Three carrier-phase GPS receivers were operated in parallel aboard the aircraft, with an identical suite at the surface camp. All GPS data sets were reduced using two different software packages -- K&RS and GIPSY-OASIS. K&RS produced the most accurate positions but is inappropriate for long baselines. While GIPSY-OASIS yields positions in circumstances unfavorable to K&RS (i.e., long baselines and lines without closure), it was about half as accurate as K&RS and was insufficient for achieving the desired accuracy of 1-2 mGal in the reduced gravity data. Gravity was measured with a Bell Aerospace BGM-3 marine gravimeter provided by the Naval Oceanographic Office and modified for airborne use. GPS data are used to correct for inertial accelerations induced by aircraft movement. Up to 21 GPS solutions were available for each line. Selection was made through correlation of the high-frequency accelerations recorded by the gravity meter and those derived from the

  12. First evidence for a late LGM subglacial lake in Pine Island Bay, Antarctica

    NASA Astrophysics Data System (ADS)

    Kuhn, Gerhard; Hillenbrand, Claus-Dieter; Kasten, Sabine; Smith, James A.; Nitsche, Frank O.; Frederichs, Thomas; Wiers, Steffen; Ehrmann, Werner; Klages, Johann P.; Mogollón, José M.

    2016-04-01

    Subglacial lakes are widespread beneath the Antarctic Ice Sheet and as a source for subglacial meltwater they are assumed to modulate ice stream velocity. Further, the evacuation of subglacial meltwater at the ice sheet margin influences ocean circulation and geochemical cycles. However, despite their importance,, subglacial lakes are one of the least explored environments on our planet. As a consequence, their importance for ice sheet dynamics and their ability to harbour life remain poorly characterised. We present the first direct evidence for a palaeo-subglacial lake on the Antarctic continental shelf, documenting that subglacial meltwater was stored during the last glacial period and evacuated during the subsequent deglaciation. A distinct sediment facies observed in a core recovered from a small bedrock basin in Pine Island Bay, Amundsen Sea, is indicative of deposition within a low-energy subglacial lake setting. Diffusive modelling demonstrates that low chloride concentrations in the pore water of this characteristic sediment facies can only be explained by original deposition in a freshwater setting. We also show that the location of the subglacial lake within a basin on the inner shelf is consistent with the predicted distribution of subglacial lakes based on bathymetric data. This finding will enable future modelling studies to investigate how the geometry and capacity of subglacial lake systems can influence ice dynamics when the substrate and profile of the ice sheet is known - especially in the highly sensitive area known as the "weak underbelly" of the WAIS. With the exception of a direct lake water access at Subglacial Lake Vostok, and some centimetres of sediment retrieval from Subglacial Lake Whillans, the subglacial hydrological system in Antarctica has hitherto mostly been explored using remote sensing and numerical models that suggest the number of potential lake sites to more than 12.000. Our study not only provides first empirical evidence

  13. Regional geoid modeling in the area of subglacial Lake Vostok, Antarctica

    NASA Astrophysics Data System (ADS)

    Schwabe, Joachim; Ewert, Heiko; Scheinert, Mirko; Dietrich, Reinhard

    2014-04-01

    We present a geoid model for the area of Lake Vostok, Antarctica, from a combination of local airborne gravity, ice-surface and ice-thickness data and a lake bathymetry model. The topography data are used for residual terrain modeling (RTM) in a remove-restore approach together with GOCE satellite data. The quasigeoid is predicted by least-squares collocation (LSC) and subsequently converted to geoid heights. Special aspects of that method in presence of an ice sheet are discussed. It is well known that a body freely floating in water is in a state of hydrostatic equilibrium (HE). This usually applies, e.g., to ice shelves or sea ice. However, it has been shown that this is valid also for the ice sheet covering the subglacial Lake Vostok. Thus, we demonstrate the use of such a refined regional geoid model for glaciological and geophysical applications by means of the HE surface of that lake. The mean quadratic residual geoid signal (0.56 m) w.r.t. the GOCE background model exceeds the residual variations of the estimated apparent lake level (ALL) (0.26 m) within the central part of the lake. An approach considering the actual geopotential at the ALL has been derived and subsequently applied. In this context, downward continuation of the potential field within the ice sheet as well as the latitudinal tilt of off-geoid equipotential surfaces are discussed. In view of the accuracy of the ice-thickness measurements that dominate the total error budget of the estimated ALL these effects are negligible. Thus, the HE surface of subglacial lakes may safely be described by a constant height bias in small-scale regional applications. However, field continuation is significant with respect to the formal uncertainty of the quasigeoid, which is at the level of 5 cm given that accurate airborne gravity data (±2 mGal) are available.

  14. Rare earth elements in the water column of Lake Vanda, McMurdo Dry Valleys, Antarctica

    NASA Astrophysics Data System (ADS)

    De Carlo, Eric Heinen; Green, William J.

    2002-04-01

    We present data on the composition of water from Lake Vanda, Antarctica. Vanda and other lakes in the McMurdo Dry Valleys of Antarctica are characterized by closed basins, permanent ice covers, and deep saline waters. The meromictic lakes provide model systems for the study of trace metal cycling owing to their pristine nature and the relative simplicity of their biogeochemical systems. Lake Vanda, in the Wright Valley, is supplied by a single input, the Onyx River, and has no output. Water input to the lake is balanced by sublimation of the nearly permanent ice cap that is broken only near the shoreline during the austral summer. The water column is characterized by an inverse thermal stratification of anoxic warm hypersaline water underlying cold oxic freshwater. Water collected under trace-element clean conditions was analyzed for its dissolved and total rare earth element (REE) concentrations by inductively coupled plasma mass spectrometry. Depth profiles are characterized by low dissolved REE concentrations (La, Ce, <15 pM) in surface waters that increase slightly (La, 70 pM; Ce, 20 pM) with increasing depth to ˜55 m, the limit of the fresh oxic waters. Below this depth, a sharp increase in the concentrations of strictly trivalent REE (e.g., La, 5 nM) is observed, and a submaximum in redox sensitive Ce (2.6 nM) is found at 60- to 62-m depth. At a slightly deeper depth, a sharper Ce maximum is observed with concentrations exceeding 11 nM at a 67-m depth, immediately above the anoxic zone. The aquatic concentrations of REE reported here are ˜50-fold higher than previously reported for marine oxic/anoxic boundaries and are, to our knowledge, the highest ever observed at natural oxic/anoxic interfaces. REE maxima occur within stable and warm saline waters. All REE concentrations decrease sharply in the sulfidic bottom waters. The redox-cline in Lake Vanda is dominated by diffusional processes and vertical transport of dissolved species driven by concentration

  15. A model of the geochemical and physical fluctuations of the lava lake at Erebus volcano, Antarctica

    NASA Astrophysics Data System (ADS)

    Molina, Indira; Burgisser, Alain; Oppenheimer, Clive

    2015-12-01

    Erebus volcano, Antarctica, exhibits periodical surface fluctuations of both geochemical and physical nature. Modeling the physics driving the lake oscillation is a challenge, even with a relatively simple theoretical framework. We present a quantitative analysis that aims to reconcile both lake level and gas geochemical cycles. Our model is based on the assumption that the periodicity is caused by the regular release of magma batches and/or core annular flow that have a fixed volume of melt and ascend and degas in equilibrium. Results suggest that cycles are not caused by the mixing between magma residing in the lake and a deep magma but by two distinct deep sources that rise separately. These sources of bubbly magma come from at most 2-3 km depth and rise buoyantly. Individual batches detach from the rising magmas at depths of 20-250 m. The two batch types can coexist in a single conduit up to a depth of ~ 30 m, above which they rise alternately to release respectively 19 and 23 kg/s of gas at the lake surface every 10 min. The temperature of the descending flow is between 890 and 950 °C, which is roughly 100 °C colder than the ascending currents. Batch pairs have shapes likely constrained by the conduit width. Regardless of their shapes, the pairs reach very high porosities near the surface and have diameters of 4-14 m that are consistent with video observations showing spreading waves at the lake surface. The alternating arrival of these large batches suggests a lava lake mostly filled with gas-rich magma.

  16. Inversion of Airborne Gravity Data over Subglacial Lakes in East Antarctica

    NASA Astrophysics Data System (ADS)

    Blankenship, D.

    2003-12-01

    The team of the University of Texas Institute for Geophysics (UTIG) has been performing airborne geophysical surveys in Antarctica since 1991. Over 260,000 line-km have been surveyed during nine field seasons. The UTIG airborne platform is a contracted DeHavilland Twin Otter instrumented with ice-penetrating radar, laser altimeter, magnetometer, and a gravimeter. The gravimeter utilized is a Bell Aerospace BGM-3 marine system, modified for airborne use, which provides measurements of vertical accelerations at 1 Hz, with verticality of the sensor maintained by a gyro-stabilized platform. The aerogeophysical surveys over subglacial Lake Concordia and Lake Vostok in East Antarctica were conducted by a team from UTIG over the course of the Antarctic field seasons. The region surrounding Lake Concordia was sampled by 6 profiles with a 10 km separation whereas the Lake Vostok survey block was 165 x 330 km with a line spacing of 7.5 km with 11.25 km and 22.5 km ties. 2D gravity inversion was performed for both lakes. The forward problem was solved using Talwani's algorithm for a 2D body of irregular shape. It is described by a non-linear equation between the body's shape and it's density contrast with surrounding rocks. The assumption was that the density contrast between ice/water and rock along the profile is constant. The densities of ice and water are close enough, so the ice and water of the lake can be considered as one body. For Lake Vostok the gravity data were inverted for 2-layered model, consisting of ice/water and sediment lying over dense bedrock. Inversion was performed by a conjugate gradient algorithm for several fixed values of density contrasts. The coordinates of layers' corners were chosen as model parameters. The model was constrained by the lake's boundaries and sub-ice topography, determined from radar sounding. Also, several pre-existing seismic soundings were used as `a priori' information incorporated into the model. The best agreement with

  17. Tracing groundwater input into Lake Vanda, Wright Valley, Antarctica using major ions, stable isotopes and noble gas

    NASA Astrophysics Data System (ADS)

    Dowling, C. B.; Poreda, R. J.; Snyder, G. T.

    2008-12-01

    The McMurdo Dry Valleys (MDV), Antarctica, is the largest ice-free region on Antarctica. Lake Vanda, located in central Wright Valley, is the deepest lake among the MDV lakes. It has a relatively fresh water layer above 50 m with a hypersaline calcium-chloride brine below (50-72 m). The Onyx River is the only stream input into Lake Vanda. It flows westward from the coastal Lower Wright Glacier and discharges into Lake Vanda. Suggested by the published literature and this study, there has been and may still be groundwater input into Lake Vanda. Stable isotopes, major ions, and noble gas data from this study coupled with previously published data indicate that the bottom waters of Lake Vanda have had significant contributions from a deep groundwater system. The dissolved gas of the bottom waters of Lake Vanda display solubility concentrations rather than the Ar-enriched dissolved gas seen in the Taylor Valley lakes (such as Lake Bonney). The isotopic data indicate that the bottom calcium-chloride-brine of Lake Vanda has undergone very little evaporation. The calcium-chloride chemistry of the groundwater that discharges into Lake Vanda most likely results from the chemical weathering and dissolution of cryogenic evaporites (antarcticite and gypsum) within the glacial sediments of Wright Valley. The high calcium concentrations of the brine have caused gypsum to precipitate on the lake bottom. Our work also supports previous physical and chemical observations suggesting that the upper portion actively circulates and the hypersaline bottom layer does not. The helium and calcium chloride values are concentrated at the bottom, with a very narrow transition layer between it and the above fresh water. If the freshwater layer did not actively circulate, then diffusion over time would have caused the helium and calcium chloride to slowly permeate upwards through the water column.

  18. Exploring Subglacial Lake Connectivity via Groundwater Aquifers in the Dome C Region, East Antarctica

    NASA Astrophysics Data System (ADS)

    Gooch, B. T.; Carter, S. P.; Blankenship, D. D.

    2011-12-01

    Subglacial lakes lying under the Antarctic Ice Sheet form part of a dynamic, interconnected hydraulic system. Most research exploring the nature of this system has focused on flow along the ice-bed interface, neglecting the effects of groundwater transport, as such systems are thought to lack the transmissivity necessary to accommodate the inferred meltwater volume. In the Dome C region of East Antarctica, however, inferred melt water volumes are relatively low due to proximity to the ice divide and hydraulic gradients are relatively high due to steep subglacial bedrock topography, such that groundwater flow might be viable as a dominant means of water transport. This region contains many small subglacial lakes residing in bedrock depressions of steep basal topography. Preliminary analysis of radar sounding data does not always reveal an obvious hydraulic connection between these lakes despite readily apparent sources of melt feeding these bodies. Here we test several simple models for groundwater flow, including both fractured rock and porous media systems using ice-surface and bedrock geometry inferred from radio-echo sounding data and a published map of melt rates, with the purpose of defining a region in which a groundwater system can account for the majority of the water budget. We then compare these results against maps of basal reflectivity and subglacial lake distribution, as determined from radar sounding data. Areas in which groundwater flow is the dominant process will lack basal lubrication and demonstrate low basal reflectivities, but could still contain small subglacial lakes. While not spatially extensive with respect to the ice sheet, these groundwater-dominated areas could occupy the headwaters of most glacial catchments representing a unique and relatively stable subglacial environment.

  19. Comparison of the Microbial Diversity and Abundance Between the Freshwater Land-Locked Lakes of Schirmacher Oasis and the Perennially Ice-Covered Lake Untersee in East Antarctica

    NASA Technical Reports Server (NTRS)

    Huang, Jonathan; Hoover, Richard B.; Swain, Ashit; Murdock, Chris; Bej, Asim K.

    2010-01-01

    Extreme conditions such as low temperature, dryness, and constant UV-radiation in terrestrial Antarctica are limiting factors of the survival of microbial populations. The objective of this study was to investigate the microbial diversity and enumeration between the open water lakes of Schirmacher Oasis and the permanently ice-covered Lake Untersee. The lakes in Schirmacher Oasis possessed abundant and diverse group of microorganisms compared to the Lake Untersee. Furthermore, the microbial diversity between two lakes in Schirmacher Oasis (Lake L27C and L47) was compared by culture-based molecular approach. It was determined that L27Chad a richer microbial diversity representing 5 different phyla and 7 different genera. In contrast L47 consisted of 4 different phyla and 6 different genera. The difference in microbial community could be due to the wide range of pH between L27C (pH 9.1) and L47 (pH 5.7). Most of the microbes isolated from these lakes consisted of adaptive biological pigmentation. Characterization of the microbial community found in the freshwater lakes of East Antarctica is important because it gives a further glimpse into the adaptation and survival strategies found in extreme conditions.

  20. The distribution and relative abundance of ammonia-oxidizing bacteria in lakes of the McMurdo Dry Valley, Antarctica

    USGS Publications Warehouse

    Voytek, M.A.; Priscu, J.C.; Ward, B.B.

    1999-01-01

    Marked differences in the concentrations of major ions and cations, macronutrient chemistry and general trophic status exist among the lakes of the McMurdo dry valleys in Antarctica. These differences have been attributed to both variations in stream inputs and in situ lake processes (Priscu, 1995; Lizotte et al., 1996, Spigel and Priscu, 1996). This study examines the role of nitrifying bacteria in nitrogen transformations in these lakes. Applying two polymerase chain reaction (PCR) assays targeting the 16S rRNA genes of ammonia-oxidizing bacteria and the active site of the ammonia monooxygenase gene (amoA), the distribution of ammonia-oxidizers was examined in six Antarctic lakes: Lake Bonney, Lake Hoare, Lake Fryxell and Lake Joyce in the Taylor Valley, Lake Miers in the the Miers Valley and Lake Vanda in the Wright Valley. Using a two stage amplification procedure, ammonia-oxidizers from both the beta and gamma- subclasses of the Proteobacteria were detected and their relative abundances were determined in samples collected from all sites. Ammonia-oxidizers were detected in all lakes sampled. Members of the gamma subclass were only present in the saline lakes. In general, nitrifiers were most abundant at depths above the pycnocline and were usually associated with lower concentrations of NH4 and elevated concentrations of NO3 or NO2. The distribution of nitrifiers suggests that the primary N2O peak observed in most of the lakes was produced via nitrification. Preliminary data on the rate of nitrification (Priscu et al., 1996) support the occurrence of nitrification and the presence of nitrifiers at the depth intervals where nitrifiers were detected. In all lakes, except Lake Miers, the data indicate that nitrifying bacteria have an important role in the vertical distribution of nitrogen compounds in these systems.

  1. Airborne Radar Sounding and Ice Thickness Measurements over Lake Vostok, East Antarctica

    NASA Astrophysics Data System (ADS)

    Peters, M. E.; Blankenship, D. D.; Morse, D. L.; Holt, J. W.; Kempf, S. D.; Richter, T. G.; Falola, B.; Oliason, S.

    2002-05-01

    Lake Vostok was discovered using airborne ice-sounding radar in East Antarctica during the mid 1970's, but interest in this largest known subglacial lake has increased in recent years. Frozen microbial discoveries from ice cores taken just above Lake Vostok suggest its potential for being an isolated biological ecosystem. Also, the lake's unique combination of glaciologic, hydrologic and geological processes make it a possible terrestrial analogue for sub-ice water on other planetary bodies. Satellite radar has mapped the spatial extent of the lake from surface topography, and Russian ground traverses have gathered radar and seismic data along select profiles, but the full subglacial environment has remained uncharted. In response to a proposal by R.E. Bell and M. Studinger at Lamont Doherty Earth Observatory, the University of Texas Institute for Geophysics (UTIG) conducted an airborne geophysical survey over Lake Vostok and its surroundings during the 2000/01 field season. The survey included 21,000 line-km of geophysical observations with a line spacing of 7.5 km and a tie-line spacing of 11.25 or 22.5 km. The instrument suite included incoherent ice-sounding radar, laser altimetry, and precise GPS positioning and navigation, as well as airborne gravity and magnetics measurements. The radar system consisted of a 60 MHz, 8000 watt peak power transmitter operating in pulsed continuous-wave mode at 12.5 kHz (with 250 ns pulse width), a log-detection incoherent receiver (with 80 dB dynamic range), and a signal digitizer with a unique capability to average signals rapidly. Incoherent radar observations constructed from 2048 averaged transmissions occurred roughly every 12 m along-track. Ice thicknesses in excess of 4000 m were routinely sounded over Lake Vostok using this system. In addition to the incoherent radar, a new acquisition system was developed on an experimental basis to coherently integrate radar signals utilizing synthetic aperture radar techniques

  2. Psychrophilic pseudomonas in antarctic freshwater lake at stornes peninsula, larsemann hills over east Antarctica.

    PubMed

    Chauhan, Abhishek; Bharti, Pawan K; Goyal, Pankaj; Varma, Ajit; Jindal, Tanu

    2015-01-01

    The Larsemann Hills is an ice-free area of approximately 50 km(2), located halfway between the Vestfold Hills and the Amery Ice Shelf on the south-eastern coast of Prydz Bay, Princess Elizabeth Land, East Antarctica (69º30'S, 76º19'58″E). The ice-free area consists of two major peninsulas (Stornes and Broknes), four minor peninsulas, and approximately 130 islands. The Larsemann Hills area contains more than 150 lakes at different Islands and Peninsulas. Nine lake water samples were collected in a gamma sterilized bottles and were kept in an ice pack to prevent any changes in the microbial flora of the samples during the transportation. The water samples were transported to the lab in vertical position maintaining the temperature 1-4 °C with ice pack enveloped conditions. Samples were studied for Psychrophilic bacterial count, Pseudomonas spp., Staphylococcus aureus, Salmonella and Total MPN Coliform per 100 ml. Psychrophillic counts were found in the range of 12 cfu to 1.6 × 10(2) cfu in all the samples. MPN Coliform per 100 ml was found to be absent in all the samples. No growth and characteristics colonies observed when tested for Salmonella and S.aureus. Pseudomonas sp. was found in ST-2 lake water sample as characteristics colonies (Optimum Growth) were observed on selective media at 22 and 25 °C. Further several biochemical tests were also performed to confirm the presence of this Potential Psychrophilic Pseudomonas sp. for its further application in Science and Technology. PMID:26543717

  3. Characterization of dissolved organic material in the interstitial brine of Lake Vida, Antarctica

    NASA Astrophysics Data System (ADS)

    Cawley, Kaelin M.; Murray, Alison E.; Doran, Peter T.; Kenig, Fabien; Stubbins, Aron; Chen, Hongmei; Hatcher, Patrick G.; McKnight, Diane M.

    2016-06-01

    Lake Vida (LV) is located in the McMurdo Dry Valleys (Victoria Valley, East Antarctica) and has no inflows, outflows, or connectivity to the atmosphere due to a thick (16 m), turbid ice surface and cold (<-20 °C) subsurface alluvium surrounding the lake. The liquid portion of LV has a salinity about seven times that of seawater and is entrained in ice and sediment below the ice cap. This subzero (-13.4 °C), anoxic brine supports a microbial community, which has low levels of activity and has been isolated from the atmosphere for at least 2800 14C years before present. The brine has high dissolved organic carbon concentration (DOC; 580 mg-C L-1 or greater); the study of which provides a unique opportunity to better understand biological and/or abiotic processes taking place in an isolated saline ecosystem with no external inputs. We isolated two sub-fractions of LV dissolved organic matter (DOM) by chemical separation using XAD-8 and XAD-4 resins in series. This separation was followed by physical separation using ultrafiltration to isolate a higher molecular weight (HMW) fraction that was retained by the membrane and a salty, dilute low molecular weight fraction. This analytical path resulted in three, low salt sub-fractions and allowed comparison to other Antarctic lake DOM samples isolated using similar procedures. Compared to other Antarctic lakes, a lower portion of the DOC was retained by XAD-8 (∼10% vs. 16-24%) resin, while the portions retained by XAD-4 (∼8%) resin and the 1 kDa ultrafiltration membrane (∼50%) were similar. The 14C radiocarbon ages of the XAD-8 (mean 3940 ybp), XAD-4 (mean 4048 ybp) and HMW (mean 3270 ybp) fractions are all older than the apparent age of ice-cover formation (2800 ybp). Ultrahigh resolution mass spectrometry showed that compounds with two and three nitrogen atoms in the molecular formulas were common in both the LV-XAD8 and LV-XAD4 fractions, consistent with microbial production and processing. The long-term oxidation

  4. Light transmission and reflection in perennially ice-covered Lake Hoare, Antarctica

    NASA Technical Reports Server (NTRS)

    Mckay, C. P.; Clow, G. D.; Andersen, D. T.; Wharton, R. A., Jr.

    1994-01-01

    We have investigated the transmission and albedo of the perennial ice cover on Lake Hoare, Antarctica. Our database consists of year-round measurements of the photosynthetically active radiation (400-700 nm) under the ice, measurements of the spatial variation of the under-ice light in midsummer, and spectrally resolved measurements from 400 to 700 nm of the albedo and transmission of the ice cover in early (November) and in midsummer (January). Our results show that the transmission decreases in the first part of summer, dropping by a factor of approximately 4 from November to January. We suggest that this is due to heating in the upper layers of the ice cover and the formation of Tyndall figures. Later in the summer when a significant liquid water fraction occurs within the ice cover, the transmission increases. In the fall when the ice cover freezes solid the transmission drops markedly. The spectrally resolved measurements from 400 to 700 nm show that approximately 2-5% of the incident light in this spectral region penetrates the 3.5-m thick ice cover. We have analyzed the spectral data using a two-stream scattering solution to the radiative transfer equation with three vertical layers in the ice cover. A surficial glaze of scattering ice 1 cm thick overlies a layer of sandy, bubbly ice about a meter thick, and below this is a thick layer of sand-free ice with bubbles. We find that the ice cover is virtually opaque at wavelengths longer than 800 nm. The net transmission of solar energy is approximately 2%. Significant changes in the thickness of the ice cover have been reported at Lake Hoare. These are due primarily to changes in the thickness of the bottom layer only. Because this layer is relatively clear, the effect on the transmission through the ice cover from these changes is less than would be predicted assuming a homogeneous ice cover.

  5. An extensive subglacial lake and canyon system in Princess Elizabeth Land, East Antarctica

    NASA Astrophysics Data System (ADS)

    Jamieson, Stewart; Ross, Neil; Greenbaum, Jamin; Young, Duncan; Aitken, Alan; Roberts, Jason; Blankenship, Donald; Bo, Sun; Siegert, Martin

    2016-04-01

    The subglacial landscape of Princess Elizabeth Land (PEL) in East Antarctica is poorly known due to a paucity of ice thickness measurements. This is problematic given its importance for understanding ice sheet dynamics and landscape and climate evolution. To address this issue, we describe the topography beneath the ice sheet by assuming that ice surface expressions in satellite imagery relate to large-scale subglacial features. We find evidence that a large, previously undiscovered subglacial drainage network is hidden beneath the ice sheet in PEL. We interpret a discrete feature that is 140 × 20 km in plan form, and multiple narrow sinuous features that extend over a distance of ~1100 km. We hypothesize that these are tectonically controlled and relate to a large subglacial basin containing a deep-water lake in the interior of PEL linked to a series of long, deep canyons. The presence of 1-km-deep canyons is confirmed at a few localities by radio-echo sounding data, and drainage analysis suggests that these canyons will direct subglacial meltwater to the coast between the Vestfold Hills and the West Ice Shelf.

  6. Microbial Metabolic Activity and Bioavailability of Dissolved Organic Matter Under the Impact of Intense UV Radiation in Pony Lake, Antarctica

    NASA Astrophysics Data System (ADS)

    Dieser, M.; Foreman, C. M.; McKnight, D. M.; Miller, P. L.; Chin, Y.

    2006-12-01

    Pony Lake is a saline and hypereutrophic coastal pond located on Cape Royds in the McMurdo Sound area of Antarctica. This shallow lake is ice-covered except in midsummer, when strong winds typically cause thorough mixing of the water column. The source of water appears to be accumulated snow; water is lost by ablation of the ice cover and evaporation of lake water in midsummer. In the west the pond is bordered by an Adelie penguin rookery. Previous studies have shown that Pony Lake can have very high dissolved organic carbon (DOC) concentrations (~ 100 mg C liter -1). Furthermore, Pony Lake is unique because it lacks terrestrial carbon inputs in the watershed, which makes this an excellent example of a system containing autochthonous microbially (algae, cyanobacteria, bacteria and viruses) derived organic matter. From an ecological perspective dissolved organic matter (DOM) acts as a carbon source for microorganisms, absorbs harmful ultraviolet radiation, and can participate in biogeochemical redox reactions, whereas different fractions and chemical characteristics influence the bioavailability and chemical reactivity of DOM in aquatic ecosystems. While the DOM concentration in Pony Lake is high, the percentage of DOC accounted for by fulvics acid is low, as is observed in other lakes with algal derived DOC sources. Algal derived fulvic acids are yellowish in color, and absorb light to a lesser extend compared to terrestrially derived fulvic acids. Fulvic acids from Pony Lake are enriched with nitrogen. Over two field seasons we have investigated the influence of photolytic processes on the microbial utilization of DOM from Pony Lake, Antarctica. We have determined that the intense ultraviolet radiation in Antarctica rapidly photo-bleaches DOM, resulting in the loss of UV absorbing compounds, and rendering fractions of the DOM pool less biologically available to microbes. We monitored microbial community structure, abundance and primary and secondary production

  7. Sedimentology and geochemistry of a perennially ice-covered epishelf lake in Bunger Hills Oasis, East Antarctica

    NASA Technical Reports Server (NTRS)

    Doran, P. T.; Wharton, R. A. Jr; Lyons, W. B.; Des Marais, D. J.; Andersen, D. T.; Wharton RA, J. r. (Principal Investigator)

    2000-01-01

    A process-oriented study was carried out in White Smoke lake, Bunger Hills, East Antarctica, a perennially ice-covered (1.8 to 2.8 m thick) epishelf (tidally-forced) lake. The lake water has a low conductivity and is relatively well mixed. Sediments are transferred from the adjacent glacier to the lake when glacier ice surrounding the sediment is sublimated at the surface and replaced by accumulating ice from below. The lake bottom at the west end of the lake is mostly rocky with a scant sediment cover. The east end contains a thick sediment profile. Grain size and delta 13C increase with sediment depth, indicating a more proximal glacier in the past. Sedimentary 210Pb and 137Cs signals are exceptionally strong, probably a result of the focusing effect of the large glacial catchment area. The post-bomb and pre-bomb radiocarbon reservoirs are c. 725 14C yr and c. 1950 14C yr, respectively. Radiocarbon dating indicates that the east end of the lake is >3 ka BP, while photographic evidence and the absence of sediment cover indicate that the west end has formed only over the last century. Our results indicate that the southern ice edge of Bunger Hills has been relatively stable with only minor fluctuations (on the scale of hundreds of metres) over the last 3000 years.

  8. On siphons and sediments: A new model for draining active subglacial lakes in Antarctica informed with satellite radar and laser altimeter observations.

    NASA Astrophysics Data System (ADS)

    Carter, S. P.; Fricker, H. A.; Siegfried, M. R.

    2014-12-01

    With the advent of repeat-pass satellite-based surface altimetry over much of Antarctica, approximately 130 new subglacial lakes have been discovered entirely from observations of surface uplift and subsidence; these are commonly referred to as "active lakes". In contrast to the ~160 lakes detected by radar sounding ("RES" lakes), which are typically in mountains bedrock terrain near the ice divide and static with residence times spanning millenia, active lakes are typically located in fast flowing ice streams far from the divides, and have short residence times. To understand how water transfers through active lake systems we have developed a new model based on earlier theoretical work and informed by lake-volume estimates inferred from of ice surface displacements detected by satellite radar and laser altimetry. We find that although the overall pattern of filling and drainage is similar to that for ice dammed lakes in alpine regions via channels thermally eroded into the ice that then creeps shut as water pressure declines, Antarctic lake drainage is better simulated by invoking a channel mechanically eroded into the underlying sediment. The necessity of an erodable deformable substrate to explain lake drainage suggests that the distribution of active lakes is an indicator for the presence of sediment. Furthermore the process of lake drainage appears quite sensitive to the composion and strength of the underlying till. We explore these possibilities by testing the model on subglacial lakes in both East and West Antarctica, including Recovery Glacier and MacAyeal Ice stream.

  9. The enigmatic nitrogen biogeochemistry of Lake Vida, Antarctica: an isolated brine cryoecosystem

    NASA Astrophysics Data System (ADS)

    Ostrom, N. E.; Murray, A.; Trubl, G. G.; Kuhn, E.

    2013-12-01

    Lake Vida, located in Victoria Valley, East Antarctica, harbors ice-entrained brine (20 % salt, > 6 times seawater) that has been isolated from the surface for more than 2,800 years. The brine conditions (permanently dark, temperature of -13.4 °C, lack of O2, and pH of 6.2) and geochemistry are highly unusual. As an example, the brine contains the highest concentrations of N2O reported for any aquatic ecosystem (86.6 μM) and exceptionally high levels of NH4+ (3.6 mM), NO3- (1.1 mM) and NO2- (27.3 μM). Though this cryoecosystem appears to be relatively inhospitable, microbial life is abundant (>10^7 cell-like particles per mL), is capable of protein production at in situ temperatures, and harbors an assemblage of bacterial phylotypes spanning at least eight phyla. To assess present and past microbial activity in situ and test hypotheses concerning energy generation in the brine cryoecosystem, the stable isotope signatures of nitrogen, oxygen, and hydrogen have been characterized in liquid and dissolved gas phases. The isotopic compositions of nitrate (δ15N = -7.9 ‰, δ18O = 31.7 ‰), ammonium (δ15N = -4.8 ‰) and dinitrogen (δ15N = 0.3 ‰) are all consistent with an atmospheric origin. Given that nearly all non-atmospheric sources of nitrate lack a 17O anomaly, a Δ17O value of nitrate in Lake Vida of 15.9 ‰ suggests that approximately half of the nitrate present is derived from atmospheric deposition. A 17O anomaly was not observed in N2O indicating that this gas was likely formed in the lake. While the bulk δ15N (-22.2 ‰) and site preference (SP; -3.6 ‰) values for N2O are consistent with a microbial origin, the δ18O value (3.0 ‰) is markedly depleted in 18O relative to the vast majority of published values. The soils surrounding Don Juan Pond, which is in a neighboring valley, have been shown to produce N2O with variable δ15N, δ18O and SP values of -45.4 to -34.5 ‰, 50.5 to 76.7 ‰, and -45.2 to 4.1 ‰, respectively, that may reflect

  10. Long-range transport of pollutants to the Falkland Islands and Antarctica: evidence from lake sediment fly ash particle records.

    PubMed

    Rose, Neil L; Jones, Vivienne J; Noon, Philippa E; Hodgson, Dominic A; Flower, Roger J; Appleby, Peter G

    2012-09-18

    (210)Pb-dated sediment cores taken from lakes on the Falkland Islands, the South Orkney Islands, and the Larsemann Hills in Antarctica were analyzed for fly ash particles to assess the temporal record of contamination from high temperature fossil-fuel combustion sources. Very low, but detectable, levels were observed in the Antarctic lakes. In the Falkland Island lakes, the record of fly ash extended back to the late-19th century and the scale of contamination was considerably higher. These data, in combination with meteorological, modeling, and fossil-fuel consumption data, indicate most likely sources are in South America, probably Chile and Brazil. Other southern hemisphere sources, notably from Australia, contribute to a background contamination and were more important historically. Comparing southern polar data with the equivalent from the northern hemisphere emphasizes the difference in contamination of the two circumpolar regions, with the Falkland Island sites only having a level of contamination similar to that of northern Svalbard. PMID:22891669

  11. Isotopic variability in the deepest Vostok (East Antarctica) ice core suggests not perfect mixing of Lake Vostok water

    NASA Astrophysics Data System (ADS)

    Ekaykin, A. A.; Lipenkov, V. Ya.

    2009-04-01

    One of the key questions about subglacial Antarctic Lake Vostok (LV) hydrological system is whether the water of the lake is well mixed or not. Not complete mixing of water from the sources feeding the lake (glacier melt and hydrothermal water) with the water of main lake body would have several important consequences: 1) lake ice retrieved from 5G-1 borehole at Vostok Station is likely formed from a water layer which is not fully representative for the entire lake; 2) effective residence time of water in the main lake body is likely significantly longer than that deduced from simple mass balance estimations; 3) and, likely most important, not perfect mixing of lake water would suggest the existence of ecological niches where micro-biota can hide from lethal influence of high oxygen concentration likely typical for the lake. A powerful and promising tool for studying hydrological regime of LV is analyses of lake ice isotope content variability. Up to now, isotopic data from the lake ice have been only used to roughly estimate the components of the lake's mass balance. However, closer view to the lake ice isotopic signal may provide with a range of valuable information about processes taking place just beneath the glacier sole. Here we present new isotopic data from the deepest part of Vostok ice core (3611-3650 m), as well as revisit the previously published data from the 3538-3611 m interval. It is shown that the lake ice isotope content experiences small-scale variability which is related to the changes of the isotopic composition of the freezing water. Since the time-scale of these oscillations is much less than the expected LV residence time, it suggests that lake water is not perfectly mixed. Most likely it is due to not complete mixing of melt water and/or hydrothermal water with lake resident water on their way to the freezing site. The work is carried out in frames of Project 4 of Russian Federal Targeted Program "Antarctica". We thank Russian Antarctic

  12. Psychrotolerant anaerobes from Lake Podprudnoye, Antarctica and penguin Spheniscus demersus colony, South Africa

    NASA Astrophysics Data System (ADS)

    Guisler, Melissa; Pikuta, Elena V.; Townsend, Alisa; Hoover, Richard B.

    2009-08-01

    The study of a sample collected from a wind-made ice sculpture near Lake Podprudnoe, Antarctica led to the isolation of the psychrotolerant strain ISLP-3. Cells of the new isolate are vibrio-shaped that measure 0.5 x 1.0-3.0 μm in size. Growth occurs within the temperature range 5-35ºC with the optimum at 22 °C. Salinity range for growth is 0-2 % NaCl with the optimum at 0.25 %. The new isolate grows within a pH range from 6.0 to 9.5 with the optimum at 7.5. Strain ISLP-3 is saccharolytic, growing on the following substrates: D-glucose, D-ribose, D-fructose, D-arabinose, maltose, sucrose, D-trehalose, D-mannose, D-cellobiose, lactose, starch, chitin, triethylamine, N-acetylglucosamine, and urea. The best growth occurred on D-cellobiose. An environmental sample of pond water near a colony of the endemic species of African penguins, Spheniscus demersus, was collected in February 2008 and delivered directly to the Astrobiology laboratory at NSSTC. The microbiological study of this sample led to the isolation of two psychrotolerant strains ARHSd-7G and ARHSd-9G. Both strains are strictly anaerobic bacteria and are able to grow at high pH and low temperatures. The cells of strain ARHSd-7G are motile, vibrio-shaped, spore-forming cells. Optimal growth of this strain occurs at 30 ºC, 3 % NaCl, and pH 8.9. The isolate ARHSd-7G combines sugarlytic and proteolytic metabolisms, growing on some proteolysis products including peptone and yeast extract and a number of sugars. The second isolate, ARHSd-9G, exhibits thin, elongated rods that measure 0.4 x 3-5 μm. The cells are motile and spore-forming. Optimal growth of strain ARHSd-9G occurs at 30 ºC, 1.75 % NaCl, and pH 8.5. The strain ARHSd-9G is sugarlytic, growing well on substrates such as D-glucose, sucrose, D-cellobiose, maltose, fructose, D-mannose, and trehalose (the only exception is positive growth on yeast extract). In this report, the physiological and morphological characteristics of the novel

  13. Psychrotolerant Anaerobes from Lake Podprudnoe, Antarctica and Penguin Spheniscus demersus Colony, South Africa

    NASA Technical Reports Server (NTRS)

    Guisler, Melissa; Pikuta, Elena V.; Townsend, Alisa; Hoover, Richard B.

    2009-01-01

    The study of a sample collected from a wind-made ice sculpture near Lake Podprudnoe, Antarctica led to the isolation of the psychrotolerant strain ISLP-3. Cells of the new isolate are vibrio-shaped that measure 0.5 x 1.0-3.0 micron in size. Growth occurs within the temperature range 5-35 C with the optimum at 22 C. Salinity range for growth is 0-2 % NaCl with the optimum at 0.25 %. The new isolate grows within a pH range from 6.0 to 9.5 with the optimum at 7.5. Strain ISLP-3 is saccharolytic, growing on the following substrates: D-glucose, D-ribose, D-fructose, D-arabinose, maltose, sucrose, D-trehalose, D-mannose, D-cellobiose, lactose, starch, chitin, triethylamine, N-acetylglucosamine, and urea. The best growth occurred on D-cellobiose. An environmental sample of pond water near a colony of the endemic species of African penguins, Spheniscus demersus, was collected in February 2008 and delivered directly to the Astrobiology laboratory at NSSTC. The microbiological study of this sample led to the isolation of two psychrotolerant strains ARHSd-7G and ARHSd-9G. Both strains are strictly anaerobic bacteria and are able to grow at high pH and low temperatures. The cells of strain ARHSd-7G are motile, vibrio-shaped, spore-forming cells. Optimal growth of this strain occurs at 30 C, 3 % NaCl, and pH 8.9. The isolate ARHSd-7G combines sugarlytic and proteolytic metabolisms, growing on some proteolysis products including peptone and yeast extract and a number of sugars. The second isolate, ARHSd-9G, exhibits thin, elongated rods that measure 0.4 x 3-5 micron. The cells are motile and spore-forming. Optimal growth of strain ARHSd-9G occurs at 30 C, 1.75 % NaCl, and pH 8.5. The strain ARHSd-9G is sugarlytic, growing well on substrates such as D-glucose, sucrose, D-cellobiose, maltose, fructose, D-mannose, and trehalose (the only exception is positive growth on yeast extract). In this report, the physiological and morphological characteristics of the novel psychrotolerant

  14. Interannual active layer thermal and dynamics evolution at the crater Lake CALM site, Deception Island (Antarctica).

    NASA Astrophysics Data System (ADS)

    Ramos, Miguel; Vieira, Gonzalo; Ángel De Pablo, Miguel; Molina, Antonio; Abramov, Andrey

    2015-04-01

    Deception Island, is an active strato-volcano on South Shetland Archipelago of Antarctica (62° 55' 0″ S, 60° 37' 0″ W), is a cold region with harsh remote and hostile environmental conditions. The permafrost and active layer existence, and the cold climate conditions together with volcanic material with height water content inside made this region of the Earth a perfect site to study the active layer and permafrost evolution involved in the Circumpolar Active Layer South (CALM-S) program. The active layer is measured in late January or firs february (during the end of the thaw period) at the "Crater Lake" CALM site (62°58'06.7''; 60°40'44.8'') on Deception Island, Antarctica, at the period 2006 to 2014 we obtained a mean annual value of 29,7±2 cm. In this paper, we describe the spatial active layer thickness distribution and report the reduction on the mean thickness between February 2006 and 2014. Below the active layer, permafrost could be also reported (with a mean thickness of 4.5± 0.5 m.) based on the temperature data acquired by sensors installed at different depth inside the soil; three different shallow boreholes was drilled (1.0 m., 1.6 m., 4.5 m. in depth) and we have been registered its temperature gradient at the 2010 to 2013 period. Here we use all those data 1) to describe the thermal behavior of the permafrost at the CALM site, and 2) to describe its evolution (aggradation/degradation) along fourteen years of continuous measurements. We develop this study, to known the thermal behavior of the permafrost and the active layer related with the air/soil interaction being one of the most important factors the snow layer that was measured by the installation of termo-snowmeters with the complement of an automatic digital camera during the 2008 to 2014 period. On the other hand, the pyroclastics soil materials has a very high values of water content then the latent heat in the freezing/thawing process controls the active layer evolution and the

  15. Precise analysis of ICESat altimetry data and assessment of the hydrostatic equilibrium for subglacial Lake Vostok, East Antarctica

    NASA Astrophysics Data System (ADS)

    Ewert, H.; Popov, S. V.; Richter, A.; Schwabe, J.; Scheinert, M.; Dietrich, R.

    2012-09-01

    Based on the Ice, Cloud and Land Elevation Satellite (ICESat) laser altimetry data, the hydrostatic equilibrium (HE) condition for the subglacial Lake Vostok, East Antarctica, is evaluated. A digital elevation model (DEM) of the ice surface is derived by a regional crossover adjustment. The analysis of the DEM and its comparison with GPS derived ice-surface elevations and an ice-surface DEM based on radar altimetry data reveal an overall accuracy of better than ± 0.7 m for the lake area. The DEM is combined with an ice-thickness model and a regional geoid model to determine the deviation of the local ice-surface height from HE. For large parts of the lake, the ice sheet fulfils the HE. Our results reveal a strong positive deviation of about 10 m along the lake shoreline. In addition, positive deviations are found in the northern part of the lake which coincide with ice rumples detected by radio-echo sounding. In the southern part of the lake, we find a linear negative deviation (-4.0 m) which coincides with the convoy route from Vostok station to Mirny base. In addition to the DEM, relative biases for the ICESat laser operational periods are determined in the regional crossover adjustment.

  16. Stable isotope and hydrogeochemical studies of Beaver Lake and Radok Lake, MacRobertson Land, East Antarctica.

    PubMed

    Wand, Ulrich; Hermichen, Wolf-Dieter; Brüggemann, Erika; Zierath, Reinhard; Klokov, Valerii Dmitrievich

    2011-12-01

    Beaver Lake and Radok Lake, the largest known epishelf lake and the deepest freshwater lake on the Antarctic continent, respectively, were isotopically (δ(2)H, δ(18)O) and hydrogeochemically studied. Radok Lake is an isothermal and non-stratified, i.e. homogeneous water body, while Beaver Lake is stratified with respect to temperature, salinity, and isotopic composition. The results for the latter attest to freshwater (derived from snow and glacier melt) overlying seawater. PMID:22092172

  17. Characteristics of tephra in Holocene lake sediments on King George Island, West Antarctica: implications for deglaciation and paleoenvironment

    NASA Astrophysics Data System (ADS)

    Lee, Yong Il; Lim, Hyoun Soo; Yoon, Ho Il; Tatur, Andrzej

    2007-12-01

    Several reworked tephra layers in gravity-flow deposits are present in lacustrine core sediments collected from Hotel and Rudy Lakes on King George Island, South Shetland Islands, maritime sub-Antarctica. This study tests the values of tephra for establishing regional tephrochronologies for lakes in ice-covered landscapes in the vicinity of volcanoes. The tephra record is more abundant in a long Hotel Lake core (515 cm long). This study uses volcanic glass samples from five tephra layers of Hotel Lake and from one tephra layer of Rudy Lake. Morphologically, tephras are mixtures of basaltic and pumice shards, both having various degrees of vesicularity. Major element analyses of glass shards reveal that the majority of the glass fragments belong to basic glass (<60 wt% SiO2), compositionally ranging from basalt to low-silica andesite and subalkaline series medium-K tholeiites, probably sourced from Deception Island located 130 km southwest of King George Island. Less than 20% of tephra belongs to silicic glass and occurs in three tephra horizons E of Hotel Lake. However, source volcano(es) for about 10% of basic tephra and silicic tephra are not readily identified from nearby volcanic centers. Except for the studied tephra in Rudy Lake, all tephra samples in Hotel Lake are not ashfall deposits but reworked and redeposited pyroclasts derived from retreating ice sheet, resulting in the occurrence of geochemically equivalent tephra samples in different tephra horizons. The dating of the studied tephra horizons represents the timing of deglaciation rather than that of volcanic eruptions. The result of this study implies that combined with sedimentological information more chemical criterion is necessary to study tephrochronology and regional correlation and to understand paleoenvironmental changes using tephra.

  18. The Holocene deglaciation of the Byers Peninsula (Livingston Island, Antarctica) based on the dating of lake sedimentary records

    NASA Astrophysics Data System (ADS)

    Oliva, M.; Antoniades, D.; Giralt, S.; Granados, I.; Pla-Rabes, S.; Toro, M.; Liu, E. J.; Sanjurjo, J.; Vieira, G.

    2016-05-01

    The process of deglaciation in the Antarctic Peninsula region has large implications for the geomorphological and ecological dynamics of the ice-free environments. However, uncertainties still remain regarding the age of deglaciation in many coastal environments, as is the case in the South Shetland Islands. This study focuses on the Byers Peninsula, the largest ice-free area in this archipelago and the one with greatest biodiversity in Antarctica. A complete lacustrine sedimentary sequence was collected from five lakes distributed along a transect from the western coast to the Rotch Dome glacier front: Limnopolar, Chester, Escondido, Cerro Negro and Domo lakes. A multiple dating approach based on 14C, thermoluminescence and tephrochronology was applied to the cores in order to infer the Holocene environmental history and identify the deglaciation chronology in the Byers Peninsula. The onset of the deglaciation started during the Early Holocene in the western fringe of the Byers Peninsula according to the basal dating of Limnopolar Lake (ca. 8.3 cal. ky BP). Glacial retreat gradually exposed the highest parts of the Cerro Negro nunatak in the SE corner of Byers, where Cerro Negro Lake is located; this lake was glacier-free since at least 7.5 ky. During the Mid-Holocene the retreat of the Rotch Dome glacier cleared the central part of the Byers plateau of ice, and Escondido and Chester lakes formed at 6 cal. ky BP and 5.9 ky, respectively. The dating of the basal sediments of Domo Lake suggests that the deglaciation of the current ice-free easternmost part of the Byers Peninsula occurred before 1.8 cal. ky BP.

  19. Draft Genome Sequence of Hymenobacter sp. Strain IS2118, Isolated from a Freshwater Lake in Schirmacher Oasis, Antarctica, Reveals Diverse Genes for Adaptation to Cold Ecosystems.

    PubMed

    Koo, Hyunmin; Ptacek, Travis; Crowley, Michael; Swain, Ashit K; Osborne, John D; Bej, Asim K; Andersen, Dale T

    2014-01-01

    Hymenobacter sp. IS2118, isolated from a freshwater lake in Schirmacher Oasis, Antarctica, produces extracellular polymeric substance (EPS) and manifests tolerance to cold, UV radiation (UVR), and oxidative stress. We report the 5.26-Mb draft genome of strain IS2118, which will help us to understand its adaptation and survival mechanisms in Antarctic extreme ecosystems. PMID:25103756

  20. Draft Genome Sequence of Hymenobacter sp. Strain IS2118, Isolated from a Freshwater Lake in Schirmacher Oasis, Antarctica, Reveals Diverse Genes for Adaptation to Cold Ecosystems

    PubMed Central

    Ptacek, Travis; Crowley, Michael; Swain, Ashit K.; Osborne, John D.; Bej, Asim K.; Andersen, Dale T.

    2014-01-01

    Hymenobacter sp. IS2118, isolated from a freshwater lake in Schirmacher Oasis, Antarctica, produces extracellular polymeric substance (EPS) and manifests tolerance to cold, UV radiation (UVR), and oxidative stress. We report the 5.26-Mb draft genome of strain IS2118, which will help us to understand its adaptation and survival mechanisms in Antarctic extreme ecosystems. PMID:25103756

  1. Possible Climatic Signal Recorded by Alkenone Distributions in Sediments from Freshwater and Saline Lakes on the Skarvsnes and Skallen Areas, Antarctica

    NASA Astrophysics Data System (ADS)

    Sawada, K.; Takeda, M.; Takano, Y.

    2014-12-01

    The distribution of long-chain (C37 - C39) alkenones in marine sediment has been well documented to record paleo-sea surface temperatures. The alkenones were also found in sediments of terrestrial saline lakes, and recently the calibrations of alkenone unsaturation indices - temperature have been established in continental areas. Furthermore, these biomarkers have been identified in lacustrine sediments on high-latitudinal terrestrial areas such as Greenland and Antarctica. In the present study, the alkenones were identified in the lacustrine sediment cores in freshwater (Lake Naga-ike) and saline lakes (Lake Suribati and Lake Funazoko) on the Skarvsnes, and a saline lake (Lake Skallen Oh-ike) on the Skallen, Antarctica. Here, we report that the alkenone distribution in the Antarctic lakes was examined as paleotemperature proxy. C37-C38 Tetra- and tri-unsaturated alkenones and C37 tetra- and tri-unsaturated alkenoates are identified in all sediment samples. The C37 di-unsaturated (C37:2) alkenones can be identified in sediments of surface layers (0-15 cm) of Lake Naga-ike and layers of 160-190 cm depth, in which age is ca. 3000 years BP by 14C dating, in Lake Skallen Ohike, and alkenone unsaturation index (UK37) is analyzed from these sediments. By using a calibration obtained from a culture strain Chrysotila lamellosa as reported by Nakamura et al. (2014), paleotemperatures are calculated to be 9.2-15ºC in surface sediments of Lake Naga-ike and 6.8-8.6ºC in Lake Skallen Oh-ike, respectively. The estimated temperatures are concordant with summer temperature of lake waters observed in Lake Naga-ike. Also, the highest concentrations of the alkenones and alkenoates are observed in deeper (older) sediment layers from Lake Naga-ikes, which has not been connected the ocean and intruded sea water. This implies that the alkenones are originated from indigenous biological organism(s) in Antarctic lake water. The class distributions (unsaturation ratios) of alkenones

  2. Geochemistry of the Onyx River (Wright Valley, Antarctica) and its role in the chemical evolution of Lake Vanda

    NASA Astrophysics Data System (ADS)

    Green, William J.; Canfield, Donald E.

    1984-12-01

    The Onyx River (Wright Valley, Antarctica) is a dilute meltwater stream originating in the vicinity of the Wright Lower Glacier. It acquires a significant fraction of its salt content when glacial meltwaters contact Wright Valley soils at Lake Brownworth and the concentrations of all ions increase with distance along the 28-km channel down to Lake Vanda. Average millimolar concentrations of major ions at the Vanda weir during the 1980-1981 flow season were: Ca = 0.119; Mg = 0.061; Na = 0.212; K = 0.033; Q = 0.212; SO4 = 0.045; HCO3 = 0.295; and SiO2 = 0.049. Based on the flow measurements of Chinn (1982), this amounts to an annual flux (in moles) to Lake Vanda of: Ca = 0.238 × 10 6; Mg = 0.122 × 10 6; Na = 0.424 × 10 6; K = 0.066 × 10 6; Cl = 0.424 × 10 6; SO4 = 0.09 × 10 6; HCO3 = 0.59 × 10 6; SiO2 = 0.098 × 10 6. In spite of the large salt input from this source, equilibrium evaporation of Onyx River water would have resulted in early calcite deposition and in the formation of a Na-Mg-Cl-HCO 3 brine rather than in the Ca-Na-Mg-Cl waters observed in Lake Vanda. The river alone could not have produced a brine having the qualitative geochemical features of the lower saline waters of Lake Vanda. It is proposed that the Vanda brine is instead the result of past ( > 1200 yrs BP) mixing events between Onyx River inflows and calcium chloride-rich deep groundwaters derived from the Don Juan Basin. The mixing model presented here shows that the Onyx River is the major contributor of K, HCO 3, SO 4, and (possibly) Mg found in the lake and a significant contributor (approximately one half) of the observed Na. Calcium and Cl, on the other hand, came largely from deep groundwater sources in the Don Juan Basin. All concentrations except Mg are well predicted by this model. The chemical composition of the geologically recent upper lake is explained in terms of ionic diffusion from the pre-formed brine, coupled with Onyx River inflow. Ionic ratios calculated from this

  3. An isotopic and chemical study of Lake Vanda and Don Juan Pond, Antarctica

    NASA Astrophysics Data System (ADS)

    Friedman, I.; Rafter, A.; Smith, G. I.

    Temperature measurements made in Lake Vanda and in the lake subbottom sediments show that the high temperatures in the lake are not due to geothermal heat flow, but are probably trapped solar energy. On the basis of Sr-87/86 ratios the salts in Lake Vanda can be derived by a mixture of 58% weathered rock plus 42% from sea water or precipitation. Loss of efflorescences high in sodium, potassium and magnesium by high winds can yield the salt compositions present in both Lake Vanda and Don Juan Pond. From isotopic data on deuterium, O-18, C-13, Sr-87/86, S-34 as well as from chemical data on Lake Vanda waters, interstitial brines contained in the subsurface sediment and C-14 dates a lake history is proposed.

  4. Diatoms in sediments of perennially ice-covered Lake Hoare, and implications for interpreting lake history in the McMurdo Dry Valleys of Antarctica

    USGS Publications Warehouse

    Spaulding, S.A.; McKnight, Diane M.; Stoermer, E.F.; Doran, P.T.

    1997-01-01

    Diatom assemblages in surficial sediments, sediment cores, sediment traps, and inflowing streams of perennially ice-covered Lake Hore, South Victorialand, Antarctica were examined to determine the distribution of diatom taxa, and to ascertain if diatom species composition has changed over time. Lake Hoare is a closed-basin lake with an area of 1.8 km2, maximum depth of 34 m, and mean depth of 14 m, although lake level has been rising at a rate of 0.09 m yr-1 in recent decades. The lake has an unusual regime of sediment deposition: coarse grained sediments accumulate on the ice surface and are deposited episodically on the lake bottom. Benthic microbial mats are covered in situ by the coarse episodic deposits, and the new surfaces are recolonized. Ice cover prevents wind-induced mixing, creating the unique depositional environment in which sediment cores record the history of a particular site, rather than a lake=wide integration. Shallow-water (<1 m) diatom assemblages (Stauroneis anceps, Navicula molesta, Diadesmis contenta var. parallela, Navicula peraustralis) were distinct from mid-depth (4-16 m) assemblages (Diadesmis contenta, Luticola muticopsis fo. reducta, Stauroneis anceps, Diadesmis contenta var. parallela, Luticola murrayi) and deep-water (2-31 m) assemblages (Luticola murrayi, Luticola muticopsis fo. reducta, Navicula molesta. Analysis of a sediment core (30 cm long, from 11 m water depth) from Lake Hoare revealed two abrupt changes in diatom assemblages. The upper section of the sediment core contained the greatest biomass of benthic microbial mat, as well as the greatest total abundance and diversity of diatoms. Relative abundances of diatoms in this section are similar to the surficial samples from mid-depths. An intermediate zone contained less organic material and lower densities of diatoms. The bottom section of core contained the least amount of microbial mat and organic material, and the lowest density of diatoms. The dominant process

  5. Exploring former subglacial Hodgson Lake, Antarctica Paper I: site description, geomorphology and limnology

    NASA Astrophysics Data System (ADS)

    Hodgson, Dominic A.; Roberts, Stephen J.; Bentley, Michael J.; Smith, James A.; Johnson, Joanne S.; Verleyen, Elie; Vyverman, Wim; Hodson, Andy J.; Leng, Melanie J.; Cziferszky, Andreas; Fox, Adrian J.; Sanderson, David C. W.

    2009-11-01

    At retreating margins of the Antarctic Ice Sheet, there are a number of locations where former subglacial lakes are emerging from under the ice but remain perennially ice-covered. This paper presents a site description of one of these lakes, Hodgson Lake, situated on southern Alexander Island, west of the Antarctic Peninsula (72° 00.549‧ S, 68° 27.708‧ W). First, we describe the physical setting of the lake using topographic and geomorphological maps. Second, we determine local ice sheet deglaciation history and the emergence of the lake using cosmogenic isotope dating of glacial erratics cross-referenced to optically stimulated luminescence dating of raised lake shoreline deltas formed during ice recession. Third we describe the physical and chemical limnology including the biological and biogeochemical evidence for life. Results show that the ice mass over Hodgson Lake was at least 295 m thick at 13.5 ka and has progressively thinned through the Holocene with the lake ice cover reaching an altitude of c. 6.5 m above the present lake ice sometime after 4.6 ka. Thick perennial ice cover persists over the lake today and the waters have remained isolated from the atmosphere with a chemical composition consistent with subglacial melting of catchment ice. The lake is ultra-oligotrophic with nutrient concentrations within the ranges of those found in the accreted lake ice of subglacial Lake Vostok. Total organic carbon and dissolved organic carbon are present, but at lower concentrations than typically recorded in continental rain. No organisms and no pigments associated with photosynthetic or bacterial activity were detected in the water column using light microscopy and high performance liquid chromatography. Increases in SO4 and cation concentrations at depth and declines in O2 provide some evidence for sulphide oxidation and very minor bacterial demand upon O2 that result in small, perhaps undetectable changes in the carbon biogeochemistry. However, in general

  6. Concerning the co-occurrence of subglacial lakes and flow bifurcations of water and ice in Antarctica

    NASA Astrophysics Data System (ADS)

    Carter, S. P.; Fricker, H. A.; Siegfried, M. R.

    2012-12-01

    Active subglacial lakes beneath the ice streams and outlet glaciers of Antarctica are frequently found in regions of the ice sheet that are potential bifurcation points - i.e. locations where a small change in surface elevation (<5 m) would make the difference between subglacial water following main ice flow and diverting to an outflow location ultimately 100's of km away. In these regions the hydropotential basins that enable the water to pond result from a combination of bedrock topography and dynamic ice topography. Consequently the stability of such lakes over long timescales is subject to many factors, but ultimately favors locations where deceleration is occurring downstream but there is still a sufficient supply of water from upstream. Here we map and model the hydraulic connections in these dynamic regions, simulating the filling and draining of several key subglacial lakes. We then compare the model output against repeat track surface altimetry and other geophysical observations. Our initial results suggest the formation and drainage of subglacial lakes comprise part of two separate but related feedback loops: 1. In these regions thickening of ice downstream will tend to form hydropotential barriers that impound large quantities of subglacial water over time. Lakes formed upstream of these barriers will reduce lubrication to points downstream through impoundment and channelization of water. This will lead to further slowing and thickening. 2. The additional water stored upstream of a slowing ice stream is can then be accessed by an accelerating ice stream can provide an additional source of water for neighboring ice streams, especially those undergoing acceleration and thinning downstream. Consequently subglacial lake dynamics contribute significantly to the ice flow variability for much of the continent. Furthermore, the inferred ice flow history for locations such as the Siple Coast, is consistent with lake clusters and the associated water storage at

  7. Per- and polyfluoroalkyl substances in snow, lake, surface runoff water and coastal seawater in Fildes Peninsula, King George Island, Antarctica.

    PubMed

    Cai, Minghong; Yang, Haizhen; Xie, Zhiyong; Zhao, Zhen; Wang, Feng; Lu, Zhibo; Sturm, Renate; Ebinghaus, Ralf

    2012-03-30

    The multi-matrices samples from snow (n=4), lake water (n=4), surface runoff water (SRW) (n=1) and coastal seawater (n=10) were collected to investigate the spatial distribution and the composition profiles of per- and polyfluoroalkyl substances (PFASs) in Fildes Peninsula, King George Island, Antarctica in 2011. All samples were prepared by solid-phase extraction and analyzed by using high performance liquid chromatography/negative electrospray ionization-tandem mass spectrometry (HPLC/(-)ESI-MS/MS). 14 PFASs in snow, 12 PFASs in lake water, 9 PFASs in SRW and 13 PFASs in coastal seawater were quantified, including C(4), C(7), C(8), C(10) PFSAs, C(4)-C(9), C(11)-C(14), C(16) PFCAs, and FOSA. PFOA was detected in all samples with the highest concentration (15,096 pg/L) in coastal seawater indicating a possible influence of local sewage effluent. High concentration and mostly frequency of PFBA occurred in snow (up to 1112 pg/L), lake water (up to 2670 pg/L) and SRW (1431 pg/L) while detected in the range of method detection limited (MDL) in the coastal seawaters indicate that PFBA is mainly originated from atmospheric dust contamination and also affected by the degradation of their precursors. No geographical differences in PFOS concentrations (n=8, 18 ± 3 pg/L) were measured in all snow and lake water samples also suggests that PFOS could be originated from the degradation of their precursors which can transported by long-range atmospheric route, but in a very low level. PMID:22305203

  8. Decadal persistence of cycles in lava lake motion at Erebus volcano, Antarctica

    NASA Astrophysics Data System (ADS)

    Peters, Nial; Oppenheimer, Clive; Kyle, Philip; Kingsbury, Nick

    2014-06-01

    Studies of Erebus volcano's active lava lake have shown that many of its observable properties (gas composition, surface motion and radiant heat output) exhibit cyclic behaviour with a period of ∼10 min. We investigate the multi-year progression of the cycles in surface motion of the lake using an extended (but intermittent) dataset of thermal infrared images collected by the Mount Erebus Volcano Observatory between 2004 and 2011. Cycles with a period of ∼5-18 min are found to be a persistent feature of the lake's behaviour and no obvious long-term change is observed despite variations in lake level and surface area. The times at which gas bubbles arrive at the lake's surface are found to be random with respect to the phase of the motion cycles, suggesting that the remarkable behaviour of the lake is governed by magma exchange rather than an intermittent flux of gases from the underlying magma reservoir.

  9. Active lakes in Antarctica survive on a sedimentary substrate - Part 1: Theory

    NASA Astrophysics Data System (ADS)

    Carter, S. P.; Fricker, H. A.; Siegfried, M. R.

    2015-03-01

    Over the past decade satellite observations have revealed that active subglacial lake systems are widespread under the Antarctic ice sheet, including the ice streams, yet we have insufficient understanding of the lake-drainage process to incorporate it into ice sheet models. Process models for drainage of ice-dammed lakes based on conventional "R-channels" incised into the base of the ice through melting are unable to reproduce the timing and magnitude of drainage from Antarctic subglacial lakes estimated from satellite altimetry given the low hydraulic gradients along which such lakes drain. We developed a process model in which channels are mechanically eroded into deformable subglacial sediment (till) instead ("T-channel"). When applied to the known lakes of the Whillans/Mercer system, the model successfully reproduced the key characteristics of estimated lake volume changes for the period 2003-2009. If our model is realistic, it implies that most active lakes are shallow and only exist in the presence of saturated sediment, explaining why they are difficult to detect with classical radar methods. It also implies that the lake-drainage process is sensitive to the composition and strength of the underlying till, suggesting that models could be improved with a realistic treatment of sediment - interfacial water exchange.

  10. Strontium isotopic signatures of the streams and lakes of Taylor Valley, Southern Victoria Land, Antarctica: Chemical weathering in a polar climate

    USGS Publications Warehouse

    Lyons, W.B.; Nezat, C.A.; Benson, L.V.; Bullen, T.D.; Graham, E.Y.; Kidd, J.; Welch, K.A.

    2002-01-01

    We have collected and analyzed a series of water samples from three closed-basin lakes (Lakes Bonney, Fryxell, and Hoare) in Taylor Valley, Antarctica, and the streams that flow into them. In all three lakes, the hypolimnetic waters have different 87Sr/86Sr ratios than the surface waters, with the deep water of Lakes Fryxell and Hoare being less radiogenic than the surface waters. The opposite occurs in Lake Bonney. The Lake Fryxell isotopic ratios are lower than modern-day ocean water and most of the whole-rock ratios of the surrounding geologic materials. A conceivable source of Sr to the system could be either the Cenozoic volcanic rocks that make up a small portion of the till deposited in the valley during the Last Glacial Maximum or from marble derived from the local basement rocks. The more radiogenic ratios from Lake Bonney originate from ancient salt deposits that flow into the lake from Taylor Glacier and the weathering of minerals with more radiogenic Sr isotopic ratios within the tills. The Sr isotopic data from the streams and lakes of Taylor Valley strongly support the notion documented by previous investigators that chemical weathering has been, and is currently, a major process in determining the overall aquatic chemistry of these lakes in this polar desert environment.

  11. Geochemistry of aquatic humic substances in the Lake Fryxell basin, Antarctica

    USGS Publications Warehouse

    Aiken, G.; McKnight, D.; Harnish, R.; Wershaw, R.

    1996-01-01

    Dissolved organic carbon (DOC) in Lake Fryxell, 10 streams flowing into the lake, and the moat surrounding the lake was studied to determine the influence of sources and biogeochemical processes on its distribution and chemical nature. Lake Fryxell is an amictic, permanently ice-covered lake in the McMurdo Dry Valleys which contains benthic and planktonic microbial populations, but receives essentially no input of organic material from the ahumic soils of the watershed. Biological activity in the water column does not appear to influence the DOC depth profile, which is similar to the profiles for conservative inorganic constituents. DOC values for the streams varied with biomass in the stream channel, and ranged from 0.2 to 9.7 mg C/L. Fulvic acids in the streams were a lower percentage of the total DOC than in the lake. These samples contain recent carbon and appear to be simpler mixtures of compounds than the lake samples, indicating that they have undergone less humification. The fulvic acids from just above the sediments of the lake have a high sulfur content and are highly aliphatic. The main transformations occurring as these fractions diffuse upward in the water column are 1) loss of sulfur groups through the oxycline and 2) decrease in aliphatic carbon and increase in the heterogeneity of aliphatic moieties. The fraction of modem 14C content of the lake fulvic acids range from a minimum of 0.68 (approximately 3000 years old) at 15m depth to 0.997 (recent material) just under the ice. The major processes controlling the DOC in the lake appear to be: 1) The transport of organic matter by the inflow streams resulting in the addition of recent organic material to the moat and upper waters of the lake; 2) The diffusion of organic matter composed of relict organic material and organic carbon resulting from the degradation of algae and bacteria from the bottom waters or sediments of the lake into overlying glacial melt water; 3) The addition of recent organic

  12. Terrestrial laser scanning observations of geomorphic changes and varying lava lake levels at Erebus volcano, Antarctica

    NASA Astrophysics Data System (ADS)

    Jones, Laura K.; Kyle, Philip R.; Oppenheimer, Clive; Frechette, Jedediah D.; Okal, Marianne H.

    2015-03-01

    A Terrestrial Laser Scanning (TLS) instrument was used to image the topography of the Main Crater at Erebus volcano each December in 2008, 2009, and 2010. Our high-spatial resolution TLS scans provide unique insights into annual and decadal scale geomorphic evolution of the summit area when integrated with comparable data collected by an airborne instrument in 2001. We observe both a pattern of subsidence within the Inner Crater of the volcano and an ~ 3 m per-year drop in the lava lake level over the same time period that are suggestive of decreasing overpressure in an underlying magma reservoir. We also scanned the active phonolite lava lake hosted within the Inner Crater, and recorded rapid cyclic fluctuations in the level of the lake. These were sporadically interrupted by minor explosions by bursting gas bubbles at the lake surface. The TLS data permit calculation of lake level rise and fall speeds and associated rates of volumetric change within the lake. These new observations, when considered with prior determinations of rates of lake surface motion and gas output, are indicative of unsteady magma flow in the conduit and its associated variability in gas volume fraction.

  13. Geochemistry and mineralogy of the phonolite lava lake, Erebus volcano, Antarctica: 1972 2004 and comparison with older lavas

    NASA Astrophysics Data System (ADS)

    Kelly, Peter J.; Kyle, Philip R.; Dunbar, Nelia W.; Sims, Kenneth W. W.

    2008-11-01

    Mount Erebus, Antarctica, is a large (3794 m) alkaline open-conduit stratovolcano that hosts a vigorously convecting and persistently degassing lake of anorthoclase phonolite magma. The composition of the lake was investigated by analyzing glass and mineral compositions in lava bombs erupted between 1972 and 2004. Matrix glass, titanomagnetite, olivine, clinopyroxene, and fluor-apatite compositions are invariant and show that the magmatic temperature (˜ 1000°C) and oxygen fugacity (ΔlogFMQ = - 0.9) have been stable. Large temperature variations at the lake surface (~ 400-500°C) are not reflected in mineral compositions. Anorthoclase phenocrysts up to 10 cm in length feature a restricted compositional range (An 10.3-22.9Ab 62.8-68.1Or 11.4-27.2) with complex textural and compositional zoning. Anorthoclase textures and compositions indicate crystallization occurs at low degrees of effective undercooling. We propose shallow water exsolution causes crystallization and shallow convection cycles the anorthoclase crystals through many episodes of growth resulting in their exceptional size. Minor variations in eruptive activity from 1972 to 2004 are decoupled from magma compositions. The variations probably relate to changes in conduit geometry within the volcano and/or variable input of CO 2-rich volatiles into the upper-level magma chamber from deeper in the system. Eleven bulk samples of phonolite lava from the summit plateau that range in age from 0 ± 4 ka to 17 ± 8 ka were analyzed for major and trace elements. Small compositional variations are controlled by anorthoclase content. The lavas are indistinguishable from modern bulk lava bomb compositions and demonstrate that Erebus volcano has been erupting lava and tephra from the summit region with the same bulk composition for ˜ 17 ka.

  14. Punctuated equilibrium of the surface above subglacial Lake Vostok in antarctica

    NASA Astrophysics Data System (ADS)

    Kotlyakov, V. M.; Vasiliev, L. N.; Kachalin, A. B.; Moskalevskii, M. Yu.; Tyuflin, A. S.

    2011-05-01

    Progress in understanding the surface dynamics above the subglacial Lake Vostok is achieved owing to use of the ICESat satellite laser elevation measurements, which enabled us to determine surface fluctuations with precision up to 3 cm. A new idea on punctuated equilibrium of the surface above Lake Vostok is elaborated; this idea is concluded in irregular, sharp vertical displacements of the ice surface by up to 40 cm. Deformation of the surface is accompanied with a common raising or lowering, and with local vertical displacements up to 20 cm in amplitude. It has been proved experimentally that snow transport on the surface above the lake causes only redistribution of snow and forms fractal structures that do not have any effect on surface deformation. The form of the surface is not an inclined plane due to many bends that are particularly related to ice flowing on the lake water area.

  15. On the abundances of noble and biologically relevant gases in Lake Vostok, Antarctica.

    PubMed

    Mousis, Olivier; Lakhlifi, Azzedine; Picaud, Sylvain; Pasek, Matthew; Chassefière, Eric

    2013-04-01

    Motivated by the possibility of comparing theoretical predictions of Lake Vostok's composition with future in situ measurements, we investigated the composition of clathrates that are expected to form in this environment from the air supplied to the lake by melting ice. To establish the best possible correlation between the lake water composition and that of air clathrates formed in situ, we used a statistical thermodynamic model based on the description of the guest-clathrate interaction by a spherically averaged Kihara potential with a nominal set of potential parameters. We determined the fugacities of the different volatiles present in the lake by defining a "pseudo" pure substance dissolved in water owning the average properties of the mixture and by using the Redlich-Kwong equation of state to mimic its thermodynamic behavior. Irrespective of the clathrate structure considered in our model, we found that xenon and krypton are strongly impoverished in the lake water (a ratio in the 0.04-0.1 range for xenon and a ratio in the ≈ 0.15-0.3 range for krypton) compared to their atmospheric abundances. Argon and methane were also found to be depleted in the Lake Vostok water by factors in the 0.5-0.95 and 0.3-0.5 ranges, respectively, compared to their atmospheric abundances. On the other hand, the carbon dioxide abundance was found to be substantially enriched in the lake water compared to its atmospheric abundance (by a factor in the 1.6-5 range at 200 residence times). The comparison of our predictions of the CO2 and CH4 mole fractions in Lake Vostok with future in situ measurements will allow disentangling between the possible supply sources. PMID:23758192

  16. Heating the Ice-Covered Lakes of the McMurdo Dry Valleys, Antarctica - Decadal Trends in Heat Content, Ice Thickness, and Heat Exchange

    NASA Astrophysics Data System (ADS)

    Gooseff, M. N.; Priscu, J. C.; Doran, P. T.; Chiuchiolo, A.; Obryk, M.

    2014-12-01

    Lakes integrate landscape processes and climate conditions. Most of the permanently ice-covered lakes in the McMurdo Dry Valleys, Antarctica are closed basin, receiving glacial melt water from streams for 10-12 weeks per year. Lake levels rise during the austral summer are balanced by sublimation of ice covers (year-round) and evaporation of open water moats (summer only). Vertical profiles of water temperature have been measured in three lakes in Taylor Valley since 1988. Up to 2002, lake levels were dropping, ice covers were thickening, and total heat contents were decreasing. These lakes have been gaining heat since the mid-2000s, at rates as high as 19.5x1014 cal/decade). Since 2002, lake levels have risen substantially (as much as 2.5 m), and ice covers have thinned (1.5 m on average). Analyses of lake ice thickness, meteorological conditions, and stream water heat loads indicate that the main source of heat to these lakes is from latent heat released when ice-covers form during the winter. An aditional source of heat to the lakes is water inflows from streams and direct glacieal melt. Mean lake temperatures in the past few years have stabilized or cooled, despite increases in lake level and total heat content, suggesting increased direct inflow of meltwater from glaciers. These results indicate that McMurdo Dry Valley lakes are sensitive indicators of climate processes in this polar desert landscape and demonstrate the importance of long-term data sets when addressing the effects of climate on ecosystem processes.

  17. Psychrophilic Biomass Producers in the Trophic Chain of the Microbial Community of Lake Untersee, Antarctica

    NASA Technical Reports Server (NTRS)

    Pikuta, Elena V.; Hoover, Richard B.

    2010-01-01

    The study of photosynthetic microorganisms from the Lake Untersee samples showed dispersed distribution of phototrophs within 80 m water column. Lake Untersee represents a unique ecosystem that experienced complete isolation: sealed by the Anuchin Glacier for many millennia. Consequently, its biocenosis has evolved over a significant period of time without exchange or external interaction with species from other environments. The major producers of organic matter in Lake Untersee are represented by phototrophic and chemolithotrophic microorganisms. This is the traditional trophic scheme for lacustrine ecosystems on Earth. Among the phototrophs, diatoms were not found, which differentiates this lake from other known ecosystems. The dominant species among phototrophs was Chlamydomonas sp. with typical morphostructure: green chloroplasts, bright red round spot, and two polar flagella near the opening. As expected, the physiology of studied phototrophs was limited by low temperature, which defined them as obligate psychrophilic microorganisms. By the quantity estimation of methanogenesis in this lake, the litho-autotrophic production of organic matter is competitive with phototrophic production. However, pure cultures of methanogens have not yet been obtained. We discuss the primary producers of organic matter and the participation of our novel psychrophilic homoacetogen into the litho-autotrophic link of biomass production in Lake Untersee.

  18. Unusual biogenic calcite structures in two shallow lakes, James Ross Island, Antarctica

    NASA Astrophysics Data System (ADS)

    Elster, J.; Nedbalová, L.; Vodrážka, R.; Láska, K.; Haloda, J.; Komárek, J.

    2016-01-01

    The floors of two shallow endorheic lakes, located on volcanic surfaces on James Ross Island, are covered with calcareous organosedimentary structures. Their biological and chemical composition, lake water characteristics, and seasonal variability of the thermal regime are introduced. The lakes are frozen down to the bottom for 8-9 months a year and their water chemistry is characterised by low conductivity and neutral to slightly alkaline pH. The photosynthetic microbial mat is composed of filamentous cyanobacteria and microalgae that are considered to be Antarctic endemic species. The mucilaginous black biofilm is covered by green spots formed by a green microalga and the macroscopic structures are packed together with fine material. Thin sections consist of rock substrate, soft biofilm, calcite spicules and mineral grains originating from different sources. The morphology of the spicules is typical of calcium carbonate monocrystals having a layered structure and specific surface texture, which reflect growth and degradation processes. The spicules' chemical composition and structure correspond to pure calcite. The lakes' age, altitude, morphometry, geomorphological and hydrological stability, including low sedimentation rates, together with thermal regime predispose the existence of this community. We hypothesise that the precipitation of calcite is connected with the photosynthetic activity of the green microalgae that were not recorded in any other lake in the region. This study has shown that the unique community producing biogenic calcite spicules is quite different to any yet described.

  19. Ecology of Subglacial Lake Vostok (Antarctica), Based on Metagenomic/Metatranscriptomic Analyses of Accretion Ice

    PubMed Central

    Rogers, Scott O.; Shtarkman, Yury M.; Koçer, Zeynep A.; Edgar, Robyn; Veerapaneni, Ram; D’Elia, Tom

    2013-01-01

    Lake Vostok is the largest of the nearly 400 subglacial Antarctic lakes and has been continuously buried by glacial ice for 15 million years. Extreme cold, heat (from possible hydrothermal activity), pressure (from the overriding glacier) and dissolved oxygen (delivered by melting meteoric ice), in addition to limited nutrients and complete darkness, combine to produce one of the most extreme environments on Earth. Metagenomic/metatranscriptomic analyses of ice that accreted over a shallow embayment and over the southern main lake basin indicate the presence of thousands of species of organisms (94% Bacteria, 6% Eukarya, and two Archaea). The predominant bacterial sequences were closest to those from species of Firmicutes, Proteobacteria and Actinobacteria, while the predominant eukaryotic sequences were most similar to those from species of ascomycetous and basidiomycetous Fungi. Based on the sequence data, the lake appears to contain a mixture of autotrophs and heterotrophs capable of performing nitrogen fixation, nitrogen cycling, carbon fixation and nutrient recycling. Sequences closest to those of psychrophiles and thermophiles indicate a cold lake with possible hydrothermal activity. Sequences most similar to those from marine and aquatic species suggest the presence of marine and freshwater regions. PMID:24832801

  20. Unusual biogenic calcite structures in two shallow lakes, James Ross Island, Antarctica

    NASA Astrophysics Data System (ADS)

    Elster, J.; Nedbalová, L.; Vodrážka, R.; Láska, K.; Haloda, J.; Komárek, J.

    2015-08-01

    The floors of two shallow endorheic lakes, located on volcanic surfaces on James Ross Island, are covered with calcareous organosedimentary structures. Their biological and chemical composition, lake water characteristics, and seasonal variability of the thermal regime are introduced. The lakes are frozen down to the bottom eight-nine months per year and their water chemistry is characterized by low conductivity and neutral to slightly alkaline pH. The photosynthetic microbial mat is composed of filamentous cyanobacteria and microalgae that are considered to be Antarctic endemic species. The mucilaginous black biofilm is covered by green spots formed by a green microalga and the macroscopic structures are packed together with fine material. Thin sections consist of rock substrate, soft biofilm, calcite spicules and mineral grains originating from different sources. The morphology of the spicules is typical of calcium carbonate monocrystals having a layered structure and worn surface, which reflect growth and degradation processes. The spicules chemical composition and structure correspond to pure calcite. Lakes age, altitude, morphometry, geomorphological and hydrological stability, including low sedimentation rates, together with thermal regime predispose the existence of this community. We hypothesize that the precipitation of calcite is connected with the photosynthetic activity of the green microalgae that were not recorded in any other lake in the region. This study has shown that the unique community producing biogenic calcite spicules is quite different to any yet described.

  1. Aquatic fulvic acids in microbially based ecosystems: results from two desert lakes in Antarctica

    USGS Publications Warehouse

    McKnight, Diane M.; Aiken, G.R.; Smith, R.L.

    1991-01-01

    These lakes receive very limited input of organic material from the surrounding barren desert, but they sustain algal and bacterial populations under permanent ice cover. One lake has an extensive anoxic zone and high salinities; the other is oxic and has low salinities. Despite these differences, fulvic acids from both lakes had similar elemental compositions, carbon distributions, and amino acid contents, indicating that the chemistry of microbially derived fulvic acvids is not strongly influenced by chemical conditions in the water column. Compared to fulvic acids from other natural waters, these fulvic acids have low C:N atomic ratios (19-25) and low contents of aromatic carbons (5-7% of total carbon atoms); they are most similar to marine fulvic acids. -from Authors

  2. Deliberations on Microbial Life in the Subglacial Lake Vostok, East Antarctica

    NASA Astrophysics Data System (ADS)

    Bulat, S.; Alekhina, I.; Lipenkov, V.; Lukin, V.; Marie, D.; Petit, J.

    2004-12-01

    The objective was to estimate microbial contents of accretion (lake originating) ice from the Lake Vostok buried beneath 4-km thick East Antarctic ice sheet with the ultimate goal to discover microbial life in this extreme icy environment featured by no light, close to freezing point temperature, ultra-low DOC contents, and an excess of oxygen. The PCR based bacterial and archaeal 16S ribosomal RNA gene sequencing constrained by Forensic Biology and Ancient DNA research criteria was used as a main approach. Epifluorescent and confocal microscopies as well as flow cytometry were implemented. DNA study showed that the accretion ice is essentially bacteria- and archaea-free. Up to now, the only accretion ice type 1 featured by mica-clay sediments presence and namely one horizon of four studied (3607m) allowed the recovery a few bacterial phylotypes. This unexpectedly included the chemolithoautotrophic thermophile Hydrogenophilus thermoluteolus and two more unclassified phylotypes all passing numerous contaminant controls. In contrast, the deeper and cleaner accretion ice 2 (three cores) with no sediments presence and near detection limit gas contents gave no reliable signals. The microbes detected in accretion ice 1 are unbelievable to resist an excess of oxygen in the lake water body (700 - 1300 mg O2/l). They are supposed to be thriving in rather warm anoxic sediments in deep faults at the lake bottom and sporadically flushing out along with sediments to the lake veins in a shallow depth bay due to a seismotectonic activity likely operating in the lake environment. A few geophysical and geological evidences support this scenario. In the bay the presence of mica-clay sediments, higher accretion rate due to relief rise and likely oxygen-depleted upper layer of water can provide microbes with a chance to escape the high oxygen tension by the rapid entrapment into accretion ice 1. Sediment-free accretion ice 2, which forms above a deeper part of the lake, shows no

  3. Vertical distribution of bacteria in a lake sediment from Antarctica by culture-independent and culture-dependent approaches.

    PubMed

    Shivaji, Sisinthy; Kumari, Kiran; Kishore, Kankipati Hara; Pindi, Pavan Kumar; Rao, Pasupuleti Sreenivasa; Radha Srinivas, Tanuku Naga; Asthana, Rajesh; Ravindra, Rasik

    2011-01-01

    Bacterial diversity of the subsurface (18-22 cm), middle (60-64 cm) and bottom (100-104 cm) of a 136-cm-long sediment core sampled from a freshwater lake in Antarctica was determined by the culturable approach, T-RFLP and 16S rRNA gene clone libraries. Using the culturable approach, 41 strains were isolated and, based on phylogenetic analysis, they could be categorized into 14 groups. Representatives of the 14 groups varied in their growth temperature range (4-30 °C), in their tolerance to NaCl (0-2 M NaCl) and in the growth pH range (5-11). Eleven of fourteen representative strains exhibited either amylase, lipase, protease and (or) urease activities at 4 °C. Bacterial diversity at the phyla level using T-RFLP and 16S rRNA clone libraries was similar and clones were affiliated with Proteobacteria, Bacteroidetes, Actinobacteria and Firmicutes. TRFs affiliated with Spirochaetes were detected only by the T-RFLP approach and clones affiliated with Caldiserica only in the clone libraries. Stratification of bacteria along the depth of the sediment was observed both with the T-RFLP and the 16S rRNA gene clone library methods, and results indicated that stratification was dependent on the nature of the organism, aerobic or anaerobic. For instance, aerobic Janthinobacterium and Polaromonas were confined to the surface of the sediment, whereas anaerobic Caldisericum was present only in the bottom portion of the core. It may be concluded that the bacterial diversity of an Antarctic lake sediment core sample varies throughout the length of the core depending on the oxic-anoxic conditions of the sediment. Furthermore, these psychrophilic bacteria, due to their ability to produce extracellular cold active enzymes, might play a key role in the transformation of complex organic compounds. PMID:21126578

  4. Perchlorate and volatiles of the brine of Lake Vida (Antarctica): Implication for the in situ analysis of Mars sediments

    NASA Astrophysics Data System (ADS)

    Kenig, Fabien; Chou, Luoth; McKay, Christopher P.; Jackson, W. Andrew; Doran, Peter T.; Murray, Alison E.; Fritsen, Christian H.

    2016-07-01

    The cold (-13.4°C), cryoencapsulated, anoxic, interstitial brine of the >27 m thick ice of Lake Vida (Victoria Valley, Antarctica) contains 49 µg · L-1 of perchlorate and 11 µg · L-1 of chlorate. Lake Vida brine (LVBr) may provide an analog for potential oxychlorine-rich subsurface brine on Mars. LVBr volatiles were analyzed by solid-phase microextraction (SPME) gas chromatography-mass spectrometry (GC-MS) with two different SPME fibers. With the exception of volatile organic sulfur compounds, most other volatiles observed were artifacts produced in the GC injector when the thermal decomposition products of oxychlorines reacted with reduced carbon derived from LVBr and the SPME fiber phases. Analysis of MilliQ water with perchlorate (40 µg · L-1) showed low level of organic artifacts, reflecting carbon limitation. In order to observe sample-derived organic compounds, both in analog samples and on Mars, the molar abundance of reduced carbon in a sample must exceed those of O2 and Cl2 produced during decomposition of oxychlorines. This suggests that the abundance of compounds observed by the Sample Analysis at Mars (SAM) instruments in Sheepbed samples (CB-3, CB5, and CB6) may be controlled by an increase in the reduced-carbon/oxychlorine ratio of these samples. To increase chances of in situ detection of Martian organics during pyrolysis-GC-MS, we propose that the derivatization agents stored on SAM may be used as an external source of reduced carbon, increasing artificially the reduced-carbon to perchlorate ratio during pyrolysis, allowing the expression of more abundant and perhaps more diverse Martian organic matter.

  5. Reflectance spectroscopy and geochemical analyses of Lake Hoare sediments, Antarctica: Implications for remote sensing of the Earth and Mars

    NASA Astrophysics Data System (ADS)

    Bishop, Janice L.; Koeberl, Christian; Kralik, Claudia; Fröschl, Heinz; Enolert, Peter A. J.; Andersen, David W.; Pieters, Carlé M.; Wharton, Robert A.

    1996-03-01

    Visible to infrared reflectance spectroscopic analyses (0.3-25 μm) have been performed on sediments from the Dry Valleys region of Antarctica. Sample characterization for these sediments includes extensive geochemical analyses and X-ray diffraction (XRD). The reflectance spectra and XRD indicate major amounts of quartz, feldspar, and pyroxene in these samples and lesser amounts of carbonate, mica, chlorite, amphibole, illite, smectite, and organic matter. Calcite is the primary form of carbonate present in these Lake Hoare sediments based on the elemental abundances and spectroscopic features. The particle size distribution of the major and secondary components influences their detection in mixtures and this sensitivity to particle size is manifested differently in the "volume scattering" and "surface scattering" infrared regions. The Christiansen feature lies between these two spectral regimes and is influenced by the spectral properties of both regions. For these mixtures the Christiansen feature was found to be dependent on physical parameters, such as particle size and sample texture, as well as the mineralogy. Semiquantitative spectroscopic detection of calcite and organic material has been tested in these quartz- and feldspar-rich sediments. The relative spectral band depths due to organics and calcite correlate in general with the wt% C from organic matter and carbonate. The amounts of organic matter and carbonate present correlate with high Br and U abundances and high Ca and Sr abundances, respectively. Variation in the elemental abundances was overall minimal, which is consistent with a common sedimentary origin for the forty-two samples studied here from Lake Hoare.

  6. The Dry Valley Lakes, Antarctica: from sulfur stains on Earth to sulfur stains in the Jovian system

    NASA Astrophysics Data System (ADS)

    Chela-Flores, Julian; Seckbach, Joseph

    2011-10-01

    Most organisms dwell in what we consider to be "normal" environments, while others, which are called extremophiles, may thrive in harsher conditions. These living organisms are mainly of unicellular (both prokaryotes and, to a lesser extent, there are some eukaryotes) But the extremophiles also include multicellular organisms, including worms, insects and crustaceans. In the present work we survey specific extremophiles in some detail. Astrobiology is concerned with all of these extremophiles, as they may be models for extant life in similar environments elsewhere in the universe. In the more restricted search for life through exploration of the Solar System, the main focus is on the preparation of suites of experiments that may attempt to discover the habitability of planets and their satellites. In this context we ask ourselves: What biosignatures can facilitate life detection, both unicellular and multicellular, in extreme environments? The environments that are within reach of present and future space missions include the Jupiter satellite Europa. The icecovered lakes of Antarctica's McMurdo Dry Valleys have long been of interest to astrobiology. These environments harbor unique microbial ecosystems that could orient us how to plan our experiments on Europa.

  7. Correlation of cycles in Lava Lake motion and degassing at Erebus Volcano, Antarctica

    NASA Astrophysics Data System (ADS)

    Peters, Nial; Oppenheimer, Clive; Killingsworth, Drea Rae; Frechette, Jed; Kyle, Philip

    2014-08-01

    studies at Erebus volcano have recorded pulsatory behavior in many of the observable properties of its active lava lake. A strong correlation between the variations in surface speed of the lake and the composition of gas emitted has previously been noted. While previous studies have shown that the SO2 flux and the surface elevation exhibit pulsatory behavior with a similar period to that of the surface speed and gas composition, suggesting they are linked, a lack of overlap between the different measurements has prevented direct comparisons from being made. Using high time-resolution measurements of surface elevation, surface speed, gas composition, and SO2 flux, we demonstrate for the first time an unambiguous link between the cyclic behavior in each of these properties. We also show that the variation in gas composition may be explained by a subtle change in oxygen fugacity. The cycles are found to be in-phase with each other, with a small but consistent lag of 1-3 min between the peaks in surface elevation and surface speed. Explosive events are found to have no observable effect on the pulsatory behavior beyond the ˜5 min period required for lake refill. The close correspondences between the varying lake surface motion, gas flux and composition, and modeled oxygen fugacity suggest strong links between magma degassing, redox change, and the fluid dynamics of the shallow magmatic system.

  8. Stratigraphy of Lake Vida, Antarctica: hydrologic implications of 27 m of ice

    NASA Astrophysics Data System (ADS)

    Dugan, H. A.; Doran, P. T.; Wagner, B.; Kenig, F.; Fritsen, C. H.; Arcone, S. A.; Kuhn, E.; Ostrom, N. E.; Warnock, J. P.; Murray, A. E.

    2015-03-01

    Lake Vida, located in Victoria Valley, is one of the largest lakes in the McMurdo dry valleys and is known to contain hypersaline liquid brine sealed below 16 m of freshwater ice. For the first time, Lake Vida was drilled to a depth of 27 m. Below 21 m the ice is marked by well-sorted sand layers up to 20 cm thick within a matrix of salty ice. From ice chemistry, isotopic composition of δ18O and δ2H, and ground penetrating radar profiles, we conclude that the entire 27 m of ice formed from surface runoff and the sediment layers represent the accumulation of surface deposits. Radiocarbon and optically stimulated luminescence dating limit the maximum age of the lower ice to 6300 14C yr BP. As the ice cover ablated downwards during periods of low surface inflow, progressive accumulation of sediment layers insulated and preserved the ice and brine beneath, analogous to the processes that preserve shallow ground ice. The repetition of these sediment layers reveals hydrologic variability in Victoria Valley during the mid- to late Holocene. Lake Vida is an exemplar site for understanding the preservation of subsurface brine, ice, and sediment in a cold desert environment.

  9. New Insights in the Existence of Lakes Beneath the Recovery Glacier Drainage Basin, Antarctica

    NASA Astrophysics Data System (ADS)

    Steinhage, D.; Helm, V.; Kasper, D.; Kleiner, T.; Humbert, A.

    2014-12-01

    The Recovery Glacier is draining about 8% of the East Antarctic ice sheet and feeds into the Filchner Ice Shelf. There were suggestions that the dynamics of the glacier is driven by large subglacial lakes that initiate the ice stream flow (Bell et al., 2008). As the Recovery Glacier is one of the least surveyed ice streams due to its remote location, this hypothesis could not be tested rigorously so far. In austral summer 2013/14 AWI carried out a survey of the Recovery Glacier including radio echo sounding, gravimetry, magnetics, and laser scanner. In total more than 22000 km survey lines were flown. Here we present an ice thickness map of the main trunk of the Recovery Glacier, as well as its tributaries Blackwall and Ramp glaciers. The ice thickness varies between 70 m in the vicinity of the Shackleton Range and nearly 3800 m close to the Bell lakes. Using different DEMs including one CryoSat-2 DEM (Helm et al., 2014), we determine the basal topography and the hydraulic head. We estimate the basal reflection coefficient and assess by this locations with potentially wet ice base. The distribution shows that few of the formerly proposed lakes show indeed a wet base, while others are missing clear lake like basal reflections.

  10. The subglacial Lake Vostok (East Antarctica) surface snow is Earth-bound DNA (and dust)-free

    NASA Astrophysics Data System (ADS)

    Bulat, S.; Marie, D.; Bulat, E.; Alekhina, I.; Petit, J.-R.

    2012-09-01

    came up with only contaminant bacterial phylotypes (mostly of human source). The bioexposure trials showed that even in one day of open exposure the gDNA of rather complex microbial community composition was fatally damaged in terms of long-, mid-range and short-size amplicon generation in PCR. All this testify for very harsh conditions for life to survive the climate conditions of Central East Antarctica which could be considered as a presentday 'zone mortale' or 'polar desert' for known Earthbound microbial life forms. In addition this means that no life seeds are expected to reach subglacial lakes and water reservoirs and establish indigenous lake microbiota during their transit through the thick and aged Antarctic ice sheet upon its bottom melting. In general the subglacial Lake Vostok surface (ice sheet as well) environ represents the unique test area (sterile - in fact Earth-bound DNA-free and clean - in fact Earth-bound dust-free) for advancing extraterrestrial (ET) life detection technologies and searching for ET life indices in AMMs and IDPs.

  11. Autonomous thermal camera system for monitoring the active lava lake at Erebus volcano, Antarctica

    NASA Astrophysics Data System (ADS)

    Peters, N.; Oppenheimer, C.; Kyle, P.

    2014-02-01

    In December 2012, the Mount Erebus Volcano Observatory installed a thermal infrared camera system to monitor the volcano's active lava lake. The new system is designed to be autonomous, and capable of capturing images of the lava lake continuously throughout the year. This represents a significant improvement over previous systems which required the frequent attention of observatory researchers and could therefore only be operated during a few weeks of the annual field campaigns. The extreme environmental conditions at the summit of Erebus pose significant challenges for continuous monitoring equipment, and a custom-made system was the only viable solution. Here we describe the hardware and software of the new system in detail and report on a publicly available online repository where data will be archived. Aspects of the technical solutions we had to find in order to overcome the challenges of automating this equipment may be relevant in other environmental science domains where remote instrument operation is involved.

  12. Autonomous thermal camera system for monitoring the active lava lake at Erebus volcano, Antarctica

    NASA Astrophysics Data System (ADS)

    Peters, N.; Oppenheimer, C.; Kyle, P.

    2013-10-01

    In December 2012, the Mount Erebus Volcano Observatory installed a thermal infrared camera system to monitor the volcano's active lava lake. The new system is designed to be autonomous, and capable of capturing images of the lava lake continuously throughout the year. This represents a significant improvement over previous systems which required the frequent attention of observatory researchers and could therefore only be operated during a few weeks of the annual field campaigns. The extreme environmental conditions at the summit of Erebus pose significant challenges for continuous monitoring equipment, and a custom made system was the only viable solution. Here we describe the hardware and software of the new system in detail and report on a publicly-available online repository where data will be archived. Aspects of the technical solutions we had to find in order to overcome the challenges of automating this equipment may be relevant in other environmental science domains where remote instrument operation is involved.

  13. Perchlorate and Volatiles in the Brine of Lake Vida (antarctica): Implication for the Analysis of Mars Sediments

    NASA Astrophysics Data System (ADS)

    Kenig, F. P. H.; Chou, L.; McKay, C.; Jackson, W. A.; Doran, P. T.; Murray, A. E.; Fritsen, C. H.

    2015-12-01

    A cold (-13.4 °C), saline (188 psu) evaporative brine is encapsulated in the thick (> 27 m) ice of Lake Vida (McMurdo Dry Valleys, Antarctica). The Lake Vida brine (LVBr), which contains abundant dissolved organic carbon (48.2 mmol/L), support an active but slow microbial community. LVBr contains oxychlorines with 50 μg/L of perchlorate and 11 μg/L of chlorate. The McMurdo Dry Valleys have often been considered as a good Mars analog. The oxychlorine-rich brine of Lake Vida constitutes a potential equivalent to perchlorate-rich preserved saline liquid water on Mars. We report here on the artifacts created by oxychlorines upon analysis of volatiles and volatile organic compounds (VOCs) of LVBr by direct immersion (DI) and head space (HS) solid phase micro extraction (SPME) gas chromatography-mass spectrometry (GCMS). We compare analytical blanks to a standard containing 40 μg/L of perchlorate and to actual LVBr sample runs. All blanks, perchlorate blanks and samples were analyzed using two types of SPME fibers, CarboxenTM/polydimethylsiloxane (PDMS) and divinylbenzene (DVB)/ PDMS. The similarities and differences between our results and those obtained by the Sample Analysis at Mars instruments of the rover Curiosity are discussed. The volatiles evolved from LVBr upon analysis with DI- and HS-SPME GCMS are dominated by CO2, dichloromethane, HCl, and volatile organic sulfur compounds (VOSCs, such as DMS, DMDS). The volatiles also include oxygenated compounds such as acids and ketones, aromatic compounds, hydrocarbons, chlorinated compounds (dominated by dichloromethane). Apart from the VOSCs, short chain hydrocarbons and some functionalized compounds derived from the brine itself, all compounds observed are artifacts formed upon oxychlorine breakdown in the injector of the GCMS. The distribution of aromatic compounds seems to be directly dependant on the type of SPME fiber used. The perchlorate blanks show a clear pattern of carbon limitation, likely affecting the

  14. Manganese reduction by microbes from oxic regions of the Lake Vanda (Antarctica) water column

    SciTech Connect

    Bratina, B.J.; Stevenson, B.S.; Schmidt, T.M.; Green, W.J.

    1998-10-01

    Depth profiles of metals in Lake Vanda, a permanently ice-covered, stratified Antarctic lake, suggest the importance of particulate manganese oxides in the scavenging, transport, and release of metals. Since manganese oxides can be solubilized by manganese-reducing bacteria, microbially mediated manganese reduction was investigated in Lake Vanda. Microbes concentrated from oxic regions of the water column, encompassing a peak of soluble manganese [Mn(II)], reduced synthetic manganese oxides (MnO{sub 2}) when incubated aerobically, Pure cultures of manganese-reducing bacteria were readily isolated from waters collected near the oxic Mn(II) peak. Based on phylogenetic analysis of the 16S rRNA gene sequence, most of the isolated manganese reducers belong to the genus Carnobacterium. Cultures of a phylogenetically representative strain of Carnobacterium reduced synthetic MnO{sub 2} in the presence of sodium azide, as was seen in field assays. Unlike anaerobes that utilize manganese oxides as terminal electron acceptors in respiration, isolates of the genus Carnobacterium reduced Mn(IV) via a diffusible compound under oxic conditions. The release of adsorbed trace metals accompanying the solubilization of manganese oxides may provide populations of Carnobacterium with a source of nutrients in this extremely oligotrophic environment.

  15. Manganese Reduction by Microbes from Oxic Regions of the Lake Vanda (Antarctica) Water Column

    PubMed Central

    Bratina, Bonnie Jo; Stevenson, Bradley S.; Green, William J.; Schmidt, Thomas M.

    1998-01-01

    Depth profiles of metals in Lake Vanda, a permanently ice-covered, stratified Antarctic lake, suggest the importance of particulate manganese oxides in the scavenging, transport, and release of metals. Since manganese oxides can be solubilized by manganese-reducing bacteria, microbially mediated manganese reduction was investigated in Lake Vanda. Microbes concentrated from oxic regions of the water column, encompassing a peak of soluble manganese [Mn(II)], reduced synthetic manganese oxides (MnO2) when incubated aerobically. Pure cultures of manganese-reducing bacteria were readily isolated from waters collected near the oxic Mn(II) peak. Based on phylogenetic analysis of the 16S rRNA gene sequence, most of the isolated manganese reducers belong to the genus Carnobacterium. Cultures of a phylogenetically representative strain of Carnobacterium reduced synthetic MnO2 in the presence of sodium azide, as was seen in field assays. Unlike anaerobes that utilize manganese oxides as terminal electron acceptors in respiration, isolates of the genus Carnobacterium reduced Mn(IV) via a diffusible compound under oxic conditions. The release of adsorbed trace metals accompanying the solubilization of manganese oxides may provide populations of Carnobacterium with a source of nutrients in this extremely oligotrophic environment. PMID:9758801

  16. Brine Assemblages of Ultrasmall Microbial Cells within the Ice Cover of Lake Vida, Antarctica

    PubMed Central

    Kuhn, Emanuele; Ichimura, Andrew S.; Peng, Vivian; Fritsen, Christian H.; Trubl, Gareth; Doran, Peter T.

    2014-01-01

    The anoxic and freezing brine that permeates Lake Vida's perennial ice below 16 m contains an abundance of very small (≤0.2-μm) particles mixed with a less abundant population of microbial cells ranging from >0.2 to 1.5 μm in length. Fluorescent DNA staining, electron microscopy (EM) observations, elemental analysis, and extraction of high-molecular-weight genomic DNA indicated that a significant portion of these ultrasmall particles are cells. A continuous electron-dense layer surrounding a less electron-dense region was observed by EM, indicating the presence of a biological membrane surrounding a cytoplasm. The ultrasmall cells are 0.192 ± 0.065 μm, with morphology characteristic of coccoid and diplococcic bacterial cells, often surrounded by iron-rich capsular structures. EM observations also detected the presence of smaller unidentified nanoparticles of 0.020 to 0.140 μm among the brine cells. A 16S rRNA gene clone library from the brine 0.1- to 0.2-μm-size fraction revealed a relatively low-diversity assemblage of Bacteria sequences distinct from the previously reported >0.2-μm-cell-size Lake Vida brine assemblage. The brine 0.1- to 0.2-μm-size fraction was dominated by the Proteobacteria-affiliated genera Herbaspirillum, Pseudoalteromonas, and Marinobacter. Cultivation efforts of the 0.1- to 0.2-μm-size fraction led to the isolation of Actinobacteria-affiliated genera Microbacterium and Kocuria. Based on phylogenetic relatedness and microscopic observations, we hypothesize that the ultrasmall cells in Lake Vida brine are ultramicrocells that are likely in a reduced size state as a result of environmental stress or life cycle-related conditions. PMID:24727273

  17. Brine assemblages of ultrasmall microbial cells within the ice cover of Lake Vida, Antarctica.

    PubMed

    Kuhn, Emanuele; Ichimura, Andrew S; Peng, Vivian; Fritsen, Christian H; Trubl, Gareth; Doran, Peter T; Murray, Alison E

    2014-06-01

    The anoxic and freezing brine that permeates Lake Vida's perennial ice below 16 m contains an abundance of very small (≤0.2-μm) particles mixed with a less abundant population of microbial cells ranging from >0.2 to 1.5 μm in length. Fluorescent DNA staining, electron microscopy (EM) observations, elemental analysis, and extraction of high-molecular-weight genomic DNA indicated that a significant portion of these ultrasmall particles are cells. A continuous electron-dense layer surrounding a less electron-dense region was observed by EM, indicating the presence of a biological membrane surrounding a cytoplasm. The ultrasmall cells are 0.192 ± 0.065 μm, with morphology characteristic of coccoid and diplococcic bacterial cells, often surrounded by iron-rich capsular structures. EM observations also detected the presence of smaller unidentified nanoparticles of 0.020 to 0.140 μm among the brine cells. A 16S rRNA gene clone library from the brine 0.1- to 0.2-μm-size fraction revealed a relatively low-diversity assemblage of Bacteria sequences distinct from the previously reported >0.2-μm-cell-size Lake Vida brine assemblage. The brine 0.1- to 0.2-μm-size fraction was dominated by the Proteobacteria-affiliated genera Herbaspirillum, Pseudoalteromonas, and Marinobacter. Cultivation efforts of the 0.1- to 0.2-μm-size fraction led to the isolation of Actinobacteria-affiliated genera Microbacterium and Kocuria. Based on phylogenetic relatedness and microscopic observations, we hypothesize that the ultrasmall cells in Lake Vida brine are ultramicrocells that are likely in a reduced size state as a result of environmental stress or life cycle-related conditions. PMID:24727273

  18. A halophilic bacterium inhabiting the warm, CaCl2-rich brine of the perennially ice-covered Lake Vanda, McMurdo Dry Valleys, Antarctica.

    PubMed

    Tregoning, George S; Kempher, Megan L; Jung, Deborah O; Samarkin, Vladimir A; Joye, Samantha B; Madigan, Michael T

    2015-03-01

    Lake Vanda is a perennially ice-covered and stratified lake in the McMurdo Dry Valleys, Antarctica. The lake develops a distinct chemocline at about a 50-m depth, where the waters transition from cool, oxic, and fresh to warm, sulfidic, and hypersaline. The bottom water brine is unique, as the highly chaotropic salts CaCl2 and MgCl2 predominate, and CaCl2 levels are the highest of those in any known microbial habitat. Enrichment techniques were used to isolate 15 strains of heterotrophic bacteria from the Lake Vanda brine. Despite direct supplementation of the brine samples with different organic substrates in primary enrichments, the same organism, a relative of the halophilic bacterium Halomonas (Gammaproteobacteria), was isolated from all depths sampled. The Lake Vanda (VAN) strains were obligate aerobes and showed broad pH, salinity, and temperature ranges for growth, consistent with the physicochemical properties of the brine. VAN strains were halophilic and quite CaCl2 tolerant but did not require CaCl2 for growth. The fact that only VAN strain-like organisms appeared in our enrichments hints that the highly chaotropic nature of the Lake Vanda brine may place unusual physiological constraints on the bacterial community that inhabits it. PMID:25576606

  19. A Halophilic Bacterium Inhabiting the Warm, CaCl2-Rich Brine of the Perennially Ice-Covered Lake Vanda, McMurdo Dry Valleys, Antarctica

    PubMed Central

    Tregoning, George S.; Kempher, Megan L.; Jung, Deborah O.; Samarkin, Vladimir A.; Joye, Samantha B.

    2015-01-01

    Lake Vanda is a perennially ice-covered and stratified lake in the McMurdo Dry Valleys, Antarctica. The lake develops a distinct chemocline at about a 50-m depth, where the waters transition from cool, oxic, and fresh to warm, sulfidic, and hypersaline. The bottom water brine is unique, as the highly chaotropic salts CaCl2 and MgCl2 predominate, and CaCl2 levels are the highest of those in any known microbial habitat. Enrichment techniques were used to isolate 15 strains of heterotrophic bacteria from the Lake Vanda brine. Despite direct supplementation of the brine samples with different organic substrates in primary enrichments, the same organism, a relative of the halophilic bacterium Halomonas (Gammaproteobacteria), was isolated from all depths sampled. The Lake Vanda (VAN) strains were obligate aerobes and showed broad pH, salinity, and temperature ranges for growth, consistent with the physicochemical properties of the brine. VAN strains were halophilic and quite CaCl2 tolerant but did not require CaCl2 for growth. The fact that only VAN strain-like organisms appeared in our enrichments hints that the highly chaotropic nature of the Lake Vanda brine may place unusual physiological constraints on the bacterial community that inhabits it. PMID:25576606

  20. A model assessment of the ability of lake water in Terra Nova Bay, Antarctica, to induce the photochemical degradation of emerging contaminants.

    PubMed

    Minella, Marco; Maurino, Valter; Minero, Claudio; Vione, Davide

    2016-11-01

    The shallow lakes located in Terra Nova Bay, Antarctica, are free from ice for only up to a couple of months (mid December to early/mid February) during the austral summer. In the rest of the year, the ice cover shields the light and inhibits the photochemical processes in the water columns. Previous work has shown that chromophoric dissolved organic matter (CDOM) in these lakes is very reactive photochemically. A model assessment is here provided of lake-water photoreactivity in field conditions, based on experimental data of lake water absorption spectra, chemistry and photochemistry obtained previously, taking into account the water depth and the irradiation conditions of the Antarctic summer. The chosen sample contaminants were the solar filter benzophenone-3 and the antimicrobial agent triclosan, which have very well known photoreactivity and have been found in a variety of environmental matrices in the Antarctic continent. The two compounds would have a half-life time of just a few days or less in the lake water during the Antarctic summertime, largely due to reaction with CDOM triplet states ((3)CDOM*). In general, pollutants that occur in the ice and could be released to lake water upon ice melting (around or soon after the December solstice) would be quickly photodegraded if they undergo fast reaction with (3)CDOM*. With some compounds, the important (3)CDOM* reactions might favour the production of harmful secondary pollutants, such as 2,8-dichlorodibenzodioxin from the basic (anionic) form of triclosan. PMID:27487093

  1. ACE blood test

    MedlinePlus

    ... to help diagnose and monitor a disorder called sarcoidosis . People with sarcoidosis may have their ACE level tested regularly to ... normal ACE level may be a sign of sarcoidosis. ACE levels may rise or fall as sarcoidosis ...

  2. Streamflow, water-temperature, and specific-conductance data for selected streams draining into Lake Fryxell, lower Taylor Valley, Victoria Land, Antarctica, 1990-92

    USGS Publications Warehouse

    Von Guerard, Paul; McKnight, Diane M.; Harnish, R.A.; Gartner, J.W.; Andrews, E.D.

    1995-01-01

    During the 1990-91 and 1991-92 field seasons in Antarctica, streamflow, water-temperature, and specific-conductance data were collected on the major streams draining into Lake Fryxell. Lake Fryxell is a permanently ice-covered, closed-basin lake with 13 tributary streams. Continuous streamflow data were collected at eight sites, and periodic streamflow measurements were made at three sites. Continuous water-temperature and specific- conductance data were collected at seven sites, and periodic water-temperature and specific-conductance data were collected at all sites. Streamflow for all streams measured ranged from 0 to 0.651 cubic meter per second. Water temperatures for all streams measured ranged from 0 to 14.3 degrees Celsius. Specific conductance for all streams measured ranged from 11 to 491 microsiemens per centimeter at 25 degrees Celsius. It is probable that stream- flow in the Lake Fryxell Basin during 1990-92 was greater than average. Examination of the 22-year streamflow record in the Onyx River in the Wright Valley revealed that in 1990 streamflow began earlier than for any previous year recorded and that the peak streamflow of record was exceeded. Similar high-flow conditions occurred during the 1991-92 field season. Thus, the data collected on streams draining into Lake Fryxell during 1990-92 are representative of greater than average stream- flow conditions.

  3. Sources of Sulfate Found in Mounds and Lakes at the Lewis Cliffs Ice Tongue, Transantarctic Mountains, Antarctica and Inferred Sub-glacial Microbial Environments

    NASA Astrophysics Data System (ADS)

    Socki, R. A.; Sun, T.; Harvey, R. P.; Bish, D. L.; Tonui, E.; Bao, H.; Niles, P. B.

    2012-12-01

    Massive but highly localized Na-sulfate mounds (mirabilite, Na2SO4.10H2O) have been found at the terminal moraine of the Lewis Cliffs Ice Tongue (LCIT), Antarctica. δ34S and δ18O values of LCIT mirabilite range from +48.8 to +49.3‰ (CDT), and -16.6 to -17.1‰ (V-SMOW), respectively, while Δ17O average -0.37‰ (V-SMOW). LCIT mirabilite mounds are isotopically different from other mirabilite mounds found in coastal regions of Antarctica, which have isotope values close to seawater compositions. δ18O and Δ17O values suggest the incorporation of isotopically light glacial water. Data point to initial sulfate formation in an anoxic water body, either as a stratified anoxic deep lake on the surface, a sub-glacial water reservoir, or a sub-glacial lake. Several surface lakes of varying size are also present within this region of the LCIT, and in some cases are adjacent to the mirabilite mounds. O and D isotope compositions of surface lakes confirm they are derived from a mixture of glacial ice and snow that underwent moderate evaporation. δ18O and δD (V-SMOW) values of snow, ice, and lake water range from -64.2 to -29.7‰, and -456.0 to -231.7‰, respectively. However, the isotope chemistry of these surface lakes is extremely different from the mounds. Dissolved SO4-2 δ34S and δ18O values range from +12.0 to +20.0‰ and -12.8 to -22.2‰ (the most negative δ18O of terrestrial sulfate ever reported), respectively, with sulfate Δ17O ranging from +0.93 to 2.24‰. Ion chromatography data show that lake water is fresh to brackish in origin, with TDS less than 1500 ppm, and sulfate concentration less than 431 ppm. Isotope and chemical data suggest that these lakes are unlikely the source of the mirabilite mounds. We suggest that lake water sulfate is potentially composed of a mixture of atmospheric sulfate and minor components of sulfate of weathering origin, much like the sulfate in the polar plateau soils of the McMurdo Dry Valleys. A simple model explains

  4. An integrated study of photochemical function and expression of a key photochemical gene (psbA) in photosynthetic communities of Lake Bonney (McMurdo Dry Valleys, Antarctica).

    PubMed

    Kong, Weidong; Li, Wei; Romancova, Ingrid; Prášil, Ondřej; Morgan-Kiss, Rachael M

    2014-08-01

    Lake Bonney is one of several permanently ice-covered lakes in the McMurdo Dry Valleys, Antarctica, which maintain the only year-round biological activity on the Antarctic continent. Vertically stratified populations of autotrophic microorganisms occupying the water columns are adapted to numerous extreme conditions, including very low light, hypersalinity, ultra-oligotrophy and low temperatures. In this study, we integrated molecular biology, microscopy, flow cytometry, and functional photochemical analyses of the photosynthetic communities residing in the east and west basins of dry valley Lake Bonney. Diversity and abundance of the psbA gene encoding a major protein of the photosystem II reaction center were monitored during the seasonal transition between Antarctic summer (24-h daylight) to winter (24-h darkness). Vertical trends through the photic zone in psbA abundance (DNA and mRNA) closely matched that of primary production in both lobes. Seasonal trends in psbA transcripts differed between the two lobes, with psbA expression in the west basin exhibiting a transient rise in early Fall. Last, using spectroscopic and flow cytometric analyses, we provide the first evidence that the Lake Bonney photosynthetic community is dominated by picophytoplankton that possess photosynthetic apparatus adapted to extreme shade. PMID:24499459

  5. Spatial variability of the active layer thickness at the Limnopolar Lake CALM-S site (Byers Peninsula, Livingston Island, Antarctica) and the role of snow cover.

    NASA Astrophysics Data System (ADS)

    de Pablo, Miguel A.; Molina, Antonio; Ramos, Miguel

    2016-04-01

    Since its establishment in early 2009, thaw depth has been measured in late January - early February at the Limnopolar Lake CALM-S site (A25) in Byers Peninsula, Livingston Island, Antarctica (62°38'59.1''S, 61°06'16.9''W). Ground, surface, and air temperatures have been also measured, as well as snow cover deep, derived from an array of miniature temperature loggers mounted into a wood mast (iButton from Maxim) (Lewcovicz, 2008). Thermal characterization of the active layer has been already done based on this data (de Pablo et al., 2013), as well as the interannual variability (de Pablo et al., 2014) and the snow cover evolution analyses (de Pablo et al., submitted). The results show that permafrost could exist at 120 cm depth, although the active layer is reducing, probably caused by the elongation on the snow cover duration. While the snow cover thickness remains approximately similar each winter, the snow offset delays, reducing the period in which solar radiation could heat the ground. In fact, during the last years, thaw depth was not able to be measured (in spite we visited the area in the approximately the same dates) due to thick snow layer remained covering the CALM-S site. However, we have not yet developed an analysis of the spatial variability of the thaw depth we measured each year, and how it could be conditioned by the ground properties (as slope or grain-size) or external factors, such as snow cover. In order to confirm the effect of the snow cover in the evolution of the active layer thickness, here we analyze the spatial variability of the thaw depth for the entire CALM-S site, and try to correlate it respect to the ground surface characteristics (grain-size, ground patterns, among others), the ground surface temperature and the snow cover thickness. Some of those data were acquired while the surface was visible during Antarctic field trips few years ago, and others (snow cover thickness) was measured by mechanical probing in each node. This

  6. New insights into the origin and evolution of Lake Vida, McMurdo Dry Valleys, Antarctica — A noble gas study in ice and brines

    NASA Astrophysics Data System (ADS)

    Malone, Jessica L.; Castro, M. Clara; Hall, Chris M.; Doran, Peter T.; Kenig, Fabien; McKay, Chris P.

    2010-01-01

    Unlike other lakes in the McMurdo Dry Valleys, Antarctica, Lake Vida has a thick (~ 19 m) ice cover sealing a liquid brine body of unusually high salinity (~ 245 g/L) from the atmosphere. To constrain the conditions under which the atypical Lake Vida ice cover formed and evolved, 19 ice samples were collected down to a depth of ~ 14 m, together with three brine samples trapped in the ice at ~ 16 m for analysis of helium, neon, argon, krypton, and xenon concentrations. The broad pattern of noble gas concentrations for Lake Vida samples is fundamentally different from that of air saturated water (ASW) at 0 °C and an elevation of 340 m for salinities of 0 (ice) and 245 g/L (brine). Overall, ice samples are enriched in He and depleted in Ne with saturation relative to ASW averages of 1.38 and 0.82, respectively, and strongly depleted in Ar, Kr, and Xe with relative saturations of 0.10, 0.06, and 0.05, respectively. By contrast, brine samples are generally depleted in He and Ne (relative saturation averages of 0.33 and 0.27, respectively) but enriched in Ar, Kr, and Xe, with relative saturation averages of 1.45, 3.15, and 8.86, respectively. A three-phase freezing partitioning model generating brine, ice and bubble concentrations for all stable noble gases was tested and compared with our data. Measured brine values are best reproduced for a salinity value of 175 g/L, a pressure of 1.1 atm, and a bubble volume of 20 cm 3 kg -1. Sensitivity tests for ice + bubble samples show an ideal fit for bubble volumes of ~ 1-2 cm 3 kg -1. Our results show that the conditions under which ice and brine formed and evolved at Lake Vida are significantly different from other ice-covered lakes in the area. Our brine data suggest that Lake Vida may be transitioning from a wet to a dry-based lake, while the ice + bubble data suggest at least partial re-equilibration of residual liquid with the atmosphere as ice forms at the top of Lake Vida ice cover.

  7. Spatial Heterogeneity of Ice Cover Sediment and Thickness and Its Effects on Photosynthetically Active Radiation and Chlorophyll-a Distribution: Lake Bonney, Antarctica

    NASA Astrophysics Data System (ADS)

    Obryk, M.; Doran, P. T.; Priscu, J. C.; Morgan-Kiss, R. M.; Siebenaler, A. G.

    2012-12-01

    The perennially ice-covered lakes in the McMurdo Dry Valleys, Antarctica have been extensively studied under the Long Term Ecological Research project. But sampling has been spatially restricted due to the logistical difficulty of penetrating the 3-6 m of ice cover. The ice covers restrict wind-driven turbulence and its associated mixing of water, resulting in a unique thermal stratification and a strong vertical gradient of salinity. The permanent ice covers also shade the underlying water column, which, in turn, controls photosynthesis. Here, we present results of a three-dimensional record of lake processes obtained with an autonomous underwater vehicle (AUV). The AUV was deployed at West Lake Bonney, located in Taylor Valley, Dry Valleys, to further understand biogeochemical and physical properties of the Dry Valley lakes. The AUV was equipped with depth, conductivity, temperature, under water photosynthetically active radiation (PAR), turbidity, chlorophyll-and-DOM fluorescence, pH, and REDOX sensors. Measurements were taken over the course of two years in a 100 x 100 meter spaced horizontal sampling grid (and 0.2 m vertical resolution). In addition, the AUV measured ice thickness and collected 200 images looking up through the ice, which were used to quantify sediment distribution. Comparison with high-resolution satellite QuickBird imagery demonstrates a strong correlation between aerial sediment distribution and ice cover thickness. Our results are the first to show the spatial heterogeneity of lacustrine ecosystems in the McMurdo Dry Valleys, significantly improving our understanding of lake processes. Surface sediment is responsible for localized thinning of ice cover due to absorption of solar radiation, which in turn increases total available PAR in the water column. Higher PAR values are negatively correlated with chlorophyll-a, presenting a paradox; historically, long-term studies of PAR and chlorophyll-a have shown positive trends. We hypothesized

  8. Distribution of cold adaptation proteins in microbial mats in Lake Joyce, Antarctica: Analysis of metagenomic data by using two bioinformatics tools.

    PubMed

    Koo, Hyunmin; Hakim, Joseph A; Fisher, Phillip R E; Grueneberg, Alexander; Andersen, Dale T; Bej, Asim K

    2016-01-01

    In this study, we report the distribution and abundance of cold-adaptation proteins in microbial mat communities in the perennially ice-covered Lake Joyce, located in the McMurdo Dry Valleys, Antarctica. We have used MG-RAST and R code bioinformatics tools on Illumina HiSeq2000 shotgun metagenomic data and compared the filtering efficacy of these two methods on cold-adaptation proteins. Overall, the abundance of cold-shock DEAD-box protein A (CSDA), antifreeze proteins (AFPs), fatty acid desaturase (FAD), trehalose synthase (TS), and cold-shock family of proteins (CSPs) were present in all mat samples at high, moderate, or low levels, whereas the ice nucleation protein (INP) was present only in the ice and bulbous mat samples at insignificant levels. Considering the near homogeneous temperature profile of Lake Joyce (0.08-0.29 °C), the distribution and abundance of these proteins across various mat samples predictively correlated with known functional attributes necessary for microbial communities to thrive in this ecosystem. The comparison of the MG-RAST and the R code methods showed dissimilar occurrences of the cold-adaptation protein sequences, though with insignificant ANOSIM (R = 0.357; p-value = 0.012), ADONIS (R(2) = 0.274; p-value = 0.03) and STAMP (p-values = 0.521-0.984) statistical analyses. Furthermore, filtering targeted sequences using the R code accounted for taxonomic groups by avoiding sequence redundancies, whereas the MG-RAST provided total counts resulting in a higher sequence output. The results from this study revealed for the first time the distribution of cold-adaptation proteins in six different types of microbial mats in Lake Joyce, while suggesting a simpler and more manageable user-defined method of R code, as compared to a web-based MG-RAST pipeline. PMID:26578243

  9. David Morrison on Lake Vostok

    NASA Video Gallery

    Dr. David Morrison discusses the implications of research possibilities at Lake Vostok, one of the largest subglacial lakes located over two miles beneath the ice in Antarctica. The lake has been c...

  10. Ciliate diversity, community structure, and novel taxa in lakes of the McMurdo Dry Valleys, Antarctica.

    PubMed

    Xu, Yuan; Vick-Majors, Trista; Morgan-Kiss, Rachael; Priscu, John C; Amaral-Zettler, Linda

    2014-10-01

    We report an in-depth survey of next-generation DNA sequencing of ciliate diversity and community structure in two permanently ice-covered McMurdo Dry Valley lakes during the austral summer and autumn (November 2007 and March 2008). We tested hypotheses on the relationship between species richness and environmental conditions including environmental extremes, nutrient status, and day length. On the basis of the unique environment that exists in these high-latitude lakes, we expected that novel taxa would be present. Alpha diversity analyses showed that extreme conditions-that is, high salinity, low oxygen, and extreme changes in day length-did not impact ciliate richness; however, ciliate richness was 30% higher in samples with higher dissolved organic matter. Beta diversity analyses revealed that ciliate communities clustered by dissolved oxygen, depth, and salinity, but not by season (i.e., day length). The permutational analysis of variance test indicated that depth, dissolved oxygen, and salinity had significant influences on the ciliate community for the abundance matrices of resampled data, while lake and season were not significant. This result suggests that the vertical trends in dissolved oxygen concentration and salinity may play a critical role in structuring ciliate communities. A PCR-based strategy capitalizing on divergent eukaryotic V9 hypervariable region ribosomal RNA gene targets unveiled two new genera in these lakes. A novel taxon belonging to an unknown class most closely related to Cryptocaryon irritans was also inferred from separate gene phylogenies. PMID:25411375

  11. Marketing ACE in Victoria.

    ERIC Educational Resources Information Center

    2001

    This publication presents options raised through various forums for marketing adult and community education (ACE) in Victoria, Australia, and suggested strategies. After an introduction (chapter 1), chapters 2 and 3 provide a broad view of the current situation for marketing ACE. Chapter 2 discusses general issues in the current position--ACE…

  12. The case study of drillbit and borehole frozen water of the subglacial Lake Vostok, East Antarctica for microbial content

    NASA Astrophysics Data System (ADS)

    Bulat, Sergey; Doronin, Maxim; Dominique, Marie; Lipenkov, Vladimir; Lukin, Valery; Karlov, Denis; Demchenko, Leonid; Khilchenko, Margarita

    The objective was to estimate microbial content and diversity in the subglacial Lake Vostok (buried beneath 4-km thick East Antarctic ice sheet) by studying the uppermost water layer which entered the borehole upon lake entry (February 5, 2012) and then shortly frozen within. The samples of so-called drillbit water frozen on a drill bit upon lake enter (RAE57) along with re-drilled so-called borehole-frozen water (RAE58) were provided for the study with the ultimate goal to discover the life in this extreme icy environment. The comprehensive analyses (constrained by Ancient DNA research criteria) of the first lake water samples - drillbit- (one sample) and borehole-frozen (3 different depths 5G-2N-3425, 3429 et 3450m), are nearly got finished. If the drillbit water sample was heavily polluted with drill fluid (at ratio 1:1), re-drilled borehole-frozen samples were proved to be rather clean but still strongly smelling kerosene and containing numerous micro-droplets of drill fluid making the ice non-transparent. The cell concentrations measured by flow cytofluorometry showed 167 cells per ml in the drillbit water sample while in borehole-frozen samples ranged from 5.5 (full-cylinder 3429m deep frozen water ice core) to 38 cells per ml (freeze-centre of 3450m deep moon-shape ice core). DNA analyses came up with total 44 bacterial phylotypes discovered by sequencing of different regions (v3-v5, v4-v8, v4-v6 et full-gene) of 16S rRNA genes. Amongst them all but two were considered to be contaminants (were present in our contaminant library, including drill fluid findings). The 1st remaining phylotype successfully passing all contamination criteria proved to be hitherto-unknown type of bacterium (group of clones, 3 allelic variants) showing less than 86% similarity with known taxa. Its phylogenetic assignment to bacterial divisions or lineages was also unsuccessful despite of the RDP has classified it belonging to OD1 uncultured Candidate Division. The 2nd phylotype was

  13. Factors controlling the geochemical composition of Limnopolar Lake sediments (Byers Peninsula, Livingston Island, South Shetland Island, Antarctica) during the last ca. 1600 years

    NASA Astrophysics Data System (ADS)

    Martínez Cortizas, A.; Rozas Muñiz, I.; Taboada, T.; Toro, M.; Granados, I.; Giralt, S.; Pla-Rabés, S.

    2014-07-01

    We sampled a short (57 cm) sediment core in Limnopolar Lake (Byers Peninsula, Livingston Island, South Shetland Islands), which spans the last ca. 1600 years. The core was sectioned at high resolution and analyzed for elemental and mineralogical composition, and scanning electron microscope and energy dispersive X-ray spectrometer (SEM-EDS) analysis of glass mineral particles in selected samples. The chemical record was characterized by a contrasted pattern of layers with high Ca, Ti, Zr, and Sr concentrations and layers with higher concentrations of K and Rb. The former were also enriched in plagioclase and, occasionally, in zeolites, while the latter were relatively enriched in 2 : 1 phyllosilicates and quartz. This was interpreted as reflecting the abundance of volcaniclastic material (Ca rich) versus Jurassic-Lower Cretaceous marine sediments (K rich) - the dominant geological material in the lake catchment. SEM-EDS analysis revealed the presence of abundant volcanic shards in the Ca-rich layers, pointing to tephras most probably related to the activity of Deception Island volcano (located 30 km to the SE). The ages of four main peaks of volcanic-rich material (AD ca. 1840-1860 for L1, AD ca. 1570-1650 for L2, AD ca. 1450-1470 for L3, and AD ca. 1300 for L4) matched reasonably well the age of tephra layers (AP1 to AP3) previously identified in lakes of Byers Peninsula. Some of the analyzed metals (Fe, Mn, Cu, and Cr) showed enrichments in the most recent tephra layer (L1), suggesting relative changes in the composition of the tephras as found in previous investigations. No evidence of significant human impact on the cycles of most trace metals (Cu, Zn, Pb) was found, probably due to the remote location of Livingston Island and the modest research infrastructures; local contamination was found by other researchers in soils, waters and marine sediments on areas with large, permanent research stations. Chromium is the only metal showing a steady enrichment in the

  14. Grounding Zone Process: Ice Mechanics and Margin Lakes, Kamb Ice Stream and Whillans Ice Stream, West Antarctica

    NASA Astrophysics Data System (ADS)

    Fried, Mason

    The lateral "corners" where Kamb and Whillans Ice Streams (KIS and WIS) discharge into the Ross Ice Shelf share common geometries and ice mechanical settings. At both corners of the now-stagnant KIS outlet, shear margins of apparently different ages confine regions with a relatively flat, smooth surface expression. These features are called the "Duckfoot" on the northern, right-lateral side and the "Goosefoot" on the other. It has been suggested, on evidence found in ice internal layers, that the flat ice terrains on KIS were afloat in the recent past, at a time when the ice stream grounding line was upstream of its present location. The overdeepening in the bed just upstream of the KIS grounding line supports this view of the past geometry. The right-lateral margin at the outlet of the currently active WIS, the location of Subglacial Lake Englehardt (SLE), appears to have many similarities with the right lateral margin of KIS, though with a less developed looking inboard margin. This paper presents a mechanical analysis using surface and bed topography and velocity datasets comparing the Duckfoot flat ice terrain with the terrain around Subglacial Lake Englehardt. At both locations mechanical thinning along shear margins and lows in the bed topography redirects basal water routing towards the features. Here, I consider the history of these features and their role in ice stream variability by comparison of the relict and modern features and via numerical modeling of ice shelf grounding and ungrounding in response to variations in ice flow. We propose two scenarios for the development of flat ice terrains/subglacial lakes at the outlets of ice streams. In the first, development of a lake in the hydraulic potential low along a shear margin forces a margin jump as shearing develops along the inboard shore of the margin lake. This thesis presents evidence for an inboard (relative to the main outboard shear margin) zone of shear along the inboard shoreline of SLE

  15. ACE blood test

    MedlinePlus

    Serum angiotensin-converting enzyme; SACE ... Chernecky CC, Berger BJ. Angiotensin-converting enzyme (ACE) - blood. In: Chernecky CC, Berger BJ, eds. Laboratory Tests and Diagnostic Procedures . 6th ed. Philadelphia, PA: Elsevier Saunders; 2013:138-139.

  16. SPME-GCMS study of the natural attenuation of aviation diesel spilled on the perennial ice cover of Lake Fryxell, Antarctica.

    PubMed

    Jaraula, Caroline M B; Kenig, Fabien; Doran, Peter T; Priscu, John C; Welch, Kathleen A

    2008-12-15

    In January 2003, a helicopter crashed on the 5 m thick perennial ice cover of Lake Fryxell (McMurdo Dry Valleys, East Antarctica), spilling approximately 730 l of aviation diesel fuel (JP5-AN8 mixture). The molecular composition of the initial fuel was analyzed by solid phase microextraction (SPME) gas chromatography-mass spectrometry (GC-MS), then compared to the composition of the contaminated ice, water, and sediments collected a year after the spill. Evaporation is the major agent of diesel weathering in meltpool waters and in the ice. This process is facilitated by the light non-aqueous phase liquid properties of the aviation diesel and by the net upward movement of the ice as a result of ablation. In contrast, in sediment-bearing ice, biodegradation by both alkane- and aromatic-degraders was the prominent attenuation mechanism. The composition of the diesel contaminant in the ice was also affected by the differential solubility of its constituents, some ice containing water-washed diesel and some ice containing exclusively relatively soluble low molecular weight aromatic hydrocarbons such as alkylbenzene and naphthalene homologues. The extent of evaporation, water washing and biodegradation between sites and at different depths in the ice are evaluated on the basis of molecular ratios and the results of JP5-AN8 diesel evaporation experiment at 4 degrees C. Immediate spread of the aviation diesel was enhanced where the presence of aeolian sediments induced formations of meltpools. However, in absence of melt pools, slow spreading of the diesel is possible through the porous ice and the ice cover aquifer. PMID:18804261

  17. Subglacial sediment provenance and transport in West Antarctica from micropaleontologic analysis of Subglacial Lake Whillans and the upstream sectors of the Whillans and Kamb ice streams

    NASA Astrophysics Data System (ADS)

    Scherer, Reed; Coenen, Jason; Warny, Sophie

    2014-05-01

    The WISSARD (Whillans Ice Stream Subglacial Access Research Drilling) project recovered sediment cores from Subglacial Lake Whillans (SLW) in West Antarctica. We report preliminary micropaleontological analyses of SLW sediments, augmented by analysis of sediments previously recovered from beneath the upstream camps of the Whillans Ice Stream (WIS) and Kamb Ice Stream (KIS). Microfossils in these sediments (notably diatoms, sponge spicules, and organic-walled palynomorphs), include information regarding sediment transport, subglacial physical processes and ice sheet history. Absolute abundance (particles per gram dry sediment) of identifiable diatoms and diatom fragments in different size classes were calculated to compare and contrast each environment. Sponge spicules are being analyzed for taphonomic effects from subglacial transport and shearing. Palynomorphs are analyzed for abundance, diversity, and source rock ages. In SLW the upper 30 cm is softer and more water-rich than the underlying sediments. However, no statistically significant variation in microfossil and fragment abundance or taphonomy is noted in these diamictons, which is in agreement with the stratigraphic homogeneity evident from geochemical and geological analyses performed to date. SLW contains 1.52x106 to 1.13x107 diatom fragments per gram, compared with 6.43x106 to 4.63x108 at upstream WIS and 6.13 107 to 1.58x108 at KIS. Whole diatoms are orders of magnitude lower in concentration. Low abundance and poor preservation of diatoms and spicules at SLW suggests relatively long distance transport from their marine sediment source, with evidence of high shear strain, following the subglacial shearing index of Scherer et al. (2004). Upper Miocene diatoms dominate all samples analyzed, though older and younger diatoms are noted as well. The WIS samples exhibit the highest diversity of diatoms, including Paleogene freshwater diatoms. KIS sediments have the highest abundance of whole diatoms, but they

  18. ACES--Today and Tomorrow.

    ERIC Educational Resources Information Center

    Hackney, Harold

    1991-01-01

    Presents text of Presidential Address delivered March 24, 1991, at the Association for Counselor Education and Supervision (ACES) luncheon, part of the American Association for Counseling and Development Convention held in Reno, Nevada. Comments on past, present, and future of ACES, particularly on future challenges and role of ACES. (ABL)

  19. An ACE diagnosis.

    PubMed

    Nasher, Omar; Gupta, Anindya

    2013-01-01

    Gaucher's disease is not commonly considered in the differential diagnosis of adult patients with hepatosplenomegaly and increased serum ACE. A 19-year-old girl presented with recurrent epigastric and left hypochondrial pain over a period of 9 years, associated with episodes of nausea and diarrhoea. She was extensively investigated and found to have splenomegaly and raised serum ACE. A screen for haematological disorders was negative. She reported an insect bite during an overseas holiday preceding her symptoms. She was therefore also screened for infectious causes of hepatosplenomegaly but without success. Later on in life, she reported joint pain and discomfort. Sarcoidosis was thought to be the putative cause on more than one occasion. However, the presence of splenomegaly and her relatively young age, led the rheumatologist to the correct diagnosis. PMID:23417380

  20. An ACE diagnosis

    PubMed Central

    Nasher, Omar; Gupta, Anindya

    2013-01-01

    Gaucher's disease is not commonly considered in the differential diagnosis of adult patients with hepatosplenomegaly and increased serum ACE. A 19-year-old girl presented with recurrent epigastric and left hypochondrial pain over a period of 9 years, associated with episodes of nausea and diarrhoea. She was extensively investigated and found to have splenomegaly and raised serum ACE. A screen for haematological disorders was negative. She reported an insect bite during an overseas holiday preceding her symptoms. She was therefore also screened for infectious causes of hepatosplenomegaly but without success. Later on in life, she reported joint pain and discomfort. Sarcoidosis was thought to be the putative cause on more than one occasion. However, the presence of splenomegaly and her relatively young age, led the rheumatologist to the correct diagnosis. PMID:23417380

  1. Lake

    ERIC Educational Resources Information Center

    Wien, Carol Anne

    2008-01-01

    The lake is blue black and deep. It is a glaciated finger lake, clawed out of rock when ice retracted across Nova Scotia in a northerly direction during the last ice age. The lake is narrow, a little over a mile long, and deep, 90 to 190 feet in places according to local lore, off the charts in others. The author loves to swim there, with a sense…

  2. The permanent ice cover of Lake Bonney, Antarctica: The influence of thickness and sediment distribution on photosynthetically available radiation and chlorophyll-a distribution in the underlying water column

    NASA Astrophysics Data System (ADS)

    Obryk, M. K.; Doran, P. T.; Priscu, J. C.

    2014-09-01

    The thick permanent ice cover on the lakes of the McMurdo Dry Valleys, Antarctica, inhibits spatial lake sampling due to logistical constraints of penetrating the ice cover. To date most sampling of these lakes has been made at only a few sites with the assumption that there is a spatial homogeneity of the physical and biogeochemical properties of the ice cover and the water column at any given depth. To test this underlying assumption, an autonomous underwater vehicle (AUV) was deployed in Lake Bonney, Taylor Valley. Measurements were obtained over the course of 2 years in a 100 × 100 m horizontal sampling grid (at a 0.2 m vertical resolution). Additionally, the AUV measured the ice thickness (in water equivalent) and collected images looking up through the ice, which were used to quantify sediment distribution on the surface and within the ice. Satellite imagery was used to map sediment distribution on the surface of the ice. We present results of the spatial investigation of the sediment distribution on the ice cover and its effects on biological processes, with particular emphasis on photosynthetically active radiation (PAR). The surface sediment is a secondary controller of the ice cover thickness, which in turn controls the depth-integrated PAR in the water column. Our data revealed that depth-integrated PAR was negatively correlated with depth-integrated chlorophyll-a (r = 0.88, p < 0.001, n = 83), which appears to be related to short-term photoadaptation of phytoplanktonic communities to spatial and temporal variation in PAR within the water column.

  3. Draft Genome Sequence of Janthinobacterium sp. Ant5-2-1, Isolated from Proglacial Lake Podprudnoye in the Schirmacher Oasis of East Antarctica.

    PubMed

    Koo, Hyunmin; Strope, Bailey M; Kim, Eddy H; Shabani, Adel M; Kumar, Ranjit; Crowley, Michael R; Andersen, Dale T; Bej, Asim K

    2016-01-01

    Janthinobacterium sp. Ant5-2-1, isolated from the Schirmacher Oasis of East Antarctica, produces a purple-violet pigment, manifests diverse energy metabolism abilities, and tolerates cold, ultraviolet radiation, and other environmental stressors. We report here the 6.19-Mb draft genome of strain Ant5-2-1, which will help understand its survival mechanisms in extreme Antarctic ecosystems. PMID:26798103

  4. Draft Genome Sequence of Janthinobacterium sp. Ant5-2-1, Isolated from Proglacial Lake Podprudnoye in the Schirmacher Oasis of East Antarctica

    PubMed Central

    Strope, Bailey M.; Kim, Eddy H.; Shabani, Adel M.; Kumar, Ranjit; Crowley, Michael R.; Andersen, Dale T.

    2016-01-01

    Janthinobacterium sp. Ant5-2-1, isolated from the Schirmacher Oasis of East Antarctica, produces a purple-violet pigment, manifests diverse energy metabolism abilities, and tolerates cold, ultraviolet radiation, and other environmental stressors. We report here the 6.19-Mb draft genome of strain Ant5-2-1, which will help understand its survival mechanisms in extreme Antarctic ecosystems. PMID:26798103

  5. ACEE composite structures technology

    NASA Technical Reports Server (NTRS)

    Klotzsche, M. (Compiler)

    1984-01-01

    The NASA Aircraft Energy Efficiency (ACEE) Composite Primary Aircraft Structures Program has made significant progress in the development of technology for advanced composites in commercial aircraft. Commercial airframe manufacturers have demonstrated technology readiness and cost effectiveness of advanced composites for secondary and medium primary components and have initiated a concerted program to develop the data base required for efficient application to safety-of-flight wing and fuselage structures. Oral presentations were compiled into five papers. Topics addressed include: damage tolerance and failsafe testing of composite vertical stabilizer; optimization of composite multi-row bolted joints; large wing joint demonstation components; and joints and cutouts in fuselage structure.

  6. Provenance and depositional environment of epi-shelf lake sediment from Schirmacher Oasis, East Antarctica, vis-à-vis scanning electron microscopy of quartz grain, size distribution and chemical parameters

    NASA Astrophysics Data System (ADS)

    Shrivastava, Prakash K.; Asthana, Rajesh; Roy, Sandip K.; Swain, Ashit K.; Dharwadkar, Amit

    2012-07-01

    The scientific study of quartz grains is a powerful tool in deciphering the depositional environment and mode of transportation of sediments, and ultimately the origin and classification of sediments. Surface microfeatures, angularity, chemical features, and grain-size analysis of quartz grains, collectively reveal the sedimentary and physicochemical processes that acted on the grains during different stages of their geological history. Here, we apply scanning electron microscopic (SEM) analysis to evaluating the sedimentary provenance, modes of transport, weathering characteristics, alteration, and sedimentary environment of selected detrital quartz grains from the peripheral part of two epi-shelf lakes (ESL-1 and ESL-2) of the Schirmacher Oasis of East Antarctica. Our study reveals that different styles of physical weathering, erosive signatures, and chemical precipitation variably affected these quartz grains before final deposition as lake sediments. Statistical analysis (central tendencies, sorting, skewness, and kurtosis) indicates that these quartz-bearing sediments are poorly sorted glaciofluvial sediments. Saltation and suspension seem to have been the two dominant modes of transportation, and chemical analysis of these sediments indicates a gneissic provenance.

  7. National Survey of ACE Programs.

    ERIC Educational Resources Information Center

    Constantino, Ernesto A.

    In 1987-88, a national survey was conducted to determine the adult/continuing education (ACE) policies and practices of large, urban community colleges. Questionnaires were mailed to ACE deans at 74 colleges, requesting information about program characteristics, funding sources, personnel, curriculum review, and marketing and publicity. Study…

  8. Subglacial Lake Vostok (Antarctica) accretion ice contains a diverse set of sequences from aquatic, marine and sediment-inhabiting bacteria and eukarya.

    PubMed

    Shtarkman, Yury M; Koçer, Zeynep A; Edgar, Robyn; Veerapaneni, Ram S; D'Elia, Tom; Morris, Paul F; Rogers, Scott O

    2013-01-01

    Lake Vostok, the 7(th) largest (by volume) and 4(th) deepest lake on Earth, is covered by more than 3,700 m of ice, making it the largest subglacial lake known. The combination of cold, heat (from possible hydrothermal activity), pressure (from the overriding glacier), limited nutrients and complete darkness presents extreme challenges to life. Here, we report metagenomic/metatranscriptomic sequence analyses from four accretion ice sections from the Vostok 5G ice core. Two sections accreted in the vicinity of an embayment on the southwestern end of the lake, and the other two represented part of the southern main basin. We obtained 3,507 unique gene sequences from concentrates of 500 ml of 0.22 µm-filtered accretion ice meltwater. Taxonomic classifications (to genus and/or species) were possible for 1,623 of the sequences. Species determinations in combination with mRNA gene sequence results allowed deduction of the metabolic pathways represented in the accretion ice and, by extension, in the lake. Approximately 94% of the sequences were from Bacteria and 6% were from Eukarya. Only two sequences were from Archaea. In general, the taxa were similar to organisms previously described from lakes, brackish water, marine environments, soil, glaciers, ice, lake sediments, deep-sea sediments, deep-sea thermal vents, animals and plants. Sequences from aerobic, anaerobic, psychrophilic, thermophilic, halophilic, alkaliphilic, acidophilic, desiccation-resistant, autotrophic and heterotrophic organisms were present, including a number from multicellular eukaryotes. PMID:23843994

  9. Subglacial Lake Vostok (Antarctica) Accretion Ice Contains a Diverse Set of Sequences from Aquatic, Marine and Sediment-Inhabiting Bacteria and Eukarya

    PubMed Central

    Edgar, Robyn; Veerapaneni, Ram S.; D’Elia, Tom; Morris, Paul F.; Rogers, Scott O.

    2013-01-01

    Lake Vostok, the 7th largest (by volume) and 4th deepest lake on Earth, is covered by more than 3,700 m of ice, making it the largest subglacial lake known. The combination of cold, heat (from possible hydrothermal activity), pressure (from the overriding glacier), limited nutrients and complete darkness presents extreme challenges to life. Here, we report metagenomic/metatranscriptomic sequence analyses from four accretion ice sections from the Vostok 5G ice core. Two sections accreted in the vicinity of an embayment on the southwestern end of the lake, and the other two represented part of the southern main basin. We obtained 3,507 unique gene sequences from concentrates of 500 ml of 0.22 µm-filtered accretion ice meltwater. Taxonomic classifications (to genus and/or species) were possible for 1,623 of the sequences. Species determinations in combination with mRNA gene sequence results allowed deduction of the metabolic pathways represented in the accretion ice and, by extension, in the lake. Approximately 94% of the sequences were from Bacteria and 6% were from Eukarya. Only two sequences were from Archaea. In general, the taxa were similar to organisms previously described from lakes, brackish water, marine environments, soil, glaciers, ice, lake sediments, deep-sea sediments, deep-sea thermal vents, animals and plants. Sequences from aerobic, anaerobic, psychrophilic, thermophilic, halophilic, alkaliphilic, acidophilic, desiccation-resistant, autotrophic and heterotrophic organisms were present, including a number from multicellular eukaryotes. PMID:23843994

  10. Biological activity at the limits of life: Microbial cycling of C, S and N in cold, permanently stratified, hypersaline Lake Vanda, Antarctica.

    NASA Astrophysics Data System (ADS)

    Joye, S. B.; Schutte, C.; Samarkin, V.; Casciotti, K. L.; Madigan, M.; Saxton, M.

    2014-12-01

    The lakes of the McMurdo Dry Valleys (MCM) are the only perennially ice covered lakes on Earth and are the primary refuge for life in this hyper-arid polar desert. As a result of the ice cover and an uncoupled day/night cycle, the physical and biogeochemical processes in the lakes are highly unusual, with biogeochemical gradients and concentrations of specific compounds often exceeding those found in other aquatic ecosystems on Earth. These lakes are ideal systems for the study of redox-sensitive biogeochemical processes, model systems for understanding the effects of global climate change on polar ecosystems, end-member systems that provide insight into biogeochemical and limnological dynamics in meromictic lakes, analogues for life on other planets, and perfect systems to study microbial life at its thermodynamic limits. Lake Vanda, in the Wright valley, is relatively deep (73 m), hypersaline and has anoxic bottom water. High concentrations of chacotrophic salts results in low water activities that exert further challenges on microbial life. We collected details geochemical profiles of nutrients, major ions, dissolved gases, and redox metabolites and measured rates of microbially-mediated processes that cycle carbon, nitrogen and sulfur in the lakes waters and sediments. Despite the harsh and extreme nature of Lake Vanda and the thermodynamic barriers to microbially-mediated geochemical reactions, microorganisms are not only present in the lake but they mediate a diverse suite of geochemical processes. Statistical correlations between geochemical parameters, microbial activity and microbial community composition shed light on the factors that regulate and limit microbial activity in this unique extreme environment.

  11. Frequency and Size of Strombolian Eruptions from the Phonolitic Lava Lake at Erebus Volcano, Antarctica: Insights from Infrasound and Seismic Observations on Bubble Formation and Ascent

    NASA Astrophysics Data System (ADS)

    Rotman, H. M. M.; Kyle, P. R.; Fee, D.; Curtis, A.

    2015-12-01

    Erebus, an active intraplate volcano on Ross Island, commonly produces bubble burst Strombolian explosions from a long-lived, convecting phonolitic lava lake. Persistent lava lakes are rare, and provide direct insights into their underlying magmatic system. Erebus phonolite is H2O-poor and contains ~30% anorthoclase megacrysts. At shallow depths lab measurements suggest the magma has viscosities of ~107 Pa s. This has implications for magma and bubble ascent rates through the conduit and into the lava lake. The bulk composition and matrix glass of Erebus ejecta has remained uniform for many thousands of years, but eruptive activity varies on decadal and shorter time scales. Over the last 15 years, increased activity took place in 2005-2007, and more recently in the 2013 austral summer. In the 2014 austral summer, new infrasound sensors were installed ~700 m from the summit crater hosting the lava lake. These sensors, supplemented by the Erebus network seismic stations, recorded >1000 eruptions between 1 January and 7 April 2015, with an average infrasound daily uptime of 9.6 hours. Over the same time period, the CTBT infrasound station IS55, ~25 km from Erebus, detected ~115 of the >1000 locally observed eruptions with amplitude decreases of >100x. An additional ~200 eruptions were recorded during local infrasound downtime. This represents an unusually high level of activity from the Erebus lava lake, and while instrument noise influences the minimum observable amplitude each day, the eruption infrasound amplitudes may vary by ~3 orders of magnitude over the scale of minutes to hours. We use this heightened period of variable activity and associated seismic and acoustic waveforms to examine mechanisms for bubble formation and ascent, such as rise speed dependence and collapsing foam; repose times for the larger eruptions; and possible eruption connections to lava lake cyclicity.

  12. Searching for traces of life in subglacial Lake Vostok (Antarctica) in terms of forward contamination: the lessons for exploration of icy environments on Mars

    NASA Astrophysics Data System (ADS)

    Bulat, S. A.; Alekhina, I. A.; Lipenkov, V. Ya.; Petit, J.-R.

    Bacterial 16S ribosomal gene analysis guarded by criteria for trace DNA analysis and Ancient DNA research clearly testifies for the very low biomass in accretion ice from giant subglacial Lake Vostok buried beneath 4-km thick East Antarctic ice sheet. It seems that the accretion ice is essentially germ-free indicating that the water body should also be hosting a highly sparse life, if any, unless the lake water lost its biological contents during accretion process. Due to this the search for life in Lake Vostok is constrained by a high chance of contamination similar to forward-contamination upon searching for life on Mars and other icy planets. Of 16 bacterial phylotypes initially recovered from the accretion ice the only one was kept with confident relevance to the lake environment while 15 others were presumed to be contaminants on the basis of indexing contaminant criteria developed for Lake Vostok and similar icy environments. The current way to avoid contamination appears to use stringent ice chemistry-based decontamination procedures and comprehensive biological controls including establishment of contemporary contaminant database as a prerequisite to identify and categorize sources of contaminants. More challenge would be to advance cleanliness and sterilization approaches and procedures in order to achieve and measure the level of cleanliness appropriate for tools exploring environments like Lake Vostok. As a guide for searching for life in (sub)glacial environments on Earth or Mars and Jovian's Europa our recommendations can be summarized as follows: (i) apply stringent ice decontamination procedures to meet chemistry and trace DNA analysis standards, (ii) document biological contents of various environments including humans in contact with ice samples (development of contaminant database), (iii) ensure in using relevant methods to cover both known and expected biodiversity and (iv) verify microbial findings through their possible metabolic profiles

  13. Characterizing Microbial Mat Morphology with Structure from Motion Techniques in Ice-Covered Lake Joyce, McMurdo Dry Valleys, Antarctica

    NASA Astrophysics Data System (ADS)

    Mackey, T. J.; Leidman, S. Z.; Allen, B.; Hawes, I.; Lawrence, J.; Jungblut, A. D.; Krusor, M.; Coleman, L.; Sumner, D. Y.

    2015-12-01

    Structure from Motion (SFM) techniques can provide quantitative morphological documentation of otherwise inaccessible benthic ecosystems such as microbial mats in Lake Joyce, a perennially ice-covered lake of the Antarctic McMurdo Dry Valleys (MDV). Microbial mats are a key ecosystem of MDV lakes, and diverse mat morphologies like pinnacles emerge from interactions among microbial behavior, mineralization, and environmental conditions. Environmental gradients can be isolated to test mat growth models, but assessment of mat morphology along these gradients is complicated by their inaccessibility: the Lake Joyce ice cover is 4-5 m thick, water depths containing diverse pinnacle morphologies are 9-14 m, and relevant mat features are cm-scale. In order to map mat pinnacle morphology in different sedimentary settings, we deployed drop cameras (SeaViewer and GoPro) through 29 GPS referenced drill holes clustered into six stations along a transect spanning 880 m. Once under the ice cover, a boom containing a second GoPro camera was unfurled and rotated to collect oblique images of the benthic mats within dm of the mat-water interface. This setup allowed imaging from all sides over a ~1.5 m diameter area of the lake bottom. Underwater lens parameters were determined for each camera in Agisoft Lens; images were reconstructed and oriented in space with the SFM software Agisoft Photoscan, using the drop camera axis of rotation as up. The reconstructions were compared to downward facing images to assess accuracy, and similar images of an object with known geometry provided a test for expected error in reconstructions. Downward facing images identify decreasing pinnacle abundance in higher sedimentation settings, and quantitative measurements of 3D reconstructions in KeckCAVES LidarViewer supplement these mat morphological facies with measurements of pinnacle height and orientation. Reconstructions also help isolate confounding variables for mat facies trends with measurements

  14. Comparison of the timings between abrupt climate changes in Greenland, Antarctica, China and Japan based on robust correlation using Lake Suigetsu as a template.

    NASA Astrophysics Data System (ADS)

    Nakagawa, T.

    2014-12-01

    High-resolution pollen-derived climate records from Lake Suigetsu varved sediment core were compared with climate archives from other regions and revealed a particular spatio-temporal structure of the monsoon climate change during so-called D-O events. Leads and lags of the climate change between different regions hold the key to understand the climate system. However, robust assessment of the relative timing of the climate change is often very challenging because correlation of the climatic archives from different regions often has inevitable uncertainties. Greenland and Cariaco basin, for example, provide two of the most frequently sited palaeoclimatic proxy data representative of the high- and low-latitudinal Atlantic regions. However, robust correlation of the records from those regions is difficult because of the uncertainties in layer countings, lack of the radiocarbon age control from ice cores, marine reservoir age of the Cariaco sediments, and the absence of the tephra layers shared by both cites. Similarly, Speleothem and ice core records are not robustly correlated to each other, either for the dead carbon fraction in the speleothems and lack of reliable correlation markers. The generally accepted hypothesis of synchronous climate change between China and the Greenland is, therefore, essentially hypothetical. Lake Suigetsu provides solution to this problem. The lake Suigetsu chronology is supposed to be coherent to the speleothems' U-Th age scale. Suigetsu's semi-continuous radiocarbon dataset, which constitutes major component of the IntCal13 radiocarbon calibration model, also provides opportunity to correlate lake Suigetsu and the Greenland and Antarctic ice cores using cosmogenic isotopes as the correlation key. Results of the correlation and timing comparison, which cast new lights to the mechanism of the monsoon change, will be presented.

  15. Field Investigation of Surface-Lake Processes on Ice Shelves: Results of the 2015/16 Field Campaign on McMurdo Ice Shelf, Antarctica

    NASA Astrophysics Data System (ADS)

    MacAyeal, Doug; Banwell, Alison; Willis, Ian; Macdonald, Grant

    2016-04-01

    Ice-shelf instability and breakup of the style exhibited by Larsen B Ice Shelf in 2002 remains the most difficult glaciological process of consequence to observe in detail. It is, however, vital to do so because ice-shelf breakup has the potential to influence the buttressing controls on inland ice discharge, and thus to affect sea level. Several mechanisms enabling Larsen B style breakup have been proposed, including the ability of surface lakes to introduce ice-shelf fractures when they fill and drain, thereby changing the surface loads the ice-shelf must adjust to. Our model suggest that these fractures resulted in a chain-reaction style drainage of >2750 surface lakes on the Larsen B in the days prior to its demise. To validate this and other models, we began a field project on the McMurdo Ice Shelf (MIS) during the 2015/16 austral summer. Advantages of the MIS study site are: there is considerable surface melting during 3-6 weeks of the summer season, the ice is sufficiently thin (< 30 m in places) to allow observable viscoelastic responses to relatively small loads, and it is close to a center of logistical support (McMurdo Station). Here we show initial results from the field campaign, including GPS and water-depth observations of a lake that has filled and drained over multiple week timescales in previous austral summers. We also report on the analysis of high-resolution WorldView satellite imagery from several summers that reveals the complexity of surface meltwater movement in channels and subsurface void spaces. Initial reconnaissance of the largest surface-lake features reveal that they have a central circular depression surrounded by an uplifted ring, which supports one of the central tenets of our ice-shelf flexure theory. A second field season is anticipated for the 2016/17 austral summer.

  16. Don Juan Pond, Antarctica: Near-surface CaCl2-brine feeding Earth's most saline lake and implications for Mars

    PubMed Central

    Dickson, James L.; Head, James W.; Levy, Joseph S.; Marchant, David R.

    2013-01-01

    The discovery on Mars of recurring slope lineae (RSL), thought to represent seasonal brines, has sparked interest in analogous environments on Earth. We report on new studies of Don Juan Pond (DJP), which exists at the upper limit of ephemeral water in the McMurdo Dry Valleys (MDV) of Antarctica, and is adjacent to several steep-sloped water tracks, the closest analog for RSL. The source of DJP has been interpreted to be deep groundwater. We present time-lapse data and meteorological measurements that confirm deliquescence within the DJP watershed and show that this, together with small amounts of meltwater, are capable of generating brines that control summertime water levels. Groundwater input was not observed. In addition to providing an analog for RSL formation, CaCl2 brines and chloride deposits in basins may provide clues to the origin of ancient chloride deposits on Mars dating from the transition period from “warm/wet” to “cold/dry” climates. PMID:23378901

  17. Don Juan Pond, Antarctica: near-surface CaCl(2)-brine feeding Earth's most saline lake and implications for Mars.

    PubMed

    Dickson, James L; Head, James W; Levy, Joseph S; Marchant, David R

    2013-01-01

    The discovery on Mars of recurring slope lineae (RSL), thought to represent seasonal brines, has sparked interest in analogous environments on Earth. We report on new studies of Don Juan Pond (DJP), which exists at the upper limit of ephemeral water in the McMurdo Dry Valleys (MDV) of Antarctica, and is adjacent to several steep-sloped water tracks, the closest analog for RSL. The source of DJP has been interpreted to be deep groundwater. We present time-lapse data and meteorological measurements that confirm deliquescence within the DJP watershed and show that this, together with small amounts of meltwater, are capable of generating brines that control summertime water levels. Groundwater input was not observed. In addition to providing an analog for RSL formation, CaCl(2) brines and chloride deposits in basins may provide clues to the origin of ancient chloride deposits on Mars dating from the transition period from "warm/wet" to "cold/dry" climates. PMID:23378901

  18. Antibacterial, antifungal and antiprotozoal activities of fungal communities present in different substrates from Antarctica

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Antarctica is a pristine and extreme environment that represents a unique opportunity for taxonomic, ecological and biotechnological studies of the microorganisms. In the present work, the fungal communities of rhizosphere soil of Deschampsia antarctica, soil, ornithogenic soil, marine and lake sedi...

  19. ACE to Ulysses Coherences

    NASA Astrophysics Data System (ADS)

    Thomson, D. J.; Maclennan, C. G.; Lanzerotti, L. J.

    2006-12-01

    The EPAM charged particle instrument on ACE is the backup for the HISCALE instrument on Ulysses making the two ideally suited for spatial coherence studies over large heliosphere distances. Fluxes of low-energy ( ~50 - 200 keV) electrons are detected in eight spatial sectors on both spacecraft. A spherical harmonic description of the particle flux as a function of time using only the l=0 and l=1 degree coefficients describes most of the observed flux. Here we concentrate on the three l=1 coefficients for the 60--100 kev electrons.Between the two spacecraft these result in nine coherence estimates that are all typically moderately coherent, but the fact that the different coefficients at each spacecraft are also coherent with each other makes interpretation difficult. To avoid this difficulty we estimated the canonical coherences between the two groups of three series. This, in effect, chooses an optimum coordinate system at each spacecraft and for each frequency and estimates the coherence in this frame. Using one--minute data, we find that the canonical coherences are generally larger at high frequencies (3 mHz and above) than they are at low frequencies. This appears to be generally true and does not depend particularly on time, range, etc. However, if the data segment is chosen too long, say > 30 days with 1--minute sampling, the coherence at high frequencies drops. This may be because the spatial and temporal features of the mode are confounded, or possibly because the solar modes p--modes are known to change frequency with solar activity, so do not appear coherent on long blocks.The coherences are not smooth functions of frequency, but have a bimodal distribution particularly in the 100 μHz to 5 mHz range. Classifying the data at frequencies where the canonical coherences are high in terms of apparent polarization and orientation, we note two major families of modes that appear to be organized by the Parker spiral. The magnetic field data on the two

  20. Stable Isotope Systematics of Cryogenic Evaporite Deposits from Lewis Cliff Ice Tongue, Antarctica: A Mars Analog

    NASA Astrophysics Data System (ADS)

    Socki, R. A.; Harvey, R. P.; Bish, D. L.; Tonui, E.; Bao, H.

    2008-03-01

    We report stable isotope results of evaporite mounds and associated moraine materials from Lewis Cliff, Antarctica. Data suggest evaporite mineral formation likely occurred sub-glacially, influenced by secondary glacial ice and/or moraine lake water.

  1. Characterization of the abundant ≤0.2 μm cell-like particles inhabiting Lake Vida brine, McMurdo Dry Valleys, Antarctica

    NASA Astrophysics Data System (ADS)

    Kuhn, E.; Ichimura, A.; Peng, V.; Fritsen, C. H.; Murray, A. E.

    2011-12-01

    Most lakes in the McMurdo Dry Valleys are perennially covered with 3 to 6 m of ice, but Lake Vida is frozen from the surface through the lake bed, with ice permeated by brine channels. Brine collected from within the ice of Lake Vida is six times saltier than seawater, anoxic, with temperature of -13.4 C, pH of 6.2, high concentrations of ferrous iron (>300 μM), NH4+ (3.6 mM), and N2O (>58 μM), making it a unique environment. The first analysis of Vida brine microbial community (sampled in 2005) detected a cell rich environment (107 cells/mL), with cells falling into two size classes: ≥0.5 μm (105 cells/mL) and ~0.2 μm (107 cells/mL). Microorganisms in the domain Bacteria were detected, but Eukarya and Archaea were not. The clone library from 2005 identified Bacteria related to the phyla Proteobacteria (γ, δ, and ɛ), Lentisphaera, Firmicutes, Spirochaeta, Bacterioidetes, Actinobacteria, Verrucomicrobia, and candidate Division TM7. Brine samples were collected again in the austral summer of 2010 in which one of the focus areas is interrogating the ~0.2 μm cell size class. Molecular, imaging, and elemental analyses were employed to characterize the population of nano-sized particles (NP) that pass through 0.2 μm filters. The aim of testing was to determine whether or not these particles are cells with a morphology resulting from environmental stresses. These results are being compared to the same analyses applied in the whole brine microbial community. A 0.2 μm filtrate of brine incubated for 25 days at -13 C was collected on a 0.1 μm filter. Analysis of the 16S rRNA gene DGGE profile showed differences in the banding pattern and relative intensity when comparing the 0.2 μm filtrate to the whole brine community. A 16S rRNA clone library from the 0.2 μm filtrate indicated the presence of genera previously described in the 2005 whole brine community clone library like Pscychrobacter, Marinobacter, and members related to candidate Division TM7. Also, the

  2. Bringing Antarctica Home

    ERIC Educational Resources Information Center

    Constible, Juanita; Williams, Lauren; Faure, Jaime; Lee, Richard E., Jr.

    2012-01-01

    When one thinks of the amazing creatures of Antarctica, an insect probably does not come to mind. But this unlikely animal, and a scientific expedition to Antarctica, was the foundation for a learning event that created a community of learners spanning kindergarten through sixth grade and extended beyond the classroom. Miami University's Antarctic…

  3. Sounding rockets in Antarctica

    NASA Technical Reports Server (NTRS)

    Alford, G. C.; Cooper, G. W.; Peterson, N. E.

    1982-01-01

    Sounding rockets are versatile tools for scientists studying the atmospheric region which is located above balloon altitudes but below orbital satellite altitudes. Three NASA Nike-Tomahawk sounding rockets were launched from Siple Station in Antarctica in an upper atmosphere physics experiment in the austral summer of 1980-81. The 110 kg payloads were carried to 200 km apogee altitudes in a coordinated project with Arcas rocket payloads and instrumented balloons. This Siple Station Expedition demonstrated the feasibility of launching large, near 1,000 kg, rocket systems from research stations in Antarctica. The remoteness of research stations in Antarctica and the severe environment are major considerations in planning rocket launching expeditions.

  4. Volcanic earthquake swarms at Mt. Erebus, Antarctica

    NASA Astrophysics Data System (ADS)

    Kaminuma, Katsutada; Ueki, Sadato; Juergen, Kienle

    1985-04-01

    Mount Erebus is an active volcano in Antarctica located on Ross Island. A convecting lava lake occupies the summit crater of Mt. Erebus. Since December 1980 the seismic activity of Mt. Erebus has been continuously monitored using a radio-telemetered network of six seismic stations. The seismic activity observed by the Ross Island network during the 1982-1983 field season shows that: (1)Strombolian eruptions occur frequently at the Erebus summit lava lake at rates of 2-5 per day; (2)centrally located earthquakes map out a nearly vertical, narrow conduit system beneath the lava lake; (3)there are other source regions of seismicity on Ross Island, well removed from Mt. Erebus proper. An intense earthquake swarm recorded in October 1982 near Abbott Peak, 10 km northwest of the summit of Mt. Erebus, and volcanic tremor accompanying the swarm, may have been associated with new dike emplacement at depth.

  5. Advanced Collaborative Emissions Study (ACES)

    SciTech Connect

    Greenbaum, Daniel; Costantini, Maria; Van Erp, Annemoon; Shaikh, Rashid; Bailey, Brent; Tennant, Chris; Khalek, Imad; Mauderly, Joe; McDonald, Jacob; Zielinska, Barbara; Bemis, Jeffrey; Storey, John; Hallberg, Lance; Clark, Nigel

    2013-12-31

    The objective of the Advanced Collaborative Emissions Study (ACES) was to determine before widespread commercial deployment whether or not the new, energy-efficient, heavy duty diesel engines (2007 and 2010 EPA Emissions Standards Compliant) may generate anticipated toxic emissions that could adversely affect the environment and human health. ACES was planned to take place in three phases. In Phase 1, extensive emissions characterization of four production-intent prototype engine and control systems designed to meet 2007 standards for nitrogen oxides (NOx) and particulate matter (PM) was conducted at an existing emissions characterization facility: Southwest Research Institute (SwRI). One of the tested engines was selected (at random, after careful comparison of results) for health testing in Phase 3. In Phase 2, extensive emission characterization of three production-intent prototype engine and control systems meeting the 2010 standards (including more advanced NOx controls to meet the more stringent 2010 NOx standards) was conducted at the same test facility. In Phase 3, one engine/aftertreatment system selected from Phase 1 was further characterized during health effects studies (at an existing inhalation toxicology laboratory: Lovelace Respiratory Research Institute, [LRRI]) to form the basis of the ACES safety assessment. The Department of Energy (DOE) award provided funding for emissions characterization in Phases 1 and 2 as well as exposure characterization in Phase 3. The main health analyses in Phase 3 were funded separately and are not reported here.

  6. Mineral resources of Antarctica

    SciTech Connect

    Rowley, P.D.; Williams, P.L.; Pride, D.E.

    1983-01-01

    Metallic and nonmetallic mineral occurrences are abundant in Antarctica. The most significant known deposits are of iron, copper, and coal. In the Precambrian shield of East Antarctica, for example, iron is present as banded iron-formation and as magnetite in veins, pods, and schist. The largest deposits of iron are in the Prince Charles Mountains, where bodies of banded iron-formation at least as thick as 400 m extend, mostly under the ice for at least 120 km. Widely scattered morainal boulders and outcrops of iron-rich rock suggest that undiscovered iron deposits are also distributed over many other parts of East Antarctica. Gondwana reconstructions suggest that many more mineral deposits occur in Antarctica. However, ice covers nearly 98 percent of the continent, and few of the bedrock areas have even been prospected or geologically, geophysically, or geochemically mapped in detail.

  7. Antarctica: up for grabs

    SciTech Connect

    Shapley, D.

    1982-11-01

    Antarctica is viewed as a special area, requiring meticulous diplomacy to develop international agreements for exploiting its resources. Little exploration has been accomplished, but oil, gas, and marine krill resources are protected by a 14-nation treaty dating from 1961. The treaty fixed national claims on specific territories and launched scientific activities that reflect national interests. Studies of meteorology, climatology, oceanography, upper-atmospheric physics, and territorial biology have revealed Antarctica's resource potential for krill, minerals, and even ice. 4 figures. (DCK)

  8. ACE VET Linkages: Provider, Student and Industry Views.

    ERIC Educational Resources Information Center

    Saunders, John

    In recent years, Australia's system of adult and community education (ACE) has broadened to include vocational learning as well as the hobby, enrichment, and personal development traditionally provided by ACE in the past. A study examined the views of ACE providers, ACE students, and industry organizations regarding ACE vocational education and…

  9. ACE inhibition reduces infarction in normotensive but not hypertensive rats: correlation with cortical ACE activity

    PubMed Central

    Porritt, Michelle J; Chen, Michelle; Rewell, Sarah S J; Dean, Rachael G; Burrell, Louise M; Howells, David W

    2010-01-01

    Angiotensin-converting enzyme (ACE) inhibition can reduce stroke risk by up to 43% in humans and reduce the associated disability, and hence understanding the mechanism of improvement is important. In animals and humans, these effects may be independent of the blood pressure-lowering effects of ACE inhibition. Normotensive (Wistar–Kyoto (WKY)) and hypertensive (spontaneously hypertensive rat (SHR)) animals were treated with the ACE inhibitors ramipril or lisinopril for 7 or 42 days before 2 hours of transient middle cerebral artery occlusion (MCAo). Blood pressure, serum ACE, and blood glucose levels were measured and stroke infarct volume was recorded 24 hours after stroke. Despite greater reductions in blood pressure, infarct size was not improved by ACE inhibition in hypertensive animals. Short-term ACE inhibition produced only a modest reduction in blood pressure, but WKY rats showed marked reductions in infarct volume. Long-term ACE inhibition had additional reductions in blood pressure; however, infarct volumes in WKY rats did not improve further but worsened. WKY rats differed from SHR in having marked cortical ACE activity that was highly sensitive to ACE inhibition. The beneficial effects of ACE inhibition on infarct volume in normotensive rats do not correlate with changes in blood pressure. However, WKY rats have ACE inhibitor-sensitive cortical ACE activity that is lacking in the SHR. PMID:20407464

  10. Living and Working in Antarctica.

    ERIC Educational Resources Information Center

    Kemp, Noel

    This source book, designed for 11- to 14-year-old students, seeks to describe what life is like in Antarctica. In spite of extreme weather conditions, people go to Antarctica to work every summer. Some of them stay there during the winter as well. This book seeks to supply answers to such questions as: How do people get to Antarctica? Why do they…

  11. ACE program/UNIX user manual

    SciTech Connect

    Feng-Berman, S.K.

    1993-01-12

    This report the following: How to use the ace program ; Introduction to the ace program; Online command; Define a macro file; Macro commands; Counters and MCA; Counters usage; Counters database; Feedback Counter Database; MCA functions and macro command; X window Interclient Communication; and How to get around in UNIX

  12. ACE program/UNIX user manual

    SciTech Connect

    Feng-Berman, S.K.

    1993-01-12

    This report the following: How to use the ace program?; Introduction to the ace program; Online command; Define a macro file; Macro commands; Counters and MCA; Counters usage; Counters database; Feedback Counter Database; MCA functions and macro command; X window Interclient Communication; and How to get around in UNIX?

  13. Geographic names of Antarctica

    USGS Publications Warehouse

    U.S. Board on Geographic Names; Department of the Interior; Burrill, Meredith F.; Bertrand, Kenneth J.; Alberts, Fred G.

    1956-01-01

    The geographic nomenclature of Antarctica was long in need of an overall systematic treatment, objective in approach and based upon thorough examination of all the evidence. The results of such treatment over a period of about three years were presented in Geographical Names of Antarctica, Special Publication No. 86 of the Board on Geographical Names, in May 1947, two supplements to which were issued in 1949 and 1951. The continuing program since that publication has now covered most of the geographic naming in Antarctica. As research has filled in many of the previous gaps in knowledge, a number of names have been modified and minor amendments have been made in the policies. This revised publication brings together the greatly enlarged body of names officially standardized for use by the United States Government, together with new pertinent background information.

  14. Antarctica, why so Blue?

    NASA Astrophysics Data System (ADS)

    Reif, C.; Williams, Q.; Manners, U.

    2006-12-01

    Are all fast seismic anomalies at the core-mantle boundary (CMB) created alike? Much attention has been paid to the relative variations of seismic wave speeds in slow regions of the lowermost mantle, but there is a wealth of information in the fast anomalies as well. Here we systematically characterize fast regions at the CMB in terms of their shear, compressional, and bulk wave speed anomalies and Poisson's ratio using the largest long-period catalog to date of S, ScS, Sdiff, P, and Pdiff arrival times. The fastest regions at the CMB occur beneath Antarctica, Central America, and eastern Asia. The latter two have been active subduction zones for more than 200 Ma. However, Antarctica is an exception in that subduction has not occurred there in the last 100 Ma. And, during the final stages of subduction, young oceanic lithosphere may be positively buoyant compared to the mantle and not be likely to sink all the way to the CMB. Therefore, the youngest (and thus coldest) material beneath Antarctica near the CMB is around 130 Ma in age. It is puzzling why the region beneath Antarctica would have one of the fastest seismic signals since plate reconstructions indicate that for the last 200 Ma, the greatest volume of material has been subducted under the northern Pacific. However, outside of Antarctica, the strongest fast anomalies at the CMB are geographically coincident with the current pattern of subduction, not that of the distant past. It has been noted that the seismic anomalies at the CMB do not fit those predicted by past plate reconstructions, and this mismatch has been explained in terms of the presence of the thermal boundary layer. Here, we examine thermal and compositional effects that could be produced by the interaction of subducted material with a basal thermal boundary layer, and probe how strong fast anomalies can be produced in both unexpected (Antarctica) and expected regions (eastern Asia), while fast anomalies anticipated elsewhere (northern Pacific

  15. Hydrogen emissions from Erebus volcano, Antarctica

    NASA Astrophysics Data System (ADS)

    Moussallam, Yves; Oppenheimer, Clive; Aiuppa, Alessandro; Giudice, Gaetano; Moussallam, Manuel; Kyle, Philip

    2012-11-01

    The continuous measurement of molecular hydrogen (H2) emissions from passively degassing volcanoes has recently been made possible using a new generation of low-cost electrochemical sensors. We have used such sensors to measure H2, along with SO2, H2O and CO2, in the gas and aerosol plume emitted from the phonolite lava lake at Erebus volcano, Antarctica. The measurements were made at the crater rim between December 2010 and January 2011. Combined with measurements of the long-term SO2 emission rate for Erebus, they indicate a characteristic H2 flux of 0.03 kg s-1 (2.8 Mg day-1). The observed H2 content in the plume is consistent with previous estimates of redox conditions in the lava lake inferred from mineral compositions and the observed CO2/CO ratio in the gas plume (˜0.9 log units below the quartz-fayalite-magnetite buffer). These measurements suggest that H2 does not combust at the surface of the lake, and that H2 is kinetically inert in the gas/aerosol plume, retaining the signature of the high-temperature chemical equilibrium reached in the lava lake. We also observe a cyclical variation in the H2/SO2 ratio with a period of ˜10 min. These cycles correspond to oscillatory patterns of surface motion of the lava lake that have been interpreted as signs of a pulsatory magma supply at the top of the magmatic conduit.

  16. Antarctica: Discovery & Exploration.

    ERIC Educational Resources Information Center

    Gascoigne, Toss; Collett, Peter

    An examination of Antarctica, from the first sightings to the heroic explorations of the late 18th and early 19th centuries to modern-day research, is presented in this book. Twelve chapters are as follows: (1) The search begins; (2) Whalers and sealers: bites and nibbles; (3) The new continent: first sight; (4) Wintering: the first party; (5)…

  17. Getting Antarctica down Cold!

    ERIC Educational Resources Information Center

    Sandmeier, Kay; Greeson, Linda

    1990-01-01

    Outlines learning activities for applying geography's five fundamental themes to studying Antarctica and points out the learning potential, for studying the economic, historical, and political geography of the continent. Groups activities for grades K-5, 6-8, and 8-12. Stresses cooperative learning in general, and includes a role play activity for…

  18. Married to Antarctica.

    ERIC Educational Resources Information Center

    Monastersky, Richard

    1991-01-01

    A novel theory about Earth's ancient history is presented. It is proposed that North America and Antarctica once lay side by side for perhaps as long as a billion years. The importance of these continental connections to geology and other disciplines is discussed. (KR)

  19. Advanced control evaluation for structures (ACES) programs

    NASA Technical Reports Server (NTRS)

    Pearson, Jerome; Waites, Henry

    1988-01-01

    The ACES programs are a series of past, present, and future activities at the Marshall Space Flight Center (MSFC) Ground facility for Large Space Structure Control Verification (GF/LSSCV). The main objectives of the ACES programs are to implement control techniques on a series of complex dynamical systems, to determine the control/structure interaction for the control techniques, and to provide a national facility in which dynamics and control verification can be effected. The focus is on these objectives and how they are implemented under various engineering and economic constraints. Future plans that will be effected in upcoming ACES programs are considered.

  20. The search for postglacial rebound near the Lambert Glacier, Antarctica

    NASA Astrophysics Data System (ADS)

    Tregoning, Paul; Welsh, Andrew; McQueen, Herbert; Lambeck, Kurt

    2000-11-01

    A GPS network has been installed to monitor vertical crustal movement in the Lambert Glacier region, East Antarctica. The program commenced in January 1998 with a solar-powered GPS system installed at Beaver Lake. Solar-powered observations were also made late in the Antarctic summer of 1999. In January 2000, two new solar-powered sites will be installed to expand the monitoring network. In addition, we will be installing a hydrogen fuel cell power system at Beaver Lake to enable the equipment to operate throughout the winter months when solar power is not available. In this paper we outline the equipment which has been developed in order to operate remote GPS equipment in Antarctica, provide predictions of the expected rate of rebound and comment on preliminary results from the data collected to date.

  1. FIRE_ACE_ER2_MAS

    Atmospheric Science Data Center

    2015-10-28

    ... First ISCCP Regional Experiment (FIRE) Arctic Cloud Experiment (ACE) NASA ER-2 Moderate Resolution Imaging ... SSFR Location:  Northern Alaska Arctic Ocean Spatial Coverage:  Fairbanks, Alaska and the surrounding ...

  2. General relativistic observables for the ACES experiment

    NASA Astrophysics Data System (ADS)

    Turyshev, Slava G.; Yu, Nan; Toth, Viktor T.

    2016-02-01

    We develop a high-precision model for relativistic observables of the Atomic Clock Ensemble in Space (ACES) experiment on the International Space Station (ISS). We develop all relativistic coordinate transformations that are needed to describe the motion of ACES in Earth orbit and to compute observable quantities. We analyze the accuracy of the required model as it applies to the proper-to-coordinate time transformations, light-time equation, and spacecraft equations of motion. We consider various sources of nongravitational noise and their effects on ACES. We estimate the accuracy of orbit reconstruction that is needed to satisfy the ACES science objectives. Based on our analysis, we derive models for the relativistic observables of ACES, which also account for the contribution of atmospheric drag on the clock rate. We include the Earth's oblateness coefficient J2 and the effects of major nongravitational forces on the orbit of the ISS. We demonstrate that the ACES reference frame is pseudoinertial at the level of accuracy required by the experiment. We construct a Doppler-canceled science observable representing the gravitational redshift. We derive accuracy requirements for ISS navigation. The improved model is accurate up to <1 ps and ˜4 ×1 0-17 for time and frequency transfers, correspondingly. These limits are determined by the higher-order harmonics in Earth's gravitational potential.

  3. The Aerosol/Cloud/Ecosystems Mission (ACE)

    NASA Technical Reports Server (NTRS)

    Schoeberl, Mark

    2008-01-01

    The goals and measurement strategy of the Aerosol/Cloud/Ecosystems Mission (ACE) are described. ACE will help to answer fundamental science questions associated with aerosols, clouds, air quality and global ocean ecosystems. Specifically, the goals of ACE are: 1) to quantify aerosol-cloud interactions and to assess the impact of aerosols on the hydrological cycle and 2) determine Ocean Carbon Cycling and other ocean biological processes. It is expected that ACE will: narrow the uncertainty in aerosol-cloud-precipitation interaction and quantify the role of aerosols in climate change; measure the ocean ecosystem changes and precisely quantify ocean carbon uptake; and, improve air quality forecasting by determining the height and type of aerosols being transported long distances. Overviews are provided of the aerosol-cloud community measurement strategy, aerosol and cloud observations over South Asia, and ocean biology research goals. Instruments used in the measurement strategy of the ACE mission are also highlighted, including: multi-beam lidar, multiwavelength high spectra resolution lidar, the ocean color instrument (ORCA)--a spectroradiometer for ocean remote sensing, dual frequency cloud radar and high- and low-frequency micron-wave radiometer. Future steps for the ACE mission include refining measurement requirements and carrying out additional instrument and payload studies.

  4. Ozone Hole Over Antarctica

    NASA Technical Reports Server (NTRS)

    2002-01-01

    These images from the Total Ozone Mapping Spectrometer (TOMS) show the progressive depletion of ozone over Antarctica from 1979 to 1999. This 'ozone hole' has extended to cover an area as large as 10.5 million square miles in September 1998. The previous record of 10.0 million square miles was set in 1996. The Antarctic ozone hole develops each year between late August and early October. Regions with higher levels of ozone are shown in red. NASA and NOAA instruments have been measuring Antarctic ozone levels since the early 1970s. Large regions of depleted ozone began to develop over Antarctica in the early 1980s. Ozone holes of substantial size and depth are likely to continue to form during the next few years, scientists hope to see a reduction in ozone loss as levels of ozone-destroying CFCs (chlorofluorocarbons) are gradually reduced. Credit: Images by Greg Shirah, NASA Goddard Space Flight Center Scientific Visualization Studio

  5. Earth - Antarctica Mosaic

    NASA Technical Reports Server (NTRS)

    1990-01-01

    This color picture of the limb of the Earth, looking north past Antarctica, is a mosaic of 11 images taken during a ten-minute period near 5:45 p.m. PST Dec. 8, 1990, by Galileo's imaging system. Red, green and violet filters were used. The picture spans about 1,600 miles across the south polar latitudes of our planet. The morning day/night terminator is toward the right. The South Pole is out of sight below the picture; the visible areas of Antarctica are those lying generally south of South America. The violet-blue envelope of Earth's atmosphere is prominent along the limb to the left. At lower left, the dark blue Amundsen Sea lies to the left of the Walgreen and Bakutis Coasts. Beyond it, Peter Island reacts with the winds to produce a striking pattern of atmospheric waves.

  6. Princess Astrid Coast, Antarctica

    NASA Technical Reports Server (NTRS)

    2002-01-01

    The continent of Antarctica is almost completely covered by a thick blanket of ice, punctuated only by steep mountain peaks and a handful of dry valleys. Antarctica is also ringed by a permanent ice shelf, and that is surrounded by seasonal sea ice. The image above, acquired by the Moderate-resolution Imaging Spectroradiometer (MODIS) on September 26, 2001, shows many of the types of ice found in Antarctica. At the bottom of the image is the ice of the continental glacier, which is up to 4,000 meters thick in the interior. These thick glaciers are held in place by coastal mountain ranges. Some ice does flow through the mountains, spilling onto the relatively flat land of the Princess Astrid Coast. Cold air also spills over the mountains, creating very strong and persistent 'katabatic' winds. These scour the snow off the tops of the glaciers, leaving pale blue patches of bare ice. Above the coastline is the ice shelf, which is much smoother. There, glacial ice actually floats on the sea surface. Beyond that is the chaotic surface of the sea ice, which has been solidifying all winter long. Credit: Jacques Descloitres, MODIS Land Rapid Response Team, NASA/GSFC

  7. Regional Aerosol Optical Depth Characteristics from Satellite Observations: ACE-1, TARFOX and ACE-2 Results

    NASA Technical Reports Server (NTRS)

    Durkee, P. A.; Nielsen, K. E.; Smith, P. J.; Russell, P. B.; Schmid, B.; Livingston, J. M.; Holben, B. N.; Tomasi, C.; Vitale, V.; Collins, D.

    1999-01-01

    Analysis of the aerosol properties during 3 recent international field campaigns ACE-1, TARFOX and ACE-2 are described using satellite retrievals from NOAA AVHRR data. Validation of the satellite retrieval procedure is performed with airborne, shipboard, and land-based sunphotometry during ACE-2. The intercomparison between satellite and surface optical depths has a correlation coefficient of 0.93 for 630 nm wavelength and 0.92 for 860 nm wavelength, The standard error of estimate is 0.025 for 630 nm wavelength and 0.023 for 860 nm wavelength. Regional aerosol properties are examined in composite analysis of aerosol optical properties from the ACE-1, TARFOX and ACE-2 regions. ACE-1 and ACE-2 regions have strong modes in the distribution of optical depth around 0.1, but the ACE-2 tails toward higher values yielding an average of 0.16 consistent with pollution and dust aerosol intrusions. The TARFOX region has a noticeable mode of 0.2, but has significant spread of aerosol optical depth values consistent with the varied continental aerosol constituents off the eastern North American Coast.

  8. Informal STEM Education in Antarctica

    NASA Astrophysics Data System (ADS)

    Chell, K.

    2010-12-01

    Tourism in Antarctica has increased dramatically with tens of thousands of tourists visiting the White Continent each year. Tourism cruises to Antarctica offer a unique educational experience for lay people through informal science-technology-engineering-mathematics (STEM) education. Passengers attend numerous scientific lectures that cover topics such as the geology of Antarctica, plate tectonics, glaciology, and climate change. Furthermore, tourists experience the geology and glaciology first hand during shore excursions. Currently, the grand challenges facing our global society are closely connected to the Earth sciences. Issues such as energy, climate change, water security, and natural hazards, are consistently on the legislative docket of policymakers around the world. However, the majority of the world’s population is uninformed about the role Earth sciences play in their everyday lives. Tourism in Antarctica provides opportunities for informal STEM learning and, as a result, tourists leave with a better understanding and greater appreciation for both Antarctica and Earth sciences.

  9. How isolated is Antarctica?

    PubMed

    Clarke, Andrew; Barnes, David K A; Hodgson, Dominic A

    2005-01-01

    The traditional view of Antarctica and the surrounding Southern Ocean as an isolated system is now being challenged by the recent discovery at the Antarctic Peninsula of adult spider crabs Hyas areneus from the North Atlantic and of larvae of subpolar marine invertebrates. These observations question whether the well described biogeographical similarities between the benthic fauna of the Antarctic Peninsula and the Magellan region of South America result from history (the two regions were once contiguous), or from a previously unrecognized low level of faunal exchange. Such exchange might be influenced by regional climate change, and also exacerbated by changes in human impact. PMID:16701330

  10. Hovercraft experience in Antarctica

    NASA Astrophysics Data System (ADS)

    Cook, Harvey C.

    The Model 1500 TD air-cushion vehicle (ACV) has been modified for the extreme conditions encountered in Antarctic operations; these operations began in the 1988-1989 austral summer. Performance evaluations covering 300 hours of engine operations have been obtained which demonstrate the basic soundness of this ACV's design and construction, and its applicability to Antarctic operations, where it was able to reduce travel time and fuel consumption in excess of 40 percent. In addition, passenger comfort was increased manyfold over wheeled and tracked vehicles for comparable missions. The ACV is judged capable of solving many of the transportation problems experienced in Antarctica.

  11. Antarctica Day: An International Celebration

    NASA Astrophysics Data System (ADS)

    Pope, A.; Hambrook Berkman, J.; Berkman, P. A.

    2013-12-01

    For more than half a century, the 1959 Antarctic Treaty continues to shine as a rare beacon of international cooperation. To celebrate this milestone of peace in our civilization with hope and inspiration for future generations, Antarctica Day is celebrated each year on December 1st , the anniversary of the Antarctic Treaty signing. As an annual event - initiated by the Foundation for the Good Governance of International Spaces (www.internationalspaces.org/) in collaboration with the Association of Polar Early Carer Scientists (www.apecs.is) - Antarctica Day encourages participation from around the world. The Antarctic Treaty set aside 10% of the earth, 'forever to be used exclusively for peaceful purposes in the interest of mankind.' It was the first nuclear arms agreement and the first institution to govern all human activities in an international region beyond sovereign jurisdictions. In this spirit, Antarctica Day aims to: - Demonstrate how diverse nations can work together peacefully, using science as a global language of cooperation for decision making beyond national boundaries, - Provide strategies for students learning about Antarctica through art, science and history at all school levels, - Increase collaboration and communication between classrooms, communities, researchers and government officials around the world, and - Provide a focus for polar educators to build on each year. Through close collaboration with a number of partners. Antarctica Day activities have included: a Polar Film Festival convened by The Explorers Club; live sessions connecting classrooms with scientists in Antarctica thanks to PolarTREC and ARCUS; an international activity that involved children from 13 countries who created over 600 flags which exemplify Antarctica Day (these were actually flown in Antarctica with signed certificates then returned to the classes); a map where Antarctica Day participants all over the world could share what they were doing; an Antarctic bird count

  12. Remarks on KERMA Factors in ACE files

    NASA Astrophysics Data System (ADS)

    Konno, C.; Ochiai, K.; Takakura, K.; Sato, S.

    2014-04-01

    Some neutron KERMA factors in ACE files are negative and extremely large if nuclear data libraries do not keep energy-balance. The status of neutron KERMA factors in the official ACE file of ENDF/B-VII.1 is examined. As a result, it is found out that neutron KERMA factors of nuclei more than 200 in ENDF/B-VII.1 have some problems. Effects of the inadequate KERMA factor are also investigated, which are large for neutron heat while those are small for total (neutron + gamma) heat. Users who use only neutron KERMA factors should check if the factors are adequate or not before they use the factors.

  13. Prokaryotic Community in Lacustrine Sediments of Byers Peninsula (Livingston Island, Maritime Antarctica).

    PubMed

    Gugliandolo, Concetta; Michaud, Luigi; Lo Giudice, Angelina; Lentini, Valeria; Rochera, Carlos; Camacho, Antonio; Maugeri, Teresa Luciana

    2016-02-01

    Byers Peninsula (Livingston Island, Antarctica), the largest seasonally ice-free region of the Maritime Antarctica, holds a large number of lakes, ponds, and streams. The prokaryotic structure and bacterial diversity in sediment samples collected during the 2008-2009 austral summer from five inland lakes, two coastal lakes, and an estuarine site were analyzed by Catalyzed Reporter Deposition Fluorescence In Situ Hybridization (CARD-FISH) and 16S rRNA 454 tag pyrosequencing techniques, respectively. Differently from inland lakes, which range around the oligotrophic status, coastal lakes are eutrophic environments, enriched by nutrient inputs from marine animals. Although the prokaryotic abundances (estimated as DAPI stained cells) in sediment samples were quite similar among inland and coastal lakes, Bacteria always far dominated over Archaea. Despite the phylogenetic analysis indicated that most of sequences were affiliated to a few taxonomic groups, mainly referred to Proteobacteria, Bacteroidetes, and Actinobacteria, their relative abundances greatly differed from each site. Differences in bacterial composition showed that lacustrine sediments were more phyla rich than the estuarine sediment. Proteobacterial classes in lacustrine samples were dominated by Betaproteobacteria (followed by Alphaproteobacteria, Deltaproteobacteria, and Gammaproteobacteria), while in the estuarine sample, they were mainly related to Gammaproteobacteria (followed by Deltaproteobacteria, Epsilonproteobacteria, Alphaproteobacteria, and Betaproteobacteria). Higher number of sequences of Alphaproteobacteria, Cyanobacteria, Verrucomicrobia, and Planctomycetes were observed in sediments of inland lakes compared to those of coastal lakes, whereas Chloroflexi were relatively more abundant in the sediments of coastal eutrophic lakes. As demonstrated by the great number of dominant bacterial genera, bacterial diversity was higher in the sediments of inland lakes than that in coastal lakes

  14. Renal ACE immunohistochemical localization in NIDDM patients with nephropathy.

    PubMed

    Mizuiri, S; Yoshikawa, H; Tanegashima, M; Miyagi, M; Kobayashi, M; Sakai, K; Hayashi, I; Aikawa, A; Ohara, T; Hasegawa, A

    1998-02-01

    A role of renal angiotensin-converting enzyme (ACE) in diabetic nephropathy has been suggested. Immunohistochemical localization of ACE was studied in 20 non-insulin-dependent diabetes mellitus patients with diabetic nephropathy and 17 healthy kidney transplant donors, with ACE gene insertion/deletion (I/D) polymorphism also examined in the latter. Immunohistochemical studies indicated that ACE staining was significantly (P < 0.01) enhanced in glomeruli and slightly decreased in proximal tubules in diabetic patients. Glomeruli positive for ACE immunostaining were observed in 23.5% of the healthy subjects and in 80% of the diabetic patients. All patients with nodular lesions had ACE-positive glomeruli and showed significantly (P < 0.01) more intense glomerular ACE immunostaining than patients without nodular lesions. Among healthy controls, subjects with the DD genotype had ACE-positive glomeruli more frequently and tended to show slightly increased intensity on proximal tubule ACE immunostaining compared with subjects with other genotypes. These observations suggest that increased ACE localization in glomeruli is likely to be one of the factors in the increased renin-angiotensin system activity in glomeruli in patients with diabetic nephropathy. There is a possibility that ACE gene I/D polymorphism may be related to renal ACE immunohistochemical localization. PMID:9469501

  15. Advanced Colloids Experiment (ACE-T1)

    NASA Technical Reports Server (NTRS)

    Meyer, William V.; Sicker, Ron; Brown, Dan; Eustace, John

    2015-01-01

    Increment 45 - 46 Science Symposium presentation of Advanced Colloids Experiment (ACE-T1) to RPO. The purpose of this event is for Principal Investigators to present their science objectives, testing approach, and measurement methods to agency scientists, managers, and other investigators.

  16. Advanced Colloids Experiment (ACE-H-2)

    NASA Technical Reports Server (NTRS)

    Meyer, William V.; Sicker, Ron; Chmiel, Alan J.; Eustace, John; LaBarbera, Melissa

    2015-01-01

    Increment 43 - 44 Science Symposium presentation of Advanced Colloids Experiment (ACE-H-2) to RPO. The purpose of this event is for Principal Investigators to present their science objectives, testing approach, and measurement methods to agency scientists, managers, and other investigators.

  17. Developing Communities: Serving ACE through Tertiary Education

    ERIC Educational Resources Information Center

    Sofo, Francesco

    2011-01-01

    Purpose: The purpose of this paper is to review the focus and practice of Adult and Community Education (ACE) as well as its conceptualization and delivery and to suggest parameters for an approach based on excellence, a balanced scorecard and performance to meet community needs. Design/methodology/approach: The review examines key aspects of the…

  18. Ace the Verbal on the SAT

    ERIC Educational Resources Information Center

    Meierding, Loren

    2005-01-01

    Many students are not accepted in to certain colleges and universities because of low SAT scores. Loren Meierding has written Ace the Verbal on the SAT to help students with minimal preparation do well by improving their vocabulary and use better techniques for finding the answers to the questions. This book provides strategies needed to score…

  19. Petroleum geology of western Antarctica

    SciTech Connect

    Kingston, J. )

    1990-05-01

    Antarctica's geology is mostly obscured by thick, moving ice that covers 95% of the land and continental shelf. Reconnaissance investigations of outcrops, shallow boreholes, and geophysical surveys are limited and peripheral owing to ice coverage. However, it is possible to outline substantial elements of the regional geology. Further insight is gained by comparison to analogous sedimentary provinces, especially provinces once adjoined within the framework of the Gondwana supercontinent until middle Cretaceous. The petroleum potential of Antarctica, as in the case of the other related high-standing Gondwana continental fragments, is in Early Cretaceous rifts associated with the Gondwana breakup and with the Pacific convergence in the west Antarctica back arc. The Pacific-facing western Antarctica includes two structural provinces: (1) the Cretaceous and younger interior rift system on the east side of the Weddell and Ross Sea embayment, which contain aulacogens that form the boundary with East Antarctica and (2) the back-arc and fore-arc basins adjoining the Antarctica Peninsula and extending into Marie Byrd Land and the Bellingshausen Sea which are associated with the eastward convergence of the Pacific plate. The petroleum potential of the rifts may be assessed by analogies with related rifts of Australia, India, and South Africa; assessment of the convergent basins of western Antarctica depends upon analogy with similar basins of South America, New Zealand, and Indonesia. An estimate of the petroleum potential of western Antarctica generally is comparable with oil and gas occurrences (both in overall quantity and in field sizes) in the other Gondwana continental fragments. However, in view of the thict moving ice cover, the remote locale, and severe climate, petroleum production is largely beyond technology at this time and probably is economically unfeasible.

  20. Seismic Tomography of Erebus Volcano, Antarctica

    NASA Astrophysics Data System (ADS)

    Zandomeneghi, Daria; Kyle, Philip; Miller, Pnina; Snelson, Catherine; Aster, Richard

    2010-02-01

    Mount Erebus (77°32'S, 167°10'E elevation 3794 meters) is the most active volcano in Antarctica and is well known for its persistent lava lake. The lake constitutes an “open window” into the conduit and underlying feeding system and offers a rare opportunity to observe a shallow convecting magmatic system. Imaging and modeling of the internal structure of Erebus volcano are best done through compiling information from arrays of seismometers positioned strategically around the volcano. From these data, the three-dimensional (3-D) structure of the conduit can be pieced together. Building this 3-D model of Erebus was a main goal of the seismic tomographic experiment Tomo Erebus (TE). During the 2007-2008 austral field season, 23 intermediate-period seismometers were installed to contribute data, through the winter, for the passive-source aspect of the experiment. One year later, 100 three-component short-period stations were deployed to record 16 chemical blasts (see Figure 1).

  1. ACES-PHARAO : Microwave link data processing

    NASA Astrophysics Data System (ADS)

    Meynadier, F.; Delva, P.; Le Poncin-Lafitte, C.; Laurent, P.; Wolf, P.

    2011-12-01

    The Atomic Clocks Ensemble in Space (PHARAO-ACES mission, te{Salomon2007}), which will be installed on board the International Space Station , uses a dedicated two-way microwave link in order to compare the timescale generated on board with those provided by many ground stations disseminated on the Earth. Phase accuracy and stability of this long range link will have a key role in the success of the PHARAO-ACES experiment. The SYRTE is heavily involved in the design and the development of the data processing software : from theoretical modelling and numerical simulations to the development of a software prototype. Our team is working on a wide range of problems that need to be solved in order to achieve high accuracy in (almost) real time. In this poster we present some key aspects of the measurement, as well as the current status of the software's development.

  2. Paleolimnology of the McMurdo Dry Valleys, Antarctica

    NASA Technical Reports Server (NTRS)

    Doran, P. T.; Wharton, R. A. Jr; Lyons, W. B.; Wharton RA, J. r. (Principal Investigator)

    1994-01-01

    The McMurdo Dry Valleys presently contain more than 20 permanent lakes and ponds, which vary markedly in character. All, with the exception of a hypersaline pond, have a perennial ice-cover. The dry valley lakes, and lakes in other ice-free regions of continental Antarctica, are unique on this planet in that they consistently maintain a thick year-round ice cover (2.8-6.0 m) over liquid water. The persistent ice covers minimize wind-generated currents and reduce light penetration, as well as restricting sediment deposition into a lake and the exchange of atmospheric gases between the water column and the atmosphere. From a paleolimnological perspective, the dry valley lakes offer an important record of catchment and environmental changes. These lakes are also modern-day equivalents of periglacial lakes that were common during glacial periods at temperate latitudes. The present lakes are mostly remnants of larger glacial lakes that occupied the valleys in the past, perhaps up to 4.6 Ma ago. Two of the valleys contain evidence of being filled with large glacial lakes within the last 10000 years. Repeated drying and filling events since then have left a characteristic impression on the salt profiles of some lakes creating a unique paleo-indicator within the water column. These events are also marked in the sediments by the concentration and dilution of certain chemical constituents, particularly salts, and are also corroborated by carbonate speciation and oxygen isotope analysis. Stratigraphic analysis of dry valley lake sediments is made difficult by the occurrence of an 'old carbon' reservoir creating spurious radiocarbon dates, and by the high degree of spatial variability in lake sedimentation. From a biological perspective, the lakes are relatively simple, containing various taxa of planktonic and benthic microorganisms, but no higher forms of life, which is an advantage to paleolimnologists because there is no bioturbation in the sediments. Useful biological

  3. Human Recombinant ACE2 Reduces the Progression of Diabetic Nephropathy

    PubMed Central

    Oudit, Gavin Y.; Liu, George C.; Zhong, JiuChang; Basu, Ratnadeep; Chow, Fung L.; Zhou, Joyce; Loibner, Hans; Janzek, Evelyne; Schuster, Manfred; Penninger, Josef M.; Herzenberg, Andrew M.; Kassiri, Zamaneh; Scholey, James W.

    2010-01-01

    OBJECTIVE Diabetic nephropathy is one of the most common causes of end-stage renal failure. Inhibition of ACE2 function accelerates diabetic kidney injury, whereas renal ACE2 is downregulated in diabetic nephropathy. We examined the ability of human recombinant ACE2 (hrACE2) to slow the progression of diabetic kidney injury. RESEARCH DESIGN AND METHODS Male 12-week-old diabetic Akita mice (Ins2WT/C96Y) and control C57BL/6J mice (Ins2WT/WT) were injected daily with placebo or with rhACE2 (2 mg/kg, i.p.) for 4 weeks. Albumin excretion, gene expression, histomorphometry, NADPH oxidase activity, and peptide levels were examined. The effect of hrACE2 on high glucose and angiotensin II (ANG II)–induced changes was also examined in cultured mesangial cells. RESULTS Treatment with hrACE2 increased plasma ACE2 activity, normalized blood pressure, and reduced the urinary albumin excretion in Akita Ins2WT/C96Y mice in association with a decreased glomerular mesangial matrix expansion and normalization of increased α-smooth muscle actin and collagen III expression. Human recombinant ACE2 increased ANG 1–7 levels, lowered ANG II levels, and reduced NADPH oxidase activity. mRNA levels for p47phox and NOX2 and protein levels for protein kinase Cα (PKCα) and PKCβ1 were also normalized by treatment with hrACE2. In vitro, hrACE2 attenuated both high glucose and ANG II–induced oxidative stress and NADPH oxidase activity. CONCLUSIONS Treatment with hrACE2 attenuates diabetic kidney injury in the Akita mouse in association with a reduction in blood pressure and a decrease in NADPH oxidase activity. In vitro studies show that the protective effect of hrACE2 is due to reduction in ANG II and an increase in ANG 1–7 signaling. PMID:19934006

  4. My IGY in Antarctica

    NASA Technical Reports Server (NTRS)

    Bentley, Charles

    2012-01-01

    Dr Charles Bentley is the A.P. Crary Professor Emeritus of Geophysics, Department of Geology and Geophysics, University of Wisconsin-Madison. Dr. Bentley joined the Arctic Institute of North America in 1956 to participate in International Geophysical Year (IGY)-related activities in the Antarctic. He wintered over consecutively in 1957 and 1958 at Byrd Station, a station in the interior of West Antarctica that housed 24 men each winter - 12 Navy support people and 12 civilian scientists/technicians. During the austral summers, he also participated in over-snow traverses, first as co-leader, then leader (the other coleader went home after the first year). These traverses consisted of six men and three vehicles, and lasted several months. These traverses covered more than 1609 kilometers (1000 miles) of largely unmapped and unphotographed terrain. During these traverses, connections to Byrd Station were by radio (daily, when the transmission conditions were good enough) and roughly every 2 weeks by resupply flight.

  5. GOCE and Antarctica

    NASA Astrophysics Data System (ADS)

    Forsberg, Rene

    2015-03-01

    GOCE has mapped the gravity field of the planet with unprecedented accuracy, and will leave a legacy gravity field measurement unmatched for many years to come. GOCE data in Antarctica demonstrate the mapping of significant crustal anomalies and deep subglacial valleys, and give for the first time a unified overlook of the gravitation field north of 83.3°S, and the accuracy and high resolution of GOCE is confirmed by comparison to recent airborne gravity data. A “beauty spot” of the global GOCE gravity field map is, however, the lack of data at the polar gaps, beyond 83.5 latitude. Although GRACE fills the polar gaps at medium to long wavelengths, the crucial wavelength band around harmonic degrees 120-240 will remain unmapped, unless terrestrial data are used. The gravity data coverage of the Arctic is pretty much done, thanks to major US, European and Russian airborne and surface surveys carried out since the early 1990’s. In the Antarctic, however, the situation is the opposite: virtually no surface or airborne data exist in the polar gap; therefore an international effort to fill in this gap by airborne gravity would be timely now, to make the final GOCE legacy gravity field models truly global. It is possible to fill this gap at a sufficient accuracy level in one field season, and plans for doing exactly that in a European-US cooperation 2015/16 are outlined.

  6. Solar Eclipses Observed from Antarctica

    NASA Astrophysics Data System (ADS)

    Pasachoff, Jay M.

    2013-01-01

    Aspects of the solar corona are still best observed during totality of solar eclipses, and other high-resolution observations of coronal active regions can be observed with radio telescopes by differentiation of occultation observations, as we did with the Jansky Very Large Array for the annular solar eclipse of 2012 May 20 in the US. Totality crossing Antarctica included the eclipse of 2003 November 23, and will next occur on 2021 December 4; annularity crossing Antarctica included the eclipse of 2008 February 7, and will next occur on 2014 April 29. Partial phases as high as 87% coverage were visible and were imaged in Antarctica on 2011 November 25, and in addition to partial phases of the total and annular eclipses listed above, partial phases were visible in Antarctica on 2001 July 2011, 2002 December 4, 2004 April 19, 2006 September 22, 2007 September 11, and 2009 January 26, and will be visible on 2015 September 13, 2016 September 1, 2017 February 26, 2018 February 15, and 2020 December 14. On behalf of the Working Group on Solar Eclipses of the IAU, the poster showed the solar eclipses visible from Antarctica and this article shows a subset (see www.eclipses.info for the full set). A variety of investigations of the Sun and of the response of the terrestrial atmosphere and ionosphere to the abrupt solar cutoff can be carried out at the future eclipses, making the Antarctic observations scientifically useful.

  7. Antarctica as a Martian model.

    NASA Technical Reports Server (NTRS)

    Vishniac, W. V.; Mainzer, S. E.

    1973-01-01

    Results of a survey of a variety of environments in the dry valleys of Antarctica, ranging from mountain crests to valley floors. The main purpose of the investigation was the determination of active microbial multiplication in the soil. A series of techniques was employed which permitted the detection of bacterial growth in situ. All evidence points to an active growth of micro-organisms in the Antarctic soil in all locations examined. The measurements were supported by electron micrographs of soil films which showed colonial growth covering soil particles. These findings suggest that Antarctica does not serve as a useful model for the Martian environment in evaluating quarantine standards.

  8. The solar array is installed on ACE in SAEF-2

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Applied Physics Laboratory engineers and technicians from Johns Hopkins University assist in leveling and orienting the Advanced Composition Explorer (ACE) as it is seated on a platform for solar array installation in KSC's Spacecraft Assembly and Encapsulation Facility-II. Scheduled for launch on a Delta II rocket from Cape Canaveral Air Station on Aug. 25, ACE will study low-energy particles of solar origin and high-energy galactic particles. The ACE observatory has six high-resolution particle detection sensors and three monitoring instruments. The collecting power of instrumentation aboard ACE is at least 100 times more sensitive than anything previously flown to collect similar data by NASA.

  9. Unraveling the Pivotal Role of Bradykinin in ACE Inhibitor Activity.

    PubMed

    Taddei, Stefano; Bortolotto, L

    2016-10-01

    Historically, the first described effect of an angiotensin converting enzyme (ACE) inhibitor was an increased activity of bradykinin, one of the substrates of ACE. However, in the subsequent years, molecular models describing the mechanism of action of ACE inhibitors in decreasing blood pressure and cardiovascular risk have focused mostly on the renin-angiotensin system. Nonetheless, over the last 20 years, the importance of bradykinin in regulating vasodilation, natriuresis, oxidative stress, fibrinolysis, inflammation, and apoptosis has become clearer. The affinity of ACE appears to be higher for bradykinin than for angiotensin I, thereby suggesting that ACE inhibitors may be more effective inhibitors of bradykinin degradation than of angiotensin II production. Data describing the effect of ACE inhibition on bradykinin signaling support the hypothesis that the most cardioprotective benefits attributed to ACE inhibition may be due to increased bradykinin signaling rather than to decreased angiotensin II signaling, especially when high dosages of ACE inhibitors are considered. In particular, modulation of bradykinin in the endothelium appears to be a major target of ACE inhibition. These new mechanistic concepts may lead to further development of strategies enhancing the bradykinin signaling. PMID:27260014

  10. Spatial variability in degassing at Erebus volcano, Antarctica

    NASA Astrophysics Data System (ADS)

    Ilanko, Tehnuka; Oppenheimer, Clive; Kyle, Philip; Burgisser, Alain

    2015-04-01

    Erebus volcano on Ross Island, Antarctica, hosts an active phonolitic lava lake, along with a number of persistently degassing vents in its summit crater. Flank degassing also occurs through ice caves and towers. The longevity of the lake, and its stable convection, have been the subject of numerous studies, including Fourier transform infrared (FTIR) spectroscopy of the lava lake. Two distinct gas compositions were previously identified in the main lava lake plume (Oppenheimer et al., 2009; 2011): a persistent 'conduit' gas with a more oxidised signature, ascribed to degassing through a permeable magma conduit; and a H2O- and SO2- enriched 'lake' composition that increases and decreases cyclically due to shallow degassing of incoming magma batches. During the past decade of annual field seasons on Erebus, gas compositions have been measured through FTIR spectroscopy at multiple sites around Erebus volcano, including flank degassing through an ice cave (Warren Cave). We present measurements from four such vents, and compare their compositions to those emitted from the main lava lake. Summit degassing involves variable proportions of H2O, CO2, CO, SO2, HF, HCl, OCS. Cyclicity is evident in some summit vents, but with signatures indicative of shallower magmatic degassing than that of the lava lake. By contrast, flank degassing at Warren Cave is dominated by H2O, CO2, and CH4. The spatial variability in gas compositions within the summit crater suggests an alternative origin for 'conduit' and 'lake' degassing to previous models that assume permeability in the main conduit. Rather, the two compositions observed in main lake degassing may be a result of decoupled 'conduit' gas and pulses of magma rising through discrete fractures before combining in the lake floor or the main plume. Smaller vents around the crater thus emit isolated 'lake' or 'conduit' compositions while their combined signature is observed in the lava lake. We suggest that this separation between gas

  11. Multiphysics Applications of ACE3P

    SciTech Connect

    K.H. Lee, C. Ko, Z. Li, C.-K. Ng, L. Xiao, G. Cheng, H. Wang

    2012-07-01

    The TEM3P module of ACE3P, a parallel finite-element electromagnetic code suite from SLAC, focuses on the multiphysics simulation capabilities, including thermal and mechanical analysis for accelerator applications. In this pa- per, thermal analysis of coupler feedthroughs to supercon- ducting rf (SRF) cavities will be presented. For the realistic simulation, internal boundary condition is implemented to capture RF heating effects on the surface shared by a di- electric and a conductor. The multiphysics simulation with TEM3P matched the measurement within 0.4%.

  12. The Distribution of Antarctic Subglacial Lake Environments With Implications for Their Origin and Evolution

    NASA Astrophysics Data System (ADS)

    Blankenship, D. D.; Young, D. A.; Carter, S. P.

    2006-12-01

    Ice-penetrating radar records across the Antarctic Ice Sheet show regions with strong flat mirror-like reflections from the subglacial interface that are interpreted to be from subglacial lakes. The majority of subglacial lakes are found in East Antarctica, primarily in topographically low areas of basins beneath the thick ice divides. Occasionally lakes are observed "perched" at higher elevations within local depressions of rough morphological regions. In addition, a correlation between the "onset" of enhanced glacial flow and subglacial lakes was identified. The greatest concentration of known lakes was found in the vicinity of Dome C. A second grouping of lakes lying near Ridge B includes Lake Vostok and several smaller lakes. Subglacial lakes were also discovered near the South Pole, within eastern Wilkes Land, west of the Transantarctic Mountains, and within West Antarctica's Whitmore Mountains. Aside from Lake Vostok, typical lengths of subglacial lakes were found to range from a few to about 20 kilometers. A recent inventory includes 145 subglacial lakes. Approximately 81% of detected lakes lie at elevations less than a few hundred meters above sea level while the majority of the remaining lakes are "perched" at higher elevations. We present the locations from the subglacial lake inventory on local "ice divides" calculated from the satellite derived surface elevations with and find the distance of each lake from these divides. Most significantly, we found that 66% of the lakes identified lie within 50 km of a local ice divide and 88% lie within 100 km of a local divide. In particular, note that lakes located far from the Dome C/Ridge B cluster and even those associated with very narrow catchments lie either on or within a few tens of kilometers of the local divide marked by the catchment boundary. The distance correlation of subglacial lakes with local ice divides leads to a fundamental question for the evolution of subglacial lake environments: Does the

  13. Surface winds over West Antarctica

    NASA Technical Reports Server (NTRS)

    Bromwich, David

    1993-01-01

    Five winter months (April-August 1988) of thermal infrared satellite images were examined to investigate the occurrence of dark (warm) signatures across the Ross Ice Shelf in the Antarctic continent. These features are inferred to be generated by katabatic winds that descend from southern Marie Byrd Land and then blow horizontally across the ice shelf. Significant mass is added to this airstream by katabatic winds blowing from the major glaciers that flow through the Transantarctic Mountains from East Antarctica. These negatively buoyant katabatic winds can reach the northwestern edge of the shelf - a horizontal propagation distance of up to 1,000 km - 14 percent of the time. Where the airstream crosses from the ice shelf to the ice-covered Ross Sea, a prominent coastal polynya is formed. Because the downslope buoyancy force is near zero over the Ross Ice Shelf, the northwestward propagation of the katabatic air mass requires pressure gradient support. The study shows that the extended horizontal propagation of this atmospheric density current occurred in conjunction with the passage of synoptic cyclones over the southern Amundsen Sea. These cyclones can strengthen the pressure gradient in the interior of West Antarctica and make the pressure field favorable for northwestward movement of the katabatic winds from West Antarctica across the ice shelf in a geostrophic direction. The glacier winds from East Antarctica are further accelerated by the synoptic pressure gradient, usually undergo abrupt adjustment beyond the exit to the glacier valley, and merge into the mountain-parallel katabatic air mass.

  14. Landsat Image Mosaic of Antarctica

    USGS Publications Warehouse

    U.S. Geological Survey

    2007-01-01

    Description Fact sheet introduces the Landsat Image Mosaic of Antarctica (LIMA) with images from a section of the mosaic over McMurdo Station, descriptions of the four versions of LIMA, where to access and download LIMA, and a brief explanation of the Antarctic Web portal.

  15. Angiotensin-converting enzyme levels and activity in Alzheimer's disease: differences in brain and CSF ACE and association with ACE1 genotypes

    PubMed Central

    Miners, Scott; Ashby, Emma; Baig, Shabnam; Harrison, Rachel; Tayler, Hannah; Speedy, Elizabeth; Prince, Jonathan A; Love, Seth; Kehoe, Patrick G

    2009-01-01

    Angiotensin-converting enzyme (ACE) has been implicated in Alzheimer's disease (AD): ACE1 variations influence plasma ACE and risk of AD, and ACE is increased in AD brain. We measured frontal ACE level and activity in 89 AD and 51 control brains, and post-mortem CSF from 101 cases and 19 controls. Neuron-specific enolase (NSE) level and Braak stage were used to indicate neuronal preservation and disease progression. We genotyped the common ACE insertion/deletion polymorphism, rs4343, rs1800764 and rs4921. ACE activity was elevated in AD and correlated with Braak stage. Crude ACE levels were unchanged but adjustment for NSE suggested increased neuronal ACE production with Braak stage. Exposing SH-SY-5Y neurons to oligomeric Aβ1-42 increased ACE level and activity, suggesting Aβ may upregulate ACE in AD. In CSF, ACE level but not activity was reduced in AD. ACE1 genotype did not predict ACE level or activity in brain or CSF. ACE activity and neuronal production increase in AD brain, possibly in response to Aβ. Peripheral measurements do not reflect ACE activity in the brain. PMID:19956428

  16. Characterization of angiotensin converting enzyme (ACE) in the testis and assessment of the in vivo effects of the ACE inhibitor perindopril

    SciTech Connect

    Jackson, B.; Cubela, R.B.; Sakaguchi, K.; Johnston, C.I.

    1988-07-01

    Angiotensin converting enzyme (ACE) was characterized by radioligand studies utilizing the potent ACE inhibitor 351A, a derivative of lisinopril. Ligand binding characteristics were similar for ACE derived from testis, lung, and kidney, despite known differences in structure between ACe from these sources. This observation suggests that the ACE active enzymatic site is similar in different tissues. The effect of the orally active ACE inhibitor perindopril was studied ex vivo in tissues of the rat after oral gavage. Radioligand bound to tissue ACE was reduced after perindopril treatment, in tissue homogenates of lung and kidney, but not testis. Autoradiographs of radioligand binding to tissue sections obtained ex vivo after oral perindopril showed inhibition of ACE in the aorta, lung, and kidney, but did not reveal any inhibition of ACE in the testis. ACE in small vessels of the testis was inhibited as in the aorta, while at the same time testicular ACE was unaffected. ACE in rat testis appears to have a similar enzymatic binding site to ACE from the lung and kidney. Perindopril inhibited ACE in the lung and kidney but did not affect ACE in the testis, suggesting the drug is limited in testicular penetration by the blood-testis barrier. This may explain the lack of any reports of adverse effects of ACE inhibitors on testicular function.

  17. Pine Island Glacier, Antarctica

    NASA Technical Reports Server (NTRS)

    2001-01-01

    This pair of MISR images of the Pine Island Glacier in western Antarctica was acquired on December 12, 2000 during Terra orbit 5246. At left is a conventional, true-color image from the downward-looking (nadir) camera. The false-color image at right is a composite of red band data taken by the MISR forward 60-degree, nadir, and aftward 60-degree cameras, displayed in red, green, and blue colors, respectively. Color variations in the left (true-color) image highlight spectral differences. In the multi-angle composite, on the other hand, color variations act as a proxy for differences in the angular reflectance properties of the scene. In this representation, clouds show up as light purple. Blue to orange gradations on the surface indicate a transition in ice texture from smooth to rough. For example, the bright orange 'carrot-like' features are rough crevasses on the glacier's tongue. In the conventional nadir view, the blue ice labeled 'rough crevasses' and 'smooth blue ice' exhibit similar coloration, but the multi-angle composite reveals their different textures, with the smoother ice appearing dark purple instead of orange. This could be an indicator of different mechanisms by which this ice is exposed. The multi-angle view also reveals subtle roughness variations on the frozen sea ice between the glacier and the open water in Pine Island Bay.

    To the left of the 'icebergs' label are chunks of floating ice. Additionally, smaller icebergs embedded in the frozen sea ice are visible below and to the right of the label. These small icebergs are associated with dark streaks. Analysis of the illumination geometry suggests that these streaks are surface features, not shadows. Wind-driven motion and thinning of the sea ice in the vicinity of the icebergs is one possible explanation.

    Recently, Robert Bindschadler, a glaciologist at the NASA Goddard Space Flight Center discovered in Landsat 7 imagery a newly-formed crack traversing the Pine Island Glacier. This crack

  18. ACE: A Collaborative School Consultation Program for Secondary School Teachers

    ERIC Educational Resources Information Center

    Couture, Caroline; Massé, Line

    2014-01-01

    This article presents a description of ACE (Accompagnement collaboratif des enseignants (Collaborative teacher accompaniment)), a new program designed to guide secondary school teachers in integrating students with behavioral problems in their classrooms. ACE proposes collaborative accompaniment inspired by behavioral and mental health…

  19. An Inclusive ACE. Broadening Participation in Adult and Community Education.

    ERIC Educational Resources Information Center

    Alt, Merilyn; Beatty, Dianne

    A project identified strategies to increase participation by community members who traditionally have not used adult and community education (ACE) in Australia. Methodology included a focus group, literature research, and interviews with 70 people. Government-supported ACE was seen as having a broad role in supporting lifelong learning. ACE…

  20. ACE and AGTR1 polymorphisms in elite rhythmic gymnastics.

    PubMed

    Di Cagno, Alessandra; Sapere, Nadia; Piazza, Marina; Aquino, Giovanna; Iuliano, Enzo; Intrieri, Mariano; Calcagno, Giuseppe

    2013-02-01

    In the angiotensin-converting enzyme (ACE) gene, Alu deletion, in intron 16, is associated with higher concentrations of ACE serum activity and this may be associated with elite sprint and power performance. The Alu insertion is associated with lower ACE levels and this could lead to endurance performance. Moreover, recent studies have identified a single-nucleotide polymorphism of the angiotensin type 1 receptor gene AGTR1, which seems to be related to ACE activity. The aim of this study was to examine the involvement of the ACE and the AGTR1 gene polymorphisms in 28 Italian elite rhythmic gymnasts (age range 21 ± 7.6 years), and compare them to 23 middle level rhythmic gymnasts (age range 17 ± 10.9 years). The ACE D allele was significantly more frequent in elite athletes than in the control population (χ(2)=4.07, p=0.04). Comparisons between the middle level and elite athletes revealed significant differences (p<0.0001) for the ACE DD genotype (OR=6.48, 95% confidence interval=1.48-28.34), which was more frequent in elite athletes. There were no significant differences in the AGTR1 A/C genotype or allele distributions between the middle level and elite athletes. In conclusion, the ACE D allele genotype could be a contributing factor to high-performance rhythmic gymnastics that should be considered in athlete development and could help to identify which skills should be trained for talent promotion. PMID:23145508

  1. The solar array is installed on ACE in SAEF-2

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Applied Physics Laboratory engineers and technicians from Johns Hopkins University install solar array panels on the Advanced Composition Explorer (ACE) in KSC's Spacecraft Assembly and Encapsulation Facility-II. The panel on which they are working is identical to the panel (one of four) seen in the foreground on the ACE spacecraft. Scheduled for launch on a Delta II rocket from Cape Canaveral Air Station on Aug. 25, ACE will study low- energy particles of solar origin and high-energy galactic particles for a better understanding of the formation and evolution of the solar system as well as the astrophysical processes involved. The ACE observatory will be placed into an orbit almost a million miles (1.5 million kilometers) away from the Earth, about 1/100 the distance from the Earth to the Sun. The collecting power of instrumentation aboard ACE is at least 100 times more sensitive than anything previously flown to collect similar data by NASA.

  2. Secular trends in plume composition of Erebus volcano, Antarctica

    NASA Astrophysics Data System (ADS)

    Ilanko, Tehnuka; Oppenheimer, Clive; Kyle, Philip; Burgisser, Alain

    2015-04-01

    Long-lived active lava lakes, such as that in the summit crater of Erebus volcano, Antarctica, provide a rare insight into sustained magma convection and degassing over long timescales. Erebus lava lake has been persistently active since 1972, and potentially for several decades or more previously (Ross, 1847). Since the 1970s, regular scientific expeditions, lasting a few weeks in the austral summers, have made observations of the lake activity. Annual Fourier transform infrared (FTIR) spectroscopic gas measurements began in 2004 (Oppenheimer and Kyle, 2008; Oppenheimer et al., 2009), yielding an extensive, if discontinuous, time series of infrared absorption spectra. These data, once processed, provide insights into temporal evolution of the gas geochemistry in terms of seven molecular species: H2O, CO2, CO, SO2, HCl, HF, and OCS. FTIR spectroscopic data are now available over ten field seasons, totalling roughly 1.8 million spectra and increasing each year. This period spans changes to crater morphology, fluctuations in lava lake surface area (Jones et al., 2014), and two episodes of increased explosive activity (2005-06 and 2013). The dataset captures both long-term degassing trends and short-lived features, such as cyclicity in gas emissions during passive degassing (Ilanko et al., 2015) and compositions released by explosive bubble-burst eruptions. We consider the longer-term changes to gas ratios occurring within (i.e. over days to weeks) and between annual field seasons, their potential causes, and their relationship to observations of eruptive behaviour and crater morphology.

  3. Desert Dust Layers Over Polluted Marine Boundary Layers: ACE-2 Measurements and ACE-Asia Plans

    NASA Technical Reports Server (NTRS)

    Russell, Philip B.; Schmid, B.; Livingston, J. M.; Redemann, J.; Bergstrom, R. W.; Condon, Estelle P. (Technical Monitor)

    2000-01-01

    Aerosols in ACE-Asia are expected to have some commonalties with those in ACE-2, along with important differences. Among the commonalities are occurrences of desert dust layers over polluted marine boundary layers. Differences include the nature of the dust (yellowish in the East Asia desert outflow, vs. reddish-brown in the Sahara Outflow measured in ACE-2) and the composition of boundary-layer aerosols (e.g., more absorbing, soot and organic aerosol in-the Asian plume, caused by coal and biomass burning, with limited controls). In this paper we present ACE-2 measurements and analyses as a guide to our plans for ACE-2 Asia. The measurements include: (1) Vertical profiles of aerosol optical depth and extinction (380-1558 nm), and of water vapor column and concentration, from the surface through the elevated desert dust, measured by the 14-channel Ames Airborne Tracking Sunphotometer (AATS-14); (2) Comparisons of airborne and shipborne sunphotometer optical depths to satellite-retrieved values, with and without desert dust; (3) Comparisons between airborne Sunphotometer optical depth and extinction spectra and those derived from coincident airborne in situ measurements of aerosol size distribution, scattering and absorption; (4) Comparisons between size distributions measured in situ and retrieved from sunphotometer optical depth spectra; (5) Comparisons between aerosol single scattering albedo values obtained by several techniques, using various combinations of measurements of backscatter, extinction, size distribution, scattering, absorption, and radiative flux. We show how analyses of these data can be used to address questions important to ACE-Asia, such as: (1) How do dust and other absorbing aerosols affect the accuracy of satellite optical depth retrievals? How important are asphericity effects? (2) How important are supermicron dust and seasalt aerosols to overall aerosol optical depth and radiative forcing? How well are these aerosols sampled by aircraft

  4. Lake Life.

    ERIC Educational Resources Information Center

    Ohrn, Deborah Gore, Ed.

    1993-01-01

    This quarterly publication of the State Historical Society of Iowa features articles and activities for elementary school students. This summer issue focuses on the topic of lake life. The issue includes the following features: (1) "Where the Lakes Are Map"; (2) "Letter from the Lake"; (3) "Lake People"; (4) "Spirit Lake"; (5) "Lake Manawa"; (6)…

  5. Chemical characterization of microbial-dominated soil organic matter in the Garwood Valley, Antarctica

    NASA Astrophysics Data System (ADS)

    Feng, Xiaojuan; Simpson, André J.; Gregorich, Edward G.; Elberling, Bo; Hopkins, David W.; Sparrow, Ashley D.; Novis, Philip M.; Greenfield, Lawrence G.; Simpson, Myrna J.

    2010-11-01

    Despite its harsh environmental conditions, terrestrial Antarctica contains a relatively large microbial biomass. Natural abundance carbon and nitrogen stable isotope signatures of organic materials in the dry valleys indicate mixed provenance of the soil organic matter (SOM) with varying proportions of contributions from lichens, mosses, lake-derived algae and cyanobacteria. Here we employed two complementary analytical techniques, biomarker measurements by gas chromatography/mass spectrometry and solution-state 1H nuclear magnetic resonance spectroscopy, to provide further information at a molecular-level about the composition and possible source of SOM in the Garwood Valley, Antarctica. The predominance of branched alkanes and short-chain lipids in the solvent extracts indicates that the primary contribution to the SOM was microbial-derived. Chemical structures in the NaOH extracts from soils were also dominated by amide, peptides, and a CH 3-dominating aliphatic region that were characteristic of microbial signatures. Furthermore, the SOM in the Garwood Valley contained compounds that were different from those in the cyanobacteria-dominated mat from a nearby lake (including monoethyl alkanes and enriched side-chain protons). This observation suggests that easily degradable carbon sources from the nearby lake did not dominate the SOM, which is consistent with a fast turnover of the mat-derived organic matter found in the valley. This study highlights the important role of native soil microbes in the carbon transformation and biogeochemistry in terrestrial Antarctica.

  6. Site-testing in Antarctica

    NASA Astrophysics Data System (ADS)

    Storey, J. W. V.; Lawrence, J. S.; Ashley, M. C. B.

    2007-10-01

    Sites on the Antarctic Plateau such as Dome A, Dome C and South Pole, offer unique and exceptionally favourable conditions for astronomy. Site testing over the past decade has revealed extremely low infrared backgrounds, low water vapour, excellent infrared transmission and very low levels of atmospheric turbulence. Although several large facilities have already been built in Antarctica and plans for many more are well underway, there is still much to learn about this unique and beautiful place.

  7. ACE inhibition in the treatment of children after renal transplantation.

    PubMed

    Arbeiter, Klaus; Pichler, Andrea; Stemberger, Regina; Mueller, Thomas; Ruffingshofer, Dagmar; Vargha, Regina; Balzar, Egon; Aufricht, Christoph

    2004-02-01

    Currently, there are no data available on long-term effects of angiotensin-converting enzyme inhibitors (ACE-I) on graft function in children after renal transplantation. We therefore analyzed all children who were transplanted at our institution between 1989 and 1998 and followed for at least 2 years. Those treated with ACE-I, mainly because of failure of other antihypertensive medications, were compared to those without ACE-I. The ACE-I-treated children ( n=19) showed significantly better blood pressure control during the 1st year of follow-up ( p<0.05). In children with chronic allograft dysfunction ( n=8), treatment with ACE-I stabilized graft function, with improvement in creatinine clearance in 50% ( p<0.01). Serum potassium and hemoglobin levels remained stable. One patient discontinued ACE-I because of renal artery stenosis. Taken together, ACE-I were effective and safe in the treatment of hypertension in children following renal transplantation. Children with chronic allograft dysfunction experienced a stabilizing effect on graft function. PMID:14673630

  8. Geological nature of subglacial Lake Vostok

    NASA Astrophysics Data System (ADS)

    Leitchenkov, G. L.; Masolov, V. N.; Lukin, V. V.; Bulat, S. A.; Kurinin, R. G.; Lipenkov, V. Ya.

    2003-04-01

    Lake Vostok is located at the edge of vast upland of East Antarctic (Precambrian) Crystalline Shield and represents a typical extensionally-induced intracontinental rift zone. Type indicators of rift nature are: width (60-80 km) and length (about 300 km) of the lake depression; several (3-5) kilometers of sediments (modeled from gravity data) infilling the lake graben, considerable amplitudes of faults bounding the lake (up to 2 km in bedrock relief and in excess of 5 km in basement topography), half-graben-like structures (rotated crustal blocks) at flanks of the lake traceable to crustal extension; along-strike segmentation of the depression (the presence of two isolated basins, recognized from seismic and gravity data); knee-shaped spatial configuration of the lake and existence of diagonal fractures (displayed in bedrock topography) normally nascent in conditions of tensional stress. The rift graben of Lake Vostok is considered to be a part (branch) of more spacious rift system, main arm of which stretched from the Prydz Bay trough the Lambert Glacier and the eastern foot of Gamburtsev Mts. to, at least, 110E. This rift system is a result of large-scale extensional event, which occurred in East Antarctica in Late Jurassic - Early Cretaceous prior to East Gondwana break-up. Sedimentary infill of this age is proposed to dominate in Vostok Lake, although postrift, preglacial (Cretaceous - Paleogene) strata can also forms significant part of depositional section. Helium isotopes data give evidence that the Lake Vostok rift is not active. On the other hand, thermophilic bacteria found in accretion ice suggest the possibility of hydrothermal activity in lake bottom. The conduits for warm underwater can be provided by deep crustal faults bordering rift graben. Microseismicity recorded in the area of Lake Vostok suggests the possibility of crustal deformations (likely during more dramatic earthquakes) providing a necessary fault permeability for water seepage from

  9. The solar array is installed on ACE in SAEF-2

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Applied Physics Laboratory engineers and technicians from Johns Hopkins University assist in guiding the Advanced Composition Explorer (ACE) as it is hoisted over a platform for solar array installation in KSC's Spacecraft Assembly and Encapsulation Facility-II. Scheduled for launch on a Delta II rocket from Cape Canaveral Air Station on Aug. 25, ACE will study low-energy particles of solar origin and high-energy galactic particles. The ACE observatory will contribute to the understanding of the formation and evolution of the solar system as well as the astrophysical processes involved. The collecting power of instruments aboard ACE is 10 to 1,000 times greater than anything previously flown to collect similar data by NASA.

  10. The solar array is installed on ACE in SAEF-2

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Applied Physics Laboratory Engineer Cliff Willey (kneeling) and Engineering Assistant Jim Hutcheson from Johns Hopkins University install solar array panels on the Advanced Composition Explorer (ACE) in KSC's Spacecraft Assembly and Encapsulation Facility-II. Scheduled for launch on a Delta II rocket from Cape Canaveral Air Station on Aug. 25, ACE will study low-energy particles of solar origin and high-energy galactic particles for a better understanding of the formation and evolution of the solar system as well as the astrophysical processes involved. The ACE observatory will be placed into an orbit almost a million miles (1.5 million kilometers) away from the Earth, about 1/100 the distance from the Earth to the Sun. The collecting power of instrumentation aboard ACE is at least 100 times more sensitive than anything previously flown to collect similar data by NASA.

  11. Landsat Image Mosaic of Antarctica (LIMA)

    USGS Publications Warehouse

    U.S. Geological Survey

    2007-01-01

    For most of us, Antarctica was at best a distant acquaintance. Now, with the Landsat Image Mosaic of Antarctica (LIMA), we are on intimate terms. In stunning, up-close and personal detail, LIMA brings Antarctica to life. Explore this virtually cloudless, seamless, most geometrically accurate, and highest resolution satellite mosaic of Antarctica. A team of scientists from the U.S. Geological Survey, the British Antarctic Survey, and the National Aeronautics and Space Administration, with funding from the National Science Foundation, created LIMA in support of the International Polar Year (IPY; 2007?08). As the first major scientific outcome of the IPY, LIMA truly fulfills the IPY goals. LIMA is an international effort, supports current scientific polar research, encourages new projects, and helps the general public visualize Antarctica and changes happening in this southernmost environment. Researchers and the general public can download LIMA and all component Landsat scenes at no charge.

  12. Role of homocysteinylation of ACE in endothelial dysfunction of arteries

    PubMed Central

    Huang, An; Pinto, John T.; Froogh, Ghezal; Kandhi, Sharath; Qin, Jun; Wolin, Michael S.; Hintze, Thomas H.

    2014-01-01

    The direct impact of de novo synthesis of homocysteine (Hcy) and its reactive metabolites, Hcy-S-S-Hcy and Hcy thiolactone (HCTL), on vascular function has not been fully elucidated. We hypothesized that Hcy synthesized within endothelial cells affects activity of angiotensin-converting enzyme (ACE) by direct homocysteinylation of its amino- and/or sulfhydryl moieties. This covalent modification enhances ACE reactivity toward angiotensin II (ANG II)-NADPH oxidase-superoxide-dependent endothelial dysfunction. Mesenteric and coronary arteries isolated from normal rats were incubated for 3 days with or without exogenous methionine (Met, 0.1–0.3 mM), a precursor to Hcy. Incubation of arteries in Met-free media resulted in time-dependent decreases in vascular Hcy formation. By contrast, vessels incubated with Met produced Hcy in a dose-dependent manner. There was a notably greater de novo synthesis of Hcy from endothelial than from smooth muscle cells. Enhanced levels of Hcy production significantly impaired shear stress-induced dilation and release of nitric oxide, events that are associated with elevated production of vascular superoxide. Each of these processes was attenuated by ANG II type I receptor blocker or ACE and NADPH oxidase inhibitors. In addition, in vitro exposure of purified ACE to Hcy-S-S-Hcy/HCTL resulted in formation of homocysteinylated ACE and an enhanced ACE activity. The enhanced ACE activity was confirmed in isolated coronary and mesenteric arteries that had been exposed directly to Hcy-S-S-Hcy/HCTL or after Met incubation. In conclusion, vasculature-derived Hcy initiates endothelial dysfunction that, in part, may be mediated by ANG II-dependent activation of NADPH oxidase in association with homocysteinylation of ACE. PMID:25416191

  13. Aerial EM Survey Reveals Groundwater Systems Beneath Taylor Valley, Antarctica

    NASA Astrophysics Data System (ADS)

    Dugan, H.; Mikucki, J.; Auken, E.; Tulaczyk, S. M.; Virginia, R. A.; Schamper, C.; Sørensen, K.; Doran, P. T.; Foley, N.

    2014-12-01

    The extent of groundwater and its potential habitability in the ice-free regions and along the coastal margins of Antarctica is poorly understood. Here we report on an airborne transient electromagnetic survey in Antarctica, which for the first time produced extensive imagery of subsurface resistivity in Taylor Valley, an ice-free margin of the Ross Sea. Wide zones of low subsurface resistivity were detected that are inconsistent with the typical high resistivity of glacier ice or dry permafrost. These results are interpreted as an indication that water, with sufficiently high solute content to remain unfrozen well below 0°C, temperatures considered within the range suitable for microbial life. The inferred subsurface brines are widespread and form two isolated groundwater systems: a near shore system, which extends from the ocean 18 km inland; and a sub-/proglacial system, which emanates from beneath Taylor Glacier into Lake Bonney and is associated with the discharge from Blood Falls. The brine networks in Taylor Valley challenge the notion that groundwater is negligible in regions of continuous permafrost, and signify the potential for a deep biosphere that is hydrologically and geochemically connected to the marine system and subglacial environments.

  14. Potential methane reservoirs beneath Antarctica.

    PubMed

    Wadham, J L; Arndt, S; Tulaczyk, S; Stibal, M; Tranter, M; Telling, J; Lis, G P; Lawson, E; Ridgwell, A; Dubnick, A; Sharp, M J; Anesio, A M; Butler, C E H

    2012-08-30

    Once thought to be devoid of life, the ice-covered parts of Antarctica are now known to be a reservoir of metabolically active microbial cells and organic carbon. The potential for methanogenic archaea to support the degradation of organic carbon to methane beneath the ice, however, has not yet been evaluated. Large sedimentary basins containing marine sequences up to 14 kilometres thick and an estimated 21,000 petagrams (1 Pg equals 10(15) g) of organic carbon are buried beneath the Antarctic Ice Sheet. No data exist for rates of methanogenesis in sub-Antarctic marine sediments. Here we present experimental data from other subglacial environments that demonstrate the potential for overridden organic matter beneath glacial systems to produce methane. We also numerically simulate the accumulation of methane in Antarctic sedimentary basins using an established one-dimensional hydrate model and show that pressure/temperature conditions favour methane hydrate formation down to sediment depths of about 300 metres in West Antarctica and 700 metres in East Antarctica. Our results demonstrate the potential for methane hydrate accumulation in Antarctic sedimentary basins, where the total inventory depends on rates of organic carbon degradation and conditions at the ice-sheet bed. We calculate that the sub-Antarctic hydrate inventory could be of the same order of magnitude as that of recent estimates made for Arctic permafrost. Our findings suggest that the Antarctic Ice Sheet may be a neglected but important component of the global methane budget, with the potential to act as a positive feedback on climate warming during ice-sheet wastage. PMID:22932387

  15. Climate-active Trace Gases from ACE Satellite Observations

    NASA Astrophysics Data System (ADS)

    Bernath, P. F.; Brown, A.; Harrison, J.; Chipperfield, M.; Boone, C.; Wilson, C.; Walker, K. A.

    2011-12-01

    ACE (also known as SCISAT) is making a comprehensive set of simultaneous measurements of more than 30 trace gases, thin clouds, aerosols and temperature by solar occultation from a satellite in low earth orbit. A high inclination (74 degrees) low earth orbit (650 km) gives ACE coverage of tropical, mid-latitudes and polar regions. A high-resolution (0.02 cm-1) infrared Fourier Transform Spectrometer (FTS) operating from 2 to 13 microns (750-4400 cm-1) is measuring the vertical distribution of trace gases, and the meteorological variables of temperature and pressure. Launched by NASA in August 2003 for a nominal two-year mission, ACE performance remains excellent after 8 years in orbit. Volume mixing ratio (VMR) profiles of sixteen halogenated trace gases are routinely retrieved from ACE-FTS atmospheric spectra: CCl4, CF4, CCl3F (CFC-11), CCl2F2 (CFC-12), C2Cl3F3 (CFC-113), CH3Cl, ClONO2, COF2, COCl2, COClF, CHF2Cl (HCFC-22), CH3CCl2F (HCFC-141b), CH3CClF2 (HCFC-142b), HCl, HF and SF6. ACE also provides VMR profiles for CH4, N2O and OCS; HCFC-23 (CHF3) is a recent research product. ACE-FTS measurements were compared to surface measurements made by the AGAGE network and output from the SLIMCAT three-dimensional (3-D) chemical transport model, which is constrained by similar surface data. ACE-FTS measurements of CFCs (and HCl) show declining trends which agree with both AGAGE and SLIMCAT values. The concentrations of HCFCs are increasing with ACE-FTS, SLIMCAT and AGAGE all showing positive trends. These results illustrate the success of the Montreal Protocol in reducing ozone depleting substances. The replacement of CFCs with HCFCs has led to an increase in the VMR of HF in the stratosphere. As chlorine containing compounds continue to be phased out and replaced by fluorine-containing molecules, it is likely that total atmospheric fluorine will continue increasing in the near future. These species are all powerful greenhouse gases. ACE provides near global VMR

  16. Unveiling subglacial geology and crustal architecture in the Recovery frontier of East Antarctica with recent aeromagnetic and airborne gravity imaging

    NASA Astrophysics Data System (ADS)

    Ferraccioli, F.; Forsberg, R.; Jordan, T. A.; Matsuoka, K.; Olsen, A.; King, O.; Ghidella, M.

    2014-12-01

    East Antarctica is the least known continent, despite being a keystone in the Gondwana, Rodinia and Columbia supercontinents. Significant progress has been made in recent years in exploring East Antarctica using aeromagnetic and airborne gravity together with radar. Major aerogeophysical campaigns over the Wilkes Subglacial Basin (Ferraccioli et al., 2009 Tectonophysics), the Aurora Subglacial Basin (Aitken et al., 2014 GRL) and the Gamburtsev Subglacial Mountains (Ferraccioli et al., 2011, Nature) provide new glimpses into the crustal architecture of East Antarctica. However, a major sector of the continent that includes key piercing points for reconstructing linkages between East Antarctica and Laurentia within Rodinia, and also the inferred remnants of a major suture zone active during Gondwana amalgamation in Pan-African times (ca 500 Ma), has remained largely terra incognita. Here we present the results of a major aerogeophysical survey flown over this sector of East Antarctica, named the Recovery Frontier, from the major ice stream flowing in the region. The survey was flown during the IceGRAV 2012-13 field season, as part of a Danish-Norwegian-UK and Argentine collaboration and led to the collection of 29,000 line km of radar, laser altimetry, gravity and magnetic data. We present the new aeromagnetic anomaly, Bouguer and residual and enhanced anomaly maps for the region. Using these images we trace the extent of major subglacial faults and interpret these to delineate the tectonic boundaries separating the Coast block, the Shackleton Range and the Dronning Maud Land crustal provinces. Forward magnetic and gravity modelling enables us to examine the inferred Pan-African age suture zone in the Shackleton Range and address its tectonic relationships with older terranes of the Mawson Craton and Grenvillian-age terranes of Dronning Maud Land and interior East Antarctica. Finally, we present new models to test our hypothesis that Paleozoic to Mesozoic rift basins

  17. Tectonic structure of East Antarctica

    NASA Astrophysics Data System (ADS)

    Leychenkov, German; Grikurov, Garrik; Golynsky, Alexander

    2013-04-01

    First overviews of tectonic structure of the Southern Continent were made by the pioneers of Antarctic earth science investigations almost 100 years ago. Despite rapidly advancing international geological studies under the Antarctic Treaty, the presentations of Antarctic tectonic structure remained largely speculative until the end of the past century when implementation of modern analytical and remote-sensing research technologies enabled compilation of more credible tectonic models of Antarctica. The East Antarctic bedrock consists mainly of the Precambrian crystalline complexes and the Paleozoic-Early Mesozoic platform units. Crystalline Shield is locally complicated by Neoproterozoic aulacogenes and Late Paleozoic to Mesozoic rifts. Shield assemblages reliably recognized in coastal outcrops indicate the predominant occurrence of Archean cratonic nuclei and Mesoproterozoic mobile belts. The undisturbed platform cover strata are exposed in East Antarctica mainly along its boundary with West Antarctica. Tectonic structure of ice-covered regions (more that 99% of the East Antarctic territory) is interpreted using mostly magnetic and bedrock topography data, but other geophysical and geological information (satellite, airborne and over-ice gravity; seismology; active seismics; erratics; detrital zircons dates; etc.) is also important. Archean cratons are geologically documented in western Dronning Maud Land, Enderby Land, Princess Elizabeth Land and in the southern Prince Charles Mts. Their distribution under the ice is marked by a specific magnetic pattern including low-amplitude mosaic and/or high-amplitude long-wavelength anomalies. The most extensive ancient craton being 1000 km across is believed to extend from the southern Prince Charles Mts. to the Gamburtsev Mts. Mesoproterozoic mobile belts are distinguished by elongated high-amplitude magnetic anomalies and are mapped along the costal area as the zone of 250-600 km wide. The Gamburtsev Mts. area is also

  18. ACE inhibitor potentiation of bradykinin-induced venoconstriction

    PubMed Central

    Hecker, Markus; Blaukat, Andree; Bara, Agnieszka T; Müller-Esterl, Werner; Busse, Rudi

    1997-01-01

    Angiotensin-converting enzyme (ACE) inhibitors exert their cardiovascular effects not only by preventing the formation of angiotensin II (AII), but also by promoting the accumulation of bradykinin in or at the vessel wall. In addition, certain ACE inhibitors have been shown to augment the vasodilator response to bradykinin, presumably by an interaction at the level of the B2 receptor. We have investigated whether this is a specific effect of the ACE inhibitor class of compounds in isolated endothelium-denuded segments of the rabbit jugular vein where bradykinin elicits a constrictor response which is exclusively mediated by activation of the B2 receptor. Moexiprilat and ramiprilat (⩽ 3 nM) enhanced the constrictor response to bradykinin three to four fold. Captopril and enalaprilat were less active by approximately one and quinaprilat by two orders of magnitude. Moexiprilat and ramiprilat, on the other hand, had no effect on the constrictor response to AII or the dilator response to acetylcholine. The bradykinin-potentiating effect of the ACE inhibitors was not mimicked by inhibitors of amino-, carboxy-, metallo- or serine peptidases or the synthetic ACE substrate, hippuryl-L-histidyl-L-leucine, at a concentration which almost abolished the residual ACE activity in the vessel wall. In contrast, angiotensin-(1–7) (10 μM), an angiotensin I metabolite, significantly enhanced the constrictor response to bradykinin. Ramiprilat did not alter the binding of [3H]-bradykinin to a membrane fraction prepared from endothelium-denuded rabbit jugular veins or to cultured fibroblasts, and there was no ACE inhibitor-sensitive, bradykinin-induced cleavage of the B2 receptor in cultured endothelial cells. These findings demonstrate that ACE inhibitors selectively potentiate the B2 receptor-mediated vascular effects of bradykinin. Their relative efficacy appears to be independent of their ACE-inhibiting properties and might be related to differences in molecule structure

  19. Contemplating Synergistic Algorithms for the NASA ACE Mission

    NASA Technical Reports Server (NTRS)

    Mace, Gerald G.; Starr, David O.; Marchand, Roger; Ackerman, Steven A.; Platnick, Steven E.; Fridlind, Ann; Cooper, Steven; Vane, Deborah G.; Stephens, Graeme L.

    2013-01-01

    ACE is a proposed Tier 2 NASA Decadal Survey mission that will focus on clouds, aerosols, and precipitation as well as ocean ecosystems. The primary objective of the clouds component of this mission is to advance our ability to predict changes to the Earth's hydrological cycle and energy balance in response to climate forcings by generating observational constraints on future science questions, especially those associated with the effects of aerosol on clouds and precipitation. ACE will continue and extend the measurement heritage that began with the A-Train and that will continue through Earthcare. ACE planning efforts have identified several data streams that can contribute significantly to characterizing the properties of clouds and precipitation and the physical processes that force these properties. These include dual frequency Doppler radar, high spectral resolution lidar, polarimetric visible imagers, passive microwave and submillimeter wave radiometry. While all these data streams are technologically feasible, their total cost is substantial and likely prohibitive. It is, therefore, necessary to critically evaluate their contributions to the ACE science goals. We have begun developing algorithms to explore this trade space. Specifically, we will describe our early exploratory algorithms that take as input the set of potential ACE-like data streams and evaluate critically to what extent each data stream influences the error in a specific cloud quantity retrieval.

  20. Geoethical approach to mineral activities in Antarctica

    NASA Astrophysics Data System (ADS)

    Talalay, Pavel

    2013-04-01

    Antarctica is the outermost from civilization space continent. From 14.0 million km2 of surface area about 98% of Antarctica is covered by ice that averages at least 1.6 km in thickness. Geologically, the continent is the least explored in the world, and it is almost absolutely unknown what mineral resources Antarctica has as they are buried in rock that is covered by a thick ice sheet. It is thought to have large and valuable mineral deposits under the ice. This is because of what has been found in samples taken from the small areas of rock that are exposed, and also from what has been found in South Africa and South America. Up until 180 million years ago, Antarctica was a part of the Gondwanaland super continent, attached to South America, the Southern part of Africa, India and Australia, these continents then drifted apart until they reached their current positions. This leads to a possibility that Antarctica may also share some of the mineral wealth of these continents. Right now on the ice-free areas of Antarctica iron ore, chromium, copper, gold, nickel, platinum, coal and hydrocarbons have been found. The Protocol on Environmental Protection to the Antarctic Treaty, also known as the Madrid Protocol, was signed in 1991 by the signatories to the Antarctic Treaty and became law in January 1998. The Protocol provides for comprehensive protection of the Antarctic environment and associated ecosystems and includes a ban on all commercial mining for at least fifty years (this is up for review in 2041). Current climate change and melting ice in Polar Regions is opening up new opportunities to exploit mineral and oil resources. Even Antarctica's weather, ice and distance from any industrialized areas mean that mineral extraction would be extremely expensive and also extremely dangerous, the depletion of mineral recourses on the Earth can reverse banning of mining in Antarctica in future. There is no question that any resource exploitation in Antarctica will cause

  1. Wind profiler installed in Antarctica

    NASA Astrophysics Data System (ADS)

    Balsley, B. B.; Carey, J.; Woodman, R. F.; Sarango, M.; Urbina, J.; Rodriguez, R.; Ragaini, E.

    A VHF (50 MHz) wind profiler was installed in Antarctica at the Peruvian Base “Machu Picchu” on King George Island from January 21 to 26. The wind profiler will provide a first look at atmospheric dynamics over the region.The profiler—the first of its kind in Antarctica—is a National Science Foundationsponsored cooperative project of the University of Colorado, the Geophysical Institute of Peru, the University of Piura (Peru), and the Peruvian Navy. This venture was also greatly facilitated by Peru's Comision Nacional de Asuntos Antartidos and Consejo Nacional de Ciencias y Tecnologia, with additional logis tics support provided by the Argentinean Navy and the Uruguayan Air Force.

  2. The seismic noise environment of Antarctica

    DOE PAGESBeta

    Anthony, Robert E.; Aster, Richard C.; Wiens, Douglas; Nyblade, Andrew; Anandakrishnan, Sridhar; Huerta, Audrey; Winberry, J. Paul; Wilson, Terry; Rowe, Charlotte

    2014-11-26

    Seismographic coverage of Antarctica prior to 2007 consisted overwhelmingly of a handful of long running and sporadically deployed transient stations, many of which were principally collocated with scientific research stations. Thus, despite very cold temperatures, sunless winters, challenging logistics, and extreme storms, recent developments in polar instrumentation driven by new scientific objectives have opened up the entirety of Antarctica to year–round and continuous seismological observation (e.g., Nyblade et al., 2012).

  3. Advanced Colloids Experiment (ACE) Science Overview

    NASA Technical Reports Server (NTRS)

    Meyer, William V.; Sicker, Ronald J.; Chiaramonte, Francis P.; Luna, Unique J.; Chaiken, Paul M.; Hollingsworth, Andrew; Secanna, Stefano; Weitz, David; Lu, Peter; Yodh, Arjun; Yunker, Peter; Lohr, Matthew; Gratale, Matthew; Lynch, Matthew; Kodger, Thomas; Piazza, Roberto; Buzzaccaro, Stefano; Cipelletti, Luca; Schall, Peter; Veen, Sandra; Wegdam, Gerhard; Lee, Chand-Soo; Choi, Chang-Hyung; Paul, Anna-Lisa; Ferl, Robert J.; Cohen, Jacob

    2013-01-01

    accessible with the availability of the Light Microscopy Module (LMM) on ISS. To meet these goals, the ACE experiment is being built-up in stages, with the availability of confocal microscopy being the ultimate objective. Supported by NASAs Physical Sciences Research Program, ESAESTEC, and the authors respective governments.

  4. Radio-echo sounding of 'active' Antarctic subglacial lakes

    NASA Astrophysics Data System (ADS)

    Siegert, M. J.; Ross, N.; Blankenship, D. D.; Young, D. A.; Greenbaum, J. S.; Richter, T.; Rippin, D. M.; Le Brocq, A. M.; Wright, A.; Bingham, R.; Corr, H.; Ferraccioli, F.; Jordan, T. A.; Smith, B. E.; Payne, A. J.; Dowdeswell, J. A.; Bamber, J. L.

    2013-12-01

    Repeat-pass satellite altimetry has revealed 124 discrete surface height changes across the Antarctic Ice Sheet, interpreted to be caused by subglacial lake discharges (surface lowering) and inputs (surface uplift). Few of these active lakes have been confirmed by radio-echo sounding (RES) despite several attempts, however. Over the last 5 years, major geophysical campaigns have acquired RES data from several 'active' lake sites, including the US-UK-Australian ICECAP programme in East Antactica and the UK survey of the Institute Ice Stream in West Antarctica. In the latter case, a targeted RES survey of one 'active' lake was undertaken. RES evidence of the subglacial bed beneath 'active' lakes in both East and West Antarctica will be presented, and the evidence for pooled subglacial water from these data will be assessed. Based on this assessment, the nature of 'active' subglacial lakes, and their associated hydrology and relationship with surrounding topography will be discussed, as will the likelihood of further 'active' lakes in Antarctica. Hydraulic potential map of the Byrd Glacier catchment with contours at 5 MPa intervals. Predicted subglacial flowpaths are shown in blue. Subglacial lakes known from previous geophysical surveys are shown as black triangles while the newly discovered 'Three-tier lakes' are shown in dashed black outline. Surface height change features within the Byrd subglacial catchment are shown in outline and are shaded to indicate whether they were rising or falling during the ICESat campaign. Those features are labelled in-line with the numbering system of Smith et al. (J. Glac. 2009).

  5. [Job satisfaction among the professionals of AceS Baixo Vouga II].

    PubMed

    Santana, Silvina; Cerdeira, José

    2011-12-01

    Job satisfaction is a measure of quality of life at work and is related to emotional states. The interest for this theme is increasing and, in the last years, many studies have attempted to demonstrate its relation with professional performance. Primary care professionals are in the first line of the Serviço Nacional de Saúde (SNS). Therefore, it is necessary that they feel satisfaction with their jobs, in order to perform the tasks with the quality required. Several factors seem to have impact in the satisfaction of these professionals, such as payment, promotion, recognition from supervisors and peers, physical conditions at work and available resources, opportunities for personal development, among others. Insatisfaction may lead to absentism and in the limit to job quit. The main objective of this work is to study job satisfaction among the professionals working at the health centers of ACeS Baixo Vouga II, namely, the relationship between job characteristics and job satisfaction and between job characteristics and considering job quit as a serious option. All the professionals working in the four health centers were inquired. Results show that job characteristics are defined by six dimensions: leadership and supervision, task characteristics and autonomy, payment, personal and professional development and promotion, peers and relations inside the organization and work environment. Globally, payment and opportunities for personal and professional development and promotion are perceived at low level by all the professional groups. Results also show that there are differences by gender and professional groups regarding job satisfaction and the will to quit job. Considering the specificity of the tasks performed by these professionals, measures should be taken in order to improve job satisfaction in the Portuguese health centers. PMID:22849951

  6. Lithospheric Structure of East Antarctica: Results From the First Year of the SSCUA Broadband Seismic Deployment

    NASA Astrophysics Data System (ADS)

    Reading, A. M.

    2004-12-01

    Recent geological and geochronological work has changed our concept of the former Gondwana continents surrounding a central Archaean craton, East Antarctica. The revised tectonic framework shows mobile belts and tectonic province boundaries which correlate well with East Antarctica's former neighbours in the supercontinent and trend perpendicular to the present day Antarctic coastline. Constraints are however restricted to those areas where the rock is exposed above the ice. Indirect, geophysical methods are required to map the extent of tectonic provinces in the continental interior and provide information on the deep structure. Following a pilot deployment in 2001/02, a set of 6 remote broadband earthquake recording stations were deployed in the Lambert Glacier region, East Antarctica, from the coast at 65°S deep into the interior to a latitude of 75°S. The aim was to determine the Seismic Structure of the Continent Under Antarctica (SSCUA) using a variety of seismological techniques. The stations were solar-powered and hence shut down during the Antarctic winter to re-commence recording after the return of daylight in the austral spring. After one year, 3 stations were relocated to further test contemporary terrane models of the lithosphere in this region. At the present time (December 2004) recording continues across the deployment with most stations due to be uplifted at the end of the 2004/05 summer season. Results of receiver function inversions for seismic structure beneath the recording stations of the first main deployment are presented. To the west of the Lambert Glacier, the Rayner province extends from Mawson Station to Beaver Lake with a fairly deep Moho at 42 km. To the east, seismic velocity profiles have a different character, showing slower crustal velocities. A province boundary exists between the Reinbolt Hills and the northern Mawson Escarpment where the crust is shallower at 34 km. These results are the first determinations of the seismic

  7. ACE inhibition, ACE2 and angiotensin-(1-7) axis in kidney and cardiac inflammation and fibrosis.

    PubMed

    Simões E Silva, Ana Cristina; Teixeira, Mauro Martins

    2016-05-01

    The Renin Angiotensin System (RAS) is a pivotal physiological regulator of heart and kidney homeostasis, but also plays an important role in the pathophysiology of heart and kidney diseases. Recently, new components of the RAS have been discovered, including angiotensin converting enzyme 2 (ACE2), Angiotensin(Ang)-(1-7), Mas receptor, Ang-(1-9) and Alamandine. These new components of RAS are formed by the hydrolysis of Ang I and Ang II and, in general, counteract the effects of Ang II. In experimental models of heart and renal diseases, Ang-(1-7), Ang-(1-9) and Alamandine produced vasodilation, inhibition of cell growth, anti-thrombotic, anti-inflammatory and anti-fibrotic effects. Recent pharmacological strategies have been proposed to potentiate the effects or to enhance the formation of Ang-(1-7) and Ang-(1-9), including ACE2 activators, Ang-(1-7) in hydroxypropyl β-cyclodextrin, cyclized form of Ang-(1-7) and nonpeptide synthetic Mas receptor agonists. Here, we review the role and effects of ACE2, ACE2 activators, Ang-(1-7) and synthetic Mas receptor agonists in the control of inflammation and fibrosis in cardiovascular and renal diseases and as counter-regulators of the ACE-Ang II-AT1 axis. We briefly comment on the therapeutic potential of the novel members of RAS, Ang-(1-9) and alamandine, and the interactions between classical RAS inhibitors and new players in heart and kidney diseases. PMID:26995300

  8. Improved ACE-FTS observations of carbon tetrachloride (CCl4)

    NASA Astrophysics Data System (ADS)

    Harrison, Jeremy; Chipperfield, Martyn; Boone, Chris; Bernath, Peter

    2016-04-01

    The Atmospheric Chemistry Experiment Fourier transform spectrometer (ACE-FTS), on board the SCISAT satellite, has been recording solar occultation spectra through the Earth's atmosphere since 2004 and continues to take measurements with only minor loss in performance. ACE-FTS time series are available for a range of chlorine 'source' gases, including CCl3F (CFC-11), CCl2F2 (CFC-12), CHF2Cl (HCFC-22), CH3Cl and CCl4. Recently there has been much community interest in carbon tetrachloride (CCl4), a substance regulated by the Montreal Protocol because it leads to the catalytic destruction of stratospheric ozone. Estimated sources and sinks of CCl4 remain inconsistent with observations of its abundance. Satellite observations of CCl4 in the stratosphere are particularly useful in validating stratospheric loss (photolysis) rates; in fact the atmospheric loss of CCl4 is essentially all due to photolysis in the stratosphere. However, the latest ACE-FTS v3.5 CCl4 retrieval is biased high by ˜ 20-30%. A new ACE-FTS retrieval scheme utilising new laboratory spectroscopic measurements of CCl4 and improved microwindow selection has recently been developed. This improves upon the v3.5 retrieval and resolves the issue of the high bias; this new scheme will form the basis for the upcoming v4 processing version of ACE-FTS data. This presentation will outline the improvements made in the retrieval, and a subset of data will be compared with modelled CCl4 distributions from SLIMCAT, a state-of-the-art three-dimensional chemical transport model. The use of ACE-FTS data to evaluate the modelled stratospheric loss rate of CCl4 will also be discussed. The evaluated model, which also includes a treatment of surface soil and ocean sinks, will then be used to quantify current uncertainties in the global budget of CCl4.

  9. Haplotypes extending across ACE are associated with Alzheimer's disease.

    PubMed

    Kehoe, Patrick G; Katzov, Hagit; Feuk, Lars; Bennet, Anna M; Johansson, Boo; Wiman, Björn; de Faire, Ulf; Cairns, Nigel J; Wilcock, Gordon K; Brookes, Anthony J; Blennow, Kaj; Prince, Jonathan A

    2003-04-15

    Numerous genes have been implicated in Alzheimer's disease (AD), but, with the exception of a demonstrated association with the epsilon 4 allele of APOE, findings have not been consistently replicated across populations. One of the most widely studied is the gene for angiotensin I converting enzyme (ACE ). A meta-analysis of published data on a common Alu indel polymorphism in ACE was performed which indicated highly significant association of the insertion allele with AD (OR 1.30; 95% CI 1.19 - 1.41; P=4 x 10(-8)). To further explore the influence of ACE on AD, several single-nucleotide polymorphisms (SNPs) were genotyped in five independent populations represented by over 3100 individuals. Analyses based upon single markers and haplotypes revealed strong evidence of association in case-control models and also in a model examining the influence of variation in ACE upon cerebrospinal fluid levels of amyloid beta42 peptide (Abeta42). The most significant evidence for association with AD was found for an SNP, A-262T, located in the ACE promoter (OR 1.64; 95% CI 1.33 -1.94; P=2 x 10(-5)). Estimates of population attributable risk for the common allele of this SNP suggest that it, or an allele in tight linkage disequilibrium (LD) with it, may contribute to as much as 35% of AD in the general population. Results support a model whereby decreased ACE activity may influence AD susceptibility by a mechanism involving beta-amyloid metabolism. PMID:12668609

  10. Volcano Monitoring with Coda Wave Interferometry at Mount Erebus, Antarctica

    NASA Astrophysics Data System (ADS)

    Gret, A.; Snieder, R.; Aster, R.

    2003-12-01

    Multiply-scattered waves dominate the late seismic coda. Small changes in the medium that would have no detectable influence on the first arrivals can be highly amplified by multiple scattering and readily observed in the coda. We apply coda wave interferometry to monitor subsurface temporal changes at Mount Erebus Volcano, Ross Island, Antarctica. Erebus is one of the few volcanoes known to have an open conduit system hosting a persistent convecting lava lake. Strombolian eruptions, caused by the explosive decompression of large bubbles of exsolved volatiles disrupt the lake itself, which subsequently refills within a few minutes. Because of the recoverability of this system, these eruptions provide a repeatable seismic source of seismic waves for sampling the strongly scattering volcano. Repeating eruption seismograms have been recorded at fixed station sites over several years, and the coda is seen to be highly reproducible over extended periods of time. We find waveform correlation coefficients as high as 0.98 for short-period seismograms recorded up to several days apart. However, in comparing seismograms separated by approximately a month, we note a small decrease in correlation. Furthermore, we see a much larger decorrelation of the waveforms spanning a time period of one or even two years. Coda energy is thus providing information on systematic source and/or subsurface changes.

  11. Performance Enhancement of the Automated Concrete Evaluation System (ACES)

    SciTech Connect

    Baumgart,C.W.; Cave,S.P.; Linder,K.E.

    2002-02-14

    The objective of this proposed research is to improve and expand the detection and analysis capabilities of the automated, concrete evaluation (ACE) system. MoDOT and Honeywell jointly developed this system. The focus of this proposed research will be on the following: Coordination of concrete imaging efforts with other states, Validation and testing of the ACE system on a broad range of concrete samples, and Identification and development of software and hardware enhancements. These enhancements will meet the needs of diverse users in the field of concrete materials, construction, and research.

  12. Defective intestinal amino acid absorption in Ace2 null mice.

    PubMed

    Singer, Dustin; Camargo, Simone M R; Ramadan, Tamara; Schäfer, Matthias; Mariotta, Luca; Herzog, Brigitte; Huggel, Katja; Wolfer, David; Werner, Sabine; Penninger, Josef M; Verrey, François

    2012-09-15

    Mutations in the main intestinal and kidney luminal neutral amino acid transporter B(0)AT1 (Slc6a19) lead to Hartnup disorder, a condition that is characterized by neutral aminoaciduria and in some cases pellagra-like symptoms. These latter symptoms caused by low-niacin are thought to result from defective intestinal absorption of its precursor L-tryptophan. Since Ace2 is necessary for intestinal B(0)AT1 expression, we tested the impact of intestinal B(0)AT1 absence in ace2 null mice. Their weight gain following weaning was decreased, and Na(+)-dependent uptake of B(0)AT1 substrates measured in everted intestinal rings was defective. Additionally, high-affinity Na(+)-dependent transport of L-proline, presumably via SIT1 (Slc6a20), was absent, whereas glucose uptake via SGLT1 (Slc5a1) was not affected. Measurements of small intestine luminal amino acid content following gavage showed that more L-tryptophan than other B(0)AT1 substrates reach the ileum in wild-type mice, which is in line with its known lower apparent affinity. In ace2 null mice, the absorption defect was confirmed by a severalfold increase of L-tryptophan and of other neutral amino acids reaching the ileum lumen. Furthermore, plasma and muscle levels of glycine and L-tryptophan were significantly decreased in ace2 null mice, with other neutral amino acids displaying a similar trend. A low-protein/low-niacin diet challenge led to differential changes in plasma amino acid levels in both wild-type and ace2 null mice, but only in ace2 null mice to a stop in weight gain. Despite the combination of low-niacin with a low-protein diet, plasma niacin concentrations remained normal in ace2 null mice and no pellagra symptoms, such as photosensitive skin rash or ataxia, were observed. In summary, mice lacking Ace2-dependent intestinal amino acid transport display no total niacin deficiency nor clear pellagra symptoms, even under a low-protein and low-niacin diet, despite gross amino acid homeostasis alterations

  13. Chlorine-36 tracing of salinity sources in the Dry Valleys of Victoria Land, Antarctica

    NASA Astrophysics Data System (ADS)

    Carlson, Catherine A.; Phillips, Fred M.; Elmore, David; Bentley, Harold W.

    1990-02-01

    Chlorine-36 was used to trace the origins of salts in six saline lakes in the Dry Valleys of Southern Victoria Land, Antarctica. Characteristic 36Cl signatures were estimated for the various potential chloride sources, which include atmospheric deposition, rock weathering, seawater, and deep ground water. 36Cl /Cl ratios were measured in natural waters and salts from the Dry Valleys. Dilute lake waters (Cl - < 100 mg/l) were found to have 36Cl /Cl ratios in the range 100 × 10 -15 to 1,700 × 10 -15, whereas saline waters (Cl - > 1000 mg/l) had ratios in the range 9 × 10 -15 to 40 × 10 -15. Simple mixing models were employed to quantify the relative contributions of the various chloride sources to Lake Vanda and Don Juan Pond. These results show that Lake Vanda has received its chloride from both deep ground water and the Onyx River. Don Juan Pond has received nearly all its chloride from deep ground water, probably ultimately from rock-water interaction. Deep ground water is the principal source of chloride to the lakes of Wright Valley. However, preliminary data suggest that marine-derived salts or relict sea water may be a significant source of chloride to the lakes of Taylor Valley, implying a possible recent marine invasion that did not affect Wright Valley.

  14. Chlorine-36 tracing of salinity sources in the dry valleys of Victoria land, Antarctica

    SciTech Connect

    Carlson, C.A.; Phillips, F.M. ); Elmore, D. ); Bentley, H.W. )

    1990-02-01

    Chlorine-36 was used to trace the origins of salts in six saline lakes in the Dry Valleys of Southern Victoria Land, Antarctica. Characteristic {sup 36}Cl signatures were estimated for the various potential chloride sources, which include atmospheric deposition, rock weathering, seawater, and deep ground water. {sup 36}Cl/Cl ratios were measured in natural waters and salts from the Dry Valleys. Dilute lake waters (Cl{sup {minus}} < 100 mg/l) were found to have {sup 36}Cl/Cl ratios in the range 100 {times} 10{sup {minus}15} to 1,700 {times} 10{sup {minus}15}, whereas saline waters (Cl{sup {minus}} > 1000 mg/l) had ratios in the range 9 {times} 10{sup {minus}15} to 40 {times} 10{sup {minus}15}. Simple mixing models were employed to quantify the relative contributions of the various chloride sources to Lake Vanda and Don Juan Pond. These results show that Lake Vanda has received its chloride from both deep ground water and the Onyx River. Don Juan Pond has received nearly all its chloride from deep ground water, probably ultimately from rock-water interaction. Deep ground water is the principal sources of chloride to the lakes of Wright Valley. However, preliminary data suggest that marine-derived salts or relict sea water may be a significant sources of chloride to the lakes of Taylor Valley, implying a possible recent marine invasion that did not affect Wright Valley.

  15. Episodic ice velocity fluctuations triggered by a subglacial flood in West Antarctica

    NASA Astrophysics Data System (ADS)

    Siegfried, Matthew R.; Fricker, Helen A.; Carter, Sasha P.; Tulaczyk, Slawek

    2016-03-01

    Height change anomalies in satellite altimeter data have been interpreted as the surface expressions of basal water moving into and out of subglacial lakes. These signals have been mapped throughout Antarctica on timescales of months to years, but only broad connections have been made between active lakes and ice dynamics. We present the first high-frequency observations of ice velocity evolution due to a cascading subglacial lake drainage event, collected over 5 years (2010-2015) using Global Positioning System data on Whillans and Mercer ice streams, West Antarctica. We observed three episodic ice velocity changes over 2 years, where flow speed increased by up to 4%, as well as an 11 month disruption of the tidally modulated stick-slip cycle that dominates regional ice motion. Our observations reveal that basal conditions of an Antarctic ice stream can rapidly evolve and drive a dynamic ice response on subannual timescales, which can bias observations used to infer long-term ice sheet changes.

  16. 77 FR 48527 - National Customs Automation Program (NCAP) Test Concerning Automated Commercial Environment (ACE...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-08-14

    ... Automated Commercial Environment (ACE) Simplified Entry: Modification of Participant Selection Criteria and... (NCAP) test concerning the simplified entry functionality in the Automated Commercial Environment (ACE...) National Customs Automation Program (NCAP) test concerning Automated Commercial Environment...

  17. Angiotensin II regulates ACE and ACE2 in neurons through p38 mitogen-activated protein kinase and extracellular signal-regulated kinase 1/2 signaling

    PubMed Central

    Xiao, Liang; Haack, Karla K. V.

    2013-01-01

    Brain ANG II plays an important role in modulating sympathetic function and homeostasis. The generation and degradation of ANG II are carried out, to a large extent, through the angiotensin-converting enzyme (ACE) and ACE2, respectively. In disease states, such as hypertension and chronic heart failure, central expression of ACE is upregulated and ACE2 is decreased in central sympathoregulatory neurons. In this study, we determined the expression of ACE and ACE2 in response to ANG II in a neuronal cell culture and the subsequent signaling mechanism(s) involved. A mouse catecholaminergic neuronal cell line (CATH.a) was treated with ANG II (30, 100, and 300 nM) for 24 h, and protein expression was determined by Western blot analysis. ANG II induced a significant dose-dependent increase in ACE and decrease in ACE2 mRNA and protein expression in CATH.a neurons. This effect was abolished by pretreatment of the cells with the p38 MAPK inhibitor SB-203580 (10 μM) 30 min before administration of ANG II or the ERK1/2 inhibitor U-0126 (10 μM). These data suggest that ANG II increases ACE and attenuates ACE2 expression in neurons via the ANG II type 1 receptor, p38 MAPK, and ERK1/2 signaling pathways. PMID:23535237

  18. ACES Attitudes: Supervision Competencies and a National Certification Program.

    ERIC Educational Resources Information Center

    Dye, Allen

    A survey was conducted to identify requisite supervisor knowledge and skills and to determine what procedures should be used in establishing a national "approved supervisor" certification program. Subjects surveyed were members of the Association for Counselor Education and Supervision (ACES); all members were invited to participate and some 724…

  19. ACE TECH: The Fourth Year of CTE and Academic Integration

    ERIC Educational Resources Information Center

    Knight, Eileen Quinn; Donahue, John; Knight, Patrick

    2008-01-01

    It only takes an hour or two of roaming the halls of Architecture, Construction and Engineering (ACE) Tech Charter High School to detect an enduring attitude of accomplishment from both the teachers and the students. This atmosphere is intentional. The school, located in Chicago, was created specifically to hone the skills of individuals choosing…

  20. POMB/ACE chemotherapy for mediastinal germ cell tumours.

    PubMed

    Bower, M; Brock, C; Holden, L; Nelstrop, A; Makey, A R; Rustin, G J; Newlands, E S

    1997-05-01

    Mediastinal germ cell tumours (MGCT) are rare and most published series reflect the experiences of individual institutions over many years. Since 1979, we have treated 16 men (12 non-seminomatous germ cell tumours and 4 seminomas) with newly diagnosed primary MGCT with POMB/ACE chemotherapy and elective surgical resection of residual masses. This approach yielded complete remissions in 15/16 (94%) patients. The median follow-up was 6.0 years and no relapses occurred more than 2 years after treatment. The 5 year overall survival in the non-seminomatous germ cell tumours (NSGCT) is 73% (95% confidence interval 43-90%). One patient with NSGCT developed drug-resistant disease and died without achieving remission and 2 patients died of relapsed disease. In addition, 4 patients with bulky and/or metastatic seminoma were treated with POMB/ACE. One died of treatment-related neutropenic sepsis in complete remission and one died of relapsed disease. Finally, 4 patients (2 NSGCT and 2 seminomas) referred at relapse were treated with POMB/ACE and one was successfully salvaged. The combination of POMB/ACE chemotherapy and surgery is effective management for MGCT producing high long-term survival rates. PMID:9291802

  1. The Clothes Line. Airing Equity Challenges for ACE.

    ERIC Educational Resources Information Center

    Whyte, Ann

    1991-01-01

    Along with schooling, technical and further education, and higher education, adult and community education (ACE) forms part of the framework of lifelong education. It makes a major contribution to the social justice performance of postsecondary education by catering to adults who cannot gain access to or succeed in mainstream postsecondary…

  2. Linkages between ACE Vocational Provision and Mainstream VET.

    ERIC Educational Resources Information Center

    Saunders, John

    A study investigated linkages between adult community education (ACE) and mainstream vocational education and training (VET) in Australia, which enable people to move between the two sectors in their pursuit of vocational learning, and the ways in which linkages might be improved or new ones developed. The data from the study were derived from 69…

  3. Yukimarimo at Dome C, Antarctica

    NASA Astrophysics Data System (ADS)

    Petenko, Igor

    2015-04-01

    Natural frostballs called "yukimarimo" were observed at at Dome C, Antarctica, during the winter of 2014. Frostballs have spheroidal or lightly oblate form. Four cases of the yukimarimo were observed in the period April - August. The characteristics concerning their sizes, density, distribution over the surface varied for different cases. The diameters ranged from several millimetres to 120 mm, the density ranged from 15 to 60 kg/m3 . The heaviest one weighted 14 g and had a diameter of ≈90 mm. The initial "material" from which they formed resembles candy floss or fluff. In one case, only the initial stage of the small-yukimarimo formation was observed; the further development was interrupted. The meteorological conditions observed diuring the yukimarimo were not particular. The near-surface temperature varied between -70° and -60°C. Winds favouring to the yukimarimo formation were low, but not less than 2 m/s^1. A two-step mechanism of their formation and development is assumed: 1) at the initial stage, an electrostatic attraction favours the clumping of ice crystals to form some ice mass resembling floss structured in spherical pieces; 2) some pieces of ice floss are rolled by the wind and collect more ice crystals and increase in size like to a tumbleweed. Special comprehensive studies of electrical properties of the frost during the initial stage are necessary. Videos of moving yukimarimo at different stages of their formation are available.

  4. Terra Nova Bay Polynya, Antarctica

    NASA Technical Reports Server (NTRS)

    2007-01-01

    In Terra Nova Bay, off the Scott Coast of Victoria Land, Antarctica, a large pocket of open water persists throughout most of the Southern Hemisphere winter, even while most of the rest of the Antarctic coastline is firmly embraced by the frozen Southern Ocean. This pocket of open water--a polynya--results from exceptionally strong winds that blow downslope from the Trans-Antarctic Mountains. These fierce katabatic winds drive the sea ice eastward. Since the dominant ice drift pattern in the area is northward, the Drygalski Ice Tongue prevents the bay from being re-populated with sea ice. This image of the Terra Nova Bay polynya was captured by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Aqua satellite on October 16, 2007. Sea ice sits over the Ross Sea like a cracked and crumbling windshield. Blue-tinged glaciers flow down from the Trans-Antarctic Mountains. Although glaciers can appear blue because of melt water, they can also get that tint when the wind scours and polishes the ice surface. Given the strength of the katabatic winds along this part of the Antarctic coast, it is likely that the blue color of these glaciers is a result of their having been swept clean of snow. The large image has a spatial resolution (level of detail) of 250 meters per pixel.

  5. Space analogue studies in Antarctica

    NASA Astrophysics Data System (ADS)

    Lugg, D.; Shepanek, M.

    1999-09-01

    Medical research has been carried out on the Australian National Antarctic Research Expeditions (ANARE) for 50 years. As an extension of this program collaborative Australian/United States research on immunology, microbiology, psychology and remote medicine has produced important data and insight on how humans adapt to the stress of extreme isolation, confinement and the harsh environment of Antarctica. An outstanding analogue for the isolation and confinement of space missions (especially planetary outposts), ANARE has been used as an international research platform by Australia and the United States since 1993. Collaborative research has demonstrated a lowered responsiveness of the immune system under the isolation and confinement of Antarctic winter-over; a reduction of almost 50% in T cell proliferation to mltogen phytohaemogglutinin, as well as changes in latent herpesvirus states and the expansion of the polyclonal latent Epstein-Barr virus infected B cell populations. Although no clinically significant disease has been found to result from these immune changes, research is currently assessing the effects of psychological factors on the immune system. This and associated research performed to date and its relevance to both organisations is discussed, and comment made on possible extensions to the program in both medical and other fields.

  6. Space analogue studies in Antarctica

    NASA Technical Reports Server (NTRS)

    Lugg, D.; Shepanek, M.

    1999-01-01

    Medical research has been carried out on the Australian National Antarctic Research Expeditions (ANARE) for 50 years. As an extension of this program collaborative Australian/United States research on immunology, microbiology, psychology and remote medicine has produced important data and insight on how humans adapt to the stress of extreme isolation, confinement and the harsh environment of Antarctica. An outstanding analogue for the isolation and confinement of space missions (especially planetary outposts), ANARE has been used as an international research platform by Australia and the United States since 1993. Collaborative research has demonstrated a lowered responsiveness of the immune system under the isolation and confinement of Antarctic winter-over; a reduction of almost 50% in T cell proliferation to mitogen phytohaemogglutinin, as well as changes in latent herpesvirus states and the expansion of the polyclonal latent Epstein-Barr virus infected B cell populations. Although no clinically significant disease has been found to result from these immune changes, research is currently assessing the effects of psychological factors on the immune system. This and associated research performed to date and its relevance to both organisations is discussed, and comment made on possible extensions to the program in both medical and other fields.

  7. Antarctica: Scientific Journeys from McMurdo to the Pole.

    ERIC Educational Resources Information Center

    Brand, Judith, Ed.

    2002-01-01

    This issue of Exploratorium Magazine focuses on Antarctica. Antarctica has one of the most extreme climates in the world with an untouched environment inviting researchers with great opportunities for study. This issue describes the journey of four Exploratorium staff members to frozen Antarctica. Chapters include: (1) "Life at the Bottom of the…

  8. [Trials with ACE-inhibitors in acute myocardial infarction].

    PubMed

    Dalla Volta, S

    1994-12-01

    In acute myocardial infarction, the results of the trials with ACE-inhibitors have not been always good, in contrast with what has been observed in chronic heart failure. The comparison of these compounds with the placebo has demonstrated lack of reduction of mortality in the study CONSENSUS II, favorable results on the survival as first endpoint and on the secondary endpoints, as reinfarction, heart failure and stroke in the studies SOLVD, AIRE, GISSI 3, ISIS 4, and uncertain (interim report) results in the Chinese study. Nevertheless, the analysis of the recruitment of the patients with acute infarction and the way these patients have been treated seem to be the most important cause of the conflicting results. ACE-inhibitors have proved no efficacy in acute myocardial infarction without signs of left ventricular failure (CONSENSUS II), have worsened the clinical picture and the mortality in patients in shock or with severe heart failure in the acute phase. On the reverse, in presence of mild to moderate left ventricular dysfunction and failure, the use of ACE-inhibitors has been followed by reduction of mortality in the early (AIRE, GISSI 3, ISIS 4), medium term (GISSI 3) and long-term follow-up (up to 4 years in the AIRE study). In parallel with the reduction of the primary endpoint, also secondary endpoints have been favorably influenced by the different ACE-inhibitors. No differences have been observed among the different class of compounds. ACE-inhibitors seem, therefore, to have a clear indication in acute myocardial infarction with mild or moderate signs and symptoms of heart failure. PMID:7634258

  9. Persistent change in cardiac fibroblast physiology after transient ACE inhibition.

    PubMed

    D'Souza, K M; Biwer, L A; Madhavpeddi, L; Ramaiah, P; Shahid, W; Hale, T M

    2015-10-01

    Transient angiotensin-converting enzyme (ACE) inhibition induces persistent changes that protect against future nitric oxide synthase (NOS) inhibitor-induced cardiac fibrosis and inflammation. Given the role of fibroblasts in mediating these effects, the present study investigates whether prior ACE inhibition produced persistent changes in cardiac fibroblast physiology. Adult male spontaneously hypertensive rats (SHRs) were treated with vehicle (C+L) or the ACE inhibitor, enalapril (E+L) for 2 wk followed by a 2-wk washout period and a subsequent 7-day challenge with the NOS inhibitor N(ω)-nitro-l-arginine methyl ester. A third set of untreated SHRs served as controls. At the end of the study period, cardiac fibroblasts were isolated from control, C+L, and E+L left ventricles to assess proliferation rate, collagen expression, and chemokine release in vitro. After 7 days of NOS inhibition, there were areas of myocardial injury but no significant change in collagen deposition in E+L and C+L hearts in vivo. In vitro, cardiac fibroblasts isolated from C+L but not E+L hearts were hyperproliferative, demonstrated increased collagen type I gene expression, and an elevated secretion of the macrophage-recruiting chemokines monocyte chemoattractant protein-1 and granulocyte macrophage-colony stimulating factor. These findings demonstrate that in vivo N(ω)-nitro-l-arginine methyl ester treatment produces phenotypic changes in fibroblasts that persist in vitro. Moreover, this is the first demonstration that transient ACE inhibition can produce a persistent modification of the cardiac fibroblast phenotype to one that is less inflammatory and fibrogenic. It may be that the cardioprotective effects of ACE inhibition are related in part to beneficial changes in cardiac fibroblast physiology. PMID:26371174

  10. Using Black Carbon as a Tracer of Human Impact in the McMurdo Dry Valleys, Antarctica

    NASA Astrophysics Data System (ADS)

    Khan, A. L.; Ding, Y.; Jaffe, R.; McKnight, D. M.

    2013-12-01

    This study focuses on quantifying human impact in the McMurdo Dry Valleys through studying black carbon in the dissolved phase in water. Robust efforts and policies exist to minimize human impact in Antarctica, the most remote and pristine continent. Previous studies have been conducted to quantify various tracers of human impact from McMurdo Station, however, no known studies have looked at Black Carbon, soot particles, or products of in-complete combustion of fossil fuels, in the dissolved phase in the lakes of the Dry Valleys. One might expect the lakes to be completely void of black carbon; however, preliminary samples from Lake Fryxell and Lake Hoare show that some BC is present in the lakes, at approximately 4-6 mg/L, one-third of the concentration of temperate lakes. Potential local sources include field camps, relatively heavy helicopter traffic, especially compared to other regions of the Antarctic, as well as generator use. During the height of the austral summer, the edges of these perennially frozen lakes thaw, enabling wind deposition of debris and particles including black carbon, onto the surface of the water. Long range transport is also potential, though previous studies have shown that few particles have the ability to make it through the strong polar vortex, additionally the southern hemisphere has much less industrial production than the north. Therefore, our assumption is that most of the BC we find in the lakes, could be traced to human impact.

  11. Lake Powell

    Atmospheric Science Data Center

    2014-05-15

    article title:  Lake Powell     View Larger Image ... (14.42 mb)   This true-color image over Lake Powell was acquired by Multi-angle Imaging SpectroRadiometer (MISR) in late March 2000. Lake Powell was formed with the construction of the Glen Canyon Dam in 1963, on the ...

  12. CONNECTICUT LAKES

    EPA Science Inventory

    This is a 1:24,000-scale datalayer of named lakes in Connecticut. It is a polygon Shapefile that includes all lakes that are named on the U.S. Geologicial Survey (USGS) 7½ minute topographic quadrangle maps that cover the State of Connecticut, plus other officially named lakes i...

  13. Lake Eyre

    Atmospheric Science Data Center

    2013-04-16

    ...   View Larger Image Lake Eyre is a large salt lake situated between two deserts in one of Australia's driest regions. ... the effect of sunglint at the nadir camera view angle. Dry, salt encrusted parts of the lake appear bright white or gray. Purple areas have ...

  14. The distribution of basal water between Antarctic subglacial lakes from radar sounding.

    PubMed

    Young, D A; Schroeder, D M; Blankenship, D D; Kempf, Scott D; Quartini, E

    2016-01-28

    Antarctica's subglacial lakes have two end member geophysical expressions: as hydraulically flat, radar reflective regions highlighted in ice surface topography and radar sounding profiles ('definite lakes'), and as localized sites of elevation change identified from repeat elevation observations ('active lakes') that are often found in fast flowing ice streams or enhanced ice flow tributaries. While 'definite lakes' can be identified readily by high bed reflectivity in radar sounding, the identification and characterization of less distinct subglacial lakes and water systems with radar sounding are complicated by variable radio-wave attenuation in the overlying ice. When relying on repeat elevation observations, the relatively short times series and biased distribution of elevation observations, along with the episodic nature of 'active lake' outflow and replenishment, limit our understanding of how water flows under the ice sheet. Using recently developed methods for quantifying the radar scattering behaviour of the basal interface of the ice, we can avoid the problem of attenuation, and observe the plumbing of the subglacial landscape. In West Antarctica's Ross Sea Embayment, we confirm that extensive distributed water systems underlie these ice streams. Distributed water sheets are upstream in the onset regions of fast flow, while canal systems underly downstream regions of fast flow. In East Antarctica, we use specularity analysis to recover substantial hydraulic connectivity extending beyond previous knowledge, connecting the lakes already delineated by traditional radar sounding or surface elevation transients. PMID:26667910

  15. The Landsat Image Mosaic of Antarctica (LIMA): A Cutting-Edge Way for Students and Teachers to Learn about Antarctica

    ERIC Educational Resources Information Center

    Campbell, Brian; Bindschadler, Robert

    2009-01-01

    By studying Antarctica via satellite and through ground-truthing research, we can learn where the ice is melting and why. The Landsat Image Mosaic of Antarctica (LIMA), a new and cutting-edge way for scientists, researchers, educators, students, and the public to look at Antarctica, supports this research and allows for unprecedented views of our…

  16. Oxygen budget of a perennially ice-covered Antarctic lake

    NASA Technical Reports Server (NTRS)

    Wharton, R. A., Jr.; Mckay, C. P.; Simmons, G. M., Jr.; Parker, B. C.

    1986-01-01

    A bulk O2 budget for Lake Hoare, Antarctica, is presented. Five years of seasonal data show the lake to be persistently supersaturated with O2. Oxygen is carried into the lake in glacial meltstreams and is left behind when this water is removed as ice by ablation and sublimation. A diffusive loss of O2 from the lake through the summer moat is suggested. Measured values of the total O2 in the water column indicate that the time scale of O2 turnover is much longer than a year. Based on these results, it is suggested that the amount of O2 in the water does not change significantly throughout the year and that the lake is also supersaturated with N2.

  17. Antarctic lakes (above and beneath the ice sheet): Analogues for Mars

    NASA Technical Reports Server (NTRS)

    Rice, J. W., Jr.

    1992-01-01

    The perennial ice covered lakes of the Antarctic are considered to be excellent analogues to lakes that once existed on Mars. Field studies of ice covered lakes, paleolakes, and polar beaches were conducted in the Bunger Hills Oasis, Eastern Antarctica. These studies are extended to the Dry Valleys, Western Antarctica, and the Arctic. Important distinctions were made between ice covered and non-ice covered bodies of water in terms of the geomorphic signatures produced. The most notable landforms produced by ice covered lakes are ice shoved ridges. These features form discrete segmented ramparts of boulders and sediments pushed up along the shores of lakes and/or seas. Sub-ice lakes have been discovered under the Antarctic ice sheet using radio echo sounding. These lakes occur in regions of low surface slope, low surface accumulations, and low ice velocity, and occupy bedrock hollows. The presence of sub-ice lakes below the Martian polar caps is possible. The discovery of the Antarctic sub-ice lakes raises possibilities concerning Martian lakes and exobiology.

  18. Frictionless Telescopes in Antarctica: Why and How?

    NASA Astrophysics Data System (ADS)

    Quattri, M.

    Seeing quality in Antarctica is in the hundredth arcseconds range out of the boundary layer. To take advantage of this quality telescopes should be in thermal equilibrium with the outside environment and should minimize the non linearity's like limit cycles which will deteriorate tracking. At the ESO Very Large Telescope (VLT) 8m telescopes this is realized using oil bearings and direct drives on the axes to avoid slip stick effects on the motion. In Antarctica this could be realized using magnetic bearings, possibly combined with motors, on the axes, with also advantages concerning power consumptions and maintenance of the system.

  19. Live from Antarctica: Then and now

    NASA Astrophysics Data System (ADS)

    This real-time educational video series, featuring Camille Jennings from Maryland Public Television, includes information from Antarctic scientists and interactive discussion between the scientists and school children from both Maryland and Hawaii. This is part of a 'Passport to Knowledge Special' series. In this part of the four part Antarctic series, the history of Antarctica from its founding to the present, its mammals, plants, and other life forms are shown and discussed. The importance of Antarctica as a research facility is explained, along with different experiments and research that the facilities there perform.

  20. Live from Antarctica: Then and Now

    NASA Technical Reports Server (NTRS)

    1994-01-01

    This real-time educational video series, featuring Camille Jennings from Maryland Public Television, includes information from Antarctic scientists and interactive discussion between the scientists and school children from both Maryland and Hawaii. This is part of a 'Passport to Knowledge Special' series. In this part of the four part Antarctic series, the history of Antarctica from its founding to the present, its mammals, plants, and other life forms are shown and discussed. The importance of Antarctica as a research facility is explained, along with different experiments and research that the facilities there perform.

  1. Acting Antarctica: science on stage

    NASA Astrophysics Data System (ADS)

    Ciceri, Piera; Tizzoni, Paola; Pierro, Luigia

    2016-04-01

    Key-words: Polar science, Earth science, Theatre, Hands on activities The legendary Antarctic Expedition of sir E. Shackleton and his crew of 27 aboard the Endurance (1914/16) trapped in the Antarctic ice has become the starting point to learn about Polar Science and Climate Change. While the students were involved into this incredible adventure by the astonishing images of the Australian photographer Frank Hurley (who joined the crew), they discovered the world in which this story happened. Students were then involved in hands-on activities and role plays and have become the writers of the play "Uomini a scienza ai confini del mondo". They act the story of Shackelton's expedition and they tell at the same time to the audience about ice pack, ice cores and their role in understanding the past of the climate, physical and geographical characteristic of polar regions, thermal phenomena related to adaptations of polar animals, solar radiation at different latitude, day/night duration. The theater was the place to "stage" some scientific experiments and to explain the current research carried out in polar regions and their importance in climate change studies and to stress some similarities between Antarctica and space. The project was carried out from teachers of science, letters and geography and was born in collaboration with the "Piccolo Teatro di Milano" and the association "Science Under 18" with the support of a professional actor and director and was played for other schools at "EXPO 2015" in Milano (Italy). In our opinion drama activities improve reading comprehension, and both verbal and non-verbal communication skills. To be able to write and to act, students need a deep understanding of contents. Arts, including theatre, are a good key to involve emotionally students. To have an audience different from their own teachers and classmates offers a real task and the opportunity to play and let grow real skills.

  2. From gene to protein—experimental and clinical studies of ACE2 in blood pressure control and arterial hypertension

    PubMed Central

    Patel, Sheila K.; Velkoska, Elena; Freeman, Melanie; Wai, Bryan; Lancefield, Terase F.; Burrell, Louise M.

    2014-01-01

    Hypertension is a major risk factor for stroke, coronary events, heart and renal failure, and the renin-angiotensin system (RAS) plays a major role in its pathogenesis. Within the RAS, angiotensin converting enzyme (ACE) converts angiotensin (Ang) I into the vasoconstrictor Ang II. An “alternate” arm of the RAS now exists in which ACE2 counterbalances the effects of the classic RAS through degradation of Ang II, and generation of the vasodilator Ang 1-7. ACE2 is highly expressed in the heart, blood vessels, and kidney. The catalytically active ectodomain of ACE2 undergoes shedding, resulting in ACE2 in the circulation. The ACE2 gene maps to a quantitative trait locus on the X chromosome in three strains of genetically hypertensive rats, suggesting that ACE2 may be a candidate gene for hypertension. It is hypothesized that disruption of tissue ACE/ACE2 balance results in changes in blood pressure, with increased ACE2 expression protecting against increased blood pressure, and ACE2 deficiency contributing to hypertension. Experimental hypertension studies have measured ACE2 in either the heart or kidney and/or plasma, and have reported that deletion or inhibition of ACE2 leads to hypertension, whilst enhancing ACE2 protects against the development of hypertension, hence increasing ACE2 may be a therapeutic option for the management of high blood pressure in man. There have been relatively few studies of ACE2, either at the gene or the circulating level in patients with hypertension. Plasma ACE2 activity is low in healthy subjects, but elevated in patients with cardiovascular risk factors or cardiovascular disease. Genetic studies have investigated ACE2 gene polymorphisms with either hypertension or blood pressure, and have produced largely inconsistent findings. This review discusses the evidence regarding ACE2 in experimental hypertension models and the association between circulating ACE2 activity and ACE2 polymorphisms with blood pressure and arterial

  3. ACE2 Decreases Formation and Severity of Angiotensin II-induced Abdominal Aortic Aneurysms

    PubMed Central

    Thatcher, Sean E.; Zhang, Xuan; Howatt, Deborah A.; Yiannikouris, Frederique; Gurley, Susan B.; Ennis, Terri; Curci, John A.; Daugherty, Alan; Cassis, Lisa A.

    2014-01-01

    Objective Angiotensin converting enzyme 2 (ACE2) cleaves angiotensin II (AngII) to form angiotensin-(1-7) (Ang-(1-7)), which generally opposes effects of AngII. AngII infusion into hypercholesterolemic male mice induces formation of abdominal aortic aneurysms (AAAs). This study tests the hypothesis that deficiency of ACE2 promotes AngII-induced AAAs, while ACE2 activation suppresses aneurysm formation. Approach and Results ACE2 protein was detectable by immunostaining in mice and human AAAs. Whole body deficiency of ACE2 significantly increased aortic lumen diameters and external diameters of suprarenal aortas from AngII-infused mice. Conversely, ACE2 deficiency in bone marrow-derived cells had no effect on AngII-induced AAAs. In contrast to AngII-induced AAAs, ACE2 deficiency had no significant effect on external aortic diameters of elastase-induced AAAs. Since ACE2 deficiency promoted AAA formation in AngII-infused mice, we determined if ACE2 activation suppressed AAAs. ACE2 activation by administration of diminazine aceturate (DIZE, 30 mg/kg/day) to Ldlr−/− mice increased kidney ACE2 mRNA abundance and activity and elevated plasma Ang-(1-7) concentrations. Unexpectedly, administration of DIZE significantly reduced total sera cholesterol and VLDL-cholesterol concentrations. Notably, DIZE significantly decreased aortic lumen diameters and aortic external diameters of AngII-infused mice resulting in a marked reduction in AAA incidence (from 73 to 29%). None of these effects of DIZE were observed in the Ace2−/y mice. Conclusions These results demonstrate that ACE2 exerts a modulatory role in AngII-induced AAA formation, and that therapeutic stimulation of ACE2 could be a benefit to reduce AAA expansion and rupture in patients with an activated renin-angiotensin system. PMID:25301841

  4. A Sled-Mounted Vibroseis Seismic Source for Geological Studies in Antarctica

    NASA Astrophysics Data System (ADS)

    Speece, M. A.; Luyendyk, B. P.; Harwood, D. M.; Powell, R. D.; Wilson, D. S.; Pekar, S. F.; Tulaczyk, S. M.; Rack, F. R.

    2013-12-01

    Given the success of recent vibrator seismic source (vibroseis) tests in Antarctica, we propose the purchase of a large vibroseis for dedicated use by United States Antarctic Program (USAP) projects in Antarctica. Long seismic reflection profiles across Antarctica can be accomplished efficiently by pulling a sled-mounted vibrator that in turn pulls a snow streamer of gimbaled geophones. A baseplate or pad in the center of the sled will be lowered to the ground and support most of the weight of the vibrator assembly while an actuator vibrates the ground at each source location. The vibroseis will be moved to remote locations using over-ice/snow traverses given the increased reliance on traversing for supplying remote sites in Antarctica. Total vibrator hold-down weight when fully assembled will be ~66,000 lbs. Other design features include a 475 HP Caterpillar C15 diesel engine for the hydraulic power unit. The new vibrator will use an INOVA P-wave vibrator system: new Model PLS-362 actuator with up to 60,000 lbs of peak force and frequency limit of 5 Hz to 250Hz. Antarctic research objectives that could be impacted by the use of a vibrator include: (1) mapping of sub-ice stratigraphic sequences for drilling for paleoclimate information, e.g. the deep sedimentary basins of West Antarctica (Ross and Ronne-Filchner Ice Shelves and related divides); (2) correlating offshore and onshore seismic data and complementing airborne geophysical surveys to help determine Antarctica's geologic history; (3) identifying ice-bedrock interface properties and exploring grounding-line processes for ice dynamics; (4) exploring subglacial lakes and water-routing systems; and, (5) investigating the physical properties of ice sheets. An Antarctic Vibroseis Advisory Committee (AVAC) will promote the use of the vibroseis capability among Antarctic geophysical, geological, glaciological and related scientists and groups by encouraging and facilitating the development and submission of

  5. A comparative Study of Circulation Patterns at Active Lava Lakes

    NASA Astrophysics Data System (ADS)

    Lev, Einat; Oppenheimer, Clive; Spampinato, Letizia; Hernandez, Pedro; Unglert, Kathi

    2016-04-01

    Lava lakes present a rare opportunity to study magma dynamics in a large scaled-up "crucible" and provide a unique natural laboratory to ground-truth dynamic models of magma circulation. The persistence of lava lakes allows for long-term observations of flow dynamics and of lava properties, especially compared to surface lava flows. There are currently five persistent lava lakes in the world: Halemaumau in Kilauea (Hawaii, USA), Erta Ale (Ethiopia), Nyiragongo (Congo), Erebus (Antarctica), and Villarica (Chile). Marum and Benbow craters of Ambrym volcano (Vanuatu) and Masaya (Nicaragua) have often hosted lava lakes as well. We use visible-light and thermal infrared time-lapse and video footage collected at all above lakes (except Villarica, where the lake is difficult to observe), and compare the circulation patterns recorded. We calculate lake surface motion from the footage using the optical flow method (Lev et al., 2012) to produce 2D velocity fields. We mined both the surface temperature field and the surface velocity field for patterns using machine learning techniques such as "self-organizing maps (SOMs)" and "principle component analysis (PCA)". We use automatic detection technique to study the configuration of crustal plates at the lakes' surface. We find striking differences among the lakes, in flow direction, flow speed, frequency of changes in flow direction and speed, location and consistency of upwelling and downwelling, and crustal plate configuration. We relate the differences to lake size, shallow conduit geometry, lava viscosity, crystal and gas content, and crust integrity.

  6. Parallel Signal Processing and System Simulation using aCe

    NASA Technical Reports Server (NTRS)

    Dorband, John E.; Aburdene, Maurice F.

    2003-01-01

    Recently, networked and cluster computation have become very popular for both signal processing and system simulation. A new language is ideally suited for parallel signal processing applications and system simulation since it allows the programmer to explicitly express the computations that can be performed concurrently. In addition, the new C based parallel language (ace C) for architecture-adaptive programming allows programmers to implement algorithms and system simulation applications on parallel architectures by providing them with the assurance that future parallel architectures will be able to run their applications with a minimum of modification. In this paper, we will focus on some fundamental features of ace C and present a signal processing application (FFT).

  7. ACE infrared spectral atlases of the Earth's atmosphere

    NASA Astrophysics Data System (ADS)

    Hughes, Ryan; Bernath, Peter; Boone, Chris

    2014-11-01

    Five infrared atmospheric atlases are presented using solar occultation spectra from the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) in low earth orbit. The spectral atlases were created for Arctic summer, Arctic winter, mid-latitude summer, mid-latitude winter and the tropics. Each covers the spectral range from 700 to 4400 cm-1 and consists of 31 spectra that span an altitude range of 6-126 km in 4-km altitude intervals. To improve the signal-to-noise ratio, each spectrum in the atlas is an average of at least several hundred individual ACE-FTS limb transmission spectra. Representative plots in pdf format at 10 km (troposphere), 30 km (stratosphere), 70 km (mesosphere), and 110 km (lower thermosphere) are also available.

  8. Phylotype diversity in a benthic cyanobacterial mat community on King George Island, maritime Antarctica.

    PubMed

    Callejas, Cecilia; Gill, Paul R; Catalán, Ana I; Azziz, Gastón; Castro-Sowinski, Susana; Batista, Silvia

    2011-06-01

    Cyanobacterial 16S ribosomal RNA gene diversity was examined in a benthic mat on Fildes Peninsula of King George Island (62º09'54.4''S, 58º57'20.9''W), maritime Antarctica. Environmental DNA was isolated from the mat, a clone library of PCR-amplified 16S rRNA gene fragments was prepared, and amplified ribosomal DNA restriction analysis (ARDRA) was done to assign clones to seven groups. Low cyanobacterial diversity in the mat was suggested in that 83% of the clones were represented by one ARDRA group. DNA sequences from this group had high similarity with 16S rRNA genes of Tychonema bourrellyi and T. bornetii isolates, whose geographic origins were southern Norway and Northern Ireland. Cyanobacterial morphotypes corresponding to Tychonema have not been reported in Antarctica, however, this morphotype was previously found at Ward Hunt Lake (83ºN), and in western Europe (52ºN). DNA sequences of three of the ARDRA groups had highest similarity with 16S rDNA sequences of the Tychonema group accounting for 9.4% of the clones. Sequences of the remaining three groups (7.6%) had highest similarity with 16S rRNA genes of uncultured cyanobacteria clones from benthic mats of Lake Fryxell and fresh meltwater on the McMurdo Ice Shelf. PMID:25187150

  9. Antarctica--the Ultimate Summer Institute.

    ERIC Educational Resources Information Center

    Van Wey, Nate J.

    1995-01-01

    Describes personal experiences of a participant in the National Science Foundation program, Teachers Experiencing Antarctica. Uses the study of the temperature history of Taylor Dome to provide teachers with the experience of research and help other teachers recognize that there are opportunities outside the classroom for personal and professional…

  10. Antarctica: What Shall We Do with It?

    ERIC Educational Resources Information Center

    Branson, Margaret S.; Long, Cathryn J.

    1977-01-01

    Describes a role playing exercise in which students act as delegates to a meeting at which they will revise the Antarctic Treaty. Background information is presented about Antarctica, the Antarctic Treaty, and positions of 19 nations with regard to the Treaty. (Author/DB)

  11. CyberHunt: Head Off to Antarctica.

    ERIC Educational Resources Information Center

    Kloza, Brad

    2001-01-01

    Explains how to take an elementary class on a cyber visit to the continent of Antarctica, the highest, driest, and coldest continent on earth. A student reproducible page presents eight web sites to visit in this quest as well as questions to answer about each site. Answers to the questions are included. (SM)

  12. Read--and Walk--to Antarctica

    ERIC Educational Resources Information Center

    Harr, Natalie; Doneyko, Kathleen; Lee, Richard E., Jr.

    2012-01-01

    The students at Crestwood Primary School proved that they have what it takes to exercise their bodies and their minds. In an effort to support their teacher's scientific expedition to Antarctica, students from kindergarten to second grade pledged to read books and do physical activity that equated to the 12,900 km (8,000-mile) journey to the…

  13. Lystrosaurus zone (triassic) fauna from antarctica.

    PubMed

    Kitching, J W; Collinson, J W; Elliot, D H; Colbert, E H

    1972-02-01

    Tetrapod skeletons recently found in the Fremouw Formation in the Shackleton Glacier area, Transantarctic Mountains, include several forms that closely compare to South African species. Faunal similarities that confirm a close connection between Antarctica and Africa during the Triassic Period lend further support to the concept of Gondwanaland and continental drift. PMID:17755654

  14. Antarctica: Is It More Than Just Ice?

    ERIC Educational Resources Information Center

    Johnson, Cheryl; Gutierrez, Melida

    2009-01-01

    The authors introduced polar science in a fourth-grade classroom by means of 3 hands-on activities that addressed (1) the melting of glaciers and ice, (2) the differences between the North and the South Pole, and (3) the geography and landforms of Antarctica. An assessment 4 months after the original activity showed that students remembered the…

  15. ACES: An Enabling Technology for Next Generation Space Transportation

    NASA Astrophysics Data System (ADS)

    Crocker, Andrew M.; Wuerl, Adam M.; Andrews, Jason E.; Andrews, Dana G.

    2004-02-01

    Andrews Space has developed the ``Alchemist'' Air Collection and Enrichment System (ACES), a dual-mode propulsion system that enables safe, economical launch systems that take off and land horizontally. Alchemist generates liquid oxygen through separation of atmospheric air using the refrigeration capacity of liquid hydrogen. The key benefit of Alchemist is that it minimizes vehicle takeoff weight. All internal and NASA-funded activities have shown that ACES, previously proposed for hypersonic combined cycle RLVs, is a higher payoff, lower-risk technology if LOX generation is performed while the vehicle cruises subsonically. Andrews Space has developed the Alchemist concept from a small system study to viable Next Generation launch system technology, conducting not only feasibility studies but also related hardware tests, and it has planned a detailed risk reduction program which employs an experienced, proven contractor team. Andrews also has participated in preliminary studies of an evolvable Next Generation vehicle architecture-enabled by Alchemist ACES-which could meet civil, military, and commercial space requirements within two decades.

  16. ACE-FTS instrument: activities in preparation for launch

    NASA Astrophysics Data System (ADS)

    Soucy, Marc-Andre; Walker, Kaley A.; Fortin, Serge; Deutsch, Christophe

    2003-11-01

    The Atmospheric Chemistry Experiment (ACE) is the mission selected by the Canadian Space Agency for its next science satellite, SCISAT-1. ACE consists of a suite of instruments in which the primary element is an infrared Fourier Transform Spectrometer (FTS) coupled with an auxiliary 2-channel visible (525 nm) and near infrared imager (1020 nm). A secondary instrument, MAESTRO, provides spectrographic data from the near ultra-violet to the near infrared, including the visible spectral range. In combination the instrument payload covers the spectral range from 0.25 to 13.3 micron. A comprehensive set of simultaneous measurements of trace gases, thin clouds, aerosols and temperature will be made by solar occultation from a satellite in low earth orbit. The ACE mission will measure and analyse the chemical and dynamical processes that control the distribution of ozone in the upper troposphere and stratosphere. A high inclination (74 degrees), low earth orbit (650 km) allows coverage of tropical, mid-latitude and polar regions. This paper presents the instrument-related activities in preparation for launch. In particular, activities related to the integration of instrument to spacecraft are presented as well as tests of the instrument on-board the SciSat-1 bus. Environmental qualification activities at spacecraft-level are described. An overview of the characterization and calibration campaign is presented. Activities for integration and verification at launch site are also covered. The latest status of the spacecraft is also presented.

  17. Effect of ace inhibitors and TMOF on growth, development, and trypsin activity of larval Spodoptera littoralis.

    PubMed

    Lemeire, Els; Borovsky, Dov; Van Camp, John; Smagghe, Guy

    2008-12-01

    Angiotensin converting enzyme (ACE) is a zinc metallopeptidase capable of cleaving dipeptide or dipeptideamide moieties at the C-terminal end of peptides. ACE is present in the hemolymph and reproductive tissues of insects. The presence of ACE in the hemolymph and its broad substrate specificity suggests an important role in processing of bioactive peptides. This study reports the effects of ACE inhibitors on larval growth in the cotton leafworm Spodoptera littoralis. Feeding ACE inhibitors ad lib decreased the growth rate, inhibited ACE activity in the larval hemolymph, and down-regulated trypsin activity in the larval gut. These results indicate that S. littoralis ACE may influence trypsin biosynthesis in the larval gut by interacting with a trypsin-modulating oostatic factor (TMOF). Injecting third instar larvae with a combination of Aea-TMOF and the ACE inhibitor captopril, down-regulated trypsin biosynthesis in the larval gut indicating that an Aea-TMOF gut receptor analogue could be present. Injecting captopril and enalapril into newly molted fifth instar larvae stopped larval feeding and decreased weight gain. Together, these results indicate that ACE inhibitors are efficacious in stunting larval growth and ACE plays an important role in larval growth and development. PMID:18949805

  18. Real-Time Data Received from Mount Erebus Volcano, Antarctica

    NASA Astrophysics Data System (ADS)

    Aster, Richard; McIntosh, William; Kyle, Philip; Esser, Richard; Bartel, Beth Ann; Dunbar, Nelia; Johns, Bjorn; Johnson, Jeffrey B.; Karstens, Richard; Kurnik, Chuck; McGowan, Murray; McNamara, Sara; Meertens, Chuck; Pauley, Bruce; Richmond, Matt; Ruiz, Mario

    2004-03-01

    Internal and eruptive volcano processes involve complex interactions of multi-phase fluids with the solid Earth and the atmosphere, and produce diverse geochemical, visible, thermal, elastic, and anelastic effects. Multidisciplinary experimental agendas are increasingly being employed to meet the challenge of understanding active volcanoes and their hazards [e.g., Ripepe et al., 2002; Wallace et al., 2003]. Mount Erebus is a large (3794 m) stratovolcano that forms the centerpiece of Ross Island, Antarctica, the site of the principal U.S. (McMurdo) and New Zealand (Scott) Antarctic bases. With an elevation of 3794 m and a volume of ~1670 km3, Erebus offers exceptional opportunities for extended study of volcano processes because of its persistent, low-level, strombolian activity (Volcano Explosivity Index 0-1) and exposed summit magma reservoir (manifested as a long-lived phonolitic lava lake). Key scientific questions include linking conduit processes to near-field deformations [e.g., Aster et al., 2003], explosion physics [e.g., Johnson et al., 2003], magmatic differentiation and residence [e.g., Kyle et al., 1992], and effects on Antarctic atmospheric and ice geochemistry [e.g., Zreda-Gostynska et al., 1997]. The close proximity of Erebus (35 km) to McMurdo, and its characteristic dry, windy, cold, and high-elevation Antarctic environment, make the volcano a convenient test bed for the general development of volcano surveillance and other instrumentation under extreme conditions.

  19. Multiple meteoroid impact in Antarctica

    NASA Astrophysics Data System (ADS)

    Weihoupt, J. W.; Rice, A.; van der Hoeven, F.

    2006-12-01

    In the late 1950's, geophysical field parties undertaking gravity surveys across Antarctica observed over a large area of Wilkes Land (> 240km across) an exceptionally pronounced negative free air anomaly ((to -158.3 mgal). This area was later interpreted as a possible meteor impact site because the gravity profiles were similar to those of known impact sites (apparent rim structures, circular basins, central peaks or rings), they possessed appropriate aspect ratios (e.g., crater diameter vs crater depth), anomalously steep negative free air gravity anomaly gradients (to 4.71 mgal/km) were characteristic of impact craters and uncharacteristic of solely mantle-related or geologic crustal variations, etc. The condition of the ice covering the anomaly (heavily crevassed), the apparent lack of isostatic compensation with surrounding environs, etc suggested the impact was geologically recent and that perhaps a tektite strewn field was associated with it. The distance from the postulated impact to the Australian strewn field was appropriate as are the ages of the tektites there. This early work has been augmented with the detection of a dominant cluster of negative free air gravity anomalies crossing the continental-oceanic boundary, and the East and West Antarctic structural boundary (i.e., Transantarctic Mountains). These anomalies are coincident with complex subglacial craterform topographic features inferred from radiosounding (to -500m below MSL). The major interior positive free air gravity anomalies are associated with subglacial topographic highs. The elliptical distribution of the negative gravity anomalies resemble known multiple impact distributions (scatter ellipses with the larger anomalies forward and the lesser ones aft). This more recent information favors expanding the original proposal to that of a multiple meteoroid impact. The multiple impact hypotheses would explain aeromagnetic surveys revealing ring-shaped structures in the subglacial rock surface

  20. Extension of the ACE solar panels is tested in SAEF-II

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Extension of the solar panels is tested on the Advanced Composition Explorer (ACE) spacecraft in KSC's Spacecraft Assembly and Encapsulation Facility-II (SAEF-II). Scheduled for launch on a Delta II rocket from Cape Canaveral Air Station on Aug. 25, ACE will study low-energy particles of solar origin and high-energy galactic particles. The collecting power of instruments aboard ACE is 10 to 1,000 times greater than anything previously flown to collect similar data by NASA.

  1. The Pharmacogenetic Footprint of ACE Inhibition: A Population-Based Metabolomics Study.

    PubMed

    Altmaier, Elisabeth; Menni, Cristina; Heier, Margit; Meisinger, Christa; Thorand, Barbara; Quell, Jan; Kobl, Michael; Römisch-Margl, Werner; Valdes, Ana M; Mangino, Massimo; Waldenberger, Melanie; Strauch, Konstantin; Illig, Thomas; Adamski, Jerzy; Spector, Tim; Gieger, Christian; Suhre, Karsten; Kastenmüller, Gabi

    2016-01-01

    Angiotensin-I-converting enzyme (ACE) inhibitors are an important class of antihypertensives whose action on the human organism is still not fully understood. Although it is known that ACE especially cleaves COOH-terminal dipeptides from active polypeptides, the whole range of substrates and products is still unknown. When analyzing the action of ACE inhibitors, effects of genetic variation on metabolism need to be considered since genetic variance in the ACE gene locus was found to be associated with ACE-concentration in blood as well as with changes in the metabolic profiles of a general population. To investigate the interactions between genetic variance at the ACE-locus and the influence of ACE-therapy on the metabolic status we analyzed 517 metabolites in 1,361 participants from the KORA F4 study. We replicated our results in 1,964 individuals from TwinsUK. We observed differences in the concentration of five dipeptides and three ratios of di- and oligopeptides between ACE inhibitor users and non-users that were genotype dependent. Such changes in the concentration affected major homozygotes, and to a lesser extent heterozygotes, while minor homozygotes showed no or only small changes in the metabolite status. Two of these resulting dipeptides, namely aspartylphenylalanine and phenylalanylserine, showed significant associations with blood pressure which qualifies them-and perhaps also the other dipeptides-as readouts of ACE-activity. Since so far ACE activity measurement is substrate specific due to the usage of only one oligopeptide, taking several dipeptides as potential products of ACE into account may provide a broader picture of the ACE activity. PMID:27120469

  2. The Pharmacogenetic Footprint of ACE Inhibition: A Population-Based Metabolomics Study

    PubMed Central

    Altmaier, Elisabeth; Menni, Cristina; Heier, Margit; Meisinger, Christa; Thorand, Barbara; Quell, Jan; Kobl, Michael; Römisch-Margl, Werner; Valdes, Ana M.; Mangino, Massimo; Waldenberger, Melanie; Strauch, Konstantin; Illig, Thomas; Adamski, Jerzy; Spector, Tim; Gieger, Christian; Suhre, Karsten; Kastenmüller, Gabi

    2016-01-01

    Angiotensin-I-converting enzyme (ACE) inhibitors are an important class of antihypertensives whose action on the human organism is still not fully understood. Although it is known that ACE especially cleaves COOH-terminal dipeptides from active polypeptides, the whole range of substrates and products is still unknown. When analyzing the action of ACE inhibitors, effects of genetic variation on metabolism need to be considered since genetic variance in the ACE gene locus was found to be associated with ACE-concentration in blood as well as with changes in the metabolic profiles of a general population. To investigate the interactions between genetic variance at the ACE-locus and the influence of ACE-therapy on the metabolic status we analyzed 517 metabolites in 1,361 participants from the KORA F4 study. We replicated our results in 1,964 individuals from TwinsUK. We observed differences in the concentration of five dipeptides and three ratios of di- and oligopeptides between ACE inhibitor users and non-users that were genotype dependent. Such changes in the concentration affected major homozygotes, and to a lesser extent heterozygotes, while minor homozygotes showed no or only small changes in the metabolite status. Two of these resulting dipeptides, namely aspartylphenylalanine and phenylalanylserine, showed significant associations with blood pressure which qualifies them—and perhaps also the other dipeptides—as readouts of ACE-activity. Since so far ACE activity measurement is substrate specific due to the usage of only one oligopeptide, taking several dipeptides as potential products of ACE into account may provide a broader picture of the ACE activity. PMID:27120469

  3. Lake Constance

    Atmospheric Science Data Center

    2013-04-17

    ... Swiss shores of Lake Constance at the town of Rorschach. Eutrophication, or the process of nutrient enrichment, is rapidly accelerated ... of the value of Lake Constance, efforts to mitigate eutrophication were initiated in the 1970's. MISR was built and is managed ...

  4. LAKE FORK

    EPA Science Inventory

    The Lake Fork of the Arkansas River Watershed has been adversely affected through mining, water diversion and storage projects, grazing, logging, and other human influences over the past 120 years. It is the goals of the LFWWG to improve the health of Lake fork by addressing th...

  5. Subglacial Lake Whillans microbial biogeochemistry: a synthesis of current knowledge.

    PubMed

    Mikucki, J A; Lee, P A; Ghosh, D; Purcell, A M; Mitchell, A C; Mankoff, K D; Fisher, A T; Tulaczyk, S; Carter, S; Siegfried, M R; Fricker, H A; Hodson, T; Coenen, J; Powell, R; Scherer, R; Vick-Majors, T; Achberger, A A; Christner, B C; Tranter, M

    2016-01-28

    Liquid water occurs below glaciers and ice sheets globally, enabling the existence of an array of aquatic microbial ecosystems. In Antarctica, large subglacial lakes are present beneath hundreds to thousands of metres of ice, and scientific interest in exploring these environments has escalated over the past decade. After years of planning, the first team of scientists and engineers cleanly accessed and retrieved pristine samples from a West Antarctic subglacial lake ecosystem in January 2013. This paper reviews the findings to date on Subglacial Lake Whillans and presents new supporting data on the carbon and energy metabolism of resident microbes. The analysis of water and sediments from the lake revealed a diverse microbial community composed of bacteria and archaea that are close relatives of species known to use reduced N, S or Fe and CH4 as energy sources. The water chemistry of Subglacial Lake Whillans was dominated by weathering products from silicate minerals with a minor influence from seawater. Contributions to water chemistry from microbial sulfide oxidation and carbonation reactions were supported by genomic data. Collectively, these results provide unequivocal evidence that subglacial environments in this region of West Antarctica host active microbial ecosystems that participate in subglacial biogeochemical cycling. PMID:26667908

  6. Subglacial lake drainage detected beneath the Greenland ice sheet

    PubMed Central

    Palmer, Steven; McMillan, Malcolm; Morlighem, Mathieu

    2015-01-01

    The contribution of the Greenland ice sheet to sea-level rise has accelerated in recent decades. Subglacial lake drainage events can induce an ice sheet dynamic response—a process that has been observed in Antarctica, but not yet in Greenland, where the presence of subglacial lakes has only recently been discovered. Here we investigate the water flow paths from a subglacial lake, which drained beneath the Greenland ice sheet in 2011. Our observations suggest that the lake was fed by surface meltwater flowing down a nearby moulin, and that the draining water reached the ice margin via a subglacial tunnel. Interferometric synthetic aperture radar-derived measurements of ice surface motion acquired in 1995 suggest that a similar event may have occurred 16 years earlier, and we propose that, as the climate warms, increasing volumes of surface meltwater routed to the bed will cause such events to become more common in the future. PMID:26450175

  7. Subglacial lake drainage detected beneath the Greenland ice sheet.

    PubMed

    Palmer, Steven; McMillan, Malcolm; Morlighem, Mathieu

    2015-01-01

    The contribution of the Greenland ice sheet to sea-level rise has accelerated in recent decades. Subglacial lake drainage events can induce an ice sheet dynamic response--a process that has been observed in Antarctica, but not yet in Greenland, where the presence of subglacial lakes has only recently been discovered. Here we investigate the water flow paths from a subglacial lake, which drained beneath the Greenland ice sheet in 2011. Our observations suggest that the lake was fed by surface meltwater flowing down a nearby moulin, and that the draining water reached the ice margin via a subglacial tunnel. Interferometric synthetic aperture radar-derived measurements of ice surface motion acquired in 1995 suggest that a similar event may have occurred 16 years earlier, and we propose that, as the climate warms, increasing volumes of surface meltwater routed to the bed will cause such events to become more common in the future. PMID:26450175

  8. 45 CFR 674.4 - Restrictions on collection of meteorites in Antarctica.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... SCIENCE FOUNDATION ANTARCTIC METEORITES § 674.4 Restrictions on collection of meteorites in Antarctica. No person may collect meteorites in Antarctica for other than scientific research purposes....

  9. 45 CFR 674.4 - Restrictions on collection of meteorites in Antarctica.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... SCIENCE FOUNDATION ANTARCTIC METEORITES § 674.4 Restrictions on collection of meteorites in Antarctica. No person may collect meteorites in Antarctica for other than scientific research purposes....

  10. Planetary geomorphology field studies: Iceland and Antarctica

    NASA Technical Reports Server (NTRS)

    Malin, M. C.

    1984-01-01

    Field studies of terrestrial landforms and the processes that shape them provide new directions to the study of planetary features. These studies, conducted in Iceland and in Antarctica, investigated physical and chemical weathering mechanisms and rates, eolitan processes, mudflow phenomena, drainage development, and catastrophic fluvial and volcanic phenomena. Continuing investigations in Iceland fall in three main catagories: (1) catastrophic floods of the Jokulsa a Fjollum, (2) lahars associated with explosive volcanic eruptions of Askja caldera, and (3) rates of eolian abrasion in cold, volcanic deserts. The ice-free valleys of Antarctica, in particular those in South Victoria Land, have much is common with the surface of Mars. In addition to providing independent support for the application of the Iceland findings to consideration of the martian erosional system, the Antarctic observations also provide analogies to other martian phenomena. For example, a family of sand dunes in Victoria Valley are stabilized by the incorporation of snow as beds.

  11. Antarctica - Lessons for a Mars exploration program

    NASA Technical Reports Server (NTRS)

    Mckay, C. P.

    1985-01-01

    The history of exploration and the international system of control of Antarctica has often been cited as a paradigm for the exploration of space. The small isolated research stations have been used to model the psychological stresses of future space missions. In addition, the programmatic structure of the U.S. Antarctic Research Program provides several possible analogs to future Mars Programs presently under discussion. These are: (1) Continued presence; (2) Civilian, military and private sector involvement; (3) Scientific activities; (4) Risk assessment and logistical support; (5) Accessibility for non-specialists; (6) Political and strategic motivations; (7) International cooperation/competition. Survival in Antarctica is contingent on advanced technology and the active transport of supplies. The scientific exploration of this remote and barren expanse without, of course, the aid and guidance of indigenous people certainly provides one of the closest analogs available to future science activities on the Martian surface.

  12. Intercomparison of ozone measurements over Antarctica

    NASA Technical Reports Server (NTRS)

    Margitan, J. J.; Farmer, C. B.; Toon, G. C.; Brothers, G. A.; Browell, E. V.; Gregory, G. L.; Hypes, W.; Larsen, J. C.; Mccormick, M. P.; Krueger, A. J.

    1989-01-01

    Measurements of the abundances of ozone over Antarctica in August and September 1987 obtained during the Airborne Antarctic Ozone Experiment are intercompared. These measurements of ozone concentrations and total column abundance were obtained by three satellite instruments, two IR and one UV column-measuring instruments aboard the DC-8, one in situ DC-8, and two in situ ER-2 instruments, an upward looking lidar aboard the DC-8, and ozone sondes from four sites in Antarctica. This paper presents a summary of the ozone data, using the data and accuracies given by the individual investigators in the individual papers in this issue, without any attempt to critically review or evaluate the data. In general, very good agreement (within about 10-20 percent, limited by natural variability) among the various techniques was found, with no systematic biases detected. These observations confirm the low ozone amounts reported in the Antarctic stratosphere.

  13. Heavy Ion Temperatures As Observed By ACE/Swics

    NASA Astrophysics Data System (ADS)

    Tracy, P.; Zurbuchen, T.; Raines, J. M.; Shearer, P.; Kasper, J. C.; Gilbert, J. A.; Alterman, B. L.

    2014-12-01

    Heavy ions observed near 1 AU, especially in fast solar wind, tend to have thermal speeds that are approximately equal, indicative of a mass proportional temperature. Additionally, observations near 1 AU have shown a streaming of heavy ions (Z>4) along the magnetic field direction at speeds faster than protons. The differential velocities observed are of the same order but typically less than the Alfven speed. Previous analysis of the behavior of ion thermal velocities with Ulysses-SWICS, focusing on daily average properties of 35 ion species at 5 AU, found only a small systematic trend with respect to q2/m. Utilizing improved data processing techniques, results from the Solar Wind Ion Composition Spectrometer (SWICS) onboard the Advanced Composition Explorer (ACE) shed new light on the thermal properties of the heavy ion population at 1 AU. A clear dependence of heavy ion thermal behavior on q2/m has now been found in the recent ACE-SWICS two hour cadence data set at 1 AU. Examining the thermal velocities of about 70 heavy ion species relative to alpha particles (He2+) shows a distinct trend from equal thermal speed toward equal temperature with increasing q2/m. When examined for solar winds of different collisional ages, the observations indicate the extent of thermal relaxation present in different solar wind types. We explore this collisional dependence with a model for the collisional thermal relaxation of the heavy ions as the solar wind propagates out to 1 AU. This model is used to subtract out the collisional effects seen in the ACE-SWICS data, providing an estimate for the temperature distribution among heavy ions at the corona to be compared to remote sensing observations that have shown that heavy ions are preferentially heated at the corona. We will discuss how this new analysis elucidates the thermal behavior and evolution of heavy ions in the solar wind, along with implications for the upcoming Solar Probe Plus and Solar Orbiter missions.

  14. Helium at Interplanetary Discontinuities: ACE STEREO Observations and Simulations

    NASA Astrophysics Data System (ADS)

    Moebius, E.; Kucharek, H.; Allegrini, F.; Desai, M.; Klecker, B.; Popecki, M.; Farrugia, C.; Galvin, A.; Bochsler, P.; Karrer, R.; Opitz, A.; Simunac, K.

    2007-12-01

    ACE/SEPICA observations showed that, on average, energetic He+ is after H+ and He2+ the third most abundant energetic particle species in the heliosphere. Depending on the type of the energetic population the He+/He2+ ratio can reach unusually high values in the energy range 250 - 800keV/n ratios up to unity. As a major source of energetic He+ interplanetary pickup ions have been identified that are preferentially accelerated at co-rotating interaction regions (CIRs), transient interaction regions (TIRs), and interplanetary traveling shocks. Most recent data from STEREO/PLASTIC in the energy range of 0.2-80keV/Q show clear evidence of abundant He+ at interplanetary discontinuities. Thus PLASTIC extends the energy range into injection region of the source. Furthermore, ACE/ULEIS and ACE/SEPICA measurements showed that very often 3He2+ and He+ are also accelerated simultaneously at CME-driven IP shocks. This is surprising because, these to species originate from different sources. However, this may indicate that the injection, or the acceleration efficiency of the accelerator for different source population may be similar. From observations, however, this cannot be differentiated easily. In numerical simulations this can be done because there is control over species and distribution functions. In a numerical study we applied test particle simulations and multi-dimensional hybrid simulations to address the contribution of source, injection and acceleration efficiency at shocks to the variability of the helium ratio. These, simulations with and without superimposed turbulence in the shock region will be compared with observations.

  15. The Landsat Image Mosaic of Antarctica

    NASA Astrophysics Data System (ADS)

    Bindschadler, R.; Vornberger, P.; Fleming, A.; Fox, A.; Morin, P.

    2008-12-01

    The first-ever true-color, high-resolution digital mosaic of Antarctica has been produced from nearly 1100 Landsat-7 ETM+ images collected between 1999 and 2003. The Landsat Image Mosaic of Antarctica (LIMA) project was an early benchmark data set of the International Polar Year and represents a close and successful collaboration between NASA, USGS, the British Antarctic Survey and the National Science Foundation. The mosaic was successfully merged with lower resolution MODIS data south of Landsat coverage to produce a complete true-color data set of the entire continent. LIMA is being used as a platform for a variety of education and outreach activities. Central to this effort is the NASA website 'Faces of Antarctica' that offers the web visitor the opportunity to explore the data set and to learn how these data are used to support scientific research. Content is delivered through a set of mysteries designed to pique the user's interest and to motivate them to delve deeper into the website where there are various videos and scientific articles for downloading. Detailed lesson plans written by teachers are provided for classroom use and Java applets let the user track the motion of ice in sequential Landsat images. Web links take the user to other sites where they can roam over the imagery using standard pan and zoom functions, or search for any named feature in the Antarctic Geographic Names data base that returns to the user a centered true-color view of any named feature. LIMA also has appeared is a host of external presentations from museum exhibits, to postcards and large posters. It has attracted various value-added providers that increase LIMA's accessibility by allowing users to specify subsets of the very large data set for individual downloads. The ultimate goal of LIMA in the public and educational sector is to enable everyone to become more familiar with Antarctica.

  16. Life on ice, Antarctica and Mars

    NASA Technical Reports Server (NTRS)

    Anderson, D. T.; Mckay, C. P.; Wharton, Robert A., Jr.; Sagan, C.; Squyres, S. W.; Simmons, G. M.

    1991-01-01

    The study of the origin of life and the prospects for human exploration of Mars are two themes developed in a new 57-minute film, Life on Ice, Antarctica, and Mars, produced by the InnerSpace Foundation and WHRO Television for broadcast by the Public Broadcasting System (PBS). A brief explanation of the film and how it relates to the future human exploration of space is presented.

  17. The Ice: A Journey to Antarctica

    NASA Astrophysics Data System (ADS)

    Ford, Arthur B.

    The title is misleading for a non—“OAE” (Old Antarctic Explorer, to whom “The Ice” is Antarctica) because The Ice is about far more than just ice. It does indeed cover just about all you'd want to know (or more) about Antarctic ice, from the vast south polar sheets and glaciers to the great tabular bergs, bergy bits, brash ice, pancake ice, frazil ice, and the pack of the polar seas; but it also explores nearly every aspect of this “Last of Lands” in an unusually comprehensive coverage. From the “Heroic Ages” of early 20th-century explorers Robert Scott, Ernest Shackleton, and Roald Amundsen to the present “Cruise Ship Age,”Antarctica has produced a wealth of literature in the “Journey to…” style — which Pyne's is not. Instead, his product from one short (3-month) visit under a National Endowment for the Humanities fellowship takes all readers o n a webwork journey through time, space, ice, and rocks for an appreciation of “ The Ice” in a way found in no other book. This, his fifth book (another one is Fire in America, Princeton University Press, Princeton, N.J., 1982), is a significant contribution to the literature of Antarctica. Pyne's prose cannot be paraphrased for a review, as the reader will be able to appreciate from the excerpts to follow.

  18. DNA Methylation Analysis of the Angiotensin Converting Enzyme (ACE) Gene in Major Depression

    PubMed Central

    Zill, Peter; Baghai, Thomas C.; Schüle, Cornelius; Born, Christoph; Früstück, Clemens; Büttner, Andreas; Eisenmenger, Wolfgang; Varallo-Bedarida, Gabriella; Rupprecht, Rainer; Möller, Hans-Jürgen; Bondy, Brigitta

    2012-01-01

    Background The angiotensin converting enzyme (ACE) has been repeatedly discussed as susceptibility factor for major depression (MD) and the bi-directional relation between MD and cardiovascular disorders (CVD). In this context, functional polymorphisms of the ACE gene have been linked to depression, to antidepressant treatment response, to ACE serum concentrations, as well as to hypertension, myocardial infarction and CVD risk markers. The mostly investigated ACE Ins/Del polymorphism accounts for ∼40%–50% of the ACE serum concentration variance, the remaining half is probably determined by other genetic, environmental or epigenetic factors, but these are poorly understood. Materials and Methods The main aim of the present study was the analysis of the DNA methylation pattern in the regulatory region of the ACE gene in peripheral leukocytes of 81 MD patients and 81 healthy controls. Results We detected intensive DNA methylation within a recently described, functional important region of the ACE gene promoter including hypermethylation in depressed patients (p = 0.008) and a significant inverse correlation between the ACE serum concentration and ACE promoter methylation frequency in the total sample (p = 0.02). Furthermore, a significant inverse correlation between the concentrations of the inflammatory CVD risk markers ICAM-1, E-selectin and P-selectin and the degree of ACE promoter methylation in MD patients could be demonstrated (p = 0.01 - 0.04). Conclusion The results of the present study suggest that aberrations in ACE promoter DNA methylation may be an underlying cause of MD and probably a common pathogenic factor for the bi-directional relationship between MD and cardiovascular disorders. PMID:22808171

  19. ACE2 overexpression inhibits acquired platinum resistance-induced tumor angiogenesis in NSCLC.

    PubMed

    Cheng, Qijian; Zhou, Ling; Zhou, Jianping; Wan, Huanying; Li, Qingyun; Feng, Yun

    2016-09-01

    Angiotensin II (AngII) is a multifunctional bioactive peptide in the renin-angiotensin system (RAS). Angiotensin-converting enzyme 2 (ACE2) is a newly identified component of RAS. We previously reported that ACE2 overexpression may inhibit cell growth and vascular endothelial growth factor (VEGF) production in vitro and in vivo. In the present study, we investigated the effect of ACE2 on tumor-associated angiogen-esis after the development of acquired platinum resistance in non-small cell lung cancer (NSCLC). Four NSCLC cell lines, A549, LLC, A549-DDP and LLC-DDP, were used in vitro, while A549 and A549-DDP cells were used in vivo. A549-DDP and LLC-DDP cells were newly established at our institution as acquired platinum-resistant sublines by culturing the former parent cells in cisplatin (CDDP)-containing conditioned medium for 6 months. These platinum-resistant cells showed significantly higher angiotensin II type 1 receptor (AT1R), ACE and VEGF production and lower ACE2 expression than their corresponding parent cells. We showed that ACE2 overexpression inhibited the production of VEGF in vitro and in vivo compared to their corresponding parent cells. We also found that ACE2 overexpression reduced the expression of AT1R and ACE. Additionally, we confirmed that ACE2 overexpres-sion inhibited cell growth and VEGF production while simultaneously suppressing ACE and AT1R expression in human lung cancer xenografts. Our findings indicate that ACE2 overexpression may potentially suppress angiogenesis in NSCLC after the development of acquired platinum resistance. PMID:27460845

  20. Effects of ACE2 deficiency on physical performance and physiological adaptations of cardiac and skeletal muscle to exercise.

    PubMed

    Motta-Santos, Daisy; Dos Santos, Robson Augusto Souza; Oliveira, Marilene; Qadri, Fatimunnisa; Poglitsch, Marko; Mosienko, Valentina; Kappes Becker, Lenice; Campagnole-Santos, Maria Jose; M Penninger, Joseph; Alenina, Natalia; Bader, Michael

    2016-07-01

    The renin-angiotensin system (RAS) is related to physiological adaptations induced by exercise. Angiotensin-converting enzyme (ACE) 2 is a major regulator of the RAS in tissues, as it metabolizes angiotensin (Ang) II to Ang-(1-7). The aim of this study was to determine the effects of ACE2 deficiency on physical performance and physiological adaptations induced by voluntary running. Physical performance, body composition and plasma angiotensin levels, as well as tissue morphology and gene expression of RAS components in the left ventricle (LV) and skeletal muscle (gastrocnemius), were evaluated in ACE2-deficient (ACE2(-/y)) and wild-type (ACE2(+/y)) mice after 6 weeks of voluntary wheel running. ACE2(-/y) mice run less than ACE2(+/y) mice (19±4.7 vs. 26±12.6 revolutions per day × 100, P<0.01). The ACE2(+/y) group presented a lower fat mass (15±1.1%) and higher muscle mass (76.6±1.6%) after 6 weeks of voluntary running compared with the sedentary control group (fat mass: 18.3±2.1%; muscle mass: 72.7±2.2). However, no change in body composition was observed in ACE2(-/y) mice after exercise. Heart and skeletal muscle hypertrophy was observed only in trained ACE2(+/y) mice. Besides a small decrease in Ang I in ACE2(-/y) mice, plasma levels of angiotensin peptides remained unchanged by exercise or ACE2 deficiency. In the LV of trained animals, AT2 gene expression was higher in ACE2(+/y) compared with ACE2(-/y) mice. ACE2 deficiency leads to an increase in AT1 gene expression in skeletal muscle. ACE expression in soleus was increased in all exercised groups. ACE2 deficiency affects physical performance and impairs cardiac and skeletal muscle adaptations to exercise. PMID:27053009

  1. Sediment oxygen profiles in a super-oxygenated antarctic lake

    NASA Technical Reports Server (NTRS)

    Wharton, R. A. Jr; Meyer, M. A.; McKay, C. P.; Mancinelli, R. L.; Simmons, G. M. Jr; Wharton RA, J. r. (Principal Investigator)

    1994-01-01

    Perennially ice-covered lakes are found in the McMurdo Dry Valleys of southern Victoria Land, Antarctica. In contrast to temperate lakes that have diurnal photic periods, antarctic (and arctic) lakes have a yearly photic period. An unusual feature of the antarctic lakes is the occurrence of O2 at supersaturated levels in certain portions of the water column. Here we report the first sediment O2 profiles obtained using a microelectrode from a perennially ice-covered antarctic lake. Sediment cores collected in January and October 1987 from Lake Hoare in Taylor Valley show oxygenation down to 15, and in some cases, 25 cm. The oxygenation of sediments several centimeters below the sediment-water interface is atypical for lake sediments and may be characteristic of perennially ice-covered lakes. There is a significant difference between the observed January and October sediment O2 profiles. Several explanations may account for the difference, including seasonality. A time-dependent model is presented which tests the feasibility of a seasonal cycle resulting from the long photoperiod and benthic primary production in sediments overlain by a highly oxygenated water column.

  2. Antarctic subglacial lake exploration: first results and future plans.

    PubMed

    Siegert, Martin J; Priscu, John C; Alekhina, Irina A; Wadham, Jemma L; Lyons, W Berry

    2016-01-28

    After more than a decade of planning, three attempts were made in 2012-2013 to access, measure in situ properties and directly sample subglacial Antarctic lake environments. First, Russian scientists drilled into the top of Lake Vostok, allowing lake water to infiltrate, and freeze within, the lower part of the ice-core borehole, from which further coring would recover a frozen sample of surface lake water. Second, UK engineers tried unsuccessfully to deploy a clean-access hot-water drill, to sample the water column and sediments of subglacial Lake Ellsworth. Third, a US mission successfully drilled cleanly into subglacial Lake Whillans, a shallow hydraulically active lake at the coastal margin of West Antarctica, obtaining samples that would later be used to prove the existence of microbial life and active biogeochemical cycling beneath the ice sheet. This article summarizes the results of these programmes in terms of the scientific results obtained, the operational knowledge gained and the engineering challenges revealed, to collate what is known about Antarctic subglacial environments and how to explore them in future. While results from Lake Whillans testify to subglacial lakes as being viable biological habitats, the engineering challenges to explore deeper more isolated lakes where unique microorganisms and climate records may be found, as exemplified in the Lake Ellsworth and Vostok missions, are considerable. Through international cooperation, and by using equipment and knowledge of the existing subglacial lake exploration programmes, it is possible that such environments could be explored thoroughly, and at numerous sites, in the near future. PMID:26667917

  3. Antarctic subglacial lake exploration: first results and future plans

    PubMed Central

    Siegert, Martin J.; Priscu, John C.; Wadham, Jemma L.; Lyons, W. Berry

    2016-01-01

    After more than a decade of planning, three attempts were made in 2012–2013 to access, measure in situ properties and directly sample subglacial Antarctic lake environments. First, Russian scientists drilled into the top of Lake Vostok, allowing lake water to infiltrate, and freeze within, the lower part of the ice-core borehole, from which further coring would recover a frozen sample of surface lake water. Second, UK engineers tried unsuccessfully to deploy a clean-access hot-water drill, to sample the water column and sediments of subglacial Lake Ellsworth. Third, a US mission successfully drilled cleanly into subglacial Lake Whillans, a shallow hydraulically active lake at the coastal margin of West Antarctica, obtaining samples that would later be used to prove the existence of microbial life and active biogeochemical cycling beneath the ice sheet. This article summarizes the results of these programmes in terms of the scientific results obtained, the operational knowledge gained and the engineering challenges revealed, to collate what is known about Antarctic subglacial environments and how to explore them in future. While results from Lake Whillans testify to subglacial lakes as being viable biological habitats, the engineering challenges to explore deeper more isolated lakes where unique microorganisms and climate records may be found, as exemplified in the Lake Ellsworth and Vostok missions, are considerable. Through international cooperation, and by using equipment and knowledge of the existing subglacial lake exploration programmes, it is possible that such environments could be explored thoroughly, and at numerous sites, in the near future. PMID:26667917

  4. Salinity control on the ratio of archaeol to caldarchaeol in highland lakes of the northern Qinghai-Tibetan Plateau: implications for paleosalinity proxies

    NASA Astrophysics Data System (ADS)

    Wang, H.; Liu, W.; Zhang, C.; Jiang, H.; Dong, H.; Lu, H.; Wang, J.

    2012-12-01

    The ratio of archaeol to caldarchaeol has been proposed recently as an index for paleosalinity reconstruction, which is principally based on archaeal core lipids (CLs) from coastal salt pans [Turich C. and Freeman K.H., 2011. Archaeal lipids record paleosalinity in hypersaline systems. Organic Geochemistry 42, 1147-1157]. Here we examined possible relationships between salinity and the ratio of archaeol to caldarchaeol (referred to as ACE') in both CLs and polar lipids (PLs) from suspended particulate matter (SPM) and surface sediments of lakes and surrounding soil on the Qinghai-Tibetan Plateau. Our results show that ACE' values were positively correlated with salinity in all samples; however, CL ACE' values were systematically higher than PL ACE' values in both lake water and soil, probably due to unequal degradation kinetics of intact polar (IP) archaeol and IP caldarchaeol. On the other hand, surface sediment ACE' values from both CLs and PLs were lower than SPM ACE' values, probably due to enhanced production of caldarchaeol relative to archaeol in the sediment. Our results demonstrate that the ratio of archaeol to caldarchaeol reflects changes in salinity in diverse environments on the Qinghai-Tibetan Plateau; however, a good understanding of degradation kinetics of polar archaeol and caldarchaeol and in situ production of caldarchaeol and archaeol in soil and the aquatic system is needed before the proposed salinity proxy can be used in paleosalinity studies of terrestrial environments.

  5. Uncertainty quantification for accident management using ACE surrogates

    SciTech Connect

    Varuttamaseni, A.; Lee, J. C.; Youngblood, R. W.

    2012-07-01

    The alternating conditional expectation (ACE) regression method is used to generate RELAP5 surrogates which are then used to determine the distribution of the peak clad temperature (PCT) during the loss of feedwater accident coupled with a subsequent initiation of the feed and bleed (F and B) operation in the Zion-1 nuclear power plant. The construction of the surrogates assumes conditional independence relations among key reactor parameters. The choice of parameters to model is based on the macroscopic balance statements governing the behavior of the reactor. The peak clad temperature is calculated based on the independent variables that are known to be important in determining the success of the F and B operation. The relationship between these independent variables and the plant parameters such as coolant pressure and temperature is represented by surrogates that are constructed based on 45 RELAP5 cases. The time-dependent PCT for different values of F and B parameters is calculated by sampling the independent variables from their probability distributions and propagating the information through two layers of surrogates. The results of our analysis show that the ACE surrogates are able to satisfactorily reproduce the behavior of the plant parameters even though a quasi-static assumption is primarily used in their construction. The PCT is found to be lower in cases where the F and B operation is initiated, compared to the case without F and B, regardless of the F and B parameters used. (authors)

  6. Signatures of interchange reconnection: STEREO, ACE and Hinode observations combined

    NASA Astrophysics Data System (ADS)

    Baker, D.; Rouillard, A. P.; van Driel-Gesztelyi, L.; Démoulin, P.; Harra, L. K.; Lavraud, B.; Davies, J. A.; Opitz, A.; Luhmann, J. G.; Sauvaud, J.-A.; Galvin, A. B.

    2009-10-01

    Combining STEREO, ACE and Hinode observations has presented an opportunity to follow a filament eruption and coronal mass ejection (CME) on 17 October 2007 from an active region (AR) inside a coronal hole (CH) into the heliosphere. This particular combination of "open" and closed magnetic topologies provides an ideal scenario for interchange reconnection to take place. With Hinode and STEREO data we were able to identify the emergence time and type of structure seen in the in-situ data four days later. On the 21st, ACE observed in-situ the passage of an ICME with "open" magnetic topology. The magnetic field configuration of the source, a mature AR located inside an equatorial CH, has important implications for the solar and interplanetary signatures of the eruption. We interpret the formation of an "anemone" structure of the erupting AR and the passage in-situ of the ICME being disconnected at one leg, as manifested by uni-directional suprathermal electron flux in the ICME, to be a direct result of interchange reconnection between closed loops of the CME originating from the AR and "open" field lines of the surrounding CH.

  7. ACE: A distributed system to manage large data archives

    NASA Technical Reports Server (NTRS)

    Daily, Mike I.; Allen, Frank W.

    1993-01-01

    Competitive pressures in the oil and gas industry are requiring a much tighter integration of technical data into E and P business processes. The development of new systems to accommodate this business need must comprehend the significant numbers of large, complex data objects which the industry generates. The life cycle of the data objects is a four phase progression from data acquisition, to data processing, through data interpretation, and ending finally with data archival. In order to implement a cost effect system which provides an efficient conversion from data to information and allows effective use of this information, an organization must consider the technical data management requirements in all four phases. A set of technical issues which may differ in each phase must be addressed to insure an overall successful development strategy. The technical issues include standardized data formats and media for data acquisition, data management during processing, plus networks, applications software, and GUI's for interpretation of the processed data. Mass storage hardware and software is required to provide cost effective storage and retrieval during the latter three stages as well as long term archival. Mobil Oil Corporation's Exploration and Producing Technical Center (MEPTEC) has addressed the technical and cost issues of designing, building, and implementing an Advanced Computing Environment (ACE) to support the petroleum E and P function, which is critical to the corporation's continued success. Mobile views ACE as a cost effective solution which can give Mobile a competitive edge as well as a viable technical solution.

  8. ACE2 Global Digital Elevation Model : User Analysis

    NASA Astrophysics Data System (ADS)

    Smith, R. G.; Berry, P. A. M.; Benveniste, J.

    2013-12-01

    Altimeter Corrected Elevations 2 (ACE2), first released in October 2009, is the Global Digital Elevation Model (GDEM) created by fusing the high accuracy of over 100 million altimeter retracked height estimates, derived primarily from the ERS-1 Geodetic Mission, with the high frequency content available within the near-global Shuttle Radar Topography Mission. This novel ACE2 GDEM is freely available at 3”, 9”, 30” and 5' and has been distributed via the web to over 680 subscribers. This paper presents the results of a detailed analysis of geographical distribution of subscribed users, along with fields of study and potential uses. Investigations have also been performed to determine the most popular spatial resolutions and the impact these have on the scope of data downloaded. The analysis has shown that, even though the majority of users have come from Europe and America, a significant number of website hits have been received from South America, Africa and Asia. Registered users also vary widely, from research institutions and major companies down to individual hobbyists looking at data for single projects.

  9. Communications, Navigation, and Surveillance Models in ACES: Design Implementation and Capabilities

    NASA Technical Reports Server (NTRS)

    Kubat, Greg; Vandrei, Don; Satapathy, Goutam; Kumar, Anil; Khanna, Manu

    2006-01-01

    Presentation objectives include: a) Overview of the ACES/CNS System Models Design and Integration; b) Configuration Capabilities available for Models and Simulations using ACES with CNS Modeling; c) Descriptions of recently added, Enhanced CNS Simulation Capabilities; and d) General Concepts Ideas that Utilize CNS Modeling to Enhance Concept Evaluations.

  10. Airspace Concept Evaluation System (ACES), Concept Simulations using Communication, Navigation and Surveillance (CNS) System Models

    NASA Technical Reports Server (NTRS)

    Kubat, Greg; Vandrei, Don

    2006-01-01

    Project Objectives include: a) CNS Model Development; b Design/Integration of baseline set of CNS Models into ACES; c) Implement Enhanced Simulation Capabilities in ACES; d) Design and Integration of Enhanced (2nd set) CNS Models; and e) Continue with CNS Model Integration/Concept evaluations.

  11. A Consolidation of ACE Research, 1990-2000. Review of Research.

    ERIC Educational Resources Information Center

    Golding, Barry; Davies, Merryn; Volkoff, Veronica

    The volume and scope of research into adult and community education (ACE) in Australia have increased significantly over the past decade. Studies designed to map, reevaluate, showcase, and promote ACE have been funded by Australia's federal and state governments and by bodies such as Adult Learning Australia. Practitioner-generated research has…

  12. Formative Evaluation of ACES Program: Findings from Surveys and Interviews Year One, Grades 11 and 12

    ERIC Educational Resources Information Center

    Wolanin, Natalie; Modarresi, Shahpar

    2015-01-01

    The Office of Shared Accountability (OSA) in Montgomery County (Maryland) Public Schools (MCPS) is conducting a multiyear evaluation of the Achieving Collegiate Excellence and Success (ACES) program. The ACES program is a collaboration between MCPS, Montgomery College (MC), and the Universities at Shady Grove (USG) to create a seamless pathway…

  13. Measurements of O3, NO2 and Temperature during the 2004 Canadian Arctic ACE Validation Campaign

    NASA Astrophysics Data System (ADS)

    Kerzenmacher, Tobias E.; Walker, Kaley A.; Strong, Kimberly; Berman, Richard; Bernath, Peter F.; Boone, Chris D.; Drummond, James R.; Fast, Hans; Fraser, Annemarie; MacQuarrie, Keith; Midwinter, Clive; Sung, Keeyoon; McElroy, C. Thomas; Mittermeier, Richard L.; Walker, Jennifer; Wu, Hongjiang

    2005-07-01

    The 2004 Canadian Arctic ACE Validation Campaign was conducted to provide correlative data for validating measurements from the Atmospheric Chemistry Experiment (ACE) satellite mission. These measurements were made at Eureka, Nunavut during polar springtime 2004. Six ground-based instruments were operated during the intensive phase of the campaign and ozonesondes and radiosondes were flown. During this time, ACE-FTS and ACE-MAESTRO were performing solar-occultation measurements over the Canadian Arctic. We report the first comparisons between campaign measurements and those from ACE, focusing on O3, NO2 and temperature. Initial mean O3 profiles from ACE-FTS and ACE-MAESTRO agree to within 20% between 10 and 30 km, and the NO2 profiles agree to within 40% between 17 and 40 km, which is within the standard deviations. The ACE-FTS temperature profiles agree to better than 2.5 K with the radiosonde temperatures from 10 to 32 km and with the lidar temperatures from 17 to 45 km.

  14. ACE expression in monocytes is induced by cytokines, phorbol ester and steroid

    SciTech Connect

    Lazarus, D.; Lanzillo, J.; Fanburg, B. )

    1991-03-15

    Angiotensin converting enzyme (ACE) levels are elevated in the serum and peripheral blood monocytes (PBM) of patients with granulomatous diseases. However, the role of ACE in (Mo) physiology and the regulation of the inflammatory response is not well understood. Since Mo can be stimulated to form giant cells using phorbol esters, glucocorticoids or certain inflammatory cytokines, the authors examined production of ACE protein by normal PBM, a Mo-like cell line, THP-1, and a macrophage-like cell line, U937 following stimulation with these agents. Using a sensitive ELISA assay, they found that in U937 cells, expression of ACE protein increased by 3.4 fold with dexamethasone, 3.7. fold with phorbol 12-myristate acetate (PMA), and 5.8 fold with the two agents combined. The cytokines IL-4 and GM-CSF substantially increased ACE expression, by 7.6 and 7.7 fold respectively, with maximal effect at 0.01 U/ml, while IFN-{gamma} and TNF-{alpha} had little effect. Similar results were found with PBM and THP-1 cells. The combination of dexamethasone and PMA also induced homotypic cluster formation in PBM, suggesting a correlation between cell adhesion and ACE production. The authors conclude that ACE expression in monocytes and macrophages is stimulated by low concentration of glucocorticoids and certain inflammatory cytokines. ACE may participate in the initiation and propagation of granulomatous inflammatory processes.

  15. 76 FR 34246 - Automated Commercial Environment (ACE); Announcement of National Customs Automation Program Test...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-06-13

    ..., 2003, CBP published a final rule in the Federal Register (68 FR 68140) to effectuate the provisions of... 27, 2006 (71 FR 62922), CBP designated the ACE Truck Manifest System as the approved system for... in which CBP had planned to require the use of ACE. See, 72 FR 53789, September 20, 2007....

  16. SCORE/ACE Counselor Handbook. Service Corps of Retired Executives. Active Corps of Executives.

    ERIC Educational Resources Information Center

    Landsverk, Arvel; And Others

    This counselor handbook is intended to help Service Corps of Retired Executives/Active Corps of Executives (SCORE/ACE) counselors to plan and conduct counseling services more effectively. Included in the introductory section are an overview of the SCORE/ACE counseling program, a discussion of what the counselor does, directions for completing…

  17. Education for 2001 and Beyond: Imperatives and Possibilities. Outcomes from the ACE "Education 2000" International Conference.

    ERIC Educational Resources Information Center

    Unicorn: Journal of the Australian College of Education, 2000

    2000-01-01

    This issue of "Unicorn," the journal of the Australian College of Education (ACE), contains extracts and summaries of 13 presentations given at the international ACE conference, "Education 2000: Priorities for the New Millennium." The papers not only address the five themes of the conference (priorities for learning, priorities for supporting…

  18. Preparing GMAT for Operational Maneuver Planning of the Advanced Composition Explorer (ACE)

    NASA Technical Reports Server (NTRS)

    Qureshi, Rizwan Hamid; Hughes, Steven P.

    2014-01-01

    The General Mission Analysis Tool (GMAT) is an open-source space mission design, analysis and trajectory optimization tool. GMAT is developed by a team of NASA, private industry, public and private contributors. GMAT is designed to model, optimize and estimate spacecraft trajectories in flight regimes ranging from low Earth orbit to lunar applications, interplanetary trajectories and other deep space missions. GMAT has also been flight qualified to support operational maneuver planning for the Advanced Composition Explorer (ACE) mission. ACE was launched in August, 1997 and is orbiting the Sun-Earth L1 libration point. The primary science objective of ACE is to study the composition of both the solar wind and the galactic cosmic rays. Operational orbit determination, maneuver operations and product generation for ACE are conducted by NASA Goddard Space Flight Center (GSFC) Flight Dynamics Facility (FDF). This paper discusses the entire engineering lifecycle and major operational certification milestones that GMAT successfully completed to obtain operational certification for the ACE mission. Operational certification milestones such as gathering of the requirements for ACE operational maneuver planning, gap analysis, test plans and procedures development, system design, pre-shadow operations, training to FDF ACE maneuver planners, shadow operations, Test Readiness Review (TRR) and finally Operational Readiness Review (ORR) are discussed. These efforts have demonstrated that GMAT is flight quality software ready to support ACE mission operations in the FDF.

  19. 77 FR 20835 - National Customs Automation Program (NCAP) Test Concerning Automated Commercial Environment (ACE...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-04-06

    ... was on trade compliance and the development of the Automated Commercial Environment (ACE), the planned... Portal Accounts and Subsequent Revision Notices: 67 FR 21800 (May 1, 2002); 70 FR 5199 (February 1, 2005); 69 FR 5360 and 69 FR 5362 (February 4, 2004); 69 FR 54302 (September 8, 2004). ACE System of...

  20. Angiotensin I-Converting Enzyme (ACE) Inhibitory Activity and ACE Inhibitory Peptides of Salmon (Salmo salar) Protein Hydrolysates Obtained by Human and Porcine Gastrointestinal Enzymes

    PubMed Central

    Darewicz, Małgorzata; Borawska, Justyna; Vegarud, Gerd E.; Minkiewicz, Piotr; Iwaniak, Anna

    2014-01-01

    The objectives of the present study were two-fold: first, to detect whether salmon protein fractions possess angiotensin I-converting enzyme (ACE) inhibitory properties and whether salmon proteins can release ACE inhibitory peptides during a sequential in vitro hydrolysis (with commercial porcine enzymes) and ex vivo digestion (with human gastrointestinal enzymes). Secondly, to evaluate the ACE inhibitory activity of generated hydrolysates. A two-step ex vivo and in vitro model digestion was performed to simulate the human digestion process. Salmon proteins were degraded more efficiently by porcine enzymes than by human gastrointestinal juices and sarcoplasmic proteins were digested/hydrolyzed more easily than myofibrillar proteins. The ex vivo digested myofibrillar and sarcoplasmic duodenal samples showed IC50 values (concentration required to decrease the ACE activity by 50%) of 1.06 and 2.16 mg/mL, respectively. The in vitro hydrolyzed myofibrillar and sarcoplasmic samples showed IC50 values of 0.91 and 1.04 mg/mL, respectively. Based on the results of in silico studies, it was possible to identify 9 peptides of the ex vivo hydrolysates and 7 peptides of the in vitro hydrolysates of salmon proteins of 11 selected peptides. In both types of salmon hydrolysates, ACE-inhibitory peptides IW, IY, TVY and VW were identified. In the in vitro salmon protein hydrolysates an ACE-inhibitory peptides VPW and VY were also detected, while ACE-inhibitory peptides ALPHA, IVY and IWHHT were identified in the hydrolysates generated with ex vivo digestion. In our studies, we documented ACE inhibitory in vitro effects of salmon protein hydrolysates obtained by human and as well as porcine gastrointestinal enzymes. PMID:25123137

  1. Trace metals in Antarctica related to climate change and increasing human impact.

    PubMed

    Bargagli, R

    2000-01-01

    in most samples of atmospheric particulates, snow, ice, soils, and marine sediments from Antarctica can be taken as global background levels. Comparison between the results of trace element surveys in marine waters of the Southern Ocean and in other seas is practically impossible. The upwelling or subduction of water masses, the seasonality in ice cover and in phytoplankton biomass, the low fallout of atmospheric dust, and many other peculiar characteristics of the Southern Ocean make concentrations of trace metals in surface waters quite variable in space and time. The depletion of nutrients in surface waters, which is a regular feature of many marine environments, rarely occurs in the Southern Ocean. Waters in some regions are characterized by very low concentrations of Fe and Mn, whereas in others the content of Cd is relatively high at the beginning of summer and may decrease about one order of magnitude during the phytoplankton bloom. Although in most Antarctic coastal ecosystems the input of metals from geochemical and anthropogenic sources and from long-range transport is negligible, concentrations of Cd in the waters and biota may be higher than in waters and related species of organisms from polluted coastal areas. Like the Southern Ocean, Antarctic lakes have many peculiar characteristics. They are often perennially ice covered and without outlet, and their water, which is gained only from short-term melting of snow and glaciers in summer, is lost mainly by sublimation of surface ice. Several lakes are distinctly stratified: the water under the ice may be cool, rich in oxygen, and among the cleanest and clearest of natural waters, whereas water near the bottom becomes anoxic, tepid, and richer in major and trace elements. Considering the specificity of Antarctic environments, to evaluate the extent and consequences of global changes and increasing human activities in Antarctica itself, research on the biogeochemistry of trace metals and monitoring programs

  2. Evolving subglacial water systems in East Antarctica from airborne radar sounding

    NASA Astrophysics Data System (ADS)

    Carter, Sasha Peter

    The cold, lightless, and high pressure aquatic environment at the base of the East Antarctic Ice Sheet is of interest to a wide range of disciplines. Stable subglacial lakes and their connecting channels remain perennially liquid three kilometers below some of the coldest places on Earth. The presence of subglacial water impacts flow of the overlying ice and provides clues to the geologic properties of the bedrock below, and may harbor unique life forms which have evolved out of contact with the atmosphere for millions of years. Periodic release of water from this system may impact ocean circulation at the margins of the ice sheet. This research uses airborne radar sounding, with its unique ability to infer properties within and at the base of the ice sheet over large spatial scales, to locate and characterize this unique environment. Subglacial lakes, the primary storage mechanism for subglacial water, have been located and classified into four categories on the basis of the radar reflection properties from the sub-ice interface: Definite lakes are brighter than their surroundings by at least two decibels (relatively bright), and are both consistently reflective (specular) and have a reflection coefficient greater than -10 decibels (absolutely bright). Dim lakes are relatively bright and specular but not absolutely bright, possibly indicating non-steady dynamics in the overlying ice. Fuzzy lakes are both relatively and absolutely bright, but not specular, and may indicate saturated sediments or high frequency spatially heterogeneous distributions of sediment and liquid water (i.e. a braided steam). Indistinct lakes are absolutely bright and specular but no brighter than their surroundings. Lakes themselves and the different classes of lakes are not arranged randomly throughout Antarctica but are clustered around ice divides, ice stream onsets and prominent bedrock troughs, with each cluster demonstrating a different characteristic lake classification distribution

  3. An ace-1 gene duplication resorbs the fitness cost associated with resistance in Anopheles gambiae, the main malaria mosquito

    PubMed Central

    Assogba, Benoît S.; Djogbénou, Luc S.; Milesi, Pascal; Berthomieu, Arnaud; Perez, Julie; Ayala, Diego; Chandre, Fabrice; Makoutodé, Michel; Labbé, Pierrick; Weill, Mylène

    2015-01-01

    Widespread resistance to pyrethroids threatens malaria control in Africa. Consequently, several countries switched to carbamates and organophophates insecticides for indoor residual spraying. However, a mutation in the ace-1 gene conferring resistance to these compounds (ace-1R allele), is already present. Furthermore, a duplicated allele (ace-1D) recently appeared; characterizing its selective advantage is mandatory to evaluate the threat. Our data revealed that a unique duplication event, pairing a susceptible and a resistant copy of the ace-1 gene spread through West Africa. Further investigations revealed that, while ace-1D confers less resistance than ace-1R, the high fitness cost associated with ace-1R is almost completely suppressed by the duplication for all traits studied. ace-1 duplication thus represents a permanent heterozygote phenotype, selected, and thus spreading, due to the mosaic nature of mosquito control. It provides malaria mosquito with a new evolutionary path that could hamper resistance management. PMID:26434951

  4. PUTATIVE STRESS REGULATED GENES OF THE ANTARCTIC MIDGE, BELGICA ANTARCTICA

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Antarctica presents one of the earth’s most inhospitable environments. Though an abundance of animals have adapted to life associated with the sea in this part of the world, few animals have adapted to the rigors of a terrestrial existence. One exception is the flightless midge Belgica antarctica ...

  5. STRESS PROTEINS OF THE ANTARCTIC MIDGE, BELGICA ANTARCTICA

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Antarctica presents one of the earth’s most inhospitable environments. Though an abundance of animals have adapted to life associated with the sea in this part of the world, few animals have adapted to the rigors of a terrestrial existence. One exception is the flightless midge Belgica antarctica ...

  6. Antarctica Research in the Polar Research Center of China

    NASA Astrophysics Data System (ADS)

    Zhang, Z.; Li, Y.; Liu, S.; Cole-Dai, J.

    2003-12-01

    The Polar Research Center of China (PRCC) was established in the early 1990s (formerly Polar Research Institute of China) to serve as the leading national organization for Antarctica-related research in China. Current research areas of center staff scientists include glaciology and paleoclimatology, upper atmospheric physics, polar and marine biology, and oceanagrphy. In addition to its own active research, PRCC on behalf of the China Antarctic and Arctic Administration coordinates and provides logistical support to Antarctica research activities by all Chinese scientists. The center organizes and manages the annual Chinese Research Expedition to Antarctica with participation from many other national and academic institutions. In its first decade of existence, PRCC has accumulated valuable experience in conducting and facilitating research in Antarctica, particularly in the areas of logistic support for field programs, staffing and managing the two permanent stations in Antarctica (Great Wall and Zhongshan). The successful operation of the Chinese Antarctica research program has benefitted from generous assistance from several more established national (for example, Australia, Japan and the United States) Antarctica programs and from frequent contact with international colleagues working on Antarctica research. Among the many issues and problems frequently encountered in the last decade are: (1) The scale of research activities is often seriously constrained by logistic capabilities and funding; (2) Limited computer network and library resources hamper speedy and timely access to relevant international scientific literature; (3) Acquisition of high quality scientific (field and laboratory) equipment and special supplies can be limited by funding and access to suppliers.

  7. The effect of saturation of ACE binding sites on the pharmacokinetics of enalaprilat in man.

    PubMed Central

    Wade, J R; Meredith, P A; Hughes, D M; Elliott, H L

    1992-01-01

    1. Eight healthy male volunteers received oral enalapril, 10 mg, in the presence and absence of pretreatment with captopril, 50 mg, twice daily for 5 days. 2. Enalaprilat pharmacokinetics were characterised after both doses of enalapril to investigate the effect of saturating ACE binding sites by pretreatment with captopril. 3. The pharmacokinetics of enalaprilat were best described by a one compartment model with zero order input incorporating saturable binding to plasma and tissue ACE. 4. Values of AUC (0.72 h) for enalaprilat were 419 +/- 97 and 450 +/- 87 ng ml-1 h in the presence and absence of captopril, respectively. The difference was not statistically significant nor were there any other differences in model parameters. 5. Induction of ACE by captopril resulting in an increase in the number of ACE binding sites, may have obscured any effect of captopril on the occupancy of ACE binding sites by enalapril. PMID:1312853

  8. Angiotensin-I-Converting Enzyme (ACE) Inhibitors from Marine Resources: Prospects in the Pharmaceutical Industry

    PubMed Central

    Wijesekara, Isuru; Kim, Se-Kwon

    2010-01-01

    Hypertension or high blood pressure is one of the major independent risk factors for cardiovascular diseases. Angiotensin-I-converting enzyme (EC 3.4.15.1; ACE) plays an important physiological role in regulation of blood pressure by converting angiotensin I to angiotensin II, a potent vasoconstrictor. Therefore, the inhibition of ACE activity is a major target in the prevention of hypertension. Recently, the search for natural ACE inhibitors as alternatives to synthetic drugs is of great interest to prevent several side effects and a number of novel compounds such as bioactive peptides, chitooligosaccharide derivatives (COS) and phlorotannins have been derived from marine organisms as potential ACE inhibitors. These inhibitory derivatives can be developed as nutraceuticals and pharmaceuticals with potential to prevent hypertension. Hence, the aim of this review is to discuss the marine-derived ACE inhibitors and their future prospects as novel therapeutic drug candidates for treat hypertension. PMID:20479968

  9. Adolescent parents and their children: a multifaceted approach to prevention of adverse childhood experiences (ACE).

    PubMed

    Mayer, Lynn Milgram; Thursby, Ellen

    2012-01-01

    Childhood experiences can have long-term effects. Research shows that children who undergo adverse childhood experiences (ACE) often have negative health and mental health outcomes later in life. Children of adolescent parents with high ACE Scores are at greater risk of ACE. As such, an intergenerational approach to preventing ACE is proposed in this article, addressing the needs of both the adolescent parent and their children. A review of the literature indicates that a public health perspective can guide the development of a prevention model aimed at reducing the effects of ACE. The current article proposes a universal, multifaceted, and interdisciplinary prevention science model that has two targets: adolescent parents and their children. Schools and early childhood programs can be mobilized to offer community prevention strategies across realms to include the individual, community, provider, coalitions/networks, organizational practices, and policy/legislation. PMID:22970783

  10. Isolation, Purification and Molecular Mechanism of a Peanut Protein-Derived ACE-Inhibitory Peptide

    PubMed Central

    Shi, Aimin; Liu, Hongzhi; Liu, Li; Hu, Hui; Wang, Qiang; Adhikari, Benu

    2014-01-01

    Although a number of bioactive peptides are capable of angiotensin I-converting enzyme (ACE) inhibitory effects, little is known regarding the mechanism of peanut peptides using molecular simulation. The aim of this study was to obtain ACE inhibiting peptide from peanut protein and provide insight on the molecular mechanism of its ACE inhibiting action. Peanut peptides having ACE inhibitory activity were isolated through enzymatic hydrolysis and ultrafiltration. Further chromatographic fractionation was conducted to isolate a more potent peanut peptide and its antihypertensive activity was analyzed through in vitro ACE inhibitory tests and in vivo animal experiments. MALDI-TOF/TOF-MS was used to identify its amino acid sequence. Mechanism of ACE inhibition of P8 was analyzed using molecular docking and molecular dynamics simulation. A peanut peptide (P8) having Lys-Leu-Tyr-Met-Arg-Pro amino acid sequence was obtained which had the highest ACE inhibiting activity of 85.77% (half maximal inhibitory concentration (IC50): 0.0052 mg/ml). This peanut peptide is a competitive inhibitor and show significant short term (12 h) and long term (28 days) antihypertensive activity. Dynamic tests illustrated that P8 can be successfully docked into the active pocket of ACE and can be combined with several amino acid residues. Hydrogen bond, electrostatic bond and Pi-bond were found to be the three main interaction contributing to the structural stability of ACE-peptide complex. In addition, zinc atom could form metal-carboxylic coordination bond with Tyr, Met residues of P8, resulting into its high ACE inhibiting activity. Our finding indicated that the peanut peptide (P8) having a Lys-Leu-Tyr-Met-Arg-Pro amino acid sequence can be a promising candidate for functional foods and prescription drug aimed at control of hypertension. PMID:25347076

  11. Source Mechanism Inversion of Very Long Period Strombolian Eruption Signals at Mount Erebus, Antarctica

    NASA Astrophysics Data System (ADS)

    McNamara, S. K.; Aster, R. C.; Kyle, P.

    2003-12-01

    Oscillatory, repeatable, very-long-period signals (25 s > T > 5 s) associated with strombolian eruptions of Mt. Erebus, Antarctica have been recorded by near-field broadband seismometers for several years. The eruptions are typically single, large (up to 10-m diameter), explosive bubble decompressions occurring at the surface of a phonolitic lava lake that eviscerate the lake to a depth of approximately 10 m. Associated VLP signals begin several seconds before, and continue for several minutes after, eruptions, becoming indistinguishable as lava lake recovery is achieved. We have performed waveform inversions of high signal-to-noise stacks to recover equivalent point-source moment tensor parameters and associated source time functions. Solutions are obtained by minimizing 2-norm residuals between synthetic and three-component observed seismograms using a modified version of the iterative inversion technique of Lay and Wallace (1995). We allow for varying degrees of source freedom, ranging from pure Mogi (explosive/implosive) to a complete set of six double couples and three single forces. Results suggest a shallow (<= 200 m) source region and negligible non-volumetric couple and single-force terms. During the VLP coda, the source model evolves in time towards an increasingly subhorizontal resonating crack. We will address the accuracy of using simple half-space Green's functions in such inversions and discuss source mechanism possibilities in terms of slow elastic, dynamic recharge, and other processes.

  12. Pressurized brines in continental Antarctica as a possible analogue of Mars.

    PubMed

    Forte, Emanuele; Dalle Fratte, Michele; Azzaro, Maurizio; Guglielmin, Mauro

    2016-01-01

    Interest in brines in extreme and cold environments has recently increased after they have been found on Mars. Those brines can be potential new subsurface habitats for peculiar ecosystems. In the McMurdo Dry Valleys of the Antarctic, the best analogue for Mars conditions, only a few cases of brines have been identified in some perennially frozen lakes and in one case in an underground aquifer. Here, we present the occurrence of pressurized brines in a shallow perennially ice-covered lake south of 70°S in an ice-free area of Victoria Land, Antarctica. For the first time, we also imaged, by means of ground penetrating radar data, the existence of a pingo-like-feature (PLF) formed by the extrusion of brines, which has also been confirmed by borehole evidence. Those brines are fed by an underground talik external to the lake basin, enhancing the possibility of unexploited ecosystems that could find an analogue in Martian environments. PMID:27616183

  13. Polyphasic characterization of 10 selected ecologically relevant filamentous cyanobacterial strains from the South Shetland Islands, Maritime Antarctica.

    PubMed

    Jancusova, Miroslava; Kovacik, Lubomir; Pereira, Antonio Batista; Dusinsky, Roman; Wilmotte, Annick

    2016-07-01

    The evolutionary relationships of 10 Antarctic cyanobacterial strains of the order Oscillatoriales isolated from King George and Deception Islands, South Shetland Islands were studied by a polyphasic approach (morphology, 16S rRNA and internal transcribed spacer sequences). The studied taxa are characteristic of coastal Antarctic biotopes, where they form distinct populations and ecologically delimited communities. They were isolated from terrestrial habitats: microbial mats in seepages; crusts on soil, rocks, bones and mosses; mud, sometimes close to bird colonies; and from guano. Based on major phenotypic features, the strains were divided into four distinct morphotypes: Leptolyngbya borchgrevinkii (A), Leptolyngbya frigida (B), Microcoleus sp. (C) and Wilmottia murrayi (D). This morphological identification was in agreement with the phylogenetic relationships. For the first time, the 16S rRNA gene sequence of a strain corresponding to the L. borchgrevinkii morphotype was determined. Morphotype B is most related to sequences assigned to L. frigida isolated from microbial mats of coastal lakes in East Antarctica. Morphotype C belongs to a cluster including strains with morphotypes corresponding to Microcoleus attenuatus, Microcoleus favosus and Microcoleus sp., which are from Antarctica and other continents. Morphotype D is grouped with sequences assigned to W. murrayi mostly isolated from Antarctica. PMID:27162184

  14. Planning Pathways for Women from Adult Community Education (ACE) to Vocational Education and Training (VET). Project Report.

    ERIC Educational Resources Information Center

    McIntyre, John; Kimberley, Helen

    The formal and informal pathways taken by Australian women from nonaccredited adult community education (ACE) to accredited programs of vocational education and training (VET) were examined in a national survey. Data were collected from a review of the literature on ACE, and telephone interviews with providers of ACE and VET (from a sample limited…

  15. Lithospheric Structure and Seismotectonics of Central East Antarctica

    NASA Astrophysics Data System (ADS)

    Reading, A. M.

    2006-12-01

    The lithosphere of central East Antarctica, the sector of the continent between 30°E - 120°E, is investigated using seismic methods including receiver function and shear-wave splitting analysis. Data from the broadband stations of the temporary SSCUA deployment (in the continental interior) are used together with records from the permanent GSN stations (on the coast) to carry out the first studies of crustal depth and structure, and patterns of seismic anisotropy across this region. The depth of the Moho is found to be 42 km (+/- 2 km) beneath Mawson station with similar structures extending southward across the Rayner province as far south as Beaver Lake. The Fisher Terrane is characterised by a crustal shear wavespeed profile showing few discontinuties with the Moho at a similar depth to the Rayner. South of Fisher, the crust becomes much shallower, with the Moho at 32 km depth. This shallow crust extends across the Lambert glacier to the Prydz coast and the Lambert Terrane. The characteristic crustal wavespeed profiles provide baseline structure for mapping the extent of the terrance beneath the Antarctic Ice Sheet in future deployments. Observations of seismic anisotropy are less well- defined but, at a reconnaissance level, show fast directions parallel to the present day coastline. This may be controlled by rift-related influences on the lithosphere associated with the breakup of East Gondwana. The seismicity is confirmed to be extremely low. The only seismogenic forces on the Antarctic plate in this region are acting at the boundary between the continental and oceanic lithosphere west of 50°E and east of 100°E and represent a superposition of tectonic and glaciogenic controls. The Lambert Glacier region shows little or no seismotectonic activity in the continental interior or on the oceanic margin.

  16. The crustal thickness of West Antarctica

    NASA Astrophysics Data System (ADS)

    Chaput, J.; Aster, R. C.; Huerta, A.; Sun, X.; Lloyd, A.; Wiens, D.; Nyblade, A.; Anandakrishnan, S.; Winberry, J. P.; Wilson, T.

    2014-01-01

    P-to-S receiver functions (PRFs) from the Polar Earth Observing Network (POLENET) GPS and seismic leg of POLENET spanning West Antarctica and the Transantarctic Mountains deployment of seismographic stations provide new estimates of crustal thickness across West Antarctica, including the West Antarctic Rift System (WARS), Marie Byrd Land (MBL) dome, and the Transantarctic Mountains (TAM) margin. We show that complications arising from ice sheet multiples can be effectively managed and further information concerning low-velocity subglacial sediment thickness may be determined, via top-down utilization of synthetic receiver function models. We combine shallow structure constraints with the response of deeper layers using a regularized Markov chain Monte Carlo methodology to constrain bulk crustal properties. Crustal thickness estimates range from 17.0±4 km at Fishtail Point in the western WARS to 45±5 km at Lonewolf Nunataks in the TAM. Symmetric regions of crustal thinning observed in a transect deployment across the West Antarctic Ice Sheet correlate with deep subice basins, consistent with pure shear crustal necking under past localized extension. Subglacial sediment deposit thicknesses generally correlate with trough/dome expectations, with the thickest inferred subice low-velocity sediment estimated as ˜0.4 km within the Bentley Subglacial Trench. Inverted PRFs from this study and other published crustal estimates are combined with ambient noise surface wave constraints to generate a crustal thickness map for West Antarctica south of 75°S. Observations are consistent with isostatic crustal compensation across the central WARS but indicate significant mantle compensation across the TAM, Ellsworth Block, MBL dome, and eastern and western sectors of thinnest WARS crust, consistent with low density and likely dynamic, low-viscosity high-temperature mantle.

  17. Recovery frontier in Antarctica: new glaciological insights from an aerogeophysical survey

    NASA Astrophysics Data System (ADS)

    Matsuoka, K.; Forsberg, R.; Ferraccioli, F.; Kohler, J.; Corr, H.; Jordan, T. A.; Olesen, A. V.

    2013-12-01

    Active subglacial lakes aligned along the Recovery Glacier that penetrates deep in the interior of East Antarctica imply movement of subglacial water on timescales of months to years (Smith et al., 2009, J. Glac.). Four giant subglacial lakes (Bell et al., 2007, Nature) are present upstream of these smaller active lakes and have been hypothesized to have drained recently (Langley et al., 2011, GRL). Dynamic behavior and potential instability for the Recovery Glacier catchment may be possible due to the combination of fast glacial flow extending hundreds of km inland, deep bedrock topography, active lakes beneath the main trunk of the glacier, and possibly coupling with giant lake reservoirs further upstream A cascade of questions remains however unresolved over this largely unexplored frontier region and this hampers our understanding of ice sheet dynamics and stability. Are these smaller active lakes and the four giant subglacial lakes hydraulically connected? How does the subglacial hydrology control basal motion of the fast-flowing Recovery Glacier? And more fundamentally, are the Recovery Glacier and the subglacial lakes locations constrained either topographically, by geological and tectonic features, and/or glaciologically? To address these major open questions we performed the first systematic reconnaissance aerogeophysical survey over the Recovery catchment. Over 29,000 line km of new radio-echo sounding, laser altimetry, gravity and magnetic data were acquired using a British Antarctic Survey Twin Otter that surveyed the region during the IceGRAV 2012-13 field season. Here we focus on the initial results derived from the new airborne radar dataset. We present the first maps of ice thickness and bedrock topography for the Recovery catchment and showcase the strong contrasts in bedrock topography and patterns of bed returned power in the upper and lower reaches of the Recovery Glacier catchment. These new survey results in the Recovery frontier are of major

  18. Antarctica: measuring glacier velocity from satellite images

    SciTech Connect

    Lucchitta, B.K.; Ferguson, H.M.

    1986-11-28

    Many Landsat images of Antarctica show distinctive flow and crevasse features in the floating part of ice streams and outlet glaciers immediately below their grounding zones. Some of the features, which move with the glacier or ice stream, remain visible over many years and thus allow time-lapse measurements of ice velocities. Measurements taken from Landsat images of features on Byrd Glacier agree well with detailed ground and aerial observations. The satellite-image technique thus offers a rapid and cost-effective method of obtaining average velocities, to a first order of accuracy, of many ice streams and outlet glaciers near their termini.

  19. Antarctica: Measuring glacier velocity from satellite images

    USGS Publications Warehouse

    Lucchitta, B.K.; Ferguson, H.M.

    1986-01-01

    Many Landsat images of Antarctica show distinctive flow and crevasse features in the floating part of ice streams and outlet glaciers immediately below their grounding zones. Some of the features, which move with the glacier or ice stream, remain visible over many years and thus allow time-lapse measurements of ice velocities. Measurements taken from Landsat images of features on Byrd Glacier agree well with detailed ground and aerial observations. The satellite-image technique thus offers a rapid and cost-effective method of obtaining average velocities, to a first order of accuracy, of many ice streams and outlet glaciers near their termini.

  20. Exhumation of the Shackleton Range, Antarctica

    NASA Astrophysics Data System (ADS)

    Lucka, Nicole; Lisker, Frank; Läufer, Andreas; Spiegel, Cornelia

    2013-04-01

    The Shackleton Range is situated between 80° - 81°S and 19° - 31°W, where it forms the continuation of the Transantarctic Mountains in the Weddell Sea sector of Antarctica. There, Precambrian igneous and metamorphic basement is overlain by (meta-) sedimentary rocks of an Early Paleozoic nappe stack and post-orogenic red beds. Nappe stacking resulted from the collision of East and West Gondwana due to the closure of the Mozambique Ocean in pan-African times. The uplift and exhumation history of the Shackleton Range has been analysed earlier based on a series of vertical fission track profiles (Schäfer, 1998; Lisker et al., 1999). Zircon ages range from ~160 to 210 Ma while apatite ages between ~95 and ~170 Ma comprise a break in slope of the altitude regression at ~110 Ma, and are accompanied by mean track lengths of 12.7 - 14.1 µm (standard deviation 1.0 - 1.4 µm). These data have been interpreted qualitatively in terms of two cooling/ exhumation stages during Jurassic and mid-Cretaceous times. However, the recognition of Jurassic volcaniclastic rocks associated with the ~180 Ma Ferrar event in the vicinity of the sample locations (Buggisch et al., 1994) challenges this exhumation concept. Moreover, new fission track proxy data (Dpar) and apatite (U-Th-Sm)/He ages between 88 and 171 Ma allow thermal history modelling of the combined thermochronological data. First tentative thermal history models suggest early Mesozoic cooling followed by (post-) Jurassic heating and final cooling since the Late Cretaceous. This scenario requires burial of the Shackleton Range region, and therefore the existence of a sedimentary basin at least during the Jurassic-Early Cretaceous, and subsequent basin inversion. The thickness of the now vanished sedimentary strata did unlikely exceed 2 - 3 km. Future work including additional apatite fission track analyses will help to quantifying geometry, depth and timing of this depocentre and evaluating potential links with the coeval

  1. Boundary layer halogens in coastal Antarctica.

    PubMed

    Saiz-Lopez, Alfonso; Mahajan, Anoop S; Salmon, Rhian A; Bauguitte, Stephane J-B; Jones, Anna E; Roscoe, Howard K; Plane, John M C

    2007-07-20

    Halogens influence the oxidizing capacity of Earth's troposphere, and iodine oxides form ultrafine aerosols, which may have an impact on climate. We report year-round measurements of boundary layer iodine oxide and bromine oxide at the near-coastal site of Halley Station, Antarctica. Surprisingly, both species are present throughout the sunlit period and exhibit similar seasonal cycles and concentrations. The springtime peak of iodine oxide (20 parts per trillion) is the highest concentration recorded anywhere in the atmosphere. These levels of halogens cause substantial ozone depletion, as well as the rapid oxidation of dimethyl sulfide and mercury in the Antarctic boundary layer. PMID:17641195

  2. Adipocyte-derived lipids increase angiotensin-converting enzyme (ACE) expression and modulate macrophage phenotype.

    PubMed

    Kohlstedt, Karin; Trouvain, Caroline; Namgaladze, Dmitry; Fleming, Ingrid

    2011-03-01

    Human monocytes/macrophages express the angiotensin-converting enzyme (ACE) but nothing is known about its role under physiological conditions. As adipose tissue contains resident macrophages that have been implicated in the generation of insulin resistance in expanding fat mass, we determined whether adipocytes release factors that affect ACE expression and function in monocytes. Incubation of human monocyte-derived macrophages with conditioned medium from freshly isolated human adipocytes (BMI = 25.4 ± 0.96) resulted in a 4-fold increase in ACE expression. The effect was insensitive to denaturation and different proteases but abolished after lipid extraction. mRNA levels of the major histocompatibility complex class II protein increased in parallel with ACE, whereas the expression of tumor necrosis factor-α (TNF-α), monocyte chemoattractant protein-1 (MCP-1), interleukin (IL)-6, and cyclooxygenase-2 decreased. As a consequence of the reduction in MCP-1, monocyte recruitment was also attenuated. Moreover, adipocyte-conditioned medium prevented the interferon (IFN)-γ induced formation of TNF-α, IL-6, and MCP-1, all markers of classically-activated (M1 type) macrophages. The decrease in cytokine expression in adipocyte-conditioned medium-treated macrophages was sensitive to ACE silencing by small interfering RNA (siRNA). Accordingly, ACE overexpression in THP-1 cells mimicked the effect of adipocyte-conditioned medium. In both cell types, ACE inhibition failed to affect the changes induced by adipocyte conditioned-medium treatment and ACE overexpression. Thus, the modulation of macrophage polarization by ACE appears to be mediated independently of enzyme activity, probably via intracellular signaling. Interestingly, human macrophage ACE expression was also upregulated by IL-4 and IL-13, which promote the "alternative" activation of macrophages and decreased by LPS and IFN-γ. Mechanistically, adipocyte-conditioned medium stimulated the phosphorylation of

  3. Risk-benefit ratio of angiotensin antagonists versus ACE inhibitors in end-stage renal disease.

    PubMed

    Sica, D A; Gehr, T W; Fernandez, A

    2000-05-01

    The effective treatment of hypertension is an extremely important consideration in patients with end-stage renal disease (ESRD). Virtually any drug class--with the possible exception of diuretics--can be used to treat hypertension in the patient with ESRD. Despite there being such a wide range of treatment options, drugs which interrupt the renin-angiotensin axis are generally suggested as agents of choice in this population, even though the evidence in support of their preferential use is quite scanty. ACE inhibitors, and more recently angiotensin antagonists, are the 2 drug classes most commonly employed to alter renin-angiotensin axis activity and therefore produce blood pressure control. ACE inhibitor use in patients with ESRD can sometimes prove an exacting proposition. ACE inhibitors are variably dialysed, with compounds such as catopril, enalapril, lisinopril and perindopril undergoing substantial cross-dialyser clearance during a standard dialysis session. This phenomenon makes the selection of a dose and the timing of administration for an ACE inhibitor a complex issue in patients with ESRD. Furthermore, ACE inhibitors are recognised as having a range of nonpressor effects that are pertinent to patients with ESRD. Such effects include their ability to decrease thirst drive and to decrease erythropoiesis. In addition, ACE inhibitors have a unique adverse effect profile. As is the case with their use in patients without renal failure, use of ACE inhibitors in patients with ESRD can be accompanied by cough and less frequently by angioneurotic oedema. In the ESRD population, ACE inhibitor use is also accompanied by so-called anaphylactoid dialyser reactions. Angiotensin antagonists are similar to ACE inhibitors in their mechanism of blood pressure lowering. Angiotensin antagonists are not dialysable and therefore can be distinguished from a number of the ACE inhibitors. In addition, the adverse effect profile for angiotensin antagonists is remarkably bland

  4. An active subglacial water system in West Antarctica mapped from space.

    PubMed

    Fricker, Helen Amanda; Scambos, Ted; Bindschadler, Robert; Padman, Laurie

    2007-03-16

    Satellite laser altimeter elevation profiles from 2003 to 2006 collected over the lower parts of Whillans and Mercer ice streams, West Antarctica, reveal 14 regions of temporally varying elevation, which we interpret as the surface expression of subglacial water movement. Vertical motion and spatial extent of two of the largest regions are confirmed by satellite image differencing. A major, previously unknown subglacial lake near the grounding line of Whillans Ice Stream is observed to drain 2.0 cubic kilometers of water into the ocean over approximately 3 years, while elsewhere a similar volume of water is being stored subglacially. These observations reveal a wide spread, dynamic subglacial water system that may exert an important control on ice flow and mass balance. PMID:17303716

  5. Clouds in the Tropical Lowermost Stratosphere Observed by ACE

    NASA Astrophysics Data System (ADS)

    Sloan, J. J.; Galkina, I.; Sioris, C. E.; Nowlan, C. R.; McElroy, T.; Zou, J.; Hu, J.; Drummond, J. R.; McLinden, C. A.

    2008-12-01

    Evidence for the occurrence of cloud particles in the tropical lowermost stratosphere in the 2004-2007 period is presented. This study is based on measurements by the three Atmospheric Chemistry Experiment (ACE) instruments onboard SCI-SAT. The Vis & NIR Imagers are used to determine the presence of clouds and their top height. The Fourier Transform Spectrometer (FTS) observations are used to determine the size distribution and composition of the aerosols. The FTS has a 4 km field-of-view. Measurements of Aerosol Extinction in the Stratosphere and Troposphere Retrieved by Occultation (MAESTRO) provide more precise altitude determination of the thermal tropopause and the cloud tops by virtue of its smaller FOV (~1 km). Clouds in the tropical lower stratosphere are a rare occurrence but April 2005 produced a few such cases, consistent with previous observations by OSIRIS. We discuss several individual case studies that demonstrate the presence of large particles (mode radius of ~8 microns) clearly above the tropopause.

  6. Cosmic Ray Helium Intensities over the Solar Cycle from ACE

    NASA Technical Reports Server (NTRS)

    DeNolfo, G. A.; Yanasak, N. E.; Binns, W. R.; Cohen, C. M. S.; Cummings, A. C.; Davis, A. J.; George, J. S.; Hink. P. L.; Israel, M. H.; Lave, K.; Leske, R. A.; Mewaldt, R. A.; Moskalenko, I. V.; Ogliore, R.; Stone, E. C.; Von Rosenvinge, T. T.; Wiedenback, M. E.

    2007-01-01

    Observations of cosmic-ray helium energy spectra provide important constraints on cosmic ray origin and propagation. However, helium intensities measured at Earth are affected by solar modulation, especially below several GeV/nucleon. Observations of helium intensities over a solar cycle are important for understanding how solar modulation affects galactic cosmic ray intensities and for separating the contributions of anomalous and galactic cosmic rays. The Cosmic Ray Isotope Spectrometer (CRIS) on ACE has been measuring cosmic ray isotopes, including helium, since 1997 with high statistical precision. We present helium elemental intensities between approx. 10 to approx. 100 MeV/nucleon from the Solar Isotope Spectrometer (SIS) and CRIS observations over a solar cycle and compare these results with the observations from other satellite and balloon-borne instruments, and with GCR transport and solar modulation models.

  7. Airborne laser swath mapping of the Denton Hills, Transantarctic Mountains, Antarctica: Applications for structural and glacial geomorphic mapping

    USGS Publications Warehouse

    Wilson, Terry; Csathó, Beata

    2007-01-01

    High-resolution digital elevation data acquired by airborne laser scanning (ALS) for the Denton Hills, along the coastal foothills of the Royal Society Range, Transantarctic Mountains, are examined for applications to bedrock and glacial geomorphic mapping. Digital elevation models (DEMs), displayed as shaded-relief images and slope maps, portray geomorphic landscape features in unprecedented detail across the region. Structures of both ductile and brittle origin, ranging in age from the Paleozoic to the Quaternary, can be mapped from the DEMs. Glacial features, providing a record of the limits of grounded ice, of lake paleoshorelines, and of proglacial lake-ice conveyor deposits, are also prominent on the DEMs. The ALS-derived topographic data have great potential for a range of mapping applications in regions of ice-free terrain in Antarctica

  8. Lake Powell

    NASA Technical Reports Server (NTRS)

    2007-01-01

    The white ring around Lake Powell tells the story. The surface is down 98 feet. This is critical, because Powell, Lake Mead, and other lakes along the Colorado River provide water for millions of people in five states. We are in the eighth year of a drought on the Colorado River. This year was the driest year ever reported in Southern California, and there is a severe drought in Northern California, down to less than 30-percent of snow pack. This ASTER image of part of Lake Powell was acquired in 2001. The gray area depicts the shrunken, reduced 2007 lake extent compared to the extended, larger black area in 2001.

    The image covers an area of 24 x 30 km, and is centered near 37.1 degrees north latitude, 111.3 degrees west longitude.

    The U.S. science team is located at NASA's Jet Propulsion Laboratory, Pasadena, Calif. The Terra mission is part of NASA's Science Mission Directorate.

  9. Polar lakes may act as ecological islands to aquatic protists

    PubMed Central

    RENGEFORS, K; LOGARES, R; LAYBOURN-PARRY, J

    2012-01-01

    A fundamental question in ecology is whether microorganisms follow the same patterns as multicellular organisms when it comes to population structure and levels of genetic diversity. Enormous population sizes, predominately asexual reproduction and presumably high dispersal because of small body size could have profound implications on their genetic diversity and population structure. Here, we have analysed the population genetic structure in a lake-dwelling microbial eukaryote (dinoflagellate) and tested the hypothesis that there is population genetic differentiation among nearby lake subpopulations. This dinoflagellate occurs in the marine-derived saline lakes of the Vestfold Hills, Antarctica, which are ice-covered most of the year. Clonal strains were isolated from four different lakes and were genotyped using amplified fragment length polymorphism (AFLP). Our results show high genetic differentiation among lake populations despite their close geographic proximity (<9 km). Moreover, genotype diversity was high within populations. Gene flow in this system is clearly limited, either because of physical or biological barriers. Our results discard the null hypothesis that there is free gene flow among protist lake populations. Instead, limnetic protist populations may differentiate genetically, and lakes act as ecological islands even on the microbial scale. PMID:22564188

  10. Recent advances in understanding Antarctic subglacial lakes and hydrology.

    PubMed

    Siegert, Martin J; Ross, Neil; Le Brocq, Anne M

    2016-01-28

    It is now well documented that over 400 subglacial lakes exist across the bed of the Antarctic Ice Sheet. They comprise a variety of sizes and volumes (from the approx. 250 km long Lake Vostok to bodies of water less than 1 km in length), relate to a number of discrete topographic settings (from those contained within valleys to lakes that reside in broad flat terrain) and exhibit a range of dynamic behaviours (from 'active' lakes that periodically outburst some or all of their water to those isolated hydrologically for millions of years). Here we critique recent advances in our understanding of subglacial lakes, in particular since the last inventory in 2012. We show that within 3 years our knowledge of the hydrological processes at the ice-sheet base has advanced considerably. We describe evidence for further 'active' subglacial lakes, based on satellite observation of ice-surface changes, and discuss why detection of many 'active' lakes is not resolved in traditional radio-echo sounding methods. We go on to review evidence for large-scale subglacial water flow in Antarctica, including the discovery of ancient channels developed by former hydrological processes. We end by predicting areas where future discoveries may be possible, including the detection, measurement and significance of groundwater (i.e. water held beneath the ice-bed interface). PMID:26667914

  11. Modeling Antarctic Subglacial Lake Filling and Drainage Cycles

    NASA Technical Reports Server (NTRS)

    Dow, Christine F.; Werder, Mauro A.; Nowicki, Sophie; Walker, Ryan T.

    2016-01-01

    The growth and drainage of active subglacial lakes in Antarctica has previously been inferred from analysis of ice surface altimetry data. We use a subglacial hydrology model applied to a synthetic Antarctic ice stream to examine internal controls on the filling and drainage of subglacial lakes. Our model outputs suggest that the highly constricted subglacial environment of our idealized ice stream, combined with relatively high rates of water flow funneled from a large catchment, can combine to create a system exhibiting slow-moving pressure waves. Over a period of years, the accumulation of water in the ice stream onset region results in a buildup of pressure creating temporary channels, which then evacuate the excess water. This increased flux of water beneath the ice stream drives lake growth. As the water body builds up, it steepens the hydraulic gradient out of the overdeepened lake basin and allows greater flux. Eventually this flux is large enough to melt channels that cause the lake to drain. Lake drainage also depends on the internal hydrological development in the wider system and therefore does not directly correspond to a particular water volume or depth. This creates a highly temporally and spatially variable system, which is of interest for assessing the importance of subglacial lakes in ice stream hydrology and dynamics.

  12. Recent advances in understanding Antarctic subglacial lakes and hydrology

    PubMed Central

    Siegert, Martin J.; Ross, Neil; Le Brocq, Anne M.

    2016-01-01

    It is now well documented that over 400 subglacial lakes exist across the bed of the Antarctic Ice Sheet. They comprise a variety of sizes and volumes (from the approx. 250 km long Lake Vostok to bodies of water less than 1 km in length), relate to a number of discrete topographic settings (from those contained within valleys to lakes that reside in broad flat terrain) and exhibit a range of dynamic behaviours (from ‘active’ lakes that periodically outburst some or all of their water to those isolated hydrologically for millions of years). Here we critique recent advances in our understanding of subglacial lakes, in particular since the last inventory in 2012. We show that within 3 years our knowledge of the hydrological processes at the ice-sheet base has advanced considerably. We describe evidence for further ‘active’ subglacial lakes, based on satellite observation of ice-surface changes, and discuss why detection of many ‘active’ lakes is not resolved in traditional radio-echo sounding methods. We go on to review evidence for large-scale subglacial water flow in Antarctica, including the discovery of ancient channels developed by former hydrological processes. We end by predicting areas where future discoveries may be possible, including the detection, measurement and significance of groundwater (i.e. water held beneath the ice-bed interface). PMID:26667914

  13. Modeling Antarctic subglacial lake filling and drainage cycles

    NASA Astrophysics Data System (ADS)

    Dow, Christine F.; Werder, Mauro A.; Nowicki, Sophie; Walker, Ryan T.

    2016-07-01

    The growth and drainage of active subglacial lakes in Antarctica has previously been inferred from analysis of ice surface altimetry data. We use a subglacial hydrology model applied to a synthetic Antarctic ice stream to examine internal controls on the filling and drainage of subglacial lakes. Our model outputs suggest that the highly constricted subglacial environment of our idealized ice stream, combined with relatively high rates of water flow funneled from a large catchment, can combine to create a system exhibiting slow-moving pressure waves. Over a period of years, the accumulation of water in the ice stream onset region results in a buildup of pressure creating temporary channels, which then evacuate the excess water. This increased flux of water beneath the ice stream drives lake growth. As the water body builds up, it steepens the hydraulic gradient out of the overdeepened lake basin and allows greater flux. Eventually this flux is large enough to melt channels that cause the lake to drain. Lake drainage also depends on the internal hydrological development in the wider system and therefore does not directly correspond to a particular water volume or depth. This creates a highly temporally and spatially variable system, which is of interest for assessing the importance of subglacial lakes in ice stream hydrology and dynamics.

  14. Economic evaluation of the Annual Cycle Energy System (ACES). Volume II. Detailed results. Final report

    SciTech Connect

    Not Available

    1980-05-01

    The energy effectiveness and the economic viability of the ACES concept are examined. ACES is studied in a variety of different applications and compared to a number of conventional systems. The different applications are studied in two groups: the class of building into which the ACES is incorporated and the climatic region in which the ACES is located. Buildings investigated include single-family and multi-family residences and a commercial office building. The application of ACES to each of these building types is studied in Minneapolis, Atlanta, and Philadelphia. The economic evaluation of the ACES is based on a comparison of the present worth of the ACES to the present worth of conventional systems; namely, electric resistance heating, electric air conditioning, and electric domestic water heating; air-to-air heat pump and electric domestic water heating; oil-fired furnace, electric air conditioning, and electric domestic water heating; and gas-fired furnace, electric air conditioning, and gas domestic water heating.

  15. Applications of Subspace Seismicity Detection in Antarctica

    NASA Astrophysics Data System (ADS)

    Myers, E. K.; Aster, R. C.; Benz, H.; McMahon, N. D.; McNamara, D. E.; Lough, A. C.; Wiens, D. A.; Wilson, T. J.

    2014-12-01

    Subspace detection can improve event recognition by enhancing the completeness of earthquake catalogs and by improving the characterization and interpretation of seismic events, particularly in regions of clustered seismicity. Recent deployments of dense networks of seismometers enable subspace detection methods to be more broadly applied to intraplate Antarctica, where historically very limited and sporadic network coverage has inhibited understanding of dynamic glacial, volcanic, and tectonic processes. In particular, recent broad seismographic networks such as POLENET/A-Net and AGAP provide significant new opportunities for characterizing and understanding the low seismicity rates of this continent. Our methodology incorporates three-component correlation to detect events in a statistical and adaptive framework. Detection thresholds are statistically assessed using phase-randomized template correlation levels. As new events are detected and the set of subspace basis vectors is updated, the algorithm can also be directed to scan back in a search for weaker prior events that have significant correlations with the updated basis vectors. This method has the resolving power to identify previously undetected areas of seismic activity under very low signal-to-noise conditions, and thus holds promise for revealing new seismogenic phenomena within and around Antarctica. In this study we investigate two intriguing seismogenic regions and demonstrate the methodology, reporting on a subspace detection-based study of recently identified clusters of deep long-period magmatic earthquakes in Marie Byrd Land, and on shallow icequakes that are dynamically triggered by teleseismic surface waves.

  16. Cenozoic motion between East and West Antarctica

    PubMed

    Cande; Stock; Muller; Ishihara

    2000-03-01

    The West Antarctic rift system is the result of late Mesozoic and Cenozoic extension between East and West Antarctica, and represents one of the largest active continental rift systems on Earth. But the timing and magnitude of the plate motions leading to the development of this rift system remain poorly known, because of a lack of magnetic anomaly and fracture zone constraints on seafloor spreading. Here we report on magnetic data, gravity data and swath bathymetry collected in several areas of the south Tasman Sea and northern Ross Sea. These results enable us to calculate mid-Cenozoic rotation parameters for East and West Antarctica. These rotations show that there was roughly 180 km of separation in the western Ross Sea embayment in Eocene and Oligocene time. This episode of extension provides a tectonic setting for several significant Cenozoic tectonic events in the Ross Sea embayment including the uplift of the Transantarctic Mountains and the deposition of large thicknesses of Oligocene sediments. Inclusion of this East-West Antarctic motion in the plate circuit linking the Australia, Antarctic and Pacific plates removes a puzzling gap between the Lord Howe rise and Campbell plateau found in previous early Tertiary reconstructions of the New Zealand region. Determination of this East-West Antarctic motion also resolves a long standing controversy regarding the contribution of deformation in this region to the global plate circuit linking the Pacific to the rest of the world. PMID:10724159

  17. The Landsat Image Mosaic of Antarctica

    USGS Publications Warehouse

    Bindschadler, R.; Vornberger, P.; Fleming, A.; Fox, A.; Mullins, J.; Binnie, D.; Paulsen, S.J.; Granneman, B.; Gorodetzky, D.

    2008-01-01

    The Landsat Image Mosaic of Antarctica (LIMA) is the first true-color, high-spatial-resolution image of the seventh continent. It is constructed from nearly 1100 individually selected Landsat-7 ETM+ scenes. Each image was orthorectified and adjusted for geometric, sensor and illumination variations to a standardized, almost seamless surface reflectance product. Mosaicing to avoid clouds produced a high quality, nearly cloud-free benchmark data set of Antarctica for the International Polar Year from images collected primarily during 1999-2003. Multiple color composites and enhancements were generated to illustrate additional characteristics of the multispectral data including: the true appearance of the surface; discrimination between snow and bare ice; reflectance variations within bright snow; recovered reflectance values in regions of sensor saturation; and subtle topographic variations associated with ice flow. LIMA is viewable and individual scenes or user defined portions of the mosaic are downloadable at http://lima.usgs.gov. Educational materials associated with LIMA are available at http://lima.nasa.gov.

  18. Developmental expression of ACE2 in the SHR kidney: a role in hypertension?

    PubMed

    Tikellis, C; Cooper, M E; Bialkowski, K; Johnston, C I; Burns, W C; Lew, R A; Smith, A I; Thomas, M C

    2006-07-01

    The abnormal development of the intrarenal renin-angiotensin system (RAS) is thought contribute to adult-onset hypertension in the spontaneously hypertensive rat (SHR). Angiotensin-converting enzyme 2 (ACE2) is a novel enzyme with complementary actions to that of ACE. Recent studies have shown that ACE2 expression is reduced in the adult SHR. However, its regulation in pre-hypertensive animals is unknown. In this study, we examine the developmental expression of ACE2 in the rodent kidney and its temporal expression, as it relates to the development of hypertension in the SHR model. Kidneys from SHR and normotensive Wistar Kyoto (WKY) rats (n=8-12/group) at birth, 6 weeks of age, and adulthood (80 days) were examined. Gene expression and activity of ACE2 were determined by real-time reverse transcription-polymerase chain reaction and quenched fluorescence assays, respectively. Renal expression was localized by in situ hybridization and immunohistochemistry. The expression and ACE2 activity are significantly increased in the SHR kidney at birth. With the onset of hypertension, the tubular expression of ACE2 falls in SHR compared to WKY and remains reduced in the adult SHR kidney. Glomerular expression is paradoxically increased in the SHR glomerulus. The overall developmental pattern of ACE2 expression in the SHR kidney is also modified, with declining expression over the course of renal development. The developmental pattern of ACE2 expression in the SHR kidney is altered before the onset of hypertension, consistent with the key role of the RAS in the pathogenesis of adult-onset hypertension. Further research is required to distinguish the contribution of these changes to the development and progression of hypertension in this model. PMID:16710353

  19. Late Archaean granulite facies metamorphism in the Vestfold Hills, East Antarctica

    NASA Astrophysics Data System (ADS)

    Zulbati, F.; Harley, S. L.

    2007-01-01

    Granulites of the Vestfold Hills record a pulsed end-Archaean to early Palaeoproterozoic M1-M2 evolution that is distinct from other Archaean areas in East Antarctica and cratonic domains placed adjacent to East Antarctica in Gondwana reconstructions. Pressure and temperature conditions of the end-Archaean to earliest Palaeoproterozoic (2501-2496 Ma) M1 granulite facies metamorphism in the Vestfold Hills have been constrained from mineral assemblages and thermobarometry of Fe-rich paragneisses. Reintegrated compositions of exsolved subcalcic clinopyroxenes and pigeonites in a metaironstone yield temperatures of 895 ± 35 °C, whilst reintegrated compositions of perthitic feldspars in semipelitic paragneisses give minimum estimates of 860 ± 30 °C. These results rule out the extreme ultrahigh temperature (UHT) conditions previously proposed for M1 in the Vestfold Hills. Pressures of metamorphism during M1 are estimated as 8.1 ± 0.9 kb at 850 ± 40 °C from hercynite + sillimanite + almandine + corundum and retrieved Fe-Mg-Al relations in orthopyroxene coexisting with garnet. A second metamorphic event, M2, occurred at 600-660 °C and 6-8 kb based on thermometry of recrystallised pyroxene neoblasts and thermobarometry applied to M2 garnet-quartz symplectites formed on orthopyroxene and garnet. The intervening emplacement of the magmatic Crooked Lake Gneiss Group precursors occurred at similar or shallower pressures prior to D2-M2, an event that caused tectonic interleaving and reactivation of the Vestfold Hills basement at mid-crustal depths in the earliest Palaeoproterozoic, prior to its unroofing to shallower levels (3-5 kb) by 2470 Ma. The lack of correlative Archaean histories in areas that were formerly adjacent in Gondwanan reconstructions is consistent with the Vestfold Hills region either being exotic to the East Antarctic Shield until the final (Neoproterozoic to Cambrian) amalgamation of Gondwana, or being accreted to part of East Antarctica in a

  20. Antarctic lakes suggest millennial reorganizations of Southern Hemisphere atmospheric and oceanic circulation

    PubMed Central

    Hall, Brenda L.; Denton, George H.; Fountain, Andrew G.; Hendy, Chris H.; Henderson, Gideon M.

    2010-01-01

    The phasing of millennial-scale oscillations in Antarctica relative to those elsewhere in the world is important for discriminating among models for abrupt climate change, particularly those involving the Southern Ocean. However, records of millennial-scale variability from Antarctica dating to the last glacial maximum are rare and rely heavily on data from widely spaced ice cores, some of which show little variability through that time. Here, we present new data from closed-basin lakes in the Dry Valleys region of East Antarctica that show high-magnitude, high-frequency oscillations in surface level during the late Pleistocene synchronous with climate fluctuations elsewhere in the Southern Hemisphere. These data suggest a coherent Southern Hemisphere pattern of climate change on millennial time scales, at least in the Pacific sector, and indicate that any hypothesis concerning the origin of these events must account for synchronous changes in both high and temperate latitudes. PMID:21115838

  1. Antarctic lakes suggest millennial reorganizations of Southern Hemisphere atmospheric and oceanic circulation.

    PubMed

    Hall, Brenda L; Denton, George H; Fountain, Andrew G; Hendy, Chris H; Henderson, Gideon M

    2010-12-14

    The phasing of millennial-scale oscillations in Antarctica relative to those elsewhere in the world is important for discriminating among models for abrupt climate change, particularly those involving the Southern Ocean. However, records of millennial-scale variability from Antarctica dating to the last glacial maximum are rare and rely heavily on data from widely spaced ice cores, some of which show little variability through that time. Here, we present new data from closed-basin lakes in the Dry Valleys region of East Antarctica that show high-magnitude, high-frequency oscillations in surface level during the late Pleistocene synchronous with climate fluctuations elsewhere in the Southern Hemisphere. These data suggest a coherent Southern Hemisphere pattern of climate change on millennial time scales, at least in the Pacific sector, and indicate that any hypothesis concerning the origin of these events must account for synchronous changes in both high and temperate latitudes. PMID:21115838

  2. Progress on the Multiphysics Capabilities of the Parallel Electromagnetic ACE3P Simulation Suite

    SciTech Connect

    Kononenko, Oleksiy

    2015-03-26

    ACE3P is a 3D parallel simulation suite that is being developed at SLAC National Accelerator Laboratory. Effectively utilizing supercomputer resources, ACE3P has become a key tool for the coupled electromagnetic, thermal and mechanical research and design of particle accelerators. Based on the existing finite-element infrastructure, a massively parallel eigensolver is developed for modal analysis of mechanical structures. It complements a set of the multiphysics tools in ACE3P and, in particular, can be used for the comprehensive study of microphonics in accelerating cavities ensuring the operational reliability of a particle accelerator.

  3. APL workers install CRIS on the Advanced Composition Explorer (ACE) in SAEF-2

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Workers from the Johns Hopkins University's Applied Physics Laboratory (APL) install the Cosmic Ray Isotope Spectrometer (CRIS) on the Advanced Composition Explorer (ACE) spacecraft in KSC's Spacecraft Assembly and Encapsulation Facility-2 (SAEF-2). From left, are Al Sadilek, Marcos Gonzalez and Cliff Willey. CRIS is one of nine instruments on ACE, which will investigate the origin and evolution of solar phenomenon, the formation of the solar corona, solar flares and the acceleration of the solar wind. ACE was developed for NASA by the APL. The spacecraft is scheduled to be launched Aug. 21 aboard a two-stage Delta II 7920-8 rocket from Space Launch Complex 17, Pad A.

  4. Oxygen supersaturation in ice-covered Antarctic lakes - Biological versus physical contributions

    NASA Technical Reports Server (NTRS)

    Craig, H.; Wharton, R. A., Jr.; Mckay, C. P.

    1992-01-01

    Lake Hoare is one of a number of ice-covered polar lakes in the Dry Valley Region of southern Victoria Land, Antarctica. Analysis of N2, O2, and Ar in bubbles from this lake's ice indicates that while O2 is about 2.4 times supersaturated in the water below the ice, only 11 percent of the O2 input to this lake is due to biological activity and the balance is derived from meltwater inflow. In Lake Hoare, as much as 70 percent of total gas loss may occur by advection through the ice cover; the remaining gas fractions are removed by respiration at the lower boundary in the case of O2, and by molecular exchange with the atmosphere in the peripheral summer moat around the ice.

  5. The Remote Sensing and Measurement of Melting Processes on Greenland and Antarctica

    NASA Astrophysics Data System (ADS)

    Steiner, Nicholas

    We report measurements of melt-related processes for Antarctic and Greenland made using novel remote sensing algorithms and in-situ measurement techniques. First, persistent melting is mapped over Antarctica at high resolution using a novel melt-detection algorithm, based on wavelet-theory and multiscale analysis for the duration of the QuikSCAT satellite record (1999 through 2009). This novel approach is compared with threshold based methods, where melting is detected at 3dB below the winter mean backscatter, indicating an agreement to within 7 percent accuracy in yearly melt index [days-km2] and within 10 percent accuracy based automated weather station (AWS) comparisons due to the omission of short-duration melting events. In further comparison with Special Sensor Microwave/Image (SSMI) melting records, a higher degree of agreement (9 percent relative difference) is obtained by employing the wavelet-based approach than threshold-based (11 percent relative difference) methods. Secondly, we assess the validity of remote sensing based multispectral bathymetry from the analysis of concurrent in-situ multi-spectral and depth measurements collected over a supraglacial lake during early July 2010 in West Greenland (Lake Olivia, 69º36'35"N, 49º29'40"W). In particular, we evaluate lake bottom albedo and the water attenuation coefficient. Analysis of in-situ data (using a remotely controlled boat equipped with a GPS, sonar and a spectrometer) illustrates the exponential trend of the water-leaving reflectance with lake depth. The attenuation factors obtained are compared with those proposed in the literature. Finally, measured ablation rates at the bottom of the two lakes, collected during the summers of 2010 and 2011, are on the order of ˜ 6 cm/day, versus a rate of ˜ 2.5 - 3 cm/day in the case of bare ice of surrounding areas. These measurements are compared with a thermodynamic model forced with the outputs of a regional climate model. In general, the model is able

  6. Snow Dynamics in a Polar Desert, McMurdo Dry Valleys, Antarctica

    NASA Astrophysics Data System (ADS)

    Eveland, J. W.; Gooseff, M. N.; Lampkin, D. J.; Barrett, J. E.; Takacs-Vesbach, C. D.

    2010-12-01

    The McMurdo Dry Valleys of Antarctica are a hyper-arid polar desert, receiving less than 10 cm of water equivalent each year. Snow dynamics of the McMurdo Dry Valleys are important to understanding the microbial ecology and possibly the long term hydrology of the region. Snow in the valleys collects in small nivation hollows to form discontinuous patches of snow across the landscape. We propose that seasonal snow on valley floors is ecologically important because it increases the availability of moisture to subnivian soils and insulates the subnivian soils from temperature extremes. In addition, seasonal snow cover may also be responsible for preserving permafrost in areas of greater accumulation. Our study sites in Taylor and Wright Valey include the surrounding areas of Lake Fryxell, Lake Hoare, Lake Bonney, Lake Brownworth, Lake Vanda, and the Labyrinth. Throughout the 2009-10 summer season, the outlines of 3 snow patches at each site were surveyed several times to monitor the areal ablation of snow cover. Snow pits at adjacent snow patches provided snow density profiles. In addition to small-scale observations, remotely sensed images from the WorldView-1 and Quickbird platforms provide valley-scale data at a spatial resolution of up to 60 cm and a temporal resolution of one week on average. Using data available from nearby meteorological stations, an energy balance approach is used in conjunction with field measurements to calculate the ablation rates over the course of the 2009-10 summer for each region. To test how the field measurements reflect ablation rates at the valley scale, an object-based classification technique is used to extract a time series of areal snow cover across the valleys from the remotely sensed imagery. Results show similar ablation rates across the 3 regions in Taylor Valley. However, the three regions in Wright Valley are markedly different. Snow cover near Lake Vanda ablated rapidly, while a significant amount of snow cover on the

  7. ACES: The ASCENDS CarbonHawk Experiment Simulator

    NASA Astrophysics Data System (ADS)

    Obland, M. D.; Prasad, N. S.; Harrison, F. W.; Browell, E. V.; Ismail, S.; Dobler, J. T.; Moore, B.; Zaccheo, T.; Campbell, J.; Chen, S.; Cleckner, C. S.; DiJoseph, M.; Little, A.; Notari, A.; Refaat, T. F.; Rosenbaum, D.; Vanek, M. D.; Bender, J.; Braun, M.; Chavez-Pirson, A.; Neal, M.; Rayner, P. J.; Rosiewicz, A.; Shure, M.; Welch, W.

    2012-12-01

    The ASCENDS CarbonHawk Experiment Simulator (ACES) is a NASA Langley Research Center project funded by NASA's Earth Science Technology Office (ESTO) Instrument Incubator Program (IIP) that seeks to advance technologies critical to measuring atmospheric column carbon dioxide (CO2) mixing ratios in support of the NASA Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) mission. The technologies being advanced are: (1) a high bandwidth detector, (2) a multi-aperture telescope assembly, (3) advanced algorithms for cloud and aerosol discrimination, and (4) high-efficiency, multiple-amplifier CO2 and O2 laser transmitters. The instrument architecture will be developed to operate on a high-altitude aircraft and will be directly scalable to meet the ASCENDS mission requirements. These technologies are viewed as critical towards developing an airborne simulator and eventual spaceborne instrument with lower size, mass, and power consumption, and improved performance. The detector effort will improve the existing detector subsystem by increasing its bandwidth to a goal of 5 MHz, reducing its overall mass from 18 lbs to <10 lbs, and stretching the duration of autonomous, service-free operation periods from 4 hrs to >24 hrs. The development goals are to permit higher laser modulation rates, which provides greater flexibility for implementing thin-cloud discrimination algorithms as well as improving range resolution and error reduction, and to enable long flights on a high-altitude unmanned aerial vehicle (UAV). The telescope development consists of a three-telescope design built for the constraints of the Global Hawk aircraft. This task addresses the ability of multiple smaller telescopes to provide equal or greater collection efficiency compared with a single larger telescope with a reduced impact on launch mass and cost. The telescope assembly also integrates fiber-coupled transmit collimators for all of the laser transmitters and fiber-coupled optical

  8. Sources appointment and ecological risk assessment of polycyclic aromatic hydrocarbons (PAHs) in sediments of Erhai Lake, a low-latitude and high-altitude lake in southwest China.

    PubMed

    Hezhong, Yuan; Enlou, Zhang; Qi, Lin; Rong, Wang; Enfeng, Liu

    2016-03-01

    Sixteen polycyclic aromatic hydrocarbons (PAHs) were analyzed from the surficial sediments in Erhai Lake, a plateau lake in China. The results showed that except for acenaphthylene (Ace) Ace and Dibenz(a,h)anthracene (DBA), the central region contained individual PAHs at concentrations lower than those in other lake regions. Total concentration of the PAHs (ΣPAHs) in the sediments from Erhai Lake ranged from 32.42 to 558.53 mg/kg with a mean value of 256.70 mg/kg. The maximum value of ΣPAHs was observed in the north region of the lake and more than 10-fold higher than the minimum values. Moreover, high molecular weight (HMW) PAHs, especially 5-ring PAHs, accounted for higher ratios up to 76 % relative to other PAHs compound in almost all sampling sites. Molecular diagnostic ratios including anthtacene (Ant)/(Ant + phenanthrene (Phe)), fluoranthene (Flt)/(Flt + pyrene (Pyr)), benz(a)anthracene (BaA)/(BaA + chrysene (Chr)), and indeno(1,2,3-cd)pyrene (IPY)/(IPY + benz(g,h,i)perylene (BPE)) were recorded at all sampling sites and indicated that the origin of PAHs in Erhai Lake was predominately pyrolytic. Furthermore, principal component analysis with component dominating by HMW PAHs showed that combustion origins were the primary contamination sources of PAHs in the sediments of Erhai Lake. Finally, ecological risk assessment indicated that the sediments from Erhai Lake are exposed to potential low risk for ΣPAHs, and the ecological risk decreases in the order of northern region > southern region > central region. PMID:26507728

  9. Angiotensin Converting Enzyme (ACE) Inhibitor Extends Caenorhabditis elegans Life Span.

    PubMed

    Kumar, Sandeep; Dietrich, Nicholas; Kornfeld, Kerry

    2016-02-01

    Animal aging is characterized by progressive, degenerative changes in many organ systems. Because age-related degeneration is a major contributor to disability and death in humans, treatments that delay age-related degeneration are desirable. However, no drugs that delay normal human aging are currently available. To identify drugs that delay age-related degeneration, we used the powerful Caenorhabditis elegans model system to screen for FDA-approved drugs that can extend the adult lifespan of worms. Here we show that captopril extended mean lifespan. Captopril is an angiotensin-converting enzyme (ACE) inhibitor used to treat high blood pressure in humans. To explore the mechanism of captopril, we analyzed the acn-1 gene that encodes the C. elegans homolog of ACE. Reducing the activity of acn-1 extended the mean life span. Furthermore, reducing the activity of acn-1 delayed age-related degenerative changes and increased stress resistance, indicating that acn-1 influences aging. Captopril could not further extend the lifespan of animals with reduced acn-1, suggesting they function in the same pathway; we propose that captopril inhibits acn-1 to extend lifespan. To define the relationship with previously characterized longevity pathways, we analyzed mutant animals. The lifespan extension caused by reducing the activity of acn-1 was additive with caloric restriction and mitochondrial insufficiency, and did not require sir-2.1, hsf-1 or rict-1, suggesting that acn-1 functions by a distinct mechanism. The interactions with the insulin/IGF-1 pathway were complex, since the lifespan extensions caused by captopril and reducing acn-1 activity were additive with daf-2 and age-1 but required daf-16. Captopril treatment and reducing acn-1 activity caused similar effects in a wide range of genetic backgrounds, consistent with the model that they act by the same mechanism. These results identify a new drug and a new gene that can extend the lifespan of worms and suggest new

  10. Angiotensin Converting Enzyme (ACE) Inhibitor Extends Caenorhabditis elegans Life Span

    PubMed Central

    Kumar, Sandeep; Dietrich, Nicholas; Kornfeld, Kerry

    2016-01-01

    Animal aging is characterized by progressive, degenerative changes in many organ systems. Because age-related degeneration is a major contributor to disability and death in humans, treatments that delay age-related degeneration are desirable. However, no drugs that delay normal human aging are currently available. To identify drugs that delay age-related degeneration, we used the powerful Caenorhabdtitis elegans model system to screen for FDA-approved drugs that can extend the adult lifespan of worms. Here we show that captopril extended mean lifespan. Captopril is an angiotensin-converting enzyme (ACE) inhibitor used to treat high blood pressure in humans. To explore the mechanism of captopril, we analyzed the acn-1 gene that encodes the C. elegans homolog of ACE. Reducing the activity of acn-1 extended the mean life span. Furthermore, reducing the activity of acn-1 delayed age-related degenerative changes and increased stress resistance, indicating that acn-1 influences aging. Captopril could not further extend the lifespan of animals with reduced acn-1, suggesting they function in the same pathway; we propose that captopril inhibits acn-1 to extend lifespan. To define the relationship with previously characterized longevity pathways, we analyzed mutant animals. The lifespan extension caused by reducing the activity of acn-1 was additive with caloric restriction and mitochondrial insufficiency, and did not require sir-2.1, hsf-1 or rict-1, suggesting that acn-1 functions by a distinct mechanism. The interactions with the insulin/IGF-1 pathway were complex, since the lifespan extensions caused by captopril and reducing acn-1 activity were additive with daf-2 and age-1 but required daf-16. Captopril treatment and reducing acn-1 activity caused similar effects in a wide range of genetic backgrounds, consistent with the model that they act by the same mechanism. These results identify a new drug and a new gene that can extend the lifespan of worms and suggest new

  11. Atmospheric Chemistry Experiment (ACE) Measurements of Tropospheric and Stratospheric Chemistry and Long-Term Trends

    NASA Technical Reports Server (NTRS)

    Rinsland, Curtis P.; Bernath, Peter; Boone, Chris; Nassar, Ray

    2007-01-01

    We highlight chemistry and trend measurement results from the Atmospheric Chemistry Experiment (ACE) which is providing precise middle troposphere to the lower thermosphere measurements with a 0.02/cm resolution Fourier transform spectrometer covering 750-4400/cm

  12. ACE2: Angiotensin II/Angiotensin-(1-7) balance in cardiorenal injury

    PubMed Central

    Varagic, Jasmina; Ahmad, Sarfaraz; Nagata, Sayaka; Ferrario, Carlos M.

    2014-01-01

    Our current recognition of the renin-angiotensin system is more convoluted than originally thought due to the discovery of multiple novel enzymes, peptides, and receptors inherent to this interactive biochemical cascade. Over the last decade angiotensin converting enzyme 2 (ACE2) has emerged as a key player in the pathophysiology of hypertension and cardiovascular and renal disease due to its pivotal role in metabolizing vasoconstrictive/hypertrophic/proliferative angiotensin II into favorable angiotensin-(1-7). This review addresses a considerable advancement in research on the role of tissue ACE2 in development and progression of hypertension and cardiorenal injury. We also summarize the results from recent clinical and experimental studies suggesting that serum or urine soluble ACE2 may serve as a novel biomarker or independent risk factor relevant for diagnosis and prognosis of cardiorenal disease. Recent proceedings on novel therapeutic approaches to enhance ACE2/angiotensin-(1-7) axis are also reviewed. PMID:24510672

  13. Dry Valley streams in Antarctica: Ecosystems waiting for water

    USGS Publications Warehouse

    McKnight, Diane M.; Niyogi, D.K.; Alger, A.S.; Bomblies, A.; Conovitz, P.A.; Tate, C.M.

    1999-01-01

    An axiom of ecology is: 'Where there is water, there is life.' In dry valley ecosystems of Antarctica, this axiom can be extended to: 'Where there has been and will be water, there is life.' Stream communities in the dry valleys can withstand desiccation on an annual basis and also for longer periods - as much as decades or even centuries. These intact ecosystems, consisting primarily of cyanobacteria and eukaryotic algae, spring back to life with the return of water. Soil organisms in the dry valleys also have remarkable survival capabilities (Virginia and Wall 1999), emerging from dormancy with the arrival of water. Streams in the dry valleys carry meltwater from a glacier or ice-field source to the lakes on the valley floors and generally flow for 4-10 weeks during the summer, depending on climatic conditions. Many of these streams contain abundant algal mats that are perennial in the sense that they are in a freeze-dried state during the winter and begin growing again within minutes of becoming wetted by the first flow of the season. The algal species present in the streams are mainly filamentous cyanobacteria (approximately 20 species of the genera Phormidium, Oscillatoria, and Nostoc), two green algal species of the genus Prasiola, and numerous diatom taxa that are characteristic of soil habitats and polar regions. Algal abundances are greatest in those streams in which periglacial processes, acting over periods of perhaps a century, have produced a stable stone pavement in the streambed. This habitat results in a less turbulent flow regime and limits sediment scour from the streambed. Because dry valley glaciers advance and retreat over periods of centuries and millennia and stream networks in the dry valleys evolve through sediment deposition and transport, some of the currently inactive stream channels may receive flow again in the future. Insights- into the process of algal persistence and reactivation will come from long-term experiments that study the

  14. Beneficial role of D allele in controlling ACE levels: a study among Brahmins of north India.

    PubMed

    Kumari, Shobha; Sharma, Nidhi; Thakur, Sunil; Mondal, Prakash R; Saraswathy, Kallur N

    2016-06-01

    India being a country with vast diversity is expected to have different dietary and life style patterns which in turn may lead to population-specific environmental risk factors. Further, the interaction of these risk factors with the genetic makeup of population makes it either susceptible or resistant to cardiovascular disease. One such candidate gene is angiotensin converting enzyme (ACE) for various cardiovascular mechanisms. ACE is the key enzyme of the renin angiotensin aldosterone system pathway which maintains homeostasis blood pressure in the body and any variation in the levels is reported to be associated with various complex diseases. The DD genotype is found to increase ACE levels, which is associated with cardiovascular diseases and decrease in ACE levels are associated with kidney diseases. The aim of this study was to understand the distribution of ACE I/D polymorphism and ACE levels among Brahmins of National Capital Region (NCR) north India, with respect to age and sex ratio distribution. In this study, 136 subjects of which 50 males and 86 females, who were unrelated up to first cousin, aged 25 to70 years were studied. ACE gene was found to be polymorphic with high frequency of heterozygote (ID) followed by II and DD genotypes. The studied population was found to be in Hardy-Weinberg equilibrium with respect to ACE I/D polymorphism (P = 0.55). I allele frequency was found to be higher (0.560) than the D allele (0.44). The median level of ACE was found to be 65.96 ng/mL (48.12-86.24) which is towards lower side of the normal range. ACE levels were found to be increased among individual having either of the homozygotes that is II or DD and higher frequency of heterozygote (ID) is indicative of advantage in the population by maintaining lower ACE levels. The limitation of the present study is low sample size, however, the merit is that the subjects belonged to a Mendalian population with a common gene pool. PMID:27350671

  15. Gas discharges in fumarolic ice caves of Erebus volcano, Antarctica

    NASA Astrophysics Data System (ADS)

    Fischer, T. P.; Curtis, A. G.; Kyle, P. R.; Sano, Y.

    2013-12-01

    reactions. We are confident that the atmospheric component is not the result of sampling procedure but intrinsic to the ice cave system. In addition to carbon dioxide, magmatic gases emitted from Erebus lava lake contain significant amounts of SO2, HCl, HF, CO and H2 [1,2]. The acid magmatic gases (SO2, HCl, HF) and a significant amount of the CO2 are likely absorbed by the subsurface ice/water system. The atmospheric components (Ar, nitrogen, oxygen) likely enter the system at shallow levels. The relative abundances of these components reflect degassing fractionation of these volatiles from liquid water at low temperatures, suggesting the presence of liquid water in the subsurface. [1] Oppenheimer, C., Kyle, P.R., 2008. Probing the magma plumbing of Erebus volcano, Antarctica, by open-path FTIR spectroscopy of gas emissions. J. Vol. Geoth. Res. 177, 743-754. [2] Moussallam, Y., Oppenheimer, C., et al., 2012. Hydrogen emission from Erebus volcano, Antarctica. Bull. Volcan 74, 2109-2120.

  16. ACE2 and vasoactive peptides: novel players in cardiovascular/renal remodeling and hypertension.

    PubMed

    Mendoza-Torres, Evelyn; Oyarzún, Alejandra; Mondaca-Ruff, David; Azocar, Andrés; Castro, Pablo F; Jalil, Jorge E; Chiong, Mario; Lavandero, Sergio; Ocaranza, María Paz

    2015-08-01

    The renin-angiotensin system (RAS) is a key component of cardiovascular physiology and homeostasis due to its influence on the regulation of electrolyte balance, blood pressure, vascular tone and cardiovascular remodeling. Deregulation of this system contributes significantly to the pathophysiology of cardiovascular and renal diseases. Numerous studies have generated new perspectives about a noncanonical and protective RAS pathway that counteracts the proliferative and hypertensive effects of the classical angiotensin-converting enzyme (ACE)/angiotensin (Ang) II/angiotensin type 1 receptor (AT1R) axis. The key components of this pathway are ACE2 and its products, Ang-(1-7) and Ang-(1-9). These two vasoactive peptides act through the Mas receptor (MasR) and AT2R, respectively. The ACE2/Ang-(1-7)/MasR and ACE2/Ang-(1-9)/AT2R axes have opposite effects to those of the ACE/Ang II/AT1R axis, such as decreased proliferation and cardiovascular remodeling, increased production of nitric oxide and vasodilation. A novel peptide from the noncanonical pathway, alamandine, was recently identified in rats, mice and humans. This heptapeptide is generated by catalytic action of ACE2 on Ang A or through a decarboxylation reaction on Ang-(1-7). Alamandine produces the same effects as Ang-(1-7), such as vasodilation and prevention of fibrosis, by interacting with Mas-related GPCR, member D (MrgD). In this article, we review the key roles of ACE2 and the vasoactive peptides Ang-(1-7), Ang-(1-9) and alamandine as counter-regulators of the ACE-Ang II axis as well as the biological properties that allow them to regulate blood pressure and cardiovascular and renal remodeling. PMID:26275770

  17. Crosstalk between ACE2 and PLGF regulates vascular permeability during acute lung injury

    PubMed Central

    Wang, Lantao; Li, Yong; Qin, Hao; Xing, Dong; Su, Jie; Hu, Zhenjie

    2016-01-01

    Angiotensin converting enzyme 2 (ACE2) treatment suppresses the severity of acute lung injury (ALI), through antagonizing hydrolyzing angiotensin II (AngII) and the ALI-induced apoptosis of pulmonary endothelial cells. Nevertheless, the effects of ACE2 on vessel permeability and its relationship with placental growth factor (PLGF) remain ill-defined. In the current study, we examined the relationship between ACE2 and PLGF in ALI model in mice. We used a previously published bleomycin method to induce ALI in mice, and treated the mice with ACE2. We analyzed the levels of PLGF in these mice. The mouse lung vessel permeability was determined by a fluorescence pharmacokinetic assay following i.v. injection of 62.5 µg/kg Visudyne. PLGF pump or soluble Flt-1 (sFlt-1) pump was given to augment or suppress PLGF effects, respectively. The long-term effects on lung function were determined by measurement of lung resistance using methacholine. We found that ACE2 treatment did not alter PLGF levels in lung, but antagonized the effects of PLGF on increases of lung vessel permeability. Ectogenic PLGF abolished the antagonizing effects of ACE2 on the vessel permeability against PLGF. On the other hand, suppression of PLGF signaling mimicked the effects of ACE2 on the vessel permeability against PLGF. The suppression of vessel permeability resulted in improvement of lung function after ALI. Thus, ACE2 may antagonize the PLGF-mediated increases in lung vessel permeability during ALI, resulting in improvement of lung function after ALI. PMID:27158411

  18. Isolation of angiotensin converting enzyme (ACE) inhibiting triterpenes from Schinus molle.

    PubMed

    Olafsson, K; Jaroszewski, J W; Smitt, U W; Nyman, U

    1997-08-01

    Bioactivity-guided fractionation of extracts of Schinus molle leaves, using an in vitro assay, led to the isolation of ACE-inhibitory steroidal triterpenes of the euphane type, identified by means of NMR spectroscopic methods. One of the triterpenes was isolated as an equilibrium mixture of epimeric aldehydes. The triterpenes showed moderate ACE-inhibitory activity (IC(50) about 250 microM). PMID:17252394

  19. Variation in the ACE, PPARGC1A and PPARA genes in Lithuanian football players.

    PubMed

    Gineviciene, Valentina; Jakaitiene, Audrone; Tubelis, Linas; Kucinskas, Vaidutis

    2014-01-01

    The aim of this study was to determine the impact of ACE (I/D), PPARGC1A (G/A) and PPARA (G/C) polymorphisms on footballers performance among 199 Lithuanian professional footballers and 167 sedentary, healthy men (controls). Genotyping was performed using polymerase chain reaction and restriction fragment length polymorphism methods on DNA from leucocytes. Results revealed that the angiotensin-1-coverting enzyme gene (ACE) genotype distribution was significantly different between total football players group (II 23.6%, ID 46.7% and DD 29.6%) and the controls (II 24.6%, ID 29.9% and DD 45.5%; P=0.002). Although investigating PPARGC1A (G/A) and PPARA (G/C) polymorphisms no significant results were obtained in the total football players group, however, significant differences were determined between forwards and controls [PPARGC1A: GG 54.6%, GA 29.5%, AA 15.9% vs. GG 49.7%, GA 44.3% and AA 6.0% (P = 0.044); PPARA: GG 52.3%, GC 40.9%, CC 6.8% vs. GG 72.4%, GC 24.6% and CC 3.0% (P = 0.034)]. In the whole cohort, the odds ratio of the genotype [ACE ID + PPARA GG] being a footballer was 1.69 (95% CI 1.04-2.74), and of [ACE ID + PPARGC1A GG] 1.93 (95% CI 1.10-3.37) and of [ACE II + PPARA GC] 2.83 (95% CI 1.02-7.91) compared to controls. It was revealed that ACE ID genotype together with PPARA GG and PPARGC1A GG as well as ACE II genotype with PPARA GC is probably the 'preferable genotype' for footballers. Summing up, the present study suggests that the ACE, PPARGC1A and PPARA polymorphisms genotypes are associated, separately and in combination, with Lithuanian footballers' performance. PMID:24444220

  20. Proposal to protect marine areas around Antarctica

    NASA Astrophysics Data System (ADS)

    Showstack, Randy

    2012-05-01

    Forty percent of Antarctica's Southern Ocean should be protected in a network of marine protected areas (MPAs) and no-take marine reserves, according to a 21 May report by the Antarctic Ocean Alliance, which is composed of about 20 environmental groups. The protected areas should include the 19 Antarctic marine habitats outlined in the report, along with existing MPAs and areas identified through previous conservation and planning analyses, the report notes. Protected areas should include the Antarctic Peninsula, the Weddell and Ross seas, the Indian Ocean Benthic Environment, and Pacific seamounts, according to the report. The Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR), which manages living resources for the Southern Ocean, has already agreed to establish an initial network of Antarctic MPAs this year, the report states.

  1. Ice-shelf melting around Antarctica.

    PubMed

    Rignot, E; Jacobs, S; Mouginot, J; Scheuchl, B

    2013-07-19

    We compare the volume flux divergence of Antarctic ice shelves in 2007 and 2008 with 1979 to 2010 surface accumulation and 2003 to 2008 thinning to determine their rates of melting and mass balance. Basal melt of 1325 ± 235 gigatons per year (Gt/year) exceeds a calving flux of 1089 ± 139 Gt/year, making ice-shelf melting the largest ablation process in Antarctica. The giant cold-cavity Ross, Filchner, and Ronne ice shelves covering two-thirds of the total ice-shelf area account for only 15% of net melting. Half of the meltwater comes from 10 small, warm-cavity Southeast Pacific ice shelves occupying 8% of the area. A similar high melt/area ratio is found for six East Antarctic ice shelves, implying undocumented strong ocean thermal forcing on their deep grounding lines. PMID:23765278

  2. Ice-Shelf Melting Around Antarctica

    NASA Astrophysics Data System (ADS)

    Rignot, E.; Jacobs, S.; Mouginot, J.; Scheuchl, B.

    2013-07-01

    We compare the volume flux divergence of Antarctic ice shelves in 2007 and 2008 with 1979 to 2010 surface accumulation and 2003 to 2008 thinning to determine their rates of melting and mass balance. Basal melt of 1325 ± 235 gigatons per year (Gt/year) exceeds a calving flux of 1089 ± 139 Gt/year, making ice-shelf melting the largest ablation process in Antarctica. The giant cold-cavity Ross, Filchner, and Ronne ice shelves covering two-thirds of the total ice-shelf area account for only 15% of net melting. Half of the meltwater comes from 10 small, warm-cavity Southeast Pacific ice shelves occupying 8% of the area. A similar high melt/area ratio is found for six East Antarctic ice shelves, implying undocumented strong ocean thermal forcing on their deep grounding lines.

  3. Iceberg B-15, Ross Ice Shelf, Antarctica

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Iceberg B-15 broke from the Ross Ice Shelf in Antarctica in late March. Among the largest ever observed, the new iceberg is approximately 170 miles long x 25 miles wide. Its 4,250 square-mile area is nearly as large as the state of Connecticut. The iceberg was formed from glacial ice moving off the Antarctic continent and calved along pre-existing cracks in the Ross Ice Shelf near Roosevelt Island. The calving of the iceberg essentially moves the northern boundary of the ice shelf about 25 miles to the south, a loss that would normally take the ice shelf as long as 50-100 years to replace. This infrared image was acquired by the DMSP (Defense Meteorological Satellite Program) F-13 satellite on April 13, 2000. For more images see Antarctic Meteorological Research Center Image courtesy of the University of Wisconsin - Madison, Space Science and Engineering Center, Antarctic Meteorological Research Center

  4. Helping Students Process a Simulated Death Experience: Integration of an NLN ACE.S Evolving Case Study and the ELNEC Curriculum.

    PubMed

    Kopka, Judith A; Aschenbrenner, Ann P; Reynolds, Mary B

    2016-01-01

    The nursing literature supports the need for end-of-life (EOL) education, but the ability to provide quality clinical experience in this area is limited by the availability of patients and nursing instructors' and preceptors' comfort and expertise in teaching EOL care. Clinical simulation allows faculty to provide the same quality EOL experience to all students. This article discusses an effective teaching strategy integrating End-of-Life Nursing Education Consortium core content with National League for Nursing ACE.S unfolding case studies, clinical simulation, and social media. PMID:27405204

  5. Occurrence and diversity of marine yeasts in Antarctica environments

    NASA Astrophysics Data System (ADS)

    Zhang, Xue; Hua, Mingxia; Song, Chunli; Chi, Zhenming

    2012-03-01

    A total of 28 yeast strains were obtained from the sea sediment of Antarctica. According to the results of routine identification and molecular characterization, the strains belonged to species of Yarrowia lipolytica, Debaryomyces hansenii, Rhodotorula slooffiae, Rhodotorula mucilaginosa, Sporidiobolus salmonicolor, Aureobasidium pullulans, Mrakia frigida and Guehomyces pullulans, respectively. The Antarctica yeasts have wide potential applications in biotechnology, for some of them can produce β-galactosidase and killer toxins.

  6. Oxygen isotope studies and compilation of isotopic dates from Antarctica

    SciTech Connect

    Grootes, P.M.; Stuiver, M.

    1986-01-01

    The Quaternary Isotope Laboratory, alone or in collaboration with other investigators, is currently involved in a number of oxygen-isotope studies mainly in Antarctica. Studies of a drill core from the South Pole, seasonal oxygen-18 signals preserved in the Dominion Range, isotope dating of the Ross Ice Shelf, oxygen-18 profiles of the Siple Coast, McMurdo Ice Shelf sampling, and a data compilation of radiometric dates from Antarctica are discussed.

  7. Ice-shelf melting around Antarctica

    NASA Astrophysics Data System (ADS)

    Rignot, E.; Jacobs, S.

    2008-12-01

    The traditional view on the mass balance of Antarctic ice shelves is that they loose mass principally from iceberg calving with bottom melting a much lower contributing factor. Because ice shelves are now known to play a fundamental role in ice sheet evolution, it is important to re-evaluate their wastage processes from a circumpolar perspective using a combination of remote sensing techniques. We present area average rates deduced from grounding line discharge, snow accumulation, firn depth correction and ice shelf topography. We find that ice shelf melting accounts for roughly half of ice-shelf ablation, with a total melt water production of 1027 Gt/yr. The attrition fraction due to in-situ melting varies from 9 to 90 percent around Antarctica. High melt producers include the Ronne, Ross, Getz, Totten, Amery, George VI, Pine Island, Abbot, Dotson/Crosson, Shackleton, Thwaites and Moscow University Ice Shelves. Low producers include the Larsen C, Princess Astrid and Ragnhild coast, Fimbul, Brunt and Filchner. Correlation between melt water production and grounding line discharge is low (R2 = 0.65). Correlation with thermal ocean forcing from the ocean are highest in the northern parts of West Antarctica where regressions yield R2 of 0.93-0.97. Melt rates in the Amundsen Sea exhibit a quadratic sensitivity to thermal ocean forcing. We conclude that ice shelf melting plays a dominant role in ice shelf mass balance, with a potential to change rapidly in response to altered ocean heat transport onto the Antarctic continental shelf.

  8. Human Activity and Pollution in Antarctica

    NASA Astrophysics Data System (ADS)

    Graf, H.-F.; Shirsat, S. V.; Podzun, R.

    2009-04-01

    A regional climate chemistry model is used to determine the level of pollution of the Antarctic continent due to anthropogenic and natural emission of sulphur species. Based on an emission inventory for the year 2004/2005 including emissions from energy use and ground traffic at and between Antarctic research stations, flight activity, tourist and scientific ship operations, and emissions from the Mt. Erebus volcano, atmospheric concentration and deposition rates of sulphur species and black carbon were simulated at 0.5 degree resolution for the whole Antarctic continent. The biggest anthropogenic source of pollution is ship operations. These concentrate near the Antarctic Peninsula and close to the big scientific stations at Queen Maud Land and in the Ross sea area. The prevailing winds guarantee that most of the anthropogenic emissions from sources near the coast will be blown to lower latitudes and do not affect the continent. While atmospheric concentrations over vast areas remain extremely low, in some places locally concentrations and deposition rates are reached that may be detectable by in-situ measurements and give rise to concern. Especially at the Peninsula atmospheric concentrations and surface deposition of sulphur and soot are dominated by ship emissions. The largest part of shipping activity in this region is from tourist ships, a strongly increasing business. The by far biggest source of sulphur species in Antarctica is the Mt. Erebus volcano. It is also the only source that remains equally strong in polar winter. However, due to its high altitude and the long life time of SO2, especially in winter resulting in long range transport and dilution, Erebus emissions contribute relatively little to deposition of sulphur in the most anthropogenic polluted areas while they dominate the sulphur deposition in central Antarctica.

  9. IT’S GOOD TO BE BIG—PHAEOCYSTIS ANTARCTICA COLONY SIZE UNDER THE INFLUENCE OF ZOOPLANKTON GRAZERS

    EPA Science Inventory

    The haptophyte Phaeocystis antarctica forms extremely dense accumulations in the Ross Sea, Antarctica, and accounts for over 60% of the seasonal primary production. Similar to the Phaeocystis species in the northern hemisphere, P. antarctica exists as solitary cells and mucilagin...

  10. It’s good to be big--- Phaeocystis antarctica colony size under the influence of zooplankton grazers

    EPA Science Inventory

    The haptophyte Phaeocystis antarctica forms extremely dense accumulations in the Ross Sea, Antarctica, and accounts for over 60% of the seasonal primary production. Similar to the Phaeocystis species in the northern hemisphere, P. antarctica exists as solitary cells and mucilagin...

  11. Exercise manual for the Augmented Computer Exercise for Inspection Training (ACE-IT) software

    SciTech Connect

    Dobranich, P.R.; Widney, T.W.; Goolsby, P.T.; Nelson, J.D.; Evanko, D.A.

    1997-09-01

    The on-site inspection provisions in many current and proposed arms control agreements require extensive preparation and training on the part of both the Inspected Party and the Inspection Team. Current training techniques include table-top inspections and practice inspections. The Augmented Computer Exercise for Inspection Training (ACE-IT), an interactive computer training tool, increases the utility of table-top inspections. ACE-IT has been designed to provide training for a hypothetical challenge inspection under the Chemical Weapons Convention (CWC); however, this training tool can be modified for other inspection regimes. Although ACE-IT provides training from notification of an inspection through post-inspection activities, the primary emphasis of ACE-IT is in the inspection itself--particularly with the concept of managed access. ACE-IT also demonstrates how inspection provisions impact compliance determination and the protection of sensitive information. The Exercise Manual supplements the ACE-IT software by providing general information on on-site inspections and detailed information for the CWC challenge inspection exercise. The detailed information includes the pre-inspection briefing, maps, list of sensitive items, medical records, and shipping records.

  12. Aerosol Characterization Data from the Asian Pacific Regional Aerosol Characterization Project (ACE-Asia)

    DOE Data Explorer

    The Aerosol Characterization Experiments (ACE) were designed to increase understanding of how atmospheric aerosol particles affect the Earth's climate system. These experiments integrated in-situ measurements, satellite observations, and models to reduce the uncertainty in calculations of the climate forcing due to aerosol particles and improve the ability of models to predict the influences of aerosols on the Earth's radiation balance. ACE-Asia was the fourth in a series of experiments organized by the International Global Atmospheric Chemistry (IGAC) Program (A Core Project of the International Geosphere Biosphere Program). The Intensive Field Phase for ACE-Asia took place during the spring of 2001 (mid-March through early May) off the coast of China, Japan and Korea. ACE-Asia pursued three specific objectives: 1) Determine the physical, chemical, and radiative properties of the major aerosol types in the Eastern Asia and Northwest Pacific region and investigate the relationships among these properties. 2) Quantify the physical and chemical processes controlling the evolution of the major aerosol types and in particular their physical, chemical, and radiative properties. 3) Develop procedures to extrapolate aerosol properties and processes from local to regional and global scales, and assess the regional direct and indirect radiative forcing by aerosols in the Eastern Asia and Northwest Pacific region [Edited and shortened version of summary at http://data.eol.ucar.edu/codiac/projs?ACE-ASIA]. The Ace-Asia collection contains 174 datasets.

  13. Technical manual for the Augmented Computer Exercise for Inspection Training (ACE-IT) software

    SciTech Connect

    Dobranich, P.R.; Horak, K.E.; Hagan, D.; Evanko, D.; Nelson, J.; Ryder, C.; Hedlund, D.

    1997-09-01

    The on-site inspection provisions in many current and proposed arms control agreements require extensive preparation and training on the part of both the Inspection Teams (inspectors) and Inspected Parties (host). Current training techniques include table-top inspections and practice inspections. The Augmented Computer Exercise for Inspection Training (ACE-IT), an interactive computer training tool, increases the utility of table-top inspections. ACE-IT has been designed to provide training for challenge inspections under the Chemical Weapons Convention (CWC); however, this training tool can be modified for other inspection regimes. Although ACE-IT provides training from notification of an inspection through post-inspection activities, the primary emphasis of ACE-IT is in the inspection itself--particularly with the concept of managed access. ACE-IT also demonstrates how inspection provisions impact compliance determination and the protection of sensitive information. This Technical Manual describes many of the technical aspects of the ACE-IT training software.

  14. Receptor and viral determinants of SARS-coronavirus adaptation to human ACE2

    PubMed Central

    Li, Wenhui; Zhang, Chengsheng; Sui, Jianhua; Kuhn, Jens H; Moore, Michael J; Luo, Shiwen; Wong, Swee-Kee; Huang, I-Chueh; Xu, Keming; Vasilieva, Natalya; Murakami, Akikazu; He, Yaqing; Marasco, Wayne A; Guan, Yi; Choe, Hyeryun; Farzan, Michael

    2005-01-01

    Human angiotensin-converting enzyme 2 (ACE2) is a functional receptor for SARS coronavirus (SARS-CoV). Here we identify the SARS-CoV spike (S)-protein-binding site on ACE2. We also compare S proteins of SARS-CoV isolated during the 2002–2003 SARS outbreak and during the much less severe 2003–2004 outbreak, and from palm civets, a possible source of SARS-CoV found in humans. All three S proteins bound to and utilized palm-civet ACE2 efficiently, but the latter two S proteins utilized human ACE2 markedly less efficiently than did the S protein obtained during the earlier human outbreak. The lower affinity of these S proteins could be complemented by altering specific residues within the S-protein-binding site of human ACE2 to those of civet ACE2, or by altering S-protein residues 479 and 487 to residues conserved during the 2002–2003 outbreak. Collectively, these data describe molecular interactions important to the adaptation of SARS-CoV to human cells, and provide insight into the severity of the 2002–2003 SARS epidemic. PMID:15791205

  15. ACE insertion/deletion polymorphism and diabetic nephropathy: clinical implications of genetic information.

    PubMed

    Ha, Sung-Kyu

    2014-01-01

    Approximately 20-40% of diabetic patients develop nephropathy which is the leading cause of ESRD in developed countries. The ACE I/D polymorphism is thought to be a marker for functional polymorphism which regulates circulating and tissue ACE activity. While the initial study found a protective effect of the II genotype on the development of nephropathy in IDDM patients, subsequent studies have addressed the role of ACE I/D polymorphism in the development and progression of diabetic nephropathy. RAAS blockers are the first line drugs for the treatment hypertension associated with diabetes and have been widely used in everyday clinical practice for the purpose of reducing proteinuria in patients with various renal diseases. However, the antiproteinuric effect of RAAS blockers is variable and the percentage of reducing proteinuria is in the range of 20-80%. The antiproteinuric effect of RAAS blockers may be related to a number of factors: the type or the dose of RAAS blockers, the duration of therapy, the level of sodium intake, and the type of patient's ACE I/D genotype. Besides the nongenetic factors, drug responses, can be influenced by ACE gene polymorphism. In this review, we discuss the relationship between ACE I/D polymorphism and diabetic nephropathy and therapeutic response of RAAS blockers. PMID:25587546

  16. Hamsters vaccinated with Ace-mep-7 DNA vaccine produced protective immunity against Ancylostoma ceylanicum infection.

    PubMed

    Wiśniewski, Marcin; Jaros, Sławomir; Bąska, Piotr; Cappello, Michael; Długosz, Ewa; Wędrychowicz, Halina

    2016-04-01

    Hookworms are intestinal nematodes that infect up to 740 million people, mostly in tropical and subtropical regions. Adult worms suck blood from damaged vessels in the gut mucosa, digesting hemoglobin using aspartic-, cysteine- and metalloproteases. Targeting aspartic hemoglobinases using drugs or vaccines is therefore a promising approach to ancylostomiasis control. Based on homology to metalloproteases from other hookworm species, we cloned the Ancylostoma ceylanicum metalloprotease 7 cDNA (Ace-mep-7). The corresponding Ace-MEP-7 protein has a predicted molecular mass of 98.8 kDa. The homology to metallopeptidases from other hookworm species and its predicted transmembrane region support the hypothesis that Ace-MEP-7 may be involved in hemoglobin digestion in the hookworm gastrointestinal tract, especially that our analyses show expression of Ace-mep-7 in the adult stage of the parasite. Immunization of Syrian golden hamsters with Ace-mep-7 cDNA resulted in 50% (p < 0.01) intestinal worm burden reduction. Additionally 78% (p < 0.05) egg count reduction in both sexes was observed. These results suggest that immunization with Ace-mep-7 may contribute to reduction in egg count released into the environment during the A. ceylanicum infection. PMID:26795262

  17. Stable isotopic biogeochemistry of carbon and nitrogen in a perennially ice-covered Antarctic lake

    NASA Technical Reports Server (NTRS)

    Wharton, R. A. Jr; Lyons, W. B.; Des Marais, D. J.; Wharton RA, J. r. (Principal Investigator)

    1993-01-01

    Lake Hoare (77 degrees 38' S, 162 degrees 53' E) is an amictic, oligotrophic, 34-m-deep, closed-basin lake in Taylor Valley, Antarctica. Its perennial ice cover minimizes wind-generated currents and reduces light penetration, as well as restricts sediment deposition into the lake and the exchange of atmospheric gases between the water column and the atmosphere. The biological community of Lake Hoare consists solely of microorganisms -- both planktonic populations and benthic microbial mats. Lake Hoare is one of several perennially ice-covered lakes in the McMurdo Dry Valleys that represent the end-member conditions of cold desert and saline lakes. The dry valley lakes provide a unique opportunity to examine lacustrine processes that operate at all latitudes, but under an extreme set of environmental conditions. The dry valley lakes may also offer a valuable record of catchment and global changes in the past and present. Furthermore, these lakes are modern-day equivalents of periglacial lakes that are likely to have been common during periods of glacial maxima at temperate latitudes. We have analyzed the dissolved inorganic carbon (DIC) of Lake Hoare for delta 13C and the organic matter of the sediments and sediment-trap material for delta 13C and delta 15N. The delta 13C of the DIC indicates that 12C is differentially removed in the shallow, oxic portions of the lake via photosynthesis. In the anoxic portions of the lake (27-34 m) a net addition of 12C to the DIC pool occurs via organic matter decomposition. The dissolution of CaCO3 at depth also contributes to the DIC pool. Except near the Canada Glacier where a substantial amount of allochthonous organic matter enters the lake, the organic carbon being deposited on the lake bottom at different sites is isotopically similar, suggesting an autochthonous source for the organic carbon. Preliminary inorganic carbon flux calculations suggest that a high percentage of the organic carbon fixed in the water column is

  18. GPS Antenna Characterization Experiment (ACE): Receiver Design and Initial Results

    NASA Technical Reports Server (NTRS)

    Martzen, Phillip; Highsmith, Dolan E.; Valdez, Jennifer E.; Parker, Joel J. K.; Moreau, Michael C.

    2015-01-01

    The GPS Antenna Characterization Experiment (ACE) is a research collaboration between Aerospace and NASA Goddard to characterize the gain patterns of the GPS L1 transmit antennas. High altitude GPS observations are collected at a ground station through a transponder-based or "bent-pipe" architecture where the GPS L1 RF spectrum is received at a platform in geosynchronous orbit and relayed to the ground for processing. The focus of this paper is the unique receiver algorithm design and implementation. The high-sensitivity GPS C/A-code receiver uses high fidelity code and carrier estimates and externally supplied GPS message bit data in a batch algorithm with settings for a 0 dB-Hz threshold. The resulting carrier-to-noise measurements are used in a GPS L1 transmit antenna pattern reconstruction. This paper shows initial transmit gain patterns averaged over each block of GPS satellites, including comparisons to available pre-flight gain measurements from the GPS vehicle contractors. These results provide never-before-seen assessments of the full, in-flight transmit gain patterns.

  19. Operation Heli-STAR - Atlanta Communications Experiment (ACE). Volume 9

    NASA Technical Reports Server (NTRS)

    1996-01-01

    Operation Heli-STAR (Helicopter Short-Haul Transportation and Aviation Research) was established and operated in Atlanta, Georgia, during the period of the 1996 Centennial Olympic Games. Heli-STAR had three major thrusts: (1) the establishment and operation of a helicopter-based cargo transportation system, (2) the management of low-altitude air traffic in the airspace of an urban area, and (3) the collection and analysis of research and development data associated with items 1 and 2. Heli-STAR was a cooperative industry/government program that included parcel package shippers and couriers in the Atlanta area, the helicopter industry, aviation electronics manufacturers, the Federal Aviation Administration (FAA), the National Aeronautics and Space Administration (NASA), and support contractors. Several detailed reports have been produced as a result of Operation Heli-STAR. These include four reports on acoustic measurements and associated analyses, and reports on the Heli-STAR tracking data including the data processing and retrieval system, the Heli-STAR cargo simulation, and the community response system. In addition, NASA's Advanced General Aviation Transport Experiments (AGATE) program has produced a report describing the Atlanta Communications Experiment (ACE) which produced the avionics and ground equipment using automatic dependent surveillance-broadcast (ADS-B) technology. This latter report is restricted to organizations belonging to NASA's AGATE industry consortium. A complete list of these reports is shown on the following page.

  20. ACE Observatory Control System - 16 years of remote intercontinental observing

    NASA Astrophysics Data System (ADS)

    Mack, Peter

    2011-03-01

    The ACE Observatory Control System has been used for remote control since 1995. The system was designed for use at isolated observatories with no-one present on the mountain-top. The software provides complete diagnostic feedback to the astronomer and is supplemented by live audio-visual. Accessories include environmental sensors (weather station, all-sky camera, constellation cameras), automated mirror covers and remote power control. This gives the astronomer the same experience as being present at the observatory. The system is installed on 30 telescopes and many of them are used for routine nightly intercontinental observations, such as Taejeon (S. Korea) to Mt. Lemmon (Arizona) and southeast USA to KPNO and CTIO. The system has fully integrated autoguider acquisition and science camera control. We describe the building blocks of the system and the accessories including automated mirror covers, weather station, all sky camera, remote power control and dome control. Future plans are presented for a fully autonomous platform-independent scheduler and robot for use on multiple telescopes.

  1. Oral Delivery of ACE2/Ang-(1–7) Bioencapsulated in Plant Cells Protects against Experimental Uveitis and Autoimmune Uveoretinitis

    PubMed Central

    Shil, Pollob K; Kwon, Kwang-Chul; Zhu, Ping; Verma, Amrisha; Daniell, Henry; Li, Qiuhong

    2014-01-01

    Hyperactivity of the renin-angiotensin system (RAS) resulting in elevated Angiotensin II (Ang II) contributes to all stages of inflammatory responses including ocular inflammation. The discovery of angiotensin-converting enzyme 2 (ACE2) has established a protective axis of RAS involving ACE2/Ang-(1–7)/Mas that counteracts the proinflammatory and hypertrophic effects of the deleterious ACE/AngII/AT1R axis. Here we investigated the hypothesis that enhancing the systemic and local activity of the protective axis of the RAS by oral delivery of ACE2 and Ang-(1–7) bioencapsulated in plant cells would confer protection against ocular inflammation. Both ACE2 and Ang-(1–7), fused with the non-toxic cholera toxin subunit B (CTB) were expressed in plant chloroplasts. Increased levels of ACE2 and Ang-(1–7) were observed in circulation and retina after oral administration of CTB-ACE2 and Ang-(1–7) expressing plant cells. Oral feeding of mice with bioencapsulated ACE2/Ang-(1–7) significantly reduced endotoxin-induced uveitis (EIU) in mice. Treatment with bioencapsulated ACE2/Ang-(1–7) also dramatically decreased cellular infiltration, retinal vasculitis, damage and folding in experimental autoimmune uveoretinitis (EAU). Thus, enhancing the protective axis of RAS by oral delivery of ACE2/Ang-(1–7) bioencapsulated in plant cells provide an innovative, highly efficient and cost-effective therapeutic strategy for ocular inflammatory diseases. PMID:25228068

  2. Inhibition Mechanism and Model of an Angiotensin I-Converting Enzyme (ACE)-Inhibitory Hexapeptide from Yeast (Saccharomyces cerevisiae)

    PubMed Central

    Ni, He; Li, Lin; Liu, Guang; Hu, Song-Qing

    2012-01-01

    Angiotensin I-converting enzyme (ACE) has an important function in blood pressure regulation. ACE-inhibitory peptides can lower blood pressure by inhibiting ACE activity. Based on the sequence of an ACE-inhibitory hexapeptide (TPTQQS) purified from yeast, enzyme kinetics experiments, isothermal titration calorimetry (ITC), and a docking simulation were performed. The hexapeptide was found to inhibit ACE in a non-competitive manner, as supported by the structural model. The hexapeptide bound to ACE via interactions of the N-terminal Thr1, Thr3, and Gln4 residues with the residues on the lid structure of ACE, and the C-terminal Ser6 attracted the zinc ion, which is vital for ACE catalysis. The displacement of the zinc ion from the active site resulted in the inhibition of ACE activity. The structural model based on the docking simulation was supported by experiments in which the peptide was modified. This study provides a new inhibitory mechanism of ACE by a peptide which broads our knowledge for drug designing against enzyme targets. PMID:22606330

  3. Mantle to surface degassing of alkalic magmas at Erebus volcano, Antarctica

    NASA Astrophysics Data System (ADS)

    Oppenheimer, Clive; Moretti, Roberto; Kyle, Philip R.; Eschenbacher, Al; Lowenstern, Jacob B.; Hervig, Richard L.; Dunbar, Nelia W.

    2011-06-01

    Continental intraplate volcanoes, such as Erebus volcano, Antarctica, are associated with extensional tectonics, mantle upwelling and high heat flow. Typically, erupted magmas are alkaline and rich in volatiles (especially CO 2), inherited from low degrees of partial melting of mantle sources. We examine the degassing of the magmatic system at Erebus volcano using melt inclusion data and high temporal resolution open-path Fourier transform infrared (FTIR) spectroscopic measurements of gas emissions from the active lava lake. Remarkably different gas signatures are associated with passive and explosive gas emissions, representative of volatile contents and redox conditions that reveal contrasting shallow and deep degassing sources. We show that this unexpected degassing signature provides a unique probe for magma differentiation and transfer of CO 2-rich oxidised fluids from the mantle to the surface, and evaluate how these processes operate in time and space. Extensive crystallisation driven by CO 2 fluxing is responsible for isobaric fractionation of parental basanite magmas close to their source depth. Magma deeper than 4 kbar equilibrates under vapour-buffered conditions. At shallower depths, CO 2-rich fluids accumulate and are then released either via convection-driven, open-system gas loss or as closed-system slugs that ascend and result in Strombolian eruptions in the lava lake. The open-system gases have a reduced state (below the QFM buffer) whereas the closed-system gases preserve their deep oxidised signatures (close to the NNO buffer).

  4. Inland diatoms from the McMurdo Dry Valleys and James Ross Island, Antarctica

    USGS Publications Warehouse

    Esposito, R.M.M.; Spaulding, S.A.; McKnight, Diane M.; Van De Vijver, B.; Kopalova, K.; Lubinski, D.; Hall, B.; Whittaker, T.

    2008-01-01

    Diatom taxa present in the inland streams and lakes of the McMurdo Dry Valleys and James Ross Island, Antarctica, are presented in this paper. A total of nine taxa are illustrated, with descriptions of four new species (Luticola austroatlantica sp. nov., Luticola dolia sp. nov., Luticola laeta sp. nov., Muelleria supra sp. nov.). In the perennially ice-covered lakes of the McMurdo Dry Valleys, diatoms are confined to benthic mats within the photic zone. In streams, diatoms are attached to benthic surfaces and within the microbial mat matrix. One species, L. austroatlantica, is found on James Ross Island, of the southern Atlantic archipelago, and the McMurdo Dry Valleys. The McMurdo Dry Valley populations are at the lower range of the size spectrum for the species. Streams flow for 6-10 weeks during the austral summer, when temperatures and solar radiation allow glacial ice to melt. The diatom flora of the region is characterized by species assemblages favored under harsh conditions, with naviculoid taxa as the dominant group and several major diatom groups conspicuously absent. ?? 2008 NRC.

  5. Mantle to surface degassing of alkalic magmas at Erebus volcano, Antarctica

    USGS Publications Warehouse

    Oppenheimer, C.; Moretti, R.; Kyle, P.R.; Eschenbacher, A.; Lowenstern, J. B.; Hervig, R.L.; Dunbar, N.W.

    2011-01-01

    Continental intraplate volcanoes, such as Erebus volcano, Antarctica, are associated with extensional tectonics, mantle upwelling and high heat flow. Typically, erupted magmas are alkaline and rich in volatiles (especially CO2), inherited from low degrees of partial melting of mantle sources. We examine the degassing of the magmatic system at Erebus volcano using melt inclusion data and high temporal resolution open-path Fourier transform infrared (FTIR) spectroscopic measurements of gas emissions from the active lava lake. Remarkably different gas signatures are associated with passive and explosive gas emissions, representative of volatile contents and redox conditions that reveal contrasting shallow and deep degassing sources. We show that this unexpected degassing signature provides a unique probe for magma differentiation and transfer of CO2-rich oxidised fluids from the mantle to the surface, and evaluate how these processes operate in time and space. Extensive crystallisation driven by CO2 fluxing is responsible for isobaric fractionation of parental basanite magmas close to their source depth. Magma deeper than 4kbar equilibrates under vapour-buffered conditions. At shallower depths, CO2-rich fluids accumulate and are then released either via convection-driven, open-system gas loss or as closed-system slugs that ascend and result in Strombolian eruptions in the lava lake. The open-system gases have a reduced state (below the QFM buffer) whereas the closed-system gases preserve their deep oxidised signatures (close to the NNO buffer). ?? 2011 Elsevier B.V.

  6. Carbon-Isotopic Dynamics of Streams, Taylor Valley, Antarctica: Biological Effects

    NASA Technical Reports Server (NTRS)

    Neumann, K.; DesMarais, D. J.

    1998-01-01

    We have investigated the role of biological processes in the C-isotopic dynamics of the aquatic ecosystems in Taylor Valley, Antarctica. This cold desert ecosystem is characterized by the complete lack of vascular plants, and the presence of algal mats in ephemeral streams and perennially ice covered lakes. Streams having abundant algal mats and mosses have very low sigma CO2 concentrations, as well as the most depleted delta C-13 values (-4%). Previous work has shown that algal mats in these streams have delta C-13 values averaging -7.01%. These values are similar to those observed in the algal mats in shallow areas of the lakes in Taylor Valley, where CO2 is thought to be colimiting to growth. These low Sigma CO2 concentrations, and delta C(13) signatures heavier than the algal mats, suggest that CO2 may be colimiting in the streams, as well. Streams with little algal growth, especially the longer ones in Fryxell Basin, have higher Sigma CO2 concentrations and much more enriched isotopic signatures (as high as +8%). In these streams, the dissolution of isotopically enriched, cryogenic CaCO3 is probably the major source of dissolved carbonate. The delta C(13) geochemistry of Antarctic streams is radically different from the geochemistry of more temperate streams, as it is not affected by terrestrially produced, isotopically depleted Sigma CO2. These results have important implications for the understanding of "biogenic" carbonate that might have been produced from aquatic ecosystems in the past on Mars.

  7. Preliminary results of a radio echo sounding survey of the Recovery Glacier, Antarctica

    NASA Astrophysics Data System (ADS)

    Humbert, Angelika; Kleiner, Thomas; Steinhage, Daniel

    2014-05-01

    The Recovery Glacier is draining about 8% of the East Antarctic ice sheet and feeds into the Filchner Ice Shelf. This ice shelf might be subjected in future to increasing basal melting (Hellmer et al., 2012) forcing potentially grounding line retreat. Compared to other areas in Antarctica this glacier is been surveyed very sparse and hence does not allow modeling studies yet. As many large and small subglacial lakes are present underneath this ice stream at different locations along the flow, the question of the influence of the lakes on ice stream genesis and ice stream dynamics arose. For investigating this influence by observation and subsequent modelling, an airborne campaign of the Alfred Wegener Institute was carried out in January 2014, covering the Recovery Ice Stream and two smaller glaciers merging with it, the Ramp Glacier and the Blackwall Glacier. The radar system uses a carrier frequency of 150MHz and a 600ns pulse. The survey includes several flights along flow lines in order to assess the basal roughness of the ice stream. Here we present the first preliminary data analysis.

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

    NASA Astrophysics Data System (ADS)

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

    2013-02-01

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

  9. ACE-Asia: Size Resolved Sampling of Aerosols on the Ronald H Brown and US Western Receptor Sites

    NASA Astrophysics Data System (ADS)

    Jimenez-Cruz, M. P.; Cliff, S. S.; Perry, K. D.; Cahill, T. A.; Bates, T. S.

    2001-12-01

    The ACE (Aerosol Characterization Experiment)-Asia project was pre-dominantly performed during the spring of 2001. In addition to the core Asian sampling sites, we sampled at 4 Western US receptor sites. The receptor sites include, Mauna Loa Observatory, Hawaii, Crater Lake Oregon, Adak Island, Alaska and Rattlesnake Mountain, Washington. A small subset of sites (Rattlesnake Mtn., MLO, and Asian sites) continued during a 6-week intensive summer study. For the spring study, an 8-stage DRUM impactor also sampled aboard the NOAA ship RV Ronald H Brown, and mix of 8- and 3-DRUM impactors were used at the western US receptor sites. The impactors are capable of size-segregated, time-resolved aerosol collection. The size categories for the 8-DRUM are inlet-5.00, 5.00-2.50, 2.50-1.15, 1.15-0.75, 0.75-0.56, 0.56-0.34, 0.34-.026, 0.26-.09 microns and 3-DRUM: 2.50-1.10, 1.10-0.34, 0.34-0.12 microns. These samples were analyzed in 6 hour time bites using synchrotron-XRF for quantitative composition for elements sodium through uranium, when present. A major dust event occurring around April 13 was detected at all receptor sites. Comparisons of key elemental ratios and conservative tracers will be presented.

  10. New Aerogeophysical exploration of the Gamburtsev Province (East Antarctica)

    NASA Astrophysics Data System (ADS)

    Ferraccioli, F.; Bell, R. E.; Studinger, M.; Damaske, D.; Jordan, T. A.; Corr, H.; Braaten, D. A.; Gogineni, P. S.; Fahnestock, M. A.; Finn, C.; Rose, K.

    2009-12-01

    The enigmatic Gamburstev Subglacial Mountains (GSM) in the interior of East Antarctica, have remained the least understood mountain range on earth, since their discovery some 50 years ago. An improved knowledge of the GSM region is however essential to underpin reconstructions of the Antarctic cryosphere and climate evolution. The GSM are a key nucleation site for the inception of the East Antarctic Ice Sheet approximately 34 Ma ago, and the adjacent Lambert Glacier played a pivotal role for ice sheet dynamics throughout the Neogene (23-0 Ma). The GSM province may also provide tectonic controls for major subglacial lakes flanking the range. In addition, the ice encasing the GSM province has been inferred to contain the oldest detailed climate record of the planet, a prime target for future deep ice core drilling. With the overarching aim of accomplishing the first systematic study of the cryosphere and lithosphere of the GSM province we launched a new geophysical exploration effort- AGAP (Antarctica’s Gamburtsev Province)-, a flagship programme of the International Polar Year. The aerogeophysical and seismology components of AGAP were accomplished by pooling resources from 7 nations. We deployed 2 Twin Otters, equipped with state-of-the art geophysical instrumentation and operating from two remote field camps on either side of Dome A. Over 120,000 line-km of new airborne radar, laser, aerogravity and aeromagnetic data survey were collected during the 2008/09 field campaign. Our grids of ice surface, ice thickness, subglacial topography, and gravity and magnetic anomalies provide a new geophysical foundation to analyse the GSM province, from the surface of the East Antarctic Ice Sheet down to mantle depths beneath the Precambrian shield. The anomalously high-elevation, alpine-type landscape of the GSM is now mapped with unprecedented detail. Two distinct branches of a subglacial rift system are imaged along the north-western and north-eastern margins of the

  11. Advances in modelling subglacial lakes and their interaction with the Antarctic ice sheet.

    PubMed

    Pattyn, Frank; Carter, Sasha P; Thoma, Malte

    2016-01-28

    Subglacial lakes have long been considered hydraulically isolated water bodies underneath ice sheets. This view changed radically with the advent of repeat-pass satellite altimetry and the discovery of multiple lake discharges and water infill, associated with water transfer over distances of more than 200 km. The presence of subglacial lakes also influences ice dynamics, leading to glacier acceleration. Furthermore, subglacial melting under the Antarctic ice sheet is more widespread than previously thought, and subglacial melt rates may explain the availability for water storage in subglacial lakes and water transport. Modelling of subglacial water discharge in subglacial lakes essentially follows hydraulics of subglacial channels on a hard bed, where ice sheet surface slope is a major control on triggering subglacial lake discharge. Recent evidence also points to the development of channels in deformable sediment in West Antarctica, with significant water exchanges between till and ice. Most active lakes drain over short time scales and respond rapidly to upstream variations. Several Antarctic subglacial lakes exhibit complex interactions with the ice sheet due to water circulation. Subglacial lakes can therefore-from a modelling point of view-be seen as confined small oceans underneath an imbedded ice shelf. PMID:26667909

  12. Enhancing the ACE control center for the multiple uses of spacecraft integration and test and mission and science operations

    NASA Technical Reports Server (NTRS)

    Snow, Frank; Garrard, Thomas L.; Steck, Jane A.; Maury, Jesse L.

    1996-01-01

    In relation to the mandate to reduce space mission development and operations costs, the advanced composition explorer (ACE) will use a version of the Transportable Payload Operations Control Center (TPOCC) for its mission operations. It was determined during the phase B of the ACE project that a potential existed for substantial savings if the adaptation of the TPOCC for the ACE mission operations could include its adaptation for use as the primary component in the ground support equipment for the integration and testing of the ACE spacecraft, and for use as the basic component in the ACE science center. The implementation of this approach required the enhancement of the TPOCC requirements, changes in the development schedule and changes in the allocation and activities of the personnel responsible for the development of ACE operations. It is discussed how these issues, and the problems that arose, were addressed.

  13. Regulation of Ace2-dependent genes requires components of the PBF complex in Schizosaccharomyces pombe

    PubMed Central

    Suárez, M Belén; Alonso-Nuñez, María Luisa; del Rey, Francisco; McInerny, Christopher J; Vázquez de Aldana, Carlos R

    2015-01-01

    The division cycle of unicellular yeasts is completed with the activation of a cell separation program that results in the dissolution of the septum assembled during cytokinesis between the 2 daughter cells, allowing them to become independent entities. Expression of the eng1+ and agn1+ genes, encoding the hydrolytic enzymes responsible for septum degradation, is activated at the end of each cell cycle by the transcription factor Ace2. Periodic ace2+ expression is regulated by the transcriptional complex PBF (PCB Binding Factor), composed of the forkhead-like proteins Sep1 and Fkh2 and the MADS box-like protein Mbx1. In this report, we show that Ace2-dependent genes contain several combinations of motifs for Ace2 and PBF binding in their promoters. Thus, Ace2, Fkh2 and Sep1 were found to bind in vivo to the eng1+ promoter. Ace2 binding was coincident with maximum level of eng1+ expression, whereas Fkh2 binding was maximal when mRNA levels were low, supporting the notion that they play opposing roles. In addition, we found that the expression of eng1+ and agn1+ was differentially affected by mutations in PBF components. Interestingly, agn1+ was a major target of Mbx1, since its ectopic expression resulted in the suppression of Mbx1 deletion phenotypes. Our results reveal a complex regulation system through which the transcription factors Ace2, Fkh2, Sep1 and Mbx1 in combination control the expression of the genes involved in separation at the end of the cell division cycle. PMID:26237280

  14. The Altus Cumulus Electrification Study (ACES): A UAV-based Investigation of Thunderstorms

    NASA Technical Reports Server (NTRS)

    Blakeslee, Richard; Arnold, James E. (Technical Monitor)

    2001-01-01

    The Altus Cumulus Electrification Study (ACES) is a NASA-sponsored and -led science investigation that utilizes an uninhabited aerial vehicle (UAV) to investigate thunderstorms in the vicinity of the NASA Kennedy Space Center, Florida. As part of NASA's UAV-based science demonstration program, ACES will provide a scientifically useful demonstration of the utility and promise of UAV platforms for Earth science and applications observations. ACES will employ the Altus 11 aircraft, built by General Atomics-Aeronautical Systems, Inc. By taking advantage of its slow flight speed (70 to 100 knots), long endurance, and high-altitude flight (up to 55,000 feet), the Altus will be flown near, and when possible, above (but never into) thunderstorms for long periods of time, allowing investigations to be conducted over entire storm life cycles. Key science objectives simultaneously addressed by ACES are to: (1) investigate lightning-storm relationships, (2) study storm electrical budgets, and (3) provide Lightning Imaging Sensor validation. The ACES payload, already developed and flown on Altus, includes electrical, magnetic, and optical sensors to remotely characterize the lightning activity and the electrical environment within and around thunderstorms. The ACES field campaign will be conducted during July 2002 with a goal of performing 8 to 10 UAV flights. Each flight will require about 4 to 5 hours on station at altitudes from 40,000 ft to 55,000 ft. The ACES team is comprised of scientists from the NASA Marshall Space Flight Center and NASA Goddard Space Flight Centers partnered with General Atomics and IDEA, LLC.

  15. Regulation of Ace2-dependent genes requires components of the PBF complex in Schizosaccharomyces pombe.

    PubMed

    Suárez, M Belén; Alonso-Nuñez, María Luisa; del Rey, Francisco; McInerny, Christopher J; Vázquez de Aldana, Carlos R

    2015-01-01

    The division cycle of unicellular yeasts is completed with the activation of a cell separation program that results in the dissolution of the septum assembled during cytokinesis between the 2 daughter cells, allowing them to become independent entities. Expression of the eng1(+) and agn1(+) genes, encoding the hydrolytic enzymes responsible for septum degradation, is activated at the end of each cell cycle by the transcription factor Ace2. Periodic ace2(+) expression is regulated by the transcriptional complex PBF (PCB Binding Factor), composed of the forkhead-like proteins Sep1 and Fkh2 and the MADS box-like protein Mbx1. In this report, we show that Ace2-dependent genes contain several combinations of motifs for Ace2 and PBF binding in their promoters. Thus, Ace2, Fkh2 and Sep1 were found to bind in vivo to the eng1(+) promoter. Ace2 binding was coincident with maximum level of eng1(+) expression, whereas Fkh2 binding was maximal when mRNA levels were low, supporting the notion that they play opposing roles. In addition, we found that the expression of eng1(+) and agn1(+) was differentially affected by mutations in PBF components. Interestingly, agn1(+) was a major target of Mbx1, since its ectopic expression resulted in the suppression of Mbx1 deletion phenotypes. Our results reveal a complex regulation system through which the transcription factors Ace2, Fkh2, Sep1 and Mbx1 in combination control the expression of the genes involved in separation at the end of the cell division cycle. PMID:26237280

  16. New aerogeophysical survey targets crustal architecture and tectonic evolution of East Antarctica in the Recovery frontier

    NASA Astrophysics Data System (ADS)

    Ferraccioli, F.; Forsberg, R.; Jordan, T. A.; Matsuoka, K.; Olesen, A. V.; Ghidella, M. E.

    2013-12-01

    block assembled onto East Antarctica? Is there a major Grenvillian-age orogenic belt, running from Coats Land across the continent towards the Denman Glacier region linked to Rodina assembly and where are its boundaries with the inferred Crohn Craton and the Mawson Craton in the Recovey region (Boger, 2011, GR)? Or is there instead a continuation of the Gamburtsev, South Pole and Recovery provinces recognised further in the interior (Ferraccioli et al., 2011, Nature)? Is there a major Pan-African and/or Ross-age suture zone in the Shackleton Range linked to Gondwana assembly? Are there any major rift structures and sedimentary basins in the Recovery region linked to Gondwana break up e.g. similar to those identified in the Weddell Sea Rift region or in the East Antarctic Rift System? What influence do major tectonic features and sedimentary basins (if they exist) exert on the dynamics of the Recovery ice stream and the large Recovery lakes?

  17. Fine-Mapping Angiotensin-Converting Enzyme Gene: Separate QTLs Identified for Hypertension and for ACE Activity

    PubMed Central

    Chung, Chia-Min; Wang, Ruey-Yun; Fann, Cathy S. J.; Chen, Jaw-Wen; Jong, Yuh-Shiun; Jou, Yuh-Shan; Yang, Hsin-Chou; Kang, Chih-Sen; Chen, Chien-Chung; Chang, Huan-Cheng; Pan, Wen-Harn

    2013-01-01

    Angiotensin-converting enzyme (ACE) has been implicated in multiple biological system, particularly cardiovascular diseases. However, findings associating ACE insertion/deletion polymorphism with hypertension or other related traits are inconsistent. Therefore, in a two-stage approach, we aimed to fine-map ACE in order to narrow-down the function-specific locations. We genotyped 31 single nucleotide polymorphisms (SNPs) of ACE from 1168 individuals from 305 young-onset (age ≤40) hypertension pedigrees, and found four linkage disequilibrium (LD) blocks. A tag-SNP, rs1800764 on LD block 2, upstream of and near the ACE promoter, was significantly associated with young-onset hypertension (p = 0.04). Tag-SNPs on all LD blocks were significantly associated with ACE activity (p-value: 10–16 to <10–33). The two regions most associated with ACE activity were found between exon13 and intron18 and between intron 20 and 3′UTR, as revealed by measured haplotype analysis. These two major QTLs of ACE activity and the moderate effect variant upstream of ACE promoter for young-onset hypertension were replicated by another independent association study with 842 subjects. PMID:23469169

  18. ACE2 Deficiency Worsens Epicardial Adipose Tissue Inflammation and Cardiac Dysfunction in Response to Diet-Induced Obesity.

    PubMed

    Patel, Vaibhav B; Mori, Jun; McLean, Brent A; Basu, Ratnadeep; Das, Subhash K; Ramprasath, Tharmarajan; Parajuli, Nirmal; Penninger, Josef M; Grant, Maria B; Lopaschuk, Gary D; Oudit, Gavin Y

    2016-01-01

    Obesity is increasing in prevalence and is strongly associated with metabolic and cardiovascular disorders. The renin-angiotensin system (RAS) has emerged as a key pathogenic mechanism for these disorders; angiotensin (Ang)-converting enzyme 2 (ACE2) negatively regulates RAS by metabolizing Ang II into Ang 1-7. We studied the role of ACE2 in obesity-mediated cardiac dysfunction. ACE2 null (ACE2KO) and wild-type (WT) mice were fed a high-fat diet (HFD) or a control diet and studied at 6 months of age. Loss of ACE2 resulted in decreased weight gain but increased glucose intolerance, epicardial adipose tissue (EAT) inflammation, and polarization of macrophages into a proinflammatory phenotype in response to HFD. Similarly, human EAT in patients with obesity and heart failure displayed a proinflammatory macrophage phenotype. Exacerbated EAT inflammation in ACE2KO-HFD mice was associated with decreased myocardial adiponectin, decreased phosphorylation of AMPK, increased cardiac steatosis and lipotoxicity, and myocardial insulin resistance, which worsened heart function. Ang 1-7 (24 µg/kg/h) administered to ACE2KO-HFD mice resulted in ameliorated EAT inflammation and reduced cardiac steatosis and lipotoxicity, resulting in normalization of heart failure. In conclusion, ACE2 plays a novel role in heart disease associated with obesity wherein ACE2 negatively regulates obesity-induced EAT inflammation and cardiac insulin resistance. PMID:26224885

  19. Accuracy assessment of satellite altimetry over central East Antarctica by kinematic GNSS and crossover analysis

    NASA Astrophysics Data System (ADS)

    Schröder, Ludwig; Richter, Andreas; Fedorov, Denis; Knöfel, Christoph; Ewert, Heiko; Dietrich, Reinhard; Matveev, Aleksey Yu.; Scheinert, Mirko; Lukin, Valery

    2014-05-01

    Satellite altimetry is a unique technique to observe the contribution of the Antarctic ice sheet to global sea-level change. To fulfill the high quality requirements for its application, the respective products need to be validated against independent data like ground-based measurements. Kinematic GNSS provides a powerful method to acquire precise height information along the track of a vehicle. Within a collaboration of TU Dresden and Russian partners during the Russian Antarctic Expeditions in the seasons from 2001 to 2013 we recorded several such profiles in the region of the subglacial Lake Vostok, East Antarctica. After 2006 these datasets also include observations along seven continental traverses with a length of about 1600km each between the Antarctic coast and the Russian research station Vostok (78° 28' S, 106° 50' E). After discussing some special issues concerning the processing of the kinematic GNSS profiles under the very special conditions of the interior of the Antarctic ice sheet, we will show their application for the validation of NASA's laser altimeter satellite mission ICESat and of ESA's ice mission CryoSat-2. Analysing the height differences at crossover points, we can get clear insights into the height regime at the subglacial Lake Vostok. Thus, these profiles as well as the remarkably flat lake surface itself can be used to investigate the accuracy and possible error influences of these missions. We will show how the transmit-pulse reference selection correction (Gaussian vs. centroid, G-C) released in January 2013 helped to further improve the release R633 ICESat data and discuss the height offsets and other effects of the CryoSat-2 radar data. In conclusion we show that only a combination of laser and radar altimetry can provide both, a high precision and a good spatial coverage. An independent validation with ground-based observations is crucial for a thorough accuracy assessment.

  20. Exceptionally preserved lacustrine ostracods from the Middle Miocene of Antarctica: implications for high-latitude palaeoenvironment at 77° south

    PubMed Central

    Williams, Mark; Siveter, David J; Ashworth, Allan C; Wilby, Philip R; Horne, David J; Lewis, Adam R; Marchant, David R

    2008-01-01

    A newly discovered Konservat-Lagerstätte from the Middle Miocene of the western Olympus Range, Dry Valleys, Antarctica, yields cypridoidean ostracods complete with preserved body and appendages. This is the first record of three-dimensionally fossilized animal soft tissues from the continent. The ostracods are preserved in goethite, secondary after pyrite, representing a novel mode of exceptional preservation. They signal a high-latitude (greater than 77° south) lake setting (Palaeolake Boreas) viable for benthic animal colonization prior to 14 Myr ago. Their presence supports the notion of warmer, tundra-like environmental conditions persisting in the Dry Valleys until the Middle Miocene. PMID:18647723

  1. Dissolved black carbon in Antarctic lakes: Chemical signatures of past and present sources

    NASA Astrophysics Data System (ADS)

    Khan, Alia L.; Jaffé, Rudolf; Ding, Yan; McKnight, Diane M.

    2016-06-01

    The perennially ice-covered, closed-basin lakes in the McMurdo Dry Valleys, Antarctica, serve as sentinels for understanding the fate of dissolved black carbon from glacial sources in aquatic ecosystems. Here we show that dissolved black carbon can persist in freshwater and saline surface waters for thousands of years, while preserving the chemical signature of the original source materials. The ancient brines of the lake bottom waters have retained dissolved black carbon with a woody chemical signature, representing long-range transport of black carbon from wildfires. In contrast, the surface waters are enriched in contemporary black carbon from fossil fuel combustion. Comparison of samples collected 25 years apart from the same lake suggests that the enrichment in anthropogenic black carbon is recent. Differences in the chemical composition of dissolved black carbon among the lakes are likely due to biogeochemical processing such as photochemical degradation and sorption on metal oxides.

  2. Inorganic chemistry, petrography and palaeobotany of Permian coals in the Prince Charles Mountains, East Antarctica

    USGS Publications Warehouse

    Holdgate, G.R.; McLoughlin, S.; Drinnan, A.N.; Finkelman, R.B.; Willett, J.C.; Chiehowsky, L.A.

    2005-01-01

    Sampled outcrops of Permian coal seams of the Bainmedart Coal Measures in the Lambert Graben, eastern Antarctica, have been analysed for their proximates, ultimates, ash constituents and trace elements. A similar series of samples has been analysed for their principle maceral and microlithotype components and vitrinite reflectance. The coals are sub-bituminous to high volatile bituminous in rank; maturity increases markedly in southern exposures around Radok Lake where the oldest part of the succession is exposed and some strata have been intruded by mafic dykes and ultramafic sills. The coal ash is mostly silica and aluminium oxides, indicating that the mineral ash component is mostly quartz and various clay minerals. The ratio of silica to aluminium oxides appears to increase in an upward stratigraphic direction. The coal macerals include a relatively high liptinite content (mainly sporinite) that is significantly higher than for typical Gondwana coals. Greater degrees of weathering within the floodbasin/peat mire environments associated with climatic drying towards the end of the Permian might account for both preferential sporopollenin preservation and increased silica:aluminium oxide ratios up-section. Correlation of the coal maceral components to adjacent peninsula India coals indicates the closest comparative coals of similar age and rank occur within the Godavari Basin, rather then the Mahanadi Basin, which is traditionally interpreted to have been contiguous with the Lambert Graben before Gondwanan breakup. The petrological characteristics suggest that either previous interpretations of Palaeozoic basin alignments between Antarctica and India are incorrect, or that environmental settings and post-Permian burial histories of these basins were strongly independent of their tectonic juxtaposition. A permineralized peat bed within the succession reveals that the coals predominantly comprise wood- and leaf-rich debris derived from low-diversity forest

  3. Experimental constraints on the crystallization and evolution of primitive magmas from Erebus volcano, Antarctica

    NASA Astrophysics Data System (ADS)

    Iacovino, K.; Oppenheimer, C.; Scaillet, B.; Kyle, P. R.

    2011-12-01

    We present the preliminary results of phase equilibria experiments on a basanite and a phonotephrite, which are used to understand the evolution of alkali magmas at Erebus volcano, Antarctica. Field observations of the Erebus lava lake indicate complex magmatic behavior at depth. In addition, the remarkably complete fractional crystallization sequence of lava types seen in outcrop and their corresponding melt inclusions give an unprecedented look into the interplay between degassing and crystallization in both deep and shallow regions within the magmatic plumbing system. We aim for the first time to experimentally constrain the pre-eruptive conditions of the crystallization and evolution of the Erebus magma suite, with particular emphasis on magma evolution from basanite to phonotephrite. Phase equilibria experiments have been performed between 1000-1150 °C and 200-400 MPa with a range of H2O/CO2 ratios from XH2Ofluid = 0-1 with two natural compositions, a basanite (SiO2 = 42.13 wt%; MgO = 8.73 wt%) and a phonotephrite (SiO2 = 47.19 wt%; MgO = 3.13 wt%), collected on Ross Island, Antarctica. For the conditions thus far explored, augite is the liquidus phase in the basanite, followed by Mg-rich olivine. In the phonotephrite, Fe-Ti oxides are always present with the addition of minor apatite and feldspar in some samples. Preliminary results indicate that fractionation of Erebus basanite to phonotephrite likely occurred at high temperature (>1100 °C), at pressures above 300 MPa, and with sufficient water to stabilize plagioclase.

  4. Distribution of ice thickness and subglacial topography of the "Chinese Wall" around Kunlun Station, East Antarctica

    NASA Astrophysics Data System (ADS)

    Cui, Xiang-Bin; Sun, Bo; Su, Xiao-Gang; Guo, Jing-Xue

    2016-03-01

    As fundamental parameters of the Antarctic Ice Sheet, ice thickness and subglacial topography are critical factors for studying the basal conditions and mass balance in Antarctica. During CHINARE 24 (the 24th Chinese National Antarctic Research Expedition, 2007/08), the research team used a deep ice-penetrating radar system to measure the ice thickness and subglacial topography of the "Chinese Wall" around Kunlun Station, East Antarctica. Preliminary results show that the ice thickness varies mostly from 1600 m to 2800 m along the "Chinese Wall", with the thickest ice being 3444 m, and the thinnest ice 1255 m. The average bedrock elevation is 1722 m, while the minimum is just 604 m. Compared with the northern side of the ice divide, the ice thickness is a little greater and the subglacial topography lower on the southern side, which is also characterized by four deep valleys. We found no basal freeze-on ice in the Gamburtsev Subglacial Mountains area, subglacial lakes, or water bodies along the "Chinese Wall". Ice thickness and subglacial topography data extracted from the Bedmap 2 database along the "Chinese Wall" are consistent with our results, but their resolution and accuracy are very limited in areas where the bedrock fluctuates intensely. The distribution of ice thickness and subglacial topography detected by ice-penetrating radar clarifies the features of the ice sheet in this "inaccessible" region. These results will help to advance the study of ice sheet dynamics and the determination of future locations of the GSM's geological and deep ice core drilling sites in the Dome A region.

  5. Cyclic degassing of Erebus volcano, Antarctica

    NASA Astrophysics Data System (ADS)

    Ilanko, Tehnuka; Oppenheimer, Clive; Burgisser, Alain; Kyle, Philip

    2015-06-01

    Field observations have previously identified rapid cyclic changes in the behaviour of the lava lake of Erebus volcano. In order to understand more fully the nature and origins of these cycles, we present here a wavelet-based frequency analysis of time series measurements of gas emissions from the lava lake, obtained by open-path Fourier transform infrared spectroscopy. This reveals (i) a cyclic change in total gas column amount, a likely proxy for gas flux, with a period of about 10 min, and (ii) a similarly phased cyclic change in proportions of volcanic gases, which can be explained in terms of chemical equilibria and pressure-dependent solubilities. Notably, the wavelet analysis shows a persistent periodicity in the CO2/CO ratio and strong periodicity in H2O and SO2 degassing. The `peaks' of the cycles, defined by maxima in H2O and SO2 column amounts, coincide with high CO2/CO ratios and proportionally smaller increases in column amounts of CO2, CO, and OCS. We interpret the cycles to arise from recharge of the lake by intermittent pulses of magma from shallow depths, which degas H2O at low pressure, combined with a background gas flux that is decoupled from this very shallow magma degassing.

  6. High resolution critical habitat mapping and classification of tidal freshwater wetlands in the ACE Basin

    NASA Astrophysics Data System (ADS)

    Strickland, Melissa Anne

    In collaboration with the South Carolina Department of Natural Resources ACE Basin National Estuarine Research Reserve (ACE Basin NERR), the tidal freshwater ecosystems along the South Edisto River in the ACE Basin are being accurately mapped and classified using a LIDAR-Remote Sensing Fusion technique that integrates LAS LIDAR data into texture images and then merges the elevation textures and multispectral imagery for very high resolution mapping. This project discusses the development and refinement of an ArcGIS Toolbox capable of automating protocols and procedures for marsh delineation and microhabitat identification. The result is a high resolution habitat and land use map used for the identification of threatened habitat. Tidal freshwater wetlands are also a critical habitat for colonial wading birds and an accurate assessment of community diversity and acreage of this habitat type in the ACE Basin will support SCDNR's conservation and protection efforts. The maps developed by this study will be used to better monitor the freshwater/saltwater interface and establish a baseline for an ACE NERR monitoring program to track the rates and extent of alterations due to projected environmental stressors. Preliminary ground-truthing in the field will provide information about the accuracy of the mapping tool.

  7. Seasonal comparisons of retrieved temperature and water vapour between ACE-FTS and COSMIC.

    NASA Astrophysics Data System (ADS)

    Olsen, Kevin; Toon, Geoff; Boone, Chris; Strong, Kim

    2015-04-01

    Motivated by the selection of a high-resolution solar occultation Fourier transform spectrometer (FTS) to fly to Mars, we developed new algorithms for retrieving vertical profiles of temperature and pressure from spectra. We present temperature retrieval results from remote sensing spectra collected by the Canadian Space Agency's (CSA) Atmospheric Chemistry Experiment (ACE), which recently celebrated its tenth year in orbit. ACE utilizes a high-resolution (0.02 cm-1) Fourier Transform Spectrometer (FTS) operating between 750-4400 cm-1 in limb-scanning mode using the sun as a light source (solar occultation). We compare our retrieved profiles to those of the ACE Science Team and the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC). COSMIC is a group of six small satellites that use signals from GPS satellites to measure water vapour pressure an temperature via radio occultation. We have collected five sets of zonal and seasonal coincidences with a tight criteria of 150 km and 1 hour. Retrieved H2O profiles from both satellites will also be presented for these data sets. Compared to ACE, we can achieve T differences between 1 and 5 K below 50 km, perform less well between 50 and 100 km. Compared to COSMIC, available below 40 km, we perform similarly, while the ACE retrievals are in close agreement.

  8. Cell cycle dependence of ACE-2 explains downregulation in idiopathic pulmonary fibrosis.

    PubMed

    Uhal, Bruce D; Dang, MyTrang; Dang, Vinh; Llatos, Roger; Cano, Esteban; Abdul-Hafez, Amal; Markey, Jonathan; Piasecki, Christopher C; Molina-Molina, Maria

    2013-07-01

    Alveolar epithelial type II cells, a major source of angiotensin-converting enzyme (ACE)-2 in the adult lung, are normally quiescent but actively proliferate in lung fibrosis and downregulate this protective enzyme. It was, therefore, hypothesised that ACE-2 expression might be related to cell cycle progression. To test this hypothesis, ACE-2 mRNA levels, protein levels and enzymatic activity were examined in fibrotic human lungs and in the alveolar epithelial cell lines A549 and MLE-12 studied at postconfluent (quiescent) versus subconfluent (proliferating) densities. ACE-2 mRNA, immunoreactive protein and enzymatic activity were all high in quiescent cells, but were severely downregulated or absent in actively proliferating cells. Upregulation of the enzyme in cells that were progressing to quiescence was completely inhibited by the transcription blocker actinomycin D or by SP600125, an inhibitor of c-Jun N-terminal kinase (JNK). In lung biopsy specimens obtained from patients with idiopathic pulmonary fibrosis, immunoreactive enzyme was absent in alveolar epithelia that were positive for proliferation markers, but was robustly expressed in alveolar epithelia devoid of proliferation markers. These data explain the loss of ACE-2 in lung fibrosis and demonstrate cell cycle-dependent regulation of this protective enzyme by a JNK-mediated transcriptional mechanism. PMID:23100504

  9. Effect of hypoxia and hypercapnia on ACE activity in the cerebral microcirculation of anesthetized dogs

    SciTech Connect

    Pitt, B.R.; Lister, G.; Dawson, C.A.; Linehan, J.H.

    1986-05-01

    Angiotensin-converting enzyme (ACE) activity of the cerebral microcirculation of anesthetized dogs was measured from cerebral venous outflow curves after bolus injection of a synthetic ACE substrate, (/sup 3/H)benzoyl-phenylalanyl-alanylproline ((/sup 3/H)BPAP), into a common carotid artery. Cerebral BPAP metabolism was quantified by measuring the concentration of (/sup 3/H)benzoyl-phenylalanine (the product of BPAP hydrolysis by ACE) in blood samples from the sagittal sinus after occlusion of the lateral sinuses with bone wax. Instantaneous BPAP metabolism in each sample increased as a function of time after injection, suggestive of perfusion heterogeneity, and averaged 59 +/- 4% (n = 8) over a single pass during normoxia and normocapnia. The ratio of Vmax (the maximal rate of cerebral BPAP metabolism) to Km (the concentration at Vmax/2), was calculated from instantaneous outflow curves using a model based on first-order kinetics. Increases in cerebral blood flow during either hypoxia or hypercapnia significantly reduced BPAP metabolism to 33 +/- 3 (n = 7) and 24 +/- 3% (n = 5), respectively; however, Vmax/Km of ACE activity (0.19 +/- 0.03 ml/s) was not affected by either condition. The lack of change in apparent kinetics of ACE activity (i.e., in Vmax/Km) during hypoxia or hypercapnia suggests that recruitment of cerebral capillaries was not a quantitatively significant factor in controlling BPAP metabolism with this degree of either hypoxia or hypercapnia.

  10. [Comparison of salvage chemotherapy regimen ACES with ESHAP for refractory or relapsed malignant lymphoma].

    PubMed

    Imataki, Osamu; Tamai, Yotaro; Kawakami, Kimihiro

    2007-10-01

    Standard salvage chemotherapy for refractory or relapsed malignant lymphoma has not been defined. The efficacy and feasibility of the ACES regimen, consisting of carboplatin at 100 mg/m(2) on day 1 to 4, etoposide at 80 mg/m(2) on day 1 to 4, high-dose Ara-C at 2 g/m(2) on day 5 and methylprednisolone at 500 mg/day for 5 days, for refractory or relapsed lymphoma were retrospectively reviewed in comparison with the ESHAP regimen. The subjects were 29 patients, including 7 aggressive follicular lymphomas, 16 large B cell lymphomas and 6 Hodgkin lymphomas. Characteristics of patients with ESHAP (19 cases) and the ACES (10 cases) group were as follows: male/female ratio, 10/9 and 3/7; median age, 49 (range, 31-72) and 54 (22-65); and initial clinical stage (I and II / III / IV), 5/8/6 and 1/1/8, respectively. Among the 29 patients, complete response was achieved in 68% (13/19) in ESHAP and 40% (4/10) in ACES.Progression-free survival and overall survival were 31.3% and 34.3%, respectively. Hematological toxicity was not significantly different between the two groups, and renal toxicity was significantly higher in ESHAP (52%) than ACES (0%). We concluded that the ACES regimen had a possibility of effective consolidation therapy for the elderly aiming to undergo autologous stem cell transplantation. PMID:17940378

  11. ace-3 plays an important role in phoxim resistance in Caenorhabditis elegans.

    PubMed

    Han, Yan; Song, Shaojuan; Guo, Yaping; Zhang, Jianzhen; Ma, Enbo

    2016-05-01

    Organophosphorus and carbamate are widely used in agricultural production. Caenorhabditis elegans is a model organism that is widely used in various toxicology studies. To understand the effects of two types of commonly used pesticides, phoxim (organophosphorus) and carbaryl (carbamate), we determined the activities of acetylcholinesterases (AChEs) and detected the expression of four ace genes by RT-qPCR in C. elegans following treatment with these pesticides. The results showed that phoxim and carbaryl could reduce acetylcholinesterase activities and up-regulate the ace-3 mRNA expression levels. We also detected the toxic effects of these pesticides on the ace-3 deletion mutant dc-2, and found that some characteristics, including LC50, development, movement, reproduction and lifespan, were reduced in the dc-2 mutant. However, the toxic effects of carbaryl were weaker than those of phoxim. Carbaryl treatment did not significantly affect the LC50, movement ability or lifespan. Interestingly, body and brood size increased with carbaryl treatment at low concentrations. These data showed that both phoxim and carbaryl could inhibit AChE but that the ace-3 was necessary for phoxim detoxification. The LC50 of phoxim and carbaryl in wild type N2 and the ace-3 deletion mutant dc-2. **Higher significant differences (P < 0.01). PMID:26947509

  12. ACE Project ∼ Advocating for Clinical Excellence: Creating Change in the Delivery of Palliative Care

    PubMed Central

    Otis-Green, Shirley; Yang, Eunice; Lynne, Lisa

    2013-01-01

    Background Psychologists, social workers and spiritual care professionals report inadequate preparation to maximize their effectiveness in advocating for institutional reform to meet oncology patients' diverse bio-psychosocial-spiritual and cultural needs. This article provides an overview of the ACE Project, a National Cancer Institute, 5 year, R25-funded transdisciplinary palliative care education program designed to enhance the advocacy and leadership skills of 301 competitively selected psycho-oncology professionals. Methods ACE Project participants identified an institutional goal, refined their goals during the course and received mentorship and support throughout the subsequent year. Participants were invited to return to a Reunion Conference in year five to report on their activities, network and share the results of their change efforts. A subset of 28 ACE Project participants contributed to this OMEGA special issue. Results Participants' goals primarily focused on strategies to improve clinical care through program development and improvements in palliative care education within their institutions. Conclusions The results of this transdisciplinary leadership skills-building program for psycho-oncology professionals affirm the feasibility and perceived need for the program. See the ACE Project website (http://www.cityofhope.org/ace-project ) for additional program information. PMID:23977775

  13. ACE inhibitory activity of pangasius catfish (Pangasius sutchi) skin and bone gelatin hydrolysate.

    PubMed

    Mahmoodani, Fatemeh; Ghassem, Masomeh; Babji, Abdul Salam; Yusop, Salma Mohamad; Khosrokhavar, Roya

    2014-09-01

    Skin and bone gelatins of pangasius catfish (Pangasius sutchi) were hydrolyzed with alcalase to isolate Angiotensin Converting Enzyme (ACE) inhibitory peptides. Samples with the highest degree of hydrolysis (DH) were separated into different fractions with molecular weight cut-off (MWCO) sizes of 10, 3 and 1 kDa, respectively and assayed for ACE inhibitory activity. Skin and bone gelatins had highest DH of 64.87 and 68.48 % after 2 and 1 h incubation, respectively. Results from this study indicated that by decreasing the molecular weight of fractions, ACE inhibitory activity was increased. Therefore, F3 permeates (MWCO < 1 kDa) of skin (IC50 = 3.2 μg/ml) and bone (IC50 = 1.3 μg/ml) gelatins possessed higher ACE inhibitory activity compared to their untreated gelatins and corresponding hydrolyzed fractions. In this study, the major amino acids were Glycine followed by Proline with an increased amount of hydrophobic amino acid content in F3 permeates of skin (4.01 %) and bone (5.79 %) gelatin. Digestion stability against gastrointestinal proteases did not show any remarkable change on ACE inhibition potency of these permeates. It was concluded that alcalase hydrolysis of P. sutchi by-products could be utilized as a part of functional food or ingredients of a formulated drug in order to control high blood pressure. PMID:25190839

  14. Preparation of ACE Inhibitory Peptides from Mytilus coruscus Hydrolysate Using Uniform Design

    PubMed Central

    Wu, Jin-Chao; Cheng, Jie; Shi, Xiao-lai

    2013-01-01

    The angiotensin-I-converting enzyme (ACE) inhibitory peptides from mussel, Mytilus coruscus, were investigated and the variable factors, protease concentration, hydrolysis time, pH, and temperature, were optimized using Uniform Design, a new statistical experimental method. The results proved that the hydrolysate of alkali proteases had high ACE-inhibitory activity, especially the alkali protease E1. Optimization by Uniform Design showed that the best hydrolysis conditions for preparation of ACE-inhibitory peptides from Mytilus coruscus were protease concentration of 36.0 U/mL, hydrolysis time of 2.7 hours, pH 8.2, and Temperature at 59.5°C, respectively. The verification experiments under optimum conditions showed that the ACE-inhibitory activity (91.3%) were agreed closely with the predicted activity of 90.7%. The amino acid composition analysis of Mytilus coruscus ACE-inhibitory peptides proved that it had high percent of lysine, leucine, glycine, aspartic acid, and glutamic acid. PMID:23484103

  15. ACE Reduces Metabolic Abnormalities in a High-Fat Diet Mouse Model

    PubMed Central

    Lee, Seong-Jong; Han, Jong-Min; Lee, Jin-Seok; Son, Chang-Gue; Im, Hwi-Jin; Jo, Hyun-Kyung; Yoo, Ho-Ryong; Kim, Yoon-Sik; Seol, In-Chan

    2015-01-01

    The medicinal plants Artemisia iwayomogi (A. iwayomogi) and Curcuma longa (C. longa) radix have been used to treat metabolic abnormalities in traditional Korean medicine and traditional Chinese medicine (TKM and TCM). In this study we evaluated the effect of the water extract of a mixture of A. iwayomogi and C. longa (ACE) on high-fat diet-induced metabolic syndrome in a mouse model. Four groups of C57BL/6N male mice (except for the naive group) were fed a high-fat diet freely for 10 weeks. Among these, three groups (except the control group) were administered a high-fat diet supplemented with ACE (100 or 200 mg/kg) or curcumin (50 mg/kg). Body weight, accumulation of adipose tissues in abdomen and size of adipocytes, serum lipid profiles, hepatic steatosis, and oxidative stress markers were analyzed. ACE significantly reduced the body and peritoneal adipose tissue weights, serum lipid profiles (total cholesterol and triglycerides), glucose levels, hepatic lipid accumulation, and oxidative stress markers. ACE normalized lipid synthesis-associated gene expressions (peroxisome proliferator-activated receptor gamma, PPARγ; fatty acid synthase, FAS; sterol regulatory element-binding transcription factor-1c, SREBP-1c; and peroxisome proliferator-activated receptor alpha, PPARα). The results from this study suggest that ACE has the pharmaceutical potential reducing the metabolic abnormalities in an animal model. PMID:26508977

  16. Icebergs in the Ross Sea, Antarctica

    NASA Technical Reports Server (NTRS)

    2001-01-01

    Two large icebergs, designated B-15A and C-16, are captured in this MISR nadir camera view of the Ross Ice Shelf and Ross Sea in Antarctica. The image was acquired on December 10, 2000 during Terra orbit 5220.

    Iceberg C-16 calved off the ice shelf in late September and is nearly 50 kilometers in length. It is seen here having migrated to the vicinity of Cape Bird on Ross Island. The initial letter designation in an iceberg's name denotes the longitudinal quadrant in which it is first seen, and new icebergs sighted in that quadrant are sequentially numbered. B-15 divided from the ice shelf last March, and initially was nearly as large as the state of Connecticut. It has since broken up into several pieces, hence the final letter designation in the berg shown in this image.

    Ross Island lies between 77 and 78 degrees south latitude, and consists of several volcanic peaks, of which the still active Mt. Erebus is the tallest (3794 meters). It overlooks McMurdo Station, a U.S. research facility located near the tip of the island's Hut Point Peninsula.

    MISR was built and is managed by NASA's Jet Propulsion Laboratory, Pasadena, CA, for NASA's Office of Earth Science, Washington, DC. The Terra satellite is managed by NASA's Goddard Space Flight Center, Greenbelt, MD. JPL is a division of the California Institute of Technology.

  17. Odd cloud in the Ross Sea, Antarctica

    NASA Technical Reports Server (NTRS)

    2002-01-01

    On January 28, 2002, MODIS captured this image of an interesting cloud formation in the boundary waters between Antarctica's Ross Sea and the Southern Ocean. A dragon? A snake? A fish? No, but it is an interesting example of the atmospheric physics of convection. The 'eye' of this dragon-looking cloud is likely a small spot of convection, the process by which hot moist air rises up into the atmosphere, often producing big, fluffy clouds as moisture in the air condenses as rises into the colder parts of the atmosphere. A false color analysis that shows different kinds of clouds in different colors reveals that the eye is composed of ice crystals while the 'body' is a liquid water cloud. This suggests that the eye is higher up in the atmosphere than the body. The most likely explanation for the eye feature is that the warm, rising air mass had enough buoyancy to punch through the liquid water cloud. As a convective parcel of air rises into the atmosphere, it pushes the colder air that is higher up out of its way. That cold air spills down over the sides of the convective air mass, and in this case has cleared away part of the liquid cloud layer below in the process. This spilling over of cold air from higher up in the atmosphere is the reason why thunderstorms are often accompanied by a cool breeze. Credit: Jacques Descloitres, MODIS Land Rapid Response Team, NASA/GSFC

  18. Sedimentary basins in Ross Sea, Antarctica

    SciTech Connect

    Cooper, A.K.; Davey, F.J.

    1986-07-01

    The Ross Sea lies in the Pacific sector of the Antarctic continental margin. Three major sedimentary basins (from east to west, the Eastern, Central, and Victoria Land basins) lie beneath the broad, deep continental shelf of the Ross Sea. These north-south-trending basins occur in the extensionally deformed region between East and West Antarctica. Multichannel seismic reflection (MCS) surveys have been conducted over these basins since 1980 by West German, French, Japanese, and US expeditions. The MCS and previous geophysical surveys have shown that the three basins contain 5-6 km of sedimentary rock, possibly Late Cretaceous and younger. An additional 6-8 km of sedimentary and volcanic rock lies within the deeper parts of the Victoria Land basin. The basins are separated by uplifted and eroded basement ridges covered by thin sedimentary sections. Each basin has distinct characteristics, commonly related to its extensional origin. Petroleum hydrocarbons are unknown from the Ross Sea region, with the possible exception of ethane gas recovered by the Deep Sea Drilling Project. Previous model studies, based on estimated sediment thickness, assumed temperature gradients, and postulated seismostratigraphy, indicate that hydrocarbons could be generated at depths of 3.5-6km within the sedimentary section. However, this hypothesis cannot be verified without further geologic and geophysical data from the Ross Sea region.

  19. Fabric and texture at Siple Dome, Antarctica

    USGS Publications Warehouse

    Diprinzio, C.L.; Wilen, L.A.; Alley, R.B.; Fitzpatrick, J.J.; Spencer, M.K.; Gow, A.J.

    2005-01-01

    Preferred c-axis orientations are present in the firn at Siple Dome, West Antarctica, and recrystallization begins as shallow as 200 m depth in ice below -20??C, based on digital analysis of c-axis fabrics, grain-sizes and other characteristics of 52 vertical thin sections prepared in the field from the kilometer-long Siple Dome ice core. The shallowest section analyzed, from 22 m, shows clustering of c axes toward the vertical. By 200 m depth, girdle fabric and other features of recrystallized ice are evident in layers (or regions), separated by layers (regions) of typically finer-grained ice lacking evidence of recrystallization. Ice from about 700-780 m depth, which was deposited during the last ice age, is especially fine-grained, with strongly vertical c axes, but deeper ice shows much larger crystals and strong evidence of recrystallization. Azimuthal asymmetry of some c-axis fabrics, trends in grain-size, and other indicators reveal additional information on processes and history of ice flow at Siple Dome.

  20. Social, occupational and cultural adaptation in Antarctica

    NASA Astrophysics Data System (ADS)

    Nicolas, Michel; Bishop, Sheryl; Weiss, Karine; Gaudino, Marvin

    2016-07-01

    Life in isolated and confined environments (ICEs, e.g., polar stations, submarine or space missions), is subject to important constraints which can generate psychosociological impaired outcomes. This study investigated psychological, social, occupational and cultural variables which are among the most important determinants in adaptation to a one-year wintering in Antarctica with 13 international participants. Our findings confirm and give further insight into the role of social (Cohesiveness, Social Support) and occupational (Implementation / Preparedness, Counterproductive Activity, Decision Latitude and Psychological Job Demands) dimensions of adaptation to ICE environments. Relationships between various social and occupational dimensions studies reflected detrimental effects ranging from decrements in cohesiveness, social support and work performance which differed across professional status and multicultural factors. These psychosocial issues have important implications for pre-mission selection and training, monitoring and support of crews during the mission and post-mission readaptation. Operational recommendations are suggested to improve adaptation, success and well-being for long-term ICE missions, e.g., to Mars and beyond.

  1. A magnetospheric substorm observed at Sanae, Antarctica

    SciTech Connect

    Gledhill, J.A.; Dore, I.S.; Haggard, R. ); Goertz, C.K. ); Hughes, W.J. ); Scourfield, M.W.J.; Wakerley, P.A.; Walker, A.D.M. ); Smits, D.P.; Sutcliffe, P.R. ); Stoker, P.H. )

    1987-03-01

    A magnetospheric substorm that occurred at Sanae, Antarctica, on July 27, 1979, was observed by a variety of techniques. A synthesis of the observations is presented, and an attempt made to deduce details of the behavior of the magnetosphere-ionosphere system during the event. While there was some evidence of a growth phase, it was inconclusive. At the onset there was a rapid change in the tail field, which assumed a more dipolar form, accompanied by Pi 2 oscillations and the precipitation of 6-keV electrons, with brightening of the auroral arc, auroral-type sporadic E ionization, and riometer absorption. A positive spike was observed in the D magnetic component, instead of the expected negative one. There was no evidence of the usual westward traveling surge at the beginning of the expansion phase during which the precipitation region, auroral arc, and electrojet moved rapidly poleward, though it may have occurred outside the field of view from Sanae. The H{beta} emission increased by a factor of less than 2, whereas the oxygen and nitrogen emissions monitored increased by 3-4. During the recovery phase, phenomena were consistent with a return of the tail field to an elongated form; a very high ratio of 557.7-nm/630-nm emissions, exceeding 10, was observed; and the electrojet lagged noticeably behind the photon emission regions.

  2. Intercomparison of ozone measurements over Antarctica

    SciTech Connect

    Margitan, J.J.; Farmer, C.B.; Toon, G.C. ); Brothers, G.A. ); Browell, E.V.; Gregory, G.L.; Hypes, W.; Larsen, J.C.; McCormick, M.P. ); Cariolle, D. ); Coffey, M.T.; Mankin, W. ); Farman, J.C. ); Harder, J.W.; Mount, G.H.; Ravishankara, A.R.; Schemeltekopf, A.L.; Tuck, A.F. ); Hofmann, D.J. ); Ismail, S.; Kooi, S. ); Jakoubek, R.O.; Proffitt, M.H.; Wahner, A.; Watterson, I. Univ. of Colorado, Boulder ); Komhyr, W. (NOAA Air Resources La

    1989-11-30

    Measurements of the abundances of ozone over Antarctic in August and September 1987 obtained during the Airborne Antarctic Ozone Experiment are intercompared. These measurements of ozone concentrations and total column abundance were obtained by three satellite instruments, two IR and one UV column-measuring instruments aboard the DC-8, one in situ DC-8, and two in situ ER-2 instruments, an upward looking lidar aboard the DC-8, and ozonesondes from four sites in Antarctica. Given the natural variability of ozone in the Antarctic and the fact that the data were not truly coincident spatially and temporally, this intercomparison is suitable only for identifying gross disparities among the techniques, rather than confirming the accuracies as rigorously as is normally done in an intercomparison. This paper presents a summary of the ozone data, using the data and accuracies given by the individual investigators in the individual papers in this issue, without any attempt to critically review or evaluate the data. In general, very good agreement (within about 10-20%, limited by natural variability) among the various techniques was found, with no systematic biases detected. These observations confirm the low ozone amounts reported in the Antarctic stratosphere.

  3. Ozone profiles above Palmer Station, Antarctica

    NASA Technical Reports Server (NTRS)

    Torres, Arnold L.; Brothers, George

    1988-01-01

    NASA's Goddard Space Flight Center/Wallops Flight Facility conducted a series of 52 balloon-borne measurements of vertical ozone profiles over the National Science Foundation (NSF) research facility at Palmer Station, Antarctica (64 deg 46 S, 64 deg 3 W) between August 9 and October 24, 1987. High resolution measurements were made from ground level to an average of 10 mb. While much variation was seen in the profile amounts of ozone, it is clear that a progressive depletion of ozone occurred during the measurement period, with maximum depletion taking place in the 17 to 19 km altitude region. Ozone partial pressures dropped by about 95 percent in this region. Shown here are plotted time dependences of ozone amounts observed at 17 km and at arbitrarily selected altitudes below (13 km) and above (24 km) the region of maximum depletion. Ozone partial pressure at 17 km is about 150nb in early August, and has decreased to less than 10nb in the minimums in October. The loss rate is of the order of 1.5 percent/day. In summary, a progressive depletion in stratospheric ozone over Palmer Station was observed from August to October, 1987. Maximum depletion occurred in the 17 to 19 km range, and amounted to 95 percent. Total ozone overburden decreased by up to 50 percent during the same period.

  4. The Center for Astrophysics in Antarctica

    NASA Technical Reports Server (NTRS)

    Pernic, Robert J.; Harper, D. AL, Jr.; Bausch, Judith A.

    1995-01-01

    Nowhere on Earth are the infrared skies clearer, darker, or more stable than on the high Antarctic Plateau. At some wavelengths, Antarctic telescopes may be more than one to two orders of magnitude more efficient than at other sites. However, exploiting these advantages requires first addressing the formidable practical difficulties of working in the remote and frigid polar environment. This was the motivation for the Center for Astrophysical Research in Antarctica (CARA), one of twenty-five National Science Foundation Science and Technology Centers. At its inception, the Center organized its research into four projects. Three - AST/RO, COBRA, and SPIREX - address key problems in star formation, evolution of galaxies, and the distribution of matter in the early universe. They feature surveys which can be conducted effectively with moderate-size telescopes operated in a highly automated mode. They also explore the potential of the Antarctic Plateau for a broad range of astrophysical research over a spectral range extending from the near-infrared to millimeter wavelengths. A fourth, ATP, was created to obtain quantitative data on the qualities of the South Pole site and to plan for future scientific projects. During the next five years, AST/RO, COBRA, and SPIREX will become operational, and the Center will begin to build a second generation of telescopes which can address a broader range of problems and accommodate a larger community of users.

  5. Mass casualty incident response and aeromedical evacuation in antarctica.

    PubMed

    Mills, Christopher N; Mills, Gregory H

    2011-02-01

    Antarctica is one of the most remote regions on Earth. Mass casualty incident (MCI) responses in Antarctica are prone to complications from multiple environmental and operational challenges. This review of the current status of MCI risks and response strategies for Antarctica focuses on aeromedical evacuation, a critical component of many possible MCI scenarios. Extreme cold and weather, a lack of medical resources and a multitude of disparate international bases all exert unique demands on MCI response planning. Increasing cruise ship traffic is also escalating the risk of MCI occurrence. To be successful, MCI response must be well coordinated and undertaken by trained rescuers, especially in the setting of Antarctica. Helicopter rescue or aeromedical evacuation of victims to off-continent facilities may be necessary. Currently, military forces have the greatest capacity for mass air evacuation. Specific risks that are likely to occur include structure collapses, vehicle incapacitations, vehicle crashes and fires. All of these events pose concomitant risks of hypothermia among both victims and rescuers. Antarctica's unique environment requires flexible yet robust MCI response planning among the many entities in operation on the continent. PMID:21691470

  6. Tectonic evolution of west Antarctica and its relation to east Antarctica

    SciTech Connect

    Dalziel, I.W.D.

    1987-05-01

    West Antarctica consists of five major blocks of continental crust separated by deep sub-ice basins. Marie Byrd Land appears to have been rifted off the adjacent margin of the East Antarctic craton along the line of the Transantarctic Mountains during the Mesozoic. Ellsworth-Whitmore mountains and Haag Nunataks blocks were also rifted from the margin of the craton. They appear to have moved together with the Antarctic Peninsula and Thurston Island blocks, segments of a Pacific margin Mesozoic-Cenozoic magmatic arc, during the Mesozoic opening of the Weddell Sea basin. Paleomagnetic data suggest that all four of these blocks remained attached to western Gondwanaland (South America-Africa) until approximately 125 m.y. ago, and that the present geographic configuration of the Antarctic continent was essentially complete by the mid-Cretaceous, although important Cenozoic rifting has also occurred. Fragmentation of the Gondwanaland supercontinent was preceded in the Middle to Late Jurassic by an important and widespread thermal event of uncertain origin that resulted in the emplacement of an extensive bimodal igneous suite in South America, Africa, Antarctica, and Australia. This was associated with the development of the composite back-arc basin along the western margin of South America. Inversion of this basin in the mid-Cretaceous initiated Andean orogenesis. The presentation will include new data from the joint US-UK West Antarctic Tectonics Project.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    The McMurdo Dry Valleys (MDV), Antarctica, represent a unique geologic setting where permanent lakes, ephemeral streams, and subglacial waters influence surface hydrology in a cold polar desert. Past research suggested that the MDV are underlain by several hundreds of meters of permafrost. Here, we present data collected from an Airborne EM (AEM) resistivity sensor flown over the MDV during the 2011-12 austral summer. A focus of our survey was over the Taylor Glacier where saline, iron-rich subglacial fluid releases at the glacier snout at a feature known as Blood Falls, and over Taylor Valley, where a series of isolated lakes lie between Taylor Glacier and the Ross Sea. Our data show that in Taylor Valley there are extensive areas of low resistivity, interpreted as hypersaline brines, beneath a relatively thin layer of high resistivity material, interpreted as dry- or ice-cemented permafrost. These hypersaline brines remain liquid at temperatures well below 0°C due to their salinity. They appear to be contained within the sedimentary fill deposited in Taylor Valley when it was still a fjord. This brine system continues up valley and has a subglacial extension beneath Taylor Glacier, where it may provide the source that feeds Blood Falls. By categorizing the resistivity measurements according to surficial land cover, we are able to distinguish between ice, permafrost, lake water, and seawater based on characteristic resistivity distributions. Furthermore, this technique shows that areas of surface permafrost become increasingly conductive (brine-filled) with depth, whereas the large lakes exhibit taliks that extend through the entire thickness of the permafrost. The subsurface brines represent a large, unstudied and potentially connected hydrogeologic system, in which subsurface flows may help transfer water and nutrients between lakes in the MDV and into the Ross Sea. Such a system is a potential habitat for extremophile life, similar to that already detected in

  8. Detrital zircons - the unique source of information on tectonics, paleogeography and denudation processes of East Antarctica (subglacial challenge)

    NASA Astrophysics Data System (ADS)

    Belyatsky, Boris; Leitchenkov, German; Rodionov, Nickolay; Antonov, Anton; Sergeev, Sergey; Savva, Helen

    2010-05-01

    Vast (about 7 billions km2) almost wholly (98%) covered with ice continental mass of East Antarctica is the central fragment of ancient supercontinents of Rodinia and Gondwana. Any information on its geologic structure is of the greatest importance for solving the problems of formation and amalgamation of lithosphere of ancient continents, processes of intraplate activity, denudation and peneplanation of the earth crust and for geodynamic reconstruction. Geologic structure of central part of the East Antarctica is still absolutely unknown due to the thick (up to 4000 m) ice cover, which is the obstacle even for modern drilling technology to sample directly the underlying rocks. The main goal of the study has been to make an attempt in fill up the hiatus in geologic knowledge on the origin of subglacial continental crust of the Antarctica. We studied detrital zircons from sedimentary and metasedimentary rocks outcropped in Prince-Charles Mts (PCM, East Antarctica). Rock specimens were sampled from the Permian-Triassic sedimentary succession outcropped along the Beaver Lake coast (sandstones and siltstones) and from moraine of the Fisher Massive (metasandstone) and Meridith Massive (sandstone). A lump of zircons which are characterized by different grain morphology from well-rounded to poorly-rounded has been extracted from rock specimens for isotopic studies and dating. The age determinations of 302 zircons from 6 specimens were conducted using secondary ion-microprobe SHRIMP-II and laser-ablation ICP-MS. The age of zircons ranges from 500 to 3200 Ma. Isotopic analysis and probability distribution diagrams for zircon populations show heterogeneity of provenance. Zircons of 500 Ma old are proposed to come from the eastern flank of Lambert Glacier and/or from central Antarctica; 900-1100 Ma old - from Proterozoic Mobile Belt (central-northern PCM); while 2400-3200 Ma old - from granite-greenstone terrain (southern PCM). Additionally, 21 trace elements and isotopic

  9. Overview of Aircraft Operations during ACE-Asia

    NASA Astrophysics Data System (ADS)

    Seinfeld, J. H.; Huebert, B.

    2001-12-01

    The NSF/NCAR C-130 flew 19 flights out of Iwakuni, Japan between March 31 and May 4, 2001, and data were collected on 7 ferry flights crossing the Pacific. Many of the instruments derived their air from low-turbulence inlets, which enabled studies of supermicron particles vs altitude. Several flights sampled two heavy dust outbreaks, where the aerosol mass concentration exceeded 1000 †g/m3. Size-dependent chemical measurements indicated that this dust did not dramatically change the sulfate size distribution (by causing SO2 to convert to sulfate on its alkaline surfaces), since the vast majority of the sulfate was still in a submicron accumulation mode. Similarly, while the scattering in dust was dominated by large particles, the particle absorption was almost exclusively submicron. We found extensive layering, with as many as 6 distinct dust layers (and clean layers between them) in one profile to 6 km. During ACE-Asia research missions were also conducted using a modified De Havilland DHC-6 Twin Otter aircraft operated by the California Institute of Technology and the Center for Interdisciplinary Remotely Piloted Aircraft studies (CIRPAS). A total of 19 research flights were conducted between March 31 and May 1, 2001 from the base of operations at the MCAS Iwakuni, Japan. The sampling area included portions of the Sea of Japan south and east of the Korean Peninsula, the East China Sea between China, Japan and Korea, and the Philippine Sea south of Japan. Collected aerosols were analyzed to determine their chemical composition and physical properties such as size distribution, hygroscopic growth, light scattering and absorption properties. Simultaneous radiative measurements were also made using the 14-channel Ames Airborne Tracking Sunphotometer (AATS-14), which measured solar beam transmission at 14 wavelengths (353-1558 nm), yielding aerosol optical depth (AOD) spectra and column water vapor (CWV). Vertical differentiation in profiles yielded aerosol

  10. Longevity of Lake Superior lake trout

    USGS Publications Warehouse

    Schram, Stephen T.; Fabrizio, Mary C.

    1998-01-01

    The age structure of mature lake trout Salvelinus namaycush from the Wisconsin waters of Lake Superior increased following a population recovery that has taken place since the 1960s. As the population aged, it became apparent that scales were unreliable aging structures. Beginning in 1986, we examined both scale and sagittal otolith ages from tagged fish with a known period at liberty. We found large discrepancies in scale and sagittal otolith ages of mature fish, such that scale ages were biased low. We estimated lake trout living up to 42 years, which is greater than previously reported from Lake Superior. Investigators studying lake trout population dynamics in the Great Lakes should be aware that lake trout can live longer than previously thought.

  11. Tissue specific up regulation of ACE2 in rabbit model of atherosclerosis by atorvastatin: role of epigenetic histone modifications.

    PubMed

    Tikoo, Kulbhushan; Patel, Gaurang; Kumar, Sandeep; Karpe, Pinakin Arun; Sanghavi, Maitri; Malek, Vajir; Srinivasan, K

    2015-02-01

    Growing body of evidence points out the crucial role of ACE2 in preventing atherosclerosis. However, data on how atherosclerosis affects ACE2 expression in heart and kidney remains unknown. Atherosclerosis was induced by feeding New Zealand White rabbits with high cholesterol diet (HCD - 2%) for 12 weeks and atorvastatin was administered (5mg/kg/day p.o) in last 3 weeks. ACE2 mRNA and protein expression was assessed by Western blotting and real time PCR. HCD fed rabbits developed atherosclerosis as confirmed by increase in plasma total cholesterol, LDL and triglycerides as well as formation atherosclerotic plaques in arch of aorta. The ACE2 protein but not mRNA expression was reduced in heart and kidney of HCD rabbits. Interestingly, atorvastatin increased the ACE2 protein expression in heart and kidney of HCD rabbits. However, atorvastatin increased ACE2 mRNA in heart but not in kidney of HCD rabbits. Atorvastatin increased the occupancy of histone H3 acetylation (H3-Ac) mark on ACE2 promoter region in heart of HCD rabbits indicating direct or indirect epigenetic up-regulation of ACE2 by atorvastatin. Further, atorvastatin suppressed Ang II-induced contractile responses and enhanced AT2 receptor mediated relaxant responses in atherosclerotic aorta. We propose that atherosclerosis is associated with reduced ACE2 expression in heart and kidney. We also show an unexplored potential of atorvastatin to up-regulate ACE2 via epigenetic histone modifications. Our data suggest a novel way of replenishing ACE2 expression for preventing not only atherosclerosis but also other cardiovascular disorders. PMID:25482567

  12. Lake Volta, Ghana

    NASA Technical Reports Server (NTRS)

    2002-01-01

    This true-color image of Lake Volta in Ghana was acquired March 31, 2002 by the Moderate Resolution Imaging Spectroradiometer (MODIS). Lake Volta is one of the world's largest artificially created lakes. Lake Volta is actually a reservoir formed from the damming of the Volta River, and extends 250 miles north of the Akosombo Dam. The lake covers an area of 8,482 square km. Credit: Jacques Descloitres, MODIS Land Rapid Response Team, NASA/GSFC

  13. Live from Antarctica: The coldest, windiest place on Earth

    NASA Astrophysics Data System (ADS)

    In this first part of a four part 'Passport to Knowledge Special', hosted by Camille Jennings from Maryland Public Television, children from Maryland and Texas schools had the opportunity to directly interact with and ask questions of scientists and researchers in Antarctica live. The physical characteristics of Antarctica are featured, along with their effects on the human and microbiological organisms living in the region. The reasons behind the clothing worn in the Antarctic and the importance of the meteorological station are featured. Interviews with Professor Ian Dolziel (U of Texas) and Lt. commander John Joseph, NSFA (the head of the Navy Meteorology Center) occur with the school children, along with actual video footage of the surrounding geological features and geography. The 'Weatherops' is located at McMurdo Station, Antarctica.

  14. Ecological Biogeography of the Terrestrial Nematodes of Victoria Land, Antarctica

    PubMed Central

    Adams, Byron J.; Wall, Diana H.; Virginia, Ross A.; Broos, Emma; Knox, Matthew A.

    2014-01-01

    Abstract The terrestrial ecosystems of Victoria Land, Antarctica are characteristically simple in terms of biological diversity and ecological functioning. Nematodes are the most commonly encountered and abundant metazoans of Victoria Land soils, yet little is known of their diversity and distribution. Herein we present a summary of the geographic distribution, habitats and ecology of the terrestrial nematodes of Victoria Land from published and unpublished sources. All Victoria Land nematodes are endemic to Antarctica, and many are common and widely distributed at landscape scales. However, at smaller spatial scales, populations can have patchy distributions, with the presence or absence of each species strongly influenced by specific habitat requirements. As the frequency of nematode introductions to Antarctica increases, and soil habitats are altered in response to climate change, our current understanding of the environmental parameters associated with the biogeography of Antarctic nematofauna will be crucial to monitoring and possibly mitigating changes to these unique soil ecosystems. PMID:25061360

  15. Live from Antarctica: the Coldest, Windiest Place on Earth

    NASA Technical Reports Server (NTRS)

    1994-01-01

    In this first part of a four part 'Passport to Knowledge Special', hosted by Camille Jennings from Maryland Public Television, children from Maryland and Texas schools had the opportunity to directly interact with and ask questions of scientists and researchers in Antarctica live. The physical characteristics of Antarctica are featured, along with their effects on the human and microbiological organisms living in the region. The reasons behind the clothing worn in the Antarctic and the importance of the meteorological station are featured. Interviews with Professor Ian Dolziel (U of Texas) and Lt. commander John Joseph, NSFA (the head of the Navy Meteorology Center) occur with the school children, along with actual video footage of the surrounding geological features and geography. The 'Weatherops' is located at McMurdo Station, Antarctica.

  16. Ongoing deformation of Antarctica following recent Great Earthquakes

    NASA Astrophysics Data System (ADS)

    King, Matt A.; Santamaría-Gómez, Alvaro

    2016-03-01

    Antarctica's secular motion is thought to be almost everywhere governed by horizontal rigid plate rotation plus three-dimensional deformations due to past and present changes in ice ocean loading, known as glacial isostatic adjustment (GIA). We use geodetic data to investigate deformation following the 1998 M ~8.2 Antarctic intraplate Earthquake and show sustained three-dimensional deformation along East Antarctica's coastline, 600 km from the rupture location. Using a model of viscoelastic deformation, we are able to match observed northward velocity changes, and either east or height, but not all three directions simultaneously, apparently partly due to lateral variations in mantle rheology. Our modeling predicts that much of Antarctica may still be deforming, with further deformation possible from the 2004 M 8 Macquarie Ridge Earthquake. This previously unconsidered mode of Antarctic deformation affects geodetic estimates of plate motion and GIA; its viscous nature raises the prospect of further present-day deformation due to earlier Great Earthquakes.

  17. Cryoconite and Ice-bubble Microbial Ecosystems in Antarctica

    NASA Technical Reports Server (NTRS)

    Hoover, Richard B.; Rose, M. Franklin (Technical Monitor)

    2000-01-01

    During the Antarctica 2000 Expedition samples of rocks and ice bubbles entrained in ice were collected from the blue ice fields near the Moulton Escarpment of the Thiel Mountains (85S, 94W) and the Morris Moraine of the Patriot Hills (80S, 8 1 W) Ellsworth Mountains of Antarctica. Investigation of the microbiota of these cryoconite and ice bubble ecosystems are now being conducted to help refine chemical and morphological biomarkers of potential significance to Astrobiology. The Antarctica 2000 Expedition will be discussed and the preliminary results of the studies of the ice bubble and cryoconite microbial ecosystems discussed. Recent ESEM images of the Antarctic microbiota will be presented a the relevance of ice ecosystems to Astrobiology will be discussed.

  18. Where does CO2 in Antarctica cool the atmosphere ?

    NASA Astrophysics Data System (ADS)

    Schmithüsen, Holger; Notholt, Justus; König-Langlo, Gert; Lemke, Peter; Jung, Thomas

    2016-04-01

    In a recent study we have shown that for the high altitude plateau in Antarctica CO2 causes a surplus in infrared emission to space compared to what is emitted from the surface. This corresponds to a negative greenhouse effect, and is due to the fact that for this region the surface is typically colder than the atmosphere above, opposite to the rest of the world. As a consequence, for this region an increase in CO2 leads to an increase in the energy loss to space, leading to an increase in the negative greenhouse effect. We now studied in more detail the radiative effect of CO2 and compared the results with available measurements from Antarctica. H. Schmithüsen, J. Notholt, G. Köngig-Langlo, T, Jung. How increasing CO2 leads to an increased negative greenhouse effect in Antarctica. Geophysical Research Letters, in press, 2015. doi: 10.1002/2015GL066749.

  19. Provenance of dust to Antarctica: A lead isotopic perspective

    NASA Astrophysics Data System (ADS)

    Gili, Stefania; Gaiero, Diego M.; Goldstein, Steven L.; Chemale, Farid, Jr.; Koester, Edinei; Jweda, Jason; Vallelonga, Paul; Kaplan, Michael R.

    2016-03-01

    Antarctic ice preserves an ~800 kyr record of dust activity in the Southern Hemisphere. Major efforts have been dedicated to elucidate the origin of this material in order to gain greater insight into the atmospheric dust cycle. On the basis of Pb isotopes in Antarctic dust samples and potential sources, this contribution demonstrates for the first time that Patagonia is the main contributor of dust to Antarctica during interglacial periods as well as glacials, although the potential importance of Tierra del Fuego remains unclear because of its geochemical similarities to Patagonia. An important new finding is that the Puna-Altiplano sector of the continent is a second important dust source to eastern Antarctica during both glacials and interglacials, being more prominent during interglacials. The data indicate South America is the primary dust source to Antarctica during both glacials and interglacials.

  20. The Delta II with ACE aboard is prepared for liftoff from Pad 17A, CCAS

    NASA Technical Reports Server (NTRS)

    1997-01-01

    The Boeing Delta II expendable launch vehicle carrying the Advanced Composition Explorer (ACE) undergoes final preparations for liftoff in the predawn hours of Aug. 25, 1997, at Launch Complex 17A, Cape Canaveral Air Station. This is the second Delta launch under the Boeing name and the first from Cape Canaveral. The first launch attempt on Aug. 24 was scrubbed by Air Force range safety personnel because two commercial fishing vessels were within the Delta's launch danger area. ACE with its combination of nine sensors and instruments will investigate the origin and evolution of solar phenomenon, the formation of solar corona, solar flares and acceleration of the solar wind. ACE was built for NASA by the Johns Hopkins Applied Physics Laboratory and is managed by the Explorer Project Office at NASA's Goddard Space Flight Center. The lead scientific institution is the California Institute of Technology.

  1. Molecular Cytogenetic Analysis of Deschampsia antarctica Desv. (Poaceae), Maritime Antarctic.

    PubMed

    Amosova, Alexandra V; Bolsheva, Nadezhda L; Samatadze, Tatiana E; Twardovska, Maryana O; Zoshchuk, Svyatoslav A; Andreev, Igor O; Badaeva, Ekaterina D; Kunakh, Viktor A; Muravenko, Olga V

    2015-01-01

    Deschampsia antarctica Desv. (Poaceae) (2n = 26) is one of the two vascular plants adapted to the harshest environment of the Antarctic. Although the species is a valuable model for study of environmental stress tolerance in plants, its karyotype is still poorly investigated. We firstly conducted a comprehensive molecular cytogenetic analysis of D. antarctica collected on four islands of the Maritime Antarctic. D. antarctica karyotypes were studied by Giemsa C- and DAPI/C-banding, Ag-NOR staining, multicolour fluorescence in situ hybridization with repeated DNA probes (pTa71, pTa794, telomere repeats, pSc119.2, pAs1) and the GAA simple sequence repeat probe. We also performed sequential rapid in situ hybridization with genomic DNA of D. caespitosa. Two chromosome pairs bearing transcriptionally active 45S rDNA loci and five pairs with 5S rDNA sites were detected. A weak intercalary site of telomere repeats was revealed on the largest chromosome in addition to telomere hybridization signals at terminal positions. This fact confirms indirectly the hypothesis that chromosome fusion might have been the cause of the unusual for cereals chromosome number in this species. Based on patterns of distribution of the examined molecular cytogenetic markers, all chromosomes in karyotypes were identified, and chromosome idiograms of D. antarctica were constructed. B chromosomes were found in most karyotypes of plants from Darboux Island. A mixoploid plant with mainly triploid cells bearing a Robertsonian rearrangement was detected among typical diploid specimens from Great Jalour Island. The karyotype variability found in D. antarctica is probably an expression of genome instability induced by environmental stress factors. The differences in C-banding patterns and in chromosome distribution of rDNA loci as well as homologous highly repeated DNA sequences detected between genomes of D. antarctica and its related species D. caespitosa indicate that genome reorganization involving

  2. Molecular Cytogenetic Analysis of Deschampsia antarctica Desv. (Poaceae), Maritime Antarctic

    PubMed Central

    Amosova, Alexandra V.; Bolsheva, Nadezhda L.; Samatadze, Tatiana E.; Twardovska, Maryana O.; Zoshchuk, Svyatoslav A.; Andreev, Igor O.; Badaeva, Ekaterina D.; Kunakh, Viktor A.; Muravenko, Olga V.

    2015-01-01

    Deschampsia antarctica Desv. (Poaceae) (2n = 26) is one of the two vascular plants adapted to the harshest environment of the Antarctic. Although the species is a valuable model for study of environmental stress tolerance in plants, its karyotype is still poorly investigated. We firstly conducted a comprehensive molecular cytogenetic analysis of D. antarctica collected on four islands of the Maritime Antarctic. D. antarctica karyotypes were studied by Giemsa C- and DAPI/C-banding, Ag-NOR staining, multicolour fluorescence in situ hybridization with repeated DNA probes (pTa71, pTa794, telomere repeats, pSc119.2, pAs1) and the GAA simple sequence repeat probe. We also performed sequential rapid in situ hybridization with genomic DNA of D. caespitosa. Two chromosome pairs bearing transcriptionally active 45S rDNA loci and five pairs with 5S rDNA sites were detected. A weak intercalary site of telomere repeats was revealed on the largest chromosome in addition to telomere hybridization signals at terminal positions. This fact confirms indirectly the hypothesis that chromosome fusion might have been the cause of the unusual for cereals chromosome number in this species. Based on patterns of distribution of the examined molecular cytogenetic markers, all chromosomes in karyotypes were identified, and chromosome idiograms of D. antarctica were constructed. B chromosomes were found in most karyotypes of plants from Darboux Island. A mixoploid plant with mainly triploid cells bearing a Robertsonian rearrangement was detected among typical diploid specimens from Great Jalour Island. The karyotype variability found in D. antarctica is probably an expression of genome instability induced by environmental stress factors. The differences in C-banding patterns and in chromosome distribution of rDNA loci as well as homologous highly repeated DNA sequences detected between genomes of D. antarctica and its related species D. caespitosa indicate that genome reorganization involving

  3. Common variants of ACE contribute to variable age-at-onset of Alzheimer's disease.

    PubMed

    Kehoe, Patrick G; Katzov, Hagit; Andreasen, Niels; Gatz, Maragaret; Wilcock, Gordon K; Cairns, Nigel J; Palmgren, Juni; de Faire, Ulf; Brookes, Anthony J; Pedersen, Nancy L; Blennow, Kaj; Prince, Jonathan A

    2004-04-01

    Studies on the role that genetic variation may play in a complex human disease can be empowered by an assessment of both disease risk in case-control or family models and of quantitative traits that reflect elements of disease etiology. An excellent example of this can be found for the epsilon4 allele of APOE in relation to Alzheimer's disease (AD) for which association with both risk and age-at-onset (AAO) is evident. Following a recent demonstration that variants of the gene encoding angiotensin I converting enzyme ( ACE) contribute to AD risk, we have explored the potential influence of ACE upon AAO in AD. A total of 2861 individuals from three European populations, including six independent AD samples, have been examined in this study. Three single nucleotide polymorphisms (SNPs) previously demonstrated to have maximum effects upon ACE plasma levels and that span the ACE locus were genotyped in these materials. A strong effect upon AAO was observed for marker rs4343 in exon 17 ( P<0.0001), but evidence was also obtained indicating a possible independent effect of marker rs4291 ( P=0.0095) located in the ACE promoter. Effects were consistent with data from previous studies suggesting association with AD in case-control models, whereby alleles demonstrated to confer risk to disease also appear to reduce AAO. Equivalent effects were evident regardless of APOE epsilon4 carrier status and in both males and females. These results provide an important complement to existing AD risk data, confirming that ACE harbors sequence variants that contribute to aspects of AD pathology. PMID:14986105

  4. SIGACE Code for Generating High-Temperature ACE Files; Validation and Benchmarking

    SciTech Connect

    Sharma, Amit R.; Ganesan, S.; Trkov, A.

    2005-05-24

    A code named SIGACE has been developed as a tool for MCNP users within the scope of a research contract awarded by the Nuclear Data Section of the International Atomic Energy Agency (IAEA) (Ref: 302-F4-IND-11566 B5-IND-29641). A new recipe has been evolved for generating high-temperature ACE files for use with the MCNP code. Under this scheme the low-temperature ACE file is first converted to an ENDF formatted file using the ACELST code and then Doppler broadened, essentially limited to the data in the resolved resonance region, to any desired higher temperature using SIGMA1. The SIGACE code then generates a high-temperature ACE file for use with the MCNP code. A thinning routine has also been introduced in the SIGACE code for reducing the size of the ACE files. The SIGACE code and the recipe for generating ACE files at higher temperatures has been applied to the SEFOR fast reactor benchmark problem (sodium-cooled fast reactor benchmark described in ENDF-202/BNL-19302, 1974 document). The calculated Doppler coefficient is in good agreement with the experimental value. A similar calculation using ACE files generated directly with the NJOY system also agrees with our SIGACE computed results. The SIGACE code and the recipe is further applied to study the numerical benchmark configuration of selected idealized PWR pin cell configurations with five different fuel enrichments as reported by Mosteller and Eisenhart. The SIGACE code that has been tested with several FENDL/MC files will be available, free of cost, upon request, from the Nuclear Data Section of the IAEA.

  5. Comparison of upper tropospheric carbon monoxide from MOPITT, ACE-FTS, and HIPPO-QCLS

    NASA Astrophysics Data System (ADS)

    Martínez-Alonso, Sara; Deeter, Merritt N.; Worden, Helen M.; Gille, John C.; Emmons, Louisa K.; Pan, Laura L.; Park, Mijeong; Manney, Gloria L.; Bernath, Peter F.; Boone, Chris D.; Walker, Kaley A.; Kolonjari, Felicia; Wofsy, Steven C.; Pittman, Jasna; Daube, Bruce C.

    2014-12-01

    Products from the Measurements Of Pollution In The Troposphere (MOPITT) instrument are regularly validated using in situ airborne measurements. However, few of these measurements reach into the upper troposphere, thus hindering MOPITT validation in that region. Here we evaluate upper tropospheric (~500 hPa to the tropopause) MOPITT CO profiles by comparing them to satellite Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) retrievals and to measurements from the High-performance Instrumented Airborne Platform for Environmental Research Pole to Pole Observations (HIPPO) Quantum Cascade Laser Spectrometer (QCLS). Direct comparison of colocated v5 MOPITT thermal infrared-only retrievals, v3.0 ACE-FTS retrievals, and HIPPO-QCLS measurements shows a slight positive MOPITT CO bias within its 10% accuracy requirement with respect to the other two data sets. Direct comparison of colocated ACE-FTS and HIPPO-QCLS measurements results in a small number of samples due to the large disparity in sampling pattern and density of these data sets. Thus, two additional indirect techniques for comparison of noncoincident data sets have been applied: tracer-tracer (CO-O3) correlation analysis and analysis of profiles in tropopause coordinates. These techniques suggest a negative bias of ACE-FTS with respect to HIPPO-QCLS; this could be caused by differences in resolution (horizontal, vertical) or by deficiencies in the ACE-FTS CO retrievals below ~20 km of altitude, among others. We also investigate the temporal stability of MOPITT and ACE-FTS data, which provide unique global CO records and are thus important in climate analysis. Our results indicate that the relative bias between the two data sets has remained generally stable during the 2004-2010 period.

  6. PAPR reduction in FBMC using an ACE-based linear programming optimization

    NASA Astrophysics Data System (ADS)

    van der Neut, Nuan; Maharaj, Bodhaswar TJ; de Lange, Frederick; González, Gustavo J.; Gregorio, Fernando; Cousseau, Juan

    2014-12-01

    This paper presents four novel techniques for peak-to-average power ratio (PAPR) reduction in filter bank multicarrier (FBMC) modulation systems. The approach extends on current PAPR reduction active constellation extension (ACE) methods, as used in orthogonal frequency division multiplexing (OFDM), to an FBMC implementation as the main contribution. The four techniques introduced can be split up into two: linear programming optimization ACE-based techniques and smart gradient-project (SGP) ACE techniques. The linear programming (LP)-based techniques compensate for the symbol overlaps by utilizing a frame-based approach and provide a theoretical upper bound on achievable performance for the overlapping ACE techniques. The overlapping ACE techniques on the other hand can handle symbol by symbol processing. Furthermore, as a result of FBMC properties, the proposed techniques do not require side information transmission. The PAPR performance of the techniques is shown to match, or in some cases improve, on current PAPR techniques for FBMC. Initial analysis of the computational complexity of the SGP techniques indicates that the complexity issues with PAPR reduction in FBMC implementations can be addressed. The out-of-band interference introduced by the techniques is investigated. As a result, it is shown that the interference can be compensated for, whilst still maintaining decent PAPR performance. Additional results are also provided by means of a study of the PAPR reduction of the proposed techniques at a fixed clipping probability. The bit error rate (BER) degradation is investigated to ensure that the trade-off in terms of BER degradation is not too severe. As illustrated by exhaustive simulations, the SGP ACE-based technique proposed are ideal candidates for practical implementation in systems employing the low-complexity polyphase implementation of FBMC modulators. The methods are shown to offer significant PAPR reduction and increase the feasibility of FBMC as

  7. The Altus Cumulus Electrification Study (ACES): A UAV-Based Science Demonstration

    NASA Technical Reports Server (NTRS)

    Blakeslee, R. J.; Croskey, C. L.; Desch, M. D.; Farrell, W. M.; Goldberg, R. A.; Houser, J. G.; Kim, H. S.; Mach, D. M.; Mitchell, J. D.; Stoneburner, J. C.

    2003-01-01

    The Altus Cumulus Electrification Study (ACES) is an unmanned aerial vehicle (UAV)- based project that investigated thunderstorms in the vicinity of the Florida Everglades in August 2002. ACES was conducted to investigate storm electrical activity and its relationship to storm morphology, and to validate satellite-based lightning measurements. In addition, as part of the NASA sponsored UAV-based science demonstration program, this project provided a scientifically useful demonstration of the utility and promise of UAV platforms for Earth science and applications observations. ACES employed the Altus II aircraft, built by General Atomics - Aeronautical Systems, Inc. Key science objectives simultaneously addressed by ACES are to: (1) investigate lightning-storm relationships, (2) study storm electrical budgets, and provide Lightning Imaging Sensor validation. The ACES payload included electrical, magnetic, and optical sensors to remotely characterize the lightning activity and the electrical environment within and around thunderstorms. ACES contributed important electrical and optical measurements not available from other sources. Also, the high altitude vantage point of the UAV observing platform (up to 55,000 feet) provided cloud-top perspective. By taking advantage of its slow flight speed (70 to 100 knots), long endurance, and high altitude flight, the Altus was flown near, and when possible, over (but never into) thunderstorms for long periods of time that allowed investigations to be conducted over entire storm life cycles. An innovative real time weather system was used to identify and vector the aircraft to selected thunderstorms and safely fly around these storms, while, at the same time monitor the weather near our base of operations. In addition, concurrent ground-based observations that included radar (Miami and Key West WSRBD, NASA NPOL), satellite imagery, and lightning (NALDN and Los Alamos EDOT) enable the UAV measurements to be more completely

  8. Recent surface temperature trends in the interior of East Antarctica from borehole firn temperature measurements and geophysical inverse methods

    USGS Publications Warehouse

    Muto, A.; Scambos, T.A.; Steffen, K.; Slater, A.G.; Clow, G.D.

    2011-01-01

    We use measured firn temperatures down to depths of 80 to 90 m at four locations in the interior of Dronning Maud Land, East Antarctica to derive surface temperature histories spanning the past few decades using two different inverse methods. We find that the mean surface temperatures near the ice divide (the highest-elevation ridge of East Antarctic Ice Sheet) have increased approximately 1 to 1.5 K within the past ???50 years, although the onset and rate of this warming vary by site. Histories at two locations, NUS07-5 (78.65S, 35.64E) and NUS07-7 (82.07S, 54.89E), suggest that the majority of this warming took place in the past one or two decades. Slight cooling to no change was indicated at one location, NUS08-5 (82.63S, 17.87E), off the divide near the Recovery Lakes region. In the most recent decade, inversion results indicate both cooler and warmer periods at different sites due to high interannual variability and relatively high resolution of the inverted surface temperature histories. The overall results of our analysis fit a pattern of recent climate trends emerging from several sources of the Antarctic temperature reconstructions: there is a contrast in surface temperature trends possibly related to altitude in this part of East Antarctica. Copyright 2011 by the American Geophysical Union.

  9. Declassified Intelligence Satellite Photography (DISP) Coverage of Antarctica

    NASA Technical Reports Server (NTRS)

    Bindschadler, Robert; Seider, Wendy

    1998-01-01

    This report summarizes the results of a nine-week summer project examining all Declassified Intelligence Satellite Photography (DISP) of Antarctica. It was discovered that the data were collected in three separate missions during 1962 and 1963. The first two missions covered only the coastal areas, while the third mission covered the entire continent. Many of the 1782 frames collected were cloudy. This is especially true of West Antarctica. An optimal set of photographs covering the entire Antarctic coastline is identified along with some examples that show changes in the coastline which have occurred since the early 1960s.

  10. Avian cholera in Southern Great Petrel (Macronectes giganteus) from Antarctica

    USGS Publications Warehouse

    Leotta, G.A.; Rivas, M.; Chinen, I.; Vigo, G.B.; Moredo, F.A.; Coria, N.; Wolcott, M.J.

    2003-01-01

    A southern giant petrel (Macronectes giganteus) was found dead at Potter Peninsula, King George Island, South Shetland, Antarctica. The adult male was discovered approximately 48 hr after death. Macroscopic and microscopic lesions were compatible with avian cholera and the bacterium Pasteurella multocida subsp. gallicida, serotype A1 was isolated from lung, heart, liver, pericardial sac, and air sacs. In addition, Escherichia coli was isolated from pericardial sac and air sacs. This is the first known report of avian cholera in a southern giant petrel in Antarctica.

  11. The Prospects of Integral-Field Spectroscopy for Antarctica

    NASA Astrophysics Data System (ADS)

    Kelz, A.

    The first suite of instruments and associated science cases for a larger facility at Dome C are mainly targeted towards imaging and surveys. While the potential advantages for astronomical observations from Antarctica are applicable to both imaging and spectroscopy, spectrographs are more complex to build and harder to use in a fully automatic and remote operation. However, the innovative technique of 3D-Spectroscopy (3DS) offers imaging and spectroscopic capabilities simultaneously with applications to a wide range of astronomical programmes. Furthermore, 3DS provides several operational benefits, that are well suited for a location such as Antarctica.

  12. Distribution of narrow-width magnetic anomalies in Antarctica

    USGS Publications Warehouse

    Behrendt, John C.

    1964-01-01

    Data for aeromagnetic profiles obtained in Antarctica during the 1963-64 austral summer were used together with earlier results to construct a map showing the areal distribution of narrow-width magnetic anomalies. Numerous anomalies are associated with known volcanic mountains in western Antarctica. A large area of few anomalies is probably a result of an extension of the thick metasedimentary section observed in the Ellsworth Mountains. Portions of the Trans-Antarctic Mountains have associated anomalies which are probably caused by late Cenozoic volcanic rocks.

  13. Practical analysis of tide gauges records from Antarctica

    NASA Astrophysics Data System (ADS)

    Galassi, Gaia; Spada, Giorgio

    2015-04-01

    We have collected and analyzed in a basic way the currently available time series from tide gauges deployed along the coasts of Antarctica. The database of the Permanent Service for Mean Sea Level (PSMSL) holds relative sea level information for 17 stations, which are mostly concentrated in the Antarctic Peninsula (8 out of 17). For 7 of the PSMSL stations, Revised Local Reference (RLR) monthly and yearly observations are available, spanning from year 1957.79 (Almirante Brown) to 2013.95 (Argentine Islands). For the remaining 11 stations, only metric monthly data can be obtained during the time window 1957-2013. The record length of the available time series is not generally exceeding 20 years. Remarkable exceptions are the RLR station of Argentine Island, located in the Antarctic Peninsula (AP) (time span: 1958-2013, record length: 54 years, completeness=98%), and the metric station of Syowa in East Antarctica (1975-2012, 37 years, 92%). The general quality (geographical coverage and length of record) of the time series hinders a coherent geophysical interpretation of the relative sea-level data along the coasts of Antarctica. However, in an attempt to characterize the relative sea level signals available, we have stacked (i.e., averaged) the RLR time series for the AP and for the whole Antarctica. The so obtained time series have been analyzed using simple regression in order to estimate a trend and a possible sea-level acceleration. For the AP, the the trend is 1.8 ± 0.2 mm/yr and for the whole Antarctica it is 2.1 ± 0.1 mm/yr (both during 1957-2013). The modeled values of Glacial Isostatic Adjustment (GIA) obtained with ICE-5G(VM2) using program SELEN, range between -0.7 and -1.6 mm/yr, showing that the sea-level trend recorded by tide gauges is strongly influenced by GIA. Subtracting the average GIA contribution (-1.1 mm/yr) to observed sea-level trend from the two stacks, we obtain 3.2 and 2.9 mm/yr for Antarctica and AP respectively, which are interpreted

  14. The GRAD high-altitude balloon flight over Antarctica

    NASA Technical Reports Server (NTRS)

    Eichhorn, G.; Coldwell, R. L.; Dunnam, F. E.; Rester, A. C.; Trombka, J. I.; Starr, R.

    1989-01-01

    The Gamma Ray Advanced Detector (GRAD) consists of a n-type germanium detector inside an active bismuth-germanate Compton and charged particle shield with additional active plastic shielding across the aperture. It will be flown on a high-altitude balloon at 36 km altitude at a latitude of 78 deg S over Antarctica for observations of gamma radiation emitted by the radioactive decay of Co-56 in the supernova SN1987A, for assessment of the performance of bismuth-germanate scintillation material in the radiation environment of near space, for gathering information on the gamma-ray background over Antarctica, and for testing fault-tolerant software.

  15. Kidney scintigraphy after ACE inhibition in the diagnosis of renovascular hypertension

    SciTech Connect

    Ghione, S.; Fommei, E.; Palombo, C.; Giaconi, S.; Mantovanelli, A.; Ragazzini, A.; Palla, L.

    1986-01-01

    Suppression of the renin-angiotensin system (RAS) by angiotensin converting enzyme (ACE) inhibition may induce renal failure in patients with bilateral renal artery stenosis. Recent scintigraphic studies with the glomerular tracer technetium-99m-diethylenetriaminepenta-acetate (99m-Tc DTPA) indicate that in patients with unilateral renal artery stenosis, glomerular filtration rate (GFR) may be markedly reduced in the affected kidney after inhibition of ACE. This finding reflects the important role of the RAS in maintaining GFR (by increasing postglomerular resistance) in states of low renal perfusion pressure. Preliminary observations suggest that this scintigraphic test might be useful in the detection of renovascular hypertension.

  16. Comparison of ARAC calculations with surface and airborne measurements for the ACE field trials

    SciTech Connect

    Foster, K.T.; Pobanz, B.

    1996-11-01

    These Atmospheric Collection Equipment (ACE) trials were sponsored by the Air Force Technical Applications Center (AFTAC) for the purpose of investigating specific tracer monitoring methods and equipment. Three different tracers (sulfur hexafluoride and two particulate tracers) were released simultaneously for each experiment. This document provides a brief summary of the sulfur hexafluoride modeling results for three of the remaining four ACE trials (the tracer plume from the fifth trial was not located by the monitoring teams and provided no tracer measurements for model comparison). This summary is followed by a discussion of model results for the two particulate tracers which were co-released with sulfur hexafluoride.

  17. VizieR Online Data Catalog: SP_Ace derived data from stellar spectra (Boeche+, 2016)

    NASA Astrophysics Data System (ADS)

    Boeche, C.; Grebel, E. K.

    2015-11-01

    SP_Ace is a software designed to derive stellar parameters and elemental abundances from stellar spectra. In this tables we report the stellar parameters Teff, logg, [M/H], and chemical abundances [El/H] for ten elements derived with the software SP_Ace from spectra of the ELODIE spectral library (Prugniel et al., 2007, Cat. III/251), the benchmark stars (Jofre et al., 2014, Cat. J/A+A/564/A133), and the S4N library (Allende Prieto et al., 2004, Cat. J/A+A/420/183) degraded to spectral resolution R=12,000 and S/N=100. (3 data files).

  18. Nh and CH in the Ace Satellite Solar Spectrumtitle of your Abstract

    NASA Astrophysics Data System (ADS)

    Bernath, P. F.; Ram, R. S.; Colin, R.

    2010-06-01

    The Canadian ACE (Atmospheric Chemistry Experiment) mission has a high resolution (0.02 cm-1) Fourier transform spectrometer (FTS) in low earth orbit. The primary ACE mission goal is the study ozone chemistry in the stratosphere although it is making a wide range of other measurements, for example, of organic molecules in the troposphere. In the normal operating mode, the ACE-FTS measures a sequence of atmospheric absorption spectra during sunrise and sunset (``solar occultation''). As part of the measurement sequence about 16 high sun exoatmospheric spectra are recorded for each occultation to serve as reference spectra. We have co-added 224782 pure solar spectra to produce the ACE solar atlas in the 750--4400 cm-1 spectral region [Hase et al., JQSRT 111, 521 (2010), see http://www.ace.uwaterloo.ca/solaratlas.html]. The ACE solar spectrum displays prominent vibration-rotation bands of CO, OH, NH and CH, and pure rotational lines of OH and NH. An improved spectroscopic analysis for OH has already been published [Bernath and Colin, JMS 257, 20 (2009)] and we now report on similar work for NH and CH. The vibration-rotation spectra of NH have been reinvestigated using laboratory spectra and infrared solar spectra recorded from orbit by the ACE and ATMOS instruments. In addition to identifying the previously unobserved 6-5 vibration-rotation band in the laboratory spectra, many additional high N rotational lines have been observed. By combining the new observations with the previously published data and recent far infrared data, an improved set of molecular constants and term values have been derived for the NH X^3Σ^- and A^3Π states. Vibration-rotation spectra of the CH X^2Π ground state have also been re-analyzed based on laboratory spectra, the ACE solar spectrum and published data. The previously unobserved 5-4 band has been measured and the other four bands (1-0 to 4-3) have been extended to higher J values. TEXT OF YOUR ABSTRACT

  19. Angiotensin-converting enzyme (ACE-I/D) polymorphism frequency in Brazilian soccer players.

    PubMed

    Coelho, Daniel Barbosa; Pimenta, Eduardo; Rosse, Izinara Cruz; Veneroso, Christiano; Pussieldi, Guilherme; Becker, Lenice Kapes; Carvalho, Maria-Raquel; Silami-Garcia, Emerson

    2016-06-01

    This study aimed to analyze the angiotensin-converting enzyme (ACE-I/D) allelic and genotypic frequencies in Brazilian soccer players of different ages. The study group comprised 353 players from first-division clubs in the under (U)-14, U-15, U-17, U-20, and professional categories. The allelic and genotypic frequencies did not differ significantly in any of the categories between the group of players and the control group. This was the first study of ACE-I/D polymorphism in Brazilian soccer players. PMID:27232187

  20. Adaptive coherence estimator (ACE) for explosive hazard detection using wideband electromagnetic induction (WEMI)

    NASA Astrophysics Data System (ADS)

    Alvey, Brendan; Zare, Alina; Cook, Matthew; Ho, Dominic K. C.

    2016-05-01

    The adaptive coherence estimator (ACE) estimates the squared cosine of the angle between a known target vector and a sample vector in a transformed coordinate space. The space is transformed according to an estimation of the background statistics, which directly effects the performance of the statistic as a target detector. In this paper, the ACE detection statistic is used to detect buried explosive hazards with data from a Wideband Electromagnetic Induction (WEMI) sensor. Target signatures are based on a dictionary defined using a Discrete Spectrum of Relaxation Frequencies (DSRF) model. Results are summarized as a receiver operator curve (ROC) and compared to other leading methods.

  1. Experimental demonstration of a classical approach for flexible structure control - The ACES testbed

    NASA Technical Reports Server (NTRS)

    Wie, Bong

    1991-01-01

    This paper describes the results of an active structural control experiment performed for the Advanced Control Evaluation for Structures (ACES) testbed at NASA-Marshall as part of the NASA Control-Structure Interaction Guest Investigator Program. The experimental results successfully demonstrate the effectiveness of a 'dipole' concept for line-of-sight control of a pointing system mounted on a flexible structure. The simplicity and effectiveness of a classical 'single-loop-at-a-time' approach for the active structural control design for a complex structure, such as the ACES testbed, are demonstrated.

  2. Identification of small open reading frames in the Glaciozyma antarctica genome

    NASA Astrophysics Data System (ADS)

    Mat-Sharani, Shuhaila; Bharudin, Izwan; Zainuddin, Nursyafiqi; Abdul-Murad, Abdul-Munir; Abu-Bakar, Farah-Diba; Najimuddin, Nazalan; Mahadi, Nor-Muhammad; Firdaus-Raih, Mohd

    2015-09-01

    Glaciozyma antarctica is an obligate psychrophilic yeast that was isolated from Casey Research Station, Antarctica. The objective of this study was to identify small Open Reading Frames (sORFs) in the G. antarctica genome. Small ORFs have been found in other organisms including Saccharomyces cerevisiae and human and they have been known to partake in a diverse variety of functions. In this study, ORFs were searched from the existing G. antarctica genome annotations and this resulted 294 sORFs (of at most 100 amino acids) which represented 4% of the 7857 annotated ORFs. Several of these sORFs were validated by mapping to EST and transcriptome of G. antarctica.

  3. Understanding the Dynamic Neotectonic System in Antarctica

    NASA Astrophysics Data System (ADS)

    Wilson, T. J.

    2004-05-01

    Feedbacks and interactions between components of the earth system are fundamental to polar geodynamic processes. The Antarctic Neotectonics (ANTEC) group has developed a vision for a major interdisciplinary program to investigate linkages between neotectonic processes in Antarctica, focused on understanding 1) how the stress/strain regimes of the lithosphere respond to changing ice mass loads; 2) how glacial isostatic adjustment and the tectono-thermal structure of the lithosphere influence modern ice sheet dynamics; 3) how tectonic motions and magmatism are linked with fluctuations of the Antarctic ice sheets through the Cenozoic; and 4) how evolving continental-scale paleogeography, volcanism, and erosion/sedimentation influence climate change. A primary focus to address these science goals is achieving continental-scale deployments of remote geodetic and geophysical observatories across the continental interior. Developing technologies are beginning to allow observatory operation through the polar night, due to advances in power sources and data storage capacity. Continued development in these areas, as well as in communications technologies to allow data transfer from remote stations, is required. Ground-based experiments must be integrated with campaigns by spaceborne instruments, to discriminate cryosphere mass flux signals from neotectonic activity. Coordination of ground-based observatory deployments with ongoing efforts to develop airborne geophysical platforms and new drilling systems will facilitate mapping and sampling unknown subglacial terrain and the earth's deep interior. Promising new areas of investigation to understand how surface processes are linked with tectonism in polar environments lie in application of new mapping technologies (LIDAR, ice-penetrating radar), new chronological tools, and assimilation of new surface information into modeling. If we can meet the logistical and funding challenges of instrumenting the Antarctic interior on a

  4. Ice megadunes on Mars: analogy with Antarctica

    NASA Astrophysics Data System (ADS)

    Herny, Clémence; Massé, Marion; Bourgeois, Olivier; Carpy, Sabrina; Le Mouélic, Stéphane; Appéré, Thomas; Smith, Isaac; Spiga, Aymeric; Rodriguez, Sébastien

    2014-05-01

    Mass and energy balance of ice sheets are driven by complex interactions between the atmosphere and the cryosphere. Feedbacks between katabatic winds and the cryosphere may lead to the formation of sedimentation waves, so-called megadunes, at the surface of ice sheets. These have been first described in Antarctica. Here we use topographic data, optical images, and spectroscopic data acquired by Mars orbiters. We show that the surface of the Martian North Polar Cap displays two superimposed sets of sedimentation waves with differing wavelengths. These sedimentation waves have similarities with Antarctic ice megadunes regarding their surface morphology, texture, grain size, and internal stratigraphic architecture. Their shallow-dipping upwind sides, their tops and the intervening troughs are covered by young ice and occasional sastrugi fields, indicative of net accumulation. On the other hand, their steep-dipping downwind sides either expose exhumed layers of dusty old ice or correspond to smooth surfaces of coarse-grained ice, indicative of net ablation or reduced net accumulation associated with sublimation and metamorphism. These surface characteristics and the internal stratigraphic architecture revealed by radar sounding are consistent with the interpretation that both sets of Martian sedimentation waves grow and migrate upwind in response to the development of periodic accumulation/ablation patterns controlled by katabatic winds. The smaller waves, characterized by reduced net accumulation on their downwind sides, are probably analogous to the Antarctic megadunes that have been described so far. On the other hand, a terrestrial equivalent remains to be discovered for the larger ones, characterized by net ablation on their downwind sides. The recognition of these sedimentation waves provides the basis for the development of a common model of ice/wind interaction at the surface of Martian and terrestrial ice sheets and for future investigations on the respective

  5. Multi-instrument MLT study in Antarctica

    NASA Astrophysics Data System (ADS)

    Tsutsumi, M.; Syowa Mlt Team

    The study of polar MLT region dynamics at Syowa station using various radio and optical instruments is overviewed. An MF radar (since 1999), applied to night time meteor wind measurement in addition to a conventional correlation measurement technique, provides wind information over a broad height range from 60 to nearly 120km. A sodium lidar (2000-2002) observed night time mesopause region temperature. The observed winter time mean temperature showed a significant difference from that at Arctic sites, suggesting a difference in the general circulation pattern and also wave activity between Arctic and Antarctic [Kawahara et al., 2002]. Wave analysis, especially tidal components, using both the MF radar and lidar is also being made. Other optical instrument observations including an all-sky monochromatic imager and a Fabry-Perot imager started recently. Behavior of small scale atmospheric waves is being studied using sodium airglow images, which are less affected by aurora activity compared with other emissions, together with background wind information observed by the MF radar. Recently SuperDARN HF radars, originally designed for polar F region plasma study, get much attention for their great potential for MLT study such as meteor wind and PMSE measurements. Using the two SuperDARN radars located at Syowa we developed a meteor measurement technique, of which quality is nearly comparable to that of a dedicated meteor radar [Yukimatu and Tsutsumi, 2002]. The new technique is planned to be applied to the almost twenty SuperDARN radars surrounding Arctic and Antarctica, and is expected to provide information on the longitudinal structure of background wind and planetary scale waves.

  6. Electric field measurements from Halley, Antarctica

    NASA Astrophysics Data System (ADS)

    Nicoll, Keri; Harrison, R. Giles

    2016-04-01

    Antarctica is a unique location for the study of atmospheric electricity. Not only is it one of the most pollutant free places on Earth, but its proximity to the south magnetic pole means that it is an ideal location to study the effects of solar variability on the atmospheric electric field. This is due to the reduced shielding effect of the geomagnetic field at the poles which leads to a greater flux of incoming Galactic Cosmic Rays (GCRs) as well as an increased probability of energetic particle precipitation from SEPs and relativistic electrons. To investigate such effects, two electric field mills of different design were installed at the British Antarctic Survey Halley base in February 2015 (75. 58 degrees south, 26.66 degrees west). Halley is situated on the Brunt Ice Shelf in the south east of the Weddell Sea and has snow cover all year round. Preliminary analysis has focused on selection of fair weather criteria using wind speed and visibility measurements which are vital to assess the effects of falling snow, blowing snow and freezing fog on the electric field measurements. When the effects of such adverse weather conditions are removed clear evidence of the characteristic Carnegie Curve diurnal cycle exists in the Halley electric field measurements (with a mean value of 50V/m and showing a 40% peak to peak variation in comparison to the 34% variation in the Carnegie data). Since the Carnegie Curve represents the variation in thunderstorm activity across the Earth, its presence in the Halley data confirms the presence of the global atmospheric electric circuit signal at Halley. The work presented here will discuss the details of the Halley electric field dataset, including the variability in the fair weather measurements, with a particular focus on magnetic field fluctuations.

  7. Soils of Marie Byrd Land, West Antarctica

    NASA Astrophysics Data System (ADS)

    Lupachev, A. V.; Abakumov, E. V.

    2013-10-01

    Soils of Marie Byrd Land-one of the remotest and difficultly accessible regions of Antarctica-were investigated in the area of the mothballed Russkaya station located to the south of 74° S. Despite the extremely severe wind regime (the average wind velocity is 13 m/s, and the maximum wind velocity is up to 60 m/s), the projective cover of vegetation in the area of the station averages 25-40% and reaches 60-80% in some places. The phenomena of physical weathering of the bedrock-exfoliation, stone pavements, residual rocks exposed by wind (hoodoos), and others-are clearly manifested. In most of the described soils, normal organic and organomineral horizons are absent. The soil profiles represent the mixture of the residues of mosses and lichens and the gravelly eluvium. The fine earth material is blown out of the surface horizons by strong winds; its residual accumulation takes place in the middle and lower parts of the profiles. The classification position of these soils is open to argument; they are close to Petrozems and Lithozems. Most of the profiles are underlain by the massive or slightly disintegrated bedrock with dry permafrost at a depth of 20 to 50 cm. Soils with dry permafrost comprise about 75% of the surveyed area. In separate loci in the depressions of the local mesorelief and on gentle slopes, the soils with clearly expressed cryoturbation features are developed; their profiles are underlain by the ice-rich permafrost and compose about 15% of the surveyed area. Anthropogenically disturbed soils and soils polluted with petroleum hydrocarbons, heavy metals, and other pollutants occupy about 10% of the surveyed area.

  8. A mesoscale vortex over Halley Station, Antarctica

    SciTech Connect

    Turner, J.; Lachlan-Cope, T.A.; Warren, D.E. ); Duncan, C.N. )

    1993-05-01

    A detailed analysis of the evolution and structure of a mesoscale vortex and associated cloud comma that developed at the eastern edge of the Weddell Sea, Antarctica, during the early part of January 1986 is presented. The system remained quasi-stationary for over three days close to the British research station Halley (75[degrees]36'S, 26'42[degrees]W) and gave severe weather with gale-force winds and prolonged snow. The formation and development of the system were investigated using conventional surface and upper-air meteorological observations taken at Halley, analyses from the U.K. Meteorological Office 15-level model, and satellite imagery and sounder data from the TIROS-N-NOAA series of polar orbiting satellites. The thermal structure of the vortex was examined using atmospheric profiles derived from radiance measurements from the TIROS Operational Vertical Sounder. Details of the wind field were examined using cloud motion vectors derived from a sequence of Advanced Very High Resolution Radiometer images. The vortex developed inland of the Brunt Ice Shelf in a strong baroclinic zone separating warm air, which had been advected polewards down the eastern Weddell Sea, and cold air descending from the Antarctic Plateau. The system intensified when cold, continental air associated with an upper-level short-wave trough was advected into the vortex. A frontal cloud band developed when slantwise ascent of warm air took place at the leading edge of the cold-air outbreak. Most of the precipitation associated with the low occurred on this cloud band. The small sea surface-atmospheric temperature differences gave only limited heat fluxes and there was no indication of deep convection associated with the system. The vortex was driven by baroclinic forcing and had some features in common with the baroclinic type of polar lows that occur in the Northern Hemisphere. 25 refs., 14 figs.

  9. Validating the ACE Model for Evaluating Student Performance Using a Teaching-Learning Process Based on Computational Modeling Systems

    ERIC Educational Resources Information Center

    Louzada, Alexandre Neves; Elia, Marcos da Fonseca; Sampaio, Fábio Ferrentini; Vidal, Andre Luiz Pestana

    2014-01-01

    The aim of this work is to adapt and test, in a Brazilian public school, the ACE model proposed by Borkulo for evaluating student performance as a teaching-learning process based on computational modeling systems. The ACE model is based on different types of reasoning involving three dimensions. In addition to adapting the model and introducing…

  10. The Two-Component System GrvRS (EtaRS) Regulates ace Expression in Enterococcus faecalis OG1RF

    PubMed Central

    Singh, Kavindra V.; La Rosa, Sabina Leanti; Cohen, Ana Luisa V.; Murray, Barbara E.

    2014-01-01

    Expression of ace (adhesin to collagen of Enterococcus faecalis), encoding a virulence factor in endocarditis and urinary tract infection models, has been shown to increase under certain conditions, such as in the presence of serum, bile salts, urine, and collagen and at 46°C. However, the mechanism of ace/Ace regulation under different conditions is still unknown. In this study, we identified a two-component regulatory system GrvRS as the main regulator of ace expression under these stress conditions. Using Northern hybridization and β-galactosidase assays of an ace promoter-lacZ fusion, we found transcription of ace to be virtually absent in a grvR deletion mutant under the conditions that increase ace expression in wild-type OG1RF and in the complemented strain. Moreover, a grvR mutant revealed decreased collagen binding and biofilm formation as well as attenuation in a murine urinary tract infection model. Here we show that GrvR plays a major role in control of ace expression and E. faecalis virulence. PMID:25385790

  11. Does Education Plus Action Lead to Leadership on Climate? Preliminary Results from the ACE Leadership Development Longitudinal Survey Project

    NASA Astrophysics Data System (ADS)

    Anderson, R. K.; Qusba, L.; Lappe, M.; Flora, J. A.

    2014-12-01

    Through education and leadership development, Alliance for Climate Education (ACE) is building a generation of confident and capable youth driving climate solutions now throughout their lives. In 2011-12, a random sample of 2,800 high school students across the country was surveyed before and after seeing the ACE Assembly on climate science and solutions. The survey showed that the ACE Assembly resulted in a 27% increase in climate science knowledge scores, with 59% of students increasing their intentions to take action on climate and a doubling of the number of students talking to parents and peers about climate change. Students were also compared to the Global Warming's Six Americas classification of Americans' views on climate. Following the ACE Assembly, 60% of students were alarmed or concerned about climate change. Building off these results, in 2014 ACE began to assess the results of its leadership development program that follows the ACE Assembly. The goal of this survey project is to measure ACE's long-term impact on students' college and career pathways, civic engagement and climate action. Preliminary results show that a majority of students in ACE's leadership development program are alarmed about global warming and are having conversations about global warming. A majority of these students also feel confident in their ability to lead a climate-related campaign in their school and community. These students will continue to be surveyed through 2015.

  12. T-lymphocyte induction of human monocyte angiotensin converting enzyme (ACE) is not dependent upon T-lymphocyte proliferation

    SciTech Connect

    Vuk-Pavlovic, Z.; Rohrbach, M.S.

    1986-03-05

    Human peripheral blood monocytes cultured in serum free media for seven days show a basal activity of the ectoenzyme ACE which is augmented 2-3 times by the presence of autologous peripheral blood T-lymphocytes. Since these two cell types are also involved in autologous mixed lymphocyte reaction if serum is present, the authors compared the ability of T-cells to stimulate ACE activity in the presence or absence of proliferation (measured by /sup 3/H-thymidine incorporation). By the seventh day, cultures with 5% AB/sup +/ serum showed significant increase in proliferation but no increase in ACE activity compared to the serum free cultures. Even higher proliferation rate achieved by co-culturing T-lymphocytes with allogeneic monocytes did not increase ACE production; on the contrary, ACE activity remained at the basal level. Monocyte-T-cell co-cultures stimulated with increasing concentrations of ConA or PHA showed dose dependent increases in proliferation but parallel decreases in ACE activity. Addition of soluble antigen (Candida albicans) also enhanced proliferation but not ACE synthesis. They conclude that T-lymphocyte induction of monocyte ACE is a result of cooperation between autologous cells which is not dependent upon T-cell proliferation.

  13. Mentoring Functions within the American Council on Education (ACE) Fellows Leadership Development Program: A Mixed Methods Study

    ERIC Educational Resources Information Center

    Grotrian-Ryan, Sheri A.

    2012-01-01

    The purpose of this study was to examine and better comprehend the concept of mentoring within the American Council on Education (ACE) Fellows Program. This study addressed the functions of mentoring and how they applied to those participating in the ACE Fellows Program--from the Fellows' (or protégés') perspectives. A sequential…

  14. Space Radar Image of Weddell Sea, Antarctica

    NASA Technical Reports Server (NTRS)

    1994-01-01

    This Spaceborne Imaging Radar-C/X-band Synthetic Aperture Radar color composite shows a po